Digestible energy (DE)

What it is

Digestible energy is a feed's gross energy minus the energy lost in the faeces ^[1]. Horse energy requirements are expressed as DE, and a calculated requirement is only a starting point because individual horses vary ^[2].

Where the figure comes from

Energy values on forage reports are usually calculated from other nutrients rather than measured directly ^[1]. One equine feed report calculates DE from protein, ADF, NDF, fat and ash; the TDN figure on most forage reports is calculated for ruminants and overestimates equine DE ^[3]. When a forage report gives several energy values, use the one labelled for horses ^[1].

What changes a horse's needs

Work raises energy needs above idle maintenance, and so do cold weather, late pregnancy and lactation ^[2]. In cold weather, extra forage is the best way to raise energy intake, because fermentation in the hindgut generates heat ^[2].

Too much

Obesity carries risks including laminitis, insulin resistance, colic from strangulating lipomas, and extra stress on joints ^[2]. In horses with equine metabolic syndrome, gradual weight loss through energy restriction improves insulin regulation ^[4].

Reading it on a label

Labels and reference books may give energy in MJ, Mcal or kcal. The thermochemical kilocalorie is exactly 4.184 kJ, so 1 Mcal is 4.184 MJ ^[5].

See also crude fat, nsc, reading feed labels.