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.     

Effect of wheat and corn variety on fiber digestion in beef steers fed high-grain diets.

Six Salers steers, fitted with ruminal and duodenal cannulas, were used in a double 3x3 Latin square design to assess the depressive effect of the nature of wheat, flint corn, and dent corn on fiber digestion in animals fed high-concentrate diets, and to determine the mechanisms involved in these negative digestive effects. Diets were balanced to be equal in starch content (47.7+/-2.3%). The three cereals were characterized by ruminal starch digestibilities of 86.6, 60.8, and 34.8% for the wheat, dent corn, and flint corn, respectively. Ruminal digestion of NDF was lower with wheat- than with corn-based diets (49.4 vs. 55.2%; P<.001), and with dent corn than with flint corn (53 vs. 57.3%; P<.01). Degradability of hay in nylon bags was not affected by the grain source in the diet (P>.1). The mean retention time of forage particles in the rumen was similar between wheat and corn diets (P>.1), but it was lower for steers fed dent corn than for those fed flint corn (P<.05). Most fibrolytic activities of the solid-associated microorganisms were lower (P<.05) in animals fed wheat than in those fed corn. Differences in fibrolytic activities of the solid-associated microorganisms between the two corn genotypes were not statistically significant (P>.1), but activities of all fibrolytic enzymes were lower (P<.05) with the dent than with the flint corn diet. Protozoal number in ruminal fluid was lower in animals receiving wheat than in those fed corn (177 vs. 789x10(3)/mL; P<.001) and was related to the high ruminal acidity (P<.01) of the wheat diet. Large modifications in the rumen microbial ecosystem between the two corn genotypes were not visible in protozoal numbers or pH. Total-tract digestion of NDF was the same for wheat and for corn diets, averaging 55% for the three diets. A postruminal compensation of NDF digestion (14% of the total tract NDF digestion) seemed to occur with the wheat diet. The lack of any postruminal NDF digestion (0%) with the two corn diets may suggest negative digestive interactions in the hindgut similar to those in the rumen.     

Impact of corn vitreousness and processing on site and extent of digestion by feedlot cattle

Eight cannulated Holstein steers (average BW: 251 kg) were used in 2 simultaneous 4 x 4 Latin squares in a split-plot arrangement to test the effects of processing method [dry-rolled (DR) vs. steam-flaked (SF); main plot] and vitreousness (V, %; subplot) of yellow dent corn (V55, V61, V63, and V65) on site of digestion of diets containing 73.2% corn grain. No vitreousness x processing method interactions were detected for ruminal digestion, but ruminal starch digestion was 14.4% lower (P < 0.01) for DR than for SF corn. Interactions were detected between vitreousness and processing method for postruminal (P < 0.10) and total tract digestion (P < 0.05). With DR, vitreousness tended to decrease (linear effect, P < 0.10) postruminal OM and starch digestion. With SF, vitreousness did not affect (P > or = 0.15) postruminal digestion of OM and starch. Postruminal N digestion tended to decrease (linear effect, P = 0.12) as vitreousness increased. Postruminal digestion was greater for SF than for DR corn OM (25.7%, P < 0.05), starch (94.3%, P < 0.10), and N (10.7%, P < 0.01). Steam flaking increased total tract digestion of OM (11%, P < 0.05), starch (16%, P < 0.01), and N (8.4%, P < 0.05) but decreased total tract ADF digestion (26.7%, P < 0.01). With DR, total tract starch digestion was lower for V65 (cubic effect, P < 0.10) than for the other hybrids. With SF, total tract starch digestion was not affected (P > or = 0.15) by vitreousness. Fecal starch and total tract starch digestion were inversely related (starch digestion, % = 101 - 0.65 x fecal starch, %; r2 = 0.94, P < 0.01). Ruminal pH was greater for steers fed DR than for steers fed SF corn (6.03 vs. 5.62, P < 0.05). Steam flaking decreased (P < 0.01) the ruminal molar proportion of acetate (24%), acetate:propionate molar ratio (55%), estimated methane production (37.5%), and butyrate (11.3%, P < 0.05). There was a vitreousness x processing interaction (P < 0.01) for acetate:propionate. For DR, acetate:propionate tended to increase (linear effect; P < 0.10) with increasing vitreousness. With SF, acetate:propionate was greater (cubic effect, P < 0.01) for V65. Starch from more vitreous corn grain was less digested when corn grain was DR, but this adverse effect of vitreousness on digestion was negated when the corn grain was SF. Of the 19% advantage in energetic efficiency associated with flaked over rolled corn grain, about 3/4 can be attributed to increased OM digestibility, with the remaining 1/4 ascribed to reduced methane loss.     

