When is a Merino not a Merino?

Story by Cameron McMaster
Sheep and wool consultant, Napier, South Africa

The Dohne originated from a single initial mating 70 years ago of two Merino strains — the pure Merino as we know it in South Africa, primarily of Peppin medium wool type, and the Merino developed in Germany from the original Spanish stock, but with greater emphasis placed on meat production.

Throughout the 70-year breeding program there has been consistent backcrossing and upgrading from countless pure Merino flocks in terms of the Dohne Foundation Flock Register followed by careful selection based on measurement for fertility meat and Merino wool traits.

So far as ancestry is concerned the Dohne can therefore claim as much purity as any other Merino strain. It is in fact a fine example of the brilliant adaptability of the Merino which, throughout the world, has been bred to suit vastly differing physical and economic environments. On the grounds of purity therefore, the Dohne appears to have equal claim to Merino status as any other Merino.

The irony is that selection for the superior traits of Dohne wool has been based on measured performance since 1970 when fleece measurements were made mandatory in Dohne studs in South Africa. This was before stud Merino breeders in South Africa or in Australia were using measurement as an aid to selection and until recently most stud Merino breeders did not use measurement other than as a sales gimmick. Until recently they had little knowledge of or control over the spinning qualities of their wool.

In contrast, from as early as 1970 the Dohne Society in South Africa set minimum standards of fibre diameter and FD deviation from the population means — standards that were strictly applied by all breeders over all of this time. This is the reason why Dohne Merino wool today has a lower average FD, CV percentage and comfort factor than most other Merino wool and does not have the tendency for FD blow out with age or under high nutrition. This is a feature that surprised many Australians when they started breeding Dohnes. The fact was that Dohne wool performed better than much of the Merino wool they were familiar with.

Dohne ram performs well

The effect of Merino ewe genes in first cross and second cross lamb production systems is being researched to improve lamb production by gaining a better understanding of the influence of Merino genes on prime lamb production.

Female progeny from rams entered into the Merino South Australian Central Test Sire Evaluation (SA CTSE) were used in the project. Ewe progeny from 23 sires evaluated in the SA CTSE at Struan Research Centre were naturally mated to Border Leicester rams as hoggets and then mated to Poll Dorset rams for their second lambing. The Border Leicester cross ewes, containing 25pc of the genes from the ram entered into the CTSE, were mated to Poll Dorset rams to produce second cross lambs. These lambs contained 12.5pc of the original genes from the rams entered into the CTSE. Conception rate, lambing percentage, ewe and lamb behaviour and lamb growth of all progeny were measured.

Flock Breeding Values (FBVs) describe the genetic performance of the sheep and take into account the gender birth type, how many pregnancies the mother has had and other environmental effects such as year of birth. Australia Sheep Genetics (ASG) calculated FBVs from the data collected on the progeny at Struan Research Centre. The FBVs describe the performance of the rams and their progeny as it looks at the genetic potential of the sheep and removes environmental effects.

The table shows the range in EBVs of the rams entered into the SA CTSE and the mean range of FBVs of their grand-lambs. The Dohne ram entered into the SA CTSE had the highest post weaning (PWWT) and maternal weaning (MWWT) weight EBV in the CTSE and also 9pc more lambs weaned than the average Merino ram. This means this particular Dohne ram will produce ewes that produce more lambs and have the ability to provide a better maternal environment. It also has the ability to grow to heavier post weaning weights than the other rams entered into the SA CTSE.

The grand-progeny FBVs reflect the expected results from the ram EBVs. The BL cross progeny with the Dohne genes had the highest average weaning weight (WWT), PWWT and number of lambs weaned (NLW).

Change of emphasis in index

More emphasis on meat production is the overall direction the new Donne breeding objective index will take when it starts being reported in April with both quality and quantity of meat production to be targeted. Faster growth of lambs, higher reproduction rate and emphasis to increase muscle size will all assist commercial Merino producers maximise their returns. Wool production is not forgotten.

The Dohne breeding objective that determines the index is still very much a dual-purpose objective. The balance in emphasis on fleece weight and fibre diameter has changed so that there is similar emphasis on both. Previously the emphasis was to reduce fibre diameter and maintain fleece production.

The upgrade in the Dohne index was based on members of the Australian Dohne Breeders Association desire to make their selections on the current market values being obtained by commercial sheep producers. In particular there has been an increase in lamb price from $45 per head in 2000 (when the last index upgrade was carried out) to $80 per head in recent years.

The higher reproduction rate of Dohne Merinos and an ability to join Dohne ewes at a younger age were also taken into account in the commercial flock production system used to establish the index. Muscle and fat depth are now traits in the Dohne index. Members recognise that both these traits have commercial value and should be included in the index. Though the genetic progress in muscle depth will only be small they are in line with market values. Dohne ram breeders' genetic progress will reflect the change in emphasis in the index.

Table 1. Comparison of Current Dohne Index and the New Dohne Index - Top 200 by 10s

Body weight gain for a standard ram breeding flock will increase from plus 4kg in 10 years up to +5kg in 10 years. Reproduction gain will also increase significantly.

The increased emphasis on meat in the Dohne breeding objective will result in a shift from a reduction in fibre diameter of 1.5 micron in 10 years, to a reduction of 0.8 micron. CV of fibre diameter will slightly improve and staple strength will be maintained.

Ram breeders will see a significant difference in the index value of the sheep they breed and select for mating. Sheep with high growth rates will get an advantage, while those with very fine fibre diameter will not get as large an advantage as they have in the past. Sheep that have above average performance for muscle depth will also have an advantage as long as they have similar performance for the other traits.

The two tables show the effect of the new index on the rank of Dohne stud sires. Table one describes the performance of the top 200 sires based on the current index and the top 200 on the new Dohne index. The performance of each 10 sires ranked on index has been combined so that the general trend can be seen for a large number of sheep.

Table 2. Comparison of Top 20 Sires on Current Dohne Index and the New Dohne Index

Table two lists the top 20 sires in late 2006 based on their index value. The sires tag number has been replaced with a number from 1 to 20 to conceal the sire's true identity. The sire's index and rank on both the current and new index is shown.

Some sires in the list have a very similar rank because they have the mix of performance that meets the new objective as well as the current objective. However some sires will drop significantly on the new objective because their mix of performance does not match the emphasis on traits in the new objective.

The new index will start being reported in April after it was decided to change the index last year Because ram sales were in full swing, the implementation of the new indices was delayed until the 2005 drop ram sales were concluded.