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1.
Eight Holstein steers with cannulas in the rumen and proximal duodenum were used in a split-plot design experiment to evaluate the interaction of body weight (175 vs. 370 kg) and level of fat supplementation (0, 3, 6, and 9% yellow grease) on characteristics of digestion and feeding value of fat in finishing diets. Dry matter intake was restricted to 2% of BW. There were no interactions between BW and level of fat supplementation (P > 0.10) on ruminal or total-tract digestion. Level of supplemental fat decreased (linear, P < 0.01) ruminal digestion of OM and NDF, and increased (linear, P < 0.05) ruminal N efficiency. There were no treatment effects (P > 0.10) on postruminal digestion of OM, NDF, and N. There tended to be an interaction (P < 0.10) between BW and level of fat supplementation on postruminal starch digestion. Increasing level of fat supplementation increased postruminal digestion of starch in heavier steers but did not affect starch digestion in lighter steers. There were no interactions (P > 0.10) between BW and level of fat supplementation on postruminal fatty acid digestion. Increasing level of fat supplementation decreased (linear, P < 0.01) postruminal fatty acid digestion, which was due to a decreased (linear, P < 0.01) postruminal digestion of C16:0 and C18:0. Supplemental fat decreased (linear, P < 0.01) total-tract digestion of OM and NDF. The estimated NEm (Mcal/kg) of yellow grease averaged (linear, P < 0.01) 6.02, 5.70, and 5.06 for the 3, 6, and 9% of level supplementation, respectively. We conclude that intestinal fatty acid digestion (FAD, %) is a predictable function (r2 = 0.89; P < 0.01) of total fatty acid intake per unit body weight (FAI, g/kg BW): FAD = 87.560 - 8.591FAI. Depressions in fatty acid digestion with increasing level of intake were due primarily to decreased intestinal absorption of palmitic and stearic acid. Level of fatty acids intake did not appreciably affect intestinal absorption of unsaturated fatty acid. Changes in intestinal fatty acid digestion accounted for most of the variation in the NE value of supplemental fat.  相似文献   

2.
Six ruminally and duodenally cannulated Angus-Jersey crossbred steers (450 kg of BW) were used in a 6 x 6 Latin square to evaluate the effect of kernel vitreousness and moisture on intake and digestibility of high-moisture corn. Arranged in a 2 x 3 factorial, diets included a floury (FLO) or a vitreous (VIT) endosperm corn hybrid harvested at 28.1% (DRY), 31.2% (MID), or 35.7% (WET) kernel moisture content. Diet DM consisted of 88.25% high-moisture corn, 6% chopped alfalfa hay, 2% corn gluten meal, 0.75% urea, and 3% supplement. Supplement was included to ensure that the diets contained a minimum (DM basis) of 0.6% Ca, 0.6% K, 0.2% S, 33 mg/kg of monensin, and 11 mg/kg of tylosin. Geometric mean diameter of lyophilized high-moisture corn tended to be less (P = 0.06) for VIT than for FLO, and the calculated particle surface area was 15.8% greater (P = 0.03). An interaction of vitreousness with the quadratic effect of moisture was noted (P < 0.001), such that fraction a and effective degradation for starch tended to be greater for the vitreous hybrid at the least and greatest moisture content but lower for the vitreous hybrid at the intermediate moisture content. Intake and ruminal disappearance of DM, OM, and starch were not influenced by vitreousness or moisture, with ruminal starch disappearance averaging 90.9%. Intestinal starch digestion measured as a percentage of starch entering the intestines averaged 91% and was greater (P < 0.05) for VIT than FLO corn. Averaged across moisture levels, total tract starch digestibility was greater (P < 0.003) for VIT than FLO. Compared with FLO kernels, VIT kernels appeared to be more brittle and therefore shattered more readily when rolled, particularly at the driest kernel moisture level. Furthermore, increased surface area of smaller particles may have been responsible for the greater starch utilization from VIT corn. In contrast with the results from other in situ and in vivo trials with dry-rolled corn grain, in which the starch from vitreous hybrids was less rapidly or completely digested, hybrids with more vitreous starch, when fed as high-moisture corn, had greater total tract starch digestibility, primarily due to greater postruminal starch digestion.  相似文献   

