Genetic relationships between meat quality traits and fatty acid composition in Japanese black cattle

Genetic parameters were estimated to investigate the relationships between meat quality traits and fatty acid composition from 11 855 Japanese Black cattle. The meat quality traits included beef marbling score (BMS), beef color score, firmness of beef (FIR), texture of beef (TEX) and beef fat color score (BFS). The data on fatty acid composition included oleic acid and monounsaturated fatty acids (MUFA) contents, the ratio of MUFA to saturated fatty acids (MUS) and the ratio of elongation. The heritability estimates for meat quality traits ranged from moderate (0.30) to high (0.72). The strong genetic correlations between them were useful for simultaneous genetic improvement. In addition, high heritability estimates of fatty acid composition, ranging from 0.60 to 0.63, indicated that they could also be improved genetically. The genetic correlations of fatty acid composition with BMS, FIR and TEX were weak and negative. In contrast, positive and stronger genetic correlations were found between BFS and fatty acid composition, in particular, related to the level of unsaturation (0.77 and 0.79 for MUFA and MUS, respectively). This implies that improving the level of unsaturation makes fat darker (more yellow) and thus requires balancing with BFS.     

Estimation of direct and maternal genetic parameters for growth and carcass traits in a herd of Japanese Black cattle in Miyagi prefecture, using a multitrait animal model

Data from 1170 records of fattening calves were collected on growth and carcass traits from a Japanese Black cattle herd located in Miyagi prefecture, Japan. The objective was to determine direct and maternal heritabilities, direct and maternal genetic correlations and phenotypic correlations between bodyweight at the beginning of the fattening period (BWS), bodyweight at the end of the fattening period (BWF), carcass weight (CW), average daily gain during the fattening period (ADG), rib eye area (REA), rib thickness, subcutaneous backfat thickness (SFT), yield estimate (YE) and beef marbling score (BMS). Direct heritability estimates of 0.16 (SFT) and 0.07 (BMS) were low, whereas estimates of the other traits were medium to high and ranged between 0.44 (REA) and 0.78 (CW). Direct genetic correlations were all positive, except those that were between BWS and SFT, and between BWS and YE (?0.49 and ?0.14, respectively). The lowest positive genetic correlation was between BWS and BMS (0.04) and the highest was between BWF and CW (0.99). The phenotypic correlation coefficients ranged between ?0.41 (between SFT and YE) and 0.96 (between BWF and CW). Maternal heritability estimates were generally low and ranged between 0.00 for BMS and 0.08 for BWS, CW and ADG. Selection programs comprising information on growth and carcass traits of calves and maternal traits of dams were suggested.     

Genomic imprinting variances of beef carcass traits and physiochemical characteristics in Japanese Black cattle

The objective of this study was to estimate variance components related to imprinting for carcass traits and physiochemical characteristics in Japanese Black cattle. The carcass records obtained from 4,220 Japanese Black feedlot cattle included carcass weight (CW), rib eye area (REA), rib thickness, subcutaneous fat thickness, and beef marbling score (BMS), and the physiochemical characteristics were fat, moisture, glycogen per proportion of moisture content, oleic acid, and monounsaturated fatty acids (MUFA). To detect gametic effects, an imprinting model was fitted. High additive heritabilities were estimated for all traits (from 0.516 for glycogen to 0.853 for fat) and were reduced in Mendelian heritability. The range of the differences was from 0.002 (CW) to 0.331 (fat and moisture), and the reductions were due to their imprinting variances. The ratio of the imprinting variance to the total additive genetic variance for REA (0.374), BMS (0.291), fat (0.387), moisture (0.388), and MUFA (0.337) were large (p < 0.05). These imprinting variances were due to the maternal contribution and suggested the existence of maternally expressed genomic imprinting effects on the traits in Japanese Black cattle. Therefore, maternal gametic effects should be considered in breeding programs for Japanese Black cattle.     

