Fecal egg count reductions and performance effect of Dectomax, Cydectin, and Cydectin plus Synanthic as used in feedlot steers

A study was conducted to assess the effectiveness (fecal egg count reductions) and benefit (improvement in feed efficiency, average daily gain, health, and so forth) of a macrocyclic lactone (moxidectin [Cydectin Injectable] or doramectin [Dectomax 1% Injectable]) alone or in combination with a benzimidazole (oxfendazole [Synanthic Bovine Dewormer]) as used in steers upon their arrival at a feedlot. The cattle were kept in the feedlot for 181 days. Only minor differences in fecal egg count reductions were seen among treatments, with all egg counts reduced by more than 98% by 28 days posttreatment. Likewise, no statistically significant differences among treatments were seen in terms of animal performance (feed efficiency, intake, gain, morbidity, mortality, and carcass quality). All three treatment regimens appear to be comparable in decreasing nematode burdens and the consequences thereof in feedlot cattle.     

Accumulation, organic carbon and dry matter concentration of sediment in commercial channel catfish ponds

Sediment depth and organic carbon (OC) concentration were measured in sediment cores (n=675) collected from 45 commercial channel catfish ponds in northwest Mississippi from April to September in 1998 and 1999. Ponds had been in continuous catfish production from 14 days to 21 years. Sediment depth ranged from 1 to 95 cm and was heterogeneously distributed within ponds: least in the shallow end (26.3 cm) and greatest in deeper areas (33.7 cm). Mean sediment depth increased with pond age, although the rate of sediment accumulation was greatest in the first year (12.5 cm per year). Organic carbon concentration varied slightly within ponds ranging from 0.76 to 3.43% of dry matter (DM). Mean organic carbon concentration in the upper 2 cm of sediment (1.77%) was significantly greater than in the deeper sediment layer (1.55%). Mean dry matter content in the upper 2 cm of sediment averaged 24.2% of total wet weight. Mean dry matter for the lower sediment fraction was 37.8% of total wet weight. Despite large inputs of organic matter from feed and primary production, sediment organic carbon concentrations did not increase with pond age.     

Transposon mutagenesis in Mycoplasma hyopneumoniae using a novel mariner-based system for generating random mutations

Mycoplasma hyopneumoniae is the cause of enzootic pneumonia in pigs, a chronic respiratory disease associated with significant economic losses to swine producers worldwide. The molecular pathogenesis of infection is poorly understood due to the lack of genetic tools to allow manipulation of the organism and more generally for the Mycoplasma genus. The objective of this study was to develop a system for generating random transposon insertion mutants in M. hyopneumoniae that could prove a powerful tool in enabling the pathogenesis of infection to be unraveled. A novel delivery vector was constructed containing a hyperactive C9 mutant of the Himar1 transposase along with a mini transposon containing the tetracycline resistance cassette, tetM. M. hyopneumoniae strain 232 was electroporated with the construct and tetM-expressing transformants selected on agar containing tetracycline. Individual transformants contained single transposon insertions that were stable upon serial passages in broth medium. The insertion sites of 44 individual transformants were determined and confirmed disruption of several M. hyopneumoniae genes. A large pool of over 10 000 mutants was generated that should allow saturation of the M. hyopneumoniae strain 232 genome. This is the first time that transposon mutagenesis has been demonstrated in this important pathogen and could be generally applied for other Mycoplasma species that are intractable to genetic manipulation. The ability to generate random mutant libraries is a powerful tool in the further study of the pathogenesis of this important swine pathogen.     

Post-Harvest Studies on Autumn-Drilled Bulb Onions. The Effect of Harvest Date,Conditioning Treatments and Field Drying on Skin Quality and on Storage Performance

Overwintered onion cvs Express Yellow and Senshyu Semi-globe Yellow were harvested at 80% foliar fall-over (early June) and two and four weeks later, in 1975 and 1976. Plants were conditioned for one (1975) or two weeks (1976) at 20°C, 70% RH or 30°C,60% RH or field dried, and then stored at ambient temperature. Measurements of fresh weight loss during the first six weeks after harvest in 1976 indicated that drying was slow and was incomplete after 14 days conditioning at 30°C. Skin staining and splitting generally increased with delay in harvest date. Skin colour improved with delay in harvest date and with conditioning at 20°C. Wastage due to both rotting and sprouting during storage was generally lower when plants from the first two harvest dates were conditioned at 30°C. These bulbs are likely to be useful for long-term storage as total wastage levels of only 20% were reached in both cultivars after 3-5 months storage. Good field drying of the bulbs could not be consistently obtained and consequently storage performance was more variable than for bulbs conditioned at 20 °C and 30 °C before storage.     