Effect of harvest date and variety on ruminal degradability of ensiled maize grains in dairy cows.

In this study we investigated the influence of harvest date and genotype on the ruminal degradability of the organic matter of ensiled maize grains. Grains of the varieties Avenir, Byzance, CGS 5104 and CGS 5107 from six different harvest dates were available; they are classified as intermediate types between flint and dent corn. The six harvest dates, during which time the dry matter content of the ensiled grains rose from 52% to 66%, extended from 1st September to 19th October. Assuming a passage rate of k = 0.08, the effective ruminal degradability declined in this period on average from 93% to just under 79%; variety-specific deviations also increased markedly during this period. The dry matter content (x, DM in %) of the ensiled grains had a profound influence on ruminal degradation: a highly significant curvilinear decline in ruminal degradability (y) was calculated at increasing DM levels (k = 0.08), which can be described by the equation y = -0.072x2 (+/- 0.010) + 7.417x (+/- 1.186) - 98.71 (+/- 34.58) (B = 0.96; sy.x[%] = 1.36). The ruminal degradability of ensiled maize grains is about 5-10% higher than that of fresh maize grains.     

玉米不同处理方式对泌乳奶牛瘤胃降解规律的影响

为了研究不同加工处理方法对玉米在奶牛瘤胃内降解率的影响,本试验选用5头荷斯坦泌乳牛利用尼龙袋法测定玉米渣、膨化玉米、玉米片和蒸汽压片玉米的干物质和淀粉在泌乳奶牛瘤胃中的降解率．．结果表明,48h的瘤胃降解率规律为：玉米片〉膨化玉米〉蒸汽压片玉米〉玉米渣。瘤胃内可降解干物质为：膨化玉米和玉米片〉蒸汽压片玉米和玉米渣;而可降解淀粉则为：膨化玉米〉玉米片〉蒸汽压片玉米〉玉米渣,以上结果表明,加工过程中温度湿度和压力的作用下,玉米籽实的结构发生变化,改变了瘤胃微生物接触淀粉的机会,从而影响玉米在瘤胃内的降解率。     

Influence of endosperm vitreousness and kernel moisture at harvest on site and extent of digestion of high-moisture corn by feedlot steers

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

Simultaneous measures of rates of ruminal digestion and passage of feeds for prediction of ruminal nitrogen and dry matter digestion in lactating dairy cows

Three ruminal-cannulated Holstein cows in early lactation were fed three diets, each containing different energy and protein supplements in two consecutive 3 X 3 Latin squares. Each supplement contained a combination of three different feedstuffs (ground corn, soybean meal and wheat mids; corn gluten feed, rolled oats and distiller's dried grains; ground barley, brewer's grains and cottonseed meal). Diets consisted of 30% corn silage, 10% alfalfa hay, 10% alfalfa haylage, 17.7% ground corn plus minerals and vitamins, with the remainder as supplemental feedstuffs individually marked for measurement of ruminal turnover and in situ digestion rates. An extra period at the end of each Latin square was used to measure ruminal turnover and in situ digestion of individual forages. Diet had no effect on dry matter intake or milk yield. Mean fractional turnover (per hour) rate, measured by labeling feedstuffs with cerium, samarium or lanthanum was .044, .048, .049, .043, .047, .046, .050, .047, .049, .037, .046 and .045 for corn, soybean meal, wheat mids, corn gluten feed, oats, distiller's dried grains with solubles, barley, brewer's dried grains, cottonseed meal, alfalfa hay, corn silage and alfalfa haylage (P greater than .1), respectively. In situ-predicted ruminal degradation of N weighted for rate of passage was 61.4, 67.0, 81.5, 74.8, 86.3, 71.0, 75.7, 52.1, 54.2, 60.8, 71.7 and 70.9% for respective feedstuffs (P less than .05). In comparison with mean literature values for in vivo-measured N degradability, mean literature value = 1.172 (in situ predicted) -9.73 (P less than .05, R2 = .51). Results are interpreted to indicate a tendency for overestimating ruminal N degradability by in situ methods in feedstuffs of low degradability, while underestimating degradability in more highly degraded feedstuffs. Estimates were 11 to 17 percentage units lower than literature values for alfalfa hay and haylage and 17 units lower than literature values for distiller's dried grains.     

