Fly strike among lambs with red and blue brands

Abstract

PWC. Amt. SOC. Anim. Prod. April I994 Vet/. 20 FLY STRIKE AMONG LAMBS WITH RED AND BLUE BRANDS P.A. KENNEY, K.L. COOPER and R.W. EDWARDS Dept of Agriculture, Rutherglen Research Institute, RMB 1145, Rutherglen, Vic. 3635 In the temperate climate of south eastern Australia, as at the Rutherglen Research Institute, we are regularly faced with the problem of sheep struck by blowfly during the spring-autumn period. Normally, strikes are confined to the area around the crutch or pizzle. However, in some of the wetter seasons such as the late spring and summer periods of both 1991-2 and 1992-3 body-strike was a serious problem. During summer 1991-2 there was some anecdotal evidence that the flies seemed to strike the body area next to where red SIROMARK brands had been used. In the following August (1992) for identification purposes, a flock of 83 ewe and SO cryptorchid lambs grazing together were branded on the mid back with SIROMARK; the ewes with red and the cryptorchids with blue. The lambs were not shorn and during October to December the weather was wet and humid and many were fly struck. Strikes were CT recorded at a weekly weighin, and identified as being the first or second time a lamb had been struck. There was greater incidence of primary and total strikes among the red-branded ewes (P < 0.05, Table 1). Table 1. Numbers of fly strikes recorded during November-December 1992 for ewe and cryptorchid lambs branded with red and blue SIROMARK. Percentages in parenthesis I nese observations supported the previous years anecdotal evidence in that significantly more of the red branded animals were struck by the blow fly. Although the effects of sex and colour have been confounded in these observations the evidence seems to suggest that colour rather than the gender of the lamb was attracting the fly. We can find no evidence of sheep gender having any effect on the attraction to f-lies and the anecdotal information which suggested flies struck near red brands was from observations taken from a 1 sex (ewe) flock. Further, it is known that some flies at least, are attracted by different colours (Agee and Patterson 19S3; Burg and Axtell 1994) and although there appears to be little objective information about the sheep blowfly and its preference for colour, a yellow colour is thought to improve attractiveness of fly baits (Anderson et nl. 1990). Further controlled observation is n eeded to esta blish why flies were attracted to the red -branded ewe lambs. The answer m ay lead to mean more care in selec ting colour of brands for sheep and improvement to baits for blowflies. AGEE, H.R. and PATTERSON, R.S. (1983). E rzvirorz. E~ttomol. 12: 1 S23-28. ANDERSON, J.M.E., MCLEOD, L-J., SHIPP, E., SWAN, A. and KENNEDY, J-P. (1990). Amt. Vet. J. 67: 93-7. BURG, J.G. and AXTELL, R.C. (1984). Erwirom Erztomol. 13: 1083-90. 407