Abstract:
314 Proc. Aust. Soc. Anim. Prod. Vol. 17 OAT HULLS IN PELLETED DIETS FOR EXPORT SHEEP M.H. ROUND* SUMMARY Three hundred and sixty Merino wethers from three different sources (15 wethers/group within each source) were fed one of four pelleted diets for six days in outdoor yards followed by 16 days in indoor pens. The four pelleted diets contained (1) 45% oat hulls, (2) 22.5% oat bulls/22.5% grass hay, (3) 45% grass hay and (4) a hay-based commercial pellet from a different manufacturer. There was no difference in pellet intake or liveweight change of sheep between diets. There was a difference between sources of sheep (P<O.05) but no significant interaction between source of sheep and diet. In a separate free choice feeding trial comparing the intakes of diets (1) and (3), wethers preferred diets containing grasshay. In a separate investigation, the apparent in vivo dry matter digestibility of four commercial sources of oat hulls were 47.7, 32.1, 36.8 and 36.7%. Keywords: oat hulls, live weight, digestibility, sheep INTRODUCTION Over 150,000 tonnes of pellets are supplied annually as the sole feed for sheep exported by sea from Australia to the Middle East. The pellets commonly contain 20-40% grain with most of the remainder consisting of roughages, generally hay and grain milling by-products including ground oat hulls. However, opinion has been expressed in some sections of the livesheep export industry that pellets containing large quantities of oat hulls are inferior to those based on hay. Because of this, an experiment was conducted to compare pellets containing three different levels of ground oat hulls substituted for hay, on the performance of export wethers held in conditions simulating both the assembly feedlot and shipping phases of the export industry. A further comparison was made with a hay-based commercial pellet from a different manufacturer. There is very little published information on the nutritive value of oat hulls;hence the chemical composition and digestibility by sheep of ground oat hulls from four commercial sources were also determined. MATERIALS AND METHODS Experiment 1 One hundred and twenty Merino wethers from each of three different sources were transported by road to the feedlot and arrived on the same morning. The bare-shorn, 3-4 year old wethers from (1) pastoral, (2) Lower North and (3) Upper South-East regions of South Australia had been trucked 380, 70 and 200km and weighed (mean 2 s.e.) 50.9 + 0.4, 50.7 + 0.4 and 61.8 + OJkg respectively at the start of the experiment. The wethers were treated with an oral anthelmintic, eartagged and within sources, randomly allocated to eight groups of 15 wethers and to two replicates of the four treatments. The wethers were held20vernight without feed or water, weighed and then held in bare earth yards (5m /head) for six days followed by 16 days in intensive indoor pens (0.34mL/head). The wethers were again weighed at the end of the experiment following 24 hours without feed or water. During days I-6 of outdoor feeding, the wethers were fed 0, 250, 400, 600, 800 and * Department of Agriculture, G.P.O. Box 1671, Adelaide, S.A. 5001. Proc. Aust. Soc. Anim. Prod. Vol. 17 315 1OOOg pellets and 900, 1000, 700, 500, 250 and Og oaten hay/head/day. During indoor feeding the wethers were fed a maximum of 1200g pellets/head/day during days l-6 and a maximum of 14OOg pellets/day during days 7-16. Pellet residues were collected on alternate days. Three of the four experimental pelleted diets (1Omm diameter) contained (1) 45% oat hulls, (2) 22.5% oat bulls/22.5% grass hay and (3) 45% grass hay, mainly mature rye grass (Lolium perenne). The fourth diet was a commercial export pellet, 1Omm diameter, producedby a different manufacturer and consisted predominantly of hay including lucerne hay. Its formulation was unknown,but its chemical compositie; was similar to that of the other diets (Table 1). Table 1 Formulation and composition of the diets in Experiment 1 A B n.a. = not available, see text. Levels assigned by compu ter formula tion Pro gram. COther consisted of 4.0% molasses, 2.0% sodium bicarb onate , 2.0% lime ston e an d 1.0% salt. Liveweight change and pellet dry matter (DM) intakes were compared by analysis of variance. Frequency distribution of liveweight change classes were compared by Chi-square analysis of contingency tables and log-linear methods. Experiment 2 To help explain the poor reputation of ground oat hulls as a pellet ingredient, the intakes by wethers fed diets 1 and 3 (Table 1) simultaneously, were measured. Both diets were offered at lOOOg/diet/head for two days to a group of four wethers from each of the three sources (Experiment 