Long enough or too long? Are extended lactations & cow longevity desirable goals? LeBlanc, Guelph

Summary

The video discusses the complexities of cow longevity, extended lactations, and their implications for the dairy industry. Dr. Steven LeBlanc presents arguments that challenge the notion that longer cow lifespans are always indicative of better management or welfare. He emphasizes the importance of economic decisions in dairy management and suggests that longevity should not be pursued as an end in itself. By exploring the balance between milk production, cow health, and reproduction, Dr. LeBlanc provides insights into optimizing dairy operations without necessarily focusing on extended longevity. The presentation concludes with a Q&A session addressing specific industry concerns.

Highlights

• Dr. LeBlanc questions the traditional focus on extended cow longevity as an indicator of success. 🌟
• The relationship between cow health, reproduction, and culling is intricate and multifaceted. 🔄
• Extended lactation might not be as economically viable as believed. ❌
• The presentation underscores the role of transition period management in dairy operations. 🚀

Key Takeaways

• Cow longevity is not always a direct indicator of good management or animal welfare. 🐄
• Economic decisions should drive culling practices rather than aiming for extended lifespans. 💰
• High milk production does not always correlate with poor cow welfare. 🥛
• Transition cow management is crucial for optimizing productivity and health. ⚖️
• The balance between cow health, longevity, and economic viability is complex. 🤔

Overview

Dr. Steven LeBlanc challenges the long-held belief that extended cow longevity is synonymous with effective dairy management. He argues that longevity should not be the sole measure of success, emphasizing instead that economic viability and cow health should guide management practices.

Throughout his discussion, Dr. LeBlanc navigates the complexity surrounding reproductive health, transition management, and milk production. His insights reveal that achieving an optimal balance in these areas is key to maintaining profitable dairy operations.

The seminar includes an engaging Q&A where industry concerns are addressed, highlighting issues like culling rates and replacement strategies. Dr. LeBlanc’s expertise offers a nuanced perspective on what truly constitutes successful dairy management.

Chapters

• 00:00 - 01:30: Introduction: New Research on Choline and Dairy Cows New research is dramatically altering the understanding of choline's impact on dairy cows and their calves. Leading scientists are presenting evidence that supports the classification of choline as an essential nutrient for optimizing milk production and promoting overall cow health.
• 01:30 - 02:30: Introduction of Dr. Steven Leblanc and Lecture Topic The chapter titled 'Introduction of Dr. Steven Leblanc and Lecture Topic' presents Dr. Steven Leblanc's lecture regarding choline as an essential nutrient. The discussion focuses on the importance of choline for improving calf health and growth, as well as increasing colostrum quantity. Recent research establishes choline's critical role for all cows, regardless of their health status, milk production, or body condition. The lecture emphasizes the scientific advancements redefining the understanding of choline's importance and mentions precision release choline from Balm as a key source.
• 02:30 - 06:30: Historical Perspective on Cow Reproduction and Longevity In this chapter, Dr. Steven Leblanc from the University of G discusses the historical perspective on cow reproduction and longevity. The focus is on cow longevity and extended lactations, with insights provided as part of the Real Science Lecture Series, hosted by Scott Surell of Balcam Animal Nutrition and Health.
• 06:30 - 09:30: Debate on Cow Longevity and Goals The chapter is titled 'Debate on Cow Longevity and Goals' and features Dr. Leblanc, a professor in the department of population medicine at the University of G, who is also the director of dairy at the center of dairy research and innovation. His academic background includes a BS in animal science from McGill University (1992), a DVM (1997), and a doctor of veterinary science (2001) from the University of G. Dr. Leblanc's research is primarily focused on the metabolic and reproductive health of dairy cows.
• 09:30 - 17:30: Factors Affecting Dairy Cow Cull Rates The chapter titled 'Factors Affecting Dairy Cow Cull Rates' introduces Dr. Leblanc, a senior editor and distinguished member of the American Dairy Science Association, known for his significant contributions to the field through over 200 publications and presentations in 20 countries. The chapter sets the stage for his insights into management precision technologies and antimicrobial stewardship, highlighting his role in influencing dairy science practices.
• 17:30 - 24:00: Impact of Health and Longevity on Economics The chapter titled 'Impact of Health and Longevity on Economics' delves into a controversial topic within the dairy industry. Although the controversy may seem settled to some, for others it is a subject of intense debate. The chapter raises two primary questions, including what is considered 'long enough', inviting readers to explore the implications of health and longevity on economic outcomes in this context.
• 24:00 - 31:00: Pregnancy and Economic Efficiency The chapter discusses aspects of cow longevity and lifespan, focusing on the appropriate length and the implications of extended lactations. It begins with a personal anecdote from 20 years ago when the speaker, then a young professor, was invited to the American Dairy Science Association's discover conference to give a talk on culling. This sets the stage for a broader discussion on how pregnancy impacts economic efficiency in dairy farming.
• 31:00 - 34:00: The Economics of Lactation Curves This chapter discusses the economics of lactation curves in cattle. It begins with a personal anecdote about attending a conference related to the topic. The speaker learned about the importance of reproduction in cow survival and replacement, highlighting the value of such conferences for gaining new insights. There's also a humorous note on learning about multiple cities named Nashville in the United States, adding a personal touch to the speaker's learning journey.
• 34:00 - 42:00: Conclusion and Q&A on Reproductive Strategies The chapter titled 'Conclusion and Q&A on Reproductive Strategies' discusses the impact of reproduction on cow survival based on the speaker's reflections and literature review. It also features an anecdote about Nashville in Indiana being a dry county, which might have influenced local perspectives or practices. The timeline is noted with a reference to a heritage font from 2004.

