Food waste-based pellets for feeding grass carp (Ctenopharyngodon idellus): Adding baker's yeast and enzymes to enhance growth and immunity.

Protein rich food waste could be used as raw materials for making fish feed pellets, which would diminish the volume of dumped waste into landfills. This study investigated the use of food waste (FW) based pellets composing of 75% food wastes derived from plant materials (cereals, fruit and vegetables) supplemented with yeast and the mixture of bromelain and papain to feed grass carp (Ctenopharyngodon idellus). Generally, improved growth performance (in terms of feed conversion ratio, protein efficiency ratio and relative weight gain) was observed in the diet groups supplemented with yeast (Saccharomyces cerevisiae). The most optimal dose was 25 g/kg yeast with enzymes (bromelain and papain, at the ratio of 1:1) and protein utilization was enhanced. Fish immunity was also stimulated, which indicated by the higher nitroblue tetrazolium and bactericidal activities. Moreover, resistance against Aeromonas hydrophilia was enhanced. It is envisaged that food waste could be widely used as feeds for culturing herbivorous fish and adding supplements such as baker's yeast and enzymes will further enhance the feed conversion ratio and fish immunity.

Upgrading food wastes by means of bromelain and papain to enhance growth and immunity of grass carp (Ctenopharyngodon idella).

The fast growing of global aquaculture industry accompanied with increasing pressure on the supply and price of traditional feed materials (e.g., fish meal and soy bean meal). This circumstance has urged the need to search alternative sources of feed stuff. Food waste was used as feed stuff in rearing fish which possess substantial protein and lipid. Grass carp are major species reared in Hong Kong with lower nutritional requirements; it is also an ideal species for investigating the feasibility of using food waste as fish feeds for local aquaculture industry. The growth and immunity, reflected by total protein, total immunologlobulin (IgI), and nitroblue tetrazolium (NBT) activity of grass carp blood, were depressed when feeding with food waste feeds without enzymes. However, the supplementation of bromelain and papain in fish feed enhanced the efficient use of food waste by grass carp, which in turn improved the fish immunity. The present results indicated that the addition of those enzymes could enhance the feed utilization by fish and hematological parameters of grass carp, and the improvement on growth and immunity superior to the control (commercial feed) was observed with the addition of bromelain and papain supplement. Addition of 1 and 2 % mixture of bromelain and papain could significantly enhance the lipid utilization in grass carp.

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

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.

Use of soybean meal and papain to partially replace animal protein for culturing three marine fish species: Fish growth and water quality.

The main aim of this study was to investigate the feasibility of using soybean meal added with papain to replace half of the fishmeal used in the moist pellets (49% fishmeal and 45% trash fish) developed by the Hong Kong Agriculture, Fisheries and Conservation Department (AFCD) for culturing marine fish. Gold-lined seabream (Rhabdosargus sarba), brown spotted grouper (Epinephelus bleekeri) and pompano (Trachinotus blochii) were farmed at one of the research stations (Kat-O) of AFCD, for a period of 340 days. Results indicated that diets containing papain resulted in better fish growth (reflected by relative weight gain and feed conversion ratio) than diets without papain. In general, wet weight gain of fish depends on the amount of papain added in diet rather than the diet composition. Soybean used in conjunction with papain also contributed to a more effective growth than fish fed with the moist pellets alone. A laboratory experiment (using tanks) was conducted to study the effects of the diets on concentrations of ammonia, nitrite and nitrate in the tank water. Results showed that concentrations of ammonia and nitrate were significantly lower (p < 0.05) when the fish were fed with papain-supplemented (with or without soybean meal) diets. It is envisaged that by using plant protein incorporated with enzymes could promote better growth of marine fish and lower the adverse impact of trash fish and fishmeal on water quality of the mariculture zones.

[Effect of intraseptal noradrenaline on somatic and visceral pain threshold of rabbits].

