Effect of forage:concentrate ratio on the quality of ewe's milk, especially on milk fat globules characteristics and fatty acids composition

Abstract

The aim of this study was to evaluate the milk quality of Massese ewes receiving diets with different forage:concentrate ratios (FC ratio), specially on milk fat globules characteristics and fatty acids composition. The diet is one of the main environmental factors that influence the lipidic content of milk. A trial was carried out on twenty ewes, which had been subdivided into two homogeneous groups and kept indoors at 25 days post partum. The experiment lasted 60 days, from 40 to 100 days post partum and the animals were fed two diets that differed in terms of the FC ratio: 60:40 and 40:60, as fed. The results obtained in this study showed that a greater proportion of forage, compared with an higher percentage of concentrate, led to an increase in the percentage of fat (+8·66%) and to a decrease in the percentage of milk fat globules with a size between 2 and 5 μm (−17·32%). However, the average diameter was not affected. There was also a decrease in the percentages of some medium chain fatty acids (C12:0, C14:0; −14·89% and −4·03 respectively) and an increase in mono and polyunsaturated ones such as trans11-C18:1 (+31·71%), total CLA (+22%), EPA (+18·18%) and DHA (+66·67%). In conclusion, a greater proportion of forage seem to improve the milk fatty acid profile by the increase of some fatty acid identified has being beneficial for human health.