More wool from SRS Merinos
SRS Merinos are plain-bodied sheep producing high density and length of wool fibres. It is the focus on selecting for very long wools that ensures that the animals never develop thick and wrinkly skins.
The very long and thin staples of SRS Merinos leads to the fleece parting along the backline (Figure 1). Traditionally, Merino breeders have assumed (incorrectly) that this indicates lack of fleece density, high dust penetration and low wool yield. They have focused, again incorrectly, on selecting for thick staples, which are usually short in length, as the source of density and fleece weight.
The assumption that thick stapled sheep, which are also wrinkly sheep, produce more wool than plain bodied sheep dates back several centuries.
This myth was first exposed in the 1930s. In an important and rarely cited scientific publication:
Belschner, H.G. Carter, H.B. and Helen Newton Turner (1937). “Fleece characteristics of stud Merino sheep in relation to the degree of wrinkliness of the skin of the breech”. Australian Veterinary Journal. pp. 16 -28,
The researchers reported that “contrary to opinions frequently expressed, there was very little difference between the wool production of the plain bodied and wrinkly types. They also reported that the wool quality was better on the plain bodied sheep.
Dr. Watts first introduced the SRS breeding system in 1988. The Merino studs, Gowandale and Wallaloo Park, in the Wimmera district of Victoria, Australia, were among the first chosen. At Gowandale in 1987, the ewe flock averaged 7.8 kilograms for greasy fleece weight and 23.5 microns for fibre diameter. By 1994 the values were 9.5kg and 21.3 microns. At Wallaloo Park the five-year averages for ewes over 1983-87 were 7.5kg and 22.2 microns, over 1990-94 were 8.6kg and 21.1 microns and for 1994 alone 9.1kg and 20.7 microns.
The increase in fleece weight is well beyond that predicted by index selection, especially when accompanied by such a substantial fall in fibre diameter. Figure 2 shows that the density, as indicated by secondary follicle to primary follicle (S/P or Ns/Np) ratio of the selected ram hoggets in both flocks had increased from the low 30s to nearly 50 over seven years. The high average S/P achieved in the ram hoggets of these two studs was higher than that for any single individual or flock previously known.
In 1995, a more detailed comparison of the fleece and skin traits of the two Merino sheep types, the SRS Merino and semi SRS Merino, was made at Wallaloo Park (see Table 1).
Table 1. Differences in wool follicle and fibre traits of Merino ewes, 20 months old, visually selected as SRS Merinos and semi SRS Merinos (35 sheep per group).
Clean fleece weight (kgs)
Fibre diameter (microns)
Fibre length ( 8 months wool growth mm)
Follicle density (per mm2)
Primary fibre diameter (microns)
Secondary fibre diameter (microns)
Footnote: means with different superscripts in the same row differ significantly (P < 0.05)
In this comparison, the SRS Merinos produced an average of 1.3 kgs more wool, and were 1.3 microns finer. The SRS Merinos were denser, longer and had finer primary fibres than the semi SRS Merinos.
In the period between 1995 to 2000, 10 demonstrations were conducted at workshops across Australia comparing the fleece weights, fibre diameter and fleece values of SRS Merinos and classic Merinos in the same flocks. SRS Merinos grossed $67 per fleece compared with $29 per fleece for traditionally selected sheep, producing 10% more wool that was 2.5 microns finer. Examples of these demonstrations are shown in Table 2.
Greasy fleece weight (kgs)
Fibre diameter (microns)
Fleece length (mm)
Bullaring WA 1998 (40 wethers per type)
Dubbo NSW 1999
(6 ewes per type)
(9 ewes per type)
Cooma NSW 2000
(5 ewes per type)
Badgingarra WA 2000 (6 sheep per type)