Horses have played an important role in the development of Portugal throughout the centuries. Nowadays there are four officially recognized Portuguese autochthonous horse breeds – Lusitano, Sorraia, Garrano, and Terceira Pony. The Terceira Pony is autochthonous to the Azorean archipelago and was recognized by the national authorities on January 27, 2014. These animals are believed to have descended from horses first brought from mainland Portugal to the islands during the 15th century and were selected for size and adaptation to the local conditions. These extremely hardy and well adapted horses were very important during the colonization for transportation of goods and people, for agriculture and, if necessary, for meat and milk (Luciano da Silva, 1971). Although they contributed substantially to the development of the islands, due to new agricultural practices and the introduction of horses from other origins, their importance gradually declined and therefore the sustainability of the Terceira Pony now depends on a shift toward new market needs.

The Terceira Pony has very correct and balanced proportions with physical and personality characteristics that conform to the image of a modern riding horse, making it popular for riding by children. The existing population of the Terceira Pony comprises about 100 animals living on Terceira island, many of them descending from 14 founders (six sires and eight dams) while a few horses are dispersed on the other islands, mainly Faial, Graciosa, S. Jorge, and S. Miguel. In order to preserve the existing animals and increase their number, the Association of Breeders and Friends of the Terceira Pony was established in 2010.

In general for a horse to be accepted to the studbook it has to conform to specific phenotypic characteristics. Body conformation is used in distinguishing, evaluating, and comparing breeds (Lawrence, 2001). The relationships among body dimensions also affect the horses’ beauty and performance in sports (Evans, 2000; Lawrence, 2001; Parker, 2002; Sadek et al., 2006). As the Terceira Pony has been recently recognized as a breed and the stud-book is in the process of being established, horses from other breeds can therefore still be used as founders provided that they fit the body conformation, gaits, and breeding goals set forth by the Association of Breeders and Friends of the Terceira Pony.

Nowadays, due to the reduced number of animals the Terceira Pony is evolving from deliberate crosses of specific sires and dams, which can lead to a loss of genetic diversity. Such a breeding program has to be carefully monitored to ensure that the decrease in variability does not adversely affect the beneficial characteristics of this breed. Microsatellites are accepted as the most suitable molecular markers to investigate breed genetic diversity (Takezaki and Nei, 1996) and differentiation, to estimate the genetic structure of populations (Pritchard et al., 2000) and comprise an attractive potential source of information about population histories and evolutionary processes (Aberle and Distl, 2004). The evaluation of genetic variability is one of the first steps in the process of species genetic conservation aimed at preserving both genetic variability and population viability (Bömcke et al., 2011).

The objective of the present study was to gather data to assist in management improvements and conservation planning by accessing the body conformation of the Terceira Pony by measuring 30 fully grown animals so that external breeders can match the required phenotype, estimate morphometric indices from these measures, assess biometric data and evaluate functional classification standards, and by analyzing 52 animals with 15 polymorphic microsatellite loci, that will enable quantifying the genetic variability within the breed.

The objective of this work was to determine the morphotype of the Terceira Pony and to analyze its genetic structure.

Horse breeding aims at influencing functional conformation for the improvement of traits such as sport performance. Identifying patterns of equine anatomy for different horse breeds could be helpful in predicting how successful the animals will be in performing different tasks. Part of the beauty of the Terceira Pony depends on its body conformation, body measurements and the relationships among the dimensions; therefore, metric features of the exterior can become a selection tool for the Terceira Pony (Koenen et al., 2004).

Among the standard measurements used in horse breeding, the most significant exterior variable is height at withers (Komosa and Purzyc, 2009). An average of height at withers of 128.00 cm for the population under study classifies these horses as ponies (Hendricks, 2007).

The present study indicated that from a morphological and zoometric point of view the Terceira Pony may be regarded as a mediline (BI = 0.877 for dams and 0.857 for sires; Oom and da Costa Ferreira, 1987), eumetric (DTI = 0.108; Cabral et al., 2004), elipometric (W < 350 kg; McManus et al., 2008), dolichocephalic and “far from ground” (CI < 0; Ribeiro, 1988; McManus et al., 2008) animal. Also the BR and QI indicate that these animals are well proportioned, with withers height, croup height, and body length approximately equal. Due to these proportions the Terceira Pony can therefore be considered as a well-proportioned saddle horse suitable for sports (Zamborlini, 2001).

The CPI defines how compact horses are and gives an indication on their aptitude for traction (McManus et al., 2005, 2008). Values obtained for the Terceira Pony are contrasting: while CPI1 showed that animals were more adapted for riding, CPI2 indicated animals adapted for light traction. The difference observed between the two indices reveals the versatility and potential of these animals, which is also supported by the variation of the angle of the shoulder. Shoulders should be efficient to transform speed into driving force transmitted by the hind limbs and therefore variations of the shoulder angle may be an indication of the potential use of the animals (Camargo and Chieffi, 1971). The longer and more obliquely positioned scapula results in a longer and more swinging gait. For the Terceira Pony the shoulder angle of sires ranges from 45 to 55° and of dams is 55° suggesting that sires can be used for draft and saddle and dams for racing (Camargo and Chieffi, 1971).

The long bones that form the limbs and thus affect height are of special importance, not only to the appearance of an animal but also to the quality of gaits and practical predispositions. From the anatomical point of view, hind limbs are used to start a stride and fore limbs are used mainly to support the body mass during movement (Mawdsley et al., 1996). The Terceira Pony has a long hind limb with indices of the metacarpus length and the metatarsus length higher than those reported for other Pony breeds (Komosa and Purzyc, 2009); this predisposition was previously associated with jumping in Polish Half-bred horses (Komosa et al., 2013).

