Abstract: The quality of meat has become a topic of discussion over the last few years mainly emphasizing on customers preference. There are many factors associated with broiler meat quality, such as pH, water holding capacity, color, tenderness, cooking losses, oil content. In order to fully understand the influence of these factors and to prevent the losses in broiler meat , it is necessary to evaluate these factors that are directly related to meat quality. The main features related to meat quality discussed in this study are genetic, age and sex, while the features related to environment conditions are alternative rearing systems, stocking density, transport and stunning, feed withdrawal, climatic factors and stress.
Key words: Meat quality, age, sex, alternative systems, enviromental conditions
Introduction
Meat quality is characterized by attributes that are preffered by consumer including both visual and sensory traits, reliance traits of safety and health, and those that are related to the ethical nature of the production system (Becker, 2000). Many factors can impact on poultry meat characteristic (Jhaturasitha et al., 2008). Age, sex, density, diet, genotype, environmental conditions , exercise, and grazing factors that effect the growth and performance of birds (Gordon and Charles, 2002). These components can be internal like species, race, type of muscle, sex, genetic origin and slaughtering age, or external like conditions of procreating, culling, nutrition, technological process and post mortem biochemical alterations (Mourot, 2008).
Some researchers suggested that broiler strain, age at slaughter and post-chilling aging are important constituents that influence meat quality (color, tenderness, cooking loss, water-holding capacity and pH) (Lyon and Lyon, 1992; Mehaffey et al., 2006; Musa et al., 2006). The muscle morphology, biochemistry and fibre configuration determines meat quality (Saxena et al., 2009).
The Related Factors Affecting Broiler Chicken on Meat Quality
Genetic- Strain
Genetic has been declared as a common component for identifing the quality features of the meat (Berri et al., 2001; Debut et al., 2003). Due to this fact, broiler industry persues to enhance the genetic selection for the growth performance and carcass quality of poultry (Mehaffey et al., 2006). Birds that are genetically selected and assoreted to enhance carcass quality relies upon genetic changeability of body weight and body structure. Many authors have explored that water holding limit, pH, color density and softness of the meat which is regulated in breast muscles are vital for the nutritive and techhnolgy qualities of chicken meat (Pikul et al., 1987, Knust and Pingel, 1992, Witkiewicz, 2000).
Because of low fat contents, cholesterol and iron white meat is regarded superior in health when compared to the red meat as suggested by the Jaturasitha et al. (2008), according to the literature that genotype such as breed , sex and strain plays an vital role in carcass fatness (DeSmet et al., 2004; Jaturasitha et al., 2004; Shahin and Elazeem, 2005). Genetic attributes for broiler traits over this period expanded the yeild of platable meat and multiplied the proportion of breast muscle in the carcase but at the same time was related to the increased fatness (Havenstein et al., 2003).
When comparing absolute abdominal fat weight of Hybro G males and Arbor Acres males it was found considerablly low. Abdominal fat and crude fat percentage also noticed low in case of Ross males and Arbor male (Farran et al, 2000). Comparing Ross and Cobb 500 genotype abdominal fat was indicated to be almost (0.4%) in broiler chickens (Ristic, 2005).
Age and Sex
Age, strain and sex have always been affect the difference in softness of meat samples along with the environmental and nutritional stress (Guhne, 1970; Lyon and Wilson, 1986; Smith and Fletcher, 1988; Sams, 2002). There is significant difference between the carcass tissue composition as well as in areas of lean meat, skin with a fat layer and bones in the carcass of young and old age birds (Murawska D ve ark., 2005; Bochno R ve ark., 2003; Murawska D ve ark., 2015).
Age is the most significant factor which affects the tenderness and juiciness of the meat in poultry and with age these two factors significantly decreases (Castellini et al., 2008). Males tend to be have lower FCR and better carcass performance when compared to the females (Salim et al., 2012). Variation in the conformation of meat analysis, among others, the substance of fat, collagen and myoglobin while as myoglobin intensifies with age, leading the meat colour towards darker and redder tonalities (Fletcher, 2002). The quality information of specific genetic lines or broilers of certain ages might also be interesting to reduce meat color variations.
Some researches also concluded that sex also affect the growth rate: females show highest breast meat percentage as compared to males and also lowest leg ang thing meat percentage (Lazzari, G.L. and J.L. Paganni, 1999). When comparing male and females broilers it was noticed male broilers have considerably higher thighs yield, while as females have increased breast yield (1.91%) (Takahashi et al., 2006). Moreover, Horsted et al. (2005) revealed that age-related changes in tenderness and toughness varied extremely within strains, and commercial line (I 675) tends towards a harder and less delicate consistency of the breast meat, while the converse is the situation for the slower developing pure breeds (New Hampshire and Light Sussex).
The Related Factors Affecting Enviromental Conditions on Meat Quality
Alternative Housing System and Stocking Density
Among the non-genetic components, the most significant influence on meat quality is system of rearing the birds moreover it also impacts on carcass quality ( Bogosavljević-Bosković et al. 2006; Fanatico et al., 2007). Meat quality of free range birds differs when compared with standard broiler because of utilizing an extensive variety of ages, breed types, feed ingredients, and rearing systems (Castellini et al., 2008). It was also noticed by some researchers that fat content (abdominal fat spacifically) in free range broilers is considerablly low because of there more locomotory activity Castellini et al. (2002), Fanatico et al. (2005) and Dou et al. (2009).
