Influences of the method of housing bulls on their body composition and muscle fibre types

The influence of the type of housing (loose or lying-type) was studied in r elation to body composition and muscular characteristics of bulls. 34 young bulls (18 Salers and 16 Limousins) were divided into two groups with equal breed representation and equal mean growth rates, to 10 months of age. One group was housed in tying-type housing (short stalls 1.8 m(2) per animal) and the other in loose housing (6.5 m(2) per animal). Samples of semitendin osus (ST) and longissimus thoracis (LT) muscle were taken at slaughter at 1 6 months. The lactate dehydrogenase (LDH) and isocitrate dehydrogenase (ICD H) activities were measured. The proportion of isoforms LDH-M and LDH-H wer e determined for each muscle. Total collagen content and solubility were me asured for ST alone. Fibres were classified by ATPase myofibrillar and succ inate dehydrogenase activities into SO (slow oxidative), FOG (fast oxidativ e glycolytic) or FG (fast glycolytic), and by immunohistochemistry by react ion with monoclonal antibodies specific to slow and fast myosin heavy chain reactions into I, IIC, IIA, IIAB and IIB fibres. Compared with animals in tying-type housing, animals in loose housing presented the following:fewer carcass adipose deposits (p < 0.01); for ST muscle, more collagen (p < 0.01 ) and a reduced glycolytic metabolism, as indicated by lower LDH activity ( p < 0.10) and a lower proportion of FG fibres (p < 0.10). In both ST and LT muscles, loose housing resulted in an increased percentage of IIC fibres ( p < 0.05) but did not alter the proportions of fast fibres. Modifications i n ST alone were increased percentage of IIA fibres (p < 0.10) and IIAB fibr es (p < 0.01) and a lower percentage of IIB fibres (p < 0.01). Thus, for a given rate of growth, the type of housing (loose or tying-type) influenced contractile characteristics, especially in muscles involved in movement. (C ) 1998 Elsevier Science Ltd. All rights reserved.