Rumen ciliate protozoa

Producing natural functional and low-carbon milk by regulating the diet of the cattle-The fatty acid associated rumen fermentation, biohydrogenation, and microorganism response

Conjugated linoleic acid (CLA) has drawn significant attention in the last two decades for its various potent beneficial effects on human health, such as anticarcinogenic and antidiabetic properties. CLA could be generally found in ruminant products, such as milk. The amount of CLA in ruminant products mainly depends on the diet of the animals. In general, the fat content in the ruminant diet is low, and dietary fat supplementation can be provided to improve rumen activity and the fatty acid (FA) profile of meat and milk. Especially, dietary 18-carbon polyunsaturated FA (C18 PUFA), the dominant fat source for ruminants, can modify the milk FA profile and other components by regulating the ruminal microbial ecosystem. In particular, it can improve the CLA in milk, intensify the competition for metabolic hydrogen for propionate producing pathways and decrease methane formation in the rumen. Therefore, lipid supplementation appears to be a promising strategy to naturally increase the additional nutritional value of milk and contribute to lower methane emissions. Meanwhile, it is equally important to reveal the effects of dietary fat supplementation on rumen fermentation, biohydrogenation (BH) process, feed digestion, and microorganisms. Moreover, several bacterial species and strains have been considered to be affected by C18 PUFA or being involved in the process of lipolysis, BH, CLA, or methane emissions. However, no review so far has thoroughly summarized the effects of C18 PUFA supplementation on milk CLA concentration and methane emission from dairy cows and meanwhile taken into consideration the processes such as the microorganisms, digestibility, rumen fermentation, and BH of dairy cattle. Therefore, this review aims to provide an overview of existing knowledge of how dietary fat affects rumen microbiota and several metabolic processes, such as fermentation and BH, and therefore contributes to functional and low-carbon milk production.

Altering Methane Emission, Fatty Acid Composition, and Microbial Profile during In Vitro Ruminant Fermentation by Manipulating Dietary Fatty Acid Ratios

This study evaluated the effects of different dietary n-6/n-3 polyunsaturated fatty acid (PUFA) ratios on in vitro ruminant fermentation. Methane production, fatty acid composition, and microbial profiles were compared after the in vitro fermentation of rumen fluid collected from cows that had been fed isoenergetic and isoproteic experimental diets at three different n-6/n-3 ratios: 3.04 (HN6, high n-6 source), 2.03 (MN6, medium n-6 source), and 0.8 (LN6, low n-6 source). The fermented rumen fluid pH and total volatile fatty acid (VFA) levels were significantly decreased (p < 0.05) in the HN6 group as compared with those in the MN6 and LN6 groups. Additionally, the HN6 group produced a significantly lower (p < 0.05) proportion of methane than the MN6 group during in vitro fermentation. The MN6 and LN6 groups had significantly increased (p < 0.05) levels of C18:2n6 and C18:3n3 in the fermented rumen fluid, respectively, as compared with the HN6 group. The Chao 1 diversity index value was lower (p < 0.05) in the HN6 group than in the MN6 and LN6 groups. The observed species richness was significantly lower (p < 0.05) in the HN6 group than in the MN6 group. The reduced relative abundances of Lachnospiraceae UCG-006 and Selenomonas in the HN6 group resulted in lower pH and VFA levels (i.e., acetate, propionate, butyrate, and total VFA) during in vitro fermentation. Furthermore, n-6 and n-3 PUFAs were toxic to Butyrivibrio_2 growth, resulting in high levels of incomplete biohydrogenation. Taken together, the study findings suggest that supplementation of high-forage diets with high levels of n-6 PUFAs could reduce methane emissions, whereas both VFA concentration and pH are reduced.

Nutritional evaluation of some Indian tree pods for livestock feeding

The objective of this study was to evaluate promising tree pods for feeding to the livestock particularly for the small ruminants. Out of eight tested tree pods, seven tree pods, i.e. White siris (Albizia procera), Siris (Albizia lebbeck), White kheri (Acacia senegal), Babul (Acacia arabica), Khejri (Prosopis cineraria), Vilayati babul (Prosopis juliflora) and Sajna (Moringa oleifera) were collected from semiarid region of Rajasthan while one tree pods e.g., Jungle jalebi (Enterolobium timoba) was collected from Dehradun, Uttrakhand, India. Most of the tree pods were rich in CP content. On an average, OM, CP, EE, NDF, ADF and cellulose content of these tree pods were found to be 91.1, 16.7, 2.5, 43.3, 34.7 and 25.4% on DM basis, respectively. Rumen protozoal number decreased due to inclusion of Enterolobium timoba tree pods in the incubation media. The TVFA and propionate production were higher for Acacia Senegal, Acacia arabica tree pods followed by Moringa oleifera tree pods while ammonia nitrogen concentration was lower due to inclusion of Enterolobium timoba tree pods in the incubation media. All the tested tree pods had no effect on xylanase, β-glucosidase and amylase enzyme activity. However, specific activity of carboxymethyl cellulase enzyme reduced due to addition of Enterolobium timoba tree pods in the incubation medium. Highest IVDMD was observed for Acacia arabica tree pods followed by Acacia senegal and Moringa oleifera tree pods. The results indicated that Acacia arabica, Acacia senegal and Moringa oleifera are good tree pods for feeding to the animals.

