Comparative tick resistance of European x British, British, and Zebu cross cattle.

Abstract

Animal Production in Australia COMPARATIVE TICK RESISTANCE OF EUROPEAN x BRITISH, BRITISH, AND ZEBU CROSS CATTLE S.J. WOOD*, P.T. KNIGHTS* and I.D. DOHERTY* Variation between British Bos resistance to cattle tick Boophilus information is available on the tick Utech et al. (1978) reported a mean 3A Charolais cattle. taurus and Zebu Bos indicus breeds to microplus is well documented. Little resistance of the large European cattle breeds. resistance level of 80.7 percent for a herd of In two experiments the tick resistance to artificial infestation by F1 Simmental x Hereford (S x H) and F, Limousin x Hereford (L x H) cattlewascompared with Hereford (H) and Zebu x Hereford cattle reared in an endemic tick area. The first compared 16 month old F, Simmental x Hereford, Hereford, and F, Brahman x Hereford (B x H) heifers. The second compared 40 month old F, Limousin x Hereford steers and speyed heifers, Hereford steers, and F, Africander x Hereford (A x H) steers. Engorging female ticks 4.5-8 mm in length, on one side, were counted over four days, 19-22 days after infestation with c. 10 000 larvae. Liveweight change during the infestation was measured. Statistical analyses were by analysis of variance of tick counts after logarithmic transformation and regression on initial live weight. The mean resistance level was calculated as the percentage of female ticks which failed to engorge in the four days assuming a 1:l sex ratio. Results are shown in the table. TABLE 1 Arithmetic mean tick counts 19-22 days after artificial infestation, resistance level (percent), and liveweight change (kg/head/day) There was no signficiant effect of tick burdens on liveweight change within breeds (or between breeds in experiment two) during the short periodofinfestation with c, 10 000 larvae. Correlations between counts on consecutive days were significant (P < 0.01) indicating that assessment on any one day would have given a similar result. The F, European x British and British cattle had similar mean resistance levels below 95 percent carrying significantly more ticks (P < 0.01) than F, Zebu x British which had mean resistance levels above 98 percent. Utech et al. (1978) suggested resistance levels below 95 percent are unsatisfactory for tick control and as a basis for selecting resistant cattle for breeding purposes. In this regard, these two large European Bos taurus breeds have no contribution to make in improving tick resistance levels of British Bos taurus herds in contrast to the Brahman or Africander Bos indicus breeds. UTECH, K.B.W., WHARTON, R.H., and KERR, J.D. (1978). Aust. J. Agric. Res. 29: 885. X * Brigalow Research Station, Qld Dept of Primary Industries, Theodore, Qld 4719. 608