Effects of Genetic Strain, Slow Versus Rapid-Feathering Maternal Genotype, and Cage Density on the Performance of Single Comb White Leghorns

Abstract

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.

Interactions Between Endogenous Virus Loci ev 6 and ev 21.

“…In crosses with RF males, SF dams pass their K gene only to male progeny; female progeny are RF, i.e., k/w. Some breeders of commercial egg layer lines, however, experience lower productivity and high mortality thought to be associated with ALV infection in RF progeny from SF dams (Harris et al, 1984;Havenstein et al, 1989). It was subsequently shown that RF hens from Subgroup Esusceptible SF dams can be congenitally infected with EV21 (Smith and Fadly, 1988).…”

Molecular Analysis of Endogenous Virus ev 21-Slow Feathering Complex of Chickens.

“…Previous reports showed that negative effects are associated with the presence of ev21 in the genome (Harris et al, 1984;Havenstein et al, 1989) and may be attributed to the production of infectious EV21 (Smith and Fadly, 1988). The present study shows that some rare RF birds may be ev21 positive.…”

“…The association between SF and £v21 in breeds other than WL should be studied, because WL feather-sexed layers often have lower productivity and higher mortality rates than comparable RF females (Harris et al, 1984;Havenstein et al, 1989). These characteristics may be related to the ev2\ locus that encodes an infectious virus, EV21, which induces tolerance to oncogenic ALV (Smith and Fadly, 1988).…”

Characterization of insertion sites and development of locus-specific assays for three broiler-derived subgroup E avian leukosis virus proviruses

“…For example, ALVE loci that are transcriptionally active cause decreases in some economically important traits such as egg production, egg weight, and egg specific gravity (Gavora et al, 1991). Moreover, slow-feathering birds that carry the ALVE-21 element have lower production and increased mortality compared with their normal-feathering counterparts (Havenstein et al, 1989). Again, it is important to point out that effects differ between loci and that each endogenous element impacts its host in a locus-specific manner.…”