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Prediction of pregnancy probability at first service in multiparous dairy cows based on early lactation data.

M. Stangaferro

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06-23-2020

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Abstract:

T96
Prediction of pregnancy probability at first service in multiparous dairy cows based on early lactation data.
M. Stangaferro*1,2, J. Giordano2, M. Toledo3, M. Wiltbank3. 1Dairy Health and Management Services Lowville, NY, 2Cornell University Ithaca, NY, 3University of Wisconsin-Madison Madison, WI.

Objectives were to identify factors associated with first service pregnancies per AI (P/AI) and develop models to predict the probability of pregnancy in dairy cows. Data from multiparous Holstein cows (n = 410) from 2 farms that received TAI at 80 � 3 DIM after the Double-Ovsynch (DO) protocol were used. Data included calving season, health records, uterine cytology, daily milk yield, biweekly milk components, and repeated body condition score (BCS), BW, and progesterone concentration (P4) measurements. Bivariate analysis with logistic regression was used to test associations between predictors and AI outcome (pregnant or not), and variables with P < 0.20 were retained for prediction. Only the variable with the smallest p-value was included if 2 variables were correlated (r ≥ 0.6, P < 0.05). Logistic regression models for prediction were developed by backward elimination (predictor removed if P > 0.10) and lowest AIC value. Predicted probabilities for each cow were obtained to generate ROC curves. First service P/AI was affected by calving season [P = 0.03; Cold = 42.0%, Warm = 55.7%; OR = 1.64 (1.05—2.56)], displaced abomasum [P = 0.03; n = 50.0%, Y = 14.3%; OR = 0.18 (0.04—0.85)], mastitis [P < 0.01; n = 54.3%, Y = 31.3%; OR = 0.40 (0.23—0.68)], lameness [P = 0.08; n = 50.7%, Y = 28.6%; OR = 0.46 (0.19—1.08)], cytological endometritis [P < 0.01; n = 54.6%, Y = 35.9%; OR = 0.52 (0.32—0.85)], P4 ≥ 2 ng/mL at last PGF of DO [P < 0.01; n = 24.1%, Y = 52.8%; OR = 3.44 (1.71—6.91)], P4 < 0.6 ng/mL at GnRH before TAI [P = 0.02; n = 15.4%, Y = 49.9%; OR = 7.53 (1.42—39.93)], fat yield at wk 4 of lactation [P = 0.03; OR = 0.93 (0.87—0.99) for every 100g increased in fat yield], and lowest BCS value between calving and TAI [P < 0.01; OR = 9.75 (3.60—26.47) for every unit increased in lowest BCS value between calving and TAI]. The AUC obtained with the ROC curve for the predicted probabilities was 0.76 (P < 0.01), with 78% sensitivity and 63% specificity using a cut-off > 0.46. We conclude that the likelihood of pregnancy at first service in multiparous cows could be approximated by using early lactation health records, body condition, hormone concentrations, and calving season data.

Keywords: prediction, pregnancy, first service.