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This experiment was carried out to investigate the response to inclusion of whole cassava plant meal as replacement for maize in the diet of growing rabbits. Fifteen New Zealand white weaner rabbits with an average initial body weight of 577g were housed individually and randomly allotted to three diets: control diet with maize grain; and 50% or 100% replacement of maize by whole cassava plant meal (cassava roots + cassava tender stem and leaves). The ratio of root to leaves and tender stem (DM basis) was 2.5:1 while that of leaves to tender stem was 5:1.
Growth rates and feed intakes were higher on the diets with whole cassava plant meal replacing the maize, but there were no differences in feed conversion. Apparent digestibility coefficients for all proximate analysis constituents were higher on the cassava diets.
It is concluded that whole cassava plant meal can be used to replace maize in the diet of weaner rabbits without any adverse effect on the performance and apparent nutrient digestibility.
The animal protein for human consumption in Nigeria (from cattle, pigs, poultry, sheep and goats) has not been able to bridge the gap between the demand and supply. Despite the numerous advantages associated with the consumption of animal protein, the minimum intake recommended by FAO (1992) has not been met. This is mostly because the price of meat has gone beyond the means of most Nigerians. To ease this problem of low animal protein intake, there should be an expansion in the production of small, highly prolific livestock with rapid turnover rate at a very low cost.
Recently, the rabbit has come under focus as an animal with enormous potential because of its attributes such as small body size, short generation interval, high reproductive potential, rapid growth rate, genetic diversity and ability to utilize forage (Cheeke et al 1986). The feeding habits of rabbit offer no appreciable competition with humans. This is because it can subsist on vegetative basal diets. The rabbit industry is growing in many countries in Africa today, hence feeding problems associated with poultry and pig farming are now being encountered by rabbit breeders who have depended solely on pelleted concentrates for their animals (Omole 1992). The new impetus for rabbit production in Africa amongst a wide range of people creates the need for alternative cheap sources of feed to replace or supplement cereals in rabbit diets in order to make rabbit production profitable (Omole 1992).
Cassava roots offer a tremendous potential as a cheap and alternative feed stuff to maize. Several researchers have confirmed the suitability of cassava root flour and peels in the diet of rabbits (Eshiet et al 1979; Eshiet et al 1980; Omole and Sonaiya 1981). There is a paucity of information on the utilization of cassava foliage by rabbits; however, positive responses have been obtained from its inclusion in the diets of growing pigs and broiler chicks (Akinfala and Tewe 2001; Akinfala et al 2002). The present study aimed to evaluate leaves, tender stems and roots of cassava (whole plant cassava meal) as replacement for maize in the diets of growing rabbits.
The treatments were three experimental diets (M, C22.5 and C45), formulated to contain about 15% crude protein , with whole cassava plant meal replacing 0, 50 and 100% of the maize in the diets (Tables 1 and 2).
Cassava leaves and tender stems were harvested from mature cassava plants grown at the Teaching and of Obafemi Awolowo University, Ile-Ife, Osun State. They were sun-dried on a concrete floor until the leaves were crispy and the tender stems could be easily broken without bending. They were later milled. The unpeeled cassava tubers were washed with water, chopped and sun-dried on a concrete floor. After drying to about 10% moisture content, they were milled. The cassava tuber meal was mixed with leaves and tender stem meal at the ratio of 2.5:1 The ratio of leaves to tender stems in the dried foliage was 5:1. These ratios were selected to give the same crude protein content (9.6%) as in maize.
This study was carried out in the Research Farm at the onset of the rainy season between March and April 2002. Fifteen (15), ten weeks old New Zealand White weaner rabbits with an average body weight of 577g were used. The fifteen rabbits were randomly chosen from a group of 22 weaned animals, the progeny of four does. They were randomly allotted to the three diets with no consideration for origin (dams) or the litter size. 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 mesh. There were two clay pots in each cage for supplying feed and water.
