Why autumn lambing suited Western District sheep farms in 1958

The question behind the paper#

Weatherly wrote from direct experience managing a merino property at Woolongoon, near Mortlake in the Western District of Victoria. The paper opens from a plain commercial premise: stock are run to produce a profit, and any change to one part of the operation has to be judged against its effect on the whole. Breeding ewes exist only to replace the flock at the rate needed for culling, because in fine wool breeds, dry sheep carried at lower cost were said to earn a better financial return for each acre than breeding ewes did.

The paper notes that reproductive rate on many properties was proving hard to maintain, which had already prompted considerable research into flock reproduction. Against that background, Weatherly set out to explain why so many Western District properties mated in late spring or early summer and lambed in late autumn, even though that mating period does not always align with the time of year when ewes are most fertile or most likely to produce twins.

The dates discussed are those used on Weatherly's own property, described as a May-June lambing. The paper notes that most other Western District merino properties ran a similar programme, though often about a fortnight to three weeks earlier across all operations. This framing matters because the argument is not that an autumn lambing programme maximises any single measure, such as lambs marked, but that it suits the whole year's run of work and feed better than the alternatives Weatherly considers.

How the case for an autumn lambing programme was built#

Rather than reporting a controlled trial with treatment groups, the paper works through a schedule of routine operations across the year, set out in a figure, and reasons through how a May-June lambing programme interacts with shearing, mating, weaning, feed supply and labour. Weatherly draws on a table of figures for reproductive rate and wastage to make the point that a fall in net reproductive rate forces a choice between reducing the culling rate or breeding from ewes for an extra year, neither of which is attractive.

The method, in effect, is comparative reasoning grounded in long practical experience on one flock, described as having been bred under these conditions for generations. Weatherly compares the May-June programme against three alternatives: autumn mating with early spring lambing, mid-winter lambing in late June or July, and June mating for a November lambing. Each alternative is assessed against the same set of practical constraints, including feed availability through the seasons, shearing timing and wool quality, lamb survival in different weather, and the clash between farm operations such as shearing and harvesting.

This is a management case study rather than an experiment with replicated animals, and the paper should be read that way. Its value lies in laying out, in detail, the seasonal trade-offs that any Western District sheep manager would have had to weigh, using the operator's own property as a concrete, fully described example rather than an average across many farms.

What favoured the autumn lambing programme#

Weatherly lists several advantages of the May-June lambing. It suits the full year's schedule of operations more comfortably than any other option he considered. Lambs born then generally do reasonably well provided the weather turns favourable in autumn before lambing and the lambs are not dropped just as rough, cold weather arrives; premating teasing with vasectomised rams made that timing more reliable. Lambs born in this window grow slowly through July, grow faster from around August, perform well up to shearing, and carry a sound fleece by the time they are shorn, after which they are weaned onto green feed with time to fend for themselves before summer.

Ewe nutrition was suitable for most of the year under this programme. Ewes were in rising condition at mating because of weaning and spring pasture growth, and took the ram reasonably well with vasectomised teasers used beforehand. During early pregnancy, summer dry feed was judged adequate, though pre-lambing feeding became necessary or unnecessary depending on how early the autumn break arrived. The most critical period for supplementary feeding fell in the depths of winter, broadly the latter half of June into August, to maintain milk supply until spring growth began.

Shearing timing was a central argument. Under the May-June programme shearing fell at a period when wool quality was at its best for bloom and yield, commanding higher prices; shearing any earlier risked mud and wet sheep, while shearing later let wool discolour, especially if held in store. The paper also describes a seasonal pattern in flock feed requirements across the year, which under this programme was well matched to the pattern of available pasture. Weatherly regarded this seasonal matching, together with shearing date, as the two strongest arguments for the autumn lambing programme.

Where the programme fell short#

The disadvantages Weatherly lists are specific rather than vague. First, the mating period used for a May-June lambing is not the period of highest fertility or fecundity, so lambing percentage could in theory be better at another time of year. Weatherly argues that fertility, meaning a healthy single lamb reared successfully, mattered more to him than fecundity, meaning higher twinning rates that often produced culls instead of two sound lambs. On a flock bred under this system for generations, a reasonable lambing percentage was still achievable, and when problems occurred they were usually traced to causes other than mating timing.

