Fat-lamb Crosses in Canterbury

New Zealand Journal of Agriculture, Volume 79, Issue 3, 15 September 1949, Page 222

Fat-lamb Crosses in Canterbury

By

I. E. COOP and V. R. CLARK,

Canterbury Agricultural College,

Lincoln. (From a paper presented to the New Zealand Animal Production Society in May, 1949.)

'T’HE province of Canterbury, extending from the Conway River in the north "*■ .to the Waitaki River in the south and stretching back to the Main Divide, occupies 9| million acres and carries 5| million sheep, of which 3| to 4 million are breeding ewes. On the tussock-land hill country store sheep are produced, and on the plains fat-lamb production is associated with arable farming. Because of the relatively dry climate and cold winter, supplementary feeding of ewes in winter and of weaned lambs in summer is necessary on most fat-lamb farms. Over Canterbury as a whole fine-woolled sheep predominate, and there are approximately 3 fine-woolled halfbred and Corriedale ewes to every 2 Romneys, both on the hill and on the plains. These factors should be borne in mind when considering the fat-lamb industry of the province.

PROM an analysis of the proportion . of fat-lamb to breeding-ewe sires it is estimated that If million ewes are mated each year to fat-lamb sires and 2 million to halfbred, Corriedale, and Romney rams. Of fat-lamb sires used 60 per cent, are Southdown, 20 per cent, are Border Leicester, and 20 per cent, are Ryeland, Suffolk, English Leicester, and other breeds, The . considered opinions of experienced Canterbury farmers and fatlamb buyers place the proportion of lambs drafted fat off the mothers on fat-lamb farms at well below 50 per cent. An .analysis of lamb killings at all Canterbury freezing works puts the percentage between 30 and 35. From this it is clear that even for Southdown cross lambs the figure is well below 50 per' cent. ■ .tio This very brief introduction to the position in Canterbury serves merely to give a background to the experiments now to be described. It was decided to compare and investigate on a strictly comparable basis the relative merits of the Southdown and Border Leicester . as fat-lamb . sires, The Southdown is usually considered to be best suited for production of milk lambs of light weight and high quality and the Border Leicester for feeder lambs of heavier weight though of poorer carcass quality.

Design of Experiments The experiments were carried out over two complete seasons (1947-48 and 1948-49) at the Kirwee Experimental Farm, which was then on loan to the Canterbury Agricultural College, Lincoln, from the Department of Agriculture. Uniform lines of 5- and 6-year-old Romney and Corriedale ewes were randomised into the following groups, each of 60 ewes, Group Ram Ewe , £?,?«!!£«,„ x ~'j Border Leicester X Romney IV Corriedale X Corriedale V Southdown X Corriedale Vl Border Leicester X Corriedale ' Just before lambing each group was subdivided into two, one of which was placed on a high plane , of nutrin and the other on a low plane. The high-plane feeding, consisting of first-class pasture, was designed to produce a large percentage of lambs drafted fat off the mothers. The low-plane feeding,' consisting of poor pasture heavily stocked, was intended primarily to provide store lambs for subsequent fattening on rape and secondarily for comparison of breed crosses under poor feeding conditions, To make the sheep used as representative of the breed as possible an entirely new set of ewes bred on different country was used in the

second year and a new set of rams was also used. All the rams were bred at the college. All ewes and lambs were weighed at approximately monthly intervals.' The final weighing and drafting were done on one day. The lamb buyer who ' drafted the lambs was instructed not to take many “seconds” and not to, be more discriminatory with any one cross than with another. Individual carcass weights, grades, and measurements were made at the freezing works. The lambs could have been drafted on a purely objective live-weight basis of Southdown cross 651 b. and over, pure Romney and Corriedale 701 b. and over, and Border Leicester cross 751 b. and over. It is believed that this is more accurate, and a column representing the percentage of lambs that would nave been drafted on such a basis has been included in the tables. Results Obtained The results obtained for the highplane single lambs during the seasons 1947-48 and 1948-49 are given in Tables 1 and 2 respectively. Twins have not been considered, as the numbers in both seasons were very small. The number of singles per group averaged 20 with extreme variations of 15 to 25.

Low-plane Lambs Drafted Very few lambs were drafted fat from the low-plane groups. On an average the lambs were 10 to 151 b. lighter than those on the high plane. As an average over both seasons the Southdown increased live weight by 41b. in comparison with the pure breeds, and increased the percentage of single • lambs drafted fat from about zero to 35 per cent. The use of the Border Leicester ' increased live weight by a further 51b. over the Southdown, but with a drop to 20 per cent, drafted fat. Here the superior conformation of the Southdown enabled more to be drafted.

Rape Lambs The weaned lambs were fattened on rape for 7 to 8 weeks in both seasons. There were 20 to 40 lambs per group.