Genome‐wide association study for carcass traits,fatty acid composition,chemical composition,sugar, and the effects of related candidate genes in Japanese Black cattle

We performed a genome‐wide association study (GWAS) and candidate gene analysis to: (i) evaluate the effectiveness of the GWAS in our small population by performing GWAS for carcass weight (CW) and fatty acid composition; (ii) detect novel candidate regions affecting non‐CW carcass traits, chemical composition and sugar; and (iii) evaluate the association of the candidate genes previously detected in CW and fatty acid composition with other economically important traits. A total of 574 Japanese Black cattle and 40 657 Single nucleotide polymorphisms were used. In addition, candidate gene analyses were performed to evaluate the association of three CW‐related genes and two fatty acid‐related genes with carcass traits, fatty acid composition, chemical composition and sugar. The significant regions with the candidate genes were detected for CW and fatty acid composition, and these results showed that a significant region would be detectable despite the small sample size. The novel candidate regions were detected on BTA23 for crude protein and on BTA19 for fructose. CW‐related genes associated with the rib‐eye area and fatty acid composition were identified, and fatty acid‐related genes had no relationship with other traits. Moreover, the favorable allele of CW‐related genes had an unfavorable effect on fatty acid composition.     

Estimation of genetic parameters for carcass grading traits,image analysis traits,and monounsaturated fatty acids in Japanese Black cattle from Hyogo Prefecture

Genetic parameters for carcass grading traits, image analysis traits, and monounsaturated fatty acid (MUFA) percentages were estimated in 29,942 Japanese Black cattle from Hyogo Prefecture. The analyzed traits included five carcass grading traits, two image analysis traits, fat area ratio and fineness index, and two MUFA traits, one measured in intermuscular fat using near-infrared spectroscopy (NIRS) and the other in intramuscular fat using gas chromatography (GC). The heritability estimates of image analysis traits and MUFA were moderate to high, ranging from 0.395 to 0.740, and it was considered that they could be improved simultaneously with carcass grading traits because no severe genetic antagonism was observed. Although the heritability of the NIRS-based intermuscular MUFA was slightly lower than that of the GC-based intramuscular MUFA, the genetic correlation between the two methods was as high as 0.804. These results indicate that the NIRS method can be used as an alternative evaluation procedure to predict MUFA in intramuscular fat in the longissimus muscle.     

Effects of parent‐of‐origin models with different pedigree information on beef carcass traits and fatty acid composition in Japanese Black cattle

Genomic imprinting should be considered in animal breeding systems to avoid lead in bias in genetic parameter estimation. The objective of this study was to clarify the effects of pedigree information on imprinting variances for carcass traits and fatty acid composition in Japanese Black cattle. Carcass records [carcass weight, rib eye area, rib thickness (RT), subcutaneous fat thickness and beef marbling score (BMS)] and fatty acid composition were obtained for 11,855 Japanese Black feedlot cattle. To estimate and compare the imprinting variances for the traits, two imprinting models with different pedigree information [the sire–dam gametic relationship matrix (Model 1) and the sire–maternal grandsire (MGS) numerator relationship matrix (Model 2)] were fitted. The ratio of the imprinting variance to the total additive genetic variance for RT (6.33%) and BMS (19.00%) was significant in Model 1, but only that for BMS (21.09%) was significant in Model 2. This study revealed that fitting the sire–MGS model could be useful in estimating imprinting variance under certain conditions, such as when restricted pedigree information is available. Furthermore, the present result suggested that the maternal gametic effects on BMS should be included in breeding programmes for Japanese Black cattle to avoid selection bias caused by imprinting effects.     

Effect of SCD and SREBP genotypes on fatty acid composition in adipose tissue of Japanese Black cattle herds

Fatty acid composition of beef adipose tissue is one of important traits because high proportions of monounsaturated fatty acid are related to favorable beef flavor and tenderness. In this study, we investigated effects of genetic factors such as stearoyl-CoA desaturase (SCD) and sterol regulatory element binding protein (SREBP) on beef carcass traits including fatty acid composition using two cattle populations. Sire effect was significantly related to almost all traits except BMS, suggesting that the trait examined in this study is highly controlled by genetic factors. The effect of SCD genotype on fatty acid composition was detected remarkably in both cattle groups, especially on stearic and oleic acids. This result was consistent with our previous studies and suggests that SCD is associated with fatty acid composition. Unlike SCD genotyping, the effect of SREBP genotype was not identified in this study. Our results suggested that SCD genotype would contribute to improving beef quality in field populations. Further studies about the relationship among these factors will bring an insight into the molecular mechanism of fatty acid metabolism in cattle.     