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Table 1:
Dietary ingredients |
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|
M |
C22.5 |
C45 |
|
Maize |
45.0 |
22.5 |
|
|
Cassava tubers |
|
16.1 |
32.2 |
|
Cassava leaves + tender stems |
|
6.43 |
12.8 |
|
Groundnut cake |
5 |
5 |
5 |
|
Palm kernel cake |
30 |
30 |
30 |
|
Wheat offal1 |
15 |
15 |
15 |
|
Fish meal |
1.5 |
1.5 |
1.5 |
|
Oyster Shell |
2 |
2 |
2 |
|
Bone Meal |
1 |
1 |
1 |
|
Premix (Vit/min) |
0.25 |
0.25 |
0.25 |
|
Salt |
0.25 |
0.25 |
0.25 |
|
Crude protein* |
15.6 |
15.4 |
15.2 |
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*Calculated |
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Table 2: Proximate analysis of diets |
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Parameters |
M |
C22.5 |
C45 |
|
Dry matter |
95.2 |
94.2 |
94.0 |
|
Crude protein |
16.3 |
15.4 |
14.3 |
|
Crude fibre |
6.85 |
9.10 |
10.80 |
|
Ash |
9.23 |
7.48 |
7.65 |
|
Ether extract |
3.35 |
4.50 |
4.10 |
|
Nitrogen free extract |
59.5 |
57.7 |
56.9 |
The study was conducted for nine weeks (eight weeks of growth trial and 1 week to measure digestibility). Feed and clean water were supplied ad libitum. Records were kept of feed consumption (daily) and body weight (weekly(.
Three animals having similar body weight were selected from each treatment. They were fasted for 24 hours prior to the commencement of the study. They were then given a fixed quantity of feed for five days during which total faecal collection was carried.
Proximate analyses of the diets and the faecal samples were carried out using the procedure of AOAC (1995). All data were subjected to analysis of variance using a computer software package (SAS 1997). Variables were treatments and error.
The average daily weight gain increased from 9.38 to 12.5g when 50% of the maize was replaced with the whole cassava plant meal; however, on all diets the growth rates were relatively low. Feed intakes were higher when the whole cassava plant meal was included in the diets. There were no differences among diets for feed conversion.
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Table 3: Performance characteristics of growing rabbits fed diets with increasing levels of whole cassava plant meal |
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M |
C22.5 |
C45 |
SEM |
|
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Body weight, g |
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Initial |
572 |
584 |
576 |
4.99 |
|
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Final |
1098b |
1282a |
1204 a |
75.4 |
|
|
Daily gain |
9.38b |
12.4a |
11.2ab |
1.55 |
|
|
DM intake, g/day |
43.9b |
56.4a |
60.8a |
8.81 |
|
|
Feed DM/gain |
5.15 |
4.89 |
6.00 |
0.47 |
|
|
Means along the same row having different superscripts differ at P<0.05 |
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Apparent digestibility coefficients, for all proximate analysis constituents, increased as the level of whole cassava plant meal in the diets was increased (Table 4). The differences were significant when the cassava product replaced completely the maize in the diet.
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Table 4: Apparent nutrient digestibility of diets with increasing levels of whole cassava plant meal |
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Parameters |
M |
C22.5 |
C45 |
SEM |
|
Dry matter |
65.4b |
71.6a |
75.0a |
3.99 |
|
Crude protein |
70.9b |
78.7ab |
82.4a |
4.88 |
|
Crude fibre |
41.9b |
48.5ab |
52.6a |
3.3 |
|
Ash |
68.19b |
81.5a |
74.3ab |
5.50 |
|
Ether extract |
72.5b |
78.2a |
81.7a |
3.80 |
|
Means along the same row having different superscripts differ at P<0.05. |
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The poor growth performance on the control diet may have been due to inadequate fibre in the diet (6.9%) as, according to Champe and Maurice (1983), rabbits require crude fibre in excess of 9% for normal growth. Reduced growth rates through lack of dietary fibre has also been reported by Cheeke and Patton (1985) and Bamgbose et al (2002). The higher growth rate when half the maize was replaced by whole cassava plant meal was therefore to be expected in view of the higher fibre levels in these diets (9.1 and 10.8% for increasing levels of maize replacement). The higher values for digestibility of all proximate analysis constituents when the cassava products replaced maize could also perhaps be attributed to the higher fibre levels on these diets. On the other hand, decreases in digestibility of fibre were reported by Adegbola and Oduoza (1992), when the level of fibre was increased.
From the results of this study, it appears that whole cassava plant
meal can be included in diets for growing rabbits at levels of up to 45%.
However, further research on this topic is required as growth rates were
less than would be expected even under tropical conditions (S Lukefahr, personal
communication).
The authors are grateful to Mr. Aderinwale, Deji,
Mr. Salami, Tajudeen and Miss Obisesan, Titilayo for their assistance in carrying
out this study.
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Received 2 November 2002; Accepted 17 May 2003