High-roughage Diet Research Articles

Supplementing fructose-based block supplements to forage-fed cattle increases capacity for lactic acid metabolism

Acidosis is one of the more important maladies afflicting cattle fed significant amounts of grain and has enormous economic impact for feedlots, dairies, and producers of seed stock. The highest incidence of acidosis occurs when animals are being transitioned from high-roughage diets to diets containing high levels of concentrates. When grain-based diets are consumed in excess, consumed too quickly, or fed without proper adaptation, digestive end products (organic acids) can accumulate within the rumen, resulting in acidosis. Lactic acid is one of the key organic compounds that accumulates under these conditions. Coupled with the animal's limited ability to metabolize lactate, accumulation of lactic acid in the rumen lowers ruminal pH and subsequently depresses feed intake. One means of preventing acidosis is to directly populate the rumen with lactate-utilizing bacteria. Alternatively, exposure to low levels of lactate (i.e., levels insufficient to harm the animal) may stimulate development of a population of lactate-utilizing bacteria. The objective of our study was to determine if supplementing low-moisture blocks made of high fructose corn syrup could increase ruminal lactate concentrations and subsequently stimulate growth of lactate-metabolizing bacteria. If successful, this could prove useful for adapting forage-fed cattle to grain-based diets.

UROLITÍASE OBSTRUTIVA EM BOVINOS NO SEMI-ÁRIDO PARAIBANO

OBSTRUCTIVE UROLITHIASIS IN CATTLE IN PARAIBA’S SEMIARID REGION This study reports three cases of bovine obstructive urolithiasis in Paraiba’s semiarid region. The animals showed depression, dehydration, strangury, abdominal discomfort, and bruxism. One of them had severe ascites and eventually died; the others were able to recover after urethrostomy. Urolithiasis frequently occurs in cattle that are not castrated and eat a highroughage diet. There is a need to carry out more studies that investigate the composition of urinary calculi and its probable causes in order to develop prophylactic measures to control urolithogenic processes.

Effects of Non-ionic Surfactant Supplementation on Ruminal Fermentation, Nutrient Digestibility and Performance of Beef Steers Fed High-roughage Diets

Three experiments were conducted to determine the effects of non-ionic surfactant (NIS) supplementation on ruminal fermentation, nutrient digestibility and performance of beef steers fed high-roughage diets. The objective of experiment 1 was to investigate the effects of NIS supplementation on in vitro ruminal fermentation of cultures administered with corn and barley as grain substrate and rice straw and timothy hay as roughage substrate. The in vivo ruminal fermentation, nitrogen balance and digestibility of nutrients were also examined with steers fed a high-roughage diet in experiment 2. The aim of experiment 3 was to determine the responses to NIS of growing steers fed a high-roughage diet. In experiment 1, ammonia nitrogen concentration for NIS supplementation was higher (p<0.05) than for the control with all substrates. However, concentrations of total volatile fatty acid (VFA), acetate, butyrate and valerate of the incubated roughage substrates, rice straw and timothy hay, were higher (p<0.05) for NIS supplementation than for the control whereas VFA concentrations in the cultures of corn and barley were unaffected. These results indicated that effects of NIS on ruminal fermentation are diet dependent, specifically on roughage sources. In experiment 2, ruminal pH of steers supplemented with NIS was lower (p<0.05) than the control. Ruminal concentrations of ammonia nitrogen, acetate, total VFA and urinary concentrations of purine derivatives were increased (p<0.05) by NIS supplementation. In experiment 3, supplementation of NIS increased (p<0.05) intakes of total feed and corn silage, average daily gain, and feed efficiency of growing steers although they varied depending on supplementation level. Due to the roughage-specific feature of NIS effects, NIS appears to enhance ruminal fermentation of fibrous parts of feeds and, consequently, performance of steers fed a high-roughage diet.