A review of genetic parameter estimates for wool, growth, meat and reproduction traits in sheep

Genetic parameters for a range of sheep production traits have been reviewed from estimates published over the last decade. Weighted means and standard errors of estimates of direct and maternal heritability, common environmental effects and the correlation between direct and maternal effects are presented for various growth, carcass and meat, wool, reproduction, disease resistance and feed intake traits. Weighted means and confidence intervals for the genetic and phenotypic correlations between these traits are also presented. A random effects model that incorporated between and within study variance components was used to obtain the weighted means and variances. The weighted mean heritability estimates for the major wool traits (clean fleece weight, fibre diameter and staple length) and all the growth traits were based on more than 20 independent estimates, with the other wool traits based on more than 10 independent estimates. The mean heritability estimates for the carcass and meat traits were based on very few estimates except for fat (27) and muscle depth (11) in live animals. There were more than 10 independent estimates of heritability for most reproduction traits and for worm resistance, but few estimates for other sheep disease traits or feed intake. The mean genetic and phenotypic correlations were based on considerably smaller numbers of independent estimates. There were a reasonable number of estimates of genetic correlations among most of the wool and growth traits, although there were few estimates for the wool quality traits and among the reproduction traits. Estimates of genetic correlations between the groups of different production traits were very sparse. The mean genetic correlations generally had wide confidence intervals reflecting the large variation between estimates and relatively small data sets (number of sires) used. More accurate estimates of genetic parameters and in particular correlations between economically important traits are required for accurate genetic evaluation and development of breeding objectives.     

Genetic relationships between temperament of calves at auction and carcass traits in Japanese Black cattle

Correlations of calves’ temperament with carcass traits were estimated to clarify the genetic relationships between them in Japanese Black cattle. The temperament records for 3128 calves during auction at a calf market were scored on a scale of 1 (calm) to 5 (nervous) as temperament score (TS ), and the TS were divided into two groups (TSG ): TS 1 and 2 comprised TSG 1, and 3 to 5 constituted TSG 2. Carcass data were obtained from 33 552 fattened cattle. A threshold animal model was used for analyzing the underlying liability for TSG , whereas a linear one was used for TS and carcass traits. The heritability estimates for TS and TSG were 0.12 and 0.11, respectively. On the other hand, moderate to high heritability estimates were obtained for carcass traits (0.40 to 0.68). The temperament scores were negatively correlated with carcass weight, rib thickness and subcutaneous fat thickness (?0.13 to ?0.59). In contrast, weak to moderate positive correlations were found between the temperament scores and rib eye area or yield estimate (0.16 to 0.45). The temperament scores and beef marbling score had no correlation. These results showed that it is possible to improve temperament and carcass traits simultaneously.     

Direct and maternal genetic relationships of lamb live weight and carcass traits in Swedish sheep breeds

Possibilities to include carcass traits recorded at commercial slaughterhouses in the genetic evaluation of sheep in Sweden were investigated by estimating direct and maternal genetic parameters for 4‐month weight (4MW), carcass weight (CW), carcass fatness grade (FAT), and carcass fleshiness (FLESH) using multiple‐trait animal models. Data included two sets of breeds, the so‐called white breeds (Swedish landrace breeds, Texel, Dorset, Oxford Down, Suffolk, East Friesian Milk Sheep, and Swedish crossbred) and the Gotland breed. There were 30 625 observations on 4MW and 5062 observations on carcass traits for the white breeds. For the Gotland breed the numbers were 43 642 and 7893, respectively. The results showed that it is feasible to use field‐recorded carcass traits in the genetic evaluation. To consider the effects of selection and to utilize all information in an optimal way multiple trait animal models should be used. Direct and maternal heritabilities for 4MW and CW varied between 0.04 and 0.18 and heritabilities for FAT and FLESH between 0.21 and 0.29. Direct and maternal genetic correlations between 4MW and CW were high (0.61–0.97). Genetic correlations were higher between the weights and FLESH (0.11–0.62) than between the weights and FAT (?0.23 to 0.40). Genetic correlations between FAT and FLESH were moderate (0.38–0.45). Heritabilities for CW were higher if 4MW was included in the analyses and the effect of selection on 4MW was stronger for CW than for FAT or FLESH. The importance of maternal effects on carcass traits was discussed.     

