Duodenal Amino Acid Flow Research Articles

Impact of a tannin extract on digestibility, ruminal fermentation and duodenal flow of amino acids in steers fed maize silage and concentrate containing soybean meal or canola meal as protein source

SUMMARYFour Holstein steers (297 ± 56 kg of body weight (BW)) fitted with duodenal cannula and rumen catheter, were housed in metabolism cages and used in a 4 × 4 Latin Square trial to evaluate the effect of both protein source andAcacia mearnsiitannin extract on digestibility, ruminal fermentation, rumen microbial protein synthesis, N utilization and on duodenal flow of individual amino acids. The diet was offered at restricted amount of 25 g of dry matter (DM)/kg BW and consisted of maize silage plus concentrate, in a proportion of 0·7:0·3 (DM basis) respectively. Concentrate was formulated with either soybean meal or canola meal as protein source, with or without 50 g/kg ofA. mearnsiitannin extract (i.e. 15 g/kg of total dietary DM). There was no effect of protein source on most variables. The apparent and true organic matter (OM) digestibilities, as well as neutral detergent fibre (NDF) digestibility were negatively affected by tannin extract inclusion without, however, affecting digestible OM intake. The amount of nitrogen (N) excreted in faeces increased whereas the urinary N excretion decreased in tannin extract treatments. No interaction time × treatment was detected for any rumen variable and no treatment effect was observed for rumen fluid pH and reducing sugars concentration. Rumen fluid concentration of ammonia N was lower for the canola meal plus tannin extract treatment. Rumen concentration ofα-amino compounds was not affected by tannin extract but was higher when canola meal was the protein source. The duodenal flow of OM, total N,α-amino N and non-ammonia non-microbial N increased with tannin extract inclusion, whereas the duodenal flow of microbial N was not affected by treatment. For both protein sources, the amount of most individual amino acids flowing to the duodenum increased due to tannin extract addition. In conclusion, the dietary inclusion of 15 g/kg DM of tannin extract fromA. mearnsiiimproved the amino acid supply independently of whether the protein source was canola meal or soybean meal, without affecting the amino acid profile, to steers fed maize silage plus concentrate, with a minor but significant impact on OM digestibility.

Towards non-invasive methods to determine the effect of treatment of soya-bean meal on lysine availability in dairy cows

Lysine (Lys) availability in three different soya-bean meal (SBM) products was determined using the following techniques: whole body (WB) net flux of Lys, digestible Lys (duodenal flow × intestinal digestibility) and the plasma Lys response curve method of Rulquin and Kowalczyk (2003). Four multiparous Holstein cows (173 days in milk) were equipped with ruminal and duodenal cannulas and used in a 4 × 4 Latin square experiment with 14-day periods. The animals were fed either solvent-extracted SBM (SE), expeller-processed SBM (EP) or lignosulphonate-treated SBM (LS) at 23% of the diet dry matter (DM). The fourth treatment (SE70) consisted of a continuous infusion of Lys (70 g/day) into the omasum of cows fed the SE diet. Chromium(III) oxide was included as a digesta marker in order to determine the duodenal flow of amino acids (AA). On day 12 of each experimental period, six blood samples were collected to determine plasma Lys concentrations. Immediately after that, a pulse dose of L-[2–15N] Lys was administered in the jugular vein. Jugular blood samples were then collected at 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 16, 19, 25 and 31 min after the injection to determine 15N Lys enrichment. On each of days 13 and 14, eight digesta samples were collected and pooled by period. Amongst the diets of SBM (SE, EP, LS), no differences were observed for duodenal Lys flow or digestible Lys. Duodenal flow of microbial N with SE was numerically higher, compared with EP and LS, indicating enhanced duodenal supply of microbial Lys for this diet, and this may have compensated for the additional Lys derived from undegradable protein in rumen-protected SBM products (EP and LS). The use of the plasma response curve method as well as the measurement of WB Lys flux also revealed no differences in Lys availability among the SBM products. The WB flux method resulted in 100% post-ruminal recovery of the Lys infused with diet SE70 compared with the control diet SE, which indicates that the method is reliable for determining Lys availability. The Lys flux approach not only allows for the estimation of intestinally available essential AA but also it avoids the use of cannulated animals.