Recurrent volvulus of the transverse colon after sigmoid resection

Recurrent volvulus of the transverse colon after sigmoid resection

Greenhouse gas emissions from the Canadian beef industry

Commodity-specific estimates of the greenhouse gas (GHG) emissions from Canadian agriculture are required in order to identify the most efficient GHG mitigation measures. In this paper, the methodology from the Intergovernmental Panel on Climate Change (IPCC) for estimating bovine GHG emissions, for census years from 1981 to 2001, was applied to the Canadian beef industry. This analysis, which is based on several adaptations of IPCC methodology already done for the Canadian dairy industry, includes the concept of a beef crop complex, the land base that feeds the beef population, and the use of recommendations for livestock feed rations and fertilizer application rates to down-scale the national area totals of each crop, regardless of the use of that crop, to the feed requirements of the Canada’s beef population. It shows how high energy feeds are reducing enteric methane emissions by displacing high roughage diets. It also calculates an emissions intensity indicator based on the total weight of live beef cattle destined for market. While total GHG from Canadian beef production have increased from 25 to 32 Tg of CO 2 equiv. between 1981 and 2001, this increase was mainly driven by expansion of the Canadian cattle industry. The emission intensity indicator showed that between 1981 and 2001, the Canadian beef industry GHG emissions per kg of live animal weight produced for market decreased from 16.4 to 10.4 kg of CO 2 equiv.

Comparison of carcass and meat characteristics of Brahman grade cattle (Bos indicus) and crossbred water buffalo (Bubalus bubalis) fed on high roughage diet

ABSTRACTThe objective of this study was to compare the carcass and meat quality in crossbred cattle and crossbred water buffalo at the same younger age and fed with high roughage in the Philippines. Ten crossbred cattle and 10 crossbred water buffalo, with an average age of 22 months (18–24 months) were used in this experiment. The animals were fed a similar diet, which consisted of 85% Napier or Para grass and 15% concentrate mixture on a dry matter basis, for 180 days before slaughter. Slaughter weight of the crossbred water buffalo was higher (P &lt; 0.05) than that of the cattle, although the dressing percentage was significantly (P &lt; 0.01) lower for the former than for the latter. The estimated lean yield was higher (P &lt; 0.05) in crossbred cattle than crossbred water buffalo. The muscle fiber diameter of loin in buffalo meat was smaller (P &lt; 0.05) than that in cattle. In regard to carcass and meat quality, the crossbred water buffalo was comparable or slightly superior to the crossbred cattle in tenderness, sensory score of color (P &lt; 0.01) and flavor (P &lt; 0.05). These results clearly indicate that at a younger age and even under high roughage‐based fattening rations, crossbred water buffalo are able to produce good quality meat, which will be by no means inferior to that of crossbred cattle in the Philippines.

Comparison of fattening performance in Brahman grade cattle (Bos indicus) and crossbred water buffalo (Bubalus bubalis) fed on high roughage diet

ABSTRACTThe objective of this study was to compare the fattening performance in Brahman grade cattle (crossbred cattle) and crossbred water buffalo at the same young age and fed with high roughage based fattening rations in the Philippines. Ten crossbred cattle and 10 crossbred water buffalo, aged between 18 and 24 months old were used in this experiment. The animals were fed diets consisting of 85% Napier or Para grass and 15% concentrate mixture (CM) on a dry matter (DM) basis. The grass, total DM intake and bodyweight gain were significantly (P &lt; 0.01) higher for the crossbred water buffalo than for the cattle. There was no species significant difference in the digestion coefficient and feed conversion rate between the crossbred cattle and water buffalo. The return over feed cost for fattening was significantly (P &lt; 0.05) higher in the crossbred water buffalo than in the cattle. These results clearly indicate that under high roughage‐based fattening rations, young crossbred water buffalo are better able to utilize the roughage and they perform better in terms of feed intake and live weight gains than the crossbred cattle in the Philippines.

Effects of Feeding Crab Processing Waste and Other Protein Supplements on Growth and Ruminal Characteristics of Steers Fed High-Roughage Diets

AbstractA 126-d growth trial was conducted with 48 Angus × Hereford and Angus × Simmental steers (average BW 223 kg). Steers were blocked by body weight andbreeding into 8 blocks and randomly allotted within blocks to 6 supplements (8 steers/treatment). Diets were formulated to contain 10.5% CP and 63% TDN, DM basis. The supplements were 1) soybean meal (SBM), control; 2) supplement based on industrial by-products ofboth plant and animal origin (IPA); 3) experimental supplement based on byproducts of animal origin; 4) hydrolyzed supplement No. 3 (HESA); 5) commercial supplement based on animal protein, Pro-Lak; and 6) crab meal. In each diet, onethird of the N was supplied by the protein supplement. Steers were full fed in individual stalls during a 16-h period daily. Lower (P < 0.05) weight gain was recorded for the cattle fed the HESA and IPA supplements compared with other supplements. Feed efficiency was lowest (P < 0.05) for cattle fed the HESA supplement. At 126 d, ruminal NH3N was higher (P < 0.05) for steers fed SBM than for those fed the IPA and HESA supplements. When included in the diet on a N equivalent basis, crab meal was comparabl to SBM or other products as a protein supplement for growing steers.

