Nitrogen Disappearance Research Articles

Using a Segmented Model to Describe In situ Nutrient Disappearance

Gunter, S.A. and Galyean, M.L. 2000. Using a segmented model to describe in situ nutrient disappearance. J. Appl. Anim. Res., 18: 1–14. The purpose of this study was to compare the predictive results and characteristics of exponential (EM) and segmented, models (SM) describing ruminal in situ nutrient disappearance data. Using masticate samples collected from esophageally cannulated steers grazing midgrass prairie rangeland (PRAIRIE) or a sideoats grama (Bouteloua curtipendula [Michx.] Torr.)/sweetclover (Melilotus officinalis [L.] Lam.) pasture (PASTURE), in situ organic matter (OMD) and nitrogen (ND)disappearance curves were fitted to a single EM (Rt=D0*e(-k[t-L])+I0) or a SM. The SM contained a quadratic segment (Y=β0+β1X +β2X2) where digestion seemed to occur and after the point where digestion had seemed to cease a (constant (Y=plateau) was fitted. With the SM, linear (β1) and quadratic (β2%%/h) effects of OMD and ND did not differ (P>0.15) between PRAIRIE and PASTURE. With the EM, the rate of OMD (%/h) was 44% faster (P=0.04) for PRAIRIE than for PASTURE, but disappearance rate did not differ (P=0.24) for ND. The hour where the plateau joined the quadratic equation in the SM did, not differ (P=0.31) between forage types (42 and 41 h for OM and N, respectively). Soluble OM and N fractions did not differ (P>0.99) between models; however the soluble OM and N concentrations were greater (P<0.004) for PRAIRIE than for PASTURE. Estimates of insoluble degradable OM and N fractions did not differ (P>0.42) between models. The insoluble degradable OM in PRAIRIE did not differ (P=0.52) from PASTURE; whereas, the insoluble degradable N in PASTURE was greater (P=0.08) than in PRIARIE. Indigestible OM and N fractions did not differ (P>0.11) between models; but the indigestible OM and N was greater (P<0.004) for PASTURE than for PRAIRIE. Using either the SM or EM revealed that OM and N in PRAIRIE masticate tended to degrade at a faster rate and was more digestible than OM and N in PASTURE. Based the correlation analysis, the SM model was generally more accurate and displayed less bias than the EM for both in situ OMD and ND, but differences were extremely small. Therefore, either model may be used when attempting to develop empirical models to predict the extent of in situ digestion.

A Rapid Technique for Determination of Total Disappearance of Dietary Nitrogen in the Digestive Tract Using Washed Fecal Sample after Freezing and Thawing

Kedah-Kelantan cattle were immunised against somatostatin (SS) and the animals slaughtered on the 45th week. Viable fat expiants were cultured in vitro in the presence of insulin (10 -10 M), cholecystokinin (CCK), gastric inhibitory polypeptide (GIF), glucagon-like polypeptide (7-35) (GLP-1) or SS (each at 10 -9 M) and the rate of lipogenesis determined. Immunisation had no effect (P>0.05) on growth performance, feed conversion .ratio or carcass weight (P>0.05). SS-immunised cattle had lower (P 0.05). CCK and GLP-1 stimulated (P 0.05) both subcutaneous back fat and subcutaneous tail fat lipogenesis. These effects were diminished for SS-immunised animals. GLP-1 did not affect subcutaneous back fat and perirenal fat in either treatment group. The effects of immunisation against SS on carcass composition may be mediated by changes in fat tissue responsiveness to hormones from the digestive tract.

