Influence of ruminal or duodenal soybean oil infusion on intake, ruminal fermentation, site and extent of digestion, and microbial protein synthesis in beef heifers consuming grass hay.

Six heifers (two Hereford X Jersey, four Hereford X Longhorn; average BW 278 kg) cannulated at the rumen and duodenum and fed a grass hay (fescue/orchardgrass) diet were used in a replicated 3 X 3 Latin square. Treatments were either no infusion (C), 150 ml of duodenally infused soybean oil (DI), or 150 ml of ruminally infused soybean oil (RI)/heifer twice daily for a total daily infusion of 300 ml of soybean oil. Periods of the Latin square included 18 d for adaptation and 5 d for collection. Forage OM, ADF, NDF, and N intakes were not affected (P greater than .10) by soybean oil infusion. Ruminal (P = .11) and total tract (P less than .10) OM digestibilities were decreased by RI compared with C or DI, but ADF and NDF digestibilities were not affected by treatment. Duodenal N (P less than .05) and microbial N flows were increased (P less than .10) for C and RI compared with DI. Microbial efficiency (g of N/kg of OM truly fermented) was improved (P less than .10) by RI compared with DI but did not differ (P greater than .10) from C. Ruminal pH was lower (P less than .05) with RI than with either C or DI. Ruminal NH3 N, total VFA, and acetate were not affected (P greater than .10) by treatment. Propionate (mol/100 mol) was greater (P less than .05) with RI than with DI and C, but the proportion of butyrate did not differ among treatments. These data indicate minimal direct benefits for improving forage usage as a result of soybean oil infusion with a 100% grass diet; however, animals should realize benefits from additional dietary energy provided by infused lipid.     

Effect of supplementation of dried distillers grains with solubles on forage intake and characteristics of digestion of beef heifers grazing small-grain pasture

Sixteen ruminally cannulated, English-crossbred heifers (378 ± 28.4 kg) grazing small-grain pasture (SGP) were used in a completely randomized design to evaluate effects of supplementing different amounts of corn dried distillers grains with solubles (DDGS; 0, 0.2, 0.4, and 0.6% of BW; as-fed basis) on forage intake, digestibility, and rumen fermentation characteristics. The experiment was conducted from April 6 through April 20, 2007. Heifers grazed in a single SGP with supplements offered individually, once daily at 0700 h. Forage and total OM, CP, and NDF intake were not affected (P ≥ 0.21) by DDGS amount. Digestibility of NDF and ether extract (EE) increased linearly (P < 0.001) when heifers consumed more DDGS. Intake of DM (kg/d and g/kg of BW), ruminal volume (L), fluid dilution rate (%/h), fluid flow rate (L/h) turnover time (h), and particle dilution rate (SGP and DDGS) were not affected (P ≥ 0.32) by increasing DDGS supplementation amount. In situ DDGS CP kinetic parameters were not affected (P ≥ 0.25) by increasing DDGS supplementation amount. Forage masticate in situ soluble CP fraction and CP effective degradability increased quadratically (P = 0.01) with increasing DDGS supplementation amount. However, amount of DDGS did not affect forage masticate CP slowly degradable fraction (%; P = 0.39) or degradation rate (%/h; P = 0.63). Rate of in situ disappearance (%/h) for DDGS DM (P = 0.94), forage masticate DM (P = 0.89), and NDF (P = 0.89) were not affected by DDGS supplementation amount, nor was rumen undegradable intake protein (% of CP) for DDGS (P = 0.28) and forage masticate samples (P = 0.93). Ruminal concentration of VFA and ammonia and ruminal pH were not affected (P ≥ 0.21) by increasing DDGS amount. Results indicated that DDGS can be used in SGP supplements without negatively affecting forage intake, digestibility, or ruminal fermentation.     

Influence of soybean meal and sorghum grain supplementation on intake, digesta kinetics, ruminal fermentation, site and extent of digestion and microbial protein synthesis in beef steers grazing blue grama rangeland

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.     

