The Effect of Dietary Protein for Lactating Sows on Sow Body Composition and Metabolism

The aim of the study was to determine the effect of increased dietary protein for lactating sows on sow body composition and metabolism. Six dietary treatments with increasing concentrations of standardized ileal digestible (SID; Pedersen and Boisen, 2002) CP (104, 114, 121, 129, 139 and 150 g/kg) and Lys (5.9, 6.5, 7.0, 7.5, 8.3 and 9.0 g/kg) was fed to sows from d 2 postpartum until weaning (d 26). The ratio of dietary Met, Thr, Trp and Val to Lys was 31, 61, 20 and 72%. Seventy-two sows (parity 2 and 3) were randomly allocated to one of the six diets and all litters were standardized to 14 piglets at d 2 postpartum. Blood samples were collected weekly and centrifuged for 10 min (1,560 x g) at room temperature before the plasma was analyzed for glucose, lactate, NEFA, creatinine and urea N. On day 2 postpartum and at weaning (d 25) body water content was measured using the deuterium oxide dilution technique. Contents of body fat, protein and ash were estimated from body water, BW and BF using equations by Rozeboom et al. (1994). The trial was a complete block design (12 blocks of 6 sows) and in the statistical analysis the individual dietary SID CP concentration of each sow was used as input. Data was analyzed using linear and linear broken-line models that were compared using Akaikes information criteria. Sows on average weaned 13.0±1.2 (P=0.31) piglets and the ADFI was 6.3±0.6 kg/d (P=0.36) with no effect of treatment. Body water and protein loss decreased with increasing dietary SID CP until a breakpoint at 130 (3.1 kg; P<0.05) and 126 g SID CP (0.69 kg; P<0.05), respectively. Body fat loss was not affected by dietary treatment (P=0.46), whereas body ash loss decreased linearly (Y=2.02 – 0.02 x SID CP_diet) with increasing dietary SID CP (P<0.01). Plasma glucose, lactate, creatinine and NEFA were not affected by dietary treatment (P>0.05). Plasma urea N increased linearly with increased dietary SID CP in week 2 (4.1±0.8 mmol/L), 3 (4.7±0.9 mmol/L) and 4 (4.9 ±1.1 mmol/L) of lactation (P<0.001). In conclusion, increased dietary protein concentration increased BF loss but BW loss was decreased until breakpoints were reached. Loss of body water and mobilization of body protein and ash was minimized with increased dietary SID CP. The increase in plasma urea N reflected the increase in protein intake.