The hypothesis that spray dried plasma (SDP) complements low crude protein (CP) phase 1 diets by improving growth performance, decreasing diarrhea, reducing immune system activation, and maintaining intestinal health of weanling pigs was tested. Four phase 1 diets were formulated (CP: 18.5% or 23.0%; SDP: 0% or 6%). One-hundred and sixty weaned pigs (5.89 ± 0.39 kg; 20 ± 2 days) were fed one of the four phase 1 diets (days 1–14) and a phase 2 diet (days 15–28). Results indicated that pigs fed the 18.5% CP diet instead of the 23.0% CP diet had reduced (P < 0.05) average daily gain (ADG) and gain to feed ratio (G:F), and pigs fed 6% SDP had greater (P < 0.05) ADG and G:F than pigs fed no SDP. Diarrhea scores were reduced (P < 0.05) for pigs fed the 18.5% CP diet. Villus height in the ileum and mucosa width in the colon increased if SDP was included in the 23.0% CP diet, but not in the 18.5% CP diet (interaction, P < 0.05). In conclusion, including 6% SDP in phase 1 diets resulted in improved ADG and G:F and reduced inflammatory responses.

Bailey, H., N. Fanelli, J. Campbell, and H. Stein. 2025. Effects of the combination of spray dried plasma and reduced crude protein in diets on growth performance, diarrhea scores, gut morphology, and immune parameters of weanling pigs. Canadian Journal of Animal Science. 105: 1-12. https://doi.org/10.1139/cjas-2025-0061