Colour variation in blue dun Polish Konik and Bilgoraj horses.pdf

Livestock Production Science 90 (2004) 201–209

www.elsevier.com/locate/livprodsci

Colour variation in blue dun Polish Konik and Bilgoraj horses

Anna Stachurska a, * , Miros

aw Pi˛ta b , Zbigniew Jaworski c , Anne P. Ussing d ,

Agnieszka Bru´niak a , Mariusz Florek e

Department of Horse Breeding and Use, Faculty of Biology and Animal Breeding, Agricultural University,

13 Akademicka str., 20-950 Lublin, Poland

b Department of Sheep and Goat Breeding, Faculty of Biology and Animal Breeding, Agricultural University,

13 Akademicka str., 20-950 Lublin, Poland

c Polish Academy of Sciences, Institute of Genetics and Animal Breeding, Postepu str., 05-552 W´ lka Kosowska, Poland

d The Danish National Library of Science and Medicine, 49 Nørre All´, DK-2200 Copenhagen N, Denmark

e Department of Animal Raw Material Estimation and Utilization, Faculty of Biology and Animal Breeding, Agricultural University,

13 Akademicka str., 20-950 Lublin, Poland

Received 30 January 2003; received in revised form 29 April 2004; accepted 29 April 2004

Abstract

The study was conducted to determine the variability of the blue dun colour of Polish Konik and Bilgoraj Horses and to

define which factors involve the variations. These horses descend from Tarpans, wild horses, which are extinct. Hair samples

were cut from the horse’s back and their measures of lightness, redness and yellowness were recorded according to international

procedures (CIE L*a*b*).

The results show that in winter the blue dun coat is lighter, less red and more yellow than in summer. The differences are

more distinct in horses living in forest reserves than in horses living in stables. This suggests that the blue dun colour may be a

protective feature. Mares are generally lighter than stallions, foals are lighter than adults. Differences were also found between

Polish Konik and Bil C goraj populations and between two Polish Konik studs. Light blue dun individuals are simultaneously the

most yellow, whereas dark blue duns are the least yellow and the least red. Minolta Chroma Meter (CR-310) comes out to be

useful for measuring the hair colour. Particular L* and b* ranges are suggested to be the most typical for the shades. They

should help the breeders to qualify correctly the shade in a blue dun horse.

Keywords: Polish Konik Horse; Coat hair colour; Blue dun; Shade; Adaptation

1. Introduction

(Pruski, 1959) . Old chronicles tell about bands of wild

blue dun (mousecoloured) horses with dorsal stripe,

living in forest zones in this European region. Most of

the horses were of a dark shade, but in some sources

very light, almost white horses are also mentioned

(Vetulani, 1946) .

The Polish Konik’s gene pool is preserved in order

not

goraj Horse

originate from the Tarpan, the last wild horse living in

Middle–East Europe until the end of the 18th century

Primitive Polish Konik Horse and Bil

* Corresponding author. Tel.: +48-81-4456072; fax: +48-81-

5333549.

E-mail address: nowina@ursus.ar.lublin.pl (A. Stachurska).

to loose the biodiversity of the species. The

goraj Horse is not included in Polish Konik breed-

doi:10.1016/j.livprodsci.2004.04.002

202

A. Stachurska et al. / Livestock Production Science 90 (2004) 201–209

ing but it is bred with extensive use of Polish Konik

sires. Both the Polish Konik and the Bi

a shade which appears as the intermediate between blue

dun and yellow dun. The latter, having a yellowish cast,

is probably the same as the American olive dun. It is

scarce in Polish horses and it seems to change slightly

towards the standard shade with the age of the animal.

The light shaded horses are sometimes nearly white

with black stripe and mixed black, grey and white mane

and tail, whereas dark blue dun horses may resemble

blacks. The nearly black individuals have a weak

greyish cast and the dorsal stripe still recognisable.

According to this distinction of shades, 9.7% of Polish

Koniks are dark shaded, 75.4% are standard, 14.6% are

light and 0.3% yellow-shaded blue dun ( Stachurska

and Brodacki, 2003b) .

The model of blue dun colour inheritance is known

(Adalsteinsson, 1974, 1978, van Vleck and Davitt,

1977; Craig and Van Vleck, 1985) . The blue dun

results from the activity of A, E and D loci. Dominant

D allele dilutes black (aaE _ ) into blue dun (aaE _ D _ ).

It is still not documented what causes its differentia-

tion into shades (Stachurska and Brodacki, 2003b) .

The colour shade of blue dun horses is recorded in

the Polish Konik Stud Book, so it is assumed to be a

rather constant property. Preliminary studies on the

coat hair colour in blue dun primitive horses were

performed with the use of a leukometer, which only

allows for a relative comparison (Stachurska et al.,

2001) . It seems important to document the hair colour

changes by absolute recording. In some horses it is

difficult to determine the colour shade. Human visual

perception is usually influenced by the average colour

in the stud. For instance, a horse of a medium shade

between light and standard will be determined as

standard if the stud consists generally of light-shaded

horses or light if standard-shaded horses predominate.