Nutritional evaluation of some Indian tree leaves and herbs as fodder and defaunating agent in sheep

Nutritional evaluation as a fodder and defaunating agent of four multipurpose tree leaves namely Ficus religiosa (Pipal), Ficus bengalensis (Bargad), Mangifera indica (Mango), Enterolobium timoba (Jungle jalebi) and two herbs namely Agave americana (Ramkanta) and Plantago major (Isafghol) was done in vitro. The mean content of OM, CP, EE, NDF, ADF, cellulose and lignin of these tree leaves and herbs were 88.6, 12.6, 2.4, 46.2, 33.5, 25.8 and 7.3% on DM basis, respectively. Enterolobium timoba leaves contained highest amount of CP (22.5%) while highest amount of ADF and lignin content was observed in Ficus bengalensis (41.1% / 12.1%) leaves. Total rumen protozoa as well as Holotrich and spirotrich protozoa number became zero due to inclusion of Agave americana and Enterolobium timoba leaves in the incubation media. Total volatile fatty acids (TVFA) and propionate production was higher where as NH3–N production was lower due to addition of Agave americana leaves in the incubation media. Highest IVTDMD and IVTOMD (61.4% / 64.1%) were observed for the Agave americana followed by Enterolobium timoba (59.8% / 62.5%) and Plantago major (57.5% / 59.2%) leaves. Activity of polysaccharide degrading enzymes like carboxymethyl cellulase and xylanase improved due to addition of Agave americana and Enterolobium timoba leaves in the incubation media. However, activity of β-glucosidase enzyme was similar among all the tested tree leaves and herbs. As a defaunating agent (removal of rumen protozoa / anti ciliate protozoal activity), Agave americana leaves were more effective in comparison to Plantage major leaves. The results indicated that among the tested tree leaves and herbs, Agave americana, Enterolobium timoba and Plantago major were good tree fodder for feeding to the animals and leaves of Agave americana and Enterolobium timoba could be used as defaunating agent for reducing rumen protozoal population to improve animal productivity.

Chemical composition and in vitro ruminal fermentation of common tree forages in the semi-arid range lands of India

The objective of study was to look for the promising tree leaves for feeding livestock particularly the small ruminants. Ten tree leaves were collected from semiarid region of Rajasthan and evaluated for their nutritional quality in terms of chemical composition as well as in vitro dry matter and organic matter digestibility (IVDMD and IVOMD). Most of the tree leaves were rich in CP content. OM, CP and ADF content of these collected tree leaves varied from 87.1 to 92.5%, 9.4 to 19.8% and 22.7 to 47.9% on DM basis, respectively. Rumen protozoal number decreased due to inclusion of Sapindus mukorossi, Azadirachta indica and Prosopis cineraria tree leaves in the incubation media. IVDMD, IVOMD, TVFA and propionate production significantly higher for Ailanthus excelsa tree leaves followed by Acacia arabica and Acacia senegal tree leaves. All the tested tree leaves had no effect on β-glucosidase and amylase enzyme activity. However, specific activity of carboxymethyl cellulase and xylanase reduced significantly due to addition of Sapindus mukorossi, Azadirachta indica and Prosopis cineraria tree leaves in the incubation medium. The results indicated that among the tree leaves tested in the present study Ailanthus excelsa, Acacia arabica and Acacia senegal are good tree fodder for feeding to the ruminants.

Assessment of fodder quality and methane production potential of north-eastern Himalayan forest tree leaves

