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Cell walls were extracted from maize endosperm and separated into different polysaccharide fractions by sequential extraction with solutions of saturated Ba(OH)₂, demineralised water and 1 and 4 M KOH. Solubilised polysaccharides were collected after each extraction. Residues were collected following the extractions with demineralised water and 1 and 4 M KOH. The original cell wall (CW) material, extracts and residues were analysed for their fermentation characteristics using an in vitro cumulative gas production technique. The rate of fermentation of the alkali-treated residues was faster than that of the original CW material, except for the 4 M KOH residue, which had a similar rate of degradation to the original CW material. The polysaccharides solubilised from the cell wall (extracts) were all rapidly fermented, more rapidly than both CW and residues. A division of the gas production profile into two phases using curve fitting was in good agreement with a division of the cell wall fermentation into the fermentation of arabinoxylans and cellulose. Therefore the likelihood of preferential degradation of arabinoxylans from the maize cell wall was discussed. The volatile fatty acid production pattern was fairly well explained by the fermentation rate and composition of the substrates. It was concluded that breaking the interactions of polysaccharides in the maize cell wall by mild alkali extraction increases the fermentability of maize cell walls in the gastrointestinal tract of farm animals. Contrarily, more severe alkali extractions will reduce the fermentability of maize cell walls.© 2002 Society of Chemical Industry

AbstractA dynamic simulation model of digestion and absorption of nutrients was modified and evaluated under non-steady state conditions. The results of detailed grazing experiments, including allowed grazing times (Exp. 1), combinations of rumen fill and starvation length before grazing (Exp. 2) and contrasting sward masses and sward heights (Exp. 3) as main treatments were used as reference values. The model was modified to run under a discontinuous feed input of ryegrass. Neutral detergent fibre (NDF) and nitrogen rumen pools were predicted with a relatively low root mean square prediction error (MSPE) of the observed means (11%) in Exps. 1 and 2, but a higher value (18%) was observed in Exp. 3. This significantly higher root MSPE was ascribed to the long period (up to 20.5 hours) of starvation that followed grazing. Prediction was poorer for organic matter rumen pool (root MSPE of 16%) than for NDF and N rumen pools, which requires further validation. Volatile fatty acid (VFA) rumen pool and VFA concentration were predicted with a root MSPE of the observed mean of 32–33%, which was close to the random variation observed in the experiments. Ammonia rumen pool was poorly predicted and the way ammonia is represented in the model must be modified to predict ammonia production and absorption under non-steady state conditions. The model can be used to predict ruminal digestion and absorption of nutrients (except ammonia) of grazing lactating dairy cows under discontinuous feeding regimens provided large periods of starvation are avoided.

A dynamic simulation model of digestion and absorption of nutrients was modified and evaluated under non-steady state conditions. The results of detailed grazing experiments, including allowed grazing times (Exp. 1), combinations of rumen fill and starvation length before grazing (Exp. 2) and contrasting sward masses and sward heights (Exp. 3) as main treatments were used as reference values. The model was modified to run under a discontinuous feed input of ryegrass. Neutral detergent fibre (NDF) and nitrogen rumen pools were predicted with a relatively low root mean square prediction error (MSPE) of the observed means (11%) in Exps. 1 and 2, but a higher value (18%) was observed in Exp. 3. This significantly higher root MSPE was ascribed to the long period (up to 20.5 hours) of starvation that followed grazing. Prediction was poorer for organic matter rumen pool (root MSPE of 16%) than for NDF and N rumen pools, which requires further validation. Volatile fatty acid (VFA) rumen pool and VFA concentration were predicted with a root MSPE of the observed mean of 32–33%, which was close to the random variation observed in the experiments. Ammonia rumen pool was poorly predicted and the way ammonia is represented in the model must be modified to predict ammonia production and absorption under non-steady state conditions. The model can be used to predict ruminal digestion and absorption of nutrients (except ammonia) of grazing lactating dairy cows under discontinuous feeding regimens provided large periods of starvation are avoided.

