EFFECT OF NITROGEN SUPPLY ON THE RETENTION AND EXCRETION OF NITROGEN AND ON ENERGY-METABOLISM OF PREGNANT SOWS

To reduce nitrogen excretion (NEx) the effect of nitrogen supply on ni trogen retention (NR) and NEx was studied in pregnant sows during thre e parities. A nitrogen supply of 40 g/day (treatment L) was compared w ith 62 g/day (treatment C) during day 0 to 85 of pregnancy. In the las t month of pregnancy nitrogen supply on treatment L was 50 g/day and o n treatment C 74 g/day. Faecal digestible lysine supply followed the s ame pattern as nitrogen. Nitrogen and energy balances were measured du ring mid pregnancy (day 50 to 60; no. = 22) and late pregnancy (day 10 5 to 112; no. = 60). During mid pregnancy treatments had a minor affec t on NR and energy metabolism. NEx on treatment L was proportionately about 0.40 lower than on treatment C. During late pregnancy NR was low er on treatment L than on treatment C. NEx on treatment L was proporti onately reduced by 0.35 compared with treatment C. In parity 1 the low er NR on treatment L was compensated by a higher fat gain. Results ind icate that nitrogen and faecal digestible lysine supply on treatment L were close to minimal requirement in late pregnancy. Assumed values f or maintenance requirement of nitrogen (0.45 g N per kg M0.75) and eff iciency of ingested nitrogen to NR (0.6) were in line with the results of the balance trials. The observed nitrogen retention of sows, espec ially during mid pregnancy, permits a reduced nitrogen supply to reduc e NEx.