Pelleted Sources of Nutrition and the Effect of Stocking Size-graded Juveniles in Low-input Farming of the Freshwater Prawn Macrobrachium rosenbergii in Earthen Ponds

Nutrient sources in pelleted form and the effect of stocking size-graded juvenile freshwater prawns Macrobrachium rosenbergii for the low-input farming of the freshwater prawn in experimental earthen ponds (0.05-0.06 ha) have been studied. For each of 4 yr, experiments were sequentially conducted, having growout durations ranging from 111 to 135 d. Generally, graded juvenile prawns (0.26-0.29 g) were stocked into earthen ponds containing artificial substrate at a density that ranged from 21,690 to 34,580/ha. For all experiments, feeding rates ranged from 10.1 to 60.8 kg/ha/d during the growout season. Survival, mean weight, and total production were compared among the treatments. There were no significant differences in survival, mean harvest weight, or total production when corn gluten pellets fed exclusively were compared to corn gluten pellets in combination (1:1) with less expensive nutrient sources, wheat midds, and range cubes. Substitution of corn gluten pellets with a commercial prawn feed fed for the last 28 d of growout had no significant effect. A total level of feeding corn gluten pellets : range cubes (1:1) at 2802 kg/ha for the growout period was as effective as 3923 and 5044 kg/ha at a stocking density of 28,405/ha. The use of trout feed in combination with the feeding of the 1:1 corn gluten pellets to range cubes for 49 d prior to harvest was effective in maintaining mean harvest weight and production at a higher stocking density (34,580/ha vs. 28,405/ha). Poultry litter pellets were ineffective substitutes for the corn gluten pellet : ranges cubes (1:1) combination. The exclusive feeding of alfalfa pellets and soy hull pellets resulted in mean harvest weights and total production that were significantly less than what was achieved with the feeding of range cubes. Engineered enterprise budgets demonstrated positive economic benefits of the low-input strategy using pellet nutrient sources that contain no less than 20% crude protein (dry weight). Highest returns were realized with the upper grade of juveniles resulting from a 60/40 split (by number), even when lower grade animals were discarded. At stocking densities of approximately 22,000-28,000/ha, nutritional requirements of the prawns appear to be satisfied by the consumption of the fed nutrient sources combined with live, natural resident pond prey organisms enhanced by organic input resulting from the breakdown of the pellets. Production levels of 900-1000 kg/ha can be consistently achieved.