Increase my flock marking percentage – South West Victoria (Lower)
Reproduction rates, normally referred to as marking percentages, for South West Victoria have been static over the last four decades. Analysis from the Livestock Farm Monitor Project (Livestock systems and benchmarks) shows that for properties focused on wool production, the long term average marking percentage is 77%, with the top 20% of producers (based on financial performance) in 2001-2011 averaging 76%. Similarly for businesses focused on lamb production the long term average for marking percentage is 99%, with the top 20% of producers in the last ten years averaging 104%.
The most profitable businesses in the Livestock Farm Monitor Project:
- ran a higher stocking rate than average
- achieved higher prices per kg wool or meat sold than average;
- spent more per ha on pastures than average farms;
- generally use more P fertiliser and have higher labour use efficiency.
In prime lamb production systems, crossbred ewes, on average, appear to return an increase in marking percentage of 40% over Merino ewes joined to terminal sires, with average marking percentages of 121% and 82% respectively for 2010-11. At the Hamilton EverGraze Proof Site, it was shown that similar profitability was achieved with Merino ewes joined to terminal sires with marking percentages of 92% compared to Coopworth ewes at 141%.
Lamb marking percentages will have a significant impact on overall farm stocking rate and labour efficiency and should be considered when reviewing the performance of farm businesses. Producers should be aiming for at least region average marking rates, given that the top 20% of farms in the south-west region achieve this whilst also running increased stocking rates.
What are the options?
Factors driving marking percentages can broadly be categorised as increasing conception rates, or increasing lamb survival from birth to marking (and subsequently weaning).
Management strategies to increase conception rates include;
- managing ewes to be in optimal condition score (condition score 3) at joining;
- changes to flock genetics;
- managing rams to ensure they are up to the job;
- flushing ewes at joining.
Management strategies to increase the survival rate of lambs from birth to marking include;
- managing ewe nutrition and condition in the lead up to and at lambing (condition score 2.8-3 for single bearing ewes 3-3.3 for twin bearing ewes) to ensure adequate birth weight, milk supply (colostrum production), lamb growth after birth and reduce ewe mortality;
- ensuring adequate pasture (1200 kg/ha for single bearing ewes and 1800 kg/ha for twin bearing ewes) is available at lambing to meet nutritional needs (above) and enable the process of ewe/lamb bonding (prevent the ewe from leaving the birth site);
- provision of shelter to lambing ewes (especially twin bearers) when lambing in adverse weather conditions;
- managing the mob size and set stocking at lambing;
- pregnancy scanning to enable separate management of twin bearing ewes to achieve the above objectives; and
- control of predators.
Altering the time of lambing (to lamb in milder conditions and/or when more high quality paddock feed is available) is another option available to farmers and will impact on conception rate and lamb survival.
What is your potential to improve?
The first step is identifying where the opportunities exist. Is the greatest opportunity in lifting conception rates, or is increasing lamb survival the largest opportunity for an increased marking percentage? Without any pregnancy scanning data, this will be a difficult question to answer. Pregnancy scanning data can be compared to lamb marking data to determine the number of lambs that are lost between scanning and lamb marking. If the flock marking percentage is well below the district average then there is likely to be gain from tackling both key areas of conception and survival. If the flock is closer to the target marking percentage, gaining a better understanding of how it is performing at different phases of reproduction will be useful in determining whether attention is needed.
Table 1 (adapted from the worksheet provided in the EverGraze Exchange – Improving the survival of lambs) provides a template for comparing conception, survival and overall marking percentage of your flock to a set of targets. Best practice targets (proposed by Lifetimewool) for survival of single (90%) and twin (70%) lambing Merino ewes are used in the example. Target conception rates (124%) are then based on what is required to achieve 100% overall marking. The actual figures used are purely an example, and show that in this case, potential gains could be made, particularly from improving lamb survival.
To use the template, enter your ultrasound scanning data, work out the potential number of lambs you should have at marking based on the best practice survival targets and then compare that to the number of lambs you actually have at marking. This will give you an estimate of how your flock compares to what could be achieved. To help establish whether problems with survival are associated with large single lambs (eg due to dystocia) or small twin lambs, it may be useful to collect dead lambs for a few days and determine causes of death. Notes on lamb autopsy can be found here, or enlist the help of your district veterinarian.
