Effect of ileal infusion of volatile fatty acids on feed intake and urinary magnesium excretion in sheep.

Abstract

Five 2-year-old female sheep fitted with cannulae in the terminal ileum and proximal colon were infused, intra-ilealy during a 24 h period, with volatile fatty acids (VFA) (ratio of acetic:propionic:butyric acid, 0.80:0.15:0.05) at rate of 0, 220, 440, 660 or 880 mmol/day in 21 deionized water. Daily feed intake was progressively depressed by VFA and reached 87 +/- 4.7% (S.E.M.) at the highest rate of infusion. Colonic digesta pH decreased by 2.1 +/- 0.48 units and Mg solubility increased from 21 +/- 2.6 to 52 +/- 1.2% 16 h after the start at the highest rate of VFA infusion. Urinary Mg excretion increased during the first 4 h of infusion on all treatments but the increase was not sustained. The results are discussed in the context of limited knowledge of the importance of the large intestine in intake regulation and Mg absorption.