Consistency key to maintaining heifer pregnancy

Casper – “Heifer development isn’t just from weaning to breeding, but also what goes on following breeding,” said George Perry of South Dakota State University at the early December Range Beef Cow Symposium XXI in Casper.
    In his presentation, which focused on post-A.I. nutrition, Perry focused on how to manage heifers after A.I. and how that management affects reproductive performance, not only for that calf but for the rest of the heifers’ reproductive lives.
    “The goals of any heifer development program are getting heifers bred early, minimizing calving difficulty, weaning an acceptable calf and longevity, which is the biggest one,” said Perry. “The longer we can keep animals in the herd, the more we increase economic efficiency. If we develop them only to lose them after one or two years we’re hurting our economics.”
    Perry said heifers need to calve by 24 months of age to reach maximum lifetime productivity. If not, or if they lose a pregnancy, they’ll breed late and lack the opportunity to get bred the next year and fall out of the herd more quickly.
    In a study tracking five herds of heifers the females were followed through their lifetime to calculate their lifetime average weaning weight. “The study found if heifers calve early with their first calf they’ll follow that up the rest of their life with calves born early in the season,” said Perry.
    Another study looked at 3,700 claves. “When calves are born after the first day of calving, for every day later than the first day you give up 2.4 pounds per day of weaning weight,” said Perry.
    Perry shifted his focus to maintaining a pregnancy. “We know from research that if a cow or heifer ovulates and we put semen in the correct place, fertilization will occur 90 percent of the time. Inherent loss occurs no matter what the situation, but what goes on with management that can influence this?”
    According to Perry, as little as a 15 percent decrease in nutrition has an effect on embryo quality. His theory is that heifers taken from a feedlot development situation, bred and then turned out to pasture suffer a dramatic effect on their weight in that first short period of time because they have to learn how and which plants to graze.
    In one of his studies half of a group of heifers were developed on grass and the other half in a feedlot.
    “Those developed on the range were gaining two pounds a day on spring forage, while those that were not lost over three pounds a day in the first week, and during the next three weeks there was still a significant difference,” said Perry.
    He said the only other data he found that showed the same dramatic weight loss in such a short period of time was a study with a group of heifers fed 120 percent of maintenance that were dropped to 40 percent maintenance. “They lost 56 pounds over two weeks,” said Perry, reminding of the mere 15 percent decrease in nutrition that can affect an embryo.
    While heifers developed in the feedlot cycle at a rate of 94 percent while those developed on range cycle at 84 percent, Perry said pregnancy success is just the opposite at 44 percent compared to 56 percent.
    “Think about what you’re doing to that embryo if you starve an animal back when you turn them out on grass,” said Perry.
    In a study that took the scenario one step farther, one group of heifers was moved to pasture, while a second group was moved to pasture and supplemented. Both groups were moderate body condition.
    “The herd that went to pasture alone lost almost a pound a day over the first few days, while the supplemented group gained a pound a day until the first pregnancy diagnosis,” said Perry. By the final preg check there was no difference in weights.
    “These heifers go through period where they crash, then come back to normal and if you don’t watch them after you breed them you never see this,” said Perry, noting most producers breed heifers and kick them out to pasture for summer without looking them over closely again until fall.
    In another study of feedlot-developed heifers, half of a group was moved to pasture 30 days before synchronization. They were brought back in, both groups weighed and A.I.’d and turned out to pasture.
    “From A.I. to preg check – about 35 days – the group turned out to pasture beforehand gained 17 pounds while the strictly feedlot group gained .6 pounds,” said Perry.
    “When we think about heifer development and management, it’s not only from weaning to breeding, but also after we breed those animals,” said Perry.
    Comparing feedlot to range development, Perry said, “Is one way better than another? Probably not, but consistency in management before and after A.I. is what matter. The method by which they’re developed and how they’re treated can have a tremendous effect on lifetime production. What are you doing after A.I. to affect reproduction that you never even know about until three or four months later when you get to preg checking?”
    “Any sudden change will affect pregnancy success, and you want to keep your animals as consistent as possible,” he said.
    Christy Hemken is managing editor of the Wyoming Livestock Roundup and can be reached at christy@wylr.net.