A Comparative Study of Carcass Characteristics and Meat Quality Traits of Breast Muscle Between Broiler and Cockerel Chicken

MATERIALS AND METHODS

Experimental birds and their management: For this experiment, 150 day old cockerel chicks (ISA Brown) and 150 broiler chicks (Cobb 500) were purchased from a reputed hatchery of the country. The experiment was conducted at local farm in Boiler village under Trishal upazila of Mymensingh district of Bangladesh during later part of 2017 (October 20 to November 30, 2017). The chicks were reared without any antibiotic or probiotic except vaccination under open sided poultry house. During the experimental period, Broiler starter (CP 21.5%, Fat 3.5%, CF 5%, Moisture 12%, ME 2900 kcal kg–1) feed was provided 0-16 days and Broiler Grower (CP 20%, Fat 3%, CF 5%, Moisture 12%, ME 3000 kcal kg–1) was maintained rest period (17-42 days). Identical management (brooding, lighting, biosecurity) and care were ensured throughout the experimental period to get optimum results.

Sample collection and preparation: For this experiment, apparently healthy twenty broilers (42 days old and 1320-1380 g body weight) and twenty cockerels (42 days old and 740-790 g body weight) were collected from the experimental house. As far as possible, all connective tissues and visible fat were trimmed off. The muscles were rinsed and washed with clean water to remove blood and cut into small pieces. All of the meat pieces were mixed properly by hand.

Lab location: Laboratory analyses of the experimental samples were carried out in the relevant laboratories of the Departments of Animal Science, Department of Food Technology and Rural Industries at Bangladesh Agricultural University, Mymensingh.

Meat chemical analyses: Meat proximate chemical analysis was done according to AOAC8.

Dry matter: Five gram meat sample was taken in pre-weighed porcelain crucibles. The crucible was kept at 105°C in an oven for a period of 24 h. After that the crucible was cooled in desiccators. The meat dry matter was calculated as a difference between the meat sample weights before and after drying.

Ether extract: Five gram ground meat sample was taken in a thimble and added 200 mL diethyl ether in a Soxhlet. At about 7-8 h extraction was done at 40-45°C. After extraction, the flask was dried at 100°C. Then the flask was cooled in desiccators and weighed.

Ash: Five gram sample was taken in porcelain crucibles and pre-ashed at 105°C for 24 h. The crucible was then placed in a muffle furnace and heated at 550°C for 6 h. The crucible was then cooled in desiccators and weighed.

pH: The meat pH was measured using a pH meter in meat homogenate, prepared by blending 10 g of meat with 50 mL distilled water. The laboratory pH meter was adjusted at room temperature (adjusted with buffer pH 7.0).

Drip loss: From each sample, a standardized muscle cylinder (30 g) was suspended in an inflated plastic box (4°C) for 24 h. This work was done within 48 hours of postmortem. The drip loss was calculated by the following formula:

Cooking loss: The meat sample was boiled to an internal temperature of hot water bath at 90°C for 30 min. Cooking loss was determined by the following calculation:

Color estimation: Samples were taken from the experimental longissimus dorsi (LD) muscles and Hunter color components lightness (L), redness (a) and yellowness (b) were recorded using Hunter Lab Tristimulus colorimeter model D25 m-2. Subsequently these samples were frozen and stored for cooking loss and shear force determinations.

Samples were taken from the experimental longissimus dorsi (LD) muscles and Hunter color components lightness (L), redness (a) and yellowness (b) were recorded using Hunter Lab Tristimulus colorimeter model D25 m-2. Subsequently these samples were frozen and stored for cooking loss and shear force determinations.

Peroxide value determination: The peroxide value was determined according to Sallam et al.9.

Where S = Volume of titration (mL) N = Normality of sodium thiosulfate solution (n = 0.01) W = Sample weight (g)

Where

Free fatty acid value: Free Fatty acid value was determined by Rukunudin et al.10.

FFA (%) = mL titration×Normality of KOH×28.2/g of sample

Crude protein: Determination of total protein was done by establishing the total nitrogen with the Kjeldahl method11, which consists in extracting the total nitrogen from a mineralized sample [as ammonium sulphate-SO4(NH4)2], then expressing it as ammonia (through distillation and caption on acid) and converting the total ammonia into protein with a correction factor. AOAC8 method was followed to determine CP using following formula:

N% = [(mL standard acid×normality acid) – (mL standard NaOH×normality NaOH)]×1.4007/g sample

Crude protein% (CP) = N%×6.25

TBARS determination: The TBARS value was measured according to Vyncke12. TBARS, expressed as micromole of malondialdehyde per kilogram of meat, was calculated using TEP/malonic aldehyde as standard.

Enumeration of Staphylococcus aureus : Baird Parker agar (Oxoid, England), a selective medium for the isolation and counting of coagulase positive staphylococci was used for the enumeration of Staphylococcus aureus as described by Bhandare et al.13.

Enumeration of Escherichia coli: Escherichia coli were counted as colonies with distinct metallic sheen13. Escherichia coli were enumerated on Eosin methylene blue agar (Oxoid, England) by plating an appropriate dilution on plates followed by aerobic incubation at 37°C for 24 h.

Dressing percentage and other organs weight: Dressing percentage (DP) = (carcass weight/live weight)×100. Weight of heart, liver, pancreas, gizzard, abdominal fat and spleen were taken with an electronic balance and the percentage of these organs to the carcass weight, were measured.

Statistical analysis: Data were analyzed using the SPSS version 2014 for windows. Results were presented as mean±standard deviation and significance level was set at 5%.