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1.
Four rumen fistulated wether and beef steers were used to evaluate differences in dry matter digestibility (DMD) between cattle and sheep. They were fed either perennial ryegrass or switchgrass hay at an ad libitum or restricted level for four experimental periods. Significant ruminant species X forage and ruminant species X level of intake (P less than .05) interactions were observed for digestible dry matter. The steers digested the switchgrass 7 percentage units greater than the wethers while ryegrass was digested equally. Digestibility differences between the steers and wethers were 6 percentage units at the ad libitum level of intake and 1 unit at the restricted level of intake. Crude protein digestibility tended to be greater (P less than .10) for sheep with a 7 unit difference for switchgrass and a 3 unit difference for ryegrass. The mean ruminal solids retention time of the digesta was approximately (P less than .01) 50% greater (26.0 vs 17.4 h) in cattle, with no difference in ruminal liquid dilution rate (LD) between animal species. Total ruminal volatile fatty acid concentration differed (P less than .01) with level of intake; however, no influence due to intake on the molar proportion of acetate (P greater than .10) or propionate (P greater than .10) was evident in spite of a difference (P less than .01) in LD. Rumen pH (P less than .05) and osmolality (P less than .01) were affected by both level of intake and forage, with the ryegrass and high level of intake decreasing pH and increasing osmolality.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

2.
Southern crabgrass (Digitaria ciliaris [Retz.] Koel.) is often viewed as an undesirable weed, largely because it encroaches upon field and forage crops, gardens, and lawns. However, visual observations of livestock grazing mixed-species pastures suggest that cattle seem to prefer crabgrass to many other summer forages. The objectives of this study were to assess the nutritive value of crabgrass sampled weekly between July 11, and August 22, 2001, and then to determine ruminal in situ disappearance kinetics of DM and NDF for these crabgrass forages. A secondary objective was to compare these kinetic estimates with those of alfalfa (Medicago sativa L.), bermudagrass (Cynodon dactylon [L.] Pers.), and orchardgrass (Dactylis glomerata L.) control hays. All forages were evaluated in situ using five (383 +/- 22.7 kg) ruminally cannulated crossbred (Gelbvieh x Angus x Brangus) steers. Whole-plant crabgrass exhibited more rapid (P < or = 0.002) ruminal disappearance rates of DM (overall range = 0.069 to 0.084 h(-1)) than did bermudagrass (0.054 h(-1)) and orchardgrass (0.060 h(-1)) hays, but disappearance rates were slower (P < 0.001) for crabgrass than for alfalfa hay (0.143 h(-1)). Effective ruminal disappearance of DM was greater (P < 0.001) for crabgrass (overall range = 69.3 to 75.4%) than for all the control hays. Similarly, disappearance rates of NDF for crabgrass (overall range = 0.069 to 0.086 h(-1)) were more rapid (P < 0.001) than observed for bermudagrass and orchardgrass hays; however, NDF in alfalfa disappeared at a faster (P < 0.001) rate (0.107 h(-1)) than crabgrass. These results indicate that crabgrass offers greater effective ruminal degradability of DM and NDF than orchardgrass or alfalfa of moderate quality. More importantly, it potentially offers faster and more extensive ruminal disappearance than perennial warm-season grasses typically found throughout the southeastern United States, and it should likely support improved performance by ruminant livestock in this region.  相似文献   

