Aetiology of clinical mastitis in six Somerset dairy herds.

Clinical mastitis was monitored in six Somerset dairy herds for one year. The herds all had three-month geometric mean bulk milk somatic cell counts of less than 250,000 cells/ml. Escherichia coli was the predominant pathogen isolated on all the farms and in all months of the year. Environmental pathogens accounted for 61.4 per cent of all cases of clinical mastitis and for 79.3 per cent of the mastitis cases in which an aetiological agent was identified. The mean annual incidence was 41.6 cases per 100 cows (range 14 to 75). Affected cows suffered a mean of 1.5 cases and 16.4 per cent of quarters suffered at least one repeat case. Mastitis due to E. coli was more severe than mastitis due to other causes and it tended to be more severe in early lactation and during the housing period. Mastitis was significantly more severe (grades 2 and 3) in the herd with the lowest bulk milk somatic cell count and in the herd which was kept indoors throughout the year than in the other four herds. Mastitis was fatal in 2.2 per cent of cases and resulted in the death of 0.6 per cent of the lactating cows.     

The effects of delays between restraint and sampling on some blood parameters in sheep

Twenty three non pregnant, non lactating aged Merino and Border Leicester ewes were subject to four jugular venipunctures one hour apart (times 0, 1, 2 and 3). Four different delay intervals of 12.5, 64.0, 128.0 and 252.9 seconds between catching and sampling (delays 1, 2, 3 and 4) were used on each sheep in a random manner. Estimates were made of packed cell volumes (PCVs), plasma and erythrocyte sodium and potassium concentrations. The mean PCV at time 0 of 35.4 per cent was significantly higher than the levels of 33.1, 31.8 and 32.2 per cent at times 1, 2 and 3 respectively. There was no significant difference between the means at times 1, 2 and 3. The mean plasma potassium concentrations at time 0 of 4.37 mmol/l was significantly higher than the levels of 4.16 and 4.14 mmol/l at times 1 and 3 respectively. Delays had no significant effects on the means of any of the parameters studied. The findings strongly suggest that sheep become excited by initial handling but not by subsequent venipunctures and that a delay between catching and sampling of between 12.5 and 252.9 second has no effect on the blood constituents studied.     

Spatial analysis of the exposure of dogs in rural north-coastal California to vectorborne pathogens

Between 0 and 50 per cent of the dogs in eight rural villages in far northern California with a high risk of tickborne diseases were seropositive for Anaplasma phagocytophilum and Bartonella vinsonii subspecies berkhoffii, and between 0 and 10 per cent were seropositive for Borrelia burgdorferi. The odds ratio for the co-exposure of individual dogs to B vinsonii berkhoffii and A phagocytophilum was 18.2. None of the diseases was associated with the sex of the dogs, whether they slept out of doors, or whether tick-preventive measures were taken. When the villages were assessed for landscape risk factors, a particularly high seroprevalence for B vinsonii berkhoffii and A phagocytophilum was observed in a village at a relatively high altitude and greater distance from the Pacific coast, and montane hardwood conifer woodland was most associated with a high seroprevalence for these two pathogens.     

A note on Ozark migrants and nonmigrants

"This study documents the extent of the population shift in five Ozark counties in Missouri. It describes the structure of the population, compares migrants and nonmigrants on the basis of various sociological and demographic indicators, and examines the extent of agreement between migrants and nonmigrants on a number of community issues." The implications for rural areas of the phenomenon of urban-rural migration are considered     

Genetics of resistance to five strains of turnip mosaic virus in Chinese cabbage

Summary Inheritance of resistance to turnip mosaic virus (TuMV) strains C1, C2, C3, C4, and C5 in Chinese cabbage (Brassica campestris subsp. pekinensis) was evaluated using monoclonal antibodies. Crosses were made between a resistant line, 0–2, and four susceptible line. Seoul (SE),SSD31 (SS), Cheongbang (CH), and Yaki 1 ho (YA), to determine the inheritance of resistance of 0–2 in different genetic backgrounds. Resistance to TuMV was controlled by a single dominant gene or double dominant genes depending on the strain and cross. The resistance genes of 0–2 were modified by susceptible parents such that a single dominant gene was involved in the SS×0–2 combination, but double dominant genes in the SE×0–2 against TuMV-C3 or TuMV-C5. ELISA tests using inoculated and noninoculated leaves in the same plant suggested that the dominant resistance genes inhibit virus movement rather than virus multiplication.     

Genetic Variation for Regenerative Response in Immature Leaflet Cultures of the Cultivated Peanut,Arachis hypogaea*

Forty-seven genotypes of the cultivated peanut, Arachis hypogaea L., were screened for regenerative responses of immature leaflet cultures on two media varying in the auxin: cytokinin ratio. Statistical analysis revealed significant media and genotype differences for rhizogenesis plus media differences for callus proliferation but no differences for shoot formation. When genotypes were categorized according to botanical types, differences between subspecies were observed for rhizogenesis. Cultivars of the Virginia botanical type (subspecies hypogaea) were significantly different from either the Valencia or Spanish botanical types (both subspecies fastigiata). Overall, rhizogenesis varied from 0 to 70% among all genotypes. Shoot production was low (30%) while callus proliferation was extremely high (70%).     

Inheritance of fiber quality and lint yield in a chemically mutated population of cotton

The narrow germplasm base of the upland cotton (Gossypium hirsutum L.), grown on the Texas high plains historically, has limited improvement of fiber quality. Chemical mutagenesis and subsequent selection have helped the development of lines with improved fiber quality in cultivars adapted to this region. This study was conducted to determine the inheritance of improvements in fiber quality. M₃ lines with divergent fiber properties of micronaire, length, and strength were selected from a population of Paymaster HS 200 treated with 3% v/v ethyl methanesulfonate (EMS) for two hours. The 115 selected lines of M₄ and M₅ generation were evaluated for fiber quality and lint yield. Regression of the M₄ and M₅ on the M₃ generation, as well as the M₅ on the M₄ was used to generate narrow sense heritability coefficients. Significant variations were observed between the mutant lines in all generations except for lint yield in the M₅ (1997). The highest heritability estimates were found in fiber length (h ²= 0.29** to 0.46**). Micronaire and strength showed intermediate heritability estimates of h ²= 0.14 to 0.19, while lint yield had a very low heritability estimate of h ²= 0.03. Fiber length and strength were correlated (r= 0.58** to 0.46**) in all the three generations. The mutants identified in these studies have the potential to improve fiber quality of upland cotton without introducing alien genes that may reduce adaptation to short growing season production regions.     

Introduction: That most remarkable of outside men – Harold Brookfield's intellectual legacy

Abstract: Harold Brookfield's academic career spans more than half a century, traversing small tropical and subtropical islands and mountainous uplands, focusing on people–environment relations and linking to a diversity of institutions and disciplines. His unwavering commitment to fieldwork at the local level and to comparative study is paralleled by a healthy scepticism with respect to academic trends and orthodoxy of any kind, whether intellectual or physical. It is the farmers of the developing world who are the source of much of his inspiration. His theoretical contributions are based essentially on his observations of their practices and his learning from their experiences. His academic insights into the processes of change in rural areas of Melanesia, East and South‐East Asia, Africa and South America, where small‐scale ecological studies are linked to global forces, are of lasting significance.