Efficacy of plastic pot scrubbers as a replacement for roughage in high-concentrate cattle diets.

Effects of plastic pot scrubbers on feedlot performance and ruminal metabolism of steers fed all-concentrate diets were determined. In Trial 1, 31 crossbred steers (means initial BW, 290 kg) were penned and fed individually. Treatments were 1) 85% concentrate-15% corn silage diet, 2) 100% concentrate diet, and 3) 100% concentrate diet + ruminal insertion of eight plastic pot scrubbers per steer. During the first 112 d of the trial, steer ADG did not differ (P greater than .10) due to treatment. From d 113 to 152, steers provided with pot scrubbers had 16% greater ADG than those fed the 100% concentrate diet without pot scrubbers (P = .18). In Trial 2, 78 crossbred steers (means initial BW, 315 kg) were penned individually and fed the diets used in Trial 1. Steers fed the 100% concentrate diet received zero, four or eight pot scrubbers. From d 113 to 167, steers provided with four or eight pot scrubbers or fed the 85% concentrate diet had greater (P less than .10) gains than steers fed the 100% concentrate diet without pot scrubbers. In Trial 3, 120 steers (means initial BW, 286 kg) were grouped in 12 pens and limit-fed an all-concentrate diet for 84 d. Sixty steers were provided with six pot scrubbers each. Performance was not affected (P greater than .10) by the use of pot scrubbers during the 84-d growing phase. During the subsequent 84-d finishing phase, half the steers receiving each treatment were switched to either an 85% concentrate-15% corn silage or an 100% concentrate diet offered for ad libitum consumption.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of flake density on the comparative feeding value of steam-flaked corn for feedlot cattle

Two trials were conducted to examine the influence of flake density (FD) on the feeding value of steam-flaked corn. Treatments consisted of corn that had been steam-flaked to mean densities of .42, .36 and .30 kg/liter (28, 24 and 20 lb/bu). In Trial 1, treatment effects on characteristics of digestion were evaluated using three crossbred steers with cannulas in the rumen and proximal duodenum. In Trial 2, treatment effects on feedlot performance were evaluated in a 112-d finishing trial involving 72 crossbred steers with an average initial weight of 312 kg. Flake density was directly related to flake thickness (P less than .01) and inversely related (P less than .01) to in vitro enzymatic digestibility of starch. Decreasing the FD resulted in a linear decrease (P less than .01) in ruminal pH and linear increases (P less than .05) in postruminal and total tract digestibility of starch. Postruminal digestibility of N and total tract digestibility of OM, N and energy also increased linearly (P less than .05) with decreasing FD. Flake density did not influence (P greater than .10) feedlot performance or carcass merit. There was a tendency (P greater than .10) for depressed rate and efficiency of gain for steers fed the 30 kg/liter FD corn. Improvements in digestibility and N utilization of SF corn-based diets as a result of decreasing FD from .42 to .30 kg/liter did not enhance feedlot performance. This may be due to digestive dysfunction, perhaps related to processing effects on ruminal pH.     

Effect of grain processing degree on intake, digestion, ruminal fermentation, and performance characteristics of steers fed medium-concentrate growing diets

Three trials were conducted to evaluate the effects of degree of barley and corn processing on performance and digestion characteristics of steers fed growing diets. Trial 1 used 14 (328 +/- 43 kg initial BW) Holstein steers fitted with ruminal, duodenal, and ileal cannulas in a completely randomized design to evaluate intake, site of digestion, and ruminal fermentation. Treatments consisted of coarsely rolled barley (2,770 microm), moderately rolled barley (2,127 microm), and finely rolled barley (1,385 microm). Trial 2 used 141 crossbred beef steers (319 +/- 5.5 kg initial BW; 441 +/- 5.5 kg final BW) fed for 84 d in a 2 x 2 factorial arrangement to evaluate the effects of grain source (barley or corn) and extent of processing (coarse or fine) on steer performance. Trial 3 investigated four degrees of grain processing in barley-based growing diets and used 143 crossbred steers (277 +/- 19 kg initial BW; 396 +/- 19 kg final BW) fed for 93 d. Treatments were coarsely, moderately, and finely rolled barley and a mixture of coarsely and finely rolled barley to approximate moderately rolled barley. In Trial 1, total tract digestibilities of OM, CP, NDF, and ADF were not affected (P > or = 0.10) by barley processing; however, total tract starch digestibility increased linearly (P < 0.05), and fecal starch output decreased linearly (P < 0.05) with finer barley processing. In situ DM, CP, starch disappearance rate, starch soluble fraction, and extent of starch digestion increased linearly (P < 0.05) with finer processing. In Trial 2, final BW and ADG were not affected by degree of processing or type of grain (P > or = 0.13). Steers fed corn had greater DMI (P = 0.05) than those fed barley. In Trial 3, DMI decreased linearly with finer degree of processing (P = 0.003). Gain efficiency, apparent dietary NEm, and apparent dietary NEg increased (P < 0.001) with increased degree of processing. Finer processing of barley improved characteristics of starch digestion and feed efficiency, but finer processing of corn did not improve animal performance in medium-concentrate, growing diets.     

