LITERATURE REVIEW

doi: 10.17533/udea.rccp.v29n1a01

Intrinsic factors affecting sheep meat quality: a review^¤

Factores intrínsecos que afectan la calidad de la carne ovina: revisión de literatura

Dorgival M de Lima Júnior^1*, Zoot, DSc; Francisco F R de Carvalho², Zoot, DSc; Felipe J S da Silva¹, Zoot; Adriano H do N Rangel³, Eng Agron, DSc; Luciano P Novaes³, Eng Agron, PhD; Gelson dos S Difante³, Zoot, DSc.

¹ Campus Arapiraca, Universidade Federal de Alagoas, Alagoas, Brazil.

² Departamento de Zootecnia, Universidade Federal Rural de Pernambuco, Pernambuco, Brazil.

*Corresponding author: Dorgival Morais de Lima Júnior. Campus Arapiraca, Universidade Federal de Alagoas, 57309-005. Tel: +55-82-34821829. Email: juniorzootec@yahoo.com.br

Received: November 27, 2014; accepted: September 15, 2015

Summary

The quality of meat is a multifactorial parameter dependent on the perspective and goals of the link in the production chain. Generally, a variety of factors directly or indirectly affect the quality characteristics of meat and, therefore, the value of meat products. Often, the literature divides the interfering factors into intrinsic and extrinsic. Intrinsic factors are related to animals; therefore, intrinsic factors are less variable. These factors include breed, sex, age, weight, genes, and type of muscle fiber. Some of these factors are not well studied, others have variable influence or are controversial and only a few are known and sometimes controlled. Thus, this study aimed to review some intrinsic factors that influence the quality of lamb meat.

Keywords: cooking losses, meat color, tenderness, water holding capacity.

Resumen

La calidad de la carne es un parámetro multifactorial que depende de la perspectiva y los objetivos del eslabón de la cadena de producción. En general, una amplia variedad de factores afectan directa o indirectamente la calidad de la carne y, en consecuencia, los valores de los productos cárnicos. A menudo, la literatura divide los factores que interfieren intrínseca y extrínsecamente. Los factores intrínsecos están relacionados con los animales, por lo tanto, son menos variable. Estos factores incluyen la raza, el género, la edad, el peso, los genes y el tipo de fibra muscular. Algunos de estos factores no están bien estudiados, otros tienen influencia variable o son polémicos, y sólo unos pocos son conocidos y a veces controlados. Por lo tanto, este trabajo pretende revisar algunos factores intrínsecos que influyen en la calidad de la carne de ovino.

Palabras clave: capacidad de retención de agua, color de la carne, perdidas por cocción, terneza.

Resumo

A qualidade da carne é um parâmetro multifatorial, dependente da perspectiva e objetivos do elo da cadeia produtiva. Geralmente, uma grande variedade de fatores afetam direta ou indiretamente as características de qualidade da carne e, consequentemente, os valores dos produtos cárneos. Frequentemente, a literatura divide os fatores interferentes em intrínsecos e extrínsecos. Os fatores intrínsecos são referentes ao animal e, portanto, menos variáveis. Esses fatores incluem raça, sexo, idade, peso, genes e tipo de fibras musculares. Alguns desses fatores não estão bem estudados, outros têm influência variável ou controvertida e somente alguns são conhecidos e, às vezes, controlados. Dessa forma, objetivou-se revisar alguns fatores intrínsecos que influenciam na qualidade da carne ovina.

Palavras chave: capacidade de retenção de água, cor da carne, maciez da carne, perdas por cocção.

Introduction

Currently, the global sheep population is more than 1 billion heads (FAO, 2015). On a global scale, sheep meat production is small, with less than 8.6 million tonnes. The largest producers of sheep meat are China, India, Sudan, Nigeria and Pakistan. The three largest destinations for sheep meat worldwide are China, EU, and US, accounting for about 60% of global exports (FAO, 2015).

Meat is the most important source of animal protein for the human diet (Lawrie, 2005; McAfee et al., 2010). However, the parameters that define its degree of acceptance and quality vary with the point of view and interest of the producer, trade, industry, and consumers.

From an industrial perspective, quality is defined and determined by objective factors relating not only to the quality demanded by the consumer, but also to industrial meat characteristics (Osório et al., 2009). In the context of the supply chain and meat science, the analysis of color, pH, water holding capacity, cooking losses, tenderness, chemical composition, fatty acid composition, among many others, are all important in the concept of integrated quality and the search for more homogeneous products.

Besides being interconnected, quality parameters defined by the final consumer and industry depend on a long list of other intrinsic (inherent to the animal) and extrinsic (inherent to management, environment, etc.) factors. Therefore, meat quality is defined by animal age, sex, and physiological state, and the post-mortem biochemistry of muscle and fat, carcass composition, feed contribution to flavour, protein and fat levels, as well as the effect of genetics on tissues and metabolism, pre and post slaughter handling, and storage, among others (Webb et al., 2005).

In the case of lamb, an increase in consumption accompanied by a demand for increased quality has been observed. This situation forces the supply chain to better understand the factors affecting meat quality; we need to consider the number of factors that affect the quality of lamb meat. The main intrinsic factors interfering with the quality of lamb meat are breed, sex, age, genetic characteristics and type of muscle fibres. The aim of this work is to describe how these intrinsic factors cause changes in the quality of sheep meat.

Intrinsic factors affecting sheep meat

Breed

Breed has a large effect on carcass morphology. It is a complex factor and difficult to assess when only its effects on the amount of fat or meat quality are considered. The problem lies at the basis of comparison, as results vary according to the chosen criterion: same carcass weight, same age, same degree of maturity, etc. (Hopkins et al., 2011). Furthermore, racial comparison is complicated due to differences in the adopted selection programs between countries (Sañudo et al., 2008).

