During a session at the 2022 Wagyu Age conference in Melbourne last week, BEEF producers were warned about the dangers of selecting an increasingly large mature cow size.
american animal scientist Dr. Ken Olson From South Dakota State University, plotting how US industry has changed over the past 20 odd years, how cow size has increased, how it matches the size of the US cow herd, and the effects of weight on cow productivity Provided an explanation of how it has grown.
Their first graph below shows how US beef production (the green line) has continued to increase over the past century, while at the same time there has been a sharp decline in US breeding herd numbers since the mid-1970s, when it peaked in population of about 45 million cows. The numbers were now on the verge of falling below the 30 million cows breeding ‘any day’.
As this graph shows, beef production per US cow has been increasing steadily over the past 20 years, rising from 316 kg/cow in 1990 to 371 kg/cow by 2009 – an increase of 17 percent over 20 years. Growth.
“How did we do that?” Prof Olsson asked. “We made big carcasses, produced offspring that could grow faster and grow bigger. But does that mean that the cows that produce those calves also get bigger?”
He said that in the 1960s-70s, the typical American breeding cow weighed 450-500 kg and was based hereford. Starting in the 1980s, the industry became largely involved in crossbreeding, bringing in a number of terminal European breeds with great growth potential.
“But in our US industry, we did a very poor job of managing our crossbreeding system, which I called the ‘Bull of the Month Club.’ It was a progression of breeds, and it was not managed well. It turned out to be a mess.”
The way commercial beef producers moved back from this was to revert to direct breeding with Angus replacing Hereford, which now accounts for the lion’s share of the US beef cattle herd.
“Angus is the breed that American industry has used to try to improve everything, and to clean up the mess we made,” he said.
So how fast did the US Angus grow up, and how big did they get?
Prof. Olson used three sources of information to explain the observed changes in the size of the American cow.
The first was the genetic predictor (US EPDs, equivalent to Australia’s EBV). EPD values are half of those observed in EBV, as only half of the genetics in an animal comes from the cow. The figures were based on a large amount of data generated by the American Angus Association.
In the US both the EPD became too large for the weight of the mature cow and the height of the mature cow. Since 1972, there has been a steady increase in the weight of a mature cow. In short, the size of the cow has increased at the rate of 1.44 kg per year for the last 50 years.
Another indicator was from the USDA ARS Germplasm Evaluation Program, which compared seven popular American breeds. This showed the average US cow size as of 2009 (environmental impact removed) was 630 kg.
“There were differences in cow size between breeds, but all were grown,” he said.
“Originally the European breeds that were brought to the US tended to have more mature cow weight. But by 2009 data, British breeds not only held up – they actually outperformed Euro and continental breeds.
The third indicator of change in the size of the American mature cow comes from simple logic. For many years the common belief in America was that the finished weight of a steer calf would match the mature weight of its mother. Research had proved this to be true.
The next graph from Professor Olson, plotting US feedlot market-ready weights for ten million steers and heifers from Kansas feedlots killed between 1990 and 2019, shows US carcase weight (as a proxy for the mature weight of their mothers). as) how far it has come. For example, Fed steer has increased from 538 kg average carcass weight to 634 kg by 2019 – an increase of 95 kg in 30 years. The trend is similar for the fed heifer (pink line).
So how do the trends in the Australian beef industry compare?
There is no shortage of evidence that a similar trend is occurring in Australia – although it is nowhere near extreme yet.
Prof Olsson extracted ‘hot off the press’ EBV data for Wagyu cattle in Australia. It showed that mature cow size increased from about 12.6 kg in Wagyu cows since 2007 to 2021.
“All you have to decide is, do I want to raise my cows?” He told the conference.
“Do I want to chase the carcass weight so hard that the cows keep getting bigger, or do I want to find a way to increase the carcass weight while keeping the genetic relationship between the carcass weight of the offspring and the weight of the mature cow? to open?
“It can be separated. It’s not easy, because the two are closely related, but at least in the US, there are some beef sires that can be used that help slow the increase in cow size.” can, while continuing to increase the size of the carcass.”
He noted that the average rate of gain in Wagyu cows in Australia, according to EBV data, was still only 0.6 kg per year, compared with earlier US Angus data, where the increase is 1.44 kg/year.
“What it says is that you guys (Australian Wagyu breeders) have cows that have been getting bigger for years, but at a much slower rate than American cattle currently.”
“From what I have noticed since arriving in Australia, it is probably because you guys are focusing more on what your breed is famous for – the marbling score, and the eatability of the product, you per animal. on maximizing the weight of .
“But the trend is there. You have to consider this data and what it means for the way genetics is managed in the Australian Wagyu cow herd. I am here to tell you what is possible, and if you can What happens if you don’t limit it?
Prof. Olsen also applied some mature cow weight numbers to its meaning from the point of view of herd management.
“If my (grazing) resources are unlimited, there’s probably no reason to care about large carcasses. But the problem is that as they get older, their nutrient needs increase.
“Fortunately, it’s not directly proportional to the rate of weight gain — it’s proportional to the surface area of the animal — and the energy they need to consume each day. So it’s about volume rather than weight.” “
“This works in our favor, because as the surface area of an animal (all animals, not just cows) goes up, its surface area increases at a slower rate than weight.
Using the graph below, Prof Olsson explains this by stating that a 635 kg cow requires 11pc more maintenance energy than a 545kg cow, which was 16pc lighter in weight.
“There’s an advantage in letting your cows grow up, just in the maintenance cost in keeping that cow alive. But to do that, the heavier cow needs to eat more. The heavier cow needs 11 percent of the nutrients it needs.” To bridge the gap an additional 478 kg of feed, dry matter basis is required in a year.
“You may have to feed that cow about 500kg more feed, or you may have to give supplemental feed to fill that gap – but one way or another, it is important for that cow to meet her lifetime requirements. And still get pregnant and take that pregnancy to end and milk until that calf is with her, and breed again – she’ll need to eat more.”
So how much more would a large cow have to produce to cover its high feed bill?
Based on typical weight loss in South Dakota, the graph below shows that a 635 kg cow would need to lose 25 kg to match the feed efficiency of a 545 kg cow.
Is this a possibility? The US Angus EPD database suggested that this was not the case, Prof Olsen said, because the weight had been left behind by the cow’s size to lose, adding only 15 kilograms over the past 20 years. All of the additional carcase growth occurring in US industry was occurring after weaning.
He said that in order to add 90 kg of cow weight to each cow in place for a given grazing asset, it was important to ask: do you have the fodder resources to meet the needs of those cows?
“In general, as cows gain weight or as they increase milk production, the need for nutrients increases. Grazing resources are quite different across the Americas, as they do in Australia. ,
“Extreme sizes rarely fit. You never want to have the biggest cow in the world, nor the smallest. Somewhere in the middle, you have to move your herd of cows relative to the available forage resources.
In a study in Wyoming looking at how cow size matters in grazing environments, three cows divided by weight, measured for animal unit equivalents. Based on daily dry matter intake, the lightest group of cows averaging 445 kg could drive 237 heads over a given area, while the heaviest average 635 kg could only accommodate a stocking rate of 186 heads.
“But how many ranchers in the US have reduced the population of their breeding herds in the past 20 years as their cows have increased in size?” Prof Olsen asked.
“The answer is none. They can’t afford. So what do they do to compensate for that? They either let too many cows fail, which is measured as pregnancy rates, or they feed too many supplements.” Let’s start bringing it.”
“And that’s what’s happening in America.”
- See today’s second story: Challenges for food service and retail customers in excessive carcass size