Source and level of energy supplementation for yearling cattle fed ammoniated hay

Brahman x British crossbred steers were used in growth and digestion trials to evaluate the response of source (corn, sugar cane molasses, or soybean hulls) and feeding rate (0, 1.4, or 2.8 kg DM per steer daily in the growth trials; 0, 15, or 30% of the ration DM in the digestion trial) of energy supplementation in cattle fed ammoniated (4% of forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Cattle on all treatments were fed 0.5 kg cottonseed meal daily. In the growth trials, steers grazed dormant bahiagrass (Paspalum notatum) pasture. Increasing the levels of supplementation decreased hay intake but increased total dietary intake for all diets (P < 0.07). Daily gain and feed efficiency of steers were improved (P < 0.03) with supplementation. Steers supplemented with corn or soybean hulls at 2.8 kg DM/d had a higher ADG (0.92 kg) and gain/feed (0.103) than steers supplemented with molasses (0.78 kg, 0.08, respectively) at the same level. Seven crossbred steers (200 kg) were used in a five-period digestion trial to evaluate apparent OM, NDF, ADF, and hemicellulose digestibility. Apparent OM digestibility of all diets increased linearly (P = 0.02) as the level of supplementation increased. Apparent NDF and ADF digestibility decreased (P < 0.03) as the level of supplementation with corn or molasses increased, whereas increasing the level of soybean hulls in the diet increased (P < 0.06) apparent NDF and ADF digestibility. Four ruminally fistulated crossbred steers (472 kg) were used in a 4 x 4 latin square design to investigate ruminal characteristics with energy supplementation at 30% of ration DM. Ruminal pH in steers supplemented with soybean hulls or corn declined after feeding. Ruminal pH decreased more rapidly with corn supplementation and remained below 6.2 for a longer period of time than with the other diets. Ruminal pH did not change within 24 h after feeding for steers fed the control or molasses diets. No change in total VFA concentration was observed in steers fed molasses or corn. Total ruminal VFA concentration in steers supplemented with soybean hulls increased initially after feeding and then declined within 24 h after feeding. Soybean hulls produced fewer negative associative effects than corn when fed with ammoniated stargrass hay at 2.8 kg DM/d. The reduced gain/feed of steers supplemented with molasses compared to soybean hulls or corn indicates that molasses was not utilized as efficiently as the other energy sources.     

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

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.     

Effects of rumen-protected amino acids on ruminant nitrogen balance, plasma amino acid concentrations and performance

A series of trials was conducted to determine the effects of supplemental rumen-protected methionine (RPMet) and lysine (RPLys) on nutrient metabolism and performance. In situ RPMet N disappearance was less than 4% following 48 h of incubation and was not affected (P greater than .05) by diet or resultant ruminal pH differences, indicating that RPMet was well protected from ruminal microbial degradation. Thirty-five Dorset-sired crossbred wether lambs (avg wt 28 kg) fed ground corn-soybean hull diets supplemented with urea were randomly assigned to one of the following treatments: 1) 0% RPMet, 2) .03% RPMet, 3) .06% RPMet, 4) .09% RPMet or 5) .12% RPMet. Dry matter, fiber and N digestibilities and N retention were not affected (P greater than .05) by treatment. Plasma methionine concentration tended to increase linearly (P less than .07) with dietary RPMet level. Six Simmental X Angus steers (avg wt 427 kg) were fed a corn grain-corn silage diet supplemented with urea and five levels of RPMet: 1) 0%, 2) .04%, 3) .08%, 4) .12% and 5) .16%. The plasma methionine concentration increased linearly (P less than .01) with dietary RPMet level. In a steer performance trial, no improvements in feedlot performance resulted due to these RPMet levels (P greater than .05), suggesting that the control diet (0% RPMet) was meeting the methionine requirement of these steers. The effects of RPMet and RPLys on growing and finishing steer feedlot performance also were evaluated. Treatments were 1) urea control, 2) soybean meal positive control, 3) .09% RPMet + .06% RPLys, 4) .12% RPMet + .08% RPLys and 5) .15% RPMet + .10% RPLys. In the growing trial, added RPMet and RPLys did not improve steer feedlot performance. In the finishing trial, only steers fed .09% RPMet + .06% RPLys had higher (P less than .05) gains than those fed the urea control diet. These trials indicate that postruminal methionine and lysine supplies were not limiting feedlot steer performance.     

