• Journal of Animal Science and Technology
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• v.61 no.5
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• pp.260-271
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• 2019

The objective of this study was to determine the effect of different stocker management programs on skeletal muscle development and growth characteristics, satellite cell (SC) activity in growing-finishing beef cattle as well as the effects of SC-conditioned media on preadipocyte gene expression and differentiation. Fall-weaned Angus steers (n = 76; $258{\pm}28kg$) were randomly assigned to 1 of 4 stocker production systems: 1) grazing dormant native range (NR) supplemented with a 40% CP cottonseed meal-based supplement ($1.02kg{\cdot}steer^{-1}{\cdot}d^{-1}$) followed by long-season summer grazing (CON, 0.46 kg/d); 2) grazing dormant NR supplemented with a ground corn and soybean meal-based supplement fed at 1% of BW followed by short-season summer grazing (CORN, 0.61 kg/d); 3) grazing winter wheat pasture (WP) at high stocking density (3.21 steers/ha) to achieve a moderate rate of gain (LGWP, 0.83 kg/d); and 4) grazing winter WP at low stocking density (0.99 steers/ha) to achieve a high rate of gain (HGWP, 1.29 kg/d). At the end of the stocker (intermediate harvest, IH) and finishing (final harvest, FH) phases, 4 steers / treatment were harvested and longissimus muscles (LM) sampled for cryohistological immunofluorescence analysis and SC culture assays. At IH, WP steers had greater LM fiber cross-sectional area than NR steers; however, at FH, the opposite was observed (p < 0.0001). At IH, CORN steers had the lowest Myf-5+:Pax7+ SC density (p = 0.020), while LGWP steers had the most Pax7+ SC (p = 0.043). At FH, CON steers had the highest LM capillary density (p = 0.003) and their cultured SC differentiated more readily than all other treatments (p = 0.017). At FH, Pax7 mRNA was more abundant in 14 d-old SC cultures from HGWP cattle (p = 0.03). Preadipocytes exposed to culture media from proliferating SC cultures from WP cattle isolated at FH had more $PPAR{\gamma}$ (p = 0.037) and less FABP4 (p = 0.030) mRNA expression compared with NR cattle. These data suggest that different stocker management strategies can impact skeletal muscle growth, SC function, and potentially impact marbling development in growing-finishing beef cattle.

• Asian-Australasian Journal of Animal Sciences
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• v.3 no.4
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• pp.299-303
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• 1990

Twenty-four Harnai lambs 6 to 7 month old, weighing $16{\pm}2kg$ were used in a completely randomized design in growth and digestibility trials to study fourwing saltbush ratio supplemented with cotton seed cake. The animal were divided at random into three groups of 8 animals each. Three iso-nitrogenous (10.5% CP) experimental rations (1, 2 and 3) containing wheat straw + lucerne hay (24:76); fourwing saltbush (Atriplex canescens) + cotton seed cake (71:29); and wheat straw + cottonseed cake (41:59); respectively, were allotted to each group randomly. All the animals were taken out for grazing in a dormant native range for about 3 hours in the afternoon during the growth trial. The growth trial lasted for 8 weeks followed by a digestibility trial. At the end of 8 weeks lambs on ration 3 had gained significantly (p<0.10) more weight compared to those on rations 1 and 2 which maintained their body weight. The crude protein digestibility of the fourwing saltbush based ration was comparable with the other two treatments (71 vs 70 and 71%). However, the digestibility of dry matter (41%), acid detergent fibre (13%) and neutral detergent fibre (22%) of this ration was significantly lower (p<0.10) than the other two diets. The results suggest that lambs can be maintained on fourwing saltbush during winter without significant loss in body weight with 30% extra protein concentrate supplementation.