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A survey was carried out to propose models of growth curves in Belgian Blue cattle less than 20 months of age and raised in commercial farms in southern Belgium. Live weight data were recorded between 1993 and 1999 from 1104 breeding heifers, and 924 growing males. The linear, polynomial group, power, logistic, Brody, Gompertz, von Bertalanffy and Richards models were used and compared. A step-wise linear growth model characterized by two periods of linear growth was also evaluated. This last model has been proposed as the reference model to characterize the growth curves of Belgian Blue cattle less than 20 months old. The animals were then ranked and divided in subgroups based on percentiles and quartiles in order to compare their performances. The subgroups performing better presented a greater homogeneity. The males ranked above the 90th percentile presented a growth rate comparable to that of young males selected for artificial insemination. Cattle ranked above the third quartile presented a growth rate comparable to that of licensed animals. When reproduction performances were related to the growth rate, it appeared that the better growing heifers were bred younger and heavier than lesser performing animals.

In Belgium, both dairy and beef cattle are managed intensively. Three commercial farms owning both a Belgian Blue —double muscled type- suckler beef herd and a Holstein-Friesian dairy herd were surveyed between 1994 and 1998. The aim of the study was to compare growth and reproduction performances of both breeds in a similar farm environment. The replacement heifers of both breeds were kept together until advanced pregnancy. Reproduction data were collected monthly from heifers older than fourteen months. The live weight of the replacement heifers was recorded quarterly until 20 months of age. Breed influenced the growth of replacement heifers at 6, 9 and 12 months (P < 0.001). The growth rate of Belgian Blue heifers was reduced after the age of one year and the live weight difference between breeds was not significant anymore. Belgian Blue heifers were always heavier than Holstein-Friesian heifers. Successfully bred heifers had a greater growth rate than non successfully bred heifers within the Belgian Blue breed. This was significant for the weight at 6 months (P < 0.05) and at 12 months (P < 0.05). Such an effect was not detected for the Holstein-Friesian breed (P > 0.05). Weight was not a limiting factor for fecundity of the Holstein-Friesian heifers. Management policies other than growth performance explained the difference between optimal fecundity and the fecundity index met in this study. Non successfully bred Belgian Blue heifers were lighter than successfully bred animals. Unsufficient weight performance had an impact on fecundity in that breed.

The systematic use of Caesarean section in "double muscled" Belgian Blue cattle can induce ethical concerns. The aims of the following study was to characterise mother-young relationships in such a situation and to assess the effect of parity. Fifteen heifers and 15 cows of the Belgian Blue breed were observed using video recording when isolated with their calf during the 3 days following Caesarean, a rapid surgery with rare occurrence of aggressive behaviour and no sign of cows' discomfort or weakness. All calves were bottle-fed mother's colostrum once before first suckling occurred. Heifers' calves received a supplementary number of three such artificial meals, while cows' calves needed only one. The overall median time to first licking of the calf by the mother was 3.3min without any effect of parity. The mean licking frequency was 29.2+/-15.8 per 24h: heifers licked their calf less frequently than cows, respectively 23.4+/-15.3 per 24h versus 35.1+/-14.5 per 24h (P

Energy and protein requirements were determined for Belgian Blue double-muscled (BB dm) bulls based on the results of two feeding trials and a trial with serial slaughtering. The results of the serial slaughter experiment allowed calculation of chemical composition and energy content of the empty body, as well as protein and energy deposition at various live weights between 350 and 650 kg. Protein requirements were calculated based on the protein requirements for maintenance, the protein mass accreted and the efficiency of protein accretion. Efficiency of protein deposition (g protein accretion/g protein intake for accretion) was derived from the feeding experiments based on marginal protein levels; it decreased from 0.53 to 0.44 with increasing live weight. Energy requirements were also derived from the same database. Net energy for maintenance was estimated, with these animals that received an optimum energy/protein ratio, by subtracting the net energy retained from the net energy intake. Requirements were then determined by summation of the energy requirements for maintenance and the energy requirements for accretion. Conclusively, energy and protein requirements were determined for BB dm bulls for live weights from 350 to 650 kg and for different growth rates. As such, surpluses of energy and protein that BB dm animals require compared to other beef breeds, were quantified.