Effects of phase feeding of protein on performance, blood urea nitrogen concentration, manure nitrogen:phosphorus ratio, and carcass characteristics of feedlot cattle

Two experiments with a randomized complete block design were conducted to determine the effects of phase feeding of CP on performance, blood urea nitrogen (BUN), manure N:P ratio, and carcass characteristics of steers fed in a feedlot. In Exp. 1, 45 crossbred steers (initial BW = 423 +/- 3.3 kg) were individually fed a diet formulated to contain 13.0% CP (DM basis) for 62 d. On d 63, the dietary CP was maintained at 13.0% or formulated to contain 11.5 or 10.0% CP until slaughter. Actual CP values were 12.8, 11.8, and 9.9%, respectively. Reducing the CP concentration of the diet did not affect ADG of steers from d 62 to 109 (P = 0.54) or over the 109-d feeding period (1.45, 1.50, and 1.49 kg/d for 13.0, 11.5, and 10.0% CP, respectively; P = 0.85). No differences (P > 0.12) among treatments were detected for BUN concentrations on d 0, 62, or 109. Gain:feed, DMI, and carcass characteristics did not differ among treatments (P > 0.10). In Exp. 2, 2 trials were conducted using 184 (initial BW = 406 +/- 2.6 kg) and 162 (initial BW = 342 +/- 1.9 kg) crossbred steers. Data from the 2 trials were pooled for statistical analysis, and trial effect was added to the statistical model. Steers were fed a diet formulated to contain 13.0% CP until reaching approximately 477 kg. When the average BW of the pen was 477 kg, diets were maintained at 13.0% CP or reduced to contain 11.5 or 10.0% CP. Actual CP values were 12.4, 11.5, and 9.3% CP for treatments 13.0, 11.5, and 10.0% CP, respectively. Reducing the CP content of the diet did not affect ADG after the diet changed (P = 0.16) or throughout the finishing period (P = 0.14). Immediately before slaughter, steers fed the 13.0% CP diet had greater (P < 0.001) BUN concentrations than steers fed the 11.5 and 10.0% CP diets. Carcasses from cattle fed the 11.5% CP diet had greater (P = 0.02) fat thickness than the 13.0 and 10.0% CP treatments, whereas carcasses from cattle fed 13.0% CP had greater (P = 0.004) marbling scores than steers fed the 11.5 or 10.0% CP diets. Other carcass characteristics, DMI, and G:F did not differ (P > 0.10) among treatments. The N:P ratio was increased with the 10.0% CP diet (P = 0.02) compared with the 11.5 or 13.5% CP treatments; however, manure composition did not differ (P > 0.10) among treatments. These results indicate that reduced CP concentration during the finishing period does not affect feedlot performance but can improve the N and P relationship in the manure.     

Effects of feeding polyclonal antibody preparations on rumen fermentation patterns, performance, and carcass characteristics of feedlot steers

In a previous study, preparations of polyclonal antibodies (PAP) against Fusobacterium necrophorum (PAP-Fn) or Streptococcus bovis (PAP-Sb) were successful in decreasing ruminal counts of target bacteria and increasing ruminal pH in steers fed high-grain diets. The objective of this study was to evaluate the effects of feeding PAP-Fn or PAP-Sb on performance, carcass characteristics, and ruminal fermentation variables of feedlot steers. In Exp. 1, during 2 consecutive years, 226 or 192 Angus and Angus crossbred steers were fed a high-grain diet containing either PAP-Sb or PAP-Fn, or both. When measured on a BW basis, steers fed only PAP-Sb had a greater G:F (P < 0.05) than those fed no PAP. Nevertheless, when both PAP were fed, feed efficiency was similar (P > 0.10) to steers fed no PAP or only PAP-Sb. Steers receiving PAP-Fn (alone or in combination with PAP-Sb) had a decreased (P < 0.05) dressing percentage. Steers receiving PAP-Fn (alone or in combination with PAP-Sb) had a decreased severity of liver abscess (P < 0.05). No differences (P > 0.10) were observed in any other carcass characteristics. In Exp. 2, sixteen ruminally cannulated Angus crossbred steers (BW = 665 +/- 86 kg) were fed a high-grain diet containing either PAP-Sb or PAP-Fn, or both. Feeding only PAP-Fn or PAP-Sb for 19 d decreased (P < 0.05) ruminal counts of S. bovis when compared with steers fed both or no PAP. The ruminal counts of F. necrophorum in steers fed PAP-Fn alone or in combination with PAP-Sb were decreased by 98% (P < 0.05) after 19 d, when compared with the counts in control steers. Mean daily ruminal pH was greater (P < 0.05) in steers fed both PAP when compared with feeding either or no PAP. Ruminal pH in the first 4 h after feeding was greater (P < 0.05) for steers receiving PAP-Fn alone or in combination with PAP-Sb. Steers receiving either PAP alone or in combination had less (P < 0.05) ruminal NH(3)-N concentrations in the first 4 h after feeding when compared with those of control steers. Polyclonal antibody preparations against S. bovis were effective in enhancing G:F of steers fed high-grain diets, but dressing percentage was decreased. Mechanisms of enhancement of G:F remain unknown but may be related to changes in ruminal counts of target bacteria and associated effects on ruminal fermentation products.     

Effects of forage and protein source on feedlot performance and carcass traits of Holstein and crossbred beef steers.

