Sky Journal of Agricultural Research Vol. 3(2), pp. 025 - 030, February, 2014
Available online http://www.skyjournals.org/SJAR
ISSN 2315-8751 ©2014 Sky Journals
Full Length Research
Effect of coat colour, ecotype, location and sex on hair
density of West African Dwarf (WAD) goats in Northern
Ghana
NAANDAM, Jakper* and ASSAN, Ishmael Kojo
Department of Animal Science, Faculty of Agriculture, University for Development Studies, P. O. Box TL 1882, Tamale,
Ghana.
Accepted 5 February, 2014
Trends in global warming call for identification and development of heat tolerant goats. Hair density as a
defining adaptive attribute would seem to assume some critical importance. A study was carried out in Bongo
and Tamale main abattoirs to establish whether there were any hair density variations in local goats belonging
to different geographical areas. Twenty four (24) West African Dwarf (WAD) goats (12 from each region) were
used for the experiment. Parameters like age, coat colour and weight were noted directly from the animals
before slaughter. For hair density determination, six point four five square centimeters (a square inch) was
randomly selected on the flayed skins of the WAD goats, shaved and the number of hair follicles was obtained
using a colony counter. Number of hair follicles per square inch at each location was used as the hair density.
The results showed significant effects for sex (p < 0.001), ecotype (p < 0.001) position of hair on the body i.e.
dorsal or ventral (p< 0.001), on hair density. In addition, age significantly (p < 0.001) affected hair density while
coat colour had no effect on hair density (p > 0.05) possibly suggesting that the Black and Brown colours used
in present study may be functionally closer in their physiological tasks.
Key words: Ecotype, hair density, hair follicles, heat tolerant goats, WAD goats.
INTRODUCTION
Livestock rearing plays a major role as a safety net that
enables households to get quick income to settle urgent
financial needs such as buying food and farm inputs,
settling hospital bills, paying school fees, expenses for
funeral and marriage (Dzoagbe et al., 2007). Goats tend
to tolerate heat better than sheep. Goats with loose skin
and floppy ears may be more heat tolerant than other
goats. Angora goats have a decreased ability to respond
to heat stress as compared to sheep and other breeds of
goats. Dark-colored animals are more susceptible to heat
stress, while light-colored animals may be proned to
sunburn. These observations were made by Schoenian
(2010). Schoenian (2010) further stated that horned
*Corresponding
author:
Tel.:+233244895504/+233205162657.
jaknaan@yahoo.com.
animals dissipate heat better than polled (or disbudded)
animals. Young animals are more susceptible to heat
stress than older animals. In fact, any animal with a poor
nutritional status or compromised immunity will be more
susceptible to environmental extremes this author wrote.
Tropical areas are endowed with a wide variety of
indigenous small ruminant breeds that have evolved to
adapt to the prevailing harsh environmental conditions
and traditional husbandry systems (Baker and Rege,
1994). This adaptation to the harsh environmental
condition may be linked to the hair density of small
ruminants, as hair is known to have some insulating role.
According to Baton et al. (2004) the coat acts as a mat to
physically prevent the sun rays from reaching the
animal’s body. Also the long hair serves as an insulator
from the heat, providing a hair buffer zone between the
outer environment and the animal’s body.
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Sky. J. Agric. Res.
Given the current trend in global warming, goats that can
withstand rising environmental temperatures will become
critical. One way to have a well adapted critical mass of
goats, is through focusing on the production and
maintenance of goats that are heat tolerant in terms of
hair density on their skin. Bongo district is a bit warmer
than Tamale metropolis and over the past 40 years
temperatures in Bongo have increased by about 1°C
(Obeng, 2005).
Consequently this study set out to examine hair density
variations, if any, as they relate to these two ecotypes
and other factors in the local WAD goats.
slaughtering, the flayed skin which naturally contains
bacteria on the death of the goat multiply that causes
putrefaction of the skin. In hot humid conditions, this
process of rottening will quickly spoil the skin (Peacock,
1996). The fresh skin was cleaned using tap water then
spread on a concrete floor, inner side facing upwards and
granulated salt applied on every part. The salt removes
water from the skin and stops bacterial growth that
caused rottening (Steele, 1996). The skins were folded
into a basket and transported to the laboratory for
analysis.
