Digestibility of Vegetative Rye for White-Tailed Deer

Abstract

Common rye (Secale cereale) vegetation, seeded in May and grazed as the sole food source (except for small amounts of contaminating lambsquarters goosefoot [Chenopodium album]) from mid-June to 7 July, was cut with grass whips and fed to 3 female white-tailed deer (Odocoileus virginianus) in metabolism cages from 7 to 21 July. Apparent digestibility estimates by total collection were as follows: dry matter (DM) 71%, gross energy (GE) 67%, crude protein (CP) 77%, ether extract (EE) 36%, neutral detergent fiber (NDF) 73%, and acid detergent fiber (ADF) 66%. Ninety-five percent of dietary acid detergent lignin (ADL) was recovered in the feces. Use of ADL as an internal indicator (uncorrected for recovery) produced digestibility estimates about 2% lower than those determined by total collection. When estimates of rye digestibility were made with grazing deer (using ADL as an internal indicator), values for GE, CP, and EE were 68, 75, and 25%, respectively, and were not different from those determined in metabolism cages. However, digestibility estimates for DM, NDF, and ADF were lower than by total collection because of contamination of feces by ingested soil. Based on analytical composition (24% CP and 5.17 kcal GE/g DM), estimated digestibility, and previously established agronomic characteristics, rye has significant potential as a part of deer habitat improvement in Michigan. J. WILDL. MANAGE. 51(1):51-53 Habitat management for white-tailed deer in several states includes use of plantings to supplement native vegetation (Crawford 1984). Because agricultural areas often support large deer populations (Nixon 1970) and there is obvious deer use of certain forage crops, interest has developed in use of plantings specifically for deer that might be of benefit during critical periods of food shortage. In Michigan plants that are cold tolerant and begin growth in early spring and in which growth persists into late fall would be particularly useful. Early spring growth would provide nutritious food for deer that nearly have exhausted their energy reserves during the winter, and late fall growth would provide nutrients to support the development of the large stores of body fat that are so essential for winter survival (Verme and Ozoga 1980). Common rye meets these criteria, is readily established (even on poor soils), and is relatively inexpensive. However, there are few data on the ability of white-tailed deer to make effective use of such forage. Therefore, this study was designed to measure the digestibility of freshly cut rye vegetation when fed to these animals in metabolism cages and to establish whether ADL might be used as an indigestible internal indicator to estimate digestibility of rye vegetation when grazed. This study was supported in part by funds from Pittman-Robertson Aid to Wildl. Restor., Mich. Proj. W-117-R. This paper is Mich. Agric. Exp. Stn. J. Art. 11723. EXPERIMENTAL PROCEDURE Common rye was seeded in 9x 18-m pens at the Houghton Lake Wildlife Research Station in May 1976. The pens were rototilled, rye was seeded at 125 kg/ha, and the seed was covered by raking. The plants were allowed to grow until there was sufficient vegetation to permit grazing by deer or to permit cutting so that fresh vegetation could be fed in metabolism