Influence of level and source of dietary fat on its comparative feeding value in finishing diets for steers: feedlot cattle growth and performance

Two hundred twenty-eight crossbred steers (304 kg) were used in a 125-d comparative slaughter trial to evaluate the influence of level and source of supplemental fats on their feeding value for feedlot cattle. Dietary treatments consisted of a steam-rolled, barley-based finishing diet containing 1) no supplemental fat; 2) 4% yellow grease (YG); 3) 4% blended animal-vegetable fat (BVF); 4) 8% YG; 5) 8% BVF or 6) 6% BVF and 2% crude soybean lecithin. Increasing level of supplemental fat in the diet resulted in linear improvements (P less than .01) in weight gain, feed conversion and NE value of the diet. Estimated NE values of YG and BVF were similar and did not appear to be influenced by level of supplementation, averaging 5.78 and 4.61 Mcal/kg for maintenance and gain, respectively. Fat supplementation resulted in linear increases in empty body fat (P less than .01), kidney, pelvic and heart fat (P less than .01) and marbling score (P less than .05). Partially replacing BVF with lecithin did not influence (P greater than .10) steer performance, carcass merit or estimated NE value of the diet. The comparative feeding value (in terms of both diet acceptability and NE value) of the supplemental fats tested was similar and was apparently not influenced by level of supplementation up to 8% of diet DM.     

Interaction of dietary magnesium level on the feeding value of supplemental fat in finishing diets for feedlot steers

A feeding trial involving 160 crossbred steers (357 kg) and a metabolism trial involving eight Holstein steers (189 kg) cannulated in the rumen and proximal duodenum were conducted to evaluate the interaction of dietary Mg level (.18 vs .32%, DM basis) and supplemental fat (0% supplemental fat vs 4% tallow [T], yellow grease [YG], or griddle grease [GG]) on growth performance and NE value of the diet. Dietary Mg level did not influence (P > .10) growth performance. Daily weight gain was lower (11%, P < .05) for steers fed GG than for those fed YG. Supplemental fat decreased (5%, P < .10) DMI and increased (P < .05) gain efficiency (7%). There was a fat x Mg level interaction (P < .01) for dietary NE. The increase in dietary NEg with T and YG supplementation was similar (8.6 vs 8.0%) for diets containing .18 and .32% Mg. In contrast, the increase in dietary NEg with GG supplementation was 8.9% with .18% dietary Mg, but the NEg value of the diet did not increase when GG was added to diets with .32% dietary Mg. Dressing percentage was lower (1.5%, P < .1) and retail yield was greater (2.2%, P < .05) for steers fed GG- than for steers fed YG-supplemented diets. Increasing dietary Mg level increased kidney, pelvic, and heart fat (5.5%, P < .05). There was a fat x Mg level interaction (P < .1) for marbling score. With diets containing no supplemental fat, increasing dietary Mg decreased (15.2%) the marbling score, and with diets containing supplemental fat, increasing dietary Mg increased (7.2%) the marbling score. Fat supplementation decreased (P < .01) ruminal and total tract digestion of OM (10 and 3.5%, respectively) and NDF (37 and 17%, respectively). Supplemental fat did not affect (P > .10) Ca digestion but decreased (41.7%, P < .01) apparent Mg digestion. Increasing dietary Mg level increased (77.7%, P < .05) apparent Mg digestion. There were no treatment effects (P > .10) on postruminal fatty acid digestion. Fat supplementation decreased (17.3%, P < .01) the acetate:propionate molar ratio. Total ruminal protozoal counts were increased (12.7%, P < .05) by increasing dietary Mg level and decreased (12.9%, P < .05) by fat supplementation. We conclude that supplemental fats may depress Mg absorption. Increasing dietary magnesium levels beyond current recommendations may increase marbling scores in cattle fed fat-supplemented diets but may not affect growth performance or dietary NE. The NE value of fat is a predictable function of level of fat intake.     

