Rumen Microflora Research Articles

Expression of the Genes celA and xylA isolated from a fragment of metagenomic DNA in Escherichia coli

The glycosyl hydrolase genes cel5A and xyl3A previously isolated by ourselves within a fragment of DNA from the methagenomic library of cow rumen microflora DNA were sub-cloned and expressed in E. coli. The recombinant proteins Cel5A and Xyl3A were purified and characterized. Cellulase Cel5A belongs to the Family 5 glycosyl hydrolases and is a one-module 38.2 kDa enzyme that hydrolyses the 1,4-glycoside bonds of soluble cellulose substrates and amorphous cellulose, showing its maximal activity (31200 u/mg) on lichenan, a soluble substrate with mixed (beta-1,3-1,4) bonds. The end product of the amorphous cellulose hydrolysis is cellobiose. Cel5A is inactive toward the crystal forms of cellulose. Cel5A is an endoglucanase capable of exohydrolysis. The molecular mass of beta-xylosidase Xyl3A belonging to the Family 3 glycosyl hydrolases is 83.7 kDa. The enzyme is active only on xylooligosaccharides, with the maximal activity shown on xylobiose, the end product of the reaction being xylose. No activity on xylane was hitherto observed. Recombinant Cel5A and Xyl3A are stable over a wide range of pH and temperatures, their maximal activity being observed at pH 6.5 and at 55 degrees C.

Electronic Nose analysis of milk from cows grazing on two different Alpine vegetation types

The nutritional distinctiveness of pasture-fed dairy products is mainly influenced by the transfer of specific chemical compounds from the grass to the milk and by their effect on rumen microflora and animal metabolism. Thus, the pasture-fed origin has to be objectively proven, using fast and reproducible analytical methods applied to finished products, in order to protect consumers against potential frauds. In this work, Electronic Nose patterns of Alpine milks produced by cows grazing Trifolium alpinum and Festuca nigrescens pasture types have been examined, in order to test the potential use of this device for routine control analyses of the botanical origin of milk and dairy products. The data have been treated with different multivariate analyses (MANOVA, LDA) and chemometrics (MPLS). The results allow a very good classification of the milks, according to the two treatments. Such results demonstrate that this device could be successfully applied to PDO dairy products food chain as a tool for the determination of their dietary origin.

Inhibition of methanogens by bromochloromethane: effects on microbial communities and rumen fermentation using batch and continuous fermentations

Bromochloromethane (BCM), a halogenated methane analogue, was evaluated for its anti-methanogenic activity in both batch and continuous fermentation systems. For batch fermentation, a roughage-based substrate was incubated with mixed rumen microflora for 24 h at two concentrations of BCM (5 and 10 microm). A 89-94 % reduction in methane was obtained in terms of volume and truly degraded substrate (TDS; P < 0.05). The partitioning factor (an index of efficiency of microbial protein production; expressed as mg TDS/ml net gas produced) increased from 3.55 to 3.73 (P < 0.05), while the acetate:propionate proportion decreased from 2.80 to 2.22 (P < 0.05). A complete inhibition of methanogens was associated with a 48 % decrease in Ruminococcus flavefaciens, a 68 % increase in Fibrobacter succinogenes and a 30 % increase in rumen fungi when quantified using qPCR. The continuous fermentation was carried out using the roughage-based substrate in four fermenters, two fermenters being control and the other two fed with BCM (5 microm) once in a day, for nine consecutive days. A persistent effect of BCM on methane reduction (85-90 %) was obtained throughout the study (P < 0.05) with no effect on gas production, SCFA production, acetate:propionate proportion, true degradability and efficiency of microbial mass synthesis (P>0.05). The complete inhibition of methane resulted in a significant decrease in R. flavefaciens and methanogens (P < 0.05) and an increase in fungal population (P < 0.05), while there was no effect on total bacterial and F. succinogenes populations (P>0.05). The batch fermentation confirms the anti-methanogenic activity of BCM, while the continuous fermentation indicates the persistency of this effect under in vitro conditions.