It is true that there is genetic variation of meat quality between populations, especially between improved breeds and native breeds. Lambe et al. (2008; 2009) showed variation (p<0.05) in final pH and tenderness between the Texel and Scottish Black Face breeds. Changes in tenderness between these genotypes can be partly explained by the difference in the number of muscle fibers (Bünger et al., 2009). Breed also influences other parameters such as the chemical composition (Table 1).

Breed may also influence other nitrogen fractions of meat, besides true protein. Esenbuga et al. (2009) observed that Awassi sheep show lower values (p<0.05) of non-protein nitrogen (2.44 ± 0.07% versus 2.91 ± 0.09%) and smaller amounts (p<0.05) of nitrogen soluble in water (5.18 ± 0.13 vs. 6.30% ± 0.16%) when compared to Morkaraman sheep.

Regarding chemical composition at the same carcass weight, animals of breeds with smaller frame size will be older and have more fat than those with larger frame size (Osório et al., 2008). Breeds such as Dorper and their crosses have greater amount of intramuscular fat at the same age than breeds not specialized for meat production such as Rambouillet breed (Arvizu et al., 2011). Barkawi et al. (2009) examined two Egyptian fat-tailed sheep breeds observing that Ossimi breed showed higher (p<0.05) fat content (4.2%) than Rahmani breed (3.3%). The authors noted that Rahmani breed had higher frame size and later maturity with higher levels of circulating insulin growth factor (IGF-I) at different ages.

Typically, selected breeds for meat production have greater number of muscle fibers and smaller amount of intramuscular fat per unit area of muscle (Bünger et al., 2009; Hopkins et al., 2011). Furthermore, Vacca et al. (2008) inferred that differences between genotypes alter the activity of lipogenic enzymes in sheep muscle, such as Δ-desaturase, and can influence the amount and composition of deposited fatty acid.

Cholesterol levels are often associated with heart disease and red meat is the primary source of this lipid. Faria et al. (2012) showed differences (p<0.05) in the order of 5.72 mg/g cholesterol lower for Texel x Polwarth lamb meat compared to Texel x Corriedale.

The marbling degree can influence various sensory impressions of sheep meat, especially its juiciness. In a study evaluating breeds with different aptitudes, Cloete et al. (2012) observed that the lower amount of intramuscular fat in meat from Merino sheep was associated with lower scores for sensory characteristics of initial juiciness and lasting succulence (after-taste succulence) when compared to sheep of double quality genotypes or cut. In an extensive review, Hopkins et al. (2011) had already noted lower juiciness in the Merino genotype.

There are few studies comparing breed and post-mortem pH evolution. Hoffman et al. (2003) observed that sheep crosses between meat breeds and wool breeds differed (p<0.05) in pH 48 hours post-mortem, with values of 5.71 and 5.79 for Merino x Dormer and Merino x Suffolk crosses, respectively. Merino breed has a high final pH, which can be derived from the predominant muscle fiber in the breed. Due to selection for production under grazing conditions, oxidative fibers (1 and 2A) may be prevalent in the muscle of these animals. These fibers are characterized by low levels of glycogen, which is closely related to high final pH values in the muscle (Pösö and Puolanne, 2005).

Associated with juiciness, meat tenderness is another attribute influenced by genotype (Martínez- Cerezo et al., 2005). The differences in the degree of muscularity, age and physiological action of the calpain–calpastatin enzyme complex are mainly responsible for the variation in tenderness of lamb meat (Thompson et al., 2006).

Teixeira et al. (2005) showed objective differences (p<0.01) in meat tenderness between Bragançano (7.8 Kg/cm²) and Mirandesa (6.8 Kg/cm²) sheep breeds. According to the authors, the sensory panel also identified differences (p<0.05) in hardness, assigning scores of 4.1 to Bragançano and just 2.8 for Mirandesa. In the latest study, Ekiz et al. (2009) evaluated the quality of sheep meat of five genotypes (Turkish Merino, Ramlic, Kivircik, Chios and Imroz ) and observed difference (p<0.01) in shear force (kgf) between genotypes.

Physical aspects such as color, water holding capacity and cooking losses are dependent to a greater or lesser extent on the final pH of meat (Table 2). The literature describes variations in color scores, juiciness and water holding capacity between breeds (Hernández-Cruz et al., 2009; Costa et al., 2011).

Osório et al. (2008) argued that the most noticeable changes are related with physical aspects of meat, mainly the color because it has a direct impact on appearance and consumer acceptability. Meat color is influenced by the muscle myoglobin content and the electrical state of muscle proteins (Ramos and Gomide, 2007; Khliji et al., 2010). Breed influences the amount of myoglobin present in muscle, as Juárez et al. (2009) showed for the Grazalema Merino breed: 3.09 mg/g myoglobin in lactation and 4.01 mg/g myoglobin in the growing phase, while Lebrijana Churra breed showed values of 1.61 mg/g and 2.79 mg/g for the same productive stages, respectively.

Genetics can also influence fatty acids composition of muscle. According to Muchenje et al. (2009), differences among breeds reflect underlying differences in gene expression or activity of enzymes involved in fatty acid synthesis, desaturation or chain elongation, and thus deserve more attention.

Demirel et al. (2006), Madruga et al. (2006), and Marino et al. (2008) observed differences in the levels of mono and polyunsaturated fatty acids for different sheep breeds and attributed it to different deposition rates of intramuscular triacylglycerols in adipocytes associated with a dilutive effect of membrane phospholipids.