Comparative feeding value of supplemental fat in finishing diets for feedlot steers supplemented with and without monensin

Two comparative slaughter trials and a metabolism trial were conducted. Treatments consisted of: 1) 0 fat, 0 monensin; 2) 4% yellow grease, 0 monensin; 3) 0 fat, 33 mg/kg monensin and 4) 4% yellow grease, 33 mg/kg monensin. Trial 1 involved 104 crossbred beef steers (267 kg) in a 140-d comparative slaughter trial. There were no interactions (P greater than .20) between supplemental fat and monensin on steer performance. Monensin supplementation decreased rate of weight gain (P less than .10) and feed intake (P less than .05) with no effect on energy value of the diet (P greater than .20). Fat supplementation increased (P less than .01) rate of weight gain 12.5% and increased the net energy for maintenance (NEm) and net energy for gain (NEg) value of the diet 8.5 and 9.4%, respectively. Trial 2 involved 154 Holstein steers (290 kg) in a 94-d comparative slaughter trial. There were no interactions between supplemental fat and monensin (P greater than .20). Monensin supplementation did not affect rate or composition of gain (P greater than .20), but supplementation reduced (P less than .05) feed intake and feed required per unit weight gain 3.6%. Fat supplementation increased (P less than .01) fat and energy gain 12.5 and 10.3%, respectively, and the NEm and NEg content of the diet 7.5 and 8.4%, respectively. Trial 3 utilized four crossbred beef steers (220 kg) with cannulas in the rumen, proximal duodenum and distal ileum. There were no interactions between supplemental fat and monensin with respect to site of digestion (P greater than .20). Supplemental fat did not affect (P greater than .20) organic matter, starch, fiber or N digestion. Intestinal digestibility of fat averaged 77.3%. Monensin increased (P less than .10) intestinal digestibility of fat 7.4%. There were negative associative effects between supplemental fat and monensin on ruminal acetate:propionate ratios and estimated methane production. It was concluded that the feeding value of feed fat is underestimated in tables of feed standards currently in use, and that the net effects of monensin on these estimates are additive.     

Comparative feeding value of supplemental fat in steam-flaked corn- and steam-flaked wheat-based finishing diets for feedlot steers.

One hundred thirty crossbred steers (324 kg) were used in a 121-d comparative slaughter trial to evaluate the feeding value of fat in steam-flaked corn- (SFC) or wheat- (SFW) based diets. Treatments consisted of an 88% concentrate finishing diet containing 1) SFC, no fat; 2) SFC, 6% yellow grease (YG); 3) SFC, 6% cottonseed oil soapstock (COS); 4) SFW, no fat; 5) SFW, 6% YG; and 6) SFW, 6% COS. There were no interactions (P greater than .10) between grain type and performance response to supplemental fat. Fat supplementation increased (P less than .05) ADG by 7.3% and decreased (P less than .01) DMI/gain by 10.6%. Fat supplementation decreased (P less than .05) ruminal OM digestion by 5% and net flow of microbial N to the small intestine by 14.5% but did not affect (P greater than .10) total tract digestion of OM, ADF, or starch. Substituting SFW for SFC did not influence (P greater than .10) ADG but tended (P greater than .10) to increase DMI/gain and decreased (P less than .05) the NEm and NEg of the diet by 3.4 and 4.3%, respectively. Ruminal OM digestion was similar (P greater than .10) for SFC and SFW. Flow of microbial N to the small intestine was 12% greater (P less than .05) with SFW. Total tract digestibilities of OM and starch were similar (P greater than .10) for both grains. However, ADF digestion was lower (34%, P less than .01) with SFW. It is concluded that the feeding value of supplemental fat is similar for wheat- and corn-based finishing diets. The performance response to supplemental YG and COS was similar. The NEm and NEg values of YG were 6.35 and 4.93 Mcal/kg, respectively, whereas the corresponding values for COS were 5.69 and 4.60 Mcal/kg. Supplementation of growing-finishing diets with up to 6% (.45 kilograms/day) of fat did not directly influence body composition. The NE value of SFW was approximately 96% of the value of SFC.     

Influence of ruminal biohydrogenation on the feeding value of fat in finishing diets for feedlot cattle