Lipogenesis and stearoyl-CoA desaturase gene expression and enzyme activity in adipose tissue of short- and long-fed Angus and Wagyu steers fed corn- or hay-based diets

Angus and Wagyu steers consuming high-roughage diets exhibit large differences in adipose tissue fatty acid composition, but there are no differences in terminal measures of stearoyl-CoA desaturase (SCD) activity or gene expression. Also, adipose tissue lipids of cattle fed corn-based diets have greater MUFA:SFA ratios than cattle fed hay-based diets. We hypothesized that any changes in SCD gene expression and activity would precede similar changes in adipose tissue lipogenesis between short- and long-fed endpoints. Furthermore, changes in SCD activity and gene expression between production endpoints would differ between corn- and hay-fed steers and between Wagyu and Angus steers. Angus (n = 8) and Wagyu (n = 8) steers were fed a corn-based diet for 8 mo (short-fed; 16 mo of age) or 16 mo (long-fed; 24 mo of age), whereas another group of Angus (n = 8) and Wagyu (n = 8) steers was fed a hay-based diet for 12 mo (short-fed; 20 mo of age) or 20 mo (long-fed; 28 mo of age) to match the end point BW of the corn-fed steers. Acetate incorporation into lipids in vitro was greater (P < 0.01) in corn-fed steers than in hay-fed steers and tended (P = 0.06) to be greater in Wagyu than in Angus s.c. adipose tissue because the rate in Wagyu was twice that of Angus adipose tissue in the corn-fed, short-fed steers. There were diet x end point interactions for lipogenesis in i.m. and s.c. adipose tissues (both P < 0.01) because lipogenesis was 60 to 90% lower in the long-fed cattle than in short-fed cattle fed the corn-based diet. The greatest SCD enzyme activity in Angus s.c. adipose tissue was observed at 24 mo of age (corn-based diet), but activity in Wagyu adipose tissue was greatest at 28 mo of age (hay-based diet; breed x diet x end point interaction, P = 0.08). For short- vs. long-fed endpoints in Angus, s.c. adipose tissue SCD activity was less (hay diet) or the same (corn diet). Conversely, SCD gene expression was greatest in long-fed Wagyu steers fed the hay- or corn-based diets (breed x end point interaction; P < 0.01). Contrary to our hypotheses, SCD activity increased over time, whereas lipogenesis from acetate decreased. However, the developmental pattern of SCD gene expression and activity differed markedly between hay-fed Angus and Wagyu adipose tissues, which may explain the differences in the MUFA:SFA ratios observed in adipose tissues from these cattle.

Influence of Dietary Salinomycin on Feeding-induced Variations of Glucose Kinetics and Blood Volatile Fatty Acids and Insulin Concentrations in Sheep Fed a High-roughage Diet

This study was conducted to determine effects of salinomycin (SL) on feeding-induced changes in glucose kinetics and blood VFA concentrations in sheep fed a high-roughage diet. Four sheep were fed the diet with or without 20 mg/kg diet of SL once daily for 21 d. Glucose entry and utilization rates were determined during the prefeeding and 3 h postfeeding periods, using a []glucose dilution method and non-steady state equations. Ruminal characteristics and concentrations of blood VFA, plasma glucose and insulin were also measured during the same periods. A feeding-induced increase in ruminal total VFA concentration tended to be inhibited (p0.10) with SL or by feeding. Salinomycin decreased (p0.10). A feeding-induced increase in blood acetate concentration was attenuated (p0.10). Plasma concentrations of glucose or insulin were unaffected (p>0.10) with SL. Salinomycin tended to enhance (p0.10). We conclude that SL possibly enhances whole body glucose entry and utilization with an increase in blood propionate concentration in sheep given a high-roughage diet, although SL does not appear to affect their responses to feeding.

