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1.
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   

2.
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   

3.
Five ruminally fistulated 3-yr-old mature Holstein steers (average BW 691+/-23 kg) were used in a 5 x 5 Latin square experiment with a 2 x 2 + 1 fact orial arrangement of treatments. Effects of protein concentration and protein source on nutrient digestibility, excretion of DM and fecal N, ruminal fluid volume and dilution rate, ruminal characteristics, and in situ DM disappearance of whole shelled corn, ground corn, and orchardgrass hay were measured in steers limit-fed high-concentrate diets at 1.5% of BW. A negative control basal diet (NC; 9% CP) was supplemented to achieve either 11 or 14% CP; supplemental CP was either from soybean meal (11 and 14% SBM) or a 50:50 ratio of CP from urea and soybean meal (11 and 14% U). Dry matter and OM digestibilities were 5% greater (P < .07) for steers fed the SBM diets than for those fed the U diets. Starch digestibility did not differ (P > .10) among steers fed any of the diets. Nitrogen source did not affect (P > .10) apparent N digestibility or fecal N excretion; however, steers fed the NC diet had the lowest (P < .10) apparent N digestibility compared with those fed all other diets. Ruminal fluid volume was lower (P < .06) when steers were fed the NC diet compared with all other diets; there were no differences (P > .74) among diets for ruminal fluid dilution rate. In general, ruminal ammonia N and VFA molar proportions were not affected by protein source or concentration. Although CP concentration affected (P < .06) in situ DM disappearance of ground corn, CP concentration did not (P > .48) affect total tract digestion of DM or OM. This indicates that CP concentration may have affected site of digestion, but not extent of digestion. When mature ruminants were limit-fed a corn-based diet to meet primarily a maintenance function, protein source and concentration had little effect on measures of nutrient digestion.  相似文献   

4.
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   

5.
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   

6.
One finishing trial and one digestibility trial were used to evaluate wet corn gluten feed (WCGF) and alfalfa hay (AH) combinations in steam-flaked corn (SFC) finishing diets. In Exp. 1, 631 crossbred heifers (initial BW = 284 +/- 7.9 kg) were fed SFC-based diets containing combinations of WCGF (25, 35, or 45% of diet DM) and AH (2 or 6% of dietary DM) in a 2 x 3 factorial arrangement of treatments. No interactions existed between WCGF and AH for heifer performance. Increasing dietary WCGF linearly decreased gain efficiency (P < 0.01), dietary NEg concentration (P < 0.05), and 12th-rib fat thickness (P = 0.10). Cattle fed 35% WCGF had the lowest occurrence of abscessed livers, resulting in a quadratic response (P < 0.05) as dietary WCGF increased. In Exp. 2, 12 ruminally cannulated Jersey steers (585 kg) were fed SFC-based diets containing combinations of WCGF (25 or 45% of diet DM) and AH (0, 2, or 6% of diet DM) in an incomplete Latin square design with a 2 x 3 factorial arrangement of treatments. Starch intake was lower (P < 0.05), but NDF intake was greater (P < 0.05) as AH and WCGF increased in the diet. Ruminal pH was increased by AH (linear, P < 0.05) and tended (P < 0.07) to increase with WCGF. Feeding 2% AH led to the greatest ruminal NH3 but the lowest total VFA and propionate (quadratic, P < 0.05). Addition of AH to diets containing 25% WCGF increased acetate to a greater extent than addition to diets containing 45% WCGF (AH x WCGF interaction, P < 0.05). Feeding 45% WCGF tended to increase passage rate (P = 0.17) and decrease (P < 0.05) total tract OM digestibility but increase (P < 0.05) in situ degradation of DM from AH and WCGF. Interactions between AH and WCGF existed (P < 0.05) for ruminal fluid volume (quadratic effect of AH x WCGF level), in situ SFC degradation (linear effect of AH x WCGF level), and in situ rate of WCGF DM disappearance (quadratic effect of AH x WCGF level). We conclude that AH levels may be decreased when WCGF is added to SFC diets as 25% or more of the dietary DM.  相似文献   