Long enough or too long? Are extended lactations & cow longevity desirable goals? LeBlanc, Guelph Transcription

• 00:00 - 00:30 [Music] New research is changing everything we thought we knew about choline's impact on the cow and her calf. And top scientists have a lot to say about it. They are presenting new research that supports choline as a required nutrient to optimize milk production. Choline as a required nutrient to support a healthy
• 00:30 - 01:00 transition, choline as a required nutrient to improve calf health and growth, and choline as a required nutrient to increase colostrum quantity. This new research is solidifying choline's role as a required nutrient for essentially every cow, regardless of health status, milk production level, or body condition score. Learn more about the science that is changing the game and the choline source that is making it happen. Reassure precision release choline from Balm. Visit
• 01:00 - 01:30 balchm.com/scientists to learn [Music] more. Hello everyone and welcome to the real science lecture series. My name is Scott Surell, director of marketing for Balcam Animal Nutrition and Health. Today we welcome Dr. Steven Leblanc from the University of G to discuss cow longevity and extended lactations. Uh
• 01:30 - 02:00 Dr. Leblanc is a professor in the department of population medicine at the University of G and director of dairy at GE the center of dairy research and innovation. He received his BS in animal science from McGill University in uh 1992 and his DVM in 1997 and doctor of vet science in 2001 from the University of G. His research focuses on dairy cow metabolic and reproductive health and
• 02:00 - 02:30 management precision technologies and antimicrobial stewardship with graduate students and collaborators. His work has resulted in 200 peer-reviewed papers and invited talks in 20 countries. He's a senior editor for the Journal of Dairy Science and serves as a member of the board of directors of the American Dairy Science Association. Dr. Leblanc, welcome to the Real Science Lecture Series. Floor is now yours. Thank you, Scott. Thanks everybody for
• 02:30 - 03:00 being here. Uh so pull up my slides here and uh today just mentioned that um I'm going to talk about a controversy that uh for some people might be uh preaching to the choir but for others um is is a hot topic in the dairy industry right now. Okay. So yeah, our two questions for today will be uh what's long enough
• 03:00 - 03:30 in terms of longevity in cow lifespan or possibly too long uh and in the the second shorter piece towards the end talk about extended lactations. So, by way of a little bit of a tea up, um, back 20 years ago, uh, a young professor, me, was, uh, invited to my first American Dairy Science Association, uh, discover conference, uh, which was on culling. And the organizers asked me to give a talk with the title that you see on the screen,
• 03:30 - 04:00 reproduction and its impact on cow survival and replacement. Uh, I learned a few things. I learned about discover conferences, these smaller interactive meetings, met a lot of people. Uh that was a a a great experience. Uh I also learned a US geography lesson that there are at least two Nashvilles in the United States. So when the invitation came and said, "Would you like to come to this conference? It's in Nashville." I thought, "Yeah, that sounds great." Nashville, you know, music, nightife, and so on. Uh and and then I discovered
• 04:00 - 04:30 that uh Nashville is also in Indiana, which at the time at least was uh one of the last dry counties in Indiana. So that that sort of changed the face of things. But uh coming back to the topic well reproduction and its impact on cow survival. So I thought about that and did a little literature review and this is what I came up with. Uh notice the heritage font uh appropriate to 2004.
• 04:30 - 05:00 But of course, you know, a cow, no matter how good she is or what her her potential is genetically or what her past production was, um, if we don't get her pregnant, she becomes a beef cow, whether we like it or not. So, the association of reproduction and culling uh looked a lot like this. However, uh since I work at a university and I had 45 minutes to fill, I I did have some other slides and it ended uh essentially with this that at least in terms of reproduction 20 years ago, one
• 05:00 - 05:30 of the major diseases of dairy cattle was semen deficiency. which obviously is uh I mean that as a joke but the the point was that uh a lot of dairies still struggle to really efficiently inseminate cows and between synchronization programs and technologies like activity monitors and better nutrition and better transition cow management um that that has been a real success story where things have gotten a lot better both in terms of
• 05:30 - 06:00 insemination rates and conception risks and so ultimately pregnancy rate. So, fewer cows have semen deficiency. Um, more cows get pregnant and and fewer cows are culled because of a failure to do so. Fast forward to 2023. Um, I guess the organizers had forgotten uh what what they may have learned from uh the mistake of inviting me the first time. And um showing that I had some longevity, I got invited again to give a
• 06:00 - 06:30 talk, this time at a discover conference uh on dairy cattle lifespan. And the title of this talk was health aspects of survival of dairy cows since since we'd apparently kind of dealt with the reproductive side of things. So again, back to the drawing board, think about, you know, what what hard science I could bring to this question. Uh and again the the conclusion was not very complicated but and that'll be the
• 06:30 - 07:00 subject for more of today. There's obviously nuances to it. So you know disease kills sometimes it depends and uh you know anybody here who works with graduate students will know that no matter what question you ask them they can always answer it depends and that's usually true. Uh but then you can learn to push back and say, well, okay, but depends on what and how and under what conditions. And so again, this this
• 07:00 - 07:30 won't be uh a revelation to most people, but it depends on milk and pregnancy. But we're going to delve into that a little bit. But to lay the table, I I wanted to um put a couple things out that are what kind of animate my interest in this question because I think we have uh differences in perspectives, which is healthy, but but possibly uh a little bit of either mixed messages or sometimes
• 07:30 - 08:00 misunderstanding about uh what we should be striving for when we talk about cattle longevity, cattle lifespan. And that connects ultimately to um not just if we want to get cows pregnant, but when we want to get them pregnant. So for example, uh in the upper left is a promotional graphic from the cow signals training company. And again, this is no criticism of them. They they do lots of good things, but um one of their taglines is two more lactations
• 08:00 - 08:30 everywhere. In other words, that that that kind of is or ought to be a goal that that we ought to be able to get two more lactations out of presumably every cow everywhere. Um, and I'm not sure that's necessarily the right goal. Uh here in Canada, our national DHI organization uh Lactonet uh gives out annual herd management awards uh based on herd records and
• 08:30 - 09:00 performance in a number of categories. One of them is longevity and that's based on what you see here which is the proportion of the herd um that's in the third or greater lactation. And and I'll take the time to read at least some of the words. So um proportion of cows that are third or grade of lactation. It's a measure of good management in regards to cow comfort, herd health, productive life and a problemfree herd. And I will challenge whether that
• 09:00 - 09:30 is in fact true or or whether that is true in both directions of that um logical statement. And the the promise is that increased longevity allows for higher production, um lower replacement costs, and and perhaps more animals to sell as replacements. And again, all of those things can be true. Uh but what I hope you go home from uh after this session
• 09:30 - 10:00 is that that's not necessarily true. uh and I'll give a spoiler alert that um I don't think longevity per se as an end in itself is what we should be pursuing. Um again there's the premise that um cow longevity begins with management and and at least in one direction that's true. If if management is poor um in whatever sense, poor health, poor nutrition, poor cow
• 10:00 - 10:30 comfort, etc. um then we will not be in a position to optimize longevity. Um you get into what's might be referred to as uneconomic culling, so-called forced culling, so-called um involuntary culling. But um so I I do think it's true that if if management in the broadest sense is not up to par um then optimizing longevity is is almost