3.
Two trials were conducted to evaluate the addition of a forage-fat blend (FFB) as a substitute for grain in finishing diets for feedlot cattle. Treatments consisted of a steam-flaked wheat-based finishing diet containing 15, 29, or 45% FFB. The FFB contained 80% chopped alfalfa hay and 20% yellow grease and was formulated to have NEm and NEg values similar to that of wheat. In Trial 1, 126 crossbred steers (225 ± 5.4 kg) were used to evaluate treatment effects on growth performance and dietary NE. In Trial 2, three Holstein steers (448 ± 21 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. Increasing the FFB did not affect (P>0.10) ADG, but decreased gain efficiency (linear effect, P<0.05) and dietary NE concentration (linear effect, P<0.01). Increasing the FFB did not affect (P>0.10) ruminal digestion of starch, N, or microbial N (MN) efficiency, but decreased (linear effect, P<0.10) ruminal digestion of OM and increased (linear effect, P<0.10) ruminal digestion of ADF. Increasing the FFB did not affect (P>0.10) postruminal digestion of OM, starch, and N, but decreased postruminal digestion of fatty acids (linear effect, P<0.05). Increasing the FFB did not affect (P>0.10) percentage of total tract starch, N, and ADF digestion, but decreased the percentage of total tract digestion of OM (linear effect, P<0.01) and DE (linear effect, P<0.05). We conclude that an isocaloric FFB can replace grain at levels of up to 45% of dietary DM without affecting ADG in feedlot cattle. However, when dietary inclusion rates are > 15%, dietary NE and, hence, BW gain efficiency may decrease. The magnitude of the effect of FFB inclusion rate on energy recovery is a predictable function of the relationship between fatty acid intake and intestinal fatty acid digestion.  相似文献   

4.
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.  相似文献   

5.
Influence of steaming time on site of digestion of flaked corn in steers   总被引：3，自引：0，他引：3  
Four crossbred steers (395 kg) with cannulas in the rumen, proximal duodenum and distal ileum were used to evaluate effects of steaming time of corn on characteristics of digestion. The basal diet contained (DM basis) 12% forage-and 75% corn. The corn portion of the diet was provided as either dry-rolled (DR) or steam-flaked (SF), which had been exposed to steam for 34, 47 or 67 min prior to flaking to a mean density of .34 kg/liter. Longer steaming times linearly increased in vitro reactivity of corn starch to amyloglucosidase. Steaming time had a quadratic effect (P less than .05) on ruminal starch digestion. Ruminal starch digestibility of corn steamed for 47 min was 7% less than for corn steamed for 34 or 67 min. Longer steaming time linearly increased (P less than .05) flow of non-ammonia N to the small intestine with the principal increase (5.4%) between 34 and 47 min steaming time. Steaming time did not influence (P greater than .10) small intestinal or total tract digestibility of OM, starch or N. Compared with DR, SF increased (P less than .01) ruminal, small intestinal and total tract digestibility of starch 21.9, 75.1 and 9.2%, respectively. Although SF resulted in marked improvements in digestibility over DR, steaming times greater than 34 min were not beneficial.  相似文献   

