The grasscutter is a robust animal with short tails, small ears
and stocky body. There are two common species-the large Thryonomys
swinderianus that has been used in this study weight up to 9 kg or
more with a head to body length of up to 60 cm. The smaller species (Thryonomys
gregorianus) may occasionally reach 8 kg and a body length
of 50 cm. They both have yellow-brown to grey-brown bodies with whitish
bellies. The fur is coarse and firm.
The grasscutter or cane rat is a wild hystricomorph rodent hunted particularly
in West Africa for its meat (Ntiamo-Baidu, 1998). It is desirable for
domestication because of its excellent taste and comparatively higher
nutritional value (Asibey and Eyeson, 1973) and meat yield (Clottey, 1981)
than most livestock species. Considerable efforts are put at the domestication
of the grasscutter (Ajayi, 1975) because the rodent has the potential
to produce more protein in a given area than small ruminants at much less
cost in terms of labour and habitat.
The demand for bush meat is high; although some species have reduced
or become extinct (Falconer, 1992; Ntiamo-Baidu, 1998). Grasscutters are
still harvested in large quantities. It is not classifies among species
presently considered to be rare or threatened. Some of the reasons for
grasscutter survival are that they breed throughout the year and their
small size put them at advantage. It was reported by Vos (1978) that rodents
do not decrease easily because of their small size that gives room for
their quick escape.
Grasscutter are found only in Africa (Rosevear, 1969; Baptist and Mensah,
1986). In Western Africa where grass provides its main habitat and food,
it is commonly known as grasscutter; while in other parts of Africa where
it is closely associated with cane fields it is called cane rat. Although
their diet in the wild has not been determined, grasscutters are vegetarians.
They consume nuts, bark and soft parts of grasses and shrubs. They particularly
favour elephant grass and sweet potatoes. They raid cassava and yam plantations.
This study is important because grasscutter is an animal in great demand.
Agboola (2000) reported that for grasscutters raised in confinement to
be in good health, reproduce and maintain a steady growth rate, they must
be provided with balanced diet or feed. The feeding of protein concentrates
is assumed to improve feed conversion efficiency thereby resulting in
faster growth. This implies more meat to the populace compared with when
grasses or fibrous feedstuffs alone are fed. For animals raised under
the intensive system of production, livestock feed accounts for about
60-80% of the total cost of raising the animal. Livestock feed have become
imperatively costly due to the competition between increasing human population
and livestock for the available feedstuffs. Hence, the aim of this study
was to examine which of these three protein sources (soyabean meal, groundnut
cake and blood meal) when fed with or without fish meal supplementation
that will best improve the performance of growing grasscutters.
MATERIALS AND METHODS
A total of 54 grasscutters of nine weeks of age were used for this
eight weeks feeding trials; which was conducted at university of Ilorin,
Ilorin, Nigeria in December, 2004. The grasscutters were randomly weighed
into 6 treatment groups, such that each treatment had three replicates
and there were 3 grasscutters on each replicate.
There were 6 experimental diets (Table 1) in which a 3x2 factorial experimental
design was adopted such that there were 3 protein sources and 2 levels
of fishmeal supplementation. The three protein sources fed were soyabeans
meal, groundnut cake and blood meal while fish meal was supplemented at
0 and 1% inclusion levels. All feed were formulated for 14% crude protein
and 2800 kcal kg-1 of metabolizable energy based on the report
of Adeniji and Ilesanmi (2004).
