24 The Effects of Vaginal pH on Fertility of Beef Cows and Heifers Enrolled in the 7-d Co-synch + Controlled Internal Drug Release (CIDR) Protocol

Abstract

Abstract The objective of this study was to evaluate the effect of vaginal pH on fertility of beef cows and heifers enrolled in a fixed-time artificial insemination (TAI) protocol. Year 1, 40 multiparous cows; and year 2, 48 multiparous cows and 41 heifers with no signs of vaginitis were enrolled. Vaginal flushes were collected for all females on D0, D7 and D10 and immediately analyzed for pH with a pH meter. As evidence of vaginitis, CIDR score was determined at CIDR removal (D7) following a 1 to 4 scoring system: 1=no secretion; 2=clear secretion; 3=purulent secretion; 4=purulent secretion and blood. Pregnancy status was determined by transrectal ultrasonography approximately 40 days after TAI. No animals had CIDR scores 1, whereas 23.7% of animals had a score 2, 69.6% a score 3, and 6.6% a score of 4. There was no effect of CIDR score on pregnancy outcome (P = 0.697). However, vaginal pH on D7, differed according to CIDR score (P = 0.045), where score 2 had greater pH (7.32±0.04) than score 4 (7.09±0.08), and score 3 were intermediate (7.25±0.02). No effect (P = 0.307) of CIDR score on vaginal pH on D10 was observed. There were no differences (P > 0.01) between vaginal pH of pregnant and open animals on D0 (7.06±0.05); D7 (7.26±0.03); and D10 (7.21±0.04). Nonetheless, on D10 females with vaginal pH 7.1 < pH ≤ 7.34 had greater (P = 0.005) PR (n=56; 66.1%) than cows with pH > 7.35 (n=33; 45.5%), and pH < 7.09 (n = 39; 33.3%). We conclude that vaginitis caused by the CIDR changes vaginal pH on D7, which is not carried on to D10. In addition, there is indication of an optimal vaginal pH range at the day of TAI for maximum PR to the protocol.