This study aimed to determine if 200 μg of GnRH (gonadorelin hydrochloride) would increase ovulatory response and pregnancies per AI (P/AI) compared with 100 at the first breeding-Ovsynch a Double-Ovsynch program (DO) in lactating Holstein cows. Weekly cohorts primiparous (n = 719) multiparous 1,191) cows submitted DO [GnRH – 7 d PGF2α 3 (G1) (PG1) 1 ~32 h (G2) ~16 TAI] for timed-artificial ins...

Hormonal synchroniza on protocols have been incorporated widely into reproduc ve management programs by dairy farmers (Caraviello et al., 2006; Norman et al., 2009). The ini al impact of TAI protocols on 21-day pregnancy rates in U.S. dairy herds has been to increase the AI service rate (Norman et al., 2009); however, a deeper understanding of the physiology underlying the Ovsynch protocol has ...

Summer heat stress depresses both milk production and reproductive performance of dairy cows. The use of efficient cooling systems is required because high milk-producing cows are not capable of maintaining normothermia in the summer. Cooling, if efficient enough, is capable of narrowing the gap between winter and summer milk production; however, its positive effect on fertility is limited. Fer...