Heavy metals and organochlorine residues were determined in water, sediment, fish muscle, and freshwater shrimps from aquatic environments in urban and peri-urban areas in Morogoro, Tanzania. Most of the water samples had heavy metal concentrations below WHO acceptable water quality guidelines. All sediment samples had comparable heavy metal concentrations that suggest natural rather than anthropogenic origin. Hexachlorobenzene, α-hexachlocychlohexane, cis-chlordane, trans-nonachlordane, cis-nonachlordane, pp′-DDE, op′-DDD, pp′-DDD, op′-DDT, and pp′-DDT in hairy river prawn (Macrobrachium rude), African sharptooth catfish (Clarias gariepinus), and Wami tilapia (Oreochromis urolepis) were detected at significant concentrations above the methods' detection limits. The ratio of pp′-DDT to ∑DDTs was 0.4 in O. urolepis and 0.3 in C. gariepinus, which indicated previous rather than current use of DDT. In M. rude, only pp′-DDE was detected and in O. urolepis and C. gariepinus there were higher levels of pp′-DDE than pp′-DDT, which demonstrate uptake of pp′-DDE, rather than pp′-DDT, from the environment. Bioaccumulation of organochlorines and mercury was the highest in C. gariepinus, cadmium in M. rude, and lead in both M. rude and O. urolepis. Maximum detected levels of organochlorine pesticides and heavy metals in M. rude, O. urolepis, and C. gariepinus were below the maximum permissible concentrations recommended by FAO/ WHO. It is concluded that, at present, the contribution of anthropogenic sources in pollution of aquatic environments in Morogoro urban and peri-urban areas are low and that the concentrations of heavy metals and organochlorine pesticides in water and fish do not indicate a risk to the consumers.

The effects of calcium (Ca), phosphorus (P) and zinc (Zn) supplementation on reproductive performance of grazing dairy cows was studied. Forty-eight cows in their first to third parity were allocated to eight groups of 6 animals each, based on stage of lactation and milk yield. Groups 1 (control), 2 (Ca), 3 (P) and 4 (Zn) received, respectively, no mineral supplement, 10 g Ca, 8 g P and 400 mg Zn. The rest of the groups received a combination of Ca/P, Ca/Zn, P/Zn or Ca/P/Zn. Animals were drenched daily. Ovarian activity was determined by progesterone concentrations in milk. Prepartum body condition score (BCS) measured using scale 1-5 was 2.5-3.5. Reproductive problems were observed in all groups except that supplemented with Ca. Cows supplemented with Ca, P, Ca/P, Ca/Zn and Ca/P/Zn had significantly (p < 0.05) shorter interval (30 days) from calving to resumption of oestrus as compared to control (69 days). Intervals from calving to conception and between calvings did not differ significantly between groups (p > 0.05), but were shorter in Ca-supplemented cows. Furthermore, cows in groups 2 and 3 needed an average of 2 services per conception against 3 for cows in other groups. Hence, supplementation with Ca, P and Zn of deficient dairy cows appears to improve reproductive performance.

Gold extraction by artisan miners in different parts of Tanzania is widely done by mercury amalgamation technique. To the people living in and around the mining cites there is a potential for exposure to contamination through consumption of Hg contaminated food stuffs. Current studies on estimates of dietary human exposure to mercury in these areas have been limited to contributions of Hg contaminated fish consumption centrally to WHO recommendation on the use of Total Diet Studies. In this study dietary Hg intake of people at Mugusu gold mining village was determined by using a total diet study approach. Results indicate that 37 types of foods are consumed in this Village. Rice, maize, tubers and fish were the most consumed food categories with an average daily consumption of 134, 270, 113 and 97 g per person per day, respectively. The fish category contained the highest average content of total Hg (0.16 g g-1 wet weight). The calculated average dietary intake of Hg was 41.05 g/day, which is 2.6 times higher than the daily intake recommended by FAO/WHO (15.5 g/day) for protection of the foetus and young children. It is therefore concluded that the current total dietary intake of Hg in the studied area is at risk level to young children born to women living in this village. It is therefore recommended that, mercury intake in artisanal gold mining settlements should be monitored regularly.

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