GOAL OF HIGHER FERTILITY

Press, Volume XCVIII, Issue 29016, 3 October 1959, Page 8

GOAL OF HIGHER FERTILITY

Breeder’s Warning About Hogget Experiment

At this year’s Massey College sheepfarmers’ conference Mr T. S. Ch’ang, lecturer in sheep husbandry, described an experiment aimed at determining the fertility of a ewe while she is still at the hogget stage by running a teaser ram with her. Mr Ch’ang, reporting the interim findings of this experiment, said it had been found that twotooths which had “cycled” or “come on heat” at the hogget stage gave 30 per cent, more lambs at weaning than two-tooths which were not marked by the teaser rams, Mr Ch’ang’s findings were subsequently reported on this page.

Mr Arthur L. Wheeler, of Leedstown, Marton, who is one of the country’s leading Romney stud breeders, has now written to “The Press” warning that this procedure instead of raising lambing percentages may result in lower percentages over a period of years, in that hoggets which “cycle” earliest and most frequently may be the better developed single lambs and that as a result twin lambs which have a higher breeding potential over a period of rears may be discarded from a flock.

Mr Wheeler comments: "If farmers adopt this practice of running teasers with their whole [ line of ewe hoggets, and in prac- j tical application they must do just this, and should it be ultimately ! established that early well-grown lambs ’cycle’ earlier than less well-developed twins, then there is a grave danger that the farmer is being led or misled into retaining early single ewe lambs and into parting with his most productive females—to the very serious detriment of the industry and New Zealand. “The experiment described by Mr Ch’ang consisted of running vasectomised rams (teasers) with 100 ewe hoggets and recording the number of times each hogget ‘came on heat’ or 'cycled,* to use Mr Ch’ang’s own very apt term. When these 100 hoggets became two-tooths they were mated in the ordinary way and the resulting lambing percentages were so very much in favour of those ewes that had ’cycled’ most often as hoggets that at first sight the result is most impressive, but that first look is misleading. Whole Line

“This autumn we ran teasers with our whole line of over 500 ewe hoggets—not with just 100

hoggets that were possibly selected by Mr Chang for evenness (but 1 do not know) but which were certainly, as their weights proclaimed, a very even line of exceptionally well-grown sheep. This autumn was not a particularly favourable one here for hoggets and just what effect varying seasonal conditions might play from year to year I do not know, but such factors could easily cause very important differences. but again no such possibility was mentioned. Points Noted "We have not recorded, as Mr Ch’ang so rightly did. the number of times each hogget has ‘cycled* but we have noted (1) those hoggets that ‘cycled’ early, which would automatically include most of those that would ‘cycle’ most often, (2) those hoggets that ‘cycled* at all, and (3) those hoggets that did not ’cycle’ at all.

•‘Among those hoggets that ’cycled’ early we have found an undue proportion of early single ewe lambs and among those that have not ’cycled’ at all there is an overlarge proportion of twins that are still comparatively backward in weight and development. At the end of the season 50 per cent, of all singles have ‘cycled’ but only 40 per cent, of all twins nd many of these are among those that ‘cycled’ late and therefore probably only ‘cycled’ once, but in one specially well done group of 50 hoggets, whose body-weight is well above average, no fewer than 70 per cent, have ‘cycled’ The hoggets that ’cycled’ early averaged 71b heavier and those that ‘cycled’ late averaged 41b heavier than the general average weight. Of the hoggets that were lambed in the first four weeks of lambing more than 50 per cent, ‘cycled’ whereas fewer than 40 per cent, of the later lambs ‘cycled.’ “•Rather Different” “A rather different, but possibly very significant light is thrown on the picture after the hoggets have been sire grouped (not mentioned by Mr Ch’ang). Of all daughters of one sire 63 per cent, have ‘cycled’ but of another sire at the other end only 30 per cent, have ’cycled.’ “I think myself that body weight will be found to have an imnortant correlation with genital maturity at the hogget stage and with lamb production at the two-tooth stage, but there are many anomalies, possibly dependent on parentage (sire grouping)

‘‘ln reply to a question Mr Ch’ang stated that he had noticed no difference in lamb production as between singles and twins." said Mr Wheeler, who proceeds to give details of all lambs dropped over four seasons by ewe lambs born in 1953 at Leedstown and grouped for breeding potential on the basis of the total production of their nearest three dams. The details of this survey are:

Group 1 (breeding potential 109 to 129 per cent.): 1955 as twotooths 121 per cent., 1956 133 per cent, 1957 121 per cent., 1958 129 per cent., overall production 126 per cent.

Group II (breeding potential 130 to 159 per cent.): 1955 135 per cent., 1956 133 per cent., 1957 152 per cent., 1958 179 per cent., overall 150 per cent. Group 111 (breeding potential 160 to 175 per cent.): 1955 152 per cent., 1956 143 per cent., 1957 166 per cent., 1958 171 per cent., over-all production 158 per cent. Group IV (breeding potential 175 per cent, upwards): 1955 130 per cent., 1956 130 per cent., 1957 186 per cent., and 1958 200 per cent., over-all 162 per cent. A Comparison "This picture shows that as twotooths the group I ewes produced nearly as many lambs as group IV. but at the end of four years group I are 36 per cent, behind group IV. One hundred ewes of .group I would produce 504 lambs in four years whereas 100 ewes of group IV would produce 646 lambs in the same time. “While in Britain in 1954 I learned that their most fertile breed of sheep is the Clun Forest breed, of which some flocks regularly produce round about the 200 per cent. (I heard over 210 per cent, mentioned) and I was assured that their high fertility was, and is, based on the continuous use of twins for generation after generation. Incidentally the Clun Forest breed, though certainly not wool-blind, is not nearly so open faced as either the Cheviot or Border Leicester, but at present far surpasses either of these breeds for fertility."

After noting the possible dangers of the most productive ewes being discarded under Mr Ch’ang’s system, Mr Wheeler states that he has the permission of Mr Walter Edgecombe, of Longridge, Hastings, to give his experience “In the bad financial 1930's Mr Edgecombe had to put the fat lamb buyer through his ewe lambs as well as his wether lambs so that most of his early ewe lambs were sold leaving him to select in due course the best of those remaining, including a big proportion of twins, for eventual inclusion in his flock. After five years of this Mr Edgecombe found that the percentage from his two-tooth ewes was still very much on a par with that of his neighbours, but that his over-all percentage had risen 18 per cent, above his neighbours whereas previously his percentages for years had been on a par with others. More Information “Though Professor John Hammond, of world-wide animal production fame, was so kind when last in New Zealand to express approval of lines adopted here in efforts to increase percentages, I nevertheless regret putting any figures at all before the public at this stage,” says Mr Wheeler. "In four or five years’ time information, both here and elsewhere, will be much more complete. “Any farmer who can draft his twins from his singles will, I believe, find the procedure (Mr Ch’ang’s) of value, but meantime I feel that fellow farmers should not be left in ignorance of the danger that this procedure now recommended by Massey College, if not used m conjunction with twin knowledge, will, I believe, surely decrease and not increase our over-all lamb production,” concludes Mr Wheeler.