Tick resistance in cattle: its stability and correlation with various genetic characteristics.

Abstract

SummaryTicks were counted on 51 Droughtmaster and 12 Bos taurus cattle on about 120 occasions during 1962–64. The mean tick count on the Bos taurus cattle was 15·94 in 1962 which fell to 2·10 by 1964. The respective figures for the Droughtmaster cattle were 2·62 and 0·18. The steady fall in numbers was attributed to the relatively small proportion of female ticks which reach maturity on Droughtmaster cattle.Within the group of 51 Droughtmaster cattle the tick burden carried by an individual varied with environmental and other factors, but did not alter much relative to other individuals (simple correlation 0·7). Similar results were obtained with the Bos taurus cattle. It is assumed that average tick numbers on the various individuals within a group were inversely related to the tick resistance of the animals concerned.There was no significant correlation between tick infestation and the distribution of alleles at the following loci: haemoglobin, albumin, transferrin, post‐albumins and soluble J antigen.There was a signiflcant association between the distribution of amylase genes and tick burden in the Droughtmaster cattle, and a similar but not significant association in the Bos taurus cattle.There was a significant difference in both the mean erythrocyte potassium concentration [K+e] and packed cell volume betweeu the Bos taurus and Droughtmaster cattle, but these characteristics were not correlated with tick burden within the Droughtmaster cattle.