In Table 3 are recorded the liveweight gains and the carcass weights of these lambs. From the results quoted the following conclusions may be drawn: — 1. By comparison with the pure breeds the Border Leicester, increases live weight, percentage drafted, and carcass weight, whereas the Southdown increases percentage drafted only. 2. Comparison of the Border Leicester with the Southdown ,on good feed, shows that lambs by the former are invariably 101 b. heavier in live weight and 41b. heavier in carcass weight at the same age at weaning.

The percentage of lambs drafted has varied somewhat between seasons and between dams, but on average there has been no difference between the Border Leicester and Southdown crosses. 3. The percentage of second-grade crosses was low, and what variations there were between breeds do not alter the conclusions mentioned. 4. From live-weight data there is no evidence that the comparisons would have been altered J significantly by drafting earlier.

5. On the low-plane feeding the Border Leicester cross lambs had a 51b. live-weight advantage over the Southdown, but this was offset by a lower percentage drafted (20 per cent, as compared with 35 per cent.). This is a strong point in favour of the Southdown under... conditions of poor feeding. ' 6. The live-weight gains of feeder lambs on rape in a given time were consistently in the order Border . Leicester, pure breed, Southdown, though, the differences were significant in only one of the two seasons. Th?, carcass weights of the Border Leicester feeder lambs were 3| to 41b. heavier than those of the Southdown, with no differences in the percentage of seconds. This offsets the advantage of the Southdown mentioned in paragraph 5. 7. Comparison of the effect of the breed of ewe shows that lambs out of the Romneys proved to be superior to those out of Corriedales in live weight, percentage drafted, and carcass weight. Interpretation of Results The results of the trials described may be summed up by saying that in comparison with , the Southdown sire the Border Leicester sire gives a 10 per cent, increase in meat production, with little if any reduction in percentage drafted off the mothers and without loss in . grading. This applies both to milk lambs and feeder lambs and to lambs out of both Romney and Corriedale ewes. The trials extended over two seasons only and on one set of environmental conditions only. For this reason they are being continued at Ashley Dene (Lincoln College). Nevertheless, in spite of these limitations, it is believed that the trials have indicated something which has hitherto not been realised fully. New.: Zealanders have always been led to believe that the Southdown is the fat lamb sire without serious rival from any quarter. Indeed the good name of New Zealand lamb and the present, status of the fat-lamb industry in the country as a whole is to a large extent dependent on the use of the Southdown sire. The greatest care

must therefore be exercised in interpreting the results of the trials described. Accordingly several aspects of the Border Leicester-Southdown comparison must be mentioned. The Southdown gained its. popularity as a sire for the 28-361 b. lamb, which was in demand before the war and for which a differential price schedule and grading system were evolved. For such lambs there is still no rival to the Southdown, but if it is desired to produce more meat, it seems a little incongruous to encourage the production of lightweight carcasses. If the trials carried out over two seasons at Kirwee can be considered a fair and accurate comparison, it appears that meat production could be increased by at least 10 per cent, by no other means than using a different sire, a heavyweight sire in place of the lightweight Southdown.

It might be argued that the 10 per cent, more weight may not contain 10 per cent, more calories. Certainly at equal carcass weights the Border Leicester cross lambs contain less fat and hence fewer calories than the Southdown cross, but with a Border Leicester cross carcass 41b. heavier than the Southdown cross the difference in calorie content is probably small. A few Border Leicester cross lambs have been dissected and shown to contain approximately 1 per cent, more bone, i per cent, more fat, and 1£ per cent, less muscle than Southdown cross lambs 4 to 51b. lighter in carcass weight.

On the question of grading it should be remembered that in Canterbury there are only two grades, Prime and Second. .In the North Island, where there is a third and top grade, Down cross, there is no doubt that the Border . Leicester would be handicapped. The Border Leicester cross carcasses are longer in the leg and few would grade Down cross, whereas many of the Southdown cross carcasses would. This difference in quality grading, together with a higher weight grade, means that in the North Island the Border Leicester cross carcass is worth |d. per lb. less than the Southdown cross lamb. Instead of getting 4s. for the extra 41b. the North Island farmer receives Is. Bd. and the South Island farmer 2s. 4d. There is little doubt that if advantage is to be taken of this means of increasing meat production, the lamb-grading system must be revised so that the farmer is encouraged to produce heavier-weight lambs and is rewarded in proportion to the extra meat produced.