Effect of a saponin-based surfactant and aging time on ruminal degradability of flaked corn grain dry matter and starch

The objectives of this study were to investigate the effect of a saponin-based surfactant, Grain Prep surfactant (GP), and hot flake aging time on starch characteristics and ruminal DM and starch degradability of steam-flaked corn grain. In 2 experiments, the moisture content of incoming corn was automatically adjusted using the Grain Prep Auto Delivery System to 19.8% (Exp. 1) and 18.5% (Exp. 2). The application rate of GP was 22 mg/kg (as-is basis). Control corn was treated with water alone. Processed corn in Exp. 2 was stored in insulated containers for 0, 4, 8, or 16 h. Flaked corn samples were incubated in the rumen of lactating dairy cows for 0, 2, 4, 6, 16, or 24 h. In Exp. 1, GP increased, compared with the control, the soluble fraction and effective degradability (ED) of DM by 17.2 and 8.6%, respectively. The ED of cornstarch was increased by 6.7%. In Exp. 2, the concentration of soluble DM and starch were increased by GP by 15 and 24% compared with the control. The ED of DM and starch were also increased by 3 and 4%, respectively. No differences in gelatinization temperatures were observed due to treatment, except that GP-treated grain had a slightly greater mean gelatinization enthalpy in Exp. 2. In a pilot study, DM degradability parameters were not affected by germination of the corn kernels. Aging of the hot flakes for up to 16 h resulted in a quadratic decrease in DM and starch ruminal degradability. The aging process affected starch gelatinization enthalpy values of flaked grain in a manner opposite to that observed for ruminal DM and starch degradation. This phenomenon was most likely explained by increased starch intramolecular associations or crystallinity associated with starch annealing, or both. This study confirmed our previous observations that Grain Prep surfactant increases flaked corn DM and starch degradability in the rumen. Because the rate of degradation was not affected by the surfactant, the increase in degradability was attributed mainly to increases in DM and starch solubility.     

Effects of pasteurization of potato slurry by-product fed in corn-or barley-based beef finishing diets

Pasteurization of vegetable by-products such as potato slurry (PS) before feeding may be necessary to prevent the spread of pathogens and beef carcass blemishes. We hypothesized that pasteurization would increase ruminal fermentability of PS starch. Four ruminally cannulated crossbred beef steers (initial BW = 432) were used in a 4 x 4 Latin square experiment with a 2 x 2 factorial arrangement of treatments to examine the main effects and interactions of pasteurization (54.4 degrees C for 2 h) of PS and grain type (GT; dry-rolled corn and barley) on ruminal and total tract digestion of beef finishing diets. Diets contained 7% alfalfa hay and 14% PS (DM basis) and were fed ad libitum three times daily. Corn-based diets had 71.7% corn, whereas barley-based diets had 60% barley and 11.7% corn. Pasteurization resulted in greater (P = 0.004) soluble, rapidly degradable starch (34.3 vs. 26.7% for pasteurized and nonpasteurized PS, respectively). Ruminal fluid pH was more acidic (P < 0.07) for corn-based diets than for barley-based diets (P = 0.07) at 0200 and 2100 (sample time x GT; P < 0.05). Ruminal fluid pH was more acidic (P = 0.06) at 1400 for corn-based diets containing pasteurized PS compared with other dietary treatments (sample time x pasteurization x GT; P = 0.04). Minimum and maximum ruminal pH were greater (P < 0.10) for barley-based diets than for corn-based diets. Ruminal fluid pH was < 6.0 for a greater (P = 0.04) proportion of the day for corn-based compared with barley-based diets. In vitro incubation measurements revealed that pasteurization of PS resulted in lower (P = 0.06) ruminal fluid ammonia N concentration. Ruminal fluid ammonia N concentration was lower (P = 0.11) for barley-based diets than for corn-based diets. Steers fed barley-based diets had greater (P = 0.02) DMI and lesser (P < 0.05) total tract digestibility of DM and ADF compared with steers fed corn diets. Pasteurization increased (P = 0.10) total tract starch digestibility. Results indicate pasteurization increased rapidly degradable starch, ruminal starch fermentability, and total tract starch digestibility of PS. Grain type interacted with pasteurization such that feeding corn-based diets containing pasteurized PS resulted in periodic reductions in ruminal pH. Feeding management may be more critical when feeding pasteurized PS in beef finishing diets.     