Comparison of feed efficiency rankings of heifers fed low and high energy dense diets (2007)

Concepts related to energy efficiency in cattle have been the basis for many research projects. Even though differences in individuals have long been recognized, little effort has been focused on the causes of the observed variations. The concept of residual feed intake was first introduced in 1963, and is calculated as the difference between actual feed intake by an animal and its expected feed intake based on body weight and growth rate. Residual feed intakes are phenotypically independent of the production traits used to calculate expected feed intake. Consequently, residual feed intake values can be useful in comparing individuals differing in level of production during a test period. These feed efficiency calculations have been shown to be a more accurate indicator of genetic variation in efficiency because they are independent of production traits. Thus, selection for improved residual feed intake makes it feasible to reduce feed intake without compromising growth performance. Hence, this trait could have great economic value to all segments of the beef industry. Energy density of cattle diets varies substantially and the selection for the ability to efficiently utilize high roughage diets does not guarantee efficient utilization of high grain diets. The objective of this study was to determine if energy density of the diet influences the ranking of cattle within a contemporary group and to determine if residual feed intake is influenced by changes in body composition and diet digestibility. Experimental Procedures

Solitary rectal ulcer syndrome in Northern Ireland. 1971-1980.

Fifty-one cases of solitary rectal ulcer syndrome diagnosed over the past 10 years have been studied. The syndrome, of which solitary ulceration was a feature in only 35 per cent of cases, included patients with multiple 'solitary' ulcers (22 per cent), broad-based polypoid lesions (25 per cent) and patchy granular hyperaemic rectal mucosa (18 per cent). The syndrome was found to be strongly associated with abnormal rectal descent. Full-thickness prolapse to or beyond the anal verge was present in 59 per cent of patients while a further 32 per cent had lesser degrees of rectal descent. In only 9 per cent was no such abnormality demonstrated. Treatment with high roughage diet supplemented with bulking agents benefited two-thirds of 27 patients so treated. Ivalon sponge rectopexy has been performed in 6 patients with associated complete rectal prolapse, and in the first 3 of these (followed for a sufficient period) the results have been satisfactory.

The Impact of Saponins or Saponin-Containing Plant Materials on Ruminant ProductionA Review

Saponins are steroid or triterpene glycoside compounds found in a variety of plants. Some saponin-containing plants, mainly legumes, have been used as animal feed, but others are toxic. Several studies on the effect of saponins on ruminant production have also been reported. Some in vitro and in vivo experiments that demonstrate the beneficial effects of saponin such as defaunation of the rumen and manipulation of the end products of fermentation are described. Defaunation is the selective removal of protozoa from the rumen microbial ecosystem by a cell membrane cholesterol-saponin interaction, which causes cell rupture. Because protozoa in the rumen cause protein turnover by predating on bacteria, defaunation increases the nitrogen utilization of the ruminant and may lead to an increase in growth, milk, or wool production. The growth-promoting effect was evident in the high roughage diet suggesting that the application of saponins or saponin-containing plant materials may be beneficial for the subsistence farmers in developing countries. Saponins are deglycosylated by rumen microbes. Some sapogenins have been detected in the digestive tract of ruminants; however, the direct action of these compounds on the host animal is still unclear. No information on the effects of saponin on ruminant reproduction is available. There is an urgent need for a systematic evaluation of the most active structural components of the saponins, and their interaction with the microbial community, the host animal, and the diet. Along with these studies, the direct effects of saponins or their microbial degradation products on the host must be examined in order to get the full understanding of the metabolism and beneficial effects of saponins on animals.

Effect of the last diet on the selective feeding behavior of heifers

ABSTRACTThe present study examined and discussed the way the basal diet (BD) during the preliminary phase and the last diet (LD) before the food selection test affected the selective feeding behavior of heifers. For the BD and LD, oat hay and concentrate were used. Three different levels of roughage content (low, medium and high) were prepared by changing the mix ratios of oat hay and concentrate. Low and high roughage diets were used for the BD, and all three of the roughage levels were used for the LD. A mixture of orchard grass and white clover (MIX), and Japanese pampas grass leaf (JP) were used as testing foods. In the preliminary phase, all heifers were fed the BD three times per day. In the test phase, heifers were fed the LD for the first meal (06.00–12.00 hours), and food selection under different BD and LD was examined during the second meal (13.00–16.00 hours) of the day. The effects of the BD were significant for MIX dry matter intake (DMI), JP DMI and the rate of MIX DMI for total DMI. Under the high roughage BD condition, heifers ingested more MIX than under the low roughage BD condition. The effect of the LD was significant on JP DMI, whereas the rate of MIX DMI for total DMI was not significant. Selective feeding behavior was strongly affected by the BD and slightly by the LD.