Sex

Proximate composition of meat is affected by sex, especially fat content (Peña et al., 2005; Gerrard and Grant, 2006; Pérez et al., 2007). Meat from females is often richer in lipids. Santos et al. (2007) observed that native animals from Spain had higher (p<0.05) lipids levels in the meat of female (2.3%) compared with male lambs (1.9%) of the same age. Rodríguez et al. (2008) also found differences (p<0.05) in the fat content of meat from males and females (1.6 vs. 2.9%, respectively) in Assaf sheep, attributing these differences (p<0.05) to the amount of carcass fat, being higher in females (10.9%) than in males (8.6%). When intact and castrated males are compared, meat from castrated animals has higher (p<0.01) fat content (Haddad et al., 2006; Warren et al., 2008).

Physical parameters of meat quality are influenced by sex. Johnson et al. (2005) evaluated muscle and meat deposition of Texel male and female lambs, observing increased (p<0.01) deposition of muscle and less fat in males for variables adjusted to the same carcass weight. In the same study, meat quality reflected differences (p<0.01) for gender in tenderness (74.5 N for females and 82.4 N for males) and final pH (5.60 for females and 5.74 for males).

Decreasing pH is influenced by many factors, among which glycogen, ATP, and creatine phosphate reserves are the most determinant. McGeehin et al. (2001) observed that pH drop is faster (p<0.05) in females than in males, with constant differences of 0.18 pH units. It can be inferred that glycogen content in females is higher due to less sexual activity. Another possible hypothesis is that the higher reactivity of males is promoted by testosterone and depletes muscle glycogen faster via catecholamines. Adrenaline recruits glucose to the bloodstream and stimulates muscle glycolysis (Pösö and Puolanne, 2005).

Okeudo and Moss (2008) evaluated the influence of sex (intact males, castrated males, vasectomized males, and females) on meat quality of sheep (Table 3).

The differences in cooking losses and shear force between males and females can be partly explained by higher intramuscular fat content of females (Okeudo and Moss, 2008). In reviewing aspects of meat quality, Koohmaraie and Geesink (2006) claimed that fat has lower water content than muscle; therefore, muscles richer in adipose tissue have reduced water loss. Moreover, authors point out that a greater amount of adipocytes implies that the amount of muscle fibers per area is reduced, thereby favouring smaller shear force values.

Frequent differences in meat tenderness are found for most species between intact and castrated males. Lage et al. (2009) observed higher shear strength and smaller values for the myofibrillar fragmentation index in Longissimus dorsi of castrated compared to non-castrated animals. The authors also observed no difference in m-calpain and μ-calpain activity 24 hours post-mortem in relation to sex. Calpastatin was 81% higher in intact animals compared with castrated males. Besides high calpastatin activity, another explanation for the low meat tenderness of non-castrated animals would be their higher zinc concentration, which is a potent inhibitor of calpain (Koohmaraie and Geesink, 2006). Furthermore, Gökdal et al. (2010) found higher (p<0.05) collagen content in meat from intact males (4.03 ± 0.44 mg/g) compared to immunologically castrated males (2.52 ± 0.28 mg/g).

Sex differences for fatty acid content are documented in the literature. Tejeda et al. (2008) showed differences (p<0.01) in fatty acid composition of Longissimus lumborum of Merino males and females. They associated it to higher levels of polyunsaturated fatty acids in intact males. Intramuscular fat is more saturated than membrane phospholipids for example, and females have higher deposition of intramuscular fat. Therefore, it is common in the literature to refer to female sheep meat as being more saturated.

In addition to fatty acid composition, castration affects cholesterol levels of meat from males. According to Madruga et al. (2001), castration increased (p<0.05) cholesterol in meat from castrated goats (62.5 mg/g) compared to that of intact animals (58.0 mg/g). It can be inferred that cholesterol mobilization by intact animals is higher because steroid hormones are derived from this lipid, which contributes to less deposition of this metabolite into the meat. The sensory panel rated by Navajas et al. (2008) and Tejeda et al. (2008) classified the meat of intact males with higher scores for ''bad taste''.

Age and body weight

These factors are analyzed together because if no manipulation of food occurs or the animal does not suffer severe food restriction, a greater weight in the same genetic background implies greater age. The slaughter weight affects consumer acceptability in many countries (Martínez-Cerezo et al., 2005; Font i Furnols et al., 2006; Muela et al., 2010) and therefore deserves special attention in the study of meat quality.

The growth curve of sheep is sigmoid, with a period of accelerated lean tissue deposition that coincides with puberty and a stabilization period of protein deposition and increased fat deposition known as maturity. The increase in protein deposition is mediated by growth hormones (GH), which increase muscle fibers hypertrophy and reduce fat hormones deposition. The increase in fat deposition amounts to the extent that sex hormones increase their concentration in the bloodstream (Gerrard and Grant, 2006).

Differences in sheep meat quality at different ages necessarily correspond to changes in the amount of carcass fat and its relationship to physical and chemical aspects of meat (Table 4). Barkawi et al. (2009) evaluated the chemical composition of meat from native lambs at two ages (270 and 360 days) and observed a reduction (p<0.01) of moisture (75.8 to 75.1%) and an increase (p<0.01) in fat (3.3 to 4.2 %) with increasing slaughter age.