Second, a late autumn break could leave pasture conditions poor at lambing, though the paper notes that early supplementary feeding should prevent this becoming a major problem. Third, winter conditions themselves were a genuine weakness: cold wet weather could retard lamb growth and reduce ewe condition enough to affect milk supply, and wet ground made supplementary feeding mechanically difficult. Weatherly describes this as one of the major disadvantages of the programme, while noting that the same weather would also affect lamb husbandry under most alternative mating dates considered, except winter mating aimed at a late spring lambing.

A dry, cold winter posed a different problem again, stopping pasture growth more severely than wet conditions, though Weatherly judged this less of an obstacle because supplementary feed could still be carted to stock even in dry, cold weather.

Comparing autumn lambing with the alternatives#

Weatherly works through three alternative timings in some detail. Autumn mating followed by early spring lambing might lift the percentage of lambs marked, but the paper argues the disadvantages generally outweigh that gain unless the improvement is considerable. A spring lambing compresses the spring workload into an even shorter period, pushes shearing later into a time that clashes with harvesting, and can reduce both fodder conservation and wool bloom, even though later shearing adds some weight to the fleece. An early spring lambing, say in August, was also judged likely to suffer high losses in bad weather, since conditions then are typically rougher than in an average autumn.

Shifting shearing itself to autumn was considered and rejected. Woolly sheep carried through summer would collect more dust, a serious issue for the Western District's reputation for fine wool. In bad fire weather, mustering woolly sheep would be difficult, increasing losses even from minor fires, and fly strike, while controllable by jetting, would add cost through extra yarding and reduced wool value from dust and poorer bloom.

Mid-winter lambing in late June or July was tested under wartime necessity, when zoning of shearing delayed shearing until November 8 and pushed mating back to around Christmas; the resulting lambing losses were described as severe. June mating aimed at a November lambing carried its own distinct problems: fly activity at both lambing and marking, feed requirements poorly matched to pasture growth through summer, lambs weaned onto dry, poor feed at the worst time of year, and weaners changing teeth in February while facing hard, dry feed.

How much weight the argument carries#

The paper is a practitioner's reasoned account rather than a replicated experiment, and it draws heavily on one property's long experience and on reasoning through a seasonal calendar rather than on measured lambing percentages, growth rates or financial returns compared across systems. That is a real limit on how far the conclusions can be generalised beyond Western District conditions and merino flocks of the kind Weatherly managed. We would treat this as a well-reasoned grazier's case for a management system rather than as quantified proof that an autumn lambing programme outperforms its alternatives on any measured scale.

Even so, the paper remains useful precisely because it lays out the full set of seasonal interactions a manager has to juggle, rather than isolating one variable such as lambing percentage. Reproductive rate, pasture growth, shearing quality, labour peaks and weather risk are all considered together, which is closer to how a grazier actually has to decide on a lambing time than a trial focused on a single outcome would be.

The paper's own conclusion is that the May-June programme was, on balance and from the most angles considered, the soundest choice for producing the best profits year on year, and that only strong evidence or materially changed conditions would justify departing from it.

Relevance beyond one Western District flock#

Although the paper is tied to one time and place, its structure of trade-offs, fertility against feed timing, shearing quality against wool price, winter weather risk against labour peaks, remains a recognisable way of thinking about lambing time decisions more generally. A later paper examined liveweight loss in Merino ewes (2011).

A later paper examined economic return from genetic improvement (2013).

A separate study looked at diet composition in autumn pastures in central Queensland (2010).

The paper sits within the early proceedings of the Australian Society of Animal Production, an organisation whose conference record forms a large part of the ASAP Conference Proceedings collection held in this index, and it is a reminder that some of the earliest contributions to that record were grounded less in replicated trials than in close, documented observation of a working property.

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