Table 1. Example template for comparing scanning and marking results to targets.
|Target scanning||Target potential lambs||Actual scanning||Potential lambs at marking||Target survival||Actual lambs marked|
|Single||140 A||x 1 = 140||100 E||x 1 = 100||x 90% = 90|
|Twin||60 B||x 2 = 120||100 F||x 2 = 200||x 70% = 140|
|Total||210 C||260 D||210 G||300 H||230 I||200 J|
|Percentages||(A+B)/C = 95%||D/C = 124%||(E+F)/G = 95%||H/G = 143%||E/H = 77%||Survival: J/H x 100 = 67%Overall: J/C x 100 = 95%|
Options in more detail
Increasing conception rate
Meeting ewe condition targets at joining
Ewe condition score targets are a key benchmark to be monitored by producers through the year. In the context of conception, the Lifetimewool project has identified that ewes in better condition score at joining will have more lambs. The average response across Merino ewes has been about 20 extra lambs born per 100 ewes joined per condition score.
This reproduction response to condition score rate can vary considerably with some flocks having a zero response (i.e. zero extra lambs per condition score) and others achieving up to an extra 40 lambs per 100 ewes per condition score. It is therefore very important for producers to understand the response rate of their ewes to an extra condition score as that knowledge will impact on management decisions. For instance if the response is 30 extra lambs for every 100 ewes per condition score then there is more benefit in feeding to gain an extra condition score than if the response is only 20 extra lambs per 100 ewes per condition score.
EverGraze utilised the principles of Lifetimewool in the management of the ewes during the experiment period. This included separating twins and singles after pregnancy scanning, managing condition score of ewes leading up to joining, during gestation and lactation, matching available feed to the demands of ewes and supplementary feeding where required. Importantly though EverGraze research demonstrated that the Lifetimewool principles, of manipulating condition score to maximise reproduction rates, can be met profitably and effectively by utilising perennial pasture systems.
Producers wishing to gain a greater understanding of how to monitor ewe condition score and allocate feed appropriately, are encouraged to participate in a Lifetime Ewe Management course.
Improving the genetic base of the ewe flock
In the case of EverGraze, the genetics of the ewes for each of the prime lamb and Merino flocks were based on breeds (in the case of the Coopworth Composite ewes used at Hamilton) or bloodlines (in the case of the Merino ewes) that have been bred from sires of known genetic merit using Australian Sheep Breeding Values (ASBV’s). This has resulted in ewes that are of greater than average genetic merit for reproductive performance. The ewes are also responsive to management aimed at manipulating their condition score to influence conception rate. More information can be found on ASBV’s at the Sheep Genetics website.
Sheep Genetics tools, Lambplan and Merino Select can assist in identifying which rams can assist in breeding replacement ewes with greater fertility and a greater ability to wean more lambs. There are a number of direct traits that can be selected for, such as number of lambs born (NLB), number of lambs weaned (NLW), scrotal circumference (SC, to assist in breeding more fertile daughters) and maternal weaning weight (MWWT). For producers buying replacement ewes, improving their fertility can be more difficult. Options such as direct sales and AuctionsPlus allow for increased communication between seller and buyer and may allow for better feedback of their performance.
Emerging research is suggesting that a range of traits not directly related to fertility or weaning percentages may also have a positive impact on marking percentages. Of particular relevance to Merino flocks, genetic muscle (post weaning muscle (PEMD)) and fat (post weaning fat (PFAT)) have been shown to increase the reproductive performance of ewes. Bred Well Fed Well, a one day workshop delivered through the Sheep CRC, is showing producers across the country how they can use this information in their flocks.
There are three new traits that can be used by producers to assist in selecting rams which will reduce problems associated with birthing difficulties, or dystocia. These traits are Lambing Ease Direct (LE DIR), which can be used by purchasers of terminal sires, and Lambing Ease Daughters (LE DTR), which can be used by purchasers of maternal sires and sires used to breed replacement ewes, and Gestation Length (GL). It is best to select sires with moderate GL ASBVs as either a too long or too short gestation length will have a negative effect on lamb survival.
Ram health and management
Any stress in the eight weeks prior to joining can affect semen production, which will affect the performance of the ram. Rams should be maintained in a condition score 3 year round, with condition score increasing leading up to joining (condition score 3.5 to 4). Rams should be shorn 10 to 12 weeks prior to joining, allowing them time to recover from any injuries or infections that may occur. In hot weather, shearing later than eight weeks before joining can be problematic as rams are less able to regulate their body temperature when bare shorn. If rams are not shorn, they should be ring crutched around the pizzle or, preferably, remove the belly wool all together, especially if there is any bur or seed. Rams should also be drenched, with an effective drench, prior to being used, as well as given an annual booster of 6 in 1 vaccination.