Regarding color, the increased weight and age at slaughter tend to increase the amount of pigments, red content (a^*) and reduced luminosity (L^*). Juárez et al. (2009) observed an increase (p<0.01) in myoglobin (3.09 to 4.01 mg/g), low (p<0.01) luminosity (45.10 to 40.19 L^*) and increased (p<0.01) redness (7.35 to 9.79 a^*) with increasing (p<0.01) slaughter weight of Grazalema Merino sheep breed. In another study, Teixeira et al. (2005) identified a reduction (p<0.05) in L^* of 40.0 ± 0.55 to 39.0 ± 0.54 when slaughter weight increased from 9-14 to 19-24 Kg.

Silva Sobrinho et al. (2005) evaluated meat quality from lambs of different exotic genotypes slaughtered at two ages. They found that Warnen- Bratzler measurement was higher in meat from animals slaughtered at 300 days compared to 150 days at slaughter, indicating that larger shear forces were required to cut the samples from older animals. Tejeda et al. (2008) studied the texture composition of sheep meat at different slaughter weights (24 or 29 Kg) observing higher meat fibrosity at 29 Kg body weight. This parameter was related to increased thermal and mechanical stability of collagen (Purslow, 2005).

Regarding juiciness, meat from young animals should be moister at the first bite and have a drier aftertaste, while heavier and older animals have a tendency toward greater juiciness due to fat content. Corroborating this assertion, Juárez et al. (2009) reported higher end juiciness with increasing age at slaughter.

Russo et al. (2003) evaluated the quality of beef carcasses, observing higher water holding capacity (0.33 for light, 0.36 medium and 0.39 for heavy carcasses); however, the increase in slaughter weight also increased cooking losses. It can be inferred that sheep meat takes longer to reach the degree of doneness (70 °C in the center of beef) as age increases, resulting in higher losses. Nevertheless, Pinheiro et al. (2009) observed contrary results, reporting higher cooking losses in lambs (46.44%) compared to adult sheep (39.33%).

The influence of weight and slaughter age on fatty acid composition in sheep meat is quite controversial. Some results indicate no influence of slaughter weight on the fatty acid composition of meat (Díaz et al., 2003). However, Wood et al. (2008) reviewed the influence of age on fatty acids concentrations in adipose tissue of ruminants and reported an increase in the proportion of monounsaturated fatty acids. According to the authors, the proportion of saturated fatty acids falls while linolenic acid levels remain constant. This study also showed that the proportion of conjugated linolenic acid (CLA) in the fat increased with the age of the animal.

Warren et al. (2008) analyzed fatty acids content, triglycerides levels, and phospholipids in Aberdeen Angus cattle at three different ages (14, 19, and 24 months). The authors observed the extent to which fattening progresses increase muscle triglycerides; however, phospholipids remain reasonably constant. The phospholipids to total lipids ratio fell by 30% at 14 months and 12% at 24 months, and these decreases were accompanied by an increase in the proportion of monounsaturated fatty acids and a decrease of ω-6 polyunsaturated in the total lipids. This seems to be similar in sheep, as Marino et al. (2008) observed increasing saturated lipids and decreasing unsaturated lipids in intramuscular (Longissimus dorsi) fat of sheep native to Italy.

Genes

The study of gene influence on meat quality is recent and its implications are still poorly understood (Thompson et al., 2006). In sheep, the main set of genes (loci of quantitative traits) affecting carcass characteristics and meat are: Callipyge, Carwell or rib eye muscling (REM), Double muscling (Cockett et al., 2005).

Recently, the existence of a gene that causes muscle hypertrophy in sheep was identified. Preliminary evidence suggests an autosomal dominant gene may be responsible for this effect in muscle and carcass composition. Compared with normal lambs, ''Callipyge'' lambs have 32.30% superior muscularity, with no change in birth weight. An advantage of the ''Callipyge'' phenotype is that unlike double muscling in cattle, the condition in sheep does not occur until a few weeks after birth. So dystocia at birth is not a problem for carrier animals (Sosnicki and Newman, 2010; Masri et al., 2011a). Despite the advantages in weight and carcass yield, the meat is considered extremely tough and somewhat bland due to low marbling (Goodson et al., 2001). Meat toughness can be attributed to high levels of calpastatin, which inhibit the calpain system - enzymes responsible for proteolysis of muscle post-mortem (Koohmaraie and Geesink, 2006; Kemp et al., 2010). ''Callipyge'' sheep meat presents significant decrease of myofibrillar fragmentation, indicative of a decrease in protein degradation (Hopkins et al., 2011). Kuber et al. (2003) observed that calpastatin activity in ''Callipyge'' phenotype was 58% higher than the normal genotype, while Abdulkhaliq et al. (2007) reported 2.9 shear force (kgF) for ''Callipyge'' sheep and 5.4 for the normal genotype.

Besides the increased hypertrophy of ''Callipyge'' sheep, changes in muscle fiber type occur. This mutation increases the amount of glycolytic fibers, which reduce oxidative metabolism. Thus, it can be inferred that the muscles of ''Callipyge'' are more sensitive to a sudden drop in pH (Warner et al., 2010). Changes in pH may be responsible for higher cooking losses (31% for mutant and 29.6% for normal genotype; Abdulkhaliq et al., 2007).

Another mutation in sheep genome influencing carcass and meat quality was documented in Poll Dorset sheep in Australia. The ''Carwell'' phenotype has 8-10% rib eye area increments at similar carcass weights (Warner et al., 2010). Significant effects on muscularity, an increase in protein deposition and up to 35% meat toughness increase have been documented in ''Carwell'' sheep (Warner et al., 2010). However, Hopkins et al. (2007) reported no increase (p>0.05) in sheer force of Longissimus or semimembranosus, or any other effects on pH or meat color. It can be inferred from the current literature that the effects of the ''Carwell'' phenotype are far less impacting on meat quality than those documented by the ''Callipyge'' phenotype (Hopkins et al., 2011).

