Effect of vitamins E and D3 on broilers blood immune cells, lymphoid organs weight and concentration of antioxidant enzymes under heat stress

Abstract

Introduction: This study aimed to evaluate the effect of different doses of vitamins E and
D3 on immune cells count, lymphoid organs weight, and concentration of antioxidant
enzymes in the blood of broilers under heat stress.
Materials & Methods: A total of 400 ROSS 308 broiler chickens were randomly divided
into 20 pens. The birds were exposed to chronic heat stress (35 ± 1 ˚C, humidity 65 to 70%)
for 7 hours daily from days 14 to 35. Experimental groups included negative control (Basal
dose of the vitamins, without heat stress), positive control group (Basal dose of the
vitamins, with heat stress), The higher dose of vitamin E, the higher dose of vitamin D3,
and a group receiving the combination of the higher dose of vitamin E and D3. The relative
weights of lymphoid organs including the spleen, bursa of Fabricius, and thymus of 8 birds
from each treatment were calculated on days 14 and 28. Blood immune cells count was
also measured after blood sampling. Blood antioxidant concentrations were also measured
weekly.
Result: The results of this experiment showed that the groups that received higher doses of
vitamin D3 and E or a combination of them, have higher thymus weight than the negative
and positive control groups under heat stress conditions (P<0.05). Heat stress caused a
significant increase in heterophile and basophil cell count and a decrease in broilers blood
lymphocytes (P<0.05). Heat stress increased the ratio of Heterophil to Lymphocyte
compared to the control group (P<0.05). The lowest concentration of superoxide dismutase
was observed in positive and negative control groups (P<0.05). However, the groups that
received high doses of vitamins D3 and E had the highest concentration of superoxide
dismutase (P<0.05). Applying heat stress, increased the blood concentration of catalase
(P<0.05) and decreased the concentration of glutathione peroxidase significantly.
Conclusion: In conclusion, it seems that the addition of a higher dose of vitamin E to the
broilers diet could suppress the effects of heat stress on lymphoid organs and improve the
status of enzymatic antioxidants in broilers blood.