Effect of Dietary Pea Supplementation on Heat Increment and Net Energy in Broilers

Field pea (Pisum sativum) is a good source of protein but can also provide energy due to high starch content (Petterson et al., 1997). The slowly digestible starch in pea may improve energy utilization in broilers because of the prolonged elevated plasma glucose levels (Enting et al., 2005). Thus, partial replacement of soybean meal and wheat with pea may affect the net energy value of the diet. This experiment was performed to investigate the effect of pea in diet formulation on heat increment and net energy in broilers using open-circuit respiratory calorimetry.

Ross 308 male broilers (n=24) were used for this study. A wheat-soybean meal based diet was used as a control and the treatment diet contained 50 % pea (by partially replacing wheat and soybean meal). The diets were formulated based on the Ross 308 nutrient specifications and were iso-energetic and iso-nitrogenous with the same levels of added oil. Energy levels were adjusted and made similar in both diets by the addition of Celite (an indigestible inert filler) in wheat-soy diet so that only the effect of added dietary pea could be investigated. Birds were fed a common starter crumble from d 0-10 and then a standard grower diet thereafter. On d 21, the birds were transferred to the open circuit chambers (n=2/chamber) and adapted for four days before three days of measurements from d 25 (daily feed intake, weight gain and excreta collection) to determine total tract digestibilities of nutrients, heat increment and net energy. Each treatment was replicated six times using two identical runs with three replications/treatment in each run. T-test was used to compare the means between the two treatments. Significance level was detected at P < 0.05 using SPSS software v. 25.

The measured apparent metabolisable energy (AME), AMEn (AME corrected to zero N retention), AMEs (AME corrected to 50 % N retention), and net energy (NE) were higher in pea-based diet compared to wheat-soy diet (P < 0.05) but there were no differences (P > 0.05) in AME and NE intakes between the two groups. Heat production, respiratory quotient, heat increment of feed, and efficiency of utilization of AME to NE (NE:AME, NE:AMEn, and NE:AMEs) did not differ (P > 0.05) between the two treatments. There was no effect (P > 0.05) of dietary pea inclusion on the total tract digestibilities of dry matter, crude protein and ash. The total tract digestibility of starch was higher (P < 0.05) in the pea-based diet (97.6 %) compared to the wheat-soy diet (95.8 %) which suggests that a greater proportion of starch from pea entered the caeca and was fermented. It may also be possible that pea starch was more slowly digested leading to a longer period of exposure of the starch to amylolytic enzymes. From the present study, it can be concluded that a slowly digestible starch in pea compared to wheat starch increases dietary AME and NE but does not affect heat increment of feed and the efficiency of utilization of AME to NE in broilers. However, it should be noted that varietal differences and processing conditions of pea may affect the results and thus these potential effects should be further explored.