Abstract:
THE EFFECTS ON LIVEWEIGHT AND WOOL PRODUCTION OF AUTUMN DEFERMENT WITH HAY FEEDING A. H. BISHOP* and T. D. KENTISH* Summary An experiment is described which studied the effects on the liveweight and wool production of wethers when deferment of grazing in the autumn was achieved by feeding hay in a feedlot. At a stocking rate of twelve per acre, matched groups of wethers, allotted to equal areas of pasture, were fed equal quantities of similar hay whilst (a) continuously grazing the pasture, or (b) confined in a feedlot during the feeding period from late summer until after the autumn break and thence on to pasture. The feedlot groups with deferred grazing had an advantage in more pasture and higher liveweight during the winter, and in increased greasy wool production. I. INTRODUCTION 'Autumn deferment' is a method of grazing management in which animals are removed from pasture after the opening rains and are fed from alternate sources while pasture re-establishes. An experiment is described in which grazing was deferred until six weeks after the autumn break. During deferment sheep were maintained in a feedlot on a sole ration of baled pasture hay; they then grazed the pasture at a high stocking rate without further supplementary feeding. The performance of these animals was compared with that of sheep fed like quantities of similar hay under continuous grazing. II. EXPERIMENTAL PROCEDURE (u) General The observations were carried out at the Pastoral Research Station situated on volcanic plains six miles south of Hamilton (Western Victoria). Mean annual rainfall is 26 in. (65 cm). The results comprise two series of observations, made in 1963 and 1964, on Iiveweight and wool production of three year old Corriedale wethers whic h grazed perennial pasture at 12 per acre and to which a supplement of hay, obtained from an outside source, was provided in the autumn and winter. The level of supplement, duration of feeding and manner of feeding supplement were varied to provide four different treatments in 1963 and two in 1964, with two replicates of each treatment. The experimental details are set out in Table 1. *Department of Agriculture, Pastoral Research Station, Hamilton, Victoria. 164 TABLE 1 Exp&men tczl de tails `% Treatments were replicated twice. f Days of feeding from March 19 in 1963, from February 13 in 1964. H- High hay M - Medium hay. F - Hay fed in Feedlot. .p-- Hay fed at Pasture. (b) Pastures and animals The pastures comprised mainly perennial rye grass (Lolium perenne L.) and subterranean clover (TrifoZium subterraneum L.) sown in May 1962 and allowed to establish without grazing until summer 1962. In both years, the animals required for the observations grazed the experimental area in common at 12 sheep per acre from mid summer until supplementary feeding became necessary. They were then grouped in greasy fleece weight classes and after ranking on the basis of liveweight, were allotted to treatments at random. Differential treatments commenced on March 19 in 1963 and on February 13 in 1964. In both years, the observations were completed at shearing in October, the interval between shearings being 8 months in 1963 and 12 months in 1964. (c) Observations Liveweight was measured at intervals of two to four weeks. The amount of pasture available during the winter was assessed by cutting to ground level and by visual assessment. The animals were shorn at the conclusion of the observations each year and greasy fleece weights were recorded. III. RESULTS (a) Seawnal Conditions The incidence of rainfall In 1963, only dry feed in late May and established following substantial rainfall is shown, by weekly periods, in Figure 1. was available in autumn until pastures germinated well. Subsequent growth of pasture was assured in winter and spring. 165 Fig. l.-Weekly rainfall, periods of hay feeding, liveweight and means of greasy fleece weight of deferred and continuously grazing sheep. 166 In occurred despite moisture 1964, the 'break ' of the season was protracted. Germinating rains in early February and were followed by falls which sustained pastures sporadic periods in which growth was restricted by shortage of soil until late April. Winter rainfall became excessive after mid-July. (b) Pasture available in winter There were differences in the amount of pasture available to the different groups at the completion of the hay feeding period. In July 1963, the deferred grazing groups HF and MF had, respectively, c. 500 and 250 lb (230 and 115 kg) per acre more green material available than groups HP and MP which had been grazing the pasture continuously. Similarly, in May 1964, group F had c. 350 lb (160 kg) per acre more green pasture than group P. In both years, the differences in amount of pasture disappeared in spring. (c) Sheep Liveweight In 1963, during the period in which hay was fed, groups HF and HP, fed hay ad libitum, maintained weight at c. 115 lb (52 kg) while groups MF and MP fed at 2 lb (0.9 kg) per day declined in weight to about 98 lb (45 kg). When hay feeding was stopped, the feedlot groups placed on deferred pasture at that time (HF and MF) maintained or increased weight slightly in winter and increased weight steeply in spring. During the same time, the groups which had been fed on pasture (HP and MP) lost a further 10 lb (5 kg) in winter but gained weight even more steeply in spring. The differences in weight between groups in spring were less than in late winter. In 1964, the two treatments F and P followed a similar pattern to the 1963 treatments, except that the difference in Iiveweight during the winter was less. (d) Wool production The differences in winter liveweight between groups were accompanied by differences in wool production (Figure 1 and Table 2). In 1963, mean greasy fleece weight was greater in group HF than in group MF and greater in group HP than in group MP (P <O.OS) . At the same time the wool production of groups HF and MF (the groups where grazing was deferred) was greater than that in groups HP and MP (where grazing was continuous) (P <O. lO>O.OS) . In 1964, wool production in the deferred group F was greater than in the continuously grazing group P although the difference did not attain statistical significance. TABLE 2 Mean greasy fleece weigh;ts - lb (kg) Differences for significance: 5% - 0.8 lb (0.4 kg) 167 IV. DISCUSSION The experiment provided a comparison between two methods of managing sheep during the late summer, autumn and winter when pasture and hay were available. Confining sheep to feedlots and feeding them hay there during late summer and until six weeks after autumn germinating rain, then allowing them on to deferred pasture, provided more pasture and higher sheep liveweights in the mid- and late-winter period and greater wool production than grazing the pasture throughout and feeding the same amount of hay over a similar period. The same result was observed at two levels of hay feeding and in each of two years. The differences in liveweight between treatments were substantial; they were the greatest at a critical period of the year - mid-winter - and continued for three months. Although by the spring the pasture differences had disappeared and the liveweight differences had been reduced, an advantage in higher wool production was observed in each case. The observations were made at a very high stocking rate and refer to a particular pasture. Further work is required to clarify the range of environmental conditions and stocking rates under which autumn deferment can be expected to make a worthwhile contribution to animal production and pasture stability. V. ACKNOWLEDGMENTS The authors are indebted to Mr. R. Jardine for assistance with the statistical analysis, and to our colleagues for helpful discussion in the preparation of this report. The experiment forms part of a larger programme supported by the Wool Production Research Advisory Committee of the Australian Wool Board.