Ruminal degradability of crude protein from different treated soybean meals in lactating cows

Ruminal crude protein (CP) degradability of four commercially available soybean meal (SBM) types--untoasted (U), toasted (T), heat-treated (H) and formaldehyde-treated (F)--was studied by the use of in sacco and in vivo techniques with lactating German Friesian cows cannulated in the rumen, duodenum and ileum. In two in sacco experiments three cows were fed a diet based either on grass hay plus ear-maize silage or on barley whole plant silage. Ruminal degradation rate of CP was estimated as percent nitrogen (N) disappearance from polyester bags incubated in the rumen for 2, 4, 6, 8, 12 and 24 h. Ruminal degradation rate of CP varied among the four SBM types as well as between the two basal diets. N disappearance from the bags after 12 h of incubation averaged 96, 67, 37, and 23% for the U, T, H, and F SBM types, respectively, in the cows fed the hay/ear-maize silage diet vs 99, 86, 58 and 41% for the four SBM types, respectively, in the cows fed the barley whole plant silage diet. In the in vivo experiment, four cows were fed diets based on meadow hay and ear-maize silage in a 4 x 4 Latin square design. The effect of SBM treatment on the flow rate of non-ammonia N (NAN) into the duodenum, and its relationship with the ruminal degradation rate of CP of the four SBM types, was studied. Formaldehyde treatment increased the amount of NAN entering the duodenum (P less than .05): 485 g cow-1 day-1 compared to 383, 418 and 428 g for U, T and H, respectively. Calculated ruminal CP degradabilities were 93, 75, 71 and 38% for SBM types U, T, H and F, respectively.     

Feeding value of wheat-based thin stillage: in vitro protein degradability and effects on ruminal fermentation.

Two experiments were conducted to evaluate the nutritive value of wheat-based thin stillage as a fluid source for ruminants. In vitro CP degradability of thin stillage was estimated relative to canola meal and heated canola meal in a completely randomized design. Four ruminally cannulated steers were used in a double cross-over design to determine the effects of consuming thin stillage or water as drinking sources on ruminal fermentation traits. The in vitro CP degradability of thin stillage (55.4%) was lower (P<.05) than that of canola meal (59.4%) and higher than that of heated canola meal (31.6%). Ruminal pH for steers consuming thin stillage was higher (P<.05) at 1000 and 1100 and lower (P<.05) at 1900 and 2000 than that for steers consuming water. Total VFA followed a pattern that was the reverse of that reported for pH. Ruminal NH3 N levels were higher (P<.05) for steers fed thin stillage than for water-fed steers through most of the collection period. Ruminal fluid and particulate matter passage rates were not affected by treatment and averaged .165 and .06 /h, respectively. The amount of thin stillage and water that did not equilibrate with the ruminal fluid and, thus, was considered to bypass the rumen was estimated to be 51.9 and 59.2% of total fluid consumed, respectively. Feeding wheat-based thin stillage had no adverse effects on ruminal metabolism.     

