Cultivated and native browse legumes as calf supplements in Ethiopia.

Abstract

Efficient use of roughages is important for calf management in the Boran pastoral system. Using local legumes as protein supplements may improve fiber utilization and thus be an appropriate intervention. Fruits (pods and seeds) of Acacia tortilis (Forsk.) Hayne subsp. spirocarpa (Hochst. ex A. Rich) Brenan, leaves of A. brevispica (Harms), and cowpea [Vigna unguiculata (L.) Walp] hay were compared with alfalfa (Medicago sativa L.) hay as protein supplements for calves using 2 approaches. Sheep fed native grass hay under confinement were used for a controlled evaluation in growth and metabolism trials. Calves grazing dry-season forage under simulated pastoral management provided in evaluation under field conditions. All supplements increased (P<0.05) nitrogen (N) intake, growth rate, and conversion of dry-matter intake into liveweight for sheep compared to unsupplemented animals. Calf growth and water intake were increased (P<0.05) relative to the control by all supplements except cowpea hay. When statistically adjusted to a common level of N intake, N retention was similar (P>0.05) among all groups of supplemented sheep. Compared to alfalfa and cowpea diets, tanniniferous Acacia diets had a negative effect (P<0.05) on true-N digestibility, but this was offset by their positive effect (P<0.05) on reducing loss of urinary N. The A. tortilis diet had a lower (P<0.05) true-N digestibility than the A. brevispica diet, which was probably influenced by soluble phenolics in pods and seeds. On a nutritional basis these Acacia and cowpea materials are suitable for inclusion in improved feeding systems for Boran calves.