Preliminary investigations into molasses and sulphur supplementation of sheep fed mulga (Acacia aneura).

Abstract

PRELIMINARY INVESTIGATIONS INTO MOLASSES AND SULPHUR SUPPLEMENTATION OF SHEEP FED MULGA (Acacia aneura) W.A. HOEY *#, B.W. NORTON, and K.W. ENTWISTLE* Summary A Individually penned wethers supplemented with 50 gm DM molasses consumed more mulga than unsupplemented controls. An identical response was observed when the 50 gm DM molasses was replaced by its ash content. A lower response in intake was observed when sheep were fed the sulphur contained in 50 gm DM molasses, as sodium sulphate. A comparison of a number of sulphur sources fed on an equal sulphur basis revealed that sheep supplemented with calcium sulphate consumed significantly more mulga than those fed methionine, sodium sulphate or elemental sulphur, but all intakes with these supplements were significantly lower than that of the group supplemented with 50 gm DM molasses. . I. INTRODUCTION Mulga (Acacia aneura F. Muell.) is widely distributed throughout inland Australia where it provides a valuable fodder for both sheep and cattle, particularly during drought (Everist 1949). Nichols (1938) fed fresh mulga ad lib. to penned sheep resulting in liveweight gain. However, Harvey (1952), Rohan-Jones et al. (1972), Norton et al. (1972) and McMeniman (1975) stressed that m-s basically a maintenance fodder. Improvements in reproductive, wool growth and liveweight status of ewes browsing mulga (McMeniman and Little 1974) and in intake and liveweight gain (McMeniman 1975) plus wool growth (Entwistle andBaird1975) in penned wethers fed mulga have been recorded by feeding molasses (M) and phosphorus (P). The largest percentage response to molasses over the range SO-200 g occurred at the 50 g level. Experiments were undertaken to determine (1) whether an intake response occurs at a level of M less than SOg, and (2) the component(s) of M responsible for this increase in mulga consumption. MATERIALS AND METHODS (a) Animals iTwenty one Merino cross wethers aged 2-3 years and weighing 0.53 kg were used in Experiments l-4. In Expt. 5, 20 two-tooth wethers weighing 26.6 f 0.26 kg were used. In all experiments, were kept in individual pens. All sheep were given a parenteral A, D and E supplement (to provide 500,000 I.U. vitamin A, 75,000 vitamin D3 and 50 I.U. vitamin E) prior to Expt. 1, and drenched with Thibenzole. II. 28.5 + Merino sheep vitamin I.U. monthly *Animal Research Institute, Yeerongpilly, Brisbane, Qld. 4105. _ '+Faculty of Agriculture, University of Queensland, St. Lucia, Brisbane, Qld. 4067. #Present Address: Dept. of Agronomy, Waite Agricultural Research Institute, Glen Osmond, South Australia 5064. APeresent Address: Dept. of Tropical Veterinary Science, James Cook University, Qld. 4811. VGiven as mean k standard error. 377 (b) Diet (c) Design and Treatments The M, which was offered separately, was consumed within 5 min. Other supplements were mixed with distilled water and given via a stomach tube. Faeces were collected during the last week of Expts. 1, 2 and4. In Expts. 1 and 5 sheep were allocated to treatments at random.' In Expts. 2 and 4 animals were also allocated with regard to previous treatment. In Expt. 3 six similar sheep were used and paired in order to test the effect of minerals added in sequence on their mulga consumptibn. For 4 weeks prior to Expt. 1 sheep were accustomed to the basal diet of mulga and phosphate drench. Between Expts. 1 and 2 and Expts. 2 and 4, the sheep were fed the basal diet for 3 weeks during which their intakes returned to a common level. (d) Measurements (i) 'Daily ad lib. intake of mulga, dry matter digestibility (DMD) of the diets, and liveweight changes in Expt. 1. 378 (ii) In vitro rumen activity of four sheep `from each of the Control and . MS0 groups in Expt. 1, using the method of Tilley and Terry (1963). Milled pangola grass (Digitaria decumbens) was the common'substrate. These results were subjected to analyses of variance. (e) Chemical Analyses Calcium (Ca), magnesium (Mg), copper (Cu), manganese'(Mn), zinc (Zn) and iron (fe) were determined by atomic absorption spectroscopy. Sodium (Na) and potassium (K) were estimated by flame photometry. P was determined using a calorimetric method based on the reduction of phosphomolybdate, and nitrogen (N) was determined by the Kjeldahl technique. III. RESULTS TABLE 3 In Expt. 3 the mean daily intake of all of the minerals except sulphur the latter supplement or feeding it 0.05) to 636 + 24.Og. TAB the controls and the group receiving was 519 + 34.5g. By adding Na2S04 to alone, increased intake (0.10 > P > LE 4 The M25 supplement induced 73 % of the intake response to the MS0 supplement. In Expts. 