Protein degradation in rumen and amino acid absorption in small intestine of lactating dairy cattle fed heat-treated whole soybeans

Four lactating Holstein cows fitted with rumen cannulae and T-type cannulae in proximal duodenum and terminal ileum were used to measure protein degradation in the rumen and amino acid flow and absorption in the small intestine. Soybean meal, whole soybeans, and whole soybeans extruded at 132 and 149 degrees C provided 50% of the protein in diets that contained 51% grain, 36% corn silage, and 13% alfalfa hay (dry matter). Spot samples of digesta were collected from duodenum and ileum during 96 h, and lanthanum was an indigestible marker to estimate flow and digestibility of nutrients. With diaminopimelic acid as a microbial marker, apparent degradations of dietary crude protein in the rumen were 73, 80, 66, and 60% for diets containing soybean meal, whole soybeans, and whole soybeans extruded at 132 and 149 degrees C. Because of the extensive degradation of protein with the raw soybean diet, less total amino acids reached the duodenum, and because of decrease of availability, absorption from the small intestine (g/day) was lowest with this diet. Feeding diets containing extruded whole soybeans increased availability of total essential amino acids in the small intestine compared with diets containing soybean meal and whole soybeans. Absorption from the small intestine (g/day and percent entering) of individual amino acids was generally higher for extruded whole soybean diets.     

Microbial degradation of rice and barley straws in the sheep rumen and the donkey caecum

The chemical composition, intake, digestibility, ultrastructure and microbial degradation of rice straw from Camargue were compared with barley straw. These variables were observed in two different herbivore digestive ecosystems: the sheep rumen and the donkey caecum. The two straws differed essentially in their ash content, which was three times higher in rice, owing to its silica content. Other chemical components were comparable, except a higher phenolic acids‐to‐lignin ratio in rice. Rice straw was better ingested than barley straw. Organic matter and neutral detergent fibre digestibilities were the same in both straws. Dry matter and cell wall disappearances could be adjusted to the exponential modelling equation with lag time, and differed between animals but not between straws. The sheep rumen had a higher extent of degradation, but the donkey caecum had a higher degradation rate. Statistical analysis revealed that cell‐wall components degradation was similar in the two straws except for ferulic acid, which was more degraded in rice straw. Scanning electron microscopy showed important differences in parenchyma degradation, which was much more effective in rice. Copyright © 2003 Society of Chemical Industry     

Enzymic and in sacco methods to estimate rumen degradation of food protein in cattle

BACKGROUND: Two factorial studies compared enzymic and in sacco methods to estimate degradation of ruminant foods. Enzyme degradation (in vitro = enzyme) was determined from the release of leucine‐equivalent amino acid (LA) crude protein (CP) from sunflower meal (SF), maize gluten meal (MG), distillers' dark grain (DG) and field beans (FB) after their separate incubations with Streptomyces griseus enzyme for 0–24 h. In sacco crude protein (CP) degradation of these foods was estimated during washing (0 h) and rumen incubations in fistulated cows for 2–24 h. The LA data were expressed as g LA per either kg of CP (LACP) or acid‐hydrolysable LA (HLA) of each food and compared with in sacco data. RESULTS: These methods showed comparable degradation with time (P < 0.01). The in sacco and HLA were greater than LACP for all foods except MG where in sacco value was either lower or equal to LACP depending upon the incubation time (P > 0.05 or P < 0.05). Conversely, HLA was significantly (P < 0.01) greater than LACP from 2 h onwards. At 0 h, in sacco values were significantly greater than those of enzyme for SF, DG and FB (P < 0.05) but not for MG. The foods differed significantly for degradation constants (a, b, c) in each method (P < 0.05). CONCLUSIONS: Despite variations between in sacco and enzyme estimates for different foods, the relationships between these estimates suggest that the HLA enzyme method has the potential to estimate food degradation. Copyright © 2007 Society of Chemical Industry     

