NUTRITIONAL AND ENVIRONMENTAL FACTORS INFLUENCING EGG PRODUCTION IN POULTRY

Abstract

Researchers in the field of agricultural science have been investigating the effects of nutrition and environmental factors on poultry egg production, especially the diet formulation, housing system, photoperiod, manipulation of gut microbial community and stress adaptation. We housed 1,200 Hy-Line Brown laying hens in six groups with three housing systems (conventional cage, enriched colony cage and free-range) and two diets (basal diet and probiotic-supplemented diet at 1×10⁹ CFU/kg) for a 12-month production period. The Ensemble Stacked Model (ESM) was the most accurate of the nine models compared (composite weighted score = 93.59, R² = 0.947 for hen-day egg production). Free-range and probiotic supplementation resulted in the highest egg mass (62.3 ± 1.8 g/hen-day), lowest feed conversion ratio (1.82 ± 0.05) and highest cecal microbial Shannon diversity index (H′ = 3.87 ± 0.21). Egg production was 34% reduced and abundance of the phylum, Proteobacteria, increased (9% to 18%, p < 0.001) when plasma levels of the stress hormone, corticosterone, were higher than 8 ng/mL. The optimal diet was a metabolizable energy (2.85 kcal/g) and crude protein (16.5%) formulation, and the optimal dose of the probiotic had a hormetic U-shaped response: 1×10⁹ CFU/kg. Structural equation modelling revealed the gut microbial diversity accounted for 52% of the total effect of housing system on egg production (indirect effect = 0.21, 95% CI: 0.17-0.25). This research shows that precision nutrition approaches tailored to the stressors of the housing system, to promote eubiosis in the cecal microbiota, increase long-term egg production and efficiency of feed conversion ratio (FCR) and egg quality of commercial layer hens.