Abstract: Regulation of feed intake rumen microbiology and fermentation nutrient absorption and splanchnic metabolism endogenous regulatory and pregnancy lactation tissue growth host resistance against parasites and pathogens.

Abstract: To assess the relative contributions of microbial groups (bacteria, protozoa, and fungi) in rumen fluids to the overall process of plant cell wall digestion in the rumen, representatives of these groups were selected by physical and chemical treatments of whole rumen fluid and used to construct an artificial rumen ecosystem. Physical treatments involved homogenization, centrifugation, filtration, and heat sterilization. Chemical treatments involved the addition of antibiotics and various chemicals to rumen fluid. To evaluate the potential activity and relative contribution to degradation of cell walls by specific microbial groups, the following fractions were prepared: a positive system (whole ruminal fluid), a bacterial (B) system, a protozoal (P) system, a fungal (F) system, and a negative system (cell-free rumen fluid). To assess the interactions between specific microbial fractions, mixed cultures (B+P, B+F, and P+F systems) were also assigned. Patterns of degradation due to the various treatments resulted in three distinct groups of data based on the degradation rate of cell wall material and on cell wall-degrading enzyme activities. The order of degradation was as follows: positive and F systems > B system > negative and P systems. Therefore, fungal activity was responsible for most of the cell wall degradation. Cell wall degradation by the anaerobic bacterial fraction was significantly less than by the fungal fraction, and the protozoal fraction failed to grow under the conditions used. In general, in the mixed culture systems the coculture systems demonstrated a decrease in cellulolysis compared with that of the monoculture systems. When one microbial fraction was associated with another microbial fraction, two types of results were obtained. The protozoal fraction inhibited cellulolysis of cell wall material by both the bacterial and the fungal fractions, while in the coculture between the bacterial fraction and the fungal fraction a synergistic interaction was detected.

Abstract: Four ruminally and duodenally cannulated multiparous Finnish Ayrshire cows were fed on diets consisting of grass silage (0·6 kg/kg DM) and one of four concentrates: barley, barley + urea, barley + rapeseed meal and barley + rapeseed cake. The objective of the present study was to compare omasal canal and duodenal digesta flows. Values for digesta flow into the omasal canal and duodenum were determined using a triple-marker method based on Co-EDTA, Yb-acetate and indigestible neutral-detergent fibre (NDF) markers. Microbial non-NH3 N (NAN) flow was assessed by purine flow. Microbial samples to determine the bacterial purine: N ratio were harvested from the rumen, omasum and duodenum. Organic matter flow was significantly lower into the omasum than the duodenum, indicating an endogenous organic matter secretion into the abomasum. In contrast, NDF and acid-detergent fibre flows were significantly higher into the omasum indicating digestion of fibre in the omasum. Microbial NAN flows were significantly different (P < 0·001) when estimates were based on bacterial samples harvested from different sites. Differences in total NAN, microbial NAN and dietary NAN flows entering the omasal canal and duodenum were non-significant. The results indicated that the omasal sampling technique provides a promising alternative to the duodenal sampling technique to investigate forestomach digestion in dairy cows and offers an alternative means to study rumen N metabolism.

Abstract: Three Holstein heifers and one nonlactating cow, fitted with ruminal and duodenal cannulas, were arranged in a 4 x 4 Latin square design to determine the effects of degree of fat saturation on ruminal neutral detergent fiber digestion and microbial protein synthesis and to determine whether changes in the efficiency of microbial protein synthesis were related to protozoal populations in the rumen. Corn silage-based diets contained no added fat or 4.85% of diet dry matter as partially hydrogenated tallow, tallow, or animal-vegetable fat. Iodine values of fat sources were 12.8, 50.6, and 109.7 for partially hydrogenated tallow, tallow, and animal-vegetable fat, respectively. Cattle were fed every 2 h and consumed 1.5% of body weight as dry matter daily. Ruminal neutral detergent fiber digestibility was decreased by added fat but was not affected by increasing iodine value. Flows of microbial N and non-NH3-nonmicrobial N to the duodenum were not affected by treatment. Ruminal protozoa concentration decreased linearly as the iodine value of fats increased. The efficiency of microbial protein synthesis was increased and protozoa concentrations tended to decrease when fat was fed. Decreased ruminal protozoa concentration may have decreased intraruminal N recycling. Biohydrogenation of added fat may result in a low ruminal concentration of unsaturated fatty acids when cows are fed frequently, reducing the negative effects of unsaturated fat sources on ruminal neutral detergent fiber digestibility. Protozoa were inhibited by unsaturated fat, but it is not clear if biohydrogenation and frequent feeding lessened inhibition.