Nutritional evaluation as tree fodder as well as a rumen manipulator of six multipurpose Himalayan forest tree leaves, viz. Kadam (Anthocephalus cadamba), Kaew (Costus speciosus), Karoi (Albizia procera), Bakful (Sasbania grandiflora), Gamar (Gmelina arborea), and Barhar (Artocarpus lakoocha), were evaluated by in vitro gas production test. The mean content of OM, CP, EE, T-CHO, NDF, ADF, cellulose and lignin of these tested tree leaves were 91.4, 14.6, 3.9, 72.8, 42.7, 31.2, 19.8, and 11.1% on DM basis, respectively. The gas production per g digested dry matter varied from 111.1 ml/g DDM/24h in Bakful (Sasbania grandiflora) to 612.3 ml/g DDM/24h in Barhar (Artocarpus lakoocha) tree leaves while methane production per gram digested dry matter varied from 14.7 ml/g DDM/24h in Kadam (Anthocephalus cadamba) to 102.2 ml/g DDM/24h in Bahar (Artocarpus lakoocha) tree leaves. TVFA and propionate production were higher due to inclusion of Karoi (Albizia procera) tree leaves in the incubation media. However, lowest NH3-N concentration and rumen protozoal population were observed due to incubation of Kadam (Anthocephalus cadamba) tree leave. Similarly, activity of polysaccharide degrading enzyme like carboxymethyl cellulase, xylanase and β-glucoidase enzymes were lower due to incubation of Kadam (Anthocephalus cadamba) in comparison to other tested tree leaves. However, activity of amylase enzyme was similar among all the tested tree leaves. Highest IVTDMD (52.3%) was observed for the Karoi (Albizia procera) tree leaves followed by Kaew (Costus speciosus) (47.9%) and Kadam (Anthocephalus cadamba) (43.8%) tree leaves. Similarly, TDN and ME content were also highest for Karoi (Albizia procera) tree leaves. The results indicated that among the tested tree leaves, Karoi (Albizia procera) was best tree fodder for feeding to the animals and Kadam (Anthocephalus cadamba) can be used as rumen manipulator to reduce ruminal methanogenesis and protozoal population for improving animal productivity.

Ionophore resistance of ruminal bacteria and its potential impact on human health

In recent years, there has been a debate concerning the causes of antibiotic resistance and the steps that should be taken. Beef cattle in feedlots are routinely fed a class of antibiotics known as ionophores, and these compounds increase feed efficiency by as much as 10%. Some groups have argued that ionophore resistance poses the same public health threat as conventional antibiotics, but humans are not given ionophores to combat bacterial infection. Many ruminal bacteria are ionophore-resistant, but until recently the mechanism of this resistance was not well defined. Ionophores are highly lipophilic polyethers that accumulate in cell membranes and catalyze rapid ion movement. When sensitive bacteria counteract futile ion flux with membrane ATPases and transporters, they are eventually de-energized. Aerobic bacteria and mammalian enzymes can degrade ionophores, but these pathways are oxygen-dependent and not functional in anaerobic environments like the rumen or lower GI tract. Gram-positive ruminal bacteria are in many cases more sensitive to ionophores than Gram-negative species, but this model of resistance is not always clear-cut. Some Gram-negative ruminal bacteria are initially ionophore-sensitive, and even Gram-positive bacteria can adapt. Ionophore resistance appears to be mediated by extracellular polysaccharides (glycocalyx) that exclude ionophores from the cell membrane. Because cattle not receiving ionophores have large populations of resistant bacteria, it appears that this trait is due to a physiological selection rather than a mutation per se. Genes responsible for ionophore resistance in ruminal bacteria have not been identified, but there is little evidence that ionophore resistance can be spread from one bacterium to another. Given these observations, use of ionophores in animal feed is not likely to have a significant impact on the transfer of antibiotic resistance from animals to man.

Influence of ciliate protozoa on biochemical changes and hydrolytic enzyme profile in the rumen ecosystem

AIMS

To assess the effect of presence or absence of rumen protozoa on fermentation characteristics and enzyme profile in growing lambs.

METHODS AND RESULTS

Weaner lambs (G1, G2, G3, G4, G5 and G6 groups) were defaunated by oral administration of sodium laurel sulphate (at 8 g 100 kg(-1) body weight). The lambs of G4, G5 and G6 groups were refaunated. The roughage and concentrate ratio in the diet of G1 and G4, G2 and G5, and G3 and G6 were 50:50 (R1), 65:35 (R2) and 80:20 (R3), respectively. Daily dry matter intake was similar in defaunated and faunated lambs. However, digestibility of organic matter (OM), cellulose and gross energy were lower in defaunated lambs while crude protein (CP) digestibility was similar in both defaunated and faunated lambs. The rumen pH and NH3-N were lower (P < 0.01) while TVFA, total-N and TCA-ppt-N were higher (P < 0.01), in defaunated lambs. Ruminal activity of carboxymethyl cellulase was lower (P < 0.01) in defaunated lambs and amylase, xylanase, protease and urease were similar in faunated and defaunated lambs. Nutrient utilization, rumen metabolites and ciliate protozoal count were higher, whereas digestibility of fibre fractions was lower in high rather than low concentrate fed lambs. The rumen protozoa present before defaunation were B-type and the protozoa which re-established on refaunation were also B-type.

CONCLUSIONS

Absence of ciliate protozoa decreased nutrient digestibility and increased ruminal TVFA and total-N with lower NH3-N concentration, indicating better energy and protein utilization in defaunated lambs.

