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Five districts in the Matabeleland region, an arid western area of Zimbabwe, were investigated for the status of Ca, P, Na, Cu and Zn in soil, forage and cattle during the wet and dry seasons over a period of one year. The cattle came from the natural grazing lands and were not supplemented at the time of sampling. Some deficiencies in soil Zn and P were found in the districts of Lupane and Bulilimamangwe, respectively. Dry season soil Ca, Cu and P concentrations were significantly higher (p < 0.05) than rainy season values owing to leaching in all five districts. Most forage samples had mineral concentrations below the critical levels known to be adequate for animal requirements. Forage levels of Ca, Na. Cu and Zn significantly increased (p < 0.05) with advancing maturity, while P significantly decreased (p < 0.05) in almost all the districts. Marked deficiencies of minerals were found in cattle tissues and these levels followed the seasonal trend seen in the forage. These results indicate that cattle in Matebeleland are deficient in P, Ca, Cu and Zn and that grazing areas in the region cannot provide adequate levels of the five minerals studied.

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Oreochromis karongae (Trewavas, 1941) is one of the indigenous Tilapia species exhibiting favourable traits for aquaculture in Malawi. However, commercial fingerling production is still a problem. An experiment was carried out to investigate the effect of raising ambient temperature to 27°C on oocyte development of the fish. Female O. karongae were reared under two temperature regimes: at room (20.3 ± 0.8°C) and at raised (26.5 ± 0.5°C) temperature for 90 days. Changes in gonadosomatic index (GSI) and oocyte developmental stages were determined every 45 days. Fish samples from the pond (22.5 ± 3.4°C) from which experimental fish were collected were used for comparison. Results showed that raising temperature to 26.5 ± 0.5°C significantly enhanced oocyte development. Higher GSIs (P £ 0.05) were obtained after 45 and 90 days in fish cultured at elevated temperature (0.82 ± 0.66 and 1.13 ± 0.47%, respectively) than at room temperature (0.06 ± 0.03 and 0.37 ± 0.05 %, respectively). GSI of fish samples from the pond were not different from that of fish from room temperature. After 45 days, relative frequency of mature oocytes was higher (P £ 0.05) in fish from raised temperature (60.42 ± 3.63%) than in fish from room (1.76 ± 0.84%) and pond temperature (2.43 ± 1.38%). After 90 days, the frequency of mature oocytes in fish from raised temperature was not different from pond fish (8.68 ± 2.40 and 10.99 ± 3.41%, respectively). Fish from room temperature had a low (P £ 0.05) frequency of mature oocytes (3.12 ± 2.03%). The results suggest that O. karongae has the potential to spawn throughout the year when the temperature is manipulated.