Flexibility in livestock systems is important for risk management in variable climates

On a perennial feedbase at Wagga Wagga, a September lambing system can run higher stocking rates and is more profitable than a traditional winter lambing Merino. However, in such systems allowing stocking rates to vary relative to seasonal conditions is important to manage risk and capture opportunities.

Main findings

• 

  Modelling showed that using perennial rather than annual pastures with a Merino system increased profit, largely because perennials allowed a later lambing time so a higher ewe stocking rate. Profit was increased further if a portion of the Merino ewes produced crossbred rather than Merino lambs.

• On the perennial pasture base (lucerne, phalaris and tall fescue) at the experimental site, a Later (September) Lambing system carried nearly twice as many ewes/ha as a Winter (July) Lambing Merino even though they had the same mid-winter stocking rate. A Split Lambing system was midway between the two.
• Although the higher number of ewes in the Later Lambing system resulted in more lambs born, these lambs did not grow well in the dry springs (2006-2009) and the resulting production (kg/ha) was similar to the Winter Lambing Merino and lower than the Split Lambing system in most years.
• Lower numbers of ewes and lambs in the Winter Lambing Merino and Split Lambing systems meant that in a wet year, lambs could be retained for longer and grown to heavier weights (on lucerne) than in the Later Lambing system, before pasture supply became limiting.
• Higher lamb growth rates from crossbred lambs together with higher stocking rates meant that the Split Lambing system produced more lamb than the Winter Lambing Merino, especially in the wet year.
• The Later Lambing system produced 64% to 106% more clean wool/ha than the Winter Lambing Merino system.
• The quantity of supplementary feeding through the dry springs was driven by stocking rate and ability to vary stocking rate such that at $300/tonne for grain, the Later Lambing system spent $105-$333/ha more than the Winter Lambing Merino system and $92-$130/ha more than the Split Lambing system in each year.
• While modelling indicated Later Lambing would produce higher gross margins than the Winter Lambing Merino in the long term, the high supplementary feeding costs through the dry years resulted in lower gross margins in those years.
• The Split Lambing system performed as well or better than the Winter Lambing Merino system in poor years, but had the capacity to be more productive in the wet year, resulting in a gross margin $156/ha greater than the Winter Lambing Merino and $104/ha greater than the Later Lambing system in that year.
• Post-experimental modelling using the last 40 years of rainfall data suggests that Spring Lambing resulted in higher average gross margin but also a greater range in gross margin than Winter Lambing. Type of sire (merino or terminal) had a smaller effect on average gross margin than choice of lambing time.
• Post-experimental modelling also showed that while stocking rate has the largest impact on gross margins, the choice of lamb sale policy may influence what month of lambing produces the highest gross margins.
• Modelling showed that it is difficult to predict when poor seasons are coming from rainfall or pasture production. The risk of feeding more than 300 kg/ha of grain was increased for September lambing systems if less than 90mm of rain fell during summer, or there was less than 1700 kg DM/ha phalaris in March.

Read more about this research

Challenges and opportunities

Key profit drivers

Key factors that influence profit in a sheep enterprise include stocking rates, supplementary feeding costs, reproductive rates, wool and lamb produced per head, and price.  All of these factors are influenced by farm enterprise selection and management, together with seasonal pasture availability and market conditions which vary from year to year.  Flexibility is an important consideration for setting up a farm enterprise to enable stocking rate and selling times to vary to make the best of good season and market opportunities and minimise losses in poor seasons.

Lambing time influences potential ewe stocking rates

In a reproductive sheep enterprise, livestock demand varies with stage of pregnancy and lactation and therefore varies throughout the year.  In most parts of south-eastern Australia, pasture supply tends to be most limiting in winter.   Therefore, the time of lambing relative to the winter period alters the number of ewes/ha which can be carried, assuming we want to avoid large amounts of supplementary feeding of ewes in winter.  More ewes can be run in a late winter or spring lambing system than a winter lambing system since ewes are dry through the most limiting winter period. More ewes/ha leads to higher wool production/ha and a greater number of lambs/ha. Lambs born in late winter or spring will normally be sold as stores (at weaning or soon after) rather than finished lambs (unless they are lot fed on farm, as there will usually be insufficient high quality pasture), but more kg lamb/ha should be achieved due to higher number of lambs born.

