Parasite penalties on production.

Abstract

Proc. Aust. Soc. Anim. Prod. (1974) 10; 180 PARASITE PENALTIES ON PRODUCTION H. McL. GORDON* Ruminants in Australia experience infections with twelve genera of helminths each capable of causing a fatal disease, and all contributing to L.O.P. (less than optimum productivity). A further four to five genera may add to ill-thrift, and four species of tapeworm cysts cause economic loss through condemnation of meat. The occurrence of damaging infections and the extent of losses are seldom precisely predictable; the risk-taking aspects of management and expenditure on preventive measures which are sometimes not required add to the economic loss from parasitic disease. Multiple infections are common, different species damage different physiologica. systems, the epidemiology of each infection is unique and the aggregate economic loss is considerable. Modern broad-spectrum anthelmintics provide a reasonable degree of control, and when applied in 'production trials' enable a better diagnosis or determination of losses, and assist in the differential diagnosis of ill-thrift and the recognition of its components. Precise measurement of economic loss is difficult and may have to include a widt 'Loss avoided' may be as important as variety of components of animal production. In a trial with groups of 40 Merino weaners, those treated direct profit gained. monthly with thiabendazole produced 3.07 kg wool, 80% weighed 35 kg or more and none The group treated only each third month produced 2.94 kg wool died during the year.' Had these been wether weaners to be sold 64% weighed 35 kg or more, and 17.5% died. at 18 months, the more uniformly grown group (80% weighing 35 kg or more) would command a better price, with minimal rejection, than the group in which only 64% reached this weight. If they were ewe weaners the loss of 17.5% from death represents not only their current value, but their life-time production of wool and lambs, and less opportunity for culling. Note also that total wool production per group was 122.8 kg for the intensively treated sheep, 97.02 kg for that treated less intensively. In another trial with groups of 30 Merino weaners, the group treated monthly with thiabendazole experienced a mortality of 6.5% and returned 103 kg wool; the group treated each second month with thiabendazole had a mortality of 10% and producec 97 kg wool, while a group treated each second month alternating thiabendazole and naphthalophos had a mortality of 20% and returned 82 kg wool. .In trials with prime lambs in the Oberon, N.S.W., district over 13 years, with groups of 25 to 50 late winter lambs, the proportion which attained market weight (3540 kg live wt.) by mid-February was greater in lambs treated monthly from 6-8 weeks of age with thiabendazole than in untreated controls in 7 of the 13 years, there was no difference in 5 years, and the controls made better gains in one of the years. I: the 7 years when more of the treated lambs attained market weight earlier than contra, the respective percentages were 80 to 52, 46 to 34, 18 to 10, 15 to 8, 40 to 20, 20 tc 10, and 65 to 45. Some relevant references include: Brunsdon, R.V. (1 966) a Gordon, H.McL. (1 ,958). Hight, G.K., and Cairns, Johnstone, I.L., James, 12: 11. McLeod, C-C., and Wolfe, Proc. N.Z.Soc,Anim.Prod. 2: 165. Proc.Aust.Soc.Anim.Prod. 2: 59. N.Z. J.agric.Res. 2: 925. G.C. (1966). Wool Technol.Sheep Breeding pa., and Branch, S.J. (1965). J.E. (1968). N.Z. J.agric.Res. 2: 407. * C.S.I.R.O,' Division of Animal Health, McMaster Laboratory, Glebe, N.S.W. 2037.