Introduction
The digestibility and energy value of pasture species fall dramatically following seed set and ‘drying off’. In Western Australia, pastures decline in quantity and quality from about October–November until the break of season (about April–May) in the following year. This means weaners and adult sheep are faced with 6-7 months of pastures declining in quantity and quality.
Merino weaners are likely to lose weight during these months and feed supplements such as lupin grain will be required to ensure that they progress to adulthood and become productive members of the flock. Failure to provide sufficient energy and protein for weaners with low liveweights leads to weakness, ill thrift, susceptibility to disease and possibly death from malnutrition. It takes good nutritional management to achieve the growth rates required to produce a saleable lamb at a target weight in a cost efficient manner.
Growth as a lamb and good preparation for weaning will help set up these sheep for life. See Lambing and lactation for more details.
Supplementary feeding is a key part of any weaner growing system. See Supplementary feeding of sheep for more details.
Poor growth and ill thrift of weaner sheep during their first year can reduce wool and meat production as well as the weaner’s reproductive performance at first joining.
Achieving production targets for prime lambs
A successful prime lamb producer identifies the market and sets production targets before joining the ewes. It is possible to produce lambs to a given specification at a set date reasonably consistently with knowledge of the ewe’s fertility, seasonal pasture availability, other available feed sources and potential lamb growth rates.
The first step is to identify the market and become familiar with the required specifications for fat cover and carcass weight. Other requirements such as access to grazing feed sources (for example, lupin stubbles) also need consideration. Then production targets and sub-targets should be set to plan the production path to meet the market requirements.
The production target normally consists of a number of lambs within a weight and condition score range at a set date. Sub-targets are set at checkpoints and ensure lambs are on track to meet the production target; they will also help to inform management or marketing decisions.
For example: the production target is to produce 95 crossbred lambs from 100 Merino ewes in condition score 2–3 at a carcass weight of 18–22 kilograms (kg) in mid–December. The sub-targets could be:
- mid-May — a 100% lambing with average birth weight 4kg
- mid-June — average marking weight of 11kg
- mid-October — average weaning weight of 32kg, this weight being maintained to early November when they go onto a grain finishing system for six weeks to meet the market specification of 40kg minimum liveweight in mid-December.
There are a number of management practices that need to be well understood and fine-tuned to meet production targets. These include:
- mating management to achieve a high ovulation and mating rate within a short period of time
- understanding the pasture or supplementary feed requirements to achieve optimum growth
- growth rates of the lambs
- knowing the genetic ability of the lambs
- understanding the flexibility within the sub-targets in order to be able to speed up or slow down lamb growth rate to achieve the ultimate target.
Mating targets
In prime lamb production it is often important to have a high lambing percentage. This is especially important where first cross ewes are being used and wool is a minor income source, or where heavy supplementary feeding of pregnant or lactating ewes is required to meet an out of season market. Money spent on dry ewes is money wasted. A condensed lambing period is also desirable to produce a uniform group of lambs. Late lambs often do not fit the market specifications at the desired time and are sold at a discounted price.
Achieving good growth rates in young lambs
The younger the lamb the higher the potential daily growth rate; therefore it is important to optimise the ewe’s milk production and growth of the lamb while on the ewe. Ewes have a genetic peak milk production potential that will only be reached by providing the ewe with an adequate feed source from the start of lambing. Restricting feed in early lactation cannot be compensated for later in lactation.
Peak milk production potential and total milk production potential is established early in lactation and can be reached by optimum feed availability all through lactation.
Finishing systems for lambs
There are several options for finishing lambs depending on your production system, season length and target market. Some producers are able to sell finished lambs straight off the ewe at 12–14 weeks while others wean the lambs and finish them on a high quality pasture or supplement. Lambs need a diet of 14–16% crude protein and at least 70% dry matter digestibility.
Growth rates will be influenced by genetic potential and available feed. As you become familiar with your bloodline you will become more accurate at estimating growth rates in different finishing systems.
| Lamb finishing system | Merino weight gain in g/hd/day | First cross weight gain in g/hd/day |
|---|---|---|
| Sucker lambs to 14 weeks | 240–280 | 300–360 |
| Weaned lambs on green fodder crops | 140–170 | 160–200 |
| Weaned lambs on lupin stubble | 80–160 | 80–200 |
| Weaned lambs on self-feeders of grain in stubble or dry pasture paddock | 130–150 | 150–220 |
| Lot fed lambs | 150–250 | 250–350 |
Sucker lamb production
When lambs are sold as suckers (straight off the ewe), the availability of suitable pasture is critical as lamb growth rates reflect the pasture quality and quantity available to the ewe. Preparation of the lambing paddock will require a feed budget to ensure that the desired level of feed on offer (FOO) is reached for the start of lambing, and a suitable stocking rate is placed on the paddock to maintain or increase this level throughout lactation. This system is often dependent on using the spring flush and produces lambs during the peak lamb supply.
