The fatty acid synthase (FASN) and stearoyl-CoA desaturase (delta-9-desaturase) (SCD) genes affect fatty acid composition. This study evaluated the contributions of polymorphisms of these genes on fatty acid composition in muscle in two different populations: 1189 and 1058 Japanese Black cattle from the Miyagi and the Yamagata populations respectively. We sampled intramuscular fat from the longissimus thoracis muscle in the Miyagi population and from the trapezius muscle in the Yamagata population. The collective contributions of FASN and SCD polymorphisms to total additive genetic variance for oleic acid were 13.46% in the Miyagi population and 16.29% in the Yamagata population and to phenotypic variance were 5.45% and 6.54% respectively. Although the individual effects of FASN and SCD polymorphisms on fatty acid composition were small, overall gene substitution may effectively improve fatty acid composition. In addition, we found that gene polymorphism contributions of fatty acids varied by population even in the same breed.

Records on 514 bulls from the sire population born from 1978 to 2004, and on 22,099 of their field progeny born from 1997 to 2003 with available pedigree information (total number = 124,458) were used to estimate genetic parameters for feed intake and energy efficiency traits of bulls and their relationships with carcass traits of field progeny. Feed intake and energetic efficiency traits were daily feed intake, TDN intake, feed conversion ratio (FCR), TDN conversion ratio (TDNCR), residual feed intake (RFI), partial efficiency of growth, relative growth rate, and Kleiber ratio. Progeny carcass traits were carcass weight (CWT), yield estimate, ribeye area, rib thickness, subcutaneous fat thickness (SFT), marbling score (MSR), meat color standard (MCS), fat color standard (FCS), and meat quality grade. All measures of feed intake and energetic efficiency were moderately heritable (ranged from 0.24 to 0.49), except for partial efficiency of growth and relative growth rate, which were high (0.58) and low (0.14), respectively. The phenotypic and genetic correlations between FCR and TDNCR were >or=0.93. Selection for Kleiber ratio will improve all of the energetic efficiency traits with no effect on feed intake measures (daily feed intake and TDN intake). The genetic correlations of FCR, TDNCR, and RFI of bulls with most of the carcass traits of their field progeny were favorable (ranged from -0.24 to -0.72), except with fat color standard (no correlation), MCS, and SFT. Positive (unfavorable) genetic correlations of MCS with FCR, TDNCR, and RFI (0.79, 0.70, and 0.51, respectively) were found. The SFT was negatively genetically correlated with FCR and TDNCR (-0.32 and -0.20, respectively); however, the genetic correlation between RFI and SFT was not significantly different from zero (r(g) = -0.08 +/- 0.12). Favorable correlated responses in CWT, yield estimate, ribeye area, rib thickness, MSR, and meat quality grade would be predicted for selection against any measure of energetic efficiency. The correlated responses in CWT and MSR of progeny were greater for selection against RFI than for selection against any other energetic efficiency trait. Results of this study indicate that RFI should be preferred over other measures of energetic efficiency to include in selection programs.

The objectives of this study were to infer phenotypic causal networks involving gestation length (GL) and calving difficulty (CD) for the primiparity of 1850 Japanese Black heifers, and the birth weight (BWT), withers height (WH) and chest girth (CHG) of their full blood calves, and to compare the causal effects among them. The inductive causation (IC) algorithm was employed to search for causal links among these traits; it was applied to the posterior distribution of the residual (co)variance matrix of a multiple-trait sire-maternal grand sire (MGS) model. The IC algorithm implemented with 95% and 90% highest posterior density intervals detected only one structure with links between GL and BWT (WH or CHG) and between BWT (WH or CHG) and CD, although their directions were not resolved. Therefore, a possible causal structure based on the networks obtained from the IC algorithm [GL→BWT (WH or CHG)→CD] was fitted using a structural equation model to infer causal structure coefficients between the traits. The structural coefficients of GL on BWT and of BWT on GL on the observable scale showed that an extra day of GL led to a 270-g gain in BWT, and a 1-kg increase in BWT increased the risk for dystocia by 1.1%, in the causal structure. Similarly, an increase in GL by 1 day resulted in a 2.1 (2.0)-mm growth in WH (CHG), and a 1-cm increase in WH (CHG) increased the risk of dystocia by 1.2% (0.9%). The structural equation model was also fitted to alternative causal structures, which involved the addition of a directed link from GL to CD, or GL→CD to the structures described above. The inferred structural coefficients with the alternative structures were almost the same as the corresponding ones that had GL→BWT (WH or CHG)→CD. However, the direct causal effect of the extra link from GL on CD was similar to the indirect causal effect of GL through the mediating effect of BWT (WH or CHG) on CD and significant (P<0.05). This suggest that maternal genetic effects might not be removed completely from the residual variance components in the sire-MGS model, and the application of the IC algorithm to the variances from the model could detect an incorrect structure. Nonetheless, fitting the structural equation model to the causal structure provided useful information such as the magnitude of the causal effects between the traits.

The objective of this study was to estimate genetic parameters for first calving reproductive traits and growth curve characteristics in Japanese Black cattle. The Gompertz growth function was fitted to body weight-age data to obtain the mature weight (MWT) and rate of maturing (ROM) of cows. Data of reproductive traits including the first service conception rate (CR) for heifers, age at the first calving (AFC), and gestation length for the first calving were collected. Records of 3,204 animals were used for analysis. Genetic parameters were estimated using a linear uni-and bivariate animal model. The heritability estimates were moderate (0.29 for ROM) and high (0.57 for MWT) for growth curve parameters and low (0.03-0.11) for reproductive traits. There was a negative genetic correlation between MWT and ROM (−0.26), suggesting that an animal with a faster ROM would show a lower MWT. CR was negatively correlated with MWT (−0.42) but significantly and positively correlated with ROM (0.91). There was a negative genetic correlation between AFC and MWT (−0.49). These results suggest that a heifer with a faster ROM and lower MWT would show a higher CR. Meanwhile, a heifer with a lower MWT would show a higher AFC.

The objectives of this study were to compare the genetic parameters for calving difficulty (CD), which were treated as both a calf trait (CD_calf) and as a dam trait (CD_dam), and to clarify genetic relationships of these CDs with body size traits of calves at birth and carcass traits. In total, the CD records and calf body measurements of 2,258 Japanese Black cattle heifers were used in this study, in addition to the carcass records of 4,300 feedlot steers and heifers. Direct heritability of CD_calf (0.44) was higher than maternal heritability of CD_calf (0.30), as well as CD_dam heritability (0.25). Direct genetic correlations between CD_calf and calf body size were moderate to strongly positive (0.64 to 0.81). The correlations between EBVs of CDs and carcass weight were also positive (0.30 to 0.64). These positive relationships showed that genetically improving CD (reducing dystocia) could produce smaller calves and carcasses. In contrast, the correlations between CDs and beef marbling score were weak, suggesting that improving CD would not influence meat quality traits. Fitting an animal model to CD_calf could be more preferred to fitting the model to CD_dam, because the former could separate the genetic effects of dams and calves.