Rate Of Ruminal Digestion Research Articles

Mathematical modeling applied to ruminal digestion and gas production in vitro

The ruminal digestion performed by ruminants is one of the essential and most important processes for the use of dietary nutrients. However, the use of mathematical models applied to digestion kinetics has been widely applied to provide prediction of animal performance, maximize the use of nutrients and reduce nutritional losses due to excreta and a reduction in the cost of animal production. In this context, it aimed to conduct a literature review on the use of mathematical models and to analyze comparisons of different models to predict ruminal digestion. The in vitro gas production technique provides direct measurement of the ruminal digestion rate associated with gas production and the respective gravimetric measurement of the food or diet under test. Nonlinear models are chosen to evaluate ruminal digestion due to a better interpretation of biological parameters, they produce exponential and sigmoidal growth equations. However, the most suitable model for evaluation depends on the type of food or diet. The two-compartment logistical model presents a better adjustment of the gas production curve, mainly for foods with a high proportion of fiber. Among this, single-compartment models can be well applied to evaluate the degradation kinetics of foods with low fibrous carbohydrate content. Therefore, the choice of the most appropriate model is up to the researcher to assess which model best suits the chemical-chemical composition of the food or diet.

Effects of substituting kraft pulp with corn silage on dry matter intake, ruminal mat formation, rumen fermentation, and rumination activity in non-lactating cows.

The present study examined the effects of substituting kraft pulp (KP) with corn silage (CS) on dry matter intake (DMI), ruminal mat and rumen fermentation characteristics, and rumination. Four non-lactating, rumen-cannulated Holstein cows were fed a CS diet comprising 36% grass silage (GS) and 64% CS or a KP diet comprising 36% GS, 57% KP, and 7% soybean meal. DMI was significantly lower in cows fed the KP diet than in those fed the CS diet (p<0.05), whereas rumination time did not significantly differ between the treatments. Dry matter content in the rumen immediately before and 3h after feeding was significantly higher in cows fed the KP diet than in those fed the CS diet (p<0.05). The consistency and thickness of the ruminal mat did not significantly differ between the treatments. The ruminal mean retention time of feed particles tended to be longer in cows fed the KP diet than in those fed the CS diet (p<0.10). The ruminal digestion rate of KP was comparable to that of GS and CS. Because ruminal mat was formed and rumination was stimulated, KP was considered to have the equivalent physical effectiveness as CS.

Starch sources and concentration in diet of dairy goats affected ruminal pH and fermentation, and inflammatory response

Corn and wheat grains are two starch sources with considerably different ruminal digestion rates, which may lead to differing lipopolysaccharide (LPS) release in both rumen and hindgut affecting animal production. The objectives of this study were to (1) investigate the effects of different ruminal and faecal LPS concentrations induced by starch source (corn vs wheat) and starch concentrations (low vs high) on DMI, ruminal pH, ruminal fermentation patterns, milk production, and inflammatory responses; and (2) evaluate the possible translocation site of LPS in dairy goats. Eight lactating dairy goats with ruminal cannulas were used in a replicated 4 × 4 Latin square design with 2 × 2 factorial arrangement of treatments. Each experimental period consisted of 24 days long including 21 days for adaption and 3 days for data and sample collection. The four treatment diets were: corn and wheat grain combined with low (LS) and high grain starch (HS). Goats were fed equal amounts of a total mixed ration twice daily at 0700 hours and 1900 hours. Replacing corn with wheat in goat diet led to longer (P &amp;lt; 0.02) duration of ruminal pH &amp;lt;5.6, higher ruminal LPS (P &amp;lt; 0.05), but lower faecal LPS concentration. However, no differences between two grains in ruminal pH (mean, minimum and maximum), volatile fatty acids (VFA) and lactic acid concentration were observed. Goats fed HS diets had lower (P &amp;lt; 0.01) ruminal pH and higher (P &amp;lt; 0.01) ruminal concentrations of VFA and lactic acid, as well as higher (P &amp;lt; 0.01) ruminal and faecal LPS concentrations. Starch source did not affect DMI, milk yield and milk components whereas feeding HS versus LS diet had higher milk yield, lactose yield and improved milk efficiency (P &amp;lt; 0.05). Feeding wheat- versus corn-based diet showed only greater (P &amp;lt; 0.05) concentration of toll-like receptor-4, whereas feeding the HS versus LS diet consistently increased blood concentrations of amyloid A, haptoglobin, LPS binding protein, and LPS (P &amp;lt; 0.05). Analysis of Pearson correlation coefficients illustrated that the ruminal LPS concentration is more important than faecal LPS in inflammatory responses. In conclusion, replacing corn with wheat in lactating goat diet had negative impact on ruminal pH but little effects on fermentation characteristics and milk production. Increasing the dietary concentration of starch decreased ruminal pH status and thus increased risk of acidosis, whereas, feeding HS versus LS diets resulted in an improvement in milk yield, milk efficiency, and immunity response. Moreover, rumen acidosis induced by wheat based diet was accompanied with more severe inflammatory responses.

