Farm Ireland
Independent.ie

Sunday 19 August 2018

Get feed right for pregnant ewes

Michael Gottstein

As ewes enter the final third of pregnancy, it is important to get nutrition right because 75pc of foetal growth takes place in the last seven weeks of pregnancy. This is why getting ewe nutrition right in the last third of pregnancy is so important.

For ewes that are starting lambing in March, now is the time to start thinking about supplementary feeding.

Where ewes are housed and fed a diet of hay or silage there will be a requirement for additional energy, protein and minerals/vitamins to meet the requirements of the growing foetus. This additional supplementation is required for two reasons. Firstly, because the conserved roughage is not balanced in terms of energy, protein and minerals/vitamins, and secondly, because the rapid growth of the foetus inhibits the ewe's ability to consume sufficient roughage.

Where the ewes are not able to consume sufficient nutrients to meet the demands of the unborn lamb(s), there can be serious consequences. At best the lambs will be small (underweight) at birth. These lambs will be weaker, resulting in higher mortality and lower lamb weaning weights and delayed drafting. It's also likely that the ewes will be short of colostrum and that subsequent milk yield will be negatively affected. More severe cases of underfeeding can trigger twin lamb disease (pregnancy toxaemia) where the ewes will die if they are not treated promptly.

In short, the message is that underfeeding the ewe in late pregnancy will compromise ewe/lamb performance, increase your workload and see an increase in both ewe and lamb mortality.

To avoid this happening on your farm you will need to understand how the nutritional needs of the ewe change throughout the last few weeks of pregnancy.

Energy is the most important portion of your ewe ration. Unfortunately, most rations in Ireland are sold on the basis of protein percentage (eg Ewe 16 or Ewe 18). We have a methodology for measuring the energy value of a ration called UFL but it is seldom used by millers and compounders when they are selling a ration. The UFL system is based on a French rating system which rates all ingredients relative to barley. One UFL is the equivalent of one kilogramme of air dry barley. Ideally concentrate feeds for ewes in late pregnancy should have a UFL value of at least 0.95.

Where a concentrate feed contains this level of energy, the ewes' nutritional needs can be met using the recommended feeding rates outlined in the accompanying table, above.

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In the absence of the miller supplying you with a UFL value for your ration, you should select a ration that contains high energy ingredients. The following ingredients are high in energy: cereals (maize, wheat, barley, oats), pulps (citrus and beet), soyabean meal, distillers' grains and, to a lesser extent, rapeseed. The last three ingredients are also high in protein.

Requirement

Protein really only becomes important in the last three weeks of pregnancy when the protein requirement of the ewe almost doubles.

From mid-pregnancy right up to the last three weeks of pregnancy, a ewe will require around 100-130g of crude protein/day.

Where good grass silage or leafy hay is being fed, the roughage alone will supply most of this protein.

Therefore, the protein level of the ration only really becomes an issue in the last three weeks of pregnancy -- it then rises to 200g/day. At this stage, the ewe's ability to eat forage will have declined and the concentrate feed will have to supply a significant portion of the protein requirement.

The amount of protein that is required at this stage will depend on the roughage being fed and the amount of meal that is being supplemented. For example, ewes on very good maize silage may need very little meal to meet their energy requirements but will be short on protein unless a high protein concentrate is fed. If you are in doubt, contact your adviser who will be able to do a quick calculation for you.

Mineral and vitamin supplementation is an important part of your winter feeding regime to correct any imbalances that exist.

While minerals are important, it is essential not to overfeed them. Studies carried out at UCD have showed that there are negative effects on lambs' ability to absorb antibodies from colostrum where certain minerals (iodine) have been overfed in late pregnancy.

Check with your supplier that the mineral level in the concentrate feed is appropriate to your stock and feeding levels (ie if you are feeding very little meal you need to have a higher mineral inclusion level).

Also check the level of salt inclusion, particularly if bedding the sheep on straw. High levels of salt in the meal will result in wetter beds, higher bedding costs and more foot problems.

Once you have worked out what type of ration you will feed your ewes, the last step is to work out how much supplementation will be required.

The table above gives guideline figures for twin-bearing ewes in good body condition. Ewes that are carrying single lambs should receive 30pc less and ewes with triplets should receive 30pc more.