More lambs from flushing on green feed

Short-term grazing of live pastures in autumn can increase the number of lambs born from autumn-joined and/or synchronised ewes.

Twin lambs – up to 21 more foetuses per 100 ewes joined on lucerne compared to those grazed on dry pasture or cereal stubble.
Twin lambs – up to 21 more foetuses per 100 ewes joined on lucerne compared to those grazed on dry pasture or cereal stubble.

Main findings

  • A short-term “flushing” effect was achieved in synchronised ewes at the Wagga Wagga Proof Site by grazing lucerne or chicory, increasing ovulation rates by an average of 10% but up to 22%.
  • In on-farm trials, flushing unsynchronised autumn joined ewes resulted in up to 21 more foetuses per 100 ewes joined on lucerne compared to those grazed on dry pasture or cereal stubble.
  • The increase in number of lambs conceived in unsynchronised ewes was a result of more twins and triplets conceived, not less dry ewes.  Sixteen more ewes per 100 joined carried multiple foetuses.  When survival of multiples was accounted for, this was estimated to result in an additional 10 lambs per 100 ewes joined. At 7 ewes/ha, this results in a return of $48/ha from the additional lambs sold.
  • For flushing, the live pasture needed to be of high quality and adequate quantity.  Flushing was achieved on as little as 350kgDM/ha of green lucerne.
  • The return from using green feed for flushing ewes compared to finishing lambs or growing out weaners varied depending on the available green feed and the market price for lambs and supplementary feed.

The following video was developed from a national EverGraze phone conference. The topic is ‘What’s the most profitable way to use limited green feed this summer?’ Presenters are Kate Sargeant and Laura Garland, Agriculture Victoria and Dr Michael Friend Charles Sturt University.

Read more about this research

The opportunity

More lambs weaned can lead to greater profits if the increase in lamb numbers can be achieved cost-effectively (Warn et al., 2006). The number of lambs weaned is a function of conception rate and their subsequent survival.

Conception rate can be increased by increasing the number of eggs the ewe ovulates (ovulation rate).  There are three ways ovulation rate can be increased:

  1. The static effect: Ewes are joined in better condition, achieving approximately two extra foetuses per 100 ewes for every kg liveweight increase at joining.
  2. The dynamic effect or “flushing”: Ewes are gaining condition/liveweight at joining.
  3. The immediate effect or “flushing”: Nutrition is increased for four to six days prior to ovulation (the critical period being days 10-14 of the oestrous cycle), without increasing liveweight or condition.

Research in recent years suggests that a spike in energy is the important factor for the flushing effect although the exact mechanism is unclear.

A response to flushing can be achieved using grain or live pastures.  Lupin grain has traditionally been used because there is a low risk of grain poisoning, compared with other grains.  However, the response to flushing can be variable, depending on the quantity and quality of feed/supplement, previous nutrition and body condition of ewes.

EverGraze research at Wagga Wagga, Hamilton and Albany has demonstrated that improvements in profitability, risk and environmental management can be achieved by including summer active perennials such as lucerne or chicory in pasture systems for sheep.  The Wagga Wagga team tested whether a flushing effect could be achieved at low cost by short-term grazing of ewes on summer active perennials at joining, thereby adding value to these systems, while minimising the cost of feed for flushing.

What was done?

Two experiments were undertaken – flushing in synchronised ewes and flushing in unsynchronised ewes.

Flushing in synchronised ewes

In 2006 to 2008, the oestrous cycle of 400 ewes was synchronised (treated to ovulate at the same time).  Ewes were allocated to graze either lucerne, chicory, senesced phalaris or senesced phalaris + 500g/head/day of lupin grain.  Ewes grazed these treatments in two replicates of 50 ewes per treatment for nine days before ovulation in January/February each year, and ovulation rate was then measured using trans-rectal ultrasound.

Flushing in unsynchronised ewes

Synchronising ewes requires additional cost and labour.  Therefore, a second experiment was conducted in 2012 to investigate the flushing effect with unsynchronised ewes.

In January 2012 Merino ewe flocks on two properties grazed cereal stubbles which had been sprayed to kill any live plants.  In February the ewes on each property were randomly allocated to four groups (50 ewes/group on Property 1, 70 ewes/group on Property 2) – two replicates each of two treatments, and grazed on either lucerne or cereal stubble for one week.  Rams were then introduced to each paddock, and rotated between treatments four days later to prevent bias between groups.  The ewes remained on the paddocks for one week after rams were added, then treatments were combined and all ewes grazed on the stubble paddocks during the second week of joining.  On day 14 of joining, all groups on each property were combined and grazed as a single flock under normal grazing conditions for the remainder of the 5-6 week joining and until pregnancy scanning at approximately 50 days.

