COMPARATIVE CHARACTERISTICS OF ARAB AND HUCUL HORSES HAIR COAT
DOI:10.30825/5.EJPAU.161.2018.21.4

Ewa Walkowicz, Katarzyna Czyż, Bożena Patkowska-Sokoła, Robert Bodkowski, Anna Wyrostek, Andrzej Filistowicz, Marzena Janczak
Institute of Animal Breeding, Faculty of Biology and Animal Science, Wrocław University of Environmental and Life Sciences, Poland

ABSTRACT

The aim of the study was a comparative analysis of Arab and Hucul hair (winter, summer, mane and tail hairs) with respect to their morphological and histological structure and elemental composition. The research material were horse hair samples collected from adult Arab and Hucul mares maintained in similar conditions. The study included determination of hair length, thickness, breaking force, extension, rupture strength, and histological analysis of scales arrangement and hair cross-section and chemical elements percentage content  obtained using roentgen analysis. The study demonstrated an ability of short hairs molting, which proves to be an adaptation of horses to changing environmental conditions. All kinds of Arab horses hair were thinner and more flexible compared to Hucul hairs. Elemental hair analysis did not demonstrate any differentiation between the examined breeds, however it pointed a potential usefulness of hair examination, e.g. in environment or health status monitoring.

Key words: Arab horses, Hucul horses, hair, histology, chemical elements.

INTRODUCTION

An understanding of mammal hair coats has been widening as a result of rapid scientific development and increasingly advanced research techniques. Animal hair fibers find an application for example in the diagnostics of diseases and mineral deficiencies. They may also play the role of a bio-indicator. The recognition of the detailed morphological, histological structure and properties of the hair fibers of specific species and breeds of animals makes it possible to use hair, for example to identify species. The feature which is most often taken into account in hair and species identification is just the histological structure of hair, and mainly the pattern of cuticle scales, cortex composition and cross-section shape, which are the features most characteristic of a given species or at least kind of animal [12]. An elemental examination of hair, on the other hand, can be used to determine the degree of organism saturation with essential mineral components and to detect the presence of toxic elements [1, 2, 14, 17]. Hair examination affords an insight into biochemical processes long before disease symptoms occur, since the elements are systematically incorporated into hair structure during the growth of hair, which provide information that could not be obtained from the analysis of, for example, blood or urine . Because of the ease of collection and storage of mammalian hair, these examinations have become increasingly common, and there is a constant search for new possibilities of their application [8, 21].

Purebred Arab horses, one of the oldest breeds, were formed under the influence of three factors: their specific natural environment (extremely difficult climatic and soil conditions of desert and semi-arid areas), their manner of use (constant movement under large load over long distances) and the breeding programs led by the Arabs, which included strict selection and pure-breed mating. The contemporary Arab horses are characterized by a distinctive structure, dry tissues, a thick skin covered with a short delicate hair coat and thin, silky hair on the mane and tail [5, 13]. Hucul horses are representatives of an old, primitive breed of small mountain horses originating from the eastern Carpathians (in the Huculszczyzna region) which were formed by the crossbreeding of various breeds of horses, such as Tarpan, Mongolian, Noric and oriental horses. Specific living conditions, i.e., a difficult climate, rearing on alpine meadows, poor fodder, long walks with heavy loads, were the most important selection factors in this breed formation . Hucul horses are characterized by a stumpy and fairly massively built, a short, dense hair coat as well as a thick mane and tail [7, 18, 19]. Both breeds were formed under very difficult, but quite entirely different environmental conditions, characterized by a deficiency of food and heavy workloads. Thus, they do in fact have numerous common features, such as courage, strength, resistance to difficult habitat conditions, good health and balanced character. Both breeds are characterized by good fodder utilization, fertility and longevity. Arab horses originate from a tropical climate, which is characterized by a levelled annual temperature with a high amplitude of daily temperatures, while, Hucul horses come from a moderate climate with distinct seasons of the year. Consequently, their hair coats have played various functions: those of Arab horses had to protect against the sun and facilitate heat transfer, while those of mountain Huculs had to protect against snow, frost and wind. Therefore, one should expect quite significant differences between them in terms of the range of hair coat characteristics.  

