• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.7
• /
• pp.936-941
• /
• 2004

Four rumen-cannulated cows (330 kg average weight at 4 years) were used to evaluate the supplement of ensiled cassava tops (ECT) (variety KM 94, 39% DM) on rumen functions, thyroid hormones and liver enzymes. The treatments, arranged in a 4 $\times$4 Latin square design, were ECT at 0, 50, 100 and 150 g CP 100 kg$^{-1}$ body weight (BW), and a basal diet of urea-treated fresh rice straw (UFRS) ad libitum and 1.1 kg dry matter (DM) cassava root meal (CRM) in each 30 day study period. The results showed a continuous decrease in dry matter intake (DMI) of UFRS with increasing level of ECT supplement (p<0.001). The highest total DMI was observed for treatment ECT$_{150}$ (2.68 kg DM 100 kg$^{-1}$ BW day$^{-1}$) followed by treatments ECT$_{100}$, ECT$_{50}$ and ECT$_{0}$, with 2.47, 2.24 and 2.06 kg DM 100 kg$^{-1}$ BW⋅day$^{-1}$, respectively. Increasing levels of ECT supplement increased the concentration of total volatile fatty acids (p<0.05) and ammonia nitrogen (p<0.05) and resulted in a decrease in pH (p<0.05). Overall average plasma triiodothyronine and thyroxine concentrations were 0.80, 0.82, 0.85 and 0.69 ng ml$^{-1}$ (p>0.05), and 50.9, 49.5, 50.7 and 42.4 ng ml-1 (p>0.05) for treatments ECT$_{0}$, ECT$_{50}$, ECT$_{100}$ and ECT$_{150}$, respectively. There were non-significant differences in alanine aminotransferase and aspartate aminotransferase among treatments. It is concluded that ECT is a valuable protein-rich feed supplement to cattle, and the highest level of on average 2.48 kg DM ECT per cow and day (28% of total DMI) did not significantly affect thyroid gland hormones and liver enzymes in cows.

• Asian-Australasian Journal of Animal Sciences
• /
• v.12 no.1
• /
• pp.104-112
• /
• 1999

Since the anaerobic rumen fungi were discovered in the rumen of a sheep over two decades ago, they have been reported in a wide range of herbivores fud on high fibre diets. The extensive colonisation and degradation of fibrous plant tissues by the fungi suggest that they have a role in fibre digestion. All rumen fungi studied so far are fibrolytic. They produce a range of hydrolytic enzymes, which include the cellulases, hemicellulases, pectinases and phenolic acid esterases, to enable them to invade and degrade the lignocellulosic plant tissues. Although rumen fungi may not seem to be essential to general rumen function since they may be absent in animals fed on low fibre diets, they, nevertheless, could contribute to the digestion of high-fibre poor-quality forages.

• Asian-Australasian Journal of Animal Sciences
• /
• v.12 no.1
• /
• pp.93-103
• /
• 1999

Recent advances in the biotechnology of ruminal bacteria have been made in the characterization of enzymes involved in plant cell wall digestion, the exploration of mechanisms of gene transfer in ruminal bacteria, and the development of vectors. These studies have culminated in the introduction and expression of heterologous glucanase and xylanase genes and a fluoroacetate dehalogenase gene in ruminal bacteria. These recent studies show the strategy of gene and vector construction necessary for the production of genetically engineered bacteria for introduction into ruminants. Molecular research on proteolytic turnover of protein in the rumen is in its infancy, but a novel protein high in essential amino acids designed for intracellular expression in ruminal organisms provides an interesting approach for improving the amino acid profile of ruminal organisms.

• Asian-Australasian Journal of Animal Sciences
• /
• v.15 no.11
• /
• pp.1659-1676
• /
• 2002

Ruminant animals develop a diverse and sophisticated microbial ecosystem for digesting fibrous feedstuffs. Plant cell walls are complex and their structures are not fully understood, but it is generally believed that the chemical properties of some plant cell wall compounds and the cross-linked three-dimensional matrix of polysaccharides, lignin and phenolic compounds limit digestion of cell wall polysaccharides by ruminal microbes. Three adaptive strategies have been identified in the ruminal ecosystem for degrading plant cell walls: production of the full slate of enzymes required to cleave the numerous bonds within cell walls; attachment and colonization of feed particles; and synergetic interactions among ruminal species. Nonetheless, digestion of fibrous feeds remains incomplete, and numerous research attempts have been made to increase this extent of digestion. Exogenous fibrolytic enzymes (EFE) have been used successfully in monogastric animal production for some time. The possibility of adapting EFE as feed additives for ruminants is under intensive study. To date, animal responses to EFE supplements have varied greatly due to differences in enzyme source, application method, and types of diets and livestock. Currently available information suggests delivery of EFE by applying them to feed offers the best chance to increase ruminal digestion. The general tendency of EFE to increase rate, but not extent, of fibre digestion indicates that the products currently on the market for ruminants may not be introducing novel enzyme activities into the rumen. Recent research suggests that cleavage of esterified linkages (e.g., acetylesterase, ferulic acid esterase) within the plant cell wall matrix may be the key to increasing the extent of cell wall digestion in the rumen. Thus, a crucial ingredient in an effective enzyme additive for ruminants may be an as yet undetermined esterase that may not be included, quantified or listed in the majority of available enzyme preparations. Identifying these pivotal enzyme(s) and using biotechnology to enhance their production is necessary for long term improvements in feed digestion using EFE. Pretreating fibrous feeds with alkali in addition to EFE also shows promise for improving the efficacy of enzyme supplements.

• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.2
• /
• pp.199-202
• /
• 2004

Cellulolytic bacterial strains have been isolated from the faeces of wild (blackbuck, Antilope cervicapra; nilgai, Baselophus tragocamelus chinkara, Gazella gazella spotted deer, Axis axis and hog deer, Cervus porcinus) and rumen liquor of domestic (sheep, Ovis aries) ruminants. Five best cellulose degrading bacterial isolates (Ruminococcus sp.) were used as microbial feed additive along with buffalo rumen liquor as inoculum to study their effect on digestibility of feed and enzyme production in in vitro conditions. The bacterial isolate from chinkara (CHI-2) showed the highest per cent apparent dry matter (DM) digestibility ($35.40{\pm}0.60$), true dry matter digestibility ($40.80{\pm}0.69$) and NDF ($26.38{\pm}0.83$) digestibility (p<0.05) compared to control ($32.73{\pm}0.56$, $36.64{\pm}0.71$ and $21.16{\pm}0.89$, respectively) and other isolates at 24 h of incubation with lignocellulosic feeds (wheat straw and wheat bran, 80:20). The same isolate also exhibited the highest activities of fibre degrading enzymes like carboxymethylcellulase, xylanase, ${\beta}$-glucosidase and acetyl esterase. The bacterial isolate from chinkara (Gazella gazella) appears to have a potential to be used as feed additive in the diet of ruminants for improving utilization of nutrients from lignocellulosic feeds.

• Asian-Australasian Journal of Animal Sciences
• /
• v.22 no.1
• /
• pp.131-138
• /
• 2009

Among rumen microbes, bacteria play important roles in the biological degradation of plant fiber due to their large biomass and high activity. To maximize the utilization of fiber components such as cellulose and hemicellulose by ruminant animals, the ecology and functions of rumen bacteria should be understood in detail. Recent genome sequencing analyses of representative fibrolytic bacterial species revealed that the number and variety of enzymes for plant fiber digestion clearly differ between Fibrobacter succinogenes and Ruminococcus flavefaciens. Therefore, the mechanism of plant fiber digestion is also thought to differ between these two species. Ecology of individual fibrolytic bacterial species has been investigated using pure cultures and electron microscopy. Recent advances in molecular biology techniques complement the disadvantages of conventional techniques and allow accurate evaluation of the ecology of specific bacteria in mixed culture, even in situ and in vivo. Molecular monitoring of fibrolytic bacterial species in the rumen indicated the predominance of F. succinogenes. Nutritive interactions between fibrolytic and non-fibrolytic bacteria are important in maintaining and promoting fibrolytic activity, mainly in terms of crossfeeding of metabolites. Recent 16S rDNA-based analyses suggest that presently recognized fibrolytic species such as F. succinogenes and two Ruminococcus species with fibrolytic activity may represent only a small proportion of the total fibrolytic population and that uncultured bacteria may be responsible for fiber digestion in the rumen. Therefore, characterization of these unidentified bacteria is important to fully understand the physiology and ecology of fiber digestion. To achieve this, a combination of conventional and modern techniques could be useful.

• Asian-Australasian Journal of Animal Sciences
• /
• v.26 no.7
• /
• pp.945-951
• /
• 2013

