Introduction

Rajasri is a designer fowl suitable for backyard production developed by P. V. Narasimha Rao Telangana Veterinary University together with Poultry Research Station (PRS), Rajendranagar, Hyderabad. Rajasri variety is developed by crossing four different breeds (two dual type, one layer type exotic breed and local non-descript poultry were involved). It is different from other rural poultry varieties as it has broad genetic base and introgressed with genes from local birds by incorporating desirable traits such as higher productivity (150-160 eggs per annum) compared to nondescript fowls under range conditions, compact body and long shank length for agility to avoid predation, capacity to withstand diseases and adverse climatic conditions and a truly dual purpose bird. The productive traits of Rajasri chicken have been studied by Viroji Rao et al., 2012 and Daida Krishna et al., 2012, but the carcass characteristics have not been studied extensively. The carcass characteristics and amount of variation present in different breeds and their crosses must be assessed accurately for the formulation of proper breeding plans for the improvement of poultry production. The study on the different carcass characteristics is very important as it implicates various aspects of economics of production and to offer solutions for improving meat yield qualitatively and quantitatively (Singh et al., 1980). Studies on the yields of different cut up parts of a carcass will give primary information on the value and preference of each cut and should form the basis for pricing policy. This study aimed to evaluate the effect of sex and age on carcass characteristics of Rajasri chicken at 16, 20 and 24 weeks of age. (From 16 weeks age onwards the birds were slaughtered as Rajasri is a slow growing chicken and attain minimum slaughter weight at this age).

Materials and Methods

Experimental Design

Day old chicks were procured from Poultry Research Station (PRS), Rajendranagar, and Hyderabad and reared in the Department of Poultry Science to the ages of 16^th, 20^th and 24^thweek, under deep litter system and actual farm conditions with identical management practices throughout the four trials each comprising six male and six females.

Carcass characteristics were studied in Department of Livestock Products Technology at 16^th, 20^th and 24^th weeks of age. A total of 144 birds were slaughtered, four trials were conducted at each age, each trail consists of six male and six female. Birds were off fed overnight and slaughtered as per standard slaughter procedure. Inedible offal weight ( blood, feather, head, shank and viscera), giblet weight [liver (without gall bladder), gizzard (without mucous membrane) and the heart (after removal of blood clot and pericardium)] and cutup parts (neck, wings, back, breast, legs and drumsticks) weights were recorded. Carcass weight calculated based on eviscerated weight. Percentage yield of inedible and edible offal calculated based on pre-slaughter live weight and cutup parts yield was calculated based on eviscerated carcass weight. Dressing percentage calculated as the ratio between carcass weight and pre-slaughter live weight.

Statistical Analysis

The data was subjected to statistical analysis by applying two ways ANOVA (Analysis of Variance), Univariate analysis using Statistical Package for Social Sciences (SPSS) version 21. Differences between means were tested using Duncan’s multiple comparison test and significance was set at P<0.05.

Results and Discussion

The results (Table 1) revealed that Pre-slaughter weight, carcass weight and dressing percentages were found significantly (P<0.05) higher in male compared to females at all the age groups studied and increased with increase in age (from 16 weeks to 24 weeks).

Table 1: Effect of sex and age on pre-slaughter weight, carcass weight and dressing percentage of Rajasri chicken at 16, 20 and 24 weeks of age

Values are Mean ± SE; (n=6). Means with different superscripts in a row (lower case letters) and in a column (upper case letters) differ significantly (P<0.05)

These results indicate a higher body weights than the findings of Daida Krishna et al., 2012, who studied Rajasri performance under backyard rearing, reported the body weight of Rajasri chicken at 16 weeks (834.8 to 977.9g in male and 825.6 to 885.5g in female) and 20 weeks age (1078 to 1204 in male and 986.5 to 1024g in female) and lower than the findings of Viroji Rao et al., 2012, who reported that the average body weight of Rajasri chicken at 20 weeks age was 1398 and 1750 g respectively in female and male. Significant (P<0.05) effect of sex and age on pre-slaughter weight in Rajasri chicken was similar to the findings of Kumar et al., 2012 and Pathak et al.,2009 in Vanaraja, Debata et al., 2012 in Black Rock, Red Cornish and Vanaraja chicken and Muthukumar et al., 2011 in broilers. In this study, male birds were significantly heavier than female birds in all age groups. This might be due to a higher growth rate and muscle mass in males resulting in higher body weight than female in mature birds (Faria et al., 2010; Lawrie, 2006). The main factor on sex differences in body weight and muscularity may be predetermined during embryonic development when the number of myofibril is established (Mitchell and Burke, 1995; Henry and Burke, 1999). It may also be attributed to the sexual dimorphism in favor of males. Males showed faster rate of growth and have much higher rate of cell multiplication than females, apart from favorable influence of androgenic hormones on growth rate of males (Ramappa, 1986).

