Pedigree Dorset Horn sheep in Australia

Transcription

1 Australian Journal of Exberimental Agriculture and Animal Husbandry: Pedigree Dorset Horn sheep in Australia I. Breed expansion and other vital s Summary-The Dorset Horn in Australia is maintained almost exclusively for producing rams for crossbreeding in the prime lamb industry. Flock Book records have been used to assess the expansion and other statistics of the breed. Dorset Horn sheep were first imported in 1895 with the first flock registered in The number of pedigree flocks increased to 1298 in 1958 and total ewes to 113,762 in Flocks declined to 614 and ewes to 60,801 in 1973, during which there was a rapid expansion in Poll Dorset flocks and ewes. Early expansion of the Dorset Horn occurred in South Australia and Victoria but over 85 per cent of flocks and ewes were located in New South Wales and Victoria in In 1973,40 per cent of flocks contained less than 51 ewes with only 2.8 per cent having more than 400 ewes. The mean age of studs in 1973 was 15.3 years, with 22 per cent established for 0 to 5 years, compared with 7.1 years and 62 per cent respectively in Stud dispersals have increased dramatically in recent years to 19.7 per cent of extant studs in Examination of flocks present in 1969 but dispersed prior to 1974, showed the proportion of dispersed flocks decreased with increasing flock size and increasing stud age, up to 40 years. Migration of sires between all regions was low, but of the migrant sires, South Australia supplied 76 per cent in 1954 and the central western region of New South Wales 57 per cent in Approximately half of the rams sampled had sires bred in the same stud. The Dorset Horn breed in Australia is maintained almost exclusively for producing rams for crossbreeding. They are used primarily as terminal sires for crossbred lamb production and recent B.A.E. (1g73a, 19736, 1g75a, 1976) surveys of lamb production in New South Wales, Victoria and Tasmania have shown Dorsets to be the most popular breed of rams joined to crossbred ewes. Dorset rams are used to a lesser extent to produce first cross Dorset x Merino prime lamb dams. Genetic improvement in the Dorset Horn is a major avenue for improvement in prime lamb production. Current interest in developing performance recording schemes for sheep meat production (Napier and Ransom 1975) makes it timely to investigate the flock size, distribution of flocks and structure of the breeds concerned, such that limited resources can be most effectively used. Dorset Horn sheep were first imported to Australia from England in 1895 and the first flock was registered with the Australian Society of Breeders of British Sheep (A.S.B.B.S.) in The Poll Dorset was developed in Australia in the 1940's to be a Dorset Horn without horns. After initial crossing with either the Ryeland or Corriedale in nine foundation flocks to introduce the poll character, continual backcrossing was practised until greater than 95 per cent Dorset Horn purity was attained. Another two foundation flocks claimed a poll mutation occurred (Dolling 1959). The Australian Poll Dorset Association was formed in 1954, and subsequently Poll Dorset flocks have been established by either purchase of Poll Dorset ewes and rams, and/or joining Poll Dorset rams to Dorset Horn ewes. The latter has occurred in many Dorset Horn flocks where breeders wished to convert all or part of their flocks to Poll Dorsets. This paper reports the expansion, flock size and distribution of pedigree Dorset Horn sheep in Australia from 1923 to 1973 as well as pedigree Poll Dorset sheep. The data are obtained from Flock Book The Author-Mr. N. M. Fogarty, Detartment of Agriculture, Cowra, New South Wales.

