Fecal pH and Defecation Rates of Eight Ruminants Fed Known Diets

Abstract

The effects of five rations and four dates postcollection on fecal pH and defecation rates were determined for eight ruminant species in penned enclosures. Only axis deer (Axis axis) had a uniquely different fecal pH (P < 0.05). Species differences and date of analysis resulted in 37.9 and 25.0%, respectively, of the observed variation in fecal pH, whereas ration accounted for only 15.4%. Fecal pH decreased as time postcollection increased. Fecal pH was of limited utility in identifying specific origin of fecal pellets. Whitetailed deer (Odocoileus virginianus) had a higher defecation rate (X = 19.6 groups/day, SE = 2.3) (P < 0.05) than did any other species. Our data suggest that previous estimates of defecation rate for white-tailed deer may be low. J. WILDL. MANAGE. 48(3):807-813 The fecal pellet group count is a common method of assessing population trends and habitat use for wild ruminants. However, problems arise when a range is occupied simultaneously by two or more ruminants because of the inability to distinguish between fecal pellets of different species. Several techniques for testing specific origin of fecal pellets have been proposed, including size/shape comparisons (Sanders 1963, Ogren 1964), fecal pH (Howard 1967, Nagy and Gilbert 1968, Howard and DeLorenzo 1974, Krausman et al. 1974, Hansen 1978, Beasom et al. 1982), scale patterns of ingested hairs (Beasom et al. 1981), and electrophoresis (Scribner et al. 1984). Differentiation by fecal pH has been the most popular approach to date, but consistency of results has been sporadic (see Beasom et al. 1982). Indeed, the inability to separate pH variation because of diet similarities from those due to inherent physiological differences has confounded most attempts (Peek and Keay 1979, MacCracken 1980, Beasom et al. 1982). MacCracken (1980) and Beasom et al. (1982) concluded that fecal pH was primarily a function of diet. Thus, if the species of interest exhibit appreciable dietary overlap, fecal pH probably will not be an accurate method of species identification (Hansen 1978, MacCracken 1980, Beasom et al. 1982). The inability to identify the specific origin of fecal pellets is especially troublesome on the Edwards Plateau of Texas, where rangelands commonly are grazed by white-tailed deer, sheep, goats, and several species of exotic ungulates. While documenting habitat use by white-tailed deer following brush removal (Rollins 1983), we encountered as many as eight sympatric ruminant species. In addition to sheep, goats, and white-tailed deer, exotic axis, fallow (Cervus dama) and sika deer (C. nippon), aoudads (Ammotragus lervia), and blackbuck antelope (Antelope cervicapra) were present. Defecation rates are another aspect of pellet group methodology that have been contested in recent years. Accurate estimates of defecation rates are necessary for 'Manuscript T-9-336, Coll. of Agric. Sci., Texas Tech Univ. 2 Present address: Department of Agronomy, Oklahoma State University, Stillwater, OK 74078. 3Present address: Department of Entomology, Texas A&M University, College Station, TX 778432475. J. Wildl. Manage. 48(3):1984 807 This content downloaded from 207.46.13.124 on Wed, 22 Jun 2016 06:00:46 UTC All use subject to http://about.jstor.org/terms 808 FECAL PH AND DEFECATION RATES * Rollins et al. computing deer-days use or other population indices. Early reports suggested that the defecation rates of white-tailed and mule deer (0. hemionus) were about 13 times/day (McCain 1948, Eberhardt and Van Etten 1956). Smith (1964) suggested a slightly higher rate (13-14 times/day), whereas Rogers et al. (1958) reported a mean rate of 15 times/day. Collins and Urness (1981) reported a rate of 21-23 times/day for mule deer. Factors that may affect defecation rate were summarized by Neff (1968) and include forage intake (Rogers et al. 1958), forage moisture content (Longhurst 1954), abrupt changes in diet and age of animal (Smith 1964), and, possibly, stress (Neff 1964). Collins and Urness (1981) and Irby (1981) found that animal activity stimulated defecation. Few reports are available on the defecation rates for ruminants other than white-tailed or mule deer. Ogren (1964) reported a defecation rate of 12.7 times/ day for aoudads. Bailey and Putman (1981) reported that fallow deer defecated about 10 times/day, whereas Dinerstein and Dublin (1982) found a much higher defecation rate in captive axis deer (9 = 28 times/day). Longhurst (1954) found that defecation rate in sheep varied from 13-16 times/day depending on forage moisture content. We are not aware of any published estimates of defecation rates for Spanish or Angora goats, sika deer, or blackbuck antelope. We initiated a penned study in April 1982 to determine the effects of different diets on fecal pH values and defecation rates of eight ruminants. We wish to thank C. S. Schreiner, IV, for use of animals and facilities, D. Frantzen for providing assistance during the feeding trial, and D. B. Wester for assistance with statistical analyses. R. L. Preston, R. Pritchard, and R. J. Warren reviewed the manuscript.