The effect of Cirina forda larva meal in rabbit diets on performance, carcass quality and nutrient digestibility

O I A Oluremi, M Bogbenda* and T P Mkah*

Department of Animal Nutrition
^*Department of Animal Production, College of Animal Science, University of Agriculture, P.M.B. 2373, Makurdi,Benue State. Nigeria
biyi1oluremi@yahoo.com

Abstract

A ten-week feeding trial was conducted to determine the nutritive potential of Cirina forda larva meal (CFLM) as an animal protein concentrate in rabbit feeding by evaluating growth response, carcass quality and nutrient digestibility. Twenty mixed breed weaner rabbits between 9-11 weeks of age were assigned randomly in groups of five to control diet (CD) and three other diets TD_2.5, TD_5.0 and TD_7.5 containing 2.5. 5.0 and 7.5% CFLM. Rabbit had unrestricted access to drinking water and their respective diets.

Diets had significant effects (p<0.01) on feed intake, water consumption and live body weight (LBW). The coefficient of nutrient digestibility, and carcass, visceral and offal indices did not have significant variations (p>0.05) except the forelimb (p<0.05). Rabbit became heavier as feed intake decreased at higher CFLM dietary inclusion, which is an indication of improved feed conversion.

The study has shown that CFLM can be used in compounding diets for grower rabbit at 7.5% level of inclusion.

Keywords: Carcass quality, Cirina forda larva meal, digestibility, performance, rabbit

Introduction

The inclusion of animal protein concentrate in livestock diets is more nutritionally beneficial than plant protein concentrates. This is because the animal protein is more complete than those of plant origins. The major normal protein sources in livestock feeding are meat, fish and their products, which have the capacity to promote better growth then other protein supplements. Nonetheless, they cost more then plant protein sources thus the preference for the later in diet formulation especially in developing countries. Consequently, some livestock species that normally respond to the quality and quantity of protein in their diets are being deprived of adequate access to these feeding stuffs.

The acceptability of rabbit as a farm animal worldwide due to its comparative advantage over other livestock species suggests that increase in its production can help to bridge the gap in the animal protein requirement for human consumption especially for developing countries. Although, rabbit makes efficient use of plant protein (Timon and Hamrahan 1985), amino acid composition of the protein has the greatest influence on its value when fed to it (Underwood 1981). This situation necessitates exploring the potentials of utilization some other animal protein sources that have not been vigorously researched as alternative feed resources in spite of their limited demand for direct human consumption. In Nigerian and the West Africa sub-region, Cirina forda larva has been reported by (Ande 1991; Odeyemi and Fasoranti 2000) as a feed resource highly associated with sheanut trees (Vitterlaria paradoxa) It is harvested, processed and utilized as food by some people in the areas where it thrives (Fasoranti and Ajiboye 1993). Ene (1963) noted that the eating of insects is fast disappearing among the educated and urbanized West Africans with the rapid improvement in education and living standards. The objective of this study is to determine the nutritive value of Cirina forda larva as an animal protein concentrate in rabbit feeding.

Materials and methods

The experiment was conducted at the Teaching and Research Farm of the University of Agriculture Makurdi with twenty crossbred rabbit between 9 and 11 weeks of age with live body weight (LBW) in the range of 520.0 to 530.0g. Each rabbit was individually caged in a rabbit hutch such that there were five replicates per treatment in a complete randomized design. The diets designated as CD, TD_2.5, TD_5.0 and TD_7.5 contained 0, 2.5, 5.0 and 7.5% Cirina forda larva by weight, respectively were compounded using dried Cirina forda larva with emptied gut. It was milled and thoroughly mixed with ground maize and full fat soybean and other feeding stuffs to obtain a homogenous mixture of each diets. The gross compositions of the experimental diets are shown in Table 1a.

Fresh portable drinking water and the experimental diets were served daily ad libitum to each rabbit for a total of ten weeks the feeding trial lasted. The feeders and drinkers used were firmly fastened to the cage floor to prevent them being tipped over by rabbit which will cause feed and water wastages that will result in overestimation of these indices thereby causing underestimation of rabbit performance. Water intake was deterrmined with the aid of a volumetric cylinder to measure water supplied and the residual amount. Fresh feed was provided and served twice daily to avoid provision of stale feed which can be unattractive to rabbits. The rabbits were individually weighed at the start of the trial and weekly thereafter to evaluate the effect of the diets on their growth rate. Feed conversion, and water:feed ratios were computed from the ratio of feed intake to body weight gain (BWG) data for the former and, water and feed intake for the later.

A digestibility trial that lasted for one week was conducted at the tenth week of the study with two rabbits per diet. Known quantities of feed and drinking water were provided for each rabbit daily and amounts consumed recorded. Corresponding daily faeces collection was done with perforated synthetic sheets tied under the floor of each cage capable of retaining only the faeces. Faeces were put in aluminum foil, weighed and oven-dried at about 105^°C. An oven-dried weight of each faecal output was taken before corresponding faeces were bulked and milled. Homogenous samples of dried faeces collected, experimental diets and Cirina forda larva meal were taken, put in air-tight bottles and analysed for their proximate nutrients using standard methods (AOAC 1990), in the Analytical Laboratory of the National Veterinary Research Institute, Vom, Nigeria.

