Low-quality roughages in high-concentrate pelleted diets for sheep: digestion and metabolism of nitrogen and energy as affected by dietary fiber concentration

Two trials were conducted to evaluate effects of, and interactions between, level and source of fiber in the diet on ruminal environment, microbial protein synthesis, nutrient digestion and flow of digesta through the gastrointestinal tract of multiple-fistulated sheep (trial 1; 4 X 4 Latin square design) and on ruminal, digestive and metabolic characteristics of early-weaned lambs (trial 2; randomized complete block design; 3 periods). All diets tested were pelleted and were formulated to contain either 39% or 25% neutral detergent fiber (NDF), with corncobs or cottonseed hulls (CSH) as the major NDF (roughage) sources. In trial 1, dry-matter (DM) and organic-matter (OM) digestibilities were not different (P greater than .05) among treatments. Digestibility of NDF was higher (P less than .05) with high-fiber. Bacterial N synthesis (g N/kg OM truly digested) was not different (P greater than .05) among treatments. Molar proportion acetate was higher (P less than .05) and molar proportion propionate lower (P less than .05) when sheep were fed high-fiber diets. In trial 2, apparent DM digestibility was higher (P less than .05) for lambs fed diets containing corncobs. Energy digestibility was higher (P less than .05) at the low-fiber level and for lambs fed diets containing corncobs. Apparent NDF digestibility by lambs was higher (P less than .05) at the high-fiber level and for lambs fed diets containing corncobs. Nitrogen retained (percentage of N intake) was higher (P less than .05) for lambs fed diets containing CSH. Ruminal pH and molar proportion acetate were higher (P less than .05) and molar proportion propionate lower (P less than .05) for lambs fed high-fiber diets. Although responses to corncob vs CSH inclusion in high-energy pelleted diets differ, both roughages are effective as fiber sources in sheep diets.     

Low-quality roughages in high-concentrate pelleted diets for sheep: digestion and metabolism characteristics as affected by corncob and(or) rice hull additions

Two trials were conducted to determine effects of feeding corncobs, rice hulls or a combination of both on nutrient digestion and flow of digesta through the gastrointestinal tract of multiple-cannulated sheep (55-kg Rambouillet X Dorset rams; trial 1; 4 X 4 Latin square) as well as ruminal, digestive and metabolic characteristics of early-weaned lambs (24.1-kg crossbred rams; trial 2; randomized complete block design; 3 periods) fed pelleted 75% concentrate-25% roughage diets. In trial 1, apparent total tract dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) digestibilities decreased and N digestibility increased as percentage of dietary corncobs decreased and percentage of rice hulls increased. Site of NDF digestion appeared to shift from the upper to the lower digestive tract as percentage of corncobs decreased and percentage of rice hulls increased. In trial 2, apparent DM digestibility decreased as corncobs were replaced with rice hulls in the diet. Neutral detergent fiber digestibility was not affected by diet except in larger lambs at higher intakes, with NDF digestibility generally decreasing as percentage of dietary rice hulls increased. Nitrogen digestibility was not affected by replacing corncobs with rice hulls in the diet. Ruminal pH decreased as rice hulls replaced corncobs in the diet. These data are interpreted to indicate that rice hulls can be effectively substituted for corncobs in sheep diets when added at levels up to 25% of the total diet.     

Effect of roughage particle size on ruminal, digestive and metabolic characteristics of early-weaned lambs fed pelleted corncob-concentrate diets

Two experiments were conducted to determine effects of feeding corncobs of various mean particle size (MPS) on ruminal, digestive and metabolic characteristics of early-weaned lambs fed pelleted 74.9% concentrate:25.1% corncob diets. The MPS of corncobs in diets was 6.5, 5.4, 1.4 and .8 mm, respectively. As particle size decreased, percentage starch decreased and percentage neutral detergent fiber (NDF), acid detergent fiber (ADF) and cellulose increased. In Exp. 1, 28 crossbred rams (seven/treatment, avg initial wt, 15.3 kg) were used in a randomized complete-block design. In Exp. 2, lambs from Exp. 1 were re-weighed (avg initial wt, 16.8 kg) and fed the same diets as in Exp. 1. In Exp. 1 and 2, lambs ingested dry matter (DM) equal to 2.68 and 3.74% of body weight, respectively. In Exp. 1, apparent DM digestibility was unaffected by corncob MPS; however, in Exp. 2, DM digestibility was highest (68.8%) for lambs fed the 6.5-mm diet and lowest (63.8%) for those fed the .8-mm diet. Apparent starch digestibility was high (greater than 98.8%) in both experiments. Neutral detergent fiber and ADF digestibilities were highest for lambs fed the 1.4-mm diet (50.5 and 43.6%, Exp. 1; 39.6 and 28.9%, Exp. 2). A dramatic increase (6.8 to 39.1%) in acid detergent lignin (ADL) digestibility was observed in Exp. 1 as corncob MPS decreased. In Exp. 2, ADL digestibilities were similar for lambs fed the 6.5-, 5.4- or 1.4-mm diets (avg value, 5.9%) and highest for those fed the .8-mm diet (29.7%). Nitrogen metabolism was unaffected by corncob MPS. In Exp. 1, digestible energy intake, corrected for urinary losses, did not differ among treatments but in Exp. 2, lambs consuming the 6.5-mm diet had higher corrected digestibility energy intakes (1,926.6 kcal/d) than did those fed other diets (avg, 1,832.4 kcal/d). Ruminal pH sampled 4 h post-feeding was highest for lambs consuming the 6.5-mm diet (6.25) in Exp. 1 and the 1.4-mm diet (5.89) in Exp. 2. Lowest ruminal pH (5.30 and 5.36, respectively) was for lambs consuming the .8-mm diet in Exp. 1 and the 5.4-mm diet in Exp. 2. Ruminal lactate concentrations were variable within and among treatments. Total ruminal volatile fatty acid (VFA) concentrations were similar across treatments but in Exp. 2, there was a shift in molar proportions from acetate to propionate as corncob MPS decreased.(ABSTRACT TRUNCATED AT 400 WORDS)     

