Aim: The present study was undertaken with the objective to obtain insight into the dynamics of the release of β-endorphin, adrenocorticotrophic hormone (ACTH) and cortisol in response to machine milking in dairy cows. Materials and Methods: A total of 10 healthy multiparous lactating Italian Friesian dairy cows were used in the study. Animals were at the 4th-5thmonth of pregnancy and were submitted to machine milking 2 times daily. Blood samples were collected in the morning: In baseline conditions, immediately before milking and after milking; and in the early afternoon: In baseline conditions, before milking and after milking, for 2 consecutive days. Endocrine variables were measured in duplicate, using a commercial radioimmunoassay for circulating β-endorphin and ACTH concentrations and a competitive enzyme-linked immunoassay for cortisol concentration. Results: Data obtained showed a similar biphasic cortisol secretion of lactating dairy cows, with a significant increase of cortisol concentration after morning machine milking, at both the 1stand the 2ndday (p<0.05), and a decrease after afternoon machine milking at the 2ndday (p<0.01). One-way RM ANOVA showed significant effects of the machine milking on the cortisol changes, at both morning (f=22.96; p<0.001) and afternoon (f=15.10; p<0.01) milking, respectively. Two-way RM ANOVA showed a significant interaction between cortisol changes at the 1stand the 2ndday (f=7.94; p<0.0002), and between the sampling times (f=6.09; p<0.001). Conversely, no significant effects of the machine milking were observed on β-endorphin and ACTH changes, but only a moderate positive correlation (r=0.94; p<0.06) after milking stimuli. Conclusions: A wide range of cortisol concentrations reported in this study showed the complex dynamic patterns of the homeostatic mechanisms involved during machine milking in dairy cows, suggesting that β-endorphin and ACTH were not the main factors that caused the adrenocortical response to milking stimuli.
Fazio, E., Medica, P., Cravana, C., & Ferlazzo, A. (2015). Release of β-endorphin, adrenocorticotropic hormone and cortisol in response to machine milking of dairy cows. Veterinary World, 8(3), 284–289. https://doi.org/10.14202/vetworld.2015.284-289