Effects of different sources of carbohydrates on intake,digestibility, chewing,and performance of Holstein dairy cows

To investigate the effects of different sources of carbohydrates on intake, digestibility, chewing, and performance, nine lactating Holstein dairy cows (day in milk= 100±21 d; body weight=645.7 ± 26.5 kg) were allotted to a 3 × 3 Latin square design at three 23-d periods. The three treatments included 34.91% (B), 18.87% (BC), and 18.86% (BB) barley that in treatment B was partially replaced with only corn or corn plus beet pulp in treatments BC and BB, respectively. The concentration of starch and neutral detergent soluble carbohydrate varied (22.2, 20.2, and 14.5; 13.6, 15.9, and 20.1% of DM in treatments B, BC, and BB, respectively). Cows in treatment BB showed a higher DMI and improved digestibility of DM, NDF, and EE compared with treatments B or BC. Ruminal pH was higher in cows fed on BB (6.83) compared with those that received B or BC treatments (6.62 and 6.73, respectively). A lower proportion of propionate accompanied the higher pH in the BB group; however, a greater proportion of acetate and acetate: propionate ratio was observed compared with cows fed either on the B or BC diet. Moreover, cows fed on the BB diet showed the lowest ruminal passage rate and longest ruminal and total retention time. Eating time did not differ among treatments, rumination time was greater among cows fed on the BB diet compared with the others, whereas total chewing activity was greater than those fed on BC, but similar to those fed on B. The treatments showed no effect on milk yield. Partially replacing barley with corn or beet pulp resulted in an increase in milk fat and a lower protein concentration. Changing dietary NFC with that of a different degradability thus altered intake, chewing activity, ruminal environment, retention time or passage rate, and lactation performance. The results of this study showed that beet pulp with a higher NDF and a detergent-soluble carbohydrate or pectin established a more consistent ruminal mat than barley and corn, thus resulting in higher mean retention time and chewing activity, whereas no changes in 3.5% FCM and milk fat were observed.     

Comparison of corn with four sorghum grain hybrids: site and extent of digestion in steers

Four diverse sorghum hybrids (yellow, cream, hetero-yellow and red) and corn grain were dry-rolled and fed in an 85% grain diet to Angus-Hereford steers (241 kg) equipped with ruminal and double L-type duodenal and ileal cannulas to compare the effects of grain source on site and extent of digestion. Yellow (yel) has a homozygous yellow endosperm, with a yellow seed coat, whereas cream and hetero-yellow (het-yel) have a heterozygous yellow endosperm with white and red seed coats, respectively. Red has a homozygous white endosperm with a red seed coat. Diets were fed at 2% of initial BW (DM basis) in a 5 x 5 Latin square. Total digestive tract starch digestibility (%) was greater (P less than .05) for corn (92.5) than for red (84.3), yel (84.3) and het-yel (82.9) but not greater (P greater than .10) than for cream (87.9). Ruminal starch digestibility (%) was greater (P less than .10) for corn (85.8) than for sorghum hybrids (69.1). Pre-cecal starch digestibility (%) was greater (P less than .05) for corn (90.6) than for het-yel (76.2), red (74.8) and yel (74.1). Ruminal escape (%) of grain N was greater (P less than .10) for red (79.9) than for het-yel (69.2), cream (66.5) and yel (66.1), with corn (53.6) being less (P less than .10) than sorghum hybrids. Pre-cecal and total tract non-NH3 N digestibilities (%) were not altered (P greater than .10) by grain source. Hybrid of sorghum altered site and extent of starch digestion and ruminal escape of grain N; hybrids had estimated gain:feed ratios that were 81 to 93% of those of rolled corn grain.     

Effect of cutting height and genetics on composition, intake, and digestibility of corn silage by beef heifers

