Effect of dietary phosphorus on finishing steer performance, bone status, and carcass maturity.

Yearling crossbred steers (n = 60; 386 kg) were individually fed in a completely randomized experimental design to determine their P requirement. Treatments were in a factorial arrangement with two levels of Ca (.35 or .70% of DM) and five concentrations of P (.14, .19, .24, .29, or .34% of DM). The finishing diet consisted of 34.5% dry-rolled corn, 22.5% brewers grits, 22.5% corn bran, 7.5% ground corncobs, 5% molasses, 3% fat, and 5% supplement. Supplemental P was provided as monosodium phosphate and Ca as limestone. Ash content was determined on the first phalanx bone from the lower front legs following slaughter, and rib bone breaking strength was determined with an Instron Universal Testing Machine. Carcass maturity and shear force were also evaluated on wholesale rib cuts. Because no interactions between Ca and P levels were detected, only main effects are presented. Daily gain, DMI, and feed efficiency were not affected by dietary P concentration or P intake. Bone ash (g or g/100 kg BW) and rib bone breaking strength were also unaffected by dietary P. Feeding .7% Ca decreased (P<.06) ADG and efficiency compared with feeding .35% Ca. Neither dietary Ca nor P had a significant effect on tenderness (shear force), skeletal maturity, or overall maturity. These results indicate that the P requirement for finishing yearlings is .14% of diet DM or less and that supplementing P above levels supplied by basal ingredients in many grain-based finishing diets is not necessary.     

A comparative molecular field analysis study of obtusifoliol 14α-methyl demethylase inhibitors

This report describes the development of a Comparative Molecular Field Analysis (CoMFA) model from a set of obtusifoliol 14α-methyl demethylase (DM) inhibitors to aid in the design of herbicides targeting sterol biosynthesis. CoMFA is a three-dimensional (3-D) quantitative structure–activity relationship (QSAR) method that is useful in the probing of receptor binding sites when experimental structure data are unavailable. Conformational analysis and SAR of some rigid and active analogs were used to build the initial model using the active analog hypothesis. The model was subsequently used to design compounds that retain the active site shape requirements, but incorporate physical properties that favor soil-applied herbicidal action. In addition, a second-generation CoMFA model incorporating the newly designed inhibitors was developed and represents the current understanding of the DM binding site. This model was derived from a pharmacophore developed from two methods, the active analog approach as well as from the Catalyst program. The fact that two independent methods produced a similar pharmacophore strengthens the validity of the model. © 1999 Society of Chemical Industry     

Nutrient Availability Response to Sulfur Amendment in Histosols having Variable Calcium Carbonates

High soil pH and excessive calcium carbonate (CaCO₃) in the Everglades Agricultural Area of south Florida reduce the availability of phosphorus and micronutrients to crops. Sulfur (S) amendment is recommended to reduce soil pH and enhance nutrient supply. The study’s objective was to determine the sulfur amendment effectiveness on soil pH and nutrient availability in organic soil as CaCO₃ content increases in soil. An experiment of four S rates (0, 90,224, and 448 kg ha^?1) and three added CaCO₃ (0%, 12.5%, and 50% by volume) in organic soil was established. Sulfur application had limited effects on soil pH reduction as CaCO₃ level increased and therefore failed to enhance nutrient availability; however, it increased sulfate concentration in soils, which could be at risk for export from the field. Unexpected increases in manganese concentration with added CaCO₃ was associated with reducing conditions due to increased soil bulk density, which changed the soil physical properties.     

