Effect of suckling during early lactation and changeover to machine milking on plasma oxytocin and cortisol levels and milking characteristics in Holstein cows

Abstract

Plasma concentrations of oxytocin and cortisol, and milk yield and flow rates, were compared in three primiparous cows and two cows in their second lactation during suckling and subsequent machine milking. After calving, cows suckled their calves for 3-4 weeks and then the experiment was carried out over 4 d. Blood samples were taken prior to, during and after suckling or evening machine milking (EMM) on day 1 of the experiment (the last day of suckling), day 2 (first EMM) and day 4 (third EMM). After weaning and rehousing, cows were machine milked twice daily. During the first EMM, average milk yield and flow rate in the second minute of milking were significantly lower (P < 0-05) than corresponding values for the other 2 d. Plasma oxytocin concentrations were lower during the first than during the third EMM (P < 0-001) and suckling (P < 0-001), and more oxytocin was released during the third EMM than during suckling (P < 0-01). Cortisol concentrations were higher during and after the first EMM than during the third EMM. Thus in cows sucked for several weeks after calving and then separated from their calves and rehoused we found a transient decrease in oxytocin release, milk yield and flow rates during the first machine milking.

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

“…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. In contrast, all three groups showed similar basal levels of CORT, and these levels were comparable to those described by other authors [7,20,22].…”

“…A similar kind of CORT profile has been reported following stress imposed by weaning. However, CORT levels generally return to normal values three or four days after weaning [7,8]. This type of adaptation was not observed in the present study because CORT levels of the Gir group remained high in response to milking throughout the experiment.…”

“…Normally, machine milking provokes an oxytocin release and milk ejection via neuroendocrine reflex, but machine milking could sometimes cause stress and entail a significant reduction in milk yield [6][7][8]. 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].…”

“…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]. Indeed, the immediate separation of the cow and calf overlooks the fact that weaning inhibits OT and PRL release [8], and is accompanied by a significant decrease in milk production [7,8].…”

“…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]. Indeed, the immediate separation of the cow and calf overlooks the fact that weaning inhibits OT and PRL release [8], and is accompanied by a significant decrease in milk production [7,8]. This contributes to the belief that Gir cows and their crossbred offspring can not adapt easily to machine milking.…”