Combinations of high-moisture harvested sorghum grain and dry-rolled corn: effects on site and extent of digestion in beef heifers

To determine the effects of blends of high-moisture harvested sorghum grain (HMS) and dry-rolled corn (DRC) on site and extent of digestion, high-grain diets were fed to Angus-Hereford heifers (315 kg) in a 5 x 5 latin square. The grain portion consisted of ratios (HMS:DRC) of 0:100, 25:75, 50:50, 75:25 and 100:0. Heifers were equipped with ruminal, duodenal and ileal T-type cannulas. Digestibilities of OM (P less than .05) and non-ammonia nitrogen (NAN; P less than .01) in the total tract declined linearly as HMS replaced DRC. Chyme flow (liters/d) through the duodenum increased linearly (P less than .01), and true ruminal OM disappearance tended to decline linearly (P less than .10) as HMS replaced DRC. A quadratic response (P less than .05) in extent of starch disappearance (g/d) in the rumen was noted; blends were lower than either individual grain. Ruminal escape of feed N tended to be quadratic (P less than .10); values for individual grain types were greater than blends. Microbial efficiency increased linearly (P less than .05) as HMS replaced DRC. Extent of starch digestion in the rumen averaged 82.7% compared to only 2.9% in the small intestine and 5.7% in the large intestine. Altering the ratio of HMS to DRC appeared to have more effect on ruminal fermentation than on digestion in the small intestine; most starch and nitrogen responses were quadratic. Increases in ruminal pH and chyme flow, potentially caused by increased salivary flow, may cause non-linear changes in the solubility of proteins in HMS and DRC, when fed as blends, altering the digestibility of protein and starch from values predicted from the individual grains.     

Effect of lasalocid on weight gains, ruminal fermentation and forage intake of stocker cattle grazing winter wheat pasture

Fifty fall-weaned heifers with initial weights of 209 kg (yr 1) and 222 kg (yr 2) were used to determine effects of lasalocid on weight gains, forage intake and ruminal fermentation of stocker cattle grazing winter wheat pasture. The heifers grazed a single wheat pasture for about 100 d each year, and were individually fed 1.06 kg of supplement (6 d/wk) pro-rated to supply 0, 100 or 200 mg lasalocid.head-1.d-1. Also, eight mature Hereford steers with large rumen cannula were used to evaluate further effects of lasalocid (0 or 300 mg) on ruminal fermentation during two grazing periods (immature and mature wheat forage) of yr 2 and an additional third year. Daily gains of heifers fed 200 mg lasalocid/d were .11 kg greater (P less than .05) than those of heifers fed 0 or 100 mg lasalocid/d. One hundred milligrams lasalocid did not increase weight gains. Digestibilities of forage dry matter (DM) and organic matter (OM) were similar (P greater than .05) among treatments, and lasalocid did not affect (P greater than .10) forage intake. Ruminal ammonia concentrations (10.57, 15.22 and 17.81 mg/dl +/- 1.71) were increased (P less than .05) by both levels of lasalocid in yr 1, but differences among treatment means of 8.32, 11.95 and 11.66 (SE +/- 1.44) were not significant in yr 2. Lasalocid did not consistently affect total volatile fatty acids concentrations. The acetic:propionic acid ratios in heifers were not different (P greater than .05) among treatments, but were decreased (P less than .10) by lasalocid in cannulated steers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of a monensin ruminal delivery device on daily gain, forage intake and ruminal fermentation of steers grazing irrigated winter wheat pasture

