India has one of the largest livestock population in the world and its feed requirement is mostly met from crop residues, grasses and agriculture by products. At present country is facing deficiency of green fodder, dry crop residues and concentrate feeds. Ruminants in India rely on low quality crop residues which are deficient in protein, energy, minerals and vitamin and also imparts poor digestibility. Thus ruminants fed low quality forage need supplementation of critically deficient nutrients for better production. Instead of the conventional feed resources, non-conventional feeds like tree leaves may be used for feeding the animals, since they are rich in nutritive value and good alternate source of proteins, vitamins and minerals. Subabul is a multipurpose tree legume. Its average yield ranges from 3 to 30 t DM/ha/year depending on soil, temperature and moisture conditions. Scientific name of Subabul is Leucaena leucocephala. It has high nutritive value and crude protein. It is highly palatable, tolerant to severe defoliation and draught and an important source of protein for ruminants.
Nutritive value of Subabul
Protein content is around 292 g/kg of crude protein in leaf meal and 220 g/kg of crude protein in foliage. Utilization of cereal straws may be enhanced by tree foliage to improve supply of fermentable nitrogen, carbohydrate and micronutrients to the animal.
Table1: Nutritive value of Subabul leaves (Dry matter basis)
Secondary metabolites in Subabul
Presence of secondary metabolites like tannin and mimosine limit the use of Subabul in the animal ration due to adverse effects. Subabul leaves contain tannin, 4.45 % hydrolysable and 0.53% condensed. A toxic non-protein amino acid mimosine (up to 12% DM in young shoots), structurally similar to tyrosine is also present in Subabul. It is broken down in rumen to DHP (3, 4 and 2,3 dihydorxy-piridine), a goitrogen which is detoxified by rumen bacteria and becomes lethal when Subabul is consumed in excess of 50% by small ruminants.
Potential benefits of incorporation of Subabul in ruminant ration
Subabul may be incorporated in ruminant feed upto certain level. In ruminant ration up to 15 % in straw based diet digestibility of feed may go up to 55.87 %. Since it has good amino acid index so it may be helpful to improve microbial fermentation, body weight gain in growing animals (upto 16 % and <32% inclusion level) and milk production. Presence of tannin is also important, as tannins form natural tannin-protein complexes and protects the dietary protein against rumen degradation by ruminal microorganisms, decreasing ammonia production and increasing the flux of dietary protein for absorption in the intestines.
Consumption of high amount of roughage diet may also lead to higher amount of methane production. Methane is a green house gas, its global warming potential is 23 times than that of CO2 and is responsible for 2-12 % of gross energy loss of feed and also negative impact on the environment. Due to the presence of tannin in the Subabul, it helps to mitigate methane production from the ruminants and saves the energy which may be reflected in the form of higher milk production. Subabul can be incorporated in the feed up to 30 and 50 % in large and small ruminants respectively. Straw intake may be improved and along with this energy and protein intake also may be pronounced in Subabul supplemented animals.
Subabul is available in huge amount particularly in tropics and it can be concluded that its inclusion in the diet up to 30 % of large and 50 % of small ruminants will be beneficial for livestock.
PhD Scholar, Animal Nutrition Division, ICAR-National Dairy Research Institute, Karnal-132001
For further reading
Devendra, C. (1993). Trees and shrubs as sustainable feed resources. Proc. 7th World Conf. Anim. Prod., Edmonton, Alta., Canada, Vol. 1, pp. 119- 136.
Helal, H. G., Eid, E.Y.; Nassar, M. S. and El Shaer, H. M. 2013. Some nutritional studies of four salt-tolerant fodder crops fed to goats. Animal Feed . Tech article .
Sallam, H.A.M.S., Bueno, I.C., Barbosa de Godoy, P., Nozella, E.F., Vitti, D.M.M.S. and Abdalla, A.L. 2010. Ruminal fermentation and tannin bioactivity of some browses using a semi-automated gas production technique. Trop. Subtrop. Agroecosyst., 12, 1- 10.
Shelton, H.M. and Brewbaker, J.L. (1994) Leucaena leucocephala - the most widely used forage tree legume, p. 15–29. In: Gutteridge, R.C. and H.M. Shelton (Eds.). Forage tree legumes in tropical agriculture. CAB International, London, UK