Effects of previous grazing nutrition and management on feedlot performance of cattle.

Management strategies designed to improve grazing animal performance can influence feedlot performance and carcass traits both positively and negatively. In spite of the economic relevance of potential interactions between grazing and finishing performance, controlled experiments evaluating integrated production systems are limited in number. Effects of grazing treatments can result from, or be overshadowed by, changes in gut fill, thus making it difficult to assign precise costs to different phases of production. Published reports have considered the effects of stocking rate, duration of grazing, forage characteristics, supplementation, and growth-promoting implants on subsequent finishing performance. Improvements in cattle performance attributed to changes in stocking rate generally have been neutral to positive with respect to effects on finishing performance. Comparisons among forages have led to the suggestion that forage species may contribute to differences in gastrointestinal fill of grazing cattle, thereby influencing gain and efficiency during the subsequent finishing phase. Creep-feeding suckling calves generally has increased preweaning performance but has had relatively little influence on performance during the subsequent finishing phase. Grain supplementation of stocker cattle during the grazing period has improved grazing performance, but effects on subsequent feedlot performance have been inconsistent. Potential carryover effects from protein and mineral supplementation also have been inconclusive. Lack of congruence among studies is puzzling but may be the consequence of highly varied production systems, differences in experimental procedures, and changes in gut fill or mass of internal organs. Based on the studies reviewed, the expression or absence of compensatory growth during the finishing phase appears to be related to the nutritional quality of forages utilized in the grazing period, with higher quality forages tending to yield greater compensatory effects. The bulk of evidence with suckling cattle and stocker implants suggests that effects on subsequent finishing performance are minimal. Attention is drawn to the noticeable lack of research pertaining to integrated production systems. A more thorough understanding of the interactions among grazing nutrition and management, finishing performance, and carcass traits is needed to facilitate greater economic exploitation of these relationships.

Effects of feeding combinations of steam-flaked grain sorghum and steam-flaked, high-moisture, or dry-rolled corn on growth performance and carcass characteristics in feedlot cattle.

The objective of these two feeding trials was to determine the associative effects of feeding steam-flaked grain sorghum (SFGS) in combination with steam-flaked (SFC), dry-rolled (DRC), or high-moisture (HMC) corn on growth performance and carcass characteristics in feedlot cattle. In Trial 1, 200 yearling heifers were blocked by weight, allotted to 25 pens, and fed one of five finishing diets (77% grain, 15% corn silage, and 8% supplement on a DM basis) for an average of 137 d. The grain combinations were 100:0, 75:25, 50:50, 25:75, and 0:100 SFC:SFGS, respectively. Treatment had no effect on DMI (P > .05), but ADG, gain efficiency, and final live and hot carcass weights decreased linearly (P < .05) as the proportion of SFGS increased in the diet. Carcass backfat, quality grade, and liver abscess score were not affected (P > .05) by treatment. In Trial 2, 306 yearling steers were blocked by weight, allotted to 30 pens, and fed diets that contained 74.5% grain, 10% corn silage, 7.5% soybean meal, 4% tallow, and 4% supplement (DM basis) for an average of 139 d. The grain and grain combinations were 100% DRC, HMC, SFC, or SFGS and a 67%:33% combination of SFGS: DRC or SFGS:HMC. For steers fed diets containing a single source of grain, those fed SFC gained 7% more live weight and had a 7% higher gain efficiency (P < .05) than those fed DRC or HMC. Growth performance of steers fed SFGS was intermediate. Feeding grain combinations (67% SFGS:33% HMC or DRC) resulted in a 5 to 6% positive associative effect (P < .05) for ADG and gain efficiency. Carcass characteristics were not affected (P > .05) by treatment. We concluded that there were significant benefits (positive associative effects) when SFGS was fed in combination with DRC or HMC, but the effects were smaller when SFGS was fed in combination with SFC.

Effect of degradable and escape protein and roughage type on performance and carcass characteristics of finishing yearling steers.

