Int. J. Morphol., 22(2):145-148, 2004.

MORPHOMETRIC STUDIES OF THE CRANIO-FACIAL REGION OF THE WEST AFRICAN DWARF GOAT IN NIGERIA

ESTUDIO MORFOMÉTRICO DE LA REGIÓN CRÁNEOFACIAL DE LA CABRA ENANA DEL OESTE AFRICANO EN NIGERIA

^*Olopade, James Olukayode & Onwuka, Silas Kalu

^* Department of Veterinary Anatomy, University of Ibadan, Ibadan, Nigeria.

Correspondence to:

SUMMARY: This study involved the measurement of some parameters in the craniofacial region of the West African Dwarf Goat (WADG). The mean weight of the head was 0.74kg. The length of the rima oris and space between the median canthi were 8.69cm ad 8.81 cm respectively. The right palpebral fissure and external nare were longer than the left. The eyeball weight was 6.87g; the left eyeball was heavier than the right.

Females had significantly heavier heads and body weights than the males. The right palpebral fissure was longer than the left in females but the reverse was the case in males.

These findings will serve as baseline information in the study of the head of WADG and in comparative anatomy with other breeds.

KEY WORDS: 1. Craniofacial region; 2. West african dwarf goat.

RESUMEN: En este estudio se midieron algunos parámetros de la región cráneofacial de la cabra enana del oeste africano (WADG). La media del peso de la cabeza fue de 0,74 kg. La longitud de la rima oral y espacio entre el canhi mediano fueron: 8,69 cm y 8,81 cm, respectivamente. La fisura palpebral derecha y la narina externa eran más largas que las izquierdas. El peso del bulbo ocular era de 6,87g; el bulbo ocular izquierdo era más pesado que el derecho.

El peso del cuerpo y de las cabezas de las hembras, eran significativamente mayores que el de los machos. La fisura palpebral derecha era más larga que la izquierda en las hembras, pero en los machos era lo contrario.

Estos datos servirán como información básica en el estudio de la cabeza de WADG y en la Anatomía Comparada con otras cabras.

KEY WORDS: 1. Región cráneofacial; 2. Cabra enana del oeste africano.

INTRODUCTION

The WADG are present in all of humid Africa from the Southern Sudan to the West Coast. They make up about 38% of the estimated 38 million goats in the West African humid zone. They are important in the socio-economic life of most rural dwellers and are managed basically through the extensive system (Gall, 1996; Osuagwuh, 2002).

There is currently a paucity of information on the cranio-facial anatomy of this breed of goat (Onwuka et al., 2002; Olopade, 2003; Olopade & Onwuka, 2003; Onwuka et al., 2003).

This study involved the investigation of the morphometry of some indices in the head of the WAD goat.

MATERIAL AND METHOD

A total of 30 clinically healthy WAD goats were used for the study.

Preparation of samples and determination of indices.

Head weight: The heads were severed at the occipitoatlantal joint and weights taken using a "Five goat" spring scale®.

Rima oris length: This was taken using a twine from the ends of the lateral commisures of closed lips. The linear measurement of the twine was then taken.

Orbit circumference: A twine was employed to get the circumference of the bony orbit beneath the skin. Linear measurement of the twine was then taken.

Palpebral fissure lengths: These were taken from the median to the lateral canthi of the eye.

Distance between the median canthi: This was measured as the distance between the median canthi of the left and right eyes.

Length of external nares: The external nares were compressed medio-laterally from philtrum before they were measured.

Removal of eyeball: The eyeballs were removed by enucleation (Keller, 1975) and put in 0.9% saline.

Eyeball Weight: The eyeballs were weighed in nylon surgical gloves (whose weight was first determined) on a "microwa-swiss" weighing machine®; the weight difference was then taken.

The mean weight of the head of WADG was 0.74±0.31kg while that of the animal body was 10.48±5.10kg. The right palpebral fissure was longer than the left as were the right external nares compared to the left. These observations were however not statistically significant (p>0.05). The mean distance between the median canthi was 8.81±1.08cm while the rima oris length was 9.69±1.64cm.

The female WADG had significantly higher body weights and longer pelpebral fissures than their male counterparts (p<0.05).

The mean right palpebral fissures of the females were longer than the left but the reverse was the case in the males. The females also had wider mean left external nares than the right but the males had equal lengths of both nares.

The mean eyeball weight of WADG was 6.87±2.01kg. The left eyeball was heavier than the right likewise the males had heavier eyeballs than the females.

Animals above 12kg body weight had significantly higher values (p<0.05) in all parameters observed than animals below this body weight.