SIGNIFICANCE AND IMPACT OF THE STUDY

Defaunation improved energy and protein utilization in lambs.

Effect of vitamin E on ruminal fermentation in vitro

The effects of vitamin E on pH value, total protozoa counts, volatile fatty acid (VFA), ammonia nitrogen and lactate levels were examined using an in vitro ruminal incubation system. The ruminal fluid (100 ml) of the first and second group was supplemented with 0.4 mg or 0.8 mg of vitamin E, respectively. Samples were taken immediately before and following 3, 6, 12 and 24 h of incubation at 39 degrees C and analysed for the total protozoa counts, the pH and the levels of ammonia nitrogen, lactate and VFA. Levels of propionate at 24 h and ammonia nitrogen at 12 and 24 h were significantly higher in the second group than in the control. In contrast, the levels of butyrate at 6, 12 and 24 h and lactate at 6, 12 and 24 h were lower in the second group than in the control. Propionate at 24 h, acetate levels at 6, 12 and 24 hand ammonia nitrogen levels at 6, 12 and 24 h and total rumen protozoa counts at 6, 12 and 24 h were significantly higher in the second group as compared with control. In contrary, butyrate levels at 6, 12 and 24 h, lactate levels at 6, 12 and 24 h were lower in second group than in control. There was no statistically significant difference among the groups in the pH values. In conclusion, the addition of vitamin E to in vitro ruminal fluid was found to increase the concentrations of acetate and propionate, total counts of protozoa, levels of ammonia nitrogen, but to decrease the butyrate and lactate levels of the ruminal aliquots in in vitro ruminal fermentation.

Influence of dietary selenium and vitamin E on the levels of fatty acids in brain and liver tissues of lambs

In this study, the effects of dietary vitamin E, selenium, and their combination on the levels of fatty acid composition of the brain and liver tissues were examined. In brain tissue, the amounts of most fatty acids increased in vitamin E, combination and selenium groups compared with control group values. While the proportions of myristic, pentadecanoic, palmitic, linoleic, and total saturated fatty acids were decreased in vitamin E, Se and combination groups, eicosapentaenoic, total unsaturated and MUFA were increased in the same groups. In addition, the proportions arachidonic, eicosapentaenoic, total unsaturated, omega 6 and MUFA in the combination group were higher than in the control group. In liver tissue, the amounts of myristic, pentadecanoic, palmitic, eicosedienoic, eicosapentaenoic, docosahexaenoic, omega 3 and PUFA were higher in the combination group than in the control group. Also the proportions of eicosapentaenoic, docosahexaenoic acids in supplemented groups were higher than those in the control group. We conclude that dietary vitamin E and selenium have an influence on the levels of fatty acids in the brain and liver.

The rate of uptake and metabolism of starch grains and cellulose particles by Entodinium species, Eudiplodinium maggii, some other entodiniomorphid protozoa and natural protozoal populations taken from the ovine rumen

The rates of engulfment and breakdown of starch grains and cellulose particles and of the rate of synthesis of amylopectin from cellulose by individual species of entodiniomorphid protozoa (grown in vivo and in vitro) and incubated anaerobically in vitro were studied. Rates of starch uptake varied from 2.3 to 770 micrograms/mg protozoal protein/min; the lowest was found with Diploplastron affine and the highest with Entodinium spp. on initial incubation with starch grains. The rate of starch breakdown varied from 0.49 to 8.6 micrograms/mg protein/min; the rate was dependent on the initial starch concentration inside the protozoa. Eudiplodinium maggii engulfed cellulose particles more rapidly (2-7 times) than rice starch grains and digested the cellulose at rates of 10 to 16.5 micrograms/mg protein/min. In a mixture of starch grains and cellulose particles, it engulfed the latter at 1.35 to 25 times the rate of the former. Eudiplodinium maggii and Epidinium caudatum, but not Entodinium spp. or Dip. affine, synthesized an amylopectin-like material from cellulose at rates of 0.4 to 4.75 micrograms/mg protein/min. If these reactions occur in the rumen in vivo, up to 9 g of amylopectin could be synthesized from cellulose each day by the entodiniomorphid protozoa.