7.
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   

8.
Corn silage with high NDF concentration has the potential to reduce DMI because it has a greater filling effect in the rumen than low-NDF corn silage. Our objective was to determine whether ruminal fill influences DMI to the same extent with low- or high-NDF corn silage-based diets. Eight ruminally cannulated Holstein steers (198 +/- 13 kg) were randomly assigned to a 2 x 2 factorial arrangement of treatments in a replicated 4 x 4 Latin square design with 16-d periods. Treatments were diets containing corn silage from a normal hybrid (low-fiber; LF) or its male-sterile isogenic counterpart (high-fiber; HF), offered for ad libitum consumption to steers with or without rumen inert bulk (RIB). The LF and HF diets contained 33.8 and 50.8% dietary NDF, respectively. Rumen inert bulk was added at 25% of pretrial ruminal volume in the form of plastic-coated tennis balls filled with sand to achieve a specific gravity of 1.1 and a total volume of 7.5 L. No fiber level x inert bulk interactions were detected for DMI or NDF intake (P > 0.10), suggesting that DMI was limited to the same extent by physical fill at both levels of dietary fiber. Addition of RIB decreased DMI by an average of 10.7%, which was 65.5 g/L of added bulk. The HF diet depressed DMI by an average of 15.5%, increased NDF intake 27.1%, and reduced ruminal NDF turnover time by 21.0% compared to the LF diet (P < 0.01), with no effect on ruminal volume or amount of NDF in the rumen (P > 0.10). Addition of RIB also reduced ruminal NDF turnover time and amount of NDF in the rumen (11.8% and 20.7%, respectively; P < 0.01), with no change in ruminal digesta volume (P > 0.10). The HF treatment decreased digestibility of DM and GE (5.5 and 5.7%, respectively; P < 0.01) but increased NDF digestibility (10.4%; P < 0.01) compared to LF. Rumen inert bulk had no effect on digestibility of DM, NDF, or GE (P > 0.10). The lack of reduction in digesta volume with addition of inert fill suggests that DMI of light-weight steers receiving corn silage-based diets within a wide range of NDF concentrations was not regulated by ruminal distension alone.  相似文献   

9.
Roughage sources were compared in flaked milo-based diets that contained 35% chopped alfalfa hay (AH, control diet) or with cottonseed hulls (CSH) or chopped wheat straw (WS) replacing half the AH. Latin square experiments were used to measure total tract digestion coefficients, particulate passage rates (rare earths), liquid turnover rates (Co-EDTA), and rumination time in six growing steers (Exp. 1) and in situ digestion of DM and NDF, ruminal pH and ruminal DM distribution in three mature, ruminally cannulated steers (Exp. 2). Rates of passage from Exp. 1 and rates and extents of digestion from Exp. 2 were used to calculate apparent extent of ruminal digestion (AED). In Exp. 1, total tract digestibilities of DM and NDF were lower (P less than .05) by 7 and 22%, respectively, when CSH, but not WS, were included in the diet. Digestibility of cell solubles was not different (P greater than .10) among diets. Inclusion of WS increased (P less than .10) rumination time by 36%, and CSH increased intake (P less than .10) by 17% over the control diet. In Exp. 2, there tended to be (P less than .20) increased in situ digestion of milo and AH in the WS diet. Measures of ruminal pH were similar for all diets. The AED for AH and milo DM and NDF, and the proportion of total tract NDF digestion occurring in the rumen (50, 47 and 62% for control, CSH and WS diets, respectively), were highest (P less than .05) for the WS diet. This resulted in similar total tract digestibilities for the WS and AH diets. The two low-digestibility roughages had different effects at this concentrate level; wheat straw enhanced apparent extent of ruminal digestion for NDF of other ingredients in the mixed diets, but cottonseed hulls did not.  相似文献   