3.
Seven trials were conducted to determine the effects of increasing amounts of silage (corn, wheat or sorghum) on forage intake, gastrointestinal tract fill, fecal output and ruminal flow and degradation of forage by cattle grazing wheat pasture or bermudagrass. In each of 3 yr, 24 steers grazed a common wheat or bermudagrass pasture and were randomly allocated to four treatments (0, .35, .70 or 1.05 kg silage DM.100 kg body weight-1.d-1). Intake and ruminal flow of forage were measured by feeding a single pulse dose of Yb-labeled forage followed by collection of fecal samples for 4 to 5 d and fitting Yb concentrations to a one-compartment, age-dependent model. Ruminal digestion kinetics of wheat forage were estimated in situ using eight ruminally cannulated steers fed 0 or .55 kg sorghum silage DM.100 kg body weight-1.d-1. Supplemental silage decreased wheat forage (P less than .10) and bermudagrass (P less than .01) intake linearly. However, total forage intake of bermudagrass plus silage increased linearly (P less than .05). Each kilogram of added silage DM decreased DM intake of wheat forage by .66 +/- .25 and of bermudagrass by .63 +/- .17 kg. Flow and turnover of wheat forage or bermudagrass were not altered (P greater than .15) by supplemental silage. Silage consumption increased extent of ruminal degradation of wheat forage DM (P less than .05; 63.1 vs 52.5%), indicating a positive associative effect of silage on wheat forage utilization.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
In an experiment to determine the effects of mastication and microbial contamination on in situ forage disappearance, samples of masticated (M) or nonmasticated alfalfa hay (AH), orchardgrass hay (OGH) and bermudagrass hay (BGH) were incubated in the rumen of two steers for 6, 12, 24, 48 and 96 h. Using diaminopimelic acid as a marker, microbial DM and CP contamination ranged from 10.3 to 22.3% and 46.3 to 95.3% of residual DM and CP, respectively. Percentage contamination was influenced by both time of incubation and forage treatment (P less than .001). Corrected DM and CP disappearances (DMD and CPD) were higher than apparent disappearances (P less than .001). Maximal NDF and ADF disappearances (NDFD and ADFD) obtained at 96 h were 58.2, 52.4; 62.7, 62.3 and 56.7, 52.6% for AH, OGH and BGH, respectively. Lag times (h) for corrected DMD and CPD were shorter (at least P less than .05) than for apparent disappearances, except for corrected CPD of AH. There were no differences (P greater than .10) in lag time of NDFD or ADFD among forages. Rates of disappearance (%/h) of corrected DMD and CPD were faster (at least P less than .01) than for apparent disappearances. The total quantity of microbial CP (mg CP/g DM) associated with residues varied with time depending on forage type (P less than .001). There was a significant relationship between the quantity of microbial CP contamination and the extent of disappearance. Masticated forages followed trends similar to those of nonmasticated forages, but the effect of mastication was not consistent. Results support the need for microbial correction of in situ forage residues.  相似文献   

5.
A study was conducted to measure the extent of DM disappearance and mineral release from six forage species within the rumen, abomasum and intestines of the adult bovine using the mobile bag technique. Three nonlactating Holstein cows, fitted with ruminal and duodenal cannulas, were given ad libitum access to alfalfa hay. One gram (DM) of alfalfa, rhizoma peanut, dwarf elephantgrass, bahiagrass, bermudagrass, and limpograss was individually weighed into 8-cm x 3-cm dacron bags. After ruminal incubation for 24 h, bags were incubated in an acid-pepsin solution (a simulated abomasal environment) for 1 h, inserted into the duodenum via cannula, and collected in the feces upon excretion. Ruminal incubation accounted for 86% to 100% of total DM disappearance. Release of Ca from all forages was at least 65%, with the majority having extents of release of over 70%. Most Ca was released in the rumen, but acid-pepsin incubation and washing increased Ca release an additional 17 to 272%. Forages with the highest NDF concentration (bermuda, bahia, and limpograss) sequestered Ca in the intestines. Total tract P release ranged from 84 to 98%, with an average of 7.5 percentage units occurring postabomasally. Grasses released more P in the intestines than legumes. Eighty-eight to 98% of total Mg was released in the rumen. Acid-pepsin incubation increased Mg release only slightly, with some Mg being sequestered in the intestines. Potassium release was complete in the rumen. Ranking of minerals based on maximal extent of release was K greater than Mg greater than P greater than Ca. With the exception of K, legumes released more of their minerals than grasses.  相似文献   