The grasscutters were housed in wire battery designed cages which allowed
for ease of feaces and urine collection. Feed and water were given to
test animal ad libitum throughout the experimental period. The
grasscutters were allowed one-week adaptation period to both the feed
and cage before the 8 weeks of data collection commenced. During the pre-one-week
adaptation period, the grasscutters were given Ivomec injection subcutanously
to treat for both internal and external parasites. At the 4th week of
experiment, the animals were given prophylactic dosage of triple-sulphur
to prevent coccidiosis.
||Composition of experimental diets (kg/100 kg)
|* Agricare product which contained: - Vit A, Vit D3,
Vit E, Riboflavin, Vit B12, Panthothenic acid, Nicotinic
acid, choline Chloride, Folic acid, Pyrioxine, Biotin, Phosphorus,
Calcium, Iodine, Copper, Manganese, Zinc, Iron, Coxistac, Terramycin,
antioxidant and anticaking agent. Percentage composition of the vitamins
and micro nutrients were not given by the manufacturer
Nitrogen digestibility was conducted during the last week of the experiment.
Weighed quantity of feed was given and feaces collected over 72 h period;
using the method of total collection. Feacal samples were weighed, then
oven-dried at 70°C for 48 h for moisture determination.
The initial and weekly body weights were recorded. Feed intake was recorded
and feed to gain ratio calculated. For the nitrogen digestibility, the
total collection method was used in which both feaces and urine were collected
over three consecutive days. Urine samples collection was treated with
sulphuric acid and stored in plastic bottles and kept in the fridge for
analysis. All proximate analysis was conducted following the procedures
described by AOAC (1980). All data collected were subjected to statistical
analysis using the model for a 3x2 factorial experiment (Steel and Torrie,
There was no significant effect of treatment on the observed feed
intake. The grasscutters fed on the blood meal diets had a feed intake
value of 29.40 g which tended to be higher but is comparable (p>0.05)
to the feed intake values obtained on the grasscutters fed on the soyabean
meal and groundnut cake diets that ate 22.03 and 23.86 g, respectively.
The grasscutters fed the 1% fishmeal supplementation seemed to have eaten
more of their feed (27.85 g), but it is comparable (p>0.05) with the
feed intake value for the grasscutters fed without fishmeal supplementation
that ate 22.27 g (Table 2).
Similarly, for body weight gain, the treatment had no significant effect
(p>0.05) on the observed weight gain in this study. The grasscutters
fed on the blood meal and soyabean meal diets seemed to have gained more
(p>0.05) weight (12.95 and 11.61 g) than the grasscutters fed on the
groundnut cake diets that tended to have the lowest (p>0.05) body weight
value of 8.93 g. The grasscutters fed the 1% fish meal supplemented diet
even-though seemed to have gained more body weight of 12.5 g, it is comparable
(p>0.05) with the weight gained by the grasscutters not fed on fishmeal
supplementation (9.52 g).
The grasscutters fed on the groundnut cake diets and those fed on the
blood meal diets have compared (p>0.05) feed to gain ratio (2.67 and
2.27, respectively), but the grasscutters fed on the soyabean meal diets
tended to have the better feed to gain ratio of 1.90, but was still not
significantly different (p>0.05) to the feed to gain ratio obtained
on the groundnut cake and blood meal fed grasscutters. The feed to gain
ratio for both the grasscutters fed 1% fish meal and those without fish
meal supplementation were very comparable (p>0.05) with values of 2.23
and 2.34, respectively.
||Effects of feeding three protein sources with or without fish meal
supplementation on the performance of grasscutters
|ns = Not significant (p>0.05),
1 = $140 as at October 2004 when the experiment was conducted
||Effects of feeding protein sources with or without fish meal supplementation
on nitrogen digestibility of feed grasscutters
|ns: Not significant (p>0.05)
In terms of feed cost, the protein sources had no effect (p>0.05) on
the prices of feed. The blood meal and groundnut cake based diets were very
28.62, respectively; but the soyabean meal diets seemed to be the most expensive
even-though still statistically comparable (p>0.05).
The diets without fishmeal supplementation tended to be cheaper than those
with the 1% fishmeal inclusion (
, respectively), but not statistically significant
In Table 3 there was no significant effect (p>0.05) of the protein
sources fed on observed nitrogen intake by grasscutters despite the nitrogen
intake on the soyabean meal seemed low. The nitrogen consumed by the grasscutters
on the different fish meal levels were comparable (p>0.05); with nitrogen
intake values of 0.76 and 0.73 g, respectively for grasscutters not fed
and those fed fishmeal supplementation.
