Use of geotextile tubes with chemical amendments to dewater dairy lagoon solids.

Three geo-textile filtration tubes were used to dewater lagoon solids from a first stage dairy lagoon using chemical amendments (aluminum sulfate and a polymer) to enhance the separation process. This experiment had previously been done without chemical amendment. The chemical amendments speeded the dewatering process so that filling could be accomplished sooner, and also increased the removal rate of nutrients, especially phosphorus into the solid phase. Chemically amended slurry was pumped from the lagoon into the tube with the filtered liquid seeping from the tube and returning to the lagoon. Each tube was filled five to six times at 2-5-day intervals, and then allowed to dewater for 2 weeks before sampling the solid fraction in the tube. Separation efficiency improved from 79% to 99% for phosphorous and from 92% to 100% for organic nitrogen with chemical amendment. Time required for dewatering was significantly reduced by chemical amendment. Cost for the tube was approximately $10/m(3) of recovered solids with no chemical amendment and cost including the chemicals was approximately $14/m(3) of recovered solids.

Responses of broilers to dietary zinc concentrations and sources in relation to environmental implications.

1. Since high concentrations of zinc are associated with reduced crop yields, environmental concerns are emerging regarding zinc accumulation in areas where poultry production is prevalent. This study investigates growth performance and zinc utilisation during the life cycle of broilers when diets were supplemented with various concentrations of zinc from two different sources. 2. A total of 740 Cobb 500 1-d-old male broiler chicks was randomly distributed into 88 battery cages. Excreta were collected over a 48-h period on d 10, 17, 24, 31, 38, and 45 to measure zinc excretion on a dry matter basis. 3. During the 45-d experimental period, broilers were given a maize-soybean meal basal diet (30 mg/kg zinc) supplemented with 0, 20, 40, and 80 mg/kg of zinc from zinc sulphate, Availa Zn amino acid complex, or an equal combination of zinc sulphate and Availa Zn amino acid complex. 4. Progressive additions of zinc to the basal diet significantly increased body weight gain of broilers, but did not affect feed conversion or mortality. Optimum body weight gain was achieved at 80 mg/kg supplemental zinc, which exceeds the NRC recommendations of 40 mg/kg. 5. During each excreta collection period, increased supplemental zinc concentrations significantly increased zinc excretion. However, the zinc source did not influence zinc utilisation. 6. As compared with zinc sulphate supplementation, the cumulative zinc excretion data indicate that adding zinc to the basal diet in the form of Availa Zn amino acid complex decreased zinc excretion.