Four Holstein steers (212 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to study the influence of degree of ruminal biohydrogenation (BH) on the feeding value of supplemental fat. Treatments consisted of an 88% concentrate finishing diet supplemented with 1) 2% yellow grease (control); 2) 4% formaldehyde-protected fat (Rumentek), 2% yellow grease (LBH); 3) 2% Rumentek, 4% yellow grease (MBH); or 4) 6% yellow grease (HBH). Ruminal BH of HBH, MBH, and LBH diets was 74, 68, and 54%, respectively. High-fat supplementation decreased (7%, P < .05) intestinal digestibility of 18:0 but increased intestinal digestibility of 18:1 (3%, P < .10), 18:2 (14%, P < .01), and 18:3 (23%, P < .05). Increases in intestinal digestibility of 18:0 (quadratic effect, P < .05), 18:1 (linear effect, P < .01), 18:2 (linear effect, P < .01), 18:3 (linear effect, P < .05), and total fatty acids (linear effect, P < .05) were inversely related to BH. For every 1% increase in the proportion of 18:1 fat entering the small intestine, the digestibility of 18:0 increased 1%. High-fat supplementation depressed ruminal digestion of OM (11%, P < .05), NDF (16%, P < .05), starch (6%, P < .05), and feed N (12%, P < .01). Formaldehyde-protein protection of fat diminished its depressing effects on ruminal digestion of NDF (quadratic effect, P < .10) and enhanced ruminal escape of feed N (linear effect, P < .10). Postruminal digestion of OM was greater (4.6%, P < .10) for high-fat diets. High-fat diets decreased (P < .05) total tract digestion of OM (1.9%), NDF (7.4%), and starch (.5%). Postruminal and total tract digestibility of OM, NDF, N, and starch was not affected (P > .10) by BH. In a 125-d finishing trial, 100 yearling steers (362 kg) were used to evaluate treatment effects on growth performance. High-fat diets did not affect (P > .10) ADG but increased (P < .10) feed efficiency (9%, P < .10), dietary NEm (7.6%, P < .05), and dressing percentage (9%, P < .05). The magnitude of the increase in dressing percentage was inversely related (linear effect, P < .10) to BH. We conclude that decreasing ruminal BH will increase postruminal digestibility of fat, and hence the NE value of dietary fat. The synergistic effect of increasing the proportion of 18:1 on intestinal digestion of fat enables higher levels of fat supplementation. Protecting fat from BH minimizes the detrimental effects of supplemental fat on fiber digestion.     

Influence of slice baling on feeding value of alfalfa hay in receiving and finishing diets for feedlot cattle

Three studies were conducted to evaluate the feeding value of slice alfalfa hay in feedlot diets. In Exp. 1, 108 steer calves (183.1 +/- 1.2 kg initial BW; 6 pens/treatment) were used in a completely randomized design to evaluate the effect of baling method on performance and morbidity of newly received calves. The study lasted 28 d. Treatments consisted of a 65% concentrate receiving diet containing 1) ground or 2) slice alfalfa hay. Steer calves were fed daily at 0800 h. Animals also received long-stem sudangrass hay the first 7 d. Steers were weighed on d 0, 16, and 28. Feed, sudangrass hay, or feed plus sudangrass hay intakes were not affected (P > 0.25) by treatment. Conversely, ADG from d 0 to 16 was greater (P < 0.001) for slice than ground (1.27 vs. 0.81 +/- 0.067 kg/d, respectively) and from d 0 to 28 (1.23 vs. 0.91 +/- 0.042 kg/d, respectively). In addition, G:F was greater (P < 0.001) for slice than ground hay from d 0 to 16 (0.39 vs. 0.25 +/- 0.021), and from d 0 to 28 (0.31 vs. 0.24 +/- 0.013 for slice and ground, respectively). Moreover, morbidity (40.5 +/- 3.9%; P = 0.20) and retreatment rates (30.7 +/- 7.5%; P = 0.14) were similar for slice and ground. In Exp. 2, 176 crossbred steers (393.9 +/- 10.8 kg initial BW) were used in an 84-d feeding experiment (4 pens/treatment) in a randomized complete block experimental design with a 2 x 2 factorial arrangement of treatments to evaluate effects of alfalfa baling method (ground or slice) and forage level (8 or 14%) on growth performance. Experimental diets were based on steam-flaked corn. Daily BW gain was greater (P = 0.10) for steers consuming ground compared with the slice hay diet. A baling method x forage level interaction (P = 0.07) was observed for DMI. Baling method did not (P = 0.98) influence DMI with 8% roughage level. But with 14% roughage, DMI was greater (P = 0.02) for steers consuming ground hay than the slice diet. The G:F ratio was affected (P = 0.03) only by forage level (0.194 vs. 0.182 +/- 0.003 for 8 and 14% roughage, respectively). In Exp. 3, 4 ruminally cannulated mixed-breed steers were used in a 4 x 4 Latin square design to evaluate effects on digestive function. No baling method effects (P >or= 0.16) were detected for DM, OM, CP, or NDF intakes or DM, OM, and NDF total tract digestibility. Digestibility of NDF and OM were greater (P 相似文献   

