Antioxidants included in the diet of fattening lambs: Effects on immune response, stress, welfare and distal gut microbiota

Thirty-two Merino lambs were fed barley straw plus a concentrate alone (CONTROL) or concentrate enriched with vitamin E (0.6 g/kg of concentrate, VITE006) or with one of two amounts of carnosic acid (0.6 g/kg of concentrate CARN006; 1.2 g/kg of concentrate, CARN012). Effects of these antioxidant compounds on the immune response, stress during road transport, and gut microbiota were assessed. After 7 weeks of being fed the experimental diets, blood samples were taken to measure blood lymphocyte subpopulations by flow cytometry and interferon-gamma (IFN-γ) production; then, all lambs were subjected to a 4-h transportation–stress period to study the evolution of haematological and biological parameters during road transport. Finally, rumen and faeces samples were collected to study microbial diversity. Carnosic acid promoted changes in the faecal bacterial community (P<0.001), whereas vitamin E enhanced IFN-γ production (P<0.05) and reduced tissue damage (creatine phosphokinase, P<0.05) during road transport. Consequently, vitamin E showed some immunological properties and protection against tissue damage during road transport. This may contribute towards improving the welfare of these animals. Changes in the faecal bacterial community promoted by carnosic acid might be related to changes in the chemical composition of the meat. No immunological properties were observed for carnosic acid, and no changes in the feacal or ruminal bacterial communities were observed when vitamine E was supplemented to fattening lambs.