Citation of this paper

Effect of fresh foliage leaves on biomass growth of crickets fed rice bran as the basal diet

Bui Phan Thu Hang^1,2, Nguyen Van Cop³, Dao Thi My Tien^1,2 and Vo Lam^1,2

¹ Department of Animal Sciences and Veterinary Medicine, An Giang University
bpthang.agu@gmail.com
² Vietnam National University Ho Chi Minh City, Vietnam
³ Long Xuyen Veterinary Station, An Giang Animal Husbandry and Veterinary Sub-Department

Abstract

Seven thousand and two hundred crickets (Gryllus bimaculatus) with a mean initial weight of 11.2±1.1 mg/cricket and an age of 1 week were housed in cages (300 per cage) and offered a basal diet of rice bran alone, or supplemented with leaves of sweet cassava (Manihot esculenta Crantz), water spinach (Ipomoea aquatica) or Coccinia grandis L. The design was a randomized block with 4 treatments (sources of leaves) and 6 replications (300 crickets per treatment/replicate).

Over a period of 5 weeks, the total biomass yield of crickets was increased by 20-131% when they had free access to fresh leaves as well as rice bran. When cassava leaves were offered as supplements they were consumed in higher quantities, as compared with water spinach and Coccinia grandis L leaves. There were dramatically benefits in biomass growth of the crickets as supplemented cassava and Coccinia grandis L leaves compared with access to rice bran alone.

Key words: cassava leaves, fresh foliage, rice bran, weight

Introduction

Rice (Oryza sativa) is the most important food for the world's human population. Rice bran is a by-product of rice milling industry with a global potential of 29.3 million tons annually. Rice bran is rich in nutrients, easy availability, low cost and high antioxidant potential (Muhammad et al 2017). Rice bran protein has shown good nutritional and biological values (Na et al 2021). In developing countries, rice bran is considered as a by-product of the milling process and commonly used in animal feed or discarded as a waste (Mian et al 2014).

Edible insects have been growing in and around South East Asia. They have great potential as highly nutritious, environmentally friendly, and economically feasible alternatives for the food industry in the future (Van Huis et al 2013). Insects as food are more sustainable compared with traditional livestock, in particular considering land use and global warming potential (Belluco et al 2013). In addition, many edible insect species have the potential to use a wide variety of plant material, such as food waste or by-products from agriculture and food industry (Van Huis and Losasso 2017).

The aim of this research was to evaluate fresh biomass yield and growth of crickets (Gryllus bimaculatus) fed cassava leaves, water spinach and Coccinia grandis L as supplements to rice bran. The hypothesis was that fresh leaves have potential to be used as cricket feed.

Materials and Methods

Location and source of crickets

The research was carried out a private farm located in Long Xuyen city, An Giang province, Vietnam. The crickets (n =7200; age 1 week) were sourced from a rearing unit in An Giang University.

Experimental design

The crickets were fed rice bran as a basal diet and three experimental diets in which the basal diet was supplemented with free access to only the leaves from sweet cassava, water spinach or Coccinia grandis L without the petiole and stems (Photo 2, 3 and 4). The allocation to treatments was according to a Completely Block Randomized Design with 6 replications (each treatment/replicate had 300 crickets). The experiment lasted for 5 weeks.

Feeds, animals and management

Rice bran was bought from the local market and offered ad libitum on plastic plates. Cassava leaves, water spinach and Coccinia grandis L. were harvested in the fields around Long Xuyen city and also offered ad libitum, but laid in the bottom of cages. The crickets were offered feed in the morning.

Seven thousand, two hundred crickets (Gryllus bimaculatus) at one week old were sourced from a rearing unit in An Giang University. They were housed in groups of 300 crickets in plastic mesh cages (50x30x20 cm) in which conventional cardboard egg holders (width 30cm, length 50 cm, height 10 cm) were placed to provide hiding and moulting places for the crickets. The crickets in each cage were weighed together at the start of the experiment and then after every week, before feeding in the morning, using an electronic scale. The amounts of feed offered and refused were recorded. Feed conversion ratio (FCR) was calculated by dividing the total feed DM consumption by the total weight gain.


Photo 1. Leaves, flowers and fruits of Coccinia grandis L.


