Globally, wildlife has great potentials for meat production and serves as an
important source of the highly desired animal protein to the people of Africa,
both in urban areas and rural communities (Fonweban and Njwe, 1990). The preference
for bush meat or the meat of commercially available game animals is widely accepted
(Baptist and Mensah, 1986; Fonweban and Njwe, 1990).
However, with ever increasing human population and obvious protein shortage
in Africa, there is the need for an exploration of other means to provide readily
acceptable meat on short term basis.
Wildlife domestication has been recognized as a way of achieving this objective.
A few number of small mammal and crop farmers, trade or breed wild rodents (Fonweban
and Njwe, 1990; NRC, 1991), but research studies in their domestication
are producing conflicting results (Baptist and Mensah, 1986;
Among the wild rodents, the grasscutter, or cane rat or cane cutter is the
most preferred (Asibey and Eyeson, 1973; Clottey,
1981). Grasscutter (Thryonomys swinderianus) is a wild hystricomorphic
rodent widely distributed in the African sub-region and exploited in most areas
as a source of animal protein (Vos, 1978; Asibey,
1974a; NRC, 1991). Being the most preferred (Martin,
1985) and most expensive meat in West Africa including Nigeria, Togo, Benin,
Ghana and Cote d voire (Baptist and Mensah, 1986;
Asibey and Addo, 2000), it contributes to both local
and export earning of most West African Countries (Asibey,
1969; NRC, 1991; Baptist and Mensah,
1986; Ntiamoa-Baidu, 1998) and is therefore hunted aggressively. Unfortunately
its collection from the wild is attended by destruction of the environment through
the setting of bush fires by hunters (NRC, 1991; Yeboah and Adamu, 1995; Ntiamo-Baidu, 1998). To alleviate this
problem, attempts are being made in the sub-region to domesticate the grasscutter
(NRC, 1991; Addo, 2002) and make
it more readily available, gain economic benefit and also reduce the environmental
destruction that accompanies its collection from the wild. For example, a major
research programme on grasscutter has been initiated in Benin Republic under
the project Benino-Allemand d Aulacodiculture (PBAA) to select genetically
improved grasscutter stocks adapted to life in captivity and to promote the
rearing of the animal in rural and sub-urban environments (Baptist
and Mensah, 1986).
CHARACTERISTICS OF THE GRASSCUTTER
The grasscutter has thickset body, measuring up to 40 to 60 cm in addition
to a 20-25 cm tail (Fitzinger, 1995). Its average weight
fluctuates between 2 to 4 kg in the females and 3 to 6 kg in the males (Baptist
and Mensah, 1986; Jori et al., 1995; Merwe,
2000). Its furs comprise a mixture of brown reddish and gray hairs that
vary depending on its habitat (Jori and Chardonnet, 2001).
Some other authors reported that the skin and hair (fur) as well as limbs and
tails are easily torn out (Rosevear, 1969; Kingdom, 1974).
This makes the animal very difficult to catch and even more difficult to handle
The grasscutter is a quick runner and a skilled swimmer, despite the blunt
snout. Its visual powers are relatively poor, making communication to be based
only on hearing and well developed sense of smell. This rodent can live up to
four years in captivity (Jori and Chardonnet, 2001).
It is a monogastric herbivore like the rabbit and other rodents; it is a good
food converter and often practices coprophagy (Hemmer, 1992).
They are considered delicacy, high prized source of protein and agricultural
pest of cereals and other crops (Yeboah and Adamu, 1995).
Distribution and Habitat of the Grasscutter
The grasscutter is found only in Africa (Rosevear, 1969; Baptist and Mensah, 1986; Adoun, 1993). In West Africa where grass provides
its main habitat and food, it is commonly known as the grasscutter or the cutting
grass, while in other parts of Africa particularly Southern Africa, where it
is closely associated with cane fields, it is called the Cane rat.
The grasscutter is found in grasslands and wooded savannah throughout the humid
and sub-humid areas, south of the Sahara (NRC, 1991), specifically from Senegal
to parts of the Cape Province in South Africa (Rosevear, 1969). The giant cane
rat can also be found in any where there is dense grass, especially reedy grass
growing in damp or wet places (Ajayi, 1971; Abioye
et al., 2008). They do not inhabit the rain forest, dry scrub or
desert regions (NRC, 1991). Its distribution is determined basically by the
availability of adequate or preferred grass species for food (NRC, 1991).
In West Africa, the grasscutter is not considered a threatened or disappearing species of wildlife (Baptist and Mensah, 1986). On the contrary, forest clearance in the Guinea zone has expanded its ecological habitat from the Savannah region into cropped areas and secondary forest, following agricultural encroachment on forests (Baptist and Mensah, 1986).
