Y. Geay

Post-natal changes in the biological characteristics of Semitendinosus muscle in male Limousin cattle

Samples of semitendinosus muscle from 45 male Limousin cattle reared under similar conditions were taken at 1, 6 and 12 months of age (biopsy) and at 16 months (at slaughter). The development of biochemical (DNA, protein/DNA), enzymic (lactic dehydrogenase, isocitric dehydrogenase), and histochemical (ATPase, succunic dehydrogenase) characteristics was studied. Muscle fibres were classified according to their contractile and metabolic properties (SO = slow oxidative; FOG = fast oxidative glycolytic; FG = fast glycolytic). DNA accumulation or hyperplasia was observed up to the age of 16 months. The period of growth and development, between 1 and 12 months of age, was characterized by increased glycolytic metabolism, as evidenced by the conversion of FOG fibres into FG fibres, a decrease in ICDH activity and a rise in LDH activity. The period between 12 and 16 months, was characterized by a slowing down of the conversion of FOG fibres into FG fibres and an increase in ICDH activity. The presence of type IIC fibres at the four ages studied is discussed. Of the muscle characteristics studied, LDH activity seemed to be a discriminating factor between animals from an early age. It could thus be used as to predict animal muscle characteristics at birth.

MUSCLE FIBRE CHARACTERISTICS IN FOUR MUSCLES OF GROWING MALE CATTLE. II. EFFECT OF CASTRATION AND FEEDING LEVEL

The impact of androgen status and energetic feeding level on metabolic and contractile muscle fibre differentiation was evaluated. Sixty male Montbeliard cattle, half of them castrated at 2 months of age, were assigned at 9 months of age to feeding groups of ad libitum or restricted, followed at 12 months of age by ad libitum feeding for all. Slaughter dates were scheduled at 4, 8, 12 and 16 months of age, and muscle samples were collected from m. semitendinosus (ST), m. biceps femoris (BF), m. longissimus dorsi (LD) and m. triceps brachii (TB). It was hypothesised that the absence of testicular androgens would delay the process of metabolic and contractile muscle fibre maturation occurring with age. In castrates aged 4 months the differentiation of hybrid fibres was retarded: IIC fibre percentage was 9.2 and 4.5 in ST of steers and bulls, respectively. Steers were less prone to hypertrophy and showed a preference for glycolytic metabolism and type IIB fibre recruitment, 56.5% vs. 50.1% for bulls aged 12 months (P<0.05, LD). Although the effects were minor, energetic feeding restriction showed a sex-specific response. Restricted bulls increased (P<0.05) oxidative enzyme activity as compared with non-restricted bulls. Compensatory growth rates could re-establish the physiological : chronological balance within the two sex groups. Both castration and feeding level affect muscle fibre diversification, whereby the individual growth pattern of a given muscle seems to play a fundamental role in deciding upon the nature and the size of the effect.

Muscle fibre characteristics in four muscles of growing bulls: I. Postnatal differentiation

Mammalian muscle fibres maturation follows a distinct programme lineage (I→IIC→IIA→(IID/X)→IIB). Changes in morphology, protein content and metabolic characteristics are related to several factors, age being one of the most crucial for muscle fibre type. Similarly, muscle fibre type affects overall muscle growth rate. The objective of this study was to characterise the profile of muscle fibre types and metabolic enzyme activities in various muscles [semitendinosus (ST), longissimus dorsi (LD), biceps femoris (BF), triceps brachii (TB)] of growing Montbeliard bulls. Groups of four or five animals were slaughtered at 4, 8, 12 and 16 months of age. Results indicated that contractile muscle fibre type maturation occurred similarly across all muscles investigated. The percentage of slow myosin heavy chain 1 (MHC1) diminished between 4 and 8 months of age (26.3% vs. 19.0%) and steadily increased until 16 months (34.4%; P<0.001). The evolution of metabolic enzyme activities in the muscles studied was related to muscle-specific growth patterns: e.g., TB showed enhanced (P<0.05) glycolytic metabolism during the final period of increased allometric growth rate (1.23). These data show that both contractile fibre categories are involved in postnatal muscle fibre differentiation of cattle, which might contribute to alterations in meat tenderness with increasing age.