This research was conducted to determine the effect of corn genetics and cutting height on the composition and nutritive characteristics of corn silage. An in situ study involving eight commercially available corn hybrids indicated main effects and interactions (P < 0.01) of hybrid and cutting height on NDF, ADF, and starch content and on in situ DM and NDF degradablility. Four ruminally cannulated Angus heifers (initial BW = 378 +/- 3 kg) were used in a 4 x 4 Latin square digestion experiment with a 2 x 2 factorial treatment arrangement. Main effects and interactions of hybrid (Pioneer Hi-Bred Int., Inc., hybrids 3335 and 3223) and cutting height (LO = 20.3 cm, and HI = 61 cm) were evaluated. Dietary treatment consisted of 40% chopped alfalfa hay and 60% corn silage. Although corn silage hybrids used were of equivalent maturity at harvest (60% milkline), 3335 treatments had 37.8% starch and 34.8% NDF, whereas 3223 treatments had 33.7% starch and 38.6% NDF. The LO treatments averaged 3.1 percentage units greater in NDF and 3.45 percentage units less in starch content than the HI treatments. Intake of DM was greater for heifers fed 3335-HI than 3335-LO; however, DMI was greater by heifers fed 3223-LO than 3223-HI (hybrid x cutting height interaction, P < 0.05). Starch intake was greater (P < 0.05) and NDF intake was less (P < 0.05) by heifers fed HI vs. LO and fed 3335 vs. 3223 dietary treatments. Digestibility of DM, starch, and NDF was greater (P < 0.05) by heifers fed 3223 than 3335 dietary treatments, but digestibility differences were not observed (P > 0.10) between cutting heights. Rate of in situ DM and starch degradability was not affected (P > 0.10) by hybrid or cutting height; however DM degradability was greater (P < 0.05) for HI than LO corn silage substrates at 8, 16, and 24 h of incubation. Rate of NDF degradability tended (P = 0.08) to be greater for 3223 than for 3335, and for LO compared with HI corn silage. Degradability of NDF was greater (P < 0.05) for 3223 compared with 3335 substrates at 24, 36, and 48 h of incubation. These data suggest fiber may not be an accurate measure of corn silage quality. Whereas cutting height affected chemical composition, we observed genetics to have a greater effect on corn silage quality.     

Effects of supplemental ruminally degradable protein versus increasing amounts of supplemental ruminally undegradable protein on site and extent of digestion and ruminal characteristics in lambs fed low-quality forage

Four ruminally and duodenally cannulated Suffolk wether lambs (34.5 +/- 2 kg initial BW) were used in a 4 x 4 Latin square designed experiment to compare effects of supplemental ruminally degradable protein (RDP) vs. increasing amounts of supplemental ruminally undegradable protein (RUP) on ruminal characteristics and site and extent of digestion in lambs. Lambs were fed a basal diet of crested wheatgrass hay (4.2% CP) for ad libitum consumption, plus 1 of 4 protein supplements: isolated soy protein (RDP source) fed to meet estimated RDP requirements assuming a microbial efficiency of 11% of TDN (CON) or corn gluten meal (RUP source) fed at 50, 100, or 150% of the supplemental N provided by CON (C50, C100, and C150, respectively). Neither NDF nor ADF intake was affected (P >/= 0.18) by protein degradability, but they increased or tended to increase (P /= 0.26) for CON and C100, but increased (P /= 0.33) by protein degradability. However, true ruminal N digestibility was greater (P = 0.03) for CON compared with C100. Ruminal ammonia concentrations were greater (P = 0.002) for CON compared with C100 lambs, and increased (P = 0.001) with increasing RUP. Microbial N flows were not affected (P >/= 0.12) by protein degradability or increasing RUP. Likewise, neither ruminal urease activity (P >/= 0.11) nor microbial efficiency (P >/= 0.50) were affected by protein degradability or level of RUP. Total tract OM, NDF, and ADF digestibility was greater (P 相似文献   

Influence of steaming time on site of digestion of flaked corn in steers

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

Effects of distillers grains with high sulfur concentration on ruminal fermentation and digestibility of finishing diets

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

Energy and nutrient digestibility in NutriDense corn and other cereal grains fed to growing pigs

