In commercial broiler production, antibiotics have been used extensively, to prevent or control infectious diseases and also to serve as a growth promoter. The misuse and incorrect application of antibiotics increases the risk of antibiotic residues in edible tissues of the chicken (Marazuela and Bogialli, 2009). Low and continuous exposure to antibiotic residues produce potential threats of direct toxicity in humans, alteration of microflora with possible development of resistant strains, that leads to failure of antibiotic therapies (Nisha, 2008). Therefore, the demand by consumers for antibiotic residue free chicken meat is growing very fast. This has led to the emergence of organic broiler farming where use of antibiotics in any form for prevention of disease or improving the productivity of birds is not allowed (Nagarajan et al., 2017). In this scenario there has been a significant increase in number of studies focused on searching for alternatives to antibiotics, having similar antimicrobial and growth promoting effects, without causing any potential side effects to the birds fed on it. Probiotics, prebiotics, organic acids, enzymes and phytobiotics have been widely studied as potential alternatives to antibiotics in feed. Numerous studies on phytobiotics have demonstrated their positive effects in terms of antimicrobial, antioxidative and anti-inflammatory activity and it has been stated that the primary mode of action of phytogenic feed additive is controlling potential pathogens and beneficially modulating the intestinal microbiota (Murugesan et al., 2015). A healthy gut is extremely important for enhanced broiler performance and production of hygienic chicken meat. However, very limited research exists on the use of a mixture of indigenous herbs as phytobiotics, it is in this context that this study was executed to evaluate two different phytobiotic mixtures on production performance and gut health in broilers.

The study of six weeks duration was carried out between the months of July and August, 2019, at Poultry Farm Complex, Department of Poultry Science, Veterinary College and Research Institute, Namakkal, Tamil Nadu, which falls in the North-Western agro climatic zone of the state (Anonymous, 2019).
 
Experimental birds and experimental design
 
One hundred and fifty, one-day-old Vencobb broiler (feather sexed) chicks belonging to the same hatch were wing banded, weighed and distributed randomly into five treatment groups, each group had three replicates, with 10 birds per replicate.
 
The treatments adopted for this study were as follows:
 
 
The following was the composition of phytobiotic mixtures used in the study.

1. Phytobiotic mixture (I) - Syzygium  aromaticum buds + Mentha spicata leaves + Emblica officinalis fruits in 1:1:1 ratio.
2. Phytobiotic mixture (II) - Emblica officinalis fruits + Murraya kenigii leaves + Syzygium  aromaticum buds in 1:1:1 ratio.

 
Management system
 
The experimental birds were reared in a deep litter system. All management practices adopted except for the feed offered, were similar to all treatments.
 
Experimental feed
 
Feed ingredients, procured locally were used for the formulation of experimental feed. Experimental broiler pre starter (0-2 weeks), starter (3-4 weeks) and finisher (5-6 weeks) feeds were formulated as per Vencobb 400 specification. The phytobiotic mixtures (ground form) at their respective levels as per the treatments were mixed with the feed. The ingredients and nutrient composition of experimental broiler pre starter, starter and finisher ration is presented in Table 1.
 

 
Production performance
 
The birds were weighed individually every week till the end of the study period (6^th week) in a calibrated electronic weighing balance of 10 g accuracy to document their body weight and calculate weight gain (g). Every day the left-over feed was weighed to record the accurate feed intake (g). Feed consumption was calculated after correction of feed wastage. The feed conversion ratio per kilogram weight gain was calculated.
 
Gut health
 
At the end of the experimental period six birds per treatment were randomly selected and slaughtered and the gut contents and portion of ileum of the birds were collected to study the microbial profile of gut contents and gut histomorphology.
 
Microbial profile of gut contents
 
To study the microbial profile, the ileum (from the duodenum and Meckel’s diverticulum) of each bird was accurately removed and samples of the intestinal contents were collected and diluted with sterile saline solution and different medias (Mac-Conkey agar (MAC), De Man Rogosa  and Sharpe agar (MRS) and C. perfringens agar were used respectively for the enumeration of E.coli, Lactobaccilli spp. and C. perfringens.  The plates were incubated at 37°C for overnight. Finally the grown colonies were counted using colony counter.
 
Histomorphology of ileum
 
A piece of the mid portion of the ileum was collected and washed with normal water and stored in 10 per cent formalin. The tissues were processed as per the method of Bancroft and Stevens (1996). The sections were examined by Carl Zeiss Image analyser using soft ware KS 300.