The effect of diet on microfaunal population and function in the caecum of a subterranean naked mole-rat, Heterocephalus glaber

The effect of dietary fibre and starch content on digestibility, microfaunal population and caecal function was investigated in a subterranean mole-rat, Heterocephalus glaber (Rodentia). Mole-rats were fed on a diet of either sweet potato (neutral-detergent fibre (NDF) 65 g/kg dry matter (DM), starch 638 g/kg DM) or carrot (NDF 157 g/kg DM, starch 258.7 g/kg DM) for 4 weeks. Daily intake and faecal output were monitored. Thereafter caecal microfaunal population, density and function were assessed using light and scanning electron microscopy and by measuring both gas and short chain fatty acid (SCFA) production. A 2.4-fold increase in fibre and 2.5-fold decrease in starch content resulted in a decrease in caecal DM content (390 g/kg). A concomitant dramatic decline (by 93%) in ciliate protozoa with a corresponding 2-fold increase in bacteria also accompanied this change in diet. Fermentative efficiency as indicated by gas production was 2.6 times greater on a carrot diet than on sweet potato. Microbial fermentation resulted in higher SCFA concentrations on the carrot diet, with a 42% reduction in SCFA concentration on the sweet potato diet. Here, SCFA contributed 5.1% of daily energy expenditure and this increased 5.0-fold on the carrot diet. Caecal micro-organism function, therefore, played an important role in the nutritional physiology of these naked mole-rats, and enabled maximum utilization of the food substrate.

Utilization of nucleic acids by Selenomonas ruminantium and other ruminal bacteria

Species of ruminal bacteria were screened for the ability to grow in media containing RNA or DNA as the energy source. Bacteroides ruminicola D31d and Selenomonas ruminantium HD4, GA192, and D effectively used RNA for growth, but not DNA. B. ruminicola D31d was able grow on nucleosides but not on bases or ribose. The S. ruminantium strains were able to grow when provided with either nucleosides or ribose but not bases. Strains of S. ruminantium, but not B. ruminicola D31d, were also able to use nucleosides as nitrogen sources. These data suggest that RNA fermentation may be a general characteristic of S. ruminantium.

In vitro metabolism of 2,2'-diaminopimelic acid from gram-positive and gram-negative bacterial cells by ruminal protozoa and bacteria

Bacillus megaterium GW1 and Escherichia coli W7-M5 were specifically radiolabeled with 2,2'-diamino[G-3H]pimelic acid [( 3H]DAP) as models of gram-positive and gram-negative bacteria, respectively. These radiolabeled bacterial mutants were incubated alone (control) and with mixed ruminal bacteria or protozoa, and the metabolic processes, rates, and patterns of radiolabeled products released from them were studied. Control incubations revealed an inherent difference between the two substrates; gram-positive supernatants consistently contained 5% radioactivity, whereas even at 0 h, those from the gram-negative mutant released 22%. Incubations with ruminal microorganisms showed that the two mutants were metabolized differently and that protozoa were the major effectors of their metabolism. Protozoa exhibited differential rates of engulfment (150 B. megaterium GW1 and 4,290 E. coli W7-M5 organisms per protozoan per h), and they extensively degraded [3H]DAP-labeled B. megaterium GW1 at rates up to nine times greater than those of ruminal bacteria. By contrast, [3H]DAP-labeled E. coli W7-M5 degradation by either ruminal bacteria or ruminal protozoa was more limited. These fundamental differences in the metabolism of the two mutants, especially by ruminal protozoa, were reflected in the patterns and rates of radiolabeled metabolites produced; many were rapidly released from [3H]DAP-labeled B. megaterium GW1, whereas few were slowly released from [3H]DAP-labeled E. coli W7-M5. Most radiolabeled products derived from [3H]DAP-labeled B. megaterium GW1 were peptides of bacterial peptidoglycan origin. The ruminal metabolism of DAP-containing gram-positive and gram-negative bacteria, even with the same peptidoglycan chemotype, is thus likely to be profoundly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of monensin on rumen ciliate protozoa in sheep

In a first experiment 4 rams consumed over a period of 70 days 0; 82; 208 and 345 mg of monensin daily, respectively. All doses of monensin caused a marked decrease in total numbers of rumen protozoa in samples taken after this period. More than 90% of total protozoal numbers belonged to the genus Entodinium. The sensitivity of the genus Entodinium to monensin was found to be lower than that of genera Dasytricha and Isotricha. In the second experiment 24 lambs were fed hay and concentrates in the ratio 60:40% (groups 1 and 2) and 40:60% (groups 3 and 4). Groups 2 and 4 received 40 mg monensin per animal daily during 16 weeks. The decrease in protozoal numbers due to monensin in samples taken after this period was significant (P less than 0.001) in lambs fed the concentrate diet (groups 3 and 4) and also in lambs from groups 1 and 2 fed the roughage diet (P less than 0.05). The statistical evaluation of the inhibition of total protozoal numbers by monensin (%) in lambs fed both diets has shown that the antiprotozoal effect of monensin was significantly more intensive with the concentrate diet (P less than 0.025) than with the roughage diet.

