Antidiuretic hormone release in the bovine: values at rest, and evidence for sex differences under stressful conditions including severe hemorrhage.

OBJECTIVES: This study investigates antidiuretic hormone (ADH) plasma concentration in bulls and heifers at rest, after transportation stress, trauma and massive hyper-acute hemorrhage at slaughter, with special attention to differences between sexes. We also quantified ADH concentration in the ADH-producing hypothalamic area.

SETTING AND DESIGN: The study was carried out on animals at the abattoir, exploiting the routinely procedure of slaughtering to obtain the experimental stressful conditions. The control group was represented by a group of animals matched for breed, age and gender.

RESULTS: ADH plasma values suggest that transportation stress has little or no effect in heifers in contrast to bulls. In both sexes ADH release increases after open head trauma due to stunning prior to slaughter. Hemorrhagic hyper-acute stress caused by bleeding induces a rapid hundredfold rise of ADH plasma concentration that becomes diergic (physiologically different between sexes), with males showing far higher values. Females show a higher ADH concentration in the hypothalamus.

MAIN FINDING: This study points out a difference in ADH output between bulls and heifers under conditions of severe hemorrhagic stress, as produced by severing of the neck vessels at slaughtering.

CONCLUSION: Extreme stress unmasks endocrine differences in bovine ADH release that may be relevant only during specific circumstances, such as fighting.