Influence of Expander Conditioning Prior to Pelleting on Pellet Quality, Broiler Digestibility and Performance at Constant Amino Acids Composition while Decreasing AME(N)

Simple Summary Modern broilers convert nutrients and energy into meat very well, responding especially well to dietary amino acids. Currently, their ability for rapid growth allows them to achieve their target weight sooner. This is partly related to their positive response to dense amino acids relative to apparent metabolizable energy corrected for Nitrogen (AME(N)) diets; as recently shown in research, broilers' energy requirement is lower than that recommended by the strain's guidelines. On the other hand, feed intake is the key factor that allows the conversion of nutrients into increased body weight. Thus, this trial proposed the investigation of diets with constant amino acid composition with a stepwise AME(N) reduction, conditioned with or without an expander prior to pelleting, aiming to produce high-quality pellets. The hypothesis was that the non-nutritional factor expander may replace the dietary reduction in AME(N) without issues on performance, enhancing broiler nutrients digestibility, and maintaining the birds' health. The results showed that broilers' performance was only slightly affected by the energy reduction and the use of expanders in the overall period. However, the use of expanders was advantageous at growing and finisher diets, probably due to the disruption of the corn oil cells, allowing faster attachment of endogenous lipase, which is extremely low in the first days and well established after 14 days of age. Broilers responded to the better pellets and higher nutrient digestibility promoted by the expander. In contrast, the AME(N) reduction allowed lower abdominal fat accumulation, and no issues in broiler health were attested by serum markers. Physical pellet quality and AME(N) concentration are strongly related to each other in broiler feeding. A study was conducted to evaluate the relationship between dietary AME(N) concentration and feed processing on pellet quality, nutrient digestibility, broiler performance, serum markers, and yield of commercial cuts. Six diets were formulated. The first diet had the recommended AME(N) concentration, each further diet was calculated with 40 kcal/kg less, from 0 to -200 kcal/kg, resulting in six levels for each feed phase: starter (1-14 d), grower (15-28 d), and finisher (29-35 d). These diets were processed with and without expander conditioning prior to pelleting, using an average corn particle size of 1.6 mm, ground with a roller mill. A total of 1008 one-day-old male Ross 308 broiler chickens were placed in a 6 x 2 (6 energy levels and 2 conditionings) factorial trial with six boxes as replications, with three in each broiler performance trial period. Excreta were collected 2 days before the end of each feed phase for apparent total tract digestibility measurement. On day 36, four broilers from each replication (pen) were weighed and then euthanized for blood collection, following which the gastrointestinal organs were weighed, and the ileal and gizzard contents were collected. On day 37, all remaining broilers were slaughtered after fasting to measure commercial cuts and abdominal fat. The results show that the pellet durability index (PDI) was most affected by energy reducing and expander conditioning prior to pelleting, and it was better when diets had energy reduced by 40 to 200 kcal/kg (p > 0.001), as when expander conditioning was used. Digestibility of nutrients was slightly affected by treatments, as was the broiler performance; however, feed efficiency was improved in broiler-fed diets without AME(N) reduction and when an expander was used, with p = 0.050 and p = 0.031, respectively. No effects were observed on the weight of gastrointestinal tract organs and serum markers, except for liver (p = 0.037) and alpha-amylase (p = 0.047). The lowest liver weight and lowest serum protein, cholesterol, triglyceride, gamma-glutamyl, and lipase concentrations were obtained when diets were formulated without energy reduction (Ross-0). There was no effect on commercial cuts relative to live weight at slaughter. The energy reduction was well reflected in the proportion of abdominal fat, which decreased when AME(N) was reduced (p = 0.001). The present study shows it is possible to use diets with up to 200 kcal/kg reduction in AME(N) without losses in performance, and the use of expander conditioning prior to pelleting promotes higher pellet quality and broiler feed efficiency.