Abstract:

Evaluation of Lablab {Lablab purpureus [Sweet]) cv Rongai as a supplementary forage legume for lactating dairy cows (Friesian x Zebu) fed on elephant grass (Pennisetum purpureum), was done at Namulonge Agricultural and Animal Production Research Institute. The effect of stage of maturity on the herbage dry matter yield (DMY), in vitro organic matter digestibility (IVOMD) and chemical composition of Lablab was assessed in Experiment I. As plant age advanced, herbage biomass DMY, spread and stem fraction increased significantly (P<0.05). Lablab biomass DMY was 6.6, 10.9 and 12.2 Mt ha'1, for the vegetative, flowering and pod-ripening stages of growth (75-, 110- and 140-days post-planting respectively). The leaf fraction decreased (P<0.05) with increasing plant age starting from FS to PS. Likewise, crude protein (CP) content decreased (P<0.05) with increasing plant age. Neutral detergent fibre (NDF) and acid detergent fibre (ADF) increased with plant age while, acid detergent lignin (ADL) remained constant. In vitro organic matter digestility of the leaf and stem fractions also declined over the growth period by 12 and 19.5%, respectively. Calcium (Ca) and phosphorus (P) contents remained unchanged during the study period. The performance of lactating dairy cows fed elephant grass-based diets supplemented with Lablab hay was studied in Experiment II. Four cross-bred Friesian (Friesian x Zebu) were used in a 4 x 4 Switch-over Latin square design. The animals had a mean milk yield of 9.5 kg day'1 and average live weight of 405.5 (S. D=+15kg). Addition of Lablab hay significantly increased elephant grass DMI.
The optimum supplement level was 3 kg day'.-1 (as fed), beyond which there was a substitution effect. Sole feeding on elephant grass resulted in lower (P<0.05) total dry matter intake (TDMI) than when lablab hay was included as a supplement. Daily milk yield was significantly (P<0.05) increased by, -l lablab hay supplementation: 9.1; 9.8 and 10.8kg day for levels: 0; 2 and 3kg day’1 respectively of lablab hay but decreased to 10.7kg day at a.-I level of 4kg day. The decrease was not significant. Milk composition was not affected by supplementation. Animal live weight decreased with sole elephant grass feeding. Supplementation with Lablab, however significantly (P<0.05) increased live weight of the animals but there were no differences among the different supplement levels. A level of 3 kg day, -1 of lablab hay was sufficient to maintain milk yields and improve animal live weight. Experiment III evaluated the effect of supplementing a concentrate to elephant grass-lablab hay basal diets. The experimental design and animal management were similar to those used in Experiment II. Mean milk yield was 8.5 kg day’1 and mean liveweight was 384.5 (+15kg). Supplementing a basal diet of elephant grass and 3 kg day of, -1 lablab hay with a concentrate, in Experiment III impaired the intake of elephant grass although TDMI increased significantly (P<0.05). Daily milk yield was increased (P<0.05) by supplementing: 9.8; 10.4 and 11.3 for levels 0; 1 and 2 kg day’1 of a concentrate but there were no significant (P<+0.05) differences beyond the level of 3 kg day’1. Milk composition, on the other hand, was not affected by concentrate supplementation. Both supplemented and Un supplemented animals gained weight. However, the difference in live weight gains were not significant (P<0.05). A simple cost benefit analysis showed an increase of 5% in gross margin when lablab was further supplemented with a concentrate. In Uganda, utilization of elephant grass accompanied by Lablab hay with a concentrate for lactating dairy cattle is a new intervention which has not now been documented especially. This practice certainly needs to be encouraged in light of the results of this study.