William W. Mautz

Role of Tannins in Defending Plants Against Ruminants: Reduction in Protein Availability

We tested the hypothesis that tannins defend plants against large herbivores by decreasing protein availability. Digestion trials were conducted with mule deer (Odo- coileus hemionus) and results from previous trials with white-tailed deer (O. virginianus), moose (Alces alces), caribou/reindeer (Rangifer tarandus), and elk (Cervus elaphus) were summarized to evaluate dietary factors affecting protein availability. The digestibility of plant protein in feeds with minimal tannins, such as grasses and agriculturally produced legumes and grains, was a highly predictable function of the total protein content and the amount of nondigestible, fiber-bound protein. Digestible protein in plants containing sig? nificant tannins was lower than predicted from regressions for low-tannin feeds. The re? duction in digestible protein was proportional to the protein-precipitating capacity of the plant tannins. Deciduous browse stems collected in winter had very low levels of protein- precipitating tannins and only a slightly lower protein availability than predicted. Tannins are not important in the defense of most deciduous tree and shrub stems consumed by these herbivores. Tannins in flowers and forb, tree, and shrub leaves markedly reduced protein availability. Tannins must be considered in understanding the defensive strategies of leaves and flowers. Voluntary intake of the high-phenolic forages was significantly re? duced below ingestion rates for grasses, legumes, and pelleted diets. It is hypothesized that soluble phenolics that do not inhibit digestion but are absorbed and reduce intake through their toxicity are more important in defending some plant parts against ruminants than are digestion-reducing tannins.

DIGESTIBILITY AND RELATED NUTRITIONAL DATA FOR SEVEN NORTHERN DEER BROWSE SPECIES

Energy use and related data are presented for seven northern winter foods of white-tailed deer (Odocoileus virginianus). Hemlock (Tsuga canadensis), balsam fir (Abies balsamea), red maple (Acer rubrum), striped maple (A. pensylvanicum), mountain maple (A. spicatum), hobblebush (Viburnum alnifolium), and hazelnut (Corylus cornuta) were fed in mixed rations to captive deer. Species tested had gross energy digestibilities ranging from 30 (red maple) to 54 percent (hobblebush). The amount of digestible, metabolizable, and net energy in each of the three maple species evaluated was very sim- ilar. Metabolizable energy ranged from 24 percent (1.2 kcal/g) for striped maple to 46 percent (2.2 kcal/g) for hobblebush. The lowest net energy was observed for striped maple (5 percent or 0.2 kcal/g), the highest for hobblebush (37 percent or 1.8 kcal/g). Crude protein was digested poorly in hemlock, balsam, and red maple (-5, 11, and 1 percent digestible, respectively) as compared with an average value of 47 percent for the remaining 4 species. The digestibilities of fat, fiber, and nitrogen-free extract of the seven plant species are presented and discussed. An example of the calculation of browse require- ment during a northern winter period, based on these and related data, is presented. J. WILDL. MANAGE. 40(4):630-638

FOOD AND ENERGY USE BY CAPTIVE COYOTES

Four eastern coyotes (Canis latrans var.) were fed white-tailed deer (Odocoileus oirginianus), showshoe hare (Lepus americanus), and laboratory mice (Mus musculus) to determine their digestion of dry matter, nutrients, and partitioning of dietary gross energy. Dry matter digestibility of the deer diet (96.8%) was higher (P < 0.05) than of the hare (81.5%) or mouse (83.2%) diets. The digestible energy value of deer (5.69 kcal/g dry matter) differed (P < 0.05) from the other diets, and metabolizable energy values of the deer and mouse diets (4.99,5.07 kcal/g dry matter) were greater (P < 0.05) than that of the hare diet (4.01 kcallg dry matter). The prey required to fulfill th e minimum energy demands at the metabolizable level of a 12.9-kg coyote was estimated to be 8 deer, 105 hares, or 4,800 mice per year.

