Effect of lactic acid bacteria inoculants on in vitro digestibility of wheat and corn silages.

The aim of the study was to determine the effect of 10 sources of lactic acid bacteria (LAB) on dry matter digestibility (DM-D) and neutral detergent fiber digestibility (NDF-D), in various combinations with starch, in vitro. The soluble starch represented a concentrate feed, whereas silage represented feeding only roughage. The DM-D and NDF-D were determined after 24 and 48 h of incubation to represent effective (24 h) and potential (48 h) digestibility. Addition of LAB was both by direct application of the inoculants to rumen fluid (directly fed microbials) and by the use of preinoculated silages. For each feed combination, tubes without added LAB served as controls. The results indicate that, overall, some LAB inoculants applied at ensiling or added directly to the rumen fluid had the potential to increase the DM-D and NDF-D. The major significant inoculant effect on NDF-D was obtained after 24 h of incubation, whereas the effect after 48 h was mainly nonsignificant. The effective inoculants seemed to minimize the inhibitory effect of the starch on NDF-D within 24 h, perhaps by competition with lactate-producing rumen microorganisms.

Composition and in vitro digestibility of monosaccharide constituents of selected byproduct feeds.

Nonforage byproduct feeds, including distillers dried grains (DDG), corn gluten feed (CGF), wheat bran (WB), beet pulp (BP), soybean hulls (SH), and dried citrus pulp (DCP), were examined for monosaccharide composition and in vitro digestibility by ruminal liquor. The dicotyledonous feeds (BP, SH, and DCP) contained more galactose, pectin, and NDF glucans and less NDF-xylan and NDF-arabinose than the monocotyledonous ones (DDG, CGF, and WB). The lowest values of lignin were found in CGF, SH, and DCP. Digestibility of total carbohydrate was around 90% in CGF, DCP, BP, and SH and around 80% in DDG and WB. Digestibility of total NDF polysaccharides was 86% in CGF and SH, 78--84% in DDG, DCP, and BP, and 56% in WB. In all byproducts, digestibility of NDF glucose and arabinose was higher than that of NDF xylose and uronic acids.

Digestibility in lactating cows of diets containing whole Pima treated with sodium hydroxide versus Akala or Pima cottonseed.

This study examines the effect of NaOH treatment on the nutritive value of Pima cottonseed for lactating cows. Treatment of Pima cottonseed with NaOH increased the extent of dry matter (DM) and neutral detergent fiber in vitro digestibility. Three groups of cows were fed 3 similar total mixed rations (TMR) differing only in the type of cottonseed fed, either whole linted Akala, whole unlinted Pima, or whole Pima treated with 4% NaOH (T-Pima). Dry matter and organic matter (OM) intakes of Akala and Pima TMR were similar and tended to be lower compared with cows fed T-Pima. This was reflected in similar intake of crude protein and lipids by cows fed the 3 TMR. Digestibility of DM, OM, and crude protein were similar in cows fed Pima and T-Pima diets, and slightly higher in cows fed the Akala TMR. Lipid digestibility was highest in cows fed Akala TMR, whereas cellulose and NDF digestibility were lowest in Pima TMR. In the 3 TMR, there was a large gap between the high values of "digestibility of intact seeds" and actual in vivo digestion of DM and OM. Similar yields of milk and milk protein were obtained in cows fed the Akala and Pima TMR, whereas higher yields of milk, milk protein, milk fat, and 4% fat-corrected milk were found in the T-Pima cows. Similar efficiency of DM intake for fat-corrected milk production was achieved by cows fed the 3 TMR.

Fate of digesta ribonucleic acid in small intestine of sheep.

A new approach for measurement of ribonucleic acid is based on extraction of ribonucleic acid by combined action of a detergent and high speed homogenization followed by precipitation of ribonucleic acid with cadmium +2 ions and its subsequent measure with orcinol. Disappearance of digesta ribonucleic acid flowing along the small intestine was measured in six rams, each equipped with three T-shaped cannulas that were placed in six sites of the small intestine. Chromic oxide was a marker to measure rate of flow of digesta. Net disappearance of ribonucleic acid was completed 7 m from the pylorus, amounting to 83.9% of the quantity which entered the duodenum. About 50% of the net degraded ribonucleic acid disappeared in the 1st m of the small intestine.