Perennials provide opportunities for later lambing and environmental benefits

The grazing areas of the southern slopes of NSW with annual rainfall above 550mm are able to sustain a number of perennial pasture species. Perennial grass pastures extend the growing season compared to annual pastures, but are dormant over summer. Summer active perennial species such as lucerne can provide quality feed during summer/autumn in suitable paddocks. The longer period of green feed, in comparison to annual pastures, provides an opportunity to lamb later and therefore run higher stocking rates to increase profits. The inclusion of summer active perennial species such as lucerne creates potential for higher profits by finishing off lambs to slaughter weight (see Wagga research message ‘More lucerne increases production and profit’). Deep rooted perennials may assist in maintaining ground cover and, in the case of lucerne, significantly reduce ground water recharge.

The need for flexibility

Modelling shows that higher profits may be achieved by lambing later and running higher stocking rates. However, this system poses a risk of high supplementary feeding costs in drought years.  Lambing in winter and running more conservative stocking rates makes it difficult to better utilise spring and early summer feed in a good season by cutting more wool, turning off more lambs, and if sufficient areas of perennial pastures such as lucerne can be established, by taking more lambs through to finishing weights.  Like most areas there can be significant variation in seasonal conditions. Seasonal variation, changes in the price of meat relative to wool means the profitability of different sheep enterprises will vary from year to year.  Increasing the flexibility of sheep enterprises may be necessary to manage cash flow and risk.

In areas similar to the southern slopes of NSW, the opportunity may exist for producers to manage risk and improve profitability by altering the pasture base to include more perennial species, by modifying the animal enterprise to efficiently utilise the pasture base, and by improving enterprise flexibility to accommodate season and price variation.

What was done?

Pre-experimental modelling

Economic modelling of different sheep enterprises using long-term average monthly rainfall data was performed to determine the effect of replacing annuals with perennial pastures, and from using terminal or Merino rams. This modelling used an optimisation approach, that is, what combination of pastures and livestock system would maximise whole farm profit?

Farm systems experiment

At the EverGraze Proof Site located in Ladysmith (between Wagga Wagga and Tarcutta), four sheep systems (Table 1) were compared on perennial pastures in a replicated grazing experiment between 2006 and 2010 to quantify increases in production possible from changing lambing time, stocking rate, ram breed and the proportion of farm area sown to lucerne.  Persistence of perennials and groundcover data (for erosion control) were also evaluated.  Key questions addressed in this study were:

1. What lambing time best suits a perennial pasture base with 20% of the farm sown to lucerne?
2. For spring lambing, is there any benefit of having more than 20% of the farm sown to a summer-active species?

The Winter Lambing, Spring Lambing and Split Lambing systems all used the same perennial pasture base of 20% lucerne, 20% tall fescue and 60% phalaris (Figure 1).  All systems used the same stocking rate (dry sheep equivalents) in July (time of most limiting feed) to enable a fair comparison. A High Lucerne treatment had the same animal system as Later Lambing but with a pasture base consisting of 40% of the farm area sown to lucerne, 45% phalaris and 15% to tall fescue. The results for the High Lucerne treatment are presented in the research message Lucerne increases production and profit.

Table 1. Summary of three sheep systems in experiment 2006-2010

*Ewes mated for four weeks, except for February joining for Split Lambing (two weeks, although post experiment recommendation is three weeks)
^ Planned sale date in most years.  In the very wet year of 2010, some lambs were retained on lucerne to grow out to higher weights

 

Sheep systems explained

Winter Lambing Merino (Control) – The traditional July lambing system with all ewes joined to Merino rams. The objective was to retain all lambs to finish to slaughter weight, dependent on seasonal conditions.  This system was used as the baseline to show the potential for alternative management to increase production where perennial pastures are used.  Systems such as this are widely used as the risk associated with the ability to finish lambs is reduced.

