311 Administering a Bovine Appeasing Substance to Beef Heifers During an Estrous Synchronization Protocol and its Impacts on Temperament and Pregnancy Rate

Abstract This experiment evaluated the impacts of administering a bovine appeasing substance (BAS) to Bos taurus (angus crossed) beef replacement heifers at the initiation of an estrous synchronization (TAI) protocol on their temperament and pregnancy rates. A total of 348 heifers at four locations were stratified by body weight (BW); reproductive tract score (RTS), and temperament score [TS; average of exit velocity (EV) and chute score (CS), determined at the day of initiation of TAI) and assigned to receive BAS (IRSEA Group, Quartier Salignan, France; n = 173) or placebo (water; CON; n = 175). Treatments (5 mL) were topically applied to the nuchal skin area of each heifer at the initiation of the TAI protocol. Within location, heifers were allocated to pens (6 pens per treatment; pen being the experimental unit) and received a free-choice total mixed ration during the duration of the experiment. Temperament (EV, CS) was assessed three times (days 0, 7 and 9) during the TAI protocol by the same trained technician. Pregnancy rate was determined by ultrasonography between days 45 and 55 post TAI. Heifer BW (379.5±5 kg), RTS (3.8±0.06), CS on days 0, 7 and 9 (2.33±0.06, 2.08±0.04, and 1.91±0.04, respectively), and EV on days 0, 7 and 9 (1.35±0.03, 1.28±0.03, and 1.39±0.03 m/s, respectively), and estrus expression prior to TAI (40.2±5.9%) were similar (P>0.10) between treatments. Pregnancy rate to TAI differed among locations (P< 0.05); however, it was not affected by treatment (39.7±8.2% and 41.0±3.7% for CON and BAS, respectively), with no treatment by location interaction. In conclusion, administration of BAS to beef heifers at the initiation of a TAI protocol did not alter temperament, measured as CS and EV, and failed to increase pregnancy rates.