Monosaccharide digestibility by dairy cows fed diets high in concentrate and containing alfalfa silages.

Alfalfa was ensiled by the conventional wilting process or as a mixture of 70% fresh alfalfa plus 30% wheat straw treated with SO2. The effects of these silages on the digestibility of monosaccharide constituents of the TMR by dairy cows was examined. Ten cows in early lactation were divided into two groups of 5 that had similar performance data at the onset of the experiment. Cows were fed for ad libitum intake for 28 d a TMR composed of 70% concentrates, 15% alfalfa hay, and 15% silage. The alfalfa silage had lower glucose, xylose, and total carbohydrates than the silage of alfalfa plus wheat straw treated with SO2. Digestibilities of DM (70 to 71%), OM (72%), and total carbohydrate (83%) were similar in the two TMR. The digestibilities of NDF carbohydrate for both TMR were similar. Regardless of treatment, NDF glucose was more digestible than NDF xylose and NDF uronic acid and less digestible than NDF arabinose, galactose, and mannose. The digestibility of total neutral detergent-soluble carbohydrates was 89% in both TMR, but those of neutral detergent-soluble xylose, mannose, and galactose were lower than those of neutral detergent-soluble glucose, arabinose, and pectin.

Digestion of cell-wall monosaccharides of ryegrass and alfalfa hays by the ruminal bacteria Fibrobacter succinogenes and Butyrivibrio fibrisolvens.

The ruminal bacteria Fibrobacter succinogenes strains S85 and BL2 were grown in monocultures or in coculture with strain D1 of Butyrivibrio fibrisolvens, and the solubilization of ryegrass and alfalfa cell walls (CW) and digestion of CW monosaccharides were measured. Fibrobacter succinogenes monocultures and cocultures with B. fibrisolvens D1 degraded 58-69% of ryegrass CW, solubilizing 67-78% of CW glucose, 65-71% of CW xylose, 69-75% of hemicellulose, and 68-77% of total CW monosaccharides. When grown on alfalfa CW, those cultures degraded 28-39% of alfalfa CW, solubilizing 42-58% of CW glucose, 30-36% of CW xylose, and 37-45% of hemicellulose. With respect to both substrates, F. succinogenes strains solubilized CW carbohydrates better than did B. fibrisolvens D1. Complementary interaction between B. fibrisolvens D1 and the F. succinogenes strains was identified with respect to the utilization of some solubilized carbohydrates, but not with respect to the extent of CW solubilization, which was determined mainly by the F. succinogenes strains. For both substrates, utilization of cellulose by F. succinogenes monocultures was high (96-98%), whereas that of hemicellulose was lower (24-26% in ryegrass and 49-50% in alfalfa). Under scanning electron microscopy, F. succinogenes bacterial cells attached to and colonized on CW particles were characterized by the appearance of protuberant surface structures that we have identified as "polycellulosome complexes."

Digestibility by sheep of total and cell wall monosaccharides of wheat straw treated chemically or chemically plus enzymatically.

Digestibility of total and cell wall monosaccharides was studied in sheep with ruminal and duodenal cannulae and fed three wheat straw-based diets: untreated, treated with SO2, treated with SO2 plus cellulase and a fourth diet, which was barley-based. In untreated straw, 90% of total monosaccharides are cell wall bound. Sulfur dioxide treatment solubilized mainly the matrix sugars, reducing their content from 22.1 to 9.76 g/100 g DM in straw. The combined treatment (SO2 plus cellulase) solubilized most of the cell wall sugars so that the most of the cell wall sugars so that the residual cell wall contained only 31% of the total sugars originally present. Treatments increased total monosaccharide digestibility from 63 to 90% and of cell wall monosaccharides from 58 to 84 and 88%. The proportion of digestible monosaccharides degraded in the rumen was increased up to 95% by the treatments. Total monosaccharide digestibility was similar in both treated straws, but degradation of the residual cell wall monosaccharides was somewhat lower in the combined treatment compared with the SO2-treated straw.

