PS1-14. The Effect of Maternal Bovine Appeasing Substance at Time of Insemination on Fertility of First Service Lactating Dairy Cows.

Abstract The objective of this study was to determine the effect of administering maternal bovine appeasing substance (mBAS) at the time of first timed artificial insemination (AI) on pregnancy per AI (P/AI) of lactating dairy cows. A total of 3,087 lactating dairy cows (890 primiparous and 2,197 multiparous) from two commercial farms in Wisconsin were enrolled. All cows received the Double Ovsynch protocol (GnRH – 7d – PGF2α – 3d – GnRH – 7d – GnRH – 7d – PGF2α – 1d – PGF2α – 32h – GnRH – 16h – timed AI) for first service. At first timed AI, cows restrained in headlocks were alternately assigned to treatments. Eligible adjacent cows next to each other (head-to-head contact) were assigned to the same treatment. Treatments consisted of control (CON; no treatment; n = 1,543) and treatment (mBAS; Ferappease, FERA Diagnostics and Biologicals; n = 1546). The mBAS (10 mL) was applied topically to the nuchal area (5 mL) and above the muzzle (5 mL). Five types of semen were used for AI: frozen homospermic beef semen (n = 358), frozen heterospermic beef semen (n = 701), frozen beef sexed semen (n = 162), frozen Holstein sexed semen (n = 1,014), and fresh beef sexed semen (n = 852). For statistical analysis, semen types were categorized as frozen beef semen, frozen sexed semen, or fresh sexed semen. Pregnancy diagnosis was performed by transrectal palpation at 39 d after timed AI. Data (P/AI) were analyzed using logistic regression with treatment and semen type as fixed effects and farm as random effect. Because of the differences in semen type distribution within parity, primiparous and multiparous cows were analyzed separately. In primiparous cows, P/AI did not differ between treatments (P = 0.61; CON: 50.1% vs. mBAS: 50.9%). However, semen type affected P/AI (P < 0.01), with greater P/AI in cows inseminated with frozen beef semen (70.4%) compared with frozen sexed semen (48.7%) and fresh sexed semen (53.2%; P < 0.05). In multiparous cows, an interaction between treatment and semen type was detected (P < 0.001). Treatment improved P/AI in cows inseminated with frozen beef semen (P = 0.01; CON: 55.3% vs. mBAS: 63.0%) and frozen sexed semen (P = 0.001; CON: 45.7% vs. mBAS: 61.5%). However, P/AI did not differ between treatments when fresh sexed semen was used (P = 0.12; CON: 59.9% vs. mBAS: 54.3%). Semen type did not affect P/AI in multiparous cows (P = 0.17; frozen beef semen: 59.1%; frozen sexed semen: 53.9%; and fresh sexed semen: 57.2%). In summary, mBAS improved fertility in first-service multiparous cows inseminated with frozen semen but had no effect in primiparous cows or in multiparous cows inseminated with fresh sexed semen.