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Working Ranch April/May 2016

MOST LIKELY CANDIDATES The USDA reproductive study Perry and Cushman participated in looked at 20,000 beef heifers. Goals of the study included identifying the traits of heifers that were most likely to be fertile, produce high quality calves and remain productive for at least 8 years. Animals in the study were divided into 3 groups according to when they were conceived. The fi rst group was conceived within the fi rst 21 days of estrous; the other two groups were conceived in the 2nd and 3rd 21-day estrous cycle. The study confi rmed that heifers conceived in the fi rst 21 days went on to breed earlier, conceive within the fi rst 21-day cycle and calve in the fi rst 21 days of the calving season. In a recent study conducted by the University of Nebraska, heifers born in the fi rst 21 days of estrous were shown to reach puberty and maturity earlier in their fi rst year. Heifers in the study also had consistently higher conception rates. Calves from these heifers consistently weaned at higher weights and were healthier overall. “Females that conceive earlier also stayed in the herd longer, which means they produced more calves,” Cushman maintains. “There’s no guarantee a heifer that fi ts this criteria will repeat that pattern every year. However, research has shown that females with these traits tend to be more productive overall.” INSIDE INFORMATION Cushman’s research has also involved ultrasound to examine a heifer’s internal structure, including the ovaries and the number of ovarian follicles (eggs) found in a heifer. Mammals such as cattle have a fi nite supply of ovarian follicles. Research has revealed that an animal’s follicle count directly impacts fertility. “There was evidence that low antral follicle count (AFC) was associated with a decreased heifer pregnancy rate,” Cushman shares. “Higher AFC counts may be linked to heifer fertility and longevity because a larger number of eggs would increase conception rates and extend productivity.” Near the start of breeding season, trans-rectal ultrasonography can be used to determine puberty status, reproductive tract score, and estrous cycling status, all of which have been shown to impact fertility and productivity. KNOW THE SCORE Ultrasound can also be used to obtain a heifer’s reproductive tract score (RTS) to help predict reproductive performance of yearling heifers. “Few producers know the pubertal status of heifers going into breeding season,” Cushman says. “Observing behavioral estrous is common, but very labor-intensive. Using RTS scores, obtained through a veterinarian’s examination, can improve A recent University of Nebraska study found that heifers born in the fi rst 21 days of estrous were shown to reach puberty and maturity earlier in their fi rst year. Heifers in the study also had consistently higher conception rates. And, calves from these heifers consistently weaned at higher weights and were healthier overall. Just to pay for themselves, heifers should produce between 3 and 5 calves without any open seasons. APRIL / MAY 2016 I WORKING RANCH I 107


Working Ranch April/May 2016
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