Inheritance of growth traits and impact of selection on carcass and egg quality traits in Vanashree, an improved indigenous chicken.

The present study was carried out to assess the inheritance of growth traits and to study the effect of selection on carcass characteristics and egg quality traits in Vanashree, an improved indigenous chicken. Estimates of heritability were high for body weights recorded at 4, 5 and 6 weeks of age and 8th week shank length, while it was moderate for 8th week body weight. Estimates of heritability on sire component of variance declined as age increased from 4 to 8 weeks of age. The genetic and phenotypic correlations among various growth traits were positive and high in magnitude. The body weight continued to increase up to 40 weeks of age particularly in male birds, while there was little increase in shank length from 20 to 40 weeks of age particularly in hens. There was no significant change in carcass characteristics and egg quality traits except that there was some improvement in dressing percentage over the generations. Sex effect was significant on relative weights of the breast, legs, gizzard, liver and heart and abdominal fat percentage. There was increase in Haugh unit and albumen index, yolk percentage, yolk to albumen ratio and yolk colour in the present generation. The results suggest that there is adequate additive genetic variation for growth traits in the population and that Vanashree chicken could continue to be improved so as to make it a promising dual purpose purebred indigenous chicken for increasing the productivity of free range or semi-intensive systems of production.

Genetic analysis of growth and egg production traits in synthetic colored broiler female line using animal model.

Variance and genetic parameters were estimated for growth and production traits of synthetic broiler female line (PB-2) using REML animal model to delineate the population status, direct additive, maternal genetic, permanent environmental effects, besides genetic trends and performance of economic traits. The overall least squares mean (LSM) for body weights at 0 day (BW0), at 2 weeks (BW2), at 4 weeks (BW4), at 5 weeks (BW5), shank length at 5 weeks (SL5), and breast angle at 5 weeks (BA5) of age were 40.03 g, 207.40 g, 589.58 g, 828.51 g, 76.89 cm, and 80.78°, respectively. The overall LSM for egg production up to 40 weeks of age (EP40) and egg weight at 40 weeks (EW40) were 66.02 eggs and 58.23 g, respectively. The heritability estimates using the best model for BW0, BW2, BW4, BW5, SL5, and BA5 were 0.06 ± 0.03, 0.19 ± 0.03, 0.15 ± 0.03, 0.14 ± 0.02, 0.08 ± 0.02, and 0.02 ± 0.01, respectively. The heritability estimates were low to moderate in the magnitude for all early growth traits. The heritability estimate for egg production up to 40 weeks (EP40) was 0.30 ± 0.05. The heritability estimates for adult body weights at 20 and 40 weeks of age (BW 20 and BW 40), age at sexual maturity (ASM), and egg weight at 40 weeks (EW40) were 0.21 ± 0.04, 0.19 ± 0.04, 0.16 ± 0.03, and 0.33 ± 0.05, respectively, and the estimates were moderate to high in magnitude. Model 4 with additive, maternal permanent environmental, residual, and phenotypic effects was the best model for growth traits except for BW0 and BA5. The average genetic gain observed in primary trait (BW5) over the five generations was 13.62 g per each generation indicating effective selection. The animal model minimized the overestimation of genetic parameters and improved the accuracy of the BV, thus enabling the breeder to select the suitable breeding strategy for genetic improvement.

Gene Expression and Polymorphism of Myostatin Gene and its Association with Growth Traits in Chicken.

Myostatin is a member of TGF-ß super family and is directly involved in regulation of body growth through limiting muscular growth. A study was carried out in three chicken lines to identify the polymorphism in the coding region of the myostatin gene through SSCP and DNA sequencing. A total of 12 haplotypes were observed in myostatin coding region of chicken. Significant associations between haplogroups with body weight at day 1, 14, 28, and 42 days, and carcass traits at 42 days were observed across the lines. It is concluded that the coding region of myostatin gene was polymorphic, with varied levels of expression among lines and had significant effects on growth traits. The expression of MSTN gene varied during embryonic and post hatch development stage.

Gene expression and silencing of activin receptor type 2A (ACVR2A) in myoblast cells of chicken.

Activin receptor type 2A (ACVR2A) acts as receptor for myostatin (MSTN) protein involved in inhibiting satellite cell proliferation and differentiation. The importance of the ACVR2A gene during embryonic and post-hatch periods in broiler and layer chicken was studied in an in vitro cell culture system. The expression pattern of the ACVR2A gene during embryonic stages was similar in broiler and layer lines. Post-hatch expression of the ACVR2A gene varied significantly between broiler and layer lines. Five shRNA molecules were designed to knockdown expression of the ACVR2A gene in chicken myoblast cells. The silencing of the ACVR2A gene in a cell culture system varied from 60% to 82%. It is concluded that between broiler and layer lines, there were no significant changes in expression of the ACVR2A gene during embryonic stages but it varied significantly during the post-hatch period. The shRNA showed silencing of the ACVR2A gene under an in vitro cell culture system.

Polymorphism and expression of insulin-like growth factor 1 (IGF1) gene and its association with growth traits in chicken.

