RESPONSE OF MALE HOLSTEIN CALVES FROM SEVEN SIRES TO FOUR MANAGEMENT STRESSES AS MEASURED BY PLASMA CORTICOID LEVELS

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Abstract
A total of 42 Holstein bull calves from 7 sires were used over three replicates, each lasting for 5 mo, to examine the adrenal cortex response, as measured by plasma corticoid level, to four environmental stresses. The four stresses examined were (1) transportation within the 1st wk of life, (2) water withdrawal for 48 h at 3 mo, (3) castration and dehorning at 4 mo, and (4) transportation at 5 mo of age. Blood samples were taken just prior to each stress (resting), immediately after (except 2), 24 h after (1, 2, 3 and 4) and 48 h after for 3 and 4. Additional resting samples were collected at 1 and 2 mo of age. The average resting plasma adrenal corticoid level was 4.11 ± 0.47 ng/ml, while the average peak plasma corticoid values for the four stresses were 21.77 ± 1.78 ng/ml, 9.61 ± 1.13 ng/ml, 10.11 ± 1.36 ng/ml, and 19.63 ± 2.10 ng/ml, respectively. The adrenal cortex response was significant in the case of both transportation stresses (P < 0.01) and for the castration and dehorning stress (P < 0.05). Forty-eight hours of water withdrawal did not elicit a significant response. Replicate had a significant effect on corticoid levels (P < 0.01), while sire had a significant effect only on the values associated with the second transportation stress (P < 0.01).