• 10:30 - 11:00 certainly not going to be possible. However, greater longevity does not necessarily mean that you have good management going in the other direction of the logic. And just in the uh journal of uh American Vet Medical Association last month, there was an excellent article, a call to action um Professor Paul Bartlett at Michigan State um around uh bovine leukemia virus, lucosis and dairy
• 11:00 - 11:30 cattle. And the article was about uh a call to action about why as an industry we ought to care about that and and ought to do something about that. And I think that's an excellent um article and piece of work. However, there's this paragraph which is on the screen that was in that paper and and again, this is no um personal criticism or anything of that sort. Um but I do think it's some really important food for thought and and very pertinent to today's
• 11:30 - 12:00 discussion. And so again, the key parts here that is the the statement or the assertion that a shortened cow lifespan uh is is evidence of reduced animal welfare. Natural lifespan is 20 years. Um an economic analysis by Albert Dres of Florida indicates that economically optimal lifespan of a dairy cow should be about seven years but in the US it's only five. Um and then goes on to say a few people would be satisfied in a society where life expectancy was only slightly past puberty. Again I think
• 12:00 - 12:30 there's a lot to unpack and discuss there um in terms of parallels between cows and people. But in any case, um, and that this shortened lifespan of cows, um, might again be reflective of poor welfare. Again, I that may be true. Um, but I I would I will argue here some more if I haven't done it enough already that um,
• 12:30 - 13:00 longevity is not a good direct measure. It's not necessarily a measure of welfare. um nor should older cows longer lifespan in and of itself be the goal that we're looking for. So what is the goal? Well, again, if we step back for a second, um there's kind of a colloquialism uh about breaking cows and and and what that sort of flippant term means is um if we don't
• 13:00 - 13:30 provide the supports for cow comfort, cow welfare, cow health with, you know, if we if we have poor stalls, poor hoof care, etc. um breaking a cow would mean um having her need to leave the herd because she's no longer fit to stay um well before her time, both in terms of her welfare and in terms of her uh economic optimum. And
• 13:30 - 14:00 and so this notion of breaking cows is is bad on a whole bunch of levels, including that that really does reflect poor welfare. That that violates the social contract we have as a dairy industry in terms of what our consumers and citizens expect us how expect us to care for the cows that provide food. Uh, and even if you want it to be entirely just a very hard-nosed dollars and cents about it, um, having cows uh, literally
• 14:00 - 14:30 forced out of a herd uh, well before their time in terms of economic optimization is also undesirable. So there's a whole lot of reasons why we don't want to have cows pushed out of the herd uh where they could have should have stayed longer uh in terms of economic optimum performance for the herd but were unable to achieve that optimization. Again um alluded to a moment ago this becomes a values
• 14:30 - 15:00 judgment and and that's not what I'm going to wade into today. But um I think when we're talking about dairy cattle there's a social expectation that we do provide a quality of life for the cows that we work with. Um but what our duty of duty towards them is in terms of the length of their life I I think is much more open to to discussion. And last but not least whenever we have inefficiency in a system um that's not
• 15:00 - 15:30 going to be good for the bottom line. It's not good for welfare. Um, but it's also not good for uh the resources, feed, land, and so on that go into um making 100 pounds of milk. So, I'm a veterinarian. My whole research program is around dairy cow health. But if I really distill it down, um we have many preventable problems and and again as as an industry we've made great
• 15:30 - 16:00 strides in improving cow health and welfare and performance. Um but if we think about what are truly careerlimiting or career ending moves or circumstances for a dairy cow, uh as I alluded to at the beginning, not getting pregnant, a cow could have the greatest potential in the world, the greatest history in the world. Um but if we don't get her pregnant again, that's that will inevitably be the end of her career as a dairy cow before long. Um similarly, low enough milk is a careerending move and
• 16:00 - 16:30 and specifically in terms of health disorders, um things that we're not able to fix very well, chronic mastitis or high cell counts, and chronic lameness. There's obviously a very long list of other issues um diseases, metabolic infections and so on that are that are important um but they're not necessarily career ending in most cases. So um these are my premises and
• 16:30 - 17:00 and in fact these will in in some respects be my conclusions. Um, first is that culling is an economic decision decision is or ought to be. Um, and so from a from a calculation standpoint, um, the time to sell a cow is not when she's 20 years old or 7 years old or 5 years old per se, but to when her net present value, her future expected profitability is less than and
• 17:00 - 17:30 available. in the last two years. That's become a constraint. But an available replacement animals net present value, her future expected profitability. And of course, dairies are run by people and and at least sometimes uh we make values or emotionbased uh decisions around our you know, children's 4 calves and those kinds of things. Fair enough. as long as
• 17:30 - 18:00 that's a conscious decision. Um, next premise. It is certainly true that poor cow health will reduce productive lifespan. Cows that have mastitis, lameness, displaced abomism, these are all career limiting or threatening things. But longevity, turning it around, is not a good measure. It is a poor measure of health and welfare. And I'll elaborate on that a little bit more. And again, it it's
• 18:00 - 18:30 my assertion that uh ethics of farming cows and the expectations of consumers require quality of life for cows that they have. Some people describe it as a a life worth living for as long as they're living it. Um but not necessarily quantity. And again, I I acknowledge that that some would disagree with that, but u uh that's
• 18:30 - 19:00 that's my what I'm putting on the table for the moment. Uh and finally, that our dairy cows are amazing animals. They're often described as metabolic athletes um in terms of the the remarkable metabolic feats that they do to convert forage into high quality human food. um that is demanding just like elite human athletes live demanding lives in terms of their training and nutrition and so on and so forth. Um but again I would assert that
• 19:00 - 19:30 that dairy cows high performance dairy cows live demanding lives but not distressed lives certainly not necessarily distressed lives. Okay, so for the producers in the audience and everybody else who works with producers, we're not going to do this as a live thing, but you can just think about this for yourself. You know, do you have a 90 pound tank average? And I I don't know, take your pick if you're already there. Do you have a 100 pound tank average? But um I'm I'm trying to identify what we might all think of as a
• 19:30 - 20:00 a high production, high performance herd. So, do you have a 90 pound tank average? If so, good for you. Um if not, you know, let's think about how to help you get towards that if that's your goal. Do you have a 90 lb tank average and also consistently less than 20% annual herd culling? And I've deliberately chosen this with the expectation that most people um would
• 20:00 - 20:30 say no that you know they might say no, excuse me, yes to one, but but often it would be no to both. it wouldn't wouldn't be both. And so if that's true, if you don't have both of those things, is it because um pushing for high production and and frankly I don't exactly know what that means, but it's something we hear about uh talked about at least sometimes um
• 20:30 - 21:00 that high production is a result of pushing cows with the collateral damage of breaking cows. In other words, that we are um pushing or demanding too much of our metabolic athletes uh and we're moving past high performance into something that's really not sustainable. So is is that you know if we don't if if many herds don't have both very high production and very low culling on an annual basis is that the reason or only two choices here there
• 21:00 - 21:30 could be others but or is the reason we don't often see those two things together because at least historically um a supply of generally genetically superior heers creates selection pressure uh that's pushing on um the herd. And so that pressure for production and health um keeps a healthy selection pressure and turnover in the herd such that typically