10.
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   

11.
Four ruminally and duodenally cannulated steers (703.4 +/- 41 kg initial BW) were used in a 4 x 4 Latin square to evaluate the effects of field pea inclusion level on intake and site of digestion in beef steers fed medium-concentrate diets. Steers were offered feed ad libitum at 0700 and 1900 daily and were allowed free access to water. Diets consisted of 45% grass hay and 55% by-products based concentrate mixture and were formulated to contain a minimum of 12% CP (DM basis). Treatments consisted of (DM basis) 1) control, no pea; 2) 15% pea; 3) 30% pea; and 4) 45% pea in the total diet, with pea replacing wheat middlings, soybean hulls, and barley malt sprouts in the concentrate mixture. Experimental periods consisted of a 9-d dietary adjustment period followed by a 5-d collection period. Grass hay was incubated in situ, beginning on d 10, for 0, 2, 5, 9, 14, 24, 36, 72, and 98 h; and field pea and soybean hulls for 0, 2, 5, 9, 14, 24, 36, 48, and 72 h. Total DMI (15.0, 13.5, 14.1, 13.5 +/- 0.65 kg/d) and OM intake (13.4, 12.0, 12.6, 12.0 +/- 0.58 kg/d) decreased linearly (P = 0.10) with field pea inclusion. Apparent ruminal (17.5, 12.0, 0.6, 6.5 +/- 4.31%) and true ruminal CP digestibility (53.5, 48.7, 37.8, 46.2 +/- 3.83) decreased linearly (P < 0.10) with increasing field pea. Neutral detergent fiber intake (8.9, 7.9, 7.8, 7.0 +/- 0.3 kg/d) and fecal NDF output (3.1, 2.9, 2.6, 2.3 +/- 0.2 k/d) decreased linearly (P < 0.03) with increasing field pea. No effects were observed for microbial efficiency or total-tract digestibility of OM, CP, NDF, and ADF (P > or = 0.16). In situ DM and NDF disappearance rates of grass hay and soybean hulls decreased linearly (P < 0.05) with increasing field pea. Field pea in situ DM disappearance rate responded quadratically (P < 0.01; 5.9, 8.4, 5.5, and 4.9 +/- 0.52%/h, for 0, 15, 30, and 45% field pea level, respectively). Rate of in situ CP disappearance of grass hay decreased linearly (P < 0.01) with increasing field pea level. Field pea is a suitable ingredient for beef cattle consuming medium-concentrate diets, and the inclusion of up to 45% pea in by-products-based medium-concentrate growing diets decreased DMI, increased dietary UIP, and did not alter OM, NDF, or ADF digestibility.  相似文献   

12.
To assess the influence of forage diets on particle size of digesta in the rumen, three ruminally fistulated steers were fed alfalfa, orchardgrass or switchgrass hays in a 3 x 3 Latin square design. Mean sieve size of ruminal digesta for alfalfa, orchardgrass and switchgrass diets was 671, 652 and 466 microns, respectively. A second experiment examined the influence of ruminal particle size on digesta passage, digestibility and intake. Four ruminally fistulated Angus-Hereford steers were given ad libitum access to different proportions of alfalfa and switchgrass in a 4 x 4 Latin square design. Either a 100% alfalfa, 50% alfalfa:50% switchgrass, 25% alfalfa:75% switchgrass or 100% switchgrass diet was offered once daily. Mean sieve sizes of the ruminal digesta of these diets responded cubically (P less than .01; 1,066, 946, 1,003 and 925 microns, respectively). Mean ruminal turnover times were 24.3, 24.8, 24.7 and 29.8 h, respectively. Dry matter intake increased linearly (P less than .10) as the proportion of legume in the diet increased; no influence of diet on DM digestibility was observed. Passage rate of dosed nylon particles 1, 3 and 5 mm in length was influenced (P less than .01) by size; however, no difference in the passage rates of the nylon particles due to diet was evident. Particle size of ruminal digesta did not respond in a linear manner to the proportion of legume in the diet. A smaller ruminal particle size was not associated with a faster turnover of digesta.  相似文献   

