Effects of environmental management on seasonal decrease in milk production in dairy cattle

Objective-To describe effects of season on milk production in Holstein dair y cows and to determine the location and effectiveness of fans and sprinkle rs in the management of stress attributable to season. Design-Longitudinal observational study. Animals-141 dairy herds for which owners used the Dairy Herd Improvement As sociation's database for production and reproduction record keeping. Procedure-Owners were interviewed to identify location of fans, shade struc tures, and sprinklers. Production and reproduction data were retrieved from the database, and a mixed model ANOVA was used to estimate effects of seas on, parity, and use of sprin klers, and fans on milk production. Results-Daily peak milk production decreased for all parity groups in the s ummer, but the effect decreased with increasing days in lactation. Use of s prinklers increased peak milk production in parity-1 and -3 or higher cows, but use of fans did not significantly alter effects of season. After calvi ng in the summer, 305-day milk production decreased in parity-2 and -3 cows . This decrease was not significantly modified by the presence of sprinkler s or fans. Clinical implications-Use of sprinklers may increase peak milk production i n high-producing cows and could be recommended for reducing heat and total stress during this time. Production-oriented veterinarians should be cautio us when recommending use of sprinklers and fans to increase production beca use of the wide confidence intervals describing their effectiveness. Manage ment of parity-2 or higher cows so that they calve from October to June cou ld increase 305-day milk production.