Hair follicle determination
MATERIALS AND METHODS
Study area
The study was carried out at the Tamale and Bongo
abattoirs. Tamale main abattoir is situated at Shishegu in
Tamale metropolis, in northern region of the Guinea
l
l
zone. It is located at 9° 24 north of the equator, 0° 50
west of the Greenwich meridian, and 120 m above sea
level. Temperature ranges from 9°C to 38°C. Bongo
abattoir on the other hand, is located in Bongo dstrict in
Upper East region on the fringes of the Sudan Savannah.
o
o
It lies between latitudes 10 54’ and 28’’ and 0 48’ and
29’’North.
Experimental animals
Twenty four (24) WAD goats were considered for the
experiment. WAD goats were identified according to
characteristics presented by Adedeji et al. (2006).
Additionally, Expert technical assistance information was
obtained from the Kintampo goat breeding station in
Ghana on height of WAD goats at withers (under 50 cm)
and weight (18 - 25 kg). Out of the 24 animals, 12
animals from Bongo abattoir comprised 6 young animals
(3 males and 3 females) with different weights and ages
and of two colours (brown and black). The remaining 6
were adult animals (3 males and 3 females), also with
varied weights, ages and of the same colours as in the
young ones. Similar data had been taken from the
Tamale abattoir.
Parameters considered
Parameters considered were colour (by observation),
weight (using a spring balance) and age (by dentition).
Hair follicle density was obtained after slaughtering.
By random sampling, six (6) sections were obtained from
each skin (2 sections from the dorsal part and 4 sections
from both the right and left ventral parts of the skin). With
the aid of a plastic meter rule and a marker, six point four
five square centimeters (i.e. a square inch) was
measured from each of the above stated sections and the
hair shorn with a blade to enhance clearer view of the
hair follicles. The colony counter gives a bright
background enhancing easy count of the hair follicles
(Plate I).
Statistical analysis
Data were analysed by regression method using
generalized linear model in Genstat (3.0 edition) Results
are presented in bar charts and tables.
RESULTS
Effects of sex, age, colour and ecological zone on
mean hair density
Figure 1 shows the effect of sex on the hair density for
WAD goats at various stages of developments. Generally
female goats had higher mean hair density (P > 0.001)
than males in absolute terms for particular age groups.
The variation in hair densities of WAD goats from
Bongo in the Upper East region and Tamale in the
Northern region of Ghana is depicted in Figure 2. Goats
from the Northern region had higher mean hair density (P
> 0.001) than those from Upper East region.
Goats with brown coat colour appeared to have higher
mean hair density than those with black coat colour in
absolute terms but the difference was not significant (P >
0.05) (Table 2 and Figure 3).
Regression analysis
Processing and preservation of skin
After animals were killed through ritualistic or religious
The genstat output for the regression analyses for
number of groups of fitted terms were as follows:
Jakper and Kojo
27
Mean Hair density
(No. per 6.45cm
sq.)
Plate I. Counting number of hair follicles on skin with the help of a colony counter.
600
400
200
0
Young females
Young males
Adult females
Adult males
sex
Figure 1. Effect of sex on mean hair densities of West African Dwarf (WAD) goats at different stages of growth.
Figure 2. Effect of ecological zone on mean hair density of West African Dwarf
goats.
Response variate: hair density
Fitted terms: constant + eco-zone + sex + colour + ageyears + location
Summary of analysis
Table 1 show the analysis of variance for the fitted terms
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Sky. J. Agric. Res.
380
375
370
Mean Hair density
(No.per 6.45 cm sq)
365
360
355
350
Black
Brown
Coat Colour
Figure 3. Effect of coat colour on hair densities of WAD goats.
Table 1. Anova table for fitted terms; eco-zone, sex, colour, age and location.
Regression
Residual
Total
Degrees of
freedom
9
134
143
Sum of squares
Mean square
F.calculated
Probabilty
255154.
77726.
332880.
28350.5
580.0
2327.8
48.88
< .001
Percentage variance accounted for 75.1.
Table 2. Standard error, t statistic and probability estimates for fitted parameters.
Parameters
Constant
Eco-zone 2
Sex 2
Colour 2
Age-years 2.5
Age-years 3.5
Age-years 4
Age-years 4.5
Age-years 5
Location 2
Maximum likelihood
estimates
319.35
19.08
27.48
8.52
28.9
91.0
72.18
50.4
56.7
-34.69
Standard Error of
estimated parameter
5.49
4.44
4.33
4.53
11.0
10.9
4.44
10.9
10.7
4.02
eco-zone, sex, colour, age (years) and location. The fitted
2
terms were highly significant (p < 0.001) with an R of
75.1%.