Abstract: A study was conducted to determine the effect of the feed intake on the chemical composition of bacteria associated with the solid (solid-associated bacteria; SAB) and liquid (liquid-associated bacteria; LAB) fractions of rumen digesta, the digestive passage kinetics and their relationships. Whole rumen contents were sampled after a period of continuous infusion of 15NH3 from four ruminally-cannulated wethers provided successively with a hay-concentrate diet (2 : 1 w/w on a DM basis) at two rates of feed intake: 40 and 80 g DM/kg body weight 0.75. SAB had a higher content of organic matter and total lipids (P < 0.001) and a similar N content as compared with LAB. The concentration of purines and 15N was lower (P = 0.011 and P < 0.001 respectively) in SAB than LAB, whereas the opposite was observed for the concentration of amino acids (mg/g DM; P = 0.031). An increase in feed intake produced an increase in the N (P = 0.034) and purine (P = 0.066) concentrations in bacteria and a decrease (P = 0.033) in their amino acid concentrations. Significant increases of rumen outflow rates of liquid and particles were also observed with increased feed intake. Rates of rumen outflow showed positive and negative linear relationships (P < 0.001) with the purine : N ratio and the proportion of amino acid on total N of bacteria respectively. SAB contained significantly higher proportions of leucine, isoleucine, lysine and phenylalanine and lower proportions of alanine, methionine and valine than LAB. The increase in feed intake also induced significant changes in the amino acid profile of bacteria, increasing arginine and methionine and decreasing alanine and glycine proportions. Results show that the outflow rate of rumen contents is a major factor in determining the proportion of nucleic acids and protein in rumen bacteria and explains some of the differences observed between LAB and SAB.

Abstract: The uptake of volatile fatty acids (VFAs) from bacterial fermentation of forage in the rumen is enhanced by the presence of papillae which greatly increase the surface area of the mucosa of the rumen. The degree of papillation, expressed as the surface enlargement factor (SEF), seems to be closely related to the level of microbial activity and the rate of production of VFAs in the rumen. In several species of wild ruminants the SEF decreases markedly in winter, apparently in response to a decrease in the quality and availability of forage and also, presumably, in the level of ruminal microbial activity. Contrary to expectation, however, no reduction in the rate of production of VFAs in winter has been detected in semi-domesticated reindeer at natural pasture in northern Norway. We investigated the body mass, the composition and quality of the diet and the morphology of rumen papillae in adult female reindeer free-living at natural pasture. Animals were slaughtered in matched aged groups of nine on four occasions: in autumn (September) and winter (November, February and March). The composition and quality of the diet was determined by morphological and chemical analysis of plant fragments recovered from the rumen. The carcass mass of the animals did not differ significantly between collections. The animals ate vascular plants and lichens from 37 different genera. The composition of the diet varied little between months except for the inclusion of a substantial proportion (25.8% of fragments) of lichens in March. The mean density of rumen papillae increased from 55.6 papillae/cm2 in September to 75.7 papillae/cm2 in March (P < 0.001). All other parameters, including the length and perimeter of the papillae and the SEF of the rumen, were lower in March compared with September. However, the mean SEF increased from 8.8 in February to 10.6 in March (P < 0.05), indicating increased ruminal fermentation in late winter. We propose that the increase in the SEF in March might be associated with the increase in the proportion of lichens in the diet. Lichens are highly digestible in reindeer but do not score highly in conventional analyses of diet quality owing to the unusual chemical structure of the structural carbohydrates of which they are composed.

