Evaluation of the impact of parasite control with the IVOMEC SR Bolus given at breeding age on first lactation yield in Holstein heifers.

This field trial was conducted to test the effect of treatment with a sustained-release ivermectin bolus on first lactation milk production (projected to 305 days) and milk composition (percent fat and protein) in breeding-aged Holstein heifers. From 12 herds, 96 heifers were randomly allocated at turnout to treatment with a commercially available ivermectin bolus (n=49) or untreated control (n=47) groups. Animals were weighed at turnout, mid-season, and at the end of the grazing season. Fecal samples were taken and nematode eggs counted. Projected 305 days milk production, fat and protein content were retrieved from PATLQ reports (Quebec DHI records) for heifers that calved during the subsequent 10 months. The heifers had a mean weight of 409 and 404 kg at turnout, respectively, for control and treated groups. Nematode egg excretion was relatively low (mean of 10 egg/g (EPG) for controls at housing) throughout the pasture season. The average daily gain (ADG) and total weight gain (TWG) over the entire pasture season was found to be higher in treated heifers compared to controls (ADG: difference=0.08 kg per day, P=0.010; TWG: difference=12.82 kg, P=0.013). Taking into account a possible farm effect, the 305 days milk production for IVOMEC SR bolus-treated heifers was significantly higher than for untreated animals (mean+/-S.D.; 348+/-476 kg; t-test=2.31, P<0.05). Overall, 8 of the 10 remaining farms in the study demonstrated a positive milk production difference in treated (n=34) versus control heifers (n=33). The results of this study suggest that preventive treatment of breeding-aged, grazing dairy heifers with a sustained-release ivermectin bolus provides a significant weight-gain which may translate to a significant milk production advantage, even in situations with commercial utilization of moderately contaminated pastures.     

Grass interference limits resource availability and reduces growth of juvenile red pine in the field

The effects of competing grasses on resource availability, growth and ecophysiological characteristics of 3-0 red pine (Pinus resinosa Ait.) seedlings were examined the first two years following outplanting in Anoka County, Minnesota, USA. Equal numbers of seedlings were planted into suppressed and undisturbed grass communities in a sandy soil. Grass suppression was maintained throughout the first growing season, but partially discontinued thereafter on the site. During the first field season interference from grass reduced pine seedling root collar diameter, needle length, number of new root tips, and lateral root length by over 40%. Mean pre-dawn needle water potential was 0.55 MPa lower in undisturbed grass plots during a brief drought in year one, but otherwise water stress was not significantly (p=0.05) influenced by grass interference. The presence of grass also reduced, up to 50%, the photosynthetically active radiation reaching the seedling canopy. At the end of year one, total biomass N, P, K, and Ca content were significantly (p=0.05) less in seedlings growing in the undisturbed grass community. Nitrogen was deficient in seedlings growing in grass. After two growing seasons, seedling shoot length (p=0.03), root collar diameter (p=0.001), and needle length (p=0.001) were significantly less (40, 54 and 20%, respectively) for seedlings growing in undisturbed grass. Seedling growth reductions induced by grass competition were associated with multiple environmental stressors in the field and not restricted to water stress as was observed in earlier studies with pine species at low and mid-latitude sites.     

Production and Interior Performances of Tropical Ornamental Foliage Plants Grown in Container Substrates Amended with Composts

Three representative Florida composts were mixed by volume with sphagnum peat and pine bark to formulate 12 container substrates. After physical and chemical characterization, the substrates, along with a control, were used to grow containerized Cordyline terminalis ‘Baby Doll’, Dieffenbachia maculata ‘Camille’, and Dracaena fragans ‘Massangeana’ cane. All substrates were able to produce marketable plants, but only five or seven, depending on plant genus, of the 12 compost-formulated substrates resulted in plants comparable or superior to those of the control substrate. The five also had substrate shrinkage equal to or less than the control. Plants were then moved to an interior evaluation site to determine the suitability of compost-formulated substrates in sustaining foliage plant growth under an interior environment. During a six-month interior evaluation, the plants maintained their aesthetic appearances. Based on plant growth parameters and quality ratings as well as substrate shrinkage both in production and interior evaluation, five of 12 compost-formulated substrates were identified to be equal or superior to the control. This study showed that the three composts, after being appropriately mixed with sphagnum peat and pine bark, can be used as container substrates in every phase of tropical foliage plant production and utilization.     

Expression of the chlamydial genus-specific lipopolysaccharide epitope in Escherichia coli

The obligate intracellular prokaryote Chlamydia trachomatis is the etiological agent of trachoma and is a primary causative pathogen of sexually transmitted genital tract disease; both diseases affect millions of people each year. The cloning of genes encoding the enzyme or enzymes producing the genus-specific lipopolysaccharide antigen of Chlamydia into Escherichia coli is reported here. The cloned chlamydial lipopolysaccharide antigen appears to be a hybrid lipopolysaccharide molecule composed of both Chlamydia and Escherichia coli components. The chlamydial lipopolysaccharide antigen is expressed on the surfaces of the viable Escherichia coli recombinants. These findings may have a significant impact on defining the role of this highly conserved antigen in the pathogenesis and diagnosis of chlamydial infections.     

