A comparison of the progeny of three breeds of fat lamb sires

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Abstract
Many trials have been carried out in Australia to assess comparative values of breeds of rams and owes for fat lamb production in various environments and for different markets. Although general trends have appeared, there is much conflicting evidence in the reports of these trials as to the order of superiority of breed for a particular environmentmarket situation, especially for that of the rams. Much of this conflicting evidence arises because no completely satisfactory method of assessment of superiority has been used. Many of the studies undertaken to compare different breeds of ram have used as their basic criterion the returns per ewe (for example, McConnell, 1910; Elliot, 1926; Colebatch & Scott, 1927; Coleman, 1927; Cook, 1934; Thompson, 1951; Coleman & McDonald, 1952). In this situation random fluctuations in lambing percentages and in percentages of lambs surviving to slaughter can affect the order of superiority of the breeds. In view of the comparatively small numbers of sheep often used in the breed comparison groups (and this is, of course, particularly true in the case of rams), these deviations can bo sorious. For example, McConnell (1910) found that Border Leicester x lambs had a higher return per ewe than Southdown x lambs, but in 1911, the same author found the reverse situation which appears to have been due to a reversal in order of lambing percentages.