The use of tannins as silage additives: effects on silage composition and mobile bag disappearance of dry matter and protein

The effects on silage composition of ensiling perennial ryegrass (PRG) with three commercial tannins (mimosa, myrabolam and quebracho tannins) were assessed (Experiment 1). The effects on silage composition and mobile bag disappearance of DM, nitrogen and true protein of the addition of these tannins or a combination of tannin plus formic acid, formaldehyde alone, formic acid alone, or a combination of formaldehyde and formic acid (Experiment 2) were also studied. In Experiment 1, the PRG was a third cut with a mean oven-dry DM content of 200 g/kg. All silages were prepared on a small laboratory scale (500 g), with the additives added in 20 ml aliquots/kg herbage fresh weight. The tannins were added at the rate of 5 or 50 g/kg herbage DM and in Experiment 1, samples were examined after 7 or 32 days of ensiling. In Experiment 2, a 1st cut PRG with a mean oven-dry DM content of 188 g/kg was used and the samples were taken on days 7, 14 and 49. In Experiment 1, treatment with tannins reduced the soluble nitrogen (SN) and ammonia content of the silages. In Experiment 2, the tannins used also reduced silage SN during ensiling, and were able to reduce degradation of silage nitrogen and true proteins in the rumen. Of the tannins used, quebracho tannin was also able to reduce SN and rumen degradation better than mimosa tannin. However, the tannins were not as good as formaldehyde at protecting silage proteins both during ensiling and in the rumen, neither were they better than formic acid in enhancing silage quality. For both the tannins and formaldehyde, formic acid addition further reduced the SN content as a result of the combined effect of rapid acidification and protein binding.

Effect of fat coating on rumen degradation and intestinal digestibility of soybean meal

Three rumen and duodenum fistulated dairy cows were used to determine the effects of fat and methionine addition to soybean meal on rumen degradation of crude protein, the amino acid pattern and the intestinal digestibility of undegraded residues. The addition of 10% and 25% fat resulted in lower DM degradation after 8 and 24 h of incubation. Protein degradation was reduced by 10% fat addition at 8 and 24 h, while 25% fat addition considerably lowered crude protein disappearance after only 8 h of incubation. A 10% fat addition increases the content of essential amino acids in the undegraded residue vs. the control, while 25% fat addition only increases the concentration of lysine, histidine and arginine. Standard soybean meal has higher intestinal dry-matter digestibility than fat-coated soybean, probably due to interference between the lipid matrix and the enteric enzyme attack which, most likely, does not affect the proteolytic enzymes, given the small differences in intestinal nitrogen disappearance found among the different soybean types.

The disappearance of dry matter, nitrogen and amino acids in the gastrointestinal tract from Calliandra leaves

The total tract disappearance of dry matter (DM), nitrogen and amino acids in different Calliandra leaves harvested from Kenya and Zimbabwe were measured using the mobile bag technique. In the mobile bag measurements, disappearance was measured in the rumen in sacco, by pepsin–HCl hydrolysis in vitro and in the intestine. The hydrolysis in the pepsin–HCl solution was designed to mimic digestion in the abomasum. The total tract disappearance of DM, nitrogen, and amino acids were generally low. The highest total apparent DM, nitrogen and total amino acid disappearance obtained were 425 (g/kg), 458 (g/kg total nitrogen), and 593 (g/kg amino acid), respectively. There were differences between the leaves in the disappearance of DM, nitrogen and amino acids, and in the proportion of nutrients lost in the rumen, after pepsin–HCl hydrolysis and in the intestine. More DM, nitrogen, and amino acids in the leaves from Kenya disappeared in the intestine in comparison to the disappearance in leaves from Zimbabwe. The reasons for the differences between the nutritive values of the leaves is unclear but appears to be strongly influenced by the stage of growth and conditions in which the plants were grown.

In situ disappearance of neutral detergent insoluble nitrogen from alfalfa and eastern gamagrass at three maturities.