Supplemental fat source affects feedlot performance and carcass traits of finishing yearling steers and estimated diet net energy value

Two trials that utilized 356 yearling steers were conducted to evaluate the effects of fat sources (3.5% of diet dry matter) in steam-flaked milo finishing diets. Fats differed in fatty acid composition and level of free fatty acids. In Trial 1, soybean oil, tallow and yellow grease were compared to a nonfat control. Feeding fat increased (P less than .05) daily gain, feed efficiency, estimated diet NE concentration, carcass weight and dressing percentage of steers. In Trial 2, fat treatments were control, acidulated soybean soapstock (SBSS), tallow, a blend of 70% SBSS:30% tallow, and yellow grease. Feeding tallow or the SBSS:tallow blend improved (P less than .05) feed efficiency and estimated dietary NE compared to control. Proportions of palmitic, stearic, oleic, linoleic and linolenic acid in longissimus muscle of steers were altered (P less than .05) by source of supplemental fat. Potential variability in animal response to fat blends was demonstrated by differences in animal response to yellow grease in the two trials. It was concluded that fats vary in feeding value and may alter carcass composition, contrary to putative thought. Further, potential associative effects of fat blends and interactions of fat with other dietary components in high-grain finishing diets require further investigation.     

Influence of free fatty acid content on the feeding value of yellow grease in finishing diets for feedlot cattle.

Holstein steers (n = 96; 375 kg) were used in a 144-d growth-performance trial to evaluate influence of level (42, 28.5, and 15%) of FFA content on feeding value of yellow grease. Two sources of yellow grease were compared: conventional yellow grease (CYG), containing 15% FFA, and griddle grease (GG), containing 42% FFA. Dietary treatments consisted of an 88% concentrate finishing diet supplemented with either 1) 0% fat, 2) 5% GG, 3) 2.5% GG and 2.5% CYG, or 4) 5% CYG. Fat supplementation increased ADG (11%; P<.05), feed efficiency (9%; P<.05), diet NE (6.4%; P<.05), carcass weight (4%; P<.10), dressing percentage (1%; P<.10), and kidney, pelvic, and heart fat (20%, P<.05). Increasing the FFA in supplemental fat increased (linear effect, P<.10) DM intake, ADG, and feed efficiency and decreased (linear effect, P<.10) retail yield. These improvements in performance were primarily due to increased DM intake. The NEm and NEg values of supplemental fats were not affected by FFA content, averaging 4.98 and 3.85 Mcal/kg, respectively. Treatment effects on characteristics of ruminal and total tract digestion were evaluated using four Holstein steers (180 kg) with cannulas in the rumen and proximal duodenum. Supplemental fat did not influence (P>.10) ruminal or total tract digestion of OM, ADF, starch or N. Postruminal fatty acid digestion was less (P<.10) for fat-supplemented diets than for unsupplemented diets (73.0 vs. 78.6%). The decrease in postruminal fatty acid digestibility with fat supplementation was mainly due to a decreased (16.7%; P<.05) digestibility of C18:0. Postruminal digestibility of the supplemental fat was 68%. There were no treatment effects (P>.10) on ruminal pH. Ruminal biohydrogenation of fatty acids was directly proportional to estimates of methane production. We conclude that the feeding value of conventional yellow grease and griddle grease is similar and that differences in the FFA content of yellow grease will not negatively affect diet acceptability and growth performance of feedlot cattle.     

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)     

Relationship between feeding behavior and performance of feedlot steers fed barley-based diets

