Rare Finding of a Full Nuchal Ligament Lamellae With Attachment Points From C2-C7 in One Australian Stock Horse

Abstract

For over 200 years, equine anatomic literature has chiefly portrayed the attachment points of the nuchal ligament lamellae (NLL) from the second to the seventh cervical vertebrae (C2-C7). However, recent studies have shown that the modern domestic horse, Equus caballus, primarily exhibits the attachments points from C2-C5. Here we present the rare finding of a complete NLL attached from C2-C7 in one Australian Stock Horse (ASH) and discuss the potential implications of these findings. Previously, this trait has only been confirmed among close descendants of Equus ferus ferus; namely the primitive Dutch Konik and Bosnian Mountain Horse. The examination of the NLL attachment points in 55 unrelated horses of mixed breeds revealed that 52 horses had attachments from C2-C5; 1 horse (Welsh Cob) had attachments from C2-C6; and only 2 horses (ASH and Dutch Konik) presented with a complete NLL attached from C2-C7. In light of earlier findings that suggest this loss of NLL attachment at C6 and C7 occurred after domestication, a possible explanation for this finding in 1 ASH is that it is a remnant trait from the founder population of Waler horses that contributed to the early development of the ASH breed. The reported rare occurrence of a complete NLL (C2-C7) in a modern domesticated equine (ASH) suggests that there may be other individuals expressing this unique trait, providing opportunity for its preservation.

Keywords: Australian stock horse; Cervical vertebrae; Dutch konik; Isolated breeds; Nuchal ligament lamellae; Waler.