Scanning to lambing
Just scanning ewes for their pregnancy status does not add value on its own unless pub talk is part of the farm value package. Selling dry ewes this year could be seen by some as all that is necessary as a scanning outcome to justify the 60 cents per ewe expense. But there is much more that can be made by using pregnancy scanning data.
Knowing the ewes that are carrying more than one lamb so that they can have special management is where most of the value of scanning is captured. Doing this can bring a 5 to 1 return on the scanning cost.
The production from multiple ewes is dependent on four major factors, three of which are between scanning and lambing. All of these factors can be managed.
Body condition score (BCS). This is the key to lamb survival and lamb growth rate. We know unequivocally that multiple ewes that lamb with a BCS less than 3 will have a lower lamb survival and will wean smaller lambs. Identifying light multiple ewes at scanning still leaves time to rescue them before lambing.
This means drafting them off at scanning, drenching them and feeding them more. To add a whole condition score requires 30kgDM over and above what is required for maintenance and pregnancy. In reality this can only happen in the 50 days after scanning which means that they need to consume over ½ kgDM extra each day. It can be done, but to do so requires that extra feed be available which is only likely if it has been planned for.
Feed intake approaching lambing. Multiple ewes that are underfed in the last 5 or 6 weeks of pregnancy will have a lower lamb survival and will wean lighter lambs. To avoid this does not mean allocating them heaps of feed. It means avoiding them losing any condition which means not grazing below 1100 kgDM/ha. Knowing the date from which this needs to happen so that plans can be put in place to allow that allocation is the key to it happening. That sort of feed is not usually going to be available by chance at that time of the year.
Adequate feed allocation at lambing. Lambing these multiples on feed that does not fall below 1200kgDM/ha is the recipe for maximum lactation performance. Again, identifying that date and planning for it is the key to achieving it. The time of the year that ewes are lambing and the stocking rate are the two variables that determine what pasture covers ewes need to lamb onto. Generally the earlier that ewes are lambing, the higher the pasture covers that are required to lamb onto. Unfortunately the last two springs have not delivered higher pasture growth rates as the spring has progressed which has really disadvantaged later lambing flocks. This spring will be a cracker though.
The fourth area of impact on ewe performance is after lambing and is about the quantity and quality of pasture that lambs in late lactation can graze. As for all of the other factors, providing this sort of pasture needs to be planned for. Springs notoriously provided only the extremes in terms of too much or too little. Either of these can have a very negative impact on lamb weaning weights.
