Simulation study of the competitive ability of erect, semi-erect and prostrate cowpea (Vigna unguiculata) genotypes

Ecophysiological simulation models provide a quantitative method to predict the effects of management practices, plant characteristics and environmental factors on crop and weed growth and competition. The INTERCOM interplant competition model was parameterised, calibrated by monoculture data for three cowpea (Vigna unguiculata) genotypes that differed in growth habit, common sunflower (Helianthus annuus) and common purslane (Portulaca oleracea), and used to simulate competition of cowpea cover crops with sunflower or purslane. The simulation results were compared with observations from field competition experiments in 2003 and 2004. INTERCOM more accurately simulated actual field data for the competition of cowpea genotypes and sunflower than companion field experiments for the competition of cowpea and purslane. The validated simulation model of cowpea and sunflower at two densities was used to study the effects of cowpea growth habit on final biomass production of cowpea and sunflower. The model suggested that erect growth habit was more competitive than semi‐erect and prostrate growth habit, when cowpea genotypes were grown with sunflower. Cowpea leaf area distribution was important to higher cowpea biomass production, while cowpea height growth was important to reduce sunflower biomass. Our simulation approach is suggested as a method for crop breeders to gauge the likely success of selection for competitive crops before undertaking expensive long‐term breeding experiments.     

Blood selenium concentrations of sheep and goats from selected areas of Kenya

A systematic mapping technique based on blood, forage and soil selenium levels was employed to locate areas of selenium deficiency, adequacy or excess in areas of Kenya where grazing of small ruminants predominates. A total of 1,478 blood samples from both sheep and goats, 180 forage samples and 90 soil samples were analysed for selenium levels. During the wet seasons 28% of the sheep and 15% of the goats had marginal to deficient blood selenium concentrations while during the dry season 20% of the sheep and 12% of the goats had marginal to deficient blood selenium concentrations. Forage samples had a range of 0.03 to 0.66 ppm selenium while soil samples had a range of 0.06 to 0.98 ppm selenium. Although many animals had blood selenium levels of less than 0.05 ppm, below which selenium deficiency signs might occur, none of the animals manifested these signs.     

Analysis and pharmacokinetics of cimaterol in growing Holstein steers.

Pharmacokinetic parameters for the beta 2-adrenergic agonist, cimaterol (CIM), were determined in growing Holstein steers. Compartmental analysis was used after measurement of CIM in body fluids by affinity chromatography and HPLC using UV detection. Recoveries from spiked plasma and urine standards were 70 +/- 1.2% and 68 +/- 1.1%, respectively. The minimum detection level in plasma was 1 ng/mL and the average CV was 5.1% for concentrations that ranged from 1 to 30 ng/mL. Four steers (276 +/- 24 kg) received 15 mg of CIM by bolus intravenous injection. Plasma CIM levels declined in a biphasic manner with half-lives of 2.5 min for the distribution phase and 54 min for the elimination phase. A two-compartment open model was used to describe the disappearance of CIM and the following pharmacokinetic parameters were obtained: central compartment volume (Vc) = .76 L/kg, apparent volume of distribution (Vd) = 4.1 L/kg, and transfer rate constants from the central to peripheral compartment (k12) = .177/min, from the peripheral to central compartment (k21) = .054/min and elimination from the central compartment (kel) = .074/min. After 8 h, total urinary CIM accounted for only 18.3% of the administered dose. Results suggest that circulating concentrations of CIM in growing steers are influenced by its accumulation in an unidentified peripheral pool and its conversion into unknown metabolite(s) before elimination.     

Canine distal renal tubular acidosis and urolithiasis

Distal RTA is characterized by decreased distal renal tubular hydrogen ion secretion, decreased ability to acidify urine, hypercalciuria, hyperphosphaturia, hypocitraturia, and metabolic acidosis. Because of the resulting alterations in urine composition and pH, patients with distal RTA are predisposed to urolithiasis and renal calcification. Diagnosis of distal RTA is important because it is a potentially reversible disorder that, left untreated, may cause nephrocalcinosis, recurrent urolith formation, moderate to severe metabolic acidosis, and renal failure.     

Phalangeal and navicular bone hypoplasia and hoof malformation in the hind limbs of a foal

Anatomical anomalies in the hind feet of a seven month old Appaloosa foal were identified and investigated through the use of gross anatomical dissection, radiography and angiography. Abnormalities were restricted to the distal aspect of both hind legs, the right hind leg being more severely affected. Anatomically the right foot resembled that of an equine fetus of approximately 120 days gestational age. Disruption of vascular perfusion to hoof structures was evident in both hind legs and was related to areas of abnormal bone conformation as well as to areas of abnormal ossification and calcification. Phalangeal and navicular bone hypoplasia were apparent as were soft tissue and joint anomalies. Although the etiology of the defects identified remains obscure, several theories are suggested, namely heritability, acquired defects and the possible teratogenic effects of clenbuterol.     

Comparison of artificial light sources and lighting programmes for laying hens on long ahemeral light cycles

Three lighting treatments were given to laying hens, for which the bright and dim light of 28-h ahemeral light cycles was provided by incandescent (tungsten filament) lamps only or by combinations of tubular fluorescent or compact gas-discharge lamps with incandescent lamps. There were no differences in entrainment (the proportion of eggs laid in 4, 6 or 8 h modal periods) between the three bright:dim treatments. A fourth ahemeral lighting treatment in which the dim lights were extinguished except during a designated work period (09.00 h to 12.00 h daily) was termed bright:dim:dark. Hens given the bright:dim:dark treatment showed an increased entrainment compared with the three bright:dim light treatments. There were no differences (P greater than 0.05) in egg numbers or mean egg weight between all 4 lighting treatments. Birds given the bright:dim:dark treatment tended to have a lower (P greater than 0.05) food intake compared to the three bright:dim treatments.