The average liveweight of the ewes was 52kg and condition score was 3.25 at the start of the experiment.

What was found?

Increased ovulation in synchronised ewes

The proportion of ewes with multiple ovulations (twins or triplets) increased by 10% on average and up to 22% in synchronised ewes flushed on lucerne or chicory compared to ewes grazed on dry phalaris pasture (Figure 1).  This equates to, on average, approximately 8, but up to 18 extra foetuses per 100 ewes joined. Approximately the same proportion of ewes with multiples was achieved on the green feed compared to feeding lupins.

Increasing ovulation rate was associated with increasing quantity of live pasture.  However, 90% of the increase in ovulation rate occurred on as little as 350 kg DM/ha of live green pasture.

Figure 1. Mean ovulations per ewe using different grazing treatments for synchronised ewes in 2006-2008 for the Wagga Wagga EverGraze flushing trial.
Figure 1. Mean ovulations per ewe using different grazing treatments for synchronised ewes in 2006-2008 for the Wagga Wagga EverGraze flushing trial.

Successful flushing in unsynchronised ewes

In the autumn joined flocks, grazing lucerne for one week prior to joining and through the first week of the joining period produced on average 18 but up to 21 more foetuses per 100 ewes joined (Table 1) when compared to ewes grazing cereal stubble.

Table 1.  Average performance of adult Merino ewes grazed on lucerne or cereal stubble in February 2012

Live lucerne (1-2 t DM/ha live green herbage) Dead cereal stubble (0-0.2 t DM/ha live green herbage)
% Ewes Lambs born *Survival % Lambs marked % Ewes Lambs born *Survival % Lambs marked
Non pregnant ewes 6 0 0 0 5 0 0 0
Ewes carrying singles 25a 25 77 19 43b 43 77 33
Ewes carrying twins 64b 128 70 90 51a 102 70 71
Ewes carrying triplets 5b 15 50 8 1a 3 50 2
Total lambs 171 117 148 106
**Total number lambs/ewe joined   1.7b 1.2b   1.5a 1.1a

*Survival percentages for twins and singles are taken from Wagga Wagga EverGraze site results.  Survival percentages for triplets are taken from Hamilton EverGraze site results since triplets were not included in the Wagga Wagga survival experiment.

**A different letter superscript indicates that results are significantly different for lucerne and stubble.

Ewes grazing green lucerne for one week prior to joining and for the first week of joining resulted in 14% more lambs born
Ewes grazing green lucerne for one week prior to joining and for the first week of joining resulted in 14% more lambs born

Grazing dead cereal stubbles
Grazing dead cereal stubbles

More twins and triplets

The percentage of non-pregnant ewes was the same in both treatments (5%).  This means that the extra foetuses were a result of 33% (52% vs 69%) more multiple pregnancies (Table 1).  That is, ewes that would have normally carried singles were now carrying twins or triplets (although the number of triplets remained low (5% vs 1%).  When estimated survival is considered, the result is an extra 10% more lambs marked when joined on lucerne compared to cereal stubble.

Flushing results in more multiple pregnancies.
Flushing results in more multiple pregnancies.

Putting the research into practice

How much green pasture is needed?

The response will vary with quality and quantity of green pasture.  Previous research suggested very low quantities were required, down to 350kg DM/ha of green lucerne on offer (King, 2010).  However, it is important that lucerne contains enough live green leaf, since mature lucerne stalk can have similar energy content to dead grass.

Live green pastures other than lucerne will also be effective.  It has been found that chicory, phalaris and annual species can also stimulate a response if they are green and vegetative.

The short two week grazing time and low levels of green feed on offer required means that the method can be used when live green pasture is scarce. This is a major benefit when compared with traditional flushing which occurred over several weeks.

As little as 350 kg DM/ha of live green pasture was required to achieve a flushing effect
As little as 350 kg DM/ha of live green pasture was required to achieve a flushing effect

Timing of grazing

In an autumn joined flock, ewes are within their natural breeding season and should be undergoing regular oestrous cycles.  Grazing the ewes one week before joining and one week into joining (Figure 2) should see the majority (approximately 60%) of the flock flushed. Even though the risk of embryo mortality due to high energy intake from pasture is considered quite low, the removal of ewes from green pasture after one week of joining is currently recommended.