Compositional data of 17 Belgian Blue double-muscled bulls with empty body weight between 276 and 669 kg were analysed. Body composition only changed slowly and linearly within the investigated live weight range. Water, protein, fat and ash in the empty body varied between 65.8 and 72.0%, 18.9 and 21.2%, 3.5 and 9.7% and 3.0 and 4.% respectively. The chemical fat con- tent in the empty body was remarkably low. The percentage of accreted energy as protein always remained higher than 50% of the total accreted energy, which is much higher than generally reported in literature. Caloric values for protein and fat were: 22.91 (± 0.90) MJ .kg -1 and 38.74 (± 1.53) MJ.kg -1 respectively. Carcass protein contained on average (in %) 8.8 Asp, 15.6 Glu, 5.3 Pro, 7.7 Gly, 6.6 Ala, 7.5 Leu, 7.4 Lys and 6.5 Arg, while the protein in the non-carcass parts contained (in %) 8.0 Asp, 12.7 Glu, 8.8 Pro, 15.1 Gly, 8.0 Ala, 6.6 Leu, 5.6 Lys and 7.2 Arg. The protein composition proved to be rather constant for the considered live weight range. double-muscling / body composition / bulls / Belgian Blue breed

Information concerning 493 single calvings of the double-muscled beef cow herd of the institute was collected to investigate the relationship between the characteristics of dams and calves with regard to dystocia. Factors affecting dystocia are similar in double-muscled cattle to those in non-double-muscled cattle but the occurrence of dystocia is greatly increased in double-muscled cows. Incidence of caesarean section was significantly correlated with parity (–0·243), age of dam (–0·232), post-partum dam weight (–0·185), and calf birth weight (0·164). Caesarean deliveries were required for 89·5% of the parturitions. Calvings without caesarean section were characterized by higher means for post-partum dam live weight (634·7 kg), age (1675·5 days), parity (3·1) and the ratio of post-partum dam weight to calf birth weight (14·4), compared with 580·2 kg, 1251·1 days, 2·1, and 11·8, respectively for births with caesarean setion, while calf birth weight was lower in non-caesarean calvings (45·8 v. 49·9 kg). Caesarean births involved more male calves than females (55 v. 45%). Even when calf birth weight was 30 kg or lower, and also in multiparous cows, 40 and 86% of the deliveries, respectively, still occurred with a caesarean section.Incidence of caesarean section could not be accurately predicted from pre-partum characteristics such as pre-partum dam weight, age and parity.

Knowledge of major gene effects for quantitative traits (e.g. milk performance traits) and the consequent selection of animals with desirable genotypes can accelerate breeding progress and can therefore equal large gain in profits. It is generally accepted that in most cases, the total breeding value for quantitative traits of any animal can be divided in one or some major gene effects and a pure random polygenic component, in which the latter results from a finite number of remaining loci (FERNANDO et al. 1994). Thus, the aim of this study was to investigate, how the estimation of heritability is influenced by the application of two different models, one of them containing a major single gene effect. The myostatin gene (MSTN) was chosen because the knowledge of this gene effect is used for selection decisions in the Dual Purpose Belgian Blue Breed (DP-BBB) in the Walloon Region of Belgium.

The effect of crossing of Black and White (BW) cows with Charolais (CHA), Limousin (LIM) and Belgian Blue (BB) sires on carcass traits of their crossbred male offspring was evaluated. The crossbred bulls were compared with pure breed BW, CHA and LIM bulls. Bulls younger than 24 months and slaughtered in Slovenian slaughterhouses from 2005 to 2008 were included in the comparison. All crossbred genotypes had heavier carcass weight and better net daily gain than pure breed BW bulls. Within crossbred groups the CHAxBW bulls had the heaviest carcasses and the greatest net daily gain. Among all genotypes the best carcass conformation had CHA and the worst BW bulls. In the comparison to pure breeds the BBxBW bulls had for 1.1 of the class better conformation than BW and for 0.5 worse than CHA bulls. Within crossbreeds the BBxBW bulls had for 0.12 and 0.30 of the class better conformation than CHAxBW and LIMxBW bulls. Carcass fatness varied from 2.3 to 2.6 among genotypes, where the BBxBW buls had the lowest fatness score.

