Soaking and pelleting of pig diets alters the apparent absorption and retention of minerals

Abstract

The effect of soaking a pig's diet in water (9 h at room temperature) or heat pelleting (81 °C) on apparent absorption and retention of intrinsic minerals was studied with and without the addition of calcium carbonate in a 2 × 3 factorial design. Thirty pigs were allocated to different diet treatments and two separate balances were calculated throughout a 33-d study. Soaking the diet significantly (P < 0.001) reduced the phytate content (IP6) and increased (P < 0.001) the fractional content of degradation products (IP3-5), whereas heat pelleting only marginally affected these compounds. Soaking and heat pelleting of feeds did not affect dry matter (DM) digestibility or N and S balances in the animals (P > 0.05), indicating that feed matrix remained unaltered by the treatments. Dietary Ca addition reduced the absorption coefficient of DM (P < 0.01), ash (P < 0.001) and Ca (P < 0.05) as well as the uptake of P (P < 0.001). Heat pelleting selectively reduced the uptake of feed Ca, Fe, Zn, Cu, and Mn compared with untreated and soaked diets (P < 0.05). In conclusion, heat pelleting of feeds showed a negative effect on mineral uptake, whereas the soaking procedure seemed to have only a very marginal positive (P > 0.05) effect on the uptake of elements in the digestive tract. Key words: Heat pelleting, soaking, inositol phosphates, phytate, calcium, trace elements