John Vipond, SAC Consulting Senior Sheep Consultant - January 2014.
85% of foetal lamb growth occurs during the last 2 months of pregnancy. The udder also develops as ewes approach lambing.
- Nutrient requirements increase by around 50% in ewes carrying a single, and 70% in ewes carrying twins at this time.
- Rapid foetal growth and the need for foetal wool deposition mean protein demand exceeds microbial supply in late pregnancy, so high DUP feed ingredients (such as soya) are best. Unfortunately UK supplies of organic high DUP feeds are limited and may be expensive.
- Organic ewes’ requirements must be met from both the diet and mobilisation of body reserves. Protein release from body reserves (muscle, etc.) can help augment protein supplies. This will be greater in ewes that: are bigger (e.g. Mule and terminal sire crosses); are in good condition; and have not been maintained for long periods on low protein feeds such as hay or straw.
- Pregnancy scanning, carried out around 80 days after the start of mating, can help to identify ewes with higher requirements, and so ensure that these requirements are met, and that feeds are used efficiently.
- Feeding according to requirements also ensures that ewes lamb down in good condition with plenty of milk and do not produce over-sized singles and/or under-sized multiple lams, reducing lambing problems and associated mortality.
- When choosing feeds for pregnant ewes it is important to consider their cost per unit of energy and protein, and the ease with which they can be fed, as this may influence wastage and handling costs.
- It is also important to remember that sheep are ruminants, and that the requirements of the rumen micro-organisms have to be satisfied in addition to those of the animal.
- Ideally ewes should be fed a forage-based diet with concentrates provided as necessary. Under the organic standards, concentrate usage is limited to a maximum of 40% of daily dry matter (DM) intake, i.e. 550g /day for a small 55kg ewe, and 850 g per day for a large 85kg ewe.
- Forage quality is notoriously variable.
- Forage analysis can help ensure that the best material is kept for late pregnancy and early lactation, when ewe nutrient requirements are at their peak.
- Analysis can also highlight any deficiencies or excesses in the forage; for example, a shortage of protein which can be compensated through appropriate choice of concentrate, or a high ash content which may indicate soil contamination and the possible risk of listeriosis.
- Most proprietary ewe concentrates are formulated to contain around 12 MJ ME (metabolisable energy) and 16-18% crude protein, per kg of dry matter. Energy values in organic sheep compounds may be below this level, so check that the first four ingredients are high in ME.
- Home-mixed concentrates can be formulated to a similar specification using cereals and a source of additional protein.
- Use of a protein source such as soya fed at 100g/day/lamb carried for the last 3 weeks of pregnancy will stimulate milk production and help prevent the increase in worm egg output often seen around lambing. Some organic farmers have only access to beans which are low in DUP, and so are a poorer quality feed than soya.
- The level of concentrate supplementation required for ewes during late pregnancy will depend on forage quality, ewe size, and the number of lambs carried.
- Feed should be provided at regular times with clean fresh water continuously available.
- Feeding concentrate ‘little and often’, or as part of a complete diet, promotes the more efficient capture of nutrients in the rumen, stimulating appetite, and helping ewes to maintain body reserves for lactation.
- Feeding cereals whole can also improve diet digestibility by reducing fluctuations in rumen pH that are detrimental to fibre-digesting micro-organisms.
- In silage-based diets around 12% whole barley may pass through the animal undigested as a consequence of reduced rumen retention times. Light processing of barley is therefore beneficial, especially where the quality of the silage is high.
- In silage based diets feed oats can be fed whole, with losses below 5%.
This Technical Summary is funded by the Scottish Government