author(s)
Saim Qureshi, HM Khan, Sana Shafi, S Adil and MS Mir

abstract
The present study was conducted to investigate the effect of cold stress and its various ameliorating measures on histomorphology of lymphoid organs in broiler chicken. 270 day-old commercial broiler chicks were used for the study. The chicks were distributed into 7 treatments of 3 replicates with 13 chicks each. Cold stress was provided at 2 ⁰C to 8 ⁰C for 8 hours from 3rd to 6th week of age in all treatment groups except first and fifth treatment groups. The broiler birds in T₁ and T₅ were reared under normal temperature conditions (25 ⁰C). T₁ was kept as control group. Antioxidant vitamin E 250 mg per kg of feed was supplemented to basal diet in T₃. Chromium 0.1 gram per kg of feed was supplemented to basal diet in T₄. The results revealed that lymphoid glands from T₁ group had no lymphoid depletion and necrosis. T₅ also revealed no lymphoid depletion and necrosis. The lymphoid glands from T₂ showed severe lymphoid depletion and necrosis. The lymphoid glands T₄ displayed moderate lymphoid depletion and necrosis, however, T₇ showed mild lymphoid depletion and necrosis. Mild lymphoid depletion and necrosis was observed in T₃ group. The lymphoid glands from treatment group T₆ revealed mild lymphoid depletion. In conclusion, the cold stress in broiler chicken caused severe pathological changes in lymphoid organs but the cold stress mitigating practices such as early cold conditioning, supplementation of vitamin E and chromium reduced the pathological effects of cold stress in these organs.