The effect of selection for growth rate and slaughter age on carcass composition and meat quality traits in rabbits

The effect of selection for growth rate on carcass and meat quality was assessed by comparing selected and control populations of rabbits measured at the same stage of maturity and slaughtered at 9 and 13 wk of age. Embryos belonging to Generation 7 were frozen, thawed, and implanted in does to produce the control group. The control group was formed from the offspring of the embryos belonging to the Generation 7. Selected animals belonging to Generation 18 (S) were compared with contemporary animals of the control group (C). Carcasses were dissected and measured according to World Rabbit Science Association recommended practices. When animals were compared at similar degrees of maturity, selection for growth rate did not produce a negative effect on carcass and meat quality. There was no increase in fat content of the carcass, and there was an improvement of the meat:bone ratio with selection, with a difference between C and S groups of -0.42. However, the carcasses of S animals have 1.45% lower water-holding capacity. Carcass quality changed markedly with animal age. Heavy rabbit carcasses had lower organ percents and a higher loin percent. Dissectible and i.m. fat content were higher in older rabbits, with older animals having 0.97 and 0.79% more dissectible and i.m. fat content, respectively. Meat quality traits improved with age of slaughter, although there was an increase in glycolytic metabolism. Results from this study indicate that selection for growth rate has little effect in carcass and meat quality when rabbits are measured at the same stage of maturity.     

The Ecological Dose of Nickel in a Semiarid Soil Amended with Sewage Sludge Related to the Unamended Soil

Nickel pollution may affect microbial communitydevelopment and its activity in soil and, therefore, itsfertility, while organic amendment may affect Ni mobilityand bioavailability. The aim of this research was toascertain the extent to which the addition of sewage sludgeto soil may affect Ni toxicity and to establish theecological dose of this heavy metal. Unamended and amendedsoils with sewage sludge were spiked with differentconcentrations of Ni (0–8000 mg kg^-1) and then incubatedfor 3 hours, 12 days and 40 days. Soil dehydrogenaseactivity, ATP content, microbial respiration and microbialbiomass C were measured in the samples containing differentNi concentrations. A mathematical model which describe theinhibition of these soil parameters were used to calculatethe ecological dose of Ni: ED₅₀. Soil microbialbiomass C measurements of all treatments better fitted themodel (r² = 0.95–0.69 with p < 0.05) than the otherparameters studied; but the ED₅₀ values predicted by the modelhad a high coefficient of variation. For both ATP contentand microbial biomass C, the ED₅₀ values calculatedfor the amended soil were higher than for the unamendedsoil and so that the effect of Ni toxicity on theseparameters of microbial activity may be considered lower inthe former. In this study, an increase in ED₅₀ valueswith the time elapsed was also observed.