Comparative analyses of tooth wear in free-ranging and captive wild equids

REASONS FOR PERFORMING STUDY

Captive breeding has played a crucial role in the conservation of threatened equid species. Grazing ruminants and rhinoceros in captivity have less abrasion-dominated tooth wear than their free-ranging conspecifics, with potential negative consequences for their health. However, a similar study on wild equids in captivity is missing.

OBJECTIVES

The aim was to establish if different tooth wear patterns are exhibited by free-ranging and captive equids.

STUDY DESIGN

Cross-sectional study of museum specimens comparing free-ranging and captive equids.

METHODS

Dental casts of maxillary cheek teeth of 228 museum specimens (122 from free-ranging and 106 from captive individuals) of 7 wild equid species were analysed using the extended mesowear method. Although teeth showing specific abnormalities were not scored, the presence of focal overgrowths (hooks) of the rostral premolars (106, 206) was recorded.

RESULTS

Captive Equus ferus przewalskii, E. grevyi, E. hemionus, E. quagga boehmi and E. zebra hartmannae have less abrasion-dominated tooth wear on their premolars than their free-ranging conspecifics (P<0.001). Fewer differences were exhibited between populations in the molars. No differences were exhibited in the distal cusp of the molars (110, 210) between populations, except in a small sample of E. kiang. Captive equids exhibited more homogeneous wear along the tooth row whereas free-ranging equids exhibited a tooth wear gradient, with more abrasion on premolars than molars. There were more rostral hooks on the premolars (106, 206) in the captive than the free-ranging population (P = 0.02).

CONCLUSIONS

Captive equids did experience less abrasion-dominated tooth wear than their free-ranging conspecifics, but the differences in tooth wear were less pronounced than those between captive and free-ranging wild ruminant and rhinoceros species. This indicates that feeding regimes for captive equids deviate less from natural diets than those for captive ruminants and rhinoceros but that factors leading to hook formation, in particular feeding height, should receive special attention. The Summary is available in Chinese - see Supporting information.

Carbonic anhydrase II is secreted from bovine parotid glands

Besides carbonic anhydrase VI (CA-VI), CA-II is suggested to be a second secreted isoenzyme in ruminant saliva. Therefore, the aim of the present study was to investigate the expression of salivary CA-II in bovine parotid glands at the protein level. Moreover, we intended to identify the cells which secrete the enzyme into the saliva. Two commercially available CA-II specific antibodies were tested for use in immunohistochemistry on frozen sections of bovine parotid tissue. Intense positive staining for CA-II was found in luminal duct cells and for the first time also inside the duct lumen, clearly demonstrating the expression and secretion of salivary CA-II in bovine parotid glands. The presence of CA-II protein was verified for parotid tissue and whole saliva using immunoblot analysis. Both salivary CA-II and CA-VI are highly active in supplying the alimentary tract with bicarbonate. It is suggested that a decrease in the expression of either one of these enzymes might severely disturb digestion and/or increase susceptibility to acidosis in ruminants.

Adhesion of bovine and goat salivary proteins to dental enamel and silicate (short communication)

Abstract. Salivary proteins may help to prevent enamel abrasion and adverse chemical effects on teeth of herbivorous mammals. To detect potential candidates for protecting proteins, bovine and goat whole saliva were incubated with dental enamel and glass powder. Salivary proteins, bound to dental enamel and glass, were analysed by SDS-PAGE. Two distinct salivary proteins were found to adhere to bovine enamel and were identified by MS/MS mass spectrometry and protein sequencing. Both the bovine odorant-binding protein (bOBP) and the carbonic anhydrase VI (CA-VI) were components of the protein layers. The bovine CA-VI adherent to teeth may serve as a pH-regulator to protect bovine enamel from bacterial acids. The bOBP may bind odorant particles right in the oral cavity and enhance their transmission to the vomeronasal organ (VNO), the signals of which are important determinants in sexual behaviour of mammals. Another protein from bovine and goat saliva seemed to preferentially bind to glass beads. These results suggest that salivary proteins may support olfaction and protect teeth of ruminants from mechanical and chemical destruction.

Design, construction and mechanical optimisation process of electrode with radial current flow in the scala tympani

A 48 contact cochlear implant electrode has been constructed for electrical stimulation of the auditory nerve. The stimulating contacts of this electrode are organised in two layers: 31 contacts on the upper surface directed towards the habenula perforata and 17 contacts connected together as one longitudinal contact on the underside. The design of the electrode carrier aims to make radial current flow possible in the cochlea. The mechanical structure of the newly designed electrode was optimised to obtain maximal insertion depth. Electrode insertion tests were performed in a transparent acrylic model of the human cochlea.