Multidimensional Approach for Investigating the Effects of an Antibiotic–Probiotic Combination on the Equine Hindgut Ecosystem and Microbial Fibrolysis

The equine hindgut ecosystem is specialized in dietary fibers’ fermentation to provide horses’ energy and contribute to its health. Nevertheless, antibiotics are known to disrupt the hindgut microbiota, affecting the fibrolytic activity of bacteria and the intestinal immune balance, leading to diseases. This in vivo study used a general and comprehensive approach for characterizing the hindgut ecosystem of 9 healthy horses over 28 days in response to a 5-day challenge with oral trimethoprim-sulfadiazine (TMS), with a special emphasis on microbial fibrolytic activity and the host immune response. Horses were supplemented with two doses of Lactobacillus acidophilus, Ligilactobacillus salivarius (formerly L. salivarius), and Bifidobacterium lactis blend or a placebo in a 3 × 3 Latin square design. Changes in fecal microbiota were investigated using 16S rRNA sequencing. Clostridioides difficile was quantified in feces using quantitative polymerase chain reaction. Anaerobic microbiological culture was used to enumerate functional bacterial groups (cellulolytic, amylolytic, and lactic acid-utilizing). The environmental dimensions were assessed by measuring the concentrations of volatile fatty acids (VFAs) and lactic acid using biochemical methods, and changes in pH and dry matter weight. Systemic and local inflammation was evaluated by determination of cytokine and immunoglobulin (Ig)A concentrations in the serum and secretory IgA (SIgA) concentrations in the feces using immuno-enzymatic methods. Oral TMS treatment strongly altered the whole hindgut ecosystem by 2 days after the first administration. Bacterial diversity decreased in proportion to the relative abundance of fibrolytic genera, which coincided with the decrease in the concentration of cellulolytic bacteria. At the same time, the composition of microbiota members was reorganized in terms of relative abundances, probably to support the alteration in fibrolysis. C. difficile DNA was not found in these horses, but the relative abundances of several potential pathobiont genera increased. 2 days after the first TMS administration, fecal concentrations of VFAs and SIgA increased in parallel with fecal water content, suggesting an alteration of the integrity of the hindgut mucosa. Recovery in bacterial composition, functions, and immune biomarkers took 2–9 days after the end of TMS administration. Supplementation with this bacterial blend did not limit bacterial alteration but might have interesting mucosal immunomodulatory effects.

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Changes of rumen pH, fermentation and microbial population as influenced by different ratios of roughage (rice straw) to concentrate in dairy steers

The Journal of Agricultural Science ◽

10.1017/s0021859613000658 ◽

2013 ◽

Vol 152 (4) ◽

pp. 675-685 ◽

Cited By ~ 25

Author(s):

M. WANAPAT ◽

P. GUNUN ◽

N. ANANTASOOK ◽

S. KANG

Keyword(s):

