Leucaena leucocephala IN RUMINANT NUTRITION

It is a common situation in extensive ruminant production systems in tropical countries to have low production indicators due to nutrient deficiencies in the diet. An economic alternative to increase animal production is the incorporation of legumes (fodder and fruits) in the diet. This review, presents an analysis of the positive and negative effects of Leucaena leucocephala consumption by ruminants, with particular emphasis on the secondary compound mimosine. Leucaena due to its high nutrient content, rumen by-pass protein supply and its possible effect on the reduction of greenhouse gas (attributed to tannins) has become one of the legumes most commonly used in ruminant feeding practices. However, in countries where leucaena has been introduced, its use is still limited to levels below 30% inclusion in the diet, due to the secondary compound mimosine and its isomers (3,4 and 2,3 DHP), which can induce toxicity, even when animals are inoculated with rumen fluid containing the bacteria Synergistes jonesii reported as responsible for degrading these compounds in the rumen. In the Yucatan Peninsula, Mexico, ruminants consuming leucaena can tolerate more than 50% inclusion in the diet, without having a negative impact on production, attributed intake to mimosine and its isomers. We conclude that in animals not adapted, the intake would be limited to low inclusion levels (less than 30% inclusion in the diet), mainly because of mimosine and its derivatives. The decrease in intake or diet digestibility seem to better explain the reduction in methane production, however, in vivo studies are required to clearly establish the mechanism of action. It has been reported the presence of different bacteria to S. jonessi that would have the ability to degrade mimosine and its derivatives, however, the activity of these bacteria and its effectiveness must be confirmed in vivo.