Epsilon Archive for Student Projects

Abstract

In the latest edition of NRC (2007) the feeding recommendations for Ca and P to growing
horses were increased with 35 and 25 %, respectively, based on results from a Canadian study
showing that daily endogenous fecal losses of Ca and P were greater than previously
suggested. A Ca absorption efficiency of 50 % is used for all horses. However, the true
absorption efficiency might be as high as 70 % in young horses. P absorption efficiency is
assumed to be higher for growing horses because their diets are often supplemented with
inorganic P. Thus, an efficiency of 45 % is used for growing horses as compared to 35 % for
mature horses. The aim of this study was to measure the digestibility of Ca and P in some
Swedish feedstuff in growing horses. An additional aim was to analyze the proportion of
soluble P in horse feces.
Four yearling Standardbred horses from Västerbo Stuteri were used in a cross-over design
with two different diets. One diet consisted of roughage alone and one of roughage and oats.
The trial started with a ten day adaptation period. Thereafter a collection period of six days
followed when feces were collected 10 hours per day and total feed intake was registered.
Feed and feces samples were analyzed for Ca and P to calculate digestibility and soluble P.
The average apparent Ca and P digestibility did not differ between diets and were 63 ± 4 %
and 23 ± 7 %, respectively, on the roughage-only diet and 49 ± 4 % and 21 ± 7 %,
respectively, on the roughage and oats diet. Using regression analyses, daily endogenous fecal
Ca and P were predicted to be 23 and 9 mg/kg body weight, respectively. The results from this
study cannot confirm that the increase in Ca- and P-recommendations to growing horses
(NRC, 2007) is justified but agrees with the results on which the previous NRC
recommendations were based. The study also indicates that most of the P (92-93 %) in horse
feces is soluble which mean that it should be gently handled to avoid environmental damage.
It also implies that horse feces are a good P fertilizer.