Dietary Selection and Nutrition of Spanish Goats as Influenced by Brush Management

Abstract

Botanical composition of Spanish goat diets was only different when diets selected from tebuthiuron-treated pastures were compared to those from untreated and mechanically treated areas in the Texas Post Oak Savannah. However, all brush management treatments significantly affected the browse component in summer diets. Diets selected from untreated and mechanically treated pastures were dominated by browse, while grasses and grasslike plants occurred most in diets selected from the tebuthiuron-treated plots. Yet, during fall and winter, vines comprised the bulk of diets collected on these areas. Forbs were a minor dietary component. Goat diets from untreated and mechanically treated pastures consistently shifted from browse to grasses and grasslike plants as seasons advanced. Selection of grasses and grasslike plants on tebuthiuron-treated pastures declined sharply from summer through winter and increased through spring. Similar but inverse trends occurred in respect to vines and browse. Mean levels of crude protein (CP) in diets selected by esophageally fistulated goats grazing chemically treated pastures were significantly greater than in diets from the other pastures in winter and spring. In summer and fall, dietary forage material from all pastures contained equivalent levels of crude protein. Dietary in vitro digestible organic matter (IVDOM) was higher in summer and winter from tebuthiuron-treated pastures compared to mechanically treated and untreated areas. In fall, diets from tebuthiuron-treated pastures were higher in IVDOM content than those from untreated ones but were similar to diets from mechanically treated pastures. However, in spring all pastures receiving brush management yielded diets with higher IVDOM content than brush-treated areas. In general, methods of brush control had greater effects on IVDOM than on CP contents of diets. Reduction of woody plant cover may be the primary step toward increasing forage production of depleted rangelands in Texas. The 2 most widely used approaches to brush management are mechanical methods and herbicide application (Scifres 1980). However, rising costs of fuel, equipment, and herbicides and lack of satisfactory control in some instances have stimulated interest in alternative control methods (Green et al. 1978). Uplands and river bottoms in the Post Oak Savannah region of east-central Texas were originally characterized as open Savannah with a ground cover of mid and tall grasses (Smeins and Slack 1978). Yet, continued heavy yearlong grazing coupled with longterm fire suppression has led to range deterioration. As a result, millions of hectares now support dense thickets of brush which severely limit herbaceous forage production (Scifres and Haas 1974). Evaluation of cattle grazing practices in this region indicated that cattle will not maintain mechanically treated rangeland, or make efficient use of brush-infested areas (Kirby and Stuth Authors are EMBRAPA (Brazilian Agriculture Research Institution) fellow and associate professor, Department of Range Science, Texas A&M University, College Station 77843. Lopes is pesently coordinator of goat research, EMBRAPA/CNP-Caprinos, Sobral, Ceara,, Brazil, 62.100 This article IS published wth the approval of the Dwector, Texas Agricultural Experiment Station,, as TA-l8090/ .92. Specml appreciatmn is extended to Dr. Charles Scifres for his professional support and suggestions provided throughout this study. Manuscript accepted February 29, 1984. 554 1982a). A combination of cattle and goats might be used to effectively manipulate woody regrowth to sustain the beneficial aspects of mechanical treatments and maximize long-term returns. Use of goats in many situations is perceived to be harmful to the environment. The goat controversy probably exists because of preconceived ideas and lack of reliable observations about this species. This unfortunately impedes a better understanding of its role in land use. The counterpart of the “maligned”image of goats is their capability to reduce brush cover on rangeland. Control of brush regrowth using goats following other brush treatments has shown good results in maintaining fuelbreaks in the southern California chaparral (Green et al. 1978), controlling brush species in Tanzania’s Massailand (Martin and Huss 1981) and in the northern and central rangelands of Mexico (Fierro et al. 1980), and in reducing Gambel oak (Quercus gambelii) sprouts in Colorado (Davis et al. 1975). In western Texas, Spanish goats were useful in conjunction with prescribed burning for suppressing woody species during the growing season (Ueckert 1980). The primary advantage of goats over other small ruminants lies in their multipurpose-utility. Since animal grazing preference is the major determinant factor in a grazing program (Davis et al. 1975), diet selection should be the first step in assessing the goat’s potential as a complementary grazer and brush management agent. The primary objective of this study was to determine effects of brush management practices and season on botanical composition and nutritional content of Spanish goat’s diets and browsing preference of goats for forage classes and plant species in Texas Post Oak