Sunflower cake in diets for beef cattle: digestibility, kinetics and &lt;i&gt;in vitro&lt;/i&gt; ruminal fermentation parameters

The objective of this study was to evaluate the effect of the inclusion of sunflower cake replacing soybean meal in beef cattle diets on the in vitro digestibility of dry matter (IVDDM), organic matter (IVDOM), crude protein (IVDCP) and the ruminal fermentation kinetics and parameters. The experiment was analyzed according to a completely randomized design. The treatments consisted of four levels of sunflower cake, 0, 200, 400, 600 g kg-1, replacing soybean meal in the concentrate of beef cattle diets. The coefficients of IVDDM, IVDOM and IVDCP presented a quadratic effect with the addition of sunflower cake. The soluble fraction (fraction B) degradation rate and total gas production decreased linearly with the inclusion of sunflower cake. Values of pH in ruminal fluid were higher for levels 0, 200 and 600 g kg-1 sunflower cake. Sunflower cake can replace soybean meal by up to 280 g kg-1 in the concentrate of beef cattle diets, improving the in vitro digestibility of dry matter organic, matter and crude protein. Levels above 400 g kg-1 reduce ruminal digestion rate, digestibility and release of final fermentation products.

Use of protected fat sources to reduce fatty acid biohydrogenation and improve abomasal flow in dry dairy cows

The objective of this study was to evaluate the effects of dietary fat supplementation on dry dairy cows feed intake, digestion, ruminal kinetics, biohydrogenation, and abomasal flow of fatty acids (FAs). Eight Holstein rumen and abomasum fistulated dry cows (average body weight of 614±59kg), were assigned to a replicated 4×4 Latin square design experiment, with 21-d periods. The experimental diets were: 1) control (CON): corn- and soybean meal-based diet, with no fat source; 2) soybean oil (SO) diet with 30g/kg dry matter (DM) of soybean oil; 3) whole raw soybean (WS) diet with 160g/kg DM of whole raw soybean grain; 4) calcium salts of fatty acids (CS) diet with 32g/kg DM of calcium salts of unsaturated FA. Fat-supplemented diets increased ether extract intake and digestibility without affecting DM intake. However, these diets promoted a decrease in DM and neutral-detergent fiber (NDF) total tract apparent digestibility. Fat sources decreased ruminal acetate to propionate ratio (C2:C3). In addition, SO diet increased ruminal propionate concentration and decreased C2:C3 in relation to protected sources of FA (CS and WS). Furthermore, cows fed CS diet exhibited higher ruminal pH, NH3-N and acetate concentration compared to those fed WS diet. Fatty acid supplementation did not alter serum glucose and urea concentration, but increased the serum cholesterol concentration. Although FA supplementation increased net energy intake of cows, energy and nitrogen balances, and microbial protein synthesis were not affected by the experimental diets. Fat supplementation had no effect on ruminal digestion neither on DM and NDF passage rates. Cows fed CS and WS diets presented higher DM and NDF ruminal digestion rates whether compared to SO one. Consequently, cows fed CS and WS had higher truly digestible NDF ruminal removal rate than those fed SO. Calcium salts of unsaturated FA increased DM and NDF rumen passage rate and decreased NDF digestibility in relation to WS diet. Fat-supplemented diets increased the abomasal flows of C18:2, trans C18:1, C18:0, C16:0 and total FA. The CS supplementation resulted in a higher abomasal flow of DM, total FA, trans C18:1, C16:0 and C18:3 when compared to WS one. On the one hand, FA supplementation increased C18:2 and C18:1 biohydrogenation rates; on the other hand, it protected FA sources decreased C18:2 and C18:1 biohydrogenation rates. In conclusion, fat-protected sources were effective to prevent FA from ruminal biohydrogenation.

