Effects of thyme, garlic, echinacea, and galbanum on performance, cecal microbiota, and immune function of native ducks

Introduction:
Antibiotics have been added to poultry diets to increase the growth performance and boost immunity. Induction of pathogens resistance and the antibiotic's residue in the final products are disadvantages that limit their use in feeding of livestock and poultry as a growth stimulant. Recent reports confirm the increasing trend in antibiotic resistance, which decreased antibiotics effectiveness, therefore, search for antibiotic growth promoter (AGP) alternatives seems inevitable. Among the AGP alternatives, phytobiotics have shown promising results. Therefore, the need to use medicinal herbs such as echinacea, thyme and garlic is felt which can both strengthen the immune system and have antimicrobial effects. The essential oil (EO) of the thyme contains phenolic compounds (carvacrol and thymol) and the main non-phenolic compound is P-cymene. Thymol and carvacrol have antimicrobial properties, reduce pathogens in the gut and improve growth rate and feed efficiency of poultry. Garlic with potential antimicrobial properties can be considered as a natural substitute for AGPs. Additionally, garlic extract contains organosulfur compounds like glutamyl-S-L-cysteine, di-alyl sulfide (DAS) and di-alyl disulfide (DADS), which, may supply the sulfur amino acids for breast muscle synthesis. The active medicinal compounds of echinacea including polysaccharides, glycoproteins, caffeic acid derivatives and alkaloids have the ability to modulate immune system, therefore, many of these compounds enhance the activity of macrophages. It has been shown that dietary Ferula gummosa can significantly decrease ileal total numbers of harmful bacteria and increase the number of lactobacilli.
Aim: Due to the limited researches on the usage of phytobiotics in duck nutrition, the aim of this experiment was to exploit the antimicrobial effect of thyme and galbanum, the anti-hyperlipidemic effect of garlic, and the immune system boosting effect of echinacea on native ducks. We have postulated that by mixing the four above-mentioned herbs, it might be possible to maximize antimicrobial, antioxidative and immunomodulatory effects and minimize the required dose of the phytobiotics. Another hypothesis was to compare the efficacy of the phytobiotics in powder form versus EOE form. Therefore, the purpose of this experiment was to examine the potential of the phytobiotics mix as an AGP alternative and to test the efficacy of the mix in powder form versus EOE form on performance, cecal microflora population, and immune status in native ducks.The purpose of this experiment was to examine the potential of a phytobiotics mix (thyme, garlic, echinacea, and galbanum) as an AGP alternative and to test the efficacy of the mix in powder form versus essential oil extract (EOE) on performance, cecal microflora and immune cell status in native ducks.
Materials and Methods: Two hundred forty male day-old ducklings were randomly allocated into 6 groups with 5 replicates and 8 ducklings per replicate in a completely randomized design (CRD). The experimental treatments were: (1) control: standard diet, (2) AGP: 10 mg/kg Avilamycin®, (3) P1: 1 gr/kg of the phytobiotics mix in powder form, (4) P2: 2 gr/kg of the phytobiotics mix in powder form, (5) EOE1: 100 mg/kg of the phytobiotics mix in essential oil extract (EOE) form and (6) EOE2: 200 mg/kg of the phytobiotics mix in EOE form. The chemical composition of the EOE was determined using gas chromatography-mass spectrometry. Performance data including FI, WG and FCR were recorded weekly and periodically.The breeding period was 42 days and the ducklings were fed the starter and grower diet. The bacteria studied were lactobacilli, coliforms, TAB and E. coli. Total leukocytes (WBCs 10³/µl) and differential leukocyte counts were determined according to common hematological examination.
Results: Based on the results, average WG and FCR were affected by the additives only during starter phase (P<0.05). The ducks fed with AGP, P2 and EOE1 had higher WG and lower FCR in the starter phase. The ducks fed with AGP and P2 had tendency (P<0.1) for higher FI in the grower and overall periods and the EOE supplemented groups had tendency for lower FI in comparison with the control group. Breast muscle weight (P<0.05) was increased and pancreas weight (P<0.05) and abdominal fat weight (P<0.01) were decreased by the experimental treatments. Moreover, the AGP or phytobiotics additives decreased liver weight (P<0.1). Based on the results, mean count of lactobacilli, coliforms, E. coli and TAB were affected by the experimental treatments (P<0.01). The AGP and EOE1 fed ducklings had highest Lactobacillus spp. and had lowest coliforms, E. coli and TAB. Control group had lowest count of lactobacillus spp. and had highest E. coli, coliforms and TAB counts. Other additives increased lactobacilli and decreased coliforms, E. coli and TAB counts in comparison with the control group. All the additives, especially EOE1, increased lactobacilli count and declined cecal counts of Escherichia coli (E.coli), coliforms and total aerobic bacteria (TAB). Based on the results, white blood cell numbers (P<0.05), heterophile percentages (P<0.01) and H/L ratio (P<0.01) were significantly affected by the experimental treatments. The highest white blood cell numbers were observed in the EOE1 treatment. Conversely, the highest heterophile percentage was in the control treatment and the lowest was related to the EOE1. The highest H/L ratio was observed in the control treatment and decreased by phytobiotics supplementation specially in the ducks fed with EOE1.Totally, the results indicated that feed additive AGP in duck nutrition can be effectively substituted by a phytogenic feed additive, especially in the essential oil form.
Conclusion: AGP can be effectively replaced by EOE or herbal mixture of thyme, garlic, echinacea, and galbanum. The EOE mix at supplementation level of 100 mg/kg was more effective on performance and immunity in native ducks.