John C. Malechek

Dietary selection by goats and sheep in a deciduous woodland of northeastern Brazil.

The dietary botanical composition of indigenous sheep and goats was determined in the semiarid tropics of northeastern Brazil, using esophageally fistulated animals. Sheep and goats selected similar diets during the dry season (May-Dec.). Main dietary components for both species were dried forbs and browse. Leaf litter from the deciduous trees provided the majority of dry season forage (NO-1,500 kg/ha) and was a crucial element of dry season diets (20-70%). During the wet season (Jan.-Apr.), sheep selected mainly grasses and forbs, while goats rapidly shifted among grasses, forbs, and browse. By displaying attributes of both browsers and grazers, neither sheep nor goats conformed to traditionally rigid characterization. We found no indication that goats are better adapted for survival in this tropical environment than are sheep because of the botanical composition of their diets. Management implications of this study for the cutrtinga vegetation zone are discussed. Although range science literature is replete with studies reporting detailed data on diets of cattle and sheep, few investigations have examined diets of goats grazing alone, or in common with other livestock (Malechek and Provenza 1983). Van Dyne et al. (1980) catalogued studies of livestock diets, and noted 5 and 38 such studies for goats and sheep, respectively. Only 3 studies listed in this paper compared dietary selections by goats and sheep grazing together on common ranges. No work has been done using esophageally fistulated animals to examine diets of either goats (Capra hircus) or sheep (&is aries) in northeastern Brazil. Generally comparisons of the dietary selections of goats have been made with sheep of European origin. Little information is currently available on selectivity of tropical hair sheep or goats. At the time of this research, authors were graduate research assistant and professor, respectively, Department of Range Science? Utah State University, Logan Utah, 84322. J. PI&r is presently research scientist, Department of Range and Wildlife Management, Texas Tech University, Lubbock 79409. Research was financed by USAID Grant No. AID/DSAN/XII-G-0049 as part of the Small Ruminant Collaborative Research Support Program in cooperation with Empress Brasileira de Pesquisa Agropecuaria. The authors wish to thank the personnel of the Centro National de Pesquisa de Caprinos for provision of physical facilities and assistance during the study. We are especially grateful to Venceslau Alves Costa, Animal Husbandryman, for his assistance. Manuscript preparation supported by Texas Tech University. Manuscript accepted 25 April 1985. 24 Goats have acquired a reputation for survivability on harsh, degraded rangeland (Devendra 1978). This may be due, in part, to unique dietary selections made by goats (McCammon-Feldman et al. 1981). French (1970) maintained that high survivability by goats was related to their relatively unspecialized feeding habits. Increased specialization implies fewer plant species or parts eaten. Observations have indicated that goats eat a wider array of plant species than do other livestock (French 1970, Wilson et al. 1975). Conversely, Van Soest (1980, 1982) stated that goats should display more specialized feeding habits than do sheep, based on body size, gastrointestinal capacity, nutrient requirements, and feeding strategy. He classified goats and sheep in 2 ways. First, goats are classified as forbor browsepreferring intermediate (between browsers and grazers) feeders, and sheep as grasspreferring intermediate feeders. Van Soest’s (1982:7) second classification lists goats as intermedite browsers, and sheep as grazers. Livestock producers in northeastern Brazil prefer to raise sheep over goats (Gutierrez et al. 1981) because of many complex socioeconomic factors (Primov 1982). For instance, sheep do not require the less penetrable, more expensive fencing required for goats, especially adjacent to cropland. On the other hand, goats are often viewed by Brazilian producers as a form of drought insurance because of their reputed survivability and minimal requirements for supplemental feeds during droughts. The objectives of this study were to determine the botanical composition of goat and sheep diets on a seasonal basis, and to evaluate the selective feeding strategies of goats and sheep. Such information would provide a basis for more sophisticated management and insight into the question of comparative adaptability of the 2 species.