According to McFarlane et al. (2005), myostatin controls muscle fiber proliferation through transcription of gene groups responsible for myoblasts and fibroblasts differentiation and their subsequent aggregation in the myotube. A mutation in the myostatin (GDF8) gene resulting in inhibited transcription has been shown to increase muscularity in Texel sheep and other breeds (Clop et al., 2006). Other studies have reported that myostatin mutations influence muscle and fat (Kijas et al., 2007; Lambe et al., 2011).

The g + 6723GNA mutation increased the percentage of glycolytic fibers, but did not affect shear force. However, a reduction of intramuscular fat and sensory scores on overall meat quality, including juiciness, was observed (Kijas et al., 2007; Hopkins et al., 2011). Masri et al. (2011b) observed that myostatin mutations in Texel and Poll Dorset breeds reduce Longissimus intramuscular fat. The authors recommend paying attention to meat quality, especially juiciness, of mutant animals.

In another study evaluating meat quality of mutant myostatin Texel sheep observed that Longissimus and Semimembranosus shear force was not affected by the mutation (Johnson et al., 2005; Lambe et al., 2011). According to Warner et al. (2010), myostatin mutations in sheep do not seem to have any influence on shearing force, despite a reduction in the perception of juiciness by consumers, perhaps due to a reduction in the amount of intramuscular fat.

Besides amount of fat, fatty acid composition of mutant beef and sheep deserves attention. Raes et al. (2003) showed that the double-muscling genotype in cattle has lower proportion of monounsaturated and higher of polyunsaturated fatty acids compared with the non-mutant genotype. The authors attributed this to a low concentration of total lipids in muscle and a higher proportion of phospholipids in the total lipids, increased by the mutation. Thus, studies on the impact of double-muscling on fatty acid composition in beef and sheep are required.

Muscle fibers

Differences in muscle fibers correspond to variations in the type of myosin chain (light or heavy) responsible for myofibril contraction. This polymorphism affects the enzymatic composition of the fiber, its buffering capacity and its biology (Gerrard and Grant, 2006; Bünger et al., 2009). Despite several nomenclatures in meat science, three types of muscle fibers with different characteristics are described (Table 5).

The number and type of muscle fibers of the species affect meat color. In sheep, the proportion of red, intermediate and white fibers is approximately 15, 31 and 54%, respectively (Gerrard and Grant, 2006). For the same species, Gallo et al. (2009) reported frequencies of 9.77, 35.01, and 55.21% for red, intermediate and white fibers, respectively. The proportions of these fibers vary between muscles and alter physical-chemical characteristics such as color (Tschirhart-Hoelscher et al., 2006).

In sheep, higher final pH value corresponds to slow-contracting muscles while lower final pH is related to the more rapidly-contracting muscles (Thompson et al., 2006; Tschirhart-Hoelscher et al., 2006). Ryu et al. (2006) reported a negative correlation between the amount of white fibers and the final pH of the muscle.

In addition to pH, fiber type and their interaction with calpastatin activity affect muscle softness (Table 6). However, the effect of fiber type is still controversial regarding softness (Lee et al., 2010).

The water content in muscle greatly varies with increasing speed of muscle contraction. Muscles rich in white fibers are larger and have more water compared to proteins (Tschirhart-Hoelscher et al., 2006). According to Lee et al. (2010), the water/protein relation affects the ability to retain water, which decreases by increasing this ratio. Thus, less water holding capacity and higher cooking losses are expected in rapidly contracting muscles.

Perspectives

Many factors influence sheep quality, and knowledge of their relevance requires more study accompanied by constant research on consumer and industry demands. Intrinsic factors such as breed, sex, age and weight at slaughter, genes, muscle fiber plasticity and meat quality referring to these factors must be considered in management practices. Due to the influence of intrinsic factors on meat characteristics, quality standards must be known by lamb producers in order to define the type of animal required to meet these demands.

Conflicts of interest

The authors declare they have no conflicts of interest with regard to the work presented in this report.

Notes

¤To cite this article: de Lima DM, de Carvalho FFR, da Silva FJS, Rangel AHN, Novaes LP, Difante GDS. Intrinsic factors affecting sheep meat quality: a review. Rev Colomb Cienc Pecu 2016; 29:3-15.

References

Abdulkhaliq AM, Meyer HH, Busboom JR, Thompson JM. Growth, carcass and cooked meat characteristics of lambs sired by Dorset rams heterozygous for the Callipyge gene and Suffolk and Texel rams. Small Ruminant Res 2007; 71:92-7.         [ Links ]

Abdullah AY, Qudsieh RI. Effect of slaughter weight and aging time on the quality of meat from Awassi ram lambs. Meat Sci 2009; 82:309-16.         [ Links ]

Abdullah AY, Qudsieh RI, Nusairat BM. Effect of crossbreeding with exotic breeds on meat quality of Awassi lambs. Livest Sci 2011; 142:121-7.         [ Links ]

Arvizu RR, Domínguez IA, Rubio MS, Bórquez JL, Pinos- Rodríguez JM, González M, Jaramillo G. Effects of genotype, level of supplementation, and organic chromium on growth performance, carcass, and meat traits grazing lambs. Meat Sci 2011; 88:404-8.         [ Links ]

Barkawi AH, El-Asheeri AK, Hafez YM, Ibrahim MA, Ali MM. Growth and carcass characteristics of lambs in relation to plasma IGF-I and some histological traits of Longissimus lumbarum and Biceps femoris as affected by breed and age at slaughter. Livest Sci 2009; 124:9-14.         [ Links ]