A genetic analysis of meat compositions in Japanese Black cattle: Genetic parameters and sex influence

Meat composition in beef is related to eating quality and food functionality. Genetic parameters for several meat compositions including free amino acid, peptide and sugar, however, remain poorly described. In this study, we estimated genetic parameters for 51 meat components, including free amino acids, peptides, sugars and fatty acid compositions, and two carcase traits in 1,354 heifers and 1,797 steers of Japanese Black cattle. Heritability estimates were generally equivalent to or moderately greater than those in previous studies of this breed. Genetic correlations between free amino acids, peptides and sugars and carcase traits were often negative, suggesting a trade‐off between traits. Using two‐trait animal models that treat records from the two sexes as different traits, we estimated sex‐specific heritabilities and cross‐sex genetic correlations which indicate the sex differences in genetic architecture. In these analyses, 12 traits showed significant heritability differences between sexes and cross‐sex genetic correlations occasionally deviated from unity. These results could be used to inform future breeding schemes and investigations of the genetic architecture of meat compositions in beef.     

基于BLUP和GBLUP方法估计北京油鸡胴体和肉质性状遗传参数的差异

旨在比较不同方法对遗传参数估计的差异,为未来北京油鸡胴体和肉质性状选育方法的制定提供参考依据。本研究利用传统最佳线性无偏预测（best linear unbiased prediction,BLUP）和基因组最佳线性无偏预测（genomic best linear unbiased prediction,GBLUP）两种方法对北京油鸡的胴体和肉质等性状进行了遗传参数估计。从系谱较为完整的北京油鸡群体中,选择100日龄体重相近的公鸡615只,测定其100日龄体重（BW）、屠宰率（EP）、胸肌率（BMP）、腿肌率（LMP）、腹脂率（AFP）、嫩度（T,以剪切力值表示）和肌内脂肪（IMF）等性状,并用SNP芯片（Illumina,60K）进行个体基因分型。结果表明,除IMF和剪切力（SF）遗传力基于两种方法的估值存在较大差异外,其余性状利用两种方法得到的遗传力估值差异较小;除嫩度外,GBLUP方法估计的遗传力均低于BLUP方法。所有胴体相关性状中,除屠宰率遗传力为低遗传力外,其余性状均属于中等遗传力性状。嫩度呈现低遗传力,而IMF基于BLUP法和GBLUP法的估计遗传力分别为中等（h² =0.256）和低遗传力（h² =0.107）。基于BLUP方法,IMF与BW、BMP和SF 3个性状间均呈高度遗传负相关（-0.572、-0.420、-0.682）,与EP的遗传相关为中度负相关（-0.234）,与AFP的遗传相关为中度正相关（0.420）;基于GBLUP方法,IMF与BW、BMP和SF 3个性状间均呈高度遗传负相关（-0.808、-0.725、-0.784）,与EP的遗传相关为高度负相关（-0.626）,与AFP的遗传相关为低度正相关（0.097）。综上,对于某些性状,基于传统的BLUP方法与新的GBLUP方法得到的遗传力与遗传相关估值存在较大差异,实际育种工作中,为提高育种效率,需要综合考虑。     

