This study was undertaken to determine the effects and nutritive value of Leucaena leucocephala when it was incorporated in a total mixed ration (TMR) fed to milk goats. This was to test the use of Leucaena to substitute for oilseed cake meals (OSCM) which are believed to be expensive and generally unavailable in many parts of the rural areas of South Africa. Four trials were conducted at the University of Pretoria Research Farm and analyses were carried out at the Nutrition laboratory of the University of Pretoria. Leucaena forage contained enough nutrients to allow it to be used as a substitute for OSCM and to a large extent was also the source of protein and roughage in the TMR. The leaves of Leucaena had a higher crude protein, mineral and mimosine concentration but lower fibre content than the pods and twigs; while the air dried Leucaena forage had a higher crude protein and lower fibre content than sun dried forage. This study showed that there was a higher crude protein and mimosine concentration but a lower fibre concentration from the Leucaena harvested in summer than that harvested in autumn. Milk yield and quality was not adversely affected by the inclusion of Leucaena in the milk goat diet at the rate of 25% of the DM, with the exception of milk urea nitrogen. The inclusion of Leucaena decreased the milk urea nitrogen as compared to that shown from TMR without Leucaena. The body weight and body condition of lactating goats were also not affected by inclusion of Leucaena during the three phases of the lactation period. Therefore, the inclusion of Leucaena in the milk goat diet has been shown to support production of milk in terms of yield and quality which was similar to that of goats fed a commercial diet. There was no significant difference in milk composition in terms of milk lactose and milk protein for milk produced in the morning and afternoon between goats fed the two diets, even though the morning milk yield was higher than the afternoon yield because of the unequal milking intervals. However, the milk composition in terms of milk urea nitrogen, milk fat and somatic cell counts varied greatly between morning and afternoon milking. The apparent digestibility, average daily gain and feed conversion ratio of Saanen male goats were not affected by the inclusion of Leucaena in the TMR, as compared to the TMR without Leucaena. However the voluntary dry matter and nutrients intake were improved by the inclusion of Leucaena in the TMR. No toxicity of mimosine was observed during this study. The results of this study also showed that the inclusion of Leucaena in the total mixed ration had no effect on the carcass characteristics and meat quality of goats as compared to those fed a TMR containing OSCM.
Dissertation (MSc(Agric))--University of Pretoria, 2011.