The relative importance of duration of sward regrowth and fill and fermentation in the rumen on the control of grazing time and intake rate during the first grazing session of the day was studied. Four lactating dairy cows were allowed to graze ryegrass (Lolium perenne) swards, with five different regrowth periods after mowing (6, 9, 16, 22, and 30 d). The cows were allowed to graze until they stopped voluntarily (cessation of grazing activity for at least 15min). Before and after grazing the rumen contents were evacuated, weighed, sampled, and returned to the animals. Samples of rumen liquid were taken immediately before rumen evacuation and approximately 30, 60, 120, and 240min after the grazing session was finished. Grazing time and intake rate did not follow a significant trend with period of regrowth. Bite rate did not change significantly with duration of regrowth with cows exhibiting high rates of biting for all the sward conditions. Rumen pools sizes of dry matter, neutral detergent fiber, and volatile fatty acids (VFA), measured after grazing, increased significantly with days of sward regrowth, even though the changes over days were small. Concentration of VFA followed a significant quadratic trend with a maximum concentration observed at approximately 110min after cessation of grazing. In this study, rumen fill, VFA (either total or major components), ammonia, pH, and osmotic pressure as individual variables were not correlated with grazing time or dry matter intake.

Primary (plant), secondary (animal), and tertiary (human) biological systems are driven by energy, either fossil or renewable energy in biomass. Their ratio shifts from about 10:90 in primary, via 25:75 in secondary, to 90:10 in tertiary systems. Energy input in ruminant production is mainly as plants and plant parts from primary production, and the amount needed per unit product (milk, meat) primarily depends on its digestibility. This is high in young, leafy, whole plants, in roots and tubers, and in reproductive organs (whole seeds) or organ parts (by-products) of mature plants. Use of fossil energy per kilogram of DM for primary production ranges from 1 to 3 MJ in forage to over 8 MJ in concentrate feeds, whereas input per kilogram of milk is 1 to 10 MJ. Biomass energy used in ruminant production contains nitrogen (N), phosphorus (P), and potassium (K), but in a ratio rarely balanced to the animals requirements. In secondary systems, energy is partitioned between foods of animal origin and waste. The latter contains OM, N, P, K, and gases (CO2, CH4), which may cause environmental problems. Losses per kilograms of milk vary and are 10 to 45 g for N, 0 to 3 g for P, and 2 to 20 g for K. Environmental impacts of animal production can be reduced by varying the use of inorganic fertilizer and changing the forage to concentrate ratio. Digestibilities can be improved by proper harvest management. Level and ratio of dietary N, P, and K can be adjusted to requirements by selecting proper ingredients, reducing their loss in waste. Limited scope exists to reduce losses in respiration and fermentation gases.

Palatability indices of dry and wilted 18 multipurpose tree species (MPTs) were determined using 12 wethers and 12 bucks (mean ± SD liveweight 17.5 ± 1.24 kg and 20.5 ± 1.46 kg, respectively), blocked into two groups on liveweight and age, housed in a roofed and half-walled shed with individual feeding pens. The 18 MPTs were randomly grouped into sets of six by form (dried and wilted), such that each animal received three samples of each form. Each animal received 0.5 kg teff straw (Eragrostis tef) in addition to 0.4 kg and 0.2 kg of the wilted and dry forms of the appropriate MPTs, respectively, daily at 08,00 h over a 12-day experimental period.

Dietary protein ingested by ruminant animals is extensively degraded by microorganisms inhabiting their forestomachs. Mechanism of microbial breakdown of dietary protein is very complicated and not yet entirely understood. Experimental results, both in vitroand in vivoshow a varying degradation of dietary protein, with differences in degradation between individual amino acids. Part of this variation, particularly in vivo, must be attributed to inadequate measuring techniques. Among other factors influencing degradation are nature and solubility of dietary protein, rate of passage of digesta through the forestomachs and level of feed intake.Decreasing the extent of degradation of dietary protein can be achieved in various ways. Two possibilities include formulation of diets from ingredients with low protein solubility and chemical treatment of the dietary protein, for instance, with formaldehyde. Under present feeding regimens this seems profitable only if level of animal production is high (early lactation, fast growing young animals). Protection may result in an inadequate supply of nitrogen or even amino acids for microbial growth in the forestomachs. Shortage of N can easily be overcome by addition of some nonprotein nitrogen such as urea to the diet, provided that the energy supply to the microbes is not a limiting factor as well.