Similarly in Ghana, the grasscutter has penetrated the high forest where there
is intensive maize, cassava, sugarcane, young cocoa, coconut, oil-palm, pineapple
and egg plant cultivation (Asibey, 1974a). However,
Thryonomys swinderianus has often been encountered in the vicinity of
water courses just as both species have also been found in the same environment
in East Africa (Kingdom, 1974).
Mode of Life of the Grasscutter
Grasscutters live above ground and are considered to be nocturnal. However,
during the rainy season when sufficient security, shade and moisture are available,
they are sometimes active during the day. After a certain period of acclimatization
to their enclosure, grasscutters under studies have also started to feed by
day (Rosevear, 1969; Kingdom, 1974; Ajayi and Tewe, 1980).
Grasscutters are harmless and their response to danger is generally to flee.
They often live in groups of 3 to 12 individuals: 1 male and 2 to 3 females
with their offspring. The search for food and mating by the grasscutter is generally
done between 5 pm and midnight and again at first light. The rest of the period
is spent in rest, chiefly grooming and searching for nest (Centre
for Biodiversity Utilization and Development, 2004).
Dentition in the Grasscutter
The dental formula of the grasscutter according to Merwe
(2000) is 2(I 1/1 CO/O Pm 3/3).
The orange or yellow colored or incisors (gnawing teeth) and broad, strong and very sharp with longitudinal groves on their surfaces. Despite their apparent strength, the teeth are believed to be brittle. According to studies of prepared grasscutter skull, they are composed mainly of dentine with very thin layer of dental enamel (Rosevear, 1969). There are four enamel covered cheek teeth, one premolar (persisting milk molar) and three molars on either side of the jaws (Rosevear, 1969). On the bases of the molars teeth development, it is possible to a certain extent, determine the age of a grass cutter.
Feeding in Grasscutter
The grasscutter is a herbivorous animal with a wide nutritional intake.
The major part of its diet is composed of grasses with fairly high crude fibre
content. It can apparently tolerate a certain level of tannin found in leaves
and bark as well as cyanogenic glycosides present in green maize, sorghum and
Manihot (Ewer, 1969). Under-altered condition, the grasscutter is able to adapt
itself to another diet.
Thus Ewer (1969) reported that shrubs and bushes growing
in the enclosure where grasscutters are kept were neglected at first but were
later-eaten readily. They always prefer grasses with lots of moisture and so
soluble carbohydrate (Ajayi and Tewe, 1980; Onadeko,
1996; Agbelusi, 1997). They equally eat fallen fruits,
nuts and many kinds of cultivated crops (Fitzinger, 1995).
The grasscutter is a wasteful feeder, cutting the grass at a characteristic
angle with its very powerful incisors to cut the more nutritious succulent inner
nodes, leaving behind scattered pieces on the ground (Ewer, 1969; Asibey,
1974b). Grasscutter can equally be raised on the backyard to provide meat
for the family by feeding them kitchen. Left-overs (Agbelusi,
1997; Addo, 1997).
However, the feeding strategy for the grasscutter is rudimentary and inadequate
for growth and reproduction (Adu et al., 2000;
Adu and Wallace, 2001).
Adu (2002) had compiled a list of feed items for the
grasscutter based on indigenous knowledge (Table 1). He reported
that certain varieties of cassava could be poisonous to the animal, particularly
when fed fresh leguminous plant such as Centrosema pubescens and Leucaenia
sp. could be poisonous when fed in large quantities.
|| Food items fed to captive-reared grasscutters in Southern
However, the nutritional status of grasscutter is improved through the provision
of pelleted concentrate for supplementary feeding (Addo, 1997).
Adu (2002) and Opara and Fagbemi
(2009) had reported that the practice of not giving the animals water (Adu,
1999) would be responsible for the high still birth weight. The lower birth
weight registered in Ghana compared to Benin where water was provided (Adu,
2002), confirmed this fact. The provision of water has also been found to
have positive effects on feed utilization, growth rate, health and reproductive
performances (Aitken and Wilson, 1962). Adu
(2002), also reported that lack of drinking water is partially responsible
for digestive disorders leading to enterotoxaemia.
The grasscutter is easy to house, though its handling requires skills. Among
rural communities and even some urban people with adequate space, the animal
has been bred and kept in boxes, empty drums, Poly Vinyl Chloride (PVC) pipes
and exclosures (Adu, 2002). However, the grasscutter
cloud be properly managed under these three systems: enclosure, cage and floor.
