The aim of supplementary feeding is to manipulate the digestible feed intake of grazing animals, says Jan Hoon of Grootfontein Agricultural Development Institute at Middelburg in the Eastern Cape.
This means supplying relatively small quantities of concentrated feedstuffs. The aim is to relieve shortages in the grazing to improve the balance between nutritional components, so available plant material is used more effectively.
The value of feed depends on its chemical composition, voluntary intake by the animal and digestibility. Its nutritional value can only be changed if one or more of these factors are altered.To get the most economic benefit from supplements, only supplement feedstuffs which are definitely deficient in the veld.Enough roughage must be available when giving supplementary feed. Providing it on overgrazed veld can cause even greater damage. The animals must be able to use the supplement on a constant basis, with voluntarily intake controlled.
One of three situations can develop when supplements are fed:
The supplement is eaten without any change in the amount of grazing consumed – but this seldom happens.The supplement lowers grazing intake, usually when large amounts are given on green pastures. The ideal situation is “complementary supplementation”. Here the supplement improves the diet balance so the animal performs better, and the intake of dry grazing or crop residue increases.
When does it pay to supplement?
Supplementary feeding has the most chance of being profitable:
During late pregnancy, to improve an animal’s condition for lactation and to limit lamb losses.
During mating, to improve ovulation, especially if a ewe’s bodyweight is below par.
In ensuring young ewes grow out well.
In finishing lambs for the market.
In improving wool staple and tensile strength.
During the dry season in grassveld regions.
The type and quantity is determined by:
Grazing quality and quantity.
Age and weight of a ewe or weaned lamb.
Stage of pregnancy or lactation.
Number of foetuses per ewe (singles or twins).
Cost and availability of the various supplements.
These are good on grassveld. Their main role is to stimulate the rumen’s microbe population when nitrogen is scarce. Digestibility improves along with feed intake and performance. Farmers can use natural protein, non-protein nitrogen (NPN), as found in urea, or a combination of the two. Natural protein includes fish meal, oil cake meal and commercial concentrates. Too much urea can be toxic, so limit intake to 15g/ewe/day and make sure the animals aren’t hungry and have had enough salt before a urea lick is given. Urea supplements must be kept dry. Natural protein sources containing bypass protein are important for ewes in late pregnancy or lactating and young lambs. Bypass protein is the part of the feed protein that isn’t degraded in the rumen, but is digested and absorbed in the small intestine. Sources high in bypass protein include fishmeal and some oilcake meals. These are, however, usually more expensive than feed with a low bypass protein content.
This type of supplement is normally associated with dry shrub veld. All grains and their byproducts can be used. Maize is a popular source of energy and so is molasses.But a high intake of maize mean lots of starch is fermented in the rumen. This can change the microbe ecology, harming rumen organisms that use fibre with an ensuing loss in feed intake. In grassveld, ensure the animal’s protein needs are met when energy supplements are given.
Salt is often used in licks to regulate intake. But as its big role is to supply sodium and chlorine, animals must have enough drinking water. The animal will also use extra energy to get rid of any excess salt.
Fortunately, too much salt in seasonal supplements doesn’t appear to permanently harm animal production or reproduction. Sheep need less phosphate than cattle do. If phosphate supplementation is needed, it will be for growing lambs or late-pregnant and lactating ewes. Phosphate is also recommended in the green season when young animals grow quickly.Sulphur is found in different quantities in natural protein sources. A sulphur shortage can occur in supplement mixes where a large percentage of the protein is from urea. Deficiencies of micro elements depend on environment and, once identified, can be rectified via feed or by injection.
When to start feeding
Start before the animals have become too weak and the alimentary canal has been affected by hunger. Remember, it takes the rumen flora two to three weeks to adapt to a new ration that consists chiefly of grain. The golden rule is to start when sheep that were in reasonable condition have lost 15% of their original weight.
Which animals to feed
Those that are likely to produce the most after the drought must get priority. That includes mothers and heavily pregnant ewes, which are the most susceptible to poor nutrition and young replacement ewes, which are usually scarce and expensive after a drought. On the other hand, mature dry ewes recover well after a drought and low feeding levels and show no permanent damage to production or reproduction. Sell old and inferior animals as soon as possible.
What to feed
Energy and protein are the two important components during drought. But you must know the energy values of the various feeds, as this will affect cost. Sometimes energy feeds can be bought cheaper than roughage. Animals must be adapted slowly to high-energy feeds, which should be buffered.
How much to feed
This depends on the energy content of the supplement, class of animal and its condition. A maintenance ration for dry, penned Merinos has been calculated at 2,3kg maize, 2,8kg oats or 4,4kg lucerne per week. But they will still lose weight.
How often to feed
When small amounts of energy are supplied the stronger animals tend to hog the feed. It’s better to put out more feed over a longer period. Feed dry animals two or three times a week and pregnant ewes or mothers every day.
When to stop feeding
Don’t stop too soon after rain. Young, green grazing is short in energy and this can lead to losses in drought-stressed sheep. Contact Jan Hoon on 049 842 1113. |fw