In situ digestion kinetics of neutral detergent insoluble nitrogen (NDIN) from alfalfa (Medicago sativa L.) harvested at one-tenth bloom and eastern gamagrass (Tripsacum dactyloides L.) harvested at the boot (GGB), anthesis (GGA), and physiological maturity (GGM) stages of growth were determined with nonlinear regression techniques. Whole-plant tissue and associated leaf and stem fractions were incubated in the ventral rumen simultaneously. On a wholeplant basis, potential extents of degradation were particularly high (> or =904 g/kg NDIN) for GGB and GGA, relative to those of GGM and alfalfa (772 and 658 g/kg NDIN, respectively). For all plant parts, degradation rates of NDIN were faster (P<.05) for alfalfa than for all gamagrass forages. Degradation rate of NDIN did not differ (P>.05) across maturities for any gamagrass tissue type. These results indicate 1) that phenological development and lignification do not limit the rate of NDIN degradation in gamagrass forages but do markedly limit the potential extent of NDIN availability and 2) that most of the NDIN in these forages is potentially available in the rumen and can contribute to the ruminal N supply. Our secondary objective was to compare estimates of N escaping ruminal degradation that were determined on the basis of NDIN degradation kinetics (NDIN method) with those determined traditionally, on the basis of total residual N. The NDIN method mathematically eliminates all neutral detergent soluble N from consideration as part of the pool of dietary N potentially escaping the rumen intact. Estimates of rumen escape nitrogen determined on the basis of degradation rates of NDIN were consistently less than corresponding estimates that were determined on the basis of total residual N. When ruminal escape N that was determined with the NDIN method was regressed on corresponding estimates with the total residual N method, the slopes of the regression lines were .53 and .66 for assumed passage rates of .02 and .06 h(-1), respectively. For the forages evaluated in this study, these results indicate that neutral detergent soluble N may make important contributions to the pool of N escaping ruminal degradation.

Effect of feed hydration on the dynamics of in situ ruminal digestion

Lucerne haylage ( Medicago sativa), maize silage ( Zea mays), ground maize, soyabean meal, and a totally mixed diet received hydration for 7 days or no hydration to test treatment effects on the dynamics of in situ dry matter (DM) and nitrogen digestion in the rumen. Duplicate samples of all feed and treatment combinations were placed in the rumen of two cannulated lactating Holstein cows for 0, 1, 2, 4, 8, 16, 32 or 64 h. Soluble, degradable, and indigestible fractions, fractional digestion rates and lag times estimated for DM differed among feeds but were unaffected by hydration. On average, 13% more DM and 19% more nitrogen were solubilized or rinsed from hydrated bags at time 0. Nitrogen disappearance was also unaffected by hydration except that the soluble and degradable fractions were higher and lower, respectively, for hydrated feeds. Although feed dry matter and nitrogen disappearance were increased by hydration at time 0, the effects of hydration on the kinetics of in situ digestion in the rumen were minor. Other factors (e.g., feed composition, particle size, microbial attachment, and rumen environment) are likely more important determinants of the kinetics of digestion in the rumen than hydration.

Ileal and total tract digestibility of leucaena meal ( Leucaena leucocephala Lam. de Wit) in growing pigs

Ileal and total tract nutrient and energy digestibility was studied in pigs fed three diets with increasing levels (0–200 g kg −1) of leucaena meal (LM). The diets contained sugar cane molasses as the major source of energy. The composition of LM on a dry basis, was: 93.9% organic matter, 42.0% crude fibre, 4.14% nitrogen, 16.95 kJ g −1 gross energy. Either at the ileal or at the total tract level, the LM significantly depressed nutrient and energy digestibility. Estimated ileal and total tract nitrogen digestibility of LM was 52.8 and 57.0% respectively indicating an almost zero disappearance of nitrogen from the large intestine. In vitro nitrogen digestibility of LM was 44.2%. Daily ileal and faecal output of both short chain fatty acids (SCFA) and ammonia showed a slight trend to be proportional to the level of LM in the diet. This indicated a rather incomplete disappearance of SCFA and ammonia in the large intestine. At first approach it can be stated that digestibility of OM and CP are not strongly impaired by the introduction of 100 g kg −1 of LM in the diet. It is suggested that methods to improve digestive utilization of nutrients contained in LM must be developed in order to avoid a deterioration of digestive efficiency in pigs fed considerable amounts of LM in the diet.

Effects of tannins, formaldehyde and formic acid on total tract disappearance of DM, nitrogen and amino acids in grass silage

A major problem with grass is that during ensilage the proteins are degraded and nitrogen lost as non protein nitrogen. In the animal a disadvantage of grass silage is that the proteinaceous nitrogen is readily degraded in the rumen to ammonia. There is considerable evidence in the literature indicating that ruminal undegradable protein is a desirable component of some feeds (AFRC, 1993). This is valuable since proteins that by-pass the rumen may be digested in the intestine and the resultant amino acids absorbed. Tannins have been identified by other workers as suitable for the protection of protein in the rumen. However, there is some dubiety regarding the subsequent efficient release of protein in the intestine (McNabb et al., 1993). The effect of quebracho or mimosa tannins or formaldehyde or a combination of tannin/formate or formaldehyde/formate on silage total tract disappearance of dry matter (DM), nitrogen and total amino acids (TAA) was examined in this study.