• 21:30 - 22:00 herds are turning over a number that's higher than 20%. And and again if I so I don't forget to say it later. Um often there are debates about you know if not what a cow's optimal or worthy lifespan should be you know is there an optimal culling rate should it be 25% 30% 35% if it's 40 is that too high if it's 20 is that too low etc and I think the the bottom line of all of that is there is
• 22:00 - 22:30 no one right answer that is not a number to target in and of itself uh as a herd number. And so again, if if uh if we're not convinced yet, again for the uh dairy managers, dairy owners in the audience, you know, do you have any below average cows in your herd? And the answer obviously is of course you do. Everyone does. you know, unless um you're in uh I think it's Lake Wagon in
• 22:30 - 23:00 in the fiction where all the children are above average or perhaps some other herd where all the cows are above average. Of course, you have some below average cows in your herd and you always will. Um but are there cows in the herd right now that you would be better off without that you would prefer to replace because they're below average in production? because they have lameness that despite our best efforts of prevention therapy, they're they're still not walking perfectly because they
• 23:00 - 23:30 have repeated cases of mastitis or a high cell count that we're not able to manage down because they're nonpreg well past the economic optimum, etc. And and pretty surely just about every herd has some of these cows and some herds might have a lot of these cows. Obviously the plot twist in the last few years um is that with the very high price for both call cows and in particular for um beef on dairy cows or
• 23:30 - 24:00 all surplus dairy cavs. Um that has had the unintended consequence of substantially reducing the supply of dairy replacements. And so intentionally or otherwise um more cows are being kept in the herd longer because that available heer who may well have a greater net present value than some of the cows in the herd. But if
• 24:00 - 24:30 she's not available um then we can't pull the trigger on that economically optimized replacement decision. But but I would just um sort of underline the point that to to the extent that this is a reality that dairy industry has been living in the last couple of years um and the average age of cows is therefore creeping up in our herds because we don't have the replacements uh available that we might like to
• 24:30 - 25:00 have. Therefore longevity is greater. Does that imply that welfare has necessarily improved? Is that because we have optimized cow health? Clearly not. So zooming out um this is from a veterinary epidemiology study that was published in 1999 and this is sort of suggested as some uh associations among a variety of
• 25:00 - 25:30 health problems that can happen in early lactation. This is all very familiar by now. And fair enough, each and all of these things are at least somewhat associated, not to say causal, but associated um with the risk of not just culling, but um economically not optimized culling, premature culling um in terms of what a cow's economically optimum lifespan should be. And perhaps if we're talking
• 25:30 - 26:00 about um you know the consequences of a severe dystocia or a down cow and so forth um those things may indeed be associated with um health and welfare problems. So again this is not to say that these things are necessarily indirectly causal. Um this is kind of an old story now, but it's worth remembering that in the 90s um understanding the associations of these things, understanding um that we needed to go back at least
• 26:00 - 26:30 into the trans that close-up period um to start to prevent these things. That that was um progress at the time. And obviously the the relationship and this is very obvious to any dairy manager and it's only sometimes a little less obvious to um people analyzing data sets but bear with me. So if if a disease was really devastating and it mostly resulted directly in and and and
• 26:30 - 27:00 truly caused death, well that's very bad. And luckily we don't have uh a lot of diseases that are in that category in dairy cattle in North America. Um, but that's easier to understand and quantify and study and and and put dollars to. Um, but the reality is more complicated than that. So, a disease may um impair a cow's milk yield temporarily or permanently and that may lead to a decision to to call that cow before what would have been her optimal time. It may
• 27:00 - 27:30 under those new realities become the the right and economically optimal thing to do. Similarly, um disease may contribute to a cow failing to get pregnant at all or in a timely way, which ultimately is a career-ending move. And but the bottom is more like the actual messier reality. These things are intertwined. So, if a cow experiences one or more health conditions, that may lead to either or both of her making less milk than she
• 27:30 - 28:00 could have or should have otherwise. Um, which may lead to a choice not to rebreed her or breed her any more times because she's had her second or third case of mastitis and so on. The point being that in real life um these things are complicated. And so much as this is exactly what dairy managers deal with every day or every week as they make culling and replacement decisions, um analyzing this in terms of epidemiology
• 28:00 - 28:30 and economics is legitimately not easy. Okay. So, I'll zoom out to um an old data set that looks at setting cows up for success or otherwise. So, this is some work that Jose Santos published uh 15 years ago um from herds in California, high producing herds. They were on preync offsync trials, but they kept very careful score of the cow's health in the transition period. And the
• 28:30 - 29:00 thing I want to underline here is um almost all of the things that can go wrong with fresh cows, tough cving, metritis, fever, mastitis, ketosis, etc. um is associated with reducing pregnancy at first insemination. Well, that that's not very surprising. Uh, I'll come back to some newer data on this in a minute. But the two things that I found really striking about this study and I think are still um worthy of note if you keep
• 29:00 - 29:30 careful track of both obvious problems like a tough cving and less obvious problems that you have to go looking for like endometritis or ketosis. um only a bare majority 56% of cows ma in these large high production well-managed herds um made it through the transition period without at least one of these issues. So that's kind of sobering. However, even then and this is
• 29:30 - 30:00 before the days of double obsync um pregnancy at first insemination in these cows that remained healthy through the transition period was over 50%. And so I think that um gives us encouragement that we don't necessarily have to choose between high production and good fertility. We need to support health as the uh pillar that that underlies that. And so being Canadian, of course,
• 30:00 - 30:30 I wanted to put this in context. Half nearly half of cows have at least one health issue. Is that is that a lot? Is that too many? Um, so I put it in terms of hockey players, professional hockey players, and sure enough, 51% of professional hockey players in the NHL miss at least one game um due to some kind of injury. So this analogy of our cows being metabolic athletes uh holds up at least as far as that goes. Um I think in the interest of
• 30:30 - 31:00 time, we'll skip over that. So here this is a study that I had a small role in. It was a data set from a large uh transition facility in Germany and um the gist of it was looking at the association between having one or more uh health issues as a fresh cow and what that look and how that was associated with survival or culling or cows remaining in the herd. So the left hand panel of this uh panels are um
• 31:00 - 31:30 primmaiparis cows so cows in their first lactation. The right hand panels are older cows, second, third, fourth, lactation, so on. Diseases here were lumped together as any of milk, fever, retain placenta, metritis, ketosis, twins, or mastitis as a fresh cow. Um the so you won't be surprised that um cows that had disease were more likely to be called. However, um and sorry, one step further. So um the green line are
• 31:30 - 32:00 cows that had no diseases in the top panel. the red liner cows that had uh one or more diseases. The bottom panels break that out a little further to in orange is a single disease. In red is more than one disease. And you can see that you know an older cow that has one or more than one disease has a substantially increased risk of culling uh including in early lactation. These panels just go out to 120 days.