With electric stimulation of the splanchnic nerve or the skin of the tip of rabbit's ear to measure visceral or somatic pain threshold, we studied the effects of noradrenaline microinjection into the septal nucleus on visceral pain and somatic pain and the relationship between the intraseptal noradrenaline and the intra-PAG opiate peptidergic system. There was no effect on visceral pain threshold after injections of alpha-agonist clonidine (10 micrograms/2 microliters) or alpha-antagonist phentolamine (10 micrograms/2 microliters). In a group injected with beta-agonist isoprenaline (1 micrograms/2 microliters), visceral pain threshold was raised remarkably, while beta-antagonist propranolol (10 micrograms/2 microliters) injected into bilateral septal nuclei decreased visceral pain threshold. Phentolamine (10 micrograms/2 microliters) or propranolol (10 micrograms/2 microliters) injected into septal nucleus induced an elevation of somatic pain threshold. The results indicate that the beta-receptor in spetal nucleus plays an important role in the modulation of visceral pain. Both alpha-and beta- adrenergic receptors have effects on the modulation of somatic pain. Intra-PAG microinjection of naloxone (1 micrograms/1 microliters) attenuated visceral analgesia produced by injection of isoprenaline (1 micrograms/2 microliters) into septal nucleus. Microinjection of anti-leu-enkephalin antiserum (1:20,000) into PAG also attenuated the analgesia. When microinjection of isoprenaline into septal nucleus produced analgesia, the release of leu-enkephalin immunoreactive-like-substance in PAG was significantly increased. The results suggest that the analgesic effect of intra-septal noradrenaline on visceral pain is somehow related with the endogenous opiate peptidergic system in PAG, and the leu-enkephalin in PAG plays an important role in this process.

Effect of combination of drugs with acupuncture on analgesic efficacy.

In rabbit experiments, some drugs used in clinics were selected and combined with electroacupuncture to observe the effect of drugs on acupuncture analgesia (AA). According to the effect of drugs on AA, the drugs were divided into three kinds: (1) Drugs with potentiating effect: fentanyl, pethidine, droperidol, perphenazine, metoclopramide, fenfluramine, tetrahydrocannabinol, fentanyl plus droperidol, fentanyl plus fenfluramine. (2) Drugs with reducing effect: ketamine and diazepam, (3) Drugs with no effect: sulpiride.

Synergism between metoclopramide and electroacupuncture analgesia.

Animal experiments revealed that the activity of the cholinergic system in certain brain areas enhanced acupuncture analgesia (AA) while that of the dopaminergic system attenuated it. Metoclopramide, having antidopamine and anticholinesterase actions, was found to be synergic with AA both in the laboratory and in the clinics. Patients having taken metoclopramide reported better analgesic effect during thyroidectomy under acupuncture anesthesia. The results suggest that metoclopramide can be used as an adjuvant to improve AA.

Effects of the modified Huanglian Jiedu decoction on the disease resistance in grey mullet (Mugil cephalus) to Lactococcus garvieae.

Lactococcosis is prevalent on grey mullet (Mugil cephalus) in Hong Kong aquaculture resulting in serious economic loss. A compound formulation of Traditional Chinese Medicines (TCM) (modified Huanglian Jiedu decoction (HLJDD)) comprising Rhizoma coptidis, Radix scutellaria, Cortex phellodendri, Fructus gardeniae, Fructus forsythiae and Flos lonicerae japonicae (in a ratio of 3:2:2:3:3:5) were applied as feed supplements to deal with the disease. The Nitroblue tetrazolium activity in blood, bactericidal activity and total immunoglobulin in plasma were significantly enhanced after feeding 1% of this TCM for 28 days. The disease resistances to Lactococcus garvieae in 1% and 2% TCM feeding groups were significantly enhanced. In the in vitro study, the modified HLJDD also activated the plasma bactericidal activities (p<0.01). Based on this study, 1% modified HLJDD feeding for 28 days may be an optimal dose to prevent L. garvieae infection and could be used in aquaculture industries.