Effect of suckling on the release of oxytocin, prolactin, cortisol, gastrin, cholecystokinin, somatostatin and insulin in dairy cows and their calves

The aim of the present study was to examine how different types of early in teraction between dairy cows and their calves influence milking/suckling-re lated hormone release in the cows and sucking/bucket-drinking related hormo ne release in calves. Eighteen cows of the Swedish Red and White breed were studied during the first week after parturition. The cows were machine mil ked twice daily, and allotted to one of three treatments: [1] cow and calf were kept together and the cow was allowed to stickle the calf for 30 min a bout 1 h before each milking; [2] cow and calf were kept together and the c alf was bucket fed twice daily; and [3] cow and calf were separated immedia tely after parturition. and the calf was kept in a single box and was bucke t fed twice daily. Blood samples were collected around day 7 from both cows and calves, The plasma levels of oxytocin. prolactin. cortisol, gastrin, c holecystokinin (CCK), somatostatin and insulin were analysed. Tit the cows the levels of oxytocin, prolactin and cortisol were influenced by all three treatments, except for the level of cortisol which did not respond to suck ling. The main finding was that the release of oxytocin was significantly g reater during suckling compared with machine milking. In the calves, the ho rmone levels were also influenced by the different milk feeding routines. T he plasma concentrations of oxytocin, gastrin, CCK and insulin increased in response to milk ingestion in all treatments. However. during sucking, the increase of oxytocin was significantly greater than during bucket drinking . In addition, a strong correlation between oxytocin and insulin was found in response to sucking. Further. significant increases in prolactin and som atostatin. and a decrease in cortisol were found during sucking. The level of somatostatin also increased in response to bucket feeding when calves we re kept separately. During bucket feeding, no significant correlation was f ound with oxytocin. but strong correlations between the gastrointestinal ho rmones gastrin. CCK, somatostatin and insulin were seen. Together these dat a suggest that different hormonal patterns were triggered in the cows by su ckling and milking, and in the calves bt sucking and bucket drinking. This is further supported by different correlation patterns, observed in the cal ves in response to sucking and bucket feeding. The present findings imply t hat management routines for cows and calves during the first week after par turition have consequences for the physiology of the animals.