Longer croups are desirable in racing, jumping and also in marchers and are associated with elongated and stronger muscles capable of powerful contractions necessary for speed and which facilitate propulsion (Jones, 1987). A short croup is tolerated only in draft horses, but this reduction in length must be compensated by greater muscle development (Nascimento, 1999). Also the slope of the croup influences the fitness of the horse. A croup with a horizontal direction (12–25°) is conducive to speed, inclined (25–35°) is suitable for light traction, jumping and riding, oblique (35–45°) should only be tolerated for heavy traction, and too steep (45 and 55°) is always undesirable (Nascimento, 1999). For the Terceira Pony, while males have croups with a horizontal direction (20.60°) favorable for speed, females stand out from the males for presenting an inclined croup (25.44°) suitable for jumping and riding.

According to Komosa et al. (2013) among the indices used for describing the differences in the exterior conformation of horses, the scapula index deserves particular attention. The scapula belongs to the flat bones and plays a considerable role in the movement of a horse (Komosa and Purzyc, 2009). By comparison with other Pony horses, the Hucul and the Konik (Komosa and Purzyc, 2009), the Terceira Pony showed generally lower values for the following indices: arm trunk, arm, forearm, greater trunk, smaller trunk, femur, and metacarpus circumference. The only exceptions were for the indices of scapula, chest, and croup where the Hucul horses showed slightly lower values; and for the index of metacarpus and metatarsus lengths where the Terceira Pony showed higher values than the other two breeds. The scapula, greater trunk, smaller trunk, and metacarpus circumference indices of the Terceira Pony were closer to those of the Polish Half-bred horse and the Thoroughbred (Komosa et al., 2013) than the Hucul and Konik breeds. Higher values of greater trunk index were reported for the Pantaneiro horse (McManus et al., 2008) and lower for the Alter Real (Oom and da Costa Ferreira, 1987) and the Mangalarga Marchador (Cabral et al., 2004) when compared with the Terceira Pony.

Based on this study, it can be stated that due to its height at withers, the Terceira Pony is different from the Thoroughbred and Polish Half-bred horses, but its exterior conformation is more similar to these riding breeds than to other primitive ponies like the Hucul and Konik horses.

Although these results may seem unexpected, the genetic background of the Terceira Pony is closer to the Polish Half-bred horse and to the Thoroughbred than to the Konik and Hucul horses. The Terceira Pony is believed to be a representative of the horses living in the Iberian Peninsula during the Portuguese and Spanish discoveries, that contributed to the development of many other European modern horse breeds that were later introduced and dispersed throughout the Americas, founding numerous breeds in the new world (Rodero et al., 1992; Luís et al., 2007; Lopes, 2011). A preliminary study conducted with 64 worldwide horse breeds including the Terceira Pony showed closest genetic similarity with breeds form Iberian origin (Lopes et al., 2011).

The genetic analysis showed that the Terceira Pony presents levels of genetic diversity similar to other, older breeds from the Iberian Peninsula, breeds from South America of Iberian origin, as well as breeds from Asia, Europe and North and South America (Luís et al., 2007; Felicetti et al., 2010; Cothran et al., 2011; Lopes, 2011). However, allelic frequencies are heterogeneous and equal to or higher than 40% for all loci except VHL20. This may be explained by the different founder lineages that the actual population may have. A census made in 2001 in Terceira island identified 144 horses with a height at withers equal or lower than 139 cm out of 726 horses (Braga, personal communication) which are believed to be the founders of the actual population. Ponies with the same phenotypic characteristics were also identified in other islands and recently introduced in the herd, who at the time this work was conducted, had few or no descendants. Nevertheless, although some founders were more represented than others, no sub division of the population was observed by either analysis methods, a result typical of a homogeneous population. According to Pedersen (1999) and Proschowsky et al. (2003) lower values for genetic diversity were expected as until now phenotypic selection has been based on a few isolated sires and dams.

The Terceira Pony has been associated with husbandry and social activities of the people from Terceira island over 100s of years. Presumably the animals that were more robust and tractable and of the “desirable type” have been bred by farmers. Therefore the Terceira Pony is a breed autochthonous of the Azorean archipelago and very well adapted to the local conditions. However, with a reduced number of animals, it still sustains relatively high genetic diversity that needs to be taken into account in future breeding strategies, for conservation purposes and in the management of the studbook to avoid genetic erosion.

The data presented in this study define this horse breed as well-proportioned with a small and narrow head, a long neck well placed between the long shoulders and leaving the withers without any convexity. The overall average of biometric variables and trends classify the Terceira Pony as having small shape, low weight, shortline, eumetric, or well balanced with strong and resistant legs considered far from ground (Figure 2). It is a fast animal, smart, extremely docile and easy to manage and therefore ideal for teaching equestrian sports to young children and for physical therapy or work with disabled people. Due to its phenotypic homogeneity in body conformation, balanced gaits, personality, and cultural importance and geographical location (FAO, 1999) the Terceira Pony was recently recognized as a breed. However, as the Terceira Pony still has an open stud book allowing the entrance of horses from other origins with a specific morphological type, and as breeds tend to change based on the function they are breed for, these results will serve as baseline data for future follow-up studies of the breed. The standard established for the Terceira Pony and the genetic data presented in this work are therefore of utmost importance, as the harmonization of selection and preservation is difficult and they may be opposed to one other (Bodó, 1990).

ACM conceived the experiment. HR and VC collected measurements and blood. MSL performed the genetic analysis. MSL, DM, and SXB analyzed the data. MSL, SXB, and ACM wrote the manuscript. All authors read the manuscript and agreed to submit it.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.