REPRODUCTION AND REPRODUCTIVE MANAGEMENT
Most farmers rely on the shapes and or size of the head to distinguish between
the sexes. The use of ano-genital distance is the second most popular method
of sex determination (Adu, 1999). The study by Adu
and Yeboah (2002) has led to the promotion of the use of ano-genital distance
as the gold standard of sex determination in the grasscutter. At birth, the
ano-genital distance is 10 mm in the males and less them 5 mm in the females.
In adults, it measures an average of 38 mm in males (n = 68) and 12 mm in females
(n = 67) (Asibey, 1974b).
The Male Genital Tract
The paired testicles are situated abdominally and there is no scrotum (Addo
et al,, 2003). Appertaining to the accessory sex glands are a pair
of seminal vesicles, the prostate gland, composed of three lobes and a pair
of compact pea-sized Cowpers glands. There is another pair of glands (glands
coagulate) between the base of the seminal vesicles and prostate glands (Addo
et al., 2003).
The Female Genital Tract
The vaginal opening between the urinary papilla and the anus is sealed with
a thin membrane, the vaginal closure membrane (Asibey, 1974b;Oduor-Okelo and Gombe, 1982). This membrane has been observed in all hystricomorphic rodents,
except the Nutria (Myocoaster coypus), studied so far.
Perforation of the membrane normally occurs only during estrus and at birth
(Weir, 1974). The vagina is simple (V. Simplex), while the uterus is bicornuate
and the horns open into the vagina through two slit-like ora cervices (U. duplex).
A transuterine migration of blastocysts is therefore excluded (Oduor-Okelo
and Gombe, 1982), but two pregnancies independent of each other are possible
at the same time (Addo et al., 2003). The ovaries
contain strikingly vasculose interstitial tissue.
Knowledge of sexual maturity in the male grasscutter is a key management
factor in grasscutter production (Adu, 2002). The male
animals housed together can engage in fatal fights, particularly in the presence
Sexual maturity in the male is usually determined using the presence of ano-genital
region stain (Adu, 1999). Males are usually housed singly
or castrated on attainment of sexual maturity. It has also been reported that
certain animals may not develop the ano-genital region stain on attainment of
sexual maturity (Adu and Yeboah, 2002), therefore males
should be separated before four months of age without regard to the development
of ano-genital region stain.
Little information is available on the reproductive pattern of grasscutters
and thus, nothing is known about the process and duration of the cycle, expression
of estrous, estrous detection and kind of ovulation. Most of the hystricomorphas
examined so far ovulate spontaneously (Addo, 1997). The
average cycle length ranges from 30-40 days indicating a long luteal phase (Oduor-Okelo and Gombe, 1982).
In female hystricomorpha kept separate from males, the interval between the first day of vaginal opening and the day prior to the next reopening corresponds to the cycle length, provided that the animals cycle is regular and the vaginal opening is not caused by other factors (Weir, 1974).
In Myomorphic rodents (rats and mice), cycling is accompanied by typical cellular modifications of the vaginal mucosa so that the exact stage of cycling can easily be determined by a vaginal smear (Oduor-Okelo and Gombe, 1982).
Mating in Grasscutter
Grasscutters are induced ovulators (Steir et al.,
1991; Addo et al., 2001) and breed all year
round (Asibey, 1974b); therefore no consideration is
given to the time of mating. However, grasscutters sometimes show variations
in their reproductive activity or sexual circle (Adjanahoun,
1989), which is manifested by their vaginal membrane. Sometimes when sexually
ready or estrus, the female grasscutter may present a perforated vaginal membrane
with (sealed) or without (open) a hardened vaginal secretion. When not sexually
ready or in estrus, it may present an intact (closed) membrane (Adjanahoun,
The female is normally transferred to the males cage but prior to this, the
females body weight, vaginal status (open, sealed, closed), date and time-of
the transfer should be noted, after which they are left till mating occurs (Addo,
During the females stay with the male, it should be examined daily before post
pairing perineal changes namely: perforation of vaginal membrane (in females
that presented closed or sealed vaginal membranes at the time of pairing), nature
of vaginal secretion if any and presence of copulatory plug in the vagina (Addo,
2002). Other mating signs looked for are copulatory plug on the cage floor
and scratches on the females trunk inflicted by the male in its attempt to mount
the female (Asibey, 1974b). On the observation of any
these signs, the female is immediately and permanently separated from the male,
weighed, transferred to its own cage and the date and time of the appearance
of the mating (s) noted (Addo, 2002).
