The Role of Supplementary Feeding
by Carole Youngs
With specific reference to ruminants
All the rain we’ve had this year has really made the grass grow! Looking out of the window, our fields look wonderfully green and lush – a far cry from the browning ‘savannahs’ we experienced following last summer’s drought. It’s very easy to be lured into the belief that all that lovely grass must be a tasty and nutritious treat for your flock, but in truth, for a sheep, this summer’s grass is the equivalent of a thin gruel – lacking in the bulky ‘dry matter’ (DM) that they need to keep the rumen working properly.
In our article 'Maximising the Value of Your Grazing' we broadly described how the sheep’s digestive system is designed to enable her to thrive on grass alone for most of the year, and many native breed ewe raising a single lamb don’t require any supplementation at all. However, today’s ‘improved’ breeds have been selectively bred to rear twins, sometimes triplets, and this means their nutritional requirements are higher and they will need additional protein and energy during the critical periods before and after lambing.
So, before looking at specific feedstuffs, or feeding guidelines, it’s worth examining how the sheep utilises feed, and how this process can be made more efficient from a very early age, making ewes thriftier and more able to cope with the additional stresses of pregnancy and lambing.
The rumen (often referred to as the sheep’s fourth ‘stomach’) is a remarkable organ: positioned on the left side of the sheep, you can actually watch and feel it working.
If you place your fist firmly into the depression just behind the sheep’s ribcage (called the ‘fossa’) you’ll feel regular, rhythmic contractions every 1-2 minutes as the rumen’s strong muscles ‘stir’ the contents to aid digestion. Inside the rumen, the surface is covered in numerous tiny lobes (called ‘papillae’) which multiply the surface area and make absorption of nutrients much more efficient. The size and number of the papillae are therefore a critical factor in how thrifty the sheep will be.
In a newborn lamb, the rumen isn’t functional: as the lamb sucks from its mother, the milk, which is easily digested by the lamb, bypasses the rumen via the oesophageal groove into the ‘true’ stomach (the abomasum). The papillae therefore don’t need to develop fully until the lamb starts to eat grass, hay or grain, all of which need the digestive action of the rumen microbes to process the feed for the lamb.
Studies have shown that the papillae in lambs reared on ewe’s milk alone for the first few weeks of life, develop at a much slower rate, and never reach the same size as those of a lamb who also had access to forage, and to an even greater degree, to grain (fed crushed or as pelleted creep feed) from a young age.
Development of the rumen is stimulated by naturally occurring microbes in the feed, which are an essential part of the ruminant’s digestive process. This early development will stay with the lamb throughout its life, giving it a nutritional advantage over others reared on milk and forage alone. Once the lamb reaches the age of 6-8 weeks, the rumen development will be sufficient for it to maximise the value of forage, and creep feed can be gradually withdrawn. A lamb reared in this way will always have a growth and feed utilisation advantage over one reared solely on its mother’s milk.
Guidelines on Supplementary Feeding for Lambs and Mature Ewes
- An element of caution is always advised when feeding grain to ruminants, as over-feeding can cause a condition called ‘acidosis’ (where the rumen function is impaired), which can be fatal.
- Lambs can be creep-fed ‘ad-lib’, but should not be given feed formulated for ewes, as this may contain high levels of calcium which can cause ‘stones’ to develop in the urethra of ram lambs.
- Adult ewes should only need supplementary feeding during the last few weeks of pregnancy, and up to 8 weeks following lambing.
- All feeds should be introduced gradually, and increased over a period of weeks to allow the gut microbes to adjust.
- An adult ewe should never be given more than 0.5kgs of feed at any one time, so if she needs more (eg. if she is carrying triplets) divide the ration into morning and evening feeds.
- Ewes should always have access to good quality forage (eg. grass, hay); this provides energy in the form or sugar, starch and fibre.
- They also need two types of protein, firstly, Rumen Degradable Protein (RDP) that feeds the rumen microbes, and the best source is grass, good quality silage or hay.
- Ewes also need a source of Digestible Undegradable Protein (DUP), which bypasses the rumen and is absorbed directly through the intestine, making it highly digestible and nutritious – legumes, such as soyameal or rapeseed, provide good sources of DUP.
- A source of DUP is especially important in the late stages of pregnancy for udder development and milk production.
- Water must be available to sheep at all times, especially for pregnant and lactating ewes who will need up to 8 litres of water per day, per ewe.
If you’re in any doubt as to the suitability of a particular feedstuff, it’s best to buy bagged, pelleted feed that will also contain minerals, vitamins and trace elements that are essential to sheep health. Remember, never give feed that is formulated for another species as it may contain inappropriate amounts of ingredients (eg. copper) that can be toxic to sheep.
Feeding the Breeding Ewe
The breeding season starts several weeks before the introduction of the ram; by ‘flushing’ the ewes on good pasture during the month before tupping you can increase both the ovulation and implantation rate to maximise the lambing percentage. Crucially, nutrition also has a key role in how successfully the ewe will cope with her pregnancy. These are all aspects of management that the shepherd can influence, both for the better – and for the worse!
Ewes shouldn’t need any supplementation at this time, but you should ensure that they are fit, with a body condition score (BCS) of around 3 (out of 5, with 1 being emaciated and 5 being grossly fat) before they go to the ram. Native breeds tend to be lighter, and a BCS of 2.5 would be appropriate. Any that don’t achieve this after a few weeks on good grass are unlikely to successfully rear a pair of twins.
After tupping, keep the ewes on grass during their pregnancy (which lasts 147 days, or 21 weeks) and monitor their condition on a regular basis, it won’t do any harm to the ewes or their unborn lambs if they lose a little weight (up to ½ BCS) during this time, but don’t allow them to become fat.
If the ewes are pregnancy scanned, and you have any ewes carrying triplets, keep a special eye on them to ensure they don’t loose weight, especially during the last few weeks of gestation. Similarly, if single-bearing ewes become too fat, it may lead to complications in the later stages of their pregnancy, as well as difficulties at lambing.
Eight weeks before the due lambing date, assess the ewes’ condition. By this time the lambs are starting to grow and the ewe’s rumen capacity is reduced, so if any are BCS2.5 or lower, start feeding a small amount of concentrate feed – up to 0.25kg per ewe per day: this will enable the rumen microbes to adjust to the change in diet, as well as getting the ewes used to your presence each day. Continue to condition score the ewes on a weekly basis, while gradually increasing the amount of feed up to a maximum of 1kg per ewe per day (split into morning and evening feeds) for a lowland breed. The aim is to maintain a BCS of 3 throughout the pregnancy – the extra feed is for udder development, milk production and lamb growth; the ewe should remain at the same level of fitness!
After lambing, continue to feed ewes for up to 8 weeks, gradually reducing the quantity week by week – and start to creep feed the lambs!
More information and practical demonstrations, see “The Breeding Flock” DVD.
This article first appeared in Smallholder Magazine, December 2012. titled 'Better Ewe Nutrition - Part 2'