Absorption of tricarballylic acid from the rumen of sheep and cattle fed forages containing trans-aconitic acid

Some forages accumulate high concentrations (< 5% of dry matter) of trans-aconitate, and this acid has been implicated in Mg chelation and the occurrence of grass tetany in ruminants. In vitro experiments have indicated that rumen microorganisms convert trans-aconitate to tricarballylate. The feeding studies described here were conducted to demonstrate absorption of tricarballylate by ruminant animals fed diets similar to those producing grass tetany. When sheep were switched from a diet containing alfalfa (lucerne) (Medicago sativa L.) hay (no detectable trans-aconitate) to wheat (Triticum aestivum L.) and rye ( Secale cereale L.) forage containing 1.52 and 1.37% trans-aconitate, respectively, there was a rapid increase in blood plasma tricarballylate. Trans-aconitate was not detected in the plasma. At 16 h after feeding, plasma tricarballylate concentrations were 0.58.0.08 and 0.48.0.21 mM in sheep fed the wheat and rye forage, respectively. Tricarballylate concentrations remained relatively constant for the remaining 60 h of the experiment. Cattle were fed rye forage one week later, and the concentration of trans-aconitate in the forage had dropped to 0.83% of the dry matter. Once again there was a rapid appearance of tricarballylate in plasma, but the maximum concentration was 0.31.0.05 mM (t = 27 h). When the cattle were removed from the rye forage, there was a linear decline in tricarballylate and none was detected 24 h later. The studies indicated that trans-aconitate is converted to tricarballylate in the rumen and that tricarballylate rather than trans-aconitate is absorbed.     

Evidence of a role for plant proteases in the degradation of herbage proteins in the rumen of grazing cattle

Protein breakdown in the rumen is generally regarded as a two-stage process in which proteases produced by rumen microorganisms cleave plant protein into peptides and amino acids. However, many of the fiber-degrading cellulolytic species in the rumen are not in fact proteolytic, and the proteolytic activity of the entire rumen microbial population is only moderate when compared to the gastric and pancreatic secretions in the abomasum. Moreover, plant cell walls remain largely intact after initial chewing (particularly in cattle), presenting a physical barrier that must be breached prior to their effective colonization. The present study considers the hypothesis that the plant enzymes are at least partly responsible for herbage protein degradation in grazing ruminants. Ryegrass, red clover, white clover, and bird's-foot trefoil were incubated in the presence and absence of rumen microorganisms. The production of volatile fatty acids indicated the level of microbial activity, whereas the relative disappearance of the large subunit of ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco LSU) indicated proteolytic activity. In all incubations, the relative abundance of the Rubisco LSU decreased as the incubation progressed. When rumen microorganisms were absent, low molecular weight peptides (below 20 kDa) accumulated as the incubation progressed. This accumulation was not observed in the presence of rumen microorganisms. Therefore we suggest that the intrinsic plant proteases contribute to the initial stages of proteolysis of grazed herbage.     

Role of rumen fungi in fiber degradation

Anaerobic fungi inhabit the rumen and actively degrade plant cell walls. Rumen fungi produce high levels of cellulases and hemicellulases and are particularly proficient in producing xylanases. These enzymes are regulated by substrate (especially soluble sugars) available to the organisms. Fungi degrade unlignified (i.e., no histochemical reaction for phenolics) plant walls totally, indicating that enzymes are able to hydrolyze or solubilize the entire plant wall. These organisms are better able to colonize and degrade the lignin-containing tissues than are bacteria; phenolics are solubilized but not metabolized from the plant wall by fungi. Anaerobic fungi are unique among rumen microorganisms in that they penetrate the cuticle. Residues after incubation with fungi are physically weaker than those incubated with whole rumen fluid or with rumen bacteria, suggesting that fungi could alter the fibrous residue for easier mastication by the animal. Data indicate that cocultures of anaerobic fungi with methanogenic bacteria stimulate cellulose degradation; other data suggest that fungi are inhibited by certain rumen microorganisms. The interaction of rumen fungi with other organisms in relation to fiber degradation in the rumen requires additional study. Rumen fungi have the potential to degrade the more recalcitrant plant walls in forages, but this potential is not always reached in the rumen.     