Paddock Size and Stocking Density Affect Spatial Heterogeneity of Grazing

Abstract The claim that intensive rotational grazing (IRG) can sustain higher stocking rates can be partially explained by more even spatial distribution of grazing such that livestock consume forage from a greater proportion of a pasture. To test the hypothesis that utilization is more even at the higher stocking densities of smaller paddocks, mean absolute deviation (heterogeneity) of utilization estimates by plot was compared in paddocks of sizes and stocking densities representing increasing subdivision from two-paddock deferred rotation grazing (DRG) to 16-, 32-, and 64-paddock, two-cycle IRG. These 70-, 4-, 2-, and 1-ha paddocks were grazed for 7 wk, 4 d, 2 d, and 1 d, respectively, at 32 animal unit days (AUD)·ha−1 during 2000 and 34 AUD·ha−1 during 2001. Within IRG there was no response to the treatment gradient. After one cycle in the IRG paddocks, heterogeneity of use was generally lower than in the DRG paddocks, in both 2000 (3–11% [outlier 18%] vs. 14–19%) and 2001 (9–17% vs. 24–28%). After a second cycle in 2001, heterogeneity in half of the IRG paddocks (17–21%) was nearly as high as the early-grazed (24%), but not the late-grazed (28%), of the DRG paddocks. This lack of a stronger difference between systems was probably due to the fixed two-cycle IRG schedule and lack of plant growth during the nongrazing interval. Across both systems heterogeneity of utilization was strongly positively correlated with paddock size. Because utilization was not severely patchy in the largest treatment, the difference between systems would likely be greater in commercial-scale paddocks. Thus grazing distribution can be more even under intensive than extensive management, but this depends on how adaptively the system, particularly the aspects of timing and frequency, is managed.

Effect of Conifer Encroachment Into Aspen Stands on Understory Biomass

Abstract Conifers (Picea and Abies spp.) have replaced aspen (Populus tremuloides Michx.) over much of aspens historic range in the western United States. We measured the impact of this change upon the production of understory vegetation potentially useful as forage for livestock and wildlife on two southern Utah national forests. A negative exponential relationship between conifer cover and understory biomass was demonstrated as log(biomass)u200au200a=u200au200a6.25u200a−u200a0.03787(% conifer), adjusted R2u200au200a=u200au200a0.57. Understory production in aspen stands begins to decline under very low levels (10% to 20%) of conifer encroachment. Management implications include loss of forage production capability and wildlife habitat and potential overstocking of livestock grazing allotments if the associated loss of forage is not considered.

Season of cutting affects biomass production by coppicing browse species of the Brazilian caatinga.

This paper reports the effect of season of cutting on coppice biomass production by S tree species common in the semiarid caatinga woodlands of northeast Brazil. Trees were cut early and late in the wet and dry seasons and coppice biomass production was monitored for 2 growing seasons after cutting. No mortality occurred as a result of cutting in any season. The effect of season of cutting on subsequent coppice production was most pronounced in the first year but differences persisted into the second year. Production by trees cut late in the wet season lagged behind that of trees cut at any other time. This was true for all species except marmeliero (Croton hemiargyreus Muell. Arg.) during both years. Pau branco (Auxemma oncocalyx Taub.) production was maximized by cutting late in the dry season. Jurema preta (Mimosa acutistipula Benth.) and catingueira (Caesalpinia pyramidalis Tul.) production was maximized by cutting early in the dry season. The season of cutting does not affect marmeliero stem production. Except for the late wet season, no treatment significantly affected sabia Mimosa caesalpinifolia production. Stem biomass production is affected more by season of cut than is leaf biomass production. The different patterns of response among these species could be the basis of a selective cutting scheme to achieve objectives such as browse and wood production.

Estimating digestibility of oak browse diets for goats by in vitro techniques.

Predicting digestibility of shrubs is important to evaluating many of the worlds rangelands. We examined laboratory procedures for predicting in vivo digestion of browse-alfalfa (Medicago sativa) mixed diets and how drying temperature and inoculum source affect digestibility. In addition, we considered the effect of oak tannin on pepsin activity and dry matter digestion. The commonly used Tilley and Terry (1963) two-stage in vitro digestion technique was a precise (r2=0.97) but inaccurate predictor of in vivo apparent digestibility of mixed oak (Quercus gambeii) and alfalfa diets for goats. The Van Soest et al. (1966) neutral detergent method for predicting true digestibility was less precise (r2=0.76). Estimates from the Goering and Van Soest (1970) summative equation were not correlated (P?0.05) with in vivo digestion. Separate regression equations are necessary if in vitro methods are to predict accurately in vivo digestibility of browse diets. In vitro digestibility was inversely related to percentage of oak in the diets and the amount of oak in the inoculum donors diets. High drying temperatures depressed digestibility of oak browse and this effect was greater for immature than for mature forage.

Heifer nutrition and growth on short duration grazed crested wheatgrass.