Rams scrotal circumference should be at least 28cm, and testicles firm and springy – not hard. If the tone or size of the testicles is not ideal 10 to 12 weeks prior to the joining period feeding will be required immediately. For rams greater than 80kg, feeding 0.5kg/head of lupins per day, combined with pasture or additional supplementary feed suitable for a dry sheep equivalent to the rams’ weight, will be sufficient to increase testicle size and tone. This will help ensure that the serving capacity of the rams is maximised.
In most circumstances a five week joining period with rams used at a rate of three rams per 200 ewes should be sufficient. If joining in very hilly terrain, or in large paddocks with multiple water points or variable feed, or during periods of expected hot weather, it may be necessary to increase this rate.
When rams are removed from the ewes they should again be assessed for injury, body condition and general health. Rams should be put onto good feed, returned to a condition score 3 and monitored for worms and drenched if needed. Where producers would like to use rams more than once in 12 months, they should be returned to condition score 3 as soon as possible after removing from the ewes, and once there they will be ready for use again in 10 weeks’ time. Workshops such as RamSelect or Bred Well Fed Well can assist produces learn how to assess a rams’ suitability for joining.
If joining in hot conditions, ensure paddocks have adequate shade, as hot weather can reduce sperm quality and also increase embryo mortality in ewes.
In an on-farm trial conducted near Wagga Wagga in NSW, ewes grazing lucerne for one week prior to joining and through the first week of joining resulted in 33% more multiple pregnancies when compared to ewes grazed solely on dry pastures during joining. There was no change in the number of non-pregnant ewes with each treatment having 6% and 5% non-pregnant ewes respectively. Full details of experiment results and how to apply to your own farm can be found in the Wagga Wagga research message: More lambs from flushing ewes on green feed.
Producers should be mindful that an increase in conception rate will not directly result in an increase of more lambs at marking. Research at Wagga Wagga and Hamilton EverGraze sites showed that survival from birth to marking for twin and triplet lambs is lower than for single lambs. However using the findings from Wagga Wagga and Hamilton it can be estimated that flushing ewes via this method can result in an extra 10% more lambs at marking.
Flushing should not be seen as a replacement for having a ewe in optimum condition score for joining, but it is a useful tool for getting the most out of ewes. It may also be useful when attempting to join ewes that are not at optimal joining condition. Producers who are considering using flushing to increase the ovulation rates of sub-optimal condition score ewes should have a plan in place for increasing condition prior to lambing to ensure that lamb and ewe survival is not compromised. Flushing also appears to have limited benefit when joining fat ewes, i.e. greater than condition score 4.
The EverGraze Exchange – Short term flushing increases ovulation is a fact sheet providing more information
The EverGraze Tactical Management for Green Feed decision support tool assists producers to determine the potential returns from flushing ewes on green feed or lupins, and to compare this to allocating the green feed to other classes of livestock (e.g. lambs or weaners). Variables such as the expected response to flushing, the available feed, the availability of lupins, farm stocking rate and the classes of livestock are considered in the tool.
Options for increasing survival from birth to lamb marking
Managing ewe nutrition and condition score during gestation and at lambing
At lambing, single-bearing ewes should have at least 1200 kg DM/ha available and twins should have 1800 kg DM/ha available to ensure that the ewe doesn’t leave the birth site before the ewe and lamb have bonded. The EverGraze Feedbase Planning and Budgeting Tools can be used to ensure that there is sufficient feed on offer at the start of lambing.
Pregnancy scanning ewes and managing ewes according to their pregnancy status assists in increasing the reproductive rate of the ewe flock, and can also add to total farm profitability. Young et al, modelled a property in south-west Victoria, using feed budgeting and the relationships developed by Lifetimewool to look at whole farm profit from scanning ewes and adjusting management accordingly. In this study it was found than an extra $1.80/ewe/year whole farm profit could be achieved.
Pregnancy scanning 90 days after the first joining day will assist in identifying which ewes are carrying multiple lambs. These are the ewes likely to be under the most nutritional stress. Once this information is obtained a number of management options are then available as outlined by Lifetimewool:
- Identify twin bearing ewes (with option to run separately in late pregnancy) and remove dry ewes at scanning
- Draft off twin bearing ewes less than condition score 2.5 at day 90 and manage separately to increase condition score
- Draft off any single ewes less than condition score 2 at day 90 and manage separately to increase condition score
To manage ewes appropriately to gain or maintain condition, producers need to be able to understand the energy requirement of the ewe, determine what is available from pasture, understand how to estimate the difference and determine how much of an appropriate supplement to give. Lifetimewool provides a number of tools to assist producers to undertake this process including:
- Feed budgeting in the dry and droughts – annual and mixed perennial pastures
- Feed budgeting at the break of season – annual clover based pastures
- Feed budgeting in the green – mixed pastures south-eastern Australia
The EverGraze Feed Budget and Rotation Planner provides simple tools for paddock budgets and ration development, based on Lifetimewool guidelines for energy requirements. See the Feed Budgeting and Tactical Management page for examples on how to use the tool.
