Calculation of cerebral hemispheres volume values (grey matter, white matter and lateral ventricle) of sheep and goat: A stereological study

Abstract

Stereology is a discipline that allows us to obtain quantitative information about the geometric structure of three‐dimensional objects. In this study, the volume of grey matter (GM), white matter (WM), and lateral ventricle (LV) of the cerebral hemispheres (CH) in sheep and goats were calculated. For this purpose, six healthy male sheep and goat brains (1–2 years old) without any anomaly were used. Brains were fixed with 10% formaldehyde in the skull. The skull was opened using standard anatomical dissection methods, and the brains were carefully removed. Brain weight and volume were measured (using Archimedes' principle) after the meninges were removed. The cerebral hemispheres were separated from the other parts of the brain by a section made in front of the rostral colliculus. In the same way, the weight and volume of the cerebral hemispheres were measured. Afterward, the cerebral hemispheres were blocked with agar, and transversal cross sections (from rostral to caudal) with an average thickness of 3.42 mm were taken from the cerebral hemispheres. Grey matter was stained with Berlin blue macroscopic staining method. The stained cross sections were scanned at 600 dpi resolution, and a point counting grid was placed on the images with the ImageJ software. Cavalieri's principle calculated the surface area and volume measurements of the grey matter, white matter, and lateral ventricle. GM, WM, and LV volumes in sheep and goat cerebral hemispheres were calculated as 54.94, 21.48 and 3.06 mL in sheep, 57.46, 24.13 and 3.12 mL in goats, respectively. The percentages of these structures in the total hemisphere volume were 71.83%, 28.17% and 4.00% in sheep, 70.42%, 29.58% and 3.82% in goats, respectively. Asymmetry was not observed in cerebral hemispheres in both species. A difference was found in the WM, LV and LV: CH ratios in the right/left comparison of the goat (p < 0.05). In comparing sheep and goats, a significant difference was observed in WM right, WM left, WM total, CH left and CH total (p < 0.05). In conclusion, the cerebral hemispheres' grey matter and white matter ratio are frequently used to diagnose neurodegenerative diseases. In recent years, the increase in neurodegenerative disease models in farm animals has been enormous. It is thought that these values obtained from healthy animals in the current study will be important for such experimental studies in the future.

Volumetric study on sheep brain using stereology technique

“…The ratio of grey to white matter in sheep (about 1.7) is different from other mentioned large domestic mammals (ox: 0.91 and horse: 1.09). Greater volume of grey matter has been previously reported in sheep compared to horses and cows (Aydoğdu & Eken, 2024). However, it has been shown that the volume of the white matter does not scale universally with the volume of the grey matter across mammals (Mota et al, 2019).…”

“…Most stereological studies on the brain have been carried out on laboratory animals such as rat (Perkins et al, 2018), mice (Ip et al, 2017), rabbit (Selçuk & Tıpırdamaz, 2020) and also on domestic animals like pig (Holm & West, 1994). Apart from the recent volumetric studies on main structures of the brain including grey matter, white matter and lateral ventricles in sheep (Aydoğdu & Eken, 2024), the detailed morphometric features of the normal brain in adult animals of this species have not been investigated stereologically, yet the purpose of the present work was to study the total volume of the sheep brain and volume fractions of its components including caudate nucleus, claustrum, corpus callosum, external capsule, internal capsule, white and grey matters using stereology technique.…”