1. The objectives of the study were to detect polymorphism in the coding region of the IGF1 gene, explore the expression profile and estimate association with growth traits in indigenous and exotic chickens. 2. A total of 12 haplotypes were found in Cornish, control layer and Aseel breeds of chicken in which the h1 haplotype was most frequent. 3. Nucleotide substitutions among haplotypes were found at 21 positions in the IGF1 gene in which 4 substitutions resulted in non-synonymous mutations in the receptor binding domain of the IGF1 protein. 4. The haplogroup showed a significant effect on body weight at 24 and 42 d of age in the control layer line, body weight at 42 d and daily weight gain between 29 and 42 d in the control broiler line, daily weight gain between 29 and 42 d in Cornish, and body weights at 42 d as well as daily weight gain between 29 and 42 d in Aseel birds. 5. IGF1 expression varied among the breeds during embryonic and post-hatch periods. The expression among the haplogroups varied in different chicken tissues. The effect of haplogroup on myofibre number in pectoral muscle was non-significant, although there was significant variation in numbers between d 1 and d 42, and between broiler and layer lines. 6. It was concluded that the coding region of the IGF1 gene was polymorphic, expressed differentially during the pre-hatch and post-hatch periods, and haplogroups showed significant association with growth traits in chicken.

Characterization of indigenous Aseel chicken breed for morphological, growth, production, and meat composition traits from India.

Aseel is an important native chicken breed of India, known for its martial qualities (aggressive fighting abilities), pugnacity, and majestic gait. The aim of the study is to conserve and characterize the Aseel germplasm, which is considered to be endangered. The birds were maintained on deep litter under a simulated backyard type of housing having night shelter and a free-range area. A total of 313 chicks produced in the second generation from the flock collected from native tract in Andhra Pradesh was characterized for morphological, growth, production, and meat quality parameters. Aseel birds were characterized by multicolored plumage (predominantly dark brown, black, golden, etc.) with solid feather patterns and normal distribution. Ear lobes were red (92%) and small in size, while 98% of the birds had red colored pea combs with variations in intensity of color. The shank color was yellow in the majority (65%) of the birds. The skin color was white (98%) with pinkish red coloration on exposed body parts, especially on the breast. The fertility and hatchability on total eggs were 67.2 and 41.4%, respectively. Cocks were heavier (P ≤ 0.05) with distinct sexual dimorphism in Aseel. The body weight of hens and cocks was 1,704.4 ± 23.2 and 2,702.5 ± 28.1 g at 40 wk and 2,333.7 ± 26.1 and 3,793.7 ± 20.8 g at 72 wk of age, respectively. The age at sexual maturity was 214.0 ± 6.0 days. The egg production up to 40, 52, and 64 wk of age was 18.0 ± 1, 30.0 ± 2.0, and 47 ± 3 eggs, respectively. The annual egg production (72 wk) was 64 ± 6 eggs. The proximate composition of breast muscle was; protein 21.5 ± 0.5%, fat 3.4 ± 0.1%, ash 2.0 ± 0.1%, and moisture 73.3 ± 0.5%. The pH of breast muscle was 6.0 ± 0.03 and the cholesterol content was 72.5 ± 6.7 mg/100 g. Efforts are on for improving the productivity in the flock without compromising the original breed characteristics.

Estimates of (co)variance components and genetic parameters for body weights and first greasy fleece weight in Bharat Merino sheep.

(Co)variance components and genetic parameters of weight at birth (BWT), weaning (3WT), 6, 9 and 12 months of age (6WT, 9WT and 12WT, respectively) and first greasy fleece weight (GFW) of Bharat Merino sheep, maintained at Central Sheep and Wool Research Institute, Avikanagar, Rajasthan, India, were estimated by restricted maximum likelihood, fitting six animal models with various combinations of direct and maternal effects. Data were collected over a period of 10 years (1998 to 2007). A log-likelihood ratio test was used to select the most appropriate univariate model for each trait, which was subsequently used in bivariate analysis. Heritability estimates for BWT, 3WT, 6WT, 9WT and 12WT and first GFW were 0.05 ± 0.03, 0.04 ± 0.02, 0.00, 0.03 ± 0.03, 0.09 ± 0.05 and 0.05 ± 0.03, respectively. There was no evidence for the maternal genetic effect on the traits under study. Maternal permanent environmental effect contributed 19% for BWT and 6% to 11% from 3WT to 9WT and 11% for first GFW. Maternal permanent environmental effect on the post-3WT was a carryover effect of maternal influences during pre-weaning age. A low rate of genetic progress seems possible in the flock through selection. Direct genetic correlations between body weight traits were positive and ranged from 0.36 between BWT and 6WT to 0.94 between 3WT and 6WT and between 6WT and 12WT. Genetic correlations of 3WT with 6WT, 9WT and 12WT were high and positive (0.94, 0.93 and 0.93, respectively), suggesting that genetic gain in post-3WT will be maintained if selection age is reduced to 3 months. The genetic correlations of GFW with live weights were 0.01, 0.16, 0.18, 0.40 and 0.32 for BWT, 3WT, 6WT, 9WT and 12WT, respectively. Correlations of permanent environmental effects of the dam across different traits were high and positive for all the traits (0.45 to 0.98).