HETEROSIS IN NORMAL OR DWARF (DW) LAYING HENS - FATNESS AND BLOOD PARAMETERS

Heterozygous Dw(+)/dw males (sex linked dwarfing gene dw) gave normal sized (Dw(+)) and dwarf (dw) pullets in a white Leghorn and a brown-eg g type line and their two reciprocal F1s. At the age of 52 wks, the le vel of uric acid, triglycerides and total proteins in the plasma was m easured for each hen, then on 15 females per subgroup (Genotype at Dw locus x line or cross) the amount of abdominal fat in per cent of live body weight was determined. The Leghorn-type hens compared to the bro wn-egg type were less fat, had less plasma triglycerides and more uric acid; the F1s were intermediate. Independently of the line or cross, the dw gene was associated with lower abdominal fat percentage, a high er plasma level of both uric acid and triglycerides. On the whole, a c onsiderable amount of positive heterosis was found for the level of tr iglycerides, and abdominal fat, and a negative heterosis for plasma ur ic acid. For these traits, the heterosis did not differ significantly between dwarf and normal hens. The phenotypic correlations between the measured variables were discussed.