Rice Straw ◽

Energy Intake ◽

Dry Matter ◽

Volatile Fatty Acids ◽

Quantitative Polymerase Chain Reaction ◽

Latin Square ◽

Cellulolytic Bacteria ◽

Positive Effects ◽

Rumen Ph ◽

16S Rna

SUMMARYThe current study was designed to determine the effect of roughage to concentrate ratio (R : C) on rumen pH, fermentation and bacterial population in dairy steers. Four rumen fistulated dairy steers (170±20 kg) were randomly assigned according to a 4×4 Latin square design, in which the steers were fed with four dietary treatments with different R : C ratios of 0·8 : 0·2, 0·6 : 0·4, 0·4 : 0·6 and 0·2 : 0·8, respectively. All animals were kept in individual pens and received feed according to the respective R : C ratios at 0·025 body weight (BW)/d; urea-treated rice straw (prepared using 3·5 kg urea+100 kg water sprayed onto 100 kg of rice straw) was used as a roughage source. The experiment was conducted for four periods of 21 days each. During the first 14 days, feed intake was measured and the animals were then moved to metabolism crates for total urine and faecal collection for 7 days. Total dry matter intake (DMI) was similar among treatments. Energy intake increased as the proportion of concentrate in the diet increased. Apparent digestibilities of dry matter (DM), organic matter (OM) and crude protein (CP) were improved, while neutral detergent fibre (NDF) and acid detergent fibre (ADF) were reduced when the levels of concentrate increased. A decreasing ratio of R : C reduced rumen pH linearly, from 6·4 to 5·9 at 0·2 : 0·8. High levels of concentrate impacted on volatile fatty acids (VFA) molar proportions and decreased acetate (C2) linearly, while propionate (C3) was increased, leading to decreased C2 : C3 ratio. Numbers of protozoa, fungi and proteolytic bacteria were not affected by R : C ratio. Cellulolytic bacteria decreased linearly while amylolytic bacteria increased linearly with 0·60 and 0·80 concentrates. Quantitative polymerase chain reaction (qPCR) based on 16S RNA revealed thatFibrobacter succinogenesnumbers were increased when steers were fed with R : C ratio of 0·8 : 0·2. Conjugated linoleic acid (CLA)-producing bacteria, especially those ofButyrivibrio fibrisolvens, increased linearly with R : C ratios of 0·8 : 0·2 and 0·6 : 0·4, whileMegasphaera elsdenii, a lactate-utilizing bacterium and reported producer oftrans-10,cis-12 CLA increased linearly with R : C ratio of 0·8 : 0·2. In addition, microbial CP synthesis increased quadratically when steers were fed high levels of concentrate. However, the efficiency microbial N synthesis (EMNS) based on OM, truly digested in the rumen, was not affected by different R : C ratios. From the current study, it can be concluded that roughage to concentrate ratio of 0·4 : 0·6 had positive effects for the creation of healthy rumen (rumen pH and ecology), and improved energy intake and rumen fermentation, particularly propionic acid and microbial protein synthesis, in dairy steers fed urea-treated rice straw as a roughage source.

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Effects of some poorly digestible carbohydrates on bile acid bacterial transformations in the rat

British Journal Of Nutrition ◽

10.1079/bjn19890011 ◽

1989 ◽

Vol 62 (1) ◽

pp. 103-119 ◽

Cited By ~ 38

Author(s):

Claude Andrieux ◽

Daniele Gadelle ◽

Christine Leprince ◽

E. Sacquet

Keyword(s):

Lactic Acid ◽

Bile Acid ◽

Cholic Acid ◽

Volatile Fatty Acids ◽

Dietary Treatment ◽

Bacterial Transformation ◽

Carbohydrate Feeding ◽

Fermentable Carbohydrates

The effects of ingestion of poorly digestible carbohydrates on bacterial transformations of cholic acid and β-muricholic acid were studied in rats fed on increasing levels of lactose, lactulose, amylomaize or potato starches. Each level was given for 3 weeks and, at the end of each dietary treatment, bile acid faecal composition was analysed and a group of six rats was killed every 4 h during 24 h to determine the amounts of fermented carbohydrate and fermentation characteristics (caecal pH, volatile fatty acids (VFA) and lactic acid concentrations). Fermentation of carbohydrates decreased caecal pH and enhanced caecal VFA and lactic acid concentrations. Irrespective of the poorly digestible carbohydrate, the variation of bacterial transformation always occurred in the same way: the bacterial transformation of β-muricholic acid into hyodeoxycholic acid was the first to disappear, while ω-muricholic acid formation increased; second, cholic acid transformation decreased and finally all bile acid transformations were strongly affected. There was a significant correlation between bile acid transfer and the minimal caecal pH in vivo. This effect of pH was similar in vitro. To determine whether the levels of bacteria which transformed bile acids were modified, rats fed on the highest amounts of poorly digestible carbohydrates were introduced into isolators and carbohydrate feeding was stopped. Caecal pH recovered its initial value but bile acid transformations remained changed, suggesting that the intestinal microflora were modified by ingestion of fermentable carbohydrates.

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Effects of riboflavin supplementation on performance, nutrient digestion, rumen microbiota composition and activities of Holstein bulls

British Journal Of Nutrition ◽

10.1017/s0007114520005243 ◽

2021 ◽

pp. 1-22

Author(s):

H.M. Wu ◽

J. Zhang ◽

C. Wang ◽

Q. Liu ◽

G. Guo ◽

...