Fertilizing Capacity of Frozen Epididymal Sperm Collected from Dogs

The collection of epididymal sperm may be a valuable tool for canine reproduction especially since it can enable collection of cells after death of a valuable dog. The aim of the present study was to evaluate the viability of epididymal sperm after freeze-thawing. Epididymides were obtained from four adult dogs by elective orchiectomy. The caudal portion of the epididymides and part of the deferential ducts were squeezed by means of an anatomic clamp into a Petri dish containing either 0.9% saline solution (Group 1) or Ringer solution without lactate (Group 2). Samples were centrifuged at 800 ×  g for 10 min, the supernatant was removed and the pellet was diluted in one step with a Tris/citric acid/OEP (Orvus Es Paste) extender containing 7% glycerol and subjected to semen freezing. Oocytes were obtained from canine ovaries, after ovariohysterectomy. Only oocytes that were approximately 100 μm in diameter, with a dark ooplasm surrounded by three- or four-well formed cumulus cell layers were used for sperm testing. Frozen semen samples were thawed in a water bath at 70°C for 8 s and analysed at room temperature for sperm motility and velocity. Oocytes were incubated with spermatozoa in humidified atmosphere containing 5% CO₂ at 38°C for 18 h. Morphological and functional characteristics of spermatozoa were similar in both groups. However, the percentage of sperm cells bound to oocytes was significantly higher in Group 2 than in Group 1. This result suggests that the Ringer solution without lactate was a more suitable medium for collecting epididymal canine sperm than 0.9% saline.     

Spread of seed-borne <Emphasis Type="Italic">Erwinia rhapontici</Emphasis> in bean,pea and wheat

Studies were conducted in the laboratory and greenhouse to determine the distribution of Erwinia rhapontici in plants arising from naturally infected seeds of pea or artificially inoculated seeds of bean and wheat, and whether the pathogen is transmitted to the subsequent generation of seeds. Infected seeds were planted in pots of Cornell mix in the greenhouse, and sampled at specified intervals throughout the plant growth cycle (seedling stage, elongation stage, flowering stage, seed formation stage, and maturity). Plating of surface sterilized lateral roots, tap roots, basal stems, mid-stems, apical stems, petioles, pods, and seeds of pea and bean, and of lateral roots, sub-crown internodes, basal stems, mid-stems, apical stems, peduncles, glumes, and seeds of wheat revealed that the bacterial pathogen spread from infected seeds to the lower parts of the plant tissues, but failed to spread further to the seeds produced on these plants. The study concludes that E. rhapontici did not establish systemic infection throughout the plants. Possible mechanisms of infection of seeds are discussed.     

Application of Reclaimed Wastewater in the Irrigation of Rosebushes

The use of reclaimed wastewater in agriculture can be a solution for regions with water shortages or low rainfall periods; besides fulfilling the crop's water needs, it would also promote the recycle of nutrients. However, care should be taken regarding soil salinization, especially in closed environments such as greenhouses for the cultivation of ornamental plants. The domestic effluents are rich in sodium which can accumulate on soil and cause soil sealing. This study evaluated the use of effluents from anaerobic filters and intermittent sand filters in the production of rosebushes (Rosa hybrida “Ambiance”). The crop yield of the rosebushes irrigated with reclaimed wastewater exceeded the one obtained with traditional cultivation, reaching a value 31.8 % higher when employing nitrified effluent originated from intermittent sand filters, with no difference in the product quality. The salinity levels are below the critical limits found in the literature; however, there was a significant increase compared to the irrigation with drinking water.     

Pathogen Inactivation In Cow Manure Compost

During aerobic composting of animal manure, microbial activity within the mixture generates heat and metabolic by-products that inactivate zoonotic pathogens. Although it is recognized that the type and level of microbial activity will vary with the nutrient availability of different compost ingredients, the degree to which these changes could impact pathogen inactivation is of interest. Towards that goal, the purpose of this study was to determine inactivation of Escherichia coli O157:H7 and Listeria monocytogenes in compost laboratory-scale bioreactor systems formulated to different initial carbon:nitrogen (C:N) ratios with cow manure, straw, and cottonseed meal. The C:N ratio did not significantly affect the time to inactivation of Listeria monocytogenes. In contrast, Escherichia coli O157:H7 survived for significantly (P < 0.05) longer periods of time in 40:1 C:N systems than in 30:1 or 20:1 systems even though the cumulative heat exposures were statistically similar in the systems. An increase of pH values to 8 to 9 occurred initially for 40:1 C:N systems, whereas the pH of the 20:1 and 30:1 systems initially declined to 5.5 to 6 before increasing to 8 to 9 after 2 days of composting.