Genetic parameters for growth and carcass traits of Brahman steers

Spring-born purebred Brahman bull calves (n = 467) with known pedigrees, sired by 68 bulls in 17 private herds in Louisiana, were purchased at weaning from 1996 through 2000 to study variation in growth, carcass, and tenderness traits. After purchase, calves were processed for stocker grazing on ryegrass, fed in a south Texas feedlot, and processed in a commercial facility. Carcass data were recorded 24 h postmortem. Muscle samples and primal ribs were taken to measure calpastatin activity and shear force. An animal model was used to estimate heritability, genetic correlations, and sire EPD. Relatively high heritability estimates were found for BW at slaughter (0.59 +/- 0.16), HCW (0.57 +/- 0.15), LM area (0.50 +/- 0.16), yield grade (0.46 +/- 0.17), calpastatin enzyme activity (0.45 +/- 0.17), and carcass quality grade (0.42 +/- 0.16); moderate heritability estimates were found for hump height (0.38 +/- 0.16), marbling score (0.37 +/- 0.16), backfat thickness (0.36 +/- 0.17), feedlot ADG (0.33 +/- 0.14), 7-d shear force (0.29 +/- 0.14), and 14-d shear force (0.20 +/- 0.11); relatively low heritability estimates were found for skeletal maturity (0.10 +/- 0.10), lean maturity (0.00 +/- 0.07), and percent KPH (0.00 +/- 0.07). Most genetic correlations were between -0.50 and +0.50. Other genetic correlations were 0.74 +/- 0.27 between calpastatin activity and 7-d shear force, 0.72 +/- 0.25 between calpastatin activity and 14-d shear force, (0.90 +/- 0.30 between yield grade and 7-d shear force, and -0.82 +/- 0.27 between backfat thickness and 7-d shear force. Heritability estimates and genetic correlations for most traits were similar to estimates reported in the literature. Sire EPD ranges for carcass traits approached those reported for sires in other breeds. The magnitude of heritability estimates suggests that improvement in carcass yield, carcass quality, and consumer acceptance traits can be made within the Brahman population.     

Identification and utilization of genes associated with beef qualities

The fatty acid composition of adipose tissue in beef has been recognized as an important trait because of its relationship with beef quality, including favorable beef flavor and tenderness. Over the last decade, we have tried to identify the genes responsible for the fatty acid composition in cattle, and have found the following. (i) Genetic polymorphism of stearoyl‐CoA desaturase (SCD) is one of the responsible genes associated with fatty acid composition. The average effects of gene substitution of the SCD type A gene on the monounsaturated fatty acid (MUFA) percentage and the melting point of intramuscular fat were approximately +1.0% and ?1.0°C, respectively. (ii) Intron polymorphism of sterol regulatory element binding protein–1 (SREBP‐1) also affected MUFA. (iii) No effect of SCD or SREBP‐1 genotypes on any representative carcass traits of Japanese Black in the field population was observed. (iv) Additional genetic markers adipocytes fatty acid binding protein 4 (FABP4) and liver X receptor α also affected the fatty acid composition. (v) SCD and FABP4 significantly affected fatty acid composition in Holstein steers. These findings will bring new insight into the fat‐related carcass traits of beef cattle and will thus contribute to the beef industry.     

Heritabilities and genetic correlations of fatty acid compositions in longissimus muscle lipid with carcass traits in Japanese Black cattle

Fatty acid composition and carcass traits of 2,275 Japanese Black steers and heifers were analyzed to estimate the heritabilities and genetic correlations using the REML procedure. Slices of LM at the 6th to 7th rib section were minced and homogenized, and total lipids were extracted for the analysis by a gas chromatograph. Oleic acid accounted for the majority (51.3%), followed by palmitic (26.4%) and stearic (10.8%) acids. Heritabilities of carcass traits were moderate to high, ranging from 0.34 to 0.61, and heritabilities of individual fatty acids varied largely from 0.00 to 0.78. Those of MUFA, SFA, and PUFA were estimated to be 0.68, 0.66, and 0.47, respectively. Predicted breeding values for MUFA in 99 sires ranged from -3.0 to 5.4%. Genetic correlations of fatty acid compositions with carcass traits were generally weak (-0.28 to 0.39). Low but positive genetic correlations were obtained between beef marbling, on which emphasis of selection has been placed, and oleic acid (0.19) or MUFA (0.23). The results indicated the possibility not only for genetic improvement in fat quality traits but also simultaneous improvements with carcass traits by appropriate selection program.     

