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Evaluation of a microbially-converted soybean meal as a substitute for fishmeal in weaned pig diets
Standard ileal digestibility (SID) values, determined previously in our laboratory, were similar between fish meal (FM) and microbially-converted soybean meal (MCSBM). A performance trial was conducted to evaluate MCSBM as a replacement for FM in weaned pig diets. A total of 184 barrows and 152 gilts were weaned at 21d of age and assigned to one of 6 experimental diets (8 pens/diet with 7 pigs/pen; barrows and gilts were balanced across treatments) fed in Phase I (d0-7) and Phase II (d8-21) of a 3-phase feeding program. All pigs received a common Phase III (d22-35) diet. Experimental diets included: 1) negative control (NEG) containing corn, soybean meal and whey, 2) NEG + acidifier, 3) NEG + fishmeal (FISH), 4) FISH + acidifier, 5) NEG + MCSBM, and 6) MCSBM + acidifier. Fish meal and MCSBM were included at 7.5% and 5.0% in Phase I and II, respectively. Diets were formulated to meet the NRC (2012) SID lysine:MEg/Mcal requirement for weaned pigs. Pig BW and feed disappearance was measured weekly. Tissue and digesta samples were collected on d7 and 21 from stomach, duodenum, ileum, cecum, and feces (1 mean pig/pen based on average daily gain and balanced for gender across treatment). Digesta pH was measured at the stomach, duodenum, jejunum, ileum, cecum, and colon. Mean initial BW was 6.1 ± 0.83kg and final BW was 20.1 ± 2.0kg. Data was analyzed by the MIXED model of SAS. Daily gain, BW, and gain:feed from d0-7, d8-21, and d22-35 were not different between treatments. Daily feed intake tended to be greater (P=0.09) in pigs fed FISH compared to NEG (954 vs 769g/d, respectively), similarly for FISH compared to MCSBM+acid (954 vs 756g/d) from d22-28. There was no difference in pH across the digestive tract between treatments at d7 (mean pH across treatments was 3.85, 5.25, 6.34, 6.95, 6.04, and 6.27 in the stomach, duodenum, jejunum, ileum, cecum, and colon, respectively). On d21, pH in the ileum was lower in pigs fed MCSBM than pigs fed NEG, MCSBM + acid, FISH + acid, and NEG + acid (5.60 vs 6.90, 6.92, 7.04, and 7.21, respectively). MCSBM affected digesta pH in the distal small intestine. Performance was similar for pigs fed FM or MCSBM thus MCSBM may be an alternative to FM in nursery diets; however, it is important to note neither FM nor MCSBM provided additional benefit over solvent extracted soybean meal (i.e. NEG diet).
Keywords: growth performance, microbially-converted soybean meal, weaned pig