Two trials evaluated the effects of a monensin ruminal delivery device (MRDD) on steers grazing winter wheat pasture. In Trial 1, 60 Hereford steers (initial wt 238.5 kg) grazed a 21.9-ha paddock of Vona-variety winter wheat for 112 d. Steers were assigned to either MRDD or control (C) treatments in a randomized complete block design. In Trial 2, eight ruminally cannulated steers (avg wt 234.4 kg) grazed a 2.4-ha paddock of Vona-variety wheat and were assigned randomly to either MRDD or C treatments. Three 11-d collection periods were conducted during early February, early March and early April. Chromic oxide was dosed to determine fecal output, and ruminal samples were collected on d 6 of each period. Nylon bags containing ground wheat forage were incubated ruminally beginning on d 8. In Trial 1, steers with MRDD tended (P less than .11) to gain more weight than C steers (.44 vs .38 kg/d). In Trial 2, wheat forage intake, in situ DM disappearance, ruminal pH, ruminal ammonia concentrations and ruminal proportions of acetate and total VFA concentrations were not affected by treatment. Ruminal proportions of propionate were increased (P less than .05) slightly by MRDD (20.3 and 19.2 mol/100 mol for MRDD and C, respectively). Butyrate proportions in ruminal samples were decreased (P less than .05) by MRDD during March but not in other sampling periods. Ruminal fluid chlorophyll concentration was less (P less than .05) for MRDD-treated vs C steers during early March but was greater (P less than .10) for MRDD-treated steers during early April. The MRDD shows promise as a method of supplying monensin to cattle grazing winter wheat forage.     

Influence of level of supplemental whole flaxseed on forage intake and site and extent of digestion in beef heifers consuming native grass hay

The objectives of this study were to evaluate the influence of supplemental whole flaxseed level on intake and site and extent of digestion in beef cattle consuming native grass hay. Nine Angus heifers (303 +/- 6.7 kg of BW) fitted with ruminal and duodenal cannulas were used in a triplicated 3 x 3 Latin square. Cattle were given ad libitum access to chopped native grass hay (9.6% CP and 77.5% NDF, OM basis). All animals were randomly allotted to 1 of 3 experimental treatments of hay plus no supplement (control); 0.91 kg/d whole flaxseed (23.0% CP, 36.3% NDF, and 25.5% total fatty acid, OM basis); or 1.82 kg/d whole flaxseed on a DM basis. Supplemental flaxseed tended to decrease (linear, P = 0.06) forage OM intake. However, total OM intake did not differ (P = 0.29) with increasing levels of flaxseed. Total duodenal OM flow increased (linear, P = 0.05) with additional flaxseed in the diet, and no differences (P = 0.29) were observed for microbial OM flow. True ruminal OM disappearance was not affected (P = 0.14) by supplemental flaxseed. Apparent lower tract OM digestibility increased (linear, P = 0.01) with level of whole flaxseed. Apparent total tract OM digestibility was not different (P = 0.41) among treatments. Nitrogen intake increased (linear, P < 0.001) with supplemental flaxseed. In addition, total duodenal N flow tended (P = 0.08) to increase with additional dietary flaxseed. However, true ruminal N digestibility did not differ (P = 0.11) across treatment. Supplemental whole flaxseed did not influence ruminal (P = 0.13) or total tract (P = 0.23) NDF digestibility. Ruminal molar proportion of propionate responded quadratically (P < 0.001) with increasing levels of whole flaxseed. An increase in the duodenal supply of 18:3n-3 (P < 0.001), total unsaturated fatty acids (P < 0.001), and total fatty acids (P < 0.001) was observed with additional dietary whole flaxseed. Apparent postruminal 18:3n-3 disappearance tended to decrease (P = 0.07) as intake of flaxseed increased. Overall, the inclusion of 1.82 kg/d of flaxseed does not appear to negatively influence nutrient digestibility of a forage-based diet and therefore can be used as an effective supplement to increase intestinal supply of key fatty acids important to human health.     

Effects of corn vs corn gluten feed on site, extent and ruminal rate of forage digestion and on rate and efficiency of gain