Production performance
 
The production performance and gut health characters of birds in the various treatments are presented in the Table 2. At the end of sixth week, significantly (P<0.05) highest body weight (2668.47 g) and body weight gain (2616.28 g) was observed in the birds of T₅ - supplemented with phytobiotic mixture II (E.officinalis fruits + M.koenigii leaves + S.aromaticum buds) at level II (2 Kg/ tonne of feed). The cumulative feed intake was significantly (P<0.05) lowest in T₁ (4013.70 g) and in T₂ compared to other treatment groups. T₃ and T₅ groups documented significantly (P<0.05) highest cumulative feed intake. No significant variations (P>0.05) were observed between treatments with respect to feed conversion ratio of birds, though numerically lowest FCR was observed in T₅. Nuan et al., (2016) also reported that the birds fed diets supplemented with Murraya koenigii powder had a higher weight gain (P<0.05; ADG), improved feed conversion ratio (P<0.05; FCR) and lower mortality (P<0.05) rates compared to the birds in the control group.
 

 
Gut health
 
Microbial profile of gut contents
 
Both the phytobiotic mixtures significantly increased Lactobacilli spp. count compared to control in the gut contents of birds. Significantly (P < 0.05) highest (60.00) Lactobacillus spp. count was observed in T₅ - birds supplemented with phytobiotic mixture II (E. officinalis fruits + M. koenigii leaves + S. aromaticum buds) at level II. Supplementing selected phytobiotic mixture II significantly reduced E.coli count compared to control in the gut contents of birds. Significantly (P<0.05) lowest E.coli (31.83 cfu /g) and C. perfringens (450.00 cfu /g) count were observed in birds supplemented with phytobiotic mixture II at level II. Supplementing selected phytobiotic mixture significantly reduced C. perfringens count compared to control in the gut contents of birds.
       
Savage et al., (1996) also reported that supplementation of oligosaccharides may have a prebiotic effect through an increase in production of lactic acid, thus increasing the proliferation of beneficial bacteria and reducing the presence of gram negative bacteria. The plant extracts are known to beneficially modulate the composition of the microflora in the ileum and caeca by increasing the number of Lactobacilli spp. and reducing harmful bacteria, such as potential pathogenic coli forms and C. perfringens (Vidanarachchi et al., 2010). In another study, colonization of beneficial bacteria such as Lactobacilli spp. and Bifidobacterium spp. and reduction in Clostridium spp. load were comparatively better in polyherbal product supplemented groups which was attributed to the presence of bioactive compounds in the herbal product (Vasanthakumar et al., 2012). The mechanism of action of phytochemicals is not clearly understood, but may depend upon the composition of the active ingredients in the product being used. The beneficial effects of phytochemicals are attributed to their antimicrobial and antioxidant properties. In addition, the inclusion of phytochemicals in the diets alters and stabilizes the intestinal microbiota and reduces microbial toxic metabolites in the gut, owing to their direct antimicrobial properties on various pathogenic bacteria, which results in relief from intestinal challenge and immune stress, thus improving performance (Kim et al., 2015).
 
Histomorphology of ileum
 
Supplementing phytobiotic mixtures I or II at either dose (level I or II) in broiler diets significantly (P<0.05) increased villus height, of the birds. Significantly (P<0.05) highest (1159.87 µm and 353.56 µm) villus height and crypt depth were observed in birds of T₅, supplemented with phytobiotic mixture II (E. officinalis fruits + M. koenigii leaves + S. aromaticum buds) at level II. Significantly (P<0.05) highest (1128.43 µm and 246.76 µm) villus height and crypt depth ratio were observed in birds of T₂ and T₃. Rajput et al., (2013) had reported that villus height was significantly (P<0.05) increased in duodenum, jejunum and ileum in curcumin supplemented broilers. In another study, basal diet supplemented with amla fruit powder at the rate of 0.25 per cent, 0.50 per cent, 0.75 per cent and 1 per cent, respectively increased the villi height and significant (P<0.05) increment was observed in one per cent supplementation (Dalal et al., 2018). Increased intestinal villi height and the ratio of villi height to crypt depth is an indication of the vast area for nutrient absorption and higher absorption function (Sieo et al., 2005). Higher villi height, low crypt depth and high villi height/crypt depth ratio are desirable parameters for better absorption of nutrients (Xu et al., 2003).

Phytobiotic mixture comprising powder of E. officinalis fruits + M. koenigii leaves + S. aromaticum buds in 1:1:1 ratio at 2 kg/tonne of feed recorded significantly (P<0.05) highest weight gain, highest Lactobacillus count, significantly (P<0.05) lowest E.coli and C. perfringens count in gut contents and significantly (P<0.05) highest villi height and crypt depth and hence this phytobiotic mixture is recommended as an alternate feed additive.

None.