Fifty-eight Holstein and 58 crossbred beef steers were individually fed one of four isonitrogenous diets to evaluate the effects of forage source (corn silage and alfalfa haylage) and protein source (soybean meal and fish meal) on feedlot performance. Phase 1 diets (up to 354 kg of BW) were 40% forage and 60% concentrates and were fed for 70 to 136 d (depending on diet and breed group). Phase 2 diets (354 kg of BW until slaughter) were 20% forage and 80% concentrates and were fed for 127 to 150 d (depending on diet and breed group). Slaughter end points were .6 cm of 12th rib fat for Holsteins and 1.0 cm of rib fat for crossbreds using real-time ultrasonic estimates. The steers were fed for a maximum of 330 d each year. Forage source was a significant component of variation for most growth, efficiency, and carcass traits. Holstein and crossbred steers fed alfalfa haylage had significantly lower average daily gain, feed efficiency, dressing percentage, and empty body fat and required more days on feed to reach slaughter end points, but had higher total feed energy intake available for production. Steers fed corn silage diets had significantly greater energetic efficiency (P less than .05) than those fed alfalfa haylage, due to increased use of ME to produce fat in the carcass. Protein type did not influence gain, feed or energetic efficiency, energy intake, or most carcass traits. A significant protein system x forage source interaction among the four diets was detected for crossbred steers fed corn silage and fish meal, for which there was significantly greater feed conversion with lower energy intake above maintenance, possibly due to better fiber digestion and(or) amino acid flow to the lower tract. Alfalfa haylage plus soybean meal diets decreased (P less than .05) the percentage of Holsteins grading USDA Choice or higher. These results indicate that corn silage, because of greater energy concentration, was a more desirable forage in feedlot diets composed of less than or equal to 40% forage and that protein type (soybean meal and fish meal) in growing diets is not an important factor in feedlot performance or carcass traits of Holstein or crossbred steers that are fed these diets.     

Effect of wheat and high-moisture sorghum grain fed singly and in combination on ruminal fermentation, solid and liquid flow, site and extent of digestion and feeding performance of cattle

Two experiments were conducted to determine how varying the proportion of wheat (W) and high-moisture sorghum grain (SG) in 80% grain dies would affect ruminal fermentation, liquid and solid flow, site and extent of digestion (Exp. 1) and feeding performance of cattle (Exp. 2). In Exp. 1, three ruminal, duodenal and ileal cannulated steers (average weight 295 kg), fed at 1.54% of body weight, were used in a six-period crossover design. Treatments were: W, 50W:50SG (W:SG) and SG. Increasing wheat level decreased ruminal pH, molar proportion of acetate, and acetate:propionate ratio (P less than .05) and increased (P less than .05) L-lactate concentration, molar proportions of propionate and valerate and total volatile fatty acid concentration. Ruminal liquid dilution and outflow rates were faster (P less than .05) and retention time was shorter (P less than .05) for the W diet. Duodenal and ileal liquid flow increased (P less than .05), and solid flow decreased (P less than .05), as dietary level of wheat increased. Apparent ruminal digestion (% of intake) of dry matter (DM) and organic matter (OM) was greater (P less than .01) with the wheat-containing diets. Intestinal DM and OM digestion (percent of intake) was higher (P less than .05) with the SG and W:SG diets. Ruminal, small intestine, large intestine and total tract starch digestion (percent of intake) was 93.5, 5.6, .7, 99.8, 71.5, 20.4, 5.7, 97.6; and 48.0, 32.5, 10.5, 91.0 with the W, W:SG and SG diets, respectively. In Exp. 2, group-fed (24 pens) steers (avg initial weight 341 kg) were fed ad libitum once daily for 121 d. Treatments were: W, 67W:33SG, 33W:67SG and SG. Rates of gain (kg/d) with the W (1.32), 67W:37SG (1.33) and 33W:67SG (1.30) diets were similar (P greater than .05), but faster (P less than .05) than those with the SG diet (1.16). Feed intake was lower (P less than .01) with the W and 67W:33SG diets, but the wheat-containing diets were utilized more efficiently (P less than .01). Increasing the proportion of wheat in sorghum grain feedlot diets improved cattle performance by optimizing ruminal and post-ruminal digestion.     

Effects of wet corn gluten feed and roughage levels on performance, carcass characteristics, and feeding behavior of feedlot cattle

