Biofuel co-products as livestock feed - Opportunities and challenges

Use of Pongamia glabra (karanj) and Azadirachta indica (neem) seed cakes for feeding livestock 383ngaflavone lanceolatin B (Limaye, 1925; Rangaswami andSeshadri, 1940; Roy, Sharma and Khanna, 1977). Amongthem, karanjin and pongamol are the most important toxicfactors due to their potentency. The bitter taste of karanjcake is attributed to the presence of these two compounds.KaranjinKaranjin (C 18 H 12 O 4 ; 3-Methoxyfurano-(2’,3’:7,8)-flavone)is the first flavonoid compound that was isolated, identifiedand characterized, and hence it is the earliest knownfuranoflavone and the most important physiologicallyactive factor of Pongamia sp. Its concentration in karanj oilis approximately 1.25 percent. Limaye (1925, 1926) isolatedkaranjin from pongamia oil. Seshadri and Venkateshwarlu(1943) identified, characterized and established the structureof karanjin. Its melting point is 158–159 °C. In theseeds of P. glabra, pongamol was subsequently identifiedalong with karanjin (Rangaswami and Seshadri, 1940). Thekaranjin content of the karanj oil has been reported to be147 mg/100 ml and 10–15 mg/100 g in SKC (Punj, 1988).Similarly, karanjin content of EKC was found to be in therange of 0.19 to 0.324 percent and 0.01–0.132 percent inSKC (Prabhu et al., 2002; Panda et al., 2006; Soren, 2006).Vinay, Appu Rao and Sindhu Kanya (2006) reported karanjincontent in the whole karanj seed to be 1.95 percent.Of the 24 furanoflavonols isolated, karanjin has beenstudied extensively and found to be hypoglycaemic. Oraladministration at a dose of 2 mg/kg per day for 7 dayscaused a reduction in blood glucose level both in normaland alloxan-induced diabetic rats (Mandal and Maity,1987). It also showed antitubercular (suppressing growthof Mycobacterium tuberculosis; Ramaswamy and Sirsi,1960), antifungal (Pan et al., 1985), antibacterial, phytotoxic(Simin et al., 2002), and central nervous systemstimulant activities (Mahali et al., 1989). Apart from theseactivities, karanjin is also a nitrification inhibitor (Majumdar,2002), juvenomimetic (Mathur et al., 1990) and synergistto insecticides (Sighamony, Naidu and Osmani, 1983). Itwas found to haemolyse red blood cells, with release ofLDH (lactate dehydrogenase) (Gandhi and Cherian, 2000).PongamolPongamol, a crystalline compound from the oil of P.glabra, was identified by Rangaswami and Sheshadri(1942). Compared to karanjin, it is a minor component,far more soluble in oils. It has the molecular formulaC 18 H 14 0 4 and contains a methoxyl group. Demethylationwith aluminium chloride yields nor-pongamol, whereastreatment with HCl gives rise to a product which is probablyisomeric but does not possess a phenolic group.Oxidation with KMnO 4 or decomposition with alkali yieldsbenzoic acid. These properties and colour reaction suggestthat pongamol is a flavone derivative (Rangaswamyand Sheshadri, 1942). Narayanaswamy, Rangaswami andSeshadri (1954) established the structure of pongamol asbenzoyl-O-methyl karanjoyl methane (S-benzolacetyl-4-methoxy benzofuran). It is the first example of a naturallyoccurring diketone related to flavones. Pongamol melts at128 °C and has relatively less bitterness compared withkaranjin. Among the flavanoid diketones, pongamol hasbeen explored extensively and found to have sedative anddepressant effects (Mahali et al., 1989). It is commerciallyused in cosmetic and sun-screen preparations (Noriaki,Masamichi and Masanori, 2001).TanninsApart from karanjin, the cake is also reported to containtannins to the extent of 3.2–3.4 percent (Natanam,Kadirvel and Ravi, 1989). Tannins are a naturally occurringgroup of phenolic compounds with a molecular weight of500–3000 daltons (Haslam, 1966). These have alkaloids,gelatins and protein precipitation properties. However,the total tannins and condensed tannins content of karanjcake was reported to be lower and protein-precipitationcapacity was not detected by Makkar, Singh and Negi(1990), suggesting that these co-products could be safefor incorporation in livestock feed. The tannin contentwas found to be slightly higher in SKC than in the expellercake (Panda et al., 2006). The SKC contained 0.94 percenttannins, along with other antinutritional factors, such asphytate (0.65 percent) and trypsin inhibitors (31 units/mg)(Vinay and Kanya, 2008).Protease inhibitorsProtease inhibitors are well known anti-nutrients thatare responsible for lower digestibility of plant proteins.Protease inhibitors, namely trypsin and chymotrypsininhibitors, are found in karanj oil seed residue (Rattansi andDikshit, 1997). These are a group of anti-nutritional factors,protein in nature, with a molecular weight between6000 and 25000 daltons, and are generally present in leguminousseeds (Birk, 1976; Liener, 1979). The expeller- andsolvent-extracted cakes contain trypsin inhibitor up to 8.7and 8.2 percent of protein, respectively (Natanam, Kadirveland Ravi, 1989). The adverse effect of trypsin inhibitors ismainly on the pancreas, which responds to the inhibitors byenhanced synthesis and secretion of proteolytic enzymes.The pancreatic enzyme secretion is regulated by a negativefeedback mechanism mediated by intestinal trypsin andchymotrypsin, and complex formation of trypsin with theinhibitors leading to a reduction of free trypsin in the smallintestine (Alumot and Nistan, 1961). This reduction activatesthe pancreas-stimulating hormone, cholecystokinin,the release of which from the intestinal mucosa is inhibitedby free trypsin (Wilson et al., 1978). As a consequence ofcholecystokinin action, the pancreas becomes hyperactive.