Here's something interesting from that I found while looking for information on why less meat consumption is better for the environment. The study is ten years old, but given that if the ag business hase improved its energy usage, all branches of it have probably done so at the same rate, the comparisons should hold.
The ratio of energy consumed to produce one unit of protein:
Milk protein 14:1
Lamb meat 50:1
Beef cattle 54:1.
I thought that was pretty interesting, because I know a lot of people along with myself who chose eggs and milk products over meat and think we're doing a good thing environmentally. It turns out - we're not.