C.D. MORRIS¹ and L.P. DU TOIT²

¹ Range and Forage Institute, Agricultural Research Council, Pietermaritzburg, South Africa
² Department of Range and Forage Resources, University of Natal, Pietermaritzburg, South Africa

Abstract

The introduction of mimosine detoxifying microbes to the rumens of African livestock eliminates the need to restrict the levels of Leucaena leucocephala in their diet to avoid mimosine toxicity. The performance of weaned Boer goats, which were inoculated with mimosine-detoxifying microbes, browsing stands of both L. leucocephala cv. Cunningham and var. Spectra was studied over 2 seasons. Goats were stocked at 8.6, 15 and 20 goats/ha for 120 days in 1994–95, and 11.5, 15, and 20 goats/ha for 140 days in 1995–96. No obvious signs of mimosine toxicity were visible during the trial. Weight gains were positive, except during the period immediately after the goats were introduced to the trial in 1994 and after short periods off the trial in the mid-summer of both seasons, necessitated by drought- and hail-induced defoliation of the leucaena trees. The mean individual animal performance over both years and leucaena types was 87 ± 6.4 g/d, with gains approaching 200 g/d at times. There were no differences (P > 0.05) in gain per animal between leucaena types or stocking rates. Therefore, gain per hectare increased with increasing stocking rate, resulting in a significantly (P < 0.05) greater gain per hectare at the high stocking rate than at the lowest rate in both seasons, for both leucaena types. In total, over the whole experimental period, the high stocking rate treatment produced 82 kg/ha more live mass than the low stocking rate treatment in 1994–95 (over 98 days) and 85 kg/ha more live mass in 1995–96 (over 126 days). The productivity of Boer goats browsing leucaena could possibly be improved by providing a mineral supplement and a high energy base fodder (e.g. grass), as leucaena foliage is inherently low in phosphorus, sodium and digestible energy.