6.
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.  相似文献   

7.
Six ruminally cannulated beef steers were used in a 6 x 6 Latin square experiment with a 3 x 2 factorial arrangement of treatments to evaluate the effects of barley supplementation (BS; 10, 30 or 50% of diet DM) and ruminal buffer (RB; Na sesquicarbonate at 0 or 4% of BS DM) addition to bromegrass hay-based diets on digestion. When early- (boot) and late- (full maturity) havested bromegrass and wheat straw substrates were incubated in situ, no interactions (P greater than .10) involving substrate with dietary BS or RB were observed, indicating that forages differing in fermentability responded similarly to different ruminal environments. Averaged across substrates, RB had no effect with 10% BS and a positive effect with 30% BS, but a negative effect with 50% BS diets (BS x RB, quadratic; P less than .05) for in situ DM and NDF disappearance for 18 and 24 h of incubation and for rate of disappearance of potentially degraded DM and NDF. Intakes of DM and digested DM were greater (P less than .01) for RB diets; however, RB had no effect (P greater than .10) on total tract DM and NDF digestibility. Intake and digestibility of DM increased linearly (P less than .01), whereas NDF digestibility decreased linearly (P less than .01) as BS percentage was increased in the diet. Sixty beef steers (avg initial wt 302 kg) were fed the same dietary treatments in a growth experiment. A numerical improvement in DM intake (P = .20) and ADG (P = .06) was observed when RB was provided with the 50% BS diet. Results of these experiments indicate that RB may moderate negative effects occurring on ruminal fiber digestion when grains are used to supplement forage-based diets; however, improvements in ruminal digestion were not translated effectively to improved animal productivity.  相似文献   

8.
Fourteen Holstein steers (446 +/- 4.4 kg of initial BW) with ruminal, duodenal, and ileal cannulas were used in a completely randomized design to evaluate effects of whole or ground canola seed (23.3% CP and 39.6% ether extract; DM basis) on intake, digestion, duodenal protein supply, and microbial efficiency in steers fed low-quality hay. Our hypothesis was that processing would be necessary to optimize canola use in diets based on low-quality forage. The basal diet consisted of ad libitum access to switchgrass hay (5.8% CP; DM basis) offered at 0700 daily. Treatments consisted of hay only (control), hay plus whole canola (8% of dietary DM), or hay plus ground canola (8% of dietary DM). Supplemental canola was provided based on the hay intake of the previous day. Steers were adapted to diets for 14 d followed by a 7-d collection period. Total DMI, OM intake, and OM digestibility were not affected (P > or = 0.31) by treatment. Similarly, no differences (P > or = 0.62) were observed for NDF or ADF total tract digestion. Bacterial OM at the duodenum increased (P = 0.01) with canola-containing diets compared with the control diet and increased (P = 0.08) in steers consuming ground canola compared with whole canola. Apparent and true ruminal CP digestibilities were increased (P = 0.01) with canola supplementation compared with the control diet. Canola supplementation decreased ruminal pH (P = 0.03) compared with the control diet. The molar proportion of acetate in the rumen tended (P = 0.10) to decrease with canola supplementation. The molar proportion of acetate in ruminal fluid decreased (P = 0.01), and the proportion of propionate increased (P = 0.01), with ground canola compared with whole canola. In situ disappearance rate of hay DM, NDF, and ADF were not altered by treatment (P > or = 0.32). In situ disappearance rate of canola DM, NDF, and ADF increased (P = 0.01) for ground canola compared with whole canola. Similarly, ground canola had greater (P = 0.01) soluble CP fraction and CP disappearance rate compared with whole canola. No treatment effects were observed for ruminal fill, fluid dilution rate, or microbial efficiency (P > or = 0.60). The results suggest that canola processing enhanced in situ degradation but had minimal effects on ruminal or total tract digestibility in low-quality, forage-based diets.  相似文献   