Disappearance of nine monoterpenes exposed in vitro to the rumen microflora of dairy goats: Effects of inoculum source, redox potential, and vancomycin

This in vitro study evaluated the roles of diet type and redox potential in the degradation of linalool, (E)- and (Z)-beta-ocimene, alpha-phellandrene, (-)-beta-pinene, (-)-alpha-pinene, (+)-alpha-pinene, sabinene, and alpha-terpinene when incubated with rumen microflora, and it provided information on the time course of their disappearance. The 9 monoterpenes are found in the winter and spring diets of dairy goats in northwestern Mediterranean grazing systems. The diets were individually exposed to rumen microflora for 3 h in 17-mL culture tubes at a concentration of 4 microL/L. The mixed flora of the inoculum was controlled by the use of vancomycin (eliminating gram-positive bacteria) and by the energy source (starch vs. structural polysaccharides) on which rumen microflora had been grown. Redox potential was controlled by addition of L-cysteine-hydrochloride. The preliminary adaptation of microbial inoculum to a diet rich in structural carbohydrates reduced the recovery yields of (E)- and (Z)-beta-ocimene, (-)-beta-pinene, (-)-alpha-pinene, (+)-alpha-pinene, and sabinene (P<0.01), whereas vancomycin was without effect. The effect of carbohydrate source likely stems from the specific composition of the microbial community rather than from its acidogenic capacity. Reducing the culture redox potential by 50 mV reduced the recovery yields of linear and monocyclic terpenes (P<0.02), and the culture redox potential interacted with the inoculum source for (E)- and (Z)-beta-ocimene and for alpha-phellandrene. The time course of terpene disappearance was studied by exposing terpenes to a rumen microflora adapted either to starch or to fiber for 3, 6, or 24 h. The degraded fraction reached a plateau within 3 h for alpha-phellandrene and for all the isomers of beta-ocimene and pinene with the fiber-adapted microflora as well as with both inocula for alpha-terpinene. With the starch-adapted microflora, this steady state was reached for most other terpenes within 6 h of incubation. Sabinene was the only compound still disappearing after an incubation period of 6 h. Biotic and environmental variables in the rumen affected terpene degradation in a way that can alter the dietary terpene profile and possibly its influence on animal product characteristics.

Cell wall fermentation kinetics are impacted more by lignin content and ferulate cross‐linking than by lignin composition

AbstractBACKGROUND: We used a biomimetic model system to ascertain how reductions in ferulate–lignin cross‐linking and shifts in lignin composition influence ruminal cell wall fermentation. Primary walls from maize cell suspensions with normal or reduced feruloylation were artificially lignified with various monolignols previously identified in normal, mutant, and transgenic plants. Cell wall fermentability was determined from gas production during in vitro incubation with rumen microflora and by analysis of non‐fermented polysaccharides.RESULTS: Hemicellulose fermentation lag time increased by 37%, rate decreased by 37%, and the extent declined by 18% as cell wall lignin content increased from 0.5 to 124 mg g−1. Lignification increased lag time for cellulose fermentation by 12‐fold. Ferulate–lignin cross‐linking accounted for at least one‐half of the inhibitory effect of lignin on cell wall fermentation. Incorporating sinapyl p‐coumarate, a precursor of p‐coumaroylated grass lignin, increased the extent of hemicellulose fermentation by 5%. Polymerizing varying ratios of coniferyl and sinapyl alcohols or incorporating 5‐hydroxyconiferyl alcohol, coniferaldehyde, sinapyl acetate, or dihydroconiferyl alcohol into lignin did not alter the kinetics of cell wall fermentation.CONCLUSION: The results indicate that selection or engineering of plants for reduced lignification or ferulate–lignin cross‐linking will improve fiber fermentability more than current approaches for shifting lignin composition. Copyright © 2008 Society of Chemical Industry

