Efficacy of Ovsynch with respect to resulting pregnancy rates

Efficacy study Vasconcelos et al

Vasconcelos et al. (1999) evaluated the influence of the day of oestrus cycle at which the Ovsynch is initiated and resulting pregnancy rates in lactating dairy cows.

Day of oestrus that the Ovsynch is initiated and resulting pregnancy rates in lactating dairy cows

Day of oestrus cycle	1st GnRH injection Ovulation	2nd GnRH injection Ovulation
1-4	23%	94%
5-9	96%	89%
10-16	54%	85%
17-21	77%	81%
Overall	64%	87%

Conclusion

Conception rates should be greatest with the Ovsynch protocol initiated between days 5 and 12 of the oestrus cycle.

Monitoring of oestrus cycles to select the most promising time for the Ovsynch protocol is impractical and contradictory to the idea of being able to initiate Ovsynch regardless of the cow's oestrus stage.

Other Ovsynch studies

Several studies conducted during the past few years compared pregnancy rates obtained with the use of Ovsynch protocol and other oestrus management programs such as:

• prostaglandins.(Pursley et al., 1997; de la Sota et al., 1998; Keister et al., 1998; Stevenson et al., 1999,2000; Cartmill 2001)
• progestagens (Gaery et al., 1998; Williams et al., 2002)
• various Ovsynch program modifications (Bartolome et al., 2002; Pancarci et al., 2002)
• natural breeding (Cordoba and Fricke 2001).

A meta-analysis performed by Rabiee et al. (2005) compared the results reported in numerous trials with the use of Ovsynch protocol, natural breeding, single, double or triple prostaglandin injection, Select Synch, Heat Synch and modified Ovsynch.

These authors concluded that:

1. Pregnancy rates for Ovsynch programs did not differ significantly from those obtained with natural breeding.
2. The risk of conception and pregnancy risk did not differ significantly between the Ovsynch group and cows treated with prostaglandins.
3. Comparison of pregnancy risk in cows treated with Ovsynch, Heat Synch and Select Synch did not differ significantly.