Keyword(s):

Volatile Fatty Acids ◽

Average Daily Gain ◽

Latin Square ◽

Linear Increase ◽

Cellulolytic Bacteria ◽

Feed Conversion ◽

Molar Percentage ◽

Nutrient Digestion ◽

Holstein Bulls ◽

Addition Level

Abstract To investigate the influences of dietary riboflavin (RF) addition on nutrient digestion and rumen fermentation, eight rumen cannulated Holstein bulls were randomly allocated into four treatments in a repeated 4 × 4 Latin square design. Daily addition level of RF for each bull in control, low-RF, medium-RF and high-RF was 0, 300, 600 and 900 mg, respectively. Increasing the addition level of RF, dry matter (DM) intake was not affected, average daily gain tended to be increased linearly and feed conversion ratio decreased linearly. Total-tract digestibilities of DM, organic matter, crude protein (CP) and neutral detergent fibre (NDF) increased linearly. Rumen pH decreased quadratically and total volatile fatty acids (VFA) increased quadratically. Acetate molar percentage and acetate to propionate ratio increased linearly, but propionate molar percentage and ammonia-N content decreased linearly. Rumen effective degradability of DM increased linearly, NDF increased quadratically but CP was unaltered. Activity of cellulase and populations of total bacteria, protozoa, fungi, dominant cellulolytic bacteria, Prevotella ruminicola and Ruminobacter amylophilus increased linearly. Linear increase was observed for urinary total purine derivatives excretion. The data suggested that dietary RF addition was essential for rumen microbial growth, and no further increase in performance and rumen total VFA concentration were observed when increasing RF level from 600 to 900 mg/d in dairy bulls.

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Addition of cellulolytic bacteria in complete feed block based on agro-industrial by-products for Kacang goats

South African Journal of Animal Science ◽

10.4314/sajas.v51i3.12 ◽

2021 ◽

Vol 51 (3) ◽

pp. 378-386

Author(s):

B. Santoso ◽

T.W. Widayati ◽

B.T. Hariadi ◽

M.N. Lekitoo

Keyword(s):

Lactic Acid ◽

Lactic Acid Bacteria ◽

Latin Square ◽

Ammonia Nitrogen ◽

Ruminal Fermentation ◽

Cellulolytic Bacteria ◽

N Retention ◽

Acid Detergent Fibre ◽

Block Based ◽

By Products

The research aimed at assessing the effects on nutrient digestion and ruminal fermentation by goats of a complete feed block (CFB) that incorporated agro-industrial by-products that were high in fibre and cellulolytic bacteria. Three Kacang goats, a native Indonesian breed, were used in a 3 × 3 Latin square experimental design with i) CFB without microbes (control), ii) CFB containing 1% Pseudomonas aeruginosa and 1% Acinetobacter baumannii, and iii) CFB containing 2% P. aeruginosa and 2% A. baumannii. Microbes in the CFBs consisted of lactic acid bacteria, yeast and cellulolytic bacteria that ranged from 106 to 108 cfu/g. The goats were fed each day at 08h00 and 16h00. The inclusion of P. aeruginosa and A. baumannii at 2% level reduced both neutral detergent fibre (NDF) and acid detergent fibre compared with other treatments. Goats fed on CFB with microbes had higher (P <0.01) digestibility of organic matter (OM) and NDF compared with control. The addition of P. aeruginosa and A. baumannii at 2% level increased (P <0.05) ruminal ammonia nitrogen (N-NH3), acetate, and total VFA. However, goats fed on CFB with microbes had lower (P <0.05) urinary N excretion, which improved (P <0.05) N retention compared with the control. It was concluded that a combination of lactic acid bacteria, yeast and cellulolytic bacteria in the CFB could modify fermentation in the rumen and increase the use of nitrogen in goats.

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The effect of dietary inclusion of yeast culture on digestion in the sheep

Animal Science ◽

10.1017/s0003356100004967 ◽

1990 ◽

Vol 50 (3) ◽

pp. 483-489 ◽

Cited By ~ 43

Author(s):

I. Chademana ◽

N. W. Offer

Keyword(s):

