Introduction: Pelleting is the most common thermal process in the poultry feed industry. Pelleting aims to compact smaller feed particles into larger ones to increase economic benefits through increased feed intake and consequently improved growth performance, safety, and health of broiler chickens. Heat, moisture, and mechanical pressure during pelleting induce chemical and physical changes that may affect feed components, bird growth, and health, From a nutritional point of view, the partial denaturation of proteins during pelleting improves their digestibility and allows easier access to proteases (Dozier, 2001). Gelatinization is the irreversible loss of the crystalline form of starch granules, which makes the surface of the starch molecule accessible to reagents, solvents and enzymes, which can then break down its glyosidic bonds and increase the digestibility of the starch (Moritz et al., 2005). Therefore this study aimed to evaluate the effects of feed processing conditions in conditioners on pellet quality and growth performance, immune response, and blood indices of broilers
Materials and Methods: A total of 480 one-day-old Ross 308 broiler chicks were used in a completely randomized design. Treatments were arranged in a 2×4 factorial arrangement with four temperature levels (70, 76, 82, and 88 °C) and two conditioning time levels (45 and 65 seconds). The pellet durability index (PDI) was calculated to determine pellet quality. The diets were fed for 42 days in diets with three periods of starter (1-10 days), grower (11-24 days), and finisher (25-42 days). Growth performance involving body weight gain, and feed intake, were measured at the end of each experimental period and the feed conversion ratio was also calculated at the same. At the end of the experimental period, two birds of each replicate were slaughtered and blood samples were collected from two birds of each replicate. After centrifuging the blood at 2500 rpm, the plasma was stored at -20°C until biochemical indices were analyzed. The plasma protein, cholesterol, triglyceride, LDLD, and HDL, and the enzyme activity of AST and ALT were determined by the autoanalyzer spectrophotometry. At the end of the experimental period, two birds from each replicate were slaughtered, and carcass weight and other internal organs were measured. Additionally, jejunal tissue samples were also collected for morphological analysis and preserved in formalin.
Results and Discussion: The results of this study showed that conditioning time and temperature did not have a significant effect on pellet quality and strength. However, performance parameters were affected by the experimental treatments (P<0.05). Pellets produced at the highest temperature had the lowest daily weight gain during the growth (P<0.05), finishing, and overall rearing periods (P<0.01). The feed conversion ratio of pellets produced at 76 and 82°C and 65 seconds improved at 14 days of age (P<0.05). At the end of the experimental period, pellets produced at lower temperatures had the lowest, and pellets produced at higher temperatures had the highest feed conversion ratio (P<0.01). Over the entire rearing period, pellets produced at 76°C and 65 seconds had the lowest, and pellets produced at 88°C and 65 seconds had the highest feed conversion ratio (P<0.01). The highest carcass and breast weight was observed in broilers consuming pellets produced at 82°C and 65 seconds (P<0.05). The experimental treatments affected the concentrations of glucose, total protein, albumin, cholesterol, triglycerides, HDL, LDL, and aspartate aminotransferase enzyme (P<0.01). Increasing the conditioning temperature reduced the concentrations of glucose, cholesterol, triglycerides, and LDL and increased the concentration of AST enzyme. The concentrations of total serum protein and albumin also decreased with decreasing conditioning time and temperature (P<0.01). Intestinal morphological indices such as villus height, villus height to crypt depth ratio, and absorptive surface area were also affected by the experimental treatments (P<0.05). Broilers consuming pellets processed at 76°C and 65 seconds had the highest villus length, villus height to crypt depth ratio, and villus surface area compared to other treatments (P<0.05).
Conclusion: Overall, the results suggest that conditioning temperature and time in pellet production did not significantly affect pellet quality and strength. Increasing the conditioning temperature in pellet production reduced daily weight gain and increased feed conversion ratio during the rearing period. Although increasing the conditioning temperature improved carcass and breast weights. A temperature of 76°C and a time of 65 seconds provided the best conditions for pellet processing and improved the health of broiler chickens and their digestive system. |
