RAM performance study

Press, Volume XCVII, Issue 28542, 22 March 1958, Page 9

RAM performance study

Several Breeds Compared With Southdown

The results of further studies of the relative performances of rams for fat lamb production made at Canterbury Agricultural College by Professor I. E. Coop and Mr V. R. Clark of the animal husbandry department have been published in the “New Zealand Journal of Science and Technology.” They show that in relation to the Southdown, the most widely used sire, the heavy sires like the Suffolk, Border Leicester and the Dorset Horn increase weaning and carcase weight but give lambs of inferior conformation while the medium range of sires such as the Hampshire Down, Dorset Down, South Suffolk, Border Leicester-Southdown cross and the Ryeland are in a sense a compromise between the heavy-weight sires and the Southdown producing lambs superior in weaning and carcase weight' and only slightly inferior in carcase conformation.

The scientists are able to say that the Southdown occupies a unique position in the scale or classification of sires. “It stands apart from all others that have been tested in this and the previous series of trials as a result of its excellence for the production of light-weight lambs. Relative to other sires it produces lambs with the slowest growth rate as measured by live-weight gain, the lowest carcase weight, but with the best conformation. The tests now described relate to studies in 1953 and 1954 when Suffolk, Border Leicester, Hampshire, Dorset Down, South Suffolk, Border Leicester-Southdown cross and Southdown sires were crossed over Corriedale ewes and in 1955 and 1956 when Suffolk, Dorset Down and Southdown sires were used with Corriedale and Border cross ewes. In the latter two years attention was paid to performance at earlier drafting in view of the current premium for light lambs.

Higher Growth Rate Discussing the results of their work, Professor Coop and Mr Clark say that as they had found previously the heavy sires—the Suffolk and Border Leicesterhad conferred on their progeny a high rate of growth. In terms of weaning weight the increase over the Southdown had been 81b (rather more for singles and less for twins) when the lambs were taken to about 110 days of age but when they were weaned at 86 to 95 days the increase was only 41b. The medium sires—the Hampshire, Dorset Down, South Suffolk, and Border LeicesterSouthdown—had given increases in weaning weight of 5 to 61b at 110 days and 3 to 41b at 86 to 95 days. Of these four the Hampshire and Dorset Down had given rather greater growth rates. Turning to percentages I>f lambs drafted fat off the mothers the workers say that even during the years of early drafting the Suffolk and Border Leicester rams gave as high a percentage (about 80 per cent, mean) as the Southdown in single lambs. The Suffolk and Border Leicester lambs had, however, not graded as well as the Southdowns, so that when the percentage was expressed in terms of prime lambs only the two heavy sires were definitely inferior—the mean percentage being 45 per cent, compared with 66 per cent, for the Southdown, and this difference had been about the same in all four years. In twin lambs the Suffolk and Border Leicester had been inferior to the Southdown, both in total lambs drafted Regardless of grading (40 as compared with 50 peg cent.) and in prime lambs only drafted (11 compared with 26).

Medium Group Within thp medium group of sires the Border Leicester-South-down and .the South Suffolk in the two years they were tested gave percentages of total lambs drafted and primes only drafted which were the same as for the Southdown in respect of single lambs, but in the case of twin Hmbs both the total drafted and primes only drafted were slightly lower than for the Southdowntotal drafted 30 to 40 per cent, compared with 50 per cent. On the other hand, the Hampshire and Dorset Down had given a higher percentage of single lambs drafted —89 per cent, compared with 77 per cent, for the Southdown—but for prime lambs only the percentages were identical at 66. The Hampshires and Dorset Downs had also recorded the same percentage of twin lambs drafted, but their proportion of prime twins was slightly inferior to the Southdown —21 per cent, to 26 per cent. Professor Coop and Mr Clark point out that it was significant that in all of the trials fewer second grade lambs had been taken from the Southdown. This was because the drafter hesitated to take very light 24 to 261 b second grade Southdown lambs, but would draft lambs of equal conformation and fatness by the heavier sires because these lambs had more weight The mean increase in the carcase weight due to the Suffolk and Border Leicester rams was 3.31 b in both single and twin lambs drafted rising to' 4 to 51b when prime carcasses only were considered. These differences were smaller in the years of very early drafting and larger in those of later drafting. For example in 1954 and 1955 the gain in both single and twin lambs drafted was only 21b, but in 1953 and 1956 increased to over 41b. The four medium sires gave increases, which among themselves were of the same order of magnitude. The means of the four years .were: single lambs 21b, prime singles 2.81 b, twin lambs 21b, prime twins 3.31 b. Again the 21b differences for single and twin lambs were down to IJlb in the years of very early drafting and up to 2jlb in 1954 and 1956.

Southdown Superior Studies of conformation based ’on the ratio of width of hindquarters to leg length have shown that the Southdown is superior to all other sires in producing a . well filled blocky hindquarter This ratio has varied from 0.94 to 0.96 for the Southdown, from 0.87 to 0.90 for the Suffolk and Border Leicester and in the case

of the medium or intermediate group from 0.91 to 0.94. Within this medium group the Dorset Down and Hampshire tended to be slightly better than the others. Discussing* dissection studies the workers say that broadly they show that differences are small in muscle and fat in lambs of the same age and in which the Suffolk and Dorset Down exceed the Southdown in carcase weight by 41b and 21b respectively. “If any difference is real it indicates that the Dorset Down produces a meatier type of carcase as both leg and loin contained 2 to 3 per cent, more muscle than the Southdown. On the other hand the differences in shape of the eye muscle (longissimus dorsi) were fairly consistent. They show that the Southdown has a deeper and moie round cross section of muscle which is the more desirable type.” The workers point out that on a price basis the heavy sires (Suffolk) give a 10 per cent better return than the Southdown under late drafting with a price schedule favourable to weight, but this drops to 5 per cent, under early drafting and a premium for lightweight lambs. On the other hand medium sires have given a consistent margin of 5 to 7 per cent, under all price conditions. The death rate of lambs by the Dorset Down and Hampshire was 2 per cent, higher than that by the Southdown due to the lambs (single iambs especially) being large at birth. This was partly offset by the fact that these rams left 1 per cent, fewer barren ewes so that differences in terms of lambs weaned were small. Losses of lambs by the heavy sires (Suffolk and Border Leicester) were similar to those by the Southdown.

The scientists conclude by saying that the scientific journal was not the place to discuss the practical and commercial implications of the results they have obtained. This, they say, would in any case be very difficult to work out as it was clear that no one sire possesses all the virtues and each represents a compromise between rate of growth and carcase weight on one hand and conformation grading and percentage fat off the mothers on the other hand. Further quality was not a fixed entity. “Under such conditions it is considered better merely to give the results of these trials which can then be interpreted at any time to meet any particular set of farming practices or market conditions.”