2 Australian Journal of Experimental Agriculture and Animal Husbandry: Volume 18 April 1978 records. Breed structure and genetic analysis, including levels of inbreeding in the Dorset Horn are reported in a following paper (Fogarty I 978). Materials and methods All pedigree Dorset Horn flocks are registered with the A.S.B.B.S. which publishes the British Breed Flock Book (B.B.F.B.) annually. Pedigree Poll Dorset flocks are registered in the Flock Book for Poll Dorset Sheep in Australia (P.D.F.B.), published annually by the Australian Poll Dorset Association. Each flock registration includes the name and address of the owner, the flock number and prefix and the year the stud was established. In addition, flock composition (number of ewes, rams, ewe lambs and ram lambs) at May I (Dorset Horn) or March 3 I (Poll Dorset), the number of ewes joined, and the individual sires used, is included. A list of flocks dispersed in the previous year is also given. The number of pedigree Dorset Horn flocks, total ewes, flock size and age of studs was collated every five years for returns at May I in the years 1923 to 1973 (B.B.F.B. published in the years 1924 to 1974). Between 1929 and 1933 some Dorset Horn flocks were registered with the Australian Longwool Sheepbreeders Association (A.L.S.A.), after which it amalgamated with the A.S.B.B.S. The A.L.S.A. did not publish a Flock Book with 1933 registrations and hence data were collated for 1934 rather than Data were collated within four New South Wales and three Victoria regions as well as the other states (see figure I). The regional boundaries were based on a combination of Department of Agriculture regions with consideration given to common communication and geographical areas. The age of studs dispersed was determined from annual flock dispersals every five years from 1938 to Data from Poll Dorset flocks were compiled within states in 1958, 1968 and Records of ewes joined are divided into polled (P), horned of polled breeding (PH), and Dorset Horn (H). The record of ewes joined was used to compile Poll Dorset ewes as there were inconsistencies in the categories of ewes (i.e. P, PH and H) included in the total ewes recorded at March 3 I. Sires used in pedigree Dorset Horn flocks must be individually registered in the B.B.F.B. Details included are breeder's stud prefix, number, month and year of birth, prefix and number of sire, prefix and number of dam and prefix and number of maternal grand sire. Region I-South Australfa Region 9-Tamanla Region 10-Western Australla Region 11-Queensland Figure I-Geographical regions used for the distribution of Dorset Horn studs in Australia. Migration of rams between regions in Australia was determined from the 425 rams individually registered in the 1974 Flock Book and a random sample of IOO rams registered in each of the 1969 and 1954 Flock Books (sampling ratios of I : 10 and I : 7.4). The regions (figure I) in which rams were bred and the regions of origin of their respective sires were determined. To quantify the migration of sires between regions the expected number of migrant sires supplied by each region to all other regions was calculated. A random model was assumed in which a sire bred in any region had an equal opportunity of being used in any region and stud rams produced one generation previously were bred in the various regions in the same proportion as in the current generation. Similar calculations were also made after deletion of rams whose sires were bred in the same stud. Region I I (Queensland) did not supply any rams or sires and is not considered in this section. The 1954 sample contained one sire that was imported and this was considered to have come from a separate region. Results and discussion Expansion The expansion in pedigree Dorset Horn flocks and total ewes from 1923 to 1973 is shown in table I.

3 Fogarty: Pedigree Dorset Horn sheep in Australia I. TABLE 1 Pedigree Dorset HornJocks and total ewes-australia and states, 1923 to State N.S.W. Vic. S. A. Tas. W.A. Qld. Australia t Flocks. $ Total ewes. The number of pedigree Dorset Horn flocks increased rapidly to 575 in After a relatively stable period from 1943 to 1953 the number of flocks almost doubled from 660 in to 1298 in I 958. Thereafter there has been an accelerating decline in flocks with only 614 registered in The national ewe flock has followed a similar pattern, although the total number of ewes registered continued to increase beyond 1958 until During the period of rapid expansion newly established flocks tended to be very small. From 1958 to I 968 there was a consolidation of ewes in extant flocks which more than compensated for the reduction in the number of registered flocks. However, the national registered ewe flock declined to 60,801 in Poll Dorset expansion, in terms of both flocks and total ewes joined, in Australia and each state is given in table 2. From 155 flocks joining 10,356 ewes in 1958, the Poll Dorset increased dramatically to 1060 flocks joining 103,687 ewes in 1968 which almost equalled the Dorset Horn breed. In the five years to 1973 there has been a further increase to I 198 flocks joining 133,542 ewes, at the same time as a dramatic decline occurred in the Dorset Horn. During this period the proportion of Dorset Horn ewes joined in Poll Dorset flocks has declined from 71 per cent in 1958, to g per cent in Distribution The number of pedigree Dorset Horn flocks and total ewes within each state are given in table I. Dorset Horn sheep were first imported to South Australia in 1895, and this state was important in the expansion of the breed during the first quarter of this century. Subsequently major expansion occurred in Victoria, with it having the largest number of flocks and registered ewes of all states from 1928 to 1958.