13.
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   

14.
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   

15.
A study involving a 2 x 2 x 2 factorial arrangement of treatments was conducted to evaluate effects of hybrid (Pioneer 3335 and 3489), maturity (half milkline and blacklayer), and mechanical processing (field chopper with and without on-board rollers engaged) on intake and digestibility of corn silage. Forty Angus steers (322 +/- 5.2 kg BW) were assigned to the eight silage treatments (five steers per treatment) and individually fed using electronic gates. Diets consisted of 60% corn silage and 40% chopped alfalfa hay (DM basis). Following a 5-d adaptation period, intake was measured for 7 d and subsequently fecal samples were collected for 5 d. Chromic oxide (5 g/d) was fed beginning 7 d before fecal sample collection and digestibility was determined by the ratio of Cr in the feed and feces. Steers were reallocated to treatments and these procedures were repeated, providing 10 observations per treatment. In addition, all silages were ruminally incubated in six mature cows for 0, 8, 16, 24, 48, and 96 h to determine extent and rate of DM, starch, NDF, and ADF disappearance. Processing increased DMI of hybrid 3489 but did not affect DMI of hybrid 3335 (hybrid x processing; P < 0.06). Total tract digestibility of DM, starch, NDF, and ADF decreased (P < 0.01) as plant maturity increased. Maturity tended to decrease starch digestibility more for hybrid 3489 than for hybrid 3335 (hybrid x maturity; P < 0.10). Processing increased (P < 0.01) starch digestibility but decreased (P < 0.01) NDF and ADF digestibility, resulting in no processing effect on DM digestibility. There was a numerical trend for processing to increase starch digestibility more for latethan for early-maturity corn silage (maturity x processing; P = 0.11). Processing increased in situ rates of DM and starch disappearance and maturity decreased in situ disappearance rates of starch and fiber. These data indicate that hybrid, maturity, and processing all affect corn silage digestibility. Mechanical processing of corn silage increased starch digestibility, which may have been associated with the observed decreased fiber digestibility.  相似文献   

16.
Three experiments were conducted to evaluate effects of supplemental protein vs energy level on dormant forage intake and utilization. In Exp. 1, 16 ruminally cannulated steers were blocked by weight (avg wt = 242 kg) and assigned randomly to a negative control or to one of three isocaloric supplement treatments fed at .4% BW: 1) control, no supplement (NS); 2) 12% CP, low protein (LP); 3) 28% CP, moderate protein (MP); 4) 41% CP, high protein (HP). In Exp. 2 and 3, 16 ruminally cannulated steers were blocked by weight (avg wt = 332 kg, Exp. 2; 401 kg, Exp. 3) and assigned randomly to a 2 x 2 factorial arrangement of treatments. The treatments contrasted low (LP) and high (HP) levels of supplemental protein (.66 g CP/kg BW vs 1.32 g CP/kg BW) with low (LE) and high (HE) levels of supplemental ME (9.2 kcal/kg BW vs 18.4 kcal/kg BW). In Exp. 1, forage DMI as well as ruminal DM and indigestible ADF fill at 4 h postfeeding were greater (P less than .10) with the MP and HP steers than with control and LP steers. Total DM digestibility increased (P less than .10) for supplemented steers (35.5% for control vs 47.3 for supplemented steers); however, LP depressed (P less than .10) NDF digestibility. In Exp. 2, forage DMI, indigestible ADF flow and liquid flow were depressed (P less than .10) in LP-HE supplemented steers. In Exp. 3, HP steers had greater (P less than .10) forage DMI, indigestible ADF fill values (4 h postfeeding), liquid volume and tended (P = .11) to have greater ruminal DM fill (4 h postfeeding). In summary, increased levels of supplemental protein increased intake and utilization of dormant tallgrass-prairie forage (less than 3% CP). Increasing supplemental energy without adequate protein availability was associated with depressed intake and digestibility.  相似文献   

