Cow nutrition’s effect on calves studied

Research in Florida, where grass quality is poor, is focusing on year-round supplements of energy and protein

EDMONTON — A pregnant cow is eating for two and the quality of nutrition throughout gestation can affect how well the calf develops.

The concept of fetal programming is fairly new and is related to cow nutrition and possible stresses it experienced during pregnancy. These factors can affect the calf’s organ and muscle development, as well as its growth and health after birth.

“There is evidence of fetal programming in other species so we know it happens. It is not as direct as people think,” said Philipe Moriel of the University of Florida.

He works at the university’s Range Cattle Research and Education Center and presented preliminary results on fetal programming at the Animal Nutrition Conference of Canada held in Edmonton May 2-3.

While swine and poultry are raised in a more controlled environment, beef cows may experience a variety of cascading effects.

“We have more variation in beef production than dairy, and different regions and environments drive the results. There is too much variation for us to claim that it happens at every location,” he said in an interview.

“I believe in cattle the fetal programming effects take longer to show. They might show in puberty or carcass quality but not necessarily on weaning weights.”

Research at the U of F is focusing on the use of year-round supplements of energy and protein at different phases of gestation. Supplementation is more common in this region where grass quality is poor.

Some regions of North America have good quality forage and there is no need for added nutrition so the effects on weaning weights, the ability of heifers to get pregnant and calf vigour may not be as noticeable.

One aspect of the Florida study put cows on a diet of 70 percent of what they would normally consume to see what happens to calves when the mothers are short of feed due to situations like drought.

Calves may be born weaker but with early intervention they can catch up. However, if deficiencies are very high, they may not be able to compensate.

“It stunts the calves forever,” he said.

So far, the preliminary work showed protein supplementation during the last trimester of gestation improved weaning weights of steers and heifers, post weaning health of steers, carcass quality of steers, puberty attainment of heifers and pregnancy rates of heifers compared to offspring of non-supplemented cows.

In addition, if the cows maintain a proper body condition score, they can get pregnant easier and colostrum is a higher quality.

Cows with a higher body condition score produce more immunoglobulins in the colostrum compared to thinner cows. This could mean cows with lower body condition scores deliver calves that have lower weaning weights. With fewer antibodies gained from colostrum, calves may be less feed efficient and may need more feed to still gain weight.

Researchers know growth and development can be marked at each trimester.

Maximum placental growth, organ development and vascularization occur during the early phase of fetal development, whereas muscle and adipose tissue developed primarily from mid gestation to calving. The number of muscle fibres starts to develop in early pregnancy but the size of the fibres comes later.

About 75 percent of calf growth happens in the last trimester so the dam’s energy requirements are high at this stage.

When there is a deficiency in a pregnant cow, there could be later repercussions.

“Steers from cows that did not get protein supplements weighed less at weaning and slaughter. Very likely we are affecting muscle,” he said.

Steers born from females with lower nutrition also had smaller lungs. That did not translate into poor performance but if they should get a respiratory illness, their breathing capacity is affected.

Heifers born from cows with poor nutrition had smaller ovaries that might affect their long-term fertility. However, they tended to have the same weaning weights as calves born to well fed mothers.

Longer-term research is needed to get a good data set. Moriel is reluctant to draw solid conclusions because there are other factors involved like diet composition and the source of energy, protein, minerals and fatty acids.

Cows of different breeds also seem to respond differently.

The next phase of research is working with a large ranch where the owner has about 30,000 cows in Florida.

He retains ownership on the calves that are placed on feed out of state. If the mother cows were on a high plane of nutrition, he wants to know how the calves perform from the feedlot to slaughter. He also wants to know how many are treated for respiratory disease and how the calves responded to a vaccine.

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