peer-reviewed Financial support of the Irish Department of Agriculture Research Stimulus Fund (RSF-06-0353; RSF-06-0428; 11/SF/311), Science Foundation Ireland (09/IN.1/B2642) and the Irish dairy and beef industry are gratefully acknowledged. The objective of this study was to evaluate, using three different genotype density panels, the accuracy of imputation from lower- to higher-density genotypes in dairy and beef cattle. High-density genotypes consisting of 777 962 single-nucleotide polymorphisms (SNP) were available on 3122 animals comprised of 269, 196, 710, 234, 719, 730 and 264 Angus, Belgian Blue, Charolais, Hereford, Holstein-Friesian, Limousin and Simmental bulls, respectively. Three different genotype densities were generated: low density (LD; 6501 autosomal SNPs), medium density (50K; 47 770 autosomal SNPs) and high density (HD; 735 151 autosomal SNPs). Imputation from lower- to higher-density genotype platforms was undertaken within and across breeds exploiting population-wide linkage disequilibrium. The mean allele concordance rate per breed from LD to HD when undertaken using a single breed or multiple breed reference population varied from 0.956 to 0.974 and from 0.947 to 0.967, respectively. The mean allele concordance rate per breed from 50K to HD when undertaken using a single breed or multiple breed reference population varied from 0.987 to 0.994 and from 0.987 to 0.993, respectively. The accuracy of imputation was generally greater when the reference population was solely comprised of the breed to be imputed compared to when the reference population comprised of multiple breeds, although the impact Department of Agriculture, Food and the Marine Science Foundation Ireland

Work on Belgian Blue cattle revealed that an 11 base pair (bp) deletion within the bovine myostatin gene (GDF8) is associated with the double-muscled phenotype seen in this breed. Investigations focusing on other European breeds known to show double-muscling identified several mutations within the coding region of the gene associated with the double-muscled phenotype in different breeds. The number of mutations found suggest that myostatin is highly variable within beef cattle. Variations that alter the structure of the gene product such that the protein is inactivated are associated with the most pronounced form of double-muscling as seen in the Belgian Blue. However, other mutations may have a less extreme affect on muscle development. While overt double-muscling gives rise to a high incidence of dystocia (calving difficulty), it is possible that some variants may give enhanced muscling, but with limited calving problems. We describe sequence analysis of the myostatin gene in ten beef breeds commonly used in the UK and show that the 11-bp deletion responsible for double-muscling in the Belgian Blue is also present in the South Devon cattle population. Allele frequencies and haplotypes in the South Devon and a polymerase chain reaction (PCR) based test for the deletion are described. PCR amplification across the deleted region provides a quick and effective test with clear identification of heterozygous individuals. We discuss our results with regard to the effect of genotype on phenotype and differences observed between the Belgian Blue and the South Devon.

Urinary creatinine excretion (UCE) and chemical body composition of 18 Belgian Blue double-muscled bulls were determined. Partly due to the large fasted live weight (fLW) range (308-710 kg), kg water and protein in the empty body were quite accurately predicted (adjR 2 = 0.94 and 0.97) by UCE. The precision of the prediction of kg empty body fat was less good (adjR 2 = 0.77). However, the empty body composition of the bulls varied only slightly and linearly with increa- sing live weight so that the fLW was the best parameter to estimate empty body water and protein with an adjR 2 value of 0.99 for both. The empty body fat was estimated from fLW with an adjR 2 = 0.75. The equations predicting relative body composition from UCE had much smaller adjR 2 values, varying from 0.53 for % empty body water to 0.30 for % empty body protein. However, the coeffi- cients of variation were much smaller. The prediction of the relative composition based on UCE was always somewhat better than based on fLW, but the improvement was not enough to justify the work involved in determining UCE. Conclusively, due to the small compositional changes, UCE did not significantly improve the estimation of the body composition from fLW. From the compari- son of the results with other studies, it can be concluded that the double-muscled bulls have an extre- mely high urinary creatinine concentration, which cannot entirely be explained by their increased protein content.