The digestion of total and cell wall monosaccharides of alfalfa by sheep.

The effect of dietary starch on the digestibility of total and cell wall (CW) monosaccharides of alfalfa hay, was examined in sheep equipped with rumen and duodenal cannulas. The experiment consisted of two treatments. In one of them the sheep received 803 g dry matter (DM) of alfalfa hay (A), and in the second, 242 g DM alfalfa hay + 553 g of a purified starchy concentrate mixture (A + conct ). Rumen volume was not significantly different between treatments, but the mean retention time of markers in the rumen was shorter, and their rate of passage was faster in the A treatment than in the A + conct treatment. The overall digestibility of total CWs and CW constituents was not depressed in the A + conct treatment, the values for total CW being: 58.2 and 58.9% for the A and A + conct treatments, respectively. However, the digestion of CW monosaccharides in the rumen of the A + conct sheep was reduced despite the 100% longer retention time of particles in the rumen. The complimentary digestion of the potentially digestible CW monosacharides has been completed in the hindgut. The digestibility of CW glucose was higher (72%) than that of xylose (57%) in both treatments. CW glucuronic acid was the least digestible constituent (40%). Soluble uronic acids, representing the pectic material, were highly digestible (86.5% in A), but this was reduced to 80.3 in the A + conct treatment.

Performance of high producing dairy cows offered drinking water of high and low salinity in the Arava desert.

The effect of supplying high producing Israeli Holstein cows with desalinated or salty water on milk composition and production was examined in the Arava desert of southern Israel. Daily water consumption of cows offered desalinated water was higher by 10.6 L than that of the group offered salty drinking water; DMI was similar for the two groups. Daily production of milk and 3.5% FCM was higher for the cows receiving desalinated water than for the cows receiving salty water; 35.2 versus 33.1 kg and 31.6 versus 29.8 kg, respectively. The percentage of protein in milk and the daily protein production were higher for the cows receiving desalinated water than for the cows receiving salty water: 2.89% and 1.01 kg versus 2.84% and .93 kg, respectively. The percentage of milk fat and the daily fat production were higher for the cows receiving desalinated water. These results indicate that water salinity negatively affects milk production. Improvement of water quality by desalination increased production of milk and milk constituents.

Digestibility by dairy cows of monosaccharide components in diets containing wheat or ryegrass silages.

Digestibility by dairy cows of monosaccharide constituents in rations based on wheat or ryegrass silage as the sole roughage component was examined in this study. Six cows in early lactation were divided into two groups with similar performance data at the onset of the experiment and fed for ad libitum intake for two 28-d periods in a change-over design. Cows were fed a TMR of concentrate plus either wheat or ryegrass silage, contributing 19% of silage NDF in the TMR. Digestibilities of ration DM and total carbohydrate were 3.3 and 3.1 percentage units higher, respectively, for ryegrass than for the wheat silage. The digestibility of ration NDF was 64.1% in ryegrass silage and 49.6% in wheat silage. The trend was similar for digestibilities of NDF monosaccharide components. Ration NDF carbohydrate digestibility was 74.8% for ryegrass silage versus 59.7% for wheat silage. For both TMR, the digestibility of NDF xylose was lower than that for NDF glucose and arabinose. Based on carbohydrate digestibility, ryegrass silage can be considered to be a successful roughage alternative for wheat silage in TMR for lactating cows.

Availability of macro and microelements from edible domestic waste fed to sheep.

Young Awassi rams fitted with rumen cannula and T-shaped cannulas in duodenum and terminal ileum were used to study net absorption of calcium, phosphorus, magnesium, zinc, manganese, and copper from edible domestic waste in comparison with a conventional concentrate diet. Mean net absorptions (% of intake) of calcium, phosphorus, and magnesium from edible domestic waste and control diets were 15.3, -.9; 54.4, 37.0; and 46.4, 58.8. The small intestine was the major site for calcium and phosphorus absorption and the rumen for absorption of magnesium. Net absorption of zinc, manganese, and copper was low in both diets, probably as a result of excessive supply and low physiological demands. There was a net gain of manganese and copper and a net loss of zinc in the stomachs. In addition to potential for energy and protein, edible domestic waste supplies macro and microelements for ruminants, and thus, it can be regarded as a complete concentrate diet.