Three digestion experiments and one growth experiment were conducted to determine site, extent and ruminal rate of forage digestion and rate and efficiency of gain by cattle offered alfalfa haylage supplemented with corn or dry corn gluten feed (CGF). In Exp. 1, eight steers were fed alfalfa haylage-based diets with substitution of corn for 0, 20, 40 or 60% of haylage in a 4 X 4 latin square. Increasing dietary corn substitution increased (P less than .05) OM, NDF and ADF digestion by steers but decreased (P less than .05) rate of in situ alfalfa DM digestion. In Exp. 2, five heifers were fed alfalfa haylage-based diets with increasing dietary levels of CGF in a 5 X 5 latin square. Increasing dietary CGF increased (P less than .05) OM, NDF and ADF digestion by heifers. In Exp. 3 and 4, cattle were fed alfalfa haylage-based diets containing either 20 or 60% corn or CGF. In Exp. 3, supplementation increased (P less than .05) OM and NDF digestion but level X supplement source interaction (P less than .05) occurred, with added CGF increasing OM and NDF digestion more than added corn. In Exp. 4, supplementation improved (P less than .05) DM intake, daily gain and feed efficiency. Dry matter intake and daily gain were greater (P less than .05) for 60% supplementation than for 20% supplementation. Overall, whereas increasing the level of dietary supplement increased (P less than .05) OM, NDF and ADF digestion, only corn addition decreased (P less than .05) rate of in situ alfalfa DM digestion. Daily gains and feed efficiencies were similar in cattle fed either corn or CGF with alfalfa haylage.     

Effects of supplementing prairie hay with corn and soybean meal on intake, digestion, and ruminal measurements by beef steers

Prairie hay supplemented with various amounts of corn and soybean meal was fed to steers in two experiments. Effects of supplementation on hay OM intake, digestion, and ruminal fermentation and kinetics were measured. A preliminary study was conducted to attain accurate values for OM intake and digestibility of prairie hay to be used in ration formulation using the NRC (1996) level 1 model. Ten steers (284 +/- 9 kg) given ad libitum access to chopped prairie hay (75% NDF, 6% CP) were supplemented with dry-rolled corn (0.75% of BW/d) plus soybean meal (0.25% of BW/d). Hay OM intake was 1.85% of BW and hay OM digestibility was 48%. Based on results from the preliminary study, eight ruminally cannulated beef steers (317 +/- 25 kg) received a sequence of eight different supplementation combinations (2 x 4 factorial arrangement of treatments). These supplements consisted of dry-rolled corn at either 0 or 0.75% of BW (DM basis) daily combined with one of four amounts of added soybean meal to provide between 0 and 1.3 g of degradable intake protein (DIP)/kg of BW. After supplements had been fed for 10 d, feces were collected for 4 d. Intake of hay and total OM increased quadratically (P < 0.01) in response to added DIP with or without supplemental corn. Hay OM digestibility increased quadratically (P = 0.03) as DIP was added when corn was fed in the supplement. Intake of digestible OM was greater (P < 0.01) with than without corn supplementation. Increasing DIP increased (P < 0.01) digestible OM intake regardless of whether corn was fed. Inadequate ruminally degraded protein in grain-based supplements decreased forage intake, digestibility, and energy intake of cattle fed low-quality prairie hay. Providing adequate supplemental DIP to meet total diet DIP needs seemed to overcome negative associative effects typically found from supplementing low-quality forages with large quantities of low-protein, high-starch feeds.     

Influence of lasalocid level on forage intake, digestibility, ruminal fermentation, liquid flow and performance of beef cattle grazing winter range

Three experiments were conducted to study the effects of lasalocid level on performance, intake, digestibility, ruminal fermentation and fluid flow of beef cattle grazing dormant, tallgrass prairie. In Exp. 1, 120 pregnant, mature beef cows of primarily Hereford breeding (avg wt = 471 kg) were randomly assigned to received 0, 100, 200 or 300 mg lasalocid X head-1 X d-1 in 1.82 kg supplement. Weight changes at 30, 60 or 90 d, condition score change and calf birth weight were not affected (P greater than .10) by lasalocid level. In Exp. 2, estimates of intake and digestibility were obtained with 40 pregnant, mature Hereford cows (avg wt = 474 kg) and 12 esophageal-cannulated, Hereford X Angus steers (avg wt = 225 kg), using Yb and indigestible acid detergent fiber as markers for fecal output and digestibility, respectively. Levels of lasalocid provided to cows and steers were similar, on a body weight (BW) basis, to those in Exp. 1 and corresponded to approximately 0, .22, .44 or .66 mg lasalocid/kg BW. Total diet and forage organic matter digestibility for beef cows decreased (P less than .01) at the .22 mg/kg BW level, but increased at the .44 and .66 mg/kg BW levels. Organic matter intake was not influenced (P greater than .10) by lasalocid addition. In Exp. 3, 16 ruminal-cannulated, Hereford X Angus steers (avg wt = 227 kg) were given the same lasalocid dosages per kg BW as in Exp. 2, and were used to study the effects of lasalocid on ruminal fermentation and fluid flow characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of lecithin and corn oil on site of digestion, ruminal fermentation and microbial protein synthesis in sheep