Steam-processed corn and sorghum grain flaked at different densities alter ruminal, small intestinal, and total tract digestibility of starch by steers.

Crossbred steers (n = 7; 400 kg BW), fitted with T-type cannulas in the duodenum and ileum, were used to examine the effects of processing method, dry-rolled (DR) vs. steam-flaked (SF) sorghum grain, and degree of processing (flake density; FD) of SF corn (SFC) and SF sorghum (SFS) grain on site and extent of DM, starch, and N digestibilities and to measure extent of microbial N flow to the duodenum. In Exp. 1, diets contained 77% DRS or 77% SFS with FD of 437, 360, and 283 g/L (SF34, SF28, and SF22). In Exp. 2, diets contained 77% SFC with FD of SF34 or SF22. For sorghum and corn diets, respective average daily intakes were as follows: DM, 6.7 and 8.1 kg; starch, 3.8 and 4.7 kg; N, 136 and 149 g. Steers fed SFS vs. DRS increased (P = .01) starch digestibilities (percentage of intake) in the rumen (82 vs. 67%) and total tract (98.9 vs. 96.5%) and decreased digestibilities in the small intestine (16 vs. 28%; P = .01) and large intestine (.5 vs 1.2%; P = .05). As a percentage of starch entering the segment, digestibility was increased (P = .01) within the small intestine (91 vs. 85%) but was not altered within the large intestine by steers fed SFS vs. DRS. Decreasing FD of SFS and of SFC, respectively, linearly increased starch digestibilities (percentage of intake) in the rumen (P = .03, .02) and total tract (P = .03, .09) and linearly diminished starch digestibilities in the small intestine (P = .04, .09). Starch digestibilities (percentage of entry) within the small or large intestine were not changed by FD. The percentage of dietary corn or sorghum starch digested in the large intestine was very small, less than 2% of intake. Microbial N flow to the duodenum was not altered by SFS compared to DRS, or by decreasing FD of SFS and SFC. Reducing FD of SFS, but not of SFC, tended to decrease (P = .07) microbial efficiency linearly and tended to increase (P = .06) total tract N digestibilities linearly. Steam flaking compared to dry rolling of sorghum grain and decreasing FD of SFC and SFS grain consistently increased starch digestibility in the rumen and total tract of growing steers. The greatest total digestibility of dietary starch occurred when the proportion digested in the rumen was maximized and the fraction digested in the small intestine was minimized. These changes in sites of digestion account, in part, for the improved N conservation and greater hepatic output of glucose by steers fed lower FD of SFS reported in our companion papers.     

日粮淀粉水平对绒山羊纤维物质消化性能的影响

9只带有瘤胃瘘管、十二指肠近端瘘管和回肠末端瘘管的内蒙古白绒山羊随机分为3组,研究了日粮精粗比(3∶7)相近的条件下,提高日粮淀粉水平对纤维物质消化性能的影响。结果表明,随日粮淀粉水平的提高,日粮纤维在胃区及全消化道消化率也随之下降,而在大肠的消化率有上升的趋势,但各组间差异均不显著(P>0.05)。     

Effect of heterogeneous digesta chemical composition on the accuracy of measurements of fiber flow in dairy cows.

