Effects of coat colour genes on body measurements, heat tolerance traits and haematological parameters in West African Dwarf sheep

doi:10.4236/ojgen.2013.34031

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Open Journal of Genetics, 2013, 3, 280-284 OJGen

http://dx.doi.org/10.4236/ojgen.2013.34031 Published Online December 2013 (http://www.scirp.org/journal/ojgen/)

Effects of coat colour genes on body measurements, heat

tolerance traits and haematological parameters in West

African Dwarf sheep

John S. Decampos1, Christian O. N. Ikeobi1*, Olajide Olowofeso1, Olusiji F. Smith2, Matthew A. Adeleke1,

Mathew Wheto1, David O. Ogunlakin1, Abubakar A. Mohammed1, Timothy M. Sanni1,

Babatunde A. Ogunfuye1, Raman A. Lawal1, Adeyemi S. Adenaike1, Samuel A. Amusan1

1Department of Animal Breeding and Genetics, Federal University of Agriculture, Abeokuta, Nigeria

2Department of Animal Physiology, Federal University of Agriculture, Abeokuta, Nigeria

Email: *[email protected]

Received 13 June 2013; revised 10 July 2013; accepted 6 August 2013

cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

With 178 West African Dwarf sheep aged 1 to 3 years,

a study was conducted to investigate the effects of

coat colour genes on body measurements, heat toler-

ance traits and haematological parameters. Body

measurements considered included body length, hair

length, ear length, hip width, tail length, height at

withers, rump height, fore cannon bone length, chest

depth, heart girth and body weight. Heat tolerance

traits considered were skin temperature, rectal tem-

perature, pulse rate and respiratory rate. Blood sam-

ples were collected for the evaluation of white blood

cell (WBC), red blood cell (RBC), haemoglobin

(HGB), haematocrit (HCT), mean corpuscular vol-

ume (MCV), mean corpuscular haemoglobin (MCH),

mean corpuscular haemoglobin cell (MCHC), red cell

distribution width (RDW), platelets (PLT), mean

platelets volume (MPV), platelets distribution width

(PDW) and plateletcrits (PCT). Results showed that

coat colour gene (CCG) had significant (P < 0.01) ef-

fect on rump height and tail length. Animals with

black (BB) coat colour had the highest mean value for

rump height (57.80 ± 1.29 cm) and tail length (22.10 ±

0.89 cm), while brown (Bb) coat colour had the least

value of 53.00 ± 6.00 cm for rump height and 17.50 ±

0.50 cm for tail length. The CCG had significant (P <

0.01) effect on body temperature and pulse rate, with

the grey/mouflon (Ag) colour possessing the highest

body temperature (38.90˚C ± 0.22˚C), and Bb having

the least value of 37.20˚C ± 0.35˚C. White/tan (Awt)

had the highest pulse rate of 28.90 ± 0.66 beats/min

and Bb had the least value of 20.00 ± 2.00 beats/min.

The CCG had significant (P < 0.01) effect on RBC

and MPV with brown (Bb) colour having the highest

RBC counts (18.20 ± 0.00 L) and badgerface (Ab)

having the least value (11.50 ± 0.62 L). The Bb had

the highest value (5.60 ± 0.00 fL) for MPV and Ab had

the least value (4.70 ± 0.15 fL). Sheep with Bb and Ab

were found to withstand heat stress better than oth-

ers.

Keywords: Coat Colour Gene; Haematological

Parameters; Morphological Indices; Sheep

1. INTRODUCTION

The animal performance is an expression of genetic and

environmental factors [1]. Genetic factors depict innate

factors. They are the factors which are inherent and

could re-occur from generation to generation. Coat col-

our which is a genetic factor is known to adapt animals

to different climatic zone s and has considerab le influence

on the performance of various stocks [2-3]. The West

African Dwarf (WAD) sheep is one of the breeds of

sheep in Nigeria with a small, compact body which may

be all white, all black, all brown, or spotted black or

brown on a white coat. It is predominantly found within

the rainforest, mangrove swamps and coastal regions in

southern Nigeria [4].

Growth, often defined as the increase in size or body

weight at a given age, is one of the important selection

criteria for the improvement of meat animals such as

sheep [5]. Body measurements can be used in assessing

growth rate, feed u tilisation an d carcass characteristics in

farm animals [6]. Body measurements are divided into

skeletal and tissue measurements according to [7]. The

*Corresponding author.

OPEN ACCESS

J. S. Decampos et al. / Open Journal of Genetics 3 (2013) 280-284 281

height at withers is part of skeletal measurements,

whereas the heart girth is part of tissue measurements [8].