9.
Twenty-four yearling Boer × Spanish wethers were used to assess effects of different forages, either fresh (Exp. 1) or as hay (Exp. 2), on feed intake, digestibilities, heat production, and ruminal methane emission. Treatments were: 1) Sericea lespedeza (SER; Lespedeza cuneata), a legume high in condensed tannins (CT; 20% and 15% in fresh forage and hay, respectively), 2) SER supplemented with polyethylene glycol (SER-PEG; 25 g/d), 3) alfalfa (Medicago sativa), a legume low in CT (ALF), and 4) sorghum-sudangrass (Sorghum bicolor), a grass low in CT (GRASS). Experiments were 22 d, which included 16 d for acclimatization followed by a 6-d period for fecal and urine collection, and gas exchange measurement (last 2 d). Intake of OM was 867, 823, 694, and 691 g/d (SEM = 20.1) with fresh forage, and 806, 887, 681, and 607 g/d with hay for SER, SER-PEG, ALF, and GRASS, respectively (SEM = 46.6). Apparent total tract N digestion was greater for SER-PEG vs. SER (P < 0.001) with fresh forage (46.3%, 66.5%, 81.7%, and 73.2%; SEM = 1.71) and hay (49.7%, 71.4%, 65.4%, and 54.8% for SER, SER-PEG, ALF, and GRASS, respectively; SEM = 1.57). Intake of ME was similar among treatments with fresh forage (8.24, 8.06, 7.42, and 7.70 MJ/d; SEM = 0.434) and with hay was greater for SER-PEG than ALF (P < 0.03) and GRASS (P < 0.001) (8.63, 10.40, 8.15, and 6.74 MJ/d for SER, SER-PEG, ALF, and GRASS, respectively; SEM = 0.655). The number of ciliate protozoa in ruminal fluid was least for SER with fresh forage (P < 0.01) (9.8, 20.1, 21.0, and 33.6 × 10(5)/ml; SEM = 2.76) and hay (P < 0.02) (6.3, 11.4, 13.6, and 12.5 × 10(5)/ml for SER, SER-PEG, ALF, and GRASS, respectively; SEM = 1.43). Methane emission as a percentage of DE intake was lower (P < 0.01) for SER vs. ALF and GRASS with fresh forage (6.6, 8.3, 9.4, and 9.2%; SEM = 0.64) and hay (4.3, 4.9, 6.4, and 6.7% for SER, SER-PEG, ALF, and GRASS, respectively; SEM = 0.38). In summary, methane emission in this short-term experiment was similar between a legume and grass low in CT as fresh forage and hay. The CT in SER markedly decreased N digestibility and elicited a moderate decline in ruminal methane emission. Supplementation with PEG alleviated the effect of CT on N digestibility but not ruminal methane emission, presumably because of different modes of action. In conclusion, potential of using CT-containing forage as a means of decreasing ruminal methane emission requires further study, such as with longer feeding periods.  相似文献   

10.
The objective of this experiment was to study the effects of level of intake and proportion of forage in the diet on site and extent of digestion of plant cell wall monomeric components (phenolics, neutral sugars) by sheep. Four Suffolk wethers (65 kg) with ruminal and duodenal cannulas were fed diets containing 75% (75A) or 25% (25A) alfalfa hay at two levels of intake, 1,700 (high intake, HI) or 1,100 (low intake, LI) g DM/d in a 4 X 4 latin-square design with a 2 X 2 factorial arrangement of treatments. The remainder of the diet consisted primarily of ground corn. Wethers had lower (P less than .05) total tract NDF and ADF digestibilities when fed 75A or at HI. An intake X forage level interaction (P less than .05) was noted for non-core lignin ferulic acid (FA) total tract disappearance, with wethers at LI having the highest, 25A-HI having the lowest, and 75A-HI having an intermediate FA disappearance. Wethers fed at LI had higher (P less than .05) total tract disappearance of non-core lignin p-coumaric acid (PCA). Wethers fed 75A had greater (P less than .05) total tract disappearances of core lignin vanillic acid (VA) and vanillin (VAN). Total tract digestibilities of the neutral monosaccharides glucose (GLC), xylose (XYL), arabinose (ARA) and galactose (GAL) were greater (P less than .05) for LI vs HI treatments. Wethers consuming 75A had greater (P less than .05) total tract ARA and GAL digestibilities, whereas wethers fed 25A had greater (P less than .05) total tract digestibilities of GLC and mannose (MAN). Diet composition and level of intake appear to influence site and extent of digestion of cell wall monomeric components.  相似文献   