Desempenho produtivo de bovinos alimentados com cana-de-açúcar com diferentes níveis de concentrado

Foram avaliados o consumo, as digestibilidades totais e ruminais e as taxas de digestão (kd) e de passagem (kp) ruminal dos nutrientes de dietas constituídas de cana-de-açúcar in naturae diferentes níveis de concentrado. Utilizaram-se cinco bovinos mestiços, fistulados no rúmen, com peso corporal inicial de 300±50kg, distribuídos em delineamento em quadrado latino 5x5. As dietas experimentais foram constituídas de: 1) 100% cana-de-açúcar in natura(CA); 2) 80% de CA + 20% de concentrado (C); 3) 60% de CA + 40% de C; 4) 40% de CA + 60% de C; e 5) 20% de CA + 80% de C. Os dados foram analisados utilizando-se o procedimento MIXED do SAS (versão 9.1), bem como análise de regressão e 5% como nível crítico de probabilidade para o erro tipo I. O consumo de matéria seca (MS), expresso em kg/dia ou g/kg de peso corporal foi influenciado (P&lt;0,05) pelos níveis de concentrado. Os demais consumos calculados em kg/dia também foram influenciados (P&lt;0,05) pelos níveis de concentrado, assim como os consumos de FDNcp, FDNi e NDT, expressos em g/kg de peso corporal. O pool (kg/dia) foi aumentado linearmente à medida que se elevaram os níveis de concentrado para MS. Comportamento similar foi observado para ki (h-1) da MS e da FDNcp. As taxas de digestão (kdh-1) da MS, da MO e da FDNcp aumentaram linearmente com a elevação dos níveis de concentrado na dieta. Estimaram-se máximos fluxos omasais (kg/dia) com 52,22 e 31,45% de concentrado na dieta, respectivamente, para MS e FDNi. A digestibilidade aparente (DA) da MS também foi influenciada pelos níveis de concentrado na dieta. As digestibilidades ruminais da MS e da FDN aumentaram linearmente (P&lt;0,05) com a adição de níveis crescentes de concentrado. Conclui-se que níveis próximos de 65% de concentrado resultam em maior ingestão de energia em dietas contendo cana-de-açúcar.

Effects of NaOH-treated wheat and a mixture of barley and oats on the voluntary feed intake and milk production in dairy cows

An experiment was conducted to examine how including NaOH-treated wheat in the diet of dairy cows affects dry matter intake (DMI) and milk production, using diets based on rolled wheat and an oat/barley mixture for comparative purposes. The study was based on 24 Swedish Red dairy cows that were 147±51d in milk (DIM), with an average milk yield of 31±5.6kg/d and a live weight of 611±66kg. The cows were blocked according to DIM and randomly assigned to six replicated 4×4 balanced Latin squares with 21-d experimental periods. The diets were fed as total mixed rations consisting of grass silage supplemented with concentrates in a ratio of 52:48. Four diets were examined: an oat/barley mixture (OBM), 100% rolled wheat (RW) of which 50 (SHW/RW) or 100% was replaced with NaOH treated wheat (SHW). Total tract digestibility was determined using acid-insoluble ash as an internal marker. Ruminal degradation parameters for the cereal feeds were estimated using an in vitro gas production technique and modelling approach. Increased inclusion of NaOH-treated wheat did not affect DMI or milk production. NaOH-treatment reduced (P<0.01) milk protein concentrations and milk N efficiency (P<0.05), and tended (P=0.10) to decrease milk protein yield. There were no differences between the OBM and RW diets in terms of DMI, milk production, or milk composition. Increased levels of NaOH-treated wheat in the diet caused linear increases (P<0.05) in faecal N output and estimated urinary volumes and decreasing milk urea concentrations. This indicates that NaOH-treatment increased the mineral load of the diet and shifted starch digestion from the rumen to the small and large intestines. These results were consistent with the lower observed in vitro ruminal digestion rates of NaOH-treated wheat. It is concluded that the oat/barley mixture and the rolled wheat had comparable feeding values despite the higher tabulated metabolisable energy and protein concentrations of the latter. It is concluded that NaOH-treatment of wheat has no beneficial effects that justify its use.