A Traditional Analysis of the First Flush Effect for Nutrients in Stormwater Runoff from Two Small Urban Catchments

Nonpoint stormwater runoff remains a major threat to surface water quality in the USA. More effective stormwater control measures can be designed by understanding patterns in pollutant export with respect to the runoff hydrograph. In particular, nutrient concentrations in urban stormwater can cause deleterious effects in sensitive watersheds in the Southeast and Mid-Atlantic USA. A year-long study captured stormwater samples from 36 storm events at two catchments (one primarily impermeable and the other substantially wooded) and analyzed for total suspended solids and various nutrient species. Using these data, the first flush effect (the assumption that the initial portion of a rainfall-runoff event is more polluted than the later portions) was evaluated based on several published methods and definitions. Based on an analysis of multiple methodologies, the ranking of first flush strength among the pollutants was total suspended solids (TSS) > ammonia (NH₃) > total Kjeldahl nitrogen > NO₂-NO₃ > total phosphorus > orthophosphate (O-PO₄). Nitrogen species generally displayed a stronger first flush than phosphorus species, with O-PO₄ showing the weakest first flush effect. Various relationships ° climate, land use, and the first flush strength were also explored. Of the rainfall characteristics analyzed, total rainfall and runoff volume each inversely affected the first flush strength of TSS on the more impervious catchment. Although orthophosphate did not have a strong first flush effect, the relative first flush strength for O-PO₄ increased with increasing rainfall or runoff. Land use did not influence the first flush strength of the pollutants. On average, most pollutants exhibited a slight first flush effect, but substantial pollutant loading still occurred in the latter portion of the storm??s total runoff volume. Thus, treating the majority of a storm??s total pollutant load requires capturing a commensurate fraction of runoff volume.     

Enhancement of conditioned arterial pressure responses in cats after brainstem lesions

Cats were classically conditioned after the baroreceptor reflexes were abolished by bilateral placement of electrolytic lesions in the nucleus tractus solitarii. The conditioned increases in arterial pressure were more than five times larger than the responses obtained in similarly trained controls. This finding suggests that the baroreceptor reflexes actively inhibit conditioned increases of arterial pressure.     

Somatic mutation in genes for the variable portion of the immunoglobulin heavy chain

The size of the gene pool potentially encoding antibodies to p-azophenyl arsonate has been examined. A heavy chain-specific full-length complementary DNA clone has been constructed with the use of messenger RNA from a hybridoma that produces antibodies to the arsonate hapten and bears nearly a full complement of the determinants comprising the cross-reactive idiotype (CRI). The sequences of both the complementary DNA clone and the corresponding immunoglobulin heavy chain have been independently determined. A probe for the variable region gene was prepared from the original heavy chain complementary DNA clone and used to analyze, by Southern filter hybridization, genomic DNA from both A/J (CRI positive) and BALB/c (CRI negative) mice. Approximately 20 to 25 restriction fragments containing "germline" variable region gene segments were detected in both strains, and many are shared by both, Since 35 CRI-positive heavy chains have been partially sequenced thus far and 31 are different, the results of the hybridization analysis suggest that somatic mutation events involving the variable region gene segments of the heavy chain play a role in the origin of the amino acid sequence diversity seen in this system.     

Modulation of growth hormone-releasing factor-induced release of growth hormone from bovine pituitary cells

Growth hormone (GH)-releasing factor (GRF) at concentrations of 10−¹² through 10−⁷M for 6 hr linearly increased GH release (b₁ = 10.4 ± .3) from bovine anterior pituitary cells in culture. Maximum release of GH (262% above controls) occurred at 10−⁷M GRF. In contrast, GH release-inhibiting factor (SRIF) at 10−¹² through 10−⁵M had no effect on basal concentrations of GH. In a second experiment, as the proportion of SRIF relative to GRF increased. SRIF suppression of GRF-induced GH release from anterior pituitary cells increased. In a third experiment, anterior pituitary cells cultured in media containing fetal calf serum (FCS) were treated with cortisol (0 or 10 ng/ml media) for 24 hr before exposure to 10−¹³ through 10−⁷M GRF. GRF linearly increased GH secretion (b₁ = 7.4 ± .3) and cortisol augmented this response (b₁ = 10.5 ± .6). However, when cells were cultured in media containing dextran-charcoal treated FCS, cortisol did not alter GRF-induced GH release. Our results demonstrate that GH response of bovine anterior pituitary cells to GRF was modulated negatively by SRIF. However, augmentation of GRF-induced GH release by cortisol was evident only when cells were cultured in media supplemented with untreated FCS.