NUTRITIONAL EVALUATION OF THREE WINTER BROWSE SPECIES OF SNOWSHOE HARES

Twelve snowshoe hares (Lepus americanus) were used in an experiment to evaluate the degree to which they are able to digest and metabolize three important winter browse species: quaking aspen (Populus tremuloides), white cedar (Thuja occidentalis), and red maple (Acer rubrum). These browse species had digestible energy values ranging from 18 percent (of gross energy) for maple to 42 percent for aspen. Metabolizable energy values ranged from 17 percent for maple to 25 percent for aspen. Cedar had intermediate digestible (32%) and metabolizable (23% ) energy values. Protein digestibilities were 0, 13 and 38 percent for cedar, maple, and aspen, respectively. There were no significant (P > 0.05) differences among consumption rates for the three browse rations, although all were significantly (P < 0.05) greater than the intake levels observed with 100 percent commercial chow.

Reevaluation of the Basal Metabolic Cycle in White-Tailed Deer

We investigated the seasonal cycle of basal metabolism in white-tailed deer (Odocoileus virginianus) by measuring basal metabolic rate (BMR) of four nonpregnant and four pregnant does from winter to summer. Metabolism was measured monthly with indirect respiration calorimetry from January–July/August, 1989. Mean monthly BMR of nonpregnant does ranged from 85.5 to 89.0kcal/kg body weight0.75/day. The mean BMR of nonpregnant does was 87.1 kcal. Individual, nonpregnant BMR, averaged across all months, varied from 80.7 to 93.5 kcal with minimal monthly or seasonal change. Metabolism of pregnant does increased curvilinearly from January to parturition. Postpartum BMR averaged 86.4 kcal, similar to nonpregnant does. Our data are similar to prior winter measurements of BMR, but are substantially lower than previously reported summer BMRs. Our data do not support the proposed existence of an inherent seasonal cycle in basal metabolism in white-tailed deer. Experimental temperatures and animal activity within metabolism chambers may have affected previous summer measurements.

Influence of seasonal temperatures on wild turkey metabolism

We measured standard metabolic rate (SMR) and the effects of temperature on metabolism of adult eastern wild turkeys (Meleagris gallopavo silvestris) during each season of the year. Female SMR was similar throughout the year, and male SMR was lower during spring. Female SMR exceeded male SMR each season and was significantly (P<0.05) higher during summer and autumn. Bothe sexes had similar lower critical temperatures (T lc ), but females lost heat faster below T lc . Low winter T lc (about −15 C) indicated that thermoregulatory costs are probably minimal for turkeys at normal winter temperatures in southcentral New Hampshire

CONFINEMENT EFFECTS ON DRY-MATTER DIGESTIBILITY COEFFICIENTS DISPLAYED BY DEER1

The effect of severe confinement on apparent dry-matter digestibility coefficients of two white- tailed deer ( Odocoileus virginianus) was investigated using the radioisotope 6lCr as a food marker. Wen first placed in collection crates, the deer showed a marked decrease in their ability to digest a standard pelleted ration. By the 9th to 12th day of confinement the digestibility coefficients of these deer were similar to coefficients they had displayed immediately prior to confinement. The level of food intake also decreased for both animals upon confinement. For one of the animals, food consumption retumed to the preconfinement level 21 days after confinement; however, the other deer still had a significantly decreased level of consumption after 25 days of confinement.