Two experiments were conducted to measure the energy and nutrient digestibilities in NutriDense corn and other cereal grains. An additional objective was to evaluate the effect of balancing diets with AA on the values measured for DE and ME of corn varieties. In Exp. 1, 6 growing pigs were fitted with a T-cannula in the distal ileum and allotted to a 6 x 6 Latin square design to measure apparent ileal digestibility (AID) and standardized ileal digestibility (SID) values for CP and AA in NutriDense corn, yellow dent corn, barley, wheat, and sorghum. Diets based on each of the 5 cereal grains were formulated, along with a N-free diet. Results of this experiment showed that the AID for most indispensable AA were greater (P < 0.05) in NutriDense corn and wheat than in the other cereal grains. The SID for Lys in NutriDense corn (77.6%) was greater (P < 0.05) than in yellow dent corn (68.5%), and sorghum (56.9%), but not different from wheat (75.1%) and barley (71.7%). The SID for Arg and Met in NutriDense corn also were greater (P < 0.05) than in yellow dent corn (88.1 and 87.2% vs. 84.5 and 82.8%, respectively). For the remaining indispensable AA, no differences in SID between NutriDense corn and yellow dent corn were observed. For all AA, the lowest values (P < 0.05) for AID and SID were obtained for sorghum. If calculated as grams of standardized ileal digestible AA per kilogram of DM, concentrations of all indispensable AA in NutriDense corn were greater (P < 0.05) than in yellow dent corn, but barley and wheat had greater concentrations of most AA than yellow dent corn and NutriDense corn. In Exp. 2, 12 growing barrows were placed in metabolism cages, and the DE and ME of NutriDense corn and yellow dent corn were measured. Both grains were used in diets without or with crystalline AA supplementation. Each diet was fed to 6 pigs in a 2-period, changeover design. The DE and the ME in NutriDense corn (4,004 and 3,922 kcal/kg of DM, respectively) were greater (P < 0.01) than in yellow dent corn (3,878 and 3,799 kcal/kg of DM, respectively). Values for DE and ME were not affected by the addition of crystalline AA to the diets. It is concluded that NutriDense corn has a greater value than yellow dent corn in diet formulations due to increased concentrations of digestible, indispensable AA and energy. However, barley and wheat have greater concentrations, whereas sorghum has lower concentrations, of many digestible AA than NutriDense corn.     

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.     

NutriDense and waxy corn hybrids: effects on site and extent of disappearance of nutrients in sheep

Six Suffolk wether lambs (40.9+/-1.05 kg) surgically fitted with ruminal and double-L-shaped duodenal and ileal cannulas were used in a 3 x 6 Latin rectangle design to investigate the effects of three corn hybrids on site and extent of disappearance of nutrients and rumen characteristics. Treatments were 1) a conventional yellow dent corn (CC) diet, 2) a NutriDense corn (NC) diet, and 3) a waxy corn (WC) diet. Diets consisted of 43.9% cracked corn grain, 39.1% cottonseed hulls, 15.3% soybean meal, 1.49% vitamin and mineral supplement, and 0.21% chromic oxide (DM basis). Lambs were fed twice daily at 1.8 x NEm requirement. Ruminal pH, fluid dilution rate, volume, NH3 N, and total VFA concentrations, as well as molar proportions of isobutyrate, butyrate, and valerate, were similar (P > 0.10) among dietary treatments. Apparent and true OM disappearances (g/d and percentage of OM intake) from the stomach were similar (P > 0.10) among dietary treatments. Apparent OM disappearance (percentage of duodenal OM flow) from the small intestine was higher (P < 0.05) for the WC than for the NC treatment. Apparent total tract OM disappearance (percentage of OM intake) was also similar (P > 0.10) among dietary treatments. Total apparent and true starch disappearances (g/d) from the stomach were higher (P < 0.05) for the WC diet than for the CC and NC diets. However, apparent and true starch disappearances from stomach as percentage of starch intake were higher (P < 0.05) for the WC diet than for the CC diet. Starch disappearance (g/d) from the small intestine was higher (P < 0.05) for the CC diet than for the WC diet; however, apparent starch disappearance (percentages of duodenal starch flow) from the small intestine was higher (P < 0.05) for the WC diet than for the CC diet. Duodenal flows of total N, bacterial N, NH3 N, and non-NH3 nonbacterial N (g/d) and efficiencies of bacterial protein production (g of bacterial N/kg of true or apparent OM disappearing in the stomach) were similar (P > 0.10) among dietary treatments. Apparent and true N disappearance from stomach (g/d) and apparent total tract N disappearance (percentage of N intake) were also similar (P > 0.10) among dietary treatments. Total N disappearance from the hindgut was -0.81, -1.06, and -1.46 g/d for CC, NC, and WC, respectively, and was different (P < 0.05) between CC and WC diets. Results indicated that higher ruminal starch disappearance in WC did not increase microbial N production or efficiency when compared to CC.