Bünger L, Navajas EA, Stevenson L, Lambe NR, Maltin CA, Simm G, Fisher AV, Chang KC. Muscle fiber characteristics of two contrasting sheep breeds: Scottish Blackface and Texel. Meat Sci 2009; 81:372-81.         [ Links ]

Cloete JJE, Hoffman LC, Cloete SWP. A comparison between slaughter traits and meat quality of various sheep breeds: Wool, dual-purpose and mutton. Meat Sci 2012; 91:318-24.         [ Links ]

Clop A, Marcq F, Takeda H, Pirrottin D, Toroir X, Bibe B. A mutation creating a potential illegitimate microRNA target site in the myostatin gene affects muscularity in sheep. Nat Genet 2006; 38:813-8.         [ Links ]

Cockett NE, Smit MA, Bidwell CA, Segers K, Hadfield TL, Snowder GD, Georges M, Charlier C. The callipyge mutation and other genes that affect muscle hypertrophy in sheep. Genet Sel Evol 2005; 37:65-81.         [ Links ]

Costa RG, Santos NM, Sousa WH, Queiroga RCRE, Azevedo OS, Cartaxo FQ. Qualidade física e sensorial da carne de cordeiros de três genótipos alimentados com rações formuladas com duas relações volumoso:concentrado. Rev Bras Zootec 2011; 40:1781-7.         [ Links ]

Demirel G, Ozpinar H, Nazli B, Keser O. Fatty acids of lamb meat from two breeds fed different forage: concentrate ratio. Meat Sci 2006; 72:229-35.         [ Links ]

Díaz MT, Velasco S, Pérez C, Lauzurica S, Huidobro F, Cañeque V. Physico-chemical characteristics of carcass and meat Manchego-breed suckling lambs slaughtered at different weights. Meat Sci 2003; 65:1247-55.         [ Links ]

Ekiz B, Yilmaz A, Ozcan M, KaptanC, Hanoglu H, Erdogan I, Yalcintan H. Carcass measurements and meat quality of Turkish Merino, Ramlic, Kivircik, Chios and Imroz lambs raised under an intensive production system. Meat Sci 2009; 82:64-70.         [ Links ]

Esenbuga N, Macit M, Karaoglu M, Aksakal V, Aksu MI, Yoruk MA, Gul M. Effect of breed on fattening performance, slaughter and meat quality characteristics of Awassi and Morkaraman lambs. Livest Sci 2009; 123:255-60.         [ Links ]

FAO. FAOSTAT. [Access date: August 19, 2015]. URL: http:// faostat3.fao.org/home/E        [ Links ]

Faria PB, Bressan MC, Vieira JO, Vicente-Neto J, Ferrão SPB, Rosa FC, Monteiro, M, Cardoso MG, Gama LT. Meat quality and lipid profiles in crossbred lambs finished on clover-rich pastures. Meat Sci 2012; 90:733-8.         [ Links ]

Font i Furnols M, San Julián R, Guerrero L, Sañdo C, Campo MM, Olleta JL, Oliver MA, Cañeque V, Álvarez I, Díaz MT, Branscheid W, Wicke M, Nute GR, Montossi F. Acceptability of lamb meat from different producing systems and ageing time to German, Spanish and British consumers. Meat Sci 2006; 72:545-54.         [ Links ]

Gallo SB, Siqueira ER, Delgado EF, Silva MDP, Rosa GT. Influence of feeding regime and finishing system on lamb muscle fiber and meat quality. Rev Bras Zootec 2009; 38:2204-10.         [ Links ]

Gerrard DE, Grant AL. Principles of animal growth and development. 1st ed. Kendall/Hunt Publishing Company. 2006.         [ Links ]

Gökdal O, Atay O, Ülker H, Kayaardi S, Kanter M, De Avila MD, Reeves JJ. The effects of immunological castration against GnRH with recombinant OL protein (Ovalbumin-LHRH-7) on carcass and meat quality characteristics, histological appearance of testes and pituitary gland in Kivircik male lambs. Meat Sci 2010; 86:692-8.         [ Links ]

Goodson KJ, Miller RK, Savell JW. Carcass traits, muscle characteristics, and palatability attributes of lambs expressing the callipyge phenotype. Meat Sci 2001; 58:381-7.         [ Links ]

Haddad SG, Husein MQ, Sweidan RW. Effects of castration on growth performance and carcass characteristics of Awassi lambs fed high concentrate diet. Texel×Welsh Mountain lambs using ultrasound and video image analyses. Small Ruminant Res 2006; 99:99-109.         [ Links ]

Hernández Cruz L, Ramírez Bribiesca1 JE, Guerrero Legarreta MI, Hernández Mendo O, Crosby Galvan MM, Hernández Calva LM. Effects of crossbreeding on carcass and meat quality of Mexican lambs. Arq Bras Med Vet Zoo 2009; 61:475-83.         [ Links ]

Hoffman LC, Muller M, Cloete SWP, Schmidt D. Comparison of six crossbred lamb types: sensory, physical and nutritional meat quality characteristics. Meat Sci 2003; 65:1265-74.         [ Links ]

Hopkins DL, Fogarty NM, Mortimer SI. Genetic related effects on sheep meat quality. Small Ruminant Res 2011; 101:160-72.         [ Links ]

Hopkins DL, Stanley DF, Martin LC, Toohey ES, Gilmour AR. Genotype and age effects on sheep meat production. 3. Meat quality. Aust J Exp Agr 2007; 47:1155-64.         [ Links ]