Effect of chitosans on in vitro rumen digestion and fermentation of maize silage

The gas in vitro technique was used to study the effects of six types of chitosans, each having different molecular weights and acetylation degrees, on rumen microbial fermentation. In a first trial, a separate concentration of 750 mg/l of culture fluid for each of the six chitosans (CHI1, CHI2, CHI3, CHI4, CHI5, and CHI6) was incubated for 24 h in diluted ruminal fluid with maize silage as the substrate. The ionophore antibiotic monensin (MON) was used as a positive control, and a negative control with no chitosan (CTR) was also included. Each treatment was tested in triplicate for three different periods. At the end of the trial, samples were collected to determine volatile fatty acid (VFA) and ammonia N concentrations, and pH and gas production values were recorded. Methane concentration was estimated stoichiometrically. In vitro true organic matter digestibility (IVOMD) and partitioning factor (PF, mg OM truly degraded/ml gas produced) were also calculated. In a second trial, a separate concentration of 750 mg/l of each of the six chitosans was incubated for 144 h in diluted ruminal fluid with maize silage as the substrate, to study the effects of these compounds on fermentation kinetics. All six chitosans decreased the IVOMD and PF values. Chitosan inclusion did not affect the fermentation of the substrate's soluble fraction, but did reduce the fermentation kinetics of the insoluble but fermentable fraction. However, only CHI5 and CHI6 decreased total VFA concentration. CHI3 and CHI6 decreased the molar proportion of acetate and increased the molar proportion of propionate, thus increasing the propionate-to-acetate ratio. Chitosan inclusion did not affect molar proportions of butyrate. With the exception of CHI2, the molar proportion of branch-chained VFA was lowered by all of the chitosan treatments. Most of the treatments also decreased methane production, also with the exception of CHI2. In conclusion, chitosan extracts may enable the manipulation of rumen microbial fermentation, but further research is required to elucidate the effect of chitosans on ruminal fermentation parameters in commercial diets as well as the adaptability of rumen microflora to these additives.

A new growth medium for rapid selection and purification of Clostridium proteoclasticum transposon mutants

Clostridium proteoclasticum is commonly associated with the rumen microflora of pasture-fed cattle and sheep and has significant hemicellulose degradation abilities. Genes involved in plant fibre breakdown are commonly identified by producing site-specific mutations. However, the genetics of C. proteoclasticum and other closely-related Butyrivibrio/ Pseudobutyrivibrio species is not well-established. Therefore random transposon mutants of C. proteoclasticum were generated by conjugation with Enterococcus faecalis containing Tn 916. A new counter-selection agar medium was developed containing L-arabinose and D-raffinose as carbon sources, both of which are utilized by C. proteoclasticum only, and also ciprofloxacin, an antibiotic that suppresses the growth of E. faecalis. With this new medium the enhanced growth and more rapid separation of C. proteoclasticum transposon mutants from the background of E. faecalis cells was made, thereby facilitating the selection of transposon mutants and the identification of their Tn 916 insertion sites.

Veterinary aspects and perspectives of nutrigenomics: A critical review

Nutrigenomics examines nutrient-gene interactions on a genome-wide scale. Increased dietary fat or higher non-esterified fatty acids (NEFA) from starvation-induced mobilisation may enhance hepatic oxidation and decrease esterification of fatty acids by reducing the expression of the fatty acid synthase gene. The key factors are the peroxisome proliferator-activated receptors (PPARs). Dietary carbohydrates--both independently and through insulin effect--influence the transcription of the fatty acid synthase gene. Oleic acid or n-3 fatty acids downregulate the expression of leptin, fatty acid synthase and lipoprotein lipase in retroperitoneal adipose tissue. Protein-rich diets entail a shortage of mRNA necessary for expression of the fatty acid synthase gene in the adipocytes. Conjugated linoleic acids (CLAs) are activators of PPAR and also induce apoptosis in adipocytes. Altered rumen microflora produces CLAs that are efficient inhibitors of milk fat synthesis in the mammary gland ('biohydrogenation theory'). Oral zinc or cadmium application enhances transcription rate in the metallothionein gene. Supplemental CLA in pig diets was found to decrease feed intake and body fat by activating PPARgamma-responsive genes in the adipose tissue. To prevent obesity and type II diabetes, the direct modulation of gene expression by nutrients is also possible. Nutrigenomics may help in the early diagnosis of genetically determined metabolic disorders and in designing individualised diets for companion animals.

The effect of different concentrate: Lucerne hay ratio on crude protein degradation of various feeds using in situ technique

Available information on the effect of ruminal pH on degradation of crude protein of various feeds is scarce. It has been reported that in a high concentrate diets, protein degradation is usually reduced (Molero et al., 2004). This reduction has been attributed to lower ruminal pH, which causes the changes in protein solubility (Loerch et al., 1983) and reduces fibrolytic activity of rumen microflora. There is also limited information concerning the requirements for rumen degradable N (RDN) when high-grain diets are given to steers, and most of that information has been obtained using urea as the source of RDN. The aim of the present experiment was to evaluate the effect of different concentrate to lucerne hay ratios (60:40, 70:30, 80:20 or 90:10) on ruminal crude protein degradation kinetic of lucerne hay, barley grain, soybean meal and fish meal.

