Adjusting energy and protein levels and their relationships for laying hens in different thermal conditions

Abstract

The adequacy of laying hens diets can become an essential strategy for the maintenance of the productive levels of the current lineages of the market. Considering that feed costs are the ones that most affect poultry activity, adjusting the energy and protein levels of laying hens diets ensure egg quality integrity, improves the quality of the environment and reduces costs inherent of food. Adult poultry maintain their thermal comfort with temperatures between 18 and 28º C and, either higher oscillations (heat stress) or lower oscillations (cold stress), are responsible for changes in food consumption by the animals, in an attempt to maintain a constant body temperature. In cold situations birds increase feed intake, in an attempt to produce metabolic heat and maintain homeothermia. In the heat, birds reduce feed intake and increase water consumption, reducing endogenous heat production and cooling the body through the gradient between water temperature and bird's body core. Although this mechanism of adjustment in food consumption is well known, it is observed that there are few scientific reports about the energy: protein ratio in laying hens diets, and thus, the main objective of this review.