The strong outlook for lamb is an even greater incentive for farmers to maximise the kilograms of product they sell next season.
Maximising lamb finishing performance was the focus of a recent Beef + Lamb New Zealand Central Otago Farming for Profit webinar featuring farm consultant and former farmer Peter Young.
He set the scene by saying the profitability of a lamb production system is determined by the reproductive performance of the flock, wastage, and pre- and post-weaning growth rates.
“The goal is to maximise the kilograms of product sold.”
He says the most efficient time to grow lambs is pre-weaning and these pre-weaning growth rates are driven by several factors. These include the body condition of the ewes at lambing, pasture covers at lambing, pasture quality, stock water, genetics and animal health factors such as internal parasites, trace element status and clostridial diseases.
To finish or to store
If a choice is necessary, the priority must be given to capital stock over finishing stock.
Peter says in making this decision, farmers need to consider how much feed they have available and how much of it is suitable for lambs.
The drench status of the farm may also influence this decision as will the market at the time. If the store market is particularly strong, it might be more profitable to sell at least a portion of the lamb crop as store, but ultimately the decision comes back to feed and the quality of feed available to finish lambs.
Forage options for finishing lambs
Forage options for lamb finishing include ryegrass and clover pastures, summer brassicas, specialist mixes such as herbs and legumes, and single species including lucerne and red clover.
Each of these has its strengths and weaknesses.
Ryegrass and clover
Under the right conditions, ryegrass and clover pastures are capable of driving high lamb growth rates, but this is dependent upon the quantity of clover in the sward. The quality of ryegrass-based pastures also deteriorates in heat and with maturity.
Peter says given a choice, lambs would choose a diet that is 70% legume and 30% ryegrass.
As soon as the quantity of legume in the pasture drops to 30%, lambs should be moved and a different stock class brought in to graze the remaining pasture covers.
This means that lamb finishing pastures should be assessed on remaining clover rather than residual covers.
“If we’re going to maintain high lamb growth rates, we need to move them on as soon as the legume has gone.”
Peter says complementary follow-up stock such as R2 cattle will still put on weight on these pastures, after lambs have picked out the legume. Cattle will also help control sheep worm larval burdens.
Brassicas
Compared to pasture, brassicas are very efficient at turning water into drymatter, growing around 34kgDM/1mm of water – provided nutrients aren’t a limiting factor.
Brassica crops are an effective way of transferring a spring surplus until later in the year, but there are costs involved with growing brassica crops, and they need to be able to fit into the farm system i.e. taking out ground in spring may not be ideal.
While brassica crops can drive high lamb growth rates, there is a transition period, so the longer the lambs are on the crops the higher the growth rates.
As a “clean” crop, brassicas can also be used to manage worm burdens, particularly on farms with drench resistance, although there can be other health risks associated with these crops.
A supplement may be required when feeding brassica crops and Peter suggests not looking at supplement as a cost, as it will add to the crop’s overall performance.
Legume/herb mix
These highly digestible mixes can drive impressive growth rates at certain times of the year, but there are health risks associated with them, particularly clostridial diseases.
From an agronomic point of view, weed control options for these mixes are limited.
Lucerne
Protein- rich lucerne is capable of very high growth rates- both animal and drymatter.
Because it has a shorter growing season (it doesn’t come away until late spring), within a breeding system, it can exacerbate the early spring feed pinch.
Lucerne is high in crude protein, so it may require a high-fibre supplement if lambs are not growing as well as expected. Peter recommends getting feed tested once factors such as internal parasites and trace element deficiencies have been ruled out.
When the lucerne stand is mature or flowering, feed quality can be variable; the stem can have an ME of 8 while the leaf has an ME of 12.
Peter recommends measuring the proportion of stalk and leaf and determining the lamb stocking rate based on this. Once the lambs have grazed the high-quality leaf, cattle can be used to utilise the stem without any risk of bloat.
Stock do need access to salt when grazing lucerne.
Red clover
Red clover can be used as an alternative crop to brassicas. It’s drymatter production is similar to that of a summer brassica and has the same potential for lamb growth.
Maximising the value of the lamb crop
Peter urges farmers to try and reduce the variability on their killing sheets by checking the fullness of the loin of every lamb above the target weight.
“Don’t use the weight of the lambs as the only selection criteria.”
The fullness of the loin in conjunction with weight can generate more consistent carcase yields.
The frequency of drafts is subject to both lamb growth rates and drench withholding periods.
In developing a sale strategy, Peter recommends farmers compare store and prime values and use this information in conjunction with feed availability, feed quality and the requirements of capital stock.
Most years the schedule will increase going into winter, but the cost of wintering also needs to be considered, as does the genetic potential of the lamb. This is affected by gender and feed quality.
Peter says terminal sire lambs may not necessarily finish earlier, they simply have the potential to put on more weight.
“Every lamb will have an optimal finished weight.”