Genetic Analysis of Three South African Horse Breeds
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Article — Artikel Genetic analysis of three South African horse breeds E G Cothrana and E van Dykb susceptible ponies. The introduction of ABSTRACT Thoroughbreds was also a disaster, as Genetic variability at 7 blood-group and 10 biochemical genetic loci was examined in they failed to adapt and initiated a race of 3 South African horse breeds, the Nooitgedacht, Boerperd and Basuto Pony. Observed clumsy animals, unable to maintain con- heterozygosity for these breeds was intermediate for domestic horses, with the highest dition at all 19. There was furthermore a heterozygosity in the Boerperd and the lowest in the Basuto Pony. The 3 breeds show need for a farm and riding horse well- greater genetic similarity to each other than to other domestic horse breeds. Compared to adapted to the rural conditions in South other breeds, the South African breeds show greater genetic similarity to breeds such as the Africa. A search was undertaken for Thoroughbred, Holstein, Trakehner and Hanovarian and also to North American breeds suitable typical Basuto ponies, and horses such as the Saddlebred, Standardbred and Morgan Horse. were found in the Molteno district that Key words: biochemical polymorphisms, blood groups, dendrogram, genetic diversity, were claimed to all be descendants of a South African horse breeds. stallion bought from Lesotho in 1902. Cothran E G, Van Dyk E Genetic analysis of three South African horse breeds. Journal of Others were selected from the Free the South African Veterinary Association (1998) 69(4): 120–125 (En.). Department of Veterinary State. In total, 12 horses were bought and Ethology,Faculty of Veterinary Science, Private Bag X4, Onderstepoort, 0110 South Africa. bred at an experimental farm2. They were selected very strictly to attain the goal set. In 1977 the herd was sold to private breed- INTRODUCTION Flemish horses to the Cape as well as ers who continued the breeding policy. The horse (Equus caballus) was unknown Hackneys, Norfolk trotters, Morgans and The origins of the 3 primary indigenous to the inhabitants of the Cape in South Cleveland Bays to satisfy an increasing South African horse breeds (the Boer- Africa before European settlement in the demand for coach horses. These breeds perd, Nooitgedacht and Basuto Pony) are Cape in 1486. The first horses brought to certainly must have influenced the devel- clearly similar. However, these breeds the Cape were Javan ponies from the opment of the Cape Horse. have had separate histories for some time East Indies that had a strong Oriental Another South African breed, the and different selective procedures and influence. Other types of horses that Basuto Pony, was initially the same as the breeding strategies have resulted in eventually reached the Cape were Persian Boerperd, as it was acquired by the Basuto horses that have distinctive characteris- Arabs, Andalusian stallions from South people by trade and by raids on the Boers. tics and are acknowledged as separate America, English Thoroughbreds and The Basuto Ponies were kept in the breeds. In this study we examined the some Spanish horses7. Two importations isolated Mountain Kingdom and as a genetic similarity of these breeds to each of horses from the United States of result of the extreme conditions and poor other and other common domestic horse America took place in 1782 and 180816. grazing, only the hardiest were able to breeds. We also examined current levels By 1800 these breeds had been mixed to survive. This natural selection turned the of genetic diversity within each breed. form what began to be called the Cape Basuto Pony into an animal renowned for Horse. The relative number of each breed its hardiness, endurance, intelligence, MATERIALS AND METHODS in the foundation stock used is not clear. tractability and remarkably hard Blood samples were collected by jugu- Additional Thoroughbreds were then hooves19. lar venipuncture in acetate dextrose brought in to improve the Cape Horse. The population size of the Cape Horse (7 m ). Boerperd samples (n = 34) were The Cape Horse was highly esteemed for was greatly reduced during the Anglo- taken from horses on different stud farms its gentleness, beauty and good service. Boer War of 1899–1902. Because the in Mpumalanga in conjunction with There was a great demand for these Boerperd of the Republics had become breed registry regulations requiring horses and the breed was exported for 130 well adapted to its environment