The use of foal and studbook traits in the breeding programmes of Finnhorse and Standardbred trotters

Genetic correlations for body measurements and subjectively scored traits between foals and studbook horses were estimated using bivariate linear mixed models. Observations for nine foal and eleven studbook traits in Finnhorses on 6529 foals and 6596 studbook horses and in Standardbred trotters on 3069 foals and 2112 studbook horses were available from the Finnish horse breeding shows. The number of sires with progeny in both foal and studbook data was 203 in Finnhorse and 145 in Standardbred trotters. Estimates of heritability for body measurements in foals and studbook horses using univariate models were high in both breeds (0.41-0.84). Heritability estimates for subjectively scored traits using univariate models were generally higher for foals (0.08-0.46) than for studbook horses (0.06-0.21) in both breeds. Genetic correlations between foals and studbook horses for body measurements were highly positive ranging from 0.74 to 0.96 in Finnhorses and from 0.79 to 0.99 in Standardbred trotters. Low to highly positive genetic correlations between foals and studbook horses for subjectively scored traits were obtained in Finnhorse trotters, whereas in Standardbred trotters genetic correlations for subjectively scored traits varied from moderately negative to highly positive. Higher estimates of heritability for foal traits and generally high genetic correlations between the foal and studbook traits indicate that an early selection for conformation traits would be efficient in the breeding programmes.     

Effects of genetic and environmental factors on muscle glycogen content in Japanese Black cattle

Monosaccharides such as glucose contribute to the development of meat flavor upon heating via the Maillard reaction; therefore, monosaccharide content is related to beef palatability. Here, we analyzed the effects of genetic and environmental factors on the content of glycogen, one of the precursors of monosaccharides, in the muscles of 958 fattened Japanese Black cattle from Yamagata Prefecture. Analysis of variance showed that muscle glycogen content was affected by the farm and postmortem periods, but not by sex, slaughter age, slaughter month or number of days detained at the slaughter yard. Additionally, consumption of digestible brown rice feed elevated muscle glycogen levels. Glycogen heritability was estimated to be 0.34, and genetic correlations between glycogen and carcass weight (CW) or beef marbling standard (BMS) were weak. The predicted breeding values varied among paternal lines. These results demonstrated that genetic factors might improve muscle glycogen content and therefore beef palatability, but do not influence CW or BMS.     

Genetic parameters for carcass and meat quality traits and their relationships to liveweight and wool production in hogget Merino rams.

Genetic parameters for carcass and meat quality traits of about 18-month-old Merino rams (n = 5870), the progeny of 543 sires from three research resource flocks, were estimated. The estimates of heritability for hot carcass weight (HCW) and the various fat and muscle dimension measurements were moderate and ranged from 0.20 to 0.37. The brightness of meat (colour L*, 0.18 +/- 0.03 standard error) and meat pH (0.22 +/- 0.03) also had moderate estimates of heritability, although meat relative redness (colour a*, 0.10 +/- 0.03) and relative yellowness (colour b*, 0.10 +/- 0.03) were lower. Heritability estimates for live weights were moderate and ranged from 0.29 to 0.41 with significant permanent maternal environmental effects (0.13 to 0.10). The heritability estimates for the hogget wool traits were moderate to high and ranged from 0.27 to 0.60. The ultrasound measurements of fat depth (FATUS) and eye muscle depth (EMDUS) on live animals were highly genetically correlated with the corresponding carcass measurements (0.69 +/- 0.09 FATC and 0.77 +/- 0.07 EMD). Carcass tissue depth (FATGR) had moderate to low genetic correlations with carcass muscle measurements [0.18 +/- 0.10 EMD and 0.05 +/- 0.10 eye muscle area (EMA)], while those with FATC were negative. The genetic correlation between EMD and eye muscle width (EMW) was 0.41 +/- 0.08, while EMA was highly correlated with EMD (0.89 +/- 0.0) and EMW (0.78 +/- 0.04). The genetic correlations for muscle colour with muscle measurements were moderately negative, while those with fat measurements were close to zero. Meat pH was positively correlated with muscle measurements (0.14 to 0.17) and negatively correlated with fat measurements (-0.06 to -0.18). EMDUS also showed a similar pattern of correlations to EMD with meat quality indicator traits, although FATUS had positive correlations with these traits which were generally smaller than their standard error. The genetic correlations among the meat colour traits were high and positive while those with meat pH were high and negative, which were all in the favourable direction. Generally, phenotypic correlations were similar or slightly lower than the corresponding genetic correlations. There were generally small to moderate negative genetic correlations between clean fleece weight (CFW) and carcass fat traits while those with muscle traits were close to zero. As the Merino is already a relatively lean breed, this implies that particular attention should be given to this relationship in Merino breeding programmes to prevent the reduction of fat reserves as a correlated response to selection for increased fleece weight. The ultrasound scan traits generally showed a similar pattern to the corresponding carcass fat and muscle traits. There was a small unfavourable genetic correlation between CFW and meat pH (0.19 +/- 0.07).     

