Abstract #309

# 309
The association between cervical and uterine size at 4 weeks postpartum and fertility in Jersey cows.
S. Poock1, P. Melendez*1, M. Caldeira2, S. Moore2, L. Mayo2, R. Molina-Coto2, M. Lucy2, 1College of Veterinary Medicine, University of Missouri, Columbia, MO, 2Department of Animal Sciences, University of Missouri, Columbia, MO.

Several studies have studied the association between cervical and/or uterine size and subsequent fertility in Holstein cows, but none in Jersey cows. The objective of this study was to determine whether cervical and uterine size at 4 weeks postpartum are correlated with subsequent early postpartum cyclicity and fertility at first insemination in Jersey cows. The Missouri commercial dairy farm on study milked cows twice a day with an ME 305 of 7,064 kg. Cows were fed a TMR and were inseminated after estrus. The herd had a 21-d annualized pregnancy rate of 36%. Cows (n = 147) selected were subjected to an ultrasound examination and blood collection for progesterone levels at 4 weeks postpartum. Body condition score at calving, parity and milk production at the 4th week of lactation were recorded. The final statistical analysis included 127 cows with pregnancy status at first insemination. For indicators of cyclicity, [progesterone concentration and presence of corpus luteum (CL) at 4 weeks postpartum] a total of 147 cows were evaluated. Logistic regression models to test the association between cervical and uterine size and presence of CL and fertility were developed. Multivariable regression models for the association of cervical and uterine size and progesterone concentration were conducted. Cows with a cervix and uterus larger than the median value (2.54 cm and 2.25 cm, respectively) were 0.29 (95% CI 0.11–0.75; P ≤ 0.05) and 0.24 (95% CI 0.09–0.63; P ≤ 0.05) as likely to become pregnant at first insemination as cows with a smaller cervical and uterine size, respectively. Cows with larger cervix were 0.44 (95% CI 0.18–1.06; P ≤ 0.05) as likely to have a CL at 4 weeks postpartum as cows with a smaller cervix. Cows with a larger uterus were 0.32 (95% CI 0.12–0.80; P ≤ 0.05) as likely to have a CL at 4 weeks postpartum as cows with a smaller uterus. Cows with a larger uterus had a lesser progesterone concentration compared with cows with a smaller uterus (P ≤ 0.05). In conclusion, uterine and cervix size at 4 wk postpartum were predictive of cyclicity (either presence of CL or elevated progesterone) and fertility at first insemination in Jersey cows.

Key Words: Jersey, uterine size, fertility