Fat globule membranes in ewes' milk : the main enzyme activities during lactation

A trial was carried out on seven Massese ewes, from which individual milk samples were taken during lactation. All the enzyme activities investigated (oxidase activity of xanthine oxidoreductase, gamma-glutamyltranspeptidase, alkaline phosphatase and 5′-nucleotidase) were affected by the lactation phase, with the exception of the dehydrogenase activity of xanthine oxidoreductase (XOR). A higher oxidase activity (XO) of XOR was found when the diameter of milk fat globules was smaller. In addition, the absence of XO in colostrum led to the hypothesis that its antibacterial role is independent of its activity. The increase in alkaline phosphatase activity during lactation requires further research to better define the criteria for pasteurised sheep milk.