Only a few papers focusing on hair coat comparisons between Arab and Hucul horses have been found in the available literature [20]; thus, the aim of this study was a comparative analysis of their hair in terms of morphological and histological structure as well as elemental composition.

MATERIALS AND METHODS

The research material consisted of 10 mares of Arab breed from the Michałow stud (Poland), and 10 Hucul mares from the ZDIZ Odrzechowa stud (Poland). An average age of the examined mares was about 6 years. Both groups were maintained in a stud-pasture system, and were fed according to generally accepted standards. The samples of summer coat were collected during routine care practices by their combing from the back of the trunk, mane and tail in July, while those of winter coat at the turn of January and February. This way of samples collection ensured animals welfare, and did not cause any unnecessary pain, stress or discomfort, and according to the opinion of the 2nd Local Ethical Committee for Experiments on Animals, Wroclaw University of Environmental and Life Sciences, Poland, the study did not require the approval of the Committee; Act of 15 January 2015 on the protection of animals used for scientific and educational purposes [15].

The following kinds of hair were separated: long hair – mane and tail; short hair from the body – summer and winter coats. Winter coat hairs were divided into two fractions: underhair and overhair. A backlit magnifying glass of 20x magnification was used for this purpose. Then, the following parameters were determined in summer and winter hair: length [mm], thickness [µm], breaking force [cN], extension [%], rupture strength [kg/mm2]. The same parameters, except the length, were examined in mane and tail hair. Hair thickness was measured using an MP3 projection microscope at 400x magnification (Carl Zeiss Inc., USA). The length of hairs was determined using an optical stereoscopic microscope (Motic, China) with a digital camera and MoticImages Plus 2.0 ML software. Measurements of breaking force and extension of the hair were performed using an electronic material test frame (Matest, Poland) with a head of a strength up to 100 N. The rupture strength of the hair was calculated using the following formula: N= (P x 104) / (π x d2 x 9.81) [kg/mm²], where: P – breaking force (cN), d – cross-section diameter of the fiber.

The above measurements were made in the Laboratory of Skin and Hair Coat Assessment, Institute of Animal Breeding, Wrocław University of Environmental and Life Sciences (Poland).

Histological images of particular fractions of the hair coat, presenting scale arrangement and cross-sections of particular types of hair, were prepared using an LEO 435 VP scanning electron microscope (Carl Zeiss SMT AG, Germany). The study also included an elemental analysis on electron level performed using AX BRUKER QUANTAX EDS roentgen analyzer (Germany) coupled with a scanning electron microscope (SEM), cooperating with Esprit 1.8.2.6. computer software (Edwards, UK). After purification, hair samples were glued on special tables assuring their higher stability during elemental analysis. The percentage content of selected chemical elements was determined. The above analyses were conducted in the Laboratory of Electron Microscopy, Wrocław University of Environmental and Life Sciences (Poland). The study was conducted in accordance with regulations concerning experiments on animals.

The data obtained were statistically analyzed using one way ANOVA (Tab. 1. Characteristics of Arab and Hucul horses) and unpaired t test (Tab. 2. Thickness, breaking force, extension and rupture strength of long hairs of Arab and Hucul horses). The statistical analysis of the results was performed using Statistica 8.0 software (StatSoft Inc., Tulsa, USA). Mean values, standard deviations and significance of the differences between the means were calculated. 

Table 1. Characteristics of Arab and Hucul horses hairs

Parameter	Horse breed	Summer hair coat	Winter hair coat
			underhair	overhair
Length [mm]	Arab horse	11.85A±1.64	22.88B±3.92	33.65C±5.95
	Hucul horse	13.19A±1.26	23.93B±2.25	44.29C±4.13
Thickness [µm]	Arab horse	27.25A±3.94	30.41a±3.16	38.84B, b±3.85
	Hucul horse	37.94a±2.56	32.33A, b±3.62	42.92B, b±4.43
Breaking force [cN]	Arab horse	30.57±2.44	40.61A±7.62	75.08B±11.77
	Hucul horse	23.43±3.22	38.69A±8.31	84.11B±11.14
Extension [%]	Arab horse	38.10±8.20	45.96±5.50	52.91±7.67
	Hucul horse	28.80±4.67	42.68a±8.77	56.78b±7.73
Rupture strength [kg/mm2]	Arab horse	12.29±2.56	14.30±1.79	15.82±1.95
	Hucul horse	8.93±2.15	12.21±2.86	15.00±2.50
a, b – values in rows with different letters differ significantly (P<0.05) A, B, C – values in rows with different letters differ significantly (P<0.01)

