High Hopes Held For Use Of Selenium

Press, Volume XCVIII, Issue 28950, 18 July 1959, Page 9

High Hopes Held For Use Of Selenium

On present evidence it seemed selenium was likely to be the answer to white muscle disease in lambs and the associated dry ewe problem, Dr. J. W. McLean, head of the veterinary department at Canterbury Agricultural College, told members of the Lauriston Fann Improvement Club at an open forum at the college following a field day recently. It did not, however, appear to be the sole solution to the ill-thrift problem as it was seen in many parts of the country. While there had been Some growth responses in lambs to selenium it did not make bad lambs good, he said.

Dr. McLean spoke after he had listened to a club member make what he described as one of the most explicit and precise statements of the problem facing many farmers to-day. The farmer said that in the last lambing season he had started off with 16 per cent, of dry ewes and since tailing he had lost 250 lambs from white muscle and ill-thrift. To get lambs to “creep’* into the works fie had had to feed 700 bales of hay and then he had had six or seven out of each draft rejected for pleurisy. Over the years he had raised his carrying capacity from 1100 ?wes to 2500 ewe equivalents and he could get the grass to grow but the problem was to get the lambs to thrive. Too Much Stock? Did he carry too much stock? Had he upset the balance of tl}e soil by too much topdressing? Was he going to be faced with a dry ewe problem again next lambing season? Dr MCLean said that the problem was not primarily associated with increased stock carrying capacity though it often occurred where there was high stocking and use of improved farming techniques, but there were other properties where these very same things had been done and as yet there had been no stock problems nor did he think that there would be. When he was told that three tons of lime to the acre had been spread on this farm. Dr McLean said there could be trouble where the lime or pH status was both low and high. The point was that as yet there was still very little known about ill-thrift. When Dr. McLean said that the dry ewe problem and white muscle disease in lambs were likely to be overcome by the use of selenium, Mr Peter Falconer, field officer to the club, said that there had been a significant response to selenium in lambs on the property in the late part of the last season. This year there was also a trial with selenium being used in ewes and if necessary it was hoped to follow up again with use of selenium in lambs. Dr. McLean said that there was also a trial at Ashley Dene in which it was hoped to compare the growth rate of lambs from ewes treated with selenium with lambs from untreated ewes. Groups of ewes had been treated before tupping and other groups 3$ days after raddling which was considered might be the best time.

It was their guess that if selenium affected the fertility of the ewe it would be in the early stages of pregnancy, said Dr. McLean. The trouble in the ewe apparently lead to reabsorption of the foetus so that to all intents it was not known whether the ewe was in lamb or not. According to Mr Lindsay Morris the ewes took the ram. If this was the situation, the question of whether there would be a dry ewe problem this year would depend on when the selenium was given to the ewe—if it was late in pregnancy then there was likely to be' trouble again. Dr. McLean said that he believed that the incidence of white muscle was greater in lambs from two-tooths than from older ewes. Give Up Breeding Professor A. H. Flay asked whether a farmer faced with this problem should not give up breeding for flock maintenance and buy in ewes. Dr. McLean said that such a course had been suggested to a farmer who in the last season had lost 75 per cent., of lambs born_ to two-tooth ewes within three days. In Kaituna Valley a higher lambing percentage had been obtained from bought-in ewes, said Mr H. E. Garrett, and here it had been established last year that copper status was very low, which he understood reduced fertility. Dr. McLean said it was possible that high superphosphate dressings might have a harmful effect on stock health in that there was some evidence of the availability of selenium being suppressed by high sulphate ion. Stating that the problem needed to be tackled from a fundamental point of view, Dr. McLean said that it would be necessary to study the changes in pasture composition from one season to the next, from one year

to the next and of different pasture species. Dr. McLean said that there was sometimes a ten fold difference in the non-protein nitrogen fraction of grass and a study was being made of these fractions to determine whether they were toxic. “In the presence of dull overcast, warm conditions there is something that the grass has or does not have which is pretty closely related to the problem of ill-thrift,” he said. Mr Garrett asked whether it was just an accident or not that a farmer on light land had in •the last season been able to fatten 800 of his own lambs and another 1500 lambs on top of that when for more than 20 years he had been using blood and bone manure. Dr. McLean said that under the farming system in New Zealand fertility build up was in organic matter which was fairly fixed in. composition. It was not known whether there was any end to this building up process and at Ruakura by putting more stock on an area an attempt was being made to find out whether there was an upper limit Apart from cropping there seemed to be no way of -using up that bank of fertility. ; On farms where there was a history of lamb troubles, Professor Flay suggested that an endeavour might be made to quit every lamb by Christmas, even if it meant having two or three per cent rejected as thins.