The effect of stress on the plasma ACTH and cortisol concentrations after administration of Arginine-Vasopressin (AVP) in cattle

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The effect of stress on the plasma concentration of ACTH and cortisol after administration of Arginin-Vasopressin (AVP) on cattle was investigated.Experiment 1. The effect of social stressFive Holstein heifers (Mx) were mixed into the herd of 5 dry cows and 3 heifers in original heifer herd as control (Cn). On 3 days before mixing, 3, 7, 14, 21 days after mixing, blood samples of hefers were collected by venous puncture just before AVP injection, 10, 30, 60 and 120 min. after the injection for plasma ACTH and cortisol measurements. Change of dominance value (ADV) of each heifer was evaluated by win and loss numbers of aggressions between cattle before and after mixing. ADV of MX decreased after mixing. Plasma ACTH concentrations of MX were not different between days. The increase of cortisol concentration after AVP administration of MX became smaller after mixing but that of Cn did not differ among experimental days. ADV had significantly positive correlation with plasma ACTH concentration (p ≦ 0.05).Experiment 2. The effect of heat stress5 heifers (HS) were kept in a outside paddock during 2 hours on a sunny summer day (highest air temperature, 38.0 ℃) and 5(NM) were in barn (34.7 ℃). Blood samples of hefers were collected by venous puncture just before AVP injection, 5, 15, 30, 60 and 120 min. after the injection for plasma ACTH and cortisol measurements. Plasma ACTH concentration did not differ between the treatments. When the two abnormal data were eliminated, ACTH concentration on 5 and I5min tended to be lower in HS than that in NM (p = 0.06). Plasma cortisol concentration did not differ between HS and MN.These results show that blood ACTH and cortisol concentrations of cattle after AVP administration may change under stressful conditions. This method may be useful to evaluate the stress of cattle.