Urinary energy losses in dogs fed commercial extruded foods.
Energy and nitrogen losses in the urine were recorded in 134 individual balances with adult (1- to 2-year-old) female Beagles that were fed 23 dry extruded dog foods ranging in crude protein (CP) content from 242 to 360 g/kg dry matter. The energy equivalent of urinary nitrogen was estimated as 33.9 kJ/g N. Both energy losses in the urine corrected for the nitrogen balance, and the metabolizable energy (MEn): digestible energy (DE) ratio were found to be closely related to diet CP content (r : 0.851 and 0.820). The MEn content of extruded dog foods can be accurately calculated from the DE content, either by subtracting 4.59 MJ/kg CP or estimating the MEn/DE ratio from the food CP content by the following equation: MEn/DE=0.98 - 3.44 +/- 0.517 x CP (kg/MJ DE).
Dog-park soils: Concentration and distribution of urine-borne constituents
Off-leash dog parks are very popular locations that allow pets to freely exercise and eliminate wastes in a controlled environment. Although dog park rules require that solid waste be removed by the pet’s owner, urine-borne constituents in dog-park soils have received little attention. This study focused on the soils within two small-dog, off-leash dog parks in Fargo, North Dakota (USA) with the objective to better understand the concentration and distribution of extractable NH4-N, NO3-N, PO4, soluble salts, and pH values in surface soils (0–10 cm) within these two dog parks. Concentrations of soil variables varied widely within each park and were distributed as both gradient and ‘hot-spots.’ The geospatial model types for each soil parameter were more dependent on park than on the constituents themselves. Flow accumulation was correlated with both nitrate-N and P but due to the lack of topography at these parks the flow accumulation was not helpful in describing most of the soil constituents. The results from this project indicate that location of parks, daily/annual use of parks, flow accumulation, and location of park entries may all influence the concentration and distribution of urine-borne constituents.
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.