Phenotypic, embryonic, and neonatal effects of a gene for sex-linked imperfect albinism (Sal-s) in chickens

Utilization of the sex-linked gene for imperfect albinism (S*ALS). 2. Yolk sac lipid utilization

The gene for sex-linked imperfect albinism (S*ALS) has been associated with reduced early growth and slow utilization of the yolk sac contents. Neonatal growth was studied using albino and nonalbino full siblings that were dissected at 2-d intervals from Day 16 of incubation to 7 d after hatch. Fatty acid composition of the yolk, yolk sac membrane, and liver was determined to study neonatal lipid metabolism. At hatch, albinos had similar BW and lower (P < 0.01) liver weights, suggesting reduced lipid transfer from the yolk sac during late incubation. Nonalbinos started gaining weight at 3 d after hatch, 1 d earlier than albino chicks. Albinos had reduced growth (P < 0.01), larger yolk sacs (P < 0.05), and similar (P > 0.05) yolk uptake from hatch to 7 d after hatch. Albino chicks also had lower body temperatures (P < 0.05) at 2, 4, and 6 d after hatch. Albinos had a slower rate of transfer of yolk lipids to the developing embryo in the last 2 d of incubation. The fatty acid composition of the yolk and yolk sac membrane was similar for both genotypes during the last 3 d of incubation, except for the level of stearic acid, which was higher (P < 0.05) for nonalbinos on Day 18 of incubation for both tissues and at 1 d after hatch for the yolk. The fatty acid composition of the livers of albinos and nonalbinos were similar (P > 0.05) during the neonatal period. For both genotypes, the hepatic level of oleic acid increased to Day 20 of incubation, remained constant to 1 d after hatch, and decreased sharply thereafter. The major difference between the genotypes was a slower rate of transfer of yolk lipids to the developing albino embryo in the last 2 d of incubation.

Utilization of the sex-linked gene for imperfect albinism (S*ALS). 1. Effect of early weight loss on chick metabolism

The sex-linked gene for imperfect albinism (S*ALS) has been associated with slow early growth in some trials but not in others. Albino (59) and nonalbino (73) chicks were raised to 3 d of age to study early growth. At 3 d of age, plasma beta-hydroxybutyrate (beta-HBA) levels were measured and the chicks were euthanatized and dissected to measure liver, gall bladder, and yolk sac weights. Fatty acids of the liver and the yolk sac were also analyzed. On average, albino chicks lost weight between hatch and 3 d of age and nonalbinos gained weight (-2.41 vs 0.74 g/d, P < 0.01). At 3 d of age, livers from albinos contained higher (P < 0.01) levels of docosahexaenoic acid than those of nonalbinos, likely reflecting the dependence on yolk sac nutrients of albinos and on dietary lipids of nonalbinos at this time. Albinos had lower body temperatures (P < 0.01), liver weights (P < 0.01) and gall bladder weights (P < 0.05), and heavier yolk sacs (P < 0.01) than did nonalbinos. Plasma levels of beta-HBA were higher (P < 0.01) for albinos than for nonalbinos. At similar body weights, chicks of both genotypes had similar body temperatures, gall bladder weights, and plasma beta-HBA levels. Linear regressions indicated that in albinos weight loss is associated with larger yolk sacs, smaller livers, larger gall bladders, lower body temperatures, and higher levels of beta-HBA. Yolk sac utilization seemed to be correlated with activation of the digestive system. The inability of starving chicks to use the yolk sac nutrients while lipolysis is taking place suggests that yolk sac absorption does not respond to lipolytic hormones. Because under certain conditions a large proportion of albinos (90% in this experiment) show the symptoms of the starve-out syndrome, the S*ALS gene could serve as a model for the study of this syndrome.

Ovarian morphology and follicular development in sex-linked imperfect albino (s(al)-s) and nonalbino hens before or after a forced moult

1. The effects of the s(al-s) gene on ovarian morphology and the development of ovarian follicles in old laying hens before and after a forced moult were investigated by measuring and weighing the ovaries and follicles. 2. The laying rate of albinos was higher than that of nonalbinos before the forced moult but not afterwards. Hierarchical follicles in albino hens were smaller than those of nonalbinos before but not after the moult. 3. Growth intensity of hierarchical follicles was greater in albino hens before the moult, suggesting that follicular maturation was more rapid, possibly explaining the higher egg production observed. 4. All differences between genotypes disappeared after the moult, suggesting that the state of the ovary before a moult is independent of that afterwards.

Production and quality of eggs from sex-linked imperfect albino (sal-s) and nonalbino (s+) hens kept under commercial conditions

The beneficial effects of the gene for imperfect albinism on egg production were investigated under commercial conditions. In one line (Line 8) but not in another (Line 3), hen-day egg production of albinos from 46 to 75 wk of age was higher than that of nonalbinos (76.1 vs 72.6%) resulting in higher overall hen-day (71.1 vs 69.3%, P < .08) and hen-housed (276.3 vs 263.6 eggs) egg production by albino hens. Egg production of Line 8 albinos was not different than that of one of two commercial strains (Strain A) included as a control (76.1 vs 75.6%, P > .05). In data from Lines 3 and 8 combined, sexual maturity of albinos was delayed by 3.0 d. Mortality was higher for albinos than nonalbinos (3.6 vs 1.8%) during the first 2 wk of brooding and lower for albinos (5.8 vs 8.9%) during the laying period. Eggs from albinos weighed less (53.8 vs 55.3 g), had smaller yolks (16.9 vs 17.6 g) and shells (5.16 vs 5.27 g), and firmer albumen (5.9 vs 5.6 mm). The results suggest that the gene produces beneficial effects on egg production under commercial conditions.

Effects of sex-linked imperfect albinism in the chicken (sal-c) on plasma luteinising hormone concentrations and early egg production

1. When measured before and after the onset of darkness, plasma LH concentrations in 40-day-old sex-linked albino pullets (sal-c) were slightly lower than those of nonalbinos (s+). 2. This finding prompted an experiment in which plasma LH concentrations were measured between 12 and 33 weeks of age when daylength was increased at 15 or 21 weeks. Egg production of the early and late maturing albino hens was measured. 3. Plasma LH concentrations overall and at 17 weeks were lower for albinos than for nonalbinos. In the early maturing group egg production of albinos was higher than that of nonalbinos. 4. Results suggest that increased egg production of albinos is not the direct result differences in plasma LH concentrations but may be a consequence of differences in the control of LH secretion.

Differential environmental effects on lesions, early growth, and mortality of imperfect albino (Sal-c) chicks

A series of experiments investigated early pleiotropic effects of a gene for imperfect albinism (s(al-c) in a population of chickens at Jouy-en-Josas, France. An elevated incidence of lesions of the navel, hocks, and nares typical of imperfect albinos were seen on these chicks, confirming their existence in this population. Variations in hatching environment and the amount of light in the hatcher both implicated in contributing to the occurrence of lesions of the hocks and nares, but not to those of the naval. In two experiments, using batteries and cages, early growth was reduced among albinos and early mortality was increased. Significant genotype by environment interactions for weight at 4 days and growth to this time, but not thereafter, suggested that the effect is restricted to this time. Unfavorable environments were most deleterious to albinos. In a third experiment, conducted in floor pens, the gene had no effect on either early growth or mortality. There was no effect of the gene on the lesions, early growth, or mortality when carried by heterozygous males (s+/s(al-c)).