Plasma vasopressin and oxytocin concentrations increase simultaneously during suckling in goats

Abstract

Goats are often kept on small farms where they suckle kids and are hand milked for human consumption. Our first objective was to investigate whether vasopressin secretion increases together with oxytocin during hand milking and suckling in seven goats 6-8 weeks after parturition. Four goats suckled and three were hand milked on the first day and the treatments were reversed on the next day. Blood samples were taken via a semi-permanent catheter. Plasma concentrations of vasopressin and oxytocin increased during suckling, but not during hand milking. Plasma cortisol concentration was elevated for 10 min after both treatments. These results initiated a second series in which the objectives were to measure vasopressin and oxytocin concentrations during hand milking in a larger number of goats and to investigate whether the rise in cortisol concentration was due to the experimental conditions or to milking, by adding a no-milking treatment. Nine goats in lactation weeks 4-10 were studied. Heart rate and arterial blood pressure were registered in eight of the goats. Oxytocin concentration did not change during hand milking and the vasopressin concentration was below the detection limit. Heart rate and blood pressure were elevated during milking and for about 10 min thereafter. Cortisol concentration increased after milking, as above. None of the variables changed in the no-milking treatment. This suggests that the rise in cortisol concentration was due to milk excretion and was not a stress reaction. In conclusion, suckling increased plasma concentrations of vasopressin and oxytocin, but hand milking did not. In a mixed system, presence of the kids may be necessary to stimulate release of the peptides and thereby contraction of the myoepithelial cells. However, milk stored in the udder cisterns can be obtained by hand milking without presence of oxytocin or vasopressin.

Relationship between cortisol and acute phase protein concentrations in female rabbits

“…Such an increase could be related to the requirement for prolactin (in association with insulin and cortisol) for initiation of milk secretion in the periparturient period (Tucker, 2000). Moreover, frequent and intensive suckling play a role in maintaining lactation, primarily via stimulation of oxytocin release, but also provoking secretion of prolactin, vasopressin, ACTH and cortisol (Bruckmaier and Wellnitz, 2008;Olsson and Högberg, 2009). This is consistent with the observation of elevated cortisol concentrations in lactating primiparous females at early lactation (group 2) compared with nulliparous females (group 1) in the present study.…”

The mechanism of life-threatening water imbalance in schizophrenia and its relationship to the underlying psychiatric illness

“…Oxytocin and AVP, however, are closely related nonapeptides differing in only two amino acids. While peripheral stimuli often increase both hormones (Olsson and Högberg, 2009), the two hormones have opposing actions in the central nervous system (CNS) (Legros, 2001). CNS AVP has been linked to aggression (Caldwell et al, 2008a; Legros, 2001) while CNS oxytocin diminishes psychological stress responses and enhances prosocial behaviors (Carter, 1999; Heinrichs et al, 2003; Keri et al, 2008; Ditzen et al, 2009;).…”

Cardiovascular, endocrine and behavioural responses to suckling and permanent separation in goats

“…No change in heart rate in response to suckling was observed. These results can be compared with an increase of about 6% in blood pressure and about 10% in heart rate, respectively, during hand milking [23]. In that experiment goats were lightly restrained and blood sampling took about 3 minutes compared with less than one minute in the unrestrained goats in the present experiment.…”

“…Increased plasma cortisol concentrations have been found during and immediately after milking in suckled cows [26,27], in cows milked by hand or machine [28], in ewes during suckling or machine milking [29], and in goats during suckling and hand milking [23]. The consistent increase in plasma cortisol concentration during and after milking suggested the metabolic effects of cortisol was the reason for the increase, although a combination with some arousal cannot be excluded.…”

“…Therefore, changes in plasma cortisol and β-endorphin concentrations during suckling and separation were compared. As both oxytocin and vasopressin increase during suckling in goats [23], these hormones were also measured in this study.…”