Comprehensive evaluation of growth performance and meat characteristics of a fattening system combining grazing with feeding rice whole-crop silage in Japanese Black steers.

We investigated the effect of a system for fattening steers combining grazing with feeding rice whole-crop silage (rWCS) on growth performance, meat characteristics, and the expression of genes involved in skeletal muscle growth. Steers were randomly assigned to grazing or concentrate-fed groups (CT). The grazing group (GZ) was fed rWCS after grazing until 16 months of age. The final body weight was the same in the two groups, but the dressed weight was lower in the GZ than in the CT. The beef color standard was higher in the GZ than in the CT. Although beef marbling did not differ between the two groups, there was less intramuscular fat and subcutaneous fat in the GZ than in the CT. The α-tocopherol and ß-carotene contents in the muscle were higher in the GZ than in the CT. The GZ showed a lower daily gain (DG) during the grazing period, which may have resulted from decelerating skeletal muscle growth caused by the increased expression of genes encoding myostatin and atrogin-1. However, the DG and feed efficiency of the GZ increased after grazing. The two groups exhibited a similar level of beef productivity.

Influence of feeding a grass hay diet during the early stage of the fattening period on growth performance, carcass characteristics, and meat production in Japanese Black steers.

The present study investigated the influence of feeding a large amount of grass hay to steers from the early to middle fattening period on growth, carcass characteristics, and meat characteristics. Steers were randomly divided into grass hay-fed (GHF, n = 6) and concentrate-fed (CF, n = 6) groups. The dressed weight of the GHF steers was lower than that of the CF steers, but the final body weight was not significantly different between the groups. The GHF steers had decreased subcutaneous fat and rib thickness compared with the CF steers. Lipid content, monounsaturated fatty acids, and drip loss in the muscles were lower in the GHF steers than in the CF steers. Furthermore, n-3 polyunsaturated fatty acids were higher in the GHF steers compared with the CF steers. The GHF steers had lower body weight during the middle fattening stage, which may have occurred as a result of muscle growth suppression caused by increased Myostatin expression; an increase in daily gain during the finishing period may have occurred as a result of muscle growth activation caused by decreased Myostatin expression. Feeding steers a grass hay-based diet during the early fattening period possibly maintains the quantitative productivity of beef similarly to feeding a concentrate-based diet.

Influence of rice whole-crop silage diet on growth performance, carcass and meat characteristics and muscle-related gene expression in Japanese Black steers.

The present study investigated the influence of a diet largely comprising rice whole-crop silage (rWCS) on growth performance, carcass and meat characteristics, and expression of genes involved in muscle growth of Japanese Black steers. Steers were randomly separated into rWCS-fed (rWCS ad libitum and restricted feeding of concentrate) and concentrate-fed groups. Total digestible nutrient intake and daily gain (DG) decreased in rWCS-fed steers in comparison with concentrate-fed steers, whereas dressed carcass weight and final body weight did not significantly differ between the groups. Decreases in drip loss in the muscle of rWCS-fed steers may be caused by α-tocopherol and ß-carotene in muscle. Feeding large amounts of rWCS to steers may maintain quantitative productivity of beef steers equally to a concentrate-based diet, and improve the qualitative productivity. Results of gene expression suggest that activation of skeletal muscle growth in rWCS-fed steers may occur at the late fattening period owing to a decrease in myostatin and increase in myosin heavy chain gene expression. Preadipocyte factor-1 and myostatin genes may be strongly involved in the control of lipid accumulation. This rearing system would allow beef production to switch to rWCS-based diets from concentrate-based diets.

Influence of different feeding systems on the growth performance and muscle development of Japanese Black steers.

This study investigated the growth performance and gene expression for muscle development between grass hay-fed (GH) and concentrate-fed (CT) steers. Daily gain and energy intake during the fattening period of the GH group were lower than those of the CT group. Analysis of C/EBPα, PPARγ2, myosin heavy chain (MHC), and myostatin gene expressions was performed by real-time PCR. Expressions of C/EBPα and myostatin in semitendinosus and longissimus lumborum (LL) muscles were higher in the CT group than in the GH group at the end of fattening. In LL muscle, MHC expression at the end of fattening was greater in the GH group than in the CT group. These results suggest that regulation of adipogenesis and myogenesis by the expression of genes involved in muscle development might have occurred in the skeletal muscle of the GH group by the feeding of grass hay and/or because of the low energy intakes.