Sheep fertility has increased significantly in recent years, with the New Zealand average lambing percentage jumping from 100 percent in the 1980s to over 130 percent today, with top performing sheep farmers attaining more than 150 percent. This is due to a combination of genetics, along with improved animal health and better feeding.
The trade-off to increasing reproductive performance however, is the concurrent issue of increasing incidences of triplets, which puts added pressure on both ewe and lambs. In a Poukawa trial, lamb mortality to 12 weeks of age increased from an average of 9.6 percent for single and twins up to 22.8 percent for triplets*.
Ewe nutrition can have a major impact on lamb survivability and growth rates and New Zealand trials have shown that improved nutrition in late pregnancy can improve lamb survivability rates**. A lamb that is born to a ewe with an enhanced nutritional status will be healthier and more likely to survive the stress of cold and wet weather. Lamb mortality can increase significantly in extreme weather conditions, with many of these deaths attributed to a lamb’s inability to generate enough body heat to keep warm. Brown adipose tissue is a type of fat that is laid down by lambs when they are in the womb. For the first few days of life, this brown fat is important for generating body heat. Heat is generated through the activation of uncoupling proteins in the brown adipose tissue, which results in the rapid dissipation of chemical energy as heat. Unbelievably, brown adipose tissue can generate up to 300 watts per kilogram of tissue compared to all other body tissues, which can only produce 1 watt. Fat reserves accumulate in the lamb in the last 60 days of pregnancy, so feeding ewes well in late pregnancy is important for maximising this lay down of fat. Feeding ewes pre-lamb with vitamin E and selenium is also thought to activate the mechanism that allows lambs to use brown fat.
Energy demands of the growing foetus increases dramatically towards the end of pregnancy, with 75 percent of the foetal growth occurring in the last trimester of gestation. This can be particularly problematic for triplet bearing ewes who can be very susceptible to pregnancy toxaemia (a severe lack of energy), which can cause death in extreme cases. During late pregnancy rumen space can be reduced significantly due to the growing foetuses, so the amount a ewe can eat is reduced. This occurs in conjunction with the stress of lambing and the need to start producing high quality colostrum and then milk to support lambs once they hit the ground. To minimise condition loss in late pregnancy and early lactation, bulky, high fibre feeds such as poor quality silage should be limited and it is beneficial to add high energy, high protein feeds to the diet. Feeding a high quality supplement to triplet bearing ewes pre and post-lambing can help to support the delivery and growth of healthy lambs.
NRM Triplet Nuts are a great supplementation option when the goal is low ewe and lamb mortality. They contain a good amount of high quality protein, along with energy in the form of molasses, grain and rumen bypass fat, all in a concentrated, highly digestible form. They also contain effective levels of trace elements and vitamins (A, D and E). 200-500 grams per triplet bearing ewe per day can be just what the ewe needs to perform optimally and overcome the risks involved with a triplet pregnancy. NRM Triplet Nuts are designed for triplet bearing ewes, so for those flocks not scanned, NRM Sheep Nuts at 150g/head/day provide a safer option for single and twin bearing ewes to lessen the risk of oversized lambs.
For more information, contact your local Nutrition Specialist.
*Litter size, lamb survival, birth and 12 week weight in lambs born to cross-bred ewes (2004). B. C. Thomson, P. D. Muir and N. B. Smith.
**Increasing lamb survival and lamb weaning weight through feeding high fecundity crossbred sheep (2016). C. Johns, J. Johns and D. R. Stevens.
Article supplied by Stacey Cosnett, Nutritionist.