Reprod. Nutr. Dev.
Volume 42, Number 4, July-August 2002
|Page(s)||373 - 380|
Effect of calf suckling on oxytocin, prolactin, growth hormone and milk yield in crossbred Gir Holstein cows during milkingJoão Alberto Negrãoa and Pierre-Guy Marnetb
a USP/FZEA, FAPESP, Cx. Postal 23, 13630-970, Pirassununga/SP, Brazil
b UMR production du lait, INRA/ENSAR, Rennes, France
(Received 18 April 2002; accepted 20 July 2002)
This study evaluated the effect of different milking managements on oxytocin, prolactin and growth hormone release in Gir 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.
Key words: cows / crossbred / milking / suckling / hormone
Correspondence and reprints: João Alberto Negrão
© INRA, EDP Sciences 2002