Feeding the Ewe for Better Returns – AHDB

29 Jan 2018

Most mammary gland development takes place during the last month of pregnancy. There is a clear relationship between the ewe’s energy intake over the last three weeks of pregnancy and colostrum production. Under-nutrition pre-lambing not only reduces the quantity of colostrum and milk produced, but also delays the onset of lactation and increases the viscosity of colostrum. Since viscosity and volume of colostrum are inversely related, this is a major issue for the newborn lamb. In addition, the lamb may find it more difficult to extract thick colostrum from the teat.

The mechanism is related to the change in hormone levels in late pregnancy. Under-nutrition delays the fall in progesterone and the udder is deprived of the blood flow it needs to access the substrates for colostrum production.

Lambs are born hypo-immunocompetent, with only a small store of energy (in the form of brown fat) for heat production and metabolism. So they are completely dependent on colostrum to supply energy and immunoglobulins. Make sure lambs receive 50ml/kg of colostrum within the first four to six hours of life and continue to consume it during the first 24 hours of life. In 24 hours, a newborn lamb must receive the equivalent of 200ml/kg bodyweight in colostrum. For example, a 5kg lamb needs 1 litre of colostrum in the first day of life. An increase may be necessary in wet and
windy conditions in outdoor lambing systems.

After six hours, the lamb’s ability to absorb the immunoglobulins into its bloodstream has reduced,
which is why it is important to get colostrum in quickly. The primary immunoglobulin in colostrum is immunoglobulin G (IgG). Its concentration in milk decreases rapidly after parturition, at approximately 3.3mg/ml per hour, diminishing to zero by about 23 hours post-lambing.

For optimum colostrum production, research shows that the ewe must have the correct balance of protein and energy and that the level of protein required is dependent on the energy available to the ewe.

If there is insufficient energy available, the rumen cannot fully utilise the RDP supply for microbial protein synthesis, leading to high levels of ammonia and excess urea production. Conversely, if low levels of protein are fed in pregnancy, this may reduce the utilisation of starch for colostrum synthesis in ewes supplemented with high-energy diets.

Cereal grains such as maize, barley or wheat have a high ME and starch content and when used as supplements in the last week of pregnancy, have been shown to enhance colostrum production. The amount of energy, especially glucose, available at the end of pregnancy plays a major role in colostrum synthesis.

Provide the correct balance of dietary energy and protein to optimise colostrum and IgG production
There is some evidence to support a detrimental effect of over-supplementation of ewes with minerals and trace elements in late pregnancy, eg the effect of excessive iodine on the absorption of IgG by the lamb. There are reports of excess selenium causing higher lamb mortality, through increased respiratory and gastrointestinal disease.

Inadequate energy and protein supply leads to poor ewe body condition, small weak lambs and poor yields of colostrum and, subsequently milk.


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