Effects of Saccharomyces cerevisiae fermentation product on ruminal starch digestion are dependent upon dry matter intake for lactating cows

This experiment was conducted to evaluate ruminal digestion responses to Saccharomyces cerevisiae fermentation product (SCFP) supplementation and to determine if responses are influenced by voluntary feed intake. Fifteen ruminally and duodenally cannulated Holstein cows with a wide range in preliminary dry matter intake (pDMI; 20.1 to 31.0kg/d) measured during a 14-d preliminary period were used in a crossover design experiment. Treatments were SCFP and control (a mix of dry ground corn and soybean meal), top-dressed at the rate of 56g/d per head. The base diet contained 28% NDF, 30% starch, and 16.5% CP and included corn silage, alfalfa silage, high-moisture corn, protein supplement, and a mineral and vitamin supplement. Treatment periods were 28d, with the final 8d used for sample and data collection. Voluntary dry matter intake was determined during the last 4d of the preliminary period. Ruminal digestion kinetics were determined using the pool-and-flux method. Main effects of SCFP treatment and their interaction with pDMI were tested by ANOVA. An interaction was detected between SCFP treatment and pDMI for ruminal digestion rate of starch; SCFP increased the rate of starch digestion compared with the control for cows with pDMI below 26kg/d and decreased it for cows with higher pDMI. This resulted in an interaction between treatment and pDMI for turnover rate of starch in the rumen and true and apparent ruminal starch digestibility because passage rate of starch from the rumen was not affected by treatment (mean=24.3%/h). Ruminal pH (mean=6.0), dry matter intake, milk yield and component percentages were not affected by treatment or its interaction with pDMI. Supplementation of SCFP reduced the rate of ruminal starch digestion for cows with higher feed intake, which could help stabilize the ruminal environment when large amounts of starch are consumed to support higher milk production.

Nutrient demand interacts with grass particle length to affect digestion responses and chewing activity in dairy cows

Effects of grass particle length on dry matter intake (DMI), milk production, ruminal fermentation and pool sizes, digestion and passage kinetics, and chewing activity and the relationship of these effects with preliminary DMI (pDMI) were evaluated using 15 ruminally and duodenally cannulated Holstein cows in a crossover design with a 14-d preliminary period and two 18-d treatment periods. During the preliminary period, pDMI of individual cows ranged from 22.6 to 29.8kg/d (mean=25.8kg/d) and 3.5% fat-corrected milk yield ranged from 29.2 to 56.9kg/d (mean=41.9kg/d). Experimental treatments were diets containing orchardgrass silage chopped to either (a) 19-mm (long) or (b) 10-mm (short) theoretical length of cut as the sole forage. Grass silages contained approximately 46% neutral detergent fiber (NDF); diets contained 50% forage, 23% forage NDF, and 28% total NDF. Preliminary DMI, an index of nutrient demand, was determined during the last 4 d of the preliminary period when cows were fed a common diet and used as a covariate. Main effects of grass particle length and their interaction with pDMI were tested by ANOVA. Grass particle length and its interaction with pDMI did not affect milk yield, milk composition, or rumen pH. Long particle length tended to decrease DMI compared with short particle length, which might have been limited by rumen fill or chewing time, or both. Passage rates of feed fractions did not differ between long and short particle lengths and were not related to level of intake. As pDMI increased, long particles decreased ruminal digestion rate of potentially digestible NDF at a faster rate than short particles. As a result, long particles decreased or tended to decrease rates of ruminal turnover for NDF, organic matter, and dry matter and increased their rumen pools compared with short particles for cows with high pDMI. Long particles increased eating time, which affected cows with high intake to the greatest extent, and total chewing time compared with short particles. As intake increased, ruminal digestion (kg/d) and digestibility (%) of starch decreased, rumen pool size of starch increased, and postruminal digestion and digestibility of starch increased quadratically. When grass silage was the only source of forage in the diet, increasing chop length from 10 to 19mm tended to decrease DMI but did not negatively affect productivity of cows, which were fed adequate fiber.