Successful mating in the grasscutter is manifested by vulval congestion, which is sometimes accompanied by vulval oedema and protrusion of the vaginal walls. The female thereafter is monitored either daily or weekly for signs of fertile mating.
Pregnancy and Birth
The grasscutter develops anatomically speaking, a placenta discoidalis.
According to histological classification, this is placenta haemochorials (Oduor-Okelo and Gombe, 1982), in which important diaplacental transmission of antibodies
takes place. According to Addo et al. (2003),
the degeneration of uterine/mucosa in rodents starts as early as the end of
pregnancy. At birth, nothing is left except a stalky connection between the
parsfetalis and the parsuterina, which after the placenta has been released,
leaves only a small injury enabling new fertilization and implantation to take
place immediately after birth.
Studies on various hystricomorphic rodents have shown that internalized interstitial
tissue and accessory corpora lutea act as additional progesterone sources (Tam,
1974). It is supposed that the high percentage of interstitial tissue and
the transformation of atretic follicles into corpus luteum tissue are necessary
for steady progesterone production to maintain the relatively long pregnancy
duration of a hystricomorphic rodent (Weir, 1974; Oduor-Okelo
and Gombe, 1982).
The exact gestation period results from interval between observed mating or presence of a copulatory play or spermatozoa in the vaginal source and after normal birth.
Since, mating is not synonymous with fertilization, it seems advisable to separate
the animals after mating. Hypothesis had it that stress released by disease,
insufficient nutrition or change of environment may disturb the pregnancy or
affect its length by delaying or blocking the embryonic development or that
sperm is preserved in the female genital tract unit, a more favourable moment
for fertilization (Addo et al., 2003) compared
with other hystricomorphic rodents which in relation to the body size, exhibit
extreme gestation length, despite the observed large variations. The shortest
gestation length observed is 52 days (Galea), the longest, 213 days (Erethizon)
or 223-283 days (Dinomys). According to Weir (1974)
this is not only a question of delayed (fertilization or implantation) but also
a question of very slow embryonic and foetal development. Placental development
takes up approximately one quarter of the total gestation length.
The grasscutter has both partial and total resorption and reproduction problem
(Asibey, 1974b; Adu and Yeboah,
2000), so there is a need for proper pregnancy diagnosis all year round.
Pregnancy diagnosis is conducted either daily or weekly, depending on the parameter
under investigation. The daily monitored parameters are: status of the vaginal
membrane (closed, sealed or opened) and the presence and characteristics of
vaginal secretion. The weekly monitored parameters are: change in body weight
and the presence of developing fetuses in-utero which is determined by abdominal
palpation (Addo, 2002).
Early pregnancy diagnosis allows for early identification of animals not conceiving
at first mating (Adu, 2002). It also allows for specialized
management of pregnant animals so as to minimize the incidence of abortion and
dystocia (Adu, 2002).
However, to conduct abdominal palpation, the animal is partially restrained in a net while the attendant holds the animal gently on the shoulders. The examiner holds the animal by the tail and places one arm between its hind legs, moves the head gently until animals lower abdomen is cupped in the hand. The uterine horns are gently passed in between the fingers and the fetuses are felt as small, slippery marbles during the early stage of gestation but gets progressively larger and elongated as the pregnancy advances. At the early stage, the diagnosis is categorized as tentative due to the semblance of the fetuses to faecal pellets, which would be felt during the palpation.
In the third week, the paired uteri are as one swollen mass with an elongated
content and in the fourth week, as a voluminous bag of soft constituents. In
the 5th week, the uterine horns maintain their voluminous nature but contain
long rods in the 6th week, the uterus becomes comparatively less voluminous
and the fetuses are felt as distinct soft rods until the 8th week (Addo,
2002). The vaginal plug formation after mating has been shown to have some
merit as a pregnancy diagnostic tool (Addo, 2002).
The intermittent vaginal bleeding 5 weeks after mating could be used for pregnancy
diagnosis. This bleeding is in implantation bleeding rather than embryo resorption
or abortion (Addo, 2002).
All the methods, except change in body weight are used for the first weeks
after mating. Weight changes are monitored until the twenty-first week of pregnancy
because it is considered to be least stressful of all the pregnancy diagnostic
methods (Addo, 2002).
The gestation length in animals has been estimated to be from the day of
appearance of mating sign (day one) to the day of parturition (Addo,
2002). The grasscutter gives birth to precocious young after 148 to 170
days of gestation (Adu, 1999; Addo,
2002: Onadeko and Amubode, 2002). This gestation
length makes it possible for the animal to farrow twice a year (Addo,
Detection of Imminent Parturition and Parturition
Parturition is the act of giving birth to young ones. In all species the
on set of Parturition is manifested by the occurrence of myometrial activity
(Arthur et al., 1982).