Two experiments were conducted to evaluate the effects of feeding different levels of wet corn gluten feed (WCGF) and dietary roughage on performance, carcass characteristics, and feeding behavior of feedlot cattle fed diets based on steam-flaked corn (SFC). In Exp. 1, crossbred steers (n = 200; BW = 314 kg) were fed 4 dietary treatments (DM basis): a standard SFC-based diet containing 9% roughage (CON) and 3 SFC-based diets containing 40% WCGF, with either 9, 4.5, or 0% roughage. A linear (P = 0.04) increase in final BW and DMI (P < 0.01) was observed in diets containing WCGF as dietary roughage increased. Steers fed WCGF and higher levels of roughage had greater (P = 0.01) ADG than steers fed lower levels of roughage. Steers fed the CON diet had lower (P = 0.04) daily DMI and greater (P = 0.03) G:F than those fed WCGF. Most carcass characteristics of steers fed CON did not differ (P > 0.10) from those of steers fed WCGF. Based on feed disappearance and visual scan data, consumption rate did not differ (P > 0.10) among treatments; however, feeding intensity (animals present at the bunk after feeding) was greater for steers fed CON (P < 0.01) than for steers fed WCGF. In Exp. 2, yearling crossbred steers (n = 1,983; BW = 339 kg) were fed 4 dietary treatments (DM basis): a standard SFC-based control diet that contained 9% roughage (CON) and 3 SFC-based diets containing either 20% WCGF and 9% roughage or 40% WCGF with 9 or 4.5% roughage. Steers fed the CON diet tended to have lower final BW (P = 0.14), ADG (P = 0.01), and DMI (P < 0.01) than steers fed diets containing WCGF. Steers fed the 20% WCGF diet had greater (P = 0.08) G:F than steers fed the 40% WCGF diets. With 40% WCGF, increasing roughage from 4.5 to 9% decreased (P < 0.01) G:F and increased (P = 0.06) DMI. Gain efficiency was improved (P < 0.01) for steers fed CON vs. those fed diets containing WCGF, whereas HCW (P = 0.02) and dressing percentage (P < 0.01) were greater for steers fed WCGF. Percentage of cattle grading USDA Choice was greater (P = 0.02) for cattle fed WCGF. Results suggest that replacing SFC with up to 40% WCGF increased ADG and decreased G:F when 4.5 to 9.0% roughage was supplied. More CON steers were present at the feed bunk during the first hour after feeding than WCGF steers, suggesting that including WCGF at 40% of the diet affected feeding behavior.     

Effects of calcium soaps of long-chain fatty acids on feedlot performance, carcass characteristics and ruminal metabolism of steers

Two trials were conducted to determine the effects of calcium soaps of long-chain fatty acids (calcium soap) on feedlot performance, diet digestibility, carcass characteristics and ruminal metabolism of steers fed diets (85% concentrate:15% corn silage) containing 0, 2, 4 or 6% calcium soap. In Trial 1, increasing calcium soap decreased (P less than .05) DM, CP and gross energy intake but increased total fatty acid intake. Feed to gain ratio tended to improve with increased calcium soap; gross energy conversion was not affected (P greater than .05) by diet. Average daily gain and hot carcass weight decreased (P less than .05) with addition of calcium soap; other carcass characteristics were not affected (P greater than .05). Apparent digestibilities of DM, N, energy and ash were not affected (P greater than .05) by calcium soap. Neutral detergent fiber digestibility increased linearly (P less than .08) with increasing calcium soap, whereas digestibility of total fatty acids was affected quadratically (P less than .05); fatty acid digestibility was similar among 0, 2 and 4% calcium soap diets but decreased for the 6% calcium soap diet. In Trial 2, increased calcium soap did not affect (P greater than .05) ruminal VFA concentrations, pH or in sacco NDF disappearance of orchardgrass following 12, 24 and 48 h of incubation. Calcium soap increased (P less than .07) ruminal concentrations of calcium soap fatty acids at 1, 2, 4 and 8 h postfeeding. Calcium soap did not improve performance of feedlot cattle fed high-concentrate diets. Further, calcium soap did not affect ruminal fermentation and did not dissociate significantly even when ruminal pH was below 6 for extended periods of time.     

Performance, methanogenesis and nitrogen metabolism of finishing steers fed monensin and nickel

Sixty-four Angus steers initially averaging 354 kg were allotted to a 2 X 2 factorial arrangement of treatments to determine the effects of dietary Ni (0 or 5 mg/kg supplemental), monensin (0 or 33 mg/kg) and their possible interaction on performance, methane production and N metabolism. The basal diet was a high energy, corn-cottonseed hull based diet containing 10.2% crude protein and .30 mg/kg Ni on a dry matter basis. Monensin reduced (P less than .05) feed intake, did not affect average daily gain and improved (P less than .05) feed conversion over the 102-d study. Nickel supplementation did not significantly alter or interact with monensin to affect steer performance. However, steers fed Ni tended to have higher average daily gains and improved feed conversions. Monensin decreased (P less than .05) in vitro methane production, altered several carcass traits, increased (P less than .05) molar proportion of ruminal propionate and decreased (P less than .05) molar proportion of ruminal acetate. Nickel did not alter methane production, carcass characteristics or ruminal volatile fatty acid proportions. Both monensin and Ni increased (P less than .05) ruminal fluid urease activity when samples were obtained before feeding. A significant monensin X Ni interaction was found to affect ruminal epithelial urease activity. Monensin increased ruminal epithelial urease in steers not receiving supplemental Ni, but had no effect on ruminal epithelial urease activity in steers fed supplemental Ni. Ruminal fluid protein and ammonia-N were decreased (P less than .05) by monensin. Results of this study indicate that Ni may interact with monensin to affect ruminal epithelial urease activity but not performance or methane production in finishing steers.     