The body colour is one of the most important characters

of the shade and an accurate means of measuring it may

enable comparison of colour shades between studs.

The objectives of the study were to define the range

of variability in coat colour of blue dun Polish Konik

and Bil

goraj Horses

inherited the colour from the Tarpan. Red dun and

black foals which appear from time to time in the

populations are excluded from the breeding

programme (Stachurska and Brodacki, 2003a) .

It is thought that the blue dun colour is a protective

colouring, which once helped the wild horses to

escape predators. Vetulani (1946) and Kownacki

(1962) observed that Polish Koniks became lighter

during winter and darkened in summer. This property

also could have helped their ancestors to survive in

wild. Lighter horses are less visible in the snow while

darker ones are less noticeable in the summer. More-

over, dark colour quickly absorbs sunrays but simul-

taneously the heat is easier eliminated from dark

surface, which is desired in hot weather (Cena et al.,

1952) . Light colour retains the heat longer and thus it

may be advantageous when it is cold.

Blue dun horses have a grey body, often with a light

brownish cast, though the colour in a population may

vary from whitish grey through grey with a yellowish,

reddish or silvery cast to almost black (Stachurska,

1997) . The head colour is either darker, or similar to,

but never lighter than the body colour. The lower legs

are darker than the body. Mane and tail consist of

strands of variously coloured hair: from white through

cream and grey, to black. Generally, the mane and tail

are darker than, or the same colours, as the body. All

blue duns have a black or dark grey dorsal stripe

(Stachurska, 1997, 1999) . It is usually accompanied

by horizontal small bars on legs and sometimes by

stripes and spots on other parts of the body.

Such a strong individual variation of the blue dun

colour involved categorising it into shades. Sponen-

berg (1996) distinguishes five blue dun modifications:

the lightest silvery so-called grullo, the medium slate

grullo, the dark grullo, the lobo dun with sooty black

countershading on dorsal areas and the olive dun with

the yellowish cast to the body colour. In Polish Konik

and Bil

goraj Horses the lobo dun variation does not

occur. The blue dun colour occurs with a percentage

of 9.8 in the Norwegian Fjord Horse (Nestaas, 1996) .

In this breed, lighter coloured horses were favoured in

the breeding programme, thus leading to very light

varieties of among others blue dun (Ussing, 2000) .

In Poland, regarding mainly the trunk colour, four

blue dun shades are identified: light, standard, dark and

goraj Horses, as well as to analyse the effect on

the colour variation of some non-genetic factors.

2. Material and methods

The study was conducted on 159 blue dun Polish

Konik horses maintained in two breeding centres:

A. Stachurska et al. / Livestock Production Science 90 (2004) 201–209

203

Popielno and Zwierzyniec, as well as 30 blue dun

Bil

horse groups distinguished according to these factors,

the least square analysis of variance was used:

goraj Horses from the Jan´w Lubelski centre. In

the three centres, horses are kept under similar con-

ditions, either stabled with daily access to pastures, or

free-ranging in forest reserves. Altogether, 479 hair

samples were taken: 169 samples from stabled horses

and 310 samples from free-ranging horses. The sam-

ples were taken through 2 years, in January and

February (221 samples) and in June and July (258

samples). In Poland, the spring shedding in Polish

Konik horses living in reserves begins in December

and lasts until April, whereas in autumn the shedding

occurs from the ultimo August till half of October

(Detkens, 1967) . Hence, hair samples were taken from

the same horses’ winter and summer coat, respective-

ly. Each hair sample was cut with a razor from the

dorsal side of a horse. The shade of the horse was

recorded at the same time.

The hair samples were cut into small pieces for

colour readings. The underhairs, if they occurred,

were not separated from outerhairs, since their colour

and structure were alike. The readings were taken with

the use of a Minolta Chroma Meter CR-310 colori-

meter with a 50-mm-diameter measurement area, in

the L*a*b* colour space (CIE, 1976) . The reflectance

spectrophotometry enables to calculate the CIE tri-

stimulus values (X, Y, Z), which after mathematical

transformations into L, a* and b* coordinates metri-

cally describe the colour’s position on the chromatic

circle. L* means the lightness, a* redness and b*

yellowness. The three coordinates together approxi-

mate human colour perception.

In order to find the typical colour coordinates for

each shade, the horses were ranged into three lists

according to increasing L*, a* and b* values. Then,

they were divided into groups in which approximately

45–50% of individuals were of a given shade.