Pregnant animals are monitored for peculiar signs that could be indicated by
imminent delivery, therefore, those with distended abdomen are observed unobtrusively
daily, from 6am to 6pm at three hours interval for changes in eating and drinking
habits as well as changes in behavior and posture (Arthur
et al., 1982; Universities Federation for Animal
The abdomen of the animal distends and takes on the shape of rugby ball (Addo,
2002). The expected mother walks on only the hind limbs termed Penguin Posture
(Addo, 2002), three days before delivery. A day before
delivery, it combines the penguin posture with frequent down ward looks at the
lower abdomen (Onadeko and Amubode, 2002).
The grasscutter litters while standing on only the hind limbs. They eat the
placenta after delivery of each baby before proceeding on to deliver the next
baby (Asibey, 1974b; Addo, 2002).
The neonates are born fully haired with their eyes open. They stand by their
mother during the delivery of the litter mates and follow their mother 32-40
min after their delivery (Addo, 2002).
Parturition lasts for 40-57 min (Asibey, 1974b; Addo,
2002; Addo et al., 2003) and has a modal litter
size of 4-6 with sex ration of unity (Addo, 1997; Addo
et al., 2003). The off springs weigh 70-130 grammes at birth with
a clear difference being observed between both litter mates and litters. Parturition
in the grasscutter as is also usual in most species is very infrequent during
the day (Baptist and Mensah, 1986).
Litter Size, Birth Weight and Suckling Position
Addo (2002), analysed the weights of 46 female grasscutters
and their off springs at birth as well as the weights of 66 killed females and
their fully developed fetuses.
The most frequent litter size is four, but litters of eight or more have also
been observed (Onadeko and Amubode, 2002; Abioye
et al., 2008).
Birth weight varies from 70-130 grammes. The sex ratio is well balanced. Both
number and size of the young seem to be influenced by the dams nutritional
state (Asibey, 1974b). There is also an indication that
larger females tend to produce larger litters. The weight of each off spring
is much more independent on its position in the uterine horn during embryonic
development (Addo et al., 2003).
The special position of the teats on the mother and the ventral position of
the mouth on the young, dictate the particular nursing posture of the grasscutter
dam that suckles her off springs, taking some of her weight on the fore and
hind limbs so that her abdomen is not flattened too much. The position of the
teats permits the young despite their ventral mouths, to suck on either side.
If the dam lies on her flank, it would be extremely difficult, or even impossible
for the young to suck the lower row of teats (Ewer, 1969; Asibey,
1974b; Kingdom, 1974).
The economic and management factors influencing efficient animal production
include the length of time between successive births (Chupin,
1992). The grasscutters are weaned within one month after birth. Adu
(1999), suggested a weaning age of 6 weeks based on the high post weaning
mortality when animals are weaned at 4 weeks. However, Adu
(2002) reported that animals could still have a lower post weaning mortality
rate. Factors influencing the post weaning mortality rate include the number
of animals per unit space (Hemmer, 1992). Hemmer
(1992) posited that rodents under stress cuddle themselves into corners
and may suffocate each other to death in the process. It has been possible to
reduce the post weaning mortality to 1.4% for animals weaned at 4 weeks (Adu,
2002), compared to 11% for those weaned at 6 weeks by keeping not more than
five animals per unit space post weaning.
According to the observations made by Asibey (1974b),
sexual maturity in female grasscutter in the wild coincides with the eruption
of the third molars, i.e., 5 months of age and with a weight of about 1 kg.
In captivity, female grasscutters at this age exhibited perforation of the vaginal
membrane but none of the observed animals became pregnant. Age at first littering
varies from 12-18 months (Ewer, 1969; Asibey,
1974b). It is not clear whether the grasscutter has a definite reproductive
season. In South and South-West Africa, it is considered to be a seasonal breeder
(Shortridge, 1934; Paradiso, 1968).
But, there is conflicting evidence on seasonality in West Africa. Ewer
(1969), reported births during the periods of January to March and July
to August. Rosevear (1969), reported that juveniles had
been collected between September and the beginning of January, but gave no indication
of site. Onadeko and Amubode (2002) reported that baby
grasscutters were born in captivity in Nigeria between November and July of
every year, although no birth was recorded in February and May. It has finally
been ascertained that grasscutters in Ghana reproduce throughout the year but
reproduction is more frequent in certain seasons (Asibey,
1974b). There is an indication that breeding is related to seasonality of
rainfall and thus, feed availability.