Effect of elevated manganese on the ultraviolet‐ and blue light‐absorbing compounds of cucumber cotyledon and leaf tissues

The effect of manganese [Mn(II)] on the pigments of cucumber (Cucumis sativus L., cv Poinsett 76) leaf and cotyledon tissues was investigated. Tissue disks (7 mm) were exposed to increasing Mn(II) concentrations from 100 μM to 2.5 mM. Acetone (carotenoid‐rich fraction) and acidified methanol (flavonoid‐rich fraction) extracts were analyzed by high performance liquid chromatography. Although none of the Mn(II)‐treated tissues showed visible damage, Mn(II) at concentrations of 250 μM and above significantly reduced (60%) the ß‐carotene levels of light‐incubated leaf tissues. A major Mn(II)‐induced, UV‐absorbing compound was observed in methanol extracts of cotyledonary tissues exposed to Mn(II) in the dark. In leaf tissues, Mn(II) reduced the levels of certain UV‐absorbing compounds under both light conditions. These results demonstrate that excess leaf Mn(II) can rapidly impair isoprenoid metabolism, altering tissue carotenoid composition. Furthermore, Mn(II) may also modify phenylpropanoid metabolism, changing the tissue flavonoid composition. Both situations could sensitize plant tissues to oxidative stresses, particularly enhanced solar UV‐B radiation, and may reduce the nutritional quality of leafy vegetables.     

Weaning and post-weaning performance by fall-born beef calves weaned on different dates in the spring from Neotyphodium coenophialum-infected tall fescue pastures

Fall-born calves grazing Neotyphodium coenophialum-infected tall fescue [E+; Lolium arundinaceum (Schreb.) Darbysh.] pastures should benefit from early weaning because of reduced exposure to fungal toxins. However, fall-born calves that grazed E+ and were weaned in mid-April had reduced post-weaning performance compared with calves managed similarly but weaned in early June. Gelbvieh × Angus calves (n = 238) were used in a 3-year study to determine the optimal time to wean fall-born calves grazing E+. Cow/calf pairs were allocated randomly to one of four weaning date treatments: 1) March 16 (177 ± 4.7 days of age; MarW), 2) April 13 (204 ± 4.7 days of age; AprW), 3) May 11 (236 ± 4.7 days of age; MayW), and 4) June 8 (264 ± 4.8 days of age; JuneW). On their assigned weaning date, calves were weighed, vaccinated, blood samples were collected, and calves were moved to 3.2-ha pastures adjacent to their dams for 14 days. After the weaning period, calves were weighed, blood samples were collected, and then calves were moved to pastures containing non-toxic forages. Birth weight and calf weights on MarW, AprW, and MayW weaning dates did not differ (P ≥ 0.21) across weaning date treatments. However, calf weaning weights on their respective weaning dates, weight on JuneW and on June 22 (14 days following the JuneW), daily gain between birth and June 22, and weight change between MarW and JuneW increased linearly (P < 0.05) across weaning dates. Linear decreases (P < 0.05) across weaning dates were noted for antibody titers to bovine virus diarrhea (BVD) and infectious bovine rhinotracheitis (IBR), serum Cu, and platelets at the time of actual weaning. Linear increases (P < 0.05) across weaning dates were noted for: i) total antioxidant potential and eosinophils at weaning; ii) changes in antibody titers to BVD and IBR, total antioxidant potential, and serum Zn during the 14-day post-weaning period; and iii) and changes in BVD and BRSV titers and serum Cu between actual weaning date and June 22. Heifer weight at breeding increased (P < 0.05) and steer weight at shipping, hot carcass weight and backfat thickness tended (P ≤ 0.10) to increase linearly across weaning dates. Final feedlot weight and gain did not differ (P ≥ 0.18) among weaning dates. Therefore, delaying weaning of fall-born calves grazing E+ pastures until early June may be beneficial for calf weight and immune function at weaning, and heifer weight at breeding, but those benefits in steers may be mitigated through the feedlot period.     

Growth,food conversion and survival of 0-group English sole (Parophrys vetulus Girard) at five temperatures and five rations

Laboratory experiments were conducted to determine the effects of temperature and food ration on growth, conversion efficiency and survival of 0-group English sole (Parophrys vetulus Girard). Young sole, fed a diet of Oregon Moist Pellets, were exposed to constant temperature-ration combinations between 9.5 and 21° C and between 0 and 16% rations (dry weight basis) for a 12-week experimental period. The juvenile sole, initially 4–6 g, grew at a rate of up to 0.95% per day at the most favorable temperature-ration combination, 9.5°C and 16% ration. Highest food conversion efficiency, 10.5%, was observed at the temperature-ration combination of 9.5°C and 8% ration. At 21°C, young sole lost weight at the ration levels fed. Based on growth rate, survival and food conversion efficiencies observed during the experiments and the temperatures to which the young sole are exposed in nature, the temperature at which greatest growth and maximum food conversion efficiency occurs is probably near or below 9.5°C. Although English sole juveniles were maintained for up to 1.5 years on Oregon Moist Pellets primarily, mortality was high during experiments (between 16 and 48%). The high mortality may have been associated with the pellet diet used, which is formulated to meet the nutritional requirements of salmonids and not flatfishes. The microsporidan protozoan Glugea sp., the monogenetic trematode Gyrodactylus sp., and Vibro bacteria also were associated with mortalities during the experiments, and one fish died of a large tumor.