Abstract:
THE CHANGING STRUCTURE AND BREEDING POLICY OF THE STUD MERINO INDUSTRY R.W. CONNORS* and R.N.D. REID* Analysis of the 'Australian Stud Merino Flock Register' revealed that 51 per cent of studs registered in mainland Australia in 1957 had discontinued by 1972. The discontinuance rate was associated with the number of registered breeding ewes in the studs, and varied from 59 per cent in flocks with up to 500 ewes, to 5 per cent in flocks with over 5,000 ewes. Within flock sizes, the breeding policy (source of sires) in 1957 was not associated with discontinuance rate. The emergence of 584 newly established studs over the same period, almost fully compensated for the discontinuing studs. In 1957, 18 I cent of studs were using their own rams as sires. per n 1972, this had increased to 32 per cent. was a corresponding There reduction in the percentage of studs that were totally dependent on other studs for their sires. The implications to the planning of extension programmes aimed at genetic progress in Merino sheep are discussed. I. INTRODUCTION The structure of the Australian stud Merino industry was first . analysed and described by Short and Carter (1955). Roberts., Jackson and Phillips (1975) revised and updated this description. Short and Carter (1955) are frequently interpreted as emphasising the . importance of parent studs to genetic progress in the stud industry. No such direct statement was made by those authors, however Ross and Turner (1959) referred to non-parent studs as 'multipliers'. Roberts, Jackson and Phillips (1975) cast family groups and general studs in the role of 'spreading and reinforcing the genetic improvement made by a parent stud.' This paper reports an attempt to assess the possible influence of flock size and breeding policy on stud viability, and the trends in dependence or independence of breeding programmes among Merino studs. II. MATERIALS AND METHODS The origin, objectives and limitations of the 'Australian Stud Merino Flock Register' have been described by Short and Carter (1955). In this study, the 1957 and 1972 Registers were used. These were the earliest and most recent editions available to us. Studs have been classified according to their breeding policy as using their 'own', 'other' or 'both' rams as sires. These classifications were defined as follows: all the sires in use in the stud were bred within that stud. all the sires in use were bred within another stud, or other studs. the sires in use were any combination of the previous two classifications. * Department of Agriculture, G.P.O. Box 192B, Hobart. 7001 From the 1957 Edition of the Register, the number of ewes put to the ram and the breeding policy were recorded for each stud. From the 1972 Edition, these studs were then recorded as discontinued or continuing. If continuing, the number of ewes put to the ram and the breeding policy in 1972 were recorded. A change in breeding policy was deemed to have occurred if the source of rams in use in 1972 was different from that in 1957. In an attempt to confirm the apparent trend toward the use of sires bred within the stud, all studs that were in the 'own' category in 1972, which were either 'both' or 'other' in 1957, were surveyed by mail. Each stud manager was asked whether this change was a deliberate shift in policy, or a chance event in the stud's breeding history. Except for the mail survey, this study encompasses a census (rather than a sample) of the population. III. RESULTS AND DISCUSSION The proportion of studs of various flock sizes which discontinued between 1957 and 1972 is given in Table 1. TABLE 1 The Australian discontinuance rate of 51 per cent involed 646 studs discontinuing from a total of 1,267 active in 1957. Nonetheless, the total number of studs in 1972 was 1,205, owing to the formation of 584 studs during the period 1957 to 1972. The future stability of the newly established studs.must be questioned Table 1 reveals that almost 60 per cent of registered flocks with up to 500 ewes were discontinued during the 1957 to 1972 period. Yet in 1972 503'(86 per cent) of the 584 newly established studs had ewe flocks of not more than 500 ewes.. In 1972, 34.4 per cent of all studs held over 500 registered ewes, at a mean flock size of 1,852. Thereby, these studs accounted for 83 per cent of all registered ewes in mainland Australia. There was no consistentassociation between breeding policy and the discontinuance rate within flock size classifications (Table 2). TABLE 2 - The percentage of studs of various flock sizes and breeding policies in 1957 that discontinued prior to 1972. 10 There is an association between breeding policy and discontinuance rate when size classifications are pooled. However, this association exists because breeding policy is counfounded with stud flock size (mean ewe flock sizes in 1957 of 1,665, 893, 289, for own, both, other, respectively). The association between flock size and discontinuance exists within each breeding policy. In 1957; 18 I cent of studs were using their own rams as sires. per n 1972, this had increased to 32 per cent. Changes in policy between 1957 and 1972 are shown in Table 3, the percentages of ewes involved in these changes being shown in parentheses. TABLE 3 . The trend toward,independence in breeding policy is evident in two ways; Firstly, there is greater stability in the Own (1957) group than in the Other (1957) group with 58.6 per cent and 30.9 per cent respectively, remaining unchanged. Secondly, those breeders using both sources of rams in 1957 could have chosen to become either more or less independent by 1972. Table 3 reveals that 27;6 per cent of breeders chose to be more independent and 4.7 per cent chose to be less independent in breeding policy. The results of the mail survey (Table 4) must be viewed with caution, because only 63 per cent of e s e , replied. p e r c e n t Of t h breeders 65 had deliberately decided to exclusively-use their own rams as sires'within their studs. TABLE 4 Response to mail survey of breeders apparently changing breeding policy The difference in response between breeders using 'other' or 'both' rams in 1957, probably reflects the consciousness of the decision. 11 A breeder using 'other'rams would almost certainly need to make a deliberate decision to use his own rams. A breeder using 'both' rams might simply cease to replace the outside rams, and thus appear to have changed his policy. The end res.ult is the same in each case: a more independent breeding programme. This study has pointed to the relative instability of small studs. There is no evidence to support a biological explanation of this instability. The explanation is probably economic, although social factors such as family tradition within larger studs may also have contributed. If the aim of extension is an improvement in the rate of genetic progress of sheep flocks, the 'targets' for an extension programme can be identified on the basis of their likely viability and industry significance, and the potential gains would still be high. However, if the aim of extension is educational then all breeders remain as 'targets'! Because breeders are becoming more independent in their breeding programmes, then the task of influencing the rate of genetic progress is expanding. A detailed analysis of the movement of genetic material between studs, and the impact of any such movement within the recipient studs, is long overdue. However, these data are consistentwith the argument that 'Parent' studs (Short and Carter 1955) would be having less influence on the rate of genetic progress in 1972 than they had in 1957. IV. ACKNOWLEDGMENTS We are grateful to T. Semmens, C. Ozogowski and J. Hudson for their assistance with this analysis, and to R. Howe for his suggestions and constructive criticism. v. REFERENCES ROBERTS, E.M., JACKSON, N. and PHILLIPS, J.M. (1975). Wool Technology and Sheep Breeding (In press) ROSS, I. CLUNIES and TURNER, HELEN NEWTON (1959). Wool Technology and Sheep Breeding 6 : 87 SHORT, B.F. and CARTER, H.B. (1955). CSIRO Bulletin 276 12