DIET, NUTRITION, AND REPRODUCTIVE ... - NWIFC Access

common method of quantifying reproductive success in ungulates (Merrill and Boyce
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1991, Post and Klein 1999, Phillips and Alldredge 2000, White et al. 2001). Herd
differences were used to avoid problems of pseudoreplication in diet composition and
home range at the scale of individual cows. My objectives were: 1) determine
reproductive success of each herd using calf:cow ratios; 2) identify vegetation types used
and available to each herd; 3) quantify diet of each herd; 4) determine nutritional quality
of forage species found in the diet; 5) identify relationships between home range size and
reproductive success; 6) identify correlations between vegetation types used and
available, diet, nutrition and reproductive success.
Thus, it was predicted that reproductive success would be positively related to
vegetation types containing abundant elk forage (timber less than 10 years old, riparian,
pasture), and negatively related to vegetation types with sparse forage (timber over 20
years old). I also predicted that reproductive success would be positively related to the
percentage of high quality forage species in the diet, and negatively related to the
percentage of forage species with low nutritional quality in the diet. High nitrogen
content grass in the diet, as well as availability of meadows for foraging, have been found
to be positively related to elk cow reproductive success (Iason et al. 1986). Similarly,
Cook et al. (2004) found that pregnancy rates of cows, calf growth, and overwinter
survival were positively influenced by digestible energy content of forage.