Abstract #T210

# T210
Effect of time to resumption of ovarian cyclicity postpartum on fertility and survival of Holstein cows.
Pablo Pinedo*1, Jose Santos2, Gustavo Schuenemann3, Rodrigo Bicalho4, Ricardo Chebel2, Klibs Galvao2, Robert Gilbert4,9, Sandra Rodriguez-Zas5, Guilherme Rosa6, Christopher Seabury7, John Fetrow8, William Thatcher2, 1Colorado State University, Fort Collins, CO, 2University of Florida, Gainesville, FL, 3The Ohio State University, Columbus, OH, 4Cornell University, Ithaca, NY, 5University of Illinois, Urbana-Champaign, IL, 6University of Wisconsin, Madison, WI, 7Texas A&M University, College Station, TX, 8University of Minnesota, Saint Paul, MN, 9Ross University, Basseterre, St. Kitts and Nevis, West Indies.

Early resumption of ovarian cyclicity (ROC) after calving is associated with reproductive outcomes. Remarkably, 20 to 40% of Holstein cows remain anovulatory by 50 DIM. Present objective is to evaluate the association among time to ROC, fertility, and survival in a multi-State Holstein population. A secondary objective is to analyze potential risk factors for delayed cyclicity. A total of 11,733 cows calving in 16 herds in 4 regions: Northeast (4), Midwest (6), Southeast (1), and Southwest (5) were enrolled at parturition and monitored weekly for reproductive events, disease occurrence, and survival. The ROC was assessed via transrectal ultrasonography at 40 ± 3 and 54 ± 3 DIM, and cows with a corpus luteum at either examination were considered to have ROC. Pregnancy was diagnosed by ultrasonography on d 32 ± 3 after AI and reconfirmed at d 60 ± 3. Diseases included retained fetal membranes, metritis (foul-smell, watery, brownish vaginal discharge at 7 ± 3 DIM), subclinical ketosis (serum BHBA > 1.0 mmol/L at 7 ± 3 DIM), clinical endometritis (mucopurulent to fetid vaginal discharge at 28 ± 3 DIM), lameness (score > 3 at 35 ± 3 DIM), mastitis (farm records), and left displaced abomasum. Multivariate logistic regression and ANOVA were used for testing potential associations between ROC and multiple explanatory and outcome variables, with farm as a random effect in all models. Early ROC was associated with parity (AOR [95% CI] = 0.79 [0.72–0.87] for primiparous cows), calf sex (0.89 [0.81–0.97] for males and twins), BCS at calving (0.71 [0.64- 0.79] for cows with BCS < 2.75), BCS at 40 DIM (0.62 [0.56- 0.68] for cows with BCS < 2.75), subclinical ketosis (0.78 [0.70–0.87] for affected cows), lameness (0.65 [0.57–0.75] for lame cows), and clinical endometritis (0.64 [0.58–0.70] for affected cows). Early ROC resulted in reduced days open (132 vs. 150 d; P < 0.001) and higher odds of pregnancy at first (1.92 [1.74–2.12]) and second (1.42 [1.26–1.60]) AI. Early ROC also was associated with lower odds of being sold after 55 DIM (0.79 [0.71–0.89]). However, the probability of pregnancy loss at first and second AI and the probability of dying after 55 DIM were not associated with early ovulation. Metrics for fertility and survival are identified.

Key Words: ovarian cyclicity, fertility, survival