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

136
Administration of Recombinant Bovine Somatotropin Prior to Fixed-Time Artificial Insemination and the Effects on Pregnancy Rates and Conceptus Development in Beef Heifers

Tuesday, July 11, 2017: 10:00 AM
307 (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
Darren D. Henry, 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
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
Vitor R. G. Mercadante, Virginia Tech - Animal and Poultry Sciences, Blacksburg, VA
Graham C Lamb, Department of Animal Science, Texas A&M University, College Station, TX
Audio File Recorded Presentation (mp4)
To determine the effects of recombinant bovine somatotropin (bST; sometribove zinc, Posilac, Elanco Animal Health, Indianapolis, IN) administration at the initiation of a fixed-time artificial insemination (TAI) protocol, on pregnancy rates and conceptus development in replacement beef heifers, 412 Bos taurus beef heifers were enrolled in a complete randomized design at 4 locations from January to July of 2016. All heifers were exposed to the 7-day CO-Synch + CIDR protocol where they received a 100-µg injection of GnRH (Factrel; gonadorelin hydrochloride; Zoetis Animal Health) and a controlled internal drug releasing (EAZI-BREED CIDR; 1.38 g of progesterone; Zoetis Animal Health) insert on d -9, heifers received 25 mg of PGF2α (Lutalyse; dinoprost tromethamine; Zoetis Animal Health) at CIDR removal on d -2, followed by a 100-µg injection of GnRH and TAI 54 ± 2 h later on d 0. Within location, all heifers were randomly assigned to one of two treatments: 1) BST (n = 191); heifers received 650 mg bST on d -9; or 2) CONTROL (n = 223); heifers received no bST on d -9. Blood samples were collected on d -9, -2, 0, 28 and 60 to determine concentrations of IGF-1. Pregnancy was diagnosed via transrectal ultrasonography on d 28 and 60 after TAI by determining the presence of a viable fetus. Conceptus development was assessed by measuring crown to rump length (CRL) on d 28 at the time of pregnancy diagnosis. Concentrations of IGF-1 were similar (P > 0.05) between treatments on d -9, 28, and 60; however, concentrations of IGF-1 were greater (P < 0.001) in bST treated heifers at TAI (372.4 vs 193.7 ng/ml). Pregnancy rates to TAI (PR/AI) were greater (P = 0.028) in CONTROL compared with BST heifers (42.5 vs 29.9%). Overall breeding season pregnancy rates did not differ (P = 0.967) between treatments. No differences (P = 0.668) in CRL (8.8 ± 1.7 mm) were determined on d 28 between CONTROL and BST heifers. Administration of bST at the initiation of a TAI protocol increased IGF-1 concentrations at TAI, failed to increase embryo size, but decreased PR/AI.
See more of: Oral Session: Beef Species II
See more of: Beef Species
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