Publications

Les huiles issues de déchets pétroliers ont des effets négatifs sur l'environnement. Même si elles ne sont pas toxiques, elles peuvent affecter négativement l'environnement si elles ne sont pas correctement mises en décharge. Une étude a été menée au Ghana pour estimer la quantité produite d'huiles de lubrification issues de produits pétroliers, leur utilisation et le schéma de mise en décharge. Un total de 184 unités a été étudié. Outre à Accra, la capitale, l'étude a été réalisée dans des grandes villes et dans des régions d'industries minières. Une grande partie des huiles aboutit sous forme de déchets qui sont jetés au hasard ou brûlés à l'air libre. Un point encourageant au sujet de la réutilisation est la disponibilité de certaines industries à utiliser ces huiles comme combustibles. Mais l'effet à long terme sur l'environnement du brûlage des huiles usagées non traitées doit être pris en considération dans la mesure où ces huiles contiennent des métaux comme additifs qui sont relâchés dans l'atmosphère en cas de brûlage. L'agence de protection de l'environnement du Ghana n'a pas de telles réglementations restreignant le brûlage des huiles usagées pour leur utilisation en tant que combustibles.

A simulation study Using Matrix formulation was used to asses the flow of genes from the nucleus to the commercial population for three nucleus dairy cattle crossbreeding schemes involving indigenous (Zebu or native ) and exotic (European) animals under Kenyan conditions: Artificial insemination (A.I.) or natural mating F{sub 1} production, continuous crossbred (F{sub 2} inter se) production and multiple ovulation and embryo transfer (MOET) F{sub 1} production. The latter two schemes used MOET in the nucleus. cumulative discounted expressions (CDES) and cumulative discounted Revenues (CDR) were calculated to rank these schemes. The Pathways considered were sires and dams to produce sires and dams. The evaluation Criterion was milk production measured in age class 3 through 10 in F{sub 1} and F{sub 2} cow populations. the schemes were evaluated over a 30-year projected period with assumed interest rates of 0% and 10%. Further, the genetic level between the indigenous nucleus animals, the F{sub 1} males and commercial female population was calculated by defining the incidence vector h as the difference between the three groups. The F{sub 1} A.I. or natural scheme had higher CDES of 0.978 and 0.161 at 0% and 10% interest rates respectively. The corresponding values for F{sub 1} MOET scheme were 0.735 and 0.070 and those of F{sub 2} inter se were 0.676 and 0.079 at 0% and 10% interest rates, respectively. For a nucleus with 64 dams, CDR (US$) were 95.50 and 15.80 at 0% and 10% interest rates, respectively for F{sub 1} A.I. or natural scheme. The F{sub 1} MOET scheme had corresponding values of 62.05 and 6.90 while F{sub 2} inter se had 66.10 and 7.75. Under both interest rates, the F{sub 1} A.I. or natural mating schemes had higher CDES and CDR than the other two schemes and is faster in dissemination of genes to the commercial population. F{sub 2} inter se was intermediate. The genetic level of nucleus animal is higher than of F{sub 1} male and females because indigenous nucleus females contribute 50% of the genes. F{sub 2} cows are expected to lag behind F{sub 1} males genetically because the latter are used as parents of F{sub 2} cows. In conclusion, although CDES and CDR are higher for the F{sub 1} A.I. or natural mating schemes using inter se mating are promising in terms of logistics and combination of breed effects as indicated in other studies.