Abdominal and subcutaneous fat are regarded as the main sources of waste in the slaughterhouse. Fat stored intramuscularly is regarded a favorite trait related to meat quality. The objective of current study was to estimate genetic parameters for fat deposition in the 3 different parts of body and their relationships with other carcass traits. Traits were recorded for 1,752 females and 1,526 males from a meat-type chicken line. Heritability estimates for abdominal fat percentage, skin percentage as a measure of subcutaneous fat, and intramuscular fat percentage were 0.71, 0.24, and 0.08, respectively. Heritabilities of the other carcass traits were moderate to high (0.28 to 0.73). There was a high genetic correlation between abdominal fat weight and skin weight (0.54), whereas the genetic correlation between abdominal fat weight and intramuscular fat percentage was almost zero (0.02). The BW at 7 wk showed a positive genetic correlation with fat production traits, which were high for intramuscular fat percentage (0.87) and moderate for skin percentage (0.17) and abdominal fat percentage (0.13). Therefore carcass traits could be improved by selection for increased breast muscle and reduced abdominal fat without decreased intramuscular fat.

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.

1. The objective was to estimate heritability, genetic and phenotypic correlations for egg quality traits of Iranian native fowl at the Yazd Breeding Centre. 2. External and internal egg quality traits were measured on 1200 eggs from 794 hens of the 6th generation. A multivariate animal model with restricted maximum likelihood procedure was applied to estimate heritability, genetic and phenotypic correlations for egg quality traits using ASREML. 3. Heritability estimates for external egg quality traits ranged from 0·18 to 0·57 and for internal egg quality traits from 0·24 to 0·60. 4. For external egg quality traits, genetic correlation between egg weight and eggshell thickness (EST) was positive (0·36) and EST showed high genetic correlations with eggshell weight (0·84) and eggshell strength (0·55). This implies that heavier eggs tend to have thicker and stronger shells. 5. For internal egg quality traits, albumen height showed high positive genetic correlations with albumen weight (0·52), albumen index (0·98), yolk height (0·72) and yolk index (0·57). 6. Our results show that it is feasible to improve egg quality in Iranian fowl through selection for albumen height.

1. Performance traits were measured on 1908 Japanese quail and egg quality traits assessed on 1800 eggs at 10 wk of age. 2. Genetic and phenotypic correlations were estimated using a bivariate animal model with restricted maximum likelihood using ASREML software. 3. Body weight at different ages showed positive genetic correlations with egg weight and most of the internal egg quality traits, whereas their genetic correlations with eggshell thickness, eggshell strength and eggshell percentage were negative. 4. Genetic correlations of age at sexual maturity and egg number with most of external and internal traits were negative. 5. It was concluded that selection for higher body weight will result in heavier and better quality eggs. Because of the negative genetic correlation between BW and egg shell quality, a selection index including BW and eggshell strength would be the best breeding strategy for genetic improvement of egg quality in Japanese quail.