Organic Matter ◽

Volatile Fatty Acids ◽

Latin Square ◽

Ammonia Concentration ◽

Nutrient Digestibility ◽

Yeast Culture ◽

Fermentative Capacity ◽

Outflow Rate ◽

Gross Energy

ABSTRACTSix mature sheep, each fitted with a rumen cannula, were assigned to six diets in a 6 × 6 Latin-square design experiment to examine the effects of a yeast culture on ruminal metabolism, rumen liquid outflow rate, fibre digestion in the rumen and overall nutrient digestibility. The yeast culture (YC) was a commercial product composed of a yeast (Saccharomyces cerevisae) and the media on which it grew and dried so as to maintain its fermentative capacity. The six dietary treatments were three diets differing in hay dry matter (DM): concentrate DM ratio (90: 10, 65: 35 and 40: 60 designated low, medium and high concentrate respectively) each given either without or with a supplement of 4 g/day of YC. Treatment periods were of 3 weeks duration. There were significant effects of dietary forage: concentrate ratio on rumen function (P< 0·05). Rumen pH, rumen liquid outflow rate, rumen ammonia concentration, total volatile fatty acids concentration, and molar proportions of acetate, propionate and butyrate were not significantly affected by the inclusion of YC (P< 0·05). Supplemental YC did not affect the overall nutrient digestibility of organic matter, neutral-detergent fibre or gross energy measuredin vivo. However, at every forage:concentrate ratio, YC increased the disappearance of hay organic matter from nylon bags incubated in the rumen for 24 h (P< 0·05). The values with and without YC were 0·482 and 0·432 for the low, 0·423 and 0·366 for the medium, and 0·360 and 0·321 for the high concentrate diets respectively. However, YC had no effect on hay disappearance when bags were incubated for 48 h. YC appeared to increase the initial rate of forage digestion in the rumen without altering overall food digestibility or the patern of production of fermentation end products.

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Frequency of concentrate supplementation for cattle fed barley straw. 2. Ruminal dilution rates, pH and metabolite concentrations

Canadian Journal of Animal Science ◽

10.4141/a03-075 ◽

2004 ◽

Vol 84 (3) ◽

pp. 467-479 ◽

Cited By ~ 4

Author(s):

R. C. Tellier ◽

G. W. Mathison ◽

E. K. Okine ◽

D. McCartney ◽

R. Soofi-Siawash

Keyword(s):

Lactic Acid ◽

Organic Acids ◽

Heat Production ◽

Volatile Fatty Acids ◽

Latin Square ◽

Isobutyric Acid ◽

Barley Straw ◽

Concentrate Supplementation ◽

Metabolite Concentrations ◽

Protein Feeding

Five ruminally cannulated crossbred steers (474 ± 30 kg) were fed diets containing 70% barley straw and 30% concentrate in an unbalanced 5 × 5 Latin square design experiment to in vestigate the effects of frequency of feeding concentrate (daily, alternate days or every third day) with different dietary protein concentrations (7.9 and 11.5%) on ruminal liquid and particulate dilution rates, pH and metabolite concentrations. Dilution rates of cobalt-ethylene diamine tetraacetic acid (Co- EDTA) and chromium-mordanted fibre did not differ when low- and high-protein concentrates were fed. Supplemental protein increased (P < 0.05) mean ruminal ammonia concentrations (3.3 vs. 1.6 mM), but had no influence on ruminal concentrations of organic acids. Frequency of concentrate feeding had no influence on dilution rate of digesta markers, pH or on mean ruminal concentrations of ammonia, lactic acid, propionic acid, isobutyric acid, valeric acid and isovaleric acid. Mean concentrations of total volatile fatty acids, acetic acid and butyric acid were, however, reduced (P < 0.05) when steers were fed concentrates on alternate days. The reduced (P < 0.01) ruminal acetic:propionic acid ratios observed in steers fed concentrates on alternate days were consistent with reduced heat productions. Positive relationships (P < 0.05) were obtained between heat production of steers and ruminal concentrations of isobutyric and valeric acids. It was concluded that the low-protein diet did not provide sufficient protein to meet microbial requirements and that under controlled feeding conditions cattle can be fed concentrate on alternate days or every third day without the occurrence of lactic acidosis. Additional research is warranted to examine the relationships between reduced heat production of steers fed concentrates on alternate days and ruminal concentration and production of organic acids. Key words: Cattle, straw, protein, feeding frequency, rumen metabolites, lactic acid

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The Fermentation of Carbohydrates in the Rumen of the Sheep

Journal of Experimental Biology ◽

10.1242/jeb.22.1-2.51 ◽

1945 ◽

Vol 22 (1-2) ◽

pp. 51-62

Author(s):

S. R. ELSDEN

Keyword(s):

Fatty Acids ◽

Acetic Acid ◽

Lactic Acid ◽

Volatile Fatty Acids ◽

In Vitro Fermentation ◽

Dietary History ◽

History Of ◽

Rumen Microflora

1. Acetic, propionic and butyric acids are the main volatile fatty acids in the rumen of the sheep. Acetic acid accounts for 55-75% of the total. 2. Cellulose, glucose and lactic acid are rapidly fermented in vitro by rumen contents with the production of acetic, propionic and butyric acids. Pro-pionic acid is the major component in all cases: very little if any butyric acid is formed from cellulose. 3. The in vitro fermentation of glucose closely resembles the in vivo. 4. The in vitro fermentation of dried grass yields the same three acids, but with acetic acid predominating. 5. Members of the genus Propionibacterium have been isolated from the rumen, and evidence is presented to show that these organisms are responsible for the production of the propionic acid found in the rumen. 6. The dietary history of the animal is shown to influence the rate at which glucose is fermented in the rumen, and the composition of the rumen microflora.

