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Evaluation of dwarf gene linked parameters in chicken
Abstract
The dwarf chicken can be a viable alternative as dwarf dam line reduces the maintenance cost, increases the fertility and hatchability, high feed efficiency and better survival.
... ASM (153.88 ± 1.38 days) in this study was reasonable as PD-3 line was rural female line. Similar results were obtained in Dwarf chicken [14], Gramapriya chicken under different rearing systems [15], Vanaraja [16] respectively. Lower ASM was observed in White Nicobari [17], White Leghorn and Brown egg Dwarf chicken [18], and Gramapriya birds reared under intensive system [19], whereas higher age of sexual maturity was found by in Aseel and Kadaknath [20] and Horro chicken [21]. ...
... The h 2 S+D estimates for 40-week body weight were comparable with the findings on research study on IWH chicken [36] and in PD1 chicken [27]. However higher heritability estimates were obtained by other authors [14,35,37]. The heritability estimates for sire, dam and sire + dam components for body weight at 52 weeks were moderate to higher values than that of values reported by authors in literature. ...
... This may be revealed that birds heavier at early age were also heavier at later age due to the pleiotropic actions of genes controlling bodyweights [26]. The correlation between BW 40 and EW 40 was similar to results obtained by in control group [36,39] whereas, higher values were obtained in Dwarf chicken [14] and in Naked Neck [13], while lower values are reported in IWI [36,38]. There was a positive association between body weights and egg weights as age advanced, heavier birds laid heavier eggs. ...
... Heat tolerance can be improved through various means like more efficient thermoregulation, through enlarged naked body surface, lowering basal metabolism, reduced feathering intensity, creating specific colors by obtaining skin having melanin and non-pigmented feathers. Various authors studied the attributes of naked neck with respect to physiological immunity, production and carcass traits under different agroclimatic conditions (Nardone et al., 2010;Rajkumar et al., 2010bRajkumar et al., , 2010cRajkumar et al., , 2011Azoulay et al., 2011;Hadad et al., 2014). The present investigation is designed to evaluate the effect of reduced feathering intensity in the naked neck birds. ...
... The dressing percentage was significantly higher in naked neck genotypes than their normal siblings, which can be attributed to higher body weight and less losses due to lack of feathers in naked neck chicken. The higher meat yield due to the presence of Na gene is well established (El-Attar and Fathi, 1995;Deeb and Cahaner, 1999;Yalcin et al., 1999;Fathi and Galal, 2001;Fathi et al., 2008;Rajkumar et al., 2010bRajkumar et al., , 2011. ...
The three naked neck broiler genotypes (NaNa, Nana and nana) were investigated for the effect of temperature on juvenile body weights, shank length, immune competence and carcass characteristics. Weekly body weights were recorded from day old to six weeks (n = 417). The body weights were significantly higher in naked neck genotypes (NaNa and Nana) at 4th, 5th and 6th week of age. Birds with NaNa and Nana genotype recorded significantly (p≤0.05) higher weight gains during 4th (211.17 g) and 5th (207.96 g) week, respectively than nana genotype. The body weight gains were numerically higher at all ages either in NaNa or Nana genotypes without any significant difference. The shank length did not show any significant variation among the genotypes, which ranged from 78.54 mm in full feathered (nana) birds to 79.67 mm in heterozygous (Nana) population with an overall mean of 79.13 mm. Mean anti SRBC titre, anti NDV titre and response to PHA-P ranged from 3.55-5.6, 2.75-5.10 and 1.35-1.47 mm, respectively in different genetic groups. The dressing percentage was significantly higher in NaNa genotypes (71.96) than their normal (nana) siblings (69.66), which can be attributed to higher body weight and less losses due to lack of feathers in naked neck chicken. The liver, heart and gizzard weights are numerically higher in NaNa and Nana genotypes. The present study invariably concluded that Na gene in homozygous and heterozygous condition is more beneficial to exploit for better performance of Naked neck in tropical conditions.
High correlation estimates between body weight and shank length revealed strong association among traits. The significant positive association between 4 and 6 weeks shank length and body weight in the Gramapriya male line chicken suggest the breeder to pre-pone the selection to 4 weeks age which economizes the production cost. Besides, the immune competence of the birds was also found to be better, making them suitable male line for production of backyard poultry varieties.
The juvenile and production performance in reciprocal crosses of dwarf and PB-2 were evaluated in the present study. The study revealed that there were no significant differences in body weights and production performance of the two reciprocals. The dwarf dam line concept to reduce the maintenance cost is coming up wherein either of the lines can be utilized for commercial colour broiler production as female or male line without affecting the performance.