Six Hampshire wethers with ruminal and duodenal cannulas were fed three diets in a replicated 3 X 3 latin square to compare phospholipids with triglycerides for their effects on ruminal digestion. The diets (56% concentrate, 44% bermuda-grass hay, air-dried basis) contained either no added fat (control), 5.2% soybean lecithin or 2.4% corn oil on a DM basis. All diets were isonitrogenous and both fat-supplemented diets had similar fatty acid and energy contents. Fat added to the diet, regardless of source, reduced digestibilities of DM, energy, ADF and fatty acids in the rumen but had no effect on total tract digestibility coefficients. Lecithin slightly increased (P = .06) fatty acid digestion in the hindgut compared to corn oil (91.0 and 87.0%, respectively). Both fat sources decreased (P less than .01) ruminal ammonia concentration and increased (P less than .10) N flow to the duodenum. Added fat also reduced ruminal (P less than .01) and total tract (P less than .05) N digestibilities. Microbial N flow to the hindgut was not affected by diet, but adding fat increased (P less than .06) true efficiency of microbial protein synthesis. Overall, phospholipids from soybean lecithin inhibited ruminal fermentation similarly to triglycerides from corn oil. Despite ruminal degradation of lecithin by microbial phospholipases as shown in other studies, feeding lecithin tended to increase fatty acid digestion in the hindgut.     

Pregnancy and lactation in beef heifers grazing tallgrass prairie in the winter: influence on intake, forage utilization, and grazing behavior.

Six ruminally and eight bifistulated (ruminal and esophageal) Hereford x Angus heifers were used to determine effects of pregnancy and early lactation on forage intake and utilization under grazing conditions. Three ruminally and three bifistulated heifers were bred (pregnant/lactating; P/L; average calving date was February 11, 1989); remaining heifers served as controls (C). The experiment consisted of three periods (P1 = average of 55 d before parturition; P2 = average of 12 d before parturition; P3 = average of 26 d after parturition). All heifers grazed the same 24-ha Flint Hills range pasture. Dehydrated alfalfa pellets were supplemented at .5% BW/heifer daily prepartum and at .8% BW/heifer daily postpartum. Treatment x period interactions were noted (P less than .10) for forage OM intake, ruminal capacity, indigestible ADF (IADF) fill, and grazing time but not for OM digestibility or IADF passage rate (P greater than .10). In P1 and P3, P/L heifers had greater (P less than .10) forage OM intake than C heifers, whereas no differences were noted (P greater than .10) in P2. Pregnant/lactating heifers spent less time (P less than .10) grazing than did controls in P2 and more time (P less than .10) than controls in P3. Ruminal IADF fill and ruminal capacity, as measured by water fill, tended (P = .14 and .16, respectively) to differ between the two groups in P2. Digestibility of OM was unaffected (P greater than .10) by physiological status, whereas IADF passage rate was greater (P less than .10) in P/L heifers. Only minor differences were noted for the chemical composition of diets selected by the two groups. Ruminal fermentation patterns shifted only slightly; the largest effects were in P3, when P/L heifers had greater (P less than .10) propionate and less (P less than .10) acetate (mol/100 mol) than C heifers. In summary, during the period just before parturition, differences in forage OM intake between P/L and C heifers disappeared, and ruminal fill and capacity tended to be lower for P/L heifers. Intake was 16% greater for P/L than for C heifers during the early postpartum period. Organic matter digestibility was not influenced by physiological status, even though IADF passage rates were greater for P/L heifers.     