Table 2. Thickness, breaking force, extension and rupture strength of long hairs of Arab and Hucul horses

Parameter	Horse breed	Mane hair	Tail hair
Thickness [µm]	Arab horse	60.70A±4,18	75.08B±5.09
	Hucul horse	66.28A±7,25	88.72B±5.43
Breaking force [cN]	Arab horse	208.48±51,48	232.36±42.91
	Hucul horse	194.98A±37,01	353.58B±48.29
Extension [%]	Arab horse	38.32±7,88	38.05±5.70
	Hucul horse	37.10±3,54	35.23±5.20
Rupture strength [kg/mm2]	Arab horse	18.21a±2,26	13.65b±2.19
	Hucul horse	14.68±2,32	14.66±1.44
a, b – values in rows with different letters differ significantly (P<0.05) A, B, C – values in rows with different letters differ significantly (P<0.01)

RESULTS AND DISCUSSION

A strict relationship between the kind of hair and its thickness was observed. The hairs of Arab horses (short hair on body) were thinner and shorter than in Hucul horses, however the differences were not confirmed statistically (Tab. 1). Overhair, both in Hucul and Arab horses, was longer and thinner compared to underhair. The shortest kinds of hairs were those from summer coats. In Arab horses, these were also the thinnest hairs, while in Hucul horses their thickness was moderate for both underhair and overhair. Summer coat hairs, in terms of breaking force, extension and rupture strength, were characterized by significantly lower parameters compared to winter coat underhair, and especially to overhair. Also, significant differences were noted between underhair and overhair from the winter period. Inter-breed differences in terms of hair strength were low (Tab. 1), while overhair was more resistant than underhair in both breeds. It should be noted that mane hairs in both breeds were thinner than tail hairs, while Hucul horses were generally characterized by thicker hairs compared to Arab horses. The extension of  mane and tail hairs was comparable in both breeds, and the highest strength was characteristic for Arab horse mane hairs. The highest breaking force was noted in tail hairs of Hucul horses, which may be explained by the fact that they are the thickest among all kinds of long hairs of both horse breeds, and moreover are built only of a cortex layer which gives high strength to the hairs. Mane hairs are thinner, and thus, despite their cortex structure, their strength is lower; tail hairs of Arab horses had distinctly developed medulla, which together with their lower thickness with respect to the tail hairs of Hucul horses resulted in their lower strength (Tab. 2).

Histological structure of the examined hairs is presented in Figures 1–5. The scales in summer coats of Arab horses are overlapped in a non-ring arrangement. The arrangement of the scales is lateral, they are wider than they are long. The cuticle is of a wavy type with irregular waves, scale margins are smooth to slightly ragged. Hair interior under the cuticle is filled with a cortex layer composed of a compact cell mass. The center is filled with large, loosely arranged cells with air inside (Fig. 1). Underhair of winter coats is characterized by a lateral arrangement, the scales are wider than they are long. Remarkably well visible scales form regular waves of mostly smooth margins. The hair is filled with a distinct cortex layer composed of a thick layer of compact cells and more loosely arranged cells inside (Fig. 2). In turn, overhair is in turn, characterized by scales of a non-ring arrangement and various margin structures: smooth wavy lines with small irregularities close to each other along the margins, and scales of distinctly ragged margins and various heights. The hairs are filled with a cortex layer and medulla (Fig. 3). Mane hairs of Arab horses are distinguished by a wavy cuticle type, with not very regular waves characterized by deep furrows. The scales are lateral, in a non-ring arrangement, not very pronounced with uneven ragged margins and with strongly coarse surfaces, they are wider than they are long. The hair is filled with a clearly loosened cortex layer (Fig. 4). Tail hairs are, in turn, characterized by not very pronounced scales arranged crosswise, wider than they are long, of strongly coarse surfaces and ragged margins. The hair is mainly filled with loosely arranged cells with air inside, forming multicellular medulla (Fig. 5).

