Use of a Phytogenic Blend of Cinnamaldehyde and Thymol Alone or in Combination with a Bacillus Probiotic Improves Performance of Broilers During High Challenge Situation

Phytogenics and probiotics are gaining more attention in the animal industries due to market trends to reduce antibiotics use, whilst still preventing disease outbreaks and maintaining, or even improving, animal performance. Phytogenics have been shown to inhibit non-beneficial, potentially pathogenic bacteria such as E. coli (Ouwehand et al., 2010, Bento et al., 2013), positively influencing the gut microbiome and inhibiting C. perfringens populations. Bacillus based probiotics have been shown to influence gastro-intestinal tract (GIT) microbial populations and reduce Avian Pathogenic E. coli counts in the GIT of broilers (Wealleans et al., 2017). The modes of action of cinnamaldehyde and thymol in terms of influencing gut health differ from Bacillus probiotics. The phytogenics have direct antibacterial effects (Bento et al., 2013) whereas Bacillus have a number of different modes of action which include outcompeting non-beneficial bacteria, encouraging growth of beneficial bacteria and aiding development of the immune system. Therefore, it is expected that their modes of action may be complementary and that using the phytogenic and probiotic together may lead to improved performance of broiler chicks during challenge situations. Few studies to date have looked at combining probiotic and phytogenic treatments.

A total of 2160 day-old Lohmann Indian River chicks were randomly allocated to 5 dietary treatments with 12 replicate pens per treatment (36 birds/pen). Birds were fed over 2 dietary phases: starter (1 to 21 days) and grower/finisher (22 to 35 days). All diets were formulated to meet the birds’ nutrient requirements and were fed ad libitum as crumble (starters) or pellet (finishers). All diets contained Buttiauxella phytase (Axtra® PHY, DuPont Animal Nutrition) at 1000 FTU/kg of feed and a combination of xylanase, amylase and protease (Avizyme® 1505X, DuPont Animal Nutrition) at 200 g/kg of feed (to provide 1840 U xylanase/kg, 320 U amylase/kg and 3200 U protease/kg of feed). The control diets (Table 1) were reduced by 0.187% phosphorus, 0.199% calcium, 126 kcal ME, 0.028% methionine plus cysteine and 0.045% lysine in line with the enzyme manufacturers recommendations for reformulation.

One group of birds was fed the control diet and was not disease challenged (UC). Challenged birds (CC) were inoculated with Coccivac, C. Perfringens and E. coli according to the schedule in Table 1. The challenged birds were also fed the control diet, or this diet supplemented with either Antibiotic Growth Promotor (AGP) at 50g/tonne, phytogenic blend (EO) at 100 g/t feed (to provide 4.5 g of cinnamaldehyde and 13.5 g of thymol/tonne of feed), or a combination (EOPRO) of EO at 100 g/t feed and 3 strains of Bacillus probiotic at 60 g/t feed (to provide 150 000 CFU/g feed). Bodyweight and feed intake were measured at the start and end of each phase. FCR and Broiler Index (BI) were then calculated. BI was calculated as:

[ ABW / Days of Age * ( 100 - (%) DEPL ) / FCR / 10 ] ;

in which: ABW = Average Body Weight; DEPL = Depletion.

Table 1 - Diet composition (g/kg).

Gut samples were taken on day 21 and day 35 from 24 birds/replicate (2 birds per pen; one male, one female). Lesions in three locations were scored: duodenum (E. acervulina), ileum (E. maxima) and caeca (E. tenella) from 0-4; good-bad (Johnson and Reid, 1970). Also, Bacterial Enteritis Scores (BES) were scored by evaluating different parameters either 0 (good) or 1 (bad) and then added together per pen; a lower score is indicative of better gut health

Table 2 - Challenge protocol.

The challenge applied during the trial was effective and negatively impacted performance, reducing bodyweight gain by 4.8% and FCR by 6 points (3.8%, P < 0.05). The challenge also resulted in a 3.2% increase in mortality and a significant decrease in the Broiler Index by 11.3% (P < 0.05).

Table 3 - Effects of phytogenic and probiotic supplementation on broiler growth performance from 1-35 days.

Challenged birds fed the EO and EOPRO treatments presented numerically improved performance versus the challenged control birds. Average daily gain was improved with the EO and EOPRO treatment compared to the challenged birds fed the control treatment, by 1.31% and 2.45%, respectively. Final bodyweight tended to improve by 1.2% and 2.2% with the EO and EOPRO treatment versus the challenged control and was not significantly different from the unchallenged birds. FCR was also numerically improved by 3 points in birds that were given the disease challenge with both the EO and the EOPRO treatments and for both the EO and EOPRO treatments ADG and FCR were not significantly different to the unchallenged control birds. In contrast, the AGP treatment did not result in any performance improvements in the challenged birds, with both the EO and EOPRO treatments numerically improving performance (ADG, FCR and broiler index) versus the AGP.

Broiler Index tended to improve (by 4.36% and 5.23%, respectively) for the EO and EOPRO treatments compared to the challenged control. Gut health scores did not differ among treatments.

Table 4 - Effects of phytogenic and probiotic supplementation on broiler gut health scores (day 35).

The challenge administered in the current study was severe, combining an Eimeria, E. coli and C. perfringens disease model. The results of the study indicated that when birds were fed either the EO treatment or the combination of EOPRO, the performance impact of the challenge was reduced and growth performance was maintained at the same level as unchallenged broilers fed the same diet. The final body weight and ADG tended to be greatest when the phytogenics and probiotic were fed in combination. The EO and Bacillus used in the study have been shown to positively influence the microbiome of broilers (Ouwehand et al., 2010, Bento et al., 2013, Wealleans et al., 2017) by supporting beneficial microbial populations (e.g. lactic acid bacteria) and reducing potentially non-beneficial populations (e.g. E. coli and C. perfringens). There is some evidence the Bacillus strains can support the development of the avian immune system, making them better equipped to deal with intestinal challenges and studies have also indicated that a cinnamaldehyde and thymol combination can help modulate the immune system and improve intestinal immunocompetence in young broilers (Bento et al., 2013). Such modes of action could explain the positive performance effects noted in the current study, although these measurements were not taken directly. This is not the first time these additives have been documented to have a beneficial effect in challenge studies. Dersjant-Li et al. (2016) reported reductions in inflammatory responses, improvements in gut structure and a maintenance of bird performance to that of the UC in a coccidiosis/necrotic enteritis study. The current study provides supporting evidence for the potential to combine feed additive solutions in an antibiotic-free diet without negatively impacting performance during times of disease challenge. It is likely that the combined influences of the probiotics and phytogenics on the nutrition, microbiome and immune status of the animal will have contributed to a favourable health status and resulted in a more robust animal with the ability to deal with pathogenic challenges more quickly, to minimize their potential negative effects.