What To Do About Over-Fat Lamb Problem?

Press, Volume CVI, Issue 31209, 5 November 1966, Page 10

What To Do About Over-Fat Lamb Problem?

The ironical situation has now arisen that some people in Canterbury are thinking about how to stop some lambs growing so fast and putting on fat that results in them being graded as over-fats and their owners suffering a heavy financial penalty. This extraordinary position is the result of an extremely good season for lamb growth a well-placed rainfall in the spring that produced an abundance of feed and then some hot weather, and there is every sign meantime that as the weather gets warmer and more summery the lambs will grow better and better.

“There is a great deal that we do not know about overfatness because virtually all the research work done in the past has been on how to fatten lambs,” Professor I. E. Coop, professor of animal science at Lincoln College, said this week, “so those who control expenditure of funds on research might now see that some is devoted to determining why some lambs put on too much fat” But of course the problem confronting a proportion of farmers, at least, is what to do now to counter this problem.

On this subject, Professor Coop said that one thing the farmer could do was to draft earlier and at lighter weights. A farmer could also draft more frequently, but an alternative to going through the whole mob more frequently would be keep the single lambs separate from the twins during the first 10 to 14 days of lambing so that the farmer would then only need to draft the single lambs early. Another possibility would be to wean only those lambs which it was suspected might be over-fat and draft them, say, two weeks later. This would only be done with those lambs which it was wished to check. It might also be possible to help this situation by going in for a higher lambing percentage—that was increasing

the number of twins—or growth rate of the single lambs might be suppressed by a higher carrying capacity. Still another possibility was to change the breed of sire to the larger, later-maturing and leaner breeds. But some of these suggestions could lead to a whole lot of conflict

If a change was made to later maturing breeds of rams, then the conformation of the lambs would not be so good, and it was his view that ultimately a decision had to be made whether the best conformation was wanted, in which case producers would always have to live with the problem of over-fatness, or whether a slight reduction in conformation could be tolerated —this involved a departure from the Southdown in a big way as a result of which the over-fat problem would be reduced.

Another point of conflict arose from the farmer deciding to take his lambs to the highest possible weight and risking a few over-fats rather than having no over-fats and killing at an unduly light weight. Professor Coop said that this problem arose in a good season like this one, but he had no doubt that Canterbury farmers would continue to produce their best lambs in drought years. Mr A. R. Watson, district

manager for Thomas Borthwicks in Christchurch, also expressed some thoughts on the over-fat lamb issue this week. Export lamb killings so far this season had produced a small but significant percentage of lambs rejected for export because of over-fatness, he said. The significance of this was that it was unusual to see many lambs in the October killings classed as overfats, and from this and general observations it was quite obvious that most lambs had done particularly well during the last three to four weeks. There was still an abundance of feed in most districts, perhaps more feed for this time of the year than for many years, and as this

feed dried off during November lambs would undoubtedly continue to thrive and fatten quickly. The present conditions, combined with an increasing awareness of over-fatness in grading, could well create a serious problem for some farmers drafting large numbers of lambs “off the mother” during November and December. Unless some action was taken now there would be some drafts with a high percentage of lambs rejected through being overfat.

Obviously there were many farmers who would not have this problem at all because of the class of land they were on, the level of fertility of their farm, their stocking rate and general management.

The farms most likely to be affected would be those with an abundance of clover-dominant feed at present, but which would have a tendency to dry off from now on, and where the farmers were planning to kill large drafts off the mothers during the next few weeks. "The over-fat lamb is really of no use to either the farmer, the freezing company, or the customer, and as these lambs become over-fat by being held for too long on too high a plane of nutrition the best course of action would seem to be: “(1) Avoid large drafts as these will invariably contain lambs which have been held

too long and could result in a substantial reduction in a farmer’s revenue. “(2) Draft a few lambs as this is the best method of ascertaining their weight and condition. “(3) In those cases where it appears that the problem is likely to be severe there can hardly be a feed shortage and the best course could well be to wean early and grass fatten the remaining lambs. There is much less likelihood of over-fats in

weaned lambs than in lambs off the mother. Lambs which are already over-fat can be retained on the farm as weaned lambs and will usually grade at a later date.” At Ashley Dene, Lincoln College’s light land property, there had been no over-fats, Professor D. J. Stewart, professor of farm management said this week. “That might have been good luck,” he added. But Professor Stewart also noted that not much was

known about this problem and there were no consistent recommendations that could be made. But they were recommending frequent drafting and taking off the tops all the time. He was suggesting to people with whom they were in contact and they were also aiming themselves to draft at 331 b or 341 b and about every 12 days. Once a lamb got over 361 b, he said, it had to be taken to 421 b before it broke even price-wise again.