17.
Five ruminally, duodenally, and ileally cannulated steers (376 +/- 8.1 kg of initial BW) were used in a 5 x 5 Latin square to evaluate effects of cooked molasses block supplementation and inclusion of fermentation extract (Aspergillus oryzae) or brown seaweed meal (Ascophyllum nodosum) on intake, site of digestion, and microbial efficiency. Diets consisted of switchgrass hay (6.0% CP; DM basis) offered ad libitum, free access to water, and one of three molasses blocks (0.341 kg of DM/d; one-half at 0600 and one-half at 1800). Treatments were no block (control), block with no additive (40.5% CP; POS), block plus fermentation extract bolused directly into the rumen via gelatin capsules (2.0 g/d; FS), fermentation extract included in the block (2.0 g/d; FB), and seaweed meal included in the block (10 g/d; SB). Steers were adapted to diets for 14 d followed by a 7-d collection period. Overall treatment effect on hay OM intake tended (8.1 vs. 7.6 +/- 0.5 kg/d; P = 0.14) to increase with block supplementation. Total OM intake (8.4 vs. 7.6 +/- 0.5 kg/d; P = 0.01) increased in steers consuming block compared with control. Apparent and true ruminal OM digestibility increased (P = 0.05) with block consumption. Steers fed SB had greater (P = 0.10) true ruminal OM digestibility compared with steers fed POS (61.0 vs. 57.9 +/- 1.6%). True ruminal CP digestibility increased (P = 0.01) with block supplementation compared with control (37.5 vs. 23.6 +/- 3.7%). Addition of fermentation extract did not affect intake or digestion. Treatments did not alter ruminal pH, total VFA, or individual VFA proportions; however, ruminal ammonia increased (P = 0.01) with block supplementation. In situ disappearance rates of hay DM (3.14 +/- 0.44 %/h), NDF (3.18 +/- 0.47 %/h), and ADF (3.02 +/- 0.57 %/h) were not altered by treatment. Seaweed block increased (P = 0.01) slowly degraded CP fraction compared with POS (39.5 vs. 34.0 +/- 2.07%). Similarly, SB increased (P = 0.01) the extent of CP degradability (74.2 vs. 68.9 +/- 1.81%). No treatment effects (P = 0.24) were observed for microbial efficiency. Block supplementation increased intake, and use of brown seaweed meal seemed to have beneficial effects on forage digestibility in low-quality forage diets.  相似文献   

18.
A feedlot growth-performance trial involving 64 yearling steers and a metabolism trial involving four steers with cannulas in the rumen, proximal duodenum, and distal ileum were conducted to evaluate the comparative feeding value of steam-flaked corn (SFC, density = .30 kg/liter) and sorghum (SFS, density = .36 kg/liter) in finishing diets supplemented with or without .75% sodium bicarbonate (BICARB). No interactions between BICARB and grain type proved to be significant. Supplemental BICARB increased ADG 5.9% (P less than .10) and DMI 4.6% (P less than .05) but did not influence (P greater than .10) the NE value of the diet. Supplemental BICARB increased ruminal pH (P less than .01) and total tract fiber digestion (P less than .05). Differences in ruminal and total tract OM, starch, and N digestion were small (P greater than .10). Replacing SFC with SFS decreased (P less than .05) ADG 6.1% and increased (P less than .01) DMI/gain 9.7%. Corresponding diet NEm and NEg were decreased (P less than .01) 7.0 and 9.3%, respectively. Ruminal digestion of OM and starch tended to be lower (11.8 and 7.2%, respectively, P less than .10) for SFS. Ruminal degradation of feed N was 31% lower (P less than .05) for the SFS diets. Total tract digestibility of OM, N, DE, and ME were 3.3, 10.8, 4.4, and 5.5% lower (P less than .05), respectively, for the SFS vs SFC diets. In conclusion, 1) SFS had 92% the NEm of SFC; 2) differences in total tract starch digestibility were small and cannot explain the higher feeding value of SFC; 3) the low ruminal degradation of sorghum N (roughly 20%) should be considered in diet formulation to avoid a deficit in ruminally available N; and 4) .75% BICARB supplementation increased DMI and ADG of cattle fed highly processed grain-based diets.  相似文献   

