Farming Density Research Articles

Understanding the rates of expansion of the farming system in Europe

If the overall expansion of the farming system was determined by the Neolithic Demographic Transition (NDT), i.e. by demographic pressure, what determined the rate of expansion? What is the link between the rate of expansion, the farming system and demographic density? In a first approach, the issue of the different rates of expansion of the farming system on the map is addressed in terms of 21 geo-ecological, climatic and cultural factors and forager populations, via an ordinary least square regression technique (OLS). In a second approach, the variability of the rate of expansion is analyzed in terms of specific patterns identified for the ceramic culture areas, via a cluster analysis. The expansion rate is negatively correlated with the intensification of the agricultural system, as well as with demographic density. Expansion is slow in ecosystems with an intensive farming system with relatively high demographic density, and vice-versa.

Determinants of Adoption of Improved Fish Production Technologies among Fish Farmers in Delta State, Nigeria

This study was conducted to isolate the determinants of improved fish production technologies in Delta State, Nigeria. Data were collected from a sample population of 250 fish farmers from ten randomly selected Local Government Areas of Delta State. The data were elicited from respondents with the use of structured interview schedule while descriptive statistics and multiple regression analysis were used to analyze the data. The recommended fish farming technologies at different stages of adoption process were pH testing and regulation, testing of dissolved oxygen level, feed formulation, polyculture, practices integrated fish/poultry or rice farming, re-circulation method, cage system, spawning and stocking density. The level of adoption was low. The grand mean adoption score and adoption index are 1.02 and 0.10, respectively. The low level of adoption was attributed to cost of the technologies, their complexities and lack of extension contact. The level of education, age of farmers, farm size, farm income and extension contact were the major determinants of fish production technologies adoption at 0.05 level of significance.

Field evaluation of safety during gestation and horizontal spread of a recombinant differential bovine herpesvirus 1 (BoHV-1) vaccine

Bovine herpesvirus type 1 (BoHV-1) is recognized as a major cause of respiratory, reproductive disease and abortion in cattle. Vaccination is widely applied to minimize losses induced by BoHV-1 infections; however, vaccination of dams during pregnancy with modified live virus (MLV) vaccines has been occasionally associated to abortions. We have previously reported the development of a BoHV-1 recombinant virus, constructed with basis on a Brazilian BoHV-1 (Franco et al. 2002a) from which the gene coding for glycoprotein E (gE) was deleted (gE-) by genetic manipulation. Such recombinant has been previously evaluated in its potential as a differential vaccine (gE- vaccine) that allows differentiation between vaccinated and infected animals. Here, in the first part of the present study, the safety of the gE- vaccine during pregnancy was evaluated by the intramuscular inoculation of 10(7.4) tissue culture 50 % infective doses (TCID50) of the virus into 22 pregnant dams (14 BoHV-1 seronegative; 8 seropositive), at different stages of gestation. Other 15 pregnant dams were kept as non-vaccinated controls. No abortions, stillbirths or fetal abnormalities were seen after vaccination. Seroconversion was observed in both groups of previously seronegative vaccinated animals. In the second part of the study, the potential of the gE- vaccine virus to spread among beef cattle under field conditions was examined. Four heifers were inoculated intranasally with a larger amount (10(7,6) TCID50) of the gE- vaccine (to increase chances of transmission) and mixed with other sixteen animals at the same age and body condition, in the same grazing area, at a population density equal to the average cattle farming density within the region (one cattle head per 10,000 m²), for 180 days. All animals were monitored daily for clinical signs. Serum samples were collected on days 0, 30, 60 and 180 post-vaccination. Seroconversion was observed only in vaccinated heifers. These results indicate that, under the conditions of the present study, the gE- vaccine virus did not cause any noticeable harmful effect on pregnant dams and on its offspring and did not spread horizontally among cattle.

Parkinson's disease mortality and the industrial use of heavy metals in Michigan.

Parkinson's disease (PD) mortality rates in Michigan counties for 1986-1988 were calculated with respect to potential heavy metal exposure (iron, zinc, copper, mercury, magnesium, and manganese) from industry based on recent census data. Individuals were counted as a PD death if the diagnosis was listed as an "underlying" or "related" cause of death on the death certificate. Counties with an industry in the paper, chemical, iron, or copper related-industrial categories (ICs) had statistically significantly (p < 0.05) higher PD death rates than counties without these industries. Significant correlations of chemical (rs = 0.22; p = 0.05), paper (rs = 0.22; p = 0.05) and iron (rs = 0.29; p = 0.008) industry densities with PD death rates were also present. Counties were divided into high (> 15/100,000 individuals 45 years old and over) and low (< = 15/100,000) PD death rate counties by cluster analysis. Geographically, counties with high PD mortality were located mainly in the southern half of the lower peninsula and eastern half of the upper peninsula; low PD death rate counties formed two distinct clusters in the western edge of the upper peninsula and the north-central portion of the lower peninsula. Other possible risk factors that may explain the varied distribution of PD death rates in Michigan were examined. Those significantly correlated with PD mortality included population density (rs = 0.31; p = 0.005), farming density (rs = 0.25; p = 0.02), and well water use (rs = -0.24; p = 0.03). These ecologic findings suggest a geographic association between PD mortality and the industrial use of heavy metals.