Morphometric and stereological methods for quantifying the coarse structural parameters of the ruminal tissues in sheep.

In ruminants, the rumen is the largest and most significant fore-stomach. Stereological analysis of important structural parameters that may be used to assess the functional capacity of the rumen is lacking. In the current investigation, five rams were used to demonstrate the methods for quantifying salient structural parameters related to rumen function. The sheep were euthanized with 20% sodium pentobarbital intravenously, the rumen was dissected out and divided into the various sacs for gross examination, and fixation by total immersion in 10% formalin. Macroscopic ruminal surface area was estimated using the point-associated area method. Volumes of the ruminal tissues were estimated by the volume displacement method, while volume densities of the components of the ruminal wall were estimated by point counting methods. Tissue blocks for histology were obtained by systematic random sampling and processed to obtain vertical sections for surface area and volume estimations. Papillary densities and numbers were estimated from horizontal sections. The volume of ruminal tissue was 536.54 ± 80.52 cm³, the macroscopic surface area was 1091 ± 115.75 cm² with a papillary packing density of 84.64 ± 10.99 cm^-2. Average absolute surface area was 4726.74 ± 628.56 cm². The total number of ruminal papillae per rumen was 92,884.91 ± 6216.46. The methods documented here provide the possibility of doing a detailed stereological analysis of ruminal tissue in different experimental or even pathological conditions.