Microbial biomass (Novacq™) stimulates feeding and improves the growth performance on extruded low to zero-fishmeal diets in tilapia (GIFT strain)

Abstract

Worldwide tilapia production is rapidly growing and becoming increasingly reliant on the provision of cost-effective sustainable formulated feeds. We assessed the capacity for various inclusion rates of the microbial biomass-based ingredient Novacq™ (0%, 2.5%, 5%, 10%) at the expense of wheat flour to improve growth performance in diets at 10% fishmeal (FM), as well as the growth response at 5% and 0% FM, with or without the addition of 10% Novacq™ in iso‑nitrogenous (CP = 34.5–36.1%) extruded diets for GIFT tilapia fingerlings. A total of 540 fish (mean weight ± SD: 11.4 ± 1.8 g) were reared for 6 weeks on 8 experimental diets and a commercial benchmark diet (6 replicate tanks on each diet) in a recirculated freshwater system. All extruded diets containing Novacq™ outperformed the benchmark commercial diet. Total replacement of fishmeal (0% FM) with soybean meal resulted in a significant decrease of around 14.5% in daily weight gain (P < .05), but 50% replacement (5% FM) did not significantly affect weight gain (P > .05). Weight gain increased in parallel with increasing inclusion rates of Novacq™, with weight gains of 7.8%, 23.6% and 34.5% in relation to an isoenergetic and isonitrogenous control diet, at 2.5%, 5% and 10% Novacq™ inclusion, respectively. Novacq™ at 10% in diets containing 5% and 0% fishmeal also significantly increased the growth performance of tilapia, producing a net improvement in weight gain of 19.5% and 15.5% against the 10% fishmeal control diet, respectively. Feed intake mirrored the growth trends. A 10% inclusion of Novacq™ resulted in approximately 33% increase in feed intake at all levels of fishmeal inclusion. Daily feed intake measurements, similar FCRs (1.05–1.18) and nutrient retention efficiencies (Protein RE = 37–46%; Energy RE = 23–30%), indicated Novacq™ principally stimulated feeding with no adverse effect on nutrient use. The use of Novacq™ as a feed additive can more than compensate for the negative impact of fully eliminating fishmeal and is likely to improve the sustainability value of tilapia diets.