Читать книгу Medicine and Surgery of Camelids - Группа авторов - Страница 15

The karyotype of all camelids is 2n = 74. All SACs have produced fertile hybrids. Dromedary and Bactrian camels also produce fertile crosses. Though less common, it is possible to produce camel – SAC hybrids, however, most experimentation with this hybridization has resulted in non‐viable offspring. Llama – camel crosses are known as camas [7], and alpaca – llama hybrids are known as wari or wakayu [8]. In Israel, a cross between an alpaca male and a dromedary female by artificial insemination produced a stillborn full‐term fetus. One report of a guanaco inseminated with camel semen produced a viable calf [9].

Significant size differences exist among camelid species, though they maintain similar anatomic relationships. Domesticated camelids tend to have a larger body size than their wild ancestors. Though there is overlap, vicuñas tend to have the smallest body size, followed by alpacas, guanacos, and llamas are the largest [10]. Environmental pressures influenced different adaptations of camels from the SACs. The camels completed Pleistocene evolution in a semidesert environment in southern Asia, the Middle East, and North Africa and developed sophisticated adaptations for dealing with heat and dehydration. The SACs became adapted to South American habitats, especially the high‐altitude lands of the Andes.

Figure 1.1 Dromedary camel cow nursing her calf (

Source: Photo courtesy of Dr. Sharon Deem at the Saint Louis Zoo Institute for Conservation Medicine

).

Figure 1.2 Bactrian camel.

Camelids are often compared to true ruminants, though distinct differences in gastrointestinal (GI) anatomy and physiology place them in separate phylogenic suborders. Geologic evidence suggests that camelids and ruminants began to diverge near the beginning of the tertiary period from primordial, monogastric species. Camelids have a complex, three‐compartmented stomach. Similar to ruminants, camelids consume fibrous forage and have developed similar foregut fermentation systems by parallel evolution (Chapters 3 and 12). Camelids regurgitate and rechew ingested forage, as do ruminants, however, camelids have more efficient mechanisms than ruminants for extracting protein and energy from poor quality forages [11]. More detail on the differences between camelids and ruminants are found in earlier editions of this text [12].