Growth and reproduction of female Nile tilapia fed diets containing different levels of protein and energy

This study evaluated the effects of diets containing different levels of digestible protein (DP) and digestible energy (DE) on the growth and reproductive performance of female Nile tilapia. In this study, 567 females (weight, 95.2 ± 15.6 g) and 189 males (weight, 168.8 ± 37.7 g) of the Thai-Chitralata lineage were housed in 27 hapa pens (21 females:7 males per hapa pen). The experiment was conducted in a randomized block design using a 3 × 3 factorial structure. For 260 days, the tilapia were fed nine different diets containing combinations of 280, 340, and 400 g kg− 1 DP and 11.72, 14.23, and 16.74 MJ kg− 1 DE. The absolute fecundity of females was not altered (P > 0.05) by the different diets. On the other hand, only DE levels had an inversely proportional effect (P < 0.05) on the number of eggs produced per gram of body weight of mated females, which indicated a greater relative fecundity when females were fed diets containing the lowest level of DE. The levels of DP and DE in the diets independently affected egg weight and the weight of the larvae after hatching, with an inversely proportional linear relationship (P < 0.05) with DP levels and a directly proportional relationship (P < 0.05) with DE levels. Thus, heavier eggs and larvae were produced with diets containing lower DP content and higher DE level. The levels of DP and DE in the diets had an interactive effect (P < 0.05) on the weight and standard length of the females, with better growth resulting from diets containing the highest levels of DE and DP. Specific growth (SG) and viscerosomatic index (VSI) only experienced a quadratic effect from DE. Regardless of protein levels, the greatest SG was obtained with diets containing 15.23 MJ kg− 1 DE (calculated value), and the greatest VSI values resulted from diets containing the highest level of DE. The condition factor, apparent feed conversion, survival, and gonadosomatic and hepatosomatic indexes of the females were not influenced (P > 0.05) by the diets. We concluded that feeding reproductively active female Nile tilapia diets containing lower amounts of DP and DE ensures egg production at the expense of somatic growth. Furthermore, diets with 280 g kg− 1 DP and 16.74 MJ kg− 1 DE are recommended because the lower egg productivity may be offset by the production of more vigorous offspring that have greater chances of survival.