The microbial flora of fish feeds was investigated in this study. Commercially available fish feed samples were procured from sales outlets in Asaba, southern Nigeria. Three common fish feeds of three different particle sizes each, Coppens (6mm, 4.5 and 3mm), Dizengolf (10mm, 4.5mm and 2mm) and Durante (6mm, 3mm and 2mm) were cultured under laboratory conditions for bacteria and fungi growth. Serial dilutions of the fish feeds were made. The sub-cultured and pure cultures of samples were obtained. Bacteria isolates were characterized and identified. Bacterial count was determined using spread plate count. Isolated and identified bacteria were Escherichia coli and Staphylococcus aureus. Out of the nine sizes of cultured fish feed samples examined, E. coli was found in eight while one had S. aureus. Four of the samples had both E. coli and S. aureus. Bacterial counts from Coppens feed was significantly higher (P<0.05) than bacterial counts from Dizengolf and Durante fish feeds which had counts not significantly different (P>0.05) from each other. No fungus was found. Results obtained show that fish feeds sold in Asaba may have microbial flora with bacteria as the dominant microorganism. Storage conditions and unhygienic handling during storage, probably introduced bacterial flora in the fish feeds. Long duration of storage and scooping of feeds in small quantities during sales should be discouraged. Also, improved storage conditions to prevent fish feed contamination by microorganisms are recommended.
In this paper an effort has been made to design a methodology for the determination of probability of selection for the cases where more than one measure of sizes are involved, especially in the case of agricultural sample surveys. So far no effort has been made for the cases of this sort in the literature of unequal probability sampling / probability proportional to size sampling. In this paper, a method has been developed to merge two measures of sizes in to one, which has combined proportional affect of both measures of sizes. The method is also valid for two measures of sizes having different units of measurements. It is also an unprecedented effort. A comparative study, using Horvitz – Thompson estimator and taking examples from agricultural surveys have been carried out to assess the performance of the new methodology.
Two best performing, morphologically different sweet potato varieties namely, Balella and Bareda, were used to determine optimum spacing between plants and rows in central rift valley of Ethiopia by participating different influential factors from the commencement of the activity. The results indicated that total tuber yield of Balella (644 ±105 q ha-1) performed better with spacing 20 cm x 80 cm than the rest of the treatments i.e., 20 cm x 60 cm (590 ±104 q ha-1) and 50 x 60 cm (522 ±137 q ha-1). But the net marketable yield obtained at spacing combination of 20 cm x 60 cm (590±104 q ha-1) was by far better being followed by 20 cm x 80 cm and 50 cm x 60 cm that gave average yield of 583±82 q ha-1 and 463±93 q ha-1, respectively. Correlation matrix of dependent variables resulted that green top weight was significantly correlated with total and marketable root yield (0.887** and 0.846**, respectively). This indicated that variation in total root yield and marketable root yield was accounted by the linear function of total green top yield r2=78.7 % and r2=71.6%, respectively. For Bareda, 20 cm x 60 cm spacing gave total yield of 409 ± 257 q ha-1 followed by 20 cm x100 cm and 30 cm x 60 cm that gave yield of 347 ±139 q ha-1 and 294 ± 63 q ha-1, respectively. The correlation of green top and total root yield obtained for Bareda was strong and positive (r=0.689**).