Luận án tiến sĩ: Evaluation of Local Feed Resources for Hybrid Catfish (Clarias macrocephalus x C. gariepinus) in Smallholder Fish Farming Systems in Central Vietnam

The aim of this thesis was to examine the current feeding situation for fresh water fish in Central Vietnam, to evaluate the potential nutritive value of locally available feed resources for hybrid catfish (Clarias macrocephalus x C. gariepinus) and Nile tilapia, to determine the dietary requirement of lysine for hybrid catfish, to estimate the requirements for the other essential amino acids (EAA) by using ideal protein concept, and finally to evaluate the suitability of cassava leaf meal and shrimp head meal  as  a  partial  replacement  for  fish  meal  in  the  diet,  without  or  with  lysine supplementation, for hybrid catfish fingerlings.  

 

The survey indicated that, in total, 22 feed ingredients were used by the farmers. The main ingredients were cassava root meal, rice bran, cassava residue, groundnut meal,  soybean  meal  and  fish  meal.  Furthermore,  several  more unconventional feedstuffs were also commonly used, such as cassava leaves, coconut meal, shrimp head meal, sesame husk and squid by-product. The combination of ingredients used in  farm-made  fish  feeds  varied  among  farms  and  districts  leading  to  a  large variation of nutrient composition and energy content. The fish yield varied among districts and ranged from 0.8 to 6.5 t ha -1 . The digestibility trial showed that the apparent  digestibility  (AD)  of  dry  matter  (DM),  organic  matter  (OM)  and  crude protein (CP) in cassava leaf meal was significantly lower than in groundnut meal, soybean meal, sesame husk meal and shrimp head meal in both hybrid catfish and Nile  tilapia.  The  AD  of  DM  and  OM  in  cassava  leaf  meal was higher in hybrid catfish than in Nile tilapia. Most EAA in the selected feedstuffs were equally well utilized  by  the  two  fish  species.  In  the  third  experiment,  the  dietary  lysine requirement  of  hybrid  catfish  fingerlings  was  found  to  be  56  g  kg -1  of  CP, corresponding  to  16.8  g  kg -1   of dry diet. In the feeding trial with hybrid catfish, replacing fish meal with shrimp head meal had no effect on final weight (FW) and specific growth rate (SGR), while replacing fish meal with cassava leaf meal led to impaired  FW  and  SGR.  Supplementing  cassava  leaf  meal  and  shrimp  head  meal diets with lysine improved FW and SGR.