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Sprinklers and Shade Cool Cows and Reduce Insect-Avoidance Behavior in Pasture-Based Dairy Systems

P. E. Kendall^*, G. A. Verkerk, J. R. Webster^* and C. B. Tucker^*,,1

^* Animal Behavior and Welfare, AgResearch Ruakura Research Centre, Private Bag 3123, Hamilton, New Zealand
Dexcel Ltd., Private Bag 3221, Hamilton, New Zealand
Department of Animal Science, University of California, Davis 95616-8521

¹ Corresponding author: cbtucker{at}ucdavis.edu

The body temperature of dairy cows in pastoral systems during summer reaches a peak during and following the p.m. milking. Shade and sprinklers can be used separately or in combination at the milking parlor to reduce heat load. Farmers anecdotally report that the use of sprinklers reduces irritation from insects that occurs while cows are waiting for milking. Once daily, we assessed the effectiveness of short-term exposure to shade and sprinklers for cooling cows [via respiration rate and body (vaginal) temperature] and reducing insect-avoidance behaviors before the p.m. milking in a pasture-based dairy system. Head position was measured as an indicator of whether cattle were avoiding water from the sprinklers. Forty-eight Holstein-Friesian dairy cows were divided into 12 groups (4 cows per group, n = 3 groups/treatment) and were exposed to 1 of 4 treatments for 90 min before the p.m. milking: 1) shade, 2) sprinklers, 3) shade and sprinklers, or 4) uncooled control. Respiration rate was reduced by 30% with shade alone compared with controls [54 vs. 78 ± 2.3 ( ± SED) breaths/min, respectively]. Sprinklers alone (30 ± 2.3 breaths/min) and the combined effects of shade and sprinklers (24 ± 2.3 breaths/min) reduced the respiration rate by 60 and 67%, respectively, compared with controls. Shaded cows had lower body temperatures during the 90-min treatment period compared with controls (shade: 38.6 ° C; shade and sprinklers: 38.6 ° C; control: 38.9 ± 0.09 ° C). The decrease in body temperature of cows under sprinklers was more marked than for shade alone and remained lower for at least 4 h after milking (sprinklers: 38.7 ° C; shade and sprinklers: 38.6 ° C; shade: 38.9 ° C; control: 39.2 ± 0.10 ° C). The sprinkler treatment reduced the number of tail flicks (control: 12.6 vs. sprinklers: 6.6 ± 2.4 flicks/min) and hoof stamps (control: 4.4 vs. sprinkler: 2.2 ± 0.5 stamps/min). Cows exposed to sprinklers spent more time with their heads lowered compared with cows in the shaded and control treatments. The reductions in body temperature and respiration rate attributable to shade and sprinklers were greatest when the temperature-humidity index and heat-load index were 69 and 77, respectively, and cows benefited from cooling when these levels were exceeded.

Key Words: heat stress • respiration rate • body temperature • thermoregulation