printStock Journal Feature - August 2024
Author: Deb Scammell, Talking Livestock
With a tough start to the season, many of the young stock that are on the ground are lighter than we would like for this time of year. Early weaning has been very successful in most cases and allowed high quality pastures to be prioritised for growing lambs and reduced the overall feed costs of feeding ewes and lambs. If you are considering early weaning, it’s important minimum age and weight targets are met before this can be considered.
Once lambs are weaned this year, it’s even more critical to set minimum weight targets going forward and ensure young stock are achieving adequate growth rates. This will reduce mortality of lambs post-weaning and also ensure that high quality sale animals and breeding stock replacements are produced.
Research has shown that maintaining a growth rate of over 50 grams per day for weaned lambs will reduce their risk of mortality until 12 months of age and can allow minimum joining targets to be reached if joining as a hogget. When setting weaning targets, we usually look at a percentage of the standard reference weight of the stock. Standard reference weight is the mature adult weight of the animal. You can calculate standard reference weight (SRW) by weighing mature breeding ewes in condition score 3 (or adjusting by 7kg per condition score under or over 3), off shears (or adjust for fleece weight present) and when they aren’t pregnant. This year many progeny have not reached minimum weaning weight targets (45% of SRW) meaning that minimum growth rates will need to be higher than this post weaning until they hit this minimum target.
It is recommended to provide adequate nutrition to achieve higher growth rates post-weaning until lambs hit their standard weaning weight targets (45% of SRW) which gets them out of the ‘risk’ period for young animals. Smaller liveweight stock that are weaned at lighter weights have less body reserves (protein and fat) which means they are less likely to withstand any ‘checks’ such as health challenges, weather events etc. Once the lambs have reached 45% of their SRW they can then go back to standard growth rates – these targets are often higher for sale stock or any ewes that are likely to be joined as lambs. The 50g/day target for replacement breeding stock is a minimum target, I would recommend slightly higher targets than this until the first Summer.
To achieve higher growth weights for these lighter lambs, protein is critical. The lighter the lamb the higher the requirement for protein. A lamb around 30kg will need around 16% protein (dependent on growth rate targets) as they are building meat and muscle, this requirement is higher again for lighter lambs. This must be balanced with adequate energy to ensure nutrition is balanced. The green feed that is present has high protein at its current stage with feed tests showing a range of 20 – 30% protein in a lot of the current sown cereals, perennial pastures and even fresh barley grass. However, with the late break the quantity of pasture available with the slow pasture growth is more of an issue. If quantity isn’t sufficient in pastures ear marked for youngstock, supplementary feed providing energy and protein is still required. This can be provided with a grain ration, including combinations of barley, peas, beans or lupins or high-quality cereal or protein hays (such as lucerne or vetch). Full feed pellets can also be a very good, well balanced option. Lambs aren’t able to eat a huge quantity of feed per day, usually around 3.5% of high-quality feed meaning a 30kg lamb will eat only around 1kg of dry matter of feed per day. Lower quality hays or short pasture isn’t able to supply the required nutrients to maximise growth for very small lambs.
Growing youngstock also requires a specific mineral balance ensuring they have adequate calcium to enable reasonable growth rates. It’s important that the calcium: phosphorus ratio has 2 parts calcium to 1 part phosphorus. If grain is being fed (high in phosphorus) then additional calcium would need to be added so that the macromineral balance isn’t reducing growth rates. If there are other micromineral deficiencies providing these minerals can assist with health, growth and immunity also.
Ewe recovery is also critical this year. Many ewes have gone through lambing below condition score targets and lost more condition than usual during lactation. Drafting ewes on condition score after lambs are weaned can enable ewes in lower condition score to be looked after better nutritionally to enable them to reach joining targets later this year or early next year. Lifetime wool research has shown that ewes in higher condition score at joining conceive more lambs with an average of 20 extra foetuses per ewe conceived with each condition score gain. This year has been tough, but it’s important to wean earlier if necessary if ewe condition score is getting critically low and look after ewes so they can gain condition and get back on track for 2025.