 SaC s (Scottish agricultural College) latest research facility gives it and Scotland a significant lead in global efforts to help farming, food and rural businesses address the challenges of climate change .  That was the view expressed by the SaC chief executive and principal, Professor Bill McKelvey, yesterday, as he invited Cabinet Secretary for Rural affairs, Richard Lochhead to open the  GreenCow  building, a new installation on SaC s Edinburgh research campus. The building houses special equipment for accurate measurements of livestock inputs and outputs.  Work at the new GreenCow unit will complement research already under way at SaC s Beef Research Centre outside Edinburgh where, for example, hi-tech feeding analysis systems have been installed.  Mr McKelvey reminded his invited audience of the tough greenhouse gas emission targets set by Scottish  