Effects of tannins, formaldehyde and formic acid on total tract disappearance of DM, nitrogen and amino acids in grass silage

A major problem with grass is that during ensilage the proteins are degraded and nitrogen lost as non protein nitrogen. In the animal a disadvantage of grass silage is that the proteinaceous nitrogen is readily degraded in the rumen to ammonia. There is considerable evidence in the literature indicating that ruminal undegradable protein is a desirable component of some feeds (AFRC, 1993). This is valuable since proteins that by-pass the rumen may be digested in the intestine and the resultant amino acids absorbed. Tannins have been identified by other workers as suitable for the protection of protein in the rumen. However, there is some dubiety regarding the subsequent efficient release of protein in the intestine (McNabb et al., 1993). The effect of quebracho or mimosa tannins or formaldehyde or a combination of tannin/formate or formaldehyde/formate on silage total tract disappearance of dry matter (DM), nitrogen and total amino acids (TAA) was examined in this study.

Nitrogen solubility in three solvents andin situ protein degradability of ruminant feedstuffs

Feedstuffs commonly fed to ruminants were assayed for nitrogen solubility by using McDougall's buffer, 0·02 M sodium hydroxide (NaOH), or 0·15 M sodium chloride (NaCl) as solvents. In addition, in situ dry matter and protein disappearance from the same feedstuffs were determined using the nylon bag technique in ruminally cannulated sheep for varying times of incubation. The mean effective nitrogen disappearance ranged from 235 for maize to 894 g kg−1 of total N for lupins, and dry matter disappearance from 240 for meat and bone meal to 793 g kg−1 for lupins. Protein solubility was lowest (<10% of total N) for oilseed by-products and animal and fish by-products, intermediate (15–30% of total N) for some cereals and highest (35–45% of total N) for wheat varieties and plant protein sources. Furthermore, solubility and degradability data for various feed proteins are presented which demonstrate the variability in solubility and degradability of ruminant feedstuffs due to protein type or processing. © 1997 SCI.

The effect of micronization of full-fat canola seed on digestion in the rumen and total tract of dairy cows

The effect of micronization of full-fat canola seed on dry matter disappearance (DMD) and total nitrogen disappearance (TND) in the rumen and intestine were investigated. Full-fat canola seed was left untreated (C) or micronized for 1.5 min (M), and left whole (CW, MW) or ground to pass through a 1.25-mm sieve (CG, MG). In vitro gas production from CW and MW were determined at 0, 1, 2, 3, 8, 12, 20, 24, 32, 48, 52, 68 and 72 h. For subsequent studies, CW was hand-cracked (CH) for comparison against MW. In situ DMD and TND from CH, MW, CG and MG were determined after 0, 2, 4, 8, 16, 24, 48 and 96 h of ruminal incubation. The mobile nylon bag technique was used to estimate intestinal digestion (DM and N disappearance) of samples incubated in the rumen for 16 h and in acid-pepsin for 1 h. Scanning electron microscopy revealed the pattern and extent of seed coat rupture from hand-cracking and from micronization to be similar, but micronization-mediated changes to the internal structures were evident in ground samples. Micronization increased (P &lt; 0.05) in vitro gas production from whole canola seed (CW vs. MW), but relative to CH, DMD and TND from MW were lower (P &lt; 0.001) in situ and in the whole digestive tract (P &lt; 0.001). Estimated intestinal DMD and TND did not differ (P &gt; 0.05) between CH and MW. Ruminal DMD and TND from ground seed were reduced (P &lt; 0.05) by micronization (CG vs. MG) in the rumen, but intestinal DMD and TND were increased (P &lt; 0.05 and P &lt; 0.01, respectively), thus in the whole digestive tract, these values did not differ (P &gt; 0.05) between treatments. Micronization reduced potential ruminal protein degradability (P &lt; 0.05) and effective ruminal protein degradability (P &lt; 0.01) of full-fat canola, and in combination with grinding, increased the proportion of protein digestion in the intestine. Key words: Micronization, full-fat canola seed, digestibility, rumen, dairy cow, in situ

