75% of foetal growth occurs in the final 6-7 weeks before lambing. The rapid growth of the foetus increases the ewe’s need for nutrients, and hence daily requirements can no longer be met by a forage based diet alone. Ewes must be correctly fed in late pregnancy in order to provide for the growing foetus and to ensure the ewe herself is prepared for the lactation period. Supplementation will frequently be needed. In late pregnancy, nutrients are required for the growing foetus (or foetuses), ewe maintenance, udder development and the build-up of colostrum. Underfeeding can lead to significant problems such as light or weak lambs at birth, higher ewe and lamb mortality, thin ewes, metabolic diseases, and lack of colostrum. Twin Lamb Disease, hypocalcaemia and uterine prolapse could also become an issue of underfeeding. Although energy is the first limiting factor in the late pregnancy diet of a ewe, the protein, mineral and vitamin intake also have important roles to play.
Hypocalcaemia (Parturient Paresis)
This refers to a sudden drop in the levels of blood calcium in the ewe. Milk fever is caused by a calcium deficiency in the bloodstream, usually occurring in the last 6 weeks of pregnancy and the first 3 months of lactation when calcium needs are the highest. Ewes could already be prone to a calcium deficiency due to a lack of calcium in the diet. For example, ewes feeding on poor quality pastures or grain diets without added calcium, or grazing oxalate-containing plants (e.g. beet or kales) that bind calcium in the intestines, preventing absorption are susceptible. Older ewes are more susceptible to milk fever. If recognised early, a simple treatment with a calcium borogluconate solution injection or oral supplements of organic calcium will effect a recovery in most ewes. For example, Provita BoviCal drench contains organic calcium and also propionate as an immediate source of extra energy to kick start the metabolism for a hypercalcaemic ewe.
Pregnancy Toxaemia (Twin Lamb Disease)
Twin Lamb Disease (TLD) is also called Pregnancy Toxaemia, most common in twin and triplet bearing ewes who have higher energy demands during the last month of gestation. It occurs following a period of severe energy shortage, whether the result of poor roughage quality, inadequate concentrate allowance or high foetal demand, but clinical signs can be precipitated by sudden stressful events.
TLD is a metabolic disease that occurs when the ewe is no longer receiving enough nutrition and energy to provide for herself and also for her lambs in utero, and hence her blood glucose drops sharply. The disease can occur in thin or over fat ewes and is triggered by a stressful event which results in a critical shortage of blood glucose causing a demand on the ewe to mobilise her backfat for energy. This fat travels to the liver to be processed into energy but if excessive amounts are mobilised, the liver begins to metabolise this fat into ketone bodies and soon a toxic state ensues. This is a state of ketosis which causes brain and kidney damage.
TLD can be triggered by several factors aside from lack of food. As aforementioned, thin and fat ewes are more likely to develop TLD. Example of stressful events that could predispose ewes to TLD are:
- Bad weather – ewes unable to access feed.
- Lameness – ewes unable to graze effectively or stand at feeders.
- Illness – again ewes unable to feed properly.
- Inadequate dry matter intake – reduced rumen fill from carrying multiples so energy density of diet needs to be higher
The early clinical signs of ovine pregnancy toxaemia include disorientation, leading to isolation from the remainder of the flock, then over the next 24-48 hours affected ewes become increasingly dull and depressed and are easily caught. Ewes displaying early symptoms of TLD should be treated with a fast acting glucose energy drench ( e.g. propylene glycol) such as Provita Ewe Two to increase their blood glucose levels quickly; this can be repeated after 4 hours and again after 24 hours if required. Propylene Glycol (PG) is a rapidly acting source of glucose which given orally increases insulin levels by 200–400% within 30 min after drenching indicating that PG is absorbed very quickly from the rumen. Provita Ewe Two also contains highly beneficial minerals and vitamins – Selenium, Vit E ,Vit B 12,Cobalt ,Iodine ,Iron, B vitamins, zinc, manganese, and methionine for correction of common deficiencies associated with TLD due to poor feed intakes.
Selenium & Vitamin E
Selenium deficiency in sheep can be quite severe resulting in white muscle disease or sub clinical symptoms causing reduced productivity, low immunity, and low conception rates. Selenium and vitamin E are therefore essential in sheep diets. Selenium is a trace element which works with vitamin E to prevent and repair cell damage in the body. Field experiments have shown that for ewes with 3 or more lambs, there was a significantly lower stillbirth rate for vitamin E supplemented ewes than for control ewes. Deficiencies of either or both selenium and vitamin E can cause weaner ill thrift, reduced wool production, reduced ewe fertility, reduced immune response and white muscle disease. Vitamin E and selenium administration to lambs can improve growth rates and prevent weaner ill thrift. ProVitaMin Sheep drench contains high levels of Vitamin E and selenium and is beneficial mid-pregnancy and at least 6 weeks pre lambing.
Cobalt & Vitamin B12
Cobalt has an important biological role as a constituent of vitamin B12 which is manufactured by micro-organisms in the (rumen). Cobalt deficiency (pine) occurs where there are low soil cobalt concentrations. Vitamin B12 also acts as a co factor with folic acid in stimulating red blood cell production. Cobalt-deficient sheep may fail to respond well to vaccinations and be more susceptible to clostridial diseases (for example pulpy kidney) and pasteurellosis (pneumonia). Cobalt/B12 deficiency in pregnant ewes can result in fewer lambs born, a higher incidence of stillbirths and more neonatal mortalities. ProVitaMin Sheep drench contains high levels of Cobalt & Vitamin B12.
Written Dr TB Barragry PhD, MSc, MVB, MRCVS, Dip ECVPT