Growth performance, nutrient utilisation and body composition of Macrobrachium rosenbergii fed graded levels of phytic acid

Information relating to the effects of phytic acid (PA), an anti-nutritional factor (ANF) commonly found in plant protein ingredients, on the growth performance, feed conversion ratio (FCR), nutrient utilisation and whole proximate composition in the Malaysian giant freshwater prawn, Macrobrachium rosenbergii, is lacking. Replicate groups of M. rosenbergii (mean initial carapace length of 6.03 +/- 0.30 mm; mean initial weight of 0.29 +/- 0.02 g; n = 20 per replicate group) were fed graded levels of PA for 140 days. The basal diet, to which different levels of PA were added to obtain 0.26 (control), 6.48, 11.28, 16.53, 21.45 and 26.16 g PA kg(-1), contained fishmeal, soy protein concentrate and wheat meal. Terminal sampling indicated that the growth performance, FCR and survival did not differ significantly between the groups receiving the different inclusions of PA within their diets. The apparent protein, lipid and energy utilisation responded negatively, decreasing significantly (p < 0.05) with an increasing inclusion of PA, particularly within the groups of prawns fed diets with the highest inclusions of PA (i.e. 21.45-26.16 g PA kg(-1)). The whole body composition of protein (p < 0.04), lipid (p < 0.01) and gross energy (p < 0.05) also decreased significantly with an increasing supplementation of PA, while the ash content significantly increased (p < 0.01), most notably in the groups of prawns receiving the highest levels of dietary PA (26.16 g PA kg(-1)). In conclusion, inclusions of up to 11.28 g PA kg(-1) appear safe but levels above this have negative impacts. The results show that PA had significant effects on the nutrient utilisation and body compositions (p < 0.05) but not on growth performance and FCR (p > 0.05) on the M. rosenbergii reared under the experimental conditions that were employed here.