The objective of the current study was to evaluate the effect of unrepresentative sampling of digesta particulate matter entering the omasal canal on the accuracy of fiber flow measurements. The experimental design comprised one period, one diet, and three cows as experimental units. Within each cow, the physical and chemical composition of digesta particulate matter was assessed at seven sites within the digestive tract. Three Finnish Ayshire dairy cows, equipped with ruminal and simple-T duodenal cannulas, in extended lactation were offered grass silage twice daily on an ad libitum basis. Digesta samples were collected from the rumen (dorsal and ventral sac), reticulum, omasal canal, omasum, duodenum, and rectum to determine particle size distribution in digesta, chemical composition of various particle size fractions, and distribution of two flow markers (Cr-labeled straw and indigestible NDF [INDF]) among particle size fractions. Digesta samples were wet-sieved using sieves of 2.50, 1.25, 0.630, 0.315, 0.160, and 0.080 mm. Particulate matter was analyzed for OM, NDF, and Cr concentrations, and INDF concentration was determined based on 12-d ruminal incubation. The particle size of digesta entering the omasal canal was larger compared with the omasum or the duodenum, suggesting that omasal canal samples were not representative of particle size distribution truly escaping the rumen. The concentration of potentially digestible NDF (PDNDF) decreased with decreasing particle size. The PDNDF concentration of particulate matter retained on all sieves was greatest in the rumen and gradually decreased along the digestive tract. From the reticulorumen to the omasum, the decrease was associated with decreased particle size, reflecting selective passage of particulate matter. In contrast, from the omasum to the duodenum and rectum, the PDNDF concentration decreased within each particle size fraction without effect on particle size, indicating a nonselective passage of particulate matter between these sites. Variation between particle size fractions was slightly greater for Cr concentration than for INDF concentration, indicating that unrepresentative sampling of particulate matter had a greater effect on Cr concentration compared with that of INDF. Owing to unrepresentative sampling, NDF entering the omasal canal was overestimated by 5% using INDF and underestimated by 7% using Cr as a particle phase marker. Of total NDF digestibility, proportionally 0.90, 0.07, and 0.03 occurred in the reticulorumen, omasum, and intestines, respectively. The current results indicate that, despite unrepresentative sampling of digesta particulate matter entering the omasal canal, the errors in determined NDF flow were small. The omasum may have a greater role in postruminal NDF digestion than the intestines.     

Effects of dietary forage proportion on digestive function in maintenance-fed beef cows. 1. Fescue and clover hays

Five crossbred beef cows (Hereford X Angus, 422 kg) with ruminal and duodenal cannulae were used in a Latin square experiment to determine the effects of dietary proportions of fescue and clover hays (0:1, .25: .75, .5:.5, .75:.25 and 1:0) on digestive function. Feed intake was 85% of ad libitum intake of fescue alone (1.03% of body weight). Fescue contained 1.26% nitrogen (N), 71.0% neutral detergent fibre (NDF) and 7.6% acid detergent lignin (ADL), and clover contained 2.43% N 50.0% NDF and 5.8% ADL in DM. Ruminal fluid ammonia-N concentration increased linearly (P less than .05) with declining dietary fescue level. Total concentration of volatile fatty acids in ruminal fluid and duodenal and rectal digesta mean particle size were not affected by fescue level. Ruminal fluid volume and flow rate increased linearly (P less than .05) with increasing dietary fescue, but fluid and particulate digesta passage rates were unchanged. Apparent ruminal organic matter (OM) digestion decreased quadratically (P less than .05) as fescue increased (74.5, 54.3, 49.8, 46.2 and 42.4% for 0, 25, 50, 75 and 100% fescue, respectively). Postruminal OM digestion as a percentage of intake was partially compensatory, increasing linearly (P less than .05) as dietary fescue level rose (2.3, 3.5, 5.1, 8.6 and 11.1% of intake). Thus, total tract OM digestion declined less as fescue replaced clover (76.8, 57.8, 55.0, 54.8 and 53.5%; linear and quadratic, P less than .05) than did apparent ruminal OM disappearance. Changes in ruminal NDF, acid detergent fibre and cellulose digestibilities were similar to those for OM. Microbial growth efficiency increased quadratically (P less than .10) as fescue intake increased. These results indicate that with low feed intake, ruminal and total tract digestion of an all-legume hay diet is greater than that of a grass hay diet. Little or no digestive advantage was achieved by substituting clover for fescue, except in the case of total replacement of fescue with clover, because of concurrent decreases in microbial growth efficiency, microbial N flow to the intestines and OM digestion in the postruminal tract. Negative associative effects in digestion observed between clover and fescue hays in this experiment deserve further study.     

Effects of dietary forage proportion on digestive function in maintenance-fed beef cows. 3. Bermudagrass and clover hays