An experiment was conducted to study effects of dietary vitamin E supplementation on animal performance, slaughter characteristics and meat quality traits in Belgian Blue double-muscled bulls. Two groups of six bulls each were offered (close to ad libitum) a fattening diet based on sugar beet pulp for 154 days, at which time they were slaughtered. The diet given to the control group (CG) contained 12.5 mg vitamin E / kg concentrate. The vitamin E-treated group (VG) received the same concentrate plus a supplement of 1000 mg vitamin E per bull daily. Steaks from m. longissimus thoracis were used to determine meat quality characteristics, alpha tocopherol concentration and thiobarbituric acid reactive substances content (TBARS), an indicator of oxidation rancidity. Supplementation had no influence on animal performance or carcass characteristics. The main findings were that vitamin E doubled the muscle alpha tocopherol level (1.9 vs. 0.9 mg / kg; P , 0.001), lipid oxidation was suppressed as indicated by TBARS values (P , 0.01 at days 7, 9, 11 and 14 after slaughter), but muscle colour was not significantly affected although a* (redness) tended to be higher for VG. © 2000 Elsevier Science B.V. All rights reserved.

Summary Urea infusions were performed on 18 Belgian blue double-muscled bulls, ranging from 308 to 710kg live weight after a fasting period of 16 h. Urea space (US) was determined from the difference in plasma urea concentration between samples taken before and 12, 18 and 24min after mean infusion time. The day after infusion, the bulls were slaughtered and subsequently the body composition was determined. Kg empty body water and empty body protein were quite accurately predicted by US. The precision of the prediction of kg empty body fat was less accurate. However, due to the large live weight interval and the small compositional variation, the fasted live weight (fLW) was a better parameter to estimate the weight of the body components. Prediction of relative body composition (as a percentage) instead of absolute (in kg) improved the standard error of the predictions. In estimating relative body composition, US has proven to be somewhat better than fLW, but the extra precision from using urea infusion was not large enough to justify the extra work of the infusion. The time for equilibration of the urea in the water compartment was obviously longer in this study than in others, presumably due to the lower capillary density of the Belgian blue double-muscled animals.

Adipose tissues from the 12th and 13th rib interface were sampled at weaning (324 cattle) and slaughter (310 cattle). The animals were progeny from Hereford dams sired by Angus, Belgian Blue, Hereford, Jersey, Limousin, South Devon and Wagyu. Fatty acid composition of the triacylglycerol fraction at both stages was measured by gas-liquid chromatography. Estimates of heritability and genetic and phenotypic correlations at weaning and slaughter were computed by restricted maximum likelihood using a sire model in both univariate and multivariate analyses. Results indicated that generally, there were strong, positive genetic correlations between fatty acids at weaning and slaughter (as high as 0.98). Phenotypic correlations were however, low and poor (0.04 to 0.44). Heritability (h2) estimates at weaning were low to moderate, ranging from 0.0 to 0.31. However, at slaughter, h2 estimates were generally higher than at weaning: Stearate, oleate and total monounsaturates had h2 estimates of 0.43, 0.37 and 0.40, respectively. Other carcass traits such as marbling score and melting point of fat had h2 estimates of 0.20 and 0.52, respectively. Significant breed, sex and location differences in fatty acid composition were also observed at weaning and slaughter.

Fatty acid composition, marbling score and melting point data collected between 1994 and 1996 were analysed. The data were from the adipose tissue of 764 Angus, Belgian Blue, Hereford, Jersey, Limousin, South Devon and Wagyu crossbred cattle slaughtered after lot-feeding at 500 days of age. The aim was to investigate sire-breed differences and to estimate heritability and genetic and phenotypic correlations. Significant breed differences were found: Jersey crosses had the highest marbling score and Belgian Blue crosses had the lowest. Limousin crosses had the highest melting point and Jersey crosses the lowest. South Devon crosses had the highest proportion of stearate and Jersey crosses the lowest. Desaturation indices in C16 and C18 fatty acids were highest in Jersey crosses and lowest in Limousin and South Devon crosses. In contrast, there were no breed differences in the proportions of palmitate, oleate, total saturated, total mono-unsaturated fatty acids and elongation index. Heritability estimates of individual fatty acids and their summations, melting point and marbling were low to moderately low (0.05 to 0.27). Strong genetic correlations of melting point and desaturation index in C16 fatty acids (-0.93), melting point and stearate (0.62), marbling and stearate (-0.71) and marbling and desaturation index in C18 fatty acids (0.62) were observed. Phenotypic correlation were generally low. The results imply that fatty acids in the adipose tissue of lot-fed cattle have a moderately low heritability, hence genetic progress might be slow.

