Silage feed value
Tim Keady, Animal & Grassland Research and Innovation Centre, Teagasc Athenry, Co. Galway examines factors influencing silage feed value.
The main factor influencing silage feed value is digestibility (DMD) (see Figure 1). Increasing DMD increased silage intake during weeks -10 to - 6 prior to lambing. When concentrate supplementation was initiated (week -6) the intake of medium DMD (70% DMD) silage remained relatively unchanged up to lambing, while that of the high DMD (79% DMD) silage declined as concentrate feed level increased. Concentrate displaced the high DMD silage in the diet.
Increasing silage DMD increased metabolisable energy (ME) intake by 53% during the final six weeks of pregnancy. The ewes offered the high DMD silage were 10kg heavier and had a one unit higher BCS at lambing. At pasture, between lambing and weaning, the ewes that had been offered the high DMD silage lost 0.5 units BCS (sacrificed body reserves in favour of milk production) while those offered the medium DMD silage gained 0.2 units BCS (partitioned energy intake to replenish their own body reserves rather than to milk production). At weaning, the BCS of the ewes offered the medium and high DMD silages were 3.1 and 3.5, respectively.
The lambs from ewes offered the high DMD silage were 0.5kg heavier at birth, 1.9 kg heavier at weaning and 17 days younger at slaughter. A reduction of 17 days at slaughter is equivalent to the response expected from feeding 19kg concentrate per lamb from birth to slaughter. As each ewe in the study reared 1.75 lambs, this would equate to 33kg concentrate/ewe – equivalent to approximately €15/ewe.
Conclusion
- Each five percentage point increase in silage DMD increases ewe weight post lambing by 6.5kg and lamb birth weight by 0.25kg.
- Ensure ewes have access to fresh silage 24 hours daily.
- Remove silage residue twice weekly.
- Construct a plan with the aim of increasing next year’s silage DMD by at least five percentage units.
Figure 1: Effect of silage feed value (DMD) on food intake in late pregnancy
This article was published in the Teagasc Sheep Newsletter January 2023. Read the full newsletter here.