HAEMATOLOGICAL AND BIOCHEMICAL VALUES IN THE GRASSCUTTERS
Studies have shown that certain factors influence haematological and biochemical
parameters (Weldy et al., 1964). Haematological
and biochemical analyses of an animals blood represent a good diagnostic
aid for the assessment of physiological, nutritional and pathological conditions
of animals (Jain, 1986; Bush, 1991;
Awah and Nottidge, 1998). Nutrition age, sex, genetics
(breed and crossbreeding), reproduction, housing, starvation, environment factors,
stress, transportation and diseases are known to affect haematological and biochemical
values (Coles, 1986) and thought to play major roles in
the differences in haematological and biochemical parameters observed between
tropical and temperate animals (Ogunriade et al.,
1981; Bush, 1991; Ogunsanmi et
al., 1994). Ogunsanmi et al. (2002) determined
the haematological, plasma biochemical and whole blood electrolytes profile
in the normal live-captive and rehabilitated adult African grasscutters. They
reported no statistical evidence of sexual dimorphism in the values of these
parameters of the cane rats, except plasma alanine transaminase (ALT), which
was significantly higher (p<0.001) in the males than in the females. In their
studies, Owolabi (2002) and Opara
et al. (2006) reported a significantly (p<0.05) higher lymphocyte,
eosinophil and basophil values for both the female and male wild grasscutters,
compared with those of captive- reared. They equally reported a significantly
higher white blood cell counts in female than male wild grasscutters and attributed
these differences to the free nature of the wild rodents which are more prone
to all kinds of infections (Gotoh et al., 2001;
Dinh, 2002). The significantly high levels of basophils
and eosinophils among the wild grasscutters (Opara et
al., 2006) were due to the presence of inhabiting parasites in the animals.
Reasons for Losses in Captive Grasscutters
In Benin, losses among captive grasscutters amount to nearly 80%, the majority
(74%) being due to accidents, injures at the time of captive, refusal to eat,
poisoning (Manioc) and disorders of the digestive system after treatment with
antibiotics (Jori and Chardonnet, 2001).
Another 17% of the losses are due to diseases including abscesses (under the tongue), pneumonic and cardio-splenic dilation.
Coccidiosis, which may be treated with Coccidiostats (used for fowls and rabbits),
helminthiasis, coughs and bacterial infections of the eyes, also occurred (Addo
et al., 2003; Abioye et al., 2008).
Parasitic Diseases of the Grasscutter
The grasscutter unlike many other livestock species such as rabbits, sheep
and goats requiring an appreciable drug input, is very hardy and requires little
or no drug input (Adu, 2002; Opara
and Fagbemi, 2008a).
Incidence, severity and disease prevalence have been shown to vary with the
management systems (Smith and van Hautert, 1984; Adu,
2002; Opara and Fagbemi, 2010). Again, Adu
(2002) reported that the major disease conditions include pulmonary congestion,
septic wounds, ruptured uterus, orchitis with septicaemia, gastro-intestinal
obstruction, gastroenteritis and pneumonia. The gastrointestinal obstruction
and gastro enteritis may be caused by helminthes parasites (Jori
et al., 2001; Awah-Ndukum et al., 2001).
The study of helminth parasites of domestic animals began as early as 1884
in America where on Act was enacted to prevent the exportation of diseased cattle
and to provide means for the suppression and extirpation of diseases among domestic
animals (Blood and Radostits, 1994). The idea came up
as a result of hardship and large economic losses brought about by these parasitic
helminthes, hence the need for control and eradication of these parasites. As
a result of this, many researches on gastrointestinal helminthes parasites have
Blood and Radostits (1994), observed that the incidence
of helminthes diseases varies between areas depending on the climate, nutritional
status of the animal, pasture management as well as the animals immunity
to worm infestation. As a result Schillhorn Van Veen et
al. (1974) reported that environmental factors such as topography, climate
and husbandry practice have led to a situation where a number of helminthes
parasites common to many parts of the world are rare or do not occur at all
in Nigeria and that some helminth parasites common in Nigeria have not been
The incidence, severity and disease prevalence have been shown to vary with
management systems. Smith and van Hautert (1984) reported
that, while infections accounted for over half of the disease conditions observed
in a group of intensively managed ruminants, they were of negligible prevalence
in a controlled group raised semi-intensively. In the later group, parasitic
gastroenteritis was the most prevalent disease condition.
