Complex sentence: Most schemes use a calculation based on the weight of the animal--for example the 2006 UK Government scheme uses a figure for ruminants of the animal's weight (in kilogrammes) divided by 650.
Split into simpler sentences: Most schemes use a calculation based on the weight of the animal. Some use figures for animals of different sizes which are directly proportional to their weight--for example the 2006 UK Government scheme uses a figure for ruminants of the animal's weight (in kilogrammes) divided by 650.