• 32:00 - 32:30 Generally speaking, calling a cow at that stage of lactation would not be economically optimal as a as a starting point. The other thing is that um you see there's differences between the first cavers and the older cows. And again, age generally is protective. other things being equal. Uh, a two-year-old is more likely to be retained in the herd and she's even she remains more likely to be retained in the herd even if she has experienced uh
• 32:30 - 33:00 one health condition as a fresh cow or even more than one condition as a fresh cow. The question is, and this study doesn't answer it, is that biology? Are are those younger those two-year-olds actually more resilient? Do they truly recover better both in terms of recovering production um and and perhaps fertility? Is that is that biology? Um
• 33:00 - 33:30 is that economics that that typically these animals have a greater future expected lifespan? So that comes into the decision and calculation. Um or is it even a little bit more uh let's go from biology to economics to psychology. it's the expectation or even the wish that they should have more life in front of them. Um the you know give them more chances and again that may or may not be the economically optimal thing to
• 33:30 - 34:00 do. Um jump ahead to one of my own data sets. So this is this was again published almost 15 years ago. uh decentsized data set over 2,000 cows in in both uh western New York and Ontario. Um what's good about this study is that we had very robust proactively collected quite comprehensive uh clinical and metabolic health data. The the missing piece which is important um is that we
• 34:00 - 34:30 didn't have lameness scores on these cows. So what I want to show you here um on the left hand panel is risk of culling by nine weeks in lactation 63 days in milk and on the right hand panel is full lactation culling by 300 days in milk and across the bottom in both cases are a variety of health disorders dystocia twins retain placenta matritis da amastitis ketosis um reproductive tract infection inflammation and most of
• 34:30 - 35:00 those um conditions. So the the orange bars are the cows that had those problems and their culling risks. The blue bars are the cows that didn't. And in for almost all of those uh health conditions of fresh cows, they were associated with increased risk of culling by 9 weeks in lactation. If we followed cows out for the whole lactation, obviously the total culling um goes
• 35:00 - 35:30 up. But now things shift a little bit. So as as that's farther into the rear view mirror, having had a tough cving twins retain placenta metritis is not associated with 300day culling risk anymore. different things are dazar, mastitis is etc. Again the the thing though is this is just looking at health and
• 35:30 - 36:00 culling. If we add in milk because you know ask any dairy manager, dairy owner, do you want healthy cows? Yes, absolutely. And I want milk and I want fertility. These these are not uh hopefully things you have to choose between. So the point is when we come and look at the data and try to understand the data better um I've got two models here again the same setup on the left is risk of culling by 9 weeks in milk on the right is culling by end
• 36:00 - 36:30 of a full lactation 300 days and and the point I want to make here simply is that when we take the same data but now add in production so in terms of early lactation culling risk we're adding in what was their milk at their first DHI test. When we're looking at the whole lactation, we're looking at what was their milk, a projected 305 milk in this case at their third test day, which is a pretty accurate projection of what they're going to do
• 36:30 - 37:00 for their whole 305. And again, this will not surprise anyone, but the more cows more milk cows made as a fresh cow or beyond that um was very protective. So many of the health variables that by themselves were associated with culling risk fall away when you also control for milk. So if cows are high producers, if they recover, well, that's protective against culling. Duh. But the point is that it's not
• 37:00 - 37:30 uncommon for studies to be published and presentations to be made um that look at these things in isolation. You know, what's what's the association of health? what's the association of milk? Uh or back to my cheesy example at the very outset, what's the association of pregnancy? Uh get pregnant or leave the herd. So the the point is again this is what dairy managers do every day. Um but it's not always what gets published and presented at
• 37:30 - 38:00 meetings. Um here are two more examples quickly and then we'll we'll turn a corner. Um so this is a data set published from Germany. a huge database 28 29,000 lactations from half as many cows so repeated over time um from two farms in in Germany and Slovakia 5 years worth of data and the what I'm they looked at a lot of things but the thing I'm showing here is the association between days in the close-up group and
• 38:00 - 38:30 probability of culling by 300 days in milk and so the headline the two headlines were time in the close-up period is really important. Um it's associated with a whole bunch of things but in this case culling risk and the there's sort of a curve a linear or quadratic type of relationship here whereby cows that spend around 3 weeks in the closeup um had a greater survival to 300 days. And if they had a really
• 38:30 - 39:00 short close-up period or a long close-up period, um, that was associated with lower probability of being around for 300 days. So the headline was that was the the the most associated thing. And and if you go one step down, well, they had data on a whole bunch of health disorders, but none of those per se were associated. But again, it depends. It depends how you look at the data. And this is not to say it's wrong. It's just
• 39:00 - 39:30 to on the contrary, but rather that it's important to look past the headline. So be in this case predictably days in the closeup is partially a planned management decision, but it also gets affected by uh a whole bunch of other things. and days in the close-up period is in turn associated with how much milk the cows made, risk of milk fever, retained placenta, ketosis, DA, and so on. So, it it doesn't negate that any or
• 39:30 - 40:00 all of those things are in their own right associated with culling risk. Um, but it's what epidemiologists refer to as a suitcase variable. A whole bunch of things get put in there together. One more, uh, still Germany. Uh this is a very large data set of cows that were on double offsync. Um so kind of our most uh interventionist state-of-the-art timed AI synchronization program for first service. So got 15,000 cows on double
• 40:00 - 40:30 offsyncing for first service and looking at how their experience as a fresh cow specifically whether they were healthy had retained placenta metritis mastitis ketosis um what that did to their pregnancy at first AI and essentially it pulled it down by 10 to 15 percentage points. So um basically all the cows got AI for the first service at about the same time on the same program. But having lived through those experiences a fresh cow even when they're on the
• 40:30 - 41:00 Cadillac synchronization program still there's a penalty to be paid um for what their experience was as a fresh cow. And the reason why that has such a long hangover is probably manyfold, but one part of that um is probably explained by what's known as the Britt hypothesis. So here we'll um get off the soap box and into the physiology for just a minute. So Jack Britt is a very
• 41:00 - 41:30 famous uh reproductive physiologist. he's still very active as a dairy scientist and and very briefly he was working from the observation that he and others made that um there seemed to be variability in the probability of success to first insemination depending on when it occurred. And to make a very long story short, the hypothesis went that most cows, if not all cows, go into negative energy balance in early lactation to support making a peak of
• 41:30 - 42:00 milk. That that's a good thing. um to a point, but also understanding that ovarian follicles and the oasite inside them um the oasite has been with the cows since before she was born. The follicle um comes out of dormcancy and starts to develop over at least two months and possibly a bit longer than that. It's hard to study, but the the picture that you see here from uh one of Brit's original papers was a schematic
• 42:00 - 42:30 explanation that that follicle that a cow might be ovulating and we're trying to get her pregnant to at first or second service began to develop and was growing up and probably affected by the metabolic and local endocrine environment. um as it came out of dormcancy and began to grow over that at least two-month period. And that as cows went through that negative energy balance, that would have directly or indirectly some consequences on the
• 42:30 - 43:00 quality of that follicle and that oy. That hypothesis helps to explain how and why a cow that had a metabolic disorder or disease experience as a fresh cow, even though that problem seems to be completely resolved, cows don't still have a retained placenta or metritis when they're 60, 70, 80, 90 days in milk. But the fact of having lived through it, at least in terms of their ovaries, has a long-term hangover.
