Effect of Varied Levels of Lysine Supplemented with Phytase on the Growth, Nutrient Digestibility, Phosphorus and Nitrogen Load of all Male Nile Tilapia, Oreochromis Niloticus

Abstract

Abstract

Phytate can chelate amino acids in plant feedstuffs and with lysine being the first limiting amino acid in wheat meals that can replace fish meal in low cost and environmentally friendly fish feed production. The study evaluated the effects of different levels of lysine -1 (Lys-HCl) and a dose of phytase (0.2 g kg diet) in wheat meal-based diets on the production of all-male Nile tilapia. Six treatments (T1-T6) were used including, diet 1 the -1 control with no phytase supplement, and diets 2-6 supplemented with (0.2 gkg ) phytase; -1 -1 -1 -1 -1 2.96 g Lys kg ; 2.96 g Lys kg + (0.2 gkg ) phytase; 5.82 g Lys kg ; and 5.82 g Lys kg + -1 (0.2 gkg ) phytase, respectively. The diets were fed to the fish for 56 days. Fish grew well c c bc ab ab from the initial weight of 6.75g to weight gain of 25.1 , 27.4 , 32.3 , 35.2 , 37.4 and a 40.5 g in treatments 1-6, respectively, increasing the weight gain by between 73 and 84%. The trend showed increasing performance with increasing levels of dietary Lys. Treatments 4, 5 and 6 produced the same (P>0.05) growth performance which was higher (P<0.05) than the performance from fish in T1 and T2. Fish in T1, T2 and T3 had the same growth performance suggesting the availability of same levels of Lys. Lysine reduced P, N and ash loadings by between 6.23 and 19.6%; 7.1 and 7.6% and 5.93-30.2%, respectively. The study demonstrated that phytase liberated more Lys in the diets which improved fish growth performance and nutrient utilization; and that when Lys is sufficient in the diets, supplementation of phytase may not be necessary.