The benefit of producing sucker lambs is that it is a low management system. Provided that the ewes are adequately catered for, they look after the lambs. There is no setback (as with weaning) or any need to introduce lambs to a new feed source. Lambs are young so growth rates and feed conversion efficiencies are maximised. Lambs are also less likely to get too fat compared with older lambs. On the other hand, there is no margin to make up weight before the planned sale date if the season prevents suitable pastures being available, and the market or turn off date may have to be changed if production sub-targets are not reached.
Lambs finished on a fodder crop
Establishing a green fodder crop can extend the length of time when high quality feed is available. Finishing lambs on a fodder crop will allow production of lambs beyond the traditional spring flush. There is also the possibility of lambing later and the pasture benchmarks for lambing and lactation are not as critical. In short, there can be more flexibility in this system compared to producing suckers.
Disadvantages include a period of about one week with negligible weight gain after weaning and the increased management required to handle a mob of weaners compared with ewes. However, there is minimal change in the feed source, which lowers the likelihood of diet-related diseases, and the feed is normally of high quality allowing maximum growth rate.
Lambs finished on crop residue in early summer
Generally cereal crop residues alone are not rich enough in protein to finish lambs on. A protein supplement such as lupins are needed, especially after the better quality feed has been eaten in the first 2–3 weeks. Lupins only need to make up 30% of the ration on fresh cereal stubble (300-400g/hd/day) to provide sufficient protein, so this is a cheap way of finishing lambs. Trail feeding twice a week may be the best method to ensure all lambs receive an equal share when there is a limited amount of supplement feed. Lupin stubbles provide an ideal source of feed for lambs provided there is no risk of lupinosis.
When lambs are allowed to select their own diet, such as on a stubble paddock, they will consume 30–40% roughage. This is higher than in feedlots because roughage normally has the lowest energy component of the diet and this limits growth rates. Provided lambs have been introduced to lupin feeding before weaning, they adapt quickly to this system and there is not normally the two week lag phase which occurs when lambs are being introduced to a feedlot.
Lambs finished on grain, cereal stubble or dry pasture
Finishing on dry stubble or pasture residue is only suitable in dry conditions. Where a green pick is present the lambs will chase the green feed and not gain weight at the desired rate. The cereal stubble or dry pasture only contributes the roughage component of the diet, which is about 30–40% of the total ration. To ensure there is always a palatable supply of roughage and prevent erosion there needs to be at least two tonnes per hectare (t/ha) of dry feed in the paddock at all times. The rest of the diet is balanced with a supply of grain normally fed in a self feeder. Because the roughage is poor quality and of low protein content, a mix of 50% lupins and 50% cereal grain is required to provide a suitable level of protein for best growth.
The cereal grain is normally oats or barley as these are safer to feed than wheat. Lambs will eat about 700g/hd/day of grain. As the grain is contributing a higher component of the diet than in the previous system it is necessary to introduce the lambs to the grain over at least a week by feeding out increasing amounts per day in a long trail. Feeding grain once or twice before weaning will help lambs to adapt to eating grain quickly. There is less of an introductory effect with grain finishing in a paddock than lot feeding.
Over a long period of time growth rates will not be as high as in a feedlot because it is difficult to reach as high an energy diet while lambs are eating 30–40% poor quality roughage. However, for finishing systems spanning less than six weeks, the benefit of the high quality diet in the feedlot may outweigh the longer introductory period where growth is negligible.
Lot feeding lambs
Lot feeding lambs is a specialised activity requiring specialised facilities. Growth rates can be higher than in other dry feed finishing systems because there is more control over the diet. Lot feeding can be done at any time of the year allowing a continuous supply to market.
Lambs take about two weeks to adjust to the feedlot environment, during which time growth rates are negligible.
Other constraints to production
Lambs require good worm control to achieve their potential growth rate. Ewes should be monitored for worms using a faecal egg count and drenched if required before placing them in the lambing paddock. Lambs should be monitored before weaning and before putting into a grain finishing system and drenched if required. This allows control before production losses occur and prevents the introduction of a worm problem into the finishing system where stocking rates are usually high and favourable to the spread of worms. Drenching may not be required if there is good worm control on the farm.
Local trace element deficiencies should be known and corrected. This is more important in a prime lamb finishing program (where maximum growth rate is the aim) than in a wool producing system. Cobalt and selenium are the two most common deficiencies.
Other diseases such as scabby mouth, pink eye, arthritis and dermatophilus (dermo, lumpy wool) can cause large setbacks in production so it is important to be aware of management practices which will minimise the occurrence and spread of these diseases. Pulpy kidney is a disease that is more common under high production systems. It is necessary to provide suitable protection with a vaccination program to prevent this disease.
Diet related diseases become important in grain finishing systems and need to be well understood.
Putting it all together
When planning a prime lamb production system:
- Determine the market for which you are aiming.
- Find out the required carcass weight range and fat score.
- Set the date for turn off.
- Decide on the finishing system to be used and the expected growth rate for that system.
From an estimation of the amount of weight to be put on in the finishing system and the start date of finishing, you can determine the required lambing date and whether you need to maintain optimum growth rates from the lamb while on the ewe. Use this information to determine the FOO required in the late pregnant, lambing and weaning paddocks.