Optaflexx1 affects rumen fermentation (2007)

Three experiments were conducted to determine effects of ractopamine-HCl, sold under the trade name Optaflexx, on rumen fermentation. In experiment 1, fermentative gas production was measured in vitro to determine the impact of increasing amounts of ractopamine- HCl added to rumen fluid. Ractopamine-HCl increased gas production when added to rumen fluid up to 10 times the assumed physiological dosage of 200 mg per head/day, but depressed gas production at 100 times the physiological dose. Experiment 2 and 3 evaluated the effects of ractopamine-HCl on production of volatile fatty acids (VFAs) by ruminal microbes. In vitro experiments revealed no effect of ractopamine on volatile fatty acid production, but VFA levels in rumen fluid of cattle 23 hours after feeding were lower for cattle fed Optaflexx then for controls (P = 0.01). Results of these studies indicate that ractopamine-HCl has a direct influence on fermentation by rumen microflora.

In vitro methods to evaluate the effects of plant waste products on rumen and gut microflora

The requirement of a safety use of additives in animal nutrition induced the EU to introduce a new regulation on feed additives. Organic wastes from the food/feed industry could include valuable substances to novel high value added products as additives. The objective of the present study was to screen in vitro effects of organic wastes on rumen microbial metabolism by batch incubator system (pH, ammonia N, VFA concentration, Total Bacterial Count) and on gut microbial flora from monogastrics by paper disc agar diffusion method (growth or inhibition of gut microbial flora). The results obtained by these preliminary in vitro tests have permitted to identify the substances with positive activities that will be evaluated in future in vivo trials.

Rumen microflora counts in milking buffalo cows fed maize silage and sorghum silage based diets

4 cannulated buffalo milking cows were administered two different diets with the same energy and protein content based on maize silage (diet G1) and sorghum silage (diet G2). Total viable bacteria, cellulolytic and xilanolytic bacteria, fungi, protozoa and pH were determined on whole rumen content samples.Total viable bacteria, xilanolytic bacteria, fungi, protozoa counts and pH values did not show any significant difference between the two diets. Only the values regarding cellulolytic bacteria showed the tendency (P≤0,10) to be higher in diet G2 in comparison with diet G1. This fact was probably due to a lower content of indigestible fiber in diet G2 with respect to diet G1 (ADF 15.6 vs. 22.4 respectively).

Metabolic profile in growing buffalo heifers fed diet with different energy content

Aim of this study was to verify the relation among the mediators and indicators of nutritional status like insulin, glucagon, urea, cholesterol, triglycerides and total proteins in growing buffalo heifers, fed diets with different energy density. 12 Murrah heifers were randomly allocated into two dietary treatments (High, Group H; Low, Group L) that differed in energetic levels (Group H: 5.8 UFL/d; Group L: 3.6 UFL/d). Every 30 days, for a total of five times, blood samples were collected at 08.00 h, before feeding, from the jugular vein in vacutainer tubes and analysed to determine metabolic profile. Data on haematic constants were analysed by ANOVA for repeated measures with treatment as the main factor. Low energy availability and low NSC reduced the glucose and insulin and increased glucagone and urea blood levels. The increase of NSC in the diet of group H during the experiment may caused a reduction of the fibre digestibility after the period of adaptation of the rumen microflora and, as a paradox effect, suffered for an energetic lack with a subsequent activation of lipolysis and mobilization of their body reserves. Liver and muscular synthesis increase in group with a high energy availability.

What is the True Supply of Amino Acids for a Dairy Cow?

