Lambing 1 - Pregnancy Management & Nutrition of the Ewe
Part 1 of a series of 5 articles:
It almost goes without saying that good care and management of the ewe throughout her pregnancy can avoid many problems and result in healthier lambs.
The average pregnancy lasts 147 days – that’s roughly 5 months, and there are three distinct phases, early, mid and late. At each stage there are specific management tasks to carry out, especially during the final 8 weeks when the lambs are growing rapidly and making great demands on the ewe’s resources.
Early Pregnancy: Conception - 40 Days.
During the early stage of pregnancy the ewes are best left well alone, as any disturbance can affect implantation of the foetus, which can be reabsorbed if the ewe suffers shock or nutritional imbalance. For the first 2 weeks following conception the embryo ‘floats’ in the uterine fluid, from which it derives oxygen and nourishment. At the 3rd week the placenta develops and from this point (implantation), the lamb – now called a foetus – derives nourishment directly from the ewe. If twins or triplets are present, they share the available nutrients, which is why lambs from multiple births tend to be smaller than singles.
Aim to maintain a level plane of nutrition from flushing (putting the ewes on your best pasture before mating to enhance the ovulation and implantation rate), through the first part of pregnancy. Good grazing, supplemented by good quality hay or haylage if the grass is sparse, should be sufficient. If the ewe loses more than 0.5 condition score at this stage, it will affect placental growth and therefore the development of the foetus, which can result in an unequal sized litter; but don’t allow ewes to become fat either, as it can predispose them to vaginal prolapse.
Mid-Pregnancy: 40 – 105 Days.
Between 40 – 90 days is the ideal time to pregnancy scan the ewes. There are a number of good management reasons for scanning: firstly, to detect pregnancy. If one of the ewes is barren, your vet can carry out a blood test to detect any infectious cause, and she can then be removed from the flock. Ewes that are scanned with twins or triplets can be monitored and fed accordingly. If any ewes scan for triplets, you can plan to ‘wet’ foster the 3rd lamb onto another ewe that’s due to have a single at around the same time. Finally, if you need to assist at lambing, you’ll know how many lambs to expect, which helps when you’re trying to identify which legs belong to which lamb!
Ewes should not require any supplemental feeding at this time, as foetal growth is slow during the first half of pregnancy: a lamb destined to weigh 5kg at birth may only weigh 500g at mid-pregnancy. In fact, it won’t do any harm if ewes lose up to 0.5 condition score during mid-pregnancy.
The other important task at this time is to vaccinate against Clostridial diseases and Pasturella. The ewe is given an injection 4-6 weeks before lambing; she’ll pass on a ‘passive’ immunity to her lambs through her colostrum (first milk), which will last 6-8 weeks, at which time the lambs start their own vaccination programme.
Late-Pregnancy: 105 Days To Birth.
The foetus grows rapidly during the last 6 weeks of pregnancy, and at the same time udder development takes place. If the ewe is undernourished during the final weeks of pregnancy she can become dangerously ill, and won’t be able to produce essential colostrum for her offspring – especially if she is carrying twins or triplets.
Good quality forage – hay, haylage or silage – will continue to be the mainstay of the ewes’ diet, but as the lambs grow her rumen capacity is reduced, so feeding a good quality concentrate (minimum 18% protein) will ensure she receives adequate nutrition. Eight weeks before lambing, start giving a small daily feed of 0.25kg per ewe per day – this will enable the rumen microbes to adjust to the change in diet, and it will help get the ewes used to your presence each day. Make sure that the ewes have enough trough space so they can all feed at the same time, otherwise a weaker ewe might miss out on her full ration.
TIP: If you’re unsure about the quality of your forage, consider having it analysed for energy, protein, vitamins and minerals: if your forage is top quality, you can save money by feeding fewer concentrates.
If any of your ewes are looking poor (condition score 2.5 or lower), ask your vet to carry out a blood test up to 4 weeks before lambing to determine their nutritional, vitamin and mineral status. This will allow sufficient time to correct the diet if deficiencies are identified, and is especially important if any of your breeding ewes are yearlings; since they are still growing themselves, their nutritional requirement is higher than that of the mature ewe.
Six weeks before lambing, step up the concentrates to 0.5kg per ewe per day, and then 0.75kg (split into morning and evening feeds) for the following 2 weeks, rising to 1kg per ewe, again split into 2 feeds, for the last two weeks. This feeding regime, designed for a lowland flock, fits in with the lambs’ growth rate during the final stage of pregnancy.
Hill and primitive breeds tend to have a lower lambing percentage, so their energy requirements are lower. Primitive breeds, such as Soay, Portland and Manx Loghtan, usually have a single lamb and any supplementary feeding should be minimal. Hill flocks present a different set of challenges to the sheep farmer: hefted flocks develop grazing behaviours over generations, and supplemental feeding can disturb this pattern. Therefore, one of the most efficient ways to provide additional energy and vitamins is by using feed blocks or buckets, together with hay in line with the availability of grazing.
More information on caring for your flock during the breeding season can be found on “The Breeding Flock” DVD.
Next month in 'Lambing 2':
This article first appeared in Smallholder Magazine, January 2012 - written by Carole Youngs of The Smallholder Series.