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This article was published in 1969-70
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Project Dan 12 — The Incidence, Importance and Control of Internal Parasites of Cattle in N.S.W.
M. SMEAL, B.V.Sc., Veterinary Research Officer, Glenfield.
This study was commenced by the N.S.W. Department of Agriculture in 1964 and is being supported by Australian Meat Research Committee finance. The aim of the project is to determine the seasonal pattern of worm burdens in young cattle, their effect on growth rate and the best method of control.
The first three years of observations were made on North Coast and Northern Tableland properties but in 1968-69 the programme has been extended to the South Coast, the Southern Tablelands and the Central Tablelands. The recent appointment of additional research personnel, the establishment of two District Veterinary Laboratories and an extension to facilities at the Veterinary Research Station, Glenfield, has allowed studies to be included on liver fluke. Properties selected for both liver fluke and roundworm observations are located at Tenterfield, Casino, Oberon, Crookwell and Cooma.
These observations consist of regular faecal egg counts, faecal cultures and progressive body weights of both monthly treated and untreated control groups. Total worm counts from steers slaughtered at two monthly intervals from eight months to 18 months of age provide valuable information on seasonal levels of worm burdens and are an essential part of the programme.
On the North Coast high worm egg counts were found in dairy calves during the summer. Intensive stocking of calf paddocks and summer rains favoured Cooperia infections and small numbers of other worms. Peaks of Cooperia infestation were also observed after falls of rain in the winter. Anthelmintic treatments during the summer and in the winter post-weaning period did not increase the growth rate. Losses in body weight during the winter in both treated and untreated animals was due to poorer nutrition.
The growth rate of beef cattle on the North Coast was not affected by worm infections. Calves showed a small winter rise in worm egg counts. Low number of Cooperia spp. were found and these rapidly declined as the animals became older. Two peaks of Ostertagia infection were observed. Small infections occurred in young weaners during the late winter and the second or major peak was found in the late summer-autumn period when the animals were 16 months of age.
A similar seasonal pattern of Ostertagia infections has been found in beef cattle on the Northern Tablelands. A small peak of infection occurs concurrently with a rise in Cooperia spp. during the winter. The number of both parasites then declines and in the late spring-early summer period a large increase of retarded Ostertagia larval stages in the abomasum occurs. The adult Ostertagia populations reaches a peak in the early autumn when the animals are 15-16 months of age and can be responsible for a loss of condition and scouring at this time.
Again, the same worm burden pattern was seen during 1968 on a Southern Tablelands property but results from other areas are not yet available.