Effects of grass and maize silage feed value, harvest system and concentrate feed level on the performance of pregnant ewes and finishing lambs
In Ireland ewes housed during the winter feeding period are predominantly offered grass silage as the sole forage supplemented with varying levels of concentrate. Approximately 20% of sheep are slaughtered in the first quarter of each year, which helps maintain continuity of supply to export markets. As grass growth rate declines during the last quarter of the year to as low as zero, a large proportion of these lambs is finished on concentrate diets or on diets containing conserved forages and/or concentrate. Digestibility is the major factor effecting grass silage feed value as determined by metabolisable energy concentration and intake characteristics. Each one unit change in silage digestibility in diets consisting of 80:20 forage:concentrate ratio increases daily carcass gain and milk yield of finishing beef cattle and lactating dairy cows by 26 g and 0.58 kg, respectively. Previous studies have clearly illustrated that reducing chop length of silage increases forage intake of sheep. Whilst it is estimated that 55% of silage on sheep farms is ensiled in big bales there is a paucity of research data to illustrate the impact the big bale silage system on ewe and subsequent lamb performance.
Major developments have occurred in plant breeding and in agronomic practices of maize production. The yield potential of maize has increased by 300% in the last 30 years due to improvements in plant breeding whilst the use of the complete cover plastic mulch system has further increased yield potential by up to 6 t DM/ha, consequently reducing the costs of production. Whilst numerous studies have shown the benefits of maize silage inclusion in the diet of beef and dairy cattle, there are few scientific studies undertaken to evaluate the impact on ewe and finishing lamb performance.
Currently there is a paucity of data on the effects of the feed value of grass and maize silages, grass silage harvest system (big bale), concentrate feed level and potential interactions on the performance of ewes during late pregnancy and finishing lambs. This project will evaluate the effects of:
- grass silage feed value
- ensiling grass silage in big bales
- stage of maturity of maize silage at harvest
- total diet crude protein concentration
on the performance of ewes in mid and late pregnancy and the performance of finishing lambs.
Furthermore the potential concentrate sparing effect of increase grass and maize silage will be determined.
Project Leader: Tim Keady
AGRIP – Athenry Grassland Science – 5657
Start Date: 1/11/06 Finish Date: 30/11/11