Eight novel and four known mutations were detected in the coding sequence of the bovine fatty acid synthase (FASN) gene of an F2 population from Japanese Black and Limousin cattle. Two mutations, g.16024A>G and g.16039T>C, detected in exon 34, which determine amino acid substitutions of threonine (T) to alanine (A) and tryptophan (W) to arginine (R), were clearly separated in the parental breeds. The haplotypes (TW and AR) segregated in F2 individuals and had a significant effect on the fatty acid composition of backfat, intermuscular fat, and intramuscular fat. The TW haplotype was associated with increasing C18:0 and C18:1 content and the ratio of monounsaturated to saturated fatty acids, and decreasing C14:0, C14:1, C16:0, and C16:1 content. The two mutations were screened in two commercial Japanese Black half-sibling populations and similarly determined the contribution to the fatty acid composition of intramuscular fat. The frequency of the TW haplotype was markedly higher in Japanese Black (0.67) than in Holstein (0.17), Angus (0.02), and Hereford (0.07). We conclude that these mutations may contribute to the characteristic fatty acid composition of Japanese Black beef.

We constructed a pig F2 resource population by crossing a Meishan sow and a Duroc boar to locate economically important trait loci. The F2 generation was composed of 865 animals (450 males and 415 females) from four F1 males and 24 F1 females and was genotyped for 180 informative microsatellite markers spanning 2,263.6 cM of the whole pig genome. Results of the genome scan showed evidence for significant quantitative trait loci (<1% genomewise error rate) affecting weight at 30 d and average daily gain on Sus scrofa chromosome (SSC) 6, carcass yield on SSC 7, backfat thickness on SSC 7 and SSC X, vertebra number on SSC 1 and SSC 7, loin muscle area on SSC 1 and SSC 7, moisture on SSC 13, intramuscular fat content on SSC 7, and testicular weight on SSC 3 and SSC X. Moreover, 5% genomewise significant QTL were found for birth weight on SSC 7, average daily gain on SSC 4, carcass length on SSC 6, SSC 7, and SSC X and lightness (L value) on SSC 3. We identified 38 QTL for 28 traits at the 5% genomewise level. Of the 38 QTL, 24 QTL for 17 traits were significant at the 1% genomewise level. Analysis of marker genotypes supported the breed of origin results and provided further evidence that a suggestive QTL for circumference of cannon bone also was segregating within the Meishan parent. We identified genomic regions related with growth and meat quality traits. Fine mapping will be required for their application in introgression programs and gene cloning.

The changes in i.m. fat deposition in the principal muscles [M. semitendinosus, M. semimembranosus, M. psoas major, M. latissimus dorsi, LM (7th to 8th and 10th to 11th thoracic vertebrae), and M. supraspinatus] from 24 to 30 mo of age were investigated using identical twins of Japanese Black steers. Four sets of identical twins of Japanese Black steers were used in this study. Animals were fattened from 10 to 24 or 30 mo of age for each pair of identical twins. Body weights of twin steers slaughtered at 24 and at 30 mo of age were similar at 10 mo of age and thereafter up to 24 mo of age. The changes in serum concentration of vitamin A, glucose, total cholesterol, albumin, and total protein were similar in each pair of twins during the first fattening stage (10 to 24 mo). Fat contents of LM (7th to 8th thoracic vertebrae) at 24 and 30 mo of age were 37.0 and 42.4%, respectively (P < 0.05). Moreover, in the principal muscles, except M. semimembranosus and M. supraspinatus, fat content at 30 mo of age was greater than at 24 mo of age (P < 0.05). The proportional increase in fat content from 24 to 30 mo of age was greatest in M. semitendinosus (+58.7%) and least in M. supraspinatus (+6.1%). These results demonstrate that i.m. fat continues to increase after 24 mo of age, and the rates of i.m. fat deposition and the ages when i.m. fat is deposited are different for every muscle.

A genome-wide scan for QTL affecting economically important traits in beef production was performed using an F(2) resource family from a Japanese Black x Limousin cross, where 186 F(2) animals were measured for growth, carcass, and meat-quality traits. All family members were genotyped for 313 informative microsatellite markers that spanned 2,382 cM of bovine autosomes. The centromeric region of BTA2 contained significant QTL (i.e., exceeding the genome-wide 5% threshold) for 5 carcass grading traits [LM area, beef marbling standards (BMS) number, luster, quality grade, and firmness), 8 computer image analysis (CIA) traits [LM lean area, ratio of fat area (RFA) to LM area, LM area, RFA to musculus (M.) trapezius area, M. trapezius lean area, M. semispinalis lean area, RFA to M. semispinalis area, and RFA to M. semispinalis capitis area], and 5 meat quality traits (contents of CP, crude fat, moisture, C16:1, and C18:2 of LM). A significant QTL for withers height was detected at 80.3 cM on BTA5. We detected significant QTL for the C14:0 content in backfat and C14:0 and C14:1 content in intermuscular fat around the 62.3 to 71.0 cM region on BTA19 and for C14:0, C14:1, C18:1, and C16:0 content and ratio of total unsaturated fatty acid content to total SFA content in intramuscular fat at 2 different regions on BTA19 (41.1 cM for C14:1 and 62.3 cM for the other 4 traits). Overall, we identified 9 significant QTL regions controlling 27 traits with genome-wide significance of 5%; of these, 22 traits exceeded the 1% genome-wide threshold. Some of the QTL affecting meat quality traits detected in this study might be the same QTL as previously reported. The QTL we identified need to be validated in commercial Japanese Black cattle populations.

Regarding the fattening of younger cattle that the Ministry of Agriculture Forestry and Fisheries (MAFF) recommends in Japan, this study looked at vitamin A control in feed and blood and its effect on performance of production and carcass composition of Wagyu steers. Five sets from 10 Wagyu artificial identical twins were divided to into 2 groups, a restricted group (Test) and a supplied group (Control). The body weight at the finishing time of the Test was significantly lower than that of the Control (p<0.05). The daily gain from 13 to 21 months old, as the animals in the Test were fed the concentrated feed without Vitamin A, was significantly different (p<0.05) between the Test and the Control. The total daily gains for the Test and the Control for the fattening period were 0.82 kg/day and 0.93 kg/day, respectively, which showed a significant difference (p<0.01). Regarding the rib thickness, the Test was thinner than the Control. The Beef Marbling Scores of the Test and Control were 3.60 and 2.80, respectively. The muscle weight of the Test was significantly smaller than that of the Control (p<0.01). However, regarding the ratio to the carcass, the Test was significantly higher than the Control (p<0.05). For the fat weight, the Test was smaller by about 15 kg than the Control (p<0.01). Furthermore, for the fat ratio to the carcass, the Test was significantly lower than the Control (p<0.05). The bone weights of the two groups were approximately the same. Regarding the ratio of bone to carcass, the Test was higher than the Control (p<0.01). For the younger fattening method, the low level vitamin A in the serum had the effect that the muscle ratio to the carcass weight was greater and the fat was less, but the carcass and muscle weight were less.