Studies on Calf Diarrhoea in Mozambique: Prevalence of Bacterial Pathogens

The prevalence of diarrhoea in calves was investigated in 8 dairy farms in Mozambique at 4 occasions during 2 consecutive years. A total of 1241 calves up to 6 months of age were reared in the farms, and 63 (5%) of them had signs of diarrhoea. Two farms had an overall higher prevalence (13% and 21%) of diarrhoea. Faecal samples were collected from all diarrhoeal calves (n = 63) and from 330 healthy calves and analysed for Salmonella species, Campylobacter jejuni and enterotoxigenic Escherichia coli (ETEC). Salmonella spp. was isolated in only 2% of all calves. Campylobacter was isolated in 11% of all calves, irrespective of health condition, and was more frequent (25%) in one of the 2 diarrhoeal farms (p = 0.001). 80% of the isolates were identified as C. jejuni. No ETEC strains were detected among the 55 tested strains from diarrhoeal calves, but 22/55 (40%) strains from diarrhoeal calves and 14/88 (16%) strains from healthy calves carried the K99 adhesin (p = 0.001). 6,757 E. coli isolates were typed with a biochemical fingerprinting method (the PhenePlate™) giving the same E. coli diversity in healthy and diarrhoeal calves. Thus it was concluded: i) the overall prevalence of diarrhoea was low, but 2 farms had a higher prevalence that could be due to an outbreak situation, ii) Salmonella did not seem to be associated with diarrhoea, iii) Campylobacter jejuni was common at one of the 2 diarrhoeal farms and iv) ETEC strains were not found, but K99 antigen was more prevalent in E. coli strains from diarrhoeal calves than from healthy, as well as more prevalent in one diarrhoeal farm

STOCHASTIC-ANALYSIS OF FIELD MEASURED UNSATURATED HYDRAULIC CONDUCTIVITY

Unsaturated hydraulic conductivity K values as a function of soil‐water pressure head h were measured in the soil at 75 cm depth at 70 different sites separated from one another by a distance of l m along a horizontal transect. K field was viewed as a random function of spatial location x. Field data were analyzed (1) to examine the isotropy and stationarity of K, (2) to check the ergodicity of K in the mean and covariance functions, and (3) to characterize the distribution properties of K by estimating the higher‐order correlations, that is, third and fourth cumulants. The mean functions were estimated by averaging over h and x. The covariance function was studied to investigate its spatial origin dependency. Logs and square roots of K were used for estimating the third and fourth cumulants. Results showed that spatial covariance functions are anisotropic and both lag and origin dependent, that is, spatially nonhomogeneous. Because the stationarity (statistical homogeneity) of K is scale dependent, which was indicated by the identification of locally stationary covariance regions, the ergodic properties of K are also scale dependent at smaller spatial scales. Results related to the distribution characteristics of K indicated that although ln K is marginally Gaussian distributed, in the context of spatial stochastic processes the random field of ln K is not Gaussian because the third and fourth cumulants of the field are still significantly different from zero and have the same order of magnitude as the first and second cumulants. The square root transformation, however, resulted in a random field that is approximately Gaussian although marginal distributions of urn:x-wiley:00431397:media:wrcr4956:wrcr4956-math-0001 remained skewed. Analyses of ln K and urn:x-wiley:00431397:media:wrcr4956:wrcr4956-math-0001 indicated that better transformations which would result in both marginal and joint Gaussian behavior for the random field of K are needed

Experimental evaluation of the effect of a light-emitting diode device on Chinook salmon smolt entrainment in a simulated river

The entrainment and impingement of fish into water diversion infrastructure is one of the several factors contributing to their decline. Here, controlled experiments assessed the potential for a behavioral guidance device [a light-emitting diode (LED) light array] strobing at various spectra to reduce the entrainment of juvenile Chinook salmon (Oncorhynchus tshawytscha) into a water diversion pipe. Fish were tested during the day and night, and under control conditions (light off) and red, blue, and white spectra strobing at 2 Hz. Fish entrainment into the diversion pipe was evaluated. Results indicated greater entrainment at night compared to day. All trials at night with the LED light strobing had higher entrainment than the control, with blue and white spectra corresponding to greater entrainment than red spectra. During the day, the white spectra treatment was different from the red treatment, with lower entrainment. LED lights employed to repel migratory juvenile salmon away from water intake structures may be ineffectual but there is potential for the light to be used as an attractant to guide fish towards desirable features such as “safe” areas (bypass channels or fishways)

Experimental evaluation of the effect of a light-emitting diode device on Chinook salmon smolt entrainment in a simulated river

The entrainment and impingement of fish into water diversion infrastructure is one of the several factors contributing to their decline. Here, controlled experiments assessed the potential for a behavioral guidance device [a light-emitting diode (LED) light array] strobing at various spectra to reduce the entrainment of juvenile Chinook salmon (Oncorhynchus tshawytscha) into a water diversion pipe. Fish were tested during the day and night, and under control conditions (light off) and red, blue, and white spectra strobing at 2 Hz. Fish entrainment into the diversion pipe was evaluated. Results indicated greater entrainment at night compared to day. All trials at night with the LED light strobing had higher entrainment than the control, with blue and white spectra corresponding to greater entrainment than red spectra. During the day, the white spectra treatment was different from the red treatment, with lower entrainment. LED lights employed to repel migratory juvenile salmon away from water intake structures may be ineffectual but there is potential for the light to be used as an attractant to guide fish towards desirable features such as “safe” areas (bypass channels or fishways)