6.
An experiment was designed to determine the effects of ruminal and postruminal infusions of ruminally degradable protein (casein) on intake and digestion of low-quality hay by beef steers. Twelve ruminally fistulated Angus x Hereford steers (initial BW = 563 kg) were blocked by weight and assigned to one of three treatments: control (C; hay only) or hay plus ruminal (R) or postruminal (P) infusion of 400 g/d of sodium caseinate. The trial consisted of five periods: 1) 10-d adaptation to the hay diet; 2) 7-d measurement of hay intake (without infusions); 3) 10-d adaptation to protein infusion treatments (intake measurements continued); 4) 7-d measurement of hay intake and digestibility (infusions continued); and 5) 3-d ruminal sampling period (infusions continued). Steers were given ad libitum access to tallgrass-prairie hay (3.4% CP, 76.6% NDF) throughout the study. Casein was administered once daily before feeding, either directly into the rumen or via anchored infusion lines into the abomasum. Hay intake was increased by supplementation (P < 0.01). Ruminal infusion elicited a greater (P = 0.04) increase in hay intake than postruminal infusion. Intake tended (P = 0.11) to be lower in period 4 than in period 2 for control steers but was greater in period 4 than in period 2 (P < or = 0.03) for both R and P steers. The increase in intake between periods 2 and 4 was greater for R than for P steers (P = 0.03). Supplementation improved diet OM digestion (P = 0.04) but not NDF digestion (P = 0.18); however, greater relative error for NDF digestion may have limited the ability to elucidate significant treatment effects. There were no differences in either OM digestion (P = 0.42) or NDF digestion (P = 0.35) between R and P steers. Plasma urea N at 0 and 3 h after feeding on the last day of the experiment was lower (P = 0.05) for C than for R and P steers, but no difference (P = 0.48) was evident between R and P steers. Ruminal ammonia N levels also were increased by supplementation (P < 0.01), with a much larger increase for R than for P steers (P < 0.01). Total VFA concentrations were not affected (P = 0.21) by treatment, but R steers exhibited lower proportions of acetate and higher proportions of isobutyrate, valerate, and isovalerate than P steers (P < 0.01). In conclusion, ruminal and postruminal infusion of a degradable protein source improved forage utilization, although the response in forage OM intake and total digestible OM intake was greater for ruminal infusion than for postruminal infusion.  相似文献   

7.
Five steers (385 kg) fitted with permanent abomasal cannulae were used to compare Ca source (limestone or dicalcium phosphate) and corn level on site and extent of digestion. Diets contained 50, 70 or 90% corn, with corn silage and supplement to provide .70% Ca from either limestone or dicalcium phosphate. Limestone did not affect ruminal digestion, but postruminal starch and neutral detergent fiber (NDF) digestion were higher (P less than .05) for limestone compared with dicalcium phosphate, which suggests that starch utilization may be increased postruminally by a compound with buffering capacity. As a percentage of total starch intake, total tract and ruminal starch digestion increased (linear, P less than .01) while postruminal starch digestion decreased (linear, P less than .01) with corn level. Neutral detergent fiber digested in the rumen decreased (linear, P less than .01) and postruminal NDF digestion increased (linear, P less than .01) when level of corn in the diet increased. Effects of corn level were not different when organic matter and starch intake were included as covariates.  相似文献   

8.
Five Holstein steers (235 kg of BW) fitted with ruminal, duodenal, and ileal cannulas were used in a 5 x 5 Latin square design experiment to determine the effects of supplemental fat source on site and extent of nutrient digestion and ruminal fermentation. Treatments were diets based on steam-flaked corn containing no supplemental fat (control) or 4% (DM basis) supplemental fat as tallow, dried full-fat corn germ (corn germ), corn oil, or flax oil. Fat supplementation decreased (P < 0.08) ruminal starch digestion but increased (P < 0.03) small intestinal starch digestion as a percentage of intake. Feeding corn germ decreased (P < 0.09) ruminal starch digestion and increased (P < 0.03) large intestinal starch digestion compared with steers fed corn oil. Large intestinal starch digestion was less (P < 0.04), and ruminal NDF digestion was greater (P < 0.09) for steers fed tallow compared with steers fed other fat sources. Small intestinal (P < 0.08) and total tract NDF digestibilities were greater (P < 0.02) for steers fed corn germ than for those fed corn oil. Feeding tallow increased total ruminal VFA (P < 0.03) and NH(3) (P < 0.07) concentrations compared with steers fed the other fat sources. Feeding corn germ led to a greater (P < 0.02) rate of ruminal liquid outflow compared with corn oil. A diet x hour interaction (P < 0.04) occurred for ruminal pH, with steers fed corn oil having the greatest ruminal pH 18 h after feeding, without differences at other time points. Fat supplementation increased (P < 0.09) ruminal concentrations of Fusobacterium necrophorum. Duodenal flow of C18:3n-3 was greater (P < 0.01) for steers fed flax oil compared with those fed corn oil. Feeding corn germ led to less (P < 0.01) ruminal biohydrogenation of fatty acids compared with corn oil. Steers fed tallow had greater small intestinal digestibility of C14:0 (P < 0.02) and C16:1 (P < 0.04) than steers fed the other fat sources. Fat supplementation decreased (P < 0.06) small intestinal digestibility of C18:0. Feeding corn germ decreased (P < 0.10) small intestinal digestibility of C18:1 compared with corn oil. It appears that source of supplemental fat can affect the site and extent of fatty acid and nutrient digestion in steers fed diets based on steam-flaked corn.  相似文献   

