PECTORALIS THORACICUS MUSCLE PERFORMANCE OF HYBRID CHICKEN ( F 1 ) DERIVED FROM CROSSBREED BETWEEN BROILER AND PELUNG ( Gallus gallus gallus )

This research purpose was to study the phenotype characters of body weight and pectoralis thoracicus muscle performance of hybrid chicken (F1) derived from crossbreed between parent stock broiler strain Cobb-500 and Pelung (Gallus gallus gallus). The chicks were divided into 3 groups and each group consists of 5 days-old chicks (DOC). Group 1 (T1) was used as control involving DOC derived from crossbreed between female and male of broiler Cobb-500 strain. Group 2 (T2) involving DOC derived from crossbreed between female and male Pelung, while Group 3 (T3) was DOC derived from crossbreed between female broiler strain Cobb-500 and male Pelung. The chicken was grown up to 49 days to evaluate the body weight, the pectoralis thoracicus weight, the pectoralis thoracicus area, and myofiber area. Data were statistically analyzed using one way Anova. The results showed that the average of body weight in T1; T2; and T3 were 2,170±86.02; 506.2±20.02; and 1,238±68.25 g, respectively (P<0.05). The average of pectoralis thoracicus muscle weight in T1; T2; and T3 were 165.04±11.97; 21.26±2.44; and 68.74±1.94 g, respectively (P<0.05). The average of pectoralis thoracicus muscle area in T1; T2; and T3 were 97.0±9,7; 61±6,4; and 63,4±1,8 cm, respectively (P<0,05). The average of pectoralis thoracicus myofiber area in T1; T2; and T3 were 14.72±1.04; 4.66±2.1; and 13.13±1.3 μm, respectively (P<0.05). It was concluded that crossbreed between broiler strain Cobb-500 and Pelung improved the body weight and pectoralis thoracicus muscle performance of hybrid chicken (F1). ____________________________________________________________________________________________________________________


INTRODUCTION
Local chicken, also known by Indonesian as domestic chicken or Buras chicken, is higly favored by people for both its meat and egg.Indonesian people love domestic chicken because its meat is more delicious and tasty than broiler chicken.Another reason is related to chicken feed.People believe feed combined with drugs such as antibiotics, can affect the quality of meat (Agustina, 2013).In 2013, the number of domestic chicken nationwide reached 290.4 million.The population of domestic chicken had increased from previous years (Dirjen Peternakan, 2013).At the same time, the market demand for domestic chicken commodity always increases, for example, in Jabodetabek area, only 5% of the demand of new chicken was fulfilled, or about 280,000 chickens per day (Anonymous, 2013).
One of the local chicken in Indonesia that has potential as broiler is Pelung chicken, which has higher body weight than domestic chiken, Bekisar chicken, and Balenggek chicken.Adult Pelung males and females can reach 3.37 kg and 2.52 kg, respectively.Pelung chicken have a large size and straight posture, with long neck and sturdy legs.A relatively large body makes the adult Pelung males to have the potential as a producer of meat (Iskandar and Susanti, 2007).The large body size of Pelung chicken allows for growth improvement of other local chickens, which have smaller body size.Study conducted by Balai Penelitian Ternak Departemen Pertanian to investigate the intensive performance potential showed that chicken Pelung can reach 1,100-1,350 gram/chicken at age of 12 weeks.This study indicated that Pelung chicken can be utilized for improvement of growth quality (Iskandar, 2006).
The ability of a local broiler had not yet able to keep up with non-local chickens, in which within 35 days can reach 1,500 g/chicken.Local chickens take about 12-16 weeks to reach this weight.The major obstacles in genetic quality improvement of genuine chicken in Indonesia which had potential as broiler among others are unclear crossbreed and minimal identification of the potential broiler.The improvement of chicken genetic quality could be carried out through crossbreeding process.The results of crossbreeding between chickens male and female conducted by Balai Penelitian Ternak Departemen Pertanian showed at week 12 th the body weight of hybrid chicken reached 1,076 g/chicken, which is 20% higher than original chicken body weight (Iskandar, 2006).
Chickens that have potential as broiler, usually refers to the muscle growth.Muscle tissue consists of many myofibers, which are known to be a major component of muscle.The appearance of myofiber in the chicken muscle is related with the acceleration of body weight and chest muscle weight (Scheuermann et al., 2004).

MATERIALS AND METHODS
Pelung chiken and broiler chiken Cobb-500 strain reared in a semi-intensive with a ratio of one male chicken to four females.The chickens were fed with medicine, vitamins, standard food in the form of BR type pellets and waters.
The DOC was divided into three groups and each group consists of five male day old chicks (DOC).Group 1 (T1) as control was DOC result of cross breeding between female broiler parent stock (PS) strain Cobb 500 with males broiler chicken strain Cobb -500.Group 2 (T2) was DOC result of cross breeding between female pelung chicken with male Pelung chickens.Group 3 (T3) was DOC result of cross breeding between PS female broiler strain Cobb-500 female with male Pelung chicken.Chicken body weight was measured when then chicks reach the age of 49 days using manual scales.Then, the chickens were sacrificed to measure the muscle weight, muscle area, and myofiber pectoralis thoracicus (PT) area.The left side of PT muscle was weighed to measure its weight, while the right side was used to measure the area of PT by using ott planimeter.Myofiber area was measured using micrometer software from histology samples of PT muscle which was previously stained with hematoxylin-eosin (Velleman et al., 2003).

