Effects of dipping for tick control on liveweight changes in Zebu crossbred heifers in the central Burnett.

Abstract

Animal Production in Australia EFFECTS OF DIPPING FOR TICK CONTROL ON LIVEWEIGHT CHANGES IN ZEBU CROSSBRED HEIFERS IN THE CENTRAL BURNETT A.H. MILLES*, A.R. LAING*, F.R. EMMERSON**, D. CRANE*** and T.A. STRACHAN SUMMARY + Bos indicus-Bos taurus heifers subjected to dipping and non-dipping regimes at each of three different sites in the Central Burnett showed no differences in liveweight change due to treatment from November 1979 to May/June 1980. Generally tick numbers were low and this was probably a reflection of seasonal conditions. But, there was circumstantial evidence that the resistance of the heifers was a contributing factor. This trial suppor ts previously publis hed results on this subject and gives local support to biolog ical control of tick populations. INTRODUCTION The use of six to eight strategic tickicide treatments annually supported bYf or in combination with pasture spelling was the basic recommendation for tick control during the late 1950's and the 1960% (Woolcock 1968). while BOS taurus cattle were the dominant genotype this was an effective means of tick control but required considerable use of chemicals and labour. Both are expensive and chemical residues are a potential threat to overseas markets. Since this period several workers reported a lack of response in terms of liveweight change in BOS ~K&LLS-B~S taurus growing cattle from tickicide treatment. Since the mid 1970's there has been a marked swing by industry advisers from chemical and pasture spelling recommendations, to biological control through breeding tick resistant cattle. Bos indicus-Bos taurus cattle are still treated with tickicides more than research r,esults indicate are necessary (Elder 1979). Further evidence is presented here in support of minimal tickicide treatment for BOS ~&US-BOS taurus growing cattle. Additional evidence is of value to industry advisers who have been set the task of advocating managerial changes that are often seen by producers as a reversal of previous advice. MATERIALS AND METHODS Three groups divided at random the November-June times depending on The Site 1. Site 2. Site 3. of heifers from three locations in the Central Burnett were into two groups. At each site one group was not dipped during period of 1979/80, while the other group was dipped five to six location. heifers were all BOS indicu~-B~~ taurus which consisted of: Brian Pastures, Gayndah - Sahiwal-Hereford. - Belmont Red. Narayen, Mundubbera Mimosa, Mundubbera - Droughtmaster. Animal Production in Australia At each location, control and treated cattle grazed together at stocking rates of: 1 beast to 4 ha of native pasture at Site 1; 1 beast to 1 ha of improved pasture at Site 2; and 1 beast to 8 ha of native pasture at Site 3. At Site 1 BOS taurus cows were also in the paddock but at the other sites only trial animals grazed the paddocks. Live weight and standard tick counts were recorded for trial animals in November 1979, one or two times during the trial and in May/June 1980. The data were analysed by the least squares method (Harvey 1960). RESULTS Rainfall immediately preceding and during the trial period was approximately 65 percent of average. Site 1 was least affected due to comparatively higher rainfall and a larger quantity of pasture available in November 1979. Site 3 was worst affected by seasonal conditions. Liveweight performance - Site 1 Table 1 summarises liveweight performance of the heifers at Brian Pastures. TABLE 1 Effect of tickicide treatment on live weight - Site 1 Initial live weight on November 14, 1979 was 188 kg at 14 months of age. There was no significant effect attributable to the tickicide at any point during the trial. Tick counts per side of the control group ranged from less than one to a peak of 18 in April. Hereford cows in the trial paddock carried up to 3.5 times more ticks than the BOS indicus-Bos taurus heifers. These heifers were both firstand second generation Sahiwal-Hereford. There was no treatment by generation interaction indicating that both generations had similar tick resistance. Liveweight performance - Site 2 Table 2 summarises liveweight performance of the heifers at Narayen. TABLE 2 Effect of tickicide treatment on live weight - Site 2 350 Animal Production in Australia Initial live weighton November 3, 1979 was 230 kg at 14 months of age. Obviously treatment had no significant effect on liveweight at either point in the trial. Tick counts the three dates. tick levels there of these heifers adjoining paddock trial. in the control group averaged less than one While seasonal conditions were probably the is circumstantial evidence to suggest that accentuated the reduction in tick numbers. carried markedly higher tick burdens on six Liveweight performance - Site 3 Table 3 TABLE 3 summarises liveweight performance at Mimosa. per side at each of major influence on the tick resistance Hereford cows in an occasions during the Effect of tickicide treatment and pregnancy/lactation status on live weight - Site 3 There was no significant treatment effect on either date. The pregnant/ lactating heifers were significantly heavier than open heifers at May 27 1980 (PC -005) but not at February 28 1980. A significant (Pd .Ol) treatment by pregnancy/lactation status on February 28 1980 liveweight confounds treatment results at this date. The most likely explanation is that differing time of calving of heifers in the control and dipped groups caused this interaction. live weights of the open heifers on February 28 1980 were, control 338 kg and dipped 328 kg. Initial weight of these heifers was 238 kg at approximately 26 months of age on November 1 1979. Tick counts for the control group were about one per side at each observation. Relatively high liveweight gains during November-February (.80 kg/d for open heifers) indicated satisfactory seasonal conditions and an opportunity for movements in tick numbers. Marked liveweight losses from February to May (.50 kg /d for open heifers) is consistent with seasonal conditions depressing tick populations. DISCUSSION These results support the recommendation for minimal tickicide treatment for growing cattle. This work was done over a range of pasture and seasonal conditions with differing sources of BOS hdhts component. It gave the same result at each site and is an agreement with previously published results. 351 Animal Production in Australia The generally low tick populations are most likely a result of the prevailing seasonal conditions. However the circumstantial evidence from the Hereford cows at two sites indicates that the resistance of the BOS h&e.icsBos taurus heifers is contributing to the low tick population. ACKNOWLEDGEMENTS Thanks are due to Mr Richard Ape1 of Mimosa Droughtmaster Stud for his assistance and to various colleagues Messrs W.J. Taylor and T.H. Rudder in particular, who have assisted in the trial work, data analyses and preparation of this paper. REFERENCES CORLIS, P.L. and SUTHERLAND, I.D. (1976). Qd. Agric. J. E 102:589. ELDER, J.K. (1979). Veterinary Services and Pathology Branches Tech. Bull. No. 1. QDPI Brisbane 1979. HARVEY, W.R. (1960). United States Department of Agriculture, Agricultural Research Science, No. A.R.S. 20-8. SEIFERT, G.W. (1971). Aust. J. Agric.. Res. Z 22:839. TURNER, K.G. and SHORT, A.J. (1972). WOOLCOCK, B.A. (1968). Aust. J. Agric. Res. 23:177. S Brigalow Development Handbook QDPI Brisbane 1968. 352