Abstract:
BIURET AS A NITROGEN SUPPLEMENT FOR CATTLE GRAZING NATIVE PASTURE AND TOWNSVILLE STYLO AT ADELAIDE RIVER, N.T. B.D. FORD * Summa t-y Biuret was fed over four dry seasons to breeding cows grazing native pasture or Townsville stylo at Adelaide River, N.T. There was no appreciable effect of the supplement on the liveweight change of cows grazing Townsville stylo. Biuret reduced liveweight and condition loss of cows grazing native pasture to some extent, but it was not sufficiently effective to prevent mortalities during the late dry season. Reasons for the responses obtained are discussed, 10 INTRODUCTION m ,Biuret, a pyrolysis product of urea, has recently become commercially available in Australia in feed grade form, In the Northern Territory it is a possible non protein nitrogen replacement for other protein supplements such as meat and bone meal and cottonseed, The use of these products has been limited by the high cost of transport per unit nitrogen and by variations in price'and supply, The use of the conventional urea/ molasses mixes has been precluded by the prohibiti-ve cost of transporting molasses from the Eastern seaboard and the risks of toxicity associated with feeding urea under extensive management conditions, T h e s a f e t y of biuret to ruminants is we1 1 establ ished (Hatfield et al, 1959) and other advantages over urea are a higher relative palatability and the abil ity to combine with a greater range of carriers due to its non hygroscopic nature, Positive responses from feeding biuret to cattle have been recorded overseas by MacKenzie and Al tona (1964) and others, but there appears to be very 1 ittle pub1 ished Austral ian work on the effic, iency of biuret as a nitrogen supplement, This experiment tested biuret as a nitrogen supplement for cattle grazing native or improved pasture at Adelaide River N.T, 11, MATERIALS AND METHODS The experiment was carried out at the Upper Adelaide River Experiment Station, 76 km south of Darwin, The area has a tropical monsoon climate with an average annual rainfall of 1270 mm, nearly 90% of which falls in the November-March period, to give an average estimated useful pasture growth period from early November to early May (McAlpine 1969. Four adjacent paddocks were used, comprising two of native pasture (N,P,) each of approx. 160 ha, and two of approx, 140 ha sown to Townsville stylo (T,S,), estimated at 40% on a ground cover basis, The main native grass species were the annuals Schizachyrium sp,, Eriachne ci 1 iata, Sorghum sp, and perennials Chrysopogon fal lax, Sorghum plumosum, Heteropogon triticeus, Themeda australis, Eriachxkittii, Chrysopogon setifolius and Bothriochloa bladhi, ;k Animal Industry and Agriculture Branch, Department of Northern Australia, Darwin, NT, 5790 357 The cattle used were l/2-3/4 brahman x shorthorn cross heifers, approx, two and a half years old at the start of the experiment and one thi rd were pregnant, They were mated to ca 1 ve each year from Nov. -Jan, and calves were weaned in May or June, `All cows were run in the T,S, paddocks during the early wet season, then re-randomised each year into supplemented (+) and control (-) groups each of 20 and 35 head on N,P, and T,S, paddocks respectively. Supplementation started early in the dry season and continued until refusal by the cattle after the first wet season showers. The cattle were rotated between paddocks within each pasture type and weighed directly off pasture each month, and scored for condition on a 1 to 10 range, The N.P, and T,S, treatments were not carried out in 1969 and 1972 resp, The source of biuret was Kedlor 230*,which has a minimum nitrogen content of -37%. Sorghum, salt and molasses were used at various stages to regulate rate of intake, The possibility of limitations on animal performance and supplement utilisation by phosphorus and sulphur were removed by the addition of Christmas Island phosphate dust (C, I,P,D,, 17% P) or Tricaphos (18% P), -and sulphur in years 3 and 4, The composition of the supplement fed each year is listed in Table 1, The supplement was fed out twice per week and the same amounts were fed to animals on both pasture types. Control groups received all components except Kedlor, TABLE 1 Components of supplement fed 1969/72 111,. RESULTS The half-week ration of the supplement was usually eaten within 2-3 days, Rate of intake was generally slower by the T,S, than by the N,P. groups, and slower by those receiving Kedlor than the controls, Table 2 shows liveweight and condition changes for the 4 years of the experiment, * Trademark of Dow Chemical Co, 358 TABLE 2 The cows grazing ToSo maintained or gained weight until