Increased Dietary Protein for Lactating Sows Improved Sow and Litter Performance

The aim of the current study was to determine the effect of increased dietary protein for lactating sows on litter weight gain, sow BW, back fat and milk composition. A total of 560 sows (parity 1 to 4) were randomly allocated to one of six diets with standardized ileal digestible (SID; Pedersen and Boisen, 2002) CP at 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). The proportion of dietary Met, Thr, Trp and Val in relation to Lys was 31, 61, 20 and 72%. The study lasted from d 2 postpartum when litters were standardized to 14 piglets until weaning (d 25). Sow BW, back fat (BF) thickness and litter weight were recorded at d 2 and at weaning. On a subsample of 12 sows per dietary group milk samples were obtained at days 2, 10 and 17 post partum. Prior to milk sampling the litter was removed from the sow for 30 min where after an intramuscular injection with 2 ml oxytocin was given. Milk samples were analyzed for lactose, fat and protein. The experimental design was a complete block design and in the statistical analysis the individual dietary SID CP concentration of each sow was used. Data was analyzed using linear and linear broken-line regression models. Litter size at weaning (13.0±1.2; P=0.31) and ADFI (6.3±0.6 kg/d; P=0.36) was unaffected by treatment. Body weight change of sows decreased until a breakpoint (-0.58 kg/day) at 143 g dietary SID protein/kg, whereas the back fat change reached a maximum (-3.0 mm) at 127 g SID protein/kg. The ADG of the litter was affected by parity (P<0.001) (2.53 vs. 3.07 kg/d for first vs. multiparous sows), but maximum was reached at same break-point (135 g dietary SID protein/kg). Milk fat, lactose and protein at d 3(8.1±1.8%, 5.2±0.6% and 5.5±0.6%) and 10 (7.3±1.2%, 5.3±0.6% and 5.0±0.4%) was not affected by treatments (P>0.05; Table 1). Milk lactose at d 17 decreased until a breakpoint was reached at 5.3% lactose at 121 g SID protein/kg (P<0.01). Milk fat (Y=4.42+0.02 x SID CP_diet) and protein (Y = 3.63 + 0.01 x SID CP_diet) at d 17 increased linearly (P<0.05) and it decreased throughout lactation (P<0.001). In conclusion, increased dietary protein concentration for lactating sows increased ADG of the litter and back fat loss of the sow, but BW loss of the sow was decreased.