Dairy cows use and prefer feed bunks fitted with sprinklers

Abstract

Sprinklers reduce heat load in cattle, but elicit variable behavioral responses: cows readily use water in some studies, but in others either avoid it or show no preference. Nevertheless, on US dairies, a common way to cool cows is with nozzles mounted over the feed bunk that intermittently spray (i.e., 5 min on, 10 min off, as in this study) animals' backs while they feed. The objectives of this study were to determine how this type of sprinkler system affects behavior (single-treatment phase), and to assess preferences when cows were allowed to choose between feed bunks with or without sprinklers (choice phase). Data were collected 24h/d for lactating Holsteins tested in groups of 3 cows (n=8 groups) in warm ambient conditions [air temperature (mean ± standard deviation): 24-h average=24.5±2.5°C, maximum=36.0±3.5°C]. In the single-treatment phase, cows were fed from shaded bunks with or without sprinklers for 2 d/treatment, with order of exposure balanced in a crossover design. When sprinklers were present, cows spent more time at the bunk, both feeding [sprinkler vs. no sprinkler: 3.5 vs. 2.5h/24h, standard error (SE)=0.12h] and standing without feeding (4.3 vs. 2.3h/24h, SE=0.32 h) than when no sprinklers were present. Sprinklers lowered the average 24-h core temperature (38.8 vs. 39.2°C, SE=0.08°C), particularly on warmer days. Water cooling also mitigated the effects of weather on feeding time, which decreased with increasing heat load (air temperature and temperature-humidity index) when cows did not have sprinklers, but was unchanged when sprinklers were provided. In the choice phase, feed was provided ad libitum in both treatments for 5 d and preference was assessed. All groups preferred the feed bunk with sprinklers (78 vs. 22% of time spent near both feed bunks, SE=3.9%), and the magnitude of this preference increased linearly with heat load. In both phases of the study, cows protected their heads from direct spray when head position was elective (i.e., standing without feeding): cows were more likely to put their heads through the head gates when the sprinklers were on than off (single-treatment phase: 78 vs. 59%, respectively, of time spent standing without feeding, SE=2.8%; choice phase: 71 vs. 52%, SE=2.0%). In conclusion, although cows avoided wetting their heads, this is the first study to demonstrate that cattle readily use and clearly prefer sprinklers mounted above the feed bunk, possibly due to the cooling provided by this resource.

Keywords: behavior; heat load; sprinkler cooling.