9.
Two experiments were conducted to evaluate the comparative feeding value of dried shredded sugarbeets (DSSB; 0, 20, and 40% of diet DM) as a replacement for steam-flaked corn (SFC) in finishing diets for feedlot cattle. In Exp. 1, 60 calf-fed Holstein steers (476 ± 6.3 kg) were used in a 97-d finishing trial. Substitution of SFC with DSSB did not affect ADG or DMI (P > 0.20). Increasing DSSB decreased gain efficiency (ADG:DMI; linear effect, P = 0.04) and dietary NE (linear effect, P = 0.03). Given that SFC has a NE(m) value of 2.38 Mcal/kg, the replacement NE(m) and NE(g) values for DSSB were 1.94 and 1.29 Mcal/kg, respectively. There were no treatment effects (P > 0.20) on carcass characteristics. In Exp. 2, 6 cannulated Holstein steers (205 kg) were used in a replicated 3 × 3 Latin square design to evaluate treatment effects on digestion. Ruminal digestion of starch, NDF, and feed N were not affected (P > 0.10) by DSSB, although ruminal OM digestion tended to increase (linear effect, P < 0.08). Replacing SFC with DSSB decreased flow of starch to the small intestine, but it increased flow of microbial N (linear effect, P = 0.05). There were no treatment effects (P > 0.14) on postruminal digestion of OM, NDF, starch, or feed N or total tract digestion of OM, starch, and N. Substitution of DSSB increased (linear effect, P = 0.05) total tract NDF digestion and decreased (linear effect, P = 0.05) dietary DE (Mcal/kg). Given that SFC has a DE value of 4.19 Mcal/kg, the replacement DE value of DSSB was 3.68 Mcal/kg. There were no treatment effects (P > 0.12) on ruminal pH or total VFA; however, DSSB decreased propionate (linear effect, P = 0.05) and increased acetate (linear effect, P = 0.07), butyrate (linear effect, P = 0.05), valerate (linear effect, P = 0.04), and estimated methane production (linear effect, P = 0.05). We concluded that DSSB may replace SFC in finishing diets at levels of up to 40% without detrimental effects on ADG and carcass characteristics. The NE value of DSSB is 82% that of SFC (DM basis). Partial replacement of SFC with DSSB alters ruminal VFA patterns, increasing estimated methane energy loss and slightly decreasing the efficiency of DE utilization.  相似文献   