11.
Nine ruminally and duodenally cannulated (172 +/- 23 kg of initial BW; Exp. 1) and 16 intact (153 +/- 28 kg of initial BW; Exp. 2) crossbred nursing steer calves were used to evaluate the effects of creep feed supplementation and advancing season on intake, digestion, microbial efficiency, ruminal fermentation, and performance while grazing native rangeland. Treatments in both experiments were no supplement or supplement fed at 0.45% of BW (DM basis) daily. Supplement consisted of 55% wheat middlings, 38.67% soyhulls, 5% molasses, and 1.33% limestone. Three 15-d collection periods occurred in June, July, and August. In Exp. 1, ruminal evacuations were performed and masticate samples were collected for diet quality analysis on d 1. Duodenal and fecal samples were collected from cannulated calves on d 7 to 12 at 0, 4, 8, and 12 h after supplementation. Ruminal fluid was drawn on d 9 and used as the inoculate for in vitro digestibility. On d 11, ruminal fluid was collected, and the pH was recorded at -1, 1, 2, 4, 8, 12, and 24 h postsupplementation. In Exp. 1 and 2, milk intake was estimated using weigh-suckle-weigh on d 15. Steers in Exp. 2 were fitted with fecal bags on d 6 to 11 to estimate forage intake. In Exp. 1, supplementation had no effect (P = 0.22 to 0.99) on grazed diet or milk composition. Apparent total tract OM disappearance increased (P = 0.03), and apparent total tract N disappearance tended (P = 0.11) to increase in supplemented calves. Microbial efficiency was not affected (P = 0.50) by supplementation. There were no differences in ruminal pH (P = 0.40) or total VFA concentration (P = 0.21) between treatments, whereas ruminal NH3 concentration increased (P = 0.03) in supplemented compared with control calves. In Exp. 2, supplementation decreased (P = 0.02) forage OM intake (OMI; % of BW) and increased (P = 0.06) total OMI (% of BW). Supplementation had no effect on ADG (P = 0.94) or G:F (P = 0.35). Supplementation with a wheat middlings and soybean hull-based creep feed reduced forage OMI but improved total tract OM and N digestion and had minimal effects on ruminal fermentation or performance. Supplementation with a wheat middlings and soybean hulls-based creep feed might improve OM and N digestion, but might not produce significantly greater BW gains compared with no supplementation.  相似文献   

12.
Nine ruminally cannulated mixed-breed steers were used in a split-plot design to evaluate effects of fat supplementation and forage maturity on intake, digestibility, and ruminal fermentation. Treatment was the main plot, and stage of forage maturity was the subplot. Treatments were supplements containing mineral pack (M) offered at 114 g/d; M plus fiber as soybean hulls-wheat middlings (MF) offered at 0.50% BW; and MF plus tallow (MFT) offered at 0.625% BW. Stages of wheat maturity were mid-March (MAR) and early April (APR). Steers grazed in a single wheat pasture with supplements offered individually at 0700 h daily. There were supplement type x forage maturity interactions (P < 0.05) for forage OM, CP, and NDF intakes. During MAR, forage OM, CP, and NDF intakes were not affected (P > 0.05) by supplementation. During APR, forage OM, CP, and NDF intakes differed (MF = M > MFT, P < 0.05). There was also supplement type x forage maturity interaction (P = 0.04) for forage OM digestibility. The OM digestibility differed during MAR (M = MF > MFT, P < 0.05) and during APR (MF > M > MFT, P < 0.05). Crude protein digestibility was affected by supplement type (M > MF > MFT, P < 0.05) and stage of forage maturity (MAR > APR, P < 0.01). Rates of DM and NDF ruminal disappearance were not affected (P > 0.05) by supplement or forage maturity. Supplementation increased (P < 0.05) ruminal propionate concentration (19.7, 21.4, and 25.1 +/- 0.49 mol/100 mol for M, MF, and MFT, respectively). Tallow can be used in supplements for cattle grazing wheat pasture to increase energy intake without negatively affecting forage intake or ruminal fermentation, particularly if used in the early stage of wheat maturity.  相似文献   