Effects of dietary methionine and lysine sources on nutrient digestion, nitrogen utilization, and duodenal amino acid flow in growing goats1

This study investigated the effects of supplementation of various sources of Met and Lys on nutrient digestion, N utilization, and duodenal AA flows in growing goats. Four 4-mo-old Liuyang Black wether goats were used in a 4 x 4 Latin square experiment and were assigned to 4 dietary treatments: (1) control, (2) control + lipid-coated Met-Zn chelate and Lys-Mn chelate (PML), (3) control + Met-Zn chelate and Lys-Mn chelate (CML), and (4) control + dl-Met, l-Lys-HCl, ZnSO(4).7H(2)O, and MnSO(4).H(2)O (FML). Compared with control, PML reduced (P < 0.05) ruminal NH(3) concentration, urinary N excretion, and plasma urea N concentration and increased (P < 0.05) the activity of ruminal endo-1,4-beta-d-glucanase and beta-glucosidase, the duodenal flow of N, N retention (g/d as well as % of absorbed N), the duodenal flows of Met, Lys, His, Val, and total essential AA, and plasma concentrations of Lys, Val, Phe, and total essential AA. Supplementing Zn-Met and Mn-Lys chelates had similar (P > 0.05) but lesser effects on these measures compared with PML, and the effects on most of the measures were not statistically significant (P > 0.05) when compared with control. Supplementing free-form Met and Lys had no effects compared with control (P > 0.05). The results indicate that lipid coating and chelating of AA provide a protection, and to a lesser extent by only chelating, of the AA from microbial degradation in the rumen and possibly has effects on rumen fermentation, which increases MP supply. This technology could improve productive performance and be of potential benefit to ruminant production if cost-effective products are developed.

Effects of bentonite on rumen fermentation and duodenal flow of dietary components in sheep fed palm kernel cake by-product

Feeding palm kernel cake (PKC) by-product, which contains relatively high levels of copper (Cu), may result in hepatic Cu accumulation in ruminants and in chronic Cu toxicity in sheep. Supplements of bentonite were efficient in alleviating accumulation of Cu in the liver. The objective of the present experiment was to determine the effects of supplementation of bentonite (2% of dietary dry matter) on rumen fermentation, duodenal flow of amino acids (AA), and digestibility in sheep fed PKC-based diets. Rumen and duodenum-cannulated sheep were fed three isonitrogenous PKC-based diets, control (C), C plus bentonite (CB) and CB plus casein (CBC) as experimental treatments. The C and CB diets contained 94.5% PKC, and were assigned four sheep each, while the CBC diet contained 82% PKC and 2.2% casein, and was assigned three sheep. Cellulose was used to bring diets C and CBC to 100% of dry matter. After 12 days on the diets the sheep were placed in metabolism cages and feces, duodenal digesta and rumen fluid were sampled on days 14 and 15, 16 and 17, and 18 and 19, respectively. On the three diets, rumen pH ranged between 5.9 and 6.0, while ammonia nitrogen (mg/100 ml) ranged between 5.2 on the C diet and 8.5 on the CBC diet. The total volatile fatty acid concentration (mmol/l) was 41, 51 and 65 on diets C, CB and CBC, respectively. The duodenal flow (g/kg organic matter intake) of total AA on the C, CB and CBC diet was 130, 141 and 136, respectively. The total tract digestibility (%) ranged between 61.9 and 71.3 for organic matter, 65.0 and 72.2 for neutral detergent fiber, and 73.5 and 76.6 for nitrogen. None of the differences among means of the measured parameters were significant in the present experiment ( p>0.05). It was concluded that supplementation of PKC-based diets with 2% bentonite had no appreciable effect on rumen fermentation, duodenal flow of AA or digestibility in sheep.

