A systems analysis of the guyanese livestock industry

This paper attempts to contribute to the capability for livestock sub-sector analysis. A model structure which offers potential for evaluation of changes of policy, available production technology, or factor and product market conditions is described. The structure integrates a multi-year biological cattle simulator with a price endogenous model of the cattle sub-sector to yield a model designed to simulate aggregate behaviour of profit maximising cattle producers interacting through competitive factor and product markets. The general model structure is specified to reflect conditions in Guyana, South America. The model, specified for Guyanese conditions, is used to evaluate the probable impact of a number of technical and economic changes in the system.     

Harvest-pruning and trellising of ‘Sultana’ vines. I. Effects on yield and vegetative growth

Yield reductions averaging 10% are reported from 2 experiments in which ‘Sultana’ vines were continuously harvest-pruned for 11 and 9 years respectively. Over the period of the study there was no evidence of the yield reduction increasing with time.Differences between treatments in bunch number, berry weight and total soluble solids did not account for the reduction in yield. However, berry number per bunch was consistently, if not always significantly, lower on treated vines. Harvest-pruned vines had lower pruning-weights than the control vines.Increases in trellis width from 0.30 to 0.45 m to 0.90 m generally led to increases in yield caused by increases in bunch number. A 0.30 m wide T-trellis, with foliage wires added to support the shoots vertically to a height of 2 m, also gave yield increases over the standard 0.30 m trellis in most seasons. Harvest-pruned vines on the 0.90 m wide trellis gave similar yields to control vines on the standard 0.30 m trellis.     

Harvest-pruning and trellising of ‘Sultana’ vines. II. Effects on early spring development

The yield reductions associated with the harvest-pruning system of drying sultanas could not be attributed to a consistent effect on any of the components of yield. However, in several experiments berry number per bunch was reduced on harvest-pruned vines and in others there was a trend in this direction. The cause of this reduction appeared to be flower number per inflorescence. A hypothesis is proposed to explain the effect.Harvest-pruning and associated trellising treatments had only small effects on bud-burst and early shoot growth.     

Differentiation of infectious laryngotracheitis virus strains using restriction endonucleases

Strains of infectious laryngotracheitis virus (ILTV) were examined using an indirect immunofluorescent test (IIF) and with restriction endonucleases for detecting intratypic differences. Electrophoretic analysis of ILTV DNA fragments cleaved with restriction endonuclease Hind 111 clearly distinguished between strains. The IIF test did not discriminate between strains. A molecular weight estimate of ILTV DNA was made by summation of restriction endonuclease fragments cleaved with BamH1 (102.1 X 10(6)) and Hind111 (97.35 X 10(6)). Differences between the estimates may indicate the presence of submolar fragments.     

Contrast radiography in the investigation of sinus tracts and abscess cavities in the horse

Contrast radiography is a valuable technique in the investigation of infected foci in the horse. Its simplest form, a metal probe, will demonstrate the direction and, in the case of a short tract, the extent of the lesion. However, liquid contrast agents often give more information by following the course of long, tortuous sinus tracts, accurately delineating the boundaries of lesions and identifying the presence of foreign bodies.     

Effects of sulfamethoxazole-trimethoprim on thyroid function in dogs

OBJECTIVE: To evaluate effects of trimethoprim-sulfamethoxazole (T/SMX) on thyroid function in dogs. ANIMALS: 6 healthy euthyroid dogs. PROCEDURE: Dogs were administered T/SMX (14.1 to 16 mg/kg, PO, q 12 h) for 3 weeks. Blood was collected weekly for 6 weeks for determination of total thyroxine (TT4), free thyroxine (fT4), and canine thyroid-stimulating hormone (cTSH) concentrations. Schirmer tear tests were performed weekly. Blood was collected for CBC prior to antimicrobial treatment and at 3 and 6 weeks. RESULTS: 5 dogs had serum TT4 concentrations equal to or less than the lower reference limit, and 4 dogs had serum fT4 less than the lower reference limit after 3 weeks of T/SMX administration; cTSH concentrations were greater than the upper reference limit in 4 dogs. All dogs had TT4 and fT4 concentrations greater than the lower reference limit after T/SMX administration was discontinued for 1 week, and cTSH concentrations were less than reference range after T/SMX administration was discontinued for 2 weeks. Two dogs developed decreased tear production, which returned to normal after discontinuing administration. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that administration of T/SMX at a dosage of 14.1 to 16 mg/kg, PO, every 12 hours for 3 weeks caused decreased TT4 and fT4 concentrations and increased cTSH concentration, conditions that would be compatible with a diagnosis of hypothyroidism. Therefore, dogs should not have thyroid function evaluated while receiving this dosage of T/SMX for >2 weeks. These results are in contrast to those of a previous study of trimethoprim-sulfadiazine.