Summary Samples of strawberries were divided into two portions, they were wrapped and one portion was irradiated at 200 krad. A total of 30 samples of Dutch strawberries (10 greenhouse-and 20 outdoor-grown) were treated. The composition of the microflora before and after irradiation was investigated.

We studied the effect of feeding young growing pigs a semisynthetic diet containing 7.5% white kidney beans-germinated (GB), pancreatin treated (PTB), or untreated (raw beans RB)--on protein and amino acid (AA) digestibilities at the terminal ileum. Eleven castrated male pigs (12.2 kg live weight) fitted with a post-valve T-cecal cannula and two blood catheters were used. The 15N-isotope dilution method was used to determine the amount of endogenous protein passing the terminal ileum and the true ileal protein digestibility. Ileal crude protein losses in pigs fed the RB, GB, and PTB diets were 51.9, 27.4, and 51.1 g/kg of DMI, respectively. The total amounts of AA passing the terminal ileum of the pigs fed the RB, GB, and PTB diets were 48.6, 21.4, and 42.2 g/kg DMI, respectively. The apparent ileal crude protein and AA digestibilities of the RB, GB, and PTB diets were 74, 87, and 75% and 76, 89, and 78%, respectively. True ileal protein digestibilities were 88, 93, and 93% for the RB, GB, and PTB diets, respectively. On the basis of this research, germination of white kidney beans improves the digestion of protein by decreasing the content of bean antinutritional factors and increasing the bean true ileal protein digestibility.

Endogenous recoveries and true ileal digestibilities of amino acids were determined in pigs fed cornstarch-based diets with untreated or protease-treated soybean meal as protein sources. Twelve pigs, fitted with a modified post valve T-cecum cannula on d 14, 15, and 16 after birth, were weaned on d 20 and assigned to one of four diets according to a two-period balanced change-over design. Diets consisted of soybean meal 1) untreated (SBM), 2) incubated (1:2 wt/vol in distilled water adjusted to pH 4.5, for 16 h at 50 °C; CI-SBM), 3) sprayed with protease (1 μL/g of soybean meal; PS-SBM), and 4) incubated, as for CI-SBM, with protease in the water (PI-SBM) at the same application rate as that for PS-SBM. Each period consisted of 5 d of adaptation to diets followed by collection of ileal digesta on d 6 and 7 to determine the apparent ileal amino acid digestibilities of the diets. On d 9, guanidinated meals were fed, followed by a 24-h continuous collection of digesta. Recoveries of chromic oxide and dysprosium from the guanidinated meals were 96.0 ± .5 and 94.5 ± 1.1%, respectively. Endogenous amino acid recoveries were similar (P> .05) for SBM, CI-SBM, and PS-SBM but less (P< .05) for PI-SBM. True digestibilities were also less (P< .05) for PI-SBM than for the other meals. Recoveries of endogenous branched-chain and aromatic amino acids were less (P< .05) during Period 2 than during Period 1, suggesting dietary change- and(or) age-dependent adaptive increases in the secretions of pepsin and pancreatic proteases. In conclusion, protease treatment did not improve the true digestibilities of amino acids in soybean meal fed to newly weaned pigs.