The relationship between feeding behavior and performance of 274 feedlot cattle was evaluated using Charolais cross steers from 2 consecutive years averaging 293 ± 41 kg for yr 1 (n = 115) and 349 ± 41 for yr 2 (n = 159). Steers were blocked by BW and assigned to 3 (yr 1) or 4 (yr 2) feedlot pens equipped with a radio frequency identification system (GrowSafe Systems). Each pen contained 5 feeding stalls that allowed individual animal access to a feed tub suspended on load cells. The system recorded animal identification, duration, and frequency of feedings as well as the amount of feed consumed during each visit. Daily variation in DMI (DVI), calculated as the absolute difference in DMI from one day to the next, as well as eating rate were determined for each steer. Barley-based diets were delivered to meet steer ad libitum intake over the 213- and 181-d feeding periods for yr 1 and 2 of the study, respectively. The backgrounding periods included the first 85 and 56 d of yr 1 and 2, respectively, in which steers were fed a 14 to 30% concentrate diet, whereas the finishing periods included the last 116 and 101 d of feeding in yr 1 and 2, respectively, with the diet consisting of 77.9% concentrate. Steers were weighed individually every 14 d. To relate feeding behavior to performance, steers were grouped by ADG and G:F and categorized as high, average, or low (based on 1 SD greater than and less than the mean). In the backgrounding and finishing periods of both years of the study, steers classified as having high ADG exhibited greater (P < 0.001) DVI than steers classified as having average or low ADG. Total daily DMI was also greater (P < 0.001) for steers in the high ADG group than those in the low ADG group. Overall, those steers with the greatest G:F also tended (P = 0.15) to have greater DVI than average or low G:F steers. Compared with average or low G:F steers, DMI by high G:F steers in both years of the study was less during backgrounding, finishing, and overall (P = 0.02). Bunk visits and bunk attendance duration were less frequent and shorter (P ≤ 0.01) overall for high compared with low G:F steers. In this study, steers with more variable eating patterns exhibited greater ADG and tended to have greater G:F, a finding that is contrary to industry perception.     

Effect of silage chop length on feed intake and feeding behaviour of finishing feedlot steers

This study determined the effects of silage chop length (20?mm; long or 10?mm; short) and diurnal time on feeding behaviour of 80 feedlots steers. Feed intake and feeding behaviour of each steer in each pen were measured continuously from 0:00 to 12:00?h (AM) and from 12:00 to 24:00?h (PM). Chop length had no effect on feed intake or the growth performance of steers, but longer chop length increased the duration of feeding and reduced the rate of intake. Head down time and head down time per feeding activities were greater during the PM than AM. There was a chop length?×?diurnal time interaction for feeding frequency with the number of bunk visits being greater in the PM than AM for both diets. Feeding activities were 50% higher during the PM than AM when steers were fed either long- or short-chopped silage diets twice daily.     

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.     

Effects of dietary copper source and concentration on carcass characteristics and lipid and cholesterol metabolism in growing and finishing steers

We conducted an experiment to determine the effects of dietary copper (Cu) source and level on carcass characteristics, longissimus muscle fatty acid composition, and serum and muscle cholesterol concentrations in steers. Sixty Angus and Angus x Hereford steers were stratified by weight and initial liver Cu concentration within a breed and randomly assigned to treatments. Treatments consisted of: 1) control (no supplemental Cu); 2) 20 mg Cu/kg DM from Cu sulfate (CuSO4); 3) 40 mg Cu/kg DM from CuSO4; 4) 20 mg Cu/kg DM from Cu citrate; 5) 20 mg Cu/kg DM from Cu proteinate; and 6) 20 mg Cu/kg DM from tribasic Cu chloride. A corn silage-soybean meal-based diet was fed for 56 d. Steers were then switched to a high-concentrate diet. Equal numbers (n = 5) of steers per treatment were slaughtered after receiving the finishing diets for either 101 or 121 d. Serum cholesterol was not affected by treatment during the growing phase but was decreased (P < .05) in steers supplemented with Cu by d 84 of the finishing period and remained lower (P < . 05) at subsequent sampling periods. Longissimus muscle cholesterol concentration tended to be reduced (P < .11) by Cu supplementation. Hot carcass weight and backfat were lower (P < .05) in animals receiving supplemental Cu. However, Cu-supplemented and control steers had similar marbling scores. Longissimus muscle polyunsaturated fatty acid concentrations (18:2 and 18:3) were increased (P < .07) and saturated fatty acid concentrations tended (P < . 11) to be reduced by Cu supplementation. These results indicate that as little as 20 mg of supplemental Cu/kg diet can reduce backfat and serum cholesterol and increase muscle polyunsaturated fatty acids in steers fed high-concentrate diets.     

