EVALUATION OF LEGUME STRAWS FOR PROTEIN FRACTIONS AND IN VITRO DIGESTIBILITY

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2 Indo-Am. J. Agric. & Vet. Sci., 2013 Raja Kishore Konka and ISSN Srinivas Kumar Dhulipalla, Vol. 1, No. 2, December Meghana Publications. All Rights Reserved Research Paper EVALUATION OF LEGUME STRAWS FOR PROTEIN FRACTIONS AND IN VITRO DIGESTIBILITY Raja Kishore Konka 1 * and Srinivas Kumar Dhulipalla 1 *Corresponding Author: Raja Kishore Konka dr_rajakishore@yahoo.co.in An experiment was conducted to evaluate nutritive value and digestibility of legume straws, viz., Red Gram Straw (RGS) and Black Gram Straw (BGS) by in vitro techniques. The percent crude protein, crude fibre and ether extract contents were at a level of 6.6, 64.2 and 1.5 in RGS and 7.7, 58.0 and 1.3 in BGS, respectively. The RGS and BGS contained 75.8, 69.2; 58.6, 54.9 and 14.9, 14.2% NDF, ADF and ADL, respectively. The average in vitro digestibility (%) of DM (58.2 vs. 56.5), CP (68.1 vs. 65.1) and ADF (55.6 vs. 54.1) were higher (P<0.01) in BGS compared to RGS, while the values for in vitro NDF digestibility (%) were similar among the straws. Soluble protein (% CP) and non-protein nitrogen (% SP) were higher (47.9 and 56.2) in BGS than in RGS (44.2 and 51.2), respectively. Neutral detergent insoluble crude protein and acid detergent insoluble crude protein (% CP) were lower (37.9 and 12.9) in BGS than in RGS (44.0 and 22.7), respectively. BGS contained higher B 1, B 2 and B 3 fractions than in RGS, while fraction C was observed at lowest in BGS. In view of the above, present study indicated BGS to be good protein source of straw origin with higher B protein fractions, in vitro DM and CP digestibilities. It is concluded that black gram straw can be better utilized than red gram straw and can be effectively included in the daily rations of livestock. Keywords: Legume straws, Protein fractions, In vitro digestibility INTRODUCTION The cost of feeding is a significant factor dictating the economic viability of livestock feeding which must be reduced by adopting alternative method of utilizing agricultural crop residues. In coastal Andhra Pradesh, large quantities of legume straws are available after harvesting for grain (MoA, ) which can be best utilized as ruminant feed. Conventional methods (Proximate and Van Soest) of feed analysis supply the information about the concentration or quantity of feed nutrients and give little indication about their availability in animal system. Evaluation of protein fractions of feeds is a good technique to get information regarding rumen protein degradability and digestibility in ruminant (Chalupa and Sniffen, 1996; Sharma 1 Sri Venkateswara Veterinary University, Department of Animal Nutrition, NTR College of Veterinary Science, Gannavaram , Andhra Pradesh, India. 59

3 et al., 2007). Rumen protein degradability of feed is directly related to its solubility (Wadhwa et al., 1993). Maintenance of fistulated animals is tedious and expensive while in vitro methods are less expensive and can be performed under laboratory conditions in short periods. A number of solvents and procedures have been used for the nitrogen fractionation of feeds (Krishnamoorthy et al., 1983). Prediction equations were developed for protein degradability of different feeds like hay, silage and concentrate in Borrough s buffer (Crawford et al., 1978). Sharma and Singh (1997) tested a number of feeds for their nitrogen fractions and degradability. Few reports are available on protein fractions in Indian feeds and degradability in ruminants (Jeya Prakash, 1999). Hence, the present study was undertaken to estimate protein fractions and in vitro digestibility of red gram straw and black gram straw used in ruminant rations. MATERIALS AND METHODS The present work has been undertaken in the Department of Animal Nutrition, NTR College of Veterinary Science, Gannavaram, Andhra Pradesh, India. Samples of locally available crop residues, viz., Red Gram Straw (RGS) and Black Gram Straw (BGS) were procured from the farmers fields in nearby villages. CHEMICAL ANALYSIS The samples were dried in a hot air oven and ground to pass through 1 mm screen in a Wiley mill and mixed to get homogenous sample before subjecting to analysis. The mixed samples of RGS and BGS were analyzed in triplicate for proximate constituents (AOAC, 2007) and forage fibre fractions (Goering and Van Soest, 1970). Non-Structural Carbohydrates (NSC) were derived by the equation given by Van Soest et al. (1991). NSC (% DM) = 100 [(NDF-NDICP)+CP+Fat+Ash] PROTEIN FRACTIONATION The protein fractionation of RGS and BGS was done according to the CNCP system (Licitra et al., 1996), where the protein was subdivided into 5 sub-fractions, viz., A, B 1, B 2, B 3 and C. The fractionation is based on the degradabilities and passage rate in gastro-intestinal tract (Pichard and Van Soest, 1977 and Van Soest, 1994). Fraction A (NPN), which is trichloro-acetic acid (TCA) soluble nitrogen was estimated by the method described by Licitra et al. (1996). Unavailable nitrogen or protein bound to cell wall (fraction C) is Acid Detergent Insoluble Crude Protein (ADICP), measured by estimating nitrogen in the ADF residue. The fraction B considered to be as true protein (Pichard and Van Soest, 1977) was further divided into 3 fractions namely, fraction B 1 (rapidly degraded true protein), B 2 (intermediately degraded true protein) and B 3 ( slowly degraded true protein) (Van Soest et al., 1981; Krishnamoorthy et al., 1983). The amount of slowly degradable fraction or soluble fibre-bound CP (fraction B 3 ) was calculated as neutral detergent insoluble crude protein (NDICP) minus ADICP. The fraction B 1 was expressed by estimating the true protein soluble in a borate-phosphate buffer at ph (Krishnamoorthy et al., 1982) and fraction B 2 known as neutral detergent soluble protein, was estimated as the difference between buffer insoluble protein (IP) and NDICP, and the latter was expressed by estimating the amount of protein recovered in the neutral detergent residue obtained upon standard fibre fraction analysis (Van Soest et al., 1991). IN VITRO STUDIES The samples were screened for in vitro digestibilities of DM (IVDMD), CP (IVCPD), NDF (IVNDFD) and ADF (IVADFD) as per the procedure described by Tilley and Terry Murrah Rumen liquor collected from 3 fistulated buffalo bulls at 2h post feeding, was filtered through double layer of muslin cloth into a previously 60