Male birds showed higher carcass weight and dressing percentage compared to female. This is in accordance with the findings of Pathak et al., 2009 and Kumar et al., 2012, in Vanaraja chicken at 80 weeks and 72 weeks of age respectively, Debata et al., 2012 in Black Rock, Red Cornish and Vanaraja chicken at 20 weeks of age and Ojedapo et al., 2008 and Raji et al., 2010 in broilers. Carcass weight and dressing percentage increased with an increase in age of bird in this present study, which is in accordance with the findings of Muthukumar et al. (2011) in broilers.

The results (Table 2) reveals that male Rajasri chicken showed significantly (P<0.05) higher weights and percent yields of inedible offal at all the age groups studied (from 16 to 24 weeks) except viscera percent yield where it found higher in female Rajasri chicken at all the age groups studied (from 16 to 24 weeks).

Table 2: Effect of sex and age on inedible offal weight and percent yield of Rajasri chicken at 16, 20 and 24 weeks of age

Values are Mean ± SE; (n=6). Means with different superscripts in a row (lower case letters) and in a column (upper case letters) differ significantly (P<0.05)

Significant (P<0.05) increase in inedible offal weights along with age and significant (P<0.05) decrease in percent yield of in inedible offal were found with increase in age (from 16 to 24 weeks) in both the sex of Rajasri chicken. These findings are similar to the findings of Pathak et al., 2009 and Kumar et al., 2012 in Vanaraja chicken respectively at 80 weeks and 72 weeks of age and Brake et al., 1993 in broilers.

The results (Table 3) reveals that male Rajasri chicken showed significantly (P<0.05) higher giblet weights at all the age groups studied and increased significantly (P<0.05) with increase in age (from 16 to 24 weeks age) in both sex studied. Percent yield of inedible offal found significantly (P<0.05) higher in female Rajasri chicken at all the age groups studied and decreased significantly (P<0.05) with increase in age (from 16 to 24 weeks age) except percent yield of heart found significantly (P<0.05) higher in male at 20^th and 24^th week age and increased with age studied. These findings were similar to the findings of Pathak et al., 2009 and Kumar et al., 2012 in Vanaraja chicken, Musa et al., 2006 in Anka and Rugao chicken, Olawumi et al.,2011 and Brake et al., 1993 in broilers.

Table 3: Effect of sex and age on edible offal weight and percent yield of Rajasri chicken at 16, 20 and 24 weeks of age

Values are Mean ± SE; (n=6). Means with different superscripts in a row (lower case letters) and in a column (upper case letters) differ significantly (P<0.05)

The results (Table 4) reveals male Rajasri chicken showed higher cutup parts weight at all the age groups studied and increased significantly (P<0.05) with increase in age (from 16 to 24 weeks age). Comparatively male showed significantly (P<0.05) higher percent yields of cutup parts than female except for breast and back where they were found higher in female. Percent yields of neck, wing, thigh and back decreased significantly (P<0.05) with increase in age but breast and back percent yields found increased. These results are in accordance with Debata et al., 2012 in Black Rock, Red Cornish and Vanaraja chicken at 20 weeks of age, Kumar et al., 2012 and Pathak et al., 2009 in Vanaraja chicken respectively at 72 weeks of age and 80 weeks of age and Muthukumar et al., 2011, Young et al., 2001, Brake et al., 1993 and Merkley et al., 1980 in broilers.

Table 4: Effect of sex and age on cutup parts weight and percent yield of Rajasri chicken at 16, 20 and 24 weeks of age

Values are Mean ± SE; (n=6). Means with different superscripts in a row (lower case letters) and in a column (upper case letters) differ significantly (P<0.05)

Conclusion

Sex and age have shown significant (P<0.05) effect on carcass characteristics. Male Rajasri chicken showed significantly (P<0.05) higher carcass yield and dressing percentage compared to females at all the age groups studied. Percent yield of inedible offal was found significantly (P<0.05) higher in male chicken except for viscera where it was higher in female and decreased with age. Giblets yield was found significantly (P<0.05) higher in male at all the groups studied and increased with age. Cutup parts yield found significantly (P<0.05) higher in male than female and increased with age in both sexes. However, there is a considerable future research is needed to study the cost effectiveness of Rajasri chicken rearing for meat purpose.

Acknowledgements

The authors are thankful to the Associate Dean, College of Veterinary Science, Rajendranagar, Hyderabad for providing necessary financial and infrastructure facilities for this study.

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