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Characterization of the microbial and biochemical profile of the different segments of the digestive tract in horses given two distinct diets

Animal Science ◽

10.1017/s1357729800059038 ◽

2003 ◽

Vol 77 (2) ◽

pp. 293-304 ◽

Cited By ~ 74

Author(s):

A. de Fombelle ◽

M. Varloud ◽

A.-G. Goachet ◽

E. Jacotot ◽

C. Philippeau ◽

...

Keyword(s):

Lactic Acid ◽

Digestive Tract ◽

Large Intestine ◽

Volatile Fatty Acids ◽

Anaerobic Bacteria ◽

Average Concentration ◽

Cellulolytic Bacteria ◽

Fibre Degradation ◽

Fermentable Carbohydrates ◽

Pelleted Food

AbstractA first group of three horses was given diet 1 (D1) allowing 1180 g per 100 kg body weight (BW) of a pelleted food rich in fibre (P1) and 556 g per 100 kg BW of straw during a 20-day period to allow for adaptation. A second group of four horses were given diet 2 (D2) allowing 1180 g per 100 kg BW of a pelleted food rich in cereals (P2) and 1000 g per 100 kg BW of meadow hay during the same period. Digesta was collected from the stomach, duodenum, jejunum, ileum, caecum, right ventral colon, left ventral colon, left dorsal colon, right dorsal colon, and small colon, and faeces were collected under general anaesthesia 2·5 h after the ingestion of the morning pelleted meal. The concentration of total anaerobic, cellulolytic and lactic acid-utilizing bacteria, lactobacilli and streptococci were determined in all these segments except for the duodenum, left ventral colon, right dorsal colon and small colon. D-/L-lactic acid, volatile fatty acids and pH were measured in all anatomic segments of the digestive tract (from stomach to small colon). The caecal concentration of total anaerobic bacteria was the lowest (7·9 5 107colony-forming units (c f. u.) per ml), whereas that of the stomach was the highest (1·4 5 109c f. u. per ml) (P< 0·001). Cellulolytic bacteria did not exceed 3·0 5 102c f u. per ml in the ante-caecal segments whereas in the hindgut the average concentration was 5·3 x 105c f u. per ml (P< 0·001). Likewise, VFA concentrations were also greater in the large intestine (on average, 96·3 mmol/l v. 8·8 mmol/l in the ante-caecal segments) (P< 0·001), confirming the limited extent of fibre degradation in these ante-caecal segments. Lactobacilli, streptococci and lactate-utilizing bacteria colonized all the digestive tract; the stomach and the small intestine tended to host the greatest numbers of these bacteria, which suggests a high interference of micro-organisms with the digestion of readily fermentable carbohydrates. Compared with the other ante-caecal segments, the stomach ecosystem seemed the most affected by the composition of the last pelleted meal ingested: the concentrations of lactobacilli and lactate-utilizing bacteria were higher (P< 0·05) with P2. The lower concentration of D-/L-lactate with P2 (P< 0·05) was concomitant with a greater proportion of propionate (P< 0·05), probably related to a greater fermentation of lactate. In the large intestine of horses given D2, cellulolytic bacteria tended to be lower, whereas VFA concentrations were higher (P < 0·05). The lower [NDF/starch] ratio of D2 was probably less propitious for the proliferation of cellulolytic bacteria but was compensated by the higher cellulose intake brought by the hay.

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Yield, chemical composition, fermentation characteristics, in vitro ruminal variables, and degradability of ensiled amaranth (Amaranthus hypochondriacus) cultivars compared with corn (Zea mays) silage

Translational Animal Science ◽

10.1093/tas/txaa180 ◽

2020 ◽

Vol 4 (4) ◽

Author(s):

Hossein Shadi ◽

Yousef Rouzbehan ◽

Javad Rezaei ◽

Hassan Fazaeli

Keyword(s):