Later Lambing – September lambing to allow a higher stocking rate to produce more wool and lambs per hectare, while producing some crossbred lambs to also increase lamb production; modelling indicated that both September lambing and use of terminal rams would increase profits.  This system joined half the ewes to Merino and half to terminal rams but retained the ability to breed replacement ewes.  The system aimed to sell lambs at weaning so only ewes were carried over summer.

Split Lambing – Half the ewes lamb to terminal rams in July and the other half to Merino rams in September.  A short (two week) joining to terminals was used in February for 60% of the ewes (although based on results three weeks is recommended), those that failed to fall pregnant and un-joined ewes were joined in April to Merino rams.  The Split Lambing system allows an intermediate stocking rate, and higher lamb production while breeding replacement ewes.  The July-born crossbred lambs can be finished to heavier weights if seasonal conditions allow, or sold at weaning as store lambs in poorer seasons.  September-born Merino lambs can be retained after weaning and sold at higher weights if seasonal conditions allow.  The use of a higher stocking rate than the Winter Lambing System, and production of crossbred lambs, were both indicated by modelling to increase profit.   The use of two joining times was thought to increase flexibility and reduce risk from varying seasons, as a compromise between a low production/lower risk (Winter Lambing Merino) and high production/higher risk (Later Lambing) enterprise.

While each system was designed to generate replacement Merino ewes, ewe lambs were not retained within any system in the experiment.

Post-experimental modelling of grazing systems

The field experiment was conducted under either drought (2006-2009) or extremely wet (2010) conditions, so the performance of the different enterprises may not well represent performance in a more normal run of years.  Therefore, using GrassGro or Ausfarm modelling, simulations of several sheep enterprises were conducted to allow comparison over a time period of 30 or 40 years. Stocking rate, lambing time, and lamb sale policies were tested.

Seasonal conditions

Rainfall patterns during the grazing experiment were far from average (Figure 3).  In each year from 2006 to 2008 and to a lesser extent 2009, rainfall during spring was unusually low.  Monthly rainfall in September and October 2006-2008 of 8 to 32 mm was well below the long-term average for Wagga Wagga of 50 to 60 mm for those months (between percentile 1 and 10 for the years 1943 to 2010).  Rainfall in 2010 was well above average in most months, with 2010 being the wettest year on record for Wagga Wagga.  High rainfall continued over the summer of 2010/2011.

What was found – pre-experimental modelling?

When grazing perennials, profit was increased if a portion of the Merino ewes produced crossbred rather than Merino lambs. The modelling (Table 2) also showed that:

• Changing from a June lambing time increased profit.  For a self-replacing Merino flock, September lambing produced 1.7 times as much whole-farm profit as a June lambing self-replacing Merino flock.
• Producing crossbred as well as Merino lambs in June only slightly increased profit compared with a June lambing self-replacing Merino flock, but using a Split Lambing system with crossbred lambs born in June and Merino lambs born in September was 1.9 times as profitable.
• As lamb values increased, producing some crossbred lambs increased profit if lambing in June, but not if lambing in September.
• The cost of ewes determined whether it was more profitable to buy or breed replacements.

Table 2. Modelling analysis of whole farm profit for changing lambing time and ram breed in a self-replacing Merino flock on perennial pastures at Tarcutta

	Merino ewe flock
	Merino lambs	Merino lambs	Merino + crossbred lambs	Merino + crossbred lambs
Lambing month	June	September	June	June (crossbreds) September (Merino)
Profit ($)	47 000	80 900	49 400	90 800
Stocking rate (dse/ha)	9.5	10.4	9.3	11
% of farm phalaris	35	51	37	52
% of farm lucerne	39	30	37	28
% of farm to crop	26	19	26	20

These results indicated that if using perennials, there are more profitable enterprises than a traditional self-replacing Merino flock lambing in winter.  Systems which join part of the flock to terminal rams, and with perennials which extend the period of quality feed to allow later lambing were clearly more profitable options.  The grazing experiment was designed to test various ways of doing this.