Uso de Saccharomyces cerevisiae y monensina sódica en raciones con distinto nivel de proteína para vaquillas holstein

Zaragoza HC, Ayala OJ, Mendoza MGD. Tec Pecu Mex 2001,39(3)207-214. It has been reported that ionophores and yeast culture can modify duodenal amino acid flow, therefore those additives were included in heifers rations with three levels of protein. Twenty seven Holstein heifers were individually fed (189 kg body weight), 10 months of age according to a completely randomized design with a 3 x 3 factorial arrangement, protein levels (12, 14 and 16 % CP), and additives (none, 10 g/ d of Saccharomyces cerevisiae, and 30 ppm monensin). There was no interaction among protein level and feed additive. Feed additives did not affect dry matter intake, daily gain, feed conversion or body condition. Dry matter intake was reduced with the medium protein level, however, no differences were observed in the rest of the variables. Estimation of metabolizable lysine and methionine indicated that requirements were met. Lack of interaction between feed additives and protein level indicates that amino acid flow was not altered. Heifers can be fed with rations with 12 % CP if requirements of metabolizable amino acids are met.

Effects of Isotricha, Dasytricha, Entodinium, and Total Fauna on Ruminal Fermentation and Duodenal Flow in Wethers Fed Different Diets

The objective was to measure rumen fermentation and duodenal flow of amino acids and nonammonia N components in five groups of five ruminally and duodenally cannulated wethers that were fauna-free, or inoculated with the ciliate protozoa genera of Isotricha, Dasytricha, Entodinium, or a normal population (total) of fauna. They were used in two 25-d periods and fed a haycrop-based diet in the first period and a corn silage-based diet in the second period. Feces, duodenal digesta, and rumen contents were sampled in each period and analyzed. The number of Entodinium in wethers containing the Entodinium monofauna was higher than the total protozoa numbers, including Entodinium, in wethers containing total fauna population. The type of diet or fauna did not affect total volatile fatty acid concentrations in rumen fluid. The ammonia N concentration in rumen fluid was higher in wethers containing total fauna (25 mg/100ml) than in fauna-free wethers fed the two diets (18 and 12 mg/100ml). In comparison with the respective fauna-free wethers, the concentration of ammonia in wethers containing Entodinium was higher when fed the corn silage diet, but not different when fed the haycrop diet. Ruminal presence of total fauna or Entodinium decreased the nonammonia N by 16 and 17%, and total amino acid flows from the stomach by 20 and 19%, respectively. Flow of bacteria Nwas decreased in wethers fed the two diets when Entodinium or total fauna were present in the rumen. The presence of Isotricha resulted in higher flow of bacteria N in wethers fed the haycrop diet, but the presence of Dasytricha resulted in higher bacteria N flow in wethers fed the corn silage diet. Entodinium was the most detrimental of ciliate protozoa species concerning protein nutrition of the host ruminant.

Comparison of two commercial yeast cultures ( Saccharomyces cerevisiae) on ruminal fermentation and digestion in sheep fed on corn-stover diet

A metabolism trial was conducted to evaluate the effect of two direct-fed microbial cultures containing Saccharomyces cerevisiae on ruminal fermentation, digestibility and duodenal amino acid flow. Nine Suffolk ewes with ruminal and duodenal cannula (29 kg BW) were assigned to a completely randomized design, where treatments were: (1) control group (CG); (2) 3 g/day of Yea–Sacc 1026 (YS, 1×10 8 CFU/g); and (3) 1 g/day of Levucell (LC, 20×10 9 CFU/g). The diet consisted of corn stover (66.5%), sorghum grain (23.5%), molasses (8.6%) and urea (1.4%). Ruminal pH was lower ( p<.01) with yeast culture (CG 6.81 a, YS 6.51 b, LC 6.61 b). No effects were detected in VFA concentration, molar proportion, ammonia-N, and protozoa population. Total tract digestibility of DM, OM, NDF, and ADF were not affected by treatments. Duodenal amino acid flow was not affected by the inclusion of yeast cultures. None of the direct-fed microbial cultures with Saccharomyces cerevisiae improved either fermentation, digestion or amino acid flow to the duodenum in sheep fed on corn-stover diet.