Carcass evaluation of the experimental rabbits was at the point of terminating the feeding trial. Two rabbits per dietary group were fasted for 18hrs, weighed, slaughtered by cutting at the neck region with a sharp knife and thereafter held head down for good blood drainage. Slaughtered rabbits were weighed and dressed by skinning and evisceration. Carcass cuts, giblets, offal, skin and fur, head and tail were weighed. Dressing percentage was calculated as recommended by Fielding (1991). The data collected was subjected to the analysis of variance. Where significant differences (p<0.05) were obtained, the means of such parameters were separated by the least significant difference technique (Steel and Torrie 1980).

Results and discussion

The nutrient compositions of the experimental diets are presented in Table 1b.

The crude protein (CP) was adequate to meet the rabbit dietary requirement for this nutrient. With the exception of the control diet, the diets containing CFLM had CP higher than 12-18% level by NRC (1977). The dietary crude fibre (CF) was comparatively lower than 13% minimum recommended for rabbits (Cheeke 1986). The CFLM diets had a higher fat content than the control due to the high fat content of the larva meal (14.79%). High dietary fat is beneficial particularly in mash diets as it helps to aggregate diet particles thereby ensuring nutrient availability for rabbit. The ash content of the diets only showed marginal difference while nitrogen free extract (NFE) decreased as dietary CFLM increased. The processing method for the larva which involves empting the abdominal gut content which is mostly the digesta of the sheabutter (Vittelaria paradoxa) leaves may have partly accounted for this.

The performance data showing the response of the experimental rabbits is in Table 2.

The dietary effect on feed intake was significant (p<0.01). Rabbits in TD_2.5 group had the highest feed intake (41.9g DM/day). Dry matter feed intake decreased as the percent inclusion of CFLM increased to 7.5%. This can be related to the increase in dietary energy and protein of the diets as CFLM inclusion increased. Feed consumption has been reported to increase in other to compensate for the reduced energy density of such diets so as to meet the caloric requirement (Cheeke 1987). The effect of diet on the water consumption of rabbit was significant (p<0.01) and it followed the same sequence as feed intake. Rabbits in TD_2.5 group had significantly higher water consumption (175.49ml/day) than rabbits in the other dietary groups. With the exception of rabbits in the control, there was a tendency for them to consume less water with increasing dietary content of CFLM. It has been reported that water consumption by rabbit is closely associated to the amount and type of feed consumed (Shoremi et al 1998). The experimental diets affected live body weight of rabbits significantly (p<0.01) and the control group had a superior average of 1022.75g. it is however important to note that rabbits on CFLM diets became heavier as feed intake decreased at higher dietary CFLM which can be as a result of the binding effect of the dietary fat on the dietary particles thus encouraging availability of various feed constituents for rabbit utilization. This is a guide that CFLM may be nutritionally adequate to promote rabbit growth. The effect of diet on body weight gain (BWG) was not significant (p>0.05). This shows that the percentage dietary inclusion of CFLM may have been low consequently its effect as an animal protein source in rabbit diet formulation on BWG is not pronounced. The feed conversion ratios (FCR) among the dietary group were not significantly different (p>0.05). The values obtained were inferior to a FCR of 2.5 reported for weaner rabbit (Oyawoye 1989). Nevertheless, it was observed that feed conversion of rabbits improved the more the quantity of CFLM in the diet. It tended towards 3.45 recorded for the control. Cirina forda larva is among the insects that are an unusually good source of fat, having a high calorific value. With this, there in the possibility that rabbit diet at certain inclusion rates of CFLM higher than in the present study can stimulate a better feed conversion than the control diet. Good quality feeds have been found to give better rate of feed conversion (Dafwang 1987). The mortality data indicated the loss of 2 rabbits one each from the control and TD_5.0 groups. Although, post-mortem examination was not done but with the dietary groups affected it is difficult to link mortality to dietary effects.

The carcass parameters evaluated are in Table 3.

The effect of the experimental diets on carcass quality indices showed significant variation (p<0.05) only for the forelimb. Dressing percentage values were within 43.84-48.22 and with this close range, it seems in spite of the significant variation (p<0.01) in the live body weight of rabbit, meat available for consumption from the four treatment groups was comparable. The diet did not have significant effect (p>0.05) on any of the internal organs and offal's. The presence of CFLM in rabbit diet did not show any negative impact on the organs. These organs are vital components of the animal body needed for maintenance of good health and animal productivity. The digestibility coefficient of nutrients is presented in Table 4.

The coefficients were high in both the control and the CFLM based diets. Thus, the addition of CFLM did not impact negatively on the degree of utilization of the dietary nutrients in this study. The total digestible nutrients (TDN) data revealed a progressive increase in the caloric value of the diets containing CFLM. This may have been due to the relative high content of the larva meal making the diets palatable to rabbit.

Conclusion

• Rabbits fed diets containing  Cirina forda larva meal (CFLM) increased in body weight as its inclusion level increased from 2.5% to 7.5% in consonance with the FCR which improved remarkably as dietary CFLM increased.

• It can be deduced that CFLM, an animal protein source known for its high biological value, may have helped to improve the dietary quality of the test diets most especially at the 7.5% level.

• CFLM as a promising feed resource for rabbits

References

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Received 3 September 2005; Accepted 8 Februay 2006; Published 18 July 2006

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