Henry L. Short

FIBER COMPOSITION AND FORAGE DIGESTIBILITY BY SMALL RUMINANTS

Cell wall constituents (CWC) were usually more plentiful in grasses than in other forages at comparable phenological stages. Acid detergent lignin (ADL) was frequently a greater proportion of the acid detergent fiber (ADF) of browse leaves than of other forages. Forbs and woody twigs usually had intermediate CWC and ADL/ADF values. CWC increased and digestibility decreased as many forages matured. The digestibility of grasses, forbs, many browse leaves, and succulent browse twigs was significantly related to true digestibility as estimated by the summative equation. Dry matter di- gestibility of mature browse twigs was significantly related to cell content values, and estimated values for true digestibility tended to exceed observed values. Foodstuffs vary in degree and rate of digest- ibility largely because of their relative fiber contents. Plants with high CWC levels, especially when combined with high lignin contents, are low-quality forage for small ruminants. J. WILDL. MANAGE. 38(2):197-209 The purposes of the present study were to determine major distinguishing charac- teristics between different types of forages and to relate these characteristics to relative digestibility estimated by the nylon bag technique in ruminally cannulated goats. A large number of grass, forb, twig, and browse leaf samples were analyzed by the comprehensive system of Van Soest (1967), and duplicate samples were subjected to in vivo microdigestion. Since fiber content is known to increase with tissue maturity, forage samples were collected at different seasons. Differences were found among forages in their fiber composition, in the compositional changes associated with in- creased maturity, and in the extent and rate at which the forages were digested. METHODS

NUTRIENT QUALITY AND DIGESTIBILITY OF SEEDS AND FRUITS FROM SOUTHERN FORESTS

Seeds of legumes were highest and fleshy fruits and acorns were lowest in protein and phos- phorus among seed and fruit samples from 103 species common to southern forests. Legume seeds and kernels of walnuts (Juglans sp.) and hickories (Carya spp.) were most digestible, and kernels were highest in crude fat and lowest in fiber content. Nylon bag dry-matter digestibility of all 103 seed and fruit samples was related significantly to acid detergent fiber content. Despite their moderately high protein and phosphorus contents, dried fruits such as achenes, samaras, and nuts had high fiber con- tents and were therefore of less use to animals than the other groups of seeds and fruits analyzed.

COMPOSITION AND SQUIRREL USE OF ACORNS OF BLACK AND WHITE OAK GROUPS

Of 11 species of oak (Quercus sp.) acorns tested, those of the white oak group were higher in nitrogen-free extract, cell wall contents, and hemicellulose than those of the black oak group, which had higher levels of dry matter and crude fat. Acorns of all 11 oak species were low in protein and phospho- rus. In feeding tests with adult fox squirrels (Sciurus niger), negative nitrogen balances were recorded for about two-thirds of the trials. Acorns of the white oak group were consumed at higher rates and thus appeared to be the more palatable of the two groups. Acorns apparently supply squirrels with ade- quate energy but do not satisfy their metabolic requirements for nitrogen or probably phosphorus. J. WILDL. MANAGE. 40(3):479-483 Oak mast is an important source of food for many wildlife species (Martin et al. 1951). Tree squirrels (Sciurus sp.) are es- pecially dependent on the presence of qual- ity acorns in their habitat, and squirrel num- bers have been reported to vary directly with acorn availability (Sharp 1960). Al- though the maintenance of huntable popu- lations of squirrels and the well-being of several other wildlife species necessitate the establishment and management of oaks in forest ecosystems, few studies have deter- mined the metabolic usefulness of acorns to squirrels. Fox squirrels have been reported to use white (Quercus alba) and black (Q. velutina) oak acorns more efficiently than those of red oak (Q. borealis maxima) and to digest lipids and nitrogen free extract more readily than crude protein and crude fiber (Baumgras 1944). Acorns with high lipid contents reportedly serve as high en- ergy rations for squirrels (Smith and Foll- mer 1972). The present paper reports both the composition of acorns of 11 species of oaks and the use of these acorns by fox squirrels. MATERIALS AND METHODS Acorns from the black and white oak groups were collected in autumn 1971 for feeding trials. Black oak group acorns were black and northern red oaks (Q. rubra), both collected in the Sylamore Experi- mental Forest in Arkansas, and water oak (Q. nigra), willow oak (Q. phellos), blue- jack oak (Q. incana), and southern red oak (Q. falcata), all collected in Nacogdoches County, Texas. White oak group acorns in- cluded white oak, swamp chestnut oak (Q. prinus), live oak (Q. virginiana), and post oak (Q. stellata), all collected in Nacogdo- ches County. Acorns from the sawtooth oak (Q. acutissima), also a member of the white oak group, were donated by the Interna- tional Paper Company, Camden, Arkansas. Acorns were selected for soundness and stored at -12 C until fed to squirrels. At the beginning of each feeding trial an ali- quot of whole acorns was dried in a forced- air oven at 40 C to determine the oven-dry weight of consumed acorns. The oven-dried acorns were ground in a Wiley mill and stored in capped glass bottles. The dried material was used for the determination of crude protein, crude fat, crude fiber, ash, Ca, and P, according to standard AOAC procedures (Horwitz 1965); cell wall con- tents (CWC), acid detergent fiber (ADF), acid detergent lignin (ADL), and silica were determined according to the proce-

