An increase in dietary non-structural carbohydrates alters the structure and metabolism of the rumen epithelium in lambs

Abstract

Steele, M. A., Greenwood, S. L., Croom, J. and McBride, B. W. 2012. An increase in dietary non-structural carbohydrates alters the structure and metabolism of the rumen epithelium in lambs. Can. J. Anim. Sci. 92: 123–130. This study investigated the effect of a grain challenge on the structure and metabolism of the rumen epithelium in lambs. In a randomized design, lambs (n = 8) received either a control diet [30% dry matter (DM) grain], or a diet of increasing amounts of grain to a maximum inclusion of 79% of DM for 12 d prior to slaughter. Rumen papillae were collected from the ventral sac on day 13 and prepared for histological and gene expression analyses. All lambs fed the high-grain diet were diagnosed with ruminal parakeratosis as the thickness of the corneum was higher (P<0.01) compared with control lambs (51.0±2.3 vs. 17.3±2.5 µm). Plasma beta-hydroxybutyric acid concentrations increased linearly (P<0.05) with increased grain consumption compared with the control. However, the relative mRNA expression of the ketogenic enzyme 3-hydroxy-3-methyl-glutaryl CoA-synthase (HMGCS2) in rumen papillae was not different between treatments. The expression of cholesterolgenic enzyme HMGCS1 was down-regulated by 0.70±0.06 (P<0.05) fold in lambs fed the high-grain diet compared with the control. These results suggest that a short-term grain challenge in lambs is associated with altered rumen epithelium metabolism and structural changes indicative of ruminal parakeratosis.