Five crossbred beef cows (Hereford X Angus, 438 kg), cannulated in the rumen and duodenum, were used in a Latin square experiment to determine the effects of dietary proportions of bermudagrass (B) and clover (C) hays (0: 1, .25: .75, .5: .5, .75: .25 and 1: 0) on digestive function. Feed intake was 85% of ad libitum intake of B alone (1.35% of body weight). Bermudagrass contained 1.88% nitrogen (N), 79.6% neutral detergent fibre (NDF) and 5.2% acid detergent lignin (ADL), and C contained 2.30% N, 55.3% NDF and 6.3% ADL. Molar proportion of acetic increased linearly while propionic acid moved in the opposite direction as B replaced C (P less than .05). Mean particle size of duodenal digesta increased linearly (P less than .05) as B increased, but specific gravity of particles was constant (P greater than .10). Fluid passage rate decreased while volume increased linearly with increasing B (P less than .05) so that ruminal fluid outflow rate increased quadratically (P less than .10). Particulate passage rate ranged from 3.0 to 3.4% h. Apparent ruminal organic matter (OM) digestion was 69.0, 54.0, 53.0, 49.1 and 49.7% for 0, 25, 50, 75 and 100% B, respectively, decreasing quadratically as B rose (P less than .05). Postruminal OM digestibilities as percentages of intake and available OM changed quadratically (P less than .05) as dietary B increased, causing total tract OM digestion to decrease linearly (P less than .05; 73.8, 66.4, 63.1, 60.3 and 58.2% for 0, 25, 50, 75 and 100% B diets, respectively). Duodenal microbial-N flow increased quadratically with increasing B (P less than .05), being 45, 108, 103, 105 and 101 g/d, and microbial growth efficiency increased quadratically as well (P less than .05). True ruminal N disappearance ranged from 69.0 to 79.4% and was not affected by diet (P greater than .10). Ruminal digestibilities of fibre fractions were similar to OM. Little digestive function benefit was achieved by mixing warm season grass and legume hays in diets of maintenance-fed beef cows.     

Fiber digestibility by the orangutan (Pongo abelii): in vitro and in vivo.

Limited nutritional information exists on diets of free-ranging orangutans, Pongo abelii and P. pygmaeus. Although they are classified as frugivores, the chemical composition of their diet and their gastrointestinal anatomy suggest that they rely on fiber fermentation for a substantial portion of energy. However, the extent to which they can ferment fiber is not known. Continuous culture systems, inoculated with orangutan fecal bacteria, were established to determine the fiber-digesting capacity of orangutan hindgut microflora. The cultures received one of four treatments: soybean hulls, ground corncobs, corn starch, or no food. Neither dry matter nor neutral detergent fiber digestibilities differed significantly among treatments. However, neutral detergent fiber digestibilities were high for both the soybean hull (88.4%) and ground corncob (86.1%) treatments, indicating that the microflora had a strong fibrolytic capability. To determine whether the same fiber-degrading capacity occurred in vivo, two adult orangutans and one juvenile were fed four gel-matrix diets containing soybean hulls, ground corncobs, or ground primate biscuits. Neutral detergent fiber concentrations (dry matter basis) of the gel matrices were 52.9% with soybean hulls, 46.8% and 63.7% with ground corncobs, and 31.3% with ground primate biscuits. A fifth diet consisted of primate biscuits with 27.3% neutral detergent fiber (dry matter basis) and was considered the baseline diet. Neutral detergent fiber digestibility (74.5%) was greatest (P < 0.05) for the soybean hull gel diet and least (57.5% and 45.0%, respectively; P < 0.05) for the 63.7% neutral detergent fiber (dry matter basis) corncob gel diet and the baseline primate biscuit diet. Total volatile fatty acid concentrations in orangutan feces were not significantly different among diets; however, molar proportions of acetic, propionic, and butyric acid differed (P < 0.05) among diets. The results from both studies indicated that orangutans are capable of extensive fiber fermentation.     

Evaluation of selected high-starch flours as ingredients in canine diets.

Cereal grains represent 30 to 60% of the DM of many companion animal diets. Once incorporated into a diet, the starch component of these grains can provide an excellent source of ME. However, crystallinity and form of starch are variable and can cause incomplete digestion within the gastrointestinal tract. Diets fed in this experiment included one of six high-starch flours as the main source of carbohydrate. The flours originated from barley, corn, potato, rice, sorghum, and wheat. The diets were extruded and kibbled. Starch fraction concentrations of flours consisted of nearly 100% rapidly digestible starch (RDS) and slowly digestible starch (SDS) combined. Starch fraction concentrations of diets paralleled concentrations in flours. Flours varied widely in concentrations of CP, fat, starch, and total dietary fiber. Ileal OM and CP digestibilities were lowest for the potato flour treatment (74 and 64%, respectively). Ileal and total tract starch digestibilities were different (P<.05) among treatments; however, the starch component of all diets was nearly completely digested (>99%). Total tract digestibility of DM and OM was lowest for sorghum (80 and 84%, respectively) compared to all other diets. Crude protein digestibility was highest for corn (87%). Wet fecal weights tended (P<.08) to be greatest for dogs fed the barley treatment (175 g/d). However, dry fecal weights (dried at 55 degrees C) were greatest for dogs consuming the sorghum diet (51 g/d). Fecal scores were consistently greater (i.e., looser stools) for the barley treatment. Any of these flours could be used without negative effects on digestion at either the ileum or in the total tract. Fecal consistency data for dogs consuming the barley treatment indicate that diets containing large amounts (>50%) of barley may not be advantageous for dog owners who house their animals indoors for most of the day.     