Apparent ileal digestibilities of amino acids were determined in pigs fed cornstarch-based diets with untreated or protease-treated soybean meal as the protein source. Sixteen pigs were fitted with a modified post valve T-cecum cannula on d 14, 15, and 16 after birth and then returned to their sows until d 20 when they were weaned. Twelve of the pigs were selected for the study, which was conducted according to a two-period balanced change-over design. Treatments consisted of soybean meal that was 1) untreated (SBM), 2) processed by incubation (1:2 wt/vol distilled water adjusted to pH 4.5, for 16 h at 50 °C; CI-SBM), 3) sprayed with protease (supplied at 1 μL/g of soybean meal; PS-SBM), and 4) processed by incubation, as for CI-SBM, with protease in the water at the rate of 1 μL/g of soybean meal (PI-SBM). Each period consisted of 5 d of adaptation to diets followed by three 8-h collection periods (total of 24 h) that alternated with 8-h periods in which digesta were not collected. Apparent CP digestibilities were similar (P> .05) at 70.4, 72.4, 65.2, and 70.3% for the SBM, CI-SBM, PS-SBM, and PI-SBM diets, respectively. Corresponding amino acid digestibilities were also similar (P> .05), ranging from 62.5, 67.5, 57.9, and 65.0% for alanine to 83.5, 83.4, 78.7, and 84.7% for arginine. Apparent digestibilities were less (P< .05) for Period 1 (on d 7 after weaning) than for Period 2 (on d 16 after weaning). In conclusion, protease treatment of soybean meal had no effect on ileal digestibilities of CP and amino acids in newly weaned pigs.

The relation between the ratio of the natural 13C and 12C isotopes of carbon in silages of a C3 species (winter-barley) and a C4 species (maize) was examined as a potential marker in rate of passage studies in ruminants concurrently with the external marker titanium(IV)-oxide (TiO2). Diets were formulated to contain 140 g crude protein kg-1 dry matter. Two ruminally cannulated steers and two wethers were fed on a diet based on whole-plant winter-barley silage (BS) once daily at 07.00 h. The animals received one single meal of whole-plant maize silage (MS), concurrently with a single dose of TiO2. Animals were then switched back to BS for the remainder of the experiment. Faeces were collected over 5 days post MS feeding. Ruminal pH in steers appeared to be unaffected by switches from C3 to C4 silage feeding, and vice-versa. In steers, faecal samples peaked in TiO2 value approximately 22 to 28 h after dosing, and then declined. Carbon isotope values peaked approximately 31 to 35 h after steers received the C4 silage, and then declined. The time of this peak corresponded closely to that from a study which used intrinsically labelled 13C forage. Carbon isotope values from faecal samples of wethers showed no clear peak and decline. However, measurement of carbon isotope ratios in neutral detergent fibre of silage and faeces instead of whole material greatly improved curve shaping. Provided that C3 and C4 forages of similar chemical composition and digestibility are used in order to minimize perturbation of rumen fermentation and subsequent passage processes, naturally occurring differences in stable carbon isotope ratios may be used as passage markers in ruminants. This restriction will limit the potential use of estimating passage rates from naturally occurring differences in carbon isotope ratios to only a few specific cases.

In addition to technological processes like heat treatment, germination can be an alternative process for the improvement of protein quality of legumes. This was demonstrated by enzymatic protein hydrolysis of flour of germinated faba and soya beans, using a pepsinpancreatin enzyme system. SDS-PAGE was used to study the changes in protein pattern of these legumes during germination. In addition, the effect of germination on the content of condensed tannins in flour from germinated faba beans and trypsin inhibitors in flour from germinated soya beans were studied. Germination for five days resulted in a maximum increase in enzymatic protein hydrolysis by 21.3% in flour from faba beans and by 25.7% in flour from soya beans after 12 hours of germination. Protein patterns, obtained with SDS-PAGE demonstrated a considerable protein breakdown during germination between day 2 and 3 in faba beans and between day 1 and 2 in soya beans. The tannin content in flour from faba beans decreased by 29.7% after seven days of germination, but the tannin content of the hulls of the faba beans did not change during that period of germination. The trypsin inhibitors in flour from soya beans decreased by 25.5% after seven days of germination. We conclude that the increased enzymatic hydrolysis of protein in both legumes cannot be explained by a decrease of tannins or trypsin inhibitors. The possible explanation is that through degradation of proteins during germination of the legumes, the cleaved protein fragments are more susceptable for hydrolysis by pepsin-pancreatin.

During the germination of legume seeds, enzymes become active in order to degrade starch, storage-protein and proteinaceous antinutritional factors. The degradation of storage-protein is necessary to make peptides and amino acids available in order to stimulate seed growth and early plant growth. Proteinaceous antinutritional factors such as amylase inhibitors, lectins and trypsin inhibitors are present in legume seeds and protect them against predators. However, during germination, they degrade to a lower level by the action of several enzymes. The effect of germination on the content and activity of amylase inhibitors, lectins, tannins and trypsin inhibitors is discussed.

