Effect of calf suckling on oxytocin, prolactin, growth hormone and milk yield in crossbred Gir $\times$ Holstein cows during milking

Abstract

International audienceThis study evaluated the effect of different milking managements on oxytocin, prolactin and growth hormone release in Gir $\times$ Holstein cows. Six cows were suckled by their calves, before and after milking (SM group); another six cows were submitted to exclusive milking (M group). High OT levels were observed during suckling of the SM group, however both groups had similar levels of OT during milking. The SM group presented PRL levels significantly higher than the M group, however only during suckling. For GH levels, the SM group showed higher levels than the M group, however this difference was significant only during the first suckling, cleaning of the teats and at the beginning of machine milking. Despite these results, SM cows produced more milk (milking plus suckling) than M cows, however milk obtained by milking was similar for both groups

Milk yield, residual milk, oxytocin and cortisol release during machine milking in Gir, Gir × Holstein and Holstein cows

“…The Hol group had baseline levels of OT similar to those described in previous studies [20,21]. Gir and GirHol cows had basal levels of OT above those for Hol cows and higher than those observed in the literature [11,20]. We have no explanation for this fact, but this higher level did not result from a conditioned release of OT because OT levels return to the same basal level at 13 min sampling and remained significantly higher than for the Hol group at this time.…”

“…Alternatively, it can be associated with milking stress and is characterised by high CORT and noradrenalin levels [16]; in this case, even OT administration did not restore complete milk ejection [6]. Recently, it was reported that Gir × Holstein cows exhibit a similar pattern of OT release during exclusive machine milking as during suckling/ milking management [11], which suggests that crossbred Gir × Holstein cows could be successfully submitted to exclusive machine milking. Taking this into account, Gir cows, Gir × Holstein cows (F3) and Holstein cows were used to compare their response when submitted to exclusive machine milking by means of oxytocin (OT) and cortisol (CORT) assay, and milk yield and residual milk were recorded during early-lactation.…”

“…As a result, some farmers allow crossbred cows to be suckled by their calves, because these cows produce more milk than those submitted to exclusive machine milkings [9][10][11]. Obviously, this mixed management increases the labour of milkers and thus many farmers wean calves at birth and submit both Gir and Gir × Holstein cows to exclusive machine milking, except for a short colostral period during suckling, as is done with dairy Bos taurus cows [7,12,13].…”

Identification of salsolinol in the mediobasal hypothalamus of lactating ewes and its relation to suckling-induced prolactin and GH release

“…Suckling of the nipple by the neonate or milking is one of the most important factors, providing a powerful prolactin stimulus, involved in maintaining a prolonged state of hyperprolactinaemia (Grattan 2002). Investigating a temporal course of prolactin and GH secretion in the individual ewes, our data show a high similarity to those obtained on lactating rats (Saunders et al 1976, Riskind et al 1984, Wehrenberg & Gaillard 1989 or cows (Negrao & Marnet 2002). It has been proposed that suckling or milking works by decreasing prolactin-inhibiting factor (DA) from the hypothalamus, and thereby increasing prolactin levels.…”

“…In the current study, we hypothesized that salsolinol, as a putative neurotransmitter, was present in the infundibular nucleus IN/ME of lactating ewes and that its extracellular concentration in the IN/ME could increase in response to suckling stimulus in a manner similar to plasma concentration of prolactin. In addition, the secretion of growth hormone (GH) was monitored throughout the experiment since both prolactin and GH are known to respond to suckling (Wehrenberg & Gaillard 1989, Negrao & Marnet 2002.…”