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Effects of condensed tannins supplementation level on weight gain and in vitro and in vivo bloat precursors in steers grazing winter wheat¹

B. R. Min^*, W. E. Pinchak^*,2, R. C. Anderson, J. D. Fulford^* and R. Puchala

^* Texas Agricultural Experiment Station, Vernon 76385, and United States Department of Agriculture, Agricultural Research Service, Southern Plains Agricultural Research Center, Food and Feed Safety Research Unit, 2881 F & B Road, College Station, TX 77845, and and E (Kika) de la Garza American Institute for Goat Research, Langston, OK 73050

	Abstract

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Research was conducted to determine the effects of level of supplementation with quebracho condensed tannins (CT) on in vitro ruminal fluid gas production, in vivo ruminal fluid protein fractions, bloat dynamics, and ADG of steers grazing winter wheat. Two experiments were conducted to 1) enumerate the effect of ruminal fluid from steers fed quebracho CT (0, 1, and 2% CT/kg of DMI) on in vitro gas and methane production from minced fresh wheat forage; and 2) quantify the influence of CT supplementation on ruminal protein characteristics, biofilm complexes, bloat potential, and ADG of steers grazing wheat pasture. Eighteen ruminally cannulated steers (386 ± 36 kg of BW) were randomly allocated to 1 of 3 treatments that included a control (water infusion) and 2 CT treatment levels (1 or 2% CT/kg of DMI). Treatments were administered daily (63 d) through the rumen cannula as pre-mixes with warm water (approximately 30 ° C). Rumen contents were collected 2 h postinfusion (at 1030 to 1130) on d 0, 20, 40, 50, and 60. Bloat was visually scored daily for 5 d each wk. In Exp. 1, supplementation of CT decreased the rate of in vitro gas production in a dose-dependent response. In Exp. 2, ADG increased (P < 0.04) at both levels of CT supplementation. Mean bloat score across stage of growth and replicates decreased linearly with increasing CT supplementation; bloat scores were greater (P < 0.001) for the vegetative than for the reproductive stage of plant growth. Biofilm production and rumen fluid protein fractions varied among CT treatments and stage of growth. Addition of CT reduced the severity of bloat, principally through reducing microbial activities, biofilm production, and ruminal gas production. Quebracho CT is potentially a value-added supplement that can decrease the impacts of frothy bloat and increase BW gains in stocker cattle-wheat systems.

Key Words: average daily gain • condensed tannin • frothy bloat • ruminal fluid protein fraction • steer

	INTRODUCTION

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Frothy bloat in cattle grazing wheat pasture is a major nonpathogenic cause of death and illness. Frothy bloat occurs when the eructation mechanisms are impaired and the rate of gas production exceeds the animal’s ability to expel the gas (Majak et al., 2003). Rapid release of soluble protein into ruminal fluid promotes formation of a polysaccharide slime (referred to as biofilm complexes) that traps rumen gases and is implicated in formation of frothy bloat (Clarke and Reid, 1974; Pinchak et al., 2005). Therefore, altering the rapid rate of proteolysis, biofilm formation, and gas production in the rumen may be central to wheat pasture bloat mitigation.

Moderate levels of condensed tannins (CT; 2 to 4% DM) reduce ruminal protein digestion and ruminal bacterial activity by forming a pH-reversible bond with soluble proteins and other macronutrients (Min et al., 2003, 2005a). Condensed tannins, including commercial quebracho CT extract, have been shown to increase animal production and reduce bloat potential (Min et al., 2003, 2005b,Min et al., c). Elevated doses of quebracho CT (0 vs. 166 g/kg of DMI) have displayed negative effects of impairing fiber digestion and toxicosis in sheep (Hervas et al., 2003). Therefore, further research on interrelationships of CT supplementation, ruminal fermentation, bloat dynamics, and animal performance in steers grazing wheat forage after exposure to quebracho CT is warranted. Objectives of this study were to determine the effects of level of quebracho CT supplementation on in vitro ruminal fluid gas production, in vivo ruminal fluid protein fractions, bloat dynamics, and ADG of steers grazing winter wheat.

