Testing two different phytases in Jatrophas carcas kernel meal based diets for Nile tilapia,Oreochromis nilticus
The current experiment tested Jatropha curcas kernel meal (JKM) as a foodstuff in terms of its effect on growth and body composition of Oreochromis niloticus, and further elucidated the efficacy of two phytases (3-phytase and 6-phytase), supplemented singly or in combination. Five diets were produced: a fishmeal based positive control diet (Diet FM), and 4 diets containing 100% protein from JKM. Of the four JKM-based diets, diet Natu containing 2000 U/kg of a 3-phytase; diet Rono containing 2000 U/kg of a 6-phytase; combined diet containing 1000 U/kg of each phytase, and a JKM diet containing no phytase which served as a negative control diet. Diet FM resulted in better body mass gain than all JKM-based diets, except for the combined diet (p = 0.05). JKM-based diets containing only one phytase (diet Rono or diet Natu), showed no growth improvement over the control diet without phytase. The combined diet resulted in significantly higher specific growth rates than the control diet (P=0.045). The combined diet also improved protein efficiency ratios suggesting better protein utilization in this diet, however these differences were not significant. All phytase-containing diets showed higher body dry matter and body ash values, presumably due to increased bone mineralization. In conclusion, JKM as the sole protein source produced lower performance than fishmeal. A single type of phytase had no impact, but applying two different types in combination showed improvement in growth parameters. Further research is required to confirm these results.