Amino acid composition of rumen bacteria and protozoa in cattle

Because microbial crude protein (MCP) constitutes more than 50% of the protein digested in cattle, its AA composition is needed to adequately estimate AA supply. Our objective was to update the AA contributions of the rumen microbial AA flowing to the duodenum using only studies from cattle, differentiating between fluid-associated bacteria (FAB), particle-associated bacteria (PAB), and protozoa, based on published literature (53, 16, and 18 treatment means were used for each type of microorganism, respectively). In addition, Cys and Met reported concentrations were retained only when an adequate protection of the sulfur groups was performed before the acid hydrolysis. The total AA (or true protein) fraction represented 82.4% of CP in bacteria. For 10 AA, including 4 essential AA, the AA composition differed between protozoa and bacteria. The most noticeable differences were a 45% lower Lys concentration and 40% higher Ala concentration in bacteria than in protozoa. Differences between FAB and PAB were less pronounced than differences between bacteria and protozoa. Assuming 33% FAB, 50% PAB, and 17% of protozoa in MCP duodenal flow, the updated concentrations of AA would decrease supply estimates of Met, Thr, and Val originating from MCP and increase those of Lys and Phe by 5 to 10% compared with those calculated using the FAB composition reported previously. Therefore, inclusion of the contribution of PAB and protozoa to the duodenal MCP flow is needed to adequately estimate AA supply from microbial origin when a factorial method is used to estimate duodenal AA flow. Furthermore, acknowledging the fact that hydrolysis of 1 kg of true microbial protein yields 1.16 kg of free AA substantially increases the estimates of AA supply from MCP.     

Effect of diet on protein degrading activity in the sheep rumen

Comparative studies on the effect of diet on ruminal protein degrading activity were made with sheep fed either maize or timothy and with sheep fed either barley or lucerne. In both studies the levels of proteolytic activity and deaminase activity in the rumen, measured as non-protein nitrogen and ammonia production, respectively, during in-vitro incubation of rumen liquor and casein, were higher when cereal was given than when forage was given. The rate of casein degradation after intra-ruminal infusion was also higher with the cereal diets, whereas outflow rate from the rumen was lower. However, with all diets the fractional hydrolysis rate of casein was considerably greater than its fractional outflow rate and the calculated proportion of protein escaping ruminal breakdown was low. The effect of diet on the degradation of the protein of natural feedstuffs was examined by measuring N disappearance when samples of the four feeds and of three protein supplements (soya bean meal, groundnut meal and fish-meal) were incubated in dacron bags in the rumen. In contrast to the findings with casein, the rate of N disappearance for all feedstuffs, except maize which was similar on the two types of diet, was lower when sheep were given cereal than when given forage.     

Determination of in vitro isoflavone degradation in rumen fluid

The aim of this study was to determine the degradation of dietary isoflavones in rumen fluid under 2 feeding regimens. The experiments were performed in vitro using a rumen fluid buffer system. The rumen fluid was taken from cows fed either a hay diet or a concentrate-rich diet (the diet consisted of 34.6% maize silage, 17.6% haylage, 12.8% alfalfa hay, and 35.0% supplemental mixture on a dry matter basis). As a source of isoflavones, 40% soybean extract (Biomedica, Prague, Czech Republic) at levels of 5, 25, 50, and 75 mg per 40 mL of rumen fluid was used. Samples of soybean extract were incubated in triplicate at 39°C for 0, 3.0, 6.0, 12.0, and 24.0 h in incubation solution. The metabolism of daidzein and genistein was faster under concentrate-rich diet conditions. In general, production of equol started after 3 to 6 h of incubation and reached the highest rate after approximately 12 h of incubation regardless of the type of diet or concentration of extract. In most of the experiments, production of equol continued after 24 h of incubation. Generally, equol production was greater under the hay diet conditions. Furthermore, experiments with higher amounts of added soybean extract revealed possible inhibitory effects of high levels of isoflavones on the rumen microflora.     