4 Australian Journal of Experimental Agriculture and Animal Husbandry: Volume 18 April 1978 In the following decade almost all the expansion in ewe numbers occurred in New South Wales. Between 1948 and 1973 the proportion of flocks registered in New South Wales and Victoria increased from 68 to 86 per cent. The corresponding increase in total ewe registrations was from 71 to 88 per cent. In all regions, except I, 2 and 3 (New South - Wales) the maximum number of flocks registered occurred in 1958 with a steady decline subsequently. In Regions I, 2 and 3 the maximum registration of flocks occurred later but there was a decline in all these regions from 1968 to The total ewes in each region followed a similar pattern to the number of flocks registered. Maximum ewe registrations occurred between 1958 and 1968 with a marked decline to 1973 in all regions. Region 2 (central western New South Wales) has been the most important region numerically since TABLE 2 Pedigree Poll Dorset jocks and ewes joined-australia states, 1958, 1968 and State N.S.W. Vic. S.A. Tas. W.A. Qld. Aust Flocks Ewes Flocks Ewes 1973 Flocks Ewes and 1963 and contained 24 per cent of total ewes in In 1973 the only regions with more than 5000 ewes were 2, 3 (New South Wales), 6 and 7 (Victoria). The Poll Dorset is of major importance in New South Wales and Victoria with each having 33 per cent of flocks and joining 39 and 29 per cent of ewes respectivefyia, 1973 (table 2). Flock size The national mean flock size increased to 96.3 ewes in 1948, but declined to 75.2 ewes in 1958 during the rapid expansion of the breed. Mean flock size subsequently increased to ewes in 1968 but declined to 99.0 ewes in 1973 (table 3). The decline in the last five years is probably due to the establishment of Poll Dorset flocks by many Dorset Horn breeders and the subsequent transfer of registration of some Dorset Horn ewes to the P.D.F.B. Mean flock size in most regions followed a similar pattern to the national mean. All regions showed a decline in average flock size during the expansionary period of the 1950's. In 1958 Region 4 (121.4 ewes flock-l) was the only region with more than 80 ewe flock-l. Region 4 also had the highest mean flock size in 1973 (172.5 ewes flock-l), with Regions 3 and 7 the only others with more than IOO ewes flock-1. Of registered flocks, a large proportion is very small. Until 1963 some 50 to 60 per cent of flocks contained less than 51 ewes, and only 3 per cent contained more than 400 ewes (table 3). In the last decade the proportion of small flocks ( < 50 ewes) has dropped to 40 per cent, with a commensurate increase in the proportion of flocks with 5 I to 200 ewes. Although a high proportion of flocks is small (< 50 ewes), they only contain a small proportion of Mean flock size and pr TABLE 3 tortion of Dorset Hornjocks (%) in variousjock size categories-australia, I923 to Attribute Proportion (%) 0-50 ewes ewes ewes ewes ewes > 1000 ewes Mean flock size (ewes)