Producers wishing to gain a greater understanding of how to monitor ewe condition score and allocate feed appropriately are encouraged to participate in a Lifetime Ewe Management course. The EverGraze Feed Budgeting and Tactical Management workshop can also provide understanding on how to develop fodder budgets and plan ahead for meeting livestock requirements throughout the growing season.
Paddock selection and mob size
Table 2: Maximum mob sizes for lambing ewes (Bred Well, Fed Well 2013)
|Mob Type||Maximum recommended number of ewes per mob|
|Single bearing mature ewes||400|
|Single bearing maiden ewes||300|
|Twin bearing mature ewes||200|
|Twin bearing maiden ewes||150|
Research is currently underway to determine the optimum mob size for different landforms, sheep genotypes, twinning rates and age groups.
EverGraze research at Hamilton has shown that shelter provided during lambing can increase survival. This is especially so for twins and triplets. The factors impacting on whether providing extra shelter to lambing ewes will be beneficial or not include;
- the proportion of the lambing period likely to experience bad chill conditions due to the combination of wind, rain and cold (shelter will be less effective if chill is not associated with wind);
- the breed of the sheep; and
- the percentage of multiple births.
The EverGraze Shelter improves lamb survival research message provides detailed results and discussion around shelter. A summary is provided below.
Shelter will be successful when it breaks the flow of wind across the lambing paddocks. There are multiple options available to producers, including hedge rows of perennial pasture plants such as *tall wheat grass (used at the Hamilton EverGraze Proof Site), mechanical structures such as hessian (used at Wagga Wagga EverGraze Proof Site), or herbaceous plants such as acacia shrubs (also at Wagga Wagga) or salt bush (used at Bengworden EverGraze Supporting Site). Producers thinking of using acacia shrubs or herbaceous plants should consider the costs associated with establishing this form of shelter and seek further advice.
In the Hamilton experiment, it was shown that wind speed next to the tall wheat grass hedge rows was reduced by up to 99% relative to the unsheltered areas and hedges were expected to reduce the average number of chill days per month by 75% or from 10-13 to just three or four days. This greatly reduced the risk of lamb mortality due to exposure.
Lamb survival is measured as the number of live lambs at marking expressed as a percentage of the number of lamb foetuses at pregnancy scanning. For lambs at average birthweight (singles, twins or triplets), the reduction in the number of bad chill days directly resulted in an average increase in survival from 69% in unsheltered paddocks to 90% in areas with shelter. This average increase in survival was observed in single and multiple birth types and across Merino and Coopworth breeds.
As could be expected, there were higher benefits for twins and triplets than there were for single born lambs. Table 1 below shows the corresponding gains in lamb survival, with combined data for Merinos and Coopworths, for single, twin and triplet born lambs.
Table 3: Lamb survival at the average birth weight when lambed in a sheltered environment provided by perennial grass hedges or in the open (EverGraze 2009)
|Lamb survival (%)|
*It should be noted that, as the numbers of triplets born in the experiment was low, the improvement in survival due to shelter is overestimated but the effect is statistically significant.
Producers should review their farm in terms of identifying suitable ‘maternity wards’ that may already exist. Paddocks that are naturally protected from prevailing winds (have gullies, rocks, hills, trees, tussocks etc.) which may provide as effective shelter at a much lower cost and management input than establishing hedgerows, should be selected as maternity ward paddocks. However, choice of such paddocks should never compromise the quality and quantity of feed available. Well sheltered paddocks but with inadequate feed will often result in poor lamb survival. At Wagga and Hamilton, sheltered paddocks that resulted in improvements in survival were always managed to have adequate high quality feed available to lambing ewes. Producers thinking of using acacia shrubs or herbaceous plants should consider the costs associated with establishing this form of shelter and seek further advice.