Abstract: A metabolism trial was conducted to evaluate the effects of supplying a yeast culture containing Saccharomyces cerevisiae (Levucell) and monensin to sheep, on ruminal fermentation and digestibility of diets. Four Suffolk sheep (30 kg BW) with ruminal cannula were used in a Latin Square design, where treatments were control (C), 1 g/day of Levucell (L, 20 10 9 CFU/g), 25 mg/ day of monensin (M) and a combination of L and M. Additives were dosed directly into the rumen. The diet was based on alfalfa hay (50%) and a concentrate containing sorghum grain (60%), molasses (24%), urea (2%) and soybean meal (14%). Digestibility of dry matter, neutral detergent fiber, and dry-matter intake were not affected (p > 0.05) by treatments. The ionophore alone or in combination, reduced (p < 0.05) the molar proportion of acetate from71.2 to 66.2, and increased propionate from18.6 to 24.4 without any effect on butyrate. Ruminal protozoa counts (organisms 10 4 ) were greater (p < 0.05) in the control group (69.4) than with feed additives (15.9‐39.7). No effects were detected in ruminal pH. Monensin and Ma L increased propionate proportion, but no effects was observed with S. cerevisiae alone. # 2000 Elsevier Science B.V. All rights reserved.

Abstract: The current experiment was conducted to study the effect of different doses of tannic acid, a hydrolysable tannin, on ruminal degradation and post-ruminal digestion of treated soya bean meals (SBM) in sheep. Samples of SBM were prepared by spraying 100 g SBM with 100 ml distilled water containing 0, 1, 5, 10, 15 or 25 g of commercial tannic acid (So, S TA1 , S TA2 , S TA3 , S TA4 and S TA5 , respectively). Three ruminally cannulated ewes, that had never consumed tannic acid previously, were used to determine in situ degradability of tannic acid-treated SBM. Intestinal digestibility of protein remaining after 16 h rumen incubation was estimated in vitro. Extent of rumen degradation of SBMs was significantly (P < 0.05) affected by the tannic acid treatment. All doses of tannic acid used in this experiment, even the lowest one (S TA1 ), significantly decreased the extent of N degradation but only doses higher than that used to treat S TA3 reduced the extent of DM degradation. This reduction in the extent of DM and N degradation was mainly due to a marked decrease in the immediately degradable fraction (a), which was observed in all treated SBM, and to a lower rate of degradation (c), observed in meals S TA3 , S TA4 and S TA5 , Intestinal digestion of the non-degraded protein was decreased (P < 0.05) by treatment with the two highest doses of tannic acid (those used to treat meals S TA4 and S TA5 ). It was therefore concluded that tannic acid can exert a negative effect both on rumen degradation and on intestinal digestion of SBM, this effect being clearly dependent on the dose used to treat the SBM.

Abstract: SUMMARY A study on the use of quebracho tannins as chemical additives was carried out at the Spanish Council for Scientific Research, Leo! n, Spain during 1998 by conducting two experiments. In the first experiment, three ruminally cannulated ewes were used to determine in situ degradability of soya bean meals (SBM) treated with dierent doses of quebracho tannin. Samples were prepared by spraying 100 g SBM with 100 ml distilled water containing 0, 1, 5, 10, 15 or 25 g of commercial quebracho powder (S ! ,S Q" ,S Q# ,S Q$ ,S Q% and S Q& , respectively). Intestinal digestibility of non-degradable protein was estimated in vitro. The rapidly degradable protein fraction of all quebracho treated soya bean meals was dierent (P!0‐05) from the non-treated SBM (S ! :0 ‐154), with values ranging from 0‐032 to 0‐133. S Q% and S Q& showed lower fractional rates of degradation of the protein than S ! (0‐042 and 0‐046 v .0 ‐082, respectively). By contrast, in vitro digestibility of the non-degradable protein was not significantly aected by the treatments imposed, with the exception of treatment with the highest dose of quebracho tannin in which intestinal digestion was reduced (0‐939 v .0 ‐826 for S ! and S Q& , respectively. P!0‐05). In the second experiment, ten ruminally cannulated ewes were used to examine the eect of a daily dosing of quebracho tannin into the rumen on the degradation of the quebrachotreated SBM. Long-term dosing of quebracho tannin did not increase the ability of the rumen microbes to degrade tannin treated SBM. It was therefore concluded that quebracho tannins could be used as chemical additives for improving the digestive utilization of protein-rich feeds in sheep.