Improving the prediction of milk protein yield relies on knowledge of both protein supply and requirement. Definition of protein/amino acid supply in ruminants is a challenging task, due to feedstuff variety and variability and to the remodeling of nutrient intake by the rumen microflora. The questions arise, therefore, how and where should we measure the real supply of AA in the dairy cow? This review will follow the downstream flow of AA from duodenum to peripheral tissue delivery, with a glance at the efficiency of transfer into milk protein. Duodenal AA flow comprises rumen undegrad-able feed, microbial protein, and endogenous secretions. Most attention has been directed toward definition of the first two contributions but the latter fraction can represent as much as 20% of duodenal flow. More information is needed on what factors affect its magnitude and overall impact. Once digested, AA are absorbed into the portal vein. The ratio of portal absorption to small intestinal apparent digestion varies among essential AA, from 0.43 (threonine) to 0.76 (phenylalanine), due to the contributions of preduodenal endogenous secretions to the digestive flow, non-reabsorption of endogenous secretions and gut oxidation of AA. Few data are available on these phenomena in dairy cows but the evidence indicates that they alter the profile of AA available for anabolic purposes. Recent comparisons of estimated duodenal flux and measured portal flux have prompted a revisit of the NRC (2001)approach to estimate AA flows at the duodenum. Changes to the model are proposed that yield predictions that better fit the current knowledge of AA metabolism across the gut. After absorption, AA flow first to the liver where substantial and differential net removal occurs, varying from zero for the branched-chain AA to 50% of portal absorption for phenylalanine. This process alters the pattern of net supply to the mammary gland. Overall, intermediary metabolism of AA between the duodenum and the mammary gland biologically explains the decreased efficiency of the transfer of absorbed AA into milk protein as maximal yield is approached. Therefore, variable, rather than fixed, factors for transfer efficiencies must be incorporated into future predictive models.

Interactions Between Euphorbia esula Toxins and Bovine Ruminal Microbes

Cattle generally avoid grazing leafy spurge (LS; Euphorbia esula), whereas sheep and goats will often eat it. Understanding metabolism of toxic phytochemicals in LS by bovine rumen microflora may help explain why cattle often develop aversions to LS after initially eating it. Toxicity of LS compounds after in vitro fermentation with normal vs. antibiotic-modified bovine rumen digesta was evaluated at different lengths of fermentation. Levels of toxic and aversion-inducing ingenols were determined for fermented and nonfermented mixtures of LS and bovine rumen digesta, and the toxicity of an aversion-inducing extract of LS to rumen microbial species that are common in cattle, sheep, and goats was evaluated. Fermentation of LS with bovine digesta increased the toxicity of extracted compounds. Introduction of neomycin (an antibiotic that preferentially inhibits gram-negative bacteria) into the LS and bovine rumen digesta mixtures did not appear to affect toxicities regardless of fermentation length. Levels of ingenol were observed in LS and bovine digesta mixtures (both fermented and nonfermented) that were consistent with levels of ingenols reported for LS. Finally, a toxic extract of LS had little or no negative effect on the growth of several common species of rumen bacteria. The results indicate that LS is not generally toxic to the ruminal bacteria, but that microbial activity in the rumen may be responsible for enhancing LS toxicity to cattle.

How Do Lignin Composition, Structure, and Cross‐Linking Affect Degradability? A Review of Cell Wall Model Studies

Because of the complexity of plant cell wall biosynthesis, the mechanisms by which lignin restrict fiber degradation are poorly understood. Many aspects of grass cell wall lignification and degradation are successfully modeled by dehydrogenation polymer‐cell wall (DHP‐CW) complexes formed with primary walls of corn Zea mays L. This system was used to assess how variations in lignin composition, structure, and cross‐linking influence the hydrolysis of cell walls by fungal enzymes. Altering the normal guaiacyl, syringyl, and p‐hydroxyphenyl makeup of lignin did not influence cell wall degradability; each unit of lignin depressed cell wall degradability by two units. Plants with perturbed lignin biosynthesis often incorporate unusual precursors into lignin and one of these, coniferaldehyde, increased lignin hydrophobicity and further depressed degradability by up to 30%. In other studies, lignin formed by gradual “bulk” or rapid “end‐wise” polymerization of monolignols had markedly different structures but similar effects on degradability. Reductions in cell wall cross‐linking, via oxidative coupling of feruloylated xylans to lignin or nucleophilic addition of cell wall sugars to lignin quinone‐methide intermediates, increased the initial hydrolysis of cell walls by up to 46% and the extent of hydrolysis by up to 28%. Overall, these studies suggest that reductions in lignin concentration, hydrophobicity, and cross‐linking will improve the enzymatic hydrolysis and utilization of structural polysaccharides for nutritional and industrial purposes. In ongoing work, we are developing a DHP‐CW system for dicots and are investigating how cross‐linking and various acylated and unusual monolignols influence the formation of lignin and the degradation of cell walls by rumen microflora.