|*While tall wheatgrass is highly suitable as a hedgerow grass species, a weed risk assessment undertaken by the Future Farm Industries CRC has identified tall wheatgrass as having a high environmental weed risk for Victoria through its capacity to invade and impact on wetlands. For this reason, the CRC does not recommend the planting of tall wheatgrass in Victoria. Agriculture Victoria considers that because tall wheatgrass is already widely distributed and has production and animal welfare benefits, its continued planting is appropriate provided that the following practices to reduce the risk to native vegetation are adopted: To minimise the risk of tall wheatgrass spreading into areas where it is unwanted, hedgerows should be grazed in January and February to remove immature seed. Areas surrounding tall wheatgrass should be sown to competitive species such as perennial ryegrass and phalaris to reduce the chance of spread outside the sown area. Hedge areas should be located well away from waterways or natural wetlands not only to reduce the chance of spread, but because these areas are often too wet for lambing and can harbour foxes.|
Time of lambing
Shifting to a later lambing allows for a higher stocking rate (due to lower demand through the winter months) thus increasing the amount of wool or lamb produced. Lambing later also allows for ewes to have naturally higher conception rates. This is due to the naturally higher ovulation rate per condition score response that was identified by Lifetimewool. As a result there may be a greater return for investment from raising condition score of ewes if lambing in spring versus winter. This combined with the fact that ewes which are non-pregnant or in early gestation require less energy than ewes in late gestation or during lambing means, that by lambing later, the autumn break can be used to gain condition on ewes, and thus increase their natural ovulation.
The time of lambing will also dictate the environmental conditions that are experienced during lambing. The provision of shelter is important when there are bad chill days, which will result in increased lamb mortalities. Lambing time will also impact on the amount of available paddock feed, with a greater quantity of highly nutritious feed available in spring than in early autumn or winter. This supply of feed is important, not only to ensure that the ewe is in good condition at lambing but also to ensure that need for supplementary feeding is reduced. Supplementary feeding of ewes during lambing can lead to ewes leaving the birth site to eat and as a result mismothering of lambs may occur. By minimising any disturbances during the lambing period, the opportunity that ewes have to bond with their lambs is maximised, reducing losses from mismothering, starvation and in some cases predation. Ideally ewes should have at least six hours at the birth site with their newborn lamb(s). See EverGraze Exchange – Improving survival of lambs for further detail.
Strategies and management to meet condition score targets
- Setting stocking rates and lambing time to best match the feed supply while also considering target markets;
- Applying the EverGraze principle Right Plant, Right Place, Right Purpose, Right Management to selection of pasture combinations that supply quality feed when it is needed;
- Understanding pasture and livestock targets, constantly monitoring, and using fodder budgets to plan ahead and take action early.
- Supplementary feeding when pastures fall below livestock requirements;
- Managing pastures with deferred grazing (to build a feed wedge), nitrogen or Gibberellic acid when required to ensure feed is available when it is most needed.
Processes for considering changes to stocking rates, lambing time and enterprise selection can be found under On-Farm Options for Livestock Systems. On-Farm Options for the Feedbase and Pasture Species provides information for selecting feedbase combinations. The Hamilton Proof Site key message Right Plant, Right Place, Right Purpose, Right Management also discusses applying the principles to the south-west Victorian region with results from the Proof Site pasture systems.
There are a number of tools available for estimating pasture quantity and quality. Lifetimewool provides a useful feed on offer (FOO) Photo Gallery for perennial and annual mixed pasture species, and EverGraze has developed feed on offer photo galleries for lucerne and chicory and native pastures.
Stuart Warner, Agristology, Beechworth, Victoria
Kate Sargeant, Agriculture Victoria, Benalla
- EverGraze Exchange: Improving survival of lambs
- EverGraze Exchange: Livestock systems for profitable and sustainable pasture use
- Hamilton and Wagga Wagga EverGraze research message – Shelter improves lamb survival
- Wagga Wagga EverGraze research message – More lambs from flushing on green feed
- Wagga Wagga EverGraze research message – Flexibility in livestock systems is important for risk management in variable climates
- Hamilton EverGraze research message – Sheep systems for maximising profit from perennials
- Hamilton EverGraze research message – Right Plant, Right Place, Right Purpose, Right Management
- EverGraze phone seminar – Increasing lamb survival
- Making More From Sheep
- Sheep Genetics Resources (Pocket Guide; Getting started with Sheep Genetics; An introduction to MERINOSELECT; An introduction to LAMBPLAN; Understanding LAMBPLAN; Maternal ASBVs)
- Condition Scoring of Sheep (Lifetimewool)
- Lifetime wool “Ewes in Better Condition at Joining Conceive More Lambs
- Lifetimewool “Improving Lamb Survival”
- Lifetimewool “More Productive Progeny through Better Ewe Management”
- Lifetimewool “Tools for Management”
- Increasing profitability by pregnancy scanning ewes
- Making More From Sheep: MODULE 10: Wean More Lambs
- Sheep Genetics “New Genetic Traits”