Effects of 2-hydroxy-4-(methylthio)-butanoic acid on performance and carcass characteristics of finishing beef cattle and on fermentation in continuous culture

Three experiments were conducted to evaluate the effects of feeding 2-hydroxy-4- (methylthio)-butanoic acid (HMTBA) on performance and carcass characteristics of feedlot cattle and on microbial fermentation in a continuous-culture system. In Exp. 1, 160 crossbred steers (initial BW = 385 +/- 10.3 kg) were assigned to 4 treatments consisting of control (0% HMTBA) or 3 diets containing HMTBA (0.069, 0.137, and 0.204%; DM basis) in a randomized complete block design. As the percent of HMTBA increased in the diet, final BW (P = 0.069), final BW adjusted to a constant dressing percent (P = 0.063), and overall ADG (P = 0.099) tended to decrease linearly. Overall DMI decreased linearly (P < or = 0.006) with increasing HMTBA dose. No differences (P > or = 0.10) were noted for carcass characteristics, except for a tendency (P = 0.078) for a linear increase in the percentage of cattle grading USDA Choice with increasing HMTBA dose. In Exp. 2, 80 crossbred steers (initial BW = 450 +/- 17 kg) in a randomized complete block design were assigned to a control (0% HMTBA) diet or to a diet in which the concentrations of HMTBA were gradually increased from 0.036 to 0.212% of DM over a 50-d period. The HMTBA-containing diet tended to decrease DMI (P = 0.132), but G:F (P = 0.319) for the overall feeding period, carcass measurements, and USDA quality grade (P > or = 0.149) did not differ between treatments. In Exp. 3, continuous culture fermenters (n = 5/treatment) were used to determine the effects of HMTBA (control vs. 0.24% HMTBA) on microbial fermentation. No differences (P > or = 0.31) were detected between treatments in ruminal OM digestibility, microbial N synthesis, pH, ammonia, molar proportions of VFA, or effluent concentration of selected long-chain fatty acids. These results suggest that HMTBA decreased DMI by feedlot steers fed a steam-flaked corn-based diet in a dose-dependent manner; however, gradually increasing the dose over time seemed to moderate effects on DMI. No major changes in microbial fermentation in continuous culture were observed with HMTBA at 0.24% of dietary DM, suggesting effects of HMTBA on DMI were not likely associated with changes in ruminal digestion or fermentation.     

Effect of undegradable intake protein supplementation on intake, digestion, microbial efficiency, in situ disappearance, and plasma hormones and metabolites in steers fed low-quality grass hay

Four ruminally and duodenally cannulated beef steers (492 +/- 30 kg) were used in a 4 x 4 Latin square design to evaluate the effect of undegradable intake protein (UIP) supplementation on intake, digestion, microbial efficiency, in situ disappearance, and plasma hormones and metabolites in steers fed low-quality grass hay. The steers were offered chopped (10.2 cm in length) grass hay (6.0% CP) ad libitum and 1 of 4 supplements. Supplemental treatments (1,040 g of DM daily), offered daily at 0800, were control (no supplement) or low, medium, or high levels of UIP (the supplements provided 8.3, 203.8, and 422.2 g of UIP/ d, respectively). The supplements were formulated to provide similar amounts of degradable intake protein (22%) and energy (1.77 Mcal of NE(m)/kg). Blood samples were taken at -2, -0.5, 1, 2, 4, 8, 12, and 24 h after supplementation on d 1 (intensive sampling) and at -0.5 h before supplementation on d 2, 3, 4, and 5 (daily sampling) of each collection period. Contrasts comparing control vs. low, medium, and high; low vs. medium and high; and medium vs. high levels of UIP were conducted. Apparent and true ruminal OM and N digestion increased (P < 0.03) in steers fed supplemental protein compared with controls, but there were no differences (P > 0.26) among supplemental protein treatments. There were no differences (P > 0.11) among treatments for NDF or ADF digestion, or total ruminal VFA or microbial protein synthesis. Ruminal pH was not different (P = 0.32) between control and protein-supplemented treatments; however, ruminal pH was greater (P = 0.02) for supplementation with medium and high compared with low UIP. Daily plasma insulin concentrations were increased (P = 0.004) in protein-supplemented steers compared with controls and were reduced (P = 0.003) in steers fed low UIP compared with steers fed greater levels of UIP. Intensive and daily plasma urea N concentrations were increased (P < 0.01) in protein-supplemented steers compared with controls and increased (P < 0.02) for intensive and daily sampling, respectively, in steers supplemented with medium and high UIP compared with low UIP. Supplemental protein increased apparent and true ruminal OM and N digestion, and medium and high levels of UIP increased ruminal pH compared with the low level. An increasing level of UIP increases urea N and baseline plasma insulin concentrations in steers fed low-quality hay.     