瘤胃蛋白降解率和添加频率对饲喂低质饲料的羔羊的影响研究

4头初始体重为34.5±2.0kg、插有瘤胃瘘管的萨福克阉公羊羔被用来评估瘤胃蛋白降解率和添加频率对饲喂低质饲料的羔羊瘤胃特性的影响。羔羊以成熟皇冠干草（含4.2%CP）为基础日粮,各日粮组分为4组,分别是：1）RDP-D：每天饲喂高的瘤胃降解蛋白质（RDP）;2）RDP-A：每隔1d饲喂高的RDP;3）RUP-A：每隔1d饲喂非瘤胃降解蛋白质（RUP）;4）MIX-A：每隔1d按照RDP：RUP=1：1的比例来饲喂。结果显示,各处理组的羔羊粗饲料的有机质（OM）、氮（N）、中性洗涤纤维（NDF）或酸性洗涤纤维（ADF）的采食量没有显著差异;混合组（MIX-A）的羔羊瘤胃有机质的消化率比其他组的要高（P〈0.001）;RUP-A组羔羊的真瘤胃氮消化率较其他处理组的低（P〈0.01）;混合组MIX-A瘤胃NDF和ADF的代谢较其他处理组高（P≤0.01）。当在羔羊日粮中添加RUP相对添加RDP-D可以降低其瘤胃氨气浓度,且RUP-A组的羔羊的瘤胃氨气浓度最低。各处理组的瘤胃脲酶活性差异不显著,瘤胃微生物N流量差异不显著,不过RDP-D组的羔羊的瘤胃微生物N合成效率有增加趋势（P=0.004）。隔天饲喂羔羊混合组的日粮可以改善低质粗饲料的消化率,这可能是由于内源性氮循环利用增强导致瘤胃氨气浓度有所下降。     

Effect of fat supplementation and wheat pasture maturity on forage intake and digestion characteristics of steers grazing wheat pasture

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.     

Influence of grain source on ruminal characteristics and rate, site, and extent of digestion in beef steers.

Six cannulated Salers steers (305 +/- 17 kg initial BW) were used in a double 3 x 3 Latin square design to compare the effects of the nature of the cereal (wheat vs corn) and the corn genotype (dent vs flint) on rate, site, and extent of digestion of high-concentrate diets. The cereals were coarsely cracked, and the diets were balanced to have the same percentage of starch (47.7 +/- 2.3%) and CP (14.6 +/- .7%). Differences in ruminal starch digestion were observed between wheat- and corn-based diets (86.6 vs 47.8%; P < .001) and between corn genotypes (60.8 vs 34.8% for dent and flint corns; P < .001). For flint corn, more than half the starch was digested in the hindgut. Total tract digestion of starch was greater (P < .001) by steers fed wheat than by those fed corn and did not differ (P > .1) between the two corn genotypes. Ruminal mean pH (P < .01) was lower and total VFA concentration (P < .1) was higher for wheat- than for corn-based diets. Ruminal acetate:propionate tended to increase with the decrease in the amount of starch degraded in the rumen, but differences were not significant (P > .1). When wheat replaced corn, nonammonia, nonmicrobial N duodenal flow decreased (P < .01), and microbial duodenal flow increased (P < .05), so there were no differences in the duodenal flow of nonammonia N duodenal flow (P > .1). The lower nonammonia N duodenal flow for the dent corn- than for the flint corn-based diet (P < .05) was related to a lower passage of nonammonia, nonmicrobial N into the duodenum. Efficiency of microbial protein synthesis was inversely correlated with the amount of starch degraded in the rumen. Nature of the cereal, wheat vs corn, and genotype of the corn, dent vs flint, alter the site and extent of starch digestion.     