In 2013 and 2014 CSU conducted two studies, funded by Meat & Livestock Australia, to determine whether the timing and quantity of lucerne eaten by ewes would alter fetal numbers.  Some parts of the sheep industry are concerned that grazing lucerne throughout joining could cause embryo mortality, reducing the number of lambs born.  These studies tested whether access to lucerne only to day 7 or for 17 days (pen study) or throughout joining increased fetal numbers.

Pen study: artificially inseminated ewes were fed fresh lucerne or pellets in pens for 7 days before and 17 days after insemination.

The same number of fetuses were produced by ewes fed maintenance levels of pellets or lucerne.  Feeding lucerne at ad libitum levels after insemination produced 12% less fetuses than if ewes were fed at maintenance levels.  Pregnancy rates were not reduced, but the proportion of ewes with twin lambs was.

Grazing study:  naturally cycling autumn-joined ewes were grazed on lucerne for 7 days before joining and to either day 7 of joining or throughout a 36 day joining.  These were compared with ewes only grazing dead pasture.

Grazing on lucerne produced 30% more fetuses per ewe compared with only grazing dead pasture (1.6 compared with 1.3), resulting in 115% lambs marked rather than 96% per ewe joined.  Leaving ewes on lucerne throughout joining did not reduce fetal numbers or pregnancy rates.

Grazing naturally cycling ewes on lucerne before and during joining is a means of increasing lambs born.  If limited lucerne is available, ewes can be removed after 7 days while still getting most ewes flushed.  However, leaving ewes grazing lucerne to the end of joining does not reduce lambs born.  Artificially mated or fed ewes should only be fed at maintenance levels to avoid reductions in lambs born.

Figure 2. Time-line of events for flushing using lucerne or other green feed
Figure 2. Time-line of events for flushing using lucerne or other green feed

Short-term flushing of unsynchronised ewes is unlikely to work in spring or early summer (November/December) joined ewes when most ewes are not naturally cycling, although this has not been tested.  Even if the grazing period were altered to fit the pattern of joining, the response is likely to be lower due to the conflict with their natural breeding season (lower ovulation rates in spring) and because they may be on or just come off a high quality spring diet.

The technique may not be as effective in maiden ewes.  Maiden ewes are likely to have a lower response because the potential twinning rate is lower than in adult ewes and maidens may be less likely to be cycling and/or express a silent first oestrus.

Condition score

The condition score at which flushing on green feed will have the greatest impact is yet to be determined.  Response to flushing using lupins is variable, but appears to be the greatest in lower condition score ewes e.g. CS 2.5 vs. 3.5.

The risk with flushing low condition scores ewes is that if they start in low condition score at joining, conceive twins and are still in low condition at lambing, there is an increased risk of mortality for both the ewe and lambs.

Survival is important

Flushing increases the proportion of multiple pregnancies, and can set up a greater potential reproductive rate. However, if additional lambs conceived from flushing have lower survival, then the benefit is reduced.

To achieve greater benefits from flushing, management of twin bearing ewes and lambs must also be addressed to increase survival. This will require extra attention in identification and separation of twin and triplet bearing ewes to ensure adequate nutrition, particularly in late pregnancy, and provision of shelter if poor weather is expected during lambing.  For information on increasing lamb survival, see the EverGraze Exchange – Improving survival of lambs and Shelter improves lamb survival.

Survival is important. Shelter hedgerows at Hamilton increased survival of twins by 15% and survival of lambs at average birthweight by 30%.
Survival is important. Shelter hedgerows at Hamilton increased survival of twins by 15% and survival of lambs at average birthweight by 30%.

Chris Shannon’s experience

When hearing about the ovulation research being undertaken at the Wagga Wagga Proof Site, Chris Shannon was interested to try to replicate the positive results from the site on his own farm under more commercial conditions.  In 2009, Chris achieved approximately 30% more foetus’s scanned from increased twinning rates from ewes flushed on lucerne compared to a control mob on native pasture.  Chris’ experience can be read in the case study ‘Lucerne leads to more legs on the ground’.

