recognize their twin-born kids. The hour post-partum and parity of does did not significantly affect Ž
. P 0.05 their kid recognition ability. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Goat maternal–filial bond; Twins; Separation response; Recognition ability
1. Introduction
Breed and litter size are two important factors that affect the abilities of ewes and Ž
. their lambs to recognize each other. For instance, Stevens et al. 1982 reported that
many fined wooled Merinos with twins became permanently separated from one twin on the first day of birth due to the ewe moving away and leaving the lamb behind. The
ewes appeared to be unconcerned if followed by only one lamb. This problem, however, does not seem to occur in other types of Merino sheep and in British breeds, which
Ž .
appear to be aware of both twins Arnold, 1985 . Studies have also shown that 12-h-old Border Leicester = Merino crosses are able to recognize their mothers more readily than
pure-bred Merino lambs of the same age when they are close together, regardless of Ž
whether they are born as singles or as twins Nowak et al., 1987; Nowak and Lindsay, .
Ž .
1990 . Nowak 1989 reported that single- and twin-born Merino lambs had striking differences in their ability to recognize their mothers. While it took up to only 24 h for
single-born lambs to recognize their mothers, it took twin-born lambs 2–3 days to do so. Ž
. Nowak 1989 further reported that single-born lambs were significantly more attracted
to an ewe at 18 and 24 h post-partum than were multiple lambs in a two-choice situation. The single-born lambs were also better at recognizing their mothers and spent
more time with them than multiple-born lambs. In another study, 24 h single-born lambs were found to be better at discriminating between their mothers and alien dams at a
Ž .
distance of less than 50 m Nowak et al., 1990 . Contrary to these findings, Oppong- Ž
. Anane 1991 did not find any significant difference in the dam recognition response
between 18-h-old single- and twin-born Merino lambs. There is a paucity of information on the effect of litter size on the dam recognition ability of newborn goats. Information
on tropical breeds of goats is even more scarce. In our previous study, we reported poor
Ž .
dam recognition ability of single-born West African dwarf goats Addae et al., in press . Ž
. At 36 h of age, nine out of 14 single-born kids i.e. 64 could recognise their dams
while at 48 h, 75 of the kids was able to recognize their dams. It is not clear whether the dam recognition ability of twins would be different from that of single-borns because
goats, as ‘hiders’, leave their young ones for periods to graze during the first few days after parturition. Thus, for both single- and twin-born kids, the periods of separation
from their dams are the same. The objective of this study, therefore, was to investigate Ž .
i the response of twin-bearing West African dwarf goats and their kids to separation Ž .
and ii the existence of mutual recognition between dams and their twin-born kids.
2. Animals, materials and methods
2.1. Experimental site and system of management The study was carried out at the National Goat Breeding Station of the Animal
Ž .
Production Department of the Ministry of Food and Agriculture Ghana . The station is
Ž
X
located at Kintampo in the Brong Ahafo region of Ghana longitude 1805 W and latitude
X
. 7840 N and is the derived Savannah zone. The station has 10 paddocks ranging in size
from 1.2 to 2.5 ha. The different flocks on the station are rotated on these paddocks containing grass forage such as Panicum maximum and Cyanodon nlemfuensis mixed
with Stylosanthes hamata and Centrosema pubescens. Two weeks prior to mating, the
Ž .
does were flushed i.e. given extra ration . Does observed to exhibit signs of parturition were sent to a holding pen and kept under 24-h observation. After kidding, does and
their kids were allowed to stay together for 4 h before the kids were weighed, sexed and ear-tagged. This period of non-interference was necessary to allow sufficient time for
does and their kids to establish a bond.
2.2. Animals Twenty-four twin-bearing West African dwarf nanny goats and their kids were used
for the study. Ten were primiparous and 14 were multiparous. Out of the 48 twin-born kids used, eight were tested at 18 h, 14 at 24 h, 14 at 36 h and 12 at 48 h. Out of the 40
kids tested between 24 and 48 h, 20 were males and 20 were females; 29 were in the Ž
. Ž
. low birthweight class F 1.2 kg and 11 were in the high birthweight class 1.2 kg .
