Effects of birth weight on nitrogen digestion and utilization in grower pigs

A low foetal growth and birth weight leads to a lower number of muscle fibres formed prenatally and a lower body protein content in low birth weight (LBW) piglets. Therefore, LBW piglets  may show a lower performance and nutrient efficiency later in life. The aim of the present study was to evaluate the effect of BW on N-digestion and N-utilization in growing pigs. Two groups of 20 piglets with a low (LBW, 1.11 kg) and high birth weight (HBW, 1.79 kg), balanced for litter were selected and subjected to N-balance measurement using quantitative urine and faeces collection over 5 d periods. Pigs were fed a protein sufficient (NCP; CP 15.5%; 100%) or a protein restricted (RCP; CP 11.8%, 70% of sufficient) diet in a change-over design starting at 14 weeks of age. Diets were fed at 2.8xM over two meals per day. LBW and HBW pigs weighed 44 and 55 and 54 and 65 kg, respectively, at the start of the sequential balance periods. Faecal digestibility of DM, N and energy were not affected by BW, while faecal N digestibility was higher for the NCP compared to the RCP diet (91.4 vs 88.8%, P<0.001). N-retention was 27.7 and  19.0 g/d for the LBW pigs on the NCP and RCP diets, respectively, and 32.0 and 21.8 g/d for the HBW pigs (P<0.001). Both N-efficiency (N-retention/N-intake;  0.629 vs 0.635, respectively) and marginal N-efficiency (0.68 and 0.69, respectively) did not differ between LBW and HBW pigs. IGF-1 (210 vs 265 µg/l) and insulin (11.0 vs 17.1 uU/ml)  concentrations in plasma were lower in LBW compared to HBW pigs (P<0.05). Birth weight is a determinant for BW  gain and N-retention later in life, however, N-efficiency at later age is not affected by birth weight.

This study is part of the Feed-a-Gene Project, funded from the European Union’s H2020 Program under grant agreement no 633531.