Metabolic rate of bobcats as influenced by seasonal temperatures

We used indirect respiration calorimetry to measure metabolic rate and delineate the lower critical temperature (T,,) of bobcats (Felis rufus) during summer, fall, winter, and spring. The yearly mean standard metabolic rate (SMR) within the thermoneutral zone was 79 kcal/kg body weight (BW)o75/day (range = 69-88 kcal/kg BW075/day). No difference (P < 0.05) was found between winter and summer SMRs. We measured T,, of 22.5, 7.7, -2.2, and 5.0 C for summer, fall, winter, and spring, respectively, which were similar to mean seasonal temperatures in New Hampshire. Bobcat metabolic rate increased linearly below TLC. Metabolic measurements and regional temperature information indicate that northern bobcats are commonly exposed to energy-costly temperatures during winter. This high thermoregulatory cost likely results in behavioral adaptations; e.g., microhabitat selection and sunning. J. WILDL. MANAGE. 53(1):202-205 Energetic information for northeastern bobcats includes food habits (Pollack 1951, Westfall 1956, Litvaitis et al. 1984) and digestibility of several prey species (Golley et al. 1965, Powers 1984); however, bobcat metabolic rate has only been measured during the winter (Gustafson 1984). Our understanding of bobcat energetics is limited beyond the scope of these studies. A knowledge of baseline energy requirements of bobcats, when coupled with food consumption and food assimilation information, allows the calculation of minimum prey budgets of freeranging bobcats. Impacts of climate, changing land-use patterns, and forestry practices on bobcats and their resources can likewise be evaluated through a better understanding of bobcat energetics. The purpose of our study was to determine seasonal metabolic rates and thermoneutral zones of bobcats acclimated to natural ambient temperature and photoperiod. We acknowledge the help of numerous students and the constructive reviews of E. N. Francq and J. A. Litvaitis. This project was supported with Pittman-Robertson funds (PR W-81This content downloaded from 157.55.39.102 on Thu, 23 Jun 2016 07:08:29 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 53(1):1989 BOBCAT METABOLISM * Mautz and Pekins 203 R-1) through the New Hampshire Fish and Game Department and McIntire-Stennis funds. This is Scientific Contribution 1538 from the New Hampshire Agricultural Experiment Sta-

ESTIMATING METHANE, URINE, AND HEAT INCREMENT FOR DEER CONSUMING BROWSE'

For white-tailed deer (Odocoileus virginianus) consuming woody browse species, significant relationships (P < 0.05) were found to exist among daily energy losses in urine, methane, and heat in- crement and several of the more easily determined measures of the conventional digestion trial. Simple linear regression as well as multiple regression analyses indicated that urine and methane energy losses may both be accurately predicted from conventional digestibility data. The highest correlations were found between urine energy losses and the single variable, fat intake (r - 0.89), and a combination of seven variables (R = 0.98). These regressions had standard errors representing :?_ 14 and ? 9 percent of the estimated mean, respectively. The best fit between methane and a single variable was found with digestible nitrogen-free extract intake (r = 0.72), whereas methane regressed on a combination of five variables had a correlation coefficient of 0.82. Standard errors for these regressions were ? 19 and + 17 percent of the estimated mean, respectively. Several single variables were significantly (P < 0.05) correlated with heat increment, although the highest of these (digestible ether extract) had a correla- tion coefficient of only 0.40. The most highly correlated multiple regression with heat increment was obtained from six variables (R - 0.75). This regression had a SE of 113 or -+-32 percent of the esti- mated mean. Predictive equations are presented for simple linear and multiple regression information on each of the dependent variables.

Digestibility of Fresh Frozen versus Pelleted Browse by Snowshoe Hares

Twelve snowshoe hares (Lepus americanus) were used to evaluate the effect of drying, grinding, and pelleting on the digestibility of browse of white cedar (Thuja occidentalis) and red maple (Acer rubrum). A significant (P < 0.05) increase in consumption was observed for the pelleted feeds. No significant effects were observed in digestibility for the combined data, although apparent differences were seen when the two species were analyzed individually. J. WILDL. MANAGE. 40(3):496-499 In food evaluation studies with any species of wild animal it is desirable to test the food as it is found in its natural state. This poses certain problems, because it is often necessary to store experimental test diets for varying lengths of time. For plant materials a convenient method of ration preparation and storage is a combination of drying, grinding, and pelleting. Ground and pelleted rations are stored easily and may be prepared in nonseparable mixtures. The disadvantage of drying, grinding, and pelleting is the possible effect this procedure may have on a foods digestibility and palatability. This paper reports a pilot study designed to evaluate the difference in digestibility between fresh-frozen and driedground-pelleted browse fed to snowshoe hares. We acknowledge R. P. Davison and C. E. Boardman for their help with care of the animals.