Ewes fed good quality grass silage need low levels (0.4-0.6 kg/d) of concentrate supplement to satisfy energy requirements in late pregnancy. However, the UK Metabolisable Protein (MP) system predicts that using a low level of a typical 180 g/kg crude protein (CP) compound will result in an undersupply of MP and therefore a higher digestible undegradable protein (DUP) content of compounds is required. Although the benefits of supplying additional DUP to lactating ewes are well established there is little or no experimental evidence to support the practice of supplementing silage based diets with supplementary DUP. The objective of the experiment was to evaluate the response to supplementary DUP in silage based diets.

One hundred and twenty five scanned Scotch Mule ewes were synchronised, mated to Texel rams and allocated to 5 treatments balanced for liveweight, condition score, litter size, and parity. Five supplements were formulated to supply varying amounts of DUP and eRDP.