| Popis: |
The objective of this study was to determine the effects of supplementing active dried yeast (ADY) on growth performance and carcass composition of feedlot cattle. Steers (n = 120) were blocked by body weight (BW) in an automated intake feeding system (164 d). A re-sort on d 70 resulted in four final treatment assignments, following a Balaam’s design: steers fed control diet before and after the re-sort (CC; n = 30), steers fed control before and ADY after the re-sort (CY; n = 30), steers fed ADY before and control after the re-sort (YC; n = 30), and steers fed ADY (YY; n = 30). Growth performance variables (BW, ultrasound characteristics, and biometrics) were modeled using linear regression. Carcass composition of sixty steers was determined by dissecting the 9th-11th rib section. There was no treatment effect on initial BW, mid-test BW, Final BW or ADG (P ≥ 0.5773). Backfat deposition rate tended to be slower for YC than CC, CY or YY (P = 0.0918). There was no treatment effect on rump fat, longissimus muscle area, or intramuscular fat deposition rate (P ≥ 0.1717). Rib girth circumference growth rate was fastest for YY and CY, intermediate for CC and slowest for YC (0.828, 0.809, 0.751 and 0.666 cm/d, respectively; P = 0.0027). Final shrunk BW was not different but BW shrink was greatest for CC, intermediate for CY and YC and lowest for YY (3.7, 3.3, 3.1, and 2.7%, respectively; P = 0.0525). There were no treatment effects on carcass characteristics (HCW, dressing %, backfat, longissimus muscle area, quality grade, or yield grade distribution; P ≥ 0.2004) or rib composition (% moisture, ash, crude protein, and fat; P ≥ 0.5197). Supplementing ADY during the finishing period may improve growth rate and reduce shrink loss, without affecting carcass composition and characteristics. |