The objectives of this study were to evaluate the effect of feed restriction and re-alimentation on the onset of puberty and IGF status in peripubertal male calves and to compare the radioimmunoassay (RIA) and western ligand blotting (WLB) methods for bovine IGFBP-2. Twelve prepubertal 290 d-old Belgian Blue bulls (mean weight: +/- 290 kg) were randomly assigned in three groups: a control group (NG; n = 4) receiving a classic fattening diet to induce "normal" growth (1.48 kg/d), a feed restricted group (RG; n = 4) to obtain reduced growth (0.50 kg/d) and, a severely restricted group (SG; n = 4) to nearly stop growth (0.08 kg/d). The feed restriction period was maintained over a period of 114 d. After the period of differential feeding, all animals received the control feed regime over a period of 100 d. Blood samples were collected at fortnightly intervals. Circulating IGF-I was measured by RIA whereas plasma IGFBPs was evaluated by WLB; IGFBP-2 was additionally quantified by RIA procedure. At the beginning of the trial, IGF-I levels were low (

Congenital vascular tumors of the skin have been described in people and a few animals, but unlike infantile hemangiomas in children, spontaneous regression has not been described in animals. A 2-day-old male Belgian Blue cross calf was presented for multiple congenital cutaneous masses that were soft, alopecic, and hyperemic; the calf had no other apparent abnormalities. Two weeks later, one mass had regressed. Surgical excision of one of the remaining masses was performed; histopathologic and immunohistochemical findings were considered diagnostic for epithelioid hemangioma. Eight months following initial presentation, all the masses had regressed spontaneously. This constitutes the first account in the veterinary literature of spontaneous regression in a congenital vascular tumor.

A Principal Component Analysis (PCA) was conducted on the matrix of correlations among P8 fat measures at seven different ages for steers and heifers. The P8 fat measures were collected from 1143 steers and heifer calves that were born to Hereford (h) dams inseminated with semen from seven different sire breeds: Angus, Belgian Blue, Hereford, Jersey, Limousin, South Devon and Wagyu, over a 4-year period (1994 to 1997). The first two principal components explained 61 and 57% of the total phenotypic variation in fatness for steers and heifers, respectively. The first component was positively correlated to all measures and was interpreted as a measure of overall fatness. The second component was positively correlated to fatness approximately pre-weaning and negatively correlated thereafter and thus was interpreted as maturity type but could be a function of milk supply. When estimated from a sire model, the heritability estimates were high for the first component (0.59 and 0.67 for steers and heifers, respectively) but low for the second component (0.05 and 0.19). The results demonstrate the value of combining information across multiple measurements to build accuracy, even when relatively crude methods are used.

Fifty double-muscled Belgian Blue bulls were divided into five groups. The first group (control, CG) was given, on an ad libitum basis, a fattening diet based on sugar-beet pulp. In G2 and G3, fattening was interrupted 103 and 187 days, respectively after the beginning of the experiment, by approximately a 2-month period of food restriction during which the animals received a maintenance ration. The last two groups, namely G4 and G5, received for about 4 months a limited amount of the restriction diet to support growth of 0·5 and 0 kg/day, respectively, before being fattened as CG. The average daily gain was 1·48 kg/day in CG v. 1·33, 1·30, 1·43 and 1·61 kg/day during the period of ad libitum feeding in G2, G3, G4 and G5. Higher nitrogen (N) balance during compensatory growth in G2, G4 and G5 (78·8, 81·0 and 74·6 v. 53·3 g N per day in CG, P < 0·001) resulted mainly from a higher efficiency of N retention. In G3, however, compensatory growth was characterized by lower N digestibility and efficiency of N retention. Muscle proportion in the carcass was higher in G3 while fat plus connective tissue proportion was lower (P < 0·05). Muscle pH values in CG were lower than in the other groups (P < 0·01) but ether extract values were higher. The intramuscular fat of G2 and G3 was characterized by higher proportions of polyunsaturated fatty acids.

