Influence of grazing dormant native range or winter wheat pasture on subsequent finishing cattle performance, carcass characteristics, and ruminal metabolism1,2

Abstract

A winter grazing/feedlot performance experiment repeated over 2 yr (Exp. 1) and a metabolism experiment (Exp. 2) were conducted to evaluate effects of grazing dormant native range or irrigated winter wheat pasture on subsequent intake, feedlot performance, carcass characteristics, total-tract digestion of nutrients, and ruminal digesta kinetics in beef cattle. In Exp. 1, 30 (yr 1) or 67 (yr 2) English crossbred steers that had previously grazed native range (n = 38) or winter wheat (n = 59) for approximately 180 d were allotted randomly within previous treatment to feedlot pens (yr 1 native range = three pens [seven steers/pen], winter wheat = two pens [eight steers/pen]; yr 2 native range = three pens [eight steers/pen], winter wheat = four pens [10 or 11 steers/pen]). As expected, winter wheat steers had greater (P < 0.01) ADG while grazing than did native range steers. In contrast, feedlot ADG and gain efficiency were greater (P < 0.02) for native range steers than for winter wheat steers. Hot carcass weight, longissimus muscle area, and marbling score were greater (P < 0.01) for winter wheat steers than for native range steers. In contrast, 12th-rib fat depth (P < 0.64) and yield grade (P < 0.77) did not differ among treatments. In Exp. 2, eight ruminally cannulated steers that had previously grazed winter wheat (n = 4; initial BW = 407 +/- 12 kg) or native range (n = 4; initial BW = 293 +/- 23 kg) were used to determine intake, digesta kinetics, and total-tract digestion while being adapted to a 90% concentrate diet. The adaptation and diets used in Exp. 2 were consistent with those used in Exp. 1 and consisted of 70, 75, 80, and 85% concentrate diets, each fed for 5 d. As was similar for intact steers, restricted growth of cannulated native range steers during the winter grazing phase resulted in greater (P < 0.001) DMI (% of BW) and ADG (P < 0.04) compared with winter wheat steers. In addition, ruminal fill (P < 0.01) and total-tract OM digestibility (P < 0.02) were greater for native range than for winter wheat steers across the adaptation period. Greater digestibility by native range steers early in the finishing period might account for some of the compensatory gain response. Although greater performance was achieved by native range steers in the feedlot, grazing winter wheat before finishing resulted in fewer days on feed, increased hot carcass weight, and improved carcass merit.

Chemical composition, intake, ruminal fermentation, plasma metabolites and hormones in range steers

“…As expected, the increases in NH 3 ÁN and VFA during wet season were due to an increase in CPI and MEI. Similar results to this study in the ruminal fermentation patterns in grazing cattle were reported by Choat et al (2003). There were no years)seasons interactions for G, UN and NEFA (P 0.05; Table 4).…”

Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers

“…Because subcutaneous fat used acetate more effectively than intramuscular adipose tissue, feeding a hay-based diet would then promote subcutaneous fat deposition over intramuscular adipose tissue accretion. Conversely, greater absorption of the gluconeogenic precursor propionate earlier in the growth period might result in increased IMF deposition and greater marbling scores as observed in winter-wheat fed steers (Choat et al, 2003). Generally speaking, diets that promote glucose supply to the muscle might increase IMF deposition in ruminants.…”

Effect of postweaning growth and bulls selected for extremes in retail beef yield and intramuscular fat on progeny liveweight and carcass traits

“…Even though there was a 79-kg difference between these two groups at weaning and only a 43-day difference at feedlot entry, it seemed to have been the growth period from weaning to feedlot entry that influenced the fat deposition, rather than the preweaning growth period. The majority of previous studies published on effect of growth rate on carcass composition report on the effects of growth restriction before feedlot entry and subsequent compensatory growth during the feedlot phase, (Drouillard and Kuhl 1999;Choat et al 2003;Sainz and Vernazza Paganini 2004), with the animals grown faster during the feedlot period tending to be fatter at slaughter. Accumulation of body fat occurs in proportion to the excess energy provided beyond that required for maintenance, skeletal growth and protein accretion.…”