The effects of thermal treatment of field peas (Pisum sativum L.) on nutrient and energy digestibility by growing pigs

¹ Department of Animal and Range Sciences, South Dakota State University, Brookings

^* To whom correspondence should be addressed. E-mail: hstein{at}uiuc.edu.

	Abstract

An experiment was conducted to measure the effect of thermal treatment on the digestibility of CP, AA, starch, NDF, ADF, and energy in field peas fed to growing pigs. Five pea-containing diets were formulated. The peas included in these diets were either not heat treated (control) or extruded at 75, 115, or 155°C, or pelleted at 75°C. A nitrogen-free (N-free) diet was also included in the experiment to measure basal endogenous losses of CP and AA. The 6 diets were fed to 6 growing pigs (initial BW: 69.3 ± 2.9 kg) that were allotted to dietary treatments in a 6 x 6 Latin square design. A T-cannula was installed in the distal ileum of each pig allowing for the collection of ileal digesta. Each experimental period lasted 9 d; fecal samples were collected on d 6 and 7 and ileal samples were collected on d 8 and 9 of each period. Apparent ileal digestibility values (AID) for CP, AA, starch, and energy and standardized ileal digestibility values (SID) for CP and AA were calculated. Apparent total tract digestibility values (ATTD) for NDF, ADF, starch, and energy were also calculated. Results of the experiment showed that the AID and SID for CP and all AA, except Pro, increased as extrusion temperature increased (quadratic, P < 0.05). In contrast, except for Arg and Pro, the peas that were pelleted at 75°C had AID and SID for CP and AA that were similar to those obtained for the control peas, but less (P < 0.05) than the AID for the peas that were extruded at 75°C. The AID for starch and energy increased (linear, P < 0.001) as the extrusion temperature increased to 155°C (from 89.8 to 95.9% and from 71.5 to 79.0%, respectively), but the AID for starch and energy in the pelleted diet was not different from the AID in the control diet (90.1 vs. 89.8% and 69.1 vs. 71.5%, respectively). The ATTD for starch was between 98.6 and 99.7% and did not differ among treatments. Likewise, no differences were observed in the ATTD of NDF and ADF. However, the ATTD for energy in the diets increased from 89.0 to 93.3% (linear and quadratic, P < 0.05) as field peas were extruded, and the ATTD for energy in the pelleted diet was also greater (P < 0.05) than in the control diet (91.6 vs. 89.0%). In conclusion, extrusion of field peas may increase the AID of CP, AA, starch, and energy, and the ATTD of energy. Pelleting field peas at 75°C does not influence the AID of nutrients or energy, but improves the ATTD of energy.

Key Words: energy digestibility, extrusion, field peas, nutrient digestibility, pigs, thermal treatment