LAUSR

The objective of this study was to evaluate changes in vaginal pH of beef cows enrolled in a 7-d CO-Synch+controlled internal drug release (CIDR) protocol and its effects on pregnancy. A total of 46 multiparous beef cows with no signs of vaginitis were enrolled. Individual vaginal flushes were collected from cows on D0, D7 and D10. Individual flushes were immediately analyzed for pH with a portable pH meter. As evidence of vaginitis, a CIDR score was determined at CIDR removal (D7), following a 1 to 4 scoring system: 1 = clean, no secretion; 2 = clean, clear secretion; 3 = purulent secretion; 4 = purulent secretion and blood. Pregnancy status was determined by rectal ultrasonography approximately 40 days after TAI. No cows had CIDR scores of 1 or 4, 19.6% of cows had a score of 2 and 80.4% a score of 3. Vaginal pH increased from D0 (6.88±0.007) to D7 (7.32±0.047), regardless of CIDR score (P < 0.001). Cows with a CIDR score 2 had greater pH on D7 (7.35±0.084) than on D0 (6.90± 0.14; P = 0.001), and pH on D10 was intermediate (7.14±0.14; P = 0.14). Cows with CIDR score 3 had reduced pH on D10 (7.09±0.07) when compared to D7 (7.29±0.04; P = 0.003), but greater pH on D10 than on D0 (6.87±0.07; P = 0.007). There was a pregnancy by day interaction for pH values (P = 0.046). Pregnant cows had greater vaginal pH in comparison with non-pregnant cows on D0 (6.99±0.081 and 6.68±0.09, respectively; P = 0.01) and D10 (7.26±0.08 and 6.89±0.09, respectively; P = 0.006), but not on D7 (7.34±0.05 and 7.27±0.06, respectively; P = 0.38). Non-pregnant cows had reduced vaginal pH on D10 in comparison to D7 (6.89±0.09 and 7.27±0.06, respectively; P < 0.001), whereas pregnant cows had similar vaginal pH on D10 and D7 (7.26±0.08 and 7.34±0.05, respectively; P = 0.35). We conclude that CIDR increases vaginal pH overtime and greater pH at TAI is beneficial to fertility.