Reproductive performance, colostrum and milk constituents of mimosine-adapted South African Nguni goats on Leucaena leucocephala-grass or natural pastures

The study evaluates the cause of the high pre-weaning kid mortality rate in South African Nguni goat (SANG) kids maintained on Leucaena leucocephala-grass pasture (LGP) as feed sources during gestation via reproductive performance, colostrum and milk constituents of mimosine-adapted South African Nguni dams. Does grazing LGP plots gained 2.9 (P < 0.05) and 5.2 kg (P < 0.01) more in body weight between gestation and kidding and were 4.7 (P < 0.05) and 5.2 kg (P < 0.01) heavier than does on natural pasture (NP) plots during the first and second trials, respectively. Conception rate in the LGP treatment group during Year 1 trial was significantly (P < 0.05) higher than in the NP treatment. The proportion of multiple births (≥2 kids) on NP treatment was 56.2% (100% versus 43.8%;P < 0.05) higher than that of the LGP treatment in Year 1. In Year 2, the proportion of multiple births on LGP treatment was 36.5% (76.5% versus 40%;P < 0.05) more than the NP treatment. Kidding rates and prolificacy on the LGP treatment were better than on the NP treatment for both trials. Pre-weaning kid mortalities for the NP treatment group was 30.6% higher (55.6% versus 25.0%) than kid mortality recorded in the LGP treatment group in Year 1 trial. The differences between colostrum constituents of does in both treatments were not significant. However, the milk total solids (TS) (P < 0.05), solids-not-fat (SNF) (P < 0.01) and lactose (P < 0.05) contents in the normal milk, and return to oestrus (P < 0.01) were significantly influenced by the pastures. Pre-weaning kid survival improved markedly in Year 2 when lactating does were offered additional nutrients during lactation and kids assisted to nurse colostrum—an indication that adequate nutrition and management practices are vital to pre-weaning kid survival. The higher productivity and reproductive performance of SANG on LGP relative to those on NP were indications that Leucaena was not detrimental to goats that are mimosine-adapted via the transfer of the bacteria Synergistes jonesii. © 2003 Published by Elsevier B.V.