Effect of replacing fish meal with house cricket Acheta domesticus meal in the diet of growing rabbits on feed intake, digestibility and N retention

Vo Lam^1,2, Truong Thanh Nha^1,2 and Bui Phan Thu Hang^1,2

¹ An Giang University, An Giang Province, Vietnam
² Vietnam National University, Ho Chi Minh City, Vietnam
bpthang.agu@gmail.com

Abstract

Thirty male crossbred rabbits (New Zealand White x local female), at 10 weeks of age and with initial live weight of 1,139 ± 140 g (Mean ± SD) were housed in individual cages to evaluate the impact of substituting fish meal with Acheta domesticus meal in the diets of growing rabbits, focusing on feed intake, nutrient digestibility, and nitrogen retention. The protein content of the fish meal in the control diet was substituted by 25%, 50%, 75% and 100% by cricket meal.

The results indicated that both nutrient intake and nutrient digestibility were improved in diets containing house cricket meal. The inclusion of cricket meal had a positive effect on nitrogen retention and nitrogen retention efficiency (expressed as a percentage of nitrogen intake). Nitrogen retention increased from 29% to 35% when more than 50% of the fish meal protein was replaced by cricket meal. Notably, complete replacement of fish meal with cricket meal resulted in the highest values of both nitrogen retention and retention efficiency. These findings suggest that house cricket meal represents a promising and sustainable alternative protein source to replace fish meal in the diets of growing rabbits.

Key words: cricket meal, crossbred rabbit, fish meal, substitute

Introduction

The increasing global demand for sustainable animal protein sources has intensified the search for alternative feed ingredients that are both nutritionally adequate and environmentally friendly. Fish meal, traditionally used as a high-quality protein source in animal diets (Samples 2014; Hicks et al 2019), faces challenges related to overfishing, fluctuating availability, and rising costs (Turchini et al 2019; Kowalska et al 2021), prompting the exploration of viable substitutes. Insects have emerged as promising alternative protein sources due to their high nutritional value, efficient feed conversion, and lower environmental impact (Bui Phan Thu Hang et al 2020 and 2022; Nguyen Thiet et al 2022; Vo lam et al 2022). Among them, the house cricket (Acheta domesticus) stands out for its favorable amino acid profile and digestibility (Volek et al 2023). Previous studies have demonstrated that incorporating A. domesticus meal into rabbit diets does not adversely affect growth performance, suggesting its potential as a sustainable protein source (Volek et al 2023; Bui Phan Thu Hang et al 2023). However, while the inclusion of insect meals like silkworm pupae has been investigated, results indicate that higher inclusion levels may negatively impact nutrient digestibility and nitrogen retention in rabbits (Gugolek et al 2022).

Therefore, it is essential to assess the effects of replacing fish meal with house cricket meal on feed intake, nutrient digestibility, and nitrogen retention in growing rabbits to determine optimal inclusion levels.

Materials and methods

Location and experimental design

The study was conducted on in a private farm in Thoai Son district, Long Xuyen city, An Giang province. Thirty male crossbred rabbits (New Zealand White x local female), at 10 weeks of age and with initial live weight of 1,139 ± 140 g (Mean ± SD) were housed in individual cages. The rabbits were fed diets composed of homemade concentrate pellet (CP=18.2%) and water spinach (Ipomoea aquatica) given ad libitum,in which fish meal was replaced with cricket meal at 0, 25, 50, 75, or 100% based as protein of fish meal (Table 1). The experiment was a complete randomized design with 6 replications. The trial lasted 21 days consisting of 14 days of adaptation and 7 days of collection of faeces and urine.

Feeds, animals and management

The New Zealand crossbred rabbits were dewormed using Ivermectin and vaccinated against rabbit hemorrhagic disease. They were fed a homemade pelleted diet provided in individual feeders, while water spinach (Ipomoea aquatica) was offered as fresh forage, suspended in bunches above the feed troughs. Forage was supplied in two equal portions, with 50% administered at 08:00 and the remaining 50% at 14:00. Fresh drinking water was available ad libitum throughout the experimental period.

Chemical analysis

The DM, CP and ash contents were determined according to AOAC (2005). The CP content of feedstuffs, refusals, fresh faeces, and urine were analysed using the Kjeldahl method.

Statistical analysis

Experimental data were analyzed using analysis of variance (ANOVA) via the General Linear Model (GLM) procedure in Minitab Software, Release Version 17 (2013), with treatment and error defined as the primary sources of variation. Polynomial regression models were applied to assess changes in nitrogen retention, utilizing the Excel function in Microsoft Office software.

Results and discussion

Fish meal and cricket meal composition

Although fish meal contained slightly higher levels of crude protein compared to cricket meal, the latter was richer in dry matter (DM), crude fiber (CF), and organic matter (OM) (Table 2).

Feed intake, live weight gain and feed conversion

Nutrient intake was not affected (p>0.05) by increasing levels of fish meal replacement with cricket meal in the diet (Table 3).

Diets containing house cricket meal resulted in higher digestibility coefficients of dry matter, organic matter, and crude protein compared to diets without cricket meal (Table 4). This improvement may be attributed not only to the protein and balanced amino acid profile provided by cricket meal, but also to its richness in lipids, including long-chain unsaturated fatty acids and essential fatty acids such as linoleic acid and α-linolenic acid (van Huis et al., 2013). Additionally, the higher fiber and organic matter content in cricket meal may contribute to enhanced gut health and improved nutrient digestibility in rabbits (Gidenne 2003; Shah et al 2022; Volek et al 2023).

Nitrogen intake ranged from 1.93 to 2.08 g/rabbitl/day and exhibited an increasing trend with higher levels of fish meal protein replacement by house cricket meal protein. Conversely, urinary and fecal nitrogen excretion showed a slight decreasing trend as the proportion of house cricket meal protein in the diet increased (Table 5).

The proportion of nitrogen retained as a percentage of nitrogen intake exhibited a positive linear relationship with the level of fish meal protein replacement by house cricket meal in the diets of the experimental rabbits (R² = 0.87; Figure 1). This indicates that nitrogen retention efficiency (% of nitrogen intake) tended to increase as the proportion of house cricket meal protein in the diet increased (Table 5; Figure 1). Similar studies have also been conducted on poultry, fish, and rabbit, demonstrating that insect meal, particularly cricket meal, can effectively replace conventional protein sources such as fish meal without adversely affecting growth performance or nutrient utilization (Tran et al 2015; Józefiak 2016; Bui Phan Thu Hang et al 2023)

Figure 1. Curvilinear trend in N retention/%N intake as cricket meal replaced fish meal in the diet of growing rabbits

Conclusions

• Increasing the level of fish meal protein replacement with house cricket meal in the diets of rabbits improved nutrient intake and digestibility.
  
  
• The cricket meal affected positively on nitrogen retention and nitrogen retention efficiency (% of nitrogen intake). Nitrogen retention was improved from 29-35% when diets had more 50% fish meal replacement by cricket meal. The cricket meal could substitute fish meal by 100% with highest nitrogen retention and nitrogen retention efficiency. Therefore, cricket meal is a promising alternative to unsustainable fish meal in growing rabbit diets.

Acknowledgements

The authors express their sincere gratitude to the smallholder rabbit farm in Thoai Son District, Long Xuyen City, An Giang Province, for providing infrastructure support essential to the completion of this research. Appreciation is also extended to the group of students from the Department of Animal Science and Veterinary Medicine for their valuable technical assistance.

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