Phytogenic cocktails fed in different feeding regimes as alternatives to antibiotics for improving performance, intestinal microbial, and carcass characteristics of slow growth chickens.

Background and Aim: The phytogenic cocktail (PC) is a unique combination of natural plant extracts consisting of coconut shell smoke, clove leaf extract, and mangosteen rind extract, predominantly containing phenol, eugenol, and α-mangostin. Chicken performance can be improved by its antibacterial properties. This study aimed to test PC as a replacement for antibiotic growth promoters (AGPs), assessing its impact on performance, intestinal microbes, and carcass traits in slow growth KUB chickens. Materials and Methods: Two hundred and forty KUB chicks were distributed randomly to five dietary groups. Each group constituted six replicates, one replicate contained eight chicks. The treatments included the control diet (CD) with no additives, CD with 50 ppm Zinc bacitracin as an additive (AGPs), CD paired with 198 mL PC/ton feed provided for the initial 12 weeks (PC1), CD with 198 mL PC/ton feed given for the first 4 weeks (PC2), and CD supplied with 198 mL PC/ton feed for the first 8 weeks (PC3). Performance and mortality indicators were assessed during the feeding stage up to 12 weeks of age, while intestinal total microbial count and carcass characteristics were determined at 12 weeks. Duncan's multiple-range test identified differences among the treatments in the randomized experiment. Results: The AGPs group weighed significantly more (p < 0.05) than PC2 but not significantly different (p > 0.05) from Control, PC1, and PC3 at 4 weeks. At 8 weeks, there was no significant difference (p > 0.05) in the body weight (BW) between the AGP, CD, and PC groups. The AGPs group had a significantly greater BW than PC1 and PC2 at 12 weeks (p < 0.05), but was comparable to CD and PC3 (p > 0.05). During the starter phase (0-4 weeks), dietary addition of AGPs or PCs significantly reduced feed intake (p < 0.05); however, no significant effect (p > 0.05) was observed during the later feeding periods (0-8 or 0-12 weeks). During the starter period, PC3 yielded the best feed conversion ratio, slightly surpassing AGPs and significantly (p < 0.05) outperforming CD. No significant variations (p > 0.05) were detected in the carcasses among the treatments. The reduction of abdominal fat relative weight was significant (p < 0.05) during the first 8 weeks of PC feeding. After the 12-week trial, no significant difference (p > 0.05) was observed in the proportionate weights of the crop, proventriculus, gizzard, pancreas, cecum, spleen, bursa of Fabricius, heart, and liver. The reduction in the intestinal microbe population due to AGPs or PC was not statistically significant (p > 0.05). About 100% viability was confirmed by the absence of mortality throughout the study. Conclusion: PC supplementation in KUB chicken feed enhances their performance. The optimal feeding regimes were effective during the first 8 weeks of age. In the 0-4 week time frame, feeding the PC to the chicken worsened performance whereas no improvement was observed in the 0-12 week period. The application enhanced weight loss, feed efficiency, and reduced abdominal fat. Based on the research findings, the PC can replace AGPs as a feed additive due to comparable or superior improvement results.