Wool quality research: tackling hauteur, nutrition and DNA tools in Merinos

Why the wool industry needed this wool quality research#

The review was written at a low point for Australian wool. Prices had only briefly recovered in 1997, and the authors pointed to two underlying problems: slow productivity growth on sheep farms and persistently low prices from the global textile trade. Spinners' demand for wool had also been squeezed through the 1990s by consumers spending less on apparel, favouring casual wear over formal wear, and waiting for sales before buying.

Ward argued the industry had only two levers left to pull: cut the cost of producing wool so growers could still turn a profit at lower prices, and improve wool's performance as a textile fibre so it could compete better against cotton and synthetic fibres. The three contributed papers that followed were built around those two aims, covering fibre processing constraints, nutrition, and the emerging role of DNA-based breeding tools.

Hauteur: the fibre length spinners actually pay for#

Adams and Oldham focused on hauteur, the mean fibre length measured in wool top after washing, carding and combing. Because little further fibre breaks during the rest of processing, hauteur carries through to the finished textile. The paper described wool apparel markets as effectively defined by a combination of fibre diameter and hauteur: knitting yarns need a hauteur no greater than 65 mm, while high twist weaving yarns need at least 70 mm. Spinning trials cited in the paper showed that lifting hauteur out to at least 95 mm, with everything else held constant, improved yarn evenness, yarn strength and spinning performance, and that an extra 10 mm of hauteur could offset a one micron reduction in fibre diameter in terms of reduced thread breakages during spinning.

Hauteur cannot be measured on raw wool directly; it depends on the original fibre length and how much breakage occurs during top-making. The paper set out the TEAM equation (Couchman et al. 1992), which predicts hauteur from staple length, staple strength, fibre diameter, mid-point breaks and vegetable matter content. Stanton's unpublished analysis, cited in the paper, found that this predicted hauteur figure was about as useful for explaining price differences between auction lots as looking at each raw wool measurement separately, underlining why growers who ignore hauteur may be leaving money on the table.

Why finer wool and heavier stocking carry hidden risk#

Adams and Oldham noted that a gross margin analysis (Atkins et al. 1995) generally favoured finer wool sheep, yet growers outside traditional fine wool districts had been slow to adopt it. They attributed this to genuine risk: finer wool prices are more volatile, and discounts for the staple strength, staple length and style traits that drive hauteur all increase as fibre diameter falls. Dust penetration risk in cropping country and low staple strength in Mediterranean-climate regions were both flagged as practical deterrents.

The paper used Doyle and Thompson's (1993) strip-grazing trial, recalculated by Oldham and colleagues (1997), to illustrate the trade-offs of tighter grazing management. Restricting intake of wethers stocked at 20 per hectare by strip grazing during spring lowered fibre diameter from 21.5 to 21.0 micron in 1989 and from 21.0 to 18.5 micron in 1990 compared with set stocking, but predicted hauteur fell from 77 to 75 mm in 1989 and from 75 to 66 mm in 1990. Clean fleece weight per head and per hectare also dropped. Using a fibre diameter by hauteur value matrix from three years of Fremantle auction data (Stanton et al. 1997), the gain in value from finer wool was partly offset by the loss in value from shorter hauteur in both years, which is exactly the kind of risk the authors said needs to be quantified before extension advice pushes growers toward heavier stocking.

Pasture use and feed conservation as untapped gains#

Masters, White and Dynes turned to nutrition, starting from the fact that Australian sheep get over 90% of their nutrients from pasture. Seasonal feed gaps, whether winter shortfalls in temperate zones or summer-autumn shortfalls under a Mediterranean pattern, were described as the first constraint on wool growth, with new pasture varieties such as improved phalaris offered as one partial remedy.

Pasture utilisation was identified as a bigger opportunity than many growers might assume. A large share of the spring pasture grown in Western Australia's lower south west region is never eaten by sheep at all, lost instead to weathering and biological breakdown. Rotational grazing with feed conservation in rested paddocks was proposed as a way to recover some of that waste in higher rainfall areas. The gap between average and top producers was stark: highly productive Western Australian enterprises ran 10.7 DSE per winter-grazed hectare and cut 53.5 kg greasy wool per hectare, against 8.8 DSE and 36.1 kg for average producers. In Victoria, the Grassland Productivity Program reported gross margin increases of $62 per hectare (26%) for spring-lambing ewe enterprises and $33 (19%) for wethers, achieved by lifting pasture production through fertiliser matched to stocking rate.