the first showers of the wet sleason when there was a short period of rapid liveweight loss, whereas those on native pasture lost weight all dry season0 Effects due to differences in T,S, paddocks were evident each year, and in both 1969 and 1970 the Kedlor group spent more grazing days than the controls on the bettler paddock (53 v 44 and 84 v 56 days resp,), In 1971 both ToSo groups spelnt equal time in each paddock. On native pasture there was very little response to the Kedlor supplement in 1970, although the supplemented cows appeared in much better condition than the controls at the end of the dry season, Control groups cows in 1971 lost substantially more condition than supplemented ones and three (19%) did not lsurvive the first fortnight after feeding out ceased, There were no deaths in the Kedlor group, The 1972 experiment was terminated approx. 5 weeks before the break of the season due to mortal ities in both. groups, Deaths numbered three (10%) and nine (30%) in the supplemented and control groups respectively, The much larger condition loss in the control group reflected the significantly larger 1 iveweight loss of that group, The breeder groups used in this experiment were too small for any meaningful trends in conception rates to be evident, and compensatory weight gain could not be assessed due to effects of subsequent calving, lV0 DISCUSSION The small liveweight advantage of the biuret-supplemented group on T,S, in 1969 and 1970 is probably mainly due to the longer time spent grazing what proved to be the better paddock, The liveweight change of the T,S, groups followed the pattern of 1 iveweight change established by Wesley-Smith (1972) for cattle grazing standing T,S, at Adelaide River, 359 Liveweight gain or maintenance up to the time of the opening rains indicates that standing T,S. by itself is an adequate protein supplement, After the early storms the standing pasture declines in qua1 ity due to leaching and fungal and bacterial decay and an energy-rich supplement is probably more appropriate, Cows grazing native pasture suffered typical dry season weight losses, and mortal,ities occurred in two years out of three, I n 1972 i t is estimated that that at least all the animals classed as 'poor' or worse would have died if left on the native pasture paddocks for the Total deaths would then have numbered 9 remainder of the dry season0 (30%) and 23 (76%) in Kedlor and control groups resp. Although it is clear that the supplement decreased mortality and slowed the rate of liveweight loss to some extent, it was not sufficiently It is not clear from this experiment effective to ensure survival o whether the lack of a favourable response was due to poor pasture qua1 ity or to the efficiency of Kedlor per se, No work has been carried out on the value of other non protein nitrogen sources, such as urea as supplements to native pasture in the Adelaide River area, however significant responses were obtained by supplementing steers with meat and bone meal on the paddocks used in this experiment (Ford, unpublished), WesleySmith (1972) has shown that the native pastures in the Adelaide River area are poorer than those at Katherine where, up to the time of the early storms, the dry, standing native pasture is an adequate source of energy if cattle are given a small quantity of high protein supplement (Norman It is likely that the digestibility of the standing forage at 1963). Adelaide River becomes too low to support an adequate response to a non protein nitrogen supplement fed with minimal energy, and that true protein supplements or improved pasture must be provided to ensure survival of cattle in this area during the dry season, VO ACKNOWLEDGEMENTS Dow Chemical (Aust.) Ltd made this experiment possible by the generous provision of the feedstuffs, cattle, yards and other facil ities, and the helpful advice of Dr, J,T, Tollett and Mr. C,B, Mutch of Dow is I wish to thank Mr, Stan Brett and the staff of grateful ly acknowledged, U,A,R,E,S, for management of the experiment, Vlo REFERENCES HATFI ELD, Eo Eo , GARR IGUS, US,, FORBES, ROM,, NEWMANN, A& and GAITHER, WILLIAM ( 195910 Journal of Animal Science 18: 1208, SC In Lands of the Adelaide - Alligator Area, _ McALPINE, JoRo (1969 1 0 C,S, I,R,0, Aust, Land Research Series No0 25, Northern Territory C,S, I .R,O,, Melbourne0 MACKENZIE, HOI0 and ALTONA, ROE0 (1964a), Journal of the South African Veterinary Medical Association 35: 301, Austral ian Journaf-of experimental Agriculture NORMAN, MoJoTo (1g63)o and Animal Husbandry 2: 280, WESLEY-SMITH, RoNo (1972)o Austral ian Journal of experimental Agriculture and Animal Husbandry. 12: 566, - -- 360