Lysine maintenance requirement and efficiency of its utilisation in young pigs as estimated by comparative slaughter technique

An experiment was carried out on weaner pigs (initial BW 10.8 kg) to estimate the maintenance requirement for lysine (Lys) and its marginal efficiency of utilisation using a comparative slaughter technique. Three groups of six pigs each were fed purified diets for 21 days supplying Lys at 19.5, 78 or 195 mg/kg W0.75, which corresponded to 50, 200 or 500% of the assumed maintenance requirement. All other essential amino acids were given at 50% excess. At the end of the experiment, pigs were killed for whole-body nitrogen (N) and amino acid analysis. A representative group of six pigs was analysed at the beginning of the experiment. Based on regression equations, relating Lys or N retention to Lys intake, Lys requirement for zero Lys retention was estimated to be 121 mg/kg W0.75, while Lys requirement corresponding to zero N retention was 41.7 mg/kg W0.75. At N equilibrium, the pigs lost 65 mg of Lys per kg W0.75 daily while at zero Lys retention, the daily N retention was 156 mg/kg W0.75 . The marginal efficiency of lysine utilisation was 0.91. It is concluded that zero lysine retention is a better criterion of lysine maintenance requirement than zero N retention.