There has been recent concern about the use of antibiotics as growth promoters in animal production due to their negative effect on human health. Plants are now used as alternatives to synthetic antibiotics because they give similar results in improving the performance, live weight and feed efficiency in animals without any adverse effect. Such plants are regarded as medicinal plants or phytobiotics which are now the object of increasing interest across livestock production as antibiotic use becomes ever-more restricted . The use of antibiotics as growth promoters has been banned in many European countries . According to [3, 4] phytobiotics are plant derived products added to feed in order to improve the performance of livestock, they originate from leaves, roots or fruits herbs, spices and other plants. They could come in several forms such as solid, dried and powder or as extracts (essential oils).
Most phytobiotics function as antibacterial, antioxidants, anticoccidial, antiviral, anti-inflammatory and antihelmintic  thus leading to increase in general performance in animals. They are cheap, affordable effective and can improve the flavor and palatability of feed. Example of such medicinal plant is Polyalthia longifolia.
Polyalthia longifolia is a lofty evergreen plant, native of india and commonly planted due to its effectiveness in alleviating noise pollution . It is a versatile plant which is used to treat skin disease, hypertension, fever and digestive disorder [7, 8], the plant have been reported to contain alkaloids, quercetin, campesterol, di-terpines, bulbocapinin and sesquiterpenoids  . Phytochemical screening test of P. longifolia also reveals the presence of saponins, tannins, resins, steroids, glycosides and flavonoids as major phytochemical constitutents . The aqueous extract of the leaf have also been reported to lower blood pressure and rate of respiration in experimental animals . P. longifolia performs several functions such as antibacterial, antifungal, antidiabetic, antitumor, anti-ulcer, antioxidant and used in the treatment of the digestive system. Pharmacological studies on the bark and leaves of the plants shows display effective antimicrobial activity , cytotoxic function , hypotensive effects . Almost all parts of P. longifolia plants are used in Indian traditional system for the treatment of various ailments and the significant medicinal properties was further reported via scientific investigation .
Several studies have reported on the oral acute toxicity of P.longifolia leaf in mice [16, 17], but there is less information on the addition of dried P. longifolia leaf meal in the diet of broilers. A timely evaluation of its effects as a phytogenic feed additive in broilers feed will provide useful information relating to the tolerable rate its inclusion in the birds. Therefore this study was conducted to evaluate the effects of various levels of mature Polyalthia longifolia leaf meal as a phytobiotic on the performance, carcass characteristics and blood profile of broiler chicks fed corn-soya meal diet.
MATERIALS AND METHODS
Site of the experiment
The experiment was carried out at Dan- malafia Farms, Oyo State, Nigeria. The area is located within the derived savanna zone of Nigeria.
Preparation and processing of experimental diets
Fresh healthy mature disease free Polyalthia longifolia leaves were harvested from Dan-malafia farms, Ibadan. The leaves were separated, first washed with running tap water and then with distilled water, shade dried without any contamination for 8 days and passed through a hammer mill to produce P. longifolia leaf meal (PLM). The test ingredient (PLM) was mixed with other ingredients to form five (5) experimental diets. The antibiotics used in this experiment as positive control contained Oxytetracycline at 25mg/kg. The first group 1 were fed on basal diet were supplemented with 0% (negative control), the second group 2 fed on basal diet containing an antibiotic (Oxytetracycline 25mg/kg) as positive control. Group 3, 4 and 5 were feed on basal diet supplemented with Polyalthia longifolia leaf meal (PLM) as phytobiotic at levels 1.5, 2.5 and 3.5 %. The diet was formulated to meet the nutrient requirement of broilers according to . Proximate and phytochemical analysis of P. longifolia leaf meal was carried out as presented in Table 1 and 2 respectively.