Fig. 1. The hairs of summer coat

Fig. 2. Underhair of winter coat

Fig. 3. Overhair of winter coat

Fig. 4. Mane hairs

Fig. 5. Tail hairs

In Hucul horses, the summer coat is characterized by hairs with coarse scales in irregular wave types, ragged or straight margins and different heights, overlapping in a non-ring arrangement. They are filled in part with a cortex layer composed of a compact cell mass, and in part with a medulla layer with loosely arranged cells filled with air (Fig. 1). Underhair is characterized by densely arranged, fine, lateral scales in irregular wave types, of ragged margins in a non-ring arrangement. Some hairs with scales of smooth margins were also observed. The interior of the hair is characterized by a distinct loosening of the cortex layer (Fig. 2). The scales in overhair form an irregular wave. The margins of the scales are smooth or ragged; they overlap each other in a non-ring arrangement. They are wider than they are long. The hairs are mainly filled with medulla formed of large cells filled with air and a thin cortex layer (Fig. 3). Hucul horse mane hairs have lateral scales in a non-ring arrangement, wider than they are long. The scales are very irregular, with poorly marked contours, ragged margins and very coarse surfaces. The hairs are entirely filled with a cortex layer (Fig. 4). The cuticle of tail hairs is almost uniform over the whole surface. Scales visible at high magnification are very irregular, with strongly ragged margins, differentiated heights and coarse surfaces. The scales are lateral, in a non-ring arrangement, wider than they are long. The hairs are filled with cortex cells (Fig. 5).

Basic chemical elements noted in all kinds of hair in the horses of both examined breeds represented structural components of hair keratin (carbon, oxygen and sulfur) (Tab. 3). Other examined elements were observed in small percentage contributions, which could have been related to feeding and environment. This proves that keratin is impregnated with various chemical elements depending on the habitat, which confirms the results of previous studies demonstrating that hairs may be e.g. an excellent tool in environmental monitoring.

Table 3. Content of selected chemical elements in Arab and Hucul horses hairs [%]

Element	Horse breed	Kind of hair
		Summer coat	Winter coat		Mane hair	Tail hair
			overhair	underhair
C	Arab	56.89±4.87	47.25±5.05	50.41±5.77	61.15±0.79	63.06±3.41
	Hucul	56.65±3.91	53.21±7.12	45.45±5.53	65.12±12.90	61.16±2.06
O	Arab	27.49±1.31	43.85±6.34	41.28±7.04	28.61±1.52	20.79±2.76
	Hucul	36.41±0.13	34.43±7.37	43.43±7.07	25.72±9.01	34.65±3.54
S	Arab	11.38±4.33	6.82±1.14	6.36±0.71	7.29±0.34	5.84±3.68
	Hucul	4.47±3.58	9.00±1.36	8.12±1.74	4.25±2.65	1.81±1.93
Al	Arab	0.66±0.15	0.22±0.22	0.26±0.24	0.92±0.55	1.64±0.74
	Hucul	0.97±0.65	0.56±0.40	0.43±0.24	1.73±0.33	1.23±0.98
Ca	Arab	0.84±0.75	0.15±0.05	0.13±0.13	0.18±0.25	1.32±1.34
	Hucul	0.09±0.13	0.24±0.24	0.42±0.25	0.24±0.16	0.22±0.31
Mg	Arab	0.41±0.21	–	–	0.24±0.09	0.39±0.05
	Hucul	0.12±0.16	0.17±0.20	0.05±0.10	0.21±0.02	0.04±0.06
Na	Arab	0.11±0.15	0.19±0.06	0.08±0.13	0.10±0.13	0.11±0.15
	Hucul	0.24±0.01	0.14±0.16	0.32±0.23	0.05±0.07	0.21±0.10
P	Arab	1.37±0.51	0.67±0.16	0.65±0.11	0.83±0.06	–
	Hucul	0.51±0.39	0.99±0.15	0.84±0.18	0.74±0.25	0.22±0.31
Si	Arab	0.88±0.37	0.32±0.29	0.44±0.07	0.70±0.25	5.66±6.14
	Hucul	0.56±0.19	0.63±0.23	0.51±0.16	1.64±0.76	0.48±0.04

The comparison of Arab and Hucul horse hair coats demonstrated large variability both in the range of physical hair features (length, thickness, strength, and extension) and in their histological structure. It should be emphasized that the differences between summer and winter coats were observed in both examined breeds – the summer coat was characterized by one kind of hair, while the winter one was composed of two kinds of hair, i.e., longer and thicker overhair and thinner and shorter underhair. This proves that molting phenomena, i.e., the periodical shedding of an excess of hair, is observed in horses as in other mammal species.

