Open AccessEffect of 17 α ‐Methyltestosterone Treatment and Withdrawal on Growth and Dietary Protein Utilization of Juvenile Rainbow Trout Fed Practical Diets Varying in Protein Level 1, 2
Author(s) -
Ostrowski Anthony C.,
Garling Donald L.
Publication year - 1987
Publication title -
journal of the world aquaculture society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 60
eISSN - 1749-7345
pISSN - 0893-8849
DOI - 10.1111/j.1749-7345.1987.tb00420.x
Subject(s) - methyltestosterone , biology , zoology , rainbow trout , feed conversion ratio , hormone , fish oil , medicine , fish meal , endocrinology , weight gain , trout , juvenile , fish <actinopterygii> , body weight , fishery , ecology
The effects of 17 α ‐methyltestosterone (MT) treatment and withdrawal on relative daily gain (RDG), protein gain (PG), productive protein value (PPV), and maximum efficient protein gain (MEPG) of juvenile rainbow trout fed practical diets varying in protein to metabolizable energy (P:ME) ratio were examined over an 18 week period. Two commercially available practical feeds with additions of dextrin and codliver oil were used to formulate diets containing 48% and 32% protein at approximately 320 kcal ME/100 grams with and without 2.0 mg MT/kg of dry diet. MT treated fish were fed hormone supplemented diets for 10 weeks (Phase 1) and hormone free diets for the final eight weeks (Phase 2) of the experiment. Control fish were fed hormone free diets for 18 weeks. MT treatment increased all growth and efficiency factors of fish during Phase 1. The increase in MEPG values due to MT treatment was more pronounced for fish fed the diet containing 48% protein than for fish fed the diet containing 32% protein. Hormone withdrawal reduced growth and efficiency values of fish to below the level of controls during Phase 2. Greater declines occurred for MT treated fish fed the diet containing 32% protein. No difference was observed between final mean RDC, PG, and MEPG values of fish initially fed MT and control fish calculated for the entire 18 weeks. Hormone withdrawal negated MT stimulated increases in empty carcass (EC) fat and whole body (WB) protein and decreases in EC and WB water contents that occurred in Phase 1. EC ash content was increased due to MT treatment and remained high through the period of withdrawal.