Experimental animals and their management
A total of 250 one-day-old commercial broiler chicks (Arbo acre) were purchased from a local hatchery in Ibadan for use in this study, the birds were weighed on arrival and were randomly allotted into five (5) groups with five replicates of 10 birds each in a completely randomized design (CRD). A deep litter poultry house was used for the experiment, prior to the commencement of the trial the house was properly cleaned and disinfected; each pen was equipped with feeders and drinkers to allow unrestricted consumption of feed and water respectively. The initial brooding temperature was 35°C in the first week of age which was gradually reduced by 2°C per week to 23°C; vaccines were administered according to the prevailing vaccination schedule in the environment. Feed and water were offered ad-libitum. The light was continuous throughout the experimental period, the performance of the birds in terms of feed intake and mortality were recorded throughout the period of the experiment which lasted for 6 weeks.
At day 42, three birds were randomly selected from each replicate for blood analysis. The sampled birds were bled from punctured brachial vein to aspire 3mls of blood from each bird. Blood samples collected with Ethylene Diamine Tetra Acetate (EDTA) were used to determine Pack cell volume (PCV), heamoglobin (Hb), white blood cell counts (WBC), red blood cell count (RBC) in the sample. The PCV was determined by micro-haematocrit method , the haemoglobin concentration (Hb) was determined by cyano methae-moglobin method, Red blood cell counts (RBC) were determined by Neubauerhaemocytometer method , white blood cell count (WBC) determined by Wintrobe’s micro heamatocrit. The Mean corpuscular volumes (MCV), mean corpuscular haemoglobin (MCH), Mean corpuscular heamoglobin concentration (MCHC) were calculated according to Bush .
At the end of the sixth week, five birds were randomly selected per treatment; fasted overnight to reduce their gut contents, weighed and slaughtered manually; birds were scalded using boiling water. The carcass weight, dress weight, weight of the cut parts and viscera’s were recorded. The organs were also carefully examined to detect any pathological lesions or damage.
The contents of dry matter, crude protein, crude fat, crude fibre and ash in the feed samples were determined with the use of .
All data collected were tabulated and subjected to one –way analysis of variance (ANOVA) using the completely randomized design . Means, where significant were separated by use of the Duncan Multiple Range Test .
Table 1: Proximate composition of P. longifolia leaf meal (PLM)
Table 2: Photochemistry of P. longifolia leaf meal (PLM)
Table 3. Composition of experimental diets of Broilers starter mash (%): 0-3 weeks
Table 4. Composition of experimental diets of Broilers starter mash (%): 4-6 weeks
Table 5. Effect of different level of Polyalthia leaf meal (PLM) and antibiotic on the performance of broilers
Figure 1. Effect of different level of Polyalthia leaf meal (PLM) and antibiotic on the performance of broilers for 42 days.
Table 6. Average pre-slaughted weight, Carcass weight, dressing percentage and primal cuts of broilers fed different level of Polyalthia leaf meal (PLM) and antibiotic (O.T.C) at day 42 of age
Table 7. Effect of different level of Polyalthia leaf meal (PLM) and antibiotic on the haematological parameters of broilers
Table 1 shows the proximate composition of Polyalthia longifolia leaf meal (test material). Its proximate components are 10.01%, 19.70%, 6.02%, 0.18%, 7.70% and 59.39% for crude protein, crude fibre, ash, ether extract, moisture and nitrogen free extract respectively. All the proximate components investigated in this study fall within the range reported by . Table 2 shows the phytochemical analysis for anti-nutritional inhibitors P. longifolia leaf meal (PLM), the results obtained are 3.87ppm, 0.42 ppm, 5.91%, 0.51%, 1.19% and 1.31% for tannin, phenols, flavonoids, alkaloids, steroids and saponins, respectively.
Table 5 shows the performance traits of birds fed varying levels PLM and antibiotics, the final live weight ranges between 1988.6g and 2407.1g. There was a significant difference (P<0.05) among the treatment in terms of final live weight.
Table 6 shows the average pre-slaughtered weight, carcass weight, dressing percentage and primal cut parts of broilers fed different levels of PLM and O.T.C, the inclusion of PLM and O.T.C did not affect the carcass and organ weights of the birds significantly (P>0.05).