Chris Shannon achieved 30% more lambs born as a result of flushing on lucerne compared to native pasture.
Chris Shannon achieved 30% more lambs born as a result of flushing on lucerne compared to native pasture.

On-farm demonstrations

As part of a national strategy to increase reproductive performance of sheep, the BESTWOOL-BESTLAMB project is conducting a series of 12 on-farm demonstration sites across Victoria and New South Wales to validate the use of a range of green feed sources (lucerne, perennial grasses, and forage brassicas) for flushing ewes.  For further information, contact Lyndon Kubeil, Agriculture Victoria.

Crunching the numbers

The value of flushing ewes on available lucerne will depend on three key variables:

  1. Income from additional lambs sold resulting from multiple births
  2. Additional feeding costs for twin-bearing ewes
  3. Opportunity costs of flushing ewes rather than grazing other stock classes (lambs or weaners) on the available green feed.

These variables will be dependent on the flushing response achieved; amount of lucerne available (area and FOO); farm stocking rate; lamb age/weight at sale; and the market value of lambs sold.

Flushing response and additional lambs sold

Flushing ewes on lucerne in the Wagga Wagga on-farm experiments resulted in an additional 14% lambs conceived and 10% more lambs marked (twin lamb survival rate of 70%) compared to ewes grazing on dead stubble. This figure will vary between farms depending both on the response to flushing and survival of the additional twin lambs.

Cost of feeding for multiple births

Twin-bearing ewes have higher energy requirements during mid-late pregnancy and lactation compared to single-bearing ewes (see Feed Budgeting for Ewe Flocks on the Lifetimewool website)

To maintain condition score 3, a twin-bearing, medium frame (50kg) ewe requires 2.5 megajoules metabolisable energy per head per day (MJME/hd/day) more than a single-bearing ewe in the last 30 days of pregnancy, and 5 MJME/hd/day more during the lactation period. Wheat at $240/tonne and 12 MJME/kg will cost 2 cents/MJME. At this cost, the additional feeding costs for twin-bearing ewes in the 30 days leading up to parturition will be $1.50/head.  During lactation, the cost will be $6/head. Overall the cost to maintain twin-bearing ewes will be $7.50/head greater than the cost to maintain a single-bearing ewe.  If lambing in spring, it is unlikely that the additional feeding costs for lactating ewes will be required due to excess pasture at this time of year.

Costs of feeding will differ with the type and price of feed on offer. The NSW DPI Feed Cost Calculator can be used to compare the cost of different feeds in cents per MJME.

Scenario assumptions

In the following sections, a series of example analyses are presented to compare the value of using available green feed for flushing ewes, finishing prime lambs for sale, and growing out replacement weaners. Within these analyses the value of flushing ewes with lupins is also calculated and used as a comparison to these options. Table 2 presents the base case variables used in all examples.

Table 2. Base case variables used in flushing, prime lamb finishing and growing out weaner scenarios

Variable Value used in base case scenario
Green feed source Lucerne, growing at 20 kg/ha/day
Available green feed at the time of flushing 2000 kg/ha (green), 75% digestibility, 20% of total farm area
Stocking rate 7 ewes/ha (35 ewes per hectare on lucerne)
Minimum amount ewes can graze down to 500 kg/ha green (minimum required to achieve flushing at Wagga was 300 kg/ha green)
Flushing response and survival of additional twins (see above) 14% response, 70% survival of additional twins = 10% more lambs sold at 35 kg/hd.
Cost of feeding ewes to produce additional lambs $7.50 per additional twin lamb (see above)
Lamb price (from Southwest Farm Monitor Project 10-year average 2001-2011) 423 c/kg cwt.  Additional lambs from flushing sold at 35 kg lwt; finished lambs in prime lamb scenario sold at 42kg liveweight; both dressing 46%.
Minimum FOO prime lambs can graze down to (to maintain acceptable growth rates). 1000 kg/ha, 75% digestibility
Prime lamb growth rate 180 g/hd/day (assumes average 1500 kg/ha available at 75% digestibility – see High Performance Weaner tables in EverGraze Feed Budget and Rotation Planner).
Weaner feeding costs (when not on lucerne) 1 kg/hd/day at $0.24 c/kg = $1.20/day (assuming 7 weaners per hectare)
Minimum FOO weaners can graze to 1000 kg/ha
Price of lupins as alternative to flushing on lucerne (5-year average price of lupins – 2005-2010 Mallee Sustainable Farming Results Compendium, 2011). $305/tonne, fed at 0.5 kg/hd/day for 14 days (total $2.14/hd)

Other considerations which vary between systems and are not included in the following analysis include lighter birth-weights of twin lambs (on average 1.12kg); lower fleece weights of twin lambs (by 0.27 kg up to 18 months of age); additional labour, vaccination and marking costs; and post weaning feeding of lambs to reach sale weights.

