Summary ― Samples of musculus longissimus dorsi, semimembranosus and semitendinosus were obtained post-slaughter from 2-week, 3-month and 10-month-old bull calves. The 2-week-old calves were fed milk only. All the remaining animals were fed grass silage or hay ad lib and a restricted amount of concentrate from 2 weeks of age onwards. Muscle fibres were differentiated according to Ziegan into fast-twitch glycolytic, fast-twitch oxidoglycolytic and slow-twitch oxidative fibres (FTG, FTO and STO, respectively). In all calves, marked fibre growth took place between 3 and 10 months of age. From the 2nd week to the 3rd month, growth was observed virtually only in the FTG fibres, irrespective of feeding. Feeding calves with a silage-based vs hay-based diet resulted in thicker muscle fibres for each type of fibre. Significant linear regression coefficients have shown the fibre diameters to be clearly related to live weight gain resulting from DM intake that was higher in the silage-based diet.calf / skeletal muscle fibre / silage / hay Résumé ― Microstructure des muscles squelettiques chez les veaux à l'ensilage ou au foin.
Summary ― As described in part I, samples of musculus longissimus dorsi, semimembranosus and semitendinosus were obtained post-slaughter from 2-week, 3-month and 10-month-old bull calves. The 2-week-old calves were fed milk only. All the remaining animals were fed grass silage or hay ad lib and a restricted amount of concentrate from 2 weeks of age onwards. Muscle fibres were differentiated according to Ziegan (1979) into fast-twitch glycolytic, fast-twitch oxidoglycolytic and slow-twitch oxidative fibres (FTG, FTO and STO, respectively). The percent distribution of individual types of fibres was estimated as related to the calves age and diet. The most numerous were always fast-twitch glycolytic fibres, the lowest values being observed in the 2-week-old calves. The effect of the diet on fibre percentage distribution in 3-month-old calves differed from that found in 10-monthold animals. This research suggests that a hay-free diet based on grass silage alters the microstructure of skeletal muscles, which thus might also affect the quality of meat.
Black-and-White bull calves aged 14 to 91 days were fed rations differing in the type of roughage offered to appetite: hay (group H) or meadow grass silage (group S) with 2 kg 80% formic acid/ton of fresh forage. Before weaning (days 14-42 of age), the average daily intake of roughage dry matter and gross energy per kg 0 ' 73 was higher (P^0.05) in group H than in group S (45.0 g and 1.1 MJ, vs. 41.1 g and 1.0 MJ, respectively). However, the differences in daily weight gains (623 and 583 g in groups H and S) and feed utilization were not significant. After weaning (43 to 91 day of life), mean daily intake of nutrients and total energy was similar in both groups with daily weight gains reaching 478 and 502 g, respectively for group H and S. Mean body weight gains during the entire experimental period were the same in both groups and equalled 530 g.The system of nutrition introduced in the present experiment may be useful for the rearing calves designed for future fattening based on roughages. However, due to the low level of Mg observed in blood plasma (0.38 mmol/1) of all the calves, the ration ought to be supplemented with a mineral mixture containing magnesium.
Feed intake proved lower while feed efficiency higher in Polish White (PW) compared to F1 (Boer x PW) kid goats. Both indicators proved higher in males than in females. These may be explained by possible differences in energy and nitrogen utilization. Because contribution of liver to total energy expenditure and to total protein synthesis in the whole body is important in other animal species, the objective of this study was to relate differences in growth between genotypes and sexes to possible differences in the liver nitrogen metabolism of the goat.
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