Sheep Scanning – an essential piece of the nutritional puzzle
January 13, 2022
With the majority of lambing taking place in March, scanning will be scheduled across the country. Optimum time for scanning will be 80 days post ram removal, any earlier and the scan may identify the ewe as barren and any later may result in an inaccurate number of lambs scanned. According to Faith Stewart, CAFRE Beef and Sheep Adviser targets to keep in mind for scanning results are:
- 100-120% for hill systems
- 120-170% for upland systems
- 170-200% for lowland. systems
These targets will be based on the farm system, land type and breed. An abortion rate of <2% is acceptable, however, if this rises sharply, investigate as there may be underlying problems, such as Enzootic or Toxoplasmosis.
The arrival of the scanner is as keenly awaited as Santa, although with a certain amount of apprehension. The results will allow us to determine grouping and feeding rates to achieve a productive and profitable lambing period. The results also allow us to look back on the mating season and potentially consider some new year’s resolutions. If we’re not happy with the results do we consider introducing a more prolific breed into the flock? Do we review the body condition score (BCS) of the ewes and rams going out to mating? Or possibly, was the ram fertility check missed? All of these are possibilities for a disappointing scan result. However, for now, let’s have a look at what we can do with the results going forward.
Prior to scanning, Faith recommends restricting the ewes feed 10 hours beforehand to allow for a more accurate ultrasound. Whilst scanning, the ewes should be marked for their litter size; single, twin or triplet, and then grouped accordingly. Ewes in poor body condition should be adjusted, for example, a twin bearing ewe in poor body condition should be grouped with the triplets to allow for extra concentrate supplementation for improved condition prior to lambing.
Optimum birthweight will vary according to the litter size. The optimum birthweight is defined as that which the lamb has the best chance of survival, coupled with the weight at which lambs can be delivered unassisted. Weak or light lambs will have a lower chance of survival as will larger lambs that may have had a difficult delivery. Optimum birth weight evidenced by research studies has been shown to be 6.0kg for singles, 5.6kg for twins and 4.7kg for triplets. Aim to maintain a steady BCS throughout the year, as any extreme changes to the diet could affect birthweight and result in large lambs, dystocia and prolapses.
Faith continues with her advice, suggesting that grouping for supplementary feeding will not only produce lambs at optimum birthweight and reduce mortality rates but will ensure ewes lamb in the correct body condition with adequate colostrum quality and quantity. Supplementary feeding will depend on the forage value, weight of the ewe and energy required (based on size of litter scanned). Silages should be well fermented, with a good energy and protein level, dry matter and D-Value. Avoid feeding silages with soil contamination and a high pH, as this may lead to Listeriosis. If you are in a BDG, contact your local Beef and Sheep Adviser for help in assessing the potential of your silage.
Feeding the correct amount of concentrate at the correct time is vital. As the lamb grows, the rumen space decreases by up to 30%, making it difficult for the ewe to meet her requirements on forage alone. The protein level and quality of the concentrate is important and especially in the final three weeks of pregnancy, where it will ensure good supply and quality of colostrum. The crude protein level should be a minimum of 18% and be sourced from good quality ingredients, such as, Soyabean Meal. Energy is also very important. Unlike crude protein, the energy level will not be stated on the label of the ration, discuss this with your supplier and aim for a ME greater than 12.5MJ/kg DM. Look for high energy ingredients such as, Barley, Wheat or Maize.
When housing, ensure the ewes have adequate feeding space to avoid competition and bullying. 45cm should be allowed for per head at the feed rail. Always ensure there is a fresh water supply.
To summarise, correct nutritional management of the ewe post scanning is critical, especially in the last 6-8 weeks prior to lambing. Level of supplementary feeding will depend on forage analysis, scanning results and body condition of the ewes. Speak to your local CAFRE Beef and Sheep Adviser for help with feed levels and rationing.