13.
Two metabolism (4 x 4 Latin square design) experiments were conducted to evaluate the effects of corn condensed distillers solubles (CCDS) supplementation on intake, ruminal fermentation, site of digestion, and the in situ disappearance rate of forage in beef steers fed low-quality switchgrass hay (Panicum virgatum L.). Experimental periods for both trials consisted of a 9-d diet adaptation and 5 d of collection. In Exp. 1, 4 ruminally and duodenally cannulated steers (561 +/- 53 kg of initial BW) were fed low-quality switchgrass hay (5.1% CP, 40.3% ADF, 7.5% ash; DM basis) and supplemented with CCDS (15.4% CP, 4.2% fat; DM basis). Treatments included 1) no CCDS; 2) 5% CCDS; 3) 10% CCDS; and 4) 15% CCDS (DM basis), which was offered separately from the hay. In Exp. 2, 4 ruminally and duodenally cannulated steers (266.7 +/- 9.5 kg of initial BW) were assigned to treatments similar to Exp. 1, except forage (Panicum virgatum L.; 3.3% CP, 42.5% ADF, 5.9% ash; DM basis) and CCDS (21.6% CP, 17.4% fat; DM basis) were fed as a mixed ration, using a forage mixer to blend the CCDS with the hay. In Exp. 1, ruminal, postruminal, and total tract OM digestibilities were not affected (P = 0.21 to 0.59) by treatment. Crude protein intake and total tract CP digestibility increased linearly with increasing CCDS (P = 0.001 and 0.009, respectively). Microbial CP synthesis tended (P = 0.11) to increase linearly with increasing CCDS, whereas microbial efficiency was not different (P = 0.38). Supplementation of CCDS to low-quality hay-based diets tended to increase total DM and OM intakes (P = 0.11 and 0.13, respectively) without affecting hay DMI (P = 0.70). In Exp. 2, ruminal OM digestion increased linearly (P = 0.003) with increasing CCDS, whereas postruminal and total tract OM digestibilities were not affected (P > or = 0.37) by treatment. Crude protein intake, total tract CP digestibility, and microbial CP synthesis increased (P < or = 0.06) with increasing level of CCDS supplementation, whereas microbial efficiency did not change (P = 0.43). Ruminal digestion of ADF and NDF increased (P = 0.02 and 0.008, respectively) with CCDS supplementation. Based on this data, CCDS used in Exp. 2 was 86.7% rumen degradable protein. The results indicate that CCDS supplementation improves nutrient availability and use of low-quality forages.  相似文献   

14.
The effects of source and level of dietary NDF on intake, ruminal digestion in situ, ruminal fermentation, and total tract digestion were evaluated in Hereford steers using a replicated 5 x 5 Latin square design. Diets contained 62 to 64% TDN and included 1) 80% control concentrate (contained pelleted ground grains) and 20% timothy hay (traditional diet), 2) 80% control concentrate and 20% alfalfa cubes, 3) 90% control concentrate and 10% cubes, 4) a completely pelleted diet using corn cobs as the primary NDF source, and 5) 80% textured (rolled instead of ground grains) concentrate and 20% hay. Dry matter intake differed (P less than .05) between the traditional and cube diets due to limited acceptance of alfalfa cubes. Increased (P less than .05) ruminal osmolality, total VFA, and NH3 N and lower (P less than .01) ruminal pH in steers fed corn cob and cube diets relative to steers fed the traditional diet were due to preferential consumption of concentrate over supplemental roughage and the resultant rapid fermentation of concentrates. Potentially degradable DM in the traditional diet exceeded (P less than .06) all other diets, resulting in the increased (P less than .10) extent of DM disappearance despite a slower (P less than .05) rate of DM disappearance. Rate of NDF disappearance and all in situ starch disappearance parameters were similar between the traditional, corn cob, and cube diets. All ruminal digestion parameters involving NDF disappearance were similar between hay diets and between cube diets, whereas rate and extent of starch disappearance differed (P less than .05) between hay diets. Although formulation of diets with different sources of dietary NDF did not affect total tract digestion of nutrients, nutrient availability and ruminal fermentation were altered due to dietary differences in sources of dietary NDF and preferential selection of feedstuffs by steers.  相似文献   

15.
A digestion and ruminal fermentation trial involving five ruminally cannulated steers assigned to a 5 x 5 Latin square with a 2 x 2 + 1 arrangement of dietary treatments was conducted to evaluate the effects of variety of rapeseed silage (RS) containing either a high (HG) or a low (LG) glucosinolate concentration when fed at 100 or 50% of diet DM. A bromegrass hay-corn-soybean meal mixture, which was expected to be isocaloric and isonitrogenous with the RS, was used as the control (C) treatment and replaced RS in the 50% diets. In situ disappearance of substrate from both RS varieties was measured in ruminal environments created by each diet. No dietary treatment x RS substrate interactions were observed for any in situ variable. Total tract digestibility and extent of in situ disappearance of both DM and NDF were greater (P less than .01) for HG than for LG. In situ DM and NDF disappearance at 8, 16 and 24 h was greater (P less than .01) for RS than for the C diet. Similarly, total tract DM digestibility was greater (P less than .01) for RS (61.0%) vs C (56.0%) diets. Diets with 50% RS had greater (P less than .01) NDF digestibility (50.4%) than 100% RS (43.6%) diets. Variety of RS had no effect on particulate passage rate. In a 77-d growth trial with 60 beef steers, ADG was greater (P less than .01) for HG vs LG (.46 vs .36 kg), 50 vs 100% (.52 vs .31) and C vs RS (.64 vs .41) diets.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

