Metabolisable energy ruminant diets

In the UK metabolisable energy system for ruminants, animal requirements are expressed in terms of net energy (NE) and food energy values are expressed as metabolisable energy (ME). Animal ME requirements are calculated using efficiency factors (k) for different productive processes (e.g. maintenance, lactation or growth), which depend on the ME concentration of the diet (M/D). 

For housed ruminants, the increases in heat loss associated with a 1 °C fall in environmental temperature are comparable (10-20 kJ per kg per day) to those for pigs and poultry, but are much greater (20-40 kJ) for ruminants kept out of doors and exposed to wind and rain. In ruminants it is often possible to influence heat production by changing the quality of the diet. Metabolisable energy derived from low-quality forage-based diets is used with a lower efficiency (k) than that derived from high-quality concentrate-based diets, and thus more heat is liberated to keep the animal warm. 

---