The enlarged muscles of certain breeds of cattle, such as the Belgian Blue, have been shown to result from a marked increase in the number of normal sized muscle fibers. Originally insulin-like growth factors (IGFs) were implicated in this myofiber hyperplasia, as IGFs have been shown to stimulate myoblast proliferation as well as maintain fiber differentiation. Recently it has been reported that mice lacking a myostatin gene, a member of the TGFbeta superfamily, have enhanced skeletal mass resulting from increased muscle fiber number and size. Mutations in this gene have been found in double-muscled cattle, indicating that myostatin is an inhibitor of muscle growth. Myostatin is expressed early in gestation and then maintained to adulthood in certain muscles. Myostatin expression in bovine muscle is highest during gestation when muscle fibers are forming and some of the myogenic regulatory factors have elevated expression over the same period as myostatin. Molecular expression of the IGF axis does not differ between Belgian Blue and normal muscled cattle, and IGF-II mRNA is increased throughout formation of secondary fibers in both breeds. However, myostatin and MyoD expression in muscle differ between normal and hypertrophied muscle cattle breeds. This evidence strongly suggests that lack of myostatin is associated with an increase in fiber number which then results in a marked increase in potential muscle mass in double-muscled cattle.

Eighty-nine calves born of dams from British (50% Hereford and 50% Red Angus) and Continental (50% Simmental and 50% Maine Anjou) breeds crossed with Charolais (CH), Belgian Blue (BB) and Piedmontese (PM) sires were used to evaluate the productivity of using double-muscled cattle in terminal crosses. Breed of sire did not exert a significant effect on any parameter measured before weaning. Calving difficulty was related to breed of dam, being higher in British than in Continental dams (P

To optimize performance and carcass quality of Belgian Blue double-muscled bulls four phased feeding regimens were evaluated. All diets were offered ad libitum and consisted of 650 g concentrates and 350 g maize silage per kg dry matter (DM). Total period was divided into three phases (ca. 360 to 460, 460 to 570 and 570 to 680 kg). All four groups received the same maize silage but the different energy and protein densities were applied using different concentrates. During the three phases, the negative control (NC) group constantly received a diet with a low protein and a moderate energy density; the second group (DP) received with each phase diets with decreasing protein density while the energy density remained moderate; the third group (IE) received diets with increasing energy density at a constantly high protein density and the last group (DPIE) received diets which decreased in protein and increased in energy density. The NC group grew significantly slower during the first interval (1·37 v. 1·62 kg/day for the other groups), resulting in a significantly longer total finishing period. During the third period IE had the slowest growth. The NC group needed 21 and 20 days more than the DP and DPIE groups, respectively, to reach the same slaughter weight. The NC group had the lowest DM intake during the first interval, the IE group during the third interval. No significant differences (P > 0·05) were found for food conversion, when expressed as DM or NEF (net energy for fattening). IE had the worst protein conversion while NC had the best, with the two other groups being intermediate. The only important significant difference concerning carcass quality was the improved dressing proportion of the IE and DP groups. Although significant, differences in the fat content of the m. longissimus thoracis are of minor importance. These results proved that for Belgian Blue double-muscled bulls, protein density of the diet can be decreased with increasing live weight, while energy should be increased to give optimal performance.

Measurements of conformation and pelvic characteristics of pedigree Belgian Blue cows were compared in cattle from 11 herds. In seven herds comprising 56 cows caesarean sections were routinely used to deliver pedigree calves and in four herds comprising 52 cows they were given the opportunity to calve naturally per vaginum. Cows in the seven herds were approximately 10 months younger than those in the other herds. External pelvic measurements were linear distances between the tuber coxae, between the tuber coxarum and the tuber ischium, between the tuber ischii, the vertical distance between the underside of the tail and the tuber ischii, and heights of the tuber coxae and tuber ischii from the floor. Internal pelvic measurements were the vertical distance between the ventral body of the sacrum and the pubic symphysis and the horizontal distance between the wings of the ileum at the widest point of the pelvic inlet, both made with a Rice pelvimeter. Condition scores were assessed for all cows. There were correlations (P < 0·001) between internal pelvic height and width, external measurements, and age. For cattle that calved unassisted, pelvic height (P < 0·05) and area (P < 0·05) were significantly larger than those delivered by elective caesarean section. From internal pelvic measurements of 74 cows, those which always delivered live calves had a larger pelvic area (P < 0·01) than cows that delivered a dead foetus following any parturition.