We evaluated protein sources for finishing steers in two randomized complete block design experiments. Experiment 1 used 144 steers (334 kg) with 2 x 3 factorially arranged treatments. Basal diets contained .9% urea or 5.6% soybean meal (SBM) and were either not supplemented or supplemented with additional protein (2%) from blood meal-corn gluten meal (BMCG) or SBM. Steers fed urea-containing diets consumed 4.6% (P < .10) more feed than those fed SBM-supplemented basal diets. On the basis of carcass weights, steers fed diets containing SBM as the basal protein source were 3.8% (P < .10) more efficient than those fed urea-containing diets; supplying additional SBM improved gain efficiency (G/F) 4.3% (P < .10) compared with BMCG. In Exp. 2, 384 steers (367 kg) were fed diets containing 1.0% urea (DM basis) and 10% roughage as either sorghum silage (four diets) or alfalfa hay (two diets). Additional protein was either not provided or provided (2%) as SBM, sunflower meal (SFM), or a 50:50 (N basis) SBM:SFM blend in silage-containing diets; for diets containing alfalfa, additional protein was either not provided or provided (2%) as SBM. Averaged across roughage source, added SBM tended (P = .16) to increase ADG. Dressing percent decreased (P = .09) with added SBM but was higher (P = .04) with alfalfa as roughage source. Feeding alfalfa vs sorghum silage as the roughage source increased carcass adjusted ADG 4.3% (P = .06) and G/F 4.8% (P = .02). Supplementing high-grain diets with SBM enhanced diet utilization, but BMCG was of little value.

Protein supplementation of ammoniated wheat straw: effect on performance and forage utilization of beef cattle.

We studied the effects of supplement CP concentration on performance and forage use of cattle allowed ad libitum access to ammoniated wheat straw. During two consecutive winters, crossbred beef cows in late gestation (n = 87 in 1990-1991, n = 84 in 1991-1992) were used in a randomized complete block design with three pens per treatment. Cows were stratified by weight, body condition score (BCS), age, and breed and randomly assigned within strata to 1) control (C, no supplement), or 2 kg/d of 2) low-protein (LP) supplement (12% CP), 3) moderate-protein (MP) supplement (20.1% CP), or 4) high-protein (HP) supplement (31.7% CP) (DM basis). The feeding period was 84 d in 1990-1991 and 60 d in 1991-1992. Supplementation (C vs LP, MP, or HP) increased (P < .01) cow weight gains (32.7 vs 60.7, 62.8, and 72.4 kg, respectively) and improved (P < .01) BCS. Calf birth weights, weaning weights, and ADG were not affected by treatment (P > or = .20). Average calving date, percentage of cows cycling at the start of the breeding season and percentage pregnant after a 60-d breeding season were also similar (P > .20) among treatments. Sixteen ruminally fistulated steers (482 kg, four steers per treatment) were blocked by weight and assigned to the same four supplements in a 30-d digestion trial. Supplementation increased (P < .01) digestible DMI and forage DMI (P < or = .04) and tended (P = .09) to increase digestible NDF intake but did not alter (P > or = .15) apparent DM or NDF digestibility.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of steam-flaked sorghum grain or corn and supplemental fat on feedlot performance, carcass traits, longissimus composition, and sensory properties of steers.

One hundred forty British x Exotic crossbred, yearling steers (370 kg) were used in a 2 x 2 factorial experiment to evaluate main effects and the interaction of grain type (steam-flaked sorghum grain [SFSG] or steam-flaked corn [SFC]) and level of supplemental far (0 or 4% yellow grease [YG]) on feedlot performance, diet NE concentration, carcass traits, and chemical composition and sensory properties of longissimus muscle. Steer performance and estimated dietary NEm and NEg values were not different between SFSG and SFC. Supplemental YG improved (P less than or equal to .05) gain/feed and estimated NEm and NEg of both SFSG and SFC diets. Compared with steers fed SFSG, steers fed SFC had a more yellow (P less than .05) subcutaneous fat color. Supplemental YG had an additive effect (P less than .025) on yellow color of subcutaneous fat but improved (P less than .08) the lean color of longissimus muscle. Grain type or supplemental YG had no effect on sensory properties or mechanical shear of longissimus muscle. Longissimus muscle cholesterol content was elevated (P less than .05) by supplemental YG (.49 vs .52 mg/g of wet tissue for 0 vs 4% YG, respectively); however, the biological significance of this result is questionable. Similarly, effects of YG on increased (P less than .05) stearic acid concentration and a higher concentration (P less than .05) of linoleic acid measured in longissimus muscle of steers fed SFSG vs SFC were small in magnitude. These data indicate that under the conditions of this experiment, NE contents of SFSG and SFC were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Supplementation of ammoniated wheat straw: performance and forage utilization characteristics in beef cattle receiving energy and protein supplements.