10.
Twelve ruminally cannulated crossbred Angus steers were used to evaluate ruminal fermentation characteristics and diet digestibility when 30% (DM) corn dried distillers grains with solubles (DDGS) containing 0.42 or 0.65% (DM) of dietary S was incorporated into finishing diets based on steam-flaked corn (SFC) or dry-rolled corn (DRC). The study was a replicated, balanced randomized incomplete block design with a 2 × 2 factorial arrangement of treatments. Factors consisted of dietary S concentration (0.42 and 0.65% of DM; 0.42S and 0.65S, respectively) and grain processing method (SFC or DRC). The 0.65S concentration was achieved by adding H(2)SO(4) to DDGS before mixing rations. Steers were assigned randomly to diets and individual, slatted-floor pens, and fed once daily for ad libitum intake. Two 15-d experimental periods were used, each consisting of a 12-d diet adaptation phase and a 3-d sample collection phase. Samples were collected at 2-h intervals postfeeding during the collection phase. Ruminal pH was measured immediately after sampling, and concentrations of ruminal ammonia and VFA were determined. Fecal samples were composited by steer within period and used to determine apparent total tract digestibilities of DM, OM, NDF, CP, starch, and ether extract. Feeding 0.65S tended (P = 0.08) to decrease DMI but resulted in greater apparent total tract digestibilities of DM (P = 0.04) and ether extract (P = 0.03). Ruminal pH increased (P < 0.05) in steers fed 0.65S diets, which may be attributable, in part, to decreased (P = 0.05) VFA concentrations and greater (P < 0.01) ruminal ammonia concentrations when 0.65S was fed, compared with feeding 0.42S. These effects were more exaggerated in steers fed DRC (interaction, P < 0.01), compared with steers fed SFC. Steers fed DRC-0.65S had greater (P < 0.01) acetate concentration than steers fed DRC-0.42S, but acetate concentration was not affected by S concentration when SFC was fed. Propionate concentration was decreased (P < 0.01) in steers fed SFC-0.65S compared with steers fed SFC-0.42S, but dietary S concentration had no effect on propionate concentration when DRC was fed. Butyrate concentration was less (P < 0.01) in steers fed 0.65S diets than in steers fed 0.42S. Lactate concentrations tended (P = 0.06) to decrease in steers fed 0.65S diets. Feeding DDGS with increased S concentration may decrease feed intake and ruminal VFA concentration but increase ruminal ammonia concentration.  相似文献   

11.
Two experiments were conducted to determine the effects of wet distillers grain plus solubles (WDG; <15% sorghum grain) concentration in steam-flaked corn (SFC) diets on feedlot performance, carcass characteristics, ruminal fermentation, and diet digestibility. In Exp. 1, six hundred crossbred steers (364 ± 35 kg of BW) were used in a randomized complete block design with 8 replications/treatment. Dietary treatments consisted of a dry-rolled corn (DRC) control diet without WDG, a SFC control without WDG, and SFC with 4 WDG concentrations (15, 30, 45, 60% DM basis) replacing SFC, cottonseed meal, urea, and yellow grease. Final BW, ADG, G:F, HCW, and 12th-rib fat depth were greater (P ≤ 0.05) for SFC compared with DRC. Dry matter intake tended (P = 0.06) to be greater for DRC compared with SFC. Final BW, ADG, G:F, HCW, 12th-rib fat depth, and marbling score decreased linearly (P < 0.01) with increasing WDG concentration. In Exp. 2, six ruminally and duodenally cannulated crossbred steers (481 ± 18 kg of BW) were used in a 6 × 6 Latin square design using the same diets as Exp. 1. Ruminal, postruminal, and total tract OM and NDF digestibility were not different (P > 0.14) for DRC compared with SFC. Ruminal and total tract starch digestibility were greater (P < 0.01) for SFC compared with DRC. Dry matter and OM intake were not different (P ≥ 0.43) among WDG treatments. Ruminal and total tract OM digestibility decreased linearly (P < 0.01) with increasing WDG concentration. Intake, ruminal digestibility, and total tract digestibility of NDF increased linearly (P < 0.01) with increasing WDG concentration. Starch intake decreased linearly (P < 0.01) with increasing WDG concentration. Ruminal starch digestibility increased (P = 0.01) with increasing concentration of WDG. Total tract starch digestibility decreased quadratically (P < 0.01) with increasing concentration of WDG. Feeding SFC improved steer performance compared with DRC. The concentration of WDG and corn processing method influences nutrient digestibility and ruminal fermentation. The addition of WDG in SFC-based diets appears to negatively affect animal performance by diluting the energy density of the diet.  相似文献   

