Cromo e selênio orgânicos na dieta de poedeiras semipesadas alojadas em ambiente com temperaturas elevadas

Abstract

Animals under heat stress conditions exhibit excessive urinary excretion of minerals and this might change their nutritional requirements. The objective of this study was to evaluate the effects of mineral supplementation of chromium (Cr) and selenium (Se) in organic form, on the performance, egg quality and heterophil/lymphocyte ratio (H / L) of laying hens housed under natural heat stress. One hundred and ninety-two layers (Hisex Brown, 62 weeks old) were divided into four treatments with three cages containing sixteen birds each. The treatments were: T1) basal diet (corn and soybean meal with no organic minerals), T2) basal diet + additional supplementation of organic Se (0.3 ppm), T3) basal diet + additional supplementation of organic Cr (400 ppm), T4) basal diet + additional supplementation of organic Se (0.3 ppm) and organic Cr (400 ppm). The birds were distributed in randomized blocks, with a 2 x 2 factorial arrangement over four consecutive experimental periods of 28 days each. The data were subjected to analysis of variance using SAS GLM tool (2008). When necessary, covariates of interest were added to the model. The interaction between the factors occurred only in the feed conversion ratio per mass (p=0.07) and per dozen (p=0.008), however, the simultaneous use of organic Cr and Se did not produce better results than single supplementation of trace minerals. Organic Cr improved feed conversion per mass (p=0.03) and per dozen (p=0.10), the percentage of egg production (p=0.01) while decreases egg weight (p=0.03). Organic Se increased the weight (p=0.004) and shell thickness (p=0.06), and increases yolk color (p=0.02). It can be concluded that organic chromium (Cr) supplementation improves egg mass, feed conversion by egg mass and egg production in hens housed under heat stress. Organic Selenium showed to improve shell quality, egg mass and yolk color.