Effect of feeding diets with varying energy levels and conditioning temperatures on broiler performance, processing yield, and nutrient digestibility

Abstract

Pelleting is the most common thermal processing method used in the manufacturing of broiler diets. It is a process that involves the use of heat, moisture, and pressure to agglomerate smaller feed particles into pellets. Previous research has demonstrated the benefits of pelleting, including increased feed intake (FI), reduced feed wastage (FW) and nutrient segregation, and increased digestibility of some dietary components. Therefore, pellets are the preferred feed form in the US broiler industry. However, there are many factors that may influence the response of birds fed pelleted diets, including conditioning temperatures and the level of metabolizable energy (ME) in the diet. For this reason, two trials were designed to evaluate the relationships between feed processing variables and the nutritional value of feed. The objective of the first experiment was to evaluate the main effects and interactions of two ME levels and three conditioning temperatures on broiler performance, processing yield, footpad lesions, tibia ash, and nutrient digestibility from 1 to 42 d of age. A total of 1,350 d-old YPM x Ross 708 male broilers were randomly distributed in 54 floor pens and assigned to six treatments (9 replicates/treatment). Diets were formulated to contain two ME levels (standard energy (SE) and -130 kcal/kg reduced energy (RE)) in all feeding phases. Basal diets for each ME level were manufactured using three conditioning temperatures (80, 84, and 88°C). Feed intake, body weight (BW), and feed conversion ratio (FCR) were determined at 14, 28, 35, and 42 d of age. On d 42, ileal digesta (5 birds/pen) was collected for nutrient digestibility analysis and broilers were processed on d 43. Broilers fed SE had improved FCR (P < 0.05) compared to broilers fed RE in every evaluated period. Performance parameters from 15-42 d and processing yields were unaffected (P > 0.05) by conditioning temperatures. Apparent ileal digestibility (AID) of fat and energy was higher (P < 0.05) in broilers fed SE compared to broilers fed RE. Broilers fed diets conditioned to 88°C had lower (P < 0.05) AID of Ca and P compared to broilers fed diets conditioned to 80 and 84°C. A second study was conducted to evaluate the main effects and interactions of two ME levels and three feed forms on broiler performance, FW, and nutrient digestibility from 1 to 21 d of age. A total of 648 YPM x Ross 708 male broilers were randomly distributed in 72 battery cages (9 birds/cage) and assigned to six treatments (12 replicates/treatment). Starter diets were formulated to contain two ME levels (2,979 [E2979] and 2,875 kcal/kg [E2875]). Both diets were fed as mash, crumbles conditioned at 85°C, and crumbles conditioned at 90°C. Body weight gain (BWG) and FI were determined at 10 and 21 d of age and FCR was adjusted for mortality. On d 10, 15, and 18, the feed spilled was collected from trays placed under each battery cage to calculate FW as g/kg. Ileal digesta (7 birds/cage) was collected for nutrient digestibility analysis on d 21. Broilers fed E2979 diets had lower (P < 0.05) FCR (1.28 vs. 1.36 g:g) from 1-21 d compared to broilers fed E2875 diets. Additionally, broilers fed mash diets had lower (P < 0.05) FI (1049 vs. 1223 and 1215 g) and higher (P < 0.05) FCR (1.34 vs. 1.30 and 1.32 g:g) and FW (28.6 vs. 2.3 and 3.0 g/kg) from 1-21 d compared to broilers fed crumbles conditioned to either 85 or 90°C. The lowest (P < 0.05) apparent ileal digestibility AID of dry matter (DM) was observed in broilers fed mash diets with E2875. Broilers fed E2979 diets had improved (P < 0.05) AID of crude protein (CP) compared to broilers fed E2875 diets. Starch digestibility was lower (P < 0.05) in broilers fed crumbles conditioned to 90°C compared to broilers fed crumbles conditioned to 85°C and mash. Overall, these studies suggest that broiler performance and nutrient digestibility are influenced by different feed processing parameters as well as by the nutritional value of feed. The obtained results highlight the importance of understanding that the response of birds to diet formulation and processing variables is closely related. Therefore, this relationship should be considered to make decisions that improve broiler performance and nutrient utilization.