PREGNANCY ATTRITION ASSOCIATED WITH PREGNANCY TESTING BY RECTAL PALPATION

The objective of this study was to estimate the effect on calving risk of interval from Al date until scheduled date of pregnancy examinatio n. First Al (n = 7105) from 65 dairy herds in the United States and Ca nada were followed for 294 d to determine whether cows calved. Calving was modeled as a function of the number of days in the interval, herd , season, and breeding at PGF(2 alpha)-induced estrus by multivariate logistic regression. The main effects of herd and Al following PGF(2 a lpha)-induced estrus were significantly associated with calving rate f rom first AI. The main effects of interval and season were not signifi cantly associated with calving.The effects of PGF(2 alpha), season, an d interval between Al and pregnancy testing varied significantly among herds. These effects appear to be symmetric in their distributions ab out their means. The risk of day of palpation on calving is herd depen dent and small compared with other herd factors.