The use of food wastes as feed ingredients for culturing grass carp (Ctenopharyngodon idellus) in Hong Kong

Abstract

Different types of food wastes, e.g., meats, bones, cereals, fruits, and vegetables, were collected from hotels in Hong Kong, mixed in different ratio, and processed into feed pellets (food wastes (FWs) A, B, and C) for feeding trials in aquaculture species. Grass carp fed with cereal-dominant feed (FW A) showed the best growth (in terms of specific growth rate, relative weight gain, and protein efficiency ratio), among all food waste feeds. However, the growth rates of food waste groups especially the meat product-contained feeds (FW B and FW C) were lower than the commercial feed, Jinfeng(®) 613 formulation (control). The results indicated that grass carp utilized plant proteins better than animal proteins and preferred carbohydrate as a major energy source than lipid. The high-lipid content in feed containing meat products was also a possible reason for hindering growth and resulted high body lipid. It is suggested that lipid should be removed in the preparation of food waste feed or further investigations by implementing supplements, e.g., enzymes in feed to enhance lipid or protein utilization by fish. This utilization of food waste could be an effective and practical way to deal with these wastes in this densely populated city.

The use of bromelain as a feed additive in fish diets: Growth performance, intestinal morphology, digestive enzyme and immune response of juvenile Sterlet (Acipenser ruthenus)

“…To the best of our knowledge, very few studies report on the positive effects of the exogenous dietary enzyme bromelain on growth performance and feed utilization in fish. The addition of a 1% or 2% mixture of bromelain and papain significantly increased the SGR, PER and apparent net protein utilization of grass carp and grey mullet (Choi, Lam, Mo, & Wong, ). In a study on shrimp, Divakaran and Velasco () found that the apparent digestibility of crude protein was significantly higher (74.3%) in Pacific white shrimp, Litopenaeus vannamei , fed a 0.4% ENZECO ® bromelain diet than those fed the control diet (65.3%).…”

“…Furthermore, total serum protein in fish is responsible for the innate immune response, and higher levels of this provide stronger responses (Sahu, Das, Mishra, Pradhan, & Sarangi, ). In this context, Choi et al () reports that levels of plasma total protein and total immunoglobulin (IgI) in common carp and mullet fed diets supplemented with a 2% of mixture of bromelain and papain were significantly higher than that in fish fed control diets. It can be concluded from this study that the use of bromelain at level of 10 or 20 g/kg could improve the growth performance, feed utilization, non‐specific humoral and cell‐mediated immunity of Sterlet.…”

Recycle food wastes into high quality fish feeds for safe and quality fish production

“…Only a small portion of farmers uses commercial feed pellets as regular feeds, due to their higher costs. Table 2 shows the categories of different food wastes, including cooked and non-cooked items produced from hotels in Hong Kong (Choi et al, 2016). It is envisaged that the major problem of utilizing food wastes to formulate feed pellets would be the diverse range of food wastes generated from different sources, e.g.…”

“…Our early laboratory experiment showed that the food waste based pellets resulted in lower growth rates of grass carp and grey mullet, when compared with the control, which fed a commercial diet: Jinfeng 613 formulated feed (with about 30% protein), containing wheat middling, flour, bean pulp, rapeseed meal, fish meal, bean oil and fish oil (Choi et al, 2016). It was also observed that Food Waste B and C (FWB and FWC) containing meat would be less suitable than FWA or Jinfeng 613 for rearing grey mullet (omnivore) and grass carp (herbivore), as they prefer plant protein rather than animal protein.…”

“…Inclusion of fruit processing residues involving papaya or pineapple, into making food waste pellets, may be a good idea to cut down the cost. Table 3 Food waste based feed pellets (containing 75% food wastes) for rearing grey mullet and grass carp Choi et al, 2016 In order to increase the nutritional qualities of animal feeds especially vegetable-based diets, adding minerals and vitamins is a common practice in animal husbandry (Deyhim et al, 1995). For fish culture, it has been shown that inclusion of vitamin-mineral premix in the feed for broadhead catfish (Clarias macrocephalus) fry enhanced the survival rate and weight gain, compared to those without inclusion (Taechajanta and Sitasit, 1981).…”