Diet of Angora in a Eucalyptus populnea semiarid woodland.

Abstract

DIET OF ANGORA AND FERAL GOATS IN A EUCALYPTUS POPULNEA SEMI-ARID WOODLAND GRAHAM N. HARRINGTON* SUMMARY The time spent eating different foods by free-ranging angora and feral goats was directly observed on three different pastures and five occasions over 12 months. The diets selected were significantly different except during an autumn flush of forb growth in response to late summer rain. In the absence of fresh herbage angoras ate more low quality grass and feral goats ate more browse and litter. The major resource of these woodlands is the high availability of browse during the dry periods. Angora goats appear to be poorly adapted to exploit this resource. INTRODUCTION Angora g South Africa Recent intere grasslands of commercially studies were angora and fe MATERIAL AND METHODS The pastures The trial took place in a Eucalyptus populnea woodland near Cobar, N.S.W. Eucalyptus trees more than 25 m high occurred with a density of 36/ha and their crowns covered 16% of the area. Six thousand small trees and shrubs per ha formed a fairly dense understorey and carried 2.4t leaf DM/ha. The most common species of shrub and their leaf DM (ks/ha) were Acacia aneura ( 180) Cassiar nemophila (240), Dodonaea viscosa ( 20) , Eremophila mitchellii ( 730) I E. sturtii (260) / Geijera parviflora (620) andMyoporum deserti (40). The herbage layer was characterised by the grass Paspalidium constrictum beneath the Eucalyptus canopy whilst Sclerolaena (= Bassia) diacantha (chenopod), dead Stipa variabilis (grass) and Hibiscus spp. (perennial forb) predominated between the trees. . A. -arid areas of Texa sr lar parts of Austra lia. semi-arid wooded s to run angora goa ts uccessful. Diet requirements for Three contra sting pa sture cond itions were created by the following treatment s which were imposed from March 1975:1. 2. 3. 'Sheep treatment' grazed at 8 ha/wether (a normal local grazing pressure). 'Goat treatment' grazed at 2 ha/doe goat. 'Cleared treatment' grazed at 2 ha/doe goat. The clearing involved bulldozing out all shrubs and trees with trunks less than 20 cm diameter. Figure 1 indicates how herbage and browse DM availability was affected by these treatments. Forage availability declined on the sheep treatment with the low rainfall from October 1974 to September 1975 but increased in response to wetter conditions thereafter; the higher grazing pressure on the goat treatment prevented this recovery. The bulldozing on the cleared treatment destroyed most of the herbage and little recovery occurred until 1976. Acceptable browse CSIRO Division of Land Resources Management, Deniliquin, N.S.W. 2710. 436 Animal Production in Australia availability on all the treatments changed principally with its rate of removal by the goats. Samples of the principal food plants for chemical analysis were hand plucked in order to collect similar parts of plants to those grazed. Diet studies Four feral and four angora goats, which were habituated to the proximity of human beings, were run as separate herds and permanently grazed at the site. Their diet was assessed quarterly from March 1975 to March 1976 (see Table 1). At least three days prior to the sampling day the herd was released into the paddock. On the sampling day the herd was located at dawn and the food eaten at 30 second intervals was recorded. After 10 observations on one animal attention was transferred to the other three in turn. Ten full rotations were completed on each sample day, which usually took until mid-afternoon, i.e. 100 observations were made of each animal on each sampling occasion. The plants which were present at the time of eating in a 2 x 1 m quadrat constructed with its long side centred on the animal's feet were also recorded and these plants are said to be 'encountered'. RESULTS On all sampling occasions except those in March 1976 the allocation of grazing time between grass, forbs, browse and litter was significantly different between angoras and ferals (Table 1). However, the differences in March 1975 on the sheep treatment and December 1975 on the goat treatment involved only minor components of the diet. The Spearman Rank Correlation Coefficient for the species eaten and encountered by the goats is indicated in Table 1. Significant correlation 437 Animal Production in Australia indicates a similar sampling occasions similar order. On in a similar order, strata in the field order of preference or encounter. Only on three out of ten did the angoras and ferals eat the available species in a five sampling occasions they failed to encounter the species indicating that their choice of food took them to different layer. Table 1 Percent of total grazing time devoted to eating grass (G), forbs (F), browse (B) and litter (L) by angora and feral goats. x2 tests independence of the data for angoras and ferals. Spearman Rank Correlation Coefficient indicates similarity of the order in which species were eaten and encountered. A major cause of the differences in species both eaten and encountered was Consumption of this species the preference of the angoras for P. constrictum. took them into the dense shrubberies beneath the Eucalyptus canopy; feral goats tended to avoid this stratum unless they were eating M. deserti. This is illustrated by Table 2 where the seven most commonly eaten plant species are listed with the percent of total grazing time devoted to them from March to December 1975. March 1976 is excluded because on that date both types of goats concentrated on eating the fresh ephemeral forbs, particularly Euphorbia drummondii, which had been induced by the good summer rainfall. Table 1 indicates similar diets for March 1976 on the sheep and cleared treatment but not on the goat treatment, where low herbage availability forced the goats to seek alternative food. Although the diets of the two types there were also important similarities. browse species were eaten to some extent and E. sturtii were unacceptable to both of goats were significantly different, All herbaceous species and all but two by both types of goat. E. mitchellii angoras and ferals. Chemical analysis of plant samples indicated that perennial forbs and browse maintained a higher N content than grasses during the dry period up to December 1975. A sample of the analyses is found in Table 2. 438 Animal Production in Australia DISCUSSION Huston et al. (1971) showed that angora goats under range conditions in Texas varied seasonally in their use of grass, forbs and browse; nutritional stress in winter resulted in a greater use of browse. Similar nutritional stress in this experiment resulted in an increased intake of low quality grass, although the feral goats concentrated on browse and litter at these times. The high intake of dry grass indicates the surprisingly low acceptability of A. aneura which is an important dry season browse plant in eastern Australia (e.g. McMeniman and Little 1974). It is important to recognise that goats are generalist herbivores not specialist browsers (e.g. Malachek and Leinweber 1972), and that they make their selection at a plant species level. Although angoras have been reported as spending year round more than 50% of their time browsing (Huston -e 1971), they did not do so in this environment. et al. These data indicate that angora goats are poorly adapted for exploiting the major resource of these woodlands, which is the availability of browse throughout dry seasons. They also confirm a suggestion by Mitchell (1973) derived from South African goat farmers, that angora goats browse less than other breeds. Table 2 The percent of total grazing time devoted to the seven most commonly eaten plant species between March and December 1975 inclusive (all treatments combined), and their nitrogen content (% DM) REFERENCES 'Nutritional Requirements HUSTON, J-E., SHELTON, M., and ELLIS, WC. (1971). of the Angora Goat' (Texas Agric. Expt. Stn. B 1105: College Station.) MALACHEK, J-C., and LEINWEBER, C.L. (1972). McMENIMAN, N.P., and LITTLE, D.A. (1974). 14: = 316. J. Range-Manage. 2: 105. Aust. J. Exp. Agric. Anim. Husb. MITCHELL, T.D. (1973). 'Goat Production' (New South Wales Department of Agriculture: Sydney.). WILSON, A-D., LEIGH, J.H., HINDLEY, N.L., and MULHAM, W.E. (1975). Exp. Agric. Anim. Hush. 15: 45. C Aust. J. 439