ABSTRACT
The objective of this research is to investigate appropriate random regression models with various covariance functions, for the genetic evaluation of test-day egg production. Data included 7,884 monthly egg production records from 657 Thai native chickens (Pradu Hang Dam) that were obtained during the first to sixth generation and were born during 2007 to 2014 at the Research and Development Network Center for Animal Breeding (Native Chickens), Khon Kaen University. Average annual and monthly egg productions were 117 ± 41 and 10.20 ± 6.40 eggs, respectively. Nine random regression models were analyzed using the Wilmink function (WM), Koops and Grossman function (KG), Legendre polynomials functions with second, third, and fourth orders (LG2, LG3, LG4), and spline functions with 4, 5, 6, and 8 knots (SP4, SP5, SP6, and SP8). All covariance functions were nested within the same additive genetic and permanent environmental random effects, and the variance components were estimated by Restricted Maximum Likelihood (REML). In model comparisons, mean square error (MSE) and the coefficient of detemination (R2) calculated the goodness of fit; and the correlation between observed and predicted values [Formula: see text] was used to calculate the cross-validated predictive abilities. We found that the covariance functions of SP5, SP6, and SP8 proved appropriate for the genetic evaluation of the egg production curves for Thai native chickens. The estimated heritability of monthly egg production ranged from 0.07 to 0.39, and the highest heritability was found during the first to third months of egg production. In conclusion, the spline functions within monthly egg production can be applied to breeding programs for the improvement of both egg number and persistence of egg production.
Subject(s)
Animal Husbandry/methods , Chickens/physiology , Models, Genetic , Ovum/physiology , Reproduction , Animals , Chickens/genetics , Regression Analysis , ThailandABSTRACT
Four Thai synthetic chicken lines (Kaen Thong, Khai Mook Esarn, Soi Nin, and Soi Pet) originated from Thai native and exotic commercial chickens were evaluated for their growth and carcass traits with the purpose of developing a Thai broiler breeding program. Insulin-like growth factor I (IGF-I) gene is known to play an important role in growth, proliferation and differentiation. Consequently, we investigated the possibility of using the IGF-I gene for marker-assisted selection in Thai synthetic chickens. We looked for variations in the IGF-I gene and studied their association with growth and carcass traits; 1046 chickens were genotyped using PCR-RFLP methods. A general linear model was used to analyze associations of the IGF-I polymorphism with growth and carcass traits. Kaen Thong, Khai Mook Esarn, and Soi Nin chickens were found to carry similar frequencies of alleles A and C (0.40-0.60), while Soi Pet chickens had high frequencies of allele C (0.75). The IGF-I gene was significantly associated with some growth traits (body weight at hatching, and at 4, 8, 12, and 14 weeks of age; average daily gain during 0-12 and 0-14 weeks of age) in all synthetic chickens. Carcass traits (the percentage of dressing and pectoralis major) were significantly different only in Khai Mook Esarn chickens. We conclude that IGF-I can be used as a marker gene for the selection of growth and carcass traits of synthetic chickens in a marker-assisted selection program.
Subject(s)
Chickens/genetics , Insulin-Like Growth Factor I/genetics , Polymorphism, Single Nucleotide , Animals , Body Weight/genetics , Breeding , Chickens/growth & development , Female , Gene Frequency , Genetic Association Studies , Male , Polymorphism, Restriction Fragment LengthABSTRACT
A single-step DNA isolation procedure from pig tissues was developed and the product used directly for polymerase chain reaction (PCR) amplification, single-strand conformational polymorphism (SSCP) analysis and sequencing. The procedure consists of proteinase K digestion of 2-10mg of fresh tissue, at 55 degrees C for 1h, followed by application of the products of digestion to filter paper. A 1.2mm-diameter punch of that paper has sufficient DNA to act as a template for PCR amplification. The quality of the genomic DNA appeared to be high as the PCR amplicons produced sharp banding patterns on both agarose gel electrophoresis and on SSCP analysis, and they could be used for DNA sequencing following cloning. The dried genomic DNA on filter paper can be kept at room temperature. The procedure is considered effective as it is simple, fast and inexpensive. It would be useful for large-scale genotyping and could be used to obtain genomic DNA from various tissues.
