Acidification of Lake Annie,Highlands Co., FL

Lake Annie, a clear-water seepage lake in south-central Florida remote from significant pollution sources, was sampled by the USGS from 1966 until 1978, and by Battoe and others from 1978 until present. Since 1966, pH and bicarbonate alkalinity have decreased (pH from above 6.0 to about 5.1; bicarbonate from 5.0 to less than 0.5 mg L^?1), while specific conductivity and sulfate concentration have increased (cond. from 30 to 55 μS; sulfate from 3.0 to 8.0 mg L^?1). The chemical changes are apparently due to acidification from atmospheric deposition. There are no proximate sources of acidity and the stability of lake level indicates there has been no significant concentration or dilution of solutes. It is suggested that Lake Annie's acidification was a threshold phenomenon wherein, following depletion of the watershed's buffering capacity, acidification of the lake was rapid.     

Technical note: A wireless telemetric method of monitoring clinical acidosis in dairy cows

Ruminant animals convert forage containing cellulose by bacterial fermentation into nutrients. The health of the bacterial culture in the rumen is essential for the health and productivity of the animal. Over a number of years fistulated animals have been used to study the rumen and its bacterial population. It has been shown that techniques to maintain the pH of the rumen between 7 and 5.5 pH are essential for the health of the dairy cow. The rumen pH has been recorded by using sensors suspended in the rumen at intervals or exceptionally with data recorders. However, fistulation of an animal requires surgery and is only suitable for a few research animals. This paper describes the development of a telemetric bolus that measured and recorded pH continuously. When interrogated by wireless the bolus transmitted the recorded data to an operator standing beside the cow with a receiving station. Boluses were placed in fistulated animals so that a comparison could be made with a laboratory instrument. Data are presented that show a close correlation between the calibrated laboratory instrument and the bolus at time intervals when the instrument was inserted. From this it can be assumed that the bolus accurately records the temporal variation in rumen pH. Data are presented to show the diurnal change in rumen pH over a 6-week period. Methods of increasing the lifetime and accuracy of the bolus are discussed.     

Estimation of premature forests in Georgia (USA) using U.S. Forest Service FIA data and Landsat imagery

We used geographic information system applications and statistical analyses to classify young, premature forest areas in southeastern Georgia using combined data from Landsat TM 5 satellite imagery and ground inventory data. We defined premature stands as forests with trees up to 15 years old. We estimated the premature forest areas using three methods: maximum likelihood classification (MLC), regression analysis, and k-nearest neighbor (kNN) modeling. Overall accuracy (OA) of classifying the premature forest using MLC was 82% and the Kappa coefficient of agreement was 0.63, which was the highest among the methods that we have tested. The kNN approach ranked second in accuracy with OA of 61% and a Kappa coefficient of agreement of 0.22. Regression analysis yielded an OA of 57% and a Kappa coefficient of 0.14. We conclude that Landsat imagery can be effectively used for estimating premature forest areas in combination with image processing classifiers such as MLC.     

Bioeconomic evaluation of sow longevity and profitability

Sow production indicators, including litter size, litter weight, and the length of time that sows remained in the herd (sow longevity), were used to characterize sow performance and profitability. Sow longevity and production records from 148,568 sows in 32 commercial herds from Central Illinois from January 1995 to May 2001 were analyzed using survival and repeatability models, respectively. The factors studied included sow genetics (32 genetic lines), with eight major lines present in multiple herds, and the combination of herd and year of entry in the herd. The largest difference in longevity between the major genetic lines was approximately one parity. There were differences (P < 0.05) in the instantaneous sow removal rate or hazard from the major lines. These differences constitute evidence that sow longevity could be improved by using replacements from specific genetic lines. The net present value per sow (present value of future cash flows and the present value of the sow) was used to evaluate the effect of sow longevity and production traits on economic returns. Assuming a zero discount rate per parity, genetic lines with longer herd life resulted in greater profit than genetic lines with shorter herd life. This difference was reduced with increasing discount rates and was reversed with high discount rates and low net income per litter. These results suggest that the magnitude of the economic improvement attained through the use of sow genetic lines with longer longevity depends on the economic context under which the evaluation is made.     

