Responses of calves to injections of ACTH and their relationship with growth rate

Abstract

A study was made of the effects of exogenous adrenocorticotropin (ACTH) on the levels of blood components in 109 dairy replacement calves and the statistical correlations between these effects and the growth rates of the calves from birth to six months. Blood samples were taken from a jugular vein before ACTH was injected and then at two, four, six and eight hours afterwards, and analysed for plasma cortisol concentration, total white cell counts, packed cell volume, haemoglobin, plasma glucose, sodium, potassium, magnesium and inorganic phosphorus, erythrocyte sodium, potassium and magnesium, serum ionised calcium and total protein and total plasma calcium concentration. The injection of 1.1 +/- 0.02 iu/kg of ACTH intramuscularly resulted in a peak plasma cortisol concentration after two hours which had not returned to normal after eight hours. It also resulted in leucocytosis, lymphopenia, neutrophilia, eosinopenia and hypophosphataemia; the mean changes were repeatable (P < 0.05) in 49 of the calves tested two months later. The weight gains to six months of age could be predicted from the degree of the changes in several blood constituents. Significant partial regression coefficients were found for the change in glucose concentration (0 to four hours), absolute neutrophil count (0 to two hours), absolute lymphocyte count (0 to four hours) and loge absolute eosinophil count (0 to two hours). The multiple regression sum of squares was highly significant (P < 0.0001), and the multiple coefficient of determination was 0.305. It was concluded that the changes in these blood components after an injection of ACTH might be used to predict the weight gains of dairy replacement calves.

Alterations of growth hormone, cortisol, luteinizing hormone, and insulin concentrations in early-postnatal calves affected with diarrhea

“…Cortisol may vary extensively [24,25], but there is indication that concentrations are high after birth and decrease during the first week of life in ruminants. The number of leukocytes, glucose concentrations and the weight gains increase in accordance with the concentrations of cortisol [26]. The results of the current work indicate that even before calves suffered from clinically apparent diarrhea, cortisol concentrations were decreased.…”