Replacing grass silage with maize requires more research
Home Message: Feeding maize silage in late pregnancy results in a similar level of ewe and lamb performance, although ewes eat more and may have more lambing difficulties.
Maize silage can replace grass silage in pregnant ewe diets with no adverse effects on lamb output. “But the higher intake characteristic of maize silage, without a concomitant increase in lamb output, suggests that feed conversion efficiency is lower than that for grass silage,” Ronald Annett of Hillsborough’s Agri-Food and Biosciences Institute of Northern Ireland told delegates at this year’s British Society of Animal Science annual conference.
His study also highlighted a higher incidence of lambing difficulties in ewes offered maize silage: “This is a major concern and requires further investigation.
“Zero silage systems, based on high concentrate inputs, can also replace grass silage-based diets without affecting lamb output, although the economics of this system is dependent on concentrate feed costs,” he added.
Rations for pregnant ewes in the UK are often based on grass silage. But due to a number of factors, not least that the cost of producing high quality grass silage has increased significantly in recent years, alternatives need to be investigated.
“Production of forage maize has the potential to reduce forage costs on mixed beef/sheep farms, with high dry-matter yields – comparable to that of a three-cut silage system – of high quality maize silage possible from a single harvesting operation,” Dr Annett told delegates.
“But there is limited information on the effects of feeding maize silage to pregnant ewes. The aim of our study was to evaluate the effects of replacing grass silage with either maize silage or concentrates on the performance of housed pregnant ewes and their lambs.”
Seven weeks prior to lambing, 104 twin-bearing ewes were housed, shorn and allocated to one of four treatments. For the final six weeks of pregnancy, ewes were offered one of four diets: precision chop grass silage + 0.5 kg/day concentrate; maize silage + 0.55kg/day concentrate; a mixture of grass silage and maize silage + 0.55kg/day; or 1.55kg/day concentrates + 50g/day chopped barley straw. All silages were offered on an ad-lib basis.
Ewe live weight and condition score were measured six, four and two weeks prior to lambing and within 24 hours of lambing. Lambs were weighed at birth, six weeks of age and weaning.
Daily live weight gain was determined by linear regression. Lambing difficulty was scored on a four-point scale where 1 equalled no assistance and 4 equalled manual delivery with difficulties.
“And we found that ewes offered maize silage as 0.5 or 1.0 total forage had higher intakes of silage DM and total DM during the final six weeks of pregnancy compared with ewes offered grass silage as the sole forage,” said Dr Annett.
“Ewes offered the complete concentrate diet had the lowest DM intake. However there was no evidence of any dietary effects on the nutritional status of ewes, in terms of changes in live weight or condition score.
“Diet in late pregnancy had no significant effects on lamb output at birth or at weaning. But there was a higher incidence of lambing difficulties with those fed the maize silage ration.
“There were no residual effects of late pregnancy diet on lamb performance,” he added.
Presented to the British Society of Animal Science Annual Meeting, March 30 to April 1, 2009, Southport, UK.
Full details: Annett RW, Carson AF: “Effects of replacing grass silage with maize silage or concentrates on lamb output from housed pregnant ewes.”
Summary (pdf) Presentation_069annett (pdf)
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