Throughout the Kir wee trials the Border Leicester sire has been used as representing the' heavy fat-lamb sires. Others may well produce a similar result. Suffolk, Shropshire, Dorset Horn, Ryeland, South-Suffolk and Southdown X Border Leicester, and other similar rams might be expected to produce heavier lambs than Southdown cross lambs. Whether they would give the same percentatge fat off the mothers has yet to be investigated. It is possible that more favourable results even than those achieved with the Border Leicester might be obtained from the heavy Down breeds, as they are less leggy and their lambs might grade better under the North Island grading system. Any change from the Southdown to the heavy sires must be slow, as the ram-breeding flocks of the latter breeds are few and small. Though a change in this direction should certainly be made if more meat is wanted, another but less tangible possibility remains to be explored. Some breeders maintain that the pre-sent-day Southdown is much smaller than it used to be 20 or 30 years ago. Such a belief would be difficult to confirm, but it suggests that Southdown breeders, having achieved conformation, might now concentrate on getting size into the breed. In other words, it may be possible to evolve within the Southdown breed itself a larger and heavier strain than that now in use. Such a procedure, if it is possible, would probably take

longer, but would have the advantage that there are already many Southdown flocks in the country and it would cause less disturbance to the present organisation of the fat-lamb industry. Basically, however, the problem lies in predicting the long-term fat-lamb market. For the next 5 or 6 years there is a guaranteed market, but what lies beyond? Will there again be a quota and a highly-selective market? If so, no move that would hinder a rapid return to the lightweight Southdown cross lamb should be made, but if world food shortages, and meat shortages in particular, are to continue for another 10 years or longer, as food production struggles to keep pace with world population trends and increasing standards of living, a different situation exists. For such a situation it seems that this country’s meat-pro-ducing potentialities are not being exploited to the full by using a lightweight sire. Probably in no place is there a brighter future for the heavy sires than in Canterbury. The low percentage of lambs drafted fat, the absence of a Down cross grade, the highly-seasonal nature of pasture production, the association of fat-lamb production with arable farming, and the presence of heavy sire studs within the province all favour continued and even greater use of the heavy sires; but if the alleviation of long-term world food shortages is taken seriously by the meat producers of New Zealand, increased meat production should be possible in all provinces.

TABLE I—HIGH-PLANE LAMBS, 1947-48. SINGLES ONLY. Average % % Drafted % Second Ram Ewe live wt. Drafted on wt. basis Av. carcass wt grade lb. lb. R X R 66.8 40 40 33.4 14 SD X R 67.8 70 65 35.4 7 BL X R 78.4 62 80 38.8 0 G X C 62.9 33 35 35.3 0 SD X C 62.3 33 42 33.6 ' . . • 0 BL X C 76.6 78 67 38.2 21 Note I. The percentage drafted (third column) is that drafted by the lamb buyer. The average carcass, weight (fifth -column) and percentage of seconds (sixth column) refer to this draft of lambs. The fourth column gives We percentage which would have been drafted on the objective weight basis mentioned. Note 2.- No corrections have been made for male to female ratio. 9: Note 3. The average age of all Southdown and Border Leicester cross groups was 111 days at drafting, and that of Romneys was 109 and Corriedales 113 days. <

TABLE 2—HIGH-PLANE LAMBS, (948-49. SINGLES ONLY. Average % % Drafted % Second Ram Ewe live wt. drafted \ on wt. basis Av. carcass wt. grade lb. lb. R X R 78.1 83 78 - 37.5 7 SD X R 77.9 100 100 37.1 0 BL X R 88.5 100 100 41.4 5 C X C 67.6 60 / 43 34.0 33 SD X C 72.9 90 85 35.7 5 BL X C 82.5 74 70 39.9 0 Note I. See note 1 above. Note 2. See note 2 above. Note 3. Because of the Christmas-New 'Year break the lambs were oh ,an . average 121 days old at drafting, with extreme group averages of 120 and 122 days. It could be said that the lambs should have been drafted earlier. They were, weighed at 90 days and on the 65/70/751b. live-weight basis already mentioned the percentages drafted would have been as follows: R x R 67 per cent, SD x R 69 per cent., BL x R 70 percent, C x C 5 per cent., SD x C 59 per cent., BL x C 35 per cent. ;

TABLE 3.—LIVE-WEIGHT INCREASES OF STORE LAMBS ON RAPE (lb.) 1947-48 1948-49 Av. Initial Av. live- Av. carcass Av. initial Av. live- Av. carcass Ram Ewe iivewt. wt. gain weight live wt. wt. gain weight R X R 57.3 24.6 36.3 56.3 25.0 35.8 SD X R 58.8 21.9 37.9 53.0 24.0 35.9 \ BL X R 65.2 27.3 41.5 62.4 25.9 40.5 C X C 56.8 23.0 36.1 55.9 21.8 35.2 SD X C 55.6 21.7 35.7 53.9 21.4 35.3 BL X C 60.4 25.4 38.6 60.4 25.5 38.9

Spraying Weeds in Growing Crops On page 36 of the July issue of the “Journal” the statement was made that linen flax could be safely sprayed with light applications of hormone weedkillers. Recent work at the Agronomy Division, Department of Scientific and Industrial Research, has shown, however, that this may result in considerable damage to the fibre, and farmers are therefore advised not to use hormone weedkillers on linen flax crops in the meantime.