The effect of partially replacing urea nitrogen with protein N on N capture in the rumen of sheep fed a purified diet.

1. The influence of replacing 10% of the urea nitrogen in a purified diet with casein, maize gluten or white fish meal on the efficiency of conversion of dietary-N into microbial N was examined using sheep equipped with rumen fistulas and duodenal re-entrant cannulas. 2. Total nitrogen (TN), non-ammonia nitrogen (NAN) and amino acid nitrogen (AAN) flowing to the proximal duodenum were significantly higher (P smaller than 0.05) when maize gluten was added to the diet, and this appeared to be due to an increased efficiency of microbial protein production. 3. Pepsin secretion was not significantly different between treatments and the daily amount of pepsin N flowing to the proximal duodenum was very small (40-53 mg). The peak of pepsin activity in duodenal digesta was reached 6-8 h after feeding. 4. The possible practical implications of the results are discussed.

Sulphur and cystine incorporation into rumen microbial protein.

1. In three series of experiments, Na235so4 was infused into the rumen of sheep consuming a variety of diets. The specific activity of the sulphur in the rumen H2S pool, rumen bacteria and of the S in bacterial cystine were determined. 2. The results showed that, depending upon the diet, the proportion of total sulphur and cystine sulphur in rumen bacteria originating in the rumen H2S pool could be as low as 0-557 and 0-280 respectively.

Solubility and net exchange of calcium, magnesium and phosphorus in digesta flowing along the gut of the sheep.

1. The changes in the solubility of calcium, magnesium and phosphorus in digesta flowing along the intestinal tract and the net movement across the intestinal wall of these elements were determined in six rams, each equipped with three T-shaped cannulas; cannulas were placed in a total of six different sites of the small intestine. Cr2O3 was used as a marker substance to measure the rate of flow of the digesta. 2. The concentrations of soluble Ca, Mg and P decreased as digesta moved along the intestine. TheMgreatest fall in soluble Ca occurred after the first 3 m of the intestine, while a significant decrease in soluble Mg was found only at 15 and 25 m from the pylorus. The concentration of soluble P in digesta decreased until the 7 m site and then remained stable. In the faeces, the level of soluble Mg was approximately 4 times higher than, and that of Ca equal to, the levels of Mg and Ca found in digesta flowing through the upper intestine. Unlike Ca and Mg, a very low concentration of soluble P was found in the faeces. 3. In the duodenum, 84, 78 and 62% of the total Ca, Mg and P respectively were soluble, whereas in the digesta flowing through the terminal ileum the corresponding values were 3-2, 7-2 and 19% for Ca, Mg and P respectively. 4. The forestomachs and the colon were found to be the main sites of g net absorption; 1-12 mmol/h was apparently absorbed from the stomach and 1-05 mmol/h from the colon. The supper small intestine (1-3 m from the pylorus) appeared to be the major site of Ca and P absorption. 5. In the last 10 m of the small intestine, considerable amounts of minerals were secreted; 4-70, 0-96 and 1-85 mmol Ca, Mg and P/h respectively were added to the digesta flowing between 15 and 25 m from the pylorus. The effect of the increase in the pH of digesta along the small intestine on the solubility of these minerals is discussed.

Effect of protein infused into sheep duodenum on activities of pancreatic proteases in intestinal digesta and on the absorption site of amino acids.

The effect of increasing the flow of protein amino acids to the small intestine on the activities of pancreatic proteases and on the absorption site of amino acids was examined in sheep equipped with intestinal cannulas at 0.05, 11 and 25 m from the pylorus. A single concentrated diet providing 85.1 g of protein amino acids/day was fed throughout the experiment. During period 1 this was the only source of protein. During period 2, a suspension of casein was infused into the duodenum through the 0.05-m cannula at a rate of 100 g/day, which supplied to the small intestine a total of 177 g amino acids/day. In period 1, 56.7 g of amino acids was absorbed per day along the entire small intestine, and 85% of it was absorbed in the anterior 11 m. Of the 143 g of amino acids absorbed per day during period 2, 63% was absorbed in the anterior 11 m. Ninety-four percent of the infused casein was absorbed. Increasing the flow of amino acids to the small intestine of sheep from 85 to 177 g/day resulted in an overall elevation in the activities of chymotrypsin, carboxypeptidase A and trypsin at the 11-m site but not the 25-m site. The greatest increase was obtained with chymotrypsin: 119 and 114% for the specific and total activities, respectively, and the least with the trypsin: 38 and 36% for the specific and total activities, respectively.