	MATERIALS AND METHODS

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Experimental Design
The Texas A & M University Animal Use and Care Committee approved the experimental protocol. An initial in vitro study was conducted to quantify the effect of ruminal fluid from steers fed quebracho CT (0, 1, and 2% CT/kg of DMI) on in vitro gas and methane production from minced fresh wheat forage incubated with ruminal inoculums obtained from cannulated steers (n = 3 steers/group) grazing 2 stages of plant growth (the vegetative vs. reproductive stage of growth). A second in vivo experiment was designed to quantify the effect of CT supplementation on ADG, bloat dynamics, biofilm production, and ruminal fluid protein fractions in steers grazing winter wheat. Three levels of quebracho CT (0, 1, and 2% CT/kg of DMI) were premixed with warm water (approximately 30 ° C) and introduced into the rumen once daily (0800) via rumen cannula. Water-soluble quebracho extract was used as the source of CT (99% solubility; Chemtan Company Inc., Exeter, NH). This type of quebracho extract contains approximately 75% CT (DM basis) and a small amount of simple phenolics. The primary hypothesis of the in vitro and in vivo research was that quebracho CT supplementation would reduce ruminal microbial activity, in vitro gas production, and methane production, and as a result would decrease the incidence of bloat and increase ADG in steers grazing wheat forage.

In Vitro Experiment (Experiment 1)
Wheat forage samples were randomly selected within pasture and hand-harvested to ground level (February 28, 2005) and stored at – 20 ° C for all in vitro ruminal gas analysis. Fresh forage was minced (blender Model DS-7, Warning Products Co., Winsted, CT) at 500 rpm before all in vitro experiments (Min et al., 2005a). Triplicate measures of in vitro ruminal gas production were made to determine the effect of source of ruminal fluid obtained from steers fed quebracho CT (0, 1, and 2% CT/kg of DMI) while grazing wheat forage on ruminal gas and methane production during the vegetative (February 28, 2005) and reproductive stage (April 20, 2005) of wheat growth. Ruminal fluid was obtained from 3 cannulated steers in each CT treatment group that were grazing wheat forage that was mixed and strained through 4 layers of cheesecloth and flushed with CO₂ gas. In vitro gas production was measured as plunger displacement (mL) at 0, 1, 2, 3, 4, 5, and 6 h of incubation, as described by Min et al. (2005a). All gases were collected from the in vitro rumen incubation for methane gas analysis (Min et al., 2005b).

In Vivo Experiment (Experiment 2)
The experiment evaluated ADG, bloat frequency, ruminal protein characteristics, and biofilm complexes from February 18 to April 20, 2005, in steers grazing winter wheat forage (Triticum aestivum L. var. "Cutter") at the Smith-Walker Research Unit of the Texas Agricultural Experiment Station at Vernon, TX. The experiment was a completely random design with a 3 (level of CT) x 2 (stage of wheat growth) factorial arrangement of treatments. Before data collection, 18 ruminally cannulated steers (386 ± 35.8 kg of BW) grazed wheat forage (15 ha paddock) continuously for up to 63 d after an 8-wk adaptation period. Steers were randomly allocated to 1 of 3 treatments that included a control (same amount of water infusion) and 2 CT treatment levels (1 and 2% CT/kg of DMI). The CT were administered once daily (at approximately 0800) through the rumen cannula as premixes with warm water. Ruminal contents were collected 2 h postCT or water infusion (at 1030 to 1130) on d 0, 20, 40, 50, and 60 for ruminal fluid protein characteristics and biofilm analyses. Cattle were weighed at 10-d intervals. From February 18 through April 20, 2005, steers were visually monitored daily 5 d each week at 0800 and scored for bloat (0 = no bloat, 3 = severe bloat; Paisley and Horn, 1998).