Modifying duodenal flow of amino acids by manipulation of dietary protein sources

Four multiparous Holstein dairy cows in mid-lactation were utilized in a 4 × 4 Latin square design experiment to measure the response in intestinal amino acid profiles to progressive substitution of blood meal for corn gluten meal as the protein supplement. In addition, the influence of these protein sources on rumen fermentation and digestion as well as forestomach bacterial growth and escape were compared with a diet supplemented with soybean meal, a rapidly rumen-degraded protein source. Cows were offered a mixed silage ration of alfalfa silage (79.8% of DM) and corn silage (20.2% of DM) twice daily. Cows were also offered mixed concentrate at 123% (DM:DM) of the mixed silage ration in six equal meals per day to provide soybean meal, corn gluten meal, blood meal or a combination of the latter two sources as the primary supplemental protein source. Rumen soluble non-ammonia N concentrations were higher in cows fed soybean meal and declined linearly as blood meal substituted for corn gluten meal in the concentrate. Forestomach disappearance of N tended (P = 0.09) to be higher for the cows fed soybean meal vs. all other diets, and tended (P = 0.09) to be higher with the combined corn gluten meal and blood meal diet vs. the diets containing either alone. The latter is consistent with higher forestomach digestion of DM and OM in cows fed the combined diet. Rumen pool sizes of most DM components were lower when cows were fed soybean meal and, with the exception of N pools, increased linearly as blood meal substituted for corn gluten meal. Duodenal flow of amino acid protein was lower when cows were fed soybean meal, due mainly to reduced bacterial flow, and was lowest for the combined diet within the corn gluten meal and blood meal diets. The amino acid profile of duodenal protein differed for 12 of 17 amino acids examined when cows were fed the soybean meal diet vs. the other diets, and 12 of 17 amino acids either increased or decreased linearly as blood meal substituted for corn gluten meal. Data reported here and by previous researchers suggest an associative effect of addition of corn gluten meal and blood meal to the diet which increased rumen degradation of dietary protein. These data also show that manipulating the dietary source of supplemental protein can influence the amino acid profile of duodenally delivered amino acid protein as well as indicate that the rate of rumen degradation of individual amino acids differs among protein sources. In this study, methionine, cystine and histidine appeared to be more rapidly degraded in corn gluten meal than in blood meal, whereas glutamic acid, proline, isoleucine, threonine and lysine were more rapidly degraded in blood meal. Key words: Dairy cow, rumen bacteria, amino acid

Nitrogen metabolism and hormonal responses of steers fed wheat silage and infused with amino acids or casein.

Four Holstein steers (159 kg) surgically fitted with abomasal-infusion cannulas were used in a 4 x 4 Latin square study to test amino acid (AA) and casein (CAS) infusions on nitrogen balance and hormonal status of steers consuming vegetative wheat (Triticum aestivum L.) silage (12.3% CP). Treatments were 5-d infusions of 1) water (CONT), 2) arginine (ARG; 13.69 g/d), 3) limiting amino acids (LAA, 13.69 g/d arginine + 10.92 g/d histidine + 28.97 g/d lysine + 10.88 g/d methionine + 16.96 g/d threonine, and 4) Na-CAS (300 g/d). Whole blood was collected for plasma AA, growth hormone (GH), insulin, and IGF-I concentrations. Data were analyzed by ANOVA, and the following orthogonal contrasts were used to separate treatment means: CONT vs ARG; ARG vs LAA; and LAA vs CAS. Urinary N increased (P < .02) for CAS vs LAA. Arginine increased N retention, as did CAS, compared to LAA. Total plasma essential AA were decreased by arginine. Mean plasma insulin concentrations were increased by CAS (P < .034). Arginine increased mean plasma GH levels, but not IGF-I. The CAS treatment increased (P < .015) IGF-I levels, but not GH. These data suggest that performance of steers fed wheat silage was limited by duodenal AA flow and that arginine was the first-limiting AA. Casein infusion increased plasma insulin and IGF-I, which would explain the improved growth noted in calves and lambs fed forages supplemented with ruminally undegraded protein.