What was found – grazing experiment?

Stocking rates higher in Later Lambing systems

A lower ewe stocking rate was utilised in 2006 given the pastures were sown in 2005.  Stocking rates were progressively increased to 2008 based on what modelling indicated was the potential stocking rate for the systems. From 2009 a more conservative stocking rate was applied after high supplementary feeding in 2008.  However, within each year the mid-winter (July) stocking rate (dry sheep equivalent) was similar in all systems.  Due to the different lambing times, the dry sheep equivalent/ha of the systems varied over the year (Figure 3).  The Later Lambing system carried nearly twice the ewes/ha as the Winter Lambing Merino, even though they had the same mid-winter DSE/ha.   The actual numbers of ewes/ha for each system in each year are shown in Table 3.

*Although in the experiment ewes in the Split Lambing system were joined for two weeks in February, it is recommended that they are joined for three weeks to avoid fertility issues.

Table 3. Stocking rate (ewes/ha) for the four systems 2006-2010

Production was not consistently higher in one system

Lamb production (kg/ha) was affected by a combination of stocking rate and lambing time.  The Later Lambing system produced a similar quantity of lamb as the Winter Lambing Merino (Table 4) because September born lambs did not grow well in the dry springs experienced through most of the experiment. In addition, the lower numbers of ewes and lambs in the Winter Lambing Merino and Split Lambing systems meant that in years with adequate spring/summer/autumn pasture growth, lambs could be retained for longer and grown to heavier weights than in the Later Lambing system, before high quality pasture supply became limiting. This meant that the Later Lambing system only had the highest lamb production (kg/ha) in 2009 (which was partly due to the very poor performance of the Split Lambing system in that year due to fertility failure, as explained later).

Lambing at different times (Split Lambing) allowed at least some lambs (July born) to grow well in variable seasons.

Producing crossbred lambs increased lamb production because crossbred lambs grew faster than Merino lambs.

Wool production (kg/ha) was driven by stocking rate.  The Later Lambing system produced 64 to 106% more clean wool/ha than Winter Lambing Merino.

Table 4. Production and gross margins for three sheep systems with 20% of the farm sown to lucerne

Treatment	2006	2007	2008	2009	2010
	Live weight of lambs sold(kg/ha)
Later Lambing	168	144	165	198	197
Split Lambing	172	207	196	144	260
Winter Lambing Merino	140	163	171	177	210
	Clean wool (kg/ha)
Later Lambing	22	27	32	29	28
Split Lambing	13	17	24	21	20
Winter Lambing Merino	11	16	18	18	15
	Supplement fed (kg/ha)
Later Lambing	1517	742	1317	1125	274
Split Lambing	796	485	882	762	0
Winter Lambing Merino	407	390	424	556	0
	Gross margin ($/ha)
Later Lambing	29	88	24	108	303
Split Lambing	113	235	117	46	417
Winter Lambing Merino	77	121	120	104	261

Feeding levels increased with stocking rate

The quantity of supplementary feeding was driven by stocking rate. This resulted in 1.9 to 3.7 times more feed used in the Later Lambing system compared with the Winter Lambing Merino during the drought years (2006-2

009) (Table 4).  Ewes were fed as required to achieve condition score targets for joining and lambing (as recommended by Lifetimewool), and sheep were removed from plots to maintain groundcover targets, which contributed to the high levels of supplementary feed required during the dry years.

Gross margins

The Later Lambing system usually produced the lowest gross margins during drought years due to much higher feeding costs than the other systems, but similar lamb production (Table 4). During the very wet year (2010) its gross margin was 16% higher than the Winter Lambing Merino system due to higher wool production.

The Split Lambing system produced higher gross margins than the Winter Lambing Merino in some drought years (2006 and 2007) and during the wet year (2010).  Very poor fertility (ram heat stress) from the two week February joining in 2009, and relatively poor fertility (due to an unknown cause) in 2010, reduced its gross margin in these years.   The system enabled the fertility failure to be ‘corrected’ by joining non-pregnant ewes again in April, but the lower growth rate of the subsequent September born lambs limited kg lamb/ha in these years.  As such, it is recommended to use a three week early joining if using this system.   If the fertility achieved in 2006-2008 for the February joining had been achieved in 2009 and 2010, it is estimated that the Split Lambing gross margins would have been $124 and $442 in 2009 and 2010 respectively.

