بررسی ارزش غذایی گاودانه خام و عمل‌آوری شده با استفاده از روش‌های آزمایشگاهی و آزمون تولیدگاز

Introduction: Heat treatment of a wide variety of feeds has been traditionally used to improve the utilization of their protein by ruminants. Heat treatment of legume seeds can inactivate anti-nutritional factors, it is also effective in increasing the digestibility (Seifdavati 2012). Chemical composition and heat processing can affects fermentability of Vicia Ervilia grain. Particle size and moisture during processing also influence the possible effects of processing. Digestibility may be directly determined in vitro or estimated by using in vitro procedures, which are cheaper and more convenient. In vitro gas production technique was widely used to evaluate the nutritive value of legume forages (Evitayani et al 2004) and tannin containing tree leaves (Rubanza et al 2003). This experiment was conducted to investigate of the nutritive value of Vicia Ervilia using the in vitro disappearance and gas production techniques.
Materials and Method: The experimental treatments were grinding Vicia Ervilia grain, steam flak, roasting and microwave. Processing steam flak, treated steam at 100°C for 30 min and then immediately passed through rollers were allowed to air for 48 h and then sealed in plastic bags. Roasting treatments at 120°C for 10 min and microwave irradiation (Nasional at a power of 800w) for 3 min. The treatments were milled through a 2.0 mm screen. Samples of treatments were dried in oven at 65°C for 24h. The gas production of treatment were recorded at 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48 h of incubation time using a water displacement apparatus. For this purpose two ruminal fistulated sheep were used. Rumen liquor samples were obtained from the two weathers that were fed a diet content 60% roughage: 40% concentrate. Rumen fluid was pumped with a manually operated vacuum pump and transferred into prewarmed thermos flask, combined, filtered through four layers of cheesecloth and flushed with CO2. McDougall (1948) buffer solution was prepared and placed in a water bath at 39°C. Samples (300 mg) were weighed into 50 ml serum vial. Each feed sample was incubated in triplicate with 20 ml of rumen liquor and buffer solution (1:2). The vials were sealed immediately after loading and were affixed to a rotary shaker platform set as (120 rpm) housed on a incubator. Vials for each time point, as well as blanks, were prepared in quadruplicate. The metabolizable energy, net energy for lactation content of feeds, short chain fatty acid and digestible organic matter were calculated using equations of Menke & Steingass (1988) and Getachew et al. (2002). For in vitro disappearance method, the incubation time were 2, 8, 12, 24 and 48 h. The rumen liquor was obtained from the same sheep used in the gas production technique and receiving the same diet to similar conditions for both techniques. Mc Dougall (1948) buffer prewarmed to 39 ºC. The inoculum was dispensed 20 ml per vial into 50 ml serum vial (containing of 300 mg sample per vial) which had been warmed to 39 ºC and flushed with oxygen free CO2. The vials were sealed immediately after loading and were affixed to a rotary shaker platform set as (120 rpm) housed in incubator. Vials for each time point, as well as blank (containing no substrate), were prepared in triplicate. Triplicate vials were removed after 2, 8, 12, 24 and 48h of incubation. The residues were washed three times in phosphate buffer followed by centrifugation (2500 rpm, 10 min) and dried at 105 ºC and determined DM disappearance. The data was analyzed by completely randomized design.
Results and Discussion: Dry matter disappearance and gas product increased with increasing incubation time. Heat processing of steam flak increasing of DM disappearance and gas produced at 48 h and higher than the other treatments (P<0.05). The gas production volume at 48 h incubation for treatments of control, microwave, roasting and steam flaking were 141, 140, 134.57 and 147 (ml/gDM), respectively. The gas production for sum of soluble and insoluble (a+b) fractions (ml/gDM) and gas production rate (ml/h) in control treatment were 142.9 and 0.106, respectively. Dry matter disappearance from in vitro increased with increasing incubation time. The disappearance percentage of DM in control treatment for 2 and 48 h of incubation were 39.88 and 83.48 and degradabilities coefficients (a, b and c) were 31.08, 48.03 and 0.088, respectively. For roasting treatments DM disappearance and gas produced at 48 h were lower than the other treatments. Barley grain treated by the steam flak, flame rusting and exploring can be decreased ruminal crude protein (McNiven 1994). Ljokjel et al (2003) reported that heat treatment decreased ruminal degradation of starch in both barley grain and pea grain. Parnian et al (2010) showed that, cumulative gas production of sorghum grain was linearly increased by altering period of microwave irradiation. Parand et al (2010) reported that the gas production of barley grain for steam flak, microwave and roasting at 48 h were obtained 239.4, 275.9 and 239.7 (ml/gDM), respectively, these values does not match with the results of this study. Similar to the latter, previous in vitro and in vivo studies (Hironaka et al 1992; Huntington 1997) have shown that steam flaking increased ruminal starch digestibility of barley in feedlot cattle. Seifdavati et al (2012) showed the gas production of Vicia Ervilia at 24 h was obtained about 246.29 ml/gDM and rate of gas product was achieved 0.063 (%h) that decreased with autoclave processing. Hadji Panayioton and Economids (2001), reported degradability characteristics of lupin (a, b and c) about 12.45%, 84.41% and 0.1 h-1, respectively. There was strong positive correlation between gas production, in vitro and in situ dry matter disappearance so that the gas production technique can be suitable replacement for in situ and in vitro DM disappearances. The steam flaking treatment showed high potential for producing of gas and high degradability of DM compared to the other treatments (P<0.05). Regarding to high gas production and in vitro degradability in steam flaking treatment, this treatment can be used to improve of digestion process in animal nutrition.