Adipocytes may not be a terminally differentiated cell type: implications for animal production

Mature adipocytes may not be a terminally differentiated cell form, as previously thought by about everyone in science. Instead, these adipocytes may be capable of re-entering the cell cycle and forming proliferative-competent precursor cells like preadipocytes, adipofibroblasts, or even other forms of cells. Why is this possibility important to animal science? The main reason is in directing the cellularity of adipocyte depots in meat animals. For example, we know that the fat characteristics of beef animals are a direct function of the ‘cellularity’ of cells committed to form adipocytes. Beef steers given a high-concentrate diet commonly possess fewer adipocytes in any given fat depot, but most of the cells are completely filled with lipid to capacity. Alternatively, steers on a high-roughage diet seem to possess more fat cells, but fewer of them are filled to capacity with storage lipid. A variety of systemic and local regulators have been implicated in altering the cellularity of any given fat depot. Major regulators appear to be growth hormone, any number of repartitioning agents, as well as adipocytokines produced by the cells within the fat depot themselves. The specific mechanisms involved in directing cellularity of any specific fat depot, however, are poorly understood.

Exsheathment of Ostertagia ostertagi infective larvae following exposure to bovine rumen contents derived from low and high roughage diets

The objective of this study was to characterize the exsheathment kinetics of Ostertagia ostertagi infective larvae (L 3) following in vivo exposure to bovine rumen contents derived from low and high roughage diets. O. ostertagi L 3 were placed in disposable dialysis bags and incubated for various time points between 0 and 360 min in the rumen of a fistulated steer maintained on a 71% grain diet or a 100% grass diet. The maximum percentage of exsheathed L 3 was observed 120 min post-exposure to grass-derived rumen contents, while maximum exsheathment for L 3 exposed to grain-derived rumen contents did not occur until 360 min. This work provides the first report of the in vivo exsheathment kinetics for O. ostertagi in its bovine host. Results of this study also support earlier reports that rumen pH may affect the exsheathment efficiency of abomasal trichostrongylids.

Effects of feeding strategy and age on live animal performance, carcass characteristics, and economics of short-term feeding programs for culled beef cows1

To evaluate production and economic effects of feeding management strategy and age on intensively managed culled beef cows, a study was conducted using 125 cows of British breeding blocked by age (Young = 3 and 4 yr olds; LowMid = 5 and 6 yr olds; HighMid = 7 and 8 yr olds; and Aged = 9 yr and older) and assigned to one of three steam-flaked corn based feeding strategies. Treatments were as follows: Conservative (CSV), 30% roughage throughout; Standard (STD), decrease roughage from 30 to 10% over 20 d; and Aggressive (AGR), decrease roughage from 30 to 10% over 10 d. There were four pens per treatment in a randomized complete block design. Cows were fed for a total of 54 d, and BW was measured on d 0, 14, 28, 42, and 54. Half the cows from each pen were randomly selected and slaughtered at a commercial abattoir, and carcass data were collected. Average daily gain, daily DMI, and G:F during each weigh period and across the entire feeding period were calculated. Over the 54-d feeding period, strategies that employed more energy-dense diets numerically increased ADG (1.28, 1.63, and 1.55 +/- 0.14 kg/d for CSV, STD, and AGR; P = 0.26) and decreased DMI (11.91, 10.74, and 10.89 +/- 0.27 kg/d for CSV, STD, and AGR; P = 0.05), such that G:F was lower for CSV than for STD or AGR (0.105, 0.150, and 0.141 +/- 0.010; P = 0.05). Carcass weight was least for the CSV strategy (298 kg) and greatest for STD (328 kg); AGR resulted in intermediate carcass weight (317 +/- 6 kg; P = 0.04). Total cost of gain was over 30% greater for CSV strategy than for STD or AGR strategies (P < 0.01). In many cases, block effects (age) had a greater effect on responses than treatments. Average daily gain, DMI, and G:F decreased linearly with age (P < 0.01). Hot carcass weight, dressing percent, and fat thickness decreased linearly with age (P < 0.03); yield grade decreased and carcass maturity attributes increased linearly with age (P < 0.02). Performance and intake differences resulted in linear increases in total cost of gain (P < 0.01) and breakeven price (P = 0.03) with increasing age. These data indicate advantages to more aggressive feeding management strategies for culled beef cows, although maximal intake may be achieved with higher-roughage diets. Despite management effects, an increase in market price above purchase price may be required for intensive feeding of culled beef cows to be a profitable enterprise.