Risk and the need for flexibility

Spring lambing was disadvantaged by four years of failed springs in this experiment.  The performance of different systems may have altered if dry autumns had occurred.  The Split Lambing system was more flexible than Later Lambing due to lower stocking rates which reduced feed costs, lambing at different times enabling one drop of lambs (July) to be sold at reasonable weights regardless of season, and the ability to react quickly (by selling lambs) to deteriorating seasonal conditions.  If a proportion of the flock were tradeable stock such as wethers, a later lambing flock would also be able to adjust to seasonal conditions more readily than the non-flexible ewe-only flock used in this grazing experiment.  The Winter Lambing Merino had the lowest production risk, but low stocking rates meant it had limited ability to increase wool or lamb production in favourable seasons.

What was found – Modelling of grazing systems performance over the long term?

The pre-experimental modelling described earlier used an optimisation approach.  A limitation with this approach is that while it optimises the farm system for a given set of climatic conditions (the ‘average’ year), it cannot account for year to year variability in farm performance due to seasonal conditions.  Once the experimental results were obtained, the data was used to validate a model (GrassGro) which can test performance over a range of years.  This modelling showed that while mean gross margin increased with an increase in stocking rate up to the optimum, the variability (risk) also increased.

Changing from a July to a September lambing time substantially increased gross margins in both Merino x Merino and Merino x terminal ram enterprises (Table 5), but the variability (range) in gross margins increased.  Increasing lamb sale age from 14 to 23 weeks only made a significant difference in gross margin for the September lambing Merino x terminal system, but this was accompanied by a greater range in gross margin because in poor years more supplement is fed when lambs are retained to 23 weeks.  In practice, when lambing in September, the sale age should be varied depending on seasonal conditions to limit costs in poor years and capture the benefits from additional lucerne in better years.

Unfortunately Split Lambing could not be modelled in GrassGro, however EverGraze is using a more complex model so that this system can be included in the analysis.

Table 5. The effect of lambing time, lamb sale age, and proportion lucerne on simulated gross margins (using 1970-2010 rainfall records)

	Merino x Merino			Merino x terminal
Lambing	Jul	Sep	Sep	Jul	Sep	Sep	Sep
Lucerne (%)	20	20	20	20	20	20	40
Lamb sale age (weeks)	23	14	23	23	14	23	23
Mean Gross margin ($/ha)	208	294	314	236	304	343	384
Range in gross margin ($/ha)	441 (-125 to 316)	625 (-175 to 450)	678 (-127 to 551)	462 (-107 to 355)	646 (-165 to 481)	739 (-127 to 612)	799 (-161 to 638)

Because Split Lambing could not be modelled in GrassGro, the more complex model AusFarm was also used to investigate the systems used in the grazing experiment, over a 40 year period. In contrast to the grazing experiment run mainly in drought years, long-term simulation (Table 6) showed that the Winter Lambing Merino system produced the lowest average gross margins due to lower per hectare production. The production of some crossbred lambs and higher ewe numbers to achieve a similar midwinter DSE/ha resulted in both the Split Lambing and Later Lambing systems achieving an average $93 or $121/ha higher gross margins. Terminal over Merino ewe systems also produced high gross margins but involve the risk of high ewe prices, introducing diseases and lacking control of genetic gain.

Further increases in gross margin were achieved using 40% (High lucerne system) rather than 20% lucerne (Later Lambing system), due to increased lamb sale weights. However, retaining lambs on lucerne to higher weights increases the risk of feeding other stock, particularly ewe weaners kept as replacements.

