The Proportion of Grass and Concentrate in the Diet of Ewes Improve the Fatty Acid Composition of Milk

摘要

The aim of this work is to study the variability of the nutritional composition of Fatty Acids in sheep's milk from different food systems with different proportions of grass and concentrate. In this study, three distinct groups (P, PC, C) of Ouled Djalel breed were used in different diet systems, the proportion of grass of which varies in each group with a complement of concentrate. The study was carried from March to May 2015. In this context, the total and defatted dry extract, proteins, lactose fat was determined. The lipid extracts are methylated and then passed in gas phase chromatography, for FA analysis. The TDE and lipids content were relatively higher (17.3% and 5.5% respectively) in the group compared with those in the group P (16.4% and 4.5%) and with group PC (16% and 4.4%). Full time grazing in the P group resulted in a decrease in the percentage of saturated fatty acids (SFA) and an increase in the proportion of unsaturated fatty acids, including C18: 3n-3 and 0.44 % compared to group (PC) 0.24% and group(C) 0.21%. A similar trend was recorded for C18: 2 cis9 trans11 with a high content in the group containing the greatest amount of grass. The n-6-3 ratio decreases with the increase on behalf of total grass in the ration and reaches values lower than 5. The pasture with grass acts in a considerable way on the improvement of the nutritional and dietary quality of the fatty acids of the milk of ewe.