Effects of postpartum acetylsalicylic acid on uterine diseases and reproductive performance in dairy cattle

Uterine diseases are some of the most prevalent and costly diseases for the dairy industry. It has been reported that an exacerbated and prolonged inflammatory response around calving can increase the risk of developing metritis, which subsequently can impair production and fertility in dairy cows. The objective of this study was to assess the effects of 2 oral administrations of acetylsalicylic acid 24 h apart on the incidence of uterine diseases [i.e., retained fetal membranes, clinical metritis, clinical endometritis) and reproductive performance [i.e., days in milk to conception, number of services to conception, proportion of cows pregnant at first service, proportion of abortion at first service (ABRT)] in dairy cows after calving. Cows from one dairy farm (n = 246) located in central Pennsylvania were included in this study. Animals were blocked by parity and randomly assigned to 1 of 2 groups: (1) ASA (n = 121): within ~12 h after parturition, cows received 2 treatments with acetylsalicylic acid (ASA; 200 mg/kg, 4 boluses) 24 h apart; or (2) UNT (n = 125): cows remained untreated. Clinical metritis was assessed at 7 ± 3 and 14 ± 3 d in milk (DIM) using a Metricheck device (Simcro Tech Ltd., Hamilton, New Zealand). Cows that presented a fetid, red-brownish, watery vaginal discharge were classified as having clinical metritis. Clinical endometritis was assessed through ultrasonography and defined as presence of hyperechoic fluid (>3 mm) in the uterus lumen at 50 ± 10 DIM. The incidence of retained fetal membranes was defined as the failure of expulsion of the placenta within 24 h after calving and recorded by farm personnel. The data were analyzed using the MIXED and GLIMMIX procedures of SAS (SAS Institute Inc., Cary, NC) as a randomized complete block design. A lower proportion of cows treated with acetylsalicylic acid developed clinical metritis at 7 ± 3 DIM (ASA = 34.97 ± 5.57%; UNT = 57.21 ± 5.80%) and tended to develop clinical endometritis at 50 ± 10 DIM (ASA = 3.84 ± 2.67%; UNT = 13.61 ± 5.23%) compared with cows that remained untreated. Cows treated with acetylsalicylic acid tended to require 18 d less to conceive compared with UNT cows (ASA = 125.63 ± 8.21 d; UNT = 143.44 ± 6.28 d). Furthermore, there was a tendency for a treatment × ABRT interaction, whereby ASA cows that aborted at first service tended to conceive 35 d sooner compared with UNT cows that aborted at first service (ASA = 151.42 ± 15.90 d; UNT = 186.38 ± 11.84 d). Although there was no difference in pregnancy per AI at first service between treatment groups (ASA = 23.88 ± 7.92%; UNT = 17.93 ± 6.31%), the proportion of cows aborting at first service in the ASA group tended to be lower than that in the UNT group (ASA = 1.03 ± 1.06%; UNT = 6.04 ± 2.62%). Results from this study suggest that a short-duration acetylsalicylic acid treatment after calving may decrease the incidence of uterine diseases and improve reproductive success in cows that aborted at first service in dairy cattle.