While the spring lambing systems have higher potential production than winter lambing systems, they also have higher risks which were not considered in the model. These include increased stock numbers (labour requirement, capital invested), increased grain fed (exposure to variable grain prices, particularly in drought), exposure to grass seeds/need for shearing, and timing of lamb sale combined with lower lamb sale weights. The potential for either sale or grain finishing of light lambs in December in poor seasonal conditions may be reduced. The relative advantage of different sheep systems may also vary with future changes in climate. Over the period 1971-2011 the Later Lambing on average produced a higher mean gross margin than the Split Lambing system. However, during the last decade, where rainfall has been lower and with dry spring conditions, the Split Lambing system often produced higher gross margins.

Table 6. Comparison of sheep systems (using 1971-2011 rainfall records) stocked at 12 DSE/ha in July, modelled using AusFarm 

	Lambing	XB lambs (kg/head)	Merino lambs (kg/head)	Lamb value ($/ha)	Wool value ($/ha)	Supplement (kg/ha)	Gross margin ($/ha)
Winter Lambing Merino	Jul		39.2	103	180	55	161
Later Lambing	Sep	32.2	27.4	197	286	139	282
Split Lambing	Jul + Sep	44.7	29.1	199	230	93	254
Terminal over Merino*	Jul	42.9		337	140	37	230
Terminal over Merino*	Sep	28.2		451	269	151	333
High Lucerne**	Sep	40.8	33.6	234	287	187	303

*Terminal over a purchased Merino ewe. All other systems are self-replacing.
**All systems use 20% lucerne except High Lucerne which used 40%.

The time or weight at which lambs are sold varied widely between the systems, so modelling was used to compare different lamb sale policies for different months of joining. A flexible policy, where lambs were sold if pasture was not adequate for lamb growth, usually produced a higher average gross margin than always selling at 45 kg or in December. However, stocking rate and month of joining had a larger impact on gross margins.

The advantage of particular lamb sale policies depended on stocking rate.  If the optimum number of ewes was carried for the month of joining, there was little difference in mean gross margin between sale policies.  However, the flexible policy often achieved a similar gross margin but with less grain feeding.  Where ewes were stocked either above or below the optimum, the differences between sale policies could be large, and which produced the highest gross margin would depend on the relative grain and meat price used, as well as whether discounts or premiums would apply for selling lambs at store or slaughter weights in particular months.

High levels of supplementary feed during drought is a large cost. Modelling showed that rainfall or pasture production at one time was poorly related to production later in the year, making it difficult to identify when a drought was going to occur. For a September lambing system, feeding more than 300 kg/ha grain during the year was more likely if there had been less than 90 mm of summer rainfall, or if there was less than 1700 kg DM/ha phalaris pasture in March.

Putting the research into practice

When considering adjustments to livestock systems, lambing times and stocking rates, it’s important to critically evaluate each option against target markets for lambs and wool and what is really required for profit/ha not just $/head.  It’s also important to consider the available facilities and management expertise, as well as your interest and passion. Most economic benchmarking data of commercial farms suggests “it is not what you do but how well you do it”.

A process for considering changes to livestock systems is discussed in detail in the EverGraze Exchange – Livestock systems for profitable use of perennials. The Hamilton EverGraze Proof Site Sheep systems for maximising profit from perennials, also provides data on the profitability of different sheep systems in the Hamilton environment; the influence of sheep breed on reproductive performance and wool production; and the effect of soil fertility on potential stocking rate.  Some of the key considerations are outlined below.

Stocking rate

Potential stocking rates will be determined by understanding your annual feed supply and demand, and its variability on your own farm.  This will be determined by climate (rainfall, the length of the growing season and its variation), soil condition and fertility, topography (risk of soil erosion) and the available feedbase.  Ground cover, feed on offer and supplementary feeding thresholds for protecting pastures and managing risk will also help to set the boundaries.

Before considering changes to stocking rate or lambing time, the first step is to calculate your current stocking rate profile. This can be done using the EverGraze stocking rate calculator. The average stocking rate can be compared to local benchmarks, although these should be considered carefully as carrying capacity will vary based on the factors described above.

