Eubiotic effect of a dietary potassium diformate (KDF) and probiotic (Lactobacillus acidophilus) on growth, hemato-biochemical indices, antioxidant status and intestinal functional topography of cultured Nile tilapia Oreochromis niloticus fed diet free fishmeal

An 84 days experimental trial was undertaken to examine the influence of potassium diformate (KDF) and Lactobacillus acidophilus and their interaction on growth, biochemical of blood parameters, enzymes of antioxidant response and intestinal topography of Nile tilapia, Oreochromis niloticus, fingerlings fed fishmeal free diets. Six functional diets were formulated to contain two levels of L. acidophilus (0, 1.47 x 10(7) CFU kg(-1)), with each level being supplemented with 0, 5 g and 10 g KDF kg(-1) diet, respectively. Fingerlings O. niloticus (n = 540; initial weight 4.29 +/- 0.06 g) were randomly allocated into six groups (30 fish group(-1) in triplicates). The results showed that the best values of growth, feed efficiency and biological parameters were recorded by fish fed diets containing 1.47 x 10(7 )L. acidophilus CFU kg(-1) and 10 g kg(-1) KDF. Lower pH values in stomach and gut were noted in fish fed diet supplemented with 1.47 x 10(7) L. acidophilus CFU kg(-1 )and 10 g kg(-1) KDF. Diets supplemented with L. acidophilus, KDF or in combination improved the hemoglobin, red blood cells and white blood cells count with insignificant differences among groups. The activities of serum alanine and aspartate aminotransferase decreased significantly (P < 0.05) by the addition of L. acidophilus and KDF in fish diets. Furthermore, addition of KDF and L. acidophilus significantly (P < 0.05) improved the serum total protein and albumin, but globulin not affected. The lowest value of uric acid was recorded in fish fed 5 g kg(-1) KDF without addition of L. acidophilus, while there were no significant (P > 0.05) differences in creatinine content were found among treatments. Diets supplemented with L. acidophilus and/or KDF significantly (P < 0.05) improved phosphorus and calcium content. However, the activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC) and catalase (CAT) were highest in fish fed diet contained either 5 g or 10 g kg(-1) KDF and 1.47 x 10(7) L. acidophilus CFU kg(-1) (D4 and D6). Villi length and width in the middle intestine and number of goblet cell were shown to be promoted in fish fed diets 10 g KDF kg(-1) or 10 g kg(-1) KDF and 1.47 x 10(7) L. acidophilus CFU kg(-1) diet. In conclusion, the administration of a mixture of a probiotic and KDF is beneficial, as it effectively improves the gut morphology and the total antioxidant enzyme activity resulting in an overall enhancement of the fish growth performance.