Influence of feed intake fluctuation and frequency of feeding on nutrient digestion, digesta kinetics, and ruminal fermentation profiles in limit-fed steers

Nine crossbred beef steers (344 +/- 26 kg) fitted with ruminal cannulas were used in a randomized complete block design to evaluate the effects of feeding frequency and feed intake fluctuation on total tract digestion, digesta kinetics, and ruminal fermentation profiles in limit-fed steers. In Period 1, steers were allotted randomly to one of four dietary treatments: 1) feed offered once daily at 0800; 2) feed offered once daily at 0800 with a 10% fluctuation in day-to-day feed intake; 3) feed offered twice daily at 0800 and 1700; and 4) feed offered twice daily at 0800 and 1700 with a 10% fluctuation in a day-to-day feed intake. In Period 2, steers were reallocated across treatments. The 90% concentrate diet was fed at 90% of the ad-libitum consumption by each steer. Chromium-EDTA and Yb-labeled steam-flaked corn were intraruminally infused at 0800 on d 1 and 3 and Co-EDTA and Er-labeled steam-flaked corn were infused on d 2 and 4 of the 4-d collection period. Ruminal samples were collected at 0, 3, 6, 9, 12, 15, 18, and 24 h after the 0800 feeding, and total feces were collected for 4 d. Total tract digestibilities of OM, N, and starch were lowest (fluctuation x frequency, P < .05) when feed was offered twice daily with a 10% fluctuation in intake. Ruminal fluid volume and passage rate were not affected (P > .10) by feeding frequency or intake fluctuation. A frequency x fluctuation x sampling time interaction occurred (P < .01) for ruminal pH. Steers fed a constant amount of feed once daily had higher (P < .05) ruminal pH at 0, 3, 18, and 24 h than steers fed once daily with a 10% fluctuation in feed intake. Total VFA concentration was greater (P < .01) at 9 h after the 0800 feeding when feed was offered once vs twice daily. Feeding twice daily increased (P < .05) the molar proportion of acetate and decreased (P < .05) the molar proportion of propionate. Increasing feeding frequency resulted in a more stable ruminal environment; however, the increased acetate:propionate ratio with twice-daily feeding might result in lower efficiency of energy utilization by limit-fed steers.     

Influence of lasalocid and monensin plus tylosin on comparative feeding value of steam-flaked versus dry-rolled corn in diets for feedlot cattle

Two trials were conducted to characterize the differences in utilization of dry-rolled and steam-flaked corn in a growing-finishing diet for feedlot cattle supplemented with and without ionophores. Ionophore treatments were: 1) no ionophore, 2) 33 mg/kg monensin sodium plus 11 mg/kg tylosin and 3) 33 mg/kg lasalocid sodium. In trial 1, treatment effects on feedlot performance were evaluated in a 239-d growing-finishing trial involving 180 crossbred steers (approximately 25% Brahman with the remainder represented by Hereford, Angus, Shorthorn and Charolais breeds in various proportions) with an average initial weight of 153 kg. In trial 2, treatment effects on characteristics of digestion were evaluated using six steers of similar breeding and background to those used in trial 1, with cannulas in the rumen and proximal duodenum. There were no interactions between corn processing and ionophore supplementation (P greater than .20). Average daily gain was not affected by steam-flaking as opposed to dry-rolling, however, feed intake was decreased 5.4% and feed conversion was improved 6.8% (P less than .01). Steam-flaking increased the estimated net energy value of the diet 7.7% and 8.5% for maintenance and gain, respectively (P less than .01). Steam-flaking increased the digestibility of starch 6.6% (P less than .01). Steam-flaking increased ruminal molar concentrations of propionate and decreased acetate:propionate ratio and estimated methane production (P less than .10). Both monensin-tylosin and lasalocid resulted in reduced feed intake (12.3 and 6.5%, respectively, P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of source of energy and rate of growth on performance,carcass characteristics,ruminal fermentation,and serum glucose and insulin of early-weaned steers

