Partitioning of dietary nitrogen between body components and waste in young growing pigs

In experiment 1, 90 female pigs were fed, from 20 to 45 kg, at two energy intake levels (2x and 3x maintenance requirement) and 15 protein intakes ranging from 127 to 350 g/day. Protein deposition increased linearly with increasing protein intake until a plateau in deposition was reached at 106 and 126 g/day at the low and high energy level, respectively. Marginal efficiency of utilization of ileal digestible lysine was 0.74 for the two energy levels. In a second experiment, 24 female pigs were fed a protein-adequate diet at six levels of energy intake ranging from 1.7x maintenance to ad libitum. Protein deposition increased from 70 to 172 g/day, with increasing feed intake. The proportion of body protein deposited as lean tissue decreased from 0.62 to 0.55 with increasing feed intake. Consequences of these results for a more sustainable animal production are discussed.