Optimal substitution of black soldier fly larvae for fish in broiler chicken diets

Abstract

In pursuit of finding the optimum substitution level of black soldier fly larvae meal (BSFLM) as an alternative protein source for fish meal (FM) in broiler diets, the effect of partial or complete substitution on feed utilization efficiency, growth performance, carcass characteristics, meat quality and marginal economic benefits was assessed. 150 Cobb500 day old chicks were randomly allocated to five treatment diets in which graded levels of BSFLM substituted. FM; SD1 (control diet with only FM), SD2 (250), SD3 (500), SD4 (750), and SD5 (1000 g/kg DM), for 28 days. Subsequently, a conventional FM-based finisher diet was fed until day 42. Weight gain, feed intake and feed conversion ratio (FCR), were determined and the second derivative of the FCR regression function used to determine the optimal inclusion of BSFLM. Further, marginal analysis was used to evaluate the marginal economic benefit of including BSFLM. The response to increasing amounts of BSFLM in the diet followed a quadratic trend (P<0.05) with a reduction in feed intake, FCR and weight gain (P<0.05) occurring after 500 g/kg substitution and reaching the nadir at complete substitution. However, birds exhibited a compensatory growth when switched to fish-based finisher diet (day 28–42). No effect of substitution was observed on carcass parts except for a decrease in dressing percentage and an increase in visceral organ weights (P<0.05) at complete substitution. The optimal substitution based on FCR was calculated to be 540 g/kg. Proximate and fatty acid analysis of muscle indicated that Substitution of FM with BSFLM, reduced (p<0.05) protein and Omega 3 fatty acids. Additionally, increasing BSFLM in the diet up to 500 g/kg DM resulted in a 23% decrease in feed cost per bird and higher net marginal benefits. Therefore, replacement of FM with up to 540 g/kg BSFLM in starter diets, does not compromise growth and meat quality in broiler chickens.