Faecal endogenous loss of calcium in young sheep

Abstract

<jats:p>1. Two groups of eight 6–7-month-old wether lambs were offered either a frozen ryegrass (<jats:italic>Lolium perenne</jats:italic> L.)-white clover (<jats:italic>Trifolium repens</jats:italic> L.) pasture or a ryegrass-white clover hay, containing 12.1 and 6.4 g calcium/ kg dry matter (DM) respectively. Within groups the amounts offered to individual sheep ranged from 0.5 to 2.0 times the estimated maintenance energy requirements.</jats:p><jats:p>2. A single intravenous injection of 150 μCi <jats:sup>45</jats:sup>Ca as CaCl<jats:sub>2</jats:sub>. 2H<jats:sub>2</jats:sub>O, and stable balances were used to determine absorption, faecal endogenous loss and balance of Ca.</jats:p><jats:p>3. Faecal endogenous loss of Ca increased by 1.2 mg/kg body-weight (W) per d with each g/kg W per d increase in DM intake regardless of the diet. At any DM intake the mean faecal endogenous loss was 5.5 mg/kg W per d higher in the sheep offered the frozen herbage diet when compared with those on the hay diet. At any Ca intake the mean faecal endogenous loss was 6.9 mg/kg W higher in sheep offered the hay diet compared with those on the frozen herbage.</jats:p><jats:p>4. At feeding levels of about 1.5–2 times the estimated maintenance energy requirement the observed faecal endogenous loss of Ca ranged from 35 to 50 mg/kg W per d, which is two- to threefold greater than the present estimate of the Agricultural Research Council (1980) of 16 mg/kg W per d.</jats:p><jats:p>5. A simple model to explain the variation in faecal endogenous loss of Ca between the present study with young sheep and that with lactating ewes (Chrisp <jats:italic>et al.</jats:italic> 1989) also offered herbage diets is developed, which incorporates the concept of a true endogenous loss related to DM intake and a net endogenous loss reflecting the extent of re-absorption of Ca endogenous losses within the gastrointestinal tract.</jats:p>