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Regulation of Food Intake in Ruminants. 6. Influence of Caloric Density of Pelleted Rations^1,2,3,

Department of Animal Science, The Pennsylvania State University, University Park 16802

ABSTRACT

The objectives of this experiment were to determine voluntary feed and energy intake of rations varying in digestibility and density and to describe rations on which intake is limited by fill. A basic concentrate mixture was diluted from 5 to 50% at 5% increments with each of four diluents: (A) oak sawdust, (B) oak sawdust with constant 3% kaolin clay, (C) verxite, an expanded hydrobiotite, and (D) as (A), except nitrogen was kept constant at 17.4% crude protein equivalent. Thus, 40 rations were evaluated. The rations were pelleted. Each ration sequence (A-D) was fed to four sheep maintained in metabolism stalls. Density of the rations was measured on a dry basis and by water displacement.

Dry matter intake (g/W_>kg^-sup>75) increased as the digestible energy per gram increased to 2.5 kcal for Ration Sequences A, B, and D. With rations having digestible energy values above 2.5 kcal/g, dry matter intake decreased and digestible energy intake (kcal/W_kg^-75) remained static. Apparently, fill limited intake of these sheep when the digestible energy of the rations was less than 2.5 kcal/g, whereas above this level energy intake was regulated. Comparable values for caloric density were 1.45 kcal/ml (based on a dry feed density) and 3.48 kcal/ml (based on water displacement density). The sheep rejected the C sequence of rations when the digestible energy was less than 3.0 kcal/g (greater than 15% verxite), possibly because the rations were unpalatable.

¹ Authorized for publication August 18, 1969, as paper no. 3646 in the Journal series of the Pennsylvania Agricultural Experiment Station.

² Data presented are taken from a thesis presented by D. A. Dinius in partial fullfillment of the requirements for the Ph. D. degree, The Pennsylvania State University, September, 1969.

³ This investigation was supported in part by a U.S. Public Health Service Grant, AM 12023.

⁴ Current address: Agricultural Research Service, Animal Husbandry Research Division, Beltsville, Maryland.