The estimates of parameters indicated very high
significant levels (P < 0.001) for all items fitted in the
regression except for colour which was not significant (P
2
> 0.05) (Table 2). R increased to 86% when eco-zone
was dropped from the fitted terms. Notwithstanding, it
demonstrated that the accuracy of predicting hair density
could be improved if a stepwise regression was carried
out.
“t”statistic
Significance (tpr)
58.19
4.30
6.34
1.88
2.63
8.38
16.27
4.64
5.29
-8.63
< .001
< .001
< .001
0.062
0.010
< .001
< .001
< .001
< .001
< .001
DISCUSSION
Effects of sex, age, colour, eco- zone and location on
the body on mean hair density
As alluded to earlier Schoenian (2010) noted that darkcolored animals are more susceptible to heat stress,
while light-colored animals may be prone to sunburn.
This assertion about coat colour adaptability is buttressed
by the fact that hair works as a temperature regulator in
association with muscles in the skin. When the outside
Jakper and Kojo
temperature is cold, these muscles pull the hair strands
upright, creating pockets that trap air which provides a
warm, insulating layer next to the skin. In case the
temperature outside is warm, the muscles relax and the
hair becomes flattened against the body, releasing the
trapped air. Low hair density should thus be a good
adaptation for extreme temperatures since more air will
be trapped for insulatory purposes during cold weather
while the same should give enough room for better
flattening of the hair during warm weather. This should
translate into less air being trapped on the skin and
consequently a resultant lesser heating effect of trapped
air. Thus the mean hair density for eco-zone (Bongo vs
Tamale) being significantly different (P < 0.001) as
illustrated in Figure 2 could probably for explained by the
fore-going. Obeng (2005) showed that temperatures in
Bongo district over the past 40 years have increased by
o
about 1 C during that period compared to the overall for
northern Ghana, supporting the hypothesis that the less
hair goats have in Bongo, the better they would be at
containing the increased temperature in the environment.
Jordan (1999) noted that, big Angora goats produce
more kids and more hair. So, there may be a relationship
between reproductive activities and hair density. This
relationship and other genetic differences may be
postulated in present study to explain why females had a
higher mean hair density than males (Figure 1 and Table
2). With age, however, Wikipedia, (2008) has noted that
the anagen is the active growth phase of hair follicles
where root of the hair are dividing rapidly in humans,
adding to the hair shaft. The amount of time the hair
follicle stays in the anagen phase is genetically
determined. If hair growth in goats is assumed to follow
this pattern, then it is easily explained why adults had a
higher mean hair density (Figure 1 and Table 2) than
young ones. At the end of the anagen phase, an
unknown signal causes the follicle to go into the catagen
phase the authors wrote.
Sponenberg (2004) explained that many different
alleles occur within the Agouti locus of goats, however all
of the caprine Agouti locus patterns are characterized by
symmetrical
arrangements
of
eumelanic
and
phaeomelanic areas. In goats, the eumelanic areas are
usually black, although can be brown when the genotype
at other loci modifies black to brown, suggesting that the
black and brown colour may be very close in their
attributes and thus explaining the possible insignificant
difference that was observed in this study between the
two colours. Whereas Siddiqua and Amin
(2009)
observed some significant effect (p < 0.001) in colour on
the hair density of goats, their work involved black and
white goats, which is to be expected as black is a distant
variant of white.
With reference to location of the hair on the body, the
study found significant differences (P < 0.00) within the
same coat colour groups. Higher hair density was found
on dorsal portion compared to the ventral, which again
29
could be an adaptive feature of insulating the dorsal
portion better than the ventral against inclement weather,
since animals are exposed to the environment more by
via those portions. The regression equation suggested
that it may be possible to predict hair density using the
2
fitted terms but the coefficient of determination R could
only account for 75% of the total variation in the
dependent variable.
Conclusion
West African Dwarf (WAD) goats found in the Northern
region of Ghana had higher hair density than those found
in the Upper East region of Ghana (Bongo). Also, female
WAD goats had more hair per unit area than males, both
for the young and adult goats. Brown and black coat
colours appear to have similar effect on hair density.
Further studies recommended to be carried out using
more animals should include animals in the forest zone to
get a better effect of climate. Molecular basis of hair
density should be explored in future research.
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