Ruminal Fluid Analysis
Six ruminal fluid protein fractions were assayed using the method described by Min et al. (2002). Whole ruminal content was collected (approximately 500 g) from each steer 2 h after CT infusion on d 0, 20, 40, 50, and 60, and strained through 2 layers of cheesecloth to separate filtrate (cheesecloth filtrate) and residual matter (particulate matter) fractions. Cheesecloth filtrate was measured for pH and centrifuged (6 mL) at 375 x g for 5 min at room temperature to sediment protozoal and small feed particles. The sediment was resuspended in 6 mL of artificial saliva (McDougall, 1948) and adjusted to the original volume (6 mL) with CO₂-saturated artificial saliva (protozoa + plant particles). The supernatant (6 mL) was centrifuged at 16,300 x g for 15 min at room temperature. The resulting pellet was resuspended in 6 mL of artificial saliva and adjusted to the original volume (6 mL) with CO₂-saturated artificial saliva (bacterial fraction), whereas the remaining supernatant fluid (cell-free supernatant) was adjusted to 6 mL of with artificial saliva.

Chemical Analysis
Total CP, soluble protein N, insoluble protein N, and nonprotein N were determined for fresh forage samples by the Kjeldahl digestion procedure (AOAC, 1990). Forage samples were prepared as described by Bartley et al. (1975) and previously utilized in our laboratory (Min et al., 2005b). One gram of the chopped (approximately 0.5 cm) plant material from each sample was analyzed for Kjeldahl N (total N). Fresh wheat forage was fractionated into soluble protein-N and nonprotein-N by blending 5 g of sample with 100 mL of distilled water, and chopped (10 g) for two 15-s intervals with a blender (blender Model DS-7; Warning Products Co., Winsted, CT). Homogenate was vacuum-filtered through Whatman number 4 filter paper (Whatman Int. Ltd., Maidstone, UK). The residue was transferred to Kjeldahl flasks to determine insoluble protein. Eighty milliliters of the measured filtrate was acidified by the addition of 10 mL of 150 g of trichloroacetic acid/L to precipitate soluble N (Waghorn and Jones, 1989) and refrigerated (4 ° C) overnight. The mixture was vacuum-filtered through Whatman number 2 filter paper, and the filtrate was transferred to Kjeldahl flasks to determine nonprotein N. Soluble protein N was calculated as

Forage samples and ruminal contents were oven dried at 60 ° C to a constant weight. The plant CP and ruminal protein fractions were calculated as a percentage on a DM basis. The NDF, ADF, and IVDMD of dried forage samples were determined using the filter bag technique (Ankom Technology Corp., Fairport, NY). Methane gas was determined from a 6-h in vitro incubation in an open-circuit respiration calorimetric system (Sable Systems, Henderson, NV; Puchala et al., 2005).

Statistical Analysis
All data were analyzed using the MIXED procedure of SAS Institute (SAS Inst. Inc., Cary, NC), with animal as the random effect. In vitro ruminal gas production, ADG, bloat score, biofilm production, and ruminal pH responses to CT supplementation and stage of plant growth were tested utilizing the MIXED procedure of SAS. Linear and quadratic effects were determined utilizing polynomial orthogonal contrasts for equally spaced treatments in SAS. A protected F-test of least squares means was used to test for differences in plant nutrient content between vegetative and reproductive stages of growth. Differences were declared significant at P < 0.05. The variables in Exp. 1 included in vitro ruminal gas and methane production, and associated interactions. The model included sources of ruminal fluid (0, 1, and 2% CT/kg of DMI) and plant stage of growth. Variables in Exp. 2 included biofilm complexes, ruminal fluid protein fractions, mean bloat score, and ADG in steers grazing winter wheat forage. The model included levels of CT (0, 1, and 2% CT/kg of DMI) supplementation and stage of growth, with animal as the random effect. The in vitro ruminal gas production (Y) was calculated using the following exponential equation (Øorskov and McDonald, 1979):

here Y = rumen gas production in time t; and a, b, and c are constants of the exponential equation, where a = the ruminal gas production at time 0, b = the proportional gas production during time (t), and c = the rate of gas production of the b fraction (mL/h). Potential ruminal gas production was calculated as a + b. The constant values (b and c) for each treatment were calculated with the method described by Min et al. (2000) and Getachew et al. (2004) using the nonlinear regression (NLIN) procedure from SAS.

