The use of computed tomography for in vivo estimation of reticulo-rumen and omasum contents in Alpine goats

Abstract

Precise in vivo measurement of reticulo-rumen content (volume and mass) is required for the study of digestive processes. Rumen-cannulated animals have been classically used for this purpose, and less invasive alternatives are currently investigated to meet the replacement, reduction, and refinement (3Rs) ethical considerations in animal science. The objective was to compare in vivo reticulo-rumen and omasum volumes assessed by computed tomography (CT) scan with postmortem measurement of their respective digesta masses in dairy goats. Twenty Alpine dairy goats were scanned by CT, and the volumes of the reticulo-rumen and omasum were measured by CT image postprocessing. Goats were slaughtered immediately after CT scan and the masses of reticulo-rumen and omasum digesta were measured. Simple linear regressions were performed between volumes measured in vivo by CT and the corresponding digesta wet masses measured postmortem. Reticulo-rumen and omasum volumes determined by CT were significantly and linearly regressed against the corresponding digesta masses measured postmortem (R² = 0.72 and 0.87, residual standard deviation = 1.18 and 0.06 kg, and residual coefficient of variation = 11% and 12%, n = 20 and 19, respectively). The use of CT is a promising noninvasive method to measure volume and estimate digesta masses of reticulo-rumen and omasum in small ruminants.

Summary: Quantification of reticulo-rumen content (volume and mass) is required in ruminant nutrition research but has traditionally relied on rumen-cannulated animals. The use of computed tomography (CT) is compatible with small ruminants. We compared the reticulo-rumen and omasum volumes measured by CT in vivo with the corresponding digesta masses measured postmortem in Alpine goats (n = 20). Reticulo-rumen and omasum volumes determined by CT were significantly and linearly regressed against the corresponding digesta masses measured postmortem (R² = 0.72 and 0.87, respectively), thus demonstrating the potential of CT to measure volume and estimate digesta masses of reticulo-rumen and omasum contents in goats.

Figure 1

Illustrative figure of Alpine goat immobilization and image acquisition. The internal volumes of reticulo-rumen (green) and omasum (violet) were measured by CT scan (horizontal image section in the top-right panel and vertical image slices in the bottom panels), based on approximately 150 to 200 images per goat, and analyzed semi-automatically.

Figure 2

Linear regressions between (A) the reticulo-rumen internal volume measured in vivo by CT scan and the reticulo-rumen digesta mass measured postmortem (R² = 0.72, rSD = 1.18 kg, n = 20), and (B) the omasum internal volume measured in vivo by CT scan and the omasum digesta mass measured postmortem (R² = 0.87, rSD = 0.06 kg, n = 19) in Alpine late-lactation goats.