A comparative study on terminal crosses involving DDL and PB-2 females with PB-1 males was evaluated for growth and immune parameters. The present findings showed the advantages of dwarf gene with respect to feed efficiency, fertility, hatchability and maintenance cost etc. These results confirmed the economic benefits of the dwarf dam line though the growth rate was lower.
A mutation in the Cornell K-strain of White Leghorns, first recognized when two adult males in a pedigreed family were definitely
smaller than their two other brothers, proved to be an autosomal recessive mutation and gave rise to the autosomal dwarf stock.
The effect of this gene (adw) can be recognized during embryonic development and leads to a normal adult, except for a 30%
reduction in body weight. Selection for small size, egg production, and egg weight over a period of 15 yr yielded an efficient
layer. Production for 11 mo from first egg was at a rate of 70%, with egg weight at 56 g and body weight at 1,160 g at 10
to 11 mo of age, based on data for the last four generations. Viability of the caged hens averaged over 95% for the 13 generations
involved. Sexual maturity was delayed by about 2 wk, and good incubation (85+%) required 18+/- more hours than normal. When
an autosomal dwarf male is used as a sire and mated to sex-linked dwarf (dw) females, all progeny are of normal size. Compared
with problems of mating normal size males with dwarf females, the use of the two types of dwarfism can yield good fertility.
Broiler crosses, viz. C1 (PB-1 × PB-2), C2 (PB-2 × PB-1), C3 (PB-1 × Dwarf), C4 (PB-2 × Dwarf) were produced in a single hatch and the immunocompetence and juvenile performance traits up to 8 weeks were studied to evaluate the performance for these traits. Response to Newcastle disease vaccine (ND), sheep red blood cell response (SRBC), cutaneous basophil hypersensitivity (CBH) response, relative spleen and bursa weights, body weight at 2WK, 4WK, 6WK and 8WK, carcass quality traits like eviscerated weight, giblet weight, fat percentage and dressing percentage were measured at 6 weeks of age. The C 4 cross significantly responded to ND vaccine and it was higher than other crosses. The SRBC antibody response in normal dam line crosses (C 1 and C2) were significantly higher than the dwarf dam line crosses (C3 and C4). However CBH response did not differ significantly among the 4 broiler crosses studied. Relative spleen weights in C1 and C3 were significantly higher than other 2 crosses. But relative bursa weight in C3 was significantly higher than other 3 crosses. The body weights at 6 weeks of age and body weight gains between 4 to 6 weeks differed significantly among the 4 crosses. Among the 4 crosses C1 ranked first, while, the C4 broiler cross ranked last for 6WK body weight. At 8WK, body weights of normal dam line crosses differed significantly from the dwarf dam line crosses. Carcass quality traits, such as giblet weight, eviscerated weight and dressing percentage were significantly better in normal dam line crosses compared to dwarf dam line crosses. Crosses involving dwarf dam line were not at par with normal dam line crosses for body weight traits. It indicated the incompletely recessive nature of the dwarf gene in heterozygous form (Dw+/dw). However, for immunocompetence traits no definite trend was observed between normal and dwarf dam line crosses.
The effect of the dw gene on growth, lipid deposition, plasma hormone concentration, and enzyme activity in a randombred population of chickens was studied. The reciprocal crosses were examined as well as purebred dwarf and normal populations. Body weight, carcass fat, plasma growth hormone (GH), triiodothyronine (T3), thyroxine (T4), hepatic malic enzyme (ME) and citrate cleavage enzyme (CCE) activities were determined at 0, 2, 4 and 6 weeks. Body weights of dwarf birds were less than normal birds and, unexpectedly, Dwdw males had greater body weights than DwDw males. Percent carcass fat was greater in dwarf birds in comparison to phenotypically normal birds. All males carrying the dw gene had greater fat pad weights than homozygous normal males. The dw- females from cross 3 had less abdominal fat than cross 4 Dw- females, while dw- females from the dwarf parental mating had fat pad weights similar to Dw- females. Plasma T4 levels were elevated in all birds carrying the dw gene in comparison to normal birds. Plasma T3 levels were depressed in all birds carrying the dw gene versus normals, although the T3 levels of Dwdw males were intermediate to dwdw and DwDw males. The homozygous dwarf progeny exhibited elevated GH levels versus normals and Dwdw males exhibited GH concentrations intermediate to dwdw and DwDw males. Malic enzyme activity was lower in all birds carrying the dw gene, while CCE activity was not effected by genotype.