Persistency of the effect ofLactuca sativaandUrtica dioicaonin vitroacidosis

As part of the EU Framework 5 project “Rumen-Up”, plants were screened for their effect on thein vitrofermentation medium pH. Common lettuce(Lactuca sativa)and stinging nettle(Urtica dioica)were identified as having a positive effect, maintaining a higher pH when fermented with wheat over 48 hours. It was considered that the rumen microflora may adapt to the inclusion of either plant in the diet, leading to negation of the effect, and therefore reducing the opportunities for use as a supplement to prevent acidosis. This study was designed to investigate the persistency of the anti-acidosis effect using the Rumen Simulation Technique (RUSITEC), together with batchin vitrofermentation using inoculum harvested from RUSITEC.

Effects of ionophores, vitamin B 6 and distiller's grains on in vitro tryptophan biosynthesis from indolepyruvic acid, and production of other related compounds by ruminal bacteria and protozoa

Tryptophan (Trp) is an essential amino acid (AA) and it may be limiting to ruminants when feed rations are based on corn (maize). Distiller's grains (DGs) from barley are the dried residue remaining after the starch fraction of corn is fermented using selected yeasts and enzymes to produce alcohol. DG is a rich source of nutrients, because it contains polyphenol, peptides, yeast extracts (nucleic acids and amino acids), citric acid, fermented barley extract and fiber. The ionophore-type feed additives (monensin and salinomycin) modify the movement of monovalent (sodium and potassium) and divalent (calcium) ions across biologic membranes, modify the rumen microflora pattern, decrease acetate and methane production, increase propionate, may improve nitrogen utilization and can increase dry matter digestibility in ruminants. Vitamin B 6 (B 6) acts as a coenzyme in many enzymatic reactions that are involved in the metabolism of AA. An in vitro study was conducted to examine the effects of salinomycin (SL), monensin (MN), B 6 and DG on the production of tryptophan (Trp) and other related compounds from indolepyruvic acid (IPA) by mixed ruminal bacteria (B), protozoa (P) and their mixture (BP). Ruminal microbial suspensions were anaerobically incubated at 39 °C for 12 h, and analyses of Trp and its related metabolites were carried out by HPLC. When 1 mM of IPA was used as a substrate, it was mainly converted to Trp and indoleacetic acid (IAA), resulting in concentrations of 300 and 131, 410 and 28, and 435 and 112 μM in B, P and BP suspensions, respectively. A considerable amount of skatole (SKT) (in B and BP) and indolelactic acid (ILA) (in B, P and BP), and small amount of p-cresol (CRL) (in B and BP) were also produced from IPA. The production of Trp from IPA with SL, MN, B 6 and DG were increased ( P < 0.05) by 18.9–55.3, 9.0–50.4 and 5.1–16.1% in B, P and BP, respectively. The increased Trp production with these additives occurred by the simultaneous inhibition of IAA from IPA. On the other hand, addition of B 6 into B, P and BP enhanced ( P < 0.05) IAA from IPA by 18.9, 26.5 and 5.1%, respectively. Trp produced from IPA with SL was 13.8, 8.8 and 5.0% higher than that with MN in B, P and BP, respectively. Salinomycin and MN completely inhibited the SKT and CRL (in B and BP), and partially inhibited ILA (in B, P and BP) from IPA. On the other hand, B 6 stimulated the production of SKT and CRL in B and BP, and ILA in B, P and BP from IPA. No effects were observed on the production of SKT, CRL and ILA by DG. We conclude that addition of these additives to feeds may increase duodenal Trp supply in ruminants. In addition, SL and MN may also inhibit the production of clinically important Trp metabolites (SKT, CRL and ILA).

Effect of anaerobic fungi on in vitro feed digestion by mixed rumen microflora of buffalo

Five strains of anaerobic fungi isolated from the faeces of wild (hog deer, Cervus porcinus; blackbuck, Antelope cervicapra; spotted deer, Axis axis; nilgai, Baselophus tragocamelus) and rumen liquor of domestic (sheep, Ovies aries) ruminants showing high fibrolytic enzyme producing ability were added to mixed rumen microflora of buffalo to study their effect on the digestibility of lignocellulosic feed (wheat straw and wheat bran in the ratio of 80:20), enzyme production and fermentation end products in in vitro conditions. Among the 5 isolates studied, FNG5 (isolated from nilgai) showed the highest stimulating effect on apparent digestibility (35.31 +/- 1.61% vs. 28.61 +/- 1.55%; P < 0.05), true digestibility (43.64 +/- 1.73% vs. 35.37 +/- 1.65%; P < 0.01), neutral detergent fiber digestibility (29.30 +/- 2.58% vs. 18.47 +/- 2.12; P < 0.01) of feed 24 h after inoculation compared to the control group. The production of carboxymethyl cellulase, xylanase, acetyl esterase and beta-glucosidase was significantly (P < 0.05) higher in the FNG5 inoculated incubation medium. There was no improvement in the digestibility and enzyme production on the addition of the other 4 isolates. Total volatile fatty acid levels as well as the concentration of acetate, propionate, isobutyrate and valerate were significantly higher in the FNG5 added group as compared to the control group. The fungal isolate FNG5 from nilgai, a wild ruminant, was found to be superior to the other isolates tested and appears to have a potential to be used as a feed additive for improving fiber degradation in domestic ruminants.