Fat proportion on muscles of thigh, breast and drum in case of free range birds were less in extant when distinguished with the birds which have no access to pasture. Likewise birds that are able to move freely in pasture have positive affect on protein proportion in commercial cuts (Sales, 2014). pH tends to be higher in case of free range birds (Alvarado et al., 2005). Muscle pH of birds reared in free range system remains totally unchanged. Water holding capacity is an important factor in terms of nutritive value of whole meat and also for processed meat product. Low water holding capacity leads to hard and stiff meat (Wang et al. 2009; Fanatico et al. (2007). Color of breast meat and fatty acid contents may be influenced by housing system.(Husak et al., 2008). Polyunsaturated fatty acids, omega-3 and omega-6 have been shown considerably high in case of free-range birds which is beneficial for meat quality and also for the customers preference by reducing the risk cardiovascular disease (Castellini et al., 2002).
Stocking density have greater impact not only on growth rate, feed efficiency ,livability but also on carcass quality by providing less air flow to bird which leads to less body heat dissipation to the air. Moreover due to less air exchange ammonia concentration inceases which affect the feed and water intake (Bessei W., 2006; Feddes, J.J.R et al; Puron, D, 1995). Legislation (Welfare of Farmed Animals, 2007) have declared extreme limit for indoor stocking density upto 39 kg/m2 and for industry assurance scheme upto 38 kg/m2 (Red Tractor, 2011) and for Freedom Food Indoor maximum limit should be upto 30 kg/m2 (RSPCA, 2011). While enhancing stocking density in broiler chickens of around 2.4 to 2.7 kg extreamly influence growth production, carcass yield, skin lacerates and injuries (Feddes et al., 2002). According to Škrbić et al., 2008, broilers reared in less stocking density yields extra growth and provides high processed carcass and better body conformation.
Transport and Stunning
Meat quality is also being affected by factors like transportation and holding hours other than biological factors (Northcutt, 1994; McKee and Sams, 1997; Petracci et al., 2001; Bianchi et al., 2004). It is also important to choose the way of stunning which ultimately affects meat quality (Craig et al., 1999; Göksoy et al., 1999). The factors like grabbing, placement and transportation increase stress in birds eventually influencing meat quality ( Knowles and Broom, 1990; Von Borrell, 2001). Birds tranported for around 2 hours does not influence breast meat although it does influence thigh meat (Debut et al, 2003).
Dadgar et al.(2010) also reported that when broiler birds are exposed to 00 C temperature for almost 3 to 4 hours during transportation , before slaughter will produce darker color in breast meat, increases pH and water holding capacity although it has no impact on the softness of breast meat. Studies show that best pH should range should be 5.7 to 6.0 (Ristic M et al., 2003; Madruga MS et al., 2005; Bihan-Duval E et al., 1999; El Rammouz R et al., 2004; Berri C et al, 2007). It is also reported by some studies that slaughter weight is also an important factor which effects meat quality for example breast meat of birds slaughterd at 1.2 kg of carcass weight have increased redness, decreased pH and cooking loss as compared to birds that are slaughtered at 1.8 and 2.4 kg of carcass weight Bianchi et al. (2007).
Meat quality is also highly affected by the techniques used to slaughter the animals as it effects the glycogen content in muscle tissue. Decapitation technique reduced 23% glycogen preserve because of increased contractation of mucsles (Edwards et al., 1999). Recently,slaughtering techniques have been changed to less-atomspheric pressure because of welfere reason.
Instead of using electrical stunning nowasdays substitute atmospheric slaughtering stunnig techniques have been invented by researchers example carbon dioxide, argon or nitrogen to avoid insensibility in broilers. (Thaxton et al., 2010). Studies show birds should bleed properly because of its profound effect on meat quality , it’s also being revealed that if birds bleed enough, yet 20 to 30 % hemoglobin exists in the carcass which directly influences meat color. (Froning, 1995).
Feed drawing before slaughter
Feed holding period is directly correlated to the carcass quality before and after chilling (Lyon, C. E et al., 1991). Before slaughtering almost 6 hr birds are not being given any food to avoid contamination during processing (Northcutt, 2000). Moreover withdrawal time leads birds to draw moisture and nutrients from the body and finally this loss may influence consumable yield (Northcut, J. K. 2000). Avoiding contamination due to gastro intestinal contents feed withdrawal time is considered to be most important factor in slaughtering processs. (Bilgili, 2002). Northcutt, 2001 concluded in his study that it is important how much is required to for withdrawal time because if the withdrawal time is short it will ultimately effect the carcass duing mechanical evisceration.
Climatic factors and Stress
Climatic factors such as temperature also change the features and hypertrophic developments of skeletal muscle fibers which ultimately affects meat characteristics (Dransfield and Sosnicki, 1999; Lefaucheur, 2010). Studies also reveal that heat stress have negative effect on meat quality and considerablly effect the economic values for example pale soft exudative (PSE) meat which is inclined to short shelf life time and color unstablity, carcass weight loss and diminished crude protein level in mucles extracts (Dai, S.F et al., 2009; Owens, C.M., 2000; Tankson, J.D et al., 2001).
By providing excellent welfare conditions helps in decresing pH in chickens meat, slows down stres before slaughter and consequently utilization of glycogen. (Castellini et al., 2002). Aberly et al., 2001 revealed that because of stress mucles tun into pale, tender and watery after 18 to 24 hours of chilling time. These features affects in lowering yield, enhanced cooking losses, and decreased platability (Aberly et al., 2001). Mitchell and Kettlewell (1998), investigated that stress plays a vital role in influencing meat quality, for example: while transporting from poultry house to slaughter house, brioler by lots of potential stresses like thermal asymetry, fluctuation, holding of water, social interruption commotion.
Conclusion
According to the results, it is reported that the factors related to the study of meat quality are influenced by the fleshy and environmental conditions. In order to protect the properties that shape the broiler quality, firstly proper cultivation methods should be chosen about the characteristics such as genotype, age, sex related to the broiler chick, environment related nutrition, growing conditions, transportation, cutting and stress.