Current research was conducted to estimate heritability and genetic correlations for carcass composition and fat deposition in Japanese quail at 42 and 91 d of age. Studied traits were BW at 42 and 91 d of age (BW42, BW91), carcass weight and percentage, breast meat weight and percentage, thigh weight and percentage, abdominal fat weight and abdominal fat percentage (AFP), skin weight and skin percentage (SP) as a measure of subcutaneous fat, and the percentage of breast intramuscular fat (IFP). Genetic parameters were estimated by restricted maximum likelihood using ASREML software. The heritability estimates of BW and the weight of carcass traits were higher (from 0.45 for BW42 to 0.63 for breast meat weight) than the percentage of carcass traits (from 0.11 for thigh percentage to 0.19 for breast meat percentage). The heritability estimates for SP, AFP, and IFP as fat deposition tissues were 0.17, 0.26, and 0.20, respectively. There were high genetic correlations between BW42 with the weight and percentage of carcass components (from 0.65 to 0.98). Body weight at 42 d of age also showed positive genetic correlations with skin weight and SP (0.80 and 0.23, respectively), abdominal fat weight and AFP (0.44 and 0.21, respectively), and IFP (0.28). A positive genetic correlation between SP and AFP (0.51) was observed. Present results indicated that the percentage of breast intramuscular fat is a heritable trait and selection for increasing BW and decreasing abdominal and subcutaneous fats will improve carcass composition and breast meat quality in Japanese quail. In addition, selection against abdominal and subcutaneous fat does not change intramuscular fat and the quality of breast meat.

Effect of polymorphic variants of growth hormone (GH), β lactoglobulin (β LG), and Pit 1 genes on milk yield was analyzed in a Holstein herd. Genotypes of the cows for these genes were determined by polymerase chain reaction restriction fragment length polymorphism (PCR RFLP) method. Allele frequen cies were 0.884 and 0.116 for L and V variants of GH, 0.170 and 0.830 for A and B variants of Pit 1, and 0.529 and 0.471 for A and B variants of β LG, respectively. GLM procedure of SAS software was used to test the effects of these genes on milk yield. Results indicated significant effects of these genes on milk yield (P < 0.05). Cows with LL genotype of GH produced more milk than cows with LV genotype (P < 0.05). Also, for Pit 1 gene, animals with AB genotype produced more milk than BB genotype (P < 0.05). In the case of β LG gene, milk yield of animals with AA genotype was more than BB genotype (P < 0.01). Therefore, it might be concluded that homozygote genotypes of GH (LL) and β LG (AA) were superior compared to heterozygote genotypes, whereas, the heterozygote genotype of Pit 1 gene (AB) was desirable.

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The effect of β-lactoglobulin (β-LG) and κ-casein (CSN3) genotypes on milk composition were evaluated in Iranian indigenous Zel sheep breed. Genotypes were determined by PCR amplification followed by digestion with RsaI enzyme for exon II of the β-LG gene and SSCP method for exon IV of the CSN3 gene. Polymorphism was detected in all PCR products. β-lactoglobulin showed two alleles and three genotypes and CSN3 gene revealed two conformational patterns, respectively. Results indicated that there were significant associations between AB genotype of β-LG gene with higher fat and lactose percentages and also between K 1 pattern of CSN3 gene with higher lactose percentage. Therefore, it is feasible to improve milk composition in Zel sheep breed using β-LG and CSN3 genes.