Nutritional value of heat-processed field pea and lentil grains as alternative feedstuffs for pigs

Abstract

Field pea and lentil grains are alternative starch and protein sources for swine; however, pulse grains have a lower energy digestibility in pigs than conventional feedstuffs, contain trypsin inhibitors that may reduce protein digestion, and may reduce feed efficiency (G:F). Processing using treatments with heat and friction and whether it reduces trypsin inhibitor activity (TIA) and increases nutritive value of field pea and lentil grains remains unknown. The objectives of this thesis were to gain insight into the effects of heat processing on nutrient digestibility of field pea and lentil grains and further our understanding of the feeding value of raw and heat processed field pea and lentil grains in weaned and growing pigs. In Chapter 2, weaned pigs (n = 236) were fed for 21 d diets including 400 g/kg raw, cold-pelleted, steam-pelleted or extruded field pea replacing 300 g/kg soybean meal (SBM) and 100 g/kg wheat grain. Average daily feed intake of pigs fed field pea diets (853–882 g/day) was greater than pigs fed SBM (813 g/day); however, the predicted net energy value was 0.7 0.76 MJ/kg lower in field pea diets than in the SBM diet. Average daily gain and final body weight did not differ between SBM diet and field pea diets, nor did it differ among field pea treatments. Thus, G:F was lower for pigs fed field pea diets (0.60–0.63) than for pigs fed SBM diet (0.68). In Chapter 3, the same raw and processed field pea grain (cold-pelleted, steam-pelleted or extruded) were included in 4 diets at 956 g/kg and fed to 8 ileal-cannulated weaned pigs in a double 4 × 4 Latin square. A N-free diet was also fed to pigs to measure basal endogenous losses of amino acids (AA). Cold-pelleting reduced TIA by 0.8 mg/g and increased digestibility of energy by 0.92 MJ/kg in field pea grain and extrusion reduced TIA by 1.1 mg/g and increased ileal digestibility of some AA compared with raw field pea grain in weaned pigs. In Chapter 4, energy and protein digestibility of raw, steam-pelleted, or extruded lentil grain was measured using 9 ileal-cannulated growing finishing pigs. Diets containing 956 g/kg of raw or processed lentil grain were fed to pigs in a triple 3 × 3 Latin square with an additional N-free diet. Steam-pelleting and extrusion increased measured starch content (91 and 89 g/kg, respectively) and digestibility of dry matter, gross energy, and crude protein of lentil grain by 2.0 to 6.5%. Ileal digestibility of all amino acids except glutamic acid were increased by steam pelleting and some were increased further by extrusion. The TIA was reduced by extrusion by >1.2 mg/g, but not steam pelleting. In summary, nursery pigs fed 400 g raw field pea/kg maintained growth, and pigs compensated for the reduced energy value of field pea with a greater average daily feed intake, which is indicative of an absence of negative effects of TIA on feed intake. Cold-pelleting and extrusion of field pea grain reduce TIA, though only cold-pelleting increased energy digestibility and only extrusion increased digestibility of some AA. Both steam-pelleting and extrusion increase digestibility of AA and energy value of lentil in growing-finishing pigs. This thesis provides information that enhances the understanding of opportunities and limitations to feed pulse grains to both weaned and growing-finishing pigs. In conclusion, feeding value and nutritive value of lentil and field pea grain may be affected by heat-processing, as indicated by increased energy digestibility, increase protein digestibility or maintained growth.