Simulation and validation of the ruminal digestion of carbohydrates in cattle from kinetic parameters obtained by in vitro gas production technique

This study aimed to validate the estimates of the ruminal degradation of total carbohydrates (TC), ruminal and total digestion of fibrous carbohydrates (FC) and microbial nitrogen flow in the abomasum evaluated by in vitro gas production technique (IVGP). Six ruminally and abomasally cannulated steers arranged in a double 3 × 3 latin square were used to measure described parameters with indigestible neutral detergent fiber (INDF) utilization as marker. Total and fibrous carbohydrates degraded in the rumen were estimated through digestion rates obtained for fibrous (FC) and non fibrous carbohydrates (NFC) using in vitro gas production technique, corrected for its respective ruminal and postruminal passage rates. The estimation of the total digestion of FC was done by the sum of ruminal and post-ruminal digestion of these compounds. The microbial nitrogen flow in the abomasum was estimated by the calculating the microbial efficiency of bacteria that ferment FC and NFC, utilizing the microbial growth rate obtained by the ruminal digestion rate for carbohydrate fractions in IVGP. The utilization of the in vitro gas production technique allows obtaining accurate estimates of the ruminal digestion of total carbohydrates, total and ruminal digestion of fiber carbohydrates and microbial protein flow in the abomasum.

Influence of condensed tannin on intake, digestibility, and efficiency of protein utilization in beef steers fed high concentrate diet

This trial was conducted to evaluate if the effect of condensed tannin (CT) is associated with a true protein source on intake, ruminal and total digestibility, ruminal digestion rate, protein efficiency, and microbial efficiency in beef steers fed high concentrate diet (87% of DM). Four Bos indicus steers (407±12kg of BW) fitted with rumen cannula were assigned to a 4×4 Latin square design, arranged in a 2×2 factorial arrangement. Treatments consisted of either inclusion (0.4% of DM) or exclusion of condensed tannin (CT) from quebracho extract (76% of CT) with or without the use of soybean meal (SBM) as source of true protein. The level of inclusion was calculated to provide a daily intake of 1g/10kg of BW of CT. Intake of DM and nutrients was not affected (P>0.10) by CT inclusion. However, there was an effect (P<0.10) of CT inclusion on ether extract digestibility. An interaction (P<0.10) was observed between CT and SBM on ruminal digestibility and digestion rate of crude protein (CP): when mixed with soybean meal, CT decreased the ruminal digestibility and, consequently, reduced the digestion rate of CP. Intake of CP increased (P<0.10) with the inclusion of SBM. No differences in DM passage rate were observed (P>0.10) among treatments. Effects of the interaction (P<0.10) between CT and SBM were observed on flux of rumen undegradable protein (RUP), metabolizable protein (MP), and on the ratio MP:CP. In the presence of soybean meal, the addition of CT increased (P<0.10) the flux of RUP and MP, and improved the ratio MP:CP. The yield of microbial protein on the abomasum and the microbial efficiency did not differ among treatments (P>0.10). There was no difference (P>0.10) on the pH, VFA, and ruminal ammonia (N-NH3) with the addition of condensed tannin. The N-NH3 increased and the ruminal pH decreased with the inclusion of soybean meal (P<0.10). The utilization of condensed tannin as an additive in beef cattle diets with high level of concentrate and soybean meal as a source of true protein implies positive effects on crude protein utilization, decreasing digestion rate and ruminal digestibility of crude protein and consequently increasing the levels of metabolizable protein, with no changes in the ruminal fermentation parameters.

Ruminal starch digestion characteristics in vitro of barley cultivars with varying amylose content

