Extrusion increased protein digestibility and energy value of lentilbased diets containing soybean meal or fish meal in growing pigs

Lentil grain is an energy and protein source for pigs. However, anti-nutritional factors and fibre in lentil may limit its inclusion in swine diets. Extrusion may increase its nutritional value, but whether plant or animal protein sources interact with lentil during extrusion is unknown. To explore, two diets were prepared: 1) soybean meal (SBM) diet, containing 50% lentil, 31% wheat and 12.8% SBM; 2) fish meal diet, containing 40% lentil, 45% wheat and 10% fish meal. Half of each diet was extruded using a single-screw extruder. The 2 extruded and 2 non-extruded diets were fed to 8 ileal-cannulated barrows (32.3 kg) for four 9-d periods in a double Latin square. Data were analyzed as a 2 × 2 factorial arrangement. Extrusion increased (P < 0.05) diet apparent ileal digestibility (AID) of crude protein (CP) and amino acids (AA) by 3.2 and 4.7%, and apparent total tract digestibility (ATTD) of gross energy (GE) by 2% and hence digestible energy (DE) values for SBM diet and fish meal diet, respectively. Interactions between protein sources and extrusion of diets were not observed. The fish meal diets had greater (P < 0.05) AID of dry matter (DM), GE, CP and all AA except methionine, and ATTD of CP, lower (P < 0.05) apparent hindgut fermentation (AHF) of DM and GE, but did not differ in ATTD of GE and AHF of CP compared with the SBM diets. Extruded SBM-lentil diet had comparable AID of CP and AA, and greater energy value compared with non-extruded fish-meal-lentil diet. In conclusion, extrusion increased the nutritional value of SBM-lentil and fish-meal-lentil diets. The protein digestibility of the extruded SBM-lentil diet was not different to that of the non-extruded fish meal diet. Thus, extrusion may help to reduce the inclusion of costly animal protein sources in swine diets. The finding is also relevant for the pet food industry that uses extrusion to produce kibbles. 

Key words: extrusion, fish meal, lentil, pig, soybean meal.

Published in the proceedings of the Animal Nutrition Conference of Canada 2020. For information on the event, past and future editions, check out https://animalnutritionconference.ca/.