Physiological Factors to Reproductive Success
Management tips suggested to shorten anestrous period.
by Kasey Brown, senior associate editor
DES MOINES, Iowa (Sept. 7, 2016) — “If there’s one thing I’d recommend in management to increase reproductive success, it would be to tighten the calving distribution,” said Justin Rhinehart. The associate extension and research professor of animal science at the University of Tennessee spoke to more than 200 attendees of the 2016 Applied Reproductive Strategies in Beef Cattle symposium in Des Moines, Iowa, Sept. 7-8.
Reproductive technologies generally are touted to quicken genetic progress, he agreed, adding that there are other benefits that are not as promoted, including tightening calving distribution.
Even missing one estrous cycle hits cattlemen in the pocket, he illustrated. An estrous cycle is 21 days, and a calf born in one later estrous cycle has automatically lost about 2 pounds (lb.) per day. If the market price for a 500 lb. calf is $1.50 per lb., then losing 2 lb. for 21 days equals 42 lb. lost. Forty-two lb. lost at $1.50 equals $63.
Managing both types of anestrous cycles — postpartum and prepubertal — is important. Puberty factors include the minimum age to be reached, which is 12-24 months on average; weight, with a long-held rule of thumb reaching 65% of mature weight prior to the breeding season; and breed or breed type.
Postpartum factors include calving difficulty, nutrition or body condition score (BCS), age, days postpartum, presence of calf, genetics, health, and more, Rhinehart said.
Gamete and embryo quality also play a large factor in reproductive success, Rhinehart said, noting semen in artificial insemination (AI), oocyte collection in in vitro fertilization (IVF) or embryo collection in embryo transfer (ET).
Reproduction isn’t just breeding, but includes pregnancy survival, he added. Factors affecting pregnancy survival include managing oocyte quality prior to fertilization; the uterine environment like timing for transfer, disease control and health management; nutrition both at pre- and post-insemination; and stress, like heat and temperament.
Cows that calve earlier in the calving distribution have more time to overcome anestrous obstacles before the next breeding season, and thus have more time to be set up for success, he concluded.
Rhinehart spoke during Wednesday’s ARSBC session focused on the basics of reproduction. Visit the Newsroom at www.appliedreprostrategies.com, which features comprehensive coverage of the symposium, to view his PowerPoint, read the proceedings or listen to the presentation. Compiled by the Angus Media editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force.