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KMID : 1025520090510060511
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Journal of Animal Science and Technology
2009 Volume.51 No. 6 p.511 ~ p.520
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Effects of Thymol, Eugenol and Malate on In vitro Rumen Microbial Fermentation.
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Kim Do-Hyung
Kim Kyoung-Hoon
Choi Chang-Won
Hong Seong-Koo
Seol Yong-Joo
Kwon Eung-Gi
Kim Wan-Young
Nam In-Sik
Lee Sung-Sill
Oh Young-Kyoon
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Abstract
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The purpose of this study was to investigate effects of increased levels of eugenol, thymol and malate on pH and the concentrations of VFA, lactate and ammonia-N during in vitro ruminal incubation. One Hanwoo beef steer(741kg) fitted with a rumen cannula was used and fed 0.5kg/day rice straw and 10kg/day corn-based concentrate(ratio of concentrate to rice straw = 95:5 on DM basis). Three different doses of thymol, eugenol and malate were used. Treatments of the experiment were as follows: Treatments of thymol were control(1g D-glucose/40ml), T1(1g D-glucose+40mg thymol/40ml), T2(1g D-glucose+50 mg thymol/40ml) and T3(1g D-glucose+60mg thymol/40ml). Treatments of eugenol were control(1g D-glucose/40ml), E1(1g D-glucose+55mg eugenol/40ml), E2(1gD-glucose+65mg eugenol/40ml) and E3(1gD-glucose+75mg eugenol/40ml). Treatments of malate were control(1gD-glucose/40ml), M1(1gD-glucose+25mg malate/40ml), M2(1g D-glucose+50mg malate/40ml) and M3(1g D-glucose+100mg malate/40ml). The results of this study showed that eugenol and thymol have improved stability of the ruminal fermentation by decreasing lactic acid concentration and increasing ruminal pH. However, it inhibited the production of total VFA, acetate and propionate. Malate also improved stability of the ruminal fermentation by decreasing lactic acid concentration and increasing ruminal pH, but it had a very little effect on ruminal lactate concentrations and pH. On the other hand, malate did not decrease the concentrations of total VFA, acetate and propionate. Therefore, at the low ruminal pH expected in high-concentrate diets, thymol, eugenol, and malate are potentially useful in Hanwoo finishing diets. Further studies are necessary for determining the effectiveness of these additives on in vivo rumen fermentation and animal performance in Hanwoo finishing steers.
The purpose of feeding managements in the finishing phage of Hanwoo beef cattle is to increase marbling score. For this reason, the general feeding management of Hanwoo cattle during the fattening period is to feed a high-concentrate(above 90%) diet or even all concentrate diet(Rural Development Administration, 2007). But, this causes a problem of decreasing ruminal pH. The normal ruminal microflora can be greatly altered, resulting in increasing a population of acid tolerant, lactic acid producing bacteria(Slyter, 1976), and sometimes cause excessive lactic acid accumulation(Russell and Hino, 1985; Dawson et al., 1997). Lactic acid accumulation occurs when abrupt introduction of rapidly fermentable carbohydrate stimulates proliferation of the rapidly growing lactic acid producing bacterium, Streptococcus bovis, so that it exceeds the growth rate of lactic acid-utilizing bacteria(Russell and Hino 1985; Dawson and Allison, 1988). As a result of the imbalance between production and utilization, an accumulation of lactic acid occurs, but often only in specific individuals. The factors(microbial or otherwise) that may predispose certain animals to lactic acid accumulation remain largely unknown (Bevans et al., 2005).
Plant extracts have been used for centuries for various purposes as traditional medicine and food preservatives due to their antimicrobial properties(Busquet et al., 2006; Davidson and Naidu, 2000). Essential oils are blends of secondary metabolites obtained from the plant volatile fraction by steam distillation (Gershenzon and Croteau, 1991). Beginning from the report of Borchers(1965), the potential benefit of essential oil have been evaluating on rumen microbial fermentation. Rumen microbial activity was affected by use of plant extracts and secondary plant metabolites(Bysquet et al., 2006). It has been reported that terpenoid and phenolic components were responsible for the antibacterial properties of many essential oils(Panizzi et al., 1993; Helander et al., 1998; Chao et al., 2000; Dorman and Deans, 2000; Benchaar et al., 2007). Among these essential oils, eugenol and thymol have been shown to alter the rumen fermentation by decreasing lactic acid and increasing ruminal pH(Castillejos et al., 2006; Evans and Martin, 2000).
Malate is a four-carbon dicarboxylic acid that is commonly found in biological tissues because it is an intermediate of the citric acid cycle(Lehninger, 1975). Malate stimulates lactate uptake by Selenomonas ruminantium, the main lactic acid using bacteria within the rumen, so improves the ruminal pH and increases propionate production(Callaway and Martin, 1996; Martin, 1998). The stimulatory effects of malate on lactic acid fermentation have been clearly demonstrated in vitro(Nisbet and Martin, 1994; Martin and Streeter, 1995; Callaway and Martin, 1996). As a key intermediate in the succinate-propionate pathway, malate enhances lactic acid fermentation by Selenomonas ruminantium (Montano et al., 1999).
Research for dietary additives that help to rumen fermentation stability in Hanwoo finishing cattle consuming a high-concentrate diet has received little attention. Therefore, the objective of this study was to investigate effects of increased levels of eugenol, thymol and malate on pH and the concentrations of VFA, lactate and ammonia-N during in vitro ruminal incubation.
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KEYWORD
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Eugenol, Thymol, Malate, Rumen fermentation
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