A study conducted by Baptist and Mensah (1986) in Ghana
reported the infestation of grasscutters by Ascaris sp., Schistosoma
haematobium and Trichuris sp., including ticks of Dermacentor
sp. and Rhipicephalus sp. But the Ascaris sp., encountered
in the grasscutter is non-pathogenic to the domestic stock until proved otherwise
since each animal species has its specific ascarid (Blood
and Radostits, 1994). The observation of Schistosoma haematobium
eggs in the grasscutter is very important in the spread of infection to both
livestock and man and the infection can only occur when part of its life cycle
passes through an intermediate fresh water mollusc host. The identification
of the eggs of Trichuris trichuria is important, in that various species
attack various domestic stock and possibility of infection of domestic stock
would be by sharing the same pasture and by domestic stock hanging around where
the wild-stock are slaughtered and faeces disposed of in the nearby bushes.
Jori et al. (2001) revealed the presence of
Paralibyostrongylus hebreniticus, Trichuris sp. and Taenia
sp. in the gastrointestinal tracts of the grasscutters. Matamorous
et al. (1991) in Costa Rica also reported the incidence of Trichuris
sp., Taenia sp., Strongyloides sp. and Ascaridia
sp., as the helminthes parasites of the grasscutters.
Yeboah and Simpson (2004) in Ghana, again reported
some ecto and end-parasites of the grasscutters. Four species of ticks found
included Rhipicephalus simpsoni, Ixodes aulacodi Ixodes sp. and
Haemaphysalis parmata. The six helminthes parasites they reported comprised
of two genera of cestode and four of nematodes. The cestodes were Furhmanella
transvaalensis, Railletina mahonae; while the nematodes were Longistriata
spira, Trachypharynx natalensis, Paralibyostrongylus vondewei
and Trichuris paravispicularis.
A study carried out in Cameroon by Mpoame (1994) and
Awah-Ndukum et al. (2001) had also reported the
presence of a flea (Xenopsylla sp.), cestode (Hymenolopsis sp.)
and Nematode (Heterakis sp.) from a dead grasscutter in captivity. Opara
and Fagbemi (2008b) in Nigeria reported a wider array of helminthes in the
wild grasscutters, which comprised of 14 nematode species, 5 trematodes, 4 cestodes
and 1 acanthocephala.
Blood Protozoan Parasites
There have been reports of few cases of naturally occurring blood parasites
of the cane rats (Namso and Okaka, 1998) since, they
co-habit with other animal species. For example Ntekim and
Braide (1981) reported the occurrence of Trypanosoma lewisi in the
blood of wild rats, while Opara and Fagbemi (2008c)
reported the natural occurrence of Trypanosoma congolense, T. vivax, T. simiae,
Plasmodium and Babesia species among wild grasscutters and Trypanosoma
congolense, T. vivax, Plasmodium and Babesia species in the captive
- reared grasscutters.
Reasons for Grasscutter Domestication
The grasscutter has desirable attributes for domestication. There is an
ever-present demand for its meat (Asibey, 1969; Ntiamoa-Baidu,
1998), so every effort should be made to domesticate it. The importance of domesticating
the species is underscored (NRC, 1991) by the fact that successful domestication
of the grasscutter species would make it equivalent of South American Guinea
pigs and bring about a reduction in Africas protein shortage.
The most recent study of the animal has over come some of the hitherto set
backs to its domestication and established that the animal can be tamed and
even used as laboratory animal under both controlled and natural environmental
conditions (Addo, 1997). However, continued dependence
on hunted wild population for the grasscutter meat does not lend itself to quality
control of the meat nor does it enhance planned production, availability and
use as and when required for any reasonable purpose. Domestication or captive
breeding is a necessity if grasscutter meat industry is to be developed because
of these major reasons.
Nutrients Derived from Grasscutter Meat
The grasscutter is a prominent and steady source of alterative dietary animal
protein in many rural areas of Nigeria and other West African countries like
Benin, Ghana, Togo, Cote D voire (Ogunsanmi et
Asibey (1974a) reported that the grasscutter meat is
of high protein quality, but lower fat content than the meat from cattle, sheep
and goat and is greatly appreciated for its tenderness and taste. The approximate
composition (%) and mineral content (mg 100 g-1) of the grasscutter
meat in relation to that of other domesticated animal meat is shown in the Table
2 by Asibey (1974b).
In Ghana, grasscutter is an important source of animal protein (Asibey,
1978; Falconer, 1992; Ntiamo-Baidu, 1998) and the
rest of West Africa (Baptist and Mensah, 1986). The meat
is appreciated because of its culinary properties (Table 2)
(Ajayi, 1971; Den Hartog and de
Vos, 1973; NRC, 1991) with high protein, calcium, phosphorous and moisture
|| Proximate composition (%) and mineral content of the grasscutter
meat in relation to other domestic animal meat
The relatively low fat content makes the grasscutter meat a choice meat for
patients with cardiac problems.