The EverGraze Green Feed Allocation Tool can be used to develop a cost-benefit analysis of your own scenario considering current prices for lambs and feed, feed on offer, ewe and lamb numbers, response to flushing and lamb survival.

Additional income from flushing

The additional income from flushing ewes on green feed or lupins is a function of the number of additional lambs sold as a result of the flushing, their weight and price.  Additional costs of running the ewes with additional twins, and the cost of feeding lupins then need to be accounted for to calculate return.  These figures for the base case variables (Table 2) are presented in Table 3.  After considering the additional feeding costs associated with running more twins, the value of flushing is $42/ha.  The value of feeding lupins to achieve a flushing effect (assuming the lupins also achieved a 10% increase in lambs marked) would be $27/ha.

Table 3. Additional lamb production and return (income from additional twins less feeding costs) from flushing ewes

Whole farm stocking rate (ewe/ha) Extra lambs sold/ha Extra lamb (CWT) Return ($/ha) Cost of lupins Extra cost of feeding twin bearing ewes during pregnancy ($/ha) Extra cost of feeding twin bearing ewes during lactation ($/ha) Extra income less feeding costs. ($/ha)
Ewes  flushed on lucerne 7 0.7 16.1 kg/ha $48 NA 1.47 4.20 42
Ewes flushed on lupin grain 7 0.7 16.1 kg/ha $48 $15/ha 1.47 4.20 27

Comparing to finishing lambs (prime lamb enterprise)

In the prime lamb enterprise scenario, the cost of flushing ewes on green feed is equivalent to the extra value that could be made from taking lambs to higher weights on the available green feed.   Should the green feed be used for finishing lambs, ewes could also be fed lupins to achieve the flushing effect.  The following examples present these options under a range of scenarios using the base case variables (Table 2).

Comparisons for different green feed on offer

Figure 3 presents a comparison of different options for using green feed when FOO is varied.  In this scenario, with green FOO greater than 1500 kg/ha, and 20% of the farm sown to green feed, there is enough to graze a portion of the total area with ewes (stocked at 7 ewes/ha farm area and 35 ewes/ha of lucerne) for the 14 days required for flushing, and still have enough area to allocate to a portion of the lambs for finishing (taking lambs from 35 kg – 42 kg lwt in 40 days).  This option will return higher margins than only using the green feed for finishing lambs, but if lupins are also used for flushing, the combined margins of the flushing and lamb finishing will be higher.  At the higher proportion of green feed (40% of the farm), it becomes possible to flush ewes and finish all lambs, so the margins become higher.  With a lower proportion of green feed (10% of the farm), it is marginally more profitable to finish lambs than flush ewes with higher feed availability.  At lower green FOO, the most profitable option is to flush the ewes as the green feed becomes unsuitable for finishing lambs at less than 1000 kg/ha.

Note that the lamb growth rates achieved in this scenario (180 g/hd/day) will not be sustained at lower feed quality.  Lucerne can lose its leaf and overall quality in hotter summer conditions so this needs to be considered and managed when estimating the length of time lambs can be grazed and their growth if the feed source is lucerne. Also note that these figures assume that the available lucerne is not needed to maintain the condition of ewes.  See Flexibility in livestock systems is important for risk management in variable climates from Wagga Wagga Proof Site which discusses the effect the proportion of lucerne, the time of lambing and the seasonal scenarios will have on the availability of lucerne for finishing lambs.

Figure 3. Effect of different green feed on offer (kgDM/ha) on return ($/ha farm area) from flushing ewes and finishing lambs on either green feed or lupins. See Table 2 for assumptions used in this analysis.
Figure 3. Effect of different green feed on offer (kgDM/ha) on return ($/ha farm area) from flushing ewes and finishing lambs on either green feed or lupins. See Table 2 for assumptions used in this analysis.

*At 800 kg/ha, pasture is unsuitable to achieve lamb growth, and at 20% lucerne, only 75% of ewes (at 7 ewes/ha) can be flushed.