Apparent digestibility of minerals by lactating cows from a total mixed ration supplemented with poultry litter.

Apparent digestibility of minerals by lactating cows from a multiple-component, conventional Israeli TMR (control) and from a TMR containing 10% poultry litter (DM basis) was examined. Ten cows in early lactation were divided into two groups of similar performance (39 kg of milk/d) and fed for ad libitum intake the two TMR for 28 d. Poultry litter contributed, as a percentage of total requirements, 44.4% of Ca, 41.0% of P, 32.0% of S, 22.8% of Mg, and 25.9% of K. Apparent digestibility of the macroelements was higher for cows fed the TMR supplemented with poultry litter than for those fed the control TMR. Apparent digestibility of the control TMR was 22.3% for Ca, 29.4% for Mg, 39.1% for P, and 62.2% for S; the apparent digestibility of the treatment TMR was 30.1% for Ca, 45.6% for Mg, 45.3% for P, and 65.6% for S. Poultry litter contributed the entire requirements of Zn, Mn, and Co; 56% of Cu; and 32% of Se. The apparent digestibility of the control TMR was 15.6% for Cu, 39.6% for Zn, 8.51% for Mn, 42.8% for Co, and 41.6% for Se, and the apparent digestibility of the treatment TMR was 27.9% for Cu, 54.0% for Zn, 17.8% for Mn, 37.0% for Co, and 63.9% for Se. Poultry litter is a good source of macro- and microelements for lactating cows and, at 10% of the TMR, could ensure against mineral deficiencies.

The ileum of the sheep as a site of protein digestion.

1. In order to study the ability of the ileum of the sheep to digest and absorb protein, casein or gluten were infused into the intestine of rams through cannulas inserted at distances of 0-05, 7, 9 and 15 m from the pylorus. Amounts of casein or gluten containing 10-20 g nitrogen were infused during 24 h, in animals given a low-N diet. 2. N balance was negative during the preliminary period when no infusion was given; infusion of casein or gluten increased the daily N retention to 5-15 g. 3. Infusion of proteins into the intestine did not induce an increased activity of pancreatic proteases in digesta withdrawn from the lower part of the intestine. 4. The increased N retention after the infusion of proteins into the lower part of the intestine indicates a considerable capacity of this section of the intestine to digest and absorb proteins.

Digestibility by dairy cows of monosaccharide components in diets containing either ground sorghum or sorghum grain treated with sodium hydroxide.

Five cows in midlactation and equipped with ruminal and abomasal canulas were fed two isonitrogenous diets composed of 46% sorghum grain, either ground or treated with 4% NaOH, plus 39% wheat silage and 15% supplements. The DMI were 16.3 and 15.8 kg/d for cows fed the diets containing ground sorghum and treated sorghum, respectively. The digestibility of NDF polysaccharides was higher for cows fed the treated sorghum, but the digestibility of neutral detergent soluble alpha-glucans (starch) was higher for cows fed ground sorghum. Digestibility of total carbohydrate was 79% for cows fed the diet containing ground sorghum and 67% for cows fed the diet containing sorghum treated with NaOH. Ruminal pH was higher in cows fed the diet with treated sorghum, but total ruminal VFA concentration was higher in cows fed the diet containing ground sorghum. Profiles of individual ruminal VFA and NH3 concentration were similar for both treatments. Flow of NAN through the abomasum of cows fed ground sorghum was higher than that of cows fed the sorghum treated with NaOH, and N absorption in the intestine followed a similar trend. The data indicated a possible advantage for dairy cows fed ground sorghum than for those fed grain treated with NaOH.