Effect of Type of Protein Supplementation on Duodenal Amino Acid Flow and Absorption in Lactating Dairy Cows

Four multiparous lactating Holstein cows, fitted with cannulas in the rumen, duodenum, and ileum, were used in a trial with a 4 × 4 Latin square design to examine the effect of source and degradability of dietary CP supplements on AA flow and absorption in the small intestine. The CP supplements consisted of fish meal or meat meal as the animal by-products supplement and soybean meal or heated soybean meal as the plant by-products supplement. Fish meal and heated soybean meal constituted the high RUP diets, and meat meal and soybean meal constituted the low RUP diets.Dry matter intakes were similar among treatments. However, intakes of OM, rumen-degradable OM, total CP, and RDP were affected by the source of the CP supplement and were higher for diets with plant by-products than for those diets with animal by-products. Data were similar for the calculated in situ digestibilities and for true in vivo digestibilities of rumen-degradable OM. Efficiency of bacterial CP synthesis was similar among diets; however, nonbacterial CP flow to the duodenum and OM, CP, and disappearance of AA from the small intestine were affected by the interaction of supplement source and degradability. Heat treatment of soybean meal reduced the availability of most of the essential AA for absorption in the small intestine by 2.3% compared with that of soybean meal; the biggest such reduction (20%) occurred for Met.Availability of AA in the small intestine was affected by source and degradability of the CP dietary supplement. Heat treatment at 140°C for 2.5h reduced the availability of Met absorption from the small intestine. Although the differences among availabilities of the individual AA in the small intestine ranged from 80 to 84% among treatments, for high yielding cows, these differences may have practical significance.

Influence of the source of protein in the ration on the duodenal flow of amino acids in lactating dairy cows

Influence of the source of protein in the ration on the duodenal flow of amino acids in lactating dairy cows

Influence of Aspergillus oryzae fermentation extract on forage intake, site of digestion, in situ degradability, and duodenal amino acid flow in steers grazing cool-season pasture.

Ten ruminally and duodenally cannulated (326 +/- 28 kg) and four esophageally fistulated (394 +/- 23 kg) steers grazing cool-season pasture throughout the growing season were used to evaluate the influence of Aspergillus oryzae fermentation extract (AO) supplementation on intake, forage nutrient utilization, and duodenal amino acid flow. Steers grazed a predominantly smooth brome (Bromus inermis L.) pasture, and measurements were taken in three periods (June, July, and August). Steers were dosed daily at 0700 via the ruminal cannula with AO (2 g of AO per steer daily; DM basis) or not supplemented with AO. Each period consisted of 18 d for adaption to AO and 7 d for collection. Forage N was greater, and ADF was lower (P < .10), in June than in July and August. Ruminal pH, ammonia, total VFA concentration, and VFA proportions were not affected (P > .10) by AO supplementation. In vitro DM digestibility (percentage) and forage OM intake (grams/kilogram of BW) were greater (P < .10) for steers supplemented with AO. Ruminal and total tract NDF and ADF digestibilities were lower in June and greater during July (P < .10) in steers supplemented with AO. Total tract percentage of N disappearance was lesser during June and greater (P < .10) during July for steers receiving AO. Total, essential, and nonessential amino acid flows were increased (P < .10) by both AO supplementation and advancing season. In situ rate of ruminal CP degradation was not affected (P < .10) by treatment during any period.(ABSTRACT TRUNCATED AT 250 WORDS)

Supplementation of pressed sugar-beet pulp silage with molasses and urea, laying hen excreta or soybean meal in ruminant nutrition