Fatty acid composition of the fats of the rumen and abomasum of sheep

The fatty acid composition of the abomasum and rumen tissues of 16-week old and 80-week old Romney ewes fed on pasture has been determined. For 16-week old lambs it was comparable to that of the longissimus dorsi of 26-week old lambs. At 80 weeks the rumen lipids showed a highly significant decrease in total saturated fatty acids, myristic acid and lower saturated acids with a corresponding increase in total unsaturated and octadecenoic (oleic) acids. The abomasum lipids showed similar changes. The reduced contents of myristic, lauric and decanoic acids in the lipids of the older animals were consistent with the removal of these acids from the diet. Whereas before weaning the dietary fetty acids are rich in myristic, lauric and decanoic acids, the fatty acids of sheep at pasture comprise mainly linotenic and palmitic acids. Consideration of the results of other investigations suggests that the changes in the fatty acid composition of the lipids of grazing sheep with age observed for the rumen and abomasum tissues may apply to muscle and fatty tissues generally.     

Effect of rumen protozoa on Escherichia coli O157:H7 in the rumen and feces of specifically faunated sheep

The effects of rumen protozoal populations on ruminal populations and fecal shedding of Escherichia coli O157:H7 were evaluated by using specifically faunated sheep. Nine fauna-free sheep (three animals per treatment) were inoculated with Dasytricha spp. (DAS sheep); with mixed population A (PopA) comprising Entodinium spp., Isotricha spp., Diplodinium spp., and Polyplastron spp.; or with mixed population B (PopB) comprising Entodinium spp., Isotricha spp., Dasytricha spp., and Epidinium spp.; six sheep were maintained fauna-free (FF sheep) to serve as controls. Sheep were fed barley silage-based diets, and treatment groups were housed in isolated rooms. Sheep were inoculated orally with 10(10) CFU of a four-strain mixture of nalidixic acid-resistant E. coli O157:H7. Samples of ruminal fluid and feces were collected over 77 days. Polyplastron spp. were detected in only one sheep in PopA, and Dasytricha spp. were detected only once within the PopB cohort. Sheep in the DAS group were 2.03 times more likely (P < 0.001) to shed E. coli O157:H7 than were those in the other three treatments, whereas the PopB sheep were less likely (0.65; P < 0.05) to shed this bacterium. The likelihood of harboring ruminal E. coli O157:H7 also tended (P = 0.06) to be higher in DAS and was lower (P < 0.01) in FF than in other cohorts. Possibly, Dasytricha spp. had a hosting effect, and Epidinium spp. had a predatory relationship, with E. coli O157:H7. Additional study into predator-prey and hosting relationships among rumen protozoa and E. coli O157:H7 is warranted.     

Dietary alteration of particle breakdown and passage from the rumen in lactating dairy cattle

To evaluate the effect of dietary alteration on the rates of ruminal small particle passage or large particle breakdown, six ruminally cannulated Holstein cows 90 d postpartum were used in a 3 X 3 Latin square design. Experimental diets were 1) control: 60% concentrate, 40% corn silage; 2) bicarbonate: 60% concentrate (containing 2% sodium bicarbonate), 40% corn silage; and 3) hay: 60% concentrate, 30% corn silage, and 10% long alfalfa hay on a DM basis. Dry matter intake (kg/d), milk production (kg/d), percentage milk fat, rumination (min/d), ruminal fluid outflow (L/d), small particle (150 to 850 micron) passage rate (%h), and large particle (greater than 4.25 mm) breakdown rate for diets control, bicarbonate, and hay were 20.2, 20.9, 22.4; 26.6, 27.7, 26.8; 3.5, 3.6, 3.2; 405, 350, 370; 167, 184, 185; 6.5, 7.6, 7.4; and 7.2, 6.8, 7.4, respectively. Rumen DM content and digesta particle size were reduced at the end of a 24-h feeding period. Data suggested that small particle passage may be more closely related to ruminal fluid outflow and DM intake than large particle breakdown rate.     

