Standard feeding recommendations and nutrient requirement tables such as the NRC and ARC pool the energy contributing portions of a diet into a single value (DE, ME, NE or TDN) without regard to the effect individual components of the diet may have on feed intake and function of high-producing ruminants. Two of the major components of the diet are the rumen fermentable fiber and the nonstructural carbohydrates (sugars and starches). Previous experiments at Cornell have shown that levels or relative proportions of fermentable fiber and nonstructural carbohydrates may significantly affect dietary intake of highly productive ruminants. Thonney and Hogue observed that lambs fed 24% indigestible neutral detergent fiber (INDF) diets consumed 18% more dry matter per day and gained 10% more than the average of lambs fed 14 and 19% INDF diets (1999) when fed a diet high in fermentable fiber. This indicates that a new system of diet formulation should be developed for highly productive ruminants based upon minimum levels of fermentable fiber and maximum levels of nonstructural carbohydrates. This experiment is designed to quantify how the level of fermentable dietary fiber affects feed intakes and collateral responses of ewes producing large amounts of milk.

Ewes and their twin or triplet lambs will be moved to elevated pens with expanded metal floors a few days after lambing and fed complete, mixed diets containing either 15, 25, or 35% fermentable fiber for 42 days. Seven ewes will be fed each diet. Feed intake, and ewe and lamb weights will be recorded. Digestibility of the diets will be determined by using chromic oxide as a marker. Blood will be drawn from the ewe to measure D-lactic acid as an indicator of metabolic acidosis. On about day 21 after lambing, milk production will be measured by administering oxytocin to cause the ewe to release milk; once to remove residual milk from the udder and about two hours later to measure the milk produced in a given number of minutes (approximately 120).