	RESULTS

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Experiment 1: Effect of Ruminal Fluid from Steers Fed Condensed Tannins on In Vitro Gas and Methane Production
There was a CT level x stage of growth interaction (P < 0.02; Table 1), as a result of rate of gas production increasing from the vegetative stage of growth (linear and quadratic; P < 0.01) to the reproductive stage of growth (linear P < 0.001, quadratic P < 0.01) during ruminal fermentation. Mean potential gas (linear; P < 0.01) and ruminal methane (linear; P < 0.05) production decreased with increasing CT supplementation, decreases were associated with reproductive stage rather than the vegetative stage of growth. Differences in stage of growth effects on responses to CT supplementation resulted in a minimal stage of growth x CT treatment interaction for methane (P = 0.11) and no interaction for potential gas production (P = 0.33).

View larger version (18K): [in this window] [in a new window]   Figure 1. Effects of quebracho condensed tannins (CT) on temporal wheat pasture bloat dynamics during vegetative and reproductive stage of growth, Vernon, TX, 2005.

View larger version (20K): [in this window] [in a new window]   Figure 2. Effects of condensed tannin (CT) supplementation on ruminal microbial protein fractions of steers grazing winter wheat forage during vegetative and reproductive stage of growth (SG). Results are the mean of duplicate determinations from 6 steers per treatment group (0, 1, and 2% CT/kg of DMI), and error bars represent SEM. Steers grazed wheat forage during vegetative (February 18 to March 31, 2005) and reproductive SG (April 1 to 20, 2005). Means in a column at each sampling time (d) with different superscript letters are different (P < 0.05). NS = not significant.

	DISCUSSION

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Condensed Tannins and Ruminal Gas Production Profiles
Cone et al. (1996, 1997) reported high levels of gas production during the first 2 h of incubation and suggested that initially high rates of gas production were caused by the fermentation of soluble and rapidly fermentable fractions in the diets (soluble protein and sugar). Recently, Min et al. (2005b) reported in vitro gas production was positively correlated with soluble protein fractions and IVDMD of fresh wheat forage. Frothy bloat results in a major increase in the rumen pool size due primarily to interference of gas outflow associated with disruption of normal eructation patterns (Clarke and Reid, 1974). The rapid release of soluble protein into ruminal fluid promotes the formation of a biofilm complex that traps rumen gases and leads to foamy bloat (Clarke and Reid, 1974; Howarth et al., 1991; Pinchak et al., 2005). Results from the current study and contemporary research (Min et al. 2005c) demonstrate quebracho CT consistently decreases the rate of ruminal gas and methane production. The ability of plant CT to inhibit the growth of microorganisms (Scalbert, 1991; Min et al., 2003) and reduce the rate of ruminal gas production (Frutos et al., 2004; Makkar et al., 1995) is well known. This ability has been attributed to the capacity of these substrates to bind strongly to nutrient molecules and polysaccharides (Jones and Mangan, 1977) and to reduce the activity of microbial enzymes (Scalbert, 1991; Jones et al., 1994). Collectively, these data suggest that rumen metabolites and foam production associated with frothy bloat are influenced by action of CT (Tanner et al., 1995). This is a similar trend to other studies (Hagerman et al., 1992; Min et al., 2005a,b).

Plant CT have been investigated for their ability to inhibit ruminal methane production (Min et al., 2005c; Puchala et al., 2005). In the current study, mean in vitro methane production decreased linearly with increasing CT supplementation. This is consistent with McMahon et al. (1999), who reported that methane production was decreased linearly with increasing CT-containing forage (sainfoin; Onobrychis viccifoli; 11.3% CT) supplementation compared with nonCT-containing forage alfalfa (Medicago sativa). It has been reported in vivo that animals fed CT-containing forages reduced methane gas production in goats (Puchala et al., 2005), sheep (Waghorn et al., 2002), and dairy cows (Woodward et al., 2002). Evidence in support of the inhibitory effect of CT was provided by Tavendale et al. (2005), who demonstrated that the accumulated methane production at 12 h incubation for Lotus pedunculatus (100 g of CT/kg of DM) was lower (8.8 vs. 12.5 mL) than alfalfa (2 g of CT/kg of DM). These effects may be due to an increase in bacteriostatic rather than bactericidal effects (Tavendale et al., 2005). The presence of quebracho CT at 1% inhibited Methanobrevibactor smithii specific growth rate by 89% (our unpublished observations).