Seasonal nutrient yield and digestibility of deer forage from a young pine plantation

Six classes of current herbaceous and woody forage were collected seasonally from a 5-yearold mixed loblolly (Pinus taeda)-shortleaf pine (Pinus echinata) plantation (in Texas) and subjected to nutrient analyses and nylon bag dry-matter digestion trials. Forages were most nutritious and digestible in the spring when tissues were succulent and growing rapidly. Browse leaves and twig tips were the most abundant forage from spring to autumn and the most nutritious and digestible forage throughout the year. Pine and the residual twigs of browse were low in quality and digestibility at all seasons. Forbs were more nutritious than grasses but both declined seasonally in nutrient quality and digestibility as their fiber content increased with maturation. A low level of phosphorus in forage tissues at all seasons appeared to be a major limiting factor for deer in the young plantation. J. WILDL. MANAGE. 41(4):667-676 For 3 to 5 years after a pine plantation is established, a wide assortment of grasses, forbs, and browse develops (Blair 1968). Between 5 and 8 years, crowns of the young pines are closing rapidly and forage growth declines with the diminishing light. Upon crown closure forage for deer remains sparse until trees are thinned or clearcut (Blair and Enghardt 1976). The capacity of a young plantation to support deer can be estimated by considering the amount of palatable vegetation available during different seasons, the yield of plant nutrients, the metabolic usefulness of forages, and the nutrient requirements of the animals. Although forage often is abundant during summer and fall (Blair 1967, 1968), tissues may be deficient in nutrient quality except in spring (Short 1969). This paper evaluates the dry-matter yield, nutrient content, and dry-matter digestibility of forage in a 5-year-old plantation of mixed loblolly and shortleaf pine. Forages were sampled at several different phenological periods and evaluated by specific classes of plants and plant tissues.

FORAGE DIGESTIBILITY AND DIET OF DEER ON SOUTHERN UPLAND RANGE

Four white-tailed deer ( Odocoileus virginisnus) were shot from a mixed pinhardwood habi- tat in east Texas at each of six consecutive 10-week intervals. Browse items made up at least 19 percent of the diet in all seasons. Forbs were important dietary constituents in May, mushrooms in July, and acorns in autumn. Acetic acid:propionic acid ratios in rumen liquor samples were wider in the spring after a poor mast year (4:1) than during other seasons (2:1). More gas (S ml gas per gram of solids per hour) was produced in controlled fennentations of rumino-reticular (R-R) contents of deer feeding on acorns than on othejr dietary items. In in vitro digestion trials, composited mixed browse, mixed forbs, mixed grasses, and loblolly pine (Pinus taedu) samples were generally highest in nutrient quality during spring. Grasses and forbs were significantly less digestible rhen mature than when imnlature. Forbs were digested better than were browse or pine tissues. Dead leaves were poorly digested. Green grasses selected during the winter were as digestible as those growing during spring and summer. For- ages most refractory to microbial fermentation had higher lignin:acid-detergent fiber (ADF) ratios than other foodstuffs.

THE USE OF NATURAL AND MODIFIED PINYON PINE-JUNIPER WOODLANDS BY DEER AND ELK

Pinyon pine (Pinus edulis)-juniper (Juniperus spp.) woodlands are important deer and elk habitats and occupy about 243,000 km2 of the western United States. In the study area at Fort Bayard, New Mexico, mule deer (Odocoileus hemionus) and elk (Cervus canadensis) ate evergreen browse exten- sively during winter. Mule deer ate more forbs during spring and summer, less browse during spring and less grass at all seasons than did elk. When woodland canopy was dense, production of midstory browse and understory herbage was reduced and deer and elk use diminished. Small clearings within the wood- lands (-0.5 km) were readily used by both deer and elk. Extensive clearing of pinyon pines and junipers increased herbage production but may have been sufficiently detrimental to wildlife to negate any addi- tional grazing values for range cattle. Although small patch-cuttings within woodlands increased useful- ness for deer and elk, large cuttings in themselves and those that isolated undisturbed woodland from contiguous protective cover were unacceptable wildlife habitat. J. WILDL. MANAGE. 41(3):543-559 Pinyon pine-juniper woodlands occupy about 243,000 km2 of the western United States and provide valuable wildlife habitat, rangeland, watersheds and recreational areas. These woodlands occupy fairly dry sites (33-51 cm precipitation/year) at ele- vations of 1,460-2,550 m, the zone below that usually occupied by ponderosa pine (P. ponderosa). A rich shrub midstory is maintained where pinyon pines and juni- pers invade brushlands but there is no mid- story where they invade grasslands. Livestock interests have frequently been concerned where increased density of these woodlands reduced herbage understory and range carrying capacity. Over 4,050 km2 in Arizona and New Mexico were recently cleared to reclaim grasslands for livestock. Conflicts arose because indigenous wildlife such as deer, elk, rabbits, coyotes, quail, tur- keys, songbirds and rodents have different habitat requirements than livestock. The

