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Both BSF pre-pupae and BSFL can be utilised as a feed ingredient in various animal’s diets, and has been researched extensively in fish but not as vastly in monogastric and other animals (Bondari & Sheppard, 1981, 1987; Newton et al., 2005a; St-Hilaire et al., 2007a; Sealey et al., 2011). Fly larvae, in general, has been tested as a potential renewable protein source for pigs, fish and poultry (Newton et al., 1977; Bondari & Sheppard, 1987; Awoniyi et al., 2003).

2.6.1 Pigs

The amino acid profile (Table 3) of BSFL is believed to be well suited for use in pig diets (Newton et al., 1977). Newton et al. (1977) found BSFL to be a suitable protein source in grower pig diets, and gave credit to the BSFL for its calcium and lipid contents. However, the same study found BSFL to be inferior in its supply of threonine, methionine and cysteine. In this study, the larvae meal was replacing soybean oilcake meal, and the BSFL digestibility was found to be significantly lower than a conventional soybean based diet. Even so, the pigs used in that study did not discriminate against the BSFL in terms of palatability. Newton et al. (2005b) later tried the BSFL in early-weaned piglet diets and substituted plasma by 50% with BSF pre-pupae. This study revealed a superior production performance (better feed efficiency and weight gains) by the BSFL treatment compared with the control diet.

Driemeyer (2016) found no significant differences on average litter live weight, feed intakes and feed conversion ratio (FCR) (P >0.05) when BSFL were supplemented into piglet creep diets at 3.5% inclusion. This study also concluded no immunological influence by BSFL inclusion.

2.6.2 Fish

Bondari & Sheppard (1981) evaluated the inclusion of BSFL into the diets of channel catfish and tilapia. No effect was found on the aroma and texture of the fish in this study and therefore was still acceptable to consumers. However, with regards to growth, Bondari & Sheppard (1987) tested a 10% BSFL substitution of fish meal and slowed growth rates were reported for caged channel catfish over a 15-week trial period. However, the diets used in this trial were not isonitrogenous or isoenergic and therefore the diets being compared were not providing equal nutrient levels. In contrast, Fasakin et al. (2003) found when defatted fly larvae was used, better overall performance was found than with full-fat fly larvae. No significant differences in growth were reported for rainbow trout given a diet with 50% BSF pre-pupae for a period of eight weeks, compared with the control diet (Sealey et al., 2011). This study also performed sensory analysis and no significant effect on fish fillet quality were found for BSF pre-pupae treatments, tested against a control. St-Hilaire et al. (2007a) also found the inclusion of BSFL into rainbow trout diets at 25% replacement of fish meal to have no effect on FCR or weight gain, this study did however have a low number of replicates and was performed over a short period of time. Similarly, juvenile turbot were reported to have accepted diets with 33% BSFL inclusion and no effects on feed intake and feed conversion were found (Kroeckel et al., 2012).

2.6.3 Poultry

Insects are included in the natural diet of wild birds and are consumed in their adult, pupal and larval forms in this way (Zuidhof et al., 2003). The feeding of BSFL to chickens is therefore not a completely original concept. Quail (Coturnix japonica) were fed a diet that included 50% BSFL and it was reported that this diet led to the quail having higher feed intakes and an improved FCR (Widjastuti et al., 2014) Agunbiade et al. (2007) studied maggot (species was left unspecified) meal as a replacement for fish meal in layer hens. Fish meal is not commonly used in layer hen diets as the trimethylamine (TMA) oxide is believed to cause a fishy taint in eggs (Pearson et al., 1983). Regardless, the maggot meal supplementation lead to no differences in egg quality (egg shape and weight, yolk index and colour and Haugh units) when compared with the control (Agunbiade et al., 2007). Soybean meal based diets were also well substituted by BSFL in the diets of layer hens with no metabolic or health stress consequence (Maurer et al., 2016).

Pretorius (2011) studied the common housefly larvae as a protein source for broiler chickens using isonitrogenous and isoenergic treatments. No significant differences were found between the housefly larvae and fish meal in productive performance. When soybean meal and housefly larvae were compared each at 10% inclusion, superior average live weights, cumulative and weekly feed intakes as well as average daily gains were found for the larvae treatment. Similar work was done by Hwangbo et al. (2009), where it was reported that the weight gain in broilers due to housefly larvae

inclusion was superior to that of chickens on a basal control diet. Adeniji (2007) reported equally successful results in housefly larvae substitution, however the control in this study made use of groundnut oilcake, which was replaced at various levels by the housefly larvae. It was concluded that the larvae could effectively replace groundnut oilcake in broiler diets with no significant differences in weight gain, FCR or nutrient retention.

In a study on the inclusion of BSF pre-pupae in broiler chicken diets, Uushona (2015) reported that the production parameters of broiler chicken and quality of meat produced were not negatively influenced by a 15% inclusion level. No adverse sensory affects were found in cooked chicken breast of broilers who consumed BSF pre-pupae in that study. It was also found that an increase in BSF pre- pupae inclusion lead to an increase in tibia bone calcium content, indicating a high bioavailability of calcium from BSF pre-pupae. It was also found in this study that defatted BSF pre-pupae had a higher nutrient digestibility compared to the full-fat BSF pre-pupae (Uushona, 2015). Unfortunately, this author did not evaluate the nutrient composition of the specific pre-pupae used in the nutrient digestibility study, which limits the possible in-depth comparisons.