Change in Adrenal Response from Free Stall Competition

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Abstract
Lactating Holsteins were monitored for differences in adrenal glucocorticoid response to exogenous ACTH as a physiological indicator of stress due to reduced numbers of available free stalls. Twenty cows were blocked by production and randomly assigned to either a control group or were exposed to 0.75, 0.63, 0.5 or 0.37 free stalls per cow for 7 days after which they were tested for adrenal response to ACTH. The latter 16 cows formed the experimental group and were housed in a facility with 4.5 m2 concrete lot and 0.38 m feed bunk per cow. Four experimental cows and 1 random control were tested for adrenal response at the end of each treatment. Time spent lying or standing in free stalls and time eating were summarized from time lapse photography at intervals of 1 min. Average time cows spent in free stalls (h) and percentage of total time stalls were occupied were 13.9, 89%; 12.8, 96%; 10.4, 99%; 8.0, 99%; for 0.75, 0.63, 0.5 and 0.37 free stalls per cow. Means and standard deviations of the integrated glucocorticoid responses for experimetnal treatments were 118 .+-. 27, 123 .+-. 22, 172 .+-. 57, and 169 .+-. 35 ng/ml. Glucocorticoid response of control cows, .apprx. 1 stall and 15 m2 of lot space/cow, was 130 .+-. 52 ng/ml. The glucocorticoid response in cows with reduced stall numbers was indicative of stress; however, milk production was not affected.