Chemical Composition ◽

Crude Protein ◽

Nutritional Value ◽

Volatile Fatty Acids ◽

Block Design ◽

Metabolizable Energy ◽

Neutral Detergent Fiber ◽

Cellulolytic Bacteria

Abstract Silages from four amaranth varieties (A5, A12, A14, and A28) were compared with corn silage (CS) in terms of their yield, chemical composition, phenolic compounds, oxalic acid and nitrate levels, silage fermentation characteristics, in vitro methane production, organic matter disappearance (OMD), microbial crude protein (MCP), ruminal ammonia (NH3-N), pH, volatile fatty acids, cellulolytic bacteria numbers, protozoa counts, and in situ dry matter (DM) and crude protein (CP) degradability were determined. Forages were harvested 93 d after planting, chopped, and ensiled in plastic buckets for 60 d. The study was based on a randomized complete block design, and data were analyzed using SAS, general linear model (GLM) procedure for normal distribution. Compared with CS, amaranth silages (AMS) had lower ash-free neutral detergent fiber nitrate, OMD (P < 0.001), phosphorus (P = 0.003), and metabolizable energy (ME) (P = 0.043) but higher (P < 0.001) CP, calcium, non-fiber carbohydrates (NFC), acid detergent lignin, ether extract, ash, total phenolics, pH, NH3-N concentration, MCP, digestible undegradable protein (DUP), and metabolizable protein (MP). Fresh, OM, OMD, ME (P < 0.001), and DM (P = 0.032) yields of AMS from different varieties were higher than CS, with the exception of A5. Overall, amaranth made good quality silage, with some variation, and A28 had the highest yield and nutritional value (CP, NFC, MCP, DUP, and MP). The yield, CP concentration, and nutritional value of A28 silage were higher than CS. Although these in vitro results are promising, they also need to be validated with future in vivo research.

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Effects of feeding quebracho tannin diets, with or without a dietary modifier, on rumen function in sheep

Animal Science ◽

10.1017/s1357729800051298 ◽

1999 ◽

Vol 69 (1) ◽

pp. 265-274 ◽

Cited By ~ 10

Author(s):

M. B. Salawu ◽

T. Acamovic ◽

C. S. Stewart ◽

F. D. DeB. Hoveli

Keyword(s):

Soluble Protein ◽

Volatile Fatty Acids ◽

Latin Square ◽

Basal Diet ◽

Gas Production ◽

Microbial Activities ◽

Rumen Microbes ◽

Quebracho Tannin

AbstractThe effect of quebracho tannin (QT) on the activities of rumen microbes was studied both in vivo and in vitro. The in vivo study was carried out in four rumen environments created by feeding four fistulated sheep a basal diet of chopped grass hay, grass cubes and whole barley (control) with or without the addition of QT and the dietary modifier Browse Plus (BP). The active ingredients in BP are polyethylene glycol (PEG, more than 0·95 of the dry material), polyvinyI pyrrolidone (PVP) and calcium hydroxide. The diets offered were control, control plus 50 g QT per kg diet (CQT), control plus 50 g QT per kg and 0·1 (CQT+ 0·1) or 1.0 g BP per kg (CQT + 1·0). The experiment was a 4 X 4 Latin-square design with periods of 4 weeks. Rumen liquor samples were collected at 0, 2, and 8 h after feeding, 18 and 25 days after commencement of each period. Changes in free and bound proanthocyanidin (PA) concentrations, rumen pH, ammonia, volatile fatty acids (VFA), soluble protein concentrations, particle-bound cellulase and xylanase activities and rumen protozoal counts were used as indices of microbial activities. The same diets were incubated with rumen contents in vitro, except that the 0.1 g/kg level of BP was replaced by a fourth treatment made up of control plus 1·0 g BP per kg DM of hay (CBP). In vivo, bound PA concentrations in the rumen liquor of all the sheep given QT-containing diets were higher than those of the free PAs. The bound PA was higher (V < 0·05) in the rumen liquor of sheep given CQT in comparison with those containing BP. There were reductions in ammonia (P > 0·05), soluble protein (P < 0·05) and total VFA (P > 0·05) concentrations in the rumen liquor of sheep given CQT in comparison with those given the control and BP-containing diets. Reductions (P > 0·05) were also observed in the cellulase and xylanase activities of the rumen microbes and in protozoal counts (P < 0·05) in the presence of QT in the diet. In vitro, QT reduced (P > 0·05) the viable bacterial counts, gas production and the total VFA concentrations after incubation. In both the in vivo and in vitro experiments, BP was able to alleviate some but not all of the depression in microbial activities. The main constituent (PEG) in BP binds to some of the tannins in solution and may displace tannins from tannin-protein complexes.

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