LIMITING CRUDE PROTEIN AND USE OF FREE AM INO-ACIDS IN FEEDS FOR LACTATING SOWS AS A MEANS FOR PREVENTING NUTRIENT EXCESSES IN PIGLET PRODUCTION

During lactation, sows were fed diets containing soybean oil meal at r espective proprotions of either 180-190 g/kg or at 90 g/kg with supple ments of L-lysine, DL-methionine and L-threonine. Thus, concentrations of crude protein were either 18 % or 15 %. Feed given to all sows dur ing pregnancy contained 13%, feed given to all piglets 17% crude prote in, respectively. 100 litters per treatment were evaluated. No signifi cant differences were found for total feed consumption or number and l ive mass of piglets weaned or reared to 26 kg, respectively. Limiting the proportion of soybean oil meal in feed for lactating sows reduced quantity,, of nitrogen in total feed by 6% and in ingredients compleme nting cereals by 19%. Calculated quantities of nitrogen excreted were reduced by 10%. The difference between quantities of N in feed ingredi ents complementing cerals and assumed quantities of N retained in the bodies of reared piglets was reduced from 1.9 to 0.3 kg per litter rea red. It is concluded that excesses of nitrogen in piglet production ca n be avoided by restricting crude protein in feeds and supplementing f ree amino acids to cover nutritional requirements as long as cereals f rom own production form the major part of feed mixtures.