Johnson PL, McEwan JC, Dodds KG, Purchas RW, Blair HT. Meat quality traits were unaffected by a quantitative trait locus affecting leg composition traits in Texel sheep. J Anim Sci 2005; 83:2729-35.         [ Links ]

Juárez M, Horcada A, Alcalde MJ, Valera M, Polvillo O, Molina A. Meat and fat quality of unweaned lambs as affected by slaughter weight and breed. Meat Sci 2009; 83:308-13.         [ Links ]

Kemp CM, Sensky PL, Bardsley RG, Buttery PJ, Parr T. Tenderness an enzymatic view. Meat Sci 2010; 84:248-56.         [ Links ]

Khliji S, Van de Ven R, Lamb TA, Lanza M, Hopkins DL. Relationship between consumer ranking of lamb colour and objective measures of colour. Meat Sci 2010; 85:224-9.         [ Links ]

Kijas JW, McCulloch R, Hocking Edwards JE, Oddy VH, Lee SH, Van der Werf J. Evidence for multiple alleles effecting muscling and fatness in the Ovine GDF8 locus. BMC Genet 2007; 8:80-9.         [ Links ]

Koohmaraie M, Geesink GH. Contribution of postmortem muscle biochemistry to the delivery of consistent meat quality with particular focus on the calpain system. Meat Sci 2006; 74:34-43.         [ Links ]

Kuber PS, Duckett SK, Busboom JR, Snowder GD, Dodson MV, Vierck JL, Bailey JF. Measuring the effects of phenotype and mechanical restraint on proteolytic degradation and rigor shortening in callipyge lamb longissimus dorsi muscle during extended aging. Meat Sci 2003; 63:325-31.         [ Links ]

Lage JF, Oliveira IM, Paulino PVR. Papel do sistema calpaína calpastatina sobre a proteólise muscular e sua relação com a maciez da carne em bovinos de corte. Rev Eletron Vet 2009; 10:1-19.         [ Links ]

Lambe NR, Navajas EA, Fisher AV, Simm G, Roehe R, Bünger L. Prediction of lamb meat eating quality in two divergent breeds using various live animal and carcass measurements. Meat Sci 2009; 83:366-75.         [ Links ]

Lambe NR, Navajas EA, Schofield CP, Fisher AV, Simm G, Roehe R, Bünger L. The use of various live animal measurements to predict carcass and meat quality in two divergent lamb breeds. Meat Sci 2008; 80:1138-49.         [ Links ]

Lambe NR, Richardson RI, Macfarlane JM, Nevison I, Haresign W, Matika O, Bünger L. Genotypic effects of the Texel Muscling QTL (TM-QTL) on meat quality in purebred Texel lambs. Meat Sci 2011; 89:125-32.         [ Links ]

Lawrie RA. Ciência da carne. 6th ed. Artimed Editora:São Paulo, 2005.         [ Links ]

Lee SH, Joo ST, Ryu YC. Skeletal muscle fiber type and myofibrillar proteins in relation to meat quality. Meat Sci 2010; 86, 166-70.

Lefaucheur L. A second look into fibre typing – Relation to meat quality. Meat Sci 2010; 84:257-70.         [ Links ]

Madruga MS, Araújo WO, Sousa WH, Cézar MF, Galvão MS, Cunha MGG. Efeito do genótipo e do sexo sobre a composição química e o perfil de ácidos graxos da carne de cordeiros. Rev Bras Zootec 2006; 35:1838-44.         [ Links ]

Madruga MS, Narain N, Souza JG, Costa RG. Castration and Slaughter age effects on fat components of ''Mestiço'' goat meat. Small Ruminant Res 2001; 42:77-82.         [ Links ]

Marino R, Albenzio M, Annicchiarico G, Caroprese M, Muscio A, Santillo A, Sevi, A. Influence of genotype and slaughtering age on meat from Altamurana and Trimeticcio lambs. Small Ruminant Res 2008; 78:144-51.         [ Links ]

Martínez-Cerezo S, Sanuudo C, Panea B, Medel I, Delfa R, Sierra I, Beltrasn JA, Cepero R, Olleta JL. Breed, slaughter weight and ageing time effects on physico-chemical characteristics of lamb meat. Meat Sci 2005; 69:325-33.         [ Links ]

Masri AY, Lambe NR, Macfarlane JM, Brotherstone S, Haresign W, Bünger L. Evaluating the effects of a single copy of a mutation in the myostatin gene (c.*1232 GNA) on carcass traits in crossbred lambs. Meat Sci 2011b; 87:412-8.         [ Links ]

Masri AY, Lambe NR, Macfarlane JM, Brotherstone S, Haresign W, Bünger L. Evaluating the effects of the c.*1232G > A mutation and TM-QTL. Small Ruminant Res 2011a; 81:29-34.         [ Links ]

McAfee AJ, McSorley EM, Cuskelly GJ, Moss BW, Wallace JMW, Bonham MP, Fearon AM. Red meat consumption: An overview of the risks and benefits. Meat Sci. 2010; 84:1-13.         [ Links ]

McFarlane C, Langley B, Thomas M, Hennebry A, Plummer E, Nicholas G, McMahon C, Sharma M, Kambadur R. Proteolytic processing of myostatin is auto-regulated during myogenesis. Dev Biol 2005; 283:58-69.         [ Links ]

McGeehin B, Sheridan JJ, Butler F. Factors affecting the pH decline in lamb after slaughter. Meat Sci 2001; 58:79-84.         [ Links ]

Muchenje V, Dzama K, Chimonyo M, Strydom PE, Hugo A, Raats JG. Some biochemical aspects pertaining to beef eating quality and consumer health: A review. Food Chem 2009; 112:279-89.         [ Links ]