Anbnal performance and nutrition under short duration grazing (SDG) and season-long grazing (SLG) were compared on qringgrazed crated whatgrass [Agropyron dh&orum (Flscb.)Scbult. and A. cr?&tuw (L.)Gaertn.] range to determine if SDG bas tbe potential to improve livestock production on such rangelands. Livertock performance was evaluated by measuring weigbt gains twice per grazing season. Diet quality was asses& by determining crude protein concentration and in vitro organic matter digatibih ity Of CxtNM samples COkCtd *OIlI erOpb@dy fiStUhtcd bdfers. Three variables of ingestive bebavior were measured: ingestion rate, biting rate, and graxing time. Daily forage iatake was calculated as tbe product of ingestion rate and graxing time. Animals in tbe SLG treatment gained signifhntly more tban those under SDG in 1983 (1.07 vs. 0.81 kg/bd/d), but no statistical differauzea were detected in 1984 (1.13 vs. 1.07 kg/ad/d for SDG and SLG, respectively). In 1985, animals under SDG gained tbe most (1.03 vs. 0.87 kg/ad/d for SDG vs. SLG, respectively). No differencea were detected in diet quality between SDG and SLG tbrougbout tbe study. No treatment differences were detected in ingestive behavior during 1984, but ingestion rate was grater and graxing time less under SDG tban SLG during 1985. Results indicate that forage intake was grater, while energy expenditures were lower under SDG tban SLG in 1985. Tbe bypotbesis that SDG extends tbe season of nutritiotw forage was not supported.

Clearcutting Brazilian caatinga: assessment of a traditional forest grazing management practice.

Clearcutting is a common practice for removing woody vegetation in the semiarid tropics of northeast Brazil. The prevalent belief is that clearing increases carrying capacity for livestock by increasing herbaceous vegetation, yet little empirical evidence exists to support or refute the contention. We investigated the implications to small ruminant nutrition of clearcutting in the semiarid tropics of northeast Brazil. We found that biomass of herbaceous species increased sixfold following cutting of trees, but much of this increase was in the form of poorly palatable stem. The large supply of leaf litter from woody species that was typical of uncleared areas during the dry season was replaced by persistent green foliage on coppicing trees the year following clearing. This green foliage may enhance the nutritional quality of the diets of sheep and goats foraging on cleared areas during the dry season.

Botanical composition of goat diets in thinned and cleared deciduous woodland in northeastern Brazil.

Clearing and thinning of caatinga vegetation in northeastern Brazil are viewed as methods of optimizing forage and wood production. Our study compared the botanical composition of goat diets relative to forage availability in undisturbed, cleared and 2 levels of thinned (25% and 55% canopy cover) stands of tropical woodland. Clearing and thinning of caatinga vegetation resulted in higher amounts of available forage through the wet season and up to the time of leaf fall. At the end of the growing season, available herbaceous biomass was generally 7 to 8 times higher on the treated pastures than on the control; biomass of available browse was about 4 times greater. After leaf fall, total available forage was similar for all 4 treatments but about 90%0 of the available forage on the control was leaf litter. Diet composition differed among the treatments only in February and May; at this time, goats on the treated pastures were selecting higher amounts of herbaceous vegetation than those on the control pastures. Even though browse availability was high throughout the wet season on the treated pastures, herbaceous vegetation was the primary dietary constituent. Only during the mid to late dry season, when herbaceous vegetation was dead and leaf:stem ratios were low, was browse consistently selected at high levels. We concluded that clearing and thinning increases the amount and diversity of available forage; thereby, improving foraging conditions. Moreover, production of herbaceous vegetation declines towards control levels only at some canopy cover higher than 55%.

Above-ground production in cleared and thinned stands of semiarid tropical woodland, Brazil

Abstract Wood and forage, both herbaceous and the foliage of woody plants, are two of the most heavily exploited and readily available resources of the caatinga vegetation zone in northeastern Brazil. Caatinga clearing (0% canopy cover), two levels of thinning (25% and 55% canopy cover) and a control (95% canopy cover) were compared in terms of above-ground production of wood and forage. At the end of the first year after treatment, total above-ground production was 5106, 6596, 6762 and 7347 kg ha−1 year−1 for the 0% (cleared), 25%, 55% and 95% (control) canopy cover treatments, respectively. Each of the three reduced-canopy treatments resulted in a seven- to eightfold increase in total herbaceous yields, with a corresponding decrease in wood production, compared to the control treatment. Total biomass of foliage from woody plants was significantly higher (P

Clearcutting Brazilian Semiarid Tropics: Observations on Its Effects on Small Ruminant Nutrition during the Dry Season

Small ruminant production in northeast Brazil is limited by prolonged nutritional stress during the dry season. Our study assessed the effects of clearcutting woody vegetation on the nutrition of goats and sheep during the initial dry season following ciearing. Dry matter intake (g *day-) was higher for animals on cleared than on uncleared areas (818 vs. 627; P 0.05), and was lower in neutral detergent fiber (49 vs. 51 %;P<0.05) and lignin (14 vs. 16%; P<0.05). Intake and diet quality declined on both cleared and uncleared areas as forage availability declined. Animals on cleared areas benefitted from increased availability of herbs and of biomass from palatable trees that coppiced and retained green leaves throughout much of the dry season. Animals on uncleared areas relied heavily on leaf litter from trees, which provided a poorer quality, but persistent, source of forage throughout the dry season.