Ruminal Fluid Protein Characteristics and BioFilm Complexes
Majak et al. (2003) reported that fresh legume forage is rapidly digested, leading to bacterial blooms producing large quantities of gas and biofilm complexes associated with frothy bloat. The importance of soluble protein fractions, ruminal gas production, and low gas permeable biofilm production was reported by Min et al. (2006a, b), who found steers grazing wheat forage containing high soluble protein fractions experienced increased bloat frequency and exhibited larger quantities of gas and biofilm production compared with bermudagrass hay diet. Subsequent work reported significant correlations between in vitro gas production and soluble protein fractions and IVDMD (Min et al., 2005b). Recently, Min et al. (2006a) reported that Streptococcus bovis was one of the major biofilm producing bacteria among 6 ruminal bacteria species tested in vitro when these bacteria were incubated with soluble wheat forage protein. Feeding CT to steers grazing winter wheat forage in the current study had no effect on ruminal microbial protein fractions but increased whole rumen content and particulate material protein fractions and reduced biofilm complexes during the reproductive stage of growth. In a corn oil experiment (Min et al., 2006b), corn oil supplementation increased biofilm assimilation, indicating that biofilm production may be affected by energy supplementation to the rumen micro-organisms, whereas CT supplementation decreased biofilm complexes through substrate complexing and antimicrobial activity. Elam and Davis (1962) reported inorganic phosphorus content in the rumen increased by 20% when the feedlot steers received soybean oil or animal fat (8% of the feed consumed) but did not increase when animals received mineral oil supplementation. Studies with Azotobacter vinelandii (Cohen and Johnstone, 1964), Staphylococcus aureus (Stringfellow et al., 1991), and S. bovis (Cheng et al., 1976) strains showed that the supplementation of energy sources (glutamate, sucrose, glucose, fructose, and ethanol) increased the biofilm production. Further studies, however, are needed to explain the effect of CT supplementation on the relationship between biofilm complexes and rumen microbial activities associated with frothy bloat.

Effect of Condensed Tannins Addition on Bloat Frequency and Animal Performance
The most significant findings in this study were that control steers experienced more frequent and severe bloat and had lower ADG than steers that receiving CT. Total and soluble forage proteins have been identified as precursors to bloat on wheat pasture (Bartley et al., 1975). The presence of CT in the diet can reduce protein degradation in the rumen (Min et al., 2003; Frutos et al., 2004). This is thought to be due to stable CT:protein complexes forming at pH 4.0 to 7.0 in the rumen, which subsequently release protein in the acidic conditions of the abomasum (Jones and Lyttleton, 1971; Min et al., 2003). This enables protein to bypass degradation in the rumen and undergo enzymatic hydrolysis in the abomasum (Jones and Mangan, 1977). Furthermore, CT decreased in vitro ruminal methane production from fresh wheat forage. The combination of increasing bypass protein flow to the small intestine and decreasing frothy bloat and methane production likely led to the 15% increase in ADG observed with CT supplementation of steers grazing wheat forage in this study.

Our results show that daily supplementing quebracho CT to steers grazing wheat forage improved animal performance and minimized bloat frequency without deleterious effects to the animals. Quebracho CT supplemented ruminal fluid incubated with minced wheat forage led to less in vitro gas and methane production. Quebracho CT supplementation is a potentially effective feed additive for decreasing bloat impacts and increasing ADG in stocker cattle-wheat systems common to the Southern Great Plains. Further research is required to define bloat, feed efficiency, and economical impact at a commercial level of CT feeding. Research to develop self-fed supplement delivery systems for quebracho CT is needed for industry adoption.

	Footnotes

 
¹ The authors wish to thank the Beef Initiative Program of the Texas Agricultural Experiment Station (TAES) for funding this research.

² Corresponding author: bpinchak{at}ag.tamu.edu

Received for publication October 12, 2005. Accepted for publication February 8, 2006.

	LITERATURE CITED

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