Myostatin is a secreted growth and differentiating factor (GDF-8) that belongs to the transforming growth factor-beta (TGF-β) superfamily. Targeted disruption of the myostatin gene in mice and a mutation in the third exon of the myostatin gene in double-muscled Belgian Blue cattle breed result in skeletal muscle hyperplasia. Hence, myostatin has been shown to be involved in the regulation of skeletal muscle mass in both mice and cattle. Previous published reports utilizing Northern hybridization had shown that myostatin expression was seen exclusively in skeletal muscle. A significantly lower level of myostatin mRNA was also reported in adipose tissue. Using a sensitive reverse transcription-polymerase chain reaction (RT-PCR) technique and Western blotting with anti-myostatin antibodies, we show that myostatin mRNA and protein are not restricted to skeletal muscle. We also show that myostatin expression is detected in the muscle of both fetal and adult hearts. Sequence analysis reveals that the Belgian Blue heart myostatin cDNA sequence contains an 11 nucleotide deletion in the third exon that causes a frameshift that eliminates virtually all of the mature, active region of the protein. Anti-myostatin immunostaining on heart sections also demonstrates that myostatin protein is localized in Purkinje fibers and cardiomyocytes in heart tissue. Furthermore, following myocardial infarction, myostatin expression is upregulated in the cardiomyocytes surrounding the infarct area. Given that myostatin is expressed in fetal and adult hearts and that myostatin expression is upregulated in cardiomyocytes after the infarction, myostatin could play an important role in cardiac development and physiology. J. Cell. Physiol. 180:1–9, 1999. © 1999 Wiley-Liss, Inc.

A total of 125 non-double-muscled Belgian Blue finishing bulls (liveweight range 375-620 kg) were used to investigate the effect of different levels of degraded protein balance in the rumen (OEB) -2, -7, -16 and -22 g/kg DM on animal performance, with the dietary content of true protein digested in the small intestine (DVE) fixed at 80 g/kg. Lower OEB levels significantly reduced daily liveweight gain from 1.57 to 1.39 kg during the first 84 days of the experiment, but not during the subsequent part. For the whole experiment, daily liveweight gain decreased from 1.40 to 1.32 kg but the difference was not significant. Intake of DM, DVE and NE for finishing was not modified by OEB level, while CP intake was reduced and OEB deficit was increased. An OEB level of -22 g/kg DM resulted in a significantly unfavourable conversion of DM and NE during the initial months (11.3 and 11.5% compared with OEB = -2 g/kg DM, respectively). For the total period the conversion of DM and NE was still less favourable, but the differences were not significant. There was a nominal decrease in cold carcass weight and dressing percentage when OEB level decreased, but the effect was not significant. The effect of different OEB levels on digestibility and rumen fermentation was investigated in a separate experiment with wethers. Apparent protein digestibility was reduced from 74.2 to 68.9% when OEB level decreased. Rumen pH and concentrations and molar percentages of volatile fatty acids were not altered by OEB level. Ammonia concentration was only reduced by a lower OEB level at 7 h after feeding. Because of a nominal reduction in daily liveweight gain, feed efficiency, carcass weight, dressing percentage and carcass conformation with decreasing OEB level, it is advisable not to feed less than -16 g OEB/kg DM in diets with 80 g DVE/kg DM to Belgian Blue non-double-muscled finishing bulls from 375 kg onwards. This tolerable OEB deficit is larger than proposed to avoid protein overfeeding.

Properties of the non-carcass parts in combination with empty body and half carcass weight (EBW and CCW; kg) were used to generate equations for predicting empty body chemical composition. Therefore, chemical composition of the non-carcass parts and weight of the depot fatty tissues were determined on 18 Belgian Blue double-muscled fattening bulls. Very high coefficients of determination (R2) were found between the empty body composition and on the one hand the non-carcass parts composition and on the other hand the weight of the fatty tissues. Fat in the empty body was most difficult to predict. The very high coefficients of determination are partly caused by the large variation in slaughter weight (309 to 723 kg). Therefore equations to estimate proportional composition of the empty body are discussed. Although R2 values are strongly reduced, residual standard deviations remain very low and the precision of prediction is good. The proportion of protein is most difficult to predict, as it shows a very small variation. Estimations based on composition of the non-carcass parts are mostly a little more precise than the estimates based on weight of the fatty tissues but as the latter are much easier to determine, these equations will be more appropriate for practical use. Similarly the little improvement of the estimation based on EBW instead of CCW, cannot account for the extra costs and time to determine EBW. The results of the homogenizations have proven that there is very little variation in composition, despite the large range in slaughter weight. As the Belgian Blue double-muscled animals are very deviant from other breeds, the equations found in this study can only be applied for this breed type.

