Evaluation of the effect of increasing dietary vitamin E in combination with different fat sources on performance, humoral immune responses and antioxidant status of weaned pigs

This study investigated the influence of different fat sources and vitamin E supplementation on performance, humoral immune responses, plasma biochemical responses, mucosal fatty acid profile, and α-tocopherol status in serum and intestine of pigs after weaning (days 28-56 of age). The experiment involved a total of 180 pigs of 20 litters. Nine pigs of each litter were allotted to 9 dietary treatments in a 3×3 factorial arrangement of treatments in a randomized complete block design, which was conducted in 20 replicates. The 9 experimental groups were fed 50g/kg diet of tallow, sunflower oil, or fish oil at three different vitamin E levels (85, 150, and 300mg all-rac-α-tocopheryl acetate/kg diet). No effect (P>0.05) of the dietary treatments was obtained on the performance of the pigs. Seven pigs from each treatment combination (n =63) were immunised with sheep red blood cells at weaning (day 28 of age), and weekly blood samples were obtained from these pigs to determine the α-tocopherol status, antibody titres and humoral immune responses. At the end of the trial, pigs were killed and samples of mucosa, intestinal epithelium and bile were obtained. The concentration of α-tocopherol in serum decreased (P<0.001) during the first week after weaning, and dietary all-rac-α-tocopheryl acetate supplementation had no influence (P>0.05) before day 42 of age. Thereafter, serum α-tocopherol concentration reflected the dietary vitamin E level and stayed above 1.5mg/L serum when pigs were fed 150 and 300mg all-rac-α-tocopheryl acetate/kg diet, whereas provision of 85mg all-rac-α-tocopheryl acetate/kg diet resulted in lower (P<0.05) serum α-tocopherol concentration. Mucosal and intestinal epithelium α-tocopherol concentration was influenced by the dietary vitamin E treatment (P<0.001) as pigs fed the 85mg all-rac-α-tocopheryl acetate/kg diet had lower α-tocopherol concentration than pigs fed 150 and 300mg all-rac-α-tocopheryl acetate/kg diet. Vitamin E supplementation had no influence (P>0.05) on the measured immune responses, serum biochemical responses or fatty acid profile of mucosal samples. When compared to tallow, pigs fed sunflower oil had higher antibody response to sheep red blood cells at days 49 (P<0.05) and 56 (P<0.05) of age, and the serum concentration of IgG was higher (P=0.01). The mucosal fatty acid composition reflected the fatty acid composition of dietary fat sources. The concentration of triglycerides (P=0.004) and cholesterol (P=0.001) was higher in pigs fed tallow than the other sources of fat. In conclusion, dietary fat source rather than vitamin E supplementation during the weaning period influenced the measured responses of the pigs, i.e. humoral immune responses, concentration of triglyceride and cholesterol in plasma, and fatty acid composition of mucosal samples. Vitamin E supplementation increased the α-tocopherol status of pigs 14 days after weaning, and a dietary concentration of 150mg vitamin E/kg diet (at the present fat level of 50g/kg diet) could be recommended to ensure a α-tocopherol status of pigs above 1.5mg/L serum.