Role of different sources of dietary PUFA supplementation on sheep welfare under high ambient temperature

The purpose of this study was to evaluate the effects of different sources of polyunsaturated fatty acids (PUFA) supplemented in the diet on the welfare of lactating sheep exposed to high ambient temperature. The experiment was conducted during summer, it involved 32 ewes divided into 4 groups, and lasted 6 weeks. All groups were fed twice daily and received 1.8 kg/ewe/d of oat hay. The control group also received 1 kg/ewe/d of pelleted concentrate, whereas ewes in the experimental groups were supplemented with whole flaxseed (FS), seaweed Ascophyllum nodosum (Tasco®, AG), or their combination (FS + AG). At the beginning of the experiment, and weekly thereafter, the respiration rate, rectal temperature, body condition score (BCS) and body weight of the ewes were recorded. Milk samples were collected from each ewe weekly for the determination of the chemical composition, somatic cell count, and coagulating properties. Milk samples were also analyzed for their concentration of plasmin. Flaxseed diet during heat stress resulted in a reduction of the respiration rate, and in an increase of both milk and fat yield. The PUFA in the combined diet influenced the rectal temperature, and the respiration rate; also the milk yield and the concentration of plasmin (PL) increased in FS + AG diet. The lowest value of BCS recorded in ewes receiving the AG diet together with a rise in the respiration rate and rectal temperature suggested poor sheep welfare. Furthermore, sheep receiving the AG diet showed a consistent increase in the milk PL concentration that was responsible of the increase of milk clotting time and rate of clot formation.