Age-related changes and location of types I, III, XII and XIV collagen during development of skeletal muscles from genetically different animals.

The ontogenesis of total collagen and of different collagen types was studied in four muscle types from genetically different cattle. Hydroxyproline content was 1.2-fold higher in muscles from cross-bred foetuses with normal muscle growth compared to those of the other genetic types (pure bred with different growth rates, double-muscled breed). A similar tendency was observed for type III collagen content. In all muscles of each animal studied, type XII and XIV collagens were colocated in perimysium. Immunolabelling obtained for type XII collagen was higher during foetal life than after birth, while for type XIV collagen, the opposite result was obtained. Whatever the muscle studied, but especially in semitendinosus muscle, during the foetal and the post-natal period until 15 months of age, immunolabelling with antibody anti-type XIV collagen tended to be more intense in muscles of animals from fathers selected for a low muscle growth capacity compared to those from fathers selected for a high muscle growth capacity. In conclusion, this study shows, that during foetal life, selection according to muscle growth capacity has no significant effect on the contents of total hydroxyproline or type III collagen, but minor effects on collagen localization.

Effect of the type of diet on muscle characteristics and meat palatability of growing Salers bulls

The effect of the type of diet (hay vs grass silage) on body composition and characteristics and palatability of semitendinosus (ST) and longissimus thoracis (LT) muscles of 16 month old Salers bulls fed at the same energy levels were studied. Animals fed hay had a lower daily weight gain and carcass weight and were leaner. There were no significant differences in the proportions of fibre types in the ST or LT due to diet. ST muscle of hay fed animals had a lower oxidative metabolism, but contained similar amounts of total and type I collagen and greater amounts, and proportions of soluble collagen and of type III collagen, than those of animals fed grass silage. ST muscles of hay-fed animals were more tender than those of silage-fed animals.

Fat partitioning and biochemical characteristics of fatty tissues in relation to plasma metabolites and hormones in normal and double-muscled young growing bulls

Plasma metabolites and hormones, and the biochemical characteristics of four fatty tissues (FT) were studied in two groups of six normal (N) or six double-muscled (DM) Belgian Blue young growing bulls fed the same net energy amount at the same live weight and slaughtered at 10 months of age. Average daily gain and feed efficiency did not significantly differ between the two groups. However, the DM bulls exhibited a higher proportion of muscles (+22%, P < 0.01) and a reduced proportion of fat (-49%, P < 0.01) mainly in the subcutaneous FT (-80%, P < 0.05). Triiodothyronine, insulin and glucose plasma concentrations tended to be lower in DM bulls (-24%, P < 0.02; -27%, P = 0.14; -7%, P = 0.06, respectively) and were positively related to the higher fat development in N bulls. From the results of total protein. DNA, lipid and TG contents of FT, it appeared that a reduction in fat storage per fat cell (hypotrophy) or a reduction in total fat cell number (hypoplasia) could explain, in DM bulls, two-thirds and one-third of the reduction of perirenal and subcutaneous FT weights, respectively, as compared to N bulls. In contrast, either hypotrophy or hypoplasia was the main cause of omental or intermuscular FT weight reduction in DM animals.

Comparison of the foetal development of muscle in normal and double-muscled cattle.