Effects of dietary forage proportion on digestive function in maintenance-fed beef cows. Fescue and bermudagrass hays

Five crossbred beef cows (Hereford x Angus, 428 kg), cannulated in the rumen and duodenum, were used in a Latin square experiment to determine the effects of dietary proportions of fescue (F) and bermudagrass (B) hays (0:1, .25: .75, .5:.5, .75: .25 and 1:0) on digestive function. Feed intake was 85% of ad libitum intake of F alone (1.04% of body weight). Fescue contained 1.19% nitrogen (N), 74.8% neutral detergent fibre (NDF) and 6.3% acid detergent lignin (ADL), and B contained 1.99% N, 84.5% NDF and 6.1% ADL. Ruminal ammonia-N decreased and four- and five-carbon fatty acid concentrations increased linearly (P less than .05) with increasing F. Mean particle size of duodenal digesta was not affected by F level, but specific gravity of duodenal particles changed quadratically (P less than .05) as F rose, being greatest with 25 and 50% F. Ruminal fluid volume was constant, but dilution rate increased linearly (P less than .05) as F increased. Passage rate of B was faster than that of F in mixed diets. Organic matter (OM) flow and digestibilities, true ruminal N disappearance and microbial efficiency were not affected (P greater than .10) by F. True ruminal N disappearance and microbial efficiency were not affected (P greater than .10) by F. True ruminal N disappearance ranged from 73 to 78%, and microbial growth efficiency was between 18 and 22 g microbial N/kg OM fermented. Ruminal digestibilities of NDF, acid detergent fibre (ADF), cellulose and hemicellulose decreased linearly (P less than .05) as F increased, being 68.2, 64.9, 65.6, 61.2 and 61.6% for NDF, 58.9, 54.7, 56.2, 53.3 and 53.2% for ADF, 64.7, 61.3, 62.1, 59.0 and 59.1% for cellulose, and 76.1, 74.4, 75.4, 70.1 and 72.2% for hemicellulose for 0, 25, 50, 75 and 100% F, respectively. Digestive function in beef cows fed mixed F-B diets at a low level of intake related directly to dietary forage proportions and digestive characteristics when forages were fed alone.     

Differential passage rates and digestion of neutral detergent fiber from grain and forages in 30, 60 and 90% concentrate diets fed to steers

Six ruminally cannulated steers were used to determine the effects of altering dietary concentrates on fiber digestion. Diets contained 30, 60 or 90% of a concentrate based on flaked sorghum grain plus a 50:50 mixture of wheat straw and alfalfa hay. Total tract digestibility of NDF was not altered, but digestibility of potentially digested NDF (PDF) decreased (P less than .05) from 92 to 48% as concentrates increased from 30 to 90% of diet DM. Ruminal passage rate for straw (3.4 and 3.0%/h) and for hay (4.6 and 4.7%/h) was unchanged when concentrate was increased from 30 to 60%, but it decreased by 28 (2.2%/h) and 13% (4.1%/h), respectively (P less than .05), when concentrates were increased to 90%. Passage rate for grain (5.3, 5.1 and 4.4%/h) and fluid (9.3, 10.0 and 8.2%/h) was not influenced by concentrate percentage. Calculated ruminal digestibilities of NDF in individual ingredients did not differ between 30 and 60% concentrates, but they decreased (P less than .05) by 72, 57 and 34% for straw, hay and grain when concentrate was increased to 90%. Because of their relative contribution to total diet NDF, straw, hay and grain accounted for 28, 18 and 54% of the total decrease in estimated fiber digestion. It is concluded that PDF as well as NDF should be evaluated in studies of concentrate effects on fiber digestion, and that dietary concentrate level has more influence on passage rate of low-quality forage than on passage rate of grain or high-quality forage. In 90% concentrate diets, although fiber digestibility was depressed more for forage than for grain, grain accounted for most of the depression in fiber digestion because grain was the primary source of dietary fiber.     

Apparent ileal and total-tract nutrient digestion by pigs as affected by dietary nondigestible oligosaccharides

The effects of two types of nondigestible oligosaccharides (NDO), fructooligosaccharides (FOS), and transgalactooligosaccharides (TOS) were studied on growing and weanling pigs' nutrient digestion. Dietary NDO were included at the expense of purified cellulose. Twenty-five 57-d-old growing pigs, averaging 15.9+/-.6 kg on d 0 of the experiment, were fed a corn-based control diet or the control with 6.8 or 13.5 g of FOS/kg or 4.0 or 8.0 g of TOS/kg (five pigs per diet). Feces were collected on d 28 to 32, and small-intestinal digesta were collected (slaughter technique) on d 42 to 47 of the experiment. Feeds, feces, and digesta were analyzed for DM, inorganic matter, CP, ether extract, and crude fiber. Dietary NDO did not significantly affect apparent fecal and small intestinal digestion of nutrients in growing pigs. After being fed a NDO-free diet through d 10 after weaning, 38-d-old weanling pigs (n = 20), averaging 10.4+/-.8 kg on d 0 of the experiment, were fed a control diet (based on cornstarch, casein, and oat husk meal) or the control with 10 or 40 g of FOS or TOS/kg (four pigs per diet). Feces and urine were collected on d 13 to 17, and ileal digesta were collected via a postvalve T-cecum cannula on d 33 to 37 of the experiment. Feeds, feces, and digesta were analyzed for DM, inorganic matter, CP, ether extract, starch, NDF, ADF, ADL, Ca, P, Mg, Fe, Cu, and Zn. Nonstarch neutral-detergent soluble carbohydrates (NNSC) completed the mass balance for the carbohydrates. Urine was analyzed for N and minerals. The apparent fecal digestion of NNSC increased in the NDO-supplemented diets. The TOS-fed pigs tended (P<.10) to have a higher apparent fecal digestion of CP than the FOS-fed and control pigs but excreted more N via the urine (P<.01). Nitrogen and mineral balances were not affected. The FOS was nearly completely degraded prececally. Mean fiber digestion was lower at the fecal compared with the ileal level, as was the extent of NDO effects. This indicates that fiber digestion requires more than 2 wk to adapt to dietary NDO. Apparent ileal digestion of hemicellulose increased for the NDO-supplemented diets (P<.05), but that of NNSC decreased (P<.001). Thus, under the well-controlled conditions of this experiment, dietary NDO hardly affected nutrient digestion in well-kept growing and weanling pigs. However, digestion of dietary nonstarch carbohydrates may be affected.     