Two experiments were conducted to evaluate performance and forage utilization characteristics of beef cattle fed ammoniated wheat straw (AWS) unsupplemented except for minerals or supplemented with energy and protein. In Exp. 1, 194 crossbred beef cows (BW = 472 kg) in late gestation were allotted by weight, breed type, and age during two consecutive winters to 12 drylot pens (three pens/treatment) for a 60-d feeding trial. The AWS (3% NH3 wt/wt) was tubground through a 7.6-cm screen, and cows were allowed ad libitum access to the AWS. In Exp. 2, 16 ruminally fistulated Angus x Hereford steers (BW = 300 kg) were blocked by weight and randomized to treatments in a 35-d intake-digestion trial. Daily supplementation treatments in both experiments were Control, no supplemental energy or protein; LSG, 1.36 kg of sorghum grain (SG); HSG, 2.72 kg of SG; and SG + SBM, 1.02 kg of SG + .34 kg of soybean meal (SBM). All animals received .23 kg of mineral mixture formulated to meet a pregnant cow's mineral requirements. Supplements LSG and SG + SBM were fed to provide the same daily ME, and HSG and SG + SBM were fed to provide the same daily CP. Cows were managed as one group during and after calving. In Exp. 1, all supplements increased gain (P less than .01) vs Control, and cows fed SG + SBM had higher (P = .05) gains than those fed LSG. The SG + SBM supplement increased (P less than .01) change in cow body condition score compared with LSG.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of sequential implanting with zeranol on steer lifetime performance.

Three trials involving 513 exotic crossbred steers were conducted to determine the effect of zeranol implanting in the suckling and growing phases on subsequent feedlot performance and carcass characteristics. Treatments were 1) unimplanted control, 0000; 2) implanted twice in the finishing phase, 00II; 3) implanted in the growing phase and twice in the finishing phase, 0III; 4) implanted in the suckling phase and twice in the finishing phase, I0II; 5) implanted in the suckling and growing phases with a single implant in the finishing phase, III0; and 6) implanted in the suckling and growing phases and twice in the finishing phase, IIII. Implanting in the suckling period did not significantly affect preweaning gain. Implanting in the growing period produced a treatment x trial interaction (P less than .05), but zeranol increased gains by an average of 8.4% over the three trials. Growing period gain was not influenced by implanting during suckling. Implanting twice during the finishing period increased gain (P less than .05) over unimplanted and III0 steers. Finishing gain was not influenced by previous suckling and(or) growing implant treatment. Lifetime ADG of steers was increased (P less than .05) by all implant treatments compared with unimplanted controls. Zeranol tended (P = .14) to improve feed conversion in the finishing phase. All implant treatments increased hot carcass weight (P less than .05), and all but III0 reduced fat deposition, as indicated by lower quality grade (P less than .05). Other carcass characteristics were not significantly affected by treatment. These trials demonstrated that implanting in the suckling and(or) growing phases of production did not reduce performance in the finishing phase.

Trace mineral intake of enlisted military personnel. Preliminary observations.

The results of this study indicate that copper intakes were generally significantly below the Food and Nutrition Board's recommended range. It is presently unknown whether the new, 1979 recommendation is too high or whether copper deficiency-related problems may eventually develop in these men. When compared with the new recommendations, zinc and manganese intakes appeared to be adequate. Individual intakes must either be monitored over several days or a large population surveyed to determine whether dietary intakes of minerals are adequate. This is due mainly to large day-to-day variations in individual dietary intakes.

Response of lipogenesis and fatty acid synthetase to physical training and exhaustive exercise in rats.

The effect of physical training and exhaustive exercise on fatty acid synthesis in rat liver and adipose tissue has been investigated. Exercise training (treadmill running) significantly (p less than 0.05) decreased body wt, eipdidymal fat pad wt, adipocyte size, and hepatic fatty acid synthetase activity. Training did not significantly affect adipose tissue cell number, lipogenesis from glucose-U-14C, or fatty acid synthetase. Exercise to exhaustion immediately prior to sacrifice significantly (p less than 0.05) decreased lipogenesis from glucose-U-14C and fatty acid synthetase in adipose tissue from trained but not untrained rats. Liver fatty acid synthetase was not significantly influenced by exhaustive exercise. The results of this study indicate that rats may adapt to physical training by decreasing adipose tissue lipogenesis during exhaustive exercise. This adaptation in energy metabolism may facilitate physically trained animals in conserving blood glucose during exhaustive exercise, thereby prolonging endurance.