Photo 2. Cassava leaves	Photo 3. Water spinach leaves	Photo 4. Coccinia leaves

Chemical analysis

Samples of feeds (rice bran, only the leaves from cassava, water spinach and Coccinia grandis) offered and refused were analysed for DM, CP, CF, EE and ash according to AOAC (1990).

Statistical analysis

The data from the experiment were subjected to analysis of variance using the General Linear Model (GLM) procedure of Minitab Software Release version 17 (2013). Sources of variation were treatments and error.

Results and discussion

The DM and CP contents of Coccinia grandis L. were similar to those in water spinach, but OM components were lower. The highest CP and OM content were observed in cassava leaves. And all the leaves were richer in crude protein and crude fiber than the rice bran (Table 1).

Table 1. Mean values for chemical composition of the feeds, %
Item	DM, %	% of DM
Item	DM, %	CP	CF	EE	OM

Rice bran	85.8	13.6	6.15	18.9	92.2
Coccinia grandis leaves	12.4	26.2	12.5	5.19	78.0
Cassava leaves	27.2	31.4	12.8	7.02	94.6
Water spinach leaves	15.4	27.0	8.59	3.69	88.5

Supplementation with all sources of leaves led to increases in the daily intake of crude protein and crude fiber. The intake of leaves was higher when these were sourced from cassava compared with water spinach or Coccinia grandis L. (Table 2).

Table 2. Feed intake during the experiment
Treatment	DM intake, mg/cricket/d			Intake, mg/cricket/d
Treatment	Rice bran	Leaves	Total	CP	CF	EE	OM

Rice bran	32.3^ab	0^d	32.3^b	4.19^d	1.83^b	7.52^a	97.7^a
Cassava leaves	27.6^bc	18.1^a	45.8^a	9.47^a	3.75^a	7.38^ab	97.0^b
Coccinia grandis L.	35.2^a	10.2^b	45.3^a	7.36^b	3.28^a	7.91^a	95.1^c
Water spinach	25.4^c	8.09^c	33.5^b	5.50^c	2.10^b	6.32^b	97.2^ab
SEM	1.60	0.50	1.90	0.32	0.15	0.30	0.17
p	0.001	<0.01	<0.01	<0.01	0.008	<0.01	<0.01
^abcd Means within columns with different superscripts are different at P<0.05

The total biomass of the crickets was increased by 131% when they had access to fresh cassava leaves as well as rice bran (Table 3). There were significantlly benefits in biomass growth when rice bran was supplemented with leaves from cassava or Coccinia grandis. Weight gain was lower in crickets fed rice bran alone compared with those fed rice bran with supplemented cassava leaves or Coccinia grandis L. (Figure 1)

Table 3. Mean values for increase in total biomass, daily weight gain and feed conversion of crickets fed rice bran alone or supplemented with fresh leaves of cassava, water spinach or Coccinia for 5 weeks.
Treatment	Gain in biomass, g	Initial weight, mg/cricket	Final weight, mg/cricket	ADG, mg/cricket/d	FCR

Rice bran	67^c	11.6	662^b	16.0^b	2.06^a
Cassava leaves	155^a	10.4	945^a	28.3^a	1.61^b
Coccinia grandis L.	129^b	11.6	861^a	25.7^a	1.76^ab
Water spinach	81^c	11.0	704^b	17.8^b	1.89^ab
SEM	5.17	0.4	30.0	0.98	0.08
p	<0.01	0.13	<0.01	<0.01	0.006
^abc Means within columns with different superscripts are different at p<0.05

Figure 1. Effect on growth rate of crickets having ss to fresh leaves as well as rice bran

Conclusions

Over a period of 5 weeks, the total biomass yield of crickets was increased by 20-131% when they had free access to fresh leaves as well as rice bran.
When cassava leaves were offered as supplements they were consumed in higher quantities, as compared with water spinach and Coccinia grandis L leaves. There were dramatically benefits in biomass growth of the crickets as supplemented cassava and Coccinia grandis L leaves compared with access to rice bran alone.

Acknowledgements

The authors are grateful for the financial for this research from An Giang University, Vietnam National University-Ho Chi Minh. The authors would also like to thank the Department of Animal Husbandry and Veterinary, Faculty of Agriculture and Natural Resources of An Giang University for infrastructure support.

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