2 and 4, the ash and MS0 treatments produced identical responses indicating that th'e mineral component of molasses was responsible for the increased mulga intake. Although Expts. 3 and 4 indicated an apparent response (0.10 > P > 0.05) to Na2S04, it was still less (0.10 > P > 0.05, Expt. 4; P < 0.05, Expt. 5) than the response to the MS0 supplement. In Expt. 5, CaS04 also significantly increased intake (P < 0.05) over the Na2S04 and remaining sulphur supplements. There were no treatment effectson D.M.D. in any of the experiments. During the acclimatisation period, all sheep lost 4.4 ? 0.72 kg. At the end of Expt. 1 the mean liveweight of the treatment groups was significantly higher than that of the controls, 28.5 2 0.46 > 25.1 k 6.81 (P < 0.05). The rumen fluid from the 50gM treatment digested the pangola grass to a significantly greater extent than that from the controls . (D.M.D.% 54 +5.4>37-+7.0 (P<O.OS)). IV. DISCUSSION The apparent intake responses to a sulphur supplement in Expts. 3 and 4 were unexpected as the N:S ratio of mulga is below 13.5:1 and therefore should be adequate for optimum utilization of dietary nitrogen (Bird 1972). The sulphur, which is probably present in the sulphur containing amino acids, could either be relatively inaccessible because of the low digestibility of the feedstuff or bound by the tannins present in mulga. Preliminary analyses have revealed S-7% tannic acid equivalent in mulga (R.J.W. Gartner - pers. comm.), which would appear sufficient to reduce the catabolism of dietary protein in the rumen (McLeod 1974). 379 From the Results of Expts. 4 and 5 it appears that the response is However a recent not solely due to sulphur but also perhaps to calcium. experiment (unpublished data) conducted at Charleville demonstrated no differences between molasses and some of the other sulphur sources tested in Expt. 5. The reasons for this apparent discrepancy have yet to be elucidated. The increased intake which occurred without any changes in D.M.D. implies.that the response was mediated by other factors which influence rate of removal of organic matter from the rumen (Weston 1967). The increased microfloral activity observed in the in vitro digestions may indicate that the rate of digestion of the feedstuff had been improved. Future experiments will be concerned with determining the effects of climatic and plant factors on the magnitude of the response in both sheep and cattle. v. ACKNOWLEDGEMENTS We wish to thank Mr. D.R. Niven for technical assistance, officers of the .Biochemistry Branch, Animal Research Institute, for chemical analyses, and Mr. R.A. Young for statistical analyses. VI. REFERENCES BIRD, P.R. (1972). Australian Journal of Biological Sciences. 25: 1073. ENTWISTLE, K.W. and BAIRD, D.A. (1975). Australian Journal of Experimental Agriculture and Animal Husbandry (In press) EVERIST, S.L. (1949). Queensland Journal of Agricultural Science, 5:87. HARVEY, J.M. (1952). Queensland Journal of Agricultural Science, .2:169. McIEOD, M.N. (1974). Nutrition Abstracts and Reviews, 44:803. McMENIMAN, N.P. and LITTLE, D.A. (1974). Australian J&nal of Experimental Agriculture and Animal Husbandry, 14:316. McMENIMAN, N.P. (1975). Australian Journal of Experizgntal Agriculture and Animal Husbandry (submitted for publication). \ NICHOLS, J.E. (1938). Journal of the Australian Institute of Agricultural Science, 4:lO. .NORTON, B.W., et al. (1972),-Proceedings of the Australian Society of Animal P&tion, 2:346. ROHAN-JONES et al. (1972). Proceedings of the Australian Society of Animal Production, 9:341. TILLEY, J.M.A. and TERRY,=R.A. (1963). Journal of the British Grassland Society, 18:104. WESTON, R.H. (1967). Australian Journal of Agricultural Research, i&983 380