Once you understand your current stocking rate profile, you then need to work out your feed supply profile. The MLA Feed Demand Calculator provides growth curves for a range of different pasture species. The Broadford Grazing Experiment page also provides growth curves for phalaris which are relevant to this region.  Using the Feed Demand Calculator, you can determine how well feed supply matches feed demand, and your current pasture utilisation. At higher rates of pasture utilisation, there will be higher risk of supplementary feeding costs in dry years and a greater demand for pasture and livestock monitoring and management skills. The availability of labour, facilities and capital also need to be considered when running higher stocking rates.

Considering changes to lambing time and flexibility

Selecting an appropriate time of lambing by matching the increased feed requirements of lambing ewes to peak pasture growth, is the first step to optimise pasture utilisation. Selecting a time of lambing for an enterprise is a compromise between many different factors including the type of enterprise (eg: meat vs. wool, store vs. finished lamb), breeding season of ewes and rams, pasture growing season, the availability of other feed resources (eg: forage crops, stubbles) and possible conflicts with other farming activities.  This also needs to be considered in the context of marketing objectives for the enterprise being run i.e. producing store lambs or finished lambs to specific liveweight or carcass weight.

The Wagga Wagga Proof Site modelling has demonstrated that long-term gross margins can be improved by lambing later to allow the stocking rate profile to better match the shape of the feed supply curve.  The key benefit of Split Lambing was that it allowed the stocking rate and sale times to vary, which allowed the system to take advantage of good years and manage the risk of high supplementary feeding costs in dry years.

If you are considering a later lambing, there needs to be enough quality pasture to meet the needs of growing stock at the end of the growing season.  In self-replacing systems, weaners ideally need to reach 45% of mature live weight before pastures dry off, to improve survival over summer (Hocking and Gould).  A higher level of management skill is required to manage spring-born lambs if pasture conditions deteriorate in spring or if lambs are carried over summer.

The Split Lambing system will add a degree of complexity to management.  Having two lambing periods means there will be a longer period when ewes are set stocked in small mobs (restricting the grazing system), and other practices will need to be done twice (eg. scanning and marking), which may be impractical on some farms.  If Split Lambing doesn’t fit with your system, consider other ways to achieve flexible stocking rates – such as trading cattle or wethers.

Producing crossbred and/or Merino lambs

If you are joining a portion of your ewes to terminal sires, consider whether ewe replacements will be bred or purchased. If breeding replacements, lamb marking percentages, average ewe mortality rate, age at which ewes are culled and the anticipated percentage of cull young ewes will determine how many ewes need to be joined to Merino rams.

Consider which ewes should be joined to terminal rams – oldest, culls, ewes in fatter condition?  If you choose to join better condition ewes to terminal sires be aware this will result in better weaning rates for these, but poorer weaning rates from those joined to Merinos, which will affect the number of replacements available. The Sheep CRC Merino v Terminal Sire Flock Model can be used for making these decisions.

If joining at two times, consider whether Merino or crossbred lambs are best born early or late.  Merino lambs have slower growth rates and may be easier to carry over summer if born early.  Crossbred lambs grow faster so if born early may achieve saleable weights in spring so are more easily sold as trade lambs if spring/summer pastures become limiting.

What it all means

Choice of lambing time, stocking rate and ram breed can considerably alter both production and the risk in adverse seasons.

If using perennial pastures, higher profits can be achieved using sheep enterprises which are capable of higher meat production.

Strategies need to be used to minimise the risk of high feeding costs and poor production in drought years, particularly with high stocking rate systems.

Acknowledgements

EverGraze is a Future Farm Industries CRC research and delivery partnership.  The Wagga Wagga EverGraze Proof Site team was led by Dr. Michael Friend at Charles Sturt University.  An enthusiastic Regional Advisory Group consisting of farmers, consultants, extension officers and Catchment Management Authority staff provided significant input into the direction, management and interpretation of outcomes from the experiment to make them relevant to farmers.

Authors and contributors

Susan Robertson, Charles Sturt University, Wagga Wagga, NSW

Michael Friend, Charles Sturt University, Wagga Wagga, NSW

Kate Sargeant, formerly Agriculture Victoria Benalla