Distribution of substance P-like immunoreactivity in the enteric neurons of the large colon of normal and amitraz-treated ponies: an immunocytochemical study

The distribution of the putative motor excitatory neurotransmitter, substance P, was studied immunocytochemically in the left dorsal colon of four normal control ponies and three ponies with amitraz-induced impaction colic. Substance P-like immunoreactivity in the control ponies was observed in nerve fibres in all layers of the bowel wall and in the nerve cell bodies of the enteric ganglia. The substance P-like immunoreactivity was clearly more intense in the cell bodies of submucosal ganglia than in those of the myenteric ganglia. The internodal nerve strands of the myenteric plexus were very rich in substance P-like immunoreactivity and within the ganglia they formed dense varicose networks around the neuronal cell bodies. Nerve bundles rich in substance P-like immunoreactivity diverged inward from the myenteric plexus to contribute an abundance of varicose immunoreactive fibres to the circular muscle of the tunica muscularis. Nerve fascicles with substance P-like immunoreactivity were sparse in the longitudinal muscle except in the thickened taenial band. In the submucosa many of the nerve fibres with substance P-like immunoreactivity appeared to arise from ganglionic cell bodies. Immunoreactive fibres commonly condensed around arterial vessels in the submucosa. Fine immunoreactive nerve fascicles from the submucosal plexus also projected internally to supply the muscularis mucosae and form periglandular arrays in the lamina propria. The distribution of substance P-like immunoreactivity in the normal equine colon differed in some respects from patterns observed in large intestines of other mammals. When the colons of normal and amitraz-treated ponies were compared no differences were discerned in the distribution or intensity of substance P-like reactivity.     

Metal Concentrations in Aquatic Macrophytes as Influenced by Soil and Acidification

Bioavailability of metals to aquatic plants is dependent on many factors including ambient metal concentration, pH of soil or water, concentration of ligands, competition with other metals for binding sites, and mode of exposure. Plants may be exposed to metals through water, air, or soil, depending on growth form. This paper examines the influence of soil type under two regimens of water acidification on metal uptake by four species of aquatic macrophytes: smartweed (Polygonum sagittatum), burreed (Sparganium americanum), pondweed (Potamogeton diversifolius), and bladderwort (Utricularia vulgaris) in constructed, experimentally acidified wetlands. Soil types consisted of a comparatively high-metal clay or a lower-metal sandy loam. Each pond was either acidified to pH ca. 4.8–5.3 or allowed to remain circumneutral. Metal concentrations tended to be higher in the submerged bladderwort and pondweed than in the emergent burreed and smartweed. Soils were important to plant metal concentrations in all species, but especially in the emergents. Acidification influenced plant concentrations of some metals and was especially important in the submerged pondweed. Bioaccumulation of metals occurred for Mn, B, Sr, Ba, and Zn, compared to soil concentrations.     

A pleiotropic effect of a mutant haemoglobin type in chickens

The growth rate, viability, and reproductive parameters of a mutant haemoglobin type in chickens were compared with that of normal and heterozygous types. There were no significant differences in the parameters of growth rate, adult body weight or the reproductive parameters of egg weight, fertility, percentage hatch‐ability or sexual maturity. Percentage egg production was significantly depressed in the mutant type compared with normal or heterozygote.     

Immunologic responses and reproductive outcomes following exposure to wild-type or attenuated porcine reproductive and respiratory syndrome virus in swine under field conditions

OBJECTIVE: To compare immunologic responses and reproductive outcomes in sows housed under field conditions following controlled exposure to a wild-type strain of porcine reproductive and respiratory syndrome virus (PRRSV strain WTV) or vaccination with a modified-live virus (MLV) vaccine. DESIGN: Randomized controlled trial. ANIMALS: 30 PRRSV-na?ve 10-week-old female pigs. PROCEDURE: Humoral and cell-mediated immune responses were monitored while pigs were held in isolation for 84 days after inoculation with the WTV strain (n = 10), inoculation with the WTV strain and 42 days later vaccination with a killed-virus vaccine (10), or vaccination with an MLV vaccine (10). Reproductive outcomes were measured after pigs were released into the farm herd. RESULTS: Inoculation with the WTV strain, regardless of whether a killed-virus vaccine was subsequently administered, elicited faster and more substantial production of strain-specific neutralizing antibodies, as well as a more rapid generation of interferon-gamma secreting cells, than did vaccination with the MLV vaccine. Despite the enhanced immune responses in pigs inoculated with the WTV strain, animals vaccinated with the MLV vaccine produced a mean of 2.45 more pigs than did sows exposed to the WTV strain, mainly because of a lower rate for failure to conceive. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that current assays of immunity to PRRSV correlate only imperfectly with degree of clinical protection and that the practice of controlled exposure of sows to a circulating PRRSV strain should be reconsidered in light of negative clinical outcomes.