Influence of ruminal biohydrogenation on the feeding value of fat in finishing diets for feedlot cattle

Four Holstein steers (212 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to study the influence of degree of ruminal biohydrogenation (BH) on the feeding value of supplemental fat. Treatments consisted of an 88% concentrate finishing diet supplemented with 1) 2% yellow grease (control); 2) 4% formaldehyde-protected fat (Rumentek), 2% yellow grease (LBH); 3) 2% Rumentek, 4% yellow grease (MBH); or 4) 6% yellow grease (HBH). Ruminal BH of HBH, MBH, and LBH diets was 74, 68, and 54%, respectively. High-fat supplementation decreased (7%, P < .05) intestinal digestibility of 18:0 but increased intestinal digestibility of 18:1 (3%, P < .10), 18:2 (14%, P < .01), and 18:3 (23%, P < .05). Increases in intestinal digestibility of 18:0 (quadratic effect, P < .05), 18:1 (linear effect, P < .01), 18:2 (linear effect, P < .01), 18:3 (linear effect, P < .05), and total fatty acids (linear effect, P < .05) were inversely related to BH. For every 1% increase in the proportion of 18:1 fat entering the small intestine, the digestibility of 18:0 increased 1%. High-fat supplementation depressed ruminal digestion of OM (11%, P < .05), NDF (16%, P < .05), starch (6%, P < .05), and feed N (12%, P < .01). Formaldehyde-protein protection of fat diminished its depressing effects on ruminal digestion of NDF (quadratic effect, P < .10) and enhanced ruminal escape of feed N (linear effect, P < .10). Postruminal digestion of OM was greater (4.6%, P < .10) for high-fat diets. High-fat diets decreased (P < .05) total tract digestion of OM (1.9%), NDF (7.4%), and starch (.5%). Postruminal and total tract digestibility of OM, NDF, N, and starch was not affected (P > .10) by BH. In a 125-d finishing trial, 100 yearling steers (362 kg) were used to evaluate treatment effects on growth performance. High-fat diets did not affect (P > .10) ADG but increased (P < .10) feed efficiency (9%, P < .10), dietary NEm (7.6%, P < .05), and dressing percentage (9%, P < .05). The magnitude of the increase in dressing percentage was inversely related (linear effect, P < .10) to BH. We conclude that decreasing ruminal BH will increase postruminal digestibility of fat, and hence the NE value of dietary fat. The synergistic effect of increasing the proportion of 18:1 on intestinal digestion of fat enables higher levels of fat supplementation. Protecting fat from BH minimizes the detrimental effects of supplemental fat on fiber digestion.     

Influence of sodium bicarbonate and magnesium oxide on digestion and metabolism in yearling beef steers abruptly changed from high forage to high energy diets

Eight rumen-cannulated steers (initial wt 330kg) were adapted to a mixed alfalfa-grass hay diet for 30 d and abruptly changed to complete mixed diets of corn silage, snapped ear corn and a corn-based supplement to determine the effects of buffers on diet adaptation, digestion and ruminal metabolism. The diets contained: 1) no buffer, 2) .5% magnesium oxide (MgO), 3) 1.0% sodium bicarbonate (NaHCO3) and 4) .5% MgO and 1.0% NaHCO3, as a percentage of diet dry matter (DM). Digestion, metabolism and ruminal characteristics were measured in each of 2 wk immediately after the diet change. The animals were then adapted to the mixed alfalfa-grass hay diet, re-randomized and assigned to the four diets, thus four steers consumed each diet. Intakes and digestibilities of DM were generally greater for the diets containing buffers. The most notable differences were a greater DM intake with added NaHCO3 and an improved DM digestibility with added MgO. The higher DM digestibility with MgO was apparently related to improved neutral detergent fiber (NDF) and starch digestion. Fecal pH was significantly increased with MgO addition. Because of the greater intake and digestibilities, the amount of DM, NDF, and starch digested tended to be greater for the buffered diets. There were no diet X week interactions for intake and digestibilities, thus the responses observed existed during both wk 1 and 2 after the change in diets. In general, intake and digestibilities were greater in wk 2 than in wk 1 for all diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Supplemental cracked corn for steers fed fresh alfalfa: I. Effects on digestion of organic matter, fiber, and starch

