Effect of a Unique Dwarfism on Growth, Production, and Reproduction Performance of the Nicobari Chicken Breed

The present study aimed to determine the inheritance and effect of dwarfism, which occurs naturally in the Nicobari chicken breed, on various growth and production traits. The dwarf character did not affect body weight for up to 4 weeks; but had a negative impact from 8 weeks onward, with body weight declining by 5.5%-9.0% in males and 9.0%-16% in females. Shank length was 22% and 27% shorter in male and female dwarf birds, respectively, than in full-size birds. The average age at first egg was 3.08% higher in dwarf hens than in their normal counterparts, and was accompanied by a non-significant decline (5.63%) in 40 weeks egg production. Egg weights were 2.23% and 2.64% lower at 32 and 40 weeks, respectively, in dwarf hens. Instead, the shape index and shell thickness were better in dwarf hens. The eggs of dwarf hens were darker and red, with less hue than those of normal hens; whereas internal egg quality was the same. Fertility and hatchability were lower in dwarf dams mated with dwarf sires than in crosses or reciprocal crosses between normal and dwarf birds. Breeding experiments and sequencing of transmembrane protein 263 ruled out the sex-linked (dw) and autosomal dwarfism (adw), as the genetic causes of dwarfism in the Nicobari breed, which instead appears to follow a novel pattern and has a unique effect on growth traits.