Invited review: adhesion mechanisms of rumen cellulolytic bacteria.

We divided the adhesion process of the predominant cellulolytic rumen bacteria Fibrobacter succinogenes, Ruminococcus flavefaciens, and Ruminococcus albus into four phases: 1) transport of the nonmotile bacteria to the substrate; 2) initial nonspecific adhesion of bacteria to unprotected sites of the substrate that is dominated by constitutive elements of bacterial glycocalyx; 3) specific adhesion via adhesins or ligands formation with the substrate, which can be dominated by several bacterial organelles including cellulosome complexes, fimbriae connections, glycosylated epitopes of cellulose-binding protein (CBP) or glycocalyx, and cellulose-binding domain (CBD) of enzymes; 4) proliferation of the attached bacteria on potentially digestible tissues of the substrate. Each of the phases and its significance in the adhesion process are described. Factors affecting bacterial adhesion are described including: 1) factors related to bacterial age, glycocalyx condition, and microbial competition; 2) factors related to the nature of substrate including, cuticle protection, surface area, hydration, and ionic charge; and 3) environmental factors including pH, temperature, and presence of cations and soluble carbohydrate. Based on the information available from the literature, it appears that each of the predominant rumen bacteria--F. succinogenes, R. flavefaciens, and R. albus--has a specific mechanism of adhesion to cellulose. In F. succinogenes, both the glycosidic residues of the outer membrane CBP and especially of the 180-kDa CBP, and the distinct CBD of EG2 EGF and Cl-stimulated cellobiosidase, may play a role in the adhesion to cellulose. No direct evidence, except scanning electron microscopy observations, yet supports the existence of either cellulosome complex or fimbriae structures involved in the adhesion mechanism of F. succinogenes. At least two mechanisms, cellulosome-like complexes and carbohydrate epitopes of the glycocalyx layer are involved in the specific adhesion of R. flavefaciens to cellulose. Ruminococcus albus possesses at least two mechanisms for specific adhesion to cellulose: a cellulosomal-like mechanism, and a CbpC (Pil)-protein mechanism that probably involves the production of fimbrial-like structures. Indirect and direct studies suggested that carbohydrate epitopes of CBPs and CBD epitope of cellulases may also be involved mostly in the nonspecific phase of adhesion of R. albus.

Effects of replacing roughage with soy hulls on feeding behavior and milk production of dairy cows under hot weather conditions.

Two total mixed rations (TMR) containing different proportions of roughage neutral detergent fiber (NDF) were fed to lactating cows under Israeli summer conditions, and the effects on feeding behavior and milk production were measured. Forty-two lactating cows were divided into 2 groups fed ad libitum a TMR containing either 18% NDF of roughage origin (control group) or only 12% roughage NDF, in which the corn silage component (16.5% of dry matter [DM]) was replaced with soy hulls (experiment group). This and additional adjustments in TMR were reflected in higher net energy for lactation and in vitro digestibility of the experimental TMR. Cow behavior was investigated at the feeding lane during June 2001; about 11,000 cow visits were analyzed. Feed intake per meal and average meal duration were significantly higher in the experiment group (1.51 kg of DM per meal and 12.1 min per meal, respectively) as compared with the control group (1.22 kg of DM per meal and 9.47 min per meal, respectively). However, number of meals per day recorded in the feeding lane was significantly higher in the control group (21.0 vs. 16.6 meals/d per cow). Distribution of meals and feed intake along the day depended more on management practices, such as milking and feed dispensing times, than on feed composition or weather conditions. These differences between groups were expressed in similar daily eating duration (approximately 200 min), and because the rate of feed consumption was similar for both treatments (approximately 127 g DM/min), the daily average DM intake was also similar (25.0 to 25.7 kg). However, NDF intake was higher in the experiment group. Consequently, the average milk yield was higher in the experimental group, and production of milk fat, 4% fat-corrected milk, and economically corrected milk were significantly higher in the experiment group than in the control group. Data imply that the experimental TMR containing only 12% NDF of roughage origin is more suitable for cows under hot climate conditions compared with the control TMR.