Effects of Extreme Heat Stress on Growth Performance, Lymphoid Organ, IgG and Cecum Microflora of Broiler Chickens

Abstract

In this study, the effect of extreme heat diet on growth performance, lymphoid organ, blood immunoglobulin and cecum microflora change in broilers exposed to continuous lighting and extreme heat stress (EHS) was studied. Broilers raised under normal environment temperature (25 degrees C) or extreme heat stress temperature (33+/-2 degrees C), and consumed chow diet (CD) or extreme heat stress diet (EHSD). Five hundred Ross 308 days-old commercial broilers were arranged in a completely randomized block design of 5 treatment groups with 4 repetitions (25 heads per repetition pen). The broilers were divided into: T1 (normal environment+CD); T2 (EHS+CD); T3 (EHS+EHSD in which the tallow in CD was substituted by soy oil and contained 5% molasses); T4 (EHS+EHSD in which the tallow in CD was substituted by soy oil and contained 5% molasses, and 1.5 times more methionine and lysine than CD), and T5 (EHS+EHSD in which the tallow in CD was substituted by soy oil, contained 5% molasses, 1.5 times more methionine and lysine than CD, and 300ppm of vitamin C). The EHS significantly reduced the body weight gain and feed intake. The blood immunoglobulin, bursa of Fabricius, thymus, and spleen weight were significantly reduced when broilers were exposed to EHS. Compared to the normal environment temperature group, the cecum Lactobacillus sp. was low in the EHS treatment group, while Escherichia sp., Salmonella sp. and total aerobic bacteria in the EHS treatment group were high A statistically significant difference was acknowledged between the treatment groups. (C) 2013 Friends Science Publishers