EFFECT OF GRAIN PARTICLE-SIZE ON PERFORMANCE .2. GRAIN TEXTURE INTERACTIONS

Diets were prepared with com, wheat, or sorghum ground in a hammer mil l and sieved to obtain coarse, medium, and fine particle size fraction s. Their effect on broiler performance from hatch to 7 d and from 7 to 21 d of age was studied. The effect of particle size on the size and pH of the gastrointestinal organs was also determined. The three textu res obtained for each grain were uniform in geometric mean diameter (G MD) and geometric standard deviation (GSD). Grain by texture interacti ons were not significant. Independent of grain source, the best perfor mance was obtained with diets prepared from the medium texture. In the se diets, the GMD of the grains varied from 1.13 to 1.23 mm and the GS D from 1.19 to 1.35. The fine fraction (GMD .57 to .67 mm) resulted in the lowest performance and that resulting from the coarse fraction (G MD 2.01 to 2.10 mm) was intermediate. At 7 and 21 d of age, gizzard we ight and content were positively related to particle size. At the age of 21 d, duodenum weight and content was highest in chicks fed the fin e diets. The pH of the gizzard content decreased with increasing grain particle size, whereas that of the small intestinal content increased . Some grain effects were also observed on the gastrointestinal tract. Gizzard weight was greatest in the corn-fed birds. Wheat-fed chicks h ad the heavier intestines and contents. After overnight feed deprivati on, feed consumption by 7-d-old chicks was related to the particle siz e during the first 2 h of refeeding, with greater intake of medium and coarse grains.