Phytobiotic Growth Promoter in Broiler Diets

Antibiotic growth promoters (AGPs) have been an integral part of the poultry feed industry for more than fifty years. However, a search for the alternatives to the AGPs has been initiated since their prolonged use has precipitated some problems such as development of resistant strains within groups of primary pathogens or opportunistic bacteria and break down of the symbiosis between the animal and desirable flora. The search is therefore on for an economically viable alternative to the AGPs. A wide variety of substances are used in conjunction with, or as alternatives to, AGPs in poultry diets. Probiotics, prebiotics and organic acids have all shown promising results in controlling a wide array of bacteria including Salmonella, Campylobacter, Clostridium and E. coli. The phytogenic feed additives are a more recent addition in this list and are composed of plant extracts (microencapsulated essential oils, bitter substances, and pungent substances and may also include an acid substance and saponin). These preparations have been shown to activate digestion, strengthen the immune system and have antibacterial properties.

The efficacy of a phytogenic growth promoter or phytobiotic (Digstarom, Microplus Konzentrate GmbH, Germany), containing natural and artificial aromatics, including natural herbs and drugs as well as natural essential oils, was tested in a broiler trial. The objective was to test the efficacy of the phytogenic growth promoter compared to an AGP (Bacitracin methylene disalicylate, BMD 10%) and to optimize its dose level in broiler diets. A flock of Cobb 400 birds (mean live weight 44.2 ±0.91 g, obtained 6 h post hatch from a commercial hatchery) were put under test for 39 days. The three dietary treatments were a basal diet without AGP or phytobiotic (negative control), basal diet + AGP (BMD 10%, 250 g/tonne) and phytobiotic (Digestarom) at graded levels viz. 50 (DG 50), 100 (DG 100) and 150 (DG 150) g/tonne.

An initial slaughter was performed on d 0 with a sub-flock of 25 birds. On day 1 the birds were weighed and placed randomly in pens (1.5 m x 1.5 m) on litter floors. The pens, each housing 10 birds (after adjusting the mortality), were the replicates and there were 6 replicates in each treatment group. The starter (d 1 to 20) and the finisher diets (d 21 to 39) were formulated to meet the requirements of the Cobb 400 broiler chickens. Feed and water was supplied for ad libitum consumption. Temperature inside the broiler room was maintained at 30 - 32°C during the initial two weeks and subsequently was reduced to 26°C towards the end of the experiment. Initial (pre-experiment) and final (after 39 days feeding) body weights were recorded before offering the morning feed. Total pen feed consumption was measured everyday.

The birds were harvested after 39 days for carcass evaluation (carcass yield, yield of the breast, frame and legs, and meat protein and fat contents).

Gut health was assessed through measuring the pH, enumeration of the common commensals and pathogens of the gastrointestinal tract and measurement of the crypt depth and villi height in the ileum. Samples were obtained at the time of harvesting. The entire gastrointestinal tract was segmented into crop, proventriculus, gizzard, duodenum and ileum. The pooled digesta was subjected to pH measurement and enumeration of bacteria like Lactobacillus, Salmonella, and Escherichia coli.

Table 1: Ingredients and chemical composition of the basal diet (as fed) ¹

Ingredients g/kg	Starter	Grower	Composition	Starter	Grower
Corn	550	625	ME Kcal/kg2	3057	3138
Soybean meal	390	320	Crude protein g/kg	224.4	199
Palm oil	30	31	Calorie: Protein²	136.4	157.1
Di-calcium phosphate	12	10	Crude fi bre, g/kg	36.9	3.43
DL methionine	1.2	1.1	Amino acids %2
Lysine hydrochloride	0.7	0.7	Lysine	1.36	1.16
Sodium bicarbonate	0.3	0.3	Methionine	0.49	0.45
Vitamin mineral premix	3	3	Cysteine	0.25	0.23
Vitamin B complex	0.25	0.25	Methionine + Cysteine	0.74	0.68
Mycotoxin binder	1	1	Arginine	1.69	1.45
Salt	1	1	Calcium%	1.21	1.31
Chromium yeast	1	1	Total P, g/kg	0.81	0.75
Filler material	9.3	5.4	Available P g/kg2	0.41	0.39

1 Starter and grower diets were fed from d 1-20 and d 21 - 39 respectively

2 Calculated values, 3 Contained 3000 mg elemental chromium per kg

Live performance and carcass traits

Addition of the phytogenic growth promoter in diet improved the live performance of the broilers significantly in a dose dependent manner (Table 2). Live weight at harvest, total gain and FCR at 39 days was higher (P < 0.05) in the DG 150 dietary group than those in the birds supplemented with BMD. These results indicated that the birds responded in a dose dependent linear manner to the level of supplemental phytobiotic (y = 51.5x + 1804.7, R2 = 0.757). Overall, the DG 150 dietary group had ~ 5% higher live weight than that in the BMD dietary group. At lower dose levels the phytobiotic (DG 50 and DG 100 dietary groups) yielded live responses similar to those obtained with the BMD group, which were in turn greater than that from the basal diet.