This classification of kids into two birthweight classes was based on the mean birthweight of West African dwarf goats, which is about 1.2 kg. Two hours prior to the
tests, the teats of the test and control does were covered with plaster to prevent their kids from sucking. Each doe and her kids were tested once to prevent familiarization with the
test procedure due to previous experience.
2.3. Testing pen Ž
. The testing pen used for all the three experiments Fig. 1 was a modification of the
Ž .
one used by Oppong-Anane 1991 . It was a funnel-shaped enclosure of wire mesh about 1.0 m high. At the smaller end were two pens for kids measuring 0.5 = 0.5 m
2
and separated by a space of the same dimensions. Seven meters away, at the opposite end of the enclosure, were two pens each measuring 1.0 = 0.8 m
2
. These pens allocated to the test and control does were separated by a space of the same dimensions. The
partitions between adjacent pens and the outside of all pens were covered with black plastic sheets to prevent animals from seeing one another or the experimenter during the
tests. The enclosure was completely weeded to eliminate any grazing material that might serve as a point of distraction.
2.4. Experiment 1: the behaÕioural response of twin-bearing does and their kids to separation when the kids had not been suckled for 2 h
Prior to the test, each test doe and her twins were confined to one of the doe pens for about 10 min to allow the animals to settle and also to ensure that they were the correct
Fig. 1. Diagram of pen used for testing the response of does and their kids to separation and their mutual recognition.
dam–offspring combination. Another doe and her twins, which were born about the same time as the test kids, were confined to the other doe pen to serve as the control. At
the beginning of the experiment, the test and control kids were removed and placed in separate kid pens with the test kids facing the control doe and the control kids facing the
test doe. The plaster, covering the teats of both the test and control does, were then removed. The behavioural response of the test doe and her twins to separation was
observed over a 5-min period and ranked according to the score used by Oppong-Anane Ž
. 1991 and shown in Table 1. Each twin was scored separately.
Table 1 Key to score used for the behavioural response of twin-born kids and their dams to separation
Score Kid
Doe 5
Very active, continuous high-pitched bleats Restless, continuous high-pitched bleats
4 Not very active, but high-pitched bleats
Continuous high-pitched bleats and a search 3
Active, but few bleats Some bleats, with a little search
2 Inactive, few bleats
Few bleats, no search 1
Down, inactive No response
2.5. Experiment 2: the ability of twin-born kids to discriminate between their own and an alien doe in a two-choice situation at a distance of 6 m when they had not been
suckled for 2 h
After the behavioural response of the doe and her kids to separation had been scored, one test kid was removed and placed at a point 6 m from the does. It was placed in a
central position directly in line with the space between the two doe pens. The kid was then gently released and observed for 5 min. Its dam recognition ability was ranked
Ž .
according to the score used by Oppong-Anane 1991 and shown in Table 2. The kid was then returned to the kid pen and the other twin taken through the same procedure.
2.6. Experiment 3: the ability of does to distinguish between their own twin-born kids and alien twins in a two-choice situation at a distance of 7 m when the kids had not
been suckled for 2 h
After experiment 2, the test doe was released and observed for 5 min for her ability to recognize her twins. She was then ranked according to the score used by Oppong-Anane
Ž .
1991 and shown in Table 3. 2.7. Statistical analysis
Ž .
The chi-square procedure of the Statistical Analysis Institute 1989
statistical package was used to determine whether age or hours post-partum had any effect on the
behavioural response to separation exhibited by does and their twins and on their mutual recognition. The procedure was also used to determine whether the sex and birthweight
Table 2 Key to score used for dam recognition ability of twin-born kids
Score Kid behaviour
5 Goes directly to mother and stays
4 Goes to mother after hesitating between both does
3 Goes to alien doe first but switches to mother and stays
2 Goes to alien doe and stays
1 Does not reach either doe
Table 3 Key to score used for kids recognition ability of twin-bearing does
Score Kid behaviour
5 Goes directly to own kids and stays
4 Goes to own kids after hesitating between the two pairs of twins
3 Goes to alien twins but switches to own twins and stays
2 Goes to alien twins and stays
1 Does not reach either pair of twins
of kids and parity of their dams had an effect on these behavioural parameters at 24–48 h post-partum. All comparisons were done at 5 level.
3. Results
