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Texas AgriLife cow environment genetics.jpg Texas A&M AgriLife photo by Blair Fannin
A cow’s environment — the available grazing and nutrition it offers — should be a deciding factor on herd genetics.

Genetic management critical to fitting cattle to environment

Balance breeding cattle selection with operation environment to optimize cattle performance.

Matching cattle to the land available to graze and the nutrition it offers is critical for optimizing production in a beef cattle operation.

“More often than not, as a nutritionist, I’m called in to fix a situation where the cattle and environment are not matched,” Texas A&M AgriLife Extension Service beef cattle specialist Jason Smith said at the recent Southwest Beef Symposium in Amarillo, Texas.

He explained how cattle selection and the operation’s environment feed off one another. Without balance, one will take away from the other, so it’s important to know both what the cattle will need as well as what the land can offer.

Smith also emphasized how important it is to keep records to document progress and problems.

“We need to ask a lot of a female if she is going to be a valuable component of the herd,” Smith said. “She needs to check a lot of boxes if she is going to be the backbone of the operation. If she can’t do those things as a calf, then as a replacement heifer and later as a mature cow, she limits the operation’s ability to make forward progress.”

If the cow is going to be kept as a replacement heifer, she must have been healthy and performed at an acceptable level as a calf, become pregnant during the breeding season, calve without assistance by her second birthday and then do it again the next year, he said, noting, “Those should be the bare minimum criteria.”

Smith also said if the female wants to continue to be employed in the herd, she needs to be able to do all that while maintaining acceptable body condition with little to no protein or energy supplementation. Then, she must continue to wean a healthy, desirable calf that meets expectations year after year.

“If she can’t do those things, she doesn’t fit your environment and will hinder your ability to move forward,” he said.

According to Smith, major traits of concern that influence input costs are mature cow size, milk yield, feed efficiency and longevity.

“We often find ourselves focusing too much on output without considering what else might come along for the ride,” he said.

Selecting only for weaning weight or yearling weight without considering other growth- or size-related traits will cause the mature cow size to increase, which also increases forage intake and total nutrient requirements, Smith said.

“That doesn’t mean we can’t use genetics to select for improvements in weaning weight; it just means that we need to divergently select the genetics that will allow for an improvement without increasing cow size. The same concept applies to milk production, although that improvement is often less rather than more,” he said.

Fit cattle to feed availability

“As cow size increases, nutrient requirements increase, and the carrying capacity of your land decreases,” Smith said. “If we lose sight of that, then we generally find ourselves in a situation where cows are too big, the ranch is overstocked and we either take a hit on productivity or have to start to make drastic modifications to the environment through supplementation.”

On the flip side, he added, thinking smaller cows are more efficient just because they’re smaller isn’t necessarily true. While there is certainly animal-to-animal variation in feed efficiency, the general rule of thumb is that efficiency of nutrient use for maintenance increases as bodyweight increases.

“What is true is that smaller cows generally eat less than larger cows, so ranch carrying capacity is often greater for smaller cows. When you’re moving from a 1,000 to 1,300 to 1,600 lb. cow, you must decrease stocking rate accordingly. How much does she weigh? That would be my first question,” he noted.

Smith said “a lot of us think we have 1,000 lb. cows, but in reality, those cows often weigh 1,200-1,300 lb. If we aren’t objectively measuring mature cow weight, we’ll almost always underestimate it. A set of scales will quickly pay you back.”

What is perceived to be mature cow weight is also heavily influenced by that cow’s condition, he said.

“If we want to get a handle on where we are as far as mature cow size, we need to level the playing field by correcting weight for body condition. Otherwise, we might inadvertently select for skinny, hard-doing cows,” Smith said.

Since cow size influences the ranch's carrying capacity, extremely large cows are problematic, according to Smith.

“It is terribly difficult to use weaning weight alone to compensate for the reduced revenue. A single unit increase in weaning rate, focusing on reproduction and health, will have a greater positive impact on herd revenue than a single unit increase in weaning weight,” he said, recommending that producers focus on both.

Smith also said there are consequences to smaller cows in that cow size also influences finished calf weight. For instance, a 1,000 lb. cow at a body condition score of five will generally produce a calf that finishes at just under 1,150 lb. if a terminal cross is not used to produce calves that can be marketed to hit industry targets.

“We probably need to have 1,200-1,300 lb. cows to finish calves that meet current industry standards for finished calf and carcass weight,” he said.

Smaller cows can be used to produce calves that meet industry targets for finished calf size, but that requires the use of different genetics to produce replacements versus the genetics used to produce the calves that will be marketed as feeders, Smith said.

“If we try to use the same cattle to do both, and cow size isn’t somewhere in that 1,200-1,300 lb. range, then either the calves run the risk of being discounted for small frame size, or cow size will increase over time,” he explained.

Smith also said that is why he believes a 1,200-1,300 lb. mature cow size is probably the sweet spot for most operations that can’t or aren’t willing to distinguish between maternal and terminal breeding decisions in their herd.

Milk production is another area for concern. Not only is milk expensive to the cow from a nutrient standpoint, but the conversion of milk to calf weight gain is poor.

“A 5 lb. increase in average daily milk yield is expected to increase daily energy requirements by a little over 15% but only increase calf growth by 0.2 lb. per day,” he said.

Because of the way cattle partition, or prioritize, the use of nutrients, reproduction is generally the first thing to go when the cow’s needs aren’t met, Smith said.

“More often than not, less milk is more economical in a resource-limited environment,” he said.

TAGS: Beef
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