Nitrogenous constituents in the urine of cattle,sheep and goats

Ten samples of urine from dairy cows, five from sheep and four from goats were analysed to assess the distribution of urinary nitrogen (N) among various chemical constituents in order to gain a better understanding of the reactions undergone by urinary N in soil. Total N in the cow urine ranged from 6.8 to 21.6 g N litre^?1, of which an average of 69% was present as urea, 7.3% as allantoin, 5.8% as hippuric acid, 3.7% as creatinine, 2.5% as creatine, 1.3% as uric acid, 0.5% as xanthine plus hypoxanthine, 1.3% as free amino acid N and 2.8% as ammonia. In the sheep urine, total N ranged from 3.0 to 13.7 g litre^?1 of which an average of 83 % was present as urea; creatine accounted for 5.3% of the N; hippuric acid and allantoin both accounted for 4.3%, while each of the other constituents amounted to less than 1% of the total N. The goat urine was similar to the sheep urine but with a lower ratio of creatine to creatinine and a somewhat higher proportion (2.0 %) of the total N as amino acid.     

Ruminal degradation of mountain pastures infested by Euphorbia polygalifolia in cattle and sheep: effect of previous grazing in invaded areas

Six cows and eight ewes were distributed in four paddocks according to a factorial design, 2 species (cattle vs sheep) × 2 grazing managements (grazing in pastures invaded vs non‐invaded by Euphorbia polygalifolia), to study the ability of sheep and cattle to ruminally degrade mountain pastures containing E. polygalifolia, as well as the influence of previous grazing in invaded areas. After a period of 17 days, rumen fluids were collected and used as microbial inoculum to examine in vitro fermentation rates and ruminal parameters of infested and non‐infested pastures. Results on parameters of gas production, extent of degradation, ammonia concentration and volatile fatty acid production of infested pastures indicate a better fermentation of this substrate in sheep than in cattle. The absence of noticeable differences when the pasture without this species of spurge was incubated suggests that most variation between ruminant species can be attributed to the presence of E. polygalifolia. The positive effect of previous grazing in invaded areas on rates of gas production, extent of degradation and ammonia concentration supports the hypothesis that the ability to degrade infested pastures may be enhanced by previous consumption, probably through an adaptation of the rumen microbiota. Copyright © 2006 Society of Chemical Industry     

Molecular basis of structural makeup of hulless barley in relation to rumen degradation kinetics and intestinal availability in dairy cattle: A novel approach

To date, no study has been done of molecular structures in relation to nutrient degradation kinetics and intestinal availability in dairy cattle. The objectives of this study were to (1) reveal molecular structures of hulless barley affected by structural alteration using molecular spectroscopy (diffuse reflectance infrared Fourier transform) as a novel approach, and (2) quantify structure features on a molecular basis in relation to digestive kinetics and nutritive value in the rumen and intestine in cattle. The modeled feeds in this study were 4 types of hulless barley (HB) cultivars modified in starch traits: (a) normal starch cultivar, (b) zero-amylose waxy, (c) waxy, and (d) high-amylose. The molecular structural features were determined using diffuse reflectance infrared Fourier transform spectroscopy in the mid-infrared region (ca. 4,000–800 cm⁻¹) of the electromagnetic spectrum. The items assessed included infrared intensity attributed to protein amide I (ca. 1,715–1,575 cm⁻¹), amide II (ca. 1,575–1,490 cm⁻¹), α-helix (ca. 1,648–1,660 cm⁻¹), β-sheet (ca. 1,625–1,640 cm⁻¹), and their ratio, β-glucan (ca. 1,445–1,400 cm⁻¹), total carbohydrates (CHO; ca. 1,188–820 cm⁻¹) and their 3 major peaks, structural carbohydrates (ca. 1,277–1,190 cm⁻¹), and ratios of amide I to II and amide I to CHO. The results show that (1) the zero-amylose waxy was the greatest in amide I and II peak areas, as well as in the ratio of protein amide I to CHO among HB; (2) α-helix-to-β-sheet ratio differed among HB: the high-amylose was the greatest, the zero-amylose waxy and waxy were the intermediate, and the normal starch was the lowest; (3) HB were similar in β-glucan and CHO molecular structural makeup; (4) altered starch HB cultivars were similar to each other, but were different from the normal starch cultivar in protein molecular makeup; and (5) the rate and extent of rumen degradation of starch and protein were highly related to the molecular structural makeup of HB. In conclusion, the molecular structural makeup on a molecular basis was related to rumen degradation kinetics and intestinal availability in dairy cattle. The alteration of starch structure in barley grain affects starch structure and the magnitude of protein and β-glucan contents, as well as the protein molecular structure of HB.     