Factors affecting the rate of breakdown of bacterial protein in rumen fluid

1. The cellular proteins of Butyrivibrio fibrisolvens, Lactobacillus casei, Megasphaera elsdenii, Selenomonas ruminantium and Streptococcus bovis were labelled by growth in the presence of L-[14C]leucine, and the breakdown of labelled protein was measured in incubations of these bacteria with rumen fluid to which unlabelled 5 mM-L-leucine was added. The rate of protein breakdown was estimated from the rate of release of radioactivity into acid-soluble material. 2. Protein breakdown occurred at different rates in different species. The mean rates for B. fibrisolvens, L. casei, M. elsdenii, Sel. ruminantium and Str. bovis were 28.6, 18.1, 17.7, 10.5 and 5.3%/h respectively in samples of strained rumen fluid (SRF) with different protozoal populations. Rates of 3%/h or less were found in SRF from ciliate-free sheep or in faunated SRF from which protozoa had been removed by centrifugation. Further removal of mixed rumen bacteria had little effect. Suspensions of washed protozoa degraded bacterial protein at rates which were of the same order as those found in SRF. 3. The rate of breakdown of bacterial protein in different samples of SRF tended to increase as the numbers of small entodiniomorphid protozoa increased. The numbers of larger entodiniomorphs and holotrichs had no obvious influence on this rate. 4. Autoclaved and u.v.-treated bacteria were generally no different from live bacteria in their susceptibility to breakdown in SRF from faunated sheep, indicating that endogenous protein turnover was not a significant cause of bacterial protein catabolism. 5. The rate of bacterial protein breakdown was unrelated to the proteolytic activity of SRF. 6. It was concluded that predation by small protozoa is by far the most important cause of bacterial protein turnover in the rumen, with autolysis, other lytic factors and endogenous proteolysis being of minor importance.

Microbial protein and peptide metabolism in rumen fluid from faunated and ciliate-free sheep

1. Protease and deaminase activities and the metabolism of peptides were measured in rumen fluid from ciliate-free sheep and from sheep with a limited population of small entodinia. The same measurements were repeated following inoculation of the latter group with a more typical mixed ciliate population. 2. Protease and dialanine uptake activities of mixed rumen micro-organisms were not significantly influenced by protozoa. Trialanine uptake, leucine aminopeptidase (EC 3.4.11.1), deaminase and trypsin-like protease activities were 70, 107, 73 and 91% higher with the limited population, and 72, 58, 64 and 55% higher when mixed protozoa were present, indicating a major role for the protozoa in these activities.

[The nutritive defaunation of the rumen in ruminants]

Two promising methods to remove the ciliate protozoa of the stomach of ruminants by simple alterations in the feeding system were examined in vivo with lambs and heifers in the present investigation. The use of pelleted concentrates fed ad libitum and of milk, especially of milk fat (cream), turned out to be effective against protozoa when given after few hours of fasting. Milk led to the defaunation of a great proportion of the animals supplied all at once in an amount of 5-10% of rumen fluid volume. With cream the amount could be lower according to the higher fat content. Defaunation with concentrate was found to be not dangerous only for animals adapted to intensive feeding sufficiently. Additionally, a series of in vitro experiments were carried out to evaluate the reasons for the anti-protozoal effects of these methods. Concentrates rich in starch had toxic effects against protozoa, which mainly derived out of the depression in ruminal pH. The formed lactic acid had further effects irrespective of pH. The addition of crude fibre, especially of cellulose or lignin, reduced or prevented the anti-protozoal effects of concentrate fed ad lib. This was not so with the addition of buffers. With milk the included fat was shown to be responsible for the anti-protozoal effects, while the other main constituents of milk were of no importance.

Role of rumen protozoa in nitrogen digestion in sheep given two isonitrogenous diets

1. The effect of protozoa on digestion in the rumen was studied using either defaunated or faunated sheep. 2. Six wethers, each fitted with rumen and simple duodenal cannulas, were given two isonitrogenous diets containing either lucerne (Medicago sativa) hay (diet L) or sodium hydroxide-treated wheat straw (diet S). The diets were given in eight equal portions per day at 3-h intervals. The mean intake of dry matter, 53 g/kg body-weight0.75 per d, was similar for the two diets and each diet had a similar digestible organic matter content. Diet L promoted a large protozoal population and was rich in nitrogen sources of low rumen-degradability, while diet S supported a smaller protozoal population and was rich in rumen-degradable N. 3. Digesta flow at the duodenum was estimated by means of a dual-marker technique using chromium-mordanted lucerne hay and polyethylene glycol as markers. The microbial flow at the duodenum was estimated using diaminopimelic acid (DAPA), nucleic-acid purine bases (PB) and 35S incorporation simultaneously. The different microbial markers were compared in the defaunated sheep. Protozoal N contribution was estimated in faunated sheep. 4. Defaunated sheep had lower rumen ammonia concentrations and molar proportions of butyric acid than faunated sheep, but they had higher molar proportions of propionic acid. 5. Rumen organic matter digestion was reduced by defaunation, but this decrease was compensated for by increased intestinal digestion. 6. There was a net increase of N flow (approximately 10 g/d) between mouth and duodenum in defaunated sheep. This was explained by increases in both microbial and dietary N flows from the rumen compared with faunated sheep. 7. The influence of protozoa on solid- and liquid-phase retention times in the rumen is discussed, as well as the protozoal contribution to microbial N flow in the duodenum of faunated sheep.