Effect of Diet Forage-to-Concentrate Ratio on Partition of Dietary Energy and Nutrients in Fed and Fasted Sheep

Sano, H., Ito, T. and Terashima, Y. 2004. Effect of diet forage-to-concentrate ratio on partition of dietary energy and nutrients in fed and fasted sheep. J. Appl. Anim. Res., 25: 101–108. A total collection method and open-circuit calorimetry were used to measure partition of dietary energy and protein and nutrient oxidation in sheep fed on a high roughage diet (HR diet) or a high concentrate diet (HC diet). Fasting metabolism was also determined. Digestible and metabolizable energy intakes did not differ between the diets. Oxygen consumption and carbon dioxide and methane emissions were similar in both diets and decreased (P=0.0001) during fasting. Digestible nitrogen (N) intake was greater (P=0.03) for the HC diet, whereas N balance remained unchanged due to enhanced (P=0.005) urinary N excretion. Heat production was similar in both diets and decreased (P=0.0002) during fasting. Carbohydrate and fat oxidation did not differ between the diets, whereas protein oxidation was greater (P=0.02) for the HC diet than for the HR diet. During fasting protein oxidation remained unchanged., carbohydrate oxidation decreased (P=0.0003) and fat oxidation tended to increase (P=0.08). In this study, type of diet influenced energy and protein partition in sheep. However, these results were not entirely attributed to type of diet because energy and protein intakes influenced these variables.

Effects of Concentrate to Roughage Ratio on the Formation of cis9, trans11-CLA and trans11-Octadecenoic Acid in Rumen Fluid and Plasma of Sheep When fed High Oleic or High Linoleic Acid Oils

A metabolism trial with four ruminally fistulated sheep was conducted in a 4x4 Latin square design to examine the effect of concentrate to roughage ratio (70:30 vs. 85:15) and oil source (soybean oil vs. rapeseed oil) on the ruminal fermentation pattern and C 1 8 -fatty acids composition including trans11-C 1 8 : 1 (trans11-ODA) and cis9, trans11-18:2 (cis9, transll-CLA) in the rumen fluid and plasma. Oil was added to the concentrate at 5% level of the total diet (DM basis) and chopped rye grass hay was fed as roughage. An increased level of concentrate (85%) within supplemented oil slightly lowered pH but increased ammonia concentration. Supplementation of rapeseed oil relatively increased pH and ammonia concentration. Higher concentrate level resulted in increased tendencies of total VFA concentration while oil source did not affect the total VFA concentration and VFA proportion. Whole tract digestibilities of DM, CP, EE, NDF and OM in diets slightly increased at higher concentrate level. Proportions of oleic acid (C 1 8 : 1 ) and linoleic acid (C 1 8 : 2 ) in the rumen fluid were influenced by the fatty acid composition of oil source but oil source did not affect the in vitro formations of trans11-ODA and cis9, trans11-CLA. Slightly increased trans11-ODA and cis9, trans11-CLA proportions, however, were observed from the sheep fed high roughage diet supplemented with both soybean oil and rapeseed oil. The C 1 8 : 1 and C 1 8 : 2 composition in supplemented oils responded to those in plasma of sheep. Effects of concentrate to roughage ratio and oil source on trans11-ODA and cis9, trans11-CLA proportions in plasma were found to be small. Proportion of cis9, trans11-CLA in plasma tended to be increased from the sheep fed high roughage diet and collection time at 9 h post feeding.

Effects of pH and Electron Donors on Nitrate and Nitrite Reduction in Ruminal Microbiota

Factors affecting nitrate and nitrite reduction in the rumen were examined. Nitrate and nitrite reduction by mixed microbes harvested from the goat rumen was increased by feeding a high-roughage diet, which contained a much higher amount of nitrate than concentrate. The activities of nitrate reductase and nitrite reductase per bacterial mass appeared to be increased by feeding a high-nitrate diet, suggesting that these enzymes are induced by substrates. Nitrate and nitrite reduction was confirmed to be the fastest at neutral pH and affected by electron supply. The supplementation of electron donors, such as formate, H2, and lactate, stimulated nitrate and nitrite reduction, especially nitrite reduction, which decreased nitrite accumulation. As a result, addition of formate or lactate in the presence of nitrate alleviated the inhibitory effect of nitrite on fermentation, and greatly reduced methanogenesis.