Some Aspects Of Lamb Parasitism

Press, Volume CI, Issue 29744, 10 February 1962, Page 7

Some Aspects Of Lamb Parasitism

ANOTHER growth retarding factor besetting lambs after weaning, especially after regular warm showers during February and April, was parasitism, said Mr Hill in his review of his work at Winchmore. The worms responsible for damage at this time of the year were largely trichostrongylus and ostertagia, for which phenothiazine was used. This drug was particularly effective against the former and moderately so against the latter. Monthly-phenothiazine dosing during January, February and March in the preceding seasons had given liveweights in April 51b to 61b greater than that of untreated mates. In both years three doses were given and it was clear from the nature of the responses that at least two doses given at the optimum time would have been necessary to obtain the same result. thus making the venture an unprofitable one. Cost and weight gain were, nevertheless, not the only factors to be considered. In one of the stocking rate trials conducted last season a worm problem had arisen in the late summer. Adequately fed lambs had only slightly been affected while those which had been reared on only short rations scoured, lost weight, and several died. A single dose of phenothiazine restored health to normal, confirming conclusions reached during the 1930’s that worms, though of minor importance to well fed lambs, could kill lambs already weakened from other causes. Surprising A surprising feature of the phenothiazine trials had been the growth stimulation induced even during almost drought conditions in the early summer months. This indicated that either the lambs were being infected by worms under these grossly unfavourable conditions, or phenothiazine was exerting its effect in some other direction. A trial conducted in the current season on unweaned lambs had failed to demonstrate any beneficial effects of phenothiazine dosing after worms had been eliminated by the use of promintic. It was possible that iodine used as a catalyst in the manufacture of phenothiazine and which was a contaminant of the commercial product was responsible for the effect. It was highly improbable that the selenium content of phenothiazine or a selenium-

like action of the phenothiazine molecule itself accounted for the peculiarity, since the effects of the two drugs were strictly additive. In one of last season's trials conducted from December 8, 1960, to April 12 last year, untreated lambs gained 31.61 b, selenium dosed 33.51 b, phenothiazine dosed 37.51 b, and lambs treated with selenium and phenothiazine 39.61 b. Thus the selenium group gained 1.91 b more than the controls, the phenothiazine group headed the controls by 5.91 b, while where both treatments were given the gain was B.olb. Developments Mr Hill said that promising developments were now taking place in the field of worm drenches and after 20 years phenothiazine was being overshadowed by several drugs. Important advantages of the new drugs were low cost, low dose rate, an extremely high level of efficiency and non-wool staining properties. It was not a very inspiring experience to see phenothiazine - dosed lambs giving the appearance of having been treated by means of a stirrup pump.

Results of preliminary drenching trials on the station had indicated that one of the new anthelmintics, kempak, was considerably more effective than phenothiazine. Ewe Effects.— As mentioned earlier moderately severe differences in ewe treatments before lambing were found to have little effect on lamb performance. Post-lambing treatments which affected lamb growth rate, however, also affected ewe growth rates and adequate levels of feed permitted substantial weight gains before weaning while j poorer regimes induced weight losses. Selenium administered to ewes before weaning significantly increased both the weight of the ewes and that of their lambs. Selenium In one typical case the weaning weights of seleniumtreated ewes was 6.91 b heavier than that of controls and lambs of treated ewes were 3.51 b heavier than those of untreated ewes. The increased lamb growth rate was probably due to a combination of increased milk production and a slight elevation of milk selenium. A trial which illustrated the importance of selenium in lamb growth, fleece weight and ewe fertility was one in which selenium and copper were administered to sheep at monthly intervals from before weaning as lambs until a month before they were due to lamb as two-tooths. The trial started in November, 1959, and the group was shorn as hoggets in August, 1960, when the controls clipped 8.31 b, the selenium group 9.01 b, the copper group 7.91 b, and the selenium and copper group 9.31 b. Liveweight gains up until just before shearing were 52.21 b, 59.51 b, 501 b, and 60.11 b respectively. Live-weight gains during the ensuing 12 months until pre-lamb two-tooth shearing were 451 b, 41.91 b. 46.31 b and 45.91 b. Fleece weights were 9.71 b, 10.21 b,

9.81 b and 10.91 b. Lambs bom to ewes lambing were 127, 128, 121 and 137 per cent. The increased fleece weights in both years were due entirely to increased staple length. Quality in all groups in both years averaged 50's. Two most interesting factors were the beneficial effects of using copper and selenium together and the fact that the two-tooth fleedes were affected by the treatments while live-weight gains were not