SummaryMuscle differentiation was studied in foetal Semitendinosus muscle from normal cattle and those with the ‘culard’ gene of muscular hypertrophy sampled at 90, 130, 170 and 210 days of foetal life. The different fibre types were characterized by immunohistochemistry with antibodies specific to different isoforms of myosin heavy chains. The isoforms were separated by electrophoresis, identified by immunoblotting and quantified by ELISA. In double-muscled animals, there was a slower rate of differentiation in the first generation of cells, most markedly apparent at 90 days. At 130 days, differentiation was retarded mainly in the second generation, while at 170 days there was no longer any difference between the two animal types in the differentiation of first generation cells, which were totally slow in both. At the same stage however, type IIC fibres in double-muscled animals were much slower in appearing and continued to be so at 210 days, albeit to a lesser extent. These findings show that differentiation of the muscle fibres occurs at a slower rate in double-muscled foetuses particularly during the first two-thirds of foetal life.

Comparison of the foetal development of fibre types in four bovine muscles

SummaryThe pattern of expression of different types of myosin heavy chains and the development of different generations of muscle cells during foetal life were studied in four bovine muscles with widely varying characteristics, the Masseter, Longissimus thoracis, Cutaneus trunci and Diaphragma. Different complementary techniques were performed: immunocytochemistry, electrophoresis, immunoblotting and ELISA. Monoclonal antibodies against different myosin heavy chain isoforms were used. The results confirmed the existence of at least two generations of cells during foetal development in cattle. A first generation, which appeared at a very early stage, gave rise to adult type I fibres. A second generation, made up of different cell populations, gave rise to adult fast type IIA and IIB fibres, and to type IIC. In the slow muscles, it also seemed to give rise to type I fibres. The beginning of myogenesis was characterized in the different cell generations by the expression of transitory myosin forms that are not found in the adult. Type 1 myosin heavy chain was observed from 90 days whereas the fast types, 2a and 2b, were present from 210 to 230 days, at which stage the foetal form disappeared. Muscles that have greatly different contractile characteristics in the adult exhibit also different profiles of differentiation: the Diaphragma was the first to develop, followed by Cutaneus trunci, Longissimus thoracis and Masseter.

Specificity of different anti-myosin heavy chain antibodies in bovine muscle

Muscle fibre types play an important role in bovine meat tenderness, and conditions the speed of ageing. Two generations of myotubes appear during foetal life. Their differentiation results in several types of fibres differing in their contractile and metabolic properties, namely type I fibres and type II fibres (IIA and IIB). Fibre types were identified using antibodies by immunohistochemistry and western-blotting techniques. The aim was to test different antibodies on foetal and adult muscles by these two techniques. Ten monoclonal antibodies reported to be specific to different myosin heavy chain (MHC) isoforms in other species were tested. Only three antibodies were selected: BF.35, specific for I and IIa MHCs, F1.652 specific for foetal MHC and SC.71 an anti II MHCs (IIa and IIb) antibody. The use of these antibodies will enable a more precise characterisation of muscle fibres and will have applications in the study of bovine muscle ontogenesis.

Comparative study of metabolic differentiation of foetal muscle in normal and double-muscled cattle

Studies of the contractile differentiation of foetal muscles in normal and double-muscled cattle have shown that double-muscled foetal muscles display comparative delayed contractile differentiation. We compared the metabolic differentiation of foetal muscles in normal and double-muscled cattle, for which no data were available. The semitendinosus (ST) muscle was excised from normal and double-muscled cattle foetuses aged 110-260 days. Isocitrate dehydrogenase (ICDH) and lactate dehydrogenase (LDH) activities, respectively representative of aerobic oxidative and anaerobic glycolytic metabolism, were assayed. The five LDH isozymes were separated by electrophoresis under non-denaturing conditions and assayed by densitometry. ICDH activity was weaker in the ST of double-muscled foetuses than in that of normal ones throughout gestation, and it increased later in the double-muscled foetuses than in normal ones. In contrast, the LDH activity increased at 180 days in both. It was greater in the double-muscled beyond that time. The proportion of LDH-M subunit was higher at all foetal ages in the double-muscled. Overall, these results show that: (1) the metabolic differentiation of muscle fibre occurs during the last third of foetal growth in both normal and double-muscled cattle; and (2) the differentiation of aerobic oxidative metabolism is delayed in double-muscled foetuses compared with normal ones.