Impact of graded levels of cassava peels meal as a replacement for maize on growth performance and nutrient digestibility in weaner rabbits

Udeh F U, Ezenwosu C and Onyimonyi A E

Department of Animal Science, University of Nigeria, Nsukka, Nigeria
celestine.ezenwosu@unn.edu.ng

Abstract

Impact of graded levels of cassava peels meal as a replacement for maize on growth performance and apparent nutrient digestibility in weaner rabbits were investigated. A total of 30 8-weeks crosses of New Zealand White x Chinchila weaner rabbits consisting of 15 males and 15 females weighing 590-680g were randomly allotted to 5 dietary treatments in a completely randomized experimental design with 3 replicates of 2 rabbits each. Treatments were 5 experimental diets (CapmL-0, CapmL-5 CapmL-10, CapmL-20 and CapmL-30) replacing 15, 30, 60 and 100% maize in the diets respectively. Results showed that rabbits on cassava peels meal had higher growth performance and percentage nutrient digestibility compared to control groups. It was also observed that total feed cost reduced as the level of the cassava peels meal increased in the diets. The highest relative cost advantage observed in treatment groups was as a result of the lower cost of cassava peels compared to maize in the diets. In conclusion, cassava peels meal can be used to replace 100% maize in diets of rabbits by rabbit producers.

Keywords: cassava peels meal, weaner rabbits, growth performance, nutrient digestibility

Introduction

Food and Agriculture Organization (FAO) recommended that 35g out of the required minimum of 65-72g of reference protein should be gotten from animal products. This is why attention is now being moved to rabbit production in order to make more quality protein available for human consumption. Clearly, rabbits hold outstanding potentials that can be exploited to solve the shortage of premium animal protein in most developing countries like Nigeria. In developing countries, rabbits are outstanding and economical producer animals for protein to cover the ever-increasing human needs (Nehad et al. 2009). Rabbit is characterized by long ears, long hind legs, soft fur and a cottony tail. Rabbit is an animal whose potentials can be tapped because of its obvious advantages over other species of farm animals. Rabbits have high reproductive potentials, ability to utilize forage and it requires low initial capital investment, less space per unit number and absence of cultural biases or religious hindrance to its consumption (NRC, 1991). Under production conditions, 20% of the feed protein consumed by rabbit is retained in the form of edible meat (Lebas, 1983).

However, in Nigeria and other developing countries, high cost and scarcity of feed ingredients has turned to be a serious hindrance to farm animal production including rabbits. The conventional feed ingredients, particularly the energy sources used in animal production such as Maize, millet, sorghum are very expensive. However, feeding accounts for approximately 70% of production costs in animal raising systems. The majority of feed types used in animal nutrition are based on ingredients such as corn and soybeans, which compete directly with human feeding and have high market costs (Silva et al 2000).

However, to make rabbit production more sustainable, there must be a solid promotion for the development of alternative feeding ingredients that would be relatively cheaper when juxtaposed with conventional feed stuffs. One of such cheaper feed stuffs that can serve as an alternative for scarce and costly convectional feed stuffs such as maize that is used in animal production is cassava peels meal. Therefore, partial or complete replacement of maize with low cost cassava peels meal would be a cost-saving step in the right direction.

Cassava peels meal offer a tremendous potential as a cheap and alternative feed stuff to maize. Cassava peel is one of such by-product emanating from industrial processing of cassava into garri, chips and industrial starch. It offers a tremendous potential as a cheap and alternative feedstuff to maize. Several researchers have confirmed the suitability of cassava root flour and peels in the diet of rabbits (Omole and Sonaiya, 1981).

Materials and methods

Ethical consideration

This experiment was conducted according to the provisions of the Ethical Committee (MUC271SOYE01) on the use of animals and humans for biomedical research of the University of Nigeria, Nsukka, Enugu, Nigeria.

Study site and duration of the study

The study was carried out at the Rabbits Section of the Department of Animal Science Teaching and Experimental Farms, University of Nigeria, Nsukka Enugu State. Nsukka lies within longitude 6˚ 45′E and 7˚ E and latitude 7˚ 12.5 ′N and on the altitude 447m above sea level. The climate of the study environment is naturally tropical, with relative humidity ranging from 65 to 80% and 26.8 ˚C mean daily temperature (Okonkwo and Akubuo, 2007). The yearly rainfall ranges from 1567.05mm-1846.98mm (Metrological Center, Crop Science Department, University of Nigeria, Nsukka Enugu State). The study lasted for 8 weeks.

Feed ingredients and preparation

Fleshly cassava peels without the outer parts not removed were collected from garri processing plant in Obollo-Afor, Udenu local government. The quantity of cassava peels collected was 1000 kg after which they peels were spread on a tarpaulin and sun dried for 7days and turned 2-3 times daily during the process of drying them. The dried peels were then stored, on a wooden bench so that it will not absorb moisture from the floor. Reason for drying the peels were to reduce water content and its cyanide content. The dried peels were later milled using hammer meal. Proximate analysis of the prepared cassava peel meal was done using (AOAC,2012) before using in diet formulation.