Domesticated animals all over the world are subjected to a wide variety of environmental conditions and challenges. Any deviation from “normal”; may result in adaptive behavior of which changes in feed intake or feed intake pattern is by far the most important. Adaptive behavior may further include influences on passage rate of feed residues through the digestive tract, resulting in changes in digestibility. Adaptive behavior may also result in changes in heat production, either to maintain body temperature constant, or as a result of an elevated body temperature.Important environmental challenges are infectious diseases. Mild (sub‐clinical) infections usually result in reduced performance, without affecting feed intake or digestibility. Severe infections may disrupt the barriers between the internal metabolism and the respiratory and/or digestive tract, resulting in severe losses of energy and protein. This situation is notably apparent in severe infections with parasites of the gastrointestinal tract and may be associated with severe protein losses. Feeding high protein diets may partly alleviate the negative effects.Contamination of air, water and feed may occasionally cause problems in farm animals. Such contamination may include pathogenic microbes, toxic secondary fungal metabolites and heavy metals. Negative effects associated with such contamination often show an impaired reproductive efficiency, but their influence on the utilization of energy and nutrients is not well documented.

In animal production, endogenous protein losses associated with the digestion process are important losses, but difficult to measure. Measuring methods include feeding N-free diets, regression techniques based on amino acid profiles, and separating feed protein and endogenous protein by markers like homoarginine, hydrolysed casein or stable isotopes like 15N. Endogenous losses arise from saliva, digestive enzymes, bile, shedded epithelial cells and mucins and may be extra stimulated by the presence in feeds of antinutritional factors (ANF) such as lectins, trypsin inhibitors (TI), tannins and fibre. The impact of such factors may differ between non-ruminants and ruminants. The magnitude of the effect of the different factors is quantified and some of the consequences for protein deposition and nitrogen losses to the environment are discussed.

This study determined nitrogen degradability and digestibility of rumen undegradable nitrogen using mobile nylon bag (MNB) and pepsin/pancreatin in vitro technique (IV) of 40 browse species. Thirty Ethiopian highland sheep fitted with rumen cannulae were used in nitrogen (N) degradability studies. Six steers fitted with rumen cannulae were used in preparation of 16-h and 24-h ruminal undegraded residues and four steers fitted with distal abomasal cannulae were used in MNB technique. The browses varied widely in nitrogen solubility (15–468 g kg^-1), potential degradability (223–976 g kg^-1), rate of degradation (0·13–24% h^-1) and effective degradability (135–821 g kg^-1). The apparent N digestibility (ND) of the rumen undegraded residues differed significantly (P&lt;0·05) among browse species. No significant difference (P>0·05) was observed in ND of 16-h and 24-h residues. The ND of the 16-h residue varied from -218 to 759 g kg^-1 and 169 to 851 g kg^-1 for MNB and IV methods, respectively. Browse species with high tannin contents such as Acacia hockii, A horrida, A melanoxylon, A persiciflora, A salicina, A saligna and Flemingia macrophylla had high rumen by-pass and a low ND, while Sesbania spp and A nilotica with low tannin contents underwent rapid and extensive dry matter and nitrogen degradation in the rumen. Acacia sieberiana, Chamaecytisus palmensis, Erythrina spp, Gliricidia sepium, Samanea saman and Enterolobium cyclocarpum had high proportions of protein escaping rumen degradation (BP) and with a high proportion of the by-pass protein digested in the intestine, therefore these browses had a high potential as protein supplements. The ND measured with the MNB were significantly lower (P&lt;0·001) than by the IV method. The correlation between MNB and IV was high and significant (R²=0·89, P&lt;0·0001) as also indicated by the regression equation (SE in parentheses): MNB=-22·8 (4·55)+1·0 (0·08)IV (RSD=10·56, R²=0·79, n=40, P&lt;0·001). The intercept of the linear relationship obtained was different from zero while the slope was not different from unity. Multiple regression analysis suggested that some of the unexplained variation could be accounted for by either nitrogen, acid detergent fibre, total phenolics or neutral detergent fibre bound tannin levels in browses. The IV method is accurate for estimating digestibility of ruminally undegradable N, and hence its use would considerably reduce the need for delicate surgery and the elaborate procedures involving the MNB technique. © 1998 SCI.

