Effect Of Drug On Wool Growth

Press, Volume CI, Issue 29994, 1 December 1962, Page 6

Effect Of Drug On Wool Growth

In a trial in South Canterbury in which the new drug, thiabendazole, has been compared with phenothiazine, an interesting effect on wool production has been noted. The trial was carried out in the district last autumn and winter. Mr M. L. Cameron, farm advisory officer of the Department of Agriculture in Timaru, says that the lambs for the trial were selected

from a line of 300 Romney ewe lambs that were not doing particularly well. Before the trial began the tailend and the tops of the mob were drafted off and the 96 animals for the trial were chosen from the middle cut. Faecal egg counts from a sample of the trial lambs indicated thait worms were present in sufficient numbers to eb pathogenic, but that the counts were not particularly high. The main comparison in the trial was between phenothiazine and thiabendazole, but since selenium has given responses in this area high rate selenium .treatments alone and in combination with the anthelmintics were included. The treatments included selenium alone, thiabendazole alone, thiabendazole plus selenium, phenothiazine alone, and phenothiazine plus selenium. To eliminate any possibility of reinfestation and to obtain a reliable measure of the efficiency of the two drugs, three doses were administered at monthly intervals beginning at the end of March. At the start of the trial the remainder of the mob were drenched with phenothiazine and the trial lambs run with them.

"At the end of the first month all lambs had shown reasonable weight gains with the thiabendazole group 60 per cent, ahead of control,” says Mr Cameron. “The phenothiazine group was intermediate and 30 per cent, better than control. Loss Of Weight "During May, in spite of good feed conditions, all lambs started to lose weight. The noticeable feature was that the thiabendazole group lost only half the weight of the control group with phenothiazine again intermediate. Up to this time the lambs were grazing on lucerne-cocksfoot pasture with feed in adequate supply. In an attempt to improve thrift they were then shifted to ryegrass-white clover pasture.

"The end of June weighing showed that they were still losing weight and again the thiabendazole group were 30 per cent better than control. Phenothiazine dosed lambs were no better than control. Towards the end of the month, lambs had begun winter feeding, in this case, soft turnips, good lucerne hay to capacity and considerable pasture pickings in the run-off.

"By the end of July all lambs had started to recover with the thiabendazole and phenothiazine-treated groups gaining considerably more than control.

“Final weighings were carried out at the end of August when all groups made similar and satisfactory weight gains.”

Total weight gains from the end of March to end of August were 6.61 b for the control group, 18.21 b for the thia-bendazole-treated lambs, and 12.41 b for the phenothiazinetreated group.

“As can be seen, the total weight gains for the fivemonth period are not high,” notes Mr Cameron. “Although little work has been done in South Canterbury on the winter growth characteristics of hoggets there is some evidence from previous trials that hoggets do little more than maintain their bodyweight during the winter and probably lose weight in the early winter. This is probably of little moment providing they are reasonably healthy, as with the onset of spring, recovery growth is very rapid. “While all lambs gained or lost weight over the same periods, throughout the trial those lambs treated with thiabendazole showed a higher rate of growth than the other two groups. The advent of this very promising material would indicate that a reassessment of the role of nematode parasites will be necessary in this district."

Referring to the effect on wool production, Mr Cameron said th ait it was far more spectacular than on rate of growth. As at shearing the average wool production of the control group was 6.51 b per head, the thiabendazole group 7.91 b and the phenothiazine group 6.91 b. “Phenothiazine gave an increase of 0.41 b a head while thiabendazole gave an increase of 1.41 b. These increases would indicate that wool growth is even more sensitive to parasitism than is body growth. It seems possible that efficienit control of internal parasites may indirectly result in greater financial returns from wool than from improved lamb fattening. An increase of 20 per cent, in wool production over the period of the year when wool production is considered to be at a minimum represents a large gain. The possibilities during the period of the year when wool growth is at a maximum are considerable. In addition it may well be that parasitism in mature sheep, although not clinical, may be a limiting factor to maximum wool production as well as acting as a reservoir of infection for young stock. These possibilities will be investigated during the coming season.”