Comparison of two alternate PGF2α products in two estrus synchronization protocols in beef heifers

Abstract

Two experiments were conducted to evaluate the effects of a high concentrate, s.c. PGF2α compared with a conventionally concentrated, i.m. PGF2α in estrus synchronization protocols for heifers. In Exp. 1, 869 Angus-based beef heifers were enrolled at 8 locations. All heifers were exposed to the 7-d CO-Synch + controlled internal drug release (CIDR) estrus synchronization protocol. On day 7 of the protocol heifers received 100 µg of GnRH i.m., and a CIDR insert for 7 d. On day 0, at CIDR removal, estrous detection patches were applied to heifers and, within location, heifers randomly received 1 of 2 PGF2α treatments: 5 mL of Lutalyse i.m. (CONTROL; n = 434) or a 2 mL of Lutalyse HighCon s.c. (HiCON; n = 435). A second GnRH injection was administered at 54 ± 2 h and heifers were fixed-time AI (TAI). Heifers were evaluated for estrous activity at TAI by determining the activation of estrous detection patches. Pregnancy rates to AI (PR/AI) were diagnosed by transrectal ultrasonography between 35 and 55 d after TAI. The percentage of heifers exhibiting estrus between day 0 and TAI did not differ (P = 0.68) between CONTROL and HiCON treatments (47 vs. 46 ± 4%, respectively). Additionally, PR/AI were similar (P = 0.65) between CONTROL and HiCON treatments (46 vs. 45 ± 3%). In Exp. 2, 190 Angus-based beef heifers were enrolled at 2 locations. Heifers were exposed to the melengestrol acetate (MGA)-PGF2α protocol where they were offered 0.5 mg MGA per day from days 1 to 14. On day 33, heifers were randomly assigned to receive CONTROL (n = 95) or HiCON (n = 95) treatment, and estrous detection aids were applied. Heifers were exposed to AI 12 h after detection of estrus. Heifers not detected in estrus at location 1 received a second PGF2α injection 6 d after the initial PGF2α injection and were placed with fertile bulls. Heifers at location 2 that did not express estrus were administered 100 µg of GnRH i.m. and exposed to TAI 96 h after the initial PGF2α injection. Transrectal ultrasonography was used to diagnose PR/AI between 51 and 57 d after the initial PGF2α injection. The percentage of heifers exhibiting estrus during the estrus detection period was similar (P = 0.40) between CONTROL and HiCON treatments (82 vs. 87 ± 4%). Furthermore, PR/AI were similar (P = 0.62) between CONTROL and HiCON treatments (60 vs. 65 ± 5%). In summary, the 2 concentrations and corresponding routes of administration of PGF2α were similar in efficacy at synchronizing estrus in beef heifers.

Sincronización del estro y ovulación en hembras bovinas de razas cárnicas. Bases endocrinas y protocolos usados

“…D) Distribución de datos de TPES a diferentes tiempos entre la aplicación de PGF2-α y la IA en vacas lactantes tratadas con protocolos basados en GnRH sin uso de un DIP. Datos recopilados de: Martínez et al, 2000;Bishop et al, 2017;Bridges et al, 2014;Macmillan et al, 2020;Burns et al, 2008;Busch et al, 2007;Busch et al, 2008;Cruppe et al, 2014;Dahlen et al, 2010;Echternkamp & Thallman, 2011;Esterman et al, 2016;Geary et al, 2001;Giles et al, 2013;Hall et al, 2017;Helguera et al, 2018;Hill et al, 2014;Hill et al, 2016a;Hill et al, 2016b;Kasimanickam et al, 2006;Kasimanickam et al, 2014;Kasimanickam et al, 2009;Kasimanickam et al, 2012;Knickmeyer et al, 2019;Lamb et al, 2001;Lamb et al, 2006;Larson et al, 2006;Marquezini et al, 2011;Marquezini et al, 2013a;Marquezini et al, 2013b;Martínez et al, 2002;Mercadante et al, 2015;Mialot et al, 2003;Nash et al, 2012;Oosthuizen et al, 2018a;Oosthuizen et al, 2018b;Oosthuizen et al, 2018c;Rosales-Torres et al, 2017;Small et al, 2009;Stevenson et al, 2003;…”

Improving the efficiency of estrus synchronization in cows

“…The first is through the use of prostaglandin F2α (PGF2α), which causes lysis of the corpus luteum (CL) [ 4 – 6 ]. The second is the alternate use of PGF2α and gonadotropin-releasing hormone (GnRH) [ 7 – 9 ], while the third is the use of progestogens that mimic the function of the CL [ 10 ].…”