Changes in the composition of the rumen and abomasum lipids of sheep from birth to maturity

The composition of the lipids of the rumen and abomasum tissues of foetal (at term), 1 month, 2 month and 1-2-year old sheep grazed on pasture has been determined. The lipid content of the rumen tissues increased from 2.0% at birth to 3.4% in 1-2-year old sheep While that of the abomasum tissues increased from 2.6 to 5.7%. The main change in the neutral lipid fraction was a decrease in the hydrocarbon content from 0.13 % in the rumen tissues and 0.08 % in the abomasum tissues at birth to 0.003% and 0.006% respectively in the 1-2-year old sheep. The main components of the phospholipid fraction of the rumen and abomasum tissues were 34.9- 46.8% phosphatidyl choline; 14.623.5 % phosphatidyl ethanolamine; 14.3-21.1 % sphingomyelin; with smaller amounts of lysophosphatidyl choline (4 13-12.6 %), acidic phospholipids (cardiolipin) (4.1-8 -5 %) and phosphatidyl inositol/phosphaticlyl serine (3.0-5.5 %). No marked changes in phos- pholipid composition with age were noted. The amounts of phosphatidyl choline and phosphatidyl ethanolamine tended to be higher in the abomasum than in the rumen whereas the sphingomyelin content of the rumen tissue phospholipids was generally greater than that of the abomasurn tissue phospholipids. From the fatty acid composition of the triglycerides of the rumen and abomasum tissues it appeared that the foetal triglycerides were largely, though not entirely, of endogenous origin. In contrast the phospholipids of the foetal rumen and abomasum tissues contained di- and poly-unsaturated as well as branched-chain fatty acids in proportions similar to those found in older animals having access to pasture. From these results it is suggested that the phospholipids of the foetus are derived to a considerable extent from the maternal phospholipids.     

Effects of variation in soluble carbohydrate intake on sulfur dynamics in the sheep rumen

Two groups of experiments were conducted (named the 15% starch and 30% starch intake experiments) to examine the effects of dietary energy levels on the synthesis of ruminal microbial protein and the absorption of sulfur from the rumen. The level of energy intake affected the absorption rate of sulfide from the rumen, the net microbial protein flow rate, the amount of microbial protein synthesized per kg organic matter ‘truly digested’ in the rumen and the daily flow of recycled sulfur. For the 15% starch and 30% starch intake experiments the absorption of sulfur from the rumen was 1.207 and 1.278 g day^?1 absorbed from 2.298 and 2.212 g intake, respectively, the flow of microbial protein was 80.2 and 92.1 g day^?1, respectively, and the estimated recycled sulfur was 0middot;357 and 0.670 g day^?1, respectively. It was estimated that 18.1 and 20.1 g of microbial protein was synthesized per 100 g of organic matter ‘truly digested’ in the rumen for 15% starch and 30% starch diets, respectively.