12.
Six ruminally and duodenally cannulated yearling steers (523 kg) were used in a replicated 3 x 3 Latin square design experiment to study the effects of corn processing on nutrient digestion, bacterial CP production, and ruminal fermentation. Dietary treatments consisted of 90% concentrate diets that were based on dry-rolled (DRC), high-moisture (HMC), or steam-flaked (SFC) corn. Each diet contained 2.0% urea (DM basis) as the sole source of supplemental nitrogen. Each period lasted 17 d, with d 1 through 14 for diet adaptation and d 15 through 17 for fecal, duodenal, and ruminal sampling. Dry matter and OM intakes were similar for DRC and SFC but were approximately 15% higher (P < 0.05) for HMC. True ruminal OM digestibilities were 18 and 10% greater (P < 0.05) for HMC than for DRC or SFC, respectively. Ruminal starch digestibilities were similar between HMC and SFC and were approximately 19% greater (P < 0.05) than DRC. Postruminal OM digestibility was similar among treatments; however, postruminal starch digestibility was 15% greater (P < 0.05) for SFC than for DRC or HMC, which were similar. Total-tract DM and OM digestibilities were similar between HMC and SFC and were 4% greater (P < 0.05) than DRC. Likewise, total-tract starch digestibilities were similar between HMC and SFC and were 3% greater (P < 0.05) than DRC. Bacterial CP flow to the duodenum was 29% greater (P < 0.05) for HMC than for DRC or SFC, which were similar. Bacterial N efficiencies were similar among treatments. Based on bacterial CP flow from the rumen, we estimate that dietary DIP requirements are approximately 12% higher for HMC-based diets than for DRC or SFC-based diets, which were similar.  相似文献   

13.
This experiment was conducted to determine the effects of tall fescue hay maturity on intake, digestion, and ruminal fermentation responses to different supplemental energy sources fed to beef steers. Twelve ruminally cannulated, crossbred steers (initial BW = 228 +/- 21 kg) were used in a split-plot experiment with a 3 x 4 factorial treatment arrangement. Steers were assigned randomly to three supplement treatments: 1) no supplement, 2) pelleted soybean hulls, or 3) coarse cracked corn. The second treatment factor was fescue hay maturity: 1) vegetative (VEG), 2) boot-stage (BOOT), 3) heading-stage (HEAD), and 4) mature (MAT). Supplements were fed once daily at 0.67% of BW (OM basis) and tall fescue hay was offered once daily at 150% of average intake. Supplement type x forage maturity interactions were not detected (P > or = 0.25) for forage, total, or digestible OM intake, which generally decreased (P < 0.01) with advancing forage maturity. Supplementation decreased (P < 0.01) forage and increased (P < 0.01) total OM intake. Supplement type had no effect (P = 0.56) on substitution ratio (unit change in forage intake per unit of supplement intake). Digestible OM intake was increased (P < 0.01) by supplementation and was greater (P = 0.05) with soybean hulls than with corn. Supplement type x forage maturity interactions (P < or = 0.10) were observed for OM and NDF digestibilities and N retention. Increases in digestibility with soybean hulls relative to corn were greater and supplementation elicited greater increases in N retention with more mature forages. Compared with soybean hulls, corn supplementation resulted in greater (P < 0.01) negative associative effects on OM digestibility. Supplementation did not affect (P > or = 0.10) ruminal pH, total VFA concentrations, or acetate:propionate ratio. Corn supplementation decreased (P < or = 0.07) ruminal NH3-N concentrations compared with control and soybean hulls; however, decreases in ruminal NH3-N concentrations were not consistent with the presence of negative associative effects. Thus, mechanisms not involving ruminal pH or NH3-N concentration seem responsible for negative associative effects observed with corn supplementation. Within the range of forage quality in this study, increases in digestible OM intake from starch- or fiber-based supplements were independent of forage maturity. When fed at similar levels of OM, soybean hull supplementation provided an average of 6% greater digestible OM intake than corn supplementation.  相似文献   

