Studies on nitrogen retention in growing pigs

Nitrogen retention (RN) was measured in 60 barrows of Danish Landrace and a total of 470 balance periods was carried out during the growth period from 20 to 85 kg live weight. In the first serie (Expt A) six different feed compounds of high biological value (HBV) were fed to 48 barrows, while in the second serie (Expt B) 12 barrows were measured on feed compounds of HBV or low biological value (LBV). Three different levels of gross energy were used in Expt B. Individual differences of 10-20% in the pigs capability for nitrogen retention were observed. Nitrogen retention increased from 12 to 21 g N/d on the HBV-compounds and was not influenced by increasing nitrogen or energy intake. Nitrogen retention was curvilinear in relation to metabolic live weight (kg0.75) in both series. A parabolic function on kg0.75 gave the best fit to the data with the following regression equations: Expt A + B: RN, g/d = 1.48 LW, kg0.75 - 0.027 LW, kg1.50 (HBV) Maximum = 20.5 g RN/d at 84 kg LW Expt B: RN, g/d = 1.03 LW, kg0.75 - 0.013 LW, kg1.50 (LBV) Maximum = 20.4 g RN/d at 133 kg LW