Performance of three diets with different protein:energy ratios on the culture of the Pacific white shrimp, Litopenaeus vannamei, under practical descending temperature conditions

Three diets with different protein:energy ratios: 66.7, 77.8, and 87.5 mg CP/kcal were evaluated for Litopenaeus vannamei farming in a 10-week trial during the fall season in Northwestern Mexico when temperature was descending. Experimental units consisted of nine 4000-L plastic tanks. For the complete 10-week set of data, no significant differences in total weight gain (2.60 to 2.83 g), weekly growth (0.26 to 0.28 g/week), percent of weight gain (176 to 188 %), fed conversion ratio (2.9 to 3.2), and survival (64.3 to 72.5%) were found among diets. Data analyzed separately, considering the first and the last 5 weeks of study, showed to be different. For the first 5 weeks (temperature > 18 super( degree )C), no differences in weight gain (2.20 to 2.42 g), weekly weight gain (0.44 to 0.48 g/week) percent weight gain (147 to 161 %), and FCR (2.1 to 2.2) were observed among diets. For the last 5 weeks (Temperature < 17 super( degree )C), all the production parameters were very poor and significant differences were found between diets, with the best results observed in the treatment 66.7 mgCP/kcal and without differences between the other two diets. The preliminary results found in the present study strongly suggest an effect of protein:energy ratio on the productive performance of Pacific white shrimp at low temperature.