Tropical legume supplementation influences microbial protein synthesis and rumen ecology
Ruminants raised in the tropics largely depend on seasonal feed resources which are relatively low in quality in terms of low crude protein (CP) but high in crude fibre (CF); thus, low digestibility and nitrogen (N) contents that further reduce voluntary intake were obtained (Dryhurst and Wood, 1998). Leguminous and fodder tree are high in crude protein and plant secondary metabolites (Salem et al., 2013). However, the limitation to effective utilization of fodder legumes as feed for ruminants is the high content of tannins and other anti‐nutrients such as saponins, cyanogens, mimosine and coumarins which limit nutrient utilization (Makkar, 1993). Leucaena leucocephala is one of multipurpose leguminous tree species which is vigorous, rapidly growing, drought tolerant, highly palatable, protein rich and high yielding and can be grown on a wide range of soils (Jones, 1979). Leucaena, highly nutritious, is an important source of feeds for ruminants. Leucaena contained plant secondary compounds which can improve nutrient digestibility, feed utilization, cow's milk production and lamb live weight gain (Hernandez et al., 2014; Salem et al., 2014). The potential attributes of Leucaena are limited because of the presence of toxic amino acid mimosine. The toxic effect of dried Leucaena feeding ad libitum for 24 days with Karan Swiss crossbred calves was characterized by poor growth, emaciation, alopecia, loss of hair from the tail switch, ear and eye lesions, ulceration of the mouth region. Mean levels of 3,4 dihydroxypyridone (DHP) were 30.35 ± 13.52 mg/100 ml in rumen liquor (Ram et al., 1994). These symptoms are because of mimosine and 3‐hydroxy 4 (1H)‐pyridone (3,4‐DHP), its metabolite produced from mimosine in the rumen (Hegarty et al., 1976). There is a paucity of information on secretion of mimosine or its metabolites, that is 3,4‐DHP or 2,3‐dihydroxy pyridine (2,3‐DHP). Barros‐Rodríguez et al. (2012) reported that sheep grazing at high densities of plantation of L. leucocephala resulted in a lower daily weight gain, possibly because of the intake of a high amount of mimosine, which may exert an adverse effect on feed intake. However, information about the optimal intake levels of L. Leucocephala is scarce, whereas data on the effect of the dried L. Leucocephala (DLL) were yet being found on feed intake and rumen ecology in swamp buffalo. Therefore, the aim of the present study was to investigate rumen fermentation and microbial population of swamp buffalo as influenced by different levels of DLL supplementation.