Experimental diet

The treatments were 5 experimental diets (CapmL-0, CapmL-5 CapmL-10, CapmL-20 and CapmL-30), formulated to contain about 15% crude protein, Metabolizable Energy of 2400kcal/kg and with cassava peels meal replacing 0, 15, 30, 60 and 100% of the maize in the diets (Tables 1). The proximate compositions of the diets are presented on Table 2.

Experimental rabbits and management procedure

A total of 30 8-week crosses of New Zealand White x Chinchila weaner rabbits consisting 15 males and 15 females initially weighing about 590-680g were randomly allotted to 5 dietary treatments (capml-0, capml-5 capml-10, capml-20 and capml-30) in a completely randomized experimental design with 3 replicates of 2 rabbits each. The 30 weaner rabbits were randomly chosen from a group of 35 weaned rabbits. The rabbits were housed in individual cages measuring 76x 62 x 42cm, elevated from the ground to a height of 90cm and bounded around with galvanized wire and also affixed with feeding and drinking troughs. The cage floors are made of perforated metal slates to allow for easy passage of faeces and urine. The experiment lasted for eight weeks. Before the arrival of the rabbits, the cage, feeder and troughs were thoroughly washed and disinfected. When the rabbits were brought to the experimental site, they were fed commercial top feed growers mash to stabilize them for one-week during which they were also prophylactically treated against internal and external parasites using ivomec. Rabbits were fed diets containing 0, 5, 10, 20, 30% cassava peel meal replacing 15, 30, 60 and 100% maize respectively. The rabbits were in each treatment were served 600g feed daily divided into two, 300g in the morning between 7 -8.00am and 300g in the evening between 3 – 4 p.m. Water was supplied ad libitum.

Parameters measured

Growth performance

At the beginning of the experiment, the rabbits were weighed to obtain their initial body weight. Subsequently, their average live-weights were measured on weekly basis by weighing all the rabbits in each replicate using a 10.1 kg aptitude precision weighing balance (models A and D Weighing GK-10K industrial balance) produced in China. The live weights gain was used to compute the average daily weight gain (ADWG) per rabbit in each replicate. Feed intake was taken from first day of the study to the end. Feed intake was measured by first weighing the feed before being given to the rabbits. Then, the difference between the feed provided the preceding day and left over feed in the feeding trough the next morning was divided with the number of rabbits in each replicate in order to get daily feed intake per rabbit for each replicate. Dry matter feed conversion ratio was calculated by dividing the feed intake of rabbits with body weight gain of rabbits.

Nutrient digestibility

At the last week of the feeding trial, one rabbit having similar body weight was selected from each replicate per treatment and moved to a clean and disinfected metabolic cages. A 3-day adaptation period was allowed before the four-day data collection period. Feed intake was measured and droppings were collected per rabbit daily. The collected droppings were air-dried at room temperature before being ground for proximate analysis using (AOAC, 2012). After the proximate analysis of the faecal samples, apparent nutrient digestibility of crude protein, crude fat, crude fiber, and dried matter was calculated using the formula below:

Experimental design

The experiment was executed using Completely Randomized Design (CRD). The experimental model of the Completely Randomized Design is written below:

Xij=µ+T₁ +∑ij

Where, Xij = any observation or measurement taken

µ = population mean

T₁ = treatment effect

∑ij =experimental error

i= number of treatments

j=number of replicates

Statistical analysis

Data generated were subjected to the analysis of variance (ANOVA) in CRD using statistical package (SPSS, 2003) Windows version 8.0. Mean differences were separated using Duncan^’s New Multiple Range Test (Duncan, 1955) as outlined by Obi (2002).

Results

Table 3. figure 1 and 2 shows the results of the impact of graded levels of cassava peels meal as a replacement for maize on growth performance of weaner rabbits. It was observed that replacement of maize with cassava peels meal caused significant effect (P<0.05) on average daily weight gain, average daily feed intake and feed conversion ratio values among the treatments. Average daily weight gain of capmL-0 and capmL-5 groups were the same (P>0.05), but significantly lower than the values of 13.10, 14.47 and 14.70 observed for rabbits on capmL-10 capmL-20 and capmL-30 diets respectively. Average daily feed intake followed the same trend that was observed in average daily weight gain among the treatments. Feed conversion ratio values of rabbits on capmL-10, capmL-20 and capmL-30 were the same (P>0.05), but significantly lower than values of 4.43 and 4.55 recorded in capmL-0 and capmL-5 respectively.