16.
Five ruminally and duodenally cannulated steers were fed bromegrass hay (H; 5.6% CP; 70.9% cell wall) substituted with 0, 15, 30, 45, or 60% soybean hulls (SH; 10.5% CP; 87.9% cell wall) at 90% of ad libitum DMI. Diets were made isonitrogenous (11% CP) by addition of isolated soybean protein (91.5% CP). Total ruminal VFA concentration, molar proportion of acetate, and molar acetate:propionate ratio increased (linear; P less than .02) with increasing level of SH substitution, but propionate (mol/100 mol) and ruminal fluid passage rate decreased (linear; P less than .01). Ruminal pH and ammonia concentration decreased more rapidly, and to a greater extent and duration, as level of SH increased; neither was decreased to levels considered detrimental to fiber digestion. Ruminal and total tract DM, OM, and cell wall digestibilities increased (linear; P less than .01), whereas total tract N digestibility decreased (linear; P = .03), as level of SH increased Total N flow to the duodenum increased (linear, P = .03) with increasing level of SH, and microbial N flow tended (cubic, P = .09) to increase. Microbial efficiencies were unchanged (P = .10) with SH level. True ruminal digestibilities of N did not differ (P greater than .10) among diets. Rate of in situ DM disappearance of H and SH was not influenced (P greater than .10) by SH substitution, although rate tended to be fastest with 30 and 45% SH (quadratic, P = .14). We infer from these data that SH can replace 60% of the DMI of a low-quality forage diet without decreasing OM or cell wall digestion.  相似文献   

17.
Six beef steers (British x Brahman) cannulated at the rumen, duodenum and ileum (avg wt 334 kg) and three mature steers (British x British) cannulated at the esophagus were used in a replicated 3 x 3 latin square design and fed no supplement (C), .5 kg soybean meal (SBM) or .5 kg steam-flaked sorghum grain (SFS).head-1.d-1 (DM basis) while grazing blue grama rangeland. Periods of the latin square included a minimum of 14 d for adaptation and 11 d for esophageal masticate collection and digesta sampling. In September, October and November, respectively, forage collected by esophageally cannulated steers averaged 74.5, 88.8 and 71.0% grasses; 2.06, 1.53 and 1.77% N and 68.3, (P greater than .10) by treatment, but total N intake was greater (P less than .05) for SBM vs C and SFS treatments. No differences (P greater than .10) were detected among treatments in OM, NDF, ADF and N digestibilities in the rumen, small intestine or hindgut, but total tract OM digestibility was greater (P less than .10) for SBM and SFS than for C, and total tract N digestibility was greater (P less than .10) for SBM than for C or SFS. Duodenal ammonia N flow was greater (P less than .05) when SBM was fed that when SFS and C were fed, but microbial N and non-ammonia, non-microbial N flows and microbial efficiency were not altered by treatment. Likewise, ileal N flow was not affected (P greater than .10) by treatment. Particulate passage rate, gastrointestinal mean retention time, forage in vitro OM disappearance and in situ rate of forage NDF digestion also were not affected (P greater than .10) by treatments. Ruminal fluid volume was greater (P less than .05) for SFS vs SBM and C treatments, but no differences were noted in fluid dilution rate. Ruminal fluid ammonia concentration was greater (P less than .05) when SBM was fed than when SFS and C were fed (13.5, 9.9 and 8.7 mg/dl, respectively), whereas pH and total VFA concentrations were not different (P greater than .10). Proportion of acetate in ruminal fluid was less (P less than .10) for SBM and SFS than for C. Small amounts of supplemental SBM and SFS had little effect on forage intake, ruminal fermentation and site of digestion but both increased total tract OM digestion in steers grazing blue grama rangeland.  相似文献   