Data Analysis
The PT muscle weight, total area of PT muscle, and myofiber area were analyzed using one way variance analysis (Anova); continued with LSD-test and Tukeytest at 5% significance level.

Body Weight
The average of chickens body weight after 49 days maintenance were presented in Table 1.The result showed that the mean body weight in T1; T2; and T3 was 2,170±86.02;506.2±20.02;and 1,238±68.25g, respectively (P<0.05).Weight gain in T1 was significantly different than other groups.It may be due to the potential of broiler chickens as as a meat producers.In broiler, during the growth period from 14-21 days, the activity of trypsin enzyme and other protease enzymes was high, so the effect of the age on amino acid absorption in the intestinal and absorption of lysine amino acids was better in young chickens than older ones.After the chicken is more than three weeks old, the activity of digestive enzymes decreased (Nitsan et al., 1991;Zuprizal, 2008).
The average crossbreed chicken weight in T3 was higher than those in T2.These results indicated that crossbreeding inherit the nature of broilers and rapid growth of broiler mothers.
According to Buckle et al. (1987), the growth was influenced by two things, intrinsic factors (hormones and genes) and extrinsic factors (temperature, disease, and feed).Genetic factors play a major role in affecting the growth.Chickens have wide genetic variations, indicated by variations of comb (pial), thyroid, and gonads whose development was regulated by the anterior pituitary hormone.Some genes appearred together, for example a single pial shape and the color of white fur of broiler are most likely present along with rapid weight gain.Genes are responsible for abnormal hormonal conditions, such as accumulation of excess fat to increase weight growth in broiler chickens.Research on the rate of weight gain and growth efficiency in pigs suggests that weight gain was influenced by hybrid vigor resulted from a more efficient metabolic system.The vigor hybrid was caused by a non-additive action of the gene.Chicken growth rate was also influenced by body weight at the age of 0-week (Mozdziak et al., 2002).Koutsos (2012) stated that the type, chemical composition, and feed consumption greatly affect growth.Feed was an extrinsic factor that had the greatest effect on growth (Mozdziak et al., 2002).According to Koutsos (2012), the effect of shortage of feed is enormous, but is determined by the age at the time of shortage of feed, the duration of the shortage of feed, and the kind of food shortage (energy, vitamins and other nutrient deficiencies).The most appropriate feed is a feed with a similar chemical composition with thes carcass, while the feed quantity will affect the sustainability of its growth.High protein feed can accelerate growth, but the increase in protein quantity is not always linear with the growth rate.
According to Heuck et al. (2009), hormones that affect growth could be divided into two groups, namely; (1) anabolic groups and (2) catabolic groups.Somatotropic hormone (STH) or somatotropin or growth hormone (GH), testosterone, and thyroxine are anabolic hormones, while estrogen is catabolic hormone.Hormones that have a direct influence on growth are somatropin, thyroxine, androgen, estrogen, and glucocorticoids (GC) which affect the growth of body mass, including bone growth and nitrogen metabolism.Furthermore, Vasilatos et al. (2000) stated that the anterior pituitary gland located within the skull at the base of the brain, secretes hormones that closely related to individual growth namely somatotropin (STH) or GH.GH is a protein secreted by asidophillic pituitary cells which affect amino acid metabolism.This effect is seen in the growth of young animals.GH decreases the amount of fat stored in the body and affects carbohydrate metabolism.
In this study, the PT muscle weight and PT muscle area on T1 showed a marked improvement on the 49 th day of treatment compared with T2 and T3.Velleman et al. (2014) reported that muscle growth after the chicken hatched, relies on the addition of new nuclei of the myoblast into myofiber formed during the embryonic period by myoblast hyperplasia.Early age chickens have active satellites cell which are responsible for nucleic accumulation in the myofiber, and also nutritional factors have an effect on these cells and contribute to myofiber size and proportion of broiler muscle (Mozdziak et al., 2002;Kornasio et al., 2011).In the early life of the chicken, nutrients would affect the activity of mitotic cell cells in the muscle, which clearly affects muscle size due to the fusion of the myonuclear growth with the satellite cell nuclei which are later required for myofiber hypertrophy (Mozdziak et al., 2002;Zielinska et al., 2010).Another possibility concerning the size of cells in young chickens is the effect of nutritional factors on deoxyribonucleic acid (DNA) units, increasing number of DNA units which then fuse with satellite cells, and will be the major determinant on muscle size (Mozdziak et al., 2002).The significant differences in PT muscle weight among broiler, Pelung, and crossbreeding between female broiler and male Pelung indicate the genetic influence on muscle growth (Burke and Henry, 1997;Scheuermann et al., 2004).

Table 1 .
Performances of pectoralis thoracicus (PT) muscles in each crossing group in age of 49 days