Effects of birth weight and genetic capacity for protein deposition on N-efficiency in growing pigs

The aim of the present study was to evaluate the effects of birth weight (BW; low vs high) and genetic capacity to deposit protein (BV; low vs high) on N-utilization in growing pigs in a N-balance study over a period of 16-18 weeks of age in a change-over design with two levels of dietary protein supply. High BW pigs had a higher N-intake, urinary N-loss (both P<0.001) and N-retention (P<0.01) compared to low BW pigs of the same age. However, N-efficiency (%) was not affected by BW. Pigs with a high BV had a lower urinary N-excretion and improved efficiency for N-retention (% of N-ingested) (both P<0.05). In conclusion, BW and BV both affect absolute retention of body protein in the grower phase. However, nitrogen efficiency (%) is only influenced by BV but not by BW.