High-concentrate alternative to silage-based diets

Having a supply of grass for early spring grazing is dependent on closing grazing ground in rotation and giving swards a rest period of 100 to 120 days. For most flocks to achieve this target, the ewe flock needs to be housed or supplemented on a dedicated area of ground.

The most common diet fed to housed ewes is silage with concentrate supplementation in the final weeks of pregnancy.

Some farmers have adapted their systems to an all-concentrate diet, with their decisions influenced on compensating for poor- quality silage or reducing labour.

Others have experimented with the idea, but found the system expensive to operate where there is availability of good-quality silage.

The last Teagasc research carried out in this area was a paper entitled Easy feeding of Housed Sheep, written by Sean Flanagan, Teagasc, and published in 2002.

In the trial, early lambing ewes were housed seven weeks pre-lambing on 17 November. Ewes had an average weight of 69kg and were divided into three groups and offered the following diets:

Feeding levels

Feeding levels offered in late pregnancy were calculated to satisfy energy requirements for a 70kg twin-bearing ewe.

Baled silage (unchopped) from a perennial ryegrass-dominant sward was the silage offered.

The loose mix consisted of whole barley, molassed sugar beet pulp and soyabean meal at a ratio of 50:30:20, with a mineral and vitamin mix added at a rate of 20g/ewe/day.

The pelleted concentrate was a commercially available ewe and lamb compound. The chemical analysis of all feeds is detailed in Table 1.

One week was allowed to get ewes accustomed to the diets, with silage and 0.5kg concentrates offered to the concentrate groups and silage gradually withdrawn and concentrate supplementation increased to 1kg.

Management

Ewes were housed in a straw-bedded shed with a space allocation of 1.4m2. Feed was offered once daily and, to ensure all could eat freely, ewes were offered a trough space of 600mm/ewe.

The labour requirement was also recorded, from opening the silage bales and feeding to trough feeding and in the case of loose concentrates, taking into account hand mixing by shovel on three days per week (converted to man hours for a seven-day week).

As can be expected, the highest labour demand was for the silage-based diet, with the lowest for pelleted concentrate at less than half the time taken.

However, given the popularity and availability in recent years in mixed or cereal-based rations, there is no difference in feeding times for pelleted or loose rations.

Where sheep are housed on straw, it is important to offer a fresh source of straw, as eating soiled bedding can trigger cases of abortion.

Cost comparison

The potential of the systems also have to take into account a cost comparison. Table 3 details updated costs.

Ewes consumed 0.25t silage over the six-week feeding period. The high quality of silage allowed concentrate supplementation to be restricted to a minimum of 20kg in late pregnancy.

It does need to be taken into account that silage quality on many sheep farms is well below the quality in the 2001 trial. Therefore, higher levels of concentrates may need to be fed.

As can be seen in the table, there is only a small difference between the silage-based diets and concentrates purchased at the lower rate.

Farmers purchasing in bulk or larger volumes will have greater purchasing power than those with small flocks and purchasing in smaller quantities. Where purchasing power is poor or concentrates increase in cost, the merit of silage-based diets heightens.

A cost should also be factored into the equation for the labour-saving element of high-concentrate diets which may be especially relevant to part-time operators.

Animal performance

Ewes on all diets performed satisfactorily. The litter size was similar across all groups at 1.84 lambs, 1.86 lambs and 1.81 lambs for the silage, loose mix and pelleted diets respectively.

Mortality figures for lambs dead to birth were described as relatively high, with no significant difference between any group at 8.9%, 8.7% and 7.9% respectively.

The birth weight of lambs on the silage and concentrate diet was lowest, at an average of 4.7kg. The pelleted concentrate diet was next, with lambs averaging 5.1kg, while the loose mix concentrate diet delivered the highest average birth weight of 5.3kg.

It should be noted that the silage used in the trial was not chopped. Recent studies undertaken in Athenry during mid- and late pregnancy showed a significant improvement in lamb birth weight (+0.2kg for ewe supplement with 18kg concentrates) and weaning weight (+1.8kg) for ewes offered precision chop versus unchopped silage.

Performance to five weeks and to sale was also examined and this, including different finishing systems for early born lambs, will be covered at a later date.

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Focus: Winter indoor management