The relationship between protein nutrition and milk urea N was investigated in three experiments with a total of 125 cows. After 4 wk of pretreatment, cows received 1 of 13 diets with different ratios of protein to energy for 16 wk. Milk was sampled individually for urea analyses during pretreatment and during wk 1, 5, 10, and 15 of treatment. Results were compared with N losses estimated from rumen fermentation and with N losses of metabolic origin.

White kidney beans (Phaseolus vulgaris), cv Processor, contain a relatively high content of phaseolin (storage protein), lectins and a special group of glycoproteins as well as a considerable amount of protein-type trypsin inhibitors. Protein digestion of raw ‘Processor’ beans in monogastrics, for example pigs, is disturbed by poorly digested, phaseolin lectins, which can bind to carbohydrates in brush border membranes of the small intestinal epithelium, and trypsin inhibitors. The effect of the germination of white kidney beans on lectins, phaseolin and trypsin inhibitors was studied in order to achieve a degradation of lectins, phaseolin and trypsin inhibitors and an increase ofin vitro enzymatic hydrolysis of the protein of bean flour. Therefore, whole bean extracts were examined throughout a germination period of up to seven days for their lectin and phaseolin pattern, lectin content, binding capacities of functional lectins towards brush border membranes and trypsin inhibitor content. In addition thein vitro enzymatic hydrolysis by pepsin and pancreatin of the protein from flours of (un)germinated white kidney beans was studied. SDS-PAGE demonstrated a degradation of E-lectins and a disappearance of L-lectins and phaseolin during germination. Results indicated a decrease of the lectin content by 85%, a loss of binding capacities of functional lectins towards brush border membranes by 91%, and a decrease of trypsin inhibitors by 76%, in bean flour after germination for seven days. A maximum inin vitro enzymatic hydrolysis of protein from bean flour was already established after germination for half a day.

In dairy cows amino acids may be required for four processes: maintenance; as precursors for the synthesis of glucose (gluconeogenesis); for protein deposition in muscle or associated with foetal growth; and for the synthesis of milk protein.

The point of amino acid supply must be defined -duodenal amino acid supply (DAAS) is now seen as crucially important in new systems for rationing protein, but metabolism of amino acids during passage across the gut wall and in the body affect supply to the liver and peripheral tissues.

The effects of the length of allowed grazing time (Experiment 1) and length of starvation period before grazing (Experiment 2) on dry-matter (DM) intake, ingestive behaviour and changes in DM rumen pool sizes during the first grazing bout were investigated in lactating Holstein-Friesian dairy cows. In Experiment 1, four lengths of allowed grazing time (1, 1·75, 2·50 and 3·25 h) after overnight starvation were compared. Increasing the length of the allowed grazing time significantly increased DM intake (P &lt; 0·01), the proportion of time spent actively eating (P &lt; 0·01) and DM rumen pool size after grazing (P &lt; 0·05). However, DM rumen pool size after grazing was smaller than that measured immediately before the start of starvation (P &lt; 0·01). Bite mass during the first hour of grazing was greater than in the following grazing time. Experiment 2 consisted of a factorial combination of two durations of starvation before grazing (16·5 h and 2·5 h) and the presence or absence in the rumen of 12·5 kg of a synthetic indigestible material. DM intake, as well as grazing time, were greater after a starvation period of 16·5 h and were reduced by the presence in the rumen of indigestible material (P &lt; 0·01). The interaction between factors on grazing time, although not significant (P &lt; 0·06), supports the idea of a combination of signals controlling meal size under grazing conditions. Bite mass was not significantly modified by the period of starvation. DM rumen pool size after grazing was reduced by the placement in the rumen of synthetic indigestible material (P &lt; 0·05) and tended to be lower in cows with the larger period of starvation (P &lt; 0·058). In both experiments, bite rate declined as the grazing session progressed, but bite rate was not affected by treatments.