Effects of ruminal dose of sucrose, lactose and starch on ruminal fermentation and expression of genes in ruminal epithelial cells

Abstract Text: The objective was to evaluate effects of ruminal dose of sucrose (SUC), lactose (LAC) and corn starch (STA) on ruminal fermentation and expression of genes in ruminal epithelial cells. Six ruminally cannulated non-lactating non-pregnant Holstein cows (BW = 725 ± 69.6 kg) were fed a diet containing whole crop barley silage and dry ground corn (dietary NDF and CP contents: 41.8 and 13.2% at DM basis, respectively), and assigned to treatments in a 3×3 Latin square design with 7-d periods; 1 d for data and sample collection followed by a 6-d washout period. Treatment was a pulse-dose of SUC, LAC, and STA (3.0, 3.0, and 2.85 kg DM, respectively, to provide similar amount of hexose across the treatments) through the rumen cannulas. All treatments were given with alfalfa silage (1.75 kg DM) to prevent acute rumen acidosis. Rumen pH was continuously monitored, and rumen fluid was sampled at 0, 30, 60, 90, 120, 150 and 180 min after the dose. In addition, ruminal papillae were sampled from the ventral sac at 180 min after the dose. Ruminal dose of SUC and LAC, compared with STA, increased (P < 0.05) ruminal total VFA concentration and molar proportion of butyrate since 60 min after the dose, and expression of genes for sodium hydrogen exchanger 1 and 2, and ATPase-1 in ruminal epithelial cells. Ruminal dose of SUC, compared with LAC and STA, decreased (P < 0.05) rumen pH since 120 min after the dose and molar proportion of acetate in ruminal fluid from 60 to 150 min after the dose, and increased (P < 0.05) molar proportion of propionate in ruminal fluid from 60 to 150 min, and expression of genes involved in butyrate metabolism (3-hydroxy-3-methylglutaryl-Coenzyme A synthase 1) and anion exchange across ruminal apical cell membrane (putative anion transporter 1). These results suggest that replacing dietary starch with sugar may affect ruminal fermentation, and metabolism regulating intracellular pH and fermentation acid absorption in ruminal epithelial cells, and that these effects can be greater for SUC than LAC.

Keywords: Sucrose, Lactose, Starch