5 Fogarty: Pedigree Dorset Horn sheep in Australia I. total ewes. For example, in 1973, 39.7 per cent of flocks had 0-50 ewes but these contained less than 12 per cent of total ewes. Conversely 10.6 per cent of flocks had more than 200 ewes which accounted for 38.4 per cent of total ewes. Similar features to that of the national pattern of flock size existed in most regions. A large proportion of flocks (30 to 60 per cent) had less than 51 ewes but these contributed only a small proportion of ewes (5 to 25 per cent) to the regional flock. Region 4 (south-western New South Wales) tended to be an exception in recent years as only 20 per cent of its flocks contained less than 51 ewes. Large flocks of more than 400 ewes occurred, in some years at least, in all regions except Region I I (Queensland). However, they occurred most con- sistently and frequently in New South Wales Regions 2, 3 and 4 and Victorian Regions 6 and 7. In 1973 the only regions to contain flocks with more than 400 ewes were 2, 3, 4 and 7. Very few flocks contained more than 1000 ewes, although they occurred in most regions in at least one year (except Regions I, 8, 9 and 11). These flocks tended to diminish to a smaller size in a short period of time. There were three of these large flocks in 1969 (the most in any year sampled), but none had more than 1000 ewes in 1973, although another such flockexisted. Age of studs The mean age of Australian Dorset Horn studs continually increased from 1928 to 1973, except during TABLE 4 Mean age andproportion (%) of Dorset Horn studs in various age categories-australia, 1923 to I 1 Attribute / Proportion (%) 0-5 years 6-10 years years years > 40 years Mean age (years) I TABLE 5 Mean age and profortion of dispersed Dorset Horn studs (%) in various age categories-australia, 1938 to I Attribute Proportion (%) 0-5 years 6-10 years years years > 40 years No. studs Mean age (years) t Percentage of extant studs in parentheses.

6 Australian Journal of Experimental Agriculture and Animal Husbandry: Volume 18 April 1978 the expansionary period of the breed in the late 1950's (table 4). A dramatic increase in stud mean age occurred from 1968 to 1973 (I 1.5 to 15.3 years), which was due mainly to the establishment of few new studs during this period (table 4). The proportion of studs established for 0-5 years was generally greater than 50 per cent up to The proportion of newly established studs has declined markedly since 1958, with only 22 per cent in this category in 1973 (table 4). There has been an increase in the proportion of old studs (greater than 20 years) from 2 per cent in 1943 to 24 per cent in Most regions have followed the national pattern of increasing stud age with time, except for a decline about The mean age of studs in South Australia and Western Australia (Regions 8 and 10 respectively) has been higher than the national mean since With the recent decline in the Dorset Horn breed, the TABLE 6 Proportion (%) of studs registered in 1969 of various age andjock site categories that were not present in Stud age Flock size (ewes) > 1000 Total years > 40 Total TABLE 7 Rams, sires and migrant sires supplied from each region in the 1954 and 1969 registered ram samples and the 1974 registered rams. I Region 1. N.S.W. 2. N.S.W. 3. N.S.W. 4. N.S.W. 5. Vic. 6. Vic. 7. Vic. 8. S.A. 9. Tas. 10. W.A. Total Rams Sires Migrant sires Rams Sires Migrant sires oot Rams Sires Migrant sires t Includes one sire imported from England. $ Percentage of total in parentheses.