1) that were housed indoors following arrival at the feedlot. The position of each diet was reversed on the second day and feed intake over 23 hours/day was recorded. Experiment 3 Four diets consisting of ground oat hulls from one Victorian and three local sources were fed to mature wethers (4/diet) in two experiments and apparent dry matter digestibility (DMD) was determined. The diets, containing 98.2% oat hulls, 1.0% urea, 0.4% limestone and 0.4% salt which were mixed dry, were fed at 55g/kg liveweight oo75/day for 18 days and faeces was collected, using harnesses, on the last six days. The oat hulls were a dusty feed and some sheep tended to spill feed onto the floor or in their water supply while feeding. Spilt fee d was recovered. DMD was also determined by a 2 stage pepsin-cellulase method (Cl .arke et al 1982). 316 Proc. Aust. Soc. Anim. Prod. Vol. 17 RESULTS Experiment 1 Two deaths, both in source 2 wethers, occurred during the experiment but were apparently unrelated to the diets. Wethers ate all of the feed offered in outdoor yards. During indoor feeding, pellets offered marginally exceeded intake by sheep from sources 1 and 2. Wethers from source 3 ate less pellets (PcO.05) and performed poorly compared with other sheep (Table 2). Pellet intake during indoor feeding and live weight change over the whole experiment were not different between diets (Table 2). There were no interactions between diet and source of sheep. The frequency distribution of wethers losing large amounts of live weight reflected mean liveweight changes. Hence, differences between diets were not significant,but the percentage of wethers from sources 1, 2 and 3 losing more than 4kg live weight were 3, 10 and 24 respectively (X.2 = 28,<P 0.01). Table 2 Liveweight change and pellet dry matter (DM) intake of wethers from three sources fed four pelleted diets (Experiment 1) Experiment 2 During each of the 23 hour periods, wethers from sources 2 and 3 ate all of diet3 (45% grass hay) and less than 35% of the diet 1 (45% oat hulls) offered. Wethers from source 1 (pastoral) did not eat during the experiment. Experiment 3 The composition and digestibilities of the four sources of oat hulls are given in Table 3. One sheep fed oat hulls from source 1 became inappetant and was removed from the experiment. Reasons for the high DMD of oat hulls from source 1 (Table 3) are not known and this source of oat hulls is no longer available. The pepsin-cellulase technique did not accurately reflect differences in in vivo DMD between the different sources of oat hulls (Table 3). Table 3 Composition (% DM) and apparent in vivo dry matter digestibility (DMD) and pepsin-cellulase (PC) DMD of four sources of oat hulls fed in Experiment 3 Proc. Aust. Soc. Anim. Prod. Vol. 17 DISCUSSION 317 In Experiment 1, the inclusion of large quantities of oat hulls in pelleted diets did not make them inferior to hay-based pellets. There was some evidence that high levels of oat hulls in pellets reduced their acceptability to sheep and this gives some support to those sections of the export industry that shun such pellets. This evidence came from the tendency of sheep to eat less (PcO.10) of the pellets containing the highest level of oat hulls (diet 1) during the first two days of indoor feeding in Experiment 1 (Table 2) and from the results of Experiment 2. However, the results of Experiment 1 indicate that any differences in the apparent acceptability by sheep of pellets containing different levels of oat hulls are unlikely to have any practical consequences. The lower intake of wethers from source 3 (Table 2) may have been associated with their high level of fatness and this supports opinion in the export industry that over-fat wethers do not travel as well as those that are less fat. The good performance of pastoral wethers in experiment 1 supports other results obtained at this feedlot (unpublished data) which suggests that pastoral wethers can be readily adapted for export if appropriate feeding conditions are provided. In conclusion, considerable quantities of oat hulls can be included in pelleted diets for export sheep without affecting sheep performance,but presumably providing that the energy content of the pellets is not lowered. Until more information on the nutritive value of oat hulls from different sources is available, pellet manufacturers should assume a value of around 37% DMD for oat hulls when formulating pellets. ACKNOWLEDGEMENTS The author wishes to thank Milling Indus tries Ltd., for financial support and M s. K. Haskard for statistical analysis of liveweight data. REFERENCES CLARKE, T., FLINN, P.C. and MCGOWAN, A.A. (1982). Grass Forage Sci. 37: 147.