In Situ Disappearance of Individual Proteins and Nitrogen from Legume Forages Containing Varying Amounts of Tannins

In situ degradability of N and proteins were studied in one cultivar of alfalfa and red clover and two cultivars each of birdsfoot trefoil and sericea lespedeza. Concentrations of tannic acid equivalents (percentage of DM) were 0.68 in one cultivar of birdsfoot trefoil and 1.77 and 2.78 in the two cultivars of lespedeza. The other forages contained essentially no tannins. Forage samples were digested in situ for 0, 2, 4, 6, and 12h. The amount of N remaining at 12h was positively correlated with concentrations of tannin. About 38% of the N remained after 12h in forages with no or low concentrations of tannins, and 86% remained in the two cultivars of lespedeza. Total electrophoretically identified proteins followed similar trends, but the percentage remaining was less than that for N. For all forages, bands were found at molecular masses of 15, 30, 45, 47, and 54 kDa. The percentage of 54-kDa protein that remained after 12h was less than that for the other four proteins (23% vs 37%). No interaction was found between forage cultivar and protein species. These results showed that tannins reduced ruminal degradation of proteins and that specific forage proteins degraded at different rates that were independent of tannin concentration.

Stability of chitosan gel as entrapment matrix of viable Scenedesmus bicellularis cells immobilized on screens for tertiary treatment of wastewater

An experiment with immobilized microalgal cells was carried out using high and low viscosity chitosan and konjac flour to enhance the stability of hardened gels during tertiary treatment of wastewaters containing a high concentration of phosphate salts (1 m Na 3PO 4). Mechanical properties as well as compression testing, moisture retention in gels and the uptake of nutrients, such as nitrogen and phosphorus, from artificial wastewater were studied in the immobilized gel state. The disruption due to chemical interactions of pure high and low viscosity chitosan or mixed gels with konjac flour was examined daily by microscopic counting of the total cells released in the medium during seven weeks. The removal of NH + 4-N and PO 3− 4-P was monitored during four nutrient starvation-removal cycles. A complete cycle consisted of starving immobilized cells for 48 h in air saturated at 100% relative humidity, followed by removal of nutrients from wastewater. The immobilization obtained from 2% (m/v) high viscosity chitosan gels showed a more significant chemical stability ( P ≤ 0.05) in medium with 1 m Na 3PO 4 that contained viable cells than low viscosity chitosan or mixed gels. Sodium pyrophosphate was the best chelating agent used for cross-linking and did not affect the diffusion of inorganic nutrients through the hardened gels or the microalgal growth inside the network of chitosan immobilized cells. After the second uptake, the elimination of NH + 4-N and PO 3− 4-P was 100% within 3 h, whereas after the fourth uptake, the nitrogen disappearance was 99% within 2 h and 100% for phosphorus with the same incubation time. After more than one month incubation of chitosan gel beads containing Scenedesmus bicellularis cells that had been soaked daily in a fresh 1 m Na 3PO 4 solution, the stability of hardened gels was not affected and no significant release ( P ≥ 0.05) of entrapped cells was observed in the medium.

Addition of different sources and levels of amino acids and sugars to broiler litter before deep-stacking

Different sources and levels of amino acids (soybean meal at 0, 10, 20 or 40% of dry matter; similar quantities of lysine and methionine in synthetic forms) and sugars were mixed with broiler litter and placed in dacron bags embedded in a deep-stack for 3 or 9 weeks to determine changes in concentrations of nitrogen fractions and digestibility in ruminants. Pepsin-insoluble nitrogen concentration after 48 h of ruminal incubation was not changed by deep-stacking for 3 wk and only slightly elevated at 9 wk. Deep-stacking did not markedly alter in situ ruminal disappearance of broiler litter nitrogen. Conversely, in situ ruminal nitrogen disappearance of soybean meal substrates was decreased by deep-stacking; the change was greater for 16 than for 48 h of ruminal incubation. Sugar addition to soybean meal substrates did not appear to enhance rumen undegradable protein concentration. In conclusion, these results suggest that potential exists to markedly increase rumen undegradable protein in soybean meal and possibly other feedstuffs high in rumen digestible protein by addition to broiler litter before deep-stacking.