4 CO 2 flushed thermo flask. Dried feed sample (500 mg, 1 mm sieve) and 40 ml of McDougall s buffer (McDougall, 1948) was taken into a 100 ml glass conical flask. Thereafter, 10 ml of strained rumen liquor was transferred into the flask with a cork fitted Bunsen valve and flushed with CO 2. The flasks were incubated at 39±1 0 C with periodical shakings. After 48 h incubation, add 2 ml of 6 N HCl and 0.1 g pepsin powder and incubated for another 24 h. Filter the contents through filter paper (Whatman No. 54) or sintered glass crucible. Dry the residue overnight at C and estimate the DM digestibility. Run parallel samples for the estimation of CP, NDF and ADF from the residues. The data was subjected to one way analysis of variance as per the procedures of Snedecor and Cochran (1994) by using SPSS 17.0 version. The differences between the means were tested for significance using Duncan s multiple range test (Duncan, 1955). RESULTS AND DISCUSSION The proximate and cell wall constituents of RGS and BGS were presented in Table 1. BGS and RGS contained 7.7 and 6.6 (% CP), 75.8 and 69.2 (% NDF), 58.6 and 54.9 (% ADF) and 14.9 and 14.2 (% ADL), respectively. The chemical composition of the straws in the present study was in similar range to values obtained by various authors (Suryanarayana et al., 2009; Suresha et al., 2009, Raja Kishore et al., 2008; Jhadhav and Deshmukh, 2001). The CP (%) content was high, while NDF and ADF (%) contents were lower in BGS when compared to RGS. The protein components of RGS and BGS were presented in Table 2. Soluble protein (% CP) and non-protein nitrogen (% SP) were higher (47.9 and 56.2) in BGS than in RGS (44.2 and 51.2), respectively. Neutral detergent insoluble crude protein and acid detergent insoluble crude protein (% CP) were lower (37.9 and 12.9) in BGS than in RGS (44.0 and 22.7), respectively. This revealed that BGS was superior to RGS by virtue of its less ADICP (% CP) and high NPN (% SP) content. The protein fractions of RGS and BGS evaluated under CNCP system were presented in Table 2. The fraction A of BGS (24.8 % CP) is Table 1: Chemical Composition (% DM basis) of Red Gram Straw and Black Gram Straw Parameter Red Gram Straw Black Gram Straw Organic Matter Total Ash Crude Protein Ether Extract Crude Fibre Nitrogen Free Extract Neutral Detergent Fibre Acid Detergent Fibre Hemi-cellulose Cellulose Acid Detergent Lignin

