PSI-18 Effects of a bovine appeasing substance applied at estrous synchronization on stress and reproductive performance.

Abstract Management practices induce stress, resulting in impaired growth and reproduction. Therefore, techniques to mitigate stress and its effects must be investigated. One strategy includes administration of a synthetic maternal bovine appeasing pheromone studied to have calming effects on cattle. The aim of this study was to evaluate the effects of a bovine appeasing substance (BAS) applied at estrous synchronization on reproductive stress and pregnancy rates. Crossbred beef cows (n = 131) were stratified by body weight (BW, 385 kg ± 0.53 kg), body condition score (BCS), and post-partum interval, then allocated to 1 of 2 pens. Pens were assigned randomly to treatment 1) administered BAS topically to the nuchal skin (5 mL) and poll (5 mL) at estrous synchronization (BAS; n = 71), or 2) control where BAS was not administered (CON; n = 60). BW was recorded on d 0, 7, breeding (d 9 and 10), and 106 to calculate change in BW. BCS was recorded on d 0 and d 106. Estrous synchronization and breeding protocols followed a 7-day-CO-Synch + CIDR combined with heat detection and timed artificial insemination (AI). Blood subsamples (BAS, n = 20; CON, n = 20) for serum cortisol analysis were collected on d 0, 7, breeding, and 106. Pregnancy was determined on d 106 via transrectal ultrasonography. Cortisol and change in BW were analyzed using the GLIMMIX procedures of SAS while GENMOD was used for AI and pregnancy variables. Significance was declared at P ≤ 0.05. There were no effects on BW for treatment by day interaction, however, BAS tended to be heavier compared to CON (P = 0.08) at breeding. There was an effect for treatment (P = 0.03), day (P ˂ 0.01), and their interaction (P = 0.03) for serum cortisol. At breeding, animals experienced greater cortisol concentrations of 11.68 ng/mL compared to d 0, 7, and 106; however, there were no differences in cortisol concentrations between treatments at breeding (P = 0.28). Overall, 51.18% of animals were open while 48.82% were bred, of those, 28.71% were bred via AI and 61.29% were bred via NS. In CON, 18 were bred via AI compared to 6 in BAS while 25 in BAS were bred via NS compared to 13 in CON (P ˂ 0.01). Previous research has reported a reduction in stress when a bovine appeasing substance was applied. In our study, applying a bovine appeasing substance at estrous synchronization did not reduce stress at the time of AI and did not impact reproductive success.