Mineral balances and calcium availability in sheep fed sugar beet pulps

Abstract

Sugar beet pulp (SBP) is known to be rich in calcium but the availability of Ca is not well known, and adverse effects of Ca overloading are strongly related to this parameter. In this trial we used a semi-purified diet where all Ca was supplied by calcium carbonate (control) or beet pulp (SBP). The Ca content (g/kg on dry matter basis) was 4.6 and 4.8 respectively. These diets were fed to 6 adult sheep by group. Following an initial 3-week feeding period which allowed the animals to adapt to the experimental diet, measurements were conducted on two 5-days collection periods while mineral balances (Ca, P and Mg) were determined. True absorption of minerals was calculated on a theoretical basis of 20 mg (Ca), 25 mg (P) and 3.5 mg (Mg) of endogenous losses per kg of liveweight per day. Results obtained by the control group are slighty lower than data found in the literature. This could be explained by the difficulty of semi-purified diets to be accepted by adult ruminants ; this effect can be reduced for SBP diets which contain 40 % of sugar beet pulps. Nevertheless, these results underline that Ca availability from SBP is markedly lower (near 50 %) than that of the carbonate one. The low availability of calcium from SBP must be taken into account for the estimation of calcium supply and mineral supplementation when SBP makes up a significant proportion of the ruminant diet.