Age-Specific Response of Broilers to Dietary Inclusion of a High-Tannin Feedstuff
The aim of this study was to determine whether the age of broilers can influence their response to tannin-rich diets. A total of 340 one-day-old mixed sex Ross 308 broiler chicks were distributed among five experimental groups with four replicates and 17 birds each in a completely randomized design. A high-tannin feedstuff, Oak acorn, was included into diets (at a level of 25%) and fed to birds at different stages of the rearing period. The control group was fed a corn-based diet (without Oak acorn) for the entirety of the study, while the other four groups were fed diets containing Oak acorn during one of the following periods: starter (d 1 to 21), finisher (d 22 to 42), last five weeks (d 8 to 42), or total period of the experiment (d 1 to 42). We found that performance traits (feed intake, body weight gain and feed conversion ratio) and tibia characteristics were similar among the control group and groups fed Oak acorn during the starter and finisher periods. However, feeding chicks with Oak acorn from 8 to 42 or 1 to 42 d of age significantly reduced overall body weight gain and increased overall feed conversion ratio (P < 0.05). Tibia characteristics were also negatively affected in chicks that received Oak acorn during the last 5 weeks and entire period of the experiment (P < 0.05). In addition, birds fed Oak acorn had higher liver weights at 21 d of age (P < 0.05). In conclusion, broilers response to dietary tannins is influenced by age. Oak acorn could be successfully included in broiler diets during the starter or finisher stages up to 25% without adverse effects on performance and tibia characteristics. In contrast, chronic inclusion of Oak acorn (5 or 6 weeks) decreases growth performance and may have deleterious effect on tibia characteristics.