Three experiments were conducted to study effects of amylose/amylopectin ratios and starch particle size on ruminal digestion characteristics of barley starch using an automated in vitro gas production system. In Experiment 1, starch digestion characteristics were measured in 12 barley cultivars with different amylose/amylopectin ratios, both as milled grain and as purified starch isolated from the original grain samples. The same 12 cultivars, harvested 1 year later from the same locations, were used in Experiment 2. Gas production was measured in milled samples, and in neutral detergent fibre (NDF) extracted from the same samples. The objective of this approach was to estimate gas production from neutral detergent solubles (NDS) as an approximation of starch. This was done by subtracting the NDF gas curve from the total gas production curve. In Experiment 3, starch digestion characteristics were measured for large and small starch granules from nine of the original cultivars used in Experiment 1. The gas curves obtained were fitted to a three-pool Gompertz model, and the effective rate of digestion (kd) was estimated with a two-compartmental rumen model. In Experiment 1, the effective starch kd for milled barley and purified starch were 0.122 and 0.118/h, respectively. Barley cultivars with low amylose (LA) had a higher effective kd (0.148/h) compared with cultivars with normal amylose (NA) (0.115/h) and high amylose (HA) (0.102/h) (P=0.010). Results obtained with milled barley were supported by the purified barley starch sample results, but differences were smaller and only numerically different. In Experiment 2, the ranking of the amylose groups was consistent with those in Experiment 1 ( i.e., LA > NA > HA) (P=0.096). However, these differences were not reflected in the effective kd for the NDS fraction (P=0.366). Thus, factors other than those related to starch per se, or other structural features, are apparently important. Barley cultivars in the LA group had a higher effective kd for aNDF (0.098/h) than did NA and HA barley (0.060 and 0.055/h, respectively). Thus, the effect of the amylose group on the effective kd for aNDF corresponded well with the milled barley results. The NDF fraction, directly or indirectly, has a clear impact on the ruminal digestion rate of barley starch. There was no difference in the effective kd for starch between the small (0.126/h) and large (0.129/h) starch granules.

Evaluation of Protein Fractionation Systems Used in Formulating Rations for Dairy Cattle

Production efficiency decreases when diets are not properly balanced for protein. Sensitivity analyses of the protein fractionation schemes used by the National Research Council Nutrient Requirement of Dairy Cattle (NRC) and the Cornell Net Carbohydrate and Protein System (CNCPS) were conducted to assess the influence of the uncertainty in feed inputs and the assumptions underlying the CNCPS scheme on metabolizable protein and amino acid predictions. Monte Carlo techniques were used. Two lactating dairy cow diets with low and high protein content were developed for the analysis. A feed database provided by a commercial laboratory and published sources were used to obtain the distributions and correlations of the input variables. Spreadsheet versions of the models were used. Both models behaved similarly when variation in protein fractionation was taken into account. The maximal impact of variation on metabolizable protein from rumen-undegradable protein (RUP) was 2.5 (CNCPS) and 3.0 (NRC) kg/d of allowable milk for the low protein diet, and 3.5 (CNCPS) and 3.9 (NRC) kg/d of allowable milk for the high protein diet. The RUP flows were sensitive to ruminal degradation rates of the B protein fraction in NRC and of the B2 protein fraction in the CNCPS for protein supplements, energy concentrates, and forages. Absorbed Met and Lys flows were also sensitive to intestinal digestibility of RUP, and the CNCPS model was sensitive to acid detergent insoluble crude protein and its assumption of complete unavailability. Neither the intestinal digestibility of the RUP nor the protein degradation rates are routinely measured. Approaches need to be developed to account for their variability. Research is needed to provide better methods for measuring pool sizes and ruminal digestion rates for protein fractionation systems.

Effect of the proportions of neutral detergent fibre and starch, and their degradation rates, on in vitro ruminal fermentation