• 43:00 - 43:30 And we could layer on top of this, and this is tongue firmly and cheek. I'm not taking credit for this, but um we could layer on top of that that we we now understand better that cows, in addition to the potential consequences of negative energy balance or possibly excessive negative energy balance. Um they also go through postpartum inflammation. And again, some is good. Um, possibly they could have not enough, but too much, too great a an amplitude,
• 43:30 - 44:00 too great a duration of postpartum inflammation plausibly, um, may also have effects on both ovaries and, uh, the uterus. And so, uh, Tony Bringing, who's my former PhD student who's now a professor at South Dakota State, one of his big PhD studies was in two herds here in Ontario, um, milking about 450 cows each and very intensively following these cows through the transition
• 44:00 - 44:30 period, uh, looking among other things at whether they expressed estrus as detected by an activity monitor and ultimately whether they got pregnant and stayed pregnant. Again, there's a great deal here, but for today, I just want to mention um remember back to that study I showed you from uh Jose Santos from 15 years ago when I said that barely half the cows make it through the transition period without at least one um health disorder or risk factor. Exactly the
• 44:30 - 45:00 same thing here. um collectively 49% of our cows in these high production, high pregnancy rate herds um had at least one clinical disease. So that that wasn't that's not just a historical artifact. Um and again, you'll be getting used to this by now. Now we're looking at the outcome being did a cow spontaneously show estrus as detected by an automated activity monitor between 50 and 75 days in milk. And again, healthy
• 45:00 - 45:30 cows, it's close to 80% 75 80% of those cows do. Cows that experience retained placenta, hyperetine anemia, endometritis, uterine infection at a month postpartum, losing more than half a point of body score. Um, that pulls that number down to 65 or even 60%. Heat is good, pregnancy is better. Um and again going through the hopper
• 45:30 - 46:00 the the filter of of all those um risk factors in the fresh period. Cows that had pus discharge perent vaginal discharge PVD at 5 weeks postpartum um that was associated with and probably at least indirectly contributed to a 10 percentage point difference reduction in pregnancy at first insemination. cows that also had or that otherwise had
• 46:00 - 46:30 excessive inflammation as measured by haptoglobin which is a acute phase protein marker of inflammation in early lactation also had a 10 percentage point reduction in their pregnancy at first AI and these things are the gift that keeps on giving. So this is also from a different paper from Tony's PhD. Um zooming out or zooming forward to not only getting pregnant. So again here
• 46:30 - 47:00 we've lumped together uterine disease being retained placenta matritis pus discharge or actual endometritis measured by cytology. Um but using uh gene expression tests for very early pregnancy diagnosis through pag blood tests uh and an ultrasound confirmation. But again, no surprise healthy cows have pregnancy losses, but cows that have experienced uterine disease even though they apparently got over it um have
• 47:00 - 47:30 substantially greater pregnancy losses. So less likely to show heat, less likely to get pregnant in the first place, more likely to lose that first pregnancy um despite having gotten through the first two hurdles. So, um, oversimplifying, but but hopefully usefully for the point of discussion. We've got a number of preventable and and more or less fixable problems for our cows, including things
• 47:30 - 48:00 like mritis, early stage um lameness, at least some cases of mastitis. But we also have some problems that despite our best efforts so far, we're not very able to fix or even prevent like chronic recurrent mastitis, uh, certain pathogens, chronic lameness, uh, yon's disease, lucosis, and and so on. So, um, to conclude here, and then I've just got a couple more slides to finish the thought.
• 48:00 - 48:30 Um, some of this, as I said, will be preaching to the choir and and obvious to people who make callulling decisions for dairy cows every week. However, um there's still a job to be done to have enough of those large enough data sets that have all of comprehensive credible health data and production um and fertility for us to to really uh do better at identifying um which of those things are most influential and do the
• 48:30 - 49:00 economics well. Calling and longevity are ultimately economic decisions. We're right now in a place where on the one hand we've got very high prices for callull cows and replacement animals, but a lack of replacement animals. Uh and the importance of disease, any disease is um what proportion of cows are affected and what's the impact per case, not just what's the impact per case. Okay, final uh couple thoughts
• 49:00 - 49:30 here and then we'll wrap it up and take some questions. Um, this is not the same question as what we started with, but I think it's related. And so, if we think about, all right, I've got this cow. She's earned a place in my heart, if not my spreadsheet, um, to say I I do want her in the herd. I I wish to get her pregnant. Obviously, if that's a failure, um, that is an going to impinge on economically optimal culling, and that's where the dollars come from. So
• 49:30 - 50:00 there's an economically optimal time for cows to get pregnant. That has a lot of variables that go into it, but one of the big drivers is the shape of cow's lactation curves. And so generally the economic meter starts running somewhere past about 120 to 120 days in milk where we're beginning to incur and acrue opportunity cost for cows. um assuming they get get pregnant but they get
• 50:00 - 50:30 pregnant later than would be economically optimal and then obviously if we fail to get them pregnant that's another loss. The part that is less obvious for for many people is uh the full list and and also the the relative importance of those costs. So, if I breed a cow today and she doesn't get pregnant, I have a cost that wasted, if you want, and air quotes dose of semen, and I'm going to have to buy another one. There's labor, there's
• 50:30 - 51:00 money for shots, there's um that cow's contribution to advertising the activity monitors or whatever. Um, there's paying the vet to tell you the bad news that the cow is open. Um, ultimately, there's the culling that we've talked about. Historically the the cash value of the calf on the ground was small but now it's large. Um but ultimately the the really big number even bigger number is that
• 51:00 - 51:30 future milk profit. And again that it depends on milk price and a whole mess of other things. Literally you can get a PhD in economics trying to figure this stuff out and model it. Um, but the key thing is the obvious things like needing another dose of semen or another goround of synchronization. That's that's the pennies and nickels. The the the dollars and big dollars um are particularly the future milk check. And again, that's a function of cow's lactation curves. And
• 51:30 - 52:00 and the the gist of this whole exercise is optimizing how much of a cow's life she spends closest to the most profitable part of her lactation curve, which generally speaking is close to peak because the lines between cost feed simply simply and revenue milk simplistically are not parallel.
