The information provided in this section is purely for educational purposes and you should check with your veterinarian for advice on dealing with health issues with your animals.


Bill McCutcheon
Ontario Sheep Specialist
OMAFRA March, 1991

Sheep are ruminant animals; this makes it possible for them to consume and utilize roughage or highly fibrous feeds. Animals with simple stomachs (pigs or dogs) are not capable of fully digesting fibrous plant material such as hay. However, the ruminant animal can digest more complex carbohydrates such as cellulose that is the major component of the fibre in hay. The microbes that inhabit the rumen of the sheep can break down the fibre and make the energy, protein and other plant components available to the sheep. It is very important that the microbial populations in the rumen are maintained at a proper level to ensure efficient breakdown of the roughage (hay) consumed by the sheep. Furthermore, much of the protein absorbed by the sheep is in the form of microbial protein. Therefore, the microbial populations in the rumen are continually being replaced. When the hay is fed in relation to when the grain ration is fed will affect the growth of microbes in the rumen and affect the ability of the microbial population to break down fibre and supply microbial protein to the ewe.

When hay is eaten by the ewe, large amounts of saliva are secreted. This saliva is basic (high pH) and creates an environment in the rumen to encourage the growth of microbial populations that will digest the fibre in the hay. The saliva also acts as a buffer to control the pH in the rumen from dropping too low When the rumen pH becomes acidic, the microbes needed for efficient digestion of the forage are killed. If the pH in the rumen falls too low, the ewe will become ill and suffer from acidosis, commonly known as grain or rumen overload.

When grain is fed to the ewe, it creates an environment in the rumen that is acid (low pH). If too much grain is fed at one time or if grain is consumed by the ewe into a rumen that has not been buffered with the ewe’s saliva, grain overload or acidosis can occur. When large amounts of grain are being fed, it is important that the rumen is properly buffered. A large amount of grain would be in excess of one pound per feeding. The rumen can be properly buffered by feeding part of the total hay consumed by the ewe to her before feeding grain. I would recommend the ewes consume hay for about 30 to 45 minutes before feeding grain. By allowing the ewe to eat hay before feeding grain a drop in rumen pH can be avoided. By feeding hay first, the forage in the rumen will break down more efficiently because the pH is maintained at the proper level to promote regeneration of microbial populations. Carbohydrates supplied by grain provide energy for microbial regeneration.

By improving the efficiency of fibre breakdown, the amount of total dry matter intake (DMI) can be increased. When DMI is increased, the amount of crude protein and TDN (energy) for the ewe is increased. This increase in nutrients should result in increased production. This increase in production is important in late gestation and during lactation. Improving DMI in late gestation, helps prevent pregnancy toxaemia and reduce the number of stillborn lambs. If DMI can be increased during lactation, the production of milk will increase and this translates to improved 50 day lamb weights. Body condition should also be more easily maintained during lactation; this may improve conception rates for ewes on an accelerated lambing program because less time will be required to get the ewe into breeding condition after weaning.

By feeding hay first, an environment in the rumen is created to promote proper microbial growth, the efficiency of fibre breakdown is improved, dry matter intakes are increased, and the risk of grain overload will be reduced. The consumption of more nutrients by the ewe will improve the production of lamb and wool and hopefully improve the profit per ewe per year.

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©Copyright 2001 Queen’s Printer for Ontario
Last Updated: January 29, 2001