This is a draft schedule. Presentation dates, times and locations may be subject to change.

510
Impact of Estrus Synchronization and Fixed-Time Artificial Insemination on Calving Distribution in Bos Indicus Influenced Beef Heifers

Tuesday, July 11, 2017
Exhibit Hall (Baltimore Convention Center)
Nicky Oosthuizen, University of Florida, North Florida Research and Education Center, Marianna, FL
Pedro L. P. Fontes, University of Florida, North Florida Research and Education Center, Marianna, FL
Carla D. Sanford, University of Florida, North Florida Research and Education Center, Marianna, FL
Francine M. Ciriaco, University of Florida, North Florida Research and Education Center, Marianna, FL
Darren D. Henry, University of Florida, North Florida Research and Education Center, Marianna, FL
Luara B. Canal, University of Florida, North Florida Research and Education Center, Marianna, FL
Nicolas DiLorenzo, University of Florida, North Florida Research and Education Center, Marianna, FL
Graham C Lamb, Department of Animal Science, Texas A&M University, College Station, TX
To determine the effects of estrus synchronization (ES) and fixed-time artificial insemination (TAI) on calving distribution in Bos indicus influenced heifers, 751 Bos taurus × Bos indicus beef heifers were enrolled in a complete randomized design at 2 locations from January to May of 2016. Within location, all heifers were randomly assigned to one of two treatments: 1) SYNCH (n = 371); heifers were exposed to the 5-day CO-Synch + CIDR protocol where they received a 100-µg injection of GnRH (Factrel; gonadorelin hydrochloride; Zoetis Animal Health), 25 mg of PGF2α (Lutalyse; dinoprost tromethamine; Zoetis Animal Health), and a controlled internal drug releasing (EAZI-BREED CIDR; 1.38 g of progesterone; Zoetis Animal Health) insert on d 0, heifers received 50 mg of PGF2α (Lutalyse; dinoprost tromethamine; Zoetis Animal Health) at CIDR removal on d 5, followed by a 100-µg injection of GnRH and TAI 66 ± 2 h later on d 8; or 2) CONTROL (n = 380); heifers were exposed to natural service without any ES or TAI. On d 9, all heifers were exposed to bulls for the remainder of the breeding season at each location. Blood samples were collected on d -9 and on d 0 to determine pretreatment estrous cyclicity (progesterone ≥ 1.0 ng/mL). Pregnancy was diagnosed via transrectal ultrasonography 54 d after TAI by determining the presence of a viable fetus. Fetal age was estimated based on fetal size and structural features at the time of pregnancy diagnosis. Pregnancy rates on d 54 differed (P < 0.001) between locations, but did not differ (P = 0.777) between CONTROL and SYNCH treatments (64.5 vs 65.7%, respectively). Pregnancy rates were greater (P < 0.001) in cycling compared with non-cycling heifers (63.9 vs 42.4%). A greater (P < 0.01) proportion of SYNCH heifers became pregnant in the first 21 d of the breeding season compared with CONTROL heifers (52.2 vs 46.4%). Overall breeding season pregnancy rates did not differ (P = 0.982) between treatments. In summary, ES and TAI increased the percentage of heifers that conceived in the first 21 d of the breeding season, and therefore, potentially altered the calving distribution by ensuring that more heifers calve early during the subsequent calving season.
See more of: Poster Session: Production, Management, and the Environment
See more of: Production, Management, and the Environment
<< Previous Abstract | Next Abstract >>

American Society of Animal Science, PO Box 7410, Champaign, IL 61826-7410 E-mail: asas@asas.org, Ph. 217.356.9050, Fax 217.689.2436 All pages Copyright © 2012 ASAS. All Rights Reserved.