Characteristics from the 8th rib cut: chemical composition, tissue composition after dissection, specific gravity (SG) and m. longissimus thoracis (LT) composition, collected on 17 Belgian Blue double-muscled fattening bulls were used to generate equations for predicting chemical carcass composition. Carcass composition was best predicted from chemical analysis of the 8th rib cut and the empty body weight (EBW) of the bull. Carcass chemical fat content (CCF, kg) was predicted from the 8th rib cut fat content (ether extract, 8RF, kg) by the following regression: CCF=1.94+27.37 8RF (R2=0.957, RSD =9.89%). A higher coefficient was found for carcass water (CCW, kg) predicted from 8RF and EBW: CCW=−2.26+0.28 EBW-34.28 8RF (R2=0.997, RSD=1.48%). No parameter was found to improve the prediction of CCP from EBW solely: CCP=−0.86+0.08 EBW (R2 =0.992, RSD=2.61%). Prediction equations based solely on LT composition had low R2 values of between 0.38 and 0.67, whereas no significant equations were found using SG. However, equations based on EBW had R2 values between 0.78 and 0.99. Chemical components of the 8th rib cut in combination with EBW are most useful in predicting the chemical composition of the carcass of Belgian-Blue double-muscled bulls.

Nitrogen balance and myofibrillar protein breakdown were studied in 16 double-muscled Belgian Blue bulls during a low growth period (0.5 kg d−1) (LGP) of 4 mo (L4), 8 mo (L8), or 14 mo (L14) and the subsequent fattening period (rapid growth period, RGP). The control group (CG) was given a conventional fattening diet; the others received a low-energy, low-protein diet during LGP, and the same diet as the CG during RGP. Measurements were made halfway through the LGP, l mo after the beginning of the fattening period, and 1 mo before slaughter. Nitrogen balance was about half of CG (P −1, for CG, L4, L8, and L14, respectively. Between LGP and RGP, N balance increased by about 18 g N d−1 above the control in the compensating groups L4, L8 and L14. This was due to the higher digestibility and the higher metabolizability of the nitrogen in the fattening diet. Lower muscle protein accretion during the LGP resulted from decreased synthesis (P

A comparison was made between fattening systems with Belgian Blue bulls of the double-muscle type, in order to assess the reponse in terms of compensatory growth when the bulls were grazed at a high stocking rate. Two groups of eight bulls were grazed on Lolium perenne and Trifolium repens pasture during an initial period of 135 days (period I). One group grazed at a stocking rate of six animals per ha allowing for normal growth at pasture (NGP); the other group grazed at stocking rate of 10 animals per ha (low growth at pasture, LGP). Both groups were then finished indoors (period II) with a concentrate based on dried sugar-beet pulp. Eight control bulls were also fattened indoors on the concentrate diet during periods I and II (CG). The bulls were slaughtered according to similar finishing fattening state. Live-weight gains were 1·47, 1·10 and 0·52 kg/day (P < 0·002) during period I in CG, NGP and LGP groups respectively. Corresponding live-weight gains during period II were 1·22, 1·37 and 1·50 kg/day (P > 0·05). The LGP group had lower food conversion ratios, slaughter weights (P < 0·05) and dressing proportions (P < 0·01). The meat from the grazed bulls had lower cooking losses (P < 0·05) and tended to have lower drip losses (P > 0·05) and higher tenderness (P > 0·05). It also had a higher cholesterol (P < 0·05) content. Large differences were observed in the fatty acid composition according to fat location (subcutaneous, intermuscular or intramuscular). The proportions of mono and polyunsaturated acids were increased in the fats of the animals previously grazed (P > 0·05, P < 0·05).