Late-gestation seasonal effects on survival and milk production of first-lactation Holstein dairy cows
2020
Toledo, I.M. | Monteiro, A.P. | Dahl, G.E.
Seasonal heat stress during late gestation influences subsequent milk yield, immunity, reproduction, and health of dairy cows. Our objective was to determine the effects of seasonal heat stress experienced by calves in utero on survival, age at first calving, and milk production during the first lactation under commercial conditions.Records of 4,274 Holstein heifers born under commercial conditions in north-central Florida during 3 consecutive years were analyzed. Based on temperature-humidity index values, heifers were considered to experience in utero heat stress during late gestation when born between July and September (hot season, HS) or no in utero heat stress when born between January and March (cool season, CS).Cool season heifers calved about one month earlier than HS heifers (P < 0.001). Cool season heifers tended (P = 0.08) to produce more milk and more protein (P < 0.001) than HS. There was no difference (P = 0.93) in survival to parity 1 and 2, but HS heifers had greater (P = 0.03) survival to parity 3. For survival after first calving up to 300 DIM, CS heifers had a greater survival rate compared with HS heifers (P = 0.04).Although the effect of different season of calving for the HS and CS heifers cannot be ruled out given the design of the present study, results are generally consistent with the effect of in utero heat stress in controlled studies on calf health and performance at maturity. Dry cow cooling during seasonal heat stress may limit negative effects on calves in utero.
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