In both breeds of horses, summer hairs were filled with a cortex and medulla; underhair lacked the medulla, while a strongly developed medulla was noted in overhair which demonstrates organism’s adaptation to low temperatures. 

It was additionally noted that short hairs had cuticles formed of clearly marked scales with smooth surfaces, while the scales of mane and tail hairs were characterized by severe damage – they were poorly pronounced, had strongly ragged margins and coarse surfaces. The external structure of long hairs confirms the fact that they are not subjected to molting; rather, they exist for many years and are subjected to severe damage, which may be observed on histological images. The coat hairs are, in turn, subjected to seasonal exchange, and thus their scales are well pronounced and undamaged.

It was observed in the study of Budzyńska et al. [3] that not only environment, but also the age of animals, their physiological status and gender affect the level of mineral components in hair fibers. In turn, a study by Dobrzański et al. [9] did not reveal any influence of environment or dietary mineral supplements on chemical element levels in hair coat (except zinc). A study conducted by Cieœla & Janiszewska [6] demonstrated statistically significant differences in magnesium and cadmium concentrations between various breeds of horses in uniform environmental conditions. This may also be modified by the genetic affiliation which was observed in Arab horses, with respect to both male and female lines [16]. There have also been some attempts to determine the relationships between the level of some elements in hairs and nervous excitability of the horses [4]; however, the results of these studies have not provided any satisfactory results so far. Hair fibers also accumulate drugs and toxins which creates additional possibilities for their utilization [10, 11]. The study conducted by Biricik et al. [2] demonstrated that mineral element contents in mares’ hair was significantly lower in winter compared to summer. The same authors also examined correlations between mineral element contents in feed, hair and serum, and they noted positive correlations between season and hair iron content. They also observed an increased iron level in hair related to an increase in dietary iron content, while no change of this kind was noted in iron serum content

CONCLUSIONS

The analysis of hair coats of Arab and Hucul horses demonstrated the ability to seasonally exchange short hairs (molting), which proves adaptation to changing environmental conditions (seasons of the year). All kinds of hair of Arab horses were thinner and more flexible compared to the corresponding hairs of Hucul horses. Elemental hair analysis did not demonstrate any differentiation between the examined breeds; however, it indicated a potential use of hair examination e.g. in environmental or health status monitoring.

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Accepted for print: 4.10.2018

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Ewa Walkowicz
Institute of Animal Breeding, Faculty of Biology and Animal Science, Wrocław University of Environmental and Life Sciences, Poland
Chełmońskiego 38C
51-630 Wrocław
Poland

Katarzyna Czyż
Institute of Animal Breeding, Faculty of Biology and Animal Science, Wrocław University of Environmental and Life Sciences, Poland
Chełmońskiego 38C
51-630 Wrocław
Poland
email: katarzyna.czyz@upwr.edu.pl

Bożena Patkowska-Sokoła
Institute of Animal Breeding, Faculty of Biology and Animal Science, Wrocław University of Environmental and Life Sciences, Poland
Chełmońskiego 38C
51-630 Wrocław
Poland

Robert Bodkowski
Institute of Animal Breeding, Faculty of Biology and Animal Science, Wrocław University of Environmental and Life Sciences, Poland
Chełmońskiego 38C
51-630 Wrocław
Poland

Anna Wyrostek
Institute of Animal Breeding, Faculty of Biology and Animal Science, Wrocław University of Environmental and Life Sciences, Poland
Chełmońskiego 38C
51-630 Wrocław
Poland

Andrzej Filistowicz
Institute of Animal Breeding, Faculty of Biology and Animal Science, Wrocław University of Environmental and Life Sciences, Poland
Chełmońskiego 38C
51-630 Wrocław
Poland

Marzena Janczak
Institute of Animal Breeding, Faculty of Biology and Animal Science, Wrocław University of Environmental and Life Sciences, Poland
Chełmońskiego 38C
51-630 Wrocław
Poland

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