Presentation (Chopped Versus Ground and Pelleted) of a Low-Quality Alfalfa Hay in Sheep: Effects on Intake, Feeding Behaviour, Rumen Fill and Digestion, and Passage.

A voluminous amount of knowledge has been collected about the effects of the rate and amount of intake and of the rate and amount of digesta flow out of the rumen on rumen fill and, hence, intake. However, the mechanisms by which small particles in the rumen are selected for passage have not been clearly identified. Grinding and pelleting have been alleged to either enhance or reduce entrapment; hence, the relationships between particle size and digestion and passage kinetics are not sufficiently clear, as it is not the effect of rumen digesta particle size on marker dilution kinetics. On these grounds, the aim of the present experiment was to examine the behaviour of small particles within the rumen and determine if their retention time by passage or digestion pathways alter under pelleting and control intake. In the present experiment, the effects of a low-quality alfalfa hay presentation (chopped vs. ground and pelleted) on intake, feeding behaviour, rumen fill and digestion, and passage were assessed in adult wethers. Pelleting increased intake without alteration of either the maximum amount of digesta present in the rumen or degradation rates. The faster dilution rate of the liquid phase with the pelleted hay, likely including significant amounts of particles <0.15 mm, should be the main factor for the higher intake with this diet.