Abstract: Rumen microbial degradation is an important route for detoxification of secondary plant compounds encountered in the diets of free-grazing ruminants. Exposure to diets containing particular secondary plant compounds can lead to increased rates of secondary compound degradation in the rumen. An experiment was conducted to determine whether rumen adaptation to oxalic acid would influence the diet selection of goats offered choices between plant species differing in their oxalic acid content. Twelve adult female goats were divided into two groups of six animals each. One group received a daily oral dose, in gelatin capsules, of 0.6 mmol oxalic acid/kg live weight per d throughout the experiment while the other group received placebos consisting of empty gelatin capsules. After an adaptation period of 8 d, the animals were allowed to graze a mixture of spinach (rich in oxalic acid) and cabbage (low in oxalic acid) for 7 h/d on two consecutive days per week during four consecutive 1-week periods. Intervening days were spent on grass pasture. Diet composition and intake were measured using cuticular wax n-alkanes as internal markers. Results showed that adapted goats included a higher proportion of spinach in their diet (P < 0.05) although absolute intakes of spinach were the same for the two groups. Goats in the oxalic-acid-adapted group consumed less cabbage than control animals (P < 0.05) suggesting that adaptation to oxalic acid at the rumen level may have interfered with detoxification of cabbage-derived secondary plant compounds. Voluntary intake increased progressively through the four experimental periods (P < 0.001) with a tendency for higher intakes among control than among adapted animals (P < 0.1). The experiment demonstrates how differences in the rate of degradation of secondary plant compounds may influence diet selection in ruminants.

Abstract: Agarwal, N., Agarwal, I., Kamra, D.N. and Chaudhary, L.C. 2000. Diurnal variations in the activities of hydrolytic enzymes in different fractions of rumen contents of Murrah buffalo. J. Appl. Anim. Res. 18: 73–80. The hydrolytic enzymes like carboxymethylcellulase, α-amylase, xylanase, microcrystalline cellulose and filter paper degrading activities were estimated in various fractions of rumen contents of Murrah buffalo. About 80–92% of the enzyme activities were associated with the particulate material, while only a negligible portion (1–4%) was present as extracellular fraction in the liquid portion of rumen contents. Rest of the activities (8–15%) were associated with freely suspended microbial cells in the liquid portion of the rumen contents. Maximum activities of carboxymethylcellulase, α-amylase, xylanase and micro-crystalline cellulase were observed at 2h post feeding while in the case of filter paper degrading activity, there was no difference in the activities in the first 4 hours of of...

Abstract: Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium moniliforme and F. proliferatum. Little is known of its metabolic fate after oral ingestion in ruminants, but these animals are reported to be tolerant towards FB1. The metabolism of this mycotoxin was evaluated following incubation (1 μg/ml) in ruminal fluid for up to 72 h, in the presence or absence of alfalfa as a substrate for microbial growth, using a model rumen (sealed flask, anaerobic conditions, exclusion of light, gentle agitation, 39°C). The decrease in FB1 concentration and the production of short-chain fatty acids were determined. FB1 had no effect on SCFA production. After 72 h incubation, FB1 depletion was 12% and 18% in samples with and without alfalfa, respectively. No hydrolysed metabolites (aminopolyols or aminopentol) were detected. These results indicate that FB1 is poorly metabolized in the rumen and suggest that such metabolism is not the cause of the tolerance to this toxin displayed by ruminants.

Abstract: The diversity and population densities of facultative anaerobic bacteria with the capacity to hydrate oleic acid and linoleic acid in the rumen of sheep and dairy cows were determined. The screening of representative colonies, from rumen fluid plated aerobically on a range of agar media, revealed that sheep rumen fluid contained hydration-positive strains of Streptococcus, Staphylococcus, Enterococcus, Lactobacillus and Pediococcus, whereas cow rumen fluid contained hydration-positive strains of Streptococcus, Lactobacillus and Staphylococcus. Mean counts of facultative anaerobic bacteria in sheep and cattle rumen were log10 7.29 and log10 6.40, respectively, and were independent of diet. Approximately 56% of facultative anaerobic bacteria were able to hydrate oleic and/or linoleic acid in anaerobic broth culture. For both sheep and cows, the most numerous hydration-positive isolates were strains of Strep. bovis. The results, which are the first to show that pediococci have the capacity to hydrate unsaturated fatty acids, suggest that lactic acid bacteria are the major unsaturated fatty acid hydrating bacteria in the rumen.

