The Role of Photoperiod in Alleviation of the Negative Impact of Heat Stress on Broiler Performance and Immunity

s of papers 105 12 dpi (P < 0.05); no difference between treatments was found at 6 dpi (P > 0.05). Secretory Ab level against a recombinant Eimeria antigen was constant (P > 0.05) in Cbirds, but increased with time (P < 0.05) in A-, AP and CP birds. Serum Ab levels were also constant in Aand CP, but increased (P < 0.05) in Cand AP after 6 dpi. The data demonstrate that this Lactobacillus-based probiotic had an immunostimulatory effect even in birds compromised by a dietary deficiency of vitamin A. Further, this effect occurs at the level of the mucosal immune system of chickens and is best manifested by apparent lower intestinal invasion and development by EA, based on higher IL-2 secretion, and lower EA oocyst production.