Other considerations

The above scenario was also run with varying lamb price, feeding costs, stocking rates, pasture growth rate and marking percentages.

Changes in the price of lupins to produce a flushing response, and changes in the price of grain to maintain twin bearing ewes during pregnancy and lactation have little overall effect on the overall return. Although stocking rate and pasture growth rate change the overall return, these do not change which is the most profitable option.

A 10% change in lamb survival can give an overall income change of $8/ha when flushing ewes on lucerne. Therefore, if lamb survival within a system is currently low, utilising green feed for other stock may be the most suitable and profitable option.

Lamb prices $1.50 above and $1.50 below the standard were examined for the finishing lambs, while the price for the additional twins was kept at the standard (Figure 4).  At the higher price, using all the lucerne for finishing lambs became more profitable than the combined finishing lambs and flushing ewes on green feed.  The lower price did not make a difference to which was the most profitable option.

Figure 4. Comparison of returns from finishing lambs and flushing ewes on green feed under three price scenarios. See Table 2 for assumptions used in this analysis.
Figure 4. Comparison of returns from finishing lambs and flushing ewes on green feed under three price scenarios. See Table 2 for assumptions used in this analysis.

In conclusion, for a prime lamb enterprise, with higher green feed availability, flushing ewes on lucerne and allocating the remaining lucerne to finishing lambs is more profitable than allocating all lucerne to lambs in most scenarios.  However, when ewes are flushed with lupins, using the lucerne for lambs can be equally or more profitable.  At lower feed availability, it is more profitable to flush ewes than to finish lambs. Varying the stocking rate, pasture growth rate, feeding costs and marking percentages makes little difference to which is the most profitable option.  Higher lamb prices make finishing lambs a more profitable option.

Comparing to growing out weaners

In a self-replacing flock, the cost of flushing ewes on green feed is equivalent to the supplementary feed costs that could be saved by grazing weaners during the summer. Other benefits of feeding lucerne to weaners may be increased weight gain, given high quality feed is available to graze, and reduced mortality, however these benefits have not been analysed in the following scenario. Like grazing lambs, if available green feed is used to graze replacement weaners, ewes could be fed lupins to achieve the flushing effect.  The following examples compare the profitability of each option under a range of scenarios.

Comparisons for different green feed on offer

Figure 5 shows a comparison of the returns from flushing and feeding weaners on lucerne when FOO is varied.  Like in the lamb example above, in this scenario, when FOO is greater than 1500 kg/ha, and at least 20% of the farm is sown to green feed, there is enough to graze a portion of the lucerne with ewes (stocked at 7 ewes/ha farm area and 35 ewes/ha of lucerne) for 14 days, and graze some weaners for 40 days on green pastures.  If there is only 10% of the farm with green feed, the returns are marginally higher for flushing than grazing weaners unless lupins are fed.  However the advantages of grazing weaners for survival probably make this a better option than flushing if FOO is above 1500 kg/ha.  At lower green FOO, the most profitable option is to flush the ewes on lucerne.

Figure 5. Comparison of returns from flushing ewes and growing out weaners on green feed. See Table 2 for assumptions used in this analysis.
Figure 5. Comparison of returns from flushing ewes and growing out weaners on green feed. See Table 2 for assumptions used in this analysis.

*Note the value from flushing assumes that the resulting additional twin lambs are sold at 35 kg/hd.

Comparisons for changes in grain price

The cost of feeding supplement to maintain weaners for 40 days will influence the overall savings to be gained when comparing to flushing ewes with lucerne. As stated above, change in grain price has little significant effect on the profitability of flushing ewes, however, will affect the cost benefit of using lucerne to graze weaners. Figure 6 shows that (with 2000 kgDM/ha and 20% of farm sown to lucerne), utilising lucerne for weaners is a more cost effective option when grain is being bought at a price above $200/tonne, provided lupins are fed to achieve a flushing effect.   Again, this does not consider the value of using the green feed to increase weaner survival.

Figure 6. Comparison of returns from flushing ewes and grazing weaners on green feed under five grain price scenarios. See Table 2 for assumptions used in this analysis.
Figure 6. Comparison of returns from flushing ewes and grazing weaners on green feed under five grain price scenarios. See Table 2 for assumptions used in this analysis.

* Weaner feeding costs (when not on lucerne) – supplement is fed at 1kg/hd/day and grain price average based on Southwest Farm Monitor Project 10-year average 2001-2011.

