Tropical pastures are characterised by fast growth and early maturity during the rain seasons and a fall in nutritive value during the dry seasons. Animals should be supplemented with minerals known to be deficient. The bioavailability of common supplements and their possible undesirable effects are hardly known. This study was conducted to determine the effect of zinc supplementation on plasma zinc, calcium and inorganic phosphate in East African local goats. The goats were randomly divided into two groups of 12 each. One group was supplemented with 24 mg/Kg body weight of Zn every other day for six weeks during the rainy and dry season. The unsupplemented group was the control. Blood samples collected from goats in both groups were analysed for plasma Zn, Ca and Pi using standard methods. The concentration of plasma Zn was significantly higher (P

A survey was carried out on 36 lactating Bos taurus/indicus crossbred dairy cows on smallholder dairy farming in Njombe district, Tanzania to assess seasonal variations in haematological and metabolic profiles. Blood was taken at an interval of two months for one year and analysed for haemoglobin concentration (Hb), packed cell volume (PCV%), total protein (TP), glucose (Glu), calcium (Ca), inorganic phosphate (Pi) and zinc (Zn) using standard methods. Hb, PCV %, plasma TP and Glu were within normal ranges. There were no differences (p>0.05) for Hb and plasma Pi. The effect of season was apparent (p 0.05) was observed in the levels between the seasons. Plasma Zn was high but at lower side of normal ranges in the wet season and below normal in the dry season. It is concluded that there is deficiency in minerals and protein in both dry and wet season. It is important to supplement minerals and protein to the animals to improve health, reproductive performance and milk production. Keywords : TP, protein, glucose, mineral, seasonal variation, PCV% haemoglobin Tanzania Vet Journal Vol. 25 (2) 2008: pp. 111-120

The quality of Hg contaminated sediments in artisanal gold mining areas of Tanzania have to date only been assessed through bulk chemical analysis. However, measurement of contaminant levels alone has a limited ability to predict adverse effects on living resources. In this study we investigated the possible effects of Hg contaminated sediments from the river Mabubi which drains the artisanal gold mine on the hatching success, larval survival and growth of the African catfish (Clarias gariepinus). The tested species is a resident fish whose demersal behaviour keeps it in frequent contact with the sediment. Sediments collected downstream of the mine decreased survival and impaired growth of Clarias gariepinus but did not affect its hatching success. These effects were observed up to six kilometres downstream of the mining activity The calculated 5 d-LC50 value (larval survival) was 1.75 mu g/g Hg dw (95% CL of 0.72 - 2.53), the 5d-NOEC for hatching was >2.3 mu g/g Hg dw and that for larval survival and growth was 0.23 mu g/g Hg dw. In conclusion, chemistry and ecotoxicity results from this study suggest that sediments collected downstream of the mine adversely affect catfish and probably other fauna and as such present a considerable local environmental risk.

In most aquatic ecosystems mercury accumulates more in the sediment than in water column. However, due to limited eco-toxicological data, it is difficult to predict the toxicity of these sediments. The present study evaluated the effects of inorganic mercury in spiked sediment on the survival, growth, and emergence of the midge Chironomus riparius and compared the results to mercury concentrations reported in streams and rivers in Africa. At 3.84 mg Hg/kg dry sediment, mercury significantly reduced larval survival and midges emergence success in comparison to control sediment (P<0.05). The growth of the larva was significantly inhibited (P<0.05) at 2.42 mg Hg/kg dry weight, while emergence of C. riparius midges was significantly delayed at 0.93 mg/kg dry wt. These results indicate that mercury inhibits C riparius characteristics at lower concentrations than those which have been measured in sediments from watersheds impacted with mercury like those found around artisanal gold mining in Africa. It is therefore possible that Chironomus and probably other fauna living in these watersheds are at risk.

Environmental contamination with mercury from artisanal gold mines in Tanzania has been widely reported. People living around mining villages keep domestic animals which are allowed to feed freely in mercury-contaminated areas. This study investigated Hg accumulation in the liver and muscle tissue of cattle and domestic fowl reared in mining villages. Total mercury levels up to 436 and 820 µg/kg wet weight were found in liver samples taken from cattle and domestic fowl, respectively. Significantly higher mercury concentrations were found in liver samples collected at mining villages (p < 0.05) than those taken from the reference area. While mercury concentrations in liver samples exceeded the acceptable maximum concentrations for humans set in the Netherlands and Poland, the Hg concentrations in muscle were below the limits of most countries. It is recommended that the keeping of freely grazing cattle and domestic fowl in or around artisanal gold mines should be avoided.