14.
Twelve ruminally cannulated Jersey steers (BW = 534 kg) were used in an incomplete Latin square design experiment with a 2 x 2 factorial arrangement of treatments to determine the effects of wet corn gluten feed (WCGF) and total DMI level on diet digestibility and ruminal passage rate. Treatments consisted of diets formulated to contain (DM basis) steam-flaked corn, 20% coarsely ground alfalfa hay, and either 0 or 40% WCGF offered once daily for ad libitum consumption or limited to 1.6% of BW (DM basis). Two consecutive 24-d periods were used, each consisting of 18 d for adaptation, 4 d for collection, and a 2-d in situ period. Rumens of all steers were evacuated once daily at 0, 4, 8, and 12 h after feeding. Chromic oxide (10 g/[steer*d]) was fed as a digestibility marker, and steers were pulse-dosed with Yb-labeled alfalfa hay to measure ruminal particulate passage rate. Dacron bags containing 5 g of steam-flaked corn, WCGF, or ground (2-mm screen) alfalfa hay were placed into the rumens of all steers and removed after 3, 6, 12, or 48 h. Wet corn gluten feed increased percent apparent total-tract digestion of OM (P < 0.01), NDF (P < 0.01), and starch (P < 0.03), decreased (P < 0.01) ruminal total VFA concentration, increased (P < 0.01) ruminal NH3 concentration, and increased (P < 0.01) ruminal pH. Wet corn gluten feed also increased (P < 0.01) ruminal passage rate of Yb. Limit feeding decreased (P < 0.01) percent apparent total-tract digestion of both OM and NDF, ruminal total VFA concentration (P < 0.01), and ruminal fill (P < 0.01), but increased (P < 0.01) ruminal NH3 concentration. Apparent total-tract digestion of starch was not affected (P = 0.70) by level of DMI. A DMI level x hour interaction (P < 0.01) occurred for ruminal pH. Limit feeding increased ruminal pH before and 12 h after feeding, but decreased ruminal pH 4 h after feeding compared with diets offered ad libitum. A diet x DMI level interaction (P < 0.02) occurred for in situ degradation of alfalfa hay, with dietary addition of WCGF increasing (P < 0.02) the extent of in situ alfalfa hay degradation in steers fed for ad libitum consumption. This study suggests that WCGF increases OM and NDF digestion, and that limit feeding diets once daily might depress OM and NDF digestion, possibly due to decreased stability of the ruminal environment.  相似文献   

15.
Two experiments were conducted to evaluate the influence of dry-rolling (DRS) and tempering agent (TA) addition during the steam-flaking of grain sorghum (SFS) for feedlot cattle. Five dietary treatments were compared: 1) DRS; 2) SFS, no TA; 3) SFS, 0.275 mg/kg of TA; 4) SFS, 1.375 mg/kg of TA; and 5) SFS, 2.750 mg/kg of TA. Bulk densities of DRS and SFS were 0.48 and 0.36 kg/L, respectively. Diets contained 70.6% grain sorghum (DM basis). One hundred fifty crossbred steers (336 kg of BW) were used in a 115-d finishing experiment to evaluate treatment effects on feedlot performance. Body weight gain averaged 1.49 kg/d and was not affected (P = 0.47) by treatments. The SFS reduced (P < 0.01) DMI (9%) and enhanced (P < 0.01) G:F (13%) and the NE(m) and NE(g) value of the diet (9 and 11%, respectively). Use of a TA before flaking sorghum did not influence (P > 0.20) cattle growth performance or NE(m) or NE(g) value of the diet. Given that the NE(m) and NE(g) values of DRS are 2.00 and 1.35 Mcal/kg, respectively (NRC, 1996), the corresponding values for SFS were 2.28 and 1.59 Mcal/kg. Five steers (397 kg of BW) with ruminal and duodenal cannulas were used in a 5 x 5 Latin square design to evaluate treatment effects on digestive function. Ruminal digestion of OM and starch was greater (14 and 16%, respectively; P < 0.01) for SFS vs. DRS. Steam-flaking sorghum increased (P < 0.01) postruminal digestion of OM (11%), N (10%), and starch (25%) and total tract digestion (P < 0.01) of OM (8.3%), N (8.2%), and starch (8.9%). Grain processing did not affect (P > 0.20) ruminal pH or VFA molar proportions. There was a cubic component (P < 0.10) to level of TA on ruminal pH and VFA molar proportions, with values being optimal at 1.375 mg/kg of tempering agent. It is concluded that steam-flaking grain sorghum will increase its NE value for maintenance and gain (14 and 18%, respectively) and enhance the MP value of the diet due to greater intestinal N digestion. The use of a TA to enhance the mechanical efficiency of the flaking process may not otherwise benefit the feeding value of sorghum.  相似文献   

