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.