Seasonal variation in fatty acid composition of milk from ruminants reared under the traditional feeding system of Sindh, Pakistan

The objective of this work was to study changes in the fatty acid (FA) profile of ruminants' milk (buffalo, cow, goat and ewe) throughout the year, raised under the conventional feeding system of Sindh, Pakistan. Milk samples were collected during the four periods of the year; in winter (Dec-Feb), spring (Mar-Apr), summer (May-Sep) and autumn season (Oct-Nov). Animals were fed on seasonal forages except in winter and late spring when shortage of green forage occurs and ruminants were fed crops byproduct and residues (wheat straw, cotton seed cake, rice husk) along with available green fodder. Overall the concentration of short chain FAs (< 14:0) in milk were highest in the winter and lowest during summer months, while the content of C-16:0 was lower in summer as compared with all months and varied by 20-38% throughout the year in all ruminant species. Summer milk produce more elevated concentration of total polyunsaturated (4-35%), trans (16-35%) and conjugated linoleic acid contents (24-48%) in comparison to winter milk among ruminant species studied. Results of present study suggest that availability of fresh grass in summer season promotes the synthesis of fatty acids beneficial for human health, including unsaturated and conjugated fatty acids in ruminants' milk, possibly due to altered biohydrogenation pathway and other unidentified characteristics. (0 2008 Elsevier B.V. All rights reserved.