STOCK PARASITES.

Waikato Times, Volume 121, Issue 20272, 14 August 1937, Page 26 (Supplement)

STOCK PARASITES.

RELATION TO PABTURE9. GRASSLAND CONFERENCE (No. 1) The stock parasite, position in relation to pasture was discussed by Mi V. G. 'Hole, Parasitologist at the Department of Agriculture’s Veterinary Laboratory, Wallaceville, In a papei given before the annual conference o) the New Zealand Grassland Association at Dunedin this- week. Mr Cole said that no clearer demonstration could be desired of the vital relationship obtaining between the condition of grasslands and the prevalence of internal parasites in sheep, than this last year’s widespread losses ol hoggets from worms. Consideration of the high standard of efficiency attained at the present time in pasture improvement and in methods of supplying supplementary feed, only made clearer the necessity for learning more of the relation of the parasite to permanent pasture, if this deterioration due to parasites was to be prevented. And whilst an effective method of medicinal treatment was still in most cases admittedly, lacking, it was obvious that proper management of the pasture was also required before the problem could be solved. A high standard of pasture management was no less essential than Is intensive pasture improvement. The influence of proper feeding was a primary factor in controlling parasitic diseases. The severity of the disease amongst hoggets was definitely influenced by the nutritional state of the

young growing animal, and an available supply of feed all the year round would prevent lambs suffering any check until they were twelve months old, after which time they became relatively immune to the effects of the parasites. The importance of nutrition was again seen in the case of older sheep which had developed a resistance to the effects of the large stomach worm, because this immunity might be broken down if the sheep were exposed to under-nutrition, which resulted during a period of drought. Besides building up a powerful resistance, a plentiful supply of feed lessened the daily grazing period of the sheep and so decreased ltie risk of infection. Means of Control. Until other effective means of controlling Internal parasites were available, therefore, Improved nutrition offered tho only solution, and it was to pasture Improvement and improved methods of supplementary feeding that they must, look In future in order to stop the present deterioration duo to increased parasitism, caused by undernutrition, and to allow for greater production than ever before. However, where the rate, of infection was high, as in tho rase of sheep grazing on heavily contaminated pastures, adequate feeding alone might not bo a NUtilrient safeguard against the development, of disease because a sufficient, thorough knowledge of proper pasture management was essential. Sown pastures were capable of being stocked at the. rate of ten or more sheep to the acre, without being overstocked. However, if the sheep were not rotated or tho numbers reduced and Hits heavy stocking was persisted j with, it, would not, be long before the more palatable species of plants were I eaten out with the result that the sheep were soon exposed to undernutrition. Given unfavourable seasonal ' conditions, grave overstocking might J result and as a oonsequence of this! lack of sufficient feed the resistance of the sheep became lowered. In addition, heavy contamination of tho I ground resulted and the sheep became < exposed to u heavy rate of infestation. I Roth factor.-, combined, resulted tn do- j ing shown and unless somelhmg was or re hieing tho numbers, mortality would result. Where overstocking no- j * hit- d on impi o\ ed pastures tin- risk j gre d»T Ih in mi ii.ilur.il pastures, duo ! Eii the increased rale of slocking which Wis .it times out Of all proportion to | clos.lv related to o\crs locking, ;in .) I led to a maximum ml dm of iiifertim j t< nded * i nibble eerl.im pi mp \r,v|

!ong periods of stocking should he j j avoided and cattle used to rlean up the iroughage. j Tlie spread of the large stomach j worm was limited by temperature parI tfoularly and required a summer rab>I fall. L _ j It was definitely not a winter pararr pile. On the other hand the small irtestlnal parasite and Us close relation •v the small stomach worm, were both ; ," r capable of developing during the winter ‘ and would extend into areas with very t _ lew temperatures. Just exactly winl part heavy frosts played on the devcdopnif’.nt of this parasite was not exactly known. The superabundance of herbage )Q which followed a wet season favoured n (he development of the parasites on pasture. In England the view had been expressed that clover pastures were 1( $ a greater source of infection than grass pastures because the structure of a clover plant was such that para1Q sites could climb up the simple leaf _ stalk and reach the trifoliate leaf wlthout being short-olrculted in any way, 0 whereas the blade and sheath of a q shoot of grass tended to divert the ascending parasites to the underside I- of the lower leaves, which were usually ,t avoided by the grazing sheep. d EfTlcaoy of Ploughing. e The view held that ploughing a padn dook would destroy the infective ; parasites it harboured was entirely ins correct in the light of recent knowo ledge. No actual experimental work j e had been carried out which showed the i i- effect of liming and topdressing on the e survival of parasites, but the applica-

3 j tion of one ton of salt per acre to a 1 [ pasture had no effect In reducing tho £ soil infestation. Although burning was , not a practice to be recommended, if )' carried out with due respect to tho . seeding of grasses so as to prevent l deterioration, it would destroy an inl festation present. Paddocks left un- - stocked following a burn would prove | - invaluable for use by lambing ewes i and young sheep. 3 From time immemorial veterinarians ; had administered medicines in the » treatment of disease and more recently - they had advocated the use of > drenches tn the control of parasitic 1 j diseases. However, without detracting I 100 much from the cfllcacy of this measure, It was only of secondary im- [ I portanco in any scheme of control to j protect hoggets from the ill-effects of tho small intestinal worm. Although ) the bluestono and nicotine mixture was j I widespread tn its use, Its efficiency was J lew aealnst tho latter parasite and ( should hr* considered only a supplementary measure, to adequate nutri- ! Hon. Also, tho nicotine fraction made ! the mixture a dangerous one, where 1 weak sheep were concerned. Tn addition, for satisfactory results, treatment should ho commenced at weaning time and repeated every three weeks until tho following spring. **