IT can be a sobering experience for sheep farmers to compare ultrasound scanning rates in February (often 205% for lowground ) to lamb weaning rates in August (often only 155% at best).
What can be done to reduce such losses, most of which occur within the first three days after birth?
The provision of a good grass sward to ewes for up to one month before mating is frequently employed to increase ovulation rate and implantation rate, resulting in larger litters. However, triplet-bearing ewes are more prone to pregnancy toxaemia, vaginal prolapse and other conditions. In some studies the mortality rate of triplet lambs was 44 per cent compared to seven per cent for twins. Nutrition throughout pregnancy is essential for triplet lamb survival but the very high price of cereals and compound feeds means that supplementary feeding to pregnant ewes must be allocated accurately to achieve maximum profits yet ensure ewe health and lamb viability.
Foetal growth and development (15-21 weeks): Ultrasound scanning should be undertaken between 45 to 90 days of gestation to determine foetal number thereby ensuring more accurate and selective concentrate feeding during the last six weeks of gestation when 75 per cent of foetal growth occurs.
The importance and influence of adequate ewe energy supply during late gestation on lamb survival cannot be overemphasised particularly in ewes carrying multiple foetuses.
Farm visit by a veterinary surgeon to assess flock nutrition:
Dietary energy supply to ewes relative to the metabolic demands of the developing foetuses can be accurately determined during late gestation by your veterinary surgeon analysing a chemical (3-OH butyrate) in the ewes' blood.
Ewes due to lamb during the first week should be body condition scored and blood sampled four to six weeks before the start of lambing time thereby allowing sufficient time to implement dietary changes. A random sample of 15 to 20 ewes (not ewe lambs or gimmers) should be blood sampled. If the flock has been scanned to determine foetal number an equal number of twin and triplet-bearing ewes (not singletons) should be sampled.
Details of the diet, forage analyses, and future alterations should be noted. Feed allocations must be checked on weigh scales and the number of sheep per group accurately determined - approximations lead to unnecessary errors.
By ensuring ewes are in good condition at vaccination time (four weeks before lambing), and receiving an appropriate level of supplementation as determined by the blood samples collected, you will guarantee plentiful accumulation of protective antibodies in the ewes' colostrum at lambing time.
Follow-up visit during lambing time:
A veterinary visit during lambing time is essential to discuss the results with the farmer and shepherd. Recording of lamb birthweights and ewe condition scores are essential to determine the success of flock nutrition advice during late gestation. Particular attention should be paid to triplet litters.
It is essential to determine any cost benefits from this exercise. Have reduced losses and greater lamb growth rates more than compensated for any increased feed bills? What are the improvements, if any, in terms of animal welfare? What improvements can be made for next year?
NADIS is sponsored by Meat and Livestock Commission, Elanco Animal Health, Merial Animal Health, English Beef and Lamb Executive.
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