Evaluation of the effect of a 3rd GnRH injection administered six days after the 2nd GnRH injection of Ovsynch on the reproductive performance of Japanese black cows

Abstract

This study was designed to evaluate the reproductive performance of Japanese black cows following the 3rd injection of gonadotropin releasing hormone (GnRH) analogue administered concurrently with Ovsynch-based treatment on day 6 (day 1 = the day of ovulation). In Experiment 1, 12 cows were allocated into three groups: a control group that was subjected to Ovsynch treatment and then injected with a placebo on day 6; group 1 (Ovsynch + GnRH), which was subjected to Ovsynch treatment and was injected with GnRH analogue on day 6, and group 2 (Ovsynch + controlled internal drug-release (CIDR) + GnRH), which received Ovsynch-CIDR treatment and was injected with GnRH analogue on day 6. Blood collection and ultrasonographic observation of the ovaries were conducted daily. Both treatments induced the formation of an accessory corpus luteum and significantly increased the cross-sectional area of the luteal tissue when compared to the control. However, plasma progesterone (P4) was significantly higher in the treatment groups than in the control group on days 11, 12, 17 and 18 in the group 1 and from day 10 to 21 in the group 2. In Experiment 2, 41 cows were assigned to the same three groups described above and then artificially inseminated on day 1. The pregnancy rates on day 45 did not differ among groups. In conclusion, administration of GnRH analogue on day 6 following Ovsynch-based treatment did not improve the reproductive performance of Japanese black cows, even though the P4 concentration was higher in groups that received the GnRH.

Pattern of induced estrus and conception rate following Ovsynch and Ovsynch based gonadotropin-releasing hormone treatments initiated on day 6 of estrous cycle in repeat breeding crossbred cows

“…These results were in agreement with the previous reported in repeat breeder cows [ 10 , 20 ]. Present findings were lower than those recorded by others [ 21 , 22 ]. Studies revealed that the initiation of Ovsynch treatment on different days of estrous cycle influenced its effectiveness [ 23 ].…”

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

“…One of the hallmarks of most TAI is that they induce a synchronized ovulation of a dominant follicle. Whereas ovulation of a smaller follicle may be positive for oocyte quality, it would result in production of a smaller corpus luteum (CL) that may produce lower progesterone (P4) concentrations than are optimal for fertility (Vasconcelos et al, 2001;Perry et al, 2005;Gaja et al, 2008) This problem is further exaggerated due to the high metabolism of P4 that is characteristic of high-producing dairy cows (Sangsritavong et al, 2002;Wiltbank et al, 2006). Progesterone is essential for pregnancy maintenance, playing a decisive role in stimulating production of a large range of endometrial compounds, growth factors, immunosuppressive agents, enzymes, ions, and steroids (Geisert et al, 1992;Hugentobler et al, 2010;Forde et al, 2011).…”