Welcome to the first SheepNet newsletter for 2019 – with some information on how to manage your lambing ewes to improve lamb survival
Lambing ewes and lamb survival
Most lamb mortality occurs on the day of birth, and up to 75% of deaths happen within the first week of life. Losing lambs reduces flock profitability and staff morale, and time spent helping lambs to suck and mothering up is costly in terms of labour use. Ideally the ewe should bond to the lamb and raise it successfully to weaning with little human intervention.
The key to ensuring lambs survive is the early intake of colostrum by the lamb from the ewe. This gives the lamb energy to maintain body temperature, immunoglobulins to fight off disease, growth factors for the gut to develop and helps bond the lamb and ewe together.
The success of the ewe-lamb bond is affected by whether she has given birth before, whether the birth process was difficult or prolonged, her nutrition during pregnancy, especially the last third of pregnancy, whether there has been stress or disturbance during lambing, the size of the litter and the genetics of the ewe and lamb.
Managing inexperienced ewes
The inexperienced ewe is more sensitive to environmental disturbances, and more likely to abandon her lamb if disturbed. However, ewes that are good mothers to their first litter of lambs will continue to be good mothers in subsequent pregnancies so it will pay to give the ewe the best opportunity for everything to work well. She needs a quiet and calm birth environment and will take longer to progress through labour and bonding with the lamb. Although her lambs may be slower to stand and suck, intervening too early can affect the development of the bond and may increase the chances of rejection. As everything is less efficient in the inexperienced ewe she is also less able to rear multiples than experienced ewes.
A difficult or prolonged birth can result in brain damage in the lamb, which will make it slower to stand and suck. This means the lamb may get less colostrum and therefore be at risk of hypothermia and starvation. About 10-20% of all lambs may need some assistance at birth. Risk factors for a difficult birth are lamb malpresentation, above average birth weight, being male and genotype. Within breeds the offspring of some rams will also need more birth assistance than others. Aiming for optimal rather than heaviest birth weights will reduce the number of lambs needing assistance, and recording or selecting sires for easy lambing traits will improve the ease of delivery of lambs, especially for inexperienced ewes.
Effect of stress
Stress during lambing can interrupt contractions and prolong birth. After lambing, disturbances may cause the ewe to leave the birth site early before she has properly bonded with the lamb. Stress during lactation reduces sucking interactions between the ewe and lambs and can make lambs grow more slowly. Ewes like a quiet, calm and familiar environment, especially when they are lambing. To reduce the impact of stress and disturbance on lambing ewes avoid excessive noise and intervention, keep dogs and other animals out of the lambing environment and avoid mixing groups of unfamiliar sheep. Do not over stock pens (> 1 m2 per ewe) and ensure that there is adequate feeder space to prevent fighting around feeding time.
Good condition score
Low body condition score in the ewe at lambing is associated with less maternal behaviour at lambing, and a slower time to stand and suck in the lamb. These are risk factors for a poor ewe-lamb bond and higher lamb mortality. Maintaining a good condition score in the ewe throughout pregnancy, and regularly monitoring ewe condition will ensure that ewes are in the best condition to show good maternal care. Trace elements and minerals are required by ewes only if there is a deficiency on the farm – supplementing ewes which already have sufficient supplies in their nutrition will not improve lamb survival.
Managing multiple births
Most ewes, especially those that have lambed before, can cope well with triplets and increase their maternal licking with the birth of each lamb. They form a new bond with each lamb and most will recognize when one lamb is not there. Triplet lambs are generally smaller and slower to stand and suck, which makes them more vulnerable to hypothermia and starvation. This means mortality in larger litters is higher than for singles or twins. Pregnancy scanning ewes and feeding for litter size will help reduce this difference, but be prepared to provide extra care for multiple lambs as they may need additional colostrum and special attention to keep them warm.
Take home messages:
- Inexperienced ewes need all the biological signals to work at the right time to be good mothers:
- low stress, good nutrition, time to progress, no interference from other ewes
- Select for sheep that have good survival traits:
- Cull/don’t breed from ewes that have needed birth assistance more than once
- Don’t reuse rams if their lambs have needed assistance – at birth or to suck
- Give the ewe time and space to do what they need to do
- Looking but not doing!
Help the ewe to rear the lamb, so that you don’t have to!
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