Farm Ireland

Tuesday 12 December 2017

Onus on ewe to bridge nutrition gap

Michael Gottstein

Grass growth has been at a virtual standstill since before last Christmas. In fact, on fields that were closed very early (late September or early October) the grass is more than likely decaying and therefore yield is actually dropping.

Experience from some sheep farms that have been measuring grass for the past few years would suggest that farm covers in February were about half of what they were last year, with little hope of the situation improving before the onset of lambing and turnout.

There are a number of issues that sheep farmers will have to deal with in the coming weeks to get their sheep fed and facilitate grass to grow when warmer weather arrives.

The most important task is to ensure that the ewes are fed adequately. When the ewes are first turned out, they will selectively graze out the better, greener and leafier material which will be of a higher food value.

However, in order to allow light to the base of the sward and to stimulate tillering, the brown-type grass will also have to be grazed off. During the period that the ewes are grazing off this grass their energy and protein intakes will be substantially reduced.

Good quality spring grass contains around 21pc crude protein and generally has an energy value of around 1.06 UFL/kg dry matter. A ewe rearing two lambs will have an intake of about 2.4kg DM/day.

Her requirements for the first six weeks post-lambing are 2.5 UFLs plus 400g of crude protein. In a normal year unsupplemented spring grass will supply her with adequate energy and protein.

However, the type of stuff that most ewes will be forced to eat this year is probably in the region of 0.85 UFL and 13-15pc crude protein and, given the lower digestibility, it is likely that intake will also be somewhat depressed.

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Therefore, even on farms where there are adequate covers of brown/green grass, the ewes will at best manage an intake of 1.7 UFL and 300g of crude protein from this type of material.

If ewes are in good body condition at lambing they can afford to milk off their backs when they are underfed for a short period of time (a few days).

Where the level of nutrients available to the ewe is deficient for longer periods of time, she will not be able to compensate by mobilising body fat and her milk yield will drop.

Having ewes that are short of milk in early lactation can create complications. For starters, the lambs will be hungry and will continually try to suckle. This can result in the ewes getting sore teats and mastitis.

In addition, lambs that are not thriving well due to poor nutrition are more susceptible to parasites and may become stunted, resulting in difficulties in achieving target drafting dates later on.

To avoid a setback in lamb thrive, ewes will need some supplementary feeding post-turnout on many farms. The purpose of the meal feeding is two-fold. Firstly, there is a need to make up for the lack of nutrients in the grass and, secondly, there will be a need to slow down the rotation to avoid running out of grass altogether.

Where there is plenty of grass available but the quality is poor, 1kg/hd/day of concentrates (18pc crude protein) should be adequate. Where grass is in short supply, extra concentrates, up to 2kg/hd/day, may be required until grass growth kicks in.

There is little point in spreading chemical fertiliser until there is a prospect of soil temperatures rising.

According to Met Eireann, soil temperatures for the past week ranged from as low as 0.8°C at Knock Airport to a high of 3.7°C in Valentia.

These figures are still well short of the target of 5°C needed to kick-start growth. Once the prospect of milder weather arises, the entire grazing ground should be blanket spread with 20-odd units of nitrogen.

Where soil samples show a requirement for chemical P, using a product such as 27:2.5:5 or similar may be beneficial in prompting growth. In spring it is better to apply a little fertilier often.

Ideally, the grazing area should get a dressing of 20-odd units of nitrogen every four weeks until grass growth takes off in late April or early May.

Remember to keep an eye on your fertiliser limits under REPS and nitrates.

Irish Independent