Abstract: A method for the preparation of fatty acid calcium salt products in which an admixture is formed of reactive ingredients consisting of (a) a C10-C22 fatty acid mixture having greater than about 45 weight % of the C10-C22 fatty acid content in the form of fatty acid glycerides, and (b) from about 10 to about 30 % of the total admixture weight of calcium oxide. Water is then added to the admixture in an amount between about 10 % and about 100 % by weight relative to the amount of calcium oxide; and the admixture is then heated to a temperature at which the fatty acid glycerides hydrolyze to form fatty acid calcium salts. Rumen bypass feed supplements are also disclosed, as well as ruminant feeds containing the feed supplements and processes for supplying the feed supplements to ruminant animals.

Abstract: The short-term actions of Lavandula officinalis and Equisetum arvense dry extracts, and of isoquercitrin, flavonoid present in Equisetum arvense, on in vitro fermentation by rumen microbes were studied in batch culture. The orchard grass hay:barley ratios in the three experimental diets were 100:0, 75:25, 50:50 on a DM basis. The production rates of all volatile fatty acids except isobutyrate were strongly influenced by the composition of the diet and to a lesser extent, by plant extracts, with significant interactions between both factors. When hay was the only substrate, the addition of L. officinalis and E. arvense enhanced the fermentation rate by 50%, through an increased release of acetate and propionate. On the contrary, with the two other diets, the fermentation rate was strongly lowered by isoquercitrin. Gas outputs were not significantly influenced by plant extracts.

Abstract: To evaluate the effect of crop maturity on digestion of maize silage in the rumen and post-ruminal digestive tract, four multiparous Holstein-Friesian cows fitted with a simple cannula in the proximal duodenum and a rumen cannula were offered four diets in a 4 ✕ 4 Latin-square design. Forage maize (cv. Hudson) was harvested and ensiled at target dry matter (DM) contents of 230, 280, 330 and 380 g per kg fresh weight (FW) to provide a range of starch contents. The mean values for volatile-corrected DM (VCDM) and starch content of the four maize silages as given were 221, 277, 308 and 372 g/kg FW and 173, 257, 328 and 382 g/kg VCDM respectively. Grass silage (GS) containing 250 g VCDM per kg FW was produced from the primary growth of a perennial ryegrass sward. The diets were 8·7 kg DM per day of a dairy concentrate supplement with one of four forage treatments offered ad libitum. The forage treatments were a 3 : 1 DM ratio of maize silage with GS, designated as T23, T28, T33 and T38. Each period lasted 6 weeks with rumen and duodenal samples being taken over 3 days in week 4 and faeces being collected in respiration chambers over 6 days in either week 5 or 6. Milk yield tended to increase with advancing maturity (30·5, 31·8, 32·5 and 32·3 kg/day) but individual treatment differences were not significant. DM intake increased from 19·62 to 21·30 kg/day (P < 0·05) but there were no significant effects on digestibility in the rumen, post-ruminal tract or total tract. Digestibility of neutral detergent fibre in the rumen declined with increasing starch content in the maize silage (P < 0·05) but total digestibility was not significantly affected. Starch intake increased from 3·11 to 5·04 kg/day (P < 0·001), duodenal flow from 0·40 to 0·89 kg/day (P < 0·01) and the amounts digested in the rumen and post-ruminal tract respectively from 2·72 and 0·34 kg/day to 4·16 and 0·71 kg/ day (P < 0·01). However the only significant effect on starch digestibility was a small fall in total digestibility from a mean of 0·981 for T23, T28 and T33 to 0·966 for T38. There were no treatment effects on nitrogen digestion. The molar proportions of acetic acid and n-caproic acid decreased and that of n-butyric acid increased with advancing maturity. It is concluded that the changes in composition of maize silage with increasing maturity result in large increases in the contribution of starch to DM digested in the rumen but only small differences in rumen fermentation. Post-ruminal starch digestion doubles but this is due to the increased starch concentration of the silage rather than major changes in digestion and the amount is small compared with that likely to result from feeding maize grain.