The feasibility of ensiling pressed sugar-beet pulp alone or supplemented with molasses and urea or laying hen excreta (LHE) was evaluated by measuring fermentation characteristics of the silages. The volatile fatty acids, lactic acid and NH 3 contents were significantly higher ( P < 0.05) for pulp supplemented with LHE. All pathogens (coliforms, Streptococci, Staphylococci, yeasts and moulds) were eliminated after ensiling, except Clostridia but these germs were present in very small quantities (less than 100 germs g −1). A second experiment was carried out with 12 adult wethers in a complete random block scheme in order to determine the apparent digestibility of the main constituents of three diets consisting of pressed pulp supplemented with molasses and urea (P-MU), LHE (P-LHE) or soybean meal (P-SM). The diets were supplemented with 10% hay of known digestibility and this latter value was deducted from the measured digestibilities in order to obtain those of the studied diets alone. The crude protein digestibility was significantly higher for P-MU ( P < 0.05), and that of organic matter significantly lower for P-LHE ( P < 0.05). Crude fibre digestibilities significantly differed for the three diets ( P < 0.05) in the following order: P-LHE < P-SM < P-MU. In a third experiment, three wethers fitted with rumen and duodenal cannulas were given, in a Latin-square design, one of the three studied diets. The NH 3 contents and pH of the rumen fluids were significantly higher ( P< 0.05) for P-LHE whereas the volatile fatty acid profile was the same for the three diets. The yield in bacterial N synthesis, estimated with the diaminopimelic acid method, was significantly higher ( P < 0.01) for P-MU: 45.3 g bacterial N kg −1 organic matter digested in the rumen versus 36.5 g and 33.9 g for P-SM and P-LHE, respectively. The proportion of bacterial N at the duodenal level was significantly lower ( P < 0.01) for P-SM (58% versus 75% and 73%, respectively for P-MU and P-LHE). The duodenal flow of amino acids was significantly lower ( P < 0.001) for P-LHE: 113 g day −1 versus 147 g day −1 and 148 g day −1 for P-SM and P-MU, respectively. It was concluded that pulp is very easy to conserve by ensiling, even when mixed with LHE and, thanks to the high degradability of its fibre in the rumen, it is a very good energy source that may be supplemented by non-protein nitrogen. The bacterial protein synthesis is optimised by supplementation with urea and molasses.

Studies on the protein requirements of growing cattle. Effects of differing intakes of protein and energy on growth and nitrogen metabolism in young entire males.

Forty-eight Friesian entire male cattle, with an initial live weight (LW) of 135 kg, were used in two experiments to measure the response to increasing levels of dietary protein (9-11 and 7.5-10.5 g nitrogen X 6.25/kg LW0.75) at differing energy levels (800-900 kJ metabolizable energy (ME) kg LW0.75) over 120-d periods. Digestibility and N balance measurements were also made during the experiments. The diets, which were based on barley and soya-bean meal, were individually fed twice daily. In a third experiment, similar diets were given to four similar animals fitted with intestinal cannulas, at constant energy intake but with variations in dietary protein of 7.5-13.5 g N X 6.25/kg LW0.75. Chromic oxide paper was used as a digesta marker. Positive responses in LW gain and N balance to additional protein were found in both experiments but these were significant (P less than 0.05) only in the second experiment and were associated with significant (P less than 0.01) increases in the digestibility of modified acid-detergent fibre and ME intake. Mean values, which were not significantly different between treatments, for the degradability of dietary protein in the rumen and the efficiency of microbial protein synthesis were 0.57 and 31.3 g/kg organic matter apparently digested in the rumen respectively. Corresponding values obtained by regression analysis were 0.56 and 28.2. The results in general support the Agricultural Research Council (1980) proposals and suggest that undegraded dietary protein was not limiting in these experiments but that rumen-degradable protein levels were limiting on some treatments. Regression analysis indicated that the mean response to additional protein (g LW gain/g N X 6.25) per kg LW was 0.52 in Expt 1 and 0.51 in Expt 2. These responses could be largely explained by increases in ME intakes. Measurements of duodenal amino acid flow showed marked increases in essential amino acids (EAA) across the rumen. However, EAA flows, were not significantly increased at higher N intakes suggesting that protein per se was not limiting in these experiments.