Body measurements of meat animals have been found to

be useful in quantifying the body size and shape [9] and

necessary for estimating genetic parameters [10]. Heat

tolerance is the ability to be comfortable when external

temperature rises. The common heat tolerance traits in-

clude sweating rate, heart and breathing rates, rectal

temperature, and skin temperature [11]. When the

physiological mechanism of the animal fails to negate

the excessive heat load, the rectal temperature increases.

At the same time, such exposure of sheep to heat stress

evokes a series of drastic changes in the biological func-

tions, which include a decrease in feed intake efficiency

and utilization, disturb ances in water, protein, en erg y and

mineral balances, enzymatic reactions, hormonal secre-

tions and blood metabolites [12].

Haematological parameters are those parameters that

are related to the blood and blood-forming organs [13].

The blood consists of components broadly divided into

three parts: leukocytes, erythrocytes and platelets, and

further sub-divided into haemoglobin (Hb), red blood

cells (RBC), packed cell volume (PCV), mean corpuscu-

lar haemoglobin (MCH), etc. These traits play important

roles in animal immune function and disease resistance

[14]. The use of blood examination as a way of assessing

the health status of animals has been well documented

[15]. This is because they play a vital role in physiologi-

cal, nutritional and pathological status of the animals

[16].

Although much work has been carried out to assess the

effects of diseases and nutrition on sheep in Nigeria, lit-

eratures on the tolerance of sheep to heat stress and its

effects on productivity are however limited [17]. Infor-

mation on the physiological responses of sheep to heat

stress will not only assist in the provision of adequate

housing, feed and other environmental conditions, but

also be useful in the selection of suitable breeds for each

ecological niche [17]. The knowledge of the response of

different coat colour types of heat stress will help in the

selection of suit able breeds for each ecological niche.

The study of haematological parameters in WAD

sheep could predetermine the genetic potential of an

animal for selection [18].

This study was therefore carried out to investigate the

influence of the coat colour gene on the productive and

adaptive traits in WAD sheep in Nigeria.

2. MATERIALS AND METHODS

2.1. Study Location and Sample Size

This study was carried out in Odeda Agro-ecological

Zone of Ogun State, Nigeria. One hundred and seventy

eight WAD sheep were sampled for eight months. West

African Dwarf sheep in the zone are usually reared under

the free-range system whereby the owners occasionally

feed their animals with kitchen wastes, cassava and yam

peels or whole cassava and corn shaff in the morning

before they are left to roam about the houses and sur-

rounding. There was no known common browse plant in

the studied area, except that the animals browse on

whatever comes their way. There was no known deliber-

ate veterinary or ethno-veterinary practice engaged in by

the livestock owners.

2.2. Data Collection and Analysis

Exactly 7 ml of blood was collected via the jugular vein

puncture of each animal using a 10 mm gauge syringe

into sample bottles containing the antico agulant, ethylene

diamine tetra acetic acid (EDTA). Sample bottles were

well-labelled for proper identification and blood samples

collected were transported to the laboratory for the

analysis of the haematological parameters which in-

cluded white blood cell (WBC), red blood cell (RBC),

haemoglobin (HGB), haematocrit (HCT), mean corpus-

cular volume (MCV), mean corpuscular haemoglobin

(MCH), mean corpuscular haemoglobin cell (MCHC),

red cell distribution width (RDW), platelets (PLT), mean

platelets volume (MPV), platelets distribution width

(PDW) and plateletcrits (PCT).

Phenotypic measurements were taken on sampled

sheep on site. These included both the quantitative and

qualitative measurements of the body. Th e major qualita-

tive description taken was the coat colour. Using the

fleece colour in sheep as earlier observed by [19], the

major coat colour gene variations observed included the

white/tan (Awt), black (BB), spotted brown (Bb), grey/

mouflon (Agt) and badgerface (Ab). The age and sex of

the animals were also noted. Quantitative measurements

of the body taken included body weight using a spring

balance attached to a scaffold, body length, heart girth,

height at withers, ear length, hair length, rump height,

hip width, tail length, fore cannon bone length and chest

depth with the use of a measuring tape. Brief descrip-

tions of the quantitative measurements are as follows:

Height at withers: which is the dorsal midline at the

highest point on the wither.

Tail length: which is the distance between the tip of

the tail and the base end tail touching the body of the

animal.

Ear length: distance between the tip of the ear and the

base of the ear.

Body length: distance between the tip of the mouth

and the base of the tail.

Heart girth: the body circumference immediately

posterior to the front legs or the body circumference on

the fore hips.

Height at hips: it will be measured mid sacrum on the

J. S. Decampos et al. / Open Journal of Genetics 3 (2013) 280-284

282

dorsal mid-line. colour genes with both black colours having the highest

mean values and the brown possessing the least values

for both parameters.

Width at hips: distance between the lateral surfaces on

the point of shoulder. Table 2 shows the least square means of the heat

stress parameters as influenced by the coat colour genes.

