Conception rate in Holstein cows treated with GnRH or hCG on the fifth day post artificial insemination during summer

Abstract

Lactating Holstein cows (n=158), at 213±112 days in milking and averaging 26±9kg of milk per day, were randomly assigned to one of three treatment groups: control (CG, n=52, saline), GnRH (GG, n=55, 100µg gonadorelin), and hCG (HG, n=51, 2500IU) given five days after artificial insemination (AI). Rectal temperature was taken at the moment of AI and blood samples were collected five, seven, and 12 days after AI. Pregnancy was determined between 42 and 49 days after AI. Concentration of progesterone (P4) in serum (ng/ml, mean±SE) for CG, GG, and HG were, respectively, 2.7±0.4, 2.5±0.4, and 3.2±0.5 on day 5; 4.8±0.4, 4.2±0.4, and 5.7±0.5 on day 7; and 5.2±0.4, 6.9±0.4, and 8.5±0.5 on day 12 after AI. P4 concentration had proportional increase in serum between days 5 and 7 after AI (CG: 178%, GG: 168%, and HG: 178%), suggesting that the treatments did not induce a luteotropic effect on the existing corpus luteum (CL). Concentrations of P4 increased between days 7 and 12 in cows treated with GnRH and hCG (GG: 164%, and HG: 149%, P<0.01); but not in control cows (GC: 18%, P=0.31), suggesting that a new CL was formed. Treatments with GnRH or hCG increased conception rates in cows with rectal temperature below 39.7°C (CG: 10.1%, n=26, GG: 36.8%, n=27; and HG: 32.8%, n=21), but not in cows with rectal temperature above 39.7°C (CG: 15.2%, n=26; GG: 17.8%, n=28; and HG: 24.4%, n=30). These data suggest that high body temperature masked the positive impact of treatment with GnRH or hCG on day 5 after AI on conception.Keywords: dairy cow, conception, progesterone, hCG, GnRH (GC, n=52, salina); GnRH (GG, n=55, 100mcg de gonadorelina); e hCG (GH, n=51, 2500UI de hCG) RESUMO Vacas da raça Holandesas em lactação (n=158) aos 213±112 dias de lactação e produção de 26±9kg leite/dia, foram aleatoriamente distribuídas em três grupos: controle

Impact of buserelin acetate or hCG administration on day 5 post-ovulation on subsequent luteal profile and conception rate in Murrah buffalo (Bubalus bubalis)

“…The greater steroidogenic capacity of CL in hCG than buserelin acetate-treated buffalo could be due to longer half life of hCG (De Rensis et al, 2008;Schmitt et al, 1996) and 3 to 30 times greater binding capacity of hCG than LH to luteal cells (Hunter et al, 1986). Similar to the present findings, Beltran and Vasconcelos (2008) also observed in cattle greater concentrations of progesterone following administration of hCG as compared to gonadorelin.…”

“…In cattle, following treatment with buserelin acetate or hCG on day 5 after estrus increased progesterone concentrations by stimulating the CL that was present at the time of treatment and also by formation of ACL (Beindorff et al, 2009;Beltran and Vasconcelos, 2008;Santos et al, 2001;Schmitt et al, 1996;Stevenson et al, 2007). In contrast, GnRH treatment on day 5 post-estrus failed to increase plasma progesterone in cows (Sterry et al, 2006).…”

Effect of treatment with human chorionic gonadotropin on day 5 after timed artificial insemination on fertility of lactating dairy cows

“…In some studies an absence of parity information (Walton et al, 1990;Schmitt et al, 1996b;Hanlon et al, 2005;Vasconcelos et al, 2011) or parity comparisons (Vasconcelos et al, 2011) was noted. Two studies did not observe any parity effect between primiparous and multiparous cows supplemented with hCG (Beltran and Vasconcelos, 2008;Fischer-Tenhagen et al, 2010). Intriguingly, one study showed higher conception rates (20% increase) in multiparous hCG-treated (56%) cows compared with multiparous controls (36%), but no effect (5% decrease) in primiparous hCG-treated cows (33%) versus controls (38%; Kendall et al, 2009).…”

Comparing the effects of heat stress and mastitis on ovarian function in lactating cows: basic and applied aspects

“…Approaches include administration of hCG on day 5 or 6 post-AI [92,93] and administration of GnRH between day 5 and 15 after AI [94][95][96]. A promising hormonal treatment to improve conception during the summer is supplementation of exogenous progesterone at the very early stages of pregnancy.…”