The experimental site, birds’ diet and management:
The experiment was conducted at Bangladesh Agricultural University Poultry Farm, Mymensingh. The duration of the research work was 35 days. A total of 320 one-day-old straight-run Cobb-500 commercial broiler chicks were considered for this research work. The experimental broiler chicks were equally and randomly divided and distributed into four dietary groups and each group was replicated to five subgroups. Corn-soya-based diet was supplied. The broiler diet was formulated for two phases (starter and grower). Starter diet was provided from 1st day to 21st days and grower diet was provided from 22nd day to 35th days. Both types of diets were supplied in mash form. The nutrient requirements (ME, CP, CF, EE, Ca, P, Lysine and Methionine) were satisfied as per the requirement as recommended for Cobb-500 broiler strain diet. The first group of chicks were maintained control diet whereas, second, third and fourth group of chicks received control diet with AGP, control diet with probiotics and control diet with AGP plus probiotics respectively.
Antibiotic growth promoter (AGP):
The trade name of antibiotic growth promoter used in the experiment was “Lincoplex” containing 2.2% Lincomycin and manufactured by an Indian Company named “Starvet”. This product was imported in Bangladesh by “Century Agro. Co. Ltd.”
Double strain probiotics- (A combination of Bacillus subtilis and Bacillus licheniformis):
Double strain probiotics has been manufactured by one of the Korean companies named “Shinil Biogen Company Limited.” and imported in Bangladesh by “Pharma and Firm Company Limited.” Dhaka, Bangladesh. This probiotic contains Bacillus subtilis CH201 (4x1010 CFU/g) and Bacillus licheniformis (4x1010 CFU/g). According to the manufacturer, dose of the product for the broiler is 250g/100 kg feed.
Processing of broilers:
At the end of the trial, one male and one female broiler having near to pen average weight were taken from each pen for recording meat yield parameters. The birds were killed and allowed to bleed for 2 minutes and immersed in hot water (51-55ºC) for 120 seconds in order to loose the feathers. The feathers were removed by hand pinning. This was done manually. Then head, shank, viscera, giblet (heart, liver and gizzard) and abdominal fat were removed for determination of meat yield parameters. Dressed broilers were cut into different parts such as breast, thigh, drumstick, wing and back. Finally, every cut-up part was weighed and recorded for male and female broiler of all replications.
Methods of cost-benefit analysis:
The cost of production was calculated based on some specific items such as chicks, feed, vaccine, test ingredients and casual labor. Cost of heads was widely varied due to fluctuating market price. The total production cost per bird and per kg bird was calculated. The additional cost incurred for test ingredients was also taken into consideration for calculating cost-benefit. The profit or loss was calculated by deducting the production cost per kg broiler and market price of per kg broiler.
All data of body weight, feed consumption, feed conversion ratio and survivability were recorded on days 7, 14, 21, 28 and 35. At the end of the trial, carcass measurements data were also collected. During the experimental period, the temperature and relative humidity of the experimental house were recorded four times in a day (6.00 AM, 2.00 PM, 6.00 PM, 11.00 PM) with the help of an automatic thermo-hygrometer. At the end of the experiment, the dressing percentage of the broiler was calculated as the dressed weight divided by final bodyweight of the broiler.
Data of body weight, body weight gain, feed consumption, feed conversion ratio (FCR), livability and edible meat characteristics of male and female broilers were subjected to analysis of variance (ANOVA) in a completely randomized design (CRD) employing SAS (2008, version 9.1) statistical computer package programme.