Need / Issue: Balance requirements against pasture quality

Introduction:

High levels of lamb performance can be achieved from well managed grazed grass offered as the sole diet. However many producers supplement lambs with concentrate to increase lamb performance. The aim of this factsheet is to present information on the effects of concentrate supplementation at pasture on lamb performance. 

Athenry Study

The effects of level of concentrate supplementation on the performance of lambs grazing pasture was determined in a 4-year study. The ewes in the study were predominantly rearing twins as the number of lambs reared per ewe ranged from 1.7 to 1.9 during the 4 years of the study.  The effects of the level of concentrate offered and grass availability, as determined by residual sward height in a set-stocked grazing system, are presented in Table 1. The data clearly show that high levels of lamb performance were achieved from grazed grass as the sole diet in a set-stocked grazing system. Increasing concentrate feed level increased lamb performance and reduced the age at slaughter, regardless of sward height.

Table 1. The effects of concentrate feed levels and grass availability on lamb performance from birth to slaughter

                                                                               (Grennan & McNamara, 2005)

Lambs offered up to a maximum of 300 g or 600 g creep/day consumed 30 kg and 50 kg concentrate respectively from birth to slaughter. Feeding 300 g concentrate per lamb daily on the low sward resulted in the same level of lamb performance pre-weaning as lambs grazing the high sward without concentrate supplementation.  Therefore, concentrate feeding replaced good grassland management.  Concentrate feeding reduced the age to slaughter by 28 days.  However, increasing grass height from 5 cm to 6 cm reduced the age at slaughter by 13 days, equivalent to feeding 16.3 kg concentrate per lamb from birth to slaughter.