The effect of supplementation with different levels of cracked corn on the sites of OM, total dietary fiber (TDF), ADF, and starch digestion in steers fed fresh alfalfa indoors was determined. Six Angus steers (338 +/- 19 kg) fitted with cannulas in the rumen, duodenum, and ileum consumed 1) alfalfa (20.4% CP, 41.6% NDF) ad libitum (AALF); 2), 3), and 4) AALF supplemented (S) with .4, .8, or 1.2%, respectively, of BW of corn; or 5) alfalfa restricted at the average level of forage intake of S steers (RALF), in a 5 x 5 Latin square design. Total OM intake was lower (P < .01) in steers fed RALF than in those fed AALF but level of forage intake did not affect sites of OM, TDF, or starch digestion (P > .05). Forage OM intake decreased (P < .01) linearly (8,496 to 5,840 g/d) but total OM intake increased (P = .03) linearly (8,496 to 9,344 g/d) as corn increased from .4 to 1.2% BW. Ruminal apparent and true OM disappearance was not affected, but OM disappearing in the small intestine increased (P < .01) linearly with increasing levels of corn. Total tract OM digestibility (71.2 to 76.2%) and the proportion of OM intake that was digested in the small intestine (15.4 to 24.5%) increased (P < .01) linearly as corn increased. The TDF and ADF intakes decreased (P < .01) linearly as level of corn increased. Total tract TDF and ADF digestibilities were not different among treatments (average 62.9 and 57.8%, respectively). Starch intake and starch digested in the rumen and small and large intestine increased (P < .01) linearly with increasing corn level. Ruminal pH and VFA concentrations decreased and increased (P < .01), respectively, with increasing corn. Supplementation with corn increased OM intake, decreased forage OM intake, and increased the proportion of OM that was digested in the small intestine, but fiber digestion was not affected.     

Apparent precaecal digestibility of nutrients and level of endogenous nitrogen in digesta of the small intestine of growing pigs as affected by various digesta viscosities.

Sixteen male growing pigs of about 24 kg BW were fitted with both a duodenal re-entrant and a post-valve T-shaped cannula inserted in the caecum. The animals were divided into four groups. Each group received one of the following diets: corn starch-soybean protein isolate-based diet without (diet C) and with carboxymethylcellulose (diet CMC) or a rye-wheat-based diet without (diet RW) and with xylanase addition (diet RWX). The diets provided similar levels of apparent precaecal digestible crude protein (CP), lysine, methionine + cystine, threonine and tryptophan. Additionally, [15N]-yeast was given with the diets during the first 10 days of the experiment. For estimation of digesta viscosity, N-flow of dietary and endogenous origin, apparent precaecal digestibilities of dry matter (DM), CP, amino acids and non starch polysaccharides (NSP) (only in pigs fed diets RW and RWX), ileal and duodenal digesta were quantitatively collected on day 16 and 17, respectively. The endogenous N-proportion was measured by the ratio of 15N enrichment in the digesta and urine. The duodenal and ileal digesta supernatant viscosity increased as carboxymethylcellulose was included into the diet. Xylanase addition to the rye-wheat based diet reduced the viscosity in the ileal digesta. There were no differences in precaecal digestibilities of DM, CP and amino acids between diet C and CMC. The precaecal digestibilities of DM and soluble and insoluble NSP increased from 69.5% to 73.9%, from 1.3% to 47.9% and from 17.0% to 35.4%, respectively, as xylanase was added to the rye-wheat-based diet. The apparent precaecal digestibility of most essential amino acids increased by 2 to 5 percent units. The amounts of endogenous N at the duodenal level were estimated to be 158, 233, 313 and 276 mg per 12 h per kg0.75 BW of pigs fed diets C, CMC, RW and RWX, respectively. The corresponding values at the ileal level were 95, 107, 164 and 150 mg per 12 h per kg0.75 BW. For endogenous N amounts, significant differences were observed between diets C and CMC (duodenum) and also between semi-purified and cereal-based diets (duodenum and ileum). Methodological aspects for the estimation of endogenous N using the isotope dilution technique are discussed. Obviously, the digesta viscosity per se does not affect the nutrient absorption and endogenous N flow within the small intestine of pigs. Other properties of complex dietary fibre, digesta passage rate or bacterial activity probably contribute to the observed changes.     