Gastrojejunal kinetics and the digestion of [15N]beta-lactoglobulin and casein in humans: the influence of the nature and quantity of the protein

The evolution and luminal effects of different quantities of casein and beta-lactoglobulin were investigated in the upper jejunum of 35 volunteers who ingested 400 mL water with either beta-lactoglobulin or casein in either low or high doses (72.6 mmol N, Lbetalg; 71.7 mmol N, LCas; 368.2 mmol N, Hbetalg; 386.8 mmol N, HCas). The flow rate of the liquid effluents as well as the nitrogen movements were measured and the exogenous ([15N]) and endogenous nitrogen fractions analyzed in the upper jejunum after milk protein ingestion. The basal jejunal liquid flow rate (mL/min) was 3.88+/-1.84 and peaked in the 0-20 min period for water (9.92+/-3.72) and Lbetalg (7.27+/-3.08) and during the 20-40 min period for LCas (5.69+/-2.49), HCas (6.32+/-1.85), and Hbetalg (6.11+/-2.31). One hour after water, LCas, Lbetalg, Hbetalg, and HCas ingestion, 100%, 95%, 85%, 71%, but only 38% of the liquid phase of the meal were passed through the jejunum, respectively. The flow rate of the endogenous nitrogen was 12.93+/-5.22 mmol N/h before meal ingestion; remained unchanged after water, LCas or Hbetalg ingestion; but increased significantly (P<0.05) after Lbetalg and HCas ingestion. The net disappearance of exogenous nitrogen in the upper jejunum 240 min after HCas, Lbetalg, LCas and Hbetalg ingestion was 82.6+/-9.5%, 61.6+/-9.6%, 58.4+/-14.7%, and 44.7%+/-24.4%, respectively. The exogenous fraction of protein nitrogen recovered in the upper intestinal lumen represented 43.3% of the ingested Hbetalg nitrogen, but only 4.9% of the ingested HCas nitrogen. In conclusion, casein and beta-lactoglobulin present differences in both the intestinal kinetics of amino acid delivery and in the nature of the products in the intestinal lumen. These differences have to be taken into account from both nutritional and physiologic points of view for the utilization of these proteins in humans.

Prediction of rumen undegradable amino acids that are digested post-ruminally

Data for in situ disappearance of DM, nitrogen (N) and amino acids in canola meal (CM) were used to determine degradation parameters required to estimate effective degradabilities of these nutrients. The non-digestible fraction of DM, N and amino acids in CM was determined using mobile bags after ruminal incubation for 12 h. Linear relationships were determined between dependent variables, ruminal disappearance (DIS) or effective degradability (EDEG) of amino acids and independent variables, DIS or EDEG of DM or N. Use of EDEG vs. EDEG relationships, (r2 greater than 0.87 for amino acids other than methionine and cystine) with the effective degradability of DM, as the independent variable, was the most effective approach over a wide range of rumen outflow rates (k) for prediction of amino acids that escaped ruminal degradation. Use of DIS vs. DIS (an estimate for EDEG of DM served as a value for the independent variable), or EDEG vs. DIS (disappearance of DM at incubation time equal to k−1 was the independent variable) relationships was not as effective. Post-ruminal digestion was predicted as the difference between ruminal escape (based on estimates of effective degradability) and that nutrient present in the residual DM in mobile bags recovered at the terminal ileum. Use of linear EDEG vs. EDEG equations, in association with a mobile bag technique, allowed for prediction of both ruminal escape and post-ruminal digestion of N and amino acids in CM over a range of outflow rates for feed particles from the rumen. Key words: Amino acids, canola meal, ruminal escape, post-ruminal digestion

Evaluation of moist heat treatment of canola meal on digestion in the rumen, small intestine, large intestine and total digestive tract of steers