16.
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.  相似文献   

17.
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.  相似文献   

18.
We studied the effects of the addition of liquefied vs prilled mostly saturated fatty acids (FA) to the concentrate portion of total mixed diets on ruminal and total tract digestibilities. Four Holstein steers (270 +/- 23 kg) fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square design with 21-d periods. Diets contained (DM basis) 30.0% corn silage, 22.2% chopped alfalfa hay, 25.0% ground shelled corn, 12.5% soybean meal, and 5% of one of the following fat sources: 1) prilled FA (PFA), 2) choice white grease (triglycerides) added in liquid form (LTG), 3) 2.5% PFA + 2.5% LTG, or 4) 2.5% liquefied PFA (LFA) + 2.5% LTG. Ad libitum OM intake was not different (P > .10) among diets (mean 7.8 kg/d). Ruminal digestibilities of OM (35.7, 39.9, 42.2, and 37.3% for Diets 1 to 4, respectively) were greatest (P < .10) for the combination of PFA + LTG and lowest for PFA alone. Ruminal digestibilities of NDF, ADF, and starch did not differ (P > .10) among diets. Total tract digestibilities of OM, NDF, and ADF were greater (P < .10) for the diet containing LTG alone than for the diet containing LFA + LTG because of trends for greater postruminal digestibilities. The LFA + LTG diet resulted in a greater proportion of acetate and lower proportion of propionate in ruminal fluid than PFA alone (P < .10). The acetate:propionate ratio (3.53, 2.96, 3.10, and 2.89 for Diets 1 to 4, respectively) was lower (P < .05) for LFA + LTG or LTG alone than for PFA alone. Postruminal and total tract digestibilities of total FA (66.0, 76.0, 71.2, and 68.9% for Diets 1 to 4, respectively) were lower (P < .05) for PFA than for other diets. Addition of saturated FA in liquid form resulted in digestibilities and ruminal effects similar to the same saturated FA added in prilled form.  相似文献   

19.
Four Holstein steers (282 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to evaluate the influence of dietary urea level (0, 0.4, 0.8, and 1.2%, DM basis) in a steam-flaked barley-based finishing diet on digestive function. There were no treatment effects (P > 0.20) on ruminal digestion of OM and ADF. Increasing dietary urea level increased (linear, P < 0.01) ruminal starch digestion. Ruminal degradability of protein in the basal diet (no supplemental urea) was 60%. Increasing dietary urea level did not increase (P > 0.20) ruminal microbial protein synthesis or nonammonia N flow to the small intestine. There were no treatment effects (P > 0.20) on total-tract ADF digestion. Total tract digestion of OM (quadratic, P < 0.01) and starch (linear, P < 0.05) increased slightly with increasing urea level. Urea supplementation increased (linear, P < 0.01) ruminal pH 1 h after feeding; however, by 3 h after feeding, ruminal pH was lower (cubic, P < 0.05) with urea-supplemented diets. Urea supplementation did not affect (P > 0.20) ruminal molar proportions of acetate and propionate. One hundred twenty crossbred steers (252 kg; approximately 25% Brahman breeding) were used in an 84-d feeding trial (five pens per treatment) to evaluate treatment effects on growth performance. Daily weight gain increased (linear, P = 0.01) with increasing urea level, tending to be maximal (1.53 kg/d; quadratic, P = 0.13) at the 0.8% level of urea supplementation. Improvements in ADG were due to treatment effects (linear, P < 0.01) on DMI. Urea supplementation did not affect (P > 0.20) the NE value of the diet for maintenance and gain. Observed dietary NE values, based on growth performance, were in close agreement with expected based on tabular values for individual feed ingredients, averaging 100.4%. We conclude that with steam-flaked barely-based finishing diets, ruminal and total-tract digestion of OM and ruminal microbial protein synthesis may not be increased by urea supplementation. In contrast, ADG was optimized by dietary inclusion of 0.8% urea. Urea supplementation may not enhance the net energy value of steam-flaked barely-based finishing diets when degradable intake protein is greater than 85% of microbial protein synthesis.  相似文献   

20.
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.  相似文献   

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