18.
Four ruminally and duodenally cannulated crossbred beef steers (397+/-55 kg initial BW) were used in a 4 x 4 Latin square to evaluate the effects of increasing level of field pea supplementation on intake, digestion, microbial efficiency, ruminal fermentation, and in situ disappearance in steers fed moderate-quality (8.0% CP, DM basis) grass hay. Basal diets, offered ad libitum twice daily, consisted of chopped (15.2-cm screen) grass hay. Supplements were 0, 0.81, 1.62, and 2.43 kg (DM basis) per steer daily of rolled field pea (23.4% CP, DM basis) offered in equal proportions twice daily. Steers were adapted to diets on d 1 to 9; on d 10 to 14, DMI were measured. Field pea and grass hay were incubated in situ, beginning on d 10, for 0, 2, 4, 8, 12, 16, 24, 36, 48, 72, and 96 h. Ruminal fluid was collected and pH recorded at -2, 0, 2, 4, 6, 8, 10, and 12 h after feeding on d 13. Duodenal samples were taken for three consecutive days beginning on d 10 in a manner that allowed for a collection to take place every other hour over a 24-h period. Linear, quadratic, and cubic contrasts were used to evaluate the effects of increasing field pea level. Total DMI and OMI increased quadratically (P = 0.09), whereas forage DMI decreased quadratically (P = 0.09) with increasing field pea supplementation. There was a cubic effect (P < 0.001) for ruminal pH. Ruminal (P = 0.02) and apparent total-tract (P = 0.09) NDF disappearance decreased linearly with increasing field pea supplementation. Total ruminal VFA concentrations responded cubically (P = 0.008). Bacterial N flow (P = 0.002) and true ruminal N disappearance (P = 0.003) increased linearly, and apparent total-tract N disappearance increased quadratically (P = 0.09) with increasing field pea supplementation. No treatment effects were observed for ruminal DM fill (P = 0.82), true ruminal OM disappearance (P = 0.38), apparent intestinal OM digestion (P = 0.50), ruminal ADF disappearance (P = 0.17), apparent total-tract ADF disappearance (P = 0.35), or in situ DM disappearance of forage (P = 0.33). Because of effects on forage intake and ruminal pH, field peas seem to act like cereal grain supplements when used as supplements for forage-based diets. Supplementing field peas seems to effectively increase OM and N intakes of moderate-quality grass hay diets.  相似文献   

19.
The objective of this study was to evaluate the effects of substituting wheat dried distillers grains with solubles (DDGS) for barley grain and barley silage on intake, digestibility, and ruminal fermentation in feedlot beef cattle. Eight ruminally cannulated Angus heifers (initial BW 455 ± 10.8 kg) were assigned to a replicated 4 × 4 Latin square design with 4 treatments: control, low (25%), medium (30%), and high (35%) wheat DDGS (DM basis). The diets consisted of barley silage, barley concentrate, and wheat DDGS in ratios of 15:85:0 (CON), 10:65:25 (25DDGS), 5:65:30 (30DDGS), and 0:65:35 (35DDGS; DM basis), respectively. The diets were formulated such that wheat DDGS was substituted for both barley grain and barley silage to evaluate whether wheat DDGS can be fed as a source of both energy (grain) and fiber in feedlot finishing diets. Intakes (kg/d) of DM and OM were not different, whereas those of CP, NDF, ADF, and ether extract (EE) were greater (P < 0.01) and intake of starch was less (P < 0.01) for the 25DDGS compared with the CON diet. The digestibilities of CP, NDF, ADF, and EE in the total digestive tract were greater (P < 0.05) for 25DDGS vs. CON. Ruminal pH and total VFA concentrations were not different (P > 0.15) between 25DDGS and CON diets. Replacing barley silage with increasing amounts of wheat DDGS (i.e., from 25DDGS to 35DDGS) linearly reduced (P < 0.05) intakes of DM and other nutrients without altering (P=0.40) CP intake. In contrast, digestibilities of DM and other nutrients in the total digestive tract linearly increased (P < 0.05) with increasing wheat DDGS except for that of EE. Additionally, with increasing amounts of wheat DDGS, mean ruminal pH tended (P=0.10) to linearly decrease, and ruminal pH status decreased with longer (P=0.04) duration of pH <5.5 and <5.2, and greater (P=0.01) curve area under pH <5.8 and <5.5 without altering (P > 0.19) ruminal VFA and NH(3)-N concentrations. Results indicated that wheat DDGS can be effectively used to replace both barley grain and silage at a moderate amount to meet energy and fiber requirements of finishing cattle. However, when silage content of the diet is low (<10%), wheat DDGS is not an effective fiber source, so replacing forage fiber with wheat DDGS in finishing diets decreases overall ruminal pH status even though the rapidly fermentable starch content of the diet is considerably reduced.  相似文献   

20.
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   

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