Genetic correlation estimates between ultrasound measurements on yearling bulls and carcass measurements on finished steers.

Carcass and growth measurements of finished crossbred steers (n = 843) and yearling ultrasound and growth measurements of purebred bulls (n = 5,654) of 11 breeds were analyzed to estimate genetic parameters. Multiple-trait restricted maximum likelihood (REML) was used to estimate heritabilities and genetic correlations between finished steer carcass measurements and yearling bull ultrasound measurements. Separate analyses were conducted to examine the effect of adjustment to three different end points: age, backfat thickness, and weight at measurement. Age-constant heritability estimates from finished steer measurements of hot carcass weight, carcass longissimus muscle area, carcass marbling score, carcass backfat, and average daily feedlot gain were 0.47, 0.45, 0.35, 0.41, and 0.30, respectively. Age-constant heritability estimates from yearling bull measurements of ultrasound longissimus muscle area, ultrasound percentage of intramuscular fat, ultrasound backfat, and average daily postweaning gain were 0.48, 0.23, 0.52, and 0.46, respectively. Similar estimates were found for backfat and weight-constant traits. Age-constant genetic correlation estimates between steer carcass longissimus muscle area and bull ultrasound longissimus muscle area, steer carcass backfat and bull ultrasound backfat, steer carcass marbling and bull ultrasound intramuscular fat, and steer average daily gain and bull average daily gain were 0.66, 0.88, 0.80, and 0.72, respectively. The strong, positive genetic correlation estimates between bull ultrasound measurements and corresponding steer carcass measurements suggest that genetic improvement for steer carcass traits can be achieved by using yearling bull ultrasound measurements as selection criteria.     

Estimation of the marbling development pattern in Japanese Black cattle by using serial ultrasound measurement data

The objective of this study was to develop mathematical equations for describing the change in marbling in Japanese Black steers using longitudinal measurements. Serial ultrasound measurements were taken at 14, 16, 20, and 26 months of age and analyzed using an image analysis software. The longitudinal marbling measurements from the ultrasound images and carcasses were fitted into a nonlinear logistic curve. Data used for the analysis consisted of 749 steers that converged in nonlinear curve fitting and showed reasonable estimated parameters of the logistic curves. The average predicted mature beef marbling score (BMS) and maturation rate were 6.26 and 0.353, respectively, and the average maturity levels at 24 months of age were 83.9%. The heritability estimates for the predicted maturity traits were moderate, indicating that these traits may have potential for genetic improvement. There was a negative relationship between the expected progeny differences between carcass BMS and maturity traits, suggesting that genetic improvement by carcass BMS may lead to the selection of bulls with late maturity for marbling. The results indicate that ultrasound and model building for marbling can be useful tools to correctly select candidate bulls with high marbling in the early fattening period.