In vitro studies were undertaken to develop an appropriate fibrolytic enzymes cocktail comprising of cellulase, xylanase and ${\beta}$-D-glucanase for maize stover with an aim to increase its nutrient utilization in sheep. Cellulase and xylanase added individually to ground maize stover at an increasing dose rates (0, 100, 200, 400, 800, 1,600, 3,200, 6,400, 12,800, 25,600, 32,000, 38,400, and 44,800 IU/g DM), increased (p<0.01) the in vitro dry matter digestibility and in vitro sugar release. The doses selected for studying the combination effect of enzymes were 6,400 to 32,000 IU/g of cellulase and 12,800 to 44,800 IU/g of xylanase. At cellulase concentration of 6,400 IU/g, IVDMD % was higher (p<0.01) at higher xylanase doses (25,600 to 44,800 IU/g). While at cellulase doses (12,800 to 32,000 IU/g), IVDMD % was higher at lower xylanase doses (12,800 and 25,600 IU/g) compared to higher xylanase doses (32,000 to 44,800 IU/g). At cellulase concentration of the 6,400 to 32,000 IU/g, the amount of sugar released increased (p<0.01) with increasing levels of xylanase concentrations except for the concentration of 44,800 IU/g. No effect of ${\beta}$-D-glucanase (100 to 300 IU/g) was observed at lower cellulase-xylanase dose (cellulase-xylanase 12,800 to 12,800 IU/g). Based on the IVDMD, the enzyme combination cellulase-xylanase 12,800 to 12,800 IU/g was selected to study its effect on feed intake and rumen fermentation pattern, conducted on 12 rams (6 to 8 months; $20.34{\pm}2.369$ kg body weight) fed 50% maize stover based TMR. The total volatile fatty acids (p<0.01) and ammonia-N concentration was higher in enzyme supplemented group, while no effect was observed on dry matter intake, ruminal pH and total nitrogen concentration.

• Asian-Australasian Journal of Animal Sciences
• /
• v.7 no.3
• /
• pp.303-316
• /
• 1994

Microbial digestion of feed in the rumen involves a sequential attack culminating in the formation of fermentation products and microbial cells that can be utilized by the host animal. Most feeds are protected by a cuticular layer which is in effect a microbial barrier that must be penetrated or circumvented for digestion to proceed. Microorganisms gain access to digestible inner plant tissues through damage to the cuticle, or via natural cell openings (e.g., stomata) and commence digestion from within the feed particles. Primary colonizing bacteria adhere to specific substrates, divide to form sister cells and the resultant microcolonies release soluble substrates which attract additional microorganisms to the digestion site. These newly attracted microorganisms associate with primary colonizers to form complex multi-species consortia. Within the consortia, microorganisms combine their metabolic activities to produce the diversity of enzymes required to digest complex substrates (e.g., cellulose, starch, protein) which comprise plant tissues. Feed characteristics that inhibit the microbial processes of penetration, colonization and consortia formation can have a profound effect on the rate and extent of feed digestion in the rumen. Strategies such as feed processing or plant breeding which are aimed at manipulating feed digestion must be based on an understanding of these basic microbial processes and their concerted roles in feed digestion in the rumen.

• Asian-Australasian Journal of Animal Sciences
• /
• v.21 no.11
• /
• pp.1604-1609
• /
• 2008

A series of in vitro and in vivo experiments were conducted to investigate the effects of the mixture of Tween 80 and cellulolytic enzymes (xylanase and cellulase) on total tract nutrient digestibility and rumen cellulolytic bacterial adhesion rates in Holstein steers. Ground timothy hay sprayed with various levels of Tween 80 and cellulolytic enzymes was used as substrates in an in vitro experiment to find out the best combinations for DM degradation. The application level of 2.5% (v/w) Tween 80 and the combination of 5 U xylanase and 2.5 U cellulase per gram of ground timothy hay (DM basis) resulted in the highest in vitro dry matter degradation rate (p<0.05). Feeding the same timothy hay to Holstein steers also improved in vivo nutrient (DM, CP, CF, NDF and ADF) digesibilities compared to non-treated hay (p<0.05). Moreover, Tween 80 and enzyme combination treatment increased total ruminal VFA and concentrations of propionic acid and isovaleric acid with decreased acetate to propionate ratio (p<0.001). However, adhesion rates of Fibrobacter succinogenes and Ruminococcus flavefaciens determined by Real Time PCR were not influenced by the treatment while that of Ruminococcus albus was decreased (p<0.05). The present results indicate that a mixture of Tween 80 and cellulolytic enzymes can improve rumen environment and feed digestibility with variable influence on cellulolytic bacterial adhesion on feed.

• Asian-Australasian Journal of Animal Sciences
• /
• v.10 no.6
• /
• pp.541-550
• /
• 1997

Anaerobic chytridiomycete fungi are now well recognized as one of the major components of rumen microflora. Since the discovery of anaerobic fungi, the knowledge upon their morphology and physiology has been accumulated. It is certain that they gave roles in ruminal fiber digestion, although their quantitative contribution to rumen digestion is still unclear. Their role in fiber digestion is complicated by the dietary factors and the interaction with other microorganisms. We aim at reviewing such information in this article. Considerable attention gas been paid to the polysaccharidase of these fungi. Analysis on the fungal genes encoding these enzymes has been performed in several laboratories. This article also covers the genetical analysis of fungal polysaccharidases.