An economic analysis of beef stocking rates.
ABSTRACT The Land Conversion Scheme and the prevailing maize and meat market situations have given rise to renewed interest in livestock production from cultivated pasture. The model developed by Jones and Sandland (1974) is used to determine optimum stocking rates under various circumstances. A micro-computer model, OPTSR, is developed for relatively quick solutions.
ONDERNEMERSKAP EN BEMARKINGSTRATEGIEë VIR VLEIS-BEESPRODUSENTE IN DIE VRYSTAATSTREEK / Entrepreneurship and marketing strategies for beef producers in the Free State region
Abstract In this investigation, production and market related factors which affect profitability and risk of beef production systems on Cenchrus ciliaris pastures were evaluated by using stochastic simulation. The results indicate that beef producers can influence their income considerably by adequately considering the following in their production and marketing strategies: Cyclical and seasonal beef price fluctuations, price differentials among markets and certain animal characteristics (age, grade and mass). In addition opportunity costs, interest and risk of market access materially affect both profitability and risk of a beef production system. Beef producers should adapt their production and marketing strategies to economic realities in order to achieve optimum results.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.