Evaluation of Microbially-converted Soybean Meal as an Alternative to Fishmeal in Weaned Pig Diets

Digestibility values determined in growing pigs may not apply to nursery pigs; thus, standardized ileal digestibility (SID) of AA in MCSBM and fishmeal (FM) were determined using 30 ± 1.6 kg BW ileal-cannulated barrows (n = 6) and 9.8 ± 1.2 kg BW barrows (n = 37; serial slaughter). Experimental diets included MCSBM, FM, and nitrogen-free where FM and MCSBM were included as the sole protein source. The SID of AA was 3-5% lower in MCSBM than FM when fed to 30 kg pigs. The SID of Arg and Met was greater (P \u3c 0.05) in MCSBM than FM when fed to 10 kg pigs. The SID of AA was 12-20% lower in FM when fed to 10 versus 30 kg pigs but only 3-9% lower in MCSBM. A total of 336 barrows and gilts were weaned at 21 d of age (initial BW 6.1 ± 0.8 kg) and used in a performance trial. Pens of pigs were assigned to one of 6 experimental diets (8 pens/diet in two blocks). Treatment diets were fed in Phase I (7 d) and Phase II (14 d) with all pigs fed a common Phase III diet (14 d). Experimental diets included: 1) negative control (NEG) containing corn, soybean meal and whey, 2) NEG + acidifier (NEGA), 3) NEG + FM (POS), 4) POS + acidifier (POSA), 5) NEG + MCSBM (MCSBM), and 6) MCSBM + acidifier (MCSBMA). The FM and MCSBM were included at 7.5% and 5.0% in Phase I and II diets, respectively. Diets were formulated to meet the standard nutrient requirements for weaned pigs. Pig BW and feed disappearance was measured weekly and fecal scores were measured daily for the first 14 d postweaning as an indicator of PWDS. Performance (BW, ADG, ADFI, and G/F) was not significantly different among treatments. Treatment for PWDS occurred on different days in each block. Analysis of fecal score was completed separately by block. Pigs fed the NEG diets had higher (P = 0.02) fecal scores than pigs fed the POS diets on d 2 and 3 (block 1) and higher (P \u3c 0.05) than pigs fed MCSBM or POS diets and diets with dietary acidifier on d 6 and 3 (block 2). At the end of Phase I and II, one pig/pen was humanely euthanized for digesta and tissue collection. Digesta pH was measured in the pyloric region of the stomach, duodenum, middle jejunum, ileum, cecum, and middle colon. There was an effect of location (P \u3c 0.0001), where the pH was lowest in the stomach and increased until the ileum with a slight dip in the cecum and increased in the colon. There was no effect of ingredient, dietary acid, or their interaction within the gastrointestinal tract. At the end of Phase I, pigs fed NEG and POSA diets had similar pH (P \u3e 0.10) from the stomach to the duodenum, and pigs fed NEG, NEGA, and POSA diets had lower (P \u3c 0.05) pH from the duodenum to the jejunum. At the end of Phase II, pigs fed NEGA diets had similar (P \u3e 0.10) pH from the stomach to the duodenum, and pigs fed MCSBM diets had lower (P \u3c 0.05) pH from the duodenum to the jejunum. There was no effect of ingredient, dietary acidifier, or their interaction in villus height, crypt depth, villus height:crypt depth, goblet cell area, Ki-67, inflammation scores in the stomach and duodenum, and mucin scoring in the stomach and upper duodenum at the end of Phase I. Phase II samples were not measured for gut health and function (other than pH measurements). Based off the lack of differences in growth performance and gut health measurements, MCSBM holds promise as an alternative for FM in nursery pig diets