Cows at a feed bunk David Bohnert

Feed cows right for better calves

What your cows eat this winter and next spring matters a lot come weaning time next year.

Calf health is complex, and we are still learning about how this can be affected by what we feed the cow during pregnancy. Indeed, research is showing that what we feed a pregnant cow can have an influence on how well her calf performs later in life, even after weaning.

“Historically, we haven’t really considered how cow nutrition during gestation affects weaning performance, but we are starting to see a lot of data showing how gestational nutrition has an effect on the lifelong productivity of that calf,” says David Bohnert, Extension specialist and ruminant nutritionist at the Eastern Oregon Agricultural Research Center at Burns, Ore.

One of the studies Bohnert was involved in looked at how a cow’s body condition and weight fluctuates throughout the year, and whether or not this fluctuation makes a difference in the calf if the cow’s body condition changes during pregnancy.

“With most spring-calving herds, cows lose condition beginning in late summer and we manage them to put it on again when it’s cheaper in the fall or winter — when the cows’ nutrient requirements have decreased. We’re not holding those cows at a constant body condition score the whole time,” says Bohnert.

“Some of the earlier data show that when we supplement a cow during late gestation, the calves seem to do better. Work in Nebraska and some of the work I did here in Oregon showed that we can increase weaning weight and also improve calf health just by how we fed and managed that cow when that calf was in utero.” If the cow is in good health, with good body condition, and her colostrum is optimal, the calf gets off to a better start.

“A subsequent study we did looked at whether it matters what period of gestation the cow starts to improve in body condition. Shortly after breeding, we allocated our cow herd into several groups. One group we held at a body condition score of 4.5 [since most of the herd was about 4.5 at that time],” he says.

They kept that group at BCS 4.5 all the way through gestation, until calving. Some of the cows had a BCS of about 6, and those were held there all the way through gestation. 

“We divided the rest of the cows into three groups. One of those groups was managed to increase from a BCS 4.5 up to a 6 by the end of the first trimester, and then held there for the rest of gestation. Another group we held at 4.5 until the beginning of the second trimester and then brought to a 6. The other group we held at 4.5 until the beginning of the third trimester when we increased them to a 6 by calving,” Bohnert says.

These groups differed in their nutritional management at different stages of pregnancy. “Compared to the cows that were 4.5 and those that were 6 the whole time, the ones we brought up to a 6 during the second or third trimester had calves that were heavier at weaning than the others. This shows that an increase in nutrients for the cow at a certain point during the second or third trimester seemed to benefit the calf a little better in terms of weight gain,” he explains.

“We saw that it benefited calf health, as well, though it was not as strong an effect,” he says. “We did see a little less sickness. This and other supporting data has demonstrated that long-term productivity of a calf can be influenced by the cow’s protein and energy status during gestation.”

Importance of minerals

Mineral supplementation is also important. When cows are fed levels above their minimal mineral requirements during gestation, the calves do better, research shows.

“During the last trimester, we had a group of cows that were getting their requirements for minerals, and two groups that were getting double their requirements for copper, zinc, manganese and cobalt. One of those groups was getting an organic source, and the other group had an inorganic source of these minerals. They only got the mineral during late gestation,” Bohnert says.

“After they calved, all of those cattle were managed the same through weaning. We found that the cows receiving organic mineral had calves that weighed roughly 50 pounds more than the group getting the assumed requirements. The group receiving the inorganic minerals had calves weighing 25 pounds above those of the control group,” he says. The greater gains with the organic minerals were probably due to the minerals being more readily absorbed and used by the body.

“We don’t have enough data to support this theory, but it is possible that as an industry, we may not have a good feel for what the actual mineral requirements are for the gestating cow and the developing fetus,” he says. “In the past, we’ve simply looked at the mineral requirements of the cow, but our data and others like it are starting to show that the mineral requirements of the cow may be higher in late gestation in terms of affecting the performance of the calf.” The fetus needs minerals as well.

“We don’t know the exact mechanism of how supplementing the gestating cow above current requirements increases calf performance, but when you realize it can make a difference of $40 to $75 per head at weaning, this is something to consider in your cow herd management plan. This will more than pay for cost of mineral supplementation [about $3 per cow],” says Bohnert.

Not only did those calves weigh more, but they also stayed healthier. The incidence of BRD (bovine respiratory disease) was less in calves from supplemented cows that received double the requirement than it was in the control cows, and the group receiving the organic mineral did the best, he says. The immune system’s function is very dependent on having adequate trace minerals.

“The interesting thing was that this supplementation was just during the last 90 days of gestation, but this had an effect on calf health at birth, all the way through the feedlot period. We took those calves into the feedlot, and they were able to maintain better health and increased weight all the way through,” says Bohnert.

Fat supplementation

“In terms of supplementation of the pregnant cow, we can also provide them with polyunsaturated fatty acids during late gestation. This seems to have an effect [in better gain and health of the calves] like we saw with the minerals, but maybe not quite as dramatic,” he observes. 

“We want to look at this a bit more in the future, because we saw that those calves seemed to have better carcass traits and a little more gain. This is all helping the health of the calves,” Bohnert says.

Smith Thomas is a rancher and freelance writer based in Salmon, Idaho.

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