SWES Student Seminars

Speaker:
Badule Pamila Ramotar and Eric Highfield

Speaker Title:
SWES M.S. Students

Event Description:

Tilapia (Oreochromis niloticus) Growth Using “standard commercial” and “alternative” Ingredients with Different Lipid and Protein Levels
Precise increases in the protein and lipid levels of tilapia diets can simultaneously reduce feed costs and the amount of underutilized protein, excreted as ammonia and lipids stored as fat in tilapia.  As a result, improved diet formulations can improve profitability and reduce environmental damages. This study investigated the potential of several protein sources and various lipid levels in several diets of juvenile Nile tilapia.  Novel sources of plant protein including new Soya, peanut and two types of algae: Chlorella and Spirulina were examined. Diets were grouped as “standard commercial formulation” (with fishmeal) and “alternative” (without fish meal).  Thirty six experimental tanks were stocked with twenty-five fish each (initial average biomass of 133g ± 2g) linked in a freshwater recirculation system within a greenhouse. Treatments were randomly assigned, with three reps per treatment and fishes were fed one of 12 diets (32%, 36% and 37% Crude Protein (CP), differing in Crude Lipid (CL) content (6%, 9% and 10% on dry weight basis). At the end of the 78 day feeding period, the average final weight per tank was 535g ± 88 g. Weight gain, standard growth rate, as well as protein efficiency were determined.   There were significant differences (P < 0.05), between the control diet 10 (37% CP:10% CL) and diet 12 (36% CP: 9% CL).  Diet 12 which contained peanut and Chlorella had the lowest growth rate of the 12 diets, whereas diet 10 had the highest growth rate. The highest FCR was diet 9 with 36% CP: 9% CL. The control diet, 10 was commercially manufactured by Star Milling of Perris, California. The comparisons among means for mortality, crude protein and lipid levels on growth or relative weight gained and “standard commercial” and “alternative” diet were non-significant (P>0.05). Substituting the alternative ingredients used in this experiment may reduce the increase demand for fish meal and the cost of tilapia feed, hence decreasing the operating cost in intensive culture.

Polyculture of Tilapia (Oreochromis niloticus) and Freshwater Shrimp (Macrobrachium rosenbergii) in a Recirculating Aquaponics System
Aquaponics has been proven as an efficient system that incorporates production of fish and plants with minimal inputs.

a) Caged Macrobrachium rosenbergii under fish vs. under plants - Macrobrachium rosenbergii, were caged in individual corrugated plastic shells and placed at two different locations within an existing aquaponics system containing Oreochromis niloticus and Lactuca sativa.  In treatment one, cages were placed at the bottom of Tilapia grow out tanks where they consumed fecal material, biofilms and undigested fish feed.  In treatment two, cages were placed underneath floating raft of lettuce where detritus material available consisted of dead and decaying plant matter, biofilms, and residual organic wastes from the fish.  Biomass increases of Macrobrachium and mortality rates were monitored after eight weeks.

b) Lactuca sativa biomass with caged Macrobrachium vs. uncaged Macrobrachium - Equal numbers of Macrobrachium rosenbergii were placed under two plant beds, one group was caged while the other was not.  After 56-day incubations, 10 heads of mature lettuce were sampled from both plant beds, and seedling rafts were introduced every seven days.  Samples were weighed, dried and re-weighed.  This process was repeated weekly for eight weeks to determine if uncaged Macrobrachium affected the growth of plants compared to caged Macrobrachium.  Mortality rates of shrimp were determined along with the overall increase in biomass.            

Macrobrachium experienced higher mortality rates, and smaller increases in biomass when caged under the floating raft lettuce compared to caged under fish.  Lettuce grown with uncaged Macrobrachium below the rafts saw an increase in weight compared to lettuce grown over caged Macrobrachium, indicating a favorable role for uncaged Macrobrachium in an aquaponics system.

Sponsors:
Soil, Water and Environmental Science

Website:
http://ag.arizona.edu/SWES/bulletin/calendar.htm