Better Ewe Nutrition, Part 1 - The Role of Grass
A report published by the National Sheep Association has highlighted the value of grazing sheep in “Less Favoured Areas” of the UK; benefits include meat that’s high in healthy Omega 3, sustainable and versatile fibre, landscape maintenance, carbon sequestration and preservation of the social fabric in remote areas – to name but a few. It makes fascinating reading, especially when you realise that all these benefits are provided by an animal that thrives on little more than grass for most of its life!
Some understanding of the sheep’s digestive system is helpful: as a ruminant they are relatively inefficient at utilising feedstuffs, with an estimated 80% of what they eat (approximately 3kgs of grass per day) being used simply to maintain their bodily functions. Effective digestion is dependent on nurturing a healthy population of microbes in the sheep’s rumen; and the best way of doing this is by feeding bulky forages that encourage the sheep to ‘chew the cud’: a healthy sheep will ‘cud’ for up to 8 hours a day, breaking down the indigestible cellulose in grass. This creates saliva, which in turn keeps the rumen at the correct level of acidity (pH6.2-6.8), for the gut microbes to complete digestion. If this gets out of balance, for example, if fed inappropriate levels of grain or concentrate feed, the sheep can suffer from a potentially dangerous condition called ‘acidosis’.
Grazed and conserved grass is not only the cheapest feedstuff for sheep, but in many cases it can also provide all the nutrients that a ewe needs to sustain both herself and her lambs year-round. However, in parts of the country, the soil, and therefore everything that grows from it, lacks many of the minerals and trace elements that are essential to health and growth. It may even contain imbalances that can be injurious to health and possibly impair the ewe’s fertility and her lamb’s ability to thrive.
So, before you even think about offering your sheep expensive bagged feed, which, following this year’s widespread drought and failed grain harvest is predicted to rise sharply in price, it will pay you to maximise the value of your pastures. The first step is to analyse the soil and forage you have at your feet.
Step One: Soil Analysis
A soil analysis will firstly give you the acidity:alkalinity balance on a scale of 1- 7, with 1 being very acid and 7 very alkaline – ideally, soil should be slightly on the acid side to promote good grass growth. The analysis will also tell you the relative amounts of nitrogen, phosphorus and potassium(the N-P-K that every good gardener should be familiar with), as well as a range of trace elements that are of specific importance to grazing sheep.
However, if any of these are out of balance with one another, it can cause problems, especially for pregnant ewes. For example, high levels of nitrogen will promote a ‘flush’ of grass growth, chiefly in spring, which can reduce the uptake of calcium and magnesium by grazing ewes who need it to ensure good bone development and muscle function in their lambs. Similarly, excessive Potassium, which will cause lush grass growth, can interfere with a ruminant’s ability to absorb magnesium and can cause fatal ‘staggers’ at or around lambing. So, if you need to apply K, don’t do it at this time.
Step Two: Forage Analysis
A forage (hay, haylage or silage) analysis will tell you the availability of nutrients to the ewes as a percentage of their needs. It can also highlight an excess of certain trace elements that may have an ‘antagonistic’ effect on others: this is an interaction that ‘locks up’ certain trace elements, reducing their availability to grazing animals and their offspring.
If the results of testing your soil and forage highlight deficiencies, you can increase both soil fertility and nutritional value of the grazing naturally, by enhancing the species diversity of your pastures. Different grasses vary in their nutrient values for sheep, with perennial ryegrass providing the highest feed value, followed by Timothy and Cocksfoot.
You can also raise the feed value of your existing pastures by overseeding to incorporate a wide range of plants whose deep-roots draw minerals from the ground, which also makes them more resistant to drought. At the same time, they are very appetising to sheep, who relish the variety. Recommended plant species include: white & red clover, chicory (which contains tannins that have been shown to repel internal parasites), sainfoin, birdsfoot trefoil (both of which also claim anthelmintic properties), plantain (highly nutritious), yarrow, burnet, sheep’s parsley, and ribgrass … and at the same time you’ll enhance the wildlife value of your pasture. However, a word of caution regarding red clover – it has been shown to have an oestrogenic effect that can affect ewe fertility, so avoid grazing pastures containing red clover for some weeks before, and during the mating season.
There’s one other factor that you need to consider: that is to recognise that cutting grass to preserve as winter forage (hay, haylage or silage) removes considerable amounts of nutrients from the field. Fields used for grazing animals don’t suffer this depletion effect, as the animals largely recycle the elements in their dung and urine. So if you do make hay from your land, you may need to test and fertilise the soil more frequently.
Once you have the chemistry and composition of your pasture in good shape, it’s essential to manage the grass, to ensure that it’s as palatable and nutritious as possible for the sheep. Regular topping of areas of long grass and weedy areas will keep the sward to the optimum length for sheep, ideally between 4 and 6cm, and stop weeds setting seed. Once grass grows above this height it both loses its nutritional value and becomes less palatable to the sheep. If you want to be chemical-free, topping is the best way of combating weeds – left uncontrolled they will quickly overtake the grass and diminish the grazing for your sheep. When the ground is dry, paddocks will also benefit from harrowing; this breaks up any dung, exposing parasite eggs to air and sunlight which will reduce their viability, as well as dragging out old, dead grass and weeds.
By understanding the value of your grass, taking care of and improving your grazing, you’ll find that grass can make a very worthwhile and cost-effective contribution to flock nutrition! However, there are two specific times of the year when the breeding ewe’s diet will need careful assessment, and possibly supplementation, to her forage diet: in preparation for tupping, and during the weeks before and after lambing.
This article first appeared in Smallholder Magazine, November 2012 - written by Carole Youngs of The Smallholder Series.