Effects of proportions of neutral detergent fibre (aNDFom) and starch, as well as their degradation rates, on rumen fermentation were tested using an in vitro rumen simulation system (SIMCO). The in vitro system was designed to simulate selective particle retention and had an average fluid volume of 1150 ml with a liquid dilution rate of approximately 0.07 h −1. Two types of hay (aNDFom sources) and two types of starch were each included at two different levels in the diet and were examined in an experiment following a 2×2×2 factorial arrangement of treatments (eight diet combinations). The hay was either late-cut timothy ( Phleum pretense L.) or early cut meadow grass ( Poa pratensis L.), with ruminal in situ aNDFom digestion rates of 0.03–0.04 and 0.07–0.08 h −1, respectively. The two starch types were raw (R) and cooked (C) potato starch with previously determined in vitro ruminal digestion rates of 0.04 and 0.20 h −1, respectively. The starch levels were 300 and 600 g/kg diet dry matter (DM) with the remaining being hay (282–682 g/kg DM) and peptone (14–111 g/kg DM). The aNDFom level varied among the diets with different starch levels and hay types. The peptone acted as a source of peptides and, together with ammonia salts from buffer, was used to balance the N contents of the diets. The feeding level for each of the eight vessels was 28 g DM/d. Two 10-day simulations were made with the system. The average pH was higher (P<0.05) for all treatments with raw potato starch (6.19) versus cooked starch (6.07). Protozoa scores, on a qualitative scale, declined faster at the higher starch level. The aNDFom digestibility was, as expected, higher (P<0.001) for meadow hay (0.57) than timothy (0.32), and was also higher (P<0.001) at the lower starch level (0.54) versus the higher (0.35). Microbial protein production efficiency (mg microbial N/g organic matter truly digested) was higher for the faster degrading aNDFom (P<0.01) and starch (P<0.05) sources, but was not affected by starch level. Cooked starch resulted in a lower acetate proportion (449 mmol/mol versus 591 mmol/mol VFA; P<0.001) but higher proportions of propionate (297 mmol/mol versus 236 mmol/mol VFA; P<0.001), and butyrate (169 mmol/mol versus 127 mmol/mol VFA; P<0.01). Butyrate increased with starch level (127 mmol/mol versus 169 mmol/mol VFA; P<0.01), and was also higher for meadow hay versus timothy (168 mmol/mol versus 128 mmol/mol VFA; P<0.01). Interactions between the treatments demonstrate that the response in VFA pattern to starch level is dependent on starch and aNDFom sources. Substrates such as starch and aNDFom are fermented differently depending on their rates of ruminal degradation.

Efeitos da defaunação em ovinos alimentados com cana-de-açúcar (Saccharum officinarum, L.) adicionada de uréia

Em delineamento inteiramente ao acaso, estudou-se o efeito da defaunação em ovinos que receberam cana-de-açúcar e uréia sobre o consumo e digestibilidade aparente de nutrientes, dinâmica da fase sólida, parâmetros de fermentação ruminal e de degradação in situ. As taxas de passagem no rúmen foram, respectivamente, de 3,05 e 1,97%/h, para ovinos faunados e defaunados. Valores mais elevados para taxa (5,4%/h) e extensão (46,7%) da digestão ruminal e de degradabilidade efetiva da FDN da cana (31,5%) foram obtidos nos ovinos faunados. Seus consumos diários (57,7 e 32,3 g/kg0,75, respectivamente para MS e FDN) foram superiores (P&lt;0,06) aos dos ovinos defaunados. Em função do tempo de amostragem observaram-se maiores (P&lt;0,05) concentrações de AGV total, acetato e propionato para os cordeiros faunados. Nos defaunados ocorreu queda pós-prandial mais acentuada (P&lt;0,04) no pH. Para digestibilidade aparente diferença (P&lt;0,05) entre tratamentos foi verificada apenas para matéria seca.

Effect of Enzyme Treatment on the Production of Reducing Sugars and Ruminal Degradability of Sugar Beet Pulp

Studies with sugar beat pulp (SBP) have suggested that high levels (up to 650/kg dry matter (DM)) in the diet may beneficially reduce voluntary intake and live-weight gain (LWG) in pregnant sows. (Brouns, Edwards and English, 1995). Similarly, increasing the ratio of SBP: barley from 0.5:0.5 to 0.8:0.2 in the diet of growing sheep reduced LWG, DMI and apparent rate of ruminal digestion (Rouzbehan, Galbraith, Rooke and Perrott, 1994). The effects recorded have been associated with increases in viscosity of digesta due to the presence of non-starch polysaccharides (NSPs). The objective of this study was to determine whether pre-treatment with enzymes (a) may reduce NSP concentrations, measured by breakdown to reducing sugars, and (b) increase the rate of utilisation of NSP in ruminant diets.

Effect of Enzyme Treatment on the Production of Reducing Sugars and Ruminal Degradability of Sugar Beet Pulp

Studies with sugar beat pulp (SBP) have suggested that high levels (up to 650/kg dry matter (DM)) in the diet may beneficially reduce voluntary intake and live-weight gain (LWG) in pregnant sows. (Brouns, Edwards and English, 1995). Similarly, increasing the ratio of SBP: barley from 0.5:0.5 to 0.8:0.2 in the diet of growing sheep reduced LWG, DMI and apparent rate of ruminal digestion (Rouzbehan, Galbraith, Rooke and Perrott, 1994). The effects recorded have been associated with increases in viscosity of digesta due to the presence of non-starch polysaccharides (NSPs). The objective of this study was to determine whether pre-treatment with enzymes (a) may reduce NSP concentrations, measured by breakdown to reducing sugars, and (b) increase the rate of utilisation of NSP in ruminant diets.

