printStock Journal Article - June 2024
Author: Deb Scammell, Talking Livestock
The late break throughout South Australia has meant that successfully managing pregnant and lactating ewes has relied heavily on supplementary feed. Green feed that has germinated is in very early growth stages and still has a very high moisture content and low dry matter content. This means that for every mouthful of feed grazing stock are getting around 90% water and only 10% of the feed contains the valuable nutrients like protein and energy.
In a lot of areas lambs are already on the ground and supplementary feed supply is quickly diminishing and the cost of feeding is becoming expensive. Early weaning can be a successful way of reducing overall feed costs during a tough season. The overall supplementation required is often reduced by around 30% when ewes and lambs are fed separately in an early weaning program. It also gives more flexibility to move ewes to lower quality feed and prioritise higher quality pasture paddocks or supplements for recently weaned lambs.
Ewe recovery is also critical in a tough year to allow ewes to be joined in a high condition score and to maximise conception the following breeding year. With a standard weaning time, ewes will have a 17-week recovery before the next joining. As many ewes have dropped condition score more than usual during lactation, a slightly earlier weaning will give them more recovery time and allow them to regain condition to hit pre-joining condition score targets.
When lambs are first born, they act as a monogastric with milk being diverted past the rumen to the abomasum in response to suckling. Once lambs start consuming pasture or supplementary feed from around 2 weeks the rumen starts to change and develop. From around 6 weeks once lambs start to consume more solid feed the rumen starts to mature adapting to the increased intake of solid food. Once the rumen is developed lambs can be successfully weaned if required often from around 8 weeks of age and at a minimum weight of 10kg.
Avoiding stress over weaning is critical, if lambs are pre-introduced to the feed type, feeding method, water, mineral licks and pasture pre-weaning with their mother they will quickly transition to life post-weaning and immediately go onto the same feed type offered. Introducing lambs to some starch-based feed pre-weaning with their mum is also an advantage for rumen development, increasing the surface area of raised papillae on the rumen wall which improves rumen efficiency. Animal health issues also need to be avoided, ensuring lambs have had a marking and weaning vaccine is crucial, worm burdens should also be monitored, and an effective weaning drench given if required.
The weaning weight target in a normal season is 45% of the standard reference weight (mature weight) of the ewe, this helps to reduce mortality post-weaning. When lambs are early weaned, they are often much lighter than this, however if they are fed for high growth rates and given correct nutrition they can still thrive.
Protein is critical in a weaner ration especially if they are lighter than usual. A 30kg weaner requires 15% protein and at least 11 MJ energy, weaners lighter than this will require higher protein to help build muscle and provide fast early growth. The ration must also contain adequate fibre to maintain rumen function. If only low-quality fibre is available (straw, dry paddock feed or older hay) it is critical to supplement weaners with high protein grains or hay and some cereal grain also. Otherwise, a well-balanced full feed lamb pellet can provide everything they need.
Post – weaning it is critical to set growth rate targets for early weaned lambs and ensure you are monitoring weights to ensure you are hitting these. Fingers crossed we will soon be moving weaner lambs to high quality green weaner paddocks!