Effects of shade and flaxseed supplementation on the welfare of lactating ewes under high ambient temperatures

Abstract

The objectives of this study were to evaluate the effects of protection from solar radiation and whole flaxseed supplementation on the welfare of ewes under high ambient temperatures. The experiment was carried out during the summer (July and August) of 2007: 40 Sarda ewes were divided into four groups of ten each, and either exposed (EXP; not offered shade) or protected from solar radiation (PRO; offered shade). For each solar radiation treatment, ewes were supplemented with whole flaxseed (EXP-F and PRO-F) or not (EXP-C and PRO-C). At the beginning of the experiment and at d 21 and 44 of the trial, the body weight and the body condition score of the ewes were recorded. Respiration rate and rectal temperature were measured twice weekly. At d 29 of the experiment, blood cortisol concentrations were measured after an injection of ACTH. Cellular immune response was evaluated by intradermic injection of phytohemagglutinin at the beginning of the experiment, and at d 14, 29, 44 of the trial. Humoral response to ovalbumin was measured at 8, 14, 28, and 44 d of the study period. At d 1, 14, 28, and 44 of the experiment, blood samples were collected from each ewe for the determination of the blood metabolites and enzymes. Behavioral observations of ewes were recorded by trained observers weekly. Flaxseed supplementation resulted in significantly lower values of respiration rate both in shaded and non-shaded ewes. Small but significant differences were found in ewe rectal temperatures, which were lower in protected than in exposed ewes, irrespective of flaxseed supplementation. The exposure to solar radiation resulted also in lower BCS. Supplemented ewes displayed higher anti-OVA IgG and cortisol levels than non supplemented ewes. Diet and solar radiation affected plasma concentration of glucose which were higher in the exposed than in the protected ewes and in the supplemented than in no supplemented ewes. Plasma levels of Cl and Na were higher in supplemented than in non supplemented ewes. Shaded groups had lower plasma concentration of NEFA, gamma-glutamyl transpeptidase, and K, and higher levels of ALT/GPT and Mg compared with non shaded groups. Solar radiation affected eating and ruminating activities: greater proportions of ewes of the exposed groups were observed eating than ewes in the shaded groups. Whole flaxseed supplementation enhanced humoral immune and thermoregulatory responses during hot season. As expected, the provision of shaded areas reduced the mobilization of body lipid resources.