Phosphorus Digestibility and Endogenous Losses in Growing Horses

Phosphorus (P) is an important mineral of the body and has a lot of functions. The hardness of skeleton and teeth are built of calcium phosphate crystals. All cells need P for generation of metabolic energy and other functions are regulation of enzymes and synthesis of nucleic acids.

P requirements are depended on the animal´s age, performance and endogenous losses. The NRC P recommendation to horses has, until 2007, been based on fecal endogenous losses corresponding to 10 mg/kg BW/d. However, there is one observation indicating that endogenous fecal P losses can be twice as high in young horses and in 2007 NRC increased the recommendation with 25%.

The Swedish mineral recommendation for horses generally follows NRCs. However, an increase of the P requirements of 25% will require substantial P supplementation of many growing horses in Sweden and the need for this should therefore be better verified.

P from mines is an endless resource and excessive P feed to farm animals can leak to surrounding surface waters and lakes and contribute to eutrofication. Preliminary results from us indicate that much of the P in feces from horses is water-soluble.

Two studies

Two studies are planned, a first at the Swedish Trotting School at Wången and a second at Hólar University College, Iceland. At Wången sixteen 2-years old standard bred gelding will be fed forage-only diets supplemented or not supplemented with P for six days in a change-over design. Spot samples of feces will be collected daily for three days and urine once during the same period.

The results will be validated by a study on six 2-years old horses on Iceland.  Horses will be fed forage-only diets containing three levels of P. Total collection of feces and urine for three days (in a change-over design 3 x 3 treatment) will be made.  At this study digestibility and endogenous losses will be estimated by established methods.

Aim of the Project

• To estimate the endogenous fecal losses of P in horses aged 18 – 26 months fed forage-only diets and suggest a P requirement.

Project manager:

Anna Jansson, anna.jansson@slu.se

PhD-student:

Gunilla Ögren

Other participant:

Kjell Holtenius 

More information

Licentiate thesis: Phosphorus to horses and cows