7 Fogarty : Pedigree Dorset Horn sheep in Australia I. age of studs in the numerically less important'regions, has increased considerably. For example, in the five years from 1968 to i973, the mean age of studs in Regions 3, 4, 9, 10 and 11 increased by more than five years. Stud dispersal In the sampled years from 1938 to 1958, studs dispersed were 6.5 to 8.5 per cent of extant studs. However, stud dispersals increased dramatically thereafter to be 19.7 per cent of extant studs in 1973 (table 5). The mean age of dispersed studs was generally about a year lower than extant studs. Of the I 058 flocks registered in I 969, 54.1 per cent were not present in 1974 (table 6). The proportion of dispersed flocks decreased with increasing flock size and increasing stud age, up to 40 years. The most stable group of studs was years old with flocks of ewes (16 per cent or 4 of 25 dispersed). A similar pattern existed for flocks registered in 1954 but not present in 1959, although total dispersal were much lower (2 I.2 per cent). Migration The migration between all regions was low, with migrant sires being approximately 43 per cent of the expected number in 1954 and 1969 and only 30 per cent in 1974, whereas region-bred sires were three to five times the expected number. As approximately half of the rams had sires bred within the same stud, the migration rate was doubled when these were deleted. In 1954, Region 8 (South Australia), as well as being the major region suppiying rams and their sires, supplied 76 per cent of all migrant sires (table 7). Although the migration rate remained the same in 1969, the source of migrant sires diversified, as they were mainly supplied from Regions 2 and 8, and to a lesser extent, Region 7. In 1974 Region 2 supplied 35 per cent of sires and 57 per cent of migrant sires; Regions 3 and 8 each supplied 15 per cent of migrant sires (table 7). Although the overall migration rate was low, one or two regions dominated the supply of migrant sires in each year sampled. These dominant regions, Region 8 in 1954 and Region 2 in 1974, supplied sires to most other regions. Because of this there is not likely to have been much division of the breed into regionally adapted strains. This is confirmed in the following paper in which a low level of strain inbreeding was found (Fogarty 1978). Conclusion The Dorset Horn has become the most important British shortwool breed in Australia. In the last decade the breed has declined in favour of the Poll Dorset which has expanded rapidly. However, the two breeds are in effect very similar as the latter was developed from continual backcrossing to the Dorset Horn, and Poll Dorset flocks are still being established from Dorset Horn ewe flocks. Expansion of the national Dorset Horn ewe flock, together with the Poll Dorset ewe flock in the last decade, has followed a similar pattern to lamb slaughterings. The latter have steadily increased from 8.6 million in to 22.3 million in (B.A.E b). The current dominance of New South Wales and Victoria with 75 per cent of the national Dorset Horn and Poll Dorset ewe flocks corresponds closely with the proportion of Australian lamb slaughterings in these two states. Some go per cent of Dorset Horn flocks consist of less than 201 ewes. The genetic progress that could be expected from implementation of a within-flock selection programme in these flocks is very limited. Participation in a group breeding scheme, where superior ewes are contributed to a ram breeding nucleus, would effectively increase flock size and consequently allow a possible increase in the rate of genetic improvement. The number of years that flocks remain in existence is important for continual long-term genetic improvement in the breed. Flocks that remain in existence for only five years contribute little genetic improvement. From the past pattern of flock dispersals, recently established flocks (0-5 years) and those with small ewe numbers (0-50 ewes) are most likely to go out of existence. Genetic improvement of the breed is also dependent on the breed structure that exists and genetic progress being made in the important flocks.-this is pursued in detail in the following paper (Fogarty 1978). Acknowledgments I thank Mr. R. Storey and the Australian Society of Breeders of British Sheep for the loan of Flock Books and other assistance. The assistance of Mrs. A. P. Haddin in compiling records and data is greatly 17'

8 Australian Journal of Experimental Agriculture and Animal Husbandry: Volume 18 April 1978 appreciated. Dr. J. W. James, University of New South Wales is thanked for derivation of the procedure quantifying migration and advice during the study. REFERENCES B.A.E. (1973~)-Lamb research report No. 1-Prime lamb production in Oberon Shire. Bureau of Agricultural Economics: Canberra. B.A.E. (19736)-Lamb research report No. 2-Prime lamb production in Tasmania. Bureau of Agricultural Economics: Canberra. B.A.E. (1975~)-Lamb research report No. 3-Prime lamb production in Victoria. Bureau of Agricultural Economics: Canberra. B.A.E. (19756)-"Statistical Handbook of the Meat Industry". Second edition. (Bureau of Agricultural Economics: Canberra). B.A.E. (1976)-Lamb research report No. 4-Prime lamb producfian in- New South Wales. Bureau of Agricultural Economics: Canberra. Dolling, C. H. S. (1959)-The Poll Dorset. Journal of the Australian Institute of Agricultural Science 25 : 259. Fogarty, N. M. (1978)-Pedigree Dorset Horn sheep in Australia. 2. Breed structure and genetic analysis. Australian Journal of Ex@erimental Agriculture and Animal Husbandry 18 : 173. Napier, K., and Ransom, K. (1975)-The Department of Agriculture's flock performance recording scheme. Journal of Agriculture, Victoria 73 : 174. Re~eived~for publication July I I, 1977