Microbiological evaluation of the intraruminal in sacculus digestion technique

The influence of nature of the feed sample, feeding frequency and pore size on the influx of bacteria and protozoa into synthetic fiber bags suspended in the rumens of sheep fed different diets was studied. Counts of total culturable bacteria in bags with a pore size of 10 microns were less than 30% of the ruminal counts for animals that were fed the lucerne hay and high-roughage diets. The maximum count (62 and 82% of the ruminal count) for these specific diets was obtained by using bags with a pore size of 53 microns. Protozoal counts in bags with pore sizes of 30 and 53 microns were equal to or higher than the ruminal counts for the lucerne hay and high-roughage diets but less than half of the ruminal count for the low-roughage diet. An interaction between incubation time, feeding frequency of the host animals, and the microbial populations developing inside the bags was also demonstrated. The results clearly show that the microbial population inside the bag differed from that of the surrounding ruminal ingesta and that caution must be taken in interpreting results on feed evaluation and especially on rates of degradation when using the in sacculus technique. Factors influencing the influx of bacteria and protozoa into bags with different pore sizes and containing a variety of substrates are discussed together with suggestions for the use of this technique.

Rumen holotrich ciliate protozoa

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Effect of reducing-equivalent disposal and NADH/NAD on deamination of amino acids by intact rumen microorganisms and their cell extracts

When mixed rumen microorganisms were incubated in media containing the amino acid source Trypticase, both monensin and carbon monoxide (a hydrogenase inhibitor) decreased methane formation and amino acid fermentation. Both of the methane inhibitors caused a significant increase in the ratio of intracellular NADH to NAD. Studies with cell extracts of rumen bacteria and protozoa indicated that the ratio of NADH to NAD had a marked effect on the deamination of reduced amino acids, in particular branched-chain amino acids. Deamination was inhibited by the addition of NADH and was stimulated by methylene blue, an agent that oxidizes NADH. Neutral and oxidized amino acids were unaffected by NADH. The addition of small amounts of 2-oxoglutarate greatly enhanced the deamination of branched-chain amino acids and indicated that transamination via glutamate dehydrogenase was important. Formation of ammonia from glutamate was likewise inhibited by NADH. These experiments indicated that reducing-equivalent disposal and intracellular NADH/NAD ratio were important effectors of branched-chain amino acid fermentation.

Quantitative effects of defaunation on rumen fermentation and digestion in sheep

Studies on the quantitative significance of protozoa on carbon and nitrogen digestion and metabolism in the rumen were carried out in sheep given a diet of pelleted concentrate (500 g/d) and chopped hay (500 g/d). Measurements were made of apparent digestibility; flows of organic matter and dietary and microbial non-ammonia N (NAN) (using 15NH4+) to the duodenum; and rates of production, interconversion and metabolism of the major C fermentation end-products (from mathematical modelling of 14C isotope values). The population density of bacteria in the rumen increased as a result of defaunation (28.6 compared with 8.2 X 10(9) organisms/ml). This high density was associated with greater utilization of volatile fatty acids (VFA) within the rumen. The rate of irreversible loss (IL) of bicarbonate + carbon dioxide from the rumen was greater in the defaunated animals (98.5 v. 57.2 g C/d) but the IL from the blood was greater in the faunated group (138.6 v. 106.1 gC/d). This is consistent with the hypothesis that the high population density of bacteria found in the rumen fluid of defaunated animals may result in increased fermentation of rumen VFA and digestible dietary carbohydrate, thereby increasing the output of CO2 from the rumen and reducing the quantity of VFA (hence energy) available to the host. There was no difference in the flow of organic matter (OM) to the duodenum but there was a higher faecal excretion of OM in defaunated animals (apparent OM digestibility: 0.72 in faunated, 0.67 in defaunated). Defaunation did not significantly increase the flow of NAN to the duodenum, the percentage of duodenal NAN of bacterial origin or the quantity of microbial NAN synthesized/g organic matter fermented. Faecal excretion of NAN was higher in defaunated animals (5.3 v. 3.6 g N/d).

