Abstract
In literature, the variability in the estimated optimal digestible protein to digestible energy ratio (DP/DE) is high. The present study aimed to estimate the optimal DP/DE ratio in Nile tilapia (Oreochromis niloticus) using different criteria (performance, energy and nitrogen balances parameters). Duplicate aquaria were randomly assigned to one of 16 diets. These diets covered a wide range of dietary DP/DE ratio (from 16.7 to 27 g MJ −1 ). DP levels ranged between 36 and 50% and DE levels between 17.5 and 22 MJ kg −1 . Fish were fed restrictively based on a similar digestible protein amount at all 16 diets. Initial fish weight was 6.7 g. Broken line analysis showed that no optimal DP/DE ratio was present for Nile tilapia within the DP/DE ratio range studied. Regression analysis showed that growth declined as DP/DE ratio increased and seemed to level off at high DP/DE ratio (25 g MJ −1 ). FCR ranged between 0.8 and 1.1 and increased linearly with increasing DP/DE ratio. Decreasing the DP/DE ratio resulted in a linear increase in protein efficiency to a highest value of 53%. However, protein efficiency did not show a plateau or a maximum value. Moreover, decreasing the DP/DE ratio resulted in a very high fat content of the fish (over 16%). In conclusion, an optimal DP/DE ratio in Nile tilapia being fed restrictively seems to be absent or to be below 16 g MJ −1 . A maximum protein deposition level is not present in 5–40 g Nile tilapia.
Original language | English |
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Pages (from-to) | 28-35 |
Journal | Aquaculture |
Volume | 489 |
DOIs | |
Publication status | Published - 20 Mar 2018 |
Keywords
- Digestible energy
- Digestible protein
- Energy utilization
- Feed evaluation
- Protein efficiency
- Protein/Energy ratio