Influence of surfactant supplementation and maceration on the feeding value of rice straw in growing-finishing diets for Holstein steers

Two trials were conducted to evaluate the interaction of the maceration process and surfactant (Tween 80) supplementation on feeding value of rice straw. Treatments were steam-flaked, corn-based diets containing 14% forage (DM basis), which was 1) Sudangrass hay; 2) ground rice straw; 3) ground rice straw plus 0.22% Tween 80; 4) macerated rice straw; and 5) macerated rice straw plus 0.22% Tween 80. In the maceration process, rice straw was passed through 2 sequentially placed pairs of corrugated rolls set at zero tolerance under a ram pressure of 62,050 millibars, similar to a conventional grain roller mill, except that the opposing rolls operated at different speeds (12 and 14 rpm, respectively). Sudangrass hay and rice straw (native and macerated) were ground through a 2.6-cm screen before incorporation into complete mixed diets. In trial 1, 125 Holstein steers (292 +/- 1.7 kg of BW) were used in a 188-d evaluation of the treatment effects on growth performance and carcass characteristics. In trial 2, 5 Holstein steers (224 +/- 3.5 kg of BW) with cannulas in the rumen and proximal duodenum were used in a 5 x 5 Latin square design to evaluate the treatment effects on digestion. There were no interactions between maceration and surfactant on growth or carcass characteristics. Tween 80 did not influence the feeding value of rice straw. Compared with grinding alone, maceration of rice straw increased the carcass-adjusted ADG (6%, P < 0.10), G:F (6%, P < 0.05), and dietary NE (5%, P < 0.05); DMI was similar across treatments. Assuming NE(m) and NE(g) of Sudangrass hay are 1.18 and 0.62 Mcal/kg, the NE(m) and NE(g) were 0.61 and 0.13 Mcal/kg for ground rice straw and 1.21 and 0.65 Mcal/kg for macerated rice straw. There were no treatment interactions on characteristics of digestion. Tween 80 did not influence ruminal or total tract digestion of OM, starch, NDF, or N. Compared with grinding alone, maceration of rice straw increased ruminal digestion of OM (7.7%, P < 0.10) and NDF (30.8%, P < 0.05), and total tract digestion of OM (2.3%, P < 0.10), NDF (21.1%, P < 0.01), and N (3.7%, P < 0.05). Total tract digestion of OM, NDF, starch, and N for the Sudangrass diet corresponded closely with that of the macerated rice straw diets. Maceration increases the feeding value of rice straw to a level similar to that of good-quality (flag stage of maturity) Sudangrass hay, which is attributable to increased OM and NDF digestion. Effects of surfactant supplementation on growth performance and digestion are not appreciable.     

Influence of dietary manganese on performance, lipid metabolism, and carcass composition of growing and finishing steers

A study was conducted to determine the effect of dietary Mn on performance of growing and finishing steers, and to evaluate the effect of pharmacological concentrations of Mn on lipid metabolism and subsequent carcass quality in steers. One hundred twenty Angus cross steers were blocked by BW and origin and assigned randomly to one of six treatments (four replicate pens per treatment) providing 0 (control), 10, 20, 30, 120, or 240 mg of supplemental Mn/kg of DM from MnSO4. Steers were fed a corn silage-based growing diet for 84 d, and then switched to a corn-based finishing diet for an average of 112 d. The control growing diet analyzed 29 mg of Mn/kg of DM, whereas the control finishing diet analyzed 8 mg of Mn/kg of DM. Jugular blood samples were obtained on d 56 of the growing and finishing phase for plasma Mn and glucose analysis. Final BW, DMI, ADG, and G:F did not differ (P = 0.38 to P = 0.98) across treatments during growing and finishing phases. Plasma Mn concentrations were not affected by treatment; however, liver and LM Mn at slaughter increased linearly (P = 0.02 and 0.002, respectively) with increasing dietary Mn. Plasma glucose concentrations did not differ (P = 0.90) among treatments. Serum nonesterified fatty acid concentrations tended (P = 0.10) to decrease linearly with increasing dietary Mn on d 56 of the finishing phase. Longissimus muscle lipid concentration was affected quadratically (P = 0.08) by dietary Mn. Muscle lipid seemed to increase slightly when steers were fed 30 or 120 mg of Mn/kg of DM, but decreased with the addition of 240 mg of Mn/kg of DM. Carcass characteristics were not affected by dietary Mn. Manganese concentrations of 29 and 8 mg/kg of DM in the growing and finishing diets, respectively, were adequate for maximizing performance of growing and finishing steers in this experiment. Supplementing physiological or pharmacological concentrations of Mn affected lipid metabolism; however, this did not result in altered carcass characteristics.     

