Targeted reproductive management for lactating Holstein cows: Reproductive and economic outcomes of Double-Ovsynch compared with a targeted approach based on resumption of estrus.

Accessibility to automated monitoring devices (AMD) has led to exploration of alternative reproductive management to ovulation synchronization protocols (OvSP) for first postpartum artificial insemination (AI) according to the cow's early postpartum estrus characteristics (EPEC). We hypothesized that pregnancy and economic outcomes of cows subjected to a targeted reproductive management (TRM) are not inferior to those of cows subjected to an OvSP for the first AI. This was a noninferiority, randomized clinical trial. Cows (n = 2,635) from one dairy were fitted with AMD and classified according to EPEC at 45 ± 3 DIM as estrual (high intensity AMD-detected estrus [primiparous: heat index ≥90, multiparous: heat index ≥70; 0 = minimum, 100 = maximum]) and anestrus (no estrus or low intensity estrus). Cows in the control treatment were enrolled in the Double-Ovsynch (GnRH on d -27, PGF on d -20, GnRH on d -17 and -10, PGF on d -3 and -2, GnRH on d -1, and timed AI [TAI] on d 0 at 73 ± 3 DIM). Anestrus cows enrolled in the TRM treatment were assigned to the hCG-Ovsynch (TRM1; hCG on d -17, GnRH on d -10, PGF on d -3 and -2, GnRH on d -1, and TAI on d 0 at 73 ± 3 DIM). Estrual cows received PGF at 60 to 73 DIM, when they were 6 to 22 d after a previous estrus, and if not AI in estrus within 7 d, were enrolled in the hCG-Ovsynch at 70 to 77 DIM (TRM2). Estrual cows in the TRM treatment that were ≥23 d from a previous estrus at 63 ± 3 DIM were enrolled in the hCG-Ovsynch at 63 ± 3 DIM and received TAI at 80 ± 3 DIM (TRM3). Pregnancy was diagnosed 32 ± 3 and 67 ± 3 d after AI. Cows were re-inseminated at AMD-detected estrus or at fixed time within 10 d after nonpregnancy diagnosis. The lactation gross profit was calculated as follows: (milk income + sale value + subsequent lactation calf value) - (feed cost + replacement cost + fixed cost + depreciation + reproductive management cost). Cows in the control treatment were more likely to be diagnosed pregnant 67 d after AI (control = 53.9% [95% CI = 51.1%, 56.6%]; TRM = 50.1% [95% CI = 47.2%, 53.0%]), independent of EPEC. The interaction between treatment and EPEC tended to affect the hazard of pregnancy throughout the lactation (control = referent; anestrus-TRM: adjusted hazard ratio = 1.01, 95% CI = 0.91, 1.13; estrual-TRM: adjusted hazard ratio = 0.83, 95% CI = 0.74, 0.94). Treatment did not affect gross profit, independent of EPEC (control = US$2,196.9 ± 25.6; TRM = US$2,221.9 ± 26.5). Alternative strategies for first postpartum AI according to a cow's EPEC may be possible with AMD, without affecting gross profit. The use of a single hCG treatment to presynchronize the estrous cycle of anestrus cows may be an alternative to the presynchronization with the Ovsynch protocol because despite slightly decreasing P/AI, it did not affect gross profit.