Figure 1. Linear body weight gain per day of weaner rabbits fed graded levels of cassava peels meal as a replacement for maize	Figure 2. Dry matter feed conversion of weaner rabbits fed graded levels of cassava peels meal as a replacement for maize

Table 4, figure 3 and 4 shows the results of the impact of graded levels of cassava peels meal as a replacement for maize on apparent nutrient digestibility (%) of crude fat, crude fiber, protein, dry matter and nitrogen free extract in weaner rabbits. Percentage digestibility values of crude protein, fiber, ether extract, nitrogen free extract and dry matter were significant (P<0.05). Crude protein apparent digestibility value of capmL-30 group was the highest, followed by capmL-20, capmL-10, capmL-5 and capmL-0 respectively. Crude fibre apparent digestibility (%) values of rabbits on capmL-30 and capmL-20 were the highest, followed by rabbits on capmL-10 and those on capmL-5, and capmL-0 that were also the same statistically. Ether extract apparent digestibility (%) value of rabbits on capmL-30 were the highest, followed by those on capmL-20, capmL-10 and those on capmL-5 and capmL-0 that were the same. Nitrogen free extract apparent digestibility (%) value of rabbits on capmL-30 were the highest, followed by rabbits on capmL-20, capmL-10 capmL-5 and capmL-0 respectively. Dry matter apparent digestibility (%) value of rabbits on capmL-30 and capmL-20 were the same (P>0.05), but significantly higher than values of 92.60, 90.60 and 90.30 observed for rabbits on capmL-10, capmL-5 and capmL-0.

Figure 3. Crude fibre apparent digestibility (%) of weaner rabbits fed graded levels of cassava peels meal as a replacement for maize	Figure 4. Crude protein apparent digestibility (%) of weaner rabbits fed graded levels of cassava peels meal as a replacement for maize

Discussion

Growth performance of rabbits on cassava peels meal diets (capmL-5, capmL-10, capmL-20 capmL-30) were better compared to those on capmL-0 (control). This may be linked to the variations in the fiber contents of the treatment groups and control group. However, when the protein need of rabbit is balanced in the feed and there is adequate supply of fibre using feeding material such as cassava peels meal that contains also some levels of protein 3-5% (Idugboe et al 2017), rabbit will attempt to increase its voluntary feed intake to satisfy its energy needs, and thus dry matter feed conversion is also improved. Complete or partial replacement of maize as energy source with cassava peels meal that contains some levels of protein and also rich in digestible fibres in the feeds of rabbits covers a double interest. Firstly, when they replaced sources of energy such as maize, its digestible fibres are highly utilized for growth, and improve the digestive health of rabbits. Secondly, its digestible fibres may also have another nutritional role in stimulating the maturation of the caecal flora in the young rabbits and thus increasing the health of gut for improved feed fermentation. This will eventually culminate into improved growth and development. Generally, rabbit is a monogastric herbivorous animal, but its digestive physiology is well adapted to high intake of plant cell walls that present in cassava peels meal. Therefore, dietary fibres are the main constituent of a rabbit complete feed. However, if we want to reduce digestive troubles in the growing rabbit and also to preserve its growth performance, we must supply adequate concentrations of fibre fractions.

So, the improved performance with regards to increase linear daily weight gain and improved dry matter conversion when maize was replaced up to 60-100 % by cassava peels meal in this present study was therefore connected to the relative high fiber levels in the diets (11.1 and 13.8 %). However, the increased weight gain recorded in this study compared favorably with the reports of Agunbiade et al. (1999) and Schiere (1999). Also, the increased mean weight gains of rabbits in favor of treatment groups could be attributed to the favorable effect of fibre, termed a “ballast” effect (Colin et al. 1976). Adequate fiber in the diet of rabbits supports performance by way of enhancing health of intestines for better nutrient digestion, transport and absorption of nutrients.

The poor growth performance of rabbits on control diet with balanced protein supply compared to treatment groups with the same protein supply may have been due to inadequate fiber in the diet (6.85%). According to Champe and Maurice (1983) rabbits require crude fibre in excess of 9% for normal growth. Reduced growth rates through lack of dietary fiber has also been reported by (Bamgbose et al 2002).

Apparent nutrient digestibility (%) results showed that treatment groups had better nutrient digestibility than those on control diet respectively. However, the digestive health (mortality and morbidity) of the weaned rabbit is reliant on the level and quality of fibre content of the feed. A fibre deficient feed weakened significantly the digestive health of growing rabbits. But, digestive issues are also rather reduced when adequate digestible fibres are included in the feed. Adequate fibre in the feed of rabbits has positive effect on the fermentative activity in the guts of rabbits (Gidenne and Bellier, 2000). Therefore, higher values of percentage digestibility of nutrients in favor of the treatment groups could also perhaps be accredited to the higher fiber levels on the diets. This may be the optimum range for efficient nutrient utilization. High percentage digestibility of fibre recorded in this present study was contrary to the decrease in percentage digestibility of fibre that was reported by Adegbola and Oduoza (1992). These differences may be as a result of type of fibre contained in the diets of rabbits in both studies. Some fibres are more digestible than the others.

It was observed that total feed cost reduced as the level of the cassava peel meal increased. The highest relative cost advantage observed in treatment groups was as a result of the lower cost of cassava peel compared to maize in the diets.

Conclusions

• It was concluded that a better source of fiber which also provides some levels of protein such as cassava peels meal used in this present study is necessary for enhanced rabbit performance.

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