Digestion Rate of Limestone Force-Fed to Pheasants

Abstract

Tests were conducted to learn the erosion (disappearance) rate of marked limestone in the digestive tracts of penned pheasants (Phasianus colchicus) force-fed known amounts. The erosion rate was progressive and amounted to approximately 46 percent in 12 hours, 89 percent in 24 hours, and 95 percent in 36 hours. These data show that all calcareous grit may not be detected by standard food-habits study procedures. This may explain why chemical analyses of principal foods of wild pheasants, as shown by a study of crop and gizzard contents, generally show levels of calcium much below known requirements for penned birds. This study was conducted to learn the rate of erosion of limestone grit through pheasant digestion and whether a true measure of calcium ingestion was detectable by standard food-habits study methods. The need for this information became evident during a study of foods and nutrition of the ring-necked pheasant in Missouri (Korschgen 1964). Chemical analyses of principal foods consumed showed consistently lower levels of calcium in average diets than growth or maintenance requirements established by Dale and DeWitt (1958) and Scott et al. (1958) for penned birds. The availability of supplementary sources of dietary calcium was indicated by healthy, wild populations in northwestern Missouri, but crop and gizzard analyses generally showed small amounts of calcareous grit in the daily diets.