Effects of supplement type on animal performance, forage intake, digestion, and ruminal measurements of growing beef cattle

Two experiments were conducted to determine the effects of supplement type on the rate of gain by heifers grazing bermudagrass and on the intake, apparent total-tract OM digestibility, ruminal fermentation, digesta kinetics, in situ DM digestibility, and forage protein degradation by steers fed prairie hay. In Exp. 1, 45 heifers (284+/-24 kg) grazed a bermudagrass pasture for 91 d in the late summer to determine the effects of no supplement (CON), or one of four individually fed monensin-containing (150 mg/[heifer x d]) supplements (MINCS; 0.1 kg of mineral mix with 0.2 kg [DM] of cottonseed hulls as a carrier/[heifer x d]), a pelleted protein supplement (PROT; 1 kg of DM, 242 g of degradable intake protein [DIP]/[heifer x d]), or high-fiber (HF) and high-grain (HG) (2 kg of DM, 243 and 257 g of DIP, respectively/[heifer x d]) pelleted energy supplements. In Exp. 2, four ruminally cannulated steers (311+/-22 kg) with ad libitum access to low-quality (4% DIP, 73% NDF, 40% ADF) prairie hay were individually fed monensin-containing (200 mg/[steer x d]) treatments consisting of 1) mineral mix + corn (MINCR; 0.1 kg of mineral and 0.4 kg of cracked corn [DM] as a carrier, 19 g of DIP/[steer x d]), 2) PROT (1.4 kg of DM, 335 g of DIP/[steer x d]), 3) HF, or 4) HG (2.9 kg of DM, 340 and 360 g of DIP, respectively/[steer x d]) in a 4 x 4 Latin square with 14-d adaptation and 6-d sampling periods. In Exp. 1, the HF-, HG-, and PROT-supplemented heifers had greater (P < 0.01) rates of gain than CON heifers, and the HF- and HG-supplemented heifers tended (P < 0.11) to gain more weight than those fed PROT. In Exp. 2, steers fed PROT consumed more (P < 0.05) hay OM than HF and HG, or MINCR. Total OM intake was greater (P < 0.01) by supplemented steers than MINCR-fed cattle. Hay OM digestibility was not affected (P = 0.19) by treatment, but total diet OM digestibility was greater (P < 0.01) for HF- and HG- than for MINCR- or PROT-fed steers. The rate of in situ DM digestibility was greater (P < 0.01) for HF, HG, and PROT than for MINCR. Results from these studies indicate that feeding milo- vs fiber-based energy supplements formulated to provide adequate DIP did not result in different forage intake, OM digestibility, or in situ DM digestibility, whereas both increased ADG in heifers consuming low-quality forages compared with unsupplemented or mineral- or protein-supplemented cattle. An adequate DIP:TDN balance decreased the negative associative effects often observed when large quantities of high-starch supplements are fed with low-quality hay.     

Effect of Yucca schidigera on ruminal fermentation and nutrient digestion in heifers.

In a replicated 3 x 3 Latin square experiment, six heifers (443 +/- 6.1 kg) fed a 61% barley grain:39% alfalfa silage diet (DM basis) were given intraruminal doses of powdered Yucca schidigera (YS). Doses of 0 (control), 20, or 60 g/d were given at 0800 daily. Ruminal content was sampled 0, 2, 4, and 6 h after dosing. Acidity, concentrations of reducing sugars, free amino acids, and peptides in the rumen were not affected (P > .05) by YS. Relative to control, ruminal ammonia concentration was reduced (P < .05) 2 h after YS dosing. Ruminal propionate concentration was increased (P < .05) by YS. Protozoal numbers in the rumen were lower (P < .05) with YS than without. Yucca did not affect (P > .05) rate or extent of in situ DM degradability. Fibrolytic, amylolytic, and proteolytic activities in ruminal contents were similar among treatments (P > .05). Dry matter intake, apparent digestibilities of DM, NDF, and CP, nitrogen balance, and microbial protein synthesis in the rumen were not affected (P > .05) by treatment. The effect of YS on ruminal ammonia concentration likely resulted from a decreased concentration of protozoa and, presumably, from ammonia binding by YS. The effect on ruminal propionate was probably a result of a selective inhibitory effect of YS on rumen microbial species.     