• 52:00 - 52:30 And so again, where does the money come from? From marginal milk. Having cows spend more of their life or perhaps more specifically having more of the slots on a dairy spaces in the parlor, spaces in the barn, um being filled by cows that are closer to their economic optimum. They spend more of their life close to that economic sweet spot which is close to peak as opposed to farther away from
• 52:30 - 53:00 peak currently. Um there's a lot of value in the calves that they produce especially dairy beef calves but replacements as well. Um and and driving up pre rates drives that. Again, this could be a whole other talk, so don't worry, it's not going to be. But my point is that at least so far, and again, there are caveats on this, but at least so far, um, the economic
• 53:00 - 53:30 models have not fundamentally changed or or or found a conclusion different than the one driven by the shape of cow's lactation curves. And yes, over the years, peaks have gotten higher. And yes, over the years, persistency, at least in some cases, has gotten better. Um, but so far, those models have not broken the mold that we would like cows, even very
• 53:30 - 54:00 high producing cows, to be back in calf again by around 120 25 days in milk. Um, it it is difficult to run controlled studies on this. So there was one done in New York from um uh Julio Jan Gerardano's research group several years ago publish published by Matias Snager where they looked at actually prospectively in a randomized control trial assigning animals to double
• 54:00 - 54:30 offsync at either 60 or 88 days in milk. The bottom line of that was that economically there was not a lot of daylight between those two options. um perhaps a small advantage over a moderate time horizon um for the the later first insemination and first cavers and and uh the opposite for the older cows but not a lot of economic daylight between the two. The thing I
• 54:30 - 55:00 want to finish with here is there's now been a couple of studies done in Sweden and in the Netherlands um that have also prospectively put animals onto extended lactation. So things like breeding cows at 80 or for the first time not till 120 days in milk or in some cases even later than that 150 plus. And kudos for getting those studies done. But but I
• 55:00 - 55:30 think the the point of discussion or the critique is um one of the main outcomes in those studies is often looking at what's the success of that insemination if that first insemination is at 80 days 120 days 150 days in milk and and and much as that's a good question I think it's really missing the bigger picture because that is not the most limiting thing. Um, we're not trying to drive this around driving conception per AI,
• 55:30 - 56:00 um, or even milk per cow per year. It should probably be on a longer horizon than that. And in fact, um, really trying to decide the optimum about this will be a bit of an it depends where it it should be profit, not conception risk or something like that, but profit per most limiting resource. So, where I am in Canada, that's going to be per kilogram of butter fat that you can sell, which is milking quota. Um, for most other dairies in the United States,
• 56:00 - 56:30 that's going to be per slot, which is space in the barn. So, whether you stock at 100% or 110% or whatever number um looks to economically optimize the spaces in your dairy, available parlor capacity, a available robot capacity. In other contexts that may look like per hectare per acre per ton of nitrogen or phosphorus per for your land base. Um in the future that might look like per ton
• 56:30 - 57:00 of greenhouse gases that the farm emits. So to wrap up, culling is an economic decision. Um ideally we want to sell cows when her net present value is less than a replacement which is hopefully available. Um, if we don't do well with managing health and cow comfort, then we will not be able to make economically optimal decisions about when to replace cows and we will not optimize cow's longevity. However,
• 57:00 - 57:30 longevity per se is a poor measure of welfare um or the success of management because there are too many other things that influence that. And again, um, the transition period certainly can be a pitfall and it is a high-risk time, but it's something to be managed, not something to be proactively avoided because it leads to
• 57:30 - 58:00 another future peak and and another time in that economically optimum uh part of the cow's profit curve. And so, uh, yes, poor health will reduce productive lifespan, but we should not seek to have herds of older cows as proof of good health and welfare. Because, for example, um, the fact that we're constrained in the supply of replacements right now and that
• 58:00 - 58:30 longevity for that reason is creeping up does not mean that we have improved welfare necessarily. and that that is causally resulting in cows having longer lives in dairy herds. And at least up until now, um there hasn't been a lactation curve, a peak, a persistency, and so on. That has fundamentally changed the economic goal that we would
• 58:30 - 59:00 like cows back in calf again uh about 4 months after their last cving. such that they're cving approximately every 13 months. And with that, I will stop. Thank you for your time and happy to take a few questions. Scott, the heat of summer is coming and it can have a big impact on your cows.
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• 59:30 - 60:00 the [Music] inside. As a reminder to our audience, you can still submit questions through the Q&A tab at the top of your screen. Um, so Stephen, your first question is going to come in from Anique. Actually, she's got a couple. She'd like you to explain PVD and then she says, "Days in closeup. Was it an individual level or herd level? And if individual level, could a short period be with an included
• 60:00 - 60:30 short pregnancy or perhaps dead calf per se causing calling or long period on individual basis could be caused by false incimination data or thus a longer nonpositive period in close-up conditions. So, so let me do those in reverse order and and briefly um yes, all of the above. So, so that study from Germany did look at individual uh cow data and and absolutely and that's a I think that's one of the points that I didn't dwell on but yeah that that's you
• 60:30 - 61:00 know you wouldn't plan for a seven days in the close-up period you know that's probably because the cow calved early for for whatever reason but but none of them are desirable so so yes to all of those things and again that's not that is expressly not to imply um that you that there's causes there that that it's the short dry period that caused that. It's the cat, you know, the cat whatever she had twins. She had a late abortion, she had whatever she had, but um that yeah, that's how that happened. And then
• 61:00 - 61:30 on the PVD side of that, that's um PVD is what was and sometimes still is called clinical endometritis. So, we're talking about pus uh that you find in the cranial vagina of the cow with a vaginoscope or a scoop called a metric check or a clean gloved hand. um that pus may in fact come from the uterus or it may come from the cervix. But either way, it's a reflection of ongoing chronic smoldering active bacterial infection the cow's reproductive tract
• 61:30 - 62:00 which unsurprisingly is no good for her fertility. All right, very well. Next question is from Dr. Greenfield. Um, as we now construct our repro programs to produce a desired number of replacements using sexed and beef semen, do we have the model telling us how many first lactation animals to keep in our herd to maximize or to optimize milk production? Uh, keep more mature cows yet productive animals in the herd, but also genetic
• 62:00 - 62:30 progress. So, how do you balance all of that? So, yeah, that is sort of the I don't know million plus dollar question. Um and so on the one hand the the ivory tower answer is it depends it's complicated etc. But um practically yes there are some tools and again they're tools they're not prescriptions about exactly what to do with each cow um or exactly what to target for for a herd. However, there are some tools. For example,
• 62:30 - 63:00 one small but but helpful tool just in terms of food for thought is um within dairy comp there's a module called cow value. It does some estimations based on numbers you put in and based on the dairy's own data that will give you some useful starting points and food for thought around um cow value which is exactly it's it's its goal is exactly to be how much more is each cow worth relative to the
• 63:00 - 63:30 average replacement heer coming into your herd given the expected lifespans of those animals. And it also calculates something called pregnancy value, which says how much does that number change if a cow's pregnancy changes. So pregnancy status changes. So if I got an open cow, you know, it would she be worth enough um that it's worth breeding her again. Again, this is not handed down on stone tablets from from some higher power. Um it's food for
• 63:30 - 64:00 thought. Uh another one that's very accessible. Victor Cabrera has has done a number of models which are available on his Wisconsin dairy management website which um which looks at um each of those questions. So, uh, lets you at least play with looking at, uh, that econ um, economically optimized replacement and helps you do some calculations, some estimations around optimizing that mix of
• 64:00 - 64:30 uh, what what proportion of my animals do I want to breed to beef, what proportion do I want to breed for replacements, how many replacements do I need, um, etc. So th those are two uh widely accessible tools that that can certainly make some headway in in helping to go from abstract ideas to to some actual numbers. All right, thank you. Uh Mario is asking your comments on twinning percent increasing in more
• 64:30 - 65:00 mature herds over 55% on third lactation. Is there any effect on reducing twinning using choline to transition cows and open cows? If you don't know that one, maybe we can bring in Clay. I I was going to say that they so I am not aware of any data that looks at uh a choline effect on twinning risk, but I will I will defer to uh the ball cam experts on on that one specifically.
