Evaluation of three hormonal protocols for anovulatory lactating cows under regulations restricting the use of estrogenic compounds

Abstract

When European Union regulations restricted the use of estrogenic compounds in food-producing animals, refined hormonal protocols were no longer applicable for anovulatory cows. However, Ovsynch and its adaptations are routinely and uniformly applied to all cows regardless of ovarian function. To evaluate their efficacy on anovulatory cows, 143, 147 and 144 anovulatory cows received Ovsynch, Presynch and G6G protocols, respectively. In comparison, 150 cyclic cows were bred without using a synchronized protocol. Results showed that cows in the Presynch group had luteolysis responding to the last prostaglandin F (PGF ) injection greater than the Ovsynch group. The serous progesterone levels at the first gonadotropin-releasing hormone of Ovsych and the last PGF injection was greater in the G6G group than the other two hormonal treatment groups. Concentrations of Ca and total protein in cervical mucus in all three hormone-treated groups before artificial insemination (AI) were significantly different from the controls. The G6G group obtained a greater pregnancy rate compared with Ovsynch and Presynch, but significantly less than the controls. For open cows in the Ovsynch group, estrus rate within 24 days after the first AI was significantly less than the controls. In conclusion, the G6G treatment resulted to better reproductive performance in anovulatory cows.

Synchronization of Estrus and Ovulation in Dairy Cattle

“…The general principle for synchronization of the follicular wave and ovulation is to control emergence of the follicular wave and establishment of a new dominant follicle in a predictable manner. Although control of the follicular wave can be achieved using estrogen and progesterone, the use of the former is forbidden in several countries (Mapletoft et al, 2018;Yapura et al, 2018;Yu et al, 2018). Today, in North America, Europe, Australia and New Zealand, all synchronization programs are based on the combination of GnRH, PGF2α and progesterone.…”

“…One of the major inconveniences of the Double-OvSynch protocol is its length (28 days) and number of cow handling. To circumvent these problems a synchronization program known as G6G (Figure 12) (Bello et al, 2006;Yu et al, 2018) was devised. It has the advantage of being 9 days shorter and it was associated with higher pregnancy/AI in multiparous cows (Astiz and Fargas, 2013).…”