Effects of dairy biomass protein on ruminal fermentation and site and extent of nutrient digestion by lambs

Twelve ruminally and abomasally cannulated lambs (27 +/- 1.16 kg) and 16 intact lambs (28 +/- 1.49 kg) were used in two trials to study the influence of dairy biomass (a cheese processing wash water sludge) as a protein source in medium-concentrate diets. In Trials 1 and 2, lambs were assigned to one of three concentrate diets containing 0, 10 or 20% biomass with an additional positive control diet in Trial 2. Biomass provided 27.4 and 52.7% of the CP in 10 and 20% biomass treatments, respectively. Diets were similar in N content and were fed at 3.5% of initial BW (as fed). Apparent ruminal OM and N digestibilities were lower (P less than .10) in lambs receiving 20% biomass than in lambs fed 0 or 10% biomass. Postruminal N digestibility was higher (P less than .10) for lambs fed 20% biomass. Apparent OM and N digestibilities in both trials were reduced (P less than .10) in lambs fed 20% biomass. Apparent OM and N digestibilities in both trials were reduced (P less than .10) in lambs receiving 10% biomass compared to lambs fed other treatments. Plasma urea N concentration (mg/dl) was higher (P less than .10) at 3 and 9 h after feeding in lambs receiving 10 and 20% biomass compared with control lambs. Although N retention was unchanged, fecal N excretion was higher (P less than .10) and urinary N excretion was lower (P less than .10) in lambs consuming 10 and 20% biomass treatments. Non-ammonia N and feed N flow (g/d) were higher (P less than .10) in abomasal contents of lambs consuming 20% biomass vs other dietary treatments but N digestibility was decreased. In conclusion, digestibility was decreased and site of N digestion was altered by feeding biomass.     

Effects of oscillating dietary protein on ruminal fermentation and site and extent of nutrient digestion in sheep

Eight cannulated wethers (BW = 52.5 +/- 5.7 kg) were used in a replicated 4 x 4 Latin square designed experiment to evaluate the effects of oscillating dietary protein concentrations on ruminal fermentation, site and extent of digestion, and serum metabolite concentrations. Four treatments consisted of a 13, 15, or 17% CP diet fed daily or a regimen in which dietary CP was oscillated between 13 and 17% on a 48-h basis (ACP). All diets consisted of 65% bromegrass hay (10.5% CP, 61.9% NDF, 37.2% ADF) plus 35% corn-based supplement and were formulated to contain the same amount of degradable intake protein (9.6% of DM) plus additional undegradable intake protein (SoyPLUS, West Central Cooperative, Ralston, IA) to accomplish CP levels above 13%. Each of four experimental periods were 16 d in duration with 12 d for diet adaptation followed by 4 d for sample collection. All wethers were fed at 3.0% of initial BW (DM basis) throughout the experiment, resulting in an average organic matter intake of 1.39 kg/d across treatments. When compared to the 15% CP daily treatment, feeding ACP had no effect (P > or = 0.10) on ruminal or lower tract N, NDF, ADF, or OM digestion. True ruminal OM digestion responded quadratically (P = 0.07) to increasing dietary CP, reaching a maximum of 52.0% of OM intake with the 15% CP treatment. Sheep fed ACP tended to have lower (P = 0.08) ruminal NH3 N concentrations and an overall higher (P = 0.0001) molar proportion of acetate compared to those fed 15% CP daily. Total VFA concentrations were not affected (P > or = 0.45) by increasing dietary CP. Microbial efficiency did not differ (P > or = 0.55); thus, bacterial N flow at the duodenum responded quadratically (P = 0.04) to increasing dietary CP. Nonbacterial N (P = 0.001) and total N (P = 0.01) flows at the duodenum and total tract N digestibility (P < or = 0.04) increased linearly as dietary CP increased. Wethers fed ACP maintained a lower (P = 0.002) serum glucose and lower (P = 0.0006) serum urea N compared to those fed 15% CP daily. Because the CP content of the diet was increased at the expense of corn, the response to increased CP observed in this experiment is most likely due to negative associative effects of supplemental starch on ruminal fermentation and microbial growth. Oscillating the CP content of the diet on a 48-h basis has little effect on digestion or N utilization in sheep compared with feeding the same quantity of protein on a daily basis.     

Effects of supplemental silage on forage intake and utilization by steers grazing wheat pasture or bermudagrass

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)