5 Table 2: Protein Fractionation of Red Gram Straw and Black Gram Straw Particular Red Gram Straw Black Gram Straw SEM Protein Components SP (% CP) ± 1.87 NPN (% SP) ± 2.46 BIP (% CP) ± 1.87 NDICP (% CP) ± 3.03 ADICP (% CP) ± 4.88 Protein Fractions (% CP) A ± 0.13 B ± 2.00 B ± 1.15 B ± 1.85 C ± 4.88 Table 3: In Vitro Digestibility (%) of DM, CP, NDF and ADF of Red Gram Straw and Black Gram Straw Nutrient Digestibility (%) Red Gram Straw Black Gram Straw IVDMD** a ± b ± 0.61 IVCPD** a ± b ± 0.81 IVNDFD ± ± 0.47 IVADFD** a ± a ± 0.61 Note: ab Values in the rows bearing different superscripts differ significantly; **P < higher than RGS which signifies the instantaneously degradable protein in the ruminant digestive system (amino acids, peptides) i.e., NPN (Pichard and Van Soest, 1977). Most of the reported concentrations of NPN in grasses and legume forages are having the range as fresh material (10-15 %), hay (15-25 %) and silage (30-65 %) (Hughes, 1970; Krishnamoorthy et al., 1982; Xu et al., 1996). Among the protein B fractions, fraction B 3 was higher in both RGS and BGS when compared to other B fractions, respectively. Sharma and Singh (1997) reported that B 3 fraction was maximum in grains. In contrast to the present findings, Kamble et al. (2010) and Mondal and Walli (2003) reported higher B 1 fraction in oil seed cakes. Fraction B 1 referred to as true soluble protein (globulins and some albumins) with rumen degradation of %/h was found to be 23.4 (% CP) in BGS. Elizalde et al. (1999) reported 17.1 % CP of B 1 fraction in alfalfa. The B 1 fraction (% CP) in oil seed cakes ranged from 13.2 to 49.4 (Kamble et al., 2010). Similarly, Singh et al. (2002) reported fraction B 1 (% CP) of 18.0 and 12.0 in groundnut haulms and jowar kadbi which were lower when compared to the 62

6 present study. The B 2 fraction (% CP) with rumen degradation of 5-15 %/h was found to be 11.9 and 14.2 in RGS and BGS which was found to be lower than other B fractions. Sharma et al. (2004) evaluated protein fractions in twelve grasses in which the fraction B 2 (% CP) ranged from 2 to 32.9%. The fractions B 1 and B 2 approx. (38% of BGS) have 100 % intestinal degradability which is higher than RGS (32%). Fraction B 3 (% CP) which have 80% intestinal degradability in ruminants was 25% in BGS and 21.3% in RGS. In contrast, cereal grains contain small amount of fraction B 3 which mainly included prolamine proteins such as Zein in corn (Van Soest et al., 1981). Fraction C (% CP) was found to be 12.9 in BGS and 22.7 in RGS. This fraction comprises protein associated with lignin, tannin-protein complexes and Maillard products that are highly resistant to microbial and mammalian enzymes and does not provide amino acids post ruminally to the ruminants (Krishnamoorthy et al., 1982). Fraction C is considered to be undegradable fraction which is resistant to ruminant degradation and digestion. Singh et al. (2002) reported 8.5 and 17.3 (% CP) of fraction C in groundnut haulms and jowar kadbi, respectively. Mondal and Walli (2003) reported 5.9% of fraction C in maize fodder, while the average C fraction content (% CP) is 19.5, and (Chaurasia et al., 2006) in tree leaves, shrubs and grasses, respectively. Sniffen et al. (1992) also reported wide variability in fraction C content in protein supplements ranging from 0-20%. The quantum of fraction C is widely variable among the straws and other ruminant feeds, which is evident from the previous studies. The in vitro digestibility studies revealed that per cent of IVDMD, IVCPD and IVADFD (Table 3) were higher (P<0.01) in BGS when compared to that of RGS. However, average IVNDFD (%) did not differ statistically among straws under study. These values corroborated with the findings of various authors for in vitro digestibility of dry matter (Raghava Rao et al., 1992 in sugarcane bagasse; Chander Dutt et al. (2004) in paddy straw, NDF and ADF (Dhore et al., 2005) in sorghum stover. The lower ADF digestibility observed in RGS than in BGS might be due to lower CP content in RGS which significantly affects ADF digestibility. CONCLUSION The present study indicated black gram straw as a good source of ruminally available protein fractions when compared to red gram straw with highest B fractions and lowest C fraction. Hence, black gram straw can be effectively included in the daily rations of livestock, especially into complete rations for effective protein utilization. REFERENCES 1. AOAC (2007), Official methods of analysis, 18 th Edition, Association of Official Analytical Chemists, Washington D C. 2. Chander Dutt, Aruna Chhabra, Niranjan M, Chattopadhyaya K, Dhiman K R and Singh N P (2004), In vitro digestibility of straw of different cultivars of paddy,. Indian J. Ani. Nutr., Vol. 2, No. 3, pp Chalupa W and Sniffen C J (1996), Protein and amino acid nutrition in lactating dairy cattle-today and tomorrow, Anim. Feed Sci. Technol., Vol. 58, pp Chaurasia M, Kundu S S, Sultan Singh and Misra A K (2006), Cornell net carbohydrate and protein system for nutritional evaluation of tree leaves, shrubs and grasses, Indian J. Ani. Sci., Vol. 76, No. 1, pp Crawford R J Jr, Hoover W H, Sniffen C J and Crooker B A (1978), Degradation of feedstuff nitrogen in the rumen and nitrogen solubility in three solvents, J. Anim. Sci., Vol. 46, pp Dhore R N, Mahurkar A V and Udar S A (2005), In vitro digestibility of sorghum 63

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