The hair colour was examined with regard to (1)

the season of the year, (2) the type of maintenance

(stabled or free-ranging), (3) gender, (4) age, (5) breed

(meaning Polish Konik breed and close Bil

Y ijklmn ¼ l þ S i þ G j þ A k þ B l þ D m þ e ijklmn

where Y ijklmn is the trait value; l the overall mean; S i

the season of the year combined with the type of

maintenance (i = 4; summer—stabled horses, winter—

stabled horses, summer—free-ranging horses, win-

ter—free-ranging horses), G j the gender ( j = 3; mares,

stallions, geldings), A k the age (k = 6; suckling foals,

yearlings, 2-year-olds, 3-year-olds, 4–9-year-olds, 10-

year-olds and older horses), B l the breed (l = 2; Polish

Koniks, Bil

goraj Horses) and D m the colour shade

(m = 3; light blue dun, standard blue dun, dark blue

dun), e ijklmn the random error.

Another analysis of variance was made to compare

Polish Konik Horses among themselves in the two

breeding centres (405 hair samples). The breed factor

(B l ) was replaced by C l the breeding centre (l =2;

Popielno, Zwierzyniec). Since the results of the anal-

ysis showed the same tendencies with regard to the

previously considered factors, only the part

concerning the breeding centres was presented in the

study.

L*, a* and b* linear regression (b yx ) was estimated

for the stabled horses, the free-ranging horses and for

all the horses thrown together, to determine how the

summer values changed in winter.

3. Results

The observed L*, a* and b* values ranged between

32.83–71.95, 1.05–5.40 and 1.31–15.58, respec-

tively. The distinction into groups, in which approx-

imately half of the individuals were of a given shade,

is presented in Table 1 . For instance, in horses of

L*< 47.5, 45.9% of individuals were dark shaded and

54.1% were standard. Some of the dark shaded horses

had L* higher than 47.5 but they were less and less

numerous. b* ranges for light shaded horses were not

distinguished since among horses of b*>4.9, all

shades were mixed on the list. It was not possible to

distinguish respective a* ranges for variously shaded

horses, either, because all three shades were spread

over the whole list.

goraj

population) and (6) registered colour shade. The

visually determined colour shade was taken into

consideration to compare it with the colorimeter read-

ings. Three yellow shaded horses were excluded from

the analysis.

To estimate the influence of the factors on the

colour parameters, as well as to compare the results in

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A. Stachurska et al. / Livestock Production Science 90 (2004) 201–209

Table 1

Percentage of variously shaded blue dun horses within groups

distinguished by suggested hair colour coordinate ranges

Table 2

L*a*b* linear regression (b yx ; y—winter, x—summer)

Horses

Distinguished groups

Mainly dark

up to 47.5

(15.4%;

N = 74)

Free-ranging

91 0.936 p < 0.01 0.377 p < 0.01 0.809 p < 0.01

Mainly

standard

47.5–61.5

(70.8%;

N = 339)

Mainly light

over 61.5

(13.8%;

N = 66)

Stabled

45 0.783 p < 0.01 0.276 p < 0.05 0.568 p < 0.01

Total

136 0.864 p < 0.01 0.390 p < 0.01 0.720 p < 0.01

Fig. 1 shows that within stabled or free-ranging

horses in the winter L* was higher than in the summer

( p < 0.01). In both seasons the free-ranging horses had

higher L* than the stabled horses ( p < 0.01). The coat

hairs showed similar L* values for free-ranging horses

in the summer as for stabled horses in the winter. The

a* coordinate was higher in summer than in winter

and higher in stabled horses than in free-ranging

horses ( p < 0.01). Simultaneously, in the summer both

stabled and free-ranging horses had lower b* values

than in the winter ( p < 0.01). Considering b*, stabled

and free-ranging horses differed only in the summer

( p < 0.01).

It should be noticed that 15% of the horses

(mainly the free-ranging) lightened so much during

winter that their shades were visually qualified one

level lighter than in summer. A few horses (2.5%)

changed their apparent shade from light or standard

Dark shaded horses

45.9%

10.3%

0.0%

Standard horses

54.1%

80.0%

50.0%

Light shaded horses

0.0%

9.7%

50.0%

Mainly dark

up to 4.9

(20.5%;

N = 98)

Standard

and light

over 4.9

(79.5%,

N = 381)

Dark shaded horses

45.0%

6.6%

Standard horses

54.0%

76.1%

Light shaded horses

1.0%

17.3%

In general, the analysed factors significantly af-

fected the body hair L*a*b* coordinates. However,

a* value was not influenced by the horse’s gender,

age and breed, whereas b* was not affected by the

gender.

Fig. 1. Effect of season of year and environment on L*, a* and b* values of coat colour shade.

A. Stachurska et al. / Livestock Production Science 90 (2004) 201–209

205

Fig. 2. Effect of gender on L*, a* and b* values of coat colour shade.

in summer into yellow-shaded in winter. The linear

regression values for L*, a*andb* colour coor-

dinates are presented in Table 2 . Theyarea l

positive, significant and higher in the free-ranging

horses than in the stabled horses. The regression

value indicates how much a parameter changes on

Fig. 3. Effect of horse age on L*, a* and b* values of coat colour shade.

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