19.
Two experiments were conducted to evaluate the effects of slow-release urea (SRU) versus feed-grade urea on ruminal metabolite characteristics in steers and DMI, gain, and G:F in growing beef steers. Experiment 1 used 12 ruminally cannulated steers (529 +/- 16 kg of BW) to monitor the behavior of SRU in the ruminal environment. Compared with feed-grade urea, SRU decreased ruminal ammonia concentration (P = 0.02) and tended to increase ruminal urease activity (P = 0.06) without affecting ruminal VFA molar proportions or total concentrations (P > 0.20). After 35 d of feeding, the in situ degradation rate of SRU was not different between animals fed urea or SRU (P = 0.48). Experiment 2 used 180 Angus-cross steers (330 +/- 2.3 kg) fed corn silage-based diets supplemented with urea or SRU for 56 d to evaluate the effects on feed intake, gain, and G:F. The design was a randomized complete block with a 2 x 4 + 1 factorial arrangement of treatments. Treatments included no supplemental urea (control) or urea or SRU at 0.4, 0.8, 1.2, or 1.6% of diet DM. Over the entire 56 d experiment, there were interactions of urea source x concentration for gain (P = 0.04) and G:F (P = 0.01) because SRU reduced ADG and G:F at the 0.4 and 1.6% supplementation concentrations but was equivalent to urea at the 0.8 and 1.2% supplementation concentrations; these effects were due to urea source x concentration interactions for gain (P = 0.06) and G:F (P = 0.05) during d 29 to 56 of the experiment. The SRU reduced DMI during d 29 to 56 (P = 0.01) but not during d 0 to 28, so that over the entire experiment there was no difference in DMI for urea source (P = 0.19). These collective results demonstrate that SRU releases N slowly in the rumen with no apparent adaptation within 35 d. Supplementation of SRU may limit N availability at low (0.4%) concentrations but is equivalent to urea at 0.8 and 1.2% concentrations.  相似文献   

20.
Two experiments were conducted to evaluate wheat middlings as a supplement for cattle consuming dormant bluestem-range forage. Effects of supplement type and amount were evaluated in Exp. 1, which consisted of feeding supplements of soybean meal:grain sorghum (22:78) or two different amounts of wheat middlings. Sixteen ruminally fistulated steers were blocked by weight (BW = 374 +/- 8.3 kg) and assigned randomly to the following treatments: 1) control, no supplement (NS); 2) soybean meal:grain sorghum (SBM/GS) formulated to contain the same CP concentration (21%) and fed to provide a similar energy level (3.5 Mcal of ME/d); 3) a supplement of 100% wheat middlings fed at a low level (LWM); and 4) 100% wheat middlings fed at twice the amount of LWM (7 Mcal of ME/d; HWM). The influence of different supplemental CP concentrations in a wheat middlings-based supplement was evaluated in Exp. 2. Sixteen ruminally fistulated steers were blocked by weight (BW = 422 +/- 8.1 kg) and assigned randomly to the following treatments: 1) control, no supplement (NS); 2) 15% CP; 3) 20% CP; and 4) 25% CP supplements. These supplements consisted of 60% wheat middlings and various ratios of soybean meal and grain sorghum to achieve the desired CP concentration. In Exp. 1, SBM/GS and HWM supplements increased (P less than .10) and LWM tended to increase (P = .16) forage DMI compared with NS. All supplements in Exp. 1 increased (P less than .10) DM digestibility, ruminal DM fill, and ruminal indigestible ADF (IADF) passage rate compared with NS, although the greatest response in fill and passage was observed with HWM. In Exp. 2, forage DMI, DM digestibility, NDF digestibility, ruminal DM and IADF fill, IADF passage rate, and fluid dilution rate were increased (P less than .01) by supplementation. Forage DMI, ruminal IADF passage rate, and fluid dilution rate increased quadratically (P less than .10), and NDF digestibility, ruminal DM and IADF fill increased linearly (P less than .10) with increased supplemental CP concentration. These experiments indicate that wheat middlings performed similarly to a SBM/GS supplement of equal CP concentration, when both were fed to provide a similar amount of energy daily. Additionally, use of poor-quality range forage was enhanced when wheat middlings-based supplements were formulated to contain a CP concentration of 20% or greater.  相似文献   

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