Variation in digestibility parameters related to feed efficiency between and within two laying hen lines

To meet the increasing demand for eggs, while limiting the environmental impact, an increased efficiency of laying hen production is required. Feed efficiency (FE) plays a major role in this. In broilers, relationships between nutrient digestibility and FE have been observed, suggesting that information on digestibility coefficients (DCs) has potential to aid in prediction of FE. This study examines whether DCs, as determined by chemical analysis of laying hen manure, can serve as a predictor of FE in laying hens. In total, 100 laying hens from two lines differing in FE (line A and B) were studied. The objective of this study was two-fold: to investigate 1) the variation in DCs between and within the two lines, and 2) the use of DCs for prediction of FE in laying hens. Differences in performance and DCs were observed between the two laying hen lines. Line A hens showed a higher daily feed consumption and daily body weight, as well as lower egg mass, daily manure weights and laying percentages. Furthermore, all DCs were higher in line A than in line B. For line A, phenotypic correlations between DCs and feed conversion ratio (FCR) were moderate and ranged from 0.31 (DC for fat hydrochloric) to 0.60 (DC for organic matter). Correlations between residual feed consumption (RFC) and DCs ranged from 0.32 (DC for fat hydrochloric) to 0.79 (DC for dry matter). For line B, correlations between FCR and the DCs were not statistically significant, while the correlations between RFC and DCs ranged from 0.31 (DC for fat hydrochloric) to 0.43 (DC for organic matter). The contribution of different DCs in prediction models for FE differed between the two lines, making across-line FE prediction challenging in laying hens. Overall, the data on DCs collected in this study contribute to an improved understanding of differences in digestibility between laying hen lines and show potential for FE prediction.