ECONOMIC POTENTIALS OF THE GRASSCUTTER
Grasscutter contributes to both the local and export earnings of the country
(Asibey, 1974b; Baptist and Mensah,
1986; Ntiamo-Baidu, 1998; NRC, 1991). At the local market level, for example,
approximately 73 tons of grasscutter meat representing more than 15,000 animals
can be sold in a year (NRC, 1991). According to recent survey, the grasscutter
continues to dominate the bush meat trade (Falconer, 1992;
Ntiamo-Baidu, 1998). The Ghana Export Promotion Council (GEPC), included the
grasscutter on the non-traditional export trade of the country (Asibey,
1974b). Smoked grasscutter meat is exported to Europe and the United States
of America (Yeboah and Adamu, 1995).
However, international trade as well as regional and continental interests in the grasscutter meat provides economic bases for the development of the grasscutter industry. The industry will be greatly enhanced through the establishment of breeding centres to provide stocks for farmers and other growers who will multiply its production.
Also it would provide additional source of income, desperately required in
the quest to help the rural poor to meet their basic necessities and sustain
their food security (Asibey, 1986).
Conservational Problems Associated with Grasscutter Demand
Over 90% of the grasscutter farmers depend on the Wild stock of their animals
(Yeboah and Adamu, 1995), yet initial high mortality resulting from the trauma
of their capture from the wild is frustrating and expensive to breeders. Consequently,
there is great demand for captive reared breeding stock for starters. There
is the need to develop the grasscutter industry to the status of a viable commercial
venture capable of meeting both local and foreign demands without depending
largely on hunting from the wild.
Moreover, continual hunting with dogs and fire has negative environmental and
economic implications in the locality where the hunting goes on. Although, it
is illegal, fire is frequently used in hunting the grasscutter (Martin,
1985; Adu, 2002). There have been complaints by farmers
that their crops got damaged by communal hunters through trampling and fire
that get out of hand. Besides the destruction of farms and other properties,
the bush fires adversely affect other animals and plants, creating immediate
and long-term ecological problems. Captive breeding of the animal will reduce
risks associated with the hunting of the grasscutter.
Grasscutter as Minilivestock
Conventional livestock such as cattle, sheep and goats are usually kept
extensively, requiring substantial areas of land. Most of the land is threatened
by human population growth, poverty, increased urbanization and increased pressure
on land for other uses with higher economic benefits (Asibey
and Addo, 2000).
On the other hand, the grasscutter does not require much land and can even
be raised in the backyard and on flat rooftops by the landless (Asibey
and Addo, 2000). They also do not produce great quantities of body waste,
which in addition to being barely odourless, can easily be disposed off. Also
the grasscutter could provide an important source of part-time job opportunities,
particularly for the landless women and children (NRC, 1991; Ehui,
1999). Therefore, in situations where agricultural land is scarce or unavailable,
small sized animals such as the grasscutter (Anandajayasekeram,
1999) whose meat is generally referred to as conventional meat (Ntiamo-Baidu, 1998) could be developed along with livestock.
The grasscutter meat is a popular food item and has high market demand and
also commands high price (Ntiamo-Baidu, 1998; Addo, 1997).
Therefore, the NRC (1991), included the grasscutter in
its list of Minilivestock, little known animals with a promising economic future.
Scientific Potentials of the Grasscutter
Africas advent into scientific research in general and biomedical
research in particular, has come along with the need to import research animals
for these purposes. These research animals are maintained in facilities whose
environment is controlled with electricity and unreliable utility service in
many parts of Africa (Asibey and Addo, 2000). Failure
to maintain the animals in the special facilities results in their destruction,
besides the generation of incorrect research data, which becomes a waste of
research resources and time. The development of an indigenous research animal
such as grasscutter (Rosevear, 1969; Baptist and Mensah, 1986; Adoun;
1993) which does not need to be placed in rigidly controlled facilities
would help eliminate these problems (Asibey and Addo, 2000).
In conclusion, literatures have established that the grasscutter, a wild African rodent can be domesticated. The distribution in Africa, south of Sahara, the management system required, nutrition and reproductive performance have all been studied. However, detailed information on health and diseases of these rodents are scanty. Furthermore, the grasscutter is known to be economically important as an agricultural pest and its meat is widely accepted by all classes of people. It is also a good laboratory animal for research studies.