Monitor body condition to improve reproduction

Breeding efficiency | Veterinarian recommends producers assess animal fat and feed accordingly before breeding

Reproduction is the most important productivity measurement affecting profitability in a cow herd.

“Cow costs are important,” said John Campbell of the Western College of Veterinary Medicine.

“We can’t ignore that, but we probably can’t sacrifice reproduction too much when we reduce cow costs. If we don’t have a calf at the end of the day, we have nothing to sell.”

Campbell said during a webinar sponsored by the Beef Cattle Re-search Council that it’s important to keep calving seasons short to produce uniform calves that gain well and make more money.

Rebreeding cows and heifers 80 to 100 days after calving results in reproductive momentum, in which cows produce calves at the same time every year.

He said a 95 percent pregnancy rate is achievable.

A cow’s gestation length is about 282 days, so it needs to conceive again within 83 days of calving if it is to have a calf every year.

Suckled beef cows do not start their estrus cycles for 50 to 60 days after calving. First-calf heifers take longer at 80 to 100 days, and dairy cows are sooner because the calves do not suckle.

There is also a 60 to 70 percent likelihood that a calf will be born from a single mating from a healthy, fertile female and bull.

“That is the best we can expect from everything working normally,” Campbell said.

As a result, cows have three chances to become pregnant in a 60 day breeding season.

Many embryos are lost at Day 14, which means cows still have time to cycle again and become pregnant within the correct time period.

Cows that deliver within the first 30 days of the calving period the following year have another 50 days to get ready for breeding again so that they stay within the 365 day period.

Calves born early in the calving period have more time to gain weight and grow to a uniform size before marketing.

Campbell recommended writing down when calves are born. Most producers do not know when the cows conceived unless artificial insemination was used.

“The only accessible reproductive event we have in a beef cow is when she calves, but we know if she calves on this date, she got bred approximately 282 days before that,” he said.

“Cows tend to calve in the same part of the calving season each year.… To maintain that pattern we have to make sure that that interval between calving and cycling does not get extended.”

Producers often blame the bulls when cows fail to become pregnant.

However, the cows may have been too thin or they had bovine viral diarrhea, parasites or some other problem that could have been prevented with vaccination.

Another explanation is they did not go into heat.

Cows should be regularly condition scored to assess how much fat they are carrying.

Campbell said most producers just look at them when they do chores, but it is better to lay hands on them to check the amount of body fat they are carrying. Skinny cows need more and better feed before calving.

“Nutrition is a major category on both sides of this equation and has a major role in affecting herd fertility.”

Cows with a body condition score of 2.5 at the beginning of the breeding season are far more likely to become pregnant.

Thin cows have difficulty rebreeding or may abort, while fat cows are prone to calving problems and excessive feed costs.

A study by Cheryl Waldner at the University of Saskatchewan found that pregnancy checking is the best time to condition score cows, partly because they are already in the chute and easy to handle.

“Body condition scores at pregnancy testing time was most strongly associated with pregnancy status. It is the easiest time to measure them,” Campbell said.

He also suggested sorting cows into management groups for winter feeding and watching their body condition so that some do not fall behind. Producers should consider feed tests to make sure their cows are receiving proper nutrition and mineral supplements.

Heifer management is also critical. They may get pregnant the first time, but many fail to conceive the second time.

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