Thermal Manipulation in Broilers and Layers

Keywords

thermal manipulation, poultry incubation, quantitative methods

Abstract

Thermal manipulation during incubation has been shown to have positive effects on performance and mortality of broilers in later life. This only holds when chickens are exposed to temperatures in later life they already experienced during the embryonic phase. Hardly known are the effects of thermal manipulation in layer chickens and furthermore the consequences of a mismatch between incubation temperature and later life ambient temperature. In this study, both cold and warm thermal manipulation was investigated in broilers and layers and the effects in later life during high temperatures. During d 7 to 16 of incubation broiler and layers eggs were exposed to an eggshell temperature (EST) of 37.5oC (C), a high EST of 39.5oC for 12 h per d (H), or a low EST of 36.5oC for 12h per d (L). Hatchability was not affected by breed, but was higher in the H treatment (96.3%) than in both other treatments (92.3% on average). Yolk free body mass was higher in C chickens, followed by H and L chickens in both breeds, whereas the opposite was found for the residual yolk. Body weight till 28d of age was hardly affected by incubation temperature treatment, but body temperature was higher in L chickens than in C and H chickens till 14d of rearing in broilers and till 21d in layers. Mortality during rearing was not affected by breed, but was considerable higher in L chickens (6.7%) than in C (1.8%) and H (1.2%) chickens. Based on this study, we concluded that layers act more or less comparable during and after thermal manipulation than broilers. Secondly, a mismatch between incubation temperature and rearing temperature will not only result in higher body temperatures, but also in considerable higher mortality in later life.

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