Food intake in sheep following intraruminal infusion of extracts from lucerne silage with particular reference to organic acids and products of protein degradation

Abstract

SummarySheep were infused intraruminally with iso-osmotic solutions of saline, organic acids or lucerne silage extracts with or without additional acids and products of protein degradation found in silage. The post-ingestive effects of silage constituents on food intake were assessed by measuring the voluntary consumption of high dry matter silage over a 20 h period following feeding. In Expt 1, three different silage extracts each depressed food intake up to 4 h following feeding. In Expt 2, one of these extracts, to which 40 g of γ-amino butyric acid (GABA) was added, depressed intake up to 4 h following feeding; with the further addition cf 10 g α-amino butyric acid (AABA) and 28 g amines to this extract, intake was enhanced within 0·5 h but depressed from 4 to 8 h following feeding. In Expt 3, infusion of organic acids alone did not significantly depress food intake relative to saline, nor was there a discernible effect on food intake when graded levels of nitrogenous constituents from silage were added to the infusates. In Expt 4, infusion of an extract, to which only AABA and four other amines were added, depressed cumulative intake up to 8 h following feeding and had a more pronounced effect on food consumption than infusion of the extract with these constituents together with GABA. It was concluded that soluble constituents in silage can inhibit intake but no single constituent is primarily responsible.