Feeding Low- and High-Fibre Sunflower Meal to Broiler Chickens—Effects of Inclusion Rate and Age of Birds on the Production Traits, Carcass Composition, Nutrient Digestibility, Gut Viscosity, and Caecal Short-Chain Fatty Acid Content

Sunflower meal (SM) is an economically important, inexpensive, and locally abundant alternative protein source in the Eurozone. The study aimed at investigating the effects of feeding two forms of SM on the production traits, carcass composition, nutrient digestibility, and some gut parameters of broiler chickens. A total of 600-day-old Ross 308 male broilers were fed five isocaloric and isonitrogenous diets. Besides the control diet (C), the high- and low-fibre SMs (HFSM and LFSM) were fed at 20% (HFSM20 and LFSM20) and 30% (HFSM30 and LFSM30). Compared to the C, feeding the SM-containing diets did not affect the feed intake (FI) of birds. In the finisher phase, the HFSM30 treatment resulted in significantly higher, while the LFSM30 diet in significantly lower body weight gain. All SM treatments impaired FCR, but the difference was significant only in the grower phase. In comparison with the C, the SM treatments failed to modify carcass composition. The fat digestibility and the AMEn content increased, while the starch digestibility decreased when SM was fed. Except the LFSM30 treatment in the grower phase, the Nitrogen retention of birds was not affected. The SM-containing diets reduced the urinary N excretion, and the total N excretion of growers. Furthermore, the HFSM30 reduced the jejunal viscosity during the grower and finisher phases. The treatments did not modify the short-chain fatty acid contents of the caeca. In conclusion, SM can be used even at 20 and 30% in the nutrition of broiler chickens. However, the responses are affected by the age and the fibre content of SM.