The results show that th e body temperature and the pu lse

rate are significantly (P < 0.01) affected by the coat col-

our genes with the grey/mouflon (Ag) having the highest

body temperature and the brown (Bb) possessing the

least body temperature, and the white/tan (Awt) colour

gene having the highest pulse rate and the brown (Bb)

having the least pulse rate.

Fore cannon length: distance between the leg bones.

The body temperature, rectal temperature, pulse rate

and respiratory rate of the animals were also taken with

the use of a thermometer and stethoscope, respectively.

The management system, environmental temperature,

geographical locations of the animals, and time of the

day were also considered. Data obtained for haemato-

logical parameters, heat tolerance traits and body meas-

urements were analyzed using the General Linear Model

Procedure of [20]. The model employed was of the form: Table 3 shows the least square means of the haemato-

logical parameters as influenced by the coat colour genes.

The results showed that the red blood cell and the mean

platelets volume were significantly (P < 0.01) affected by

the coat colour genes with the brown (Bb) colour genes

having the highest red blood cell count and the badger-

face (Ab) having the least red blood cell count. The mean

platelets volume showed the brown colour (Bb) with the

highest value and the badgerface had the least value of

the mean platelets volume.



ijkij kijk

YMSPSP





 

where Yijk = The parameter of interest, µ = Overall mean

for the parameter of interest, Mi = Fixed effect of ith age

(i = 1 - 3), Sj = Fixed effect of the jth sex (j = 1 - 2), Pk =

Fixed effect of the kth coat colour gene (k = 1 - 5),



k = Interaction effect of the jth sex and kth coat

colour genes and

ijk



= Random error associated with

each record.

Correlation was also computed using [20] to ascertain

relationships among measurable traits. Means that dif-

fered significantly were separated using Duncan’s Multi-

ple Range Test [21].

4. DISCUSSION

From the results of the expe riment presented in Tables 1

and 2, the high temperature is as a result of the effect of

the high absorption rate of the ultraviolet rays of the

sunlight by the pigments on the skin of the animals and

the influence of the environmental temperature. This

agrees with the result of [22] who reported that surface

body temperature of white cattle was consistently lower

than coloured cattle. The authors further concluded that

3. RESULTS

Table 1 shows the least square means of the effects of

coat colour genes on the linear body measurements of the

WAD sheep. It revealed that the rump length and the tail

length were significantly (P < 0.054) affected by the

Table 1. Least square means ± standard error of the linear body measurements as affected by colour gene.

Colour

Body measurements White/tan (Awt) Badgerface (Ab) Grey/mouflon (Ag) Black (BB) Brown (Bb)

Body weight (kg) 17.89 ± 0.69 19.91 ± 1.13 16.19 ± 2.44 18.04 ± 1.52 19.10 ± 6.10

Height at withers (cm) 54.78 ± 0.52 54.31 ± 0.91 52.70 ± 1.96 54.83 ± 1.42 51.25 ± 1.75

Rump length (cm) 56.66 ± 0.49ab 56.14 ± 0.71ab 55.20 ± 1.87ab 57.75 ± 1.29a 53.00 ± 6.00b

Fore cannon bone length (cm) 13.82 ± 0.19 13.53 ± 0.23 12.35 ± 0.43 13.53 ± 0.43 12.50 ± 0.50

Chest depth (cm) 27.97 ± 0.41 28.19 ± 0.46 26.40 ± 1.18 27.30 ± 0.88 26.75 ± 3.25

Hip width (cm) 12.75 ± 0.23 13.65 ± 0.38 13.60 ± 0.70 13.33 ± 0.67 14.00 ± 2.00

Ear length (cm) 10.68 ± 0.18 10.31 ± 0.29 10.00 ± 0.49 10.33 ± 0.39 11.00 ± 1.00

Heart girth (cm) 64.47 ± 0.77 65.22 ± 1.15 60.60 ± 2.65 61.60 ± 2.92 60.50 ± 7.50

Tail length (cm) 20.82 ± 0.33ab 21.39 ± 0.51a 21.80 ± 1.13a 22.13 ± 0.89a 17.50 ± 0.5a

Hair length (cm) 4.16 ± 0.11 4.11 ± 0.14 4.70 ± 0.39 4.60 ± 0.40 4.75 ± 0.25

Body length (cm) 69.72 ± 0.89 69.87 ± 1.16 70.6 ± 2.63 71.87 ± 1.74 69.00 ± 1.00

Different superscripts of a and b in the same row mean a significant difference between the values at P < 0.05.

OPEN ACCESS

J. S. Decampos et al. / Open Journal of Genetics 3 (2013) 280-284 283

Table 2. Least square means ± standard error of heat stress parameters as influenced by colour genes.