The phytobiotic growth promoters had few effects on carcass traits. The hot carcass weight was higher when the birds received BMD (P < 0.01). Weight of the breast, frame and legs, expressed as a percentage of harvest weight was similar across the dietary groups.

Table 2: Effects of treatments on live performance and carcass traits

Response variable	Negative control	+BMD	+DG 50	+DG 100	+DG 150	SE	Significance
Live weight g
Day 1	52.5	53.7	52.1	51.9	53.7
Day 39	1457^c	1886^b	1873^b	1847^b	1976^a	5.97	***
Total gain g	1404.4^c	1832.1^b	1821^b	1822^b	1922^b	5.93	***
ADFI g	82.6	82.5	82.5	82.7	82.4	0.03	NS
Total intake kg	3.22	3.21	3.20	3.23	3.21	0.03	NS
FCR	2.29^c	1.76^b	1.77^b	1.77^b	1.67^a	0.012	***

Different superscripts within a row are different (*** at P<0.01). NS not significant

Gastrointestinal tract health and milieu

Dietary supplementation of antibiotic and phytobiotic growth promoters has significant effects on gut microbiology, particularly with regards to the counts of the Lactobacilli spp (Table 3). E. coli and Salmonella were not detected in the crop, proventriculus, gizzard and small intestine in the birds receiving antibiotic or phytobiotic supplementations. The phytobiotic growth promoter stimulated proliferation of Lactobacilli in the gastrointestinal tract in a dose dependent linear fashion (P < 0.001). Therefore, it may be inferred that an increment in supplemental dose level the phytobiotic growth promoter may facilitate establishing a healthy flora in the gut. It was interesting that Lactobacilli vanished altogether in the proventriculus and gizzard when the diet was supplemented with BMD. The deleterious effect of the AGPs on gut flora was brought into the fore by the Lactobacillus count in the crop which was significantly lower in the BMD supplemented birds than that enumerated even in the negative control group of birds. Overall, the findings indicated the beneficial effects of phytobiotic growth promoters on the beneficial microbes of the gut flora and concomitantly bolstered the deleterious effect of AGPs on the favorable microbes present in the small intestine. The BMD or the phytobiotics did not influence the pH of the gastrointestinal tract (Table 4). However, the phytobiotic growth promoter appeared to sustain the crypt depth and the villi height in a much better way than did the BMD (P < 0.001).

Table 3: Microbiological counts (log₁₀ CFU/ g) in gastrointestinal tract contents

Part of the GI tract	Diet	*E. coli*	*Lactobacillus*	Salmonella
Crop	Negative control	36	182^b	28
	BMD	Not detected	62.8^a	Not detected
	DG 50	Not detected	703.6^c	Not detected
	DG 100	Not detected	710.1^c	Not detected
	DG 150	Not detected	714.4^c	Not detected
	SE	-	9.2	-
	Significance	-	P < 0.001	-
Proventriculus	Negative control	Not detected	0^a	Not detected
	BMD	Not detected	0^a	Not detected
	DG 50	Not detected	51.8^b	Not detected
	DG 100	Not detected	59.7^b	Not detected
	DG 150	Not detected	64.6^b	Not detected
	SE	-	1.94	-
	Significance	-	P < 0.001	-
Gizzard	Negative control	Not detected	0^a	Not detected
	BMD	Not detected	0^a	Not detected
	DG 50	Not detected	118^b	Not detected
	DG 100	Not detected	120.3^b	Not detected
	DG 150	Not detected	126.6^b	Not detected
	SE	-	4.54	-
	Significance	-	P < 0.001	-
Small intestine	Negative control	4	0^a	8
	BMD	Not detected	211.6^b	Not detected
	DG 50	Not detected	590^c	Not detected
	DG 100	Not detected	610.3^c	Not detected
	DG 150	Not detected	654^c	Not detected
	SE	-	15.12	-
	Significance	-	P < 0.001	-

* Statistical analyses not performed

Dissimilar superscripts within column indicate signifi cant variation (*** at P < 0.0001)

Summary

A phytobiotic product was found to improve weight gains and FCR over that of birds supplemented with an AGP. Counts of the Lactobacilli spp. E. coli and Salmonella were reduced to zero in the crop, proventriculus, gizzard and small intestine of birds receiving antibiotic or phytobiotic supplementations. The phytobiotic growth promoter stimulated proliferation of Lactobacilli in the gastrointestinal tract. These findings confirmed the beneficial effects of a phytobiotic growth promoter on the beneficial microbes of the gut flora. The phytobiotic growth promoter sustained the crypt depth and the villi height to a greater degree than did the AGP.

The article was published in the June 2009 issue of the Asian Poultry Magazine