The contamination of sediments by mercury from in artisanal gold mining has been only assessed through bulk chemical analysis and subsequent comparison with reference values from uncontaminated areas. However, measurement of contaminant levels alone has a limited ability to predict adverse effects on living resources. This study investigated the possible effects of contamination of sediments in Mabubi River by mercury drained from Mugusu artisanal gold mine on the survival, growth and emergency of the benthic midge Chironomus riparius. Sediments collected downstream from the Mugusu Mine impaired growth and delayed emergence of the midges but did not impair survival. Mean dry body weight of larvae from sediments collected 3km down stream (1012μg) was significantly lower than those from the control sediment (p<0.05). Compared to the control sediment, the emergence of the midges from sediments collected up to 6km downstream of the mining activity were delayed for four days. In conclusion, chemistry and ecotoxicity results from this study suggest that sediments collected in the Mabubi River downstream of the Mugusu mine adversely affect C. riparius and probably other fauna and as such present a considerable local environmental risk.

Two experiments were conducted in the Makambako division of the southern highlands of Tanzania to investigate the effects of regrowth period, season and harvesting frequency on the yield and nutritive value of Chloris gayana. The first experiment was conducted in 2002 in a 4×2 factorial arrangement in a complete randomised block design with six replications. The treatments were period of regrowth (three, six, nine and 12 weeks) and season (early wet season January–March and late wet season April–June). The second experiment was conducted in 2003 in a complete randomised design with six replications. The treatments were four cutting frequencies (three, six, nine and 12 weeks). In Experiment 1, the dry matter yield (DMY) ranged from 1.09–7.99t ha−1 and from 0.97–3.53t ha−1 (P < 0.05), while the crude protein (CP) content ranged from 13.9–8.25% and 16.09–9.85% (P < 0.05) in the early and late wet seasons, respectively. In vitro dry matter digestibility (IVDMD) and metabolisable energy (ME) declined faster with increasing periods of growth in the early than in the late wet season. ME ranged from 9.21–7.29MJ kg−1 DM (P < 0.05) and 8.02–7.87MJ kg−1 DM (P > 0.05) in the early and late wet seasons, respectively. For Experiment 2, the nine- and 12-week cutting frequencies did not differ (P > 0.05) in terms of cumulative DMY (19.07 versus 18.93t ha−1) but produced nearly twice as much as the three- and six- week cutting frequencies (10.18 and 8.32t ha−1). CP, IVDMD and ME decreased while neutral detergent fibre (NDF) increased with decreased cutting frequency. The results of the present study suggest that the optimal balance of dry matter yield and nutritive value of C. gayana at Makambako is reached at the ninth week of regrowth. Regardless of season, dairy farmers in this area who are feeding pure C. gayana must provide energy supplement to their dairy cows.

A heat-intolerance (HI) syndrome in cattle in Tanzania was suspected to be associated with previous, clinical foot-and-mouth disease (FMD). A participatory appraisal (PA) method called "matrix scoring" was used to explore livestock-keeper perceptions of association between HI and cattle diseases. A PA method called 'proportional piling' was used to estimate herd incidence of FMD and other diseases, herd incidence of HI, and association between HI and other cattle diseases. Use of matrix scoring and proportional piling with pastoral Maasai informants demonstrated association between FMD and HI. With agropastoral Sukuma informants, the matrix-scoring method did not indicate an association between FMD and HI, whereas the proportional piling method indicated a weak association. Results were supported by calculation of positive predictive values for herder diagnosis of HI and FMD. Clinical examination of cattle by veterinarians was used to confirm HI cases and detection of antibody to non-structural proteins of FMD virus was used to confirm previous clinical FMD.

Coccidial oocysts were detected in 35% of 445 cattle in four medium-scale and 20 small-scale dairy farms in Morogoro municipality, Tanzania. The highest prevalence (56%) was observed in animals aged between 5 and 18 months, whereas lower prevalences were observed in calves (29%) aged between 12 days and 4 months and adults (30%). No coccidial oocysts were detected in calves less than 12 days old. The oocyst output was high in calves, followed by weaners; adults had the lowest oocyst output. The number of oocysts per gram of faeces was significantly higher (P < 0.001) in diarrhoeic animals than in non-diarrhoeic animals, and more so in young calves. Eimeria species infecting the animals included Eimeria bovis (68%) and Eimeria zuemii (57%), Eimeria ellipsoidalis (25%), Eimeria cylindrica (23%), Eimeria auburnensis (22%), Eimeria alabamensis (12%) and Eimeria subspherica (5%). Mixed infections involving two or three species were common. Our findings indicate that eimeriosis is common in cattle in Morogoro municipality.