Effects of Diet and Body Condition on Fecal Progestagen Excretion in Elk

Abstract

Recent research demonstrated the utility of fecal progestagens (P 4 ) for detecting pregnancy in elk (Cervus elaphus) during mid-to late gestation. Several factors, however, may influence fecal P 4 excretion and limit its use in free-ranging animals. We investigated the effects of nutrition and body condition (percent ingesta-free body fat) on fecal P 4 concentrations and incidence of abortion. During mid-gestation (late December 1997 through early March 1998), 40 gravid cow elk varying in body condition were placed on three diets (high, medium, and low) in which the amount of food offered varied. Feces were collected periodically and analyzed for P 4 via radioimmunoassay. We found no significant effect of dietary treatment on P 4 concentrations, but as body condition declined, P 4 concentrations declined significantly. This decline did not impede the ability to detect pregnancy based on previously reported criteria, even for elk in such poor condition that they aborted. However, fecal P 4 concentrations in 10% (4/39) of samples collected from 13 non-pregnant animals maintained on a high plane of nutrition were falsepositive for pregnancy. We suggest alternate criteria for determining pregnancy in elk using fecal P 4 values: Ͼ1.25 g/g feces as pregnant, Ͻ1.0 g/g feces as non-pregnant, and 1.0-1.25 g/g feces as inconclusive. Finally, two cows that aborted did not abort until weeks after being classified as emaciated and near death, suggesting that nutrition-associated abortion in elk may not occur during mid-gestation except under extremely harsh conditions.

The many uses of non‐invasive faecal steroid monitoring in zoo and wildlife species

“…Although feed intake did influence plasma progesterone concentrations, faecal progesterone metabolites were not affected by the level of feed intake or faecal output, but the daily excretion rate of faecal metabolites was associated with the volume of faeces. Comparable results have been found in an Elk (C. elaphus, Cook et al, 2002) on a restricted diet. Derived from this experiment, it is likely that seasonal variation in faecal cortisol metabolites, as described in, for example, Red deer C. elaphus (Huber et al, 2003), Chacma baboons Papio hamadryas (Weingrill et al, 2004) and Chamois Rupicapra rupicapra (Hoby et al, 2006), is influenced by an endogenous rhythm.…”

Nutrition integrates environmental responses of ungulates

“…With low fat levels, there may be increased incidence of embryonic mortality in some species (caribou: Russell et al . 1998), although there is strong selection to maintain pregnancy at almost any cost in other species (elk: Cook et al . 2002).…”

“…Winter and spring body fat levels buffer the effects of declining food supplies when energetic demands can not be met by foraging alone (Parker et al 1999). With low fat levels, there may be increased incidence of embryonic mortality in some species (caribou: Russell et al 1998), although there is strong selection to maintain pregnancy at almost any cost in other species (elk: Cook et al 2002). Differences in body condition thresholds for aborting the foetus may reflect the likelihood of recovering condition during gestation; long winters limit recovery of body condition lost in early winter and favour a greater incidence of abortion in caribou.…”

Body condition and pregnancy in northern Yellowstone elk: Evidence for predation risk effects?

“…The fecal progesterone methodology for assessing pregnancy in elk was initially developed and tested by two of the authors of this article using radio-collared adult female elk in the Madison headwaters of Yellowstone (White et al 1995a, Garrott et al 1998, and validated with captive female elk by Cook et al (2002). However, subsequent assays of feces collected from this elk herd in some pre-and post-wolf years revealed substantial errors of misclassifying pregnant animals as nonpregnant based on observations of calves with marked females and population measures of calf production (Garrott et al 2003.…”