CALCIUM, MAGNESIUM AND PHOSPHORUS BALANCE OF SOWS DURING LACTATION FOR 3 PARITIES

The effects of two diets, differing by total phosphorus and calcium co ntents, on retention and excretion of Ca, P and Mg were studied in lac tating sows. Mineral balances (n = 60) were measured during lactation (day 4 to 25) for three successive parities. Mineral retention in the litter was measured by chemical analysis of weaned piglets. The contro l diet (C) contained 7.2 g P, 9.4 g Ca and 2.6 g Mg kg(-1) DM and the experimental diet (R) 6.5, 8.1, 2.5, respectively. Calculated digestib le phosphorus level was 3.5 g kg(-1) DM in both diets. Mean litter siz e was 10.4 piglets and mean litter gain was 2.7 kg d(-1). Calcium, mag nesium and phosphorus retentions in the piglets were not affected by d ietary treatments. Mean retention in the sows was slightly negative fo r calcium and phosphorus, but positive for magnesium. Daily recommende d allowances for lactating sows were 23.5 g digestible calcium and 16. 5 g digestible phosphorus (both including a safety margin of 25%). Exc retion of phosphorus in urine and faeces on diet R was 0.53 kg and on diet C 0.61 kg during a 25-day lactation. The possibilities for reduci ng phosphorus excretion during lactation are limited compared to those during pregnancy. Some reduction during lactation can be achieved by increasing phosphorus digestibility in the diet. (C) 1998 Elsevier Sci ence B.V.