Influence of steam-peeled potato-processing waste inclusion level in beef finishing diets: effects on digestion, feedlot performance, and meat quality

Inclusion of potato-processing waste (PW) from the frozen potato products industry in high-grain beef cattle finishing diets was evaluated in two studies. In a randomized complete block design, 125 crossbred yearling heifers (365 +/- 0.3 kg initial BW; five pens per treatment; five heifers per pen) were used to evaluate PW level on feedlot performance and meat quality. Heifers were fed for 85 (two blocks) or 104 d (three blocks). In a digestion study, four ruminally, duodenally, and ileally cannulated Holstein steers (474.7 +/- 26.6 kg initial BW) were used in a 4 x 4 Latin square design to evaluate effects of PW level on ruminal fermentation, site of digestion, and microbial protein synthesis. The control diet for both studies contained 80% corn, 10% alfalfa hay, 5% concentrated separator by-product (CSB), and 5% supplement (DM basis). Potato waste replaced corn and separator by-product (DM basis) in the diet at 0, 10, 20, 30, and 40% in the feedlot study, and at 0, 13, 27, and 40% in the digestion study. In the feedlot study, DMI decreased (linear; P = 0.007) with increasing inclusion of PW. Increasing PW decreased ADG and feed efficiency from 0 to 30% and then increased at 40% (quadratic; P < 0.01). Calculated dietary NEg concentrations did not differ among treatments (P = 0.18). Hot carcass weight decreased as PW increased from 0 to 30% and then increased at 40% PW (cubic; P < 0.01). Fat thickness and longissimus muscle area decreased with increasing PW (linear; P < 0.05). Level of PW did not affect marbling or liver scores (P > 0.30). No difference (P > 0.20) was observed for Warner-Bratzler shear force at 0, 10, 20, and 30% PW levels; however, 40% PW resulted in lower (P = 0.05) shear force values. Taste panel scores for juiciness and flavor intensity did not differ with increasing PW (P > 0.30). Steaks from cattle fed 0% were scored less tender than 10 and 40% PW (cubic; P < 0.05). In the digestion study, DMI decreased (quadratic; P < 0.01) with increasing PW. Ruminal pH and total VFA concentration increased (linear; P < 0.05) and true N disappearance from the stomach complex and apparent total-tract N disappearance decreased with increasing level of PW (linear; P < 0.01). Starch intake and ruminal disappearance decreased with increasing level of PW (quadratic; P < 0.05). Inclusion of PW decreased feedlot performance, with little effect on carcass characteristics or meat quality. Optimal inclusion of PW in finishing diets may depend on the cost of transportation and other dietary ingredients.     

Effects of forage level in feedlot finishing diets on carcass characteristics and palatability of Jersey beef

Jersey cattle are known for producing carcasses with a greater amount of marbling, but they require more days on feed to achieve acceptable market weights compared with other breeds. The objective of this study was to evaluate the effect of dietary forage (12 vs. 24% sudangrass:alfalfa hay, DM basis) in steam-flaked, corn-based finishing diets on carcass characteristics, beef palatability, and retail color stability of steaks from Jersey beef compared with conventionally fed commodity beef strip loins (COM) of identified quality (Choice(-) and Select(+)). Jersey steers (n = 77) were blocked by BW and randomly assigned to 1 of the following treatments for a 383-d trial period: Jersey low 12% (JL; n = 38) or Jersey high 24% (JH; n = 39) forage (DM basis). A comparison group was selected from conventionally fed cattle on the same day of slaughter as the Jersey treatments, and strip loins from USDA Select(+) (COM; n = 20) and Choice(-) (COM; n = 20) were removed for data analysis. Seventy-two hours postmortem, strip loins were removed, vacuum-packaged, and aged at 3°C for 18 d postmortem. After the aging period, steaks from the LM were sliced, vacuum-packaged, and frozen (-20°C) until analyzed. Jersey steaks had reduced (P < 0.05) Warner-Bratzler shear force values compared with COM steaks. Trained sensory panelists rated JL greater (P < 0.05) for initial and sustained tenderness and initial juiciness than COM, whereas JH was intermediate. As expected, marbling was greater (P < 0.05) for both JL and JH compared with COM, and trained sensory panel sustained juiciness, beef flavor intensity, and overall acceptability scores were greater (P < 0.05) for both JL and JH compared with COM; however, no differences (P = 0.14) were reported for consumer tenderness and flavor. Objective color (L*, a*, b*) measurements decreased (P < 0.05) over time across treatments. There were no differences among treatments for lightness (L*); however, overall during retail display JL were less (P < 0.05) red (a*) and yellow (b*) than JH and COM. Subjective color scores indicated both JL and JH were less red (P < 0.05) than COM. Steaks from Jersey were equal to and on some measurements more desirable than steaks from COM carcasses for both color stability and palatability. These results suggest that dietary forage level had minimal effects on carcass characteristics and beef palatability. However, feeding a low-forage diet decreases input cost and potentially results in a greater valued carcass. Finishing long-fed (383 d) Jersey steers can meet beef industry expectations with respect to quality grade.     

