Effects of Phase-Feeding Decreasing Levels of Dietary Protein on Growth and Diet Utilization of the Red Drum, Sciaenops ocellatus

摘要

Two experiments were conducted to evaluate phase-feeding strategies on growth and nutrient retention of red drum, Sciaenops ocellatus. The first experiment was conducted over a 17-week period, utilizing sub-adult (initial mean weight, 70,8 g/fish) reddrum, Treatments included three fixed-feeding regimes in which the fish were offered diets containing either 44,40 or 36% protein throughout the growth trial (F44, F40, F36, respectively) and two phased-feeding regimes. The phased-feeding regimes included feeding the 44% protein diet the first 8 weeks after which the fish were switched to the 40 (P44/40) or 36% (P44/36) protein diets. At the conclusion of the experiment, final mean weights ranged from 592.8 to 543.3 g/fish (F44 and F36, respectively).Although statistical differences were not found in final weights (P = 0.1015) of the fish, percent weight gain was significantly reduced as the protein content of the diet was reduced. Similarly, feed efficiency (FE) values decreased as the protein content of the diet was reduced. Although protein conversion efficiency (PCE) values generally decreased with protein content of the diet, there were no statistical differences. The second experiment was initiated with 281 g mean weight fish and was conductedover a 14-week period. Three fixed-feeding regimes (FF44, F40 and F36) and three phased-feeding regimes were evaluated. After six weeks some of the fish (mean weight 448 g) were switched from 44% protein diet to diets containing 40, 36 and 32% protein (P44/40, P44/36, P44/28, respectively). Results of this feeding trial were similar to the first in that performance followed protein intake which in turn paralleled protein content of the diet. In both experiments, considerable differences in final weightwere observed, but due to variation in the data statistical differences were minimal but the same ranking occurred. Overall, it would appear that fish up to about 450 g will perform best on a 44% protein diet but minimal reduction in growth occurs afterthis point if the protein content of the diet is reduced to as low as 36%.