Effects of corn processing and dietary fiber source on feedlot performance, visceral organ weight, diet digestibility, and nitrogen metabolism in lambs

In Exp. 1, early-weaned Targhee and Polypay crossbred lambs (60 ewes and 66 rams; initial BW 24 +/- 1.0 kg) were used in a 2 x 3 factorial experiment to determine the effects of corn processing (whole shelled corn [WSC] or ground and pelleted corn [GC]) in combination with supplemental fiber (none [control]; soybean hulls, SBH [highly digestible]; or peanut hulls, PH [highly indigestible]) on DMI, ADG, feed efficiency, and visceral organ weight. For the total trial, WSC resulted in a 4% increase (P < .01) in ADG vs GC, and supplemental fiber resulted in increased (P < .01) DMI and ADG vs the control diet. Experiment 2 was conducted using 12 Targhee and Polypay crossbred wether lambs (initial BW 25 +/- 7 kg) to determine the effects of corn processing and fiber source in high-concentrate diets on diet digestibility and N retention using the same diets as in Exp. 1. Lambs fed WSC had greater (P < .001) apparent N digestion, true N digestion, and N retention (P < .01) than those fed GC. The apparent digestibilities of DM, OM, and NDF were greater (P < .001) for WSC than for GC diets. Peanut hulls resulted in decreased (P < .01) DM, OM, and NDF apparent digestibilities compared with the control and SBH diets. Starch digestion was not affected (P > .10) by diet. Whole corn resulted in improved DM, OM, NDF, and N digestibility compared with GC. Overall, both the SBH and PH diets resulted in greater DMI and ADG than the control diet, which lacked supplemental fiber.     

Effect of pelleting and beta-glucanase supplementation on the ileal and fecal digestibility of a barley-based diet in the pig

The influences of pelleting and beta-glucanase supplementation on the digestibility of dietary components in a barley-based diet were investigated in pigs fitted with cannulas in the terminal ileum. The diet contained 49.0% starch, 18.9% crude protein and 14.8% dietary fiber, with arabinoxylans (4.9%), mixed-linked beta-glucans (3.4%) and cellulose (3.3%) as the main fiber components. Pelleting increased mixed-linked beta-glucan solubility from 45 to 62%. Neither treatment influenced the ileal or fecal apparent digestibilities of dry matter (64 and 80%, respectively), energy (62 and 79%), crude protein (53 and 75%), crude fat (26 and 27%) or dietary fiber (58 and 72%). However, pelleting increased (P less than .01) the pre-ileal apparent digestibility of starch from 91.5 to 95.3% and decreased (P less than .03) that of ash from -10 to -23%, while increasing (P less than .005) the fecal apparent digestibility of starch from 98.6 to 99.7%. The solubility of mixed-linked beta-glucans in ileal digesta was lower (P less than .001) in pelleted (26%) than in unpelleted (58%) diets. beta-glucanase supplementation also increased (P less than .05) the ileal apparent digestibility of starch, from 92.6 to 94.3%, and of mixed-linked beta-glucans, from 95.7 to 97.1%. Significant between-pig differences in the apparent digestibility of dietary components were observed. In conclusion, treatments that disrupt the endosperm cell walls in barley can increase the proportion of the diet digested prior to the large intestine.     

Amino acid digestibilities in different samples of wheat shorts for growing pigs.

An experiment was carried out to investigate the variability in apparent ileal amino acid (AA) digestibilities in simulated samples of wheat shorts consisting of different proportions of wheat bran (WB), wheat shorts (WS), and wheat flour (WF), hereafter referred to as wheat fractions. The proportions of WS, WB, and WF and the NDF content (DM basis) of the wheat fractions were as follows: A, 70% WS, 30% WB, and 42.3% NDF; B, 85% WS, 15% WB, and 41.8% NDF; C, 100% WS and 41.3% NDF; D, 85% WS, 15% WF, and 35.2% NDF; and E, 70% WS, 30% WF, and 29.5% NDF. Six barrows, average initial BW of 37.2 kg, fitted with a simple T-cannula at the distal ileum, were fed one of six experimental diets according to a 6 x 6 Latin square design. Six diets were formulated to contain 17% CP (as-fed basis). Diets A, B, C, D, and E contained 17.53% soybean meal (SBM), which contributed 50% of the CP in these diets. The wheat fractions contributed the remaining 50% of the CP in these diets. Diet F contained 35.05% SBM, which was the sole source of dietary CP. Chromic oxide was used as the digestibility marker. During the first experimental period, the daily dietary allowance was provided at a rate of 5% (wt/wt) of the average BW. Thereafter, the daily dietary allowance was increased by 100 g at each successive period. Each experimental period comprised 12 d. Following a 7-d adaptation period, feces were collected for 48 h and ileal digesta for a total of 24 h. The apparent ileal digestibilities of AA in the wheat fractions were calculated using the difference method. The digestibilities were usually lowest in the wheat fractions containing WB and highest in those containing no WB. The average of the digestibilities of the indispensable AA was 63.5% for wheat fraction A, which contained 30% WB, and 71.9% for wheat fraction C, which did not contain WB. There were no differences (P > .05) in lysine digestibilities among the wheat fractions, which ranged from 54.7 to 64.1%. Of the indispensable AA, with the exception of arginine, lysine, and methionine, the apparent ileal digestibility values of AA were negatively correlated (P < .05) with the NDF content in the wheat fractions.