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)     

Mixtures of wheat and high-moisture corn in finishing diets: feedlot performance and in situ rate of starch digestion in steers

Wheat and high-moisture corn (HMC) were fed singly and in three combinations using dry-rolled wheat (DRW) (ratios of 75:25, 50:50, and 25:75, respectively, Trial 1), or singly and in two combinations using steam-rolled wheat (SRW) (ratios of 67:33 and 33:67, respectively, Trial 2) to finishing beef cattle fed a high-concentrate diet. In situ rate of starch digestion (Trial 3) was measured on grains used in Trial 1 (excluding the 25 HMC: 75 DRW mixture) and ground dry corn. In Trial 1 (132 d), gain/feed did not differ (P greater than .10); however, final weight, hot carcass weight, and ADG decreased linearly (P less than .05) and DMI exhibited a cubic response (P less than .05) as the percentage of wheat in the diet increased. Carcass characteristics were not different. In Trial 2 (113 d), there were no differences attributable to treatment for ADG, DMI, gain/feed, or carcass characteristics. Positive associative responses for gain efficiency (gain/feed) were greatest for the first increment of wheat addition (25% DRW and 33% SRW in Trials 1 and 2, respectively) and for the early portion of the feeding period (57 and 28 d for Trials 1 and 2, respectively), indicating a more rapid diet adaptation and(or) less propensity for subacute acidosis. In Trial 3, the treatment grains or mixtures did not differ in rate of starch digestion. Although the differences were not statistically significant, starch in the 100% wheat diet was digested twice as fast as the 100 or 75% HMC mixtures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary energy level and protein source on nutrient digestion and ruminal nitrogen metabolism in steers.

Four Simmental steers with ruminal, duodenal, and ileal cannulas were used to examine effects of dietary forage: concentrate ratio and supply of ruminally degradable true protein on site of nutrient digestion and net ruminal microbial protein synthesis. Steers (345 kg) were fed ammoniated corn cob (high forage; HF)- or corn cob/ground corn/cornstarch (low forage; LF)-based diets supplemented with soybean meal (SBM) or a combination of corn gluten meal and blood meal (CB). Diets were fed at 2-h intervals with average DM intake equal to 2.2% of BW. Feeding LF vs HF increased (P less than .05) OM digestion (percentage of intake) in the stomach, small intestine, and total tract. Efficiency of microbial CP synthesis (EMCP; g of N/kg of OM truly fermented) decreased (P less than .05) for LF vs HF (24.1 vs 26.8), but microbial N and total N flows to the small intestine were similar (P greater than .05) between energy levels (average 112 and 209 g/d, respectively). Total N flows to the small intestine were 13.1% greater (P less than .05) for CB than for SBM because of increased (P less than .05) passage of nonmicrobial N. Feeding SBM vs CB increased (P less than .05) EMCP (27.3 vs 23.3) and microbial N flow to the small intestine (127.5 vs 112.5 g/d), but these increases were not likely due to increased ruminal concentrations of ammonia N (NH3 N). Decreased (P less than .05) incorporation of NH3 N into bacterial N and slower turnover rates of ruminal NH3 N for SBM vs CB suggest that direct incorporation of preformed diet components into cell mass increased when SBM was fed. Results of this study suggest that the inclusion of ruminally degradable protein in the diet may increase the supply of products from proteolysis and that this can increase EMCP and microbial protein flow to the small intestine.