Farm Forum - Marking the best time to cull ewes
By Mary Crawford
Lamb marking is an ideal opportunity to assess ewes and is the first step to improving the reproductive efficiency of your flock. Poor performing ewes, that are dry or have lambed and failed a lamb, should be removed from the flock.
It is important this year, due to seasonal conditions that lambs are given the best opportunity for maximum growth before weaning. Lactating ewes need protein from green feed or high protein supplements to produce milk and should be given every opportunity to access the best feed available. It makes sense to remove non performing ewes from the flock and cull as soon as practical, to focus on productive ewes with lambs at foot.
Often ewes are culled because they are considered to be in poor condition, and robust ewes in good condition are then kept for the following years breeding. This, however, may be the wrong approach as a robust ewe may not have raised a lamb, while ewe in poorer condition may have raised twins. If there is a high percentage of ewes in the flock that have raised a lamb in condition score 2.5 or less, nutritional requirements need to be addressed before ewes are mated again.
Most lambs die within three days of being born, so undertaking an udder assessment at lamb marking is ideal. Ewe milk production declines between 10 and 12 weeks as lambs are eating mainly pasture, therefore checking udders at weaning runs the risk of incorrectly deciding that a ewe is dry. The advantage of udder assessment at marking is that ewes are drafted off from the lambs and wet udders have a chance to fill with milk.
There are a number of key criteria to assess when manually checking the udder.
Feel each udder for size, warmth and density, and whether each side is equal. Use the thumb and fingers to feel the size of the teat and strip any milk or fluid out onto a cupped hand. All wet ewes suckling a lamb will have a ring of clean skin on and around the teat. All ewes that have lambed will have birth stains on the breach. If you are not certain what you are feeling, tip the ewe up and inspect the udder to determine what is happening.
Retain ewes in the flock that have full, warm udders. Teats should express warm, opaque white milk. Check that teats have not been damaged during shearing, and are not enlarged making it hard for a new born lamb to suckle.
Ewes with acute mastitis where the udder is damaged, udders with lumps, watery or opaque milk, clots or pus, should be culled.
It is important to identify any ewes with udder abnormalities as they will not be able to rear lambs as effectively as those with sound udders.
Dry ewes that have given birth and lost may develop an udder which will be cool, often soft and floppy. Teats usually feel greasy and dirty. The milk is hard to strip and will have different characteristics to a wet ewe.
Dry maiden ewes are easy to detect as there is no udder or teat development. In older ewes it is harder to pick dry ewes however, they are usually in better condition and have the smallest udders. The behavior of dry ewes is different to wet ewes and ewes that have lambed and lost.
Identify any ewes which have lambed and lost or are dry with an ear tag or ear notch. If they have not produced a lamb the following year they should be culled.
Keeping highly productive ewes and culling poor performers can generate a 15% improvement in net reproduction rates over a 10 year period as the ability to rear a lamb is passed on to subsequent generations, especially if ram selection includes maternal rearing ability.
This technical article is sponsored Natural Resources Eyre Peninsula.
For further information on how to check ewes for wet and dry udders:
• Factsheet: Sheep udder assessment at lamb marking