Effect of the Dietary Ratio of Digestible Energy to Crude Protein on Growth and Feed Conversion in Juvenile Pacific White Shrimp Litopenaeus vannamei under Similar Levels of Daily Protein Consumption

摘要

We evaluated the effect of the dietary ratio of digestible energy (DE) : crude protein (CP) on growth performance and nutrient utilization in juvenile Pacific white shrimp Litopenaeus vannamei fed various diets with a constant daily protein input. Juveniles (weight = 0.94 +/- 0.04 g [mean +/- SE]; n = 30) were stocked in an indoor recirculating-water system (173-L polyethylene tanks; 20 shrimp/tank) and were assigned to four different treatments. Two treatments consisted of 30% and 40% CP diets (30 isoenergetic [ISO]-100% and 40 ISO-75%, respectively) with a constant level of de (3.28 kcal/g). Two treatments consisted of 30% and 40% CP diets with variable levels of de (2.70 and 3.6 kcal/g, respectively) that maintained a constant DE : CP ratio of 9 kcal/g of protein (30 ratio [RAT]-100% and 40 RAT-75%, respectively). At the end of the 49-d trial, final weight and weight gain did not differ among the treatments. However, feed conversion ratio (FCR) was significantly lower (P < 0.01) for the 40 RAT-75% and 40 ISO-75% groups than for the 30 ISO-100% and 30 RAT-100% groups. Final body composition (dry matter, CP, and gross energy) and protein conversion efficiency were not significantly different among the four treatments. However, energy conversion efficiency was significantly higher for the 40 ISO-75% group than for the 30 ISO-100% group. This study demonstrates that when the level of energy is appropriate, increasing dietary protein content allows for reduced feed inputs without affecting shrimp growth performance, while actually improving FCR and water quality due to presumably lower wastage of feed.