Interactions Among Forages and Nonforage Fiber Sources

Source, amount, and physical characteristics of dietary forage can interact with nonforage fiber sources and influence ruminal and total tract fiber digestion, passage, and performance of dairy cows fed diets containing substantial nonforage fiber in place of forage. Dietary NDF from forage can be reduced to ≤60% and still provide sufficient amounts of effective fiber for FCM production that is similar to or superior to that with high forage diets. Because of small particle size and high specific gravity, increased ruminal rate of passage may be responsible for lower ruminal NDF digestibility of nonforage fiber sources fed at high dietary amounts. As the amount of soybean hulls increased from 50 to 95% of a pelleted mix for dairy cows, passage rate increased by 8%. In five studies, the digestion of soybean hull diets was improved by the addition of coarse forage. Fiber digestibility might have improved because coarse hay increased ruminal retention time of nonforage fiber sources and allowed more complete digestion. Addition of coarsely chopped alfalfa hay to diets based on silage containing 25% soybean hulls increased ruminal mat consistency by 49% and tended to slow the ruminal escape rate of soybean hulls by 16%. When high percentages of nonforage fiber are fed, the amount of dietary forage is necessarily low, and forage particle size should be adequate to stimulate rumination and entrap small feed particles. The amount and particle size of forage in the diet interacts with the substituted nonforage fiber source to determine the net impact on the rate of ruminal digestion and passage of nonforage fiber.

Digestive kinetics of moose (Alces alces), wapiti (Cervus elaphus) and cattle

ABSTRACTIntake, rumen digesta pool sizes, ruminal digestion rates, passage rates of liquid and particle pools and faecal particle-size distrubutions of grass, browse and lucerne diets were compared in ruminally fistulated moose, wapiti and cattle. For each diet, ruminal digestion rates (nylon bag technique) were similar for the three ruminants. Intakes, rumen digesta pool sizes and passage rates varied among species and higher rates were associated with passage of larger faecal particles. However, it was not possible to simply rank the three ruminants as representative grazers (cattle), browsers (moose) and mixed feeders (wapiti) since intakes, passage rates and rumen pool sizes interacted with diet and season. Contrary to expectation, digestible dry matter intakes of each species were not greatest for their respective typical diets.

Influence of supplemental nitrogen source on digestion of nitrogen, dry matter and organic matter and on in vivo rate of ruminal protein degradation.

Seven Holstein steers (340 kg) fitted with ruminal, duodenal and ileal cannulae were used to measure the influence of supplemental N source on digestion of dietary crude protein (CP) and on ruminal rates of protein degradation. Diets used were corn-based (isonitrogenous, 12% CP on a dry matter basis, and isocaloric, 80% total digestible nutrients) with urea, soybean meal (SBM), linseed meal (LSM) or corn gluten meal (CGM) as supplemental N. Ruminal ammonia N concentrations were higher (P less than .05) in steers fed LSM than in those fed CGM, but did not differ from those in steers fed urea or SBM (11.7, 6.7, 9.1 and 9.2 mg/100 ml, respectively). Due to the high degradability of urea, ruminal digestion of dietary CP was greater (P less than .05) in steers fed urea than in those fed CGM, but intermediate in steers fed SBM and LSM (58.4, 48.8, 53.1 and 53.9%, respectively). Flow of bacterial nonammonia N to the duodenum was highest (P less than .05) in steers fed SBM or LSM, intermediate (P less than .05) for urea and lowest (P less than .05) for CGM (86.8, 86.1, 76.3 and 65.9 g/d, respectively). Efficiency of bacterial protein synthesis was lowest in steers fed CGM and differed (P less than .05) from SBM (15.6 vs 21.8 g N/kg organic matter truly digested, respectively). Rate of ruminal digestion for SBM-CP differed (P less than .05) from that of CGM-CP but not from that of LSM-CP (17.70, 5.20 and 10.13%/h, respectively). The slow rate of ruminal degradability of CGM resulted in increased amounts of dietary protein reaching the intestinal tract but lower amounts of bacterial protein, thus intestinal protein supply was not appreciably altered.