Colour

Heat tolerance traits White/tan (Awt) Badgerface (Ab) Grey/mouflon (Ag) Black (BB) Brown (Bb)

Body temperature (˚C) 38.65 ± 0.14a 38.78 ± 0.11a 38.87 ± 0.22a 38.86 ± 0.22a 37.15 ± 0.35b

Pulse rate (beats/min) 28.91 ± 0.66a 26.51 ± 0.74a 26.00 ± 1.23ab 27.87 ± 1.27a 20.00 ± 2.00b

Respiratory rate (breaths/min) 17.80 ± 0.48 20.63 ± 1.30 18.90 ± 2.02 21.33 ± 1.55 14.00 ± 4.00

Rectal temperature (˚C) 39.22 ± 0.13 39.20 ± 0.10 39.15 ± 0.23 39.29 ± 0.19 38.60 ± 0.60

Different superscripts of a and b in the same row mean a significant difference between the values at P < 0.05.

Table 3. Least square means ± standard error of haematological parameters as influenced by colour genes.

Colour

Haematological Parameters White/tan (Awt) Badgerface (Ab) Grey/mouflon (Ag) Black (BB) Brown (Bb)

WBC(L) 11.42 ± 0.96 8.46 ± 1.28 7.79 ± 2.66 11.65 ± 2.11 0.00 ± 0.00

RBC(L) 11.64 ± 0.39b 11.54 ± 0.62b 14.61 ± 1.60ab 12.77 ± 1.08ab 18.16 ± 0.00a

HGB(g/l) 100.74 ± 3.83 100.00 ± 6.09 132 ± 18.37 110.00 ± 9.82 150.00 ± 0.00

HCT(%) 30.70 ± 1.04 30.69 ± 1.68 39.49 ± 4.57 32.62 ± 2.77 45.20 ± 0.00

MCV(fl) 26.50 ± 0.23 26.67 ± 0.30 27.34 ± 1.18 25.69 ± 0.49 24.90 ± 0.00

MCH(Pg) 8.54 ± 0.06 8.49 ± 0.09 8.83 ± 0.29 8.56 ± 0.12 8.20 ± 0.00

RDW(%) 17.69 ± 0.14 17.64 ± 0.19 18.22 ± 0.42 17.93 ± 0.27 19.40 ± 0.00

PLT(L) 209.71 ± 10.17 187.33 ± 15.50 161.60 ± 16.96 173.6 ± 18.27 71.00 ± 0.00

MPV(F/L) 4.88 ± 0.03ab 4.70 ± 0.15b 5.04 ± 0.12ab 4.94 ± 0.06ab 5.60 ± 0.00a

PDW(%) 13.19 ± 0.03 12.66 ± 0.39 13.05 ± 0.04 13.13 ± 0.03 12.90 ± 0.00

PCT(%) 1.29 ± 1.19 0.09 ± 0.01 0.08 ± 0.01 0.08 ± 0.01 0.04 ± 0.00

Different superscripts of a and b in the same row mean a significant difference between the values at P < 0.05. Abbreviations are as defined within text.

with exposure to sunlight, coloured cattle should be more

adapted to tropical or sub-tropical conditions in confined

situations.

The highest pulse rate was recorded for white/tan (Awt)

colour gene. This result do es not agree with the report of

[23] which showed that heat flow from the environment

into the body of a black steer on a hot sunny day was

30% greater than that of a white steer thereby resulting in

an increase in the pulse rate of the black steer. The possi-

ble reason for this result could be due to the environ-

mental influence on the animals.

Furthermore, from Table 3, it could be deduced that

the highest red blood cell count possessed by the brown

coat animals could be as a result of exposure of the skin

to the sunlight and due to heat stress prevalence in the

environment. This agrees with the results of [24] which

reported significant effect of coat colour genes on the red

blood cell, but the author however recorded the black

coat colour as having the highest red blood cell count

amongst other colours. The high red blood cells count in

this study also agrees with the findings of [25] which

reported an increase in the quantity of the red blood cell

with heat stress. Based on the results of study, it can be

concluded that WAD sheep with brown (Bb) and bad-

gerface (Ab) coat colour genes could adapt and survive

better than others in the tropical environment.

In conclusion, the influence of the coat colour genes

on animals could determine the adaptability and surviv-

ability of the animal in a particular environment. The

genetic potential of an animal could be predetermined

through the influence of the coat colour on heat stress

traits and the haematological parameters. However, fol-

low-up resear ch should be carried out on the influence of

the coat colour genes on the morphological indices of

West African Dwarf sheep using an intensive manage-

ment system. In this study, both West African Dwarf

sheep with brown (Bb) and badgerface coat colour (Ab)

were found to withstand heat stress better than sheep

with other coat colours.

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