Effect of a slow-intake urea supplementation on growing kids fed corn stubble or alfalfa with a balanced concentrate

One hundred and sixty Alpine kids (16 kg BW) were studied for 150 days with two diets, evaluating in situ DM disappearance, VDMI, OMI, rumen degradation, rate of passage, ammonia (NH3) and volatile fatty acids (VFA) concentrations, apparent digestibility, pH, total fermentable carbohydrates (FC), and BW gains. Group 1, designated as CS/SIUS (n=80 plus two cannulated goats) was offered corn stubble (CS) 800 g per day and alfalfa hay (AH) 100 g per day, with 150 g per day of a slow-intake urea supplement (SIUS) consisting of 16.5% molasses, 5% urea, 4% fishmeal, 2% limestone, 16% cottonseed meal, 17.5% rice polishing, 14.5% corn, 9.5% poultry litter, 4.1% commercial mineral salt, 0.9% orthophosphate, 2% ammonium sulfate, 1.5% cement kiln dust, and 6.5% animal lard. Group 2, designated as AH/BC (n=80 plus two cannulated goats) were fed 550 g AH per day supplemented with 450 g of a balanced concentrate (BC) per day, consisting of 1.1% mineral salt, 1.2% orthophosphate, 40.0% corn, 25.9% wheat bran, 25.8% barley, and 6.0% soybean meal. VDMI and OMI were similar for 150 days for the two experimental diets fed to goats. NH3 concentration and degradation of potential non-degradable DM fractions were augmented by SIUS (P<0.05). Rumen pH rose to 6.9 by 2 h after CS/SIUS was offered and stayed above 6.6 for 12 h, while the rumen pH in AH/BC goats decreased to 5.57 by 6 h and rose again to 6.50 after 12 h. N intake with CS/SIUS was 18.60 g per day versus 14.57 g per day with AH/BC (P<0.05). In vivo N digestibililty was 76.63% in the CS/SIUS diet and 54.16% in AH/BC (P<0.05). In vivo digestibility of NDF was greater for CS/SIUS (P<0.05) (77.14% versus 65.11% for AH/BC). Degradation rate constant (kd) of NDF also favored the CS/SIUS diet (P<0.05) and non-degradable fiber was less (P<0.05) (35.18% versus 63.32% for AH/BC). Half-time (t1/2, h) disappearance of cellulose and hemicellulose in the CS/SIUS diet were 29.34 and 29.14 compared to 16.54 and 20.16 in the AH/BC diet, respectively (P<0.05) and passage rates differed similarly (P<0.05). True digestibility of cellulose in CS/SIUS at 46.24% was higher (P<0.5) than that of AH at 33.22%. Growth in 150 days averaged 112±23 g gain per day for CS/SIUS compared to 86±21 g per day for the AH/BC diet (P<0.05). SIUS supplement intake per kg BW ranged from 6.57 to 3.12 g per day for the CS fed goats and 21.02 to 11.80 g per day for the AH/BC fed control goat kids (P<0.05). Rumen NH3 was higher for CS/SIUS (12.3 mg per 100 ml versus 6.8 mg per 100 ml for AH/BC) (P<0.01). Rumen acetic and butyric acids increased with the CS/SIUS diet (P<0.05), while propionic acid was less and total VFA were not different. Supplementation of a high fiber diet with a slow-intake NPN supplement improved rumen fermentation. SIUS supplied critical nutrients to the rumen microflora, improved rate of passage, ruminal pH, NH3 contents, and resulted in higher weight gain than the AH/BC fed control goat kids. Results showed that high fiber forages like CS can be used efficiently by growing goats, when conditions for ruminal microorganisms are improved with a continuous slow-intake N supplementation.