Herbage Mass and Chemical Composition of Hinson Long Juvenile Forage Soybean and Lablab cv. Rongai.

Forage soybean cv. Hinson long Juvenile (HLJ; Glycine max) and Lablab (LL; Lablab purpureus) are fast growing legumes with potential for use in forage conservations systems in Puerto Rico.  At least two to three regrowths of LL are possible in the tropics.  However, there is limited information on herbage mass (HM) and chemical composition [crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF)] on either HLJ or LL.  The objectives of this study were to compare HM of HLJ (sequential plantings in April and June 2007) and LL (April planting and a 70 d regrowth) and to determine CP, NDF and ADF concentrations.  The design was a randomized complete block with four replicates. The HLJ was harvested at pre-pod stage (approximately 70 d for the April planting and 78 d for June planting) and LL was harvested at the same time.  Herbage mass was estimated by clipping 1 m² quadrats to ground level and sub-samples (500 g) were oven-dried at 65° C for 48 hrs to determine dry matter percentage and chemical composition.  Forage soybean HM was similar (1.47 Mg ha^-1) to LL (1.63 Mg ha^-1) for the April planting.  There were differences (P<0.05) on HM of HLJ when compared to the June 2007 planting (2.48 Mg ha^-1).  However, HM of LL (4.5 Mg ha^-1) was much higher for the regrowth.  Crude protein, NDF, ADF did not differ between legumes, averaging 17%, 55% and 30.3%, respectively. This study shows that the June summer plantings of HLJ have higher HM than the April plantings (>1 Mg ha^-1) and that LL HM are much higher from regrowth.  The study also shows that nutritive value of HLJ and LL are similar to imported alfalfa.  In conclusion, both HLJ and LL can replace alfalfa in total mixed rations diets of dairy cows in Puerto Rico.