Other considerations

Similarly to the grazing lambs scenario, lamb price, and marking percentages will have small effect on the profitability of flushing and should also be considered when making a decision on utilising available green feed.

When grazing weaners on lucerne over summer and for long periods of time, feed needs to be monitored to ensure quality does not fall below 60% digestibility and 800-1000 kg/ha of green feed is available so weaners can be maintained at acceptable growth rates. Note that these figures also assume that the available lucerne is not needed to maintain the condition of ewes.

Tools you can use

There are a number of tools available which can be used to help determine the amount of green feed available for grazing as well as provide decision support for how feed can be managed:

Is synchronisation worth considering?

Synchronisation may be considered if a very short joining period is required.  The key benefit of synchronising ewes is a shorter period (5-9 days vs. 14 days) on green feed or lupins compared to unsynchronised ewes.  The cost of synchronisation is $1.50/ewe joined, without including the costs of extra labour and additional rams (10% compared with 1%, unless synchronising in batches, which increases labour).

What it all means

Flushing with green feed provides a cost-effective means for achieving more lambs from an autumn joining.

The Wagga Wagga on-farm experiment showed that ewes grazed on green feed for a week prior and a week during joining can achieve a flushing effect resulting in 14% more lambs born (foetuses scanned) and 10% more lambs marked compared to ewes grazing on dead stubble. The response to flushing will vary above and below the level achieved at Wagga Wagga with the amount and quality of feed and the condition and genetic potential of ewes.

The increase in lambs marked and additional income to be made from flushing will be unique to the enterprise set-up and the season and market conditions in a given year.  Use the EverGraze Green Feed Allocation Tool to work out the scenario that will return the highest margins for your unique situation.

The following factors should be considered;

Flushing responses have been determined during autumn joining when ewes are naturally cycling, however a flushing response has not been tested for spring-joined flocks (out-of-season breeding) or in maiden ewes where responses may be lower.<td”>Higher stocking rates will return higher margins from flushing as there will be a relatively higher number of lambs born from multiple births.<td”>If current lamb survival rates are low, the returns from flushing ewes will be reduced.  Twins have a much higher risk of mortality than singles, so additional requirements for ewe nutrition and management need to be in place for managing more twins.

Time of joining Flushing responses have been determined during autumn joining when ewes are naturally cycling, however a flushing response has not been tested for spring-joined flocks (out-of-season breeding) or in maiden ewes where responses may be lower.
Stocking rate Higher stocking rates will return higher margins from flushing as there will be a relatively higher number of lambs born from multiple births.
Lamb survival and management of twins. If current lamb survival rates are low, the returns from flushing ewes will be reduced. Twins have a much higher risk of mortality than singles, so additional requirements for ewe nutrition and management need to be in place for managing more twins.
The need to feed ewes during pregnancy and lactation In the scenarios presented above, the additional cost of supplementary feeding ewes with twins was $1.50 during pregnancy and $6 during lactation.  This cost will depend on the price of grain and the available pasture, especially during lactation.
Market value of additional twin lambs Market value will depend on price and weight at sale.  Additional feeding costs to raise twin lambs to sale weight may also need to be considered.
The amount and quality of live pasture, and availability of lupin grain. This will determine the number of ewes that can be flushed and which stock class will produce the greatest returns from the available green feed.  Flushing ewes will give greater returns than feeding lambs or weaners if there is limited green feed on offer. With a lower percentage of the farm sown to green feed, it is equal or more profitable to finish lambs.  The greatest return will be made if enough feed is available to both flush ewes and graze lambs or weaners. Using lupins to flush ewes (and graze lambs or weaners on green feed) can also result in higher overall margins under some scenarios.In years with good summer rainfall, it is possible that flushing will be possible on green grass-based pastures (as little as 350 kg/ha green), so this should also be considered.
Price of grain In a self-replacing system, if the price of grain is high, it will be more profitable to graze weaners on the available green feed than flush ewes.

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 and included staff at Charles Sturt University and the Department of Primary Industries NSW.  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

Dr Susan Robertson, Charles Sturt University, Wagga Wagga, NSW

Anita Morant, formerly Agriculture Victoria, Hamilton

Dr Michael Friend, Charles Sturt University, Wagga Wagga, NSW

Kate Sargeant, formerly Agriculture Victoria, Benalla

Laura Garland, Agriculture Victoria, Hamilton

Research

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