Effect of reduced dietary protein on productivity and plasma, urine, and milk metabolites in organic sows during winter conditions

Summary

Oversupply of protein is a challenge in organic sow production. Currently, organic sow feed is composed in accordance with feeding standards of conventional sows, which do not take the higher daily feed allowance and nutritional contribution from roughage into consideration. The objective of the current study was to investigate the effect of reduced dietary protein in gestational compound feed for organic outdoor sows during winter conditions, using metabolites in plasma, urine, and milk as indicators of sows’ metabolic status.
In total, 20 sows (Topigs Norsvin; TN70) were included in the experiment, lasting from d30 of gestation until weaning at d49 of lactation under outdoor conditions during winter. During gestation, sows were fed one of two isoenergetic diets containing 88 g SID CP pr. kg DM (Control) and 72 g SID CP pr. kg DM (Low protein), corrresponding to 16% and 31% below the current recommendation for indoor sows. In lactation, all sows were fed a standard diet containing 125 g SID CP pr. kg DM.
Sow performance traits were not affected by dietary protein level during gestation. An interaction indicated that sows fed the control diet had 23% and 11% higher urinary urea concentrations at d60 and d100 of gestation, respectively, compared with the low protein diet. During lactation, the milk yield of sows fed low protein in gestation increased more than that of control sows (P < 0.05). Concurrently, the litter gain of the low protein sows was improved, and their litters were heavier at d49 compared to control sows (276 kg vs. 238 kg; P < 0.001).
In conclusion, organic outdoor sows benefitted from reduced dietary protein during gestation in winter conditions, as indicated by urinary urea concentration, milk yield, and litter gain.