The haematological parameters are presented on Table 7; pack cell volume (PCV) values obtained are 37.10, 37.60, 38.50, 38.34 and 38.90 % for diets 1,2,3,4 and 5 respectively while those of haemoglobin are 11.10, 11.60, 12.08, 12.45 and 12.66 g/dl for diets 1,2,3,4 and 5 respectively. The values obtained for Red blood cell count (RBC) are 4.10, 4.31, 4.65, 4.51 and 4.70 (×106 µl) for diets 1, 2, 3, 4 and 5 respectively.
White blood cell count (WBC) values obtained are 4.09, 4.22, 4.26, 4.30 and 4.32 (×106µl) for diets 1,2,3,4 and 5 respectively while those of Mean cell volume (MCV) are 81.02, 83.45, 85.07, 87.12 and 89.03 fl for diets 1,2,3 4 and 5 respectively.
The mean corpuscular haemoglobin concentration (MCHC) values are 31.09, 31.89, 32.75, 33.08 and 33.22 g/dl for diets 1, 2, 3, 4 and 5 respectively while those of mean corpuscular haemoglobin (MCH) are 27.11, 27.32, 28.09, 28.67 and 28.75 pg for diet 1,2,3,4 and 5.
The pack cell volume (PCV), haemoglobin (Hb), red blood cells (RBC), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) values were not significantly affected (P>0.05) with the inclusion PLM and antibiotics (O.T.C) in the diet, however, values of RBC increased from diet 1 to 5.
White blood cells (WBC), lymphocytes, neutrophils, monocytes, eosinophils were not significantly affected (P>0.05) with the inclusion of PLM and O.T.C in the diet.
The result on the proximate composition of PLM clearly shows that it cannot be used as a good alternative protein source in poultry; this observation disagrees with the views of  on the principles and practices of feed manufacturing. The low level of total ash in PLM also agrees with the findings of  on the effects of feeding different levels of dried pawpaw seed on the performance of broilers.
The result on phytochemical analysis of PLM agrees with the reports of  on the phytochemical contents of mature P. longifolia Sonn. Leaves.
The inclusion of PLM significantly (P<0.05) affected the final live weight of the birds, highest final live weight 2407.1g/bird and feed intake 3322.6g/bird were observed in birds feed diet containing 3.5% dietary PLM followed by birds fed diet containing 2.5% with final weight of 2300.1g/bird and a feed intake of 3390.8g/bird. The lowest final weight was observed in birds feed 0% PLM and O.T.C with 1988.6 g/bird and a feed intake of 3300.0g/bird. Birds fed diet 5 also had a better FCR, least cost ration (N 140.2) and no mortality was recorded throughout the experimental period, these findings disagree with the report of  when wild Sunflower leaf and blood meal mixture were fed to weaner rabbits. The low feed intake in birds fed diet 5, could also be as a result of presence of chemical substances such as alkaloids . PLM used in this experiment has demonstrated multiple biological activities, including antibacterial and antiviral properties, thereby reducing disease pressure, increasing the opportunity to achieve better weight gain, feed conversion ratio and improved performance.
Data on carcass characteristics and organ weight was not statistically (P>0.05) influenced by the dietary treatments. However, the inclusion of PLM at 3.5% caused a slight increase in the thigh of the birds. This study shows that the dressing percentage of the birds which ranged from 72.2-77.1% were not significantly (P>0.05) different from each other. According to , age, body weight and diet can affect the organ weight of birds.
The values for all the parameters measured fall within the same reference range of broilers ,  and . According to  blood pictures of animals might be influenced by nutrition and  feed processing.
Haematological studies are also useful for disease prognosis and for therapeutic feed stress monitoring . The stable level in the haematological values observed could be as a result of nutritional adequacy and safety margins of PLM. According to  pack cell volume (PCV) is involved in the transportation of oxygen and absorbed nutrients. Red blood cell serves as a carrier of haemoglobin which reacts with oxygen to form oxyhaemoglobin during respiration . PCV, Hb and MCH are major indices for the diagnosis of anemia .
From the results obtained in this study, it is therefore concluded that the inclusion of Polyalthia longifolia leaf meal up to 3.5% does not have any deleterious effect on the performance, carcass characteristics and haematology of broilers. PLM is a substitute for antibiotics and can be used as natural growth promoter because it enhances higher and better performance translating to better profit margin.
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