H—29

Percentage of Lambs Carrying Infestations of Ostertagia, December, 1947, to February, 1948

Infestations with Ostertagia were also widespread and heavy infestations (over 2,000) were not very common. The range of Ostertagia extends further south than that of Hcemonchus. Liver Fluke in Bay of Plenty. —The presence of liver fluke in small areas in the Bay of Plenty has been confirmed „ It has occurred on farms near Whakatane on which many miles of watercourses occur. For this reason attempts to control the intermediate host snail (Myxas ampulla) would prove very difficult and uneconomic. An excellent response to carbon-tetrachloride drenching has been obtained, and regular drenching once or twice per year should keep the parasite under control. There is a history suggestive of black disease in this area, but the diagnosis has not yet been confirmed. If black disease is present, vaccination will be advisable. Regurgitation of Tablets Dosed to Sheep.—As a result of reports from Australia that a proportion of phenothiazine tablets dosed to sheep was regurgitated some time after dosing, an attempt was made to determine whether the same problem existed in New Zealand. Groups of sheep were dosed with two types of tablets. None of the tablets in use in New Zealand was regurgitated, but 14 per cent, of another type of tablet was. The difference is due to the rates at which the tablets disintegrate in the rumen. Phenothiazine Drenching.—On a property in the Waikato where a heavy hogget mortality (20 per cent.) was experienced during autumn and winter and where all the surviving animals were unthrifty, a drenching experiment was carried out comparing two dose rates of phenothiazine with untreated controls. At the end of August the hoggets were weighed, drenched, and samples of faeces obtained for worm-egg counts. Five weeks later the animals were weighed again and further fsecal samples obtained. The results are summarized in the following table :

89

District. Number of lambs Examined. Number of Worms. 0. 1-500. 1 501-2,000. 1 Over 2,000. Per Cent. Per Cent. Per Cent. Per Cent. North Auckland 31 9 43 39 9 Waikato 116 10 38 43 9 Poverty Bay 93 17 42 30 11 Taranaki 90 15 50 32 3 Southland 77 21 33 30 16

— Group I: 15 Gramme Phenothiazine. Group II: 30 Gramme Phenothiazine. Group III: Undrenched. Mean body weights— 31st August, 1948 4th October, 1948 50-8 lb. 61-3 lb. 50-8 lb. 61-9 lb. 51-4 lb. 61-0 lb. Gain 10-5 lb. Il l lb. 9-6 lb. Mean egg counts— 31st August, 1948 4th October, 1948 Percentage reduction 622 e.p.g. 262 e.p.g. 58 per cent. 851 e.p.g. 462 e.p.g. 46 per cent. 856 e.p.g. 843 e.p.g. 1 • 8 per cent.