There was no significant effect (p>0.05) of the protein sources fed
on the values obtained for the total nitrogen output. Blood meal and groundnut
cake meal fed grasscutters had very comparable (p>0.05) values for
total nitrogen output of 0.16 and 0.14 g, respectively. The total nitrogen
outputs for the two fishmeal levels were comparable.
The soyabean meal and blood meal fed grasscutters retained 0.38 and 0.65
g of nitrogen respectively while the groundnut cake fed grasscutters retained
0.84 g (p>0.05). The 0% fishmeal fed grasscutters retained 0.64 g of
nitrogen while those fed the 1% fish meal retained 0.60 g.
The nitrogen digestibility results showed that the grasscutters had comparable
(p>0.05) nitrogen digestibility values. The soyabean meal fed grasscutters
seemed to have the best (p>0.05) nitrogen digestibility value of 83.91%
compared (p>0.05) with those fed groundnut cake which had 73.52% and
those on bloodmeal with 78.90% digestibility. In terms of fishmeal levels,
those fed the 1% fishmeal had 82.81% digestibility which was comparable
(p>0.05) to 74.73% obtained on the grasscutters not fed fish meal.
Blood meal as animal protein source has been shown to be high (80%) in
crude protein, which might be responsible for the better weight gain obtained
on the grasscutters fed bloodmeal. Protein as a nutrient is responsible
for growth and muscle building. Blood meal is poor in protein quality.
This is in reference to its amino acid profile. Blood meal is deficient
in isoleucine. Spreadbury (1978) reported that feed intake is a reflection
of protein quality. The grasscutters in this study might have increased
the feed intake on the blood meal diets to meet up with the amino acid
deficiencies. The lower metabolizable energy value of blood meal compared
to soyabean meal and groundnut cake that are proteins from oil meals,
could have been responsible for the increased feed intake on blood meal
for the grasscutters to meet and maintain their energy needs. Generally,
animals are reported to eat to meet their energy demands. But contrary
to expectations that soyabean meal which is of better protein quality
should give higher body weight gain; this could be because grasscutter
is a non-ruminant herbivores and can survive on and utilize fibrous feedstuffs
solely. Barnes et al. (1963) reported that coprophagy which the
grasscutter also practice contributes 12-25% of the growth of rabbits.
Fishmeal as a feed stuff has an attractive odour and can be used as feed
stimulant and flavourant to increased feed intake, this is observed in
the better feed intake on the feed supplemented diets. Fish meal is of
good quality protein and which is responsible for the high price of fishmeal
in the market, hence the quality of fish meal has reflected in the fed
grasscutters gaining more body weight.
The better feed gain ratio obtained on soyabeasn meal fed grasscutters
may be due to the fact that soyabean meal is highly rated as number one
plant protein source. Similarly, with fishmeal as a good animal protein
source, the feed to gain ratio on the fed grasscutters was better.
The digestibility values for all the fed proteins were high. This is
probably because the diets were low in dietary fiber. Eggum (1973) studying
factors affecting protein utilization noted a negative influence of dietary
fiber levels on nitrogen digestibility. Onwudike (1986) also reported
that increased crude fiber content of a diet reduces feed efficiency.
Though the results of this study showed that both the growth performance
parameters and nitrogen digestibility of the fed grasscutters were not
significantly affected by the fed protein sources; but the soyabean meal
fed grasscutters tended to have given the best performance in terms of
feed to gain ratio of 1.90 and a nitrogen digestibility value of 83.91%.
Soyabean meal has been reported to be a good source of plant protein (Hittle,
1975). Soyabean meal has well balanced amino acid profile, which makes
it of better quality than other plant-rich supplements. The fish meal
supplemented diets also seemed to have given a better performance over
the unsupplemented fish in diets. Fish meal has been reported to be ideally
balanced in terms of the ratio of its essential amino acids (Fowler, 1997).