Nutrition and Growth Characteristics of Trichomitopsis termopsidis , a Cellulolytic Protozoan from Termites

Putatively axenic cultures of Trichomitopsis termopsidis 6057, isolated by M. A. Yamin (J. Protozool. 25:535-538, 1978) from the hindgut of Zootermopsis termites, apparently contained methanogenic bacteria, inasmuch as small amounts of CH 4 were produced during growth. However, T. termopsidis could be “cured” of methanogenic activity by incubation in the presence of bromoethanesulfonate. Both the cured derivative (6057C) and the parent strain (6057) required NaHCO 3 and fetal bovine serum for good growth; the presence of yeast extract in media was stimulatory. Growth of both strains was markedly improved by substituting heat-killed cells of Bacteroides sp. strain JW20 (a termite gut isolate) for heat-killed rumen bacteria in media as a source of bacterial cell material. Heat-killed Bacteroides sp. strain JW20 was the best of a number of bacteria tested, and under these conditions H 2 was a major protozoan fermentation product. Growth of T. termopsidis strains was further improved by co-cultivation in the presence of Methanospirillum hungatii. M. hungatii was the best of a number of H 2 -consuming bacteria tested, and under these conditions CH 4 , but not H 2 , was produced, indicating interspecies transfer of H 2 between the protozoa and M. hungatii. Both strains of T. termopsidis used powdered, particulate forms of cellulose (e.g., pure cellulose, corncob, cereal leaves) as fermentable energy sources, although powdered wood, chitin, or xylan supported little or no growth. Cells of the cellulose-forming coccus Sarcina ventriculi also served as a fermentable energy source, but these were used poorly as a source of bacterial cell material. The only substantial difference between T. termopsidis 6057 and 6057C was that the latter grew poorly or not at all with rumen bacteria as a source of bacterial cell material. The improved growth of T. termopsidis in vitro should facilitate further studies on the cell biology and biochemistry of these symbiotic, anaerobic protozoa.

Protease activities of rumen protozoa

Intact, metabolically active rumen protozoa prepared by gravity sedimentation and washing in a mineral solution at 10 to 15 degrees C had comparatively low proteolytic activity on azocasein and low endogenous proteolytic activity. Protozoa washed in 0.1 M potassium phosphate buffer (pH 6.8) at 4 degrees C and stored on ice autolysed when they were warmed to 39 degrees C. They also exhibited low proteolytic activity on azocasein, but they had a high endogenous proteolytic activity with a pH optimum of 5.8. The endogenous proteolytic activity was inhibited by cysteine proteinase inhibitors, for example, iodoacetate (63.1%) and the aspartic proteinase inhibitor, pepstatin (43.9%). Inhibitors specific for serine proteinases and metalloproteinases were without effect. The serine and cysteine proteinase inhibitors of microbial origin, including antipain, chymostatin, and leupeptin, caused up to 67% inhibition of endogenous proteolysis. Hydrolysis of casein by protozoa autolysates was also inhibited by cysteine proteinase inhibitors. Some of the inhibitors decreased endogenous deamination, in particular, phosphoramidon, which had little inhibitory effect on proteolysis. Protozoal and bacterial preparations exhibited low hydrolytic activities on synthetic proteinase and carboxypeptidase substrates, although the protozoa had 10 to 78 times greater hydrolytic activity (per milligram of protein) than bacteria on the synthetic aminopeptidase substrates L-leucine-p-nitroanilide, L-leucine-beta-naphthylamide, and L-leucinamide. The aminopeptidase activity was partially inhibited by bestatin. It was concluded that cysteine proteinases and, to a lesser extent, aspartic proteinases are primarily responsible for proteolysis in autolysates of rumen protozoa. The protozoal autolysates had high aminopeptidase activity; low deaminase activity was observed on endogenous amino acids.

Proteolytic activity of rumen microorganisms and effects of proteinase inhibitors

Proteolytic activity of the bovine rumen microflora was studied with azocasein as the substrate. Approximately 25% of the proteolytic activity of rumen contents was recovered in the strained rumen fluid fraction, and the balance of the activity was associated with the particulate fraction. The proportion of proteinase activity associated with particulate material decreased when the quantity of particulate material in rumen contents was reduced. The specific activity of the proteinase from the bacterial fraction was 6 to 10 times higher than that from the protozoal fraction. Proteinase inhibitors of synthetic, plant, and microbial origin were tested on proteolytic activity of the separated bacteria. Synthetic proteinase inhibitors that caused significant inhibition of proteolysis included phenylmethylsulfonyl fluoride, N-tosyl-1-lysine chloromethyl ketone, N-tosylphenylalanine chloromethyl ketone, EDTA, cysteine, dithiothreitol, iodoacetate, and Merthiolate. Plant proteinase inhibitors that had an inhibitory effect included soybean trypsin inhibitors types I-S and II-S and the lima bean trypsin inhibitor. Proteinase inhibitors of microbial origin that showed an inhibitory effect included antipain, leupeptin, and chymostatin; phosphoramidon and pepstatin had little effect. We tentatively concluded that rumen bacteria possess, primarily, serine, cysteine, and metalloproteinases.