• 65:00 - 65:30 um to to zoom out a little bit. One of the reasons why uh we would typically see more twins in older cows, again it's kind of a long physiology story, but the short version of it is that one of the risk factors for double ovulation, which is what leads to twins, is that the follicles um in that last follicular wave before insemination are growing up under a lower progesterone environment.
• 65:30 - 66:00 And that allows two follicles to be dominant. And so the cow double ovulates instead of single ovulates as she ought to. And cows with a higher metabolic rate, which on average means higher producing cows and or older cows. Um that's one of the reasons why you may well see often would see more twins in older animals.
• 66:00 - 66:30 All right. Um, Ryan is asking, "When I hear extended lactations, I think fat dry cows. Have these studies uh followed up on the subsequent lactation health and performance of extended lactation cows?" Some of them have. Again, there, you know, there are not many of them. They are tough studies to do. Um, so kudos to to those researchers who who who have pulled that off. Um yes that some of
• 66:30 - 67:00 them have uh my caveats would be that these are studies with tens or at most hundreds of cows um which means they're not necessarily powered for looking at future um health or disease risks um big picture fertility outcomes and so on. and um they they were done in
• 67:00 - 67:30 somewhat different management cir and nutrition circumstances to to what might be typical um in United States or Canada. So so I I think my point is um that there's several grains of salt we need to take there. I I don't think it's it it's not impossible hypothetically that we could manage cows if if it truly were desirable to to have extended
• 67:30 - 68:00 lactations that could be manageable through through different grouping and feeding strategies. I I I think I've made it clear by now that I would certainly worry about whether that is economically optimal, but I don't think it's impossible. All right. Um, Carrie's asking, "Doesn't it reduce the carbon footprint of a dairy if we keep cows longer and have fewer replacements?"
• 68:00 - 68:30 Depends. Um and and so no to to be serious um it depends is is how you're measuring that because if you're looking at the carbon footprint per cow then the argument and and this even became almost national policy in uh Denmark for example um was on that premise we we'll keep cows around longer therefore we'll need fewer replacements therefore there will be fewer total
• 68:30 - 69:00 cattle in the country, you know, with mouths to belch methane and and therefore that will reduce methane. I think the part that's at least very debatable is if we were to look at a slightly different denominator like how much methane per pound or kilogram of milk produced per how much per unit of human food produced. I think
• 69:00 - 69:30 that that very likely changes that equation considerably. And so that's where I think we need to be careful about um what exactly we're talking about and what the calculation is. All right, one last question then we'll let you go Dr. Leblanc. But um next one is uh what other metrics do we need to consider when determining whether we have a healthy culling rate? uh maybe heers versus cows PTAs
• 69:30 - 70:00 again um in ter those culling decisions really ideally are made at the individual animal level and so I I I guess I guess I would just uh underline that the take-home is there is no one optimal culling rate you know people economists h have have tried to put reasonable assumptions into models and try to answer that question of given
• 70:00 - 70:30 a bunch of reason what seem to be reasonable assumptions what might be a reasonable ballpark and and they often come up with numbers that are in the magnitude of of a 30% annual herd turnover but I I really really caution that that is not a take-home and just apply it it's really a cow level decision and again it's it's complicated And so one dairy this year their best culling rate may
• 70:30 - 71:00 turn out to be 25%. Another because they're trying to grow or whatever. There are a lot of variables. The same dairy next year their optimal culling rate might be 10 percentage points different and the neighbor would be different again because they've they've just got different inputs into there. So um yeah, I I think the take-home is there is no one optimal culling rate that that that should not be an end or a
• 71:00 - 71:30 target um in itself. All right. Thank you. Uh thank you Dr. Leblanc and thank you everyone for attending today's webinar. If you have additional questions, please submit them to an&h.marketing balm.com. We're excited to announce a new webinar series called the real producer exchange designed to explore the real world decision shaping today's dairy operations. In our first episode, we're excited to welcome uh
• 71:30 - 72:00 Claire Otter Rank, manager of RiseBold Dairy in Bailey, Michigan. Uh that's a 3000 cow operation at the forefront of innovation. Claire has been hands-on in testing some of the industry's leading and latest technologies. We take a deep dive into how his tracking uh uh results adapting to real time and making datadriven decisions that improve both productivity and profitability. Scan the
• 72:00 - 72:30 QR code on the screen to register. The real science lecture series continues with educational topic each and every month, including the next one on June 3rd with Got More Milk, the latest research on fueling dairy cows with high oleic soybeans featuring Dr. Adam Lockach from Michigan State University. Visit balkkim.com/realcience for details on future webinars and to register for upcoming events. Balk Kim's podcast series, The Real Science Exchange,
• 72:30 - 73:00 continues to offer a deeper dive into our webinar topics. Log on to your favorite podcast platform and just simply search for Realcience Exchange or visit balkkim.com/mpodcast. And if you want a really cool Real Science Exchange t-shirt, just subscribe to the Real Science Exchange. Send us a screenshot along with your address to ah.marketingbalim.com. We'll get that off to you right away. And on behalf of Balk Kim and Dr.