Effects of genetic strain, slow versus rapid-feathering maternal genotype, and cage density on the performance of Single Comb White Leghorns.

Two hatches involving 11,158 pullets from 22 Single Comb White Leghorn strain crosses were used in these experiments: 13 from rapid-feathering (k+/-) and 9 from slow-feathering (K/-) dams, some of which shared common genetic backgrounds; and all from 5 homozygous k+ sire types. Birds were grown intermingled within hatch, and were subsequently caged in two laying houses, one with 30.5 cm x 40.6-cm cages and the other with 40.6 cm x 30.5-cm cages, at densities of three or four birds/cage. Data were collected by cage on hen-day rate of lay from 50% production to 52 wk of age; (HD%), number of eggs produced per hen housed (EHH), percentage mortality (%M) to 52 wk of age; 35-wk BW (BW35); egg weight (EW34), specific gravity (SG34), and percentage bloodspots (BS%34) at 34 wk of age. The effects of hatches or house (H), density (D), maternal feathering type (MFT), genetic strain within MFT (GS/MFT), bank level within house (BL/H), and all possible interactions were included in the analysis model. Hatch, house, and cage type were completely confounded, so no general conclusion can be made concerning the effects of the reverse and standard cages on performance. The H effects were significant for all traits except HD%. Cage D significantly affected all traits except SG34 and BS%34. Pullets housed at three/cage weighed 26 g less, produced 5.5 more eggs that were .3 g/egg lighter, laid at a 1.7% higher hen-day rate, and had 3.6 less %M from 20 to 52 wk of age than those housed at four/cage. The MFT significantly affected all traits except %M, SG34, and BS%34. The k+/- daughters from K/- dams weighed 34 g less, produced at a 2.8% lower HD%, laid 6.9 fewer eggs, which eggs averaged .6 g/egg less than the eggs from the k+/- daughters of the k+/- dams. Interactions were in general small and nonsignificant. However, the H x GS/MFT interactions were significant for HD%, EHH, BW35, %M, and EW34 (P less than .05); their significance is suggestive of the presence of genotype x environment interactions.