The effect of protein- and non-protein-nitrogen supplements to maize silage on total amino acid supply in young cattle

1. A total of six diets based on maize silage were formulated to examine the effect of protein- and non-protein-nitrogen, and energy supplementation on the flow of amino acids to the small intestine and the synthesis of microbial amino acids in the rumen of growing cattle. All diets contained 24 g totai nitrogen (N)/kg dry matter (DM), of which 550 g N/kg total N was supplied by either urea or fish meal. Four diets contained low levels of barley (estimated total dietary metabolizable energy content of 10·4 M J/kgDM) and urea-N and fish meal-N were supplied in the ratios 3:1, 1·4:1, 0·6:1 and 0·3:1. The other two diets contained between 300 and 400 g barley/kg total diet (11·3 MJ metabolizable energy/kg DM) and the urea-N to fish meal-N ratios were 3:1 and 0·3:1.2. On the four low-energy diets, fish meal inclusion tended to reduce the extent of organic matter (OM) digestion in the rumen but significantly increased duodenal amino acid supply (P&lt; 0·05) in a quadratic manner. Microbial-N synthesis was increased by the two intermediate levels of fish meal supplementation but declined at the highest level of inclusion. With increasing levels of fish meal inclusion, a greater proportion of the dietary protein was found to escape rumen degradation and the apparent degradabilities of fish meal and maize-silage protein of all four diets were estimated to be 0·22 and 0·73 respectively.3. The substitution of barley for part of the maize silage enhanced duodenal supply of amino acids, irrespective of the form of the N supplement, and stimulated microbial amino acid synthesis. For all diets efficiency of microbial-N synthesis was found to vary between 22·5 and 46 g N/kg rumen-digested OM. Contrary to what was found for low-energy diets, the inclusion of fish meal tended to reduce the flow of dietary protein to the small intestine, but these differences were not statistically significant.4. The results appertaining to microbial synthesis, dietary protein degradabilities and duodenal amino acid flow for all diets are discussed in relation to the Agricultural Research Council (1980) proposals for the protein requirements of ruminants, and the production responses observed when similar diets were fed to growing cattle.

Interactions between dietary carbohydrate and nitrogen and digestion in sheep

SummaryRumen fermentation, duodenal digesta flow and N balance were studied in three sheep fed diets which contained urea or fishmeal as nitrogen supplement and either barley straw, barley + corn starch or molassed wheat straw (60% molasses) as carbo-hydrate source.The molar composition of rumen volatile fatty acids (VFA) with straw diets was high in acetate (64–68%), with barley diets high in propionate (32–36%) and with molasses diets high in butyrate (28–34%). Rumen ammonia concentrations (RAC) were low and constant with fishmeal diets (&lt; 10 mM) but varied with carbohydrate source with urea diets. RAC was very high (24 mM) after feeding molasses + urea.With barley and molasses diets 73–75% of digestible dry matter (DDM) was digested in the stomach, but only 54–59% with ground and pelleted straw diets. For all diets less N passed the duodenum than was eaten. The lowest daily duodenal N passage was with molasses + urea. Daily urinary N output was highest (P &lt; 0·01) for this diet and nitrogen balance lowest.Daily intakes of amino acids differed widely between diets but differences in duodenal passage were not so great. Molasses + urea provided the lowest values for daily duodenal amino acid flow. The amino acid content of duodenal N (mM amino acid/16 g N) was relatively constant despite broad variation between diets. Digesta alanine and valine (mM/16 g N) were higher for barley than for straw diets (P&lt; 0·05). Digesta methionine (mM/16 g N) was lower for fishmeal than for urea diets (P&lt; 0·01).Very little sucrose reached the duodenum with any diet.It was concluded that the form of energy-yielding nutrient inuflenced duodenal N flow by affecting ammonia-N capture in the rumen, but that the amino acid content of duodenal N was little affected. The interaction between molasses and urea was not beneficial to efficient use of urea-N in this work when molasses was the major carbohydrate component of the diet.