Introduction Guar plant is grown to the guar bean’s gum that has many food and industrial application. Isolation of gum (a galactomannan) from guar seed led to yield a high protein by-product containing 55 to 60 percent crude protein (CP), which has been used as a protein sources in ruminant and non-ruminants livestock feeding. However, information about the kinetic of nutrient disappearance of guar meal in ruminants is very low. The aim of the present study was to evaluate in vitro first order dry matter (DM) disappearance kinetics of guar meal. Materials and methods Samples of guar meal as non-heat processed (CP: 566 and 580 g/kg DM; GM566 and GM580, respectively) and heat processed (CP: 594 g/ kg DM; GM594P) were provided. They were dried using a forced-air oven at 60 °C for 48 h. All feed samples were ground to pass through a 2-mm screen and then analyzed for crude protein (CP), ether extract (EE) and ash (AOAC, 1995). Neutral detergent fibre (NDF), and acid detergent fibre (ADF) were determined using the method of Van Soest et al. (1991). Samples were incubated in a medium prepared as described by Arroquy et al. (2005). Fifty-five ml of medium were supplied into 100 ml bottles that approximately containing 0.45 g of feed (6 replicate for each feed). Then, each bottle was inoculated under carbon dioxide with 5 ml of mixed rumen microbes. Rumen fluid was obtained from three sheep (49.5 ± 2.5 kg) fitted by rumen fistulae, before the morning feeding, and immediately strained through four layers of cheesecloth. The animals fed 1 kg d-1 of DM of lucerne hay and 0.3 kg d-1 of DM concentrates (165 g CP/ kg of DM). The bottles were incubated for 4, 8, 16 and 24 h at 39 ºC. Then, bottle content was filtered through a 42 µm filter, and DM of the unfiltered medium was determined. Non-linear first order model was used to estimate the digestion kinetic parameters of DM. The model was: D(t)= D(i).exp (-kd. time)+ I; Where, D(t) is residual DM at any time, , D(i) potentially digestible fraction , kd is fractional rate constant of digestion (h-1) and I is indigestible fraction. Results Chemical compositions of the samples are shown in Table 1. Non-linear first order parameters of In vitro DM digestion of the samples are presented in Table 2. Results of the present study indicated that DM of various guar meals, except for GM60P, is completely digestible. The kd was significantly (P< 0.05) higher in GM566 compared with G580 and GM594P. Table 1: Chemical compassion of the samples (g/ kg) Nutrients Feed EE NDF ADF Ash GM566 36.6 218.0 131.0 52.0 GM580 75.2 205.0 144.0 50.9 GM594P 71.9 238.0 140.0 51.7 Table 2: In vitro first order DM disappearance parameters of guar meal Parameters Feed Kd I Di R2 GM566 0.13± 0.007 0.0 1.02±0.02 0.99 GM580 0.108± 0.005 0.0 1.04± 0.017 0.99 GM594P 0.101± 0.011 0.07± 0.03 0.91± 0.035 0.95 D(i) = potentially digestible fraction, kd = fractional rate constant of digestion (h-1), I = indigestible fraction. Conclusion Results of the present study demonstrated that in vitro DM indigestible fraction of various guar meals is influenced by heat processing. While the DM of GM566 and GM580 Were completely disappeared after 24 h of incubation, about 7% of DM of GM594P was remained in the medium. It was also concluded that the rate of DM disappearance of GM566 was higher than the other samples. Acknowledgement The authors wish to Acknowledgement the financial support received from Aria Shirin Nosh Company and Ferdowsi University of Mashhad. References AOAC, 2000. Official Methods of Analysis, 17th ed. Official Methods of Analysis of AOAC International, Gaithersburg, MD, USA. Arroquy, J.I., R.C. Cochran, T.G. Nagaraja, E.C. Titgemeyer and D.E. Johnson, 2005. Effectof types of non-fiber carbohydrate on in vitro forage fiber disappearance of low-quality grass hay. Anim. Feed Sci. Technol. 120, 93–106. Van Soest P. J., J. B. Robertson, and B. A. Lewis. 1991. Methods for dietary fibre, neutral detergent fibre, and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74: 3583-3597.

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