Ruminoreticular Characteristics of Mule Deer

The combined rumen–reticulum of 30 mule deer ( Odocoileus hemionus ), collected throughout 1962, was excised and examined. Several relationships between the rumen–reticulum and body weight are described and compared to published data for the domestic cow. The volume of the mule deer rumen–reticulum is about 10% of body weight, and rumen–reticulum contents and dry matter are about 7.4% and 1%, respectively, of body weight. The relatively small size of the deer rumen seems to have important physiological implications.

Seasonal variations in volatile fatty acids in the rumen of mule deer.

Thirty mule deer (Odocoileus hemionus) were collected throughout 1962. The rumino-re- ticular contents of each deer were sampled for (1) pH, (2) percent dry matter, and (3) the molar proportions of the individual volatile fatty acids (VFA) present. These data were compared to the seasonal dry matter level of several important deer browse species occurring on the same range. The pH, rumino-reticular dry matter, and acetic acid levels measured during the winter-early spring period were significantly greater than those obtained during the summer. The butyric and higher (valeric + isovaleric) acid proportions were significantly increased in the summer samples. During the autumn, pH, rumino-reticular dry matter, and acetic acid values increased and butyric and higher acid propor- tions decreased. Propionic acid proportions remained similar throughout the year. These relationships are interpreted as indicating an increased rumen fermentation rate during the summer season when range forage is succulent.

RUMINO-RETICULAR CHARACTERISTICS OF DEER ON FOOD OF TWO TYPES

Ten white-tailed deer (Odocoileus virginianus) that fed mainly on acorns had markedly dif- ferent rumino-reticular (R-R) characteristics from ten that ate mostly grasses and browse. The per- centage of dry matter in R-R contents was significantly greater for deer eating acorns (27 vs. 15 percent). Although deer on the two diets had similar total volatile fatty acid concentrations in rumen liquor, the deer eating acorns had a significantly lower R-R pH (5.5 vs. 5.9) and molar percent of acetic acid (59 vs. 73 percent), while the deer that ate browse and grass had lower R-R levels of propionic (16 vs. 22 percent) and butyric (9 vs. 15 percent) acids. More gas was produced by in vitro fermentations of rumen liquor from acorn-fed than from browse-fed deer. This paper reports rumino-reticular (R-R) characteristics and the results of controlled in vitro fermentations of rumen liquor from

Effects of cellulose levels on the apparent digestibility of feeds eaten by mule deer.

Three artificial diets that varied in cellulose content but were similar in protein and energy levels were fed to three mule deer according to a latin square design. Food intake for each deer, on each diet, during each feeding period was similar. Energy and dry matter digestion varied between diets (P < 0.05) and both digestible energy and digestible dry matter were inversely related to dietary cellulose content. Cellulose digestion was somewhat variable between animals, feeds, and feeding trial periods. Protein digestion was similar in all feeding trials but crude fat digestion was somewhat greater on the low-cellulose diet. Limited cellulose digestion occurs in mule deer and affects energy and dry matter digestion of foodstuffs. The proximate analysis of important species of deer browse has many times been shown to have little value in predicting how a deer digests a particular forage item. Digestion trials with wild forages have been performed many times with deer of the genus Odocoileus. These investigations have shown differences in the value of par- ticular forages to deer and have compared the manner in which domestic and wild ruminants utilize the same forage. A diges- tion trial using wild forages and deer is seriously limited when the food presented to the deer has been selected by the investi- gator rather than by the animal. Sometimes this selected forage has been extensively modified by air drying, grinding, pelleting, or other treatment so that the foodstuff may bear little resemblance to the growing plant. Information about the comparative digestibility of the ration must then be analyzed with the realization that some circumstances were artificial. Important generalities describing how deer utilize foodstuffs should therefore be cross-checked with experiments that remove as many var- iables as possible from the digestion trials. Artificially compounded rations in which the variable components are reduced to only one may be used to allow a more rigorous statistical and biological analysis. This is a popular technique for examining, among other things, a general relationship between the level of a particular dietary constituent within a feed and the digest- ibility of that feed. Digestion trials with mule deer (0. hem- ionus) and feeds compounded from native browse plants demonstrated (Short and Remmenga 1965) a significant relationship between the cellulose content and the digestible energy of the feed. These find-