The effect of heat treatment on canola meal (CM) dry matter (DM) and nitrogen (N) degradability in the rumen and digestion in the small and large intestines and total digestive tract of steers was determined. CM was moist-heat-treated at 127 °C for 15 and 45 min. The degradation of DM and N was estimated using small nylon bags in the rumen for 0.1, 4, 8, 12, 16, 24, 48 and 72 h. The mobile bag technique with an in vitro incubation in an acid-pepsin solution was used with a separate set of bags to estimate the digestion of each nutrient in the small and large intestines as well as the total digestive tract for rumen incubation times of 8, 16 and 24 h. Chemical analysis of heated CM showed a significant reduction in soluble N, sucrose and glucosinolate content while the concentration of ADIN increased. Treatment significantly reduced the degradation of DM and N in the rumen while the digestibility of DM and N in the small intestine increased with both treatments proportional to the decreased rumen degradation. Heat treatment had no effect on DM and N digestibility at the large intestine site. Total tract disappearance of DM and N were not affected by 15 min heating; however, after 45 min heating, DM and N disappearances were reduced. Moist heat treatment was effective in reducing rumen disappearance of CM nitrogen while it increased the N digestion in the small intestine. Key words: Heat treatment, canola meal, ruminant intestine, protein digestion

Effects of roasting of lupins ( Lupinus albus) and high protein variety of soybeans ( AC Proteus) on chemical composition and in situ dry matter and nitrogen disappearance in dairy cows

The effects of roasting of lupins or soybeans were evaluated for chemical composition and in situ rumen degradability. Sweet white lupins ( Lupinus albus) and a high protein variety of soybeans, AC Proteus (HPSB), were roasted in an electric roaster at a temperature of 300°C with a residence time of 1, 2, 3, or 4 min. Raw and roasted samples were analysed for total nitrogen, acid detergent insoluble nitrogen (ADIN) and protease insoluble nitrogen (PIN), and available rumen by-pass protein (RBP) was determined. In situ degradability of dry matter (DM) and nitrogen (N) was determined using Dacron bags in the rumen of three ruminally cannulated dry cows. Soybean meal (SBM) served as a control treatment. Total N content of lupins and HPSB was not affected by roasting. Heat treatment increased linearly ( P < 0.02) the PIN content of lupins and HPSB. ADIN content of lupins and HPSB significantly increased with increasing roasting time from 1 to 4 min. Available RBP increased more in roasted HPSB than in roasted lupins with increasing roasting time. SBM had lower available RBP than roasted lupins or HPSB. Roasting significantly ( P < 0.01) reduced effective degradation of DM and N in roasted lupins and HPSB at a calculated outflow rate in the rumen of 0.06 h −1. The effective degradation of N of HPSB or lupins at 4 min roasting was 10 percentage units lower than SBM. It can be concluded that roasting of lupins or soybeans is a useful tool to increase available rumen by-pass protein and to reduce the effective degradation of N in the rumen of dairy cows.

In sacco disappearance of starch nitrogen and fat in processed grains

The effect of extrusion or expansion treatment of wheat, barley, corn and sorghum grains on characteristics of rumen degradation was studied. Ruminal disappearance characteristics of dry matter, starch, nitrogen and fat in control and processed grains was determined using the in sacco method. In expanded cereals DM degradation rate was reduced in all grain types. In expanded corn the degradable DM fraction was also reduced. In extruded corn and sorghum rumen DM degradation rate was also reduced. In sorghum, ruminal escape of DM increased by 8% and 5%, in extruded and expanded grains, respectively. The degradation rate of starch was reduced in expanded wheat and barley. Effective degradation of starch in the rumen was considerably lowered in expanded grains by 34%, 27%, 14% and 9% in wheat, barley, sorghum and corn, respectively. Extrusion also resulted in comparable reduction in effective degradation of starch in these grains by 27%, 27%, 17% and 6%, respectively. Expansion decreased the N-degradation rate in all cereal types, and extrusion decreased this in corn and wheat only. Negative fat degradation values were found at zero incubation time. However the data suggest that extensive disappearance of fat from cereals occurs in the rumen. It was concluded that thermal processing of grains alters fermentation characteristics and may facilitate the achievement of optimal ruminal availability of energy: protein for microbial synthesis.