Decrease of plasmatic aldosterone of growing half–bred zebu calves

Resumen

It was suggested that the growth delay of early–weaned calf would
be attributed to stress. In this case, plasmatic increases of aldosterone concentration should
have occurred. To prove this hypothesis, values of this hormone were determined in 120 half–
bred zebu calves (2 months old, 50% each sex). Sixty of them were weaned at 60–70 days
post–partum (lot W), while the rest continued nursing (lot U). Using a repeated measures
design, aldosterone was evaluated by radioimmunoassay on days 0 (early weaning), 7, 14, 21,
28, 60, 90 and 120 (traditional weaning). Concentrations were 348±12 and 351±13 pg/ml on
day 0, as well as 288±11 and 291±14 pg/ml on day 120, in U and W, respectively. This falling
tendency was statistically significant (p < 0.05) and it is attributed to the ontogeny. However,
in each sampling date, significant differences between lots were not registered, moving away
the possibility of stress.