Abstract
Three experiments were conducted. In first experiment, nature of dwarf gene in Bangladeshi dwarf chicken (DD) was tested by crossing with Rhode Island Red (RIR) and physical features, egg production and egg quality characteristics were compared between deshi normal (DN) and DD chicken. In second experiment, the effect of dwarf gene from DD on reproductive fitness was examined making a diallel crossing using RIR, White Leghorn (WLH), Fayoumi (FO), DN and DD to produce eight genotypes; RIR, WLH, FO, DN, DD, RIR X DD, WLH x DD and FO x DD progenies. In the third experiment, growth performances of 8 genotypes were compared up to 18 weeks of age. At 19 weeks of age, the crossbreds; RIR X DD, WLH x DD and FO x DD were separated into normal and dwarf types on the basis of shank length and thus 11 genetic groups; RIR, WLH, FO, DN, DD, RIR X DD normal, RIR X DD dwarf, WLH x DD normal, WLH x DD dwarf, FO x DD normal and FO x DD dwarf were obtained. At 19 weeks of age, a total of 154 pullets, 14 from each genetic group were individually caged to compare egg production and egg quality up to 46 weeks of age. Test cross result revealed that the dwarf gene in DD is autosomal recessive (adw) in nature. No variation in reproductive fitness (fertility and hatchability) was found to attribute to the action of adw gene. Crossbred of deshi dwarf and pure breeds had a tendency to have a reduced juvenile weight and increased survivability than that of pure breeds. Introgression of adw gene to exotic pure breeds reduced live weight between 19 and 46 weeks of age by 17.98-35.06% in dwarf genetic groups depending on age and genotype. The dwarf crossbred genetic groups had 13.09-22.31% depressed live weight than their normal size crossbred counterparts also depending on age and genotype. Degree of live weight depression for introgression of adw gene was higher in smaller breeds. The adw genetic groups had markedly shortened shank length (2.40 to 56.30%) when compared with their corresponding pure breeds, normal size crossbreds and deshi normal size counterparts depending on sex and age. The differences in shank length between dwarf (adw) and normal genetic groups increased with age up to 18 weeks and thereafter, the differences remained almost static. Introgression of adw gene increased breast meat, thigh meat, and body lipid and body compactness. The RIR, WLH and FO dwarf (adw) crossbred pullets had remarkably reduced feed intake than their respective crossbred normal size pullets by 10.79%, 11.15% and 15.11% respectively. The corresponding reduction of feed intake of adw crossbreds in comparison with respective pure breeds were 21.38%, 24.38% and 28.16%. Despite slightly depressed egg production and egg weight, adw crossbred pullets were more efficient in converting feed into egg mass in comparison with their normal crossbred counterparts. However, effect of adw gene on egg weight was breed dependent. It was suggested to conserve and improve deshi dwarf chicken for future use in breeding to increase egg production potential.