and had blood typing. Nooitgedacht (n = 21) years, which brought the Cape Horse established some resistance to the deadly samples were collected from stud farms acclaim as a battle horse from throughout African horsesickness virus, it was a in Gauteng and Mpumalanga. Basuto the British Empire. With the Great Trek military animal superior to the imported ponies (n =34) were sampled on a farm in (1836–1838), the Boers took their horses cavalry horses of the British. This resulted the Mulimo Ntuse district in Lesotho. inland with them, after which these in a concerted effort by the British to These horses were not registered in a horses were known as the Boerperd16. eliminate the horses20. Today only a few studbook as were the other 2 breeds. Meanwhile, in the Cape, the Cape stud farms remain that still have horses of Standard immunological procedures Horse continued to be bred true for some old Boerperd origin. involving haemagglutination and com- time. Later there was importation of The Nooitgedacht was developed as a plement-mediated haemolysis17,18 were breed, starting in 1951, in an attempt to used to detect variation of red-cell allo- save the Basuto Pony, which was on the antigens at 7 blood-group loci. aDepartment of Veterinary Science, University of Kentucky, Lexington, Kentucky 40546-0076, USA. verge of extinction owing to popular Starch and polyacrylamide gel electro- bDepartment of Veterinary Ethology, University of Pretoria, demand as remounts during the war, the phoresis and isoelectric focusing were Private Bag X4, Onderstepoort, 0110 South Africa. great blizzard of 1902, and the introduc- used to detect variation at 10 serum and 5,6,9,10,13,15 Received: March 1998. Accepted: August 1998. tion of diseases amongst the highly rbc lysate protein loci . 120 0038-2809 Tydskr.S.Afr.vet.Ver. (1998) 69(4): 120–125 The loci examined were the A, C, K, P,Q, Table 1: Allele frequencies for 17 genetic loci examined in South African horse breeds. HBG and U horse blood-group loci and the bio- = horse blood group. See text for additional information about the loci. chemical protein loci were alpha-I beta glycoprotein (A1B), albumin (Al), serum Locus Allele Nooitgedacht Boerperd Basuto Pony esterase (Est), vitamin D binding protein Trf D 0.024 0.396 0.147 (Gc), glucosephosphate isomerase (GPI), D2 0.000 0.000 0.059 alpha-haemoglobin (Hb), 6-phospho- E 0.000 0.015 0.029 F1 0.333 0.015 0.074 gluconate dehydrogenase (6-PGD), F2 0.357 0.250 0.427 phosphoglucomutase (PGM), protease F3 0.024 0.074 0.088 inhibitor (Pi) and transferrin (Trf). H2 0.095 0.059 0.103 O 0.071 0.015 0.029 Nomenclature for variants at all 17 loci R 0.096 0.176 0.044 was in accord with internationally stand- A1B F 0.000 0.015 0.000 ardised usage for horses3,4, except for K 1.000 0.985 0.985 variants at some loci that have not yet S 0.000 0.000 0.015 Est F 0.118 0.044 0.029 received international recognition. G 0.000 0.015 0.044 Gene frequencies for biochemical loci H 0.000 0.015 0.015 were calculated by direct count. Fre- I 0.810 0.867 0.883 R 0.024 0.000 0.000 quencies of alleles at blood-group loci S 0.048 0.059 0.029 were calculated by the allocation A1 A 0.548 0.618 0.368 method1. Genetic variation was measured B 0.452 0.382 0.632 Gc F 0.952 0.985 0.956 as observed heterozygosity (Ho), Hardy- S 0.048 0.015 0.044 Weinberg expected heterozygosity (He), 6-PGD F 0.952 0.956 0.824 unbiased expected heterozygosity (Hu)11, S 0.048 0.044 0.176 PGM F 0.071 0.132 0.044 effective number of alleles (Ae), and the S 0.929 0.824 0.956 total number of variants found in each V 0.000 0.044 0.000 population (Na). Ho was calculated for GPI F 0.286 0.162 0.059 biochemical loci only on account of the I 0.714 0.794 0.883 Hb AII 0.000 0.044 0.000 presence of recessive alleles and/or BI 0.143 0.618 0.559 ambiguous genotypes at blood-group BII 0.857 0.338 0.441 loci. Therefore, for direct comparison, He Pi F 0.238 0.250 0.176 G 0.048 0.250 0.044 and Hu were calculated for biochemical I 0.000 0.132 0.015 loci only (in an ideal population, He (Hu) J 0.000 0.015 0.000 should equal Ho), for blood-group loci, L 0.381 0.103 0.323 L2 0.000 0.000 0.015 and for all 17 loci. In addition, population N 0.000 0.044 0.059 inbreeding level was estimated by O 0.214 0.000 0.015 Wright’s Fis=1(Ho/He). Values of genetic Q 0.000 0.015 0.000 R 0.000 0.044 0.074 variation of the South African breeds S 0.024 0.000 0.132 were compared to those of domestic T 0.000 0.044 0.000 horse populations that have been tested U 0.095 0.059 0.088 Z 0.000 0.044 0.029 at the University of Kentucky.