RESULTS

The result of the parameters measured in the goat heads are shown in Tables I and II presented as meant ± SD. The results were compared using the student t test at 0.05% level of significance.

DISCUSSION

The mean weight of head of the WADG was 0.74±0.31kg. This is smaller than that of Red Sokoto goats (0.90±0.16kg) obtained in the same environment (Olopade, Onwuka). Both breeds, however, had the same relative weight of 0.07 indicating that percentage head to body weight between goat breeds could be fairly constant. The palpebral fissure lengths of 2.16±0.25cm and 2.14±0.28cm for right and left eyes respectively were smaller than those of Red Sokoto goats in which the fissures had equal length (2.50±0.17cm). The mean of the palpebral fissure lengths between the WADG and the Red Sokoto was however not much different from each other as it has been observed (Schmidt & Coulter, 1981) that the lengths of palpebral fissures was fairly constant among breeds. The distance (8.81±1.08cm) between the median canthi (DMC) was shorter in the WADG than the 10.19±0.66cm of Red Sokoto goats (Olopade & Onwuka). The DMC was also shorter than the distance between the orbits (15.14cm and 17.28cm) in bovine and equine respectively but longer than the 3.55cm obtained in dogs and the 2.30cm in cats (Gelatt, 1981). These morphometric findings are consistent with the fact that animals that are hunted preys (herbivores e.g. ruminants and horse) have wider faces with more laterally placed eyes than their hunters or predators (Dyce et al., 1996).

The results in this study indicate that although they have similar relative head weight, the WADG is smaller than the Red Sokoto goats. They also have a narrower eye bridge and shorter eyelids.

The mean weight of head of the females was significantly higher than that of the males. This could be due to a higher bone and muscle mass. The longer palpebral fissures, external nares and rima oris obtained in females in this study could be size dependent as similarly observed by (Olopade & Onwuka) in Red Sokoto goats. Females for the reasons of being kept longer for reproductive purposes even when they attain market weight are usually older and heavier at any given time on the farm (Onwuka et al.). The female WADG also had a longer DMC and thus have wider spaced eyes than the males.

Slight asymmetry was seen in between the left and right palpebral fissures and external nares in this work irrespective of sex and weight. Similar asymmetry had been reported between the two halves of the bodies of animals (Sisson & Grossman, 1975).

Animals above 12kg body weight had significantly heavier heads. They also had wider face, larger external nares, longer palpebral fissures and lips which tends to suggest that to a large extent the parameters observed in this study are size dependent.

The mean eyeball weight of WADG in this study was 6.87±2.01kg. This is heavier than the 6.77g and 3.00g obtained in man and rabbits respectively but lighter than the 15.09g, 7.25g and 29.29g obtained for sheep, pig and cattle (Jaffe, 1969), and the 100.89g, 14.2g and 10.79g obtained for horse and large and small dogs respectively (Bayer, 1914).

The female had lighter eyeballs than the male despite their heavier weight. The right eyeball was lighter than the left in agreement with an earlier observation (Sisson & Grossman). This lighter right eyeball was however, expressed through a longer palpebral fissure. The mean orbit circumference of the eye was 10.92±0.83cm; the orbit circumference of the left eye was wider than the right in correspondence with the differences in eyeball weight .The heavier left eyeball obviously had a larger surface area requiring in the process wider orbits for rotation.

In conclusion, the results obtained in this study could be used as baseline research data in bioengineering and optometric studies as eyelid measurements and eyeball movements have been used to determine level of a resting animal's awareness (Nemoto et al., 2000), and in comparative and regional anatomy of the goat head (Dyce)

REFERENCES

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Dyce, K. M.; Sack, W. O. & Wensing, C. J. G. Textbook of Veterinary Anatomy. 2nd ed. W. B Saunders Company Philadelphia, 1996.

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Osuagwuh, A. I. A. Nutritional Engineering in Mammalian Reproduction: Obstetric and Gynecologic concerns. Inaugural Lecture University of Ibadan. Sibon books, Ibadan, 2002.

Schmidt, & Coulter. In Gelatt, K.N. Veterinary Ophthalmology. 1st ed. Lea and Febiger, London,1981.

Sisson, S. & Grossman, D. The Anatomy of the Domestic Animals. Getty, R. (ed.) (15th edition), WB Saunders Company, Philadelphia, 1975.

Correspondence to:

Prof. Dr. James O. Olopade
Department of Veterinary Anatomy
University of Ibadan
Ibadan
Nigeria

E-mail jkayodeolopade@yahoo.com

Received : 28-02-2004
Accepted: 12-04-2004