Protein quality and the amino acid gap in wool growth#

A recurring theme in the nutrition paper was that not all protein is equal for wool growth. Formaldehyde treatment of oilseed meals, which reduces how readily protein breaks down in the rumen, has been known for over 20 years to increase wool growth by up to 80%, yet oilseed meals remained too costly for routine use. Lupins, by contrast, were shown to be an inefficient wool-growing feed: at matched energy intake, sheep grew no more wool from lupins with 32% protein than they did from a much lower protein oat ration, because lupin protein breaks down too readily in the rumen.

Supplying protected methionine, an amino acid that is often limiting for wool growth, raised the efficiency of converting metabolisable protein into wool from 12.3% to 17.2% in wethers fed to maintenance, with a corresponding lift in measured daily wool output. Field trials conducted near Armidale found that delivering a small daily dose of methionine straight into the intestine boosted wool growth substantially on native pasture, and by a smaller but still useful margin on improved pasture. An economic calculation for weaners grazing dry pasture in Western Australia put the benefit of four months of protected methionine supplementation at $7, against a cost of about $10, meaning the cost of the supplement needed to fall by at least 30% before it paid its way. Separately, supplying other limiting amino acids alongside methionine was reported to lift wool growth by a further 38%, implying gains of over 70% were achievable experimentally once the full amino acid balance was corrected.

Breeding for size and efficiency, not just fibre diameter#

The nutrition paper also addressed sheep genotype. Within Merino breeds, larger mature sheep consistently out-eat and out-produce smaller ones on a wool-per-head basis, with feed conversion efficiency to wool staying the same regardless of frame size. Because pasture costs are counted per hectare while handling costs are counted per head, this makes larger sheep more profitable to run, a conclusion reinforced by an economic modelling exercise (Donnelly 1998) predicting a 30% higher gross margin for a flock of 60 kg ewes compared with 48 kg ewes at Mt Barker in Western Australia. However, the genetic relationships between fibre diameter, wool cut and liveweight meant that producers starting with sheep of similar size would gain more from breeding objectives weighted toward wool traits than toward liveweight.

The authors pointed to alkane technology as a now-available tool for selecting sheep that convert pasture into wool more efficiently, framing the long-term breeding challenge as combining large frame size, high fleece weight, low fibre diameter and high feed conversion efficiency in the same animal.

DNA tools: maps, markers and parentage testing#

Nancarrow's contribution surveyed molecular genetics as a route to faster, more precise genetic gain in Merinos. Most economically important wool traits are governed by many genes among the roughly 70,000 to 100,000 genes in sheep, though a few single genes with large effects were already known, including fecundity genes identified in Australian and New Zealand flocks. The first published sheep gene map appeared in 1995, and several groups were building denser maps aimed at locating quantitative trait loci, or QTL, that could eventually be tracked through pedigrees via marker-assisted selection.

DNA pedigreeing was presented as a near-term, practical application: it can correct parentage errors caused by mis-mothering or stray rams, and selecting animals with accurate full pedigree information was estimated to offer genetic gain improvements of around 20%. Candidate gene studies, using partial sequence data and a gel-based comparison technique to find genes active in wool follicles, were underway within the Wool CRC, alongside work on gene transfer. Transgenic sheep production remained inefficient, at around a 1% success rate without guaranteed gene expression, though the paper noted that the then-recent report of sheep cloned from cultured cells by nuclear transfer (Campbell et al. 1996) could reduce the cost of producing transgenic animals by allowing large numbers of cell fusions to be screened before transfer.

What this body of work adds up to#

Read together, the three papers make a consistent case: wool growers face compounding constraints across fibre processing, nutrition and genetics, and tackling any one in isolation risks unintended losses elsewhere, as the strip-grazing example showed when a gain in fineness was partly cancelled out by a loss in hauteur. We think the strongest parts of this review are the processing and nutrition sections, which lean on specific trial data and dollar figures; the genetics section is more a survey of emerging tools than evidence of results achieved, which is unsurprising given how early DNA technologies were in 1998.

The review was published through the Australian Society of Animal Production conference proceedings, now continued as the Australian Association of Animal Sciences, and appears in this index's ASAP Conference Proceedings collection. The general Livestock Library catalogue holds further related material from the same period, including work by some of the same authors such as progesterone and ovarian follicle growth in anoestrous ewes.

Sources and further reading#

• Australian Association of Animal Sciences: successor to ASAP
• Trove library search: find a library that holds the paper
• Meat & Livestock Australia: red meat industry research and marketing body
• Australian Wool Innovation: wool industry research and marketing body

Questions#

— The Livestock Library team