Seventy-three crossbred steers (initial BW = 170.5 +/- 5.5 kg) from The Ohio State University (Exp. 1) and 216 crossbred steers (initial BW 135.4 +/- 4.4 kg) from the University of Illinois (Exp. 2) were used to determine the effect of source of energy and rate of growth on performance, carcass characteristics, and glucose and insulin profiles on early-weaned steers. Effects of the diets used in Exp. 1 and 2 on ruminal pH and VFA concentrations were quantified using ruminally fistulated steers (Exp. 3). Cattle were weaned at an average age of 119 d in all experiments and were allotted by age, BW, and breed to one of four diets: high-concentrate, fed ad libitum (ALCONC), high-concentrate fed to achieve a gain of either 1.2 kg/d (1.2CONC) or 0.8 kg/d (0.8CONC), or high-fiber, fed ad libitum (ALFIBER). At 218 d of age, all steers were placed on the ALCONC diet until slaughter. Steers were implanted with Compudose at the initiation of all experiments and with Revalor-S when they were estimated to be 100 d from slaughter. When steers in Exp. 1 averaged 181 and 279 d of age, serum samples were collected to determine glucose and insulin concentrations. Steers were slaughtered when a fat thickness of 1.27 cm was reached (Exp. 1) or after 273 d on feed (Exp. 2). In Exp. 1, days in the feedlot (P < 0.01) and age at slaughter (P < 0.01) were lowest for ALCONC and ALFIBER steers, and greatest for 0.8CONC steers. Overall, ADG was greatest for ALCONC and lowest for 0.8CONC steers; feed efficiency was lowest (P < 0.01) for ALFIBER steers. Final BW did not differ (P > 0.57) among treatments. At 181 and 218 d of age, serum insulin was increased (P < 0.10) and intramuscular fat percentage was greatest (P < 0.07), respectively, for ALCONC steers. In Exp. 2, overall ADG (P < 0.06) and final BW (P < 0.04) were greatest for ALCONC and lowest for 1.2CONC and 0.8CONC steers. Overall feed efficiency was greatest for 0.8CONC and lowest for ALFIBER (P < 0.01). Growing phase diet did not affect marbling score at 218 d of age or at slaughter (P > 0.81). In Exp. 3, differences in ruminal pH after feeding may have been a consequence of increasing acetate (ALFIBER), propionate (ALCONC), or a combination of VFA (0.8CONC and 1.2CONC), respectively (diet x time after feeding, P < 0.10). Controlling growth by limit-feeding a high-concentrate diet for only 100 d does not extend the growth curve of early-weaned steers or enhance intramuscular fat deposition at slaughter compared to ad libitum intake of a high-concentrate or high-fiber diet.     

Influence of forage level on response of feedlot steers to salinomycin supplementation

Two trials were conducted to evaluate the influence of forage level on the response of feedlot cattle to salinomycin. Diets containing 10, 15 and 20% forage were compared with 0 or 11 mg/kg salinomycin. In trial 1, treatment effects on feedlot performance were evaluated using 108 crossbred steers (295 kg) in a crossover design experiment. There were no salinomycin X forage level interactions (P greater than .20). Weight gain response to salinomycin supplementation averaged 5.4, 5.3 and 6.9%, respectively, for diets containing 10, 15 and 20% forage. Corresponding values for feed conversion response to salinomycin supplementation were 5.1, 3.9 and 5.9%. Averaged across forage level, salinomycin supplementation improved rate of weight gain and feed conversion by 5.9 and 5.2%, respectively (P less than .01). In trial 2, treatment effects on characteristics of ruminal and total tract digestion were evaluated in a 6 X 6 Latin-square design trial involving six crossbred steers (191 kg) with cannulae in the rumen and proximal duodenum. There were no interactions between salinomycin supplementation and forage level on characteristics of ruminal digestion (P greater than .20). Salinomycin supplementation did not influence synthesis of microbial N, ruminal digestion of organic matter, acid detergent fiber and starch, or molar proportions of acetate, propionate and butyrate (P greater than .20). Salinomycin supplementation increased passage of non-ammonia N to the small intestine (5.4%, P less than .10) and increased ruminal escape of feed N (24%, P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of imposed feed intake variation on acidosis and performance of finishing steers.

Four metabolism and two finishing trials were conducted to determine the effects of imposed feed intake variation on acidosis and performance of finishing steers. In Metabolism Trial 1, four ruminally fistulated steers were limit-fed and subjected to either a constant amount of feed per day (C) or low intake variation of .7 kg/d (LV). No treatment differences were found for intake or measures of acidosis. Metabolism Trial 2 was conducted similarly to Metabolism Trial 1 with treatments of C and high intake variation of 1.4 kg/d (HV). Treatment HV increased (P < .05) acidosis, as indicated by the area of ruminal pH below 5.6. In Metabolism Trial 3, four steers were fed at ad libitum levels of intake and subjected to three levels of intake variation: ad libitum intake with no imposed intake variation (AL), LV of .7 kg/d, and HV of 1.4 kg/d. No treatment differences were found. In Metabolism Trial 4, six ruminally fistulated steers were fed at ad libitum levels and subjected to three levels of intake variation: AL, LV of .9 kg/d, and HV of 1.8 kg/d. Average ruminal pH increased (P < .05) and area of ruminal pH below 5.6 decreased (P < .05) as level of intake variation was increased. In Finishing Trial 1, 75 steers were assigned to eight pens and two treatments: AL or HV of 1.8 kg/d. Dry matter intake increased (P < .05) from AL to HV. Daily gain and gain/feed were not affected by treatment. In Finishing Trial 2, 94 steers were assigned to 12 pens and two treatments: AL or HV of 1.8 kg/d. No treatment differences were noted in DMI, daily gain, or gain/ feed. Therefore, results of these trials indicate that intake variation of up to 1.8 kg/d does not increase acidosis or decrease performance of finishing steers fed at ad libitum levels of intake.