Muela E, Sañudo C, Campo MM, Medel I, Beltrán JA. Effects of cooling temperature and hot carcass weight on the quality of lamb. Meat Sci 2010; 84:101-7.         [ Links ]

Navajas EA, Lambe NR, Fisher AV, Nute GR, Bünger L, Simm G. Muscularity and eating quality of lambs: Effects of breed, sex and selection of sires using muscularity measurements by computed tomography. Meat Sci 2008; 79:105-12.         [ Links ]

Okeudo NJ, Moss BW. Production performance and meat quality characteristics of sheep comprising four sex-types over a range of slaughter weights produced following commercial practice. Meat Sci 2008; 80:522-8.         [ Links ]

Osório JCS, Osório MTM, Silva Sobrinho AG. Avaliação instrumental da carne ovina. In: Silva Sobrinho AG, Sanudo C, Osório JCS, Arribas MMC, Osório MTM. Produção de carne ovina. Jaboticabal: Funep 2008, p.129-76.         [ Links ]

Osório JCS, Osório MTM, Sañudo C. Características sensoriais da carne ovina. R Bras Zootec 2009; 38:292-300.         [ Links ]

Peña F, Cano T, Domenech V, Alcalde M, Martos J, García- Martinez A, Herrera, Rodero ME. Influence of sex, slaughter weight and carcass weight on ''non-carcass'' and carcass quality in segureña lambs. Small Ruminant Res 2005; 60:247-54.         [ Links ]

Pérez P, Maino M, Morales MS, Köbrich C, Bardon C, Pokniak J. Gender and slaughter weight effects on carcass quality traits of suckling lambs from four different genotypes. Small Ruminant Res 2007; 70:124-30.         [ Links ]

Pinheiro RSB, Silva Sobrinho AG, Souza HBA, Yamamoto SM. Qualidade de carnes provenientes de cortes da carcaça de cordeiros e de ovinos adultos. Rev Bras Zootec 2009; 38:1790-6.         [ Links ]

Pösö AR, Puolanne, E. Carbohydrate metabolism in meat animals. Meat Sci 2005; 70:423-34.         [ Links ]

Purslow PP. Intramuscular connective tissue and its role in meat quality. Meat Sci 2005; 70:435-47.         [ Links ]

Raes K, Balcean A, Dirink P, Winne AD, Clayes E, Demeyer D, Smet SD. Meat quality, fatty acid composition and flavour analysis in Belgian retail beef. Meat Sci 2003; 65:1237-46.         [ Links ]

Ramos EM, Gomide LAM. Avaliação da qualidade de carne: fundamentos e metodologias. 1st ed. Viçosa-MG:Editora UFV, 2007.         [ Links ]

Rodríguez AB, Landa R, Bodas R, Prieto N, Mantecón AR, Giráldez FJ. Carcass and meat quality of Assaf milk fed lambs: Effect of rearing system and sex. Meat Sci 2008; 80:225-30.         [ Links ]

Russo C, Preziuso G, Verita P. EU carcass classification system: carcass and meat quality in light lambs. Meat Sci 2003; 64:411-6.         [ Links ]

Ryu YC, Lee MH, Lee SK, Kim BC. Effect of muscle mass and fiber type composition of longissimus dorsi muscle on postmortem metabolic rate and meat quality in pigs. J Muscle Foods 2006; 17:343-53.         [ Links ]

Santos VAC, Silva SR, Mena EG, Azevedo JMT. Live weight and sex effects on carcass and meat quality of ''Borrego terrincho– PDO'' suckling lambs. Meat Sci 2007; 77:654-61.         [ Links ]

Sañudo C, Arribas MMC, Silva Sobrinho AG. Qualidade da carcaça e da carne ovina e seus fatores determinantes. In: Silva Sobrinho, A. G., Sanudo, C., Osório, J. C. S., Arribas, M. M. C., Osório, M. T. M. Produção de carne ovina. Jaboticabal: Funep, 2008, p.171-228.         [ Links ]

Sazili AQ, Parr T, Sensky PL, Jones SW, Bardsley RG, Buttery PJ. The relationship between slow and fast myosin heavy chain content, calpastatin, and meat tenderness in different ovine skeletal muscles. Meat Sci 2005; 69:17-25.         [ Links ]

Silva Sobrinho AG, Purchas RW, Kadim IT. Características de qualidade da carne de ovinos de diferentes genótipos e idades ao abate. Rev Bras Zootec 2005; 34:1070-8.         [ Links ]

Sosnicki AA, Newma S. The support of meat value chains by genetic technologies. Meat Sci 2010; 86:129-37.         [ Links ]

Teixeira A, Batista S, Delfa R. Lamb meat quality of two breeds with protected origin designation. Influence of breed, sex and live weight. Meat Sci 2005; 71:530-6.         [ Links ]

Tejeda JF, Peña RE, Andrés AI. Effect of live weight and sex on physico-chemical and sensorial characteristics of Merino lamb meat. Meat Sci 2008; 80:1061-7.         [ Links ]

Thompson JM, Perry D, Daly B, Gardner GE, Johnston DJ, Pethick DW. Genetic and environmental effects on the muscle structure response post-mortem. Meat Sci 2006; 74:59-65.         [ Links ]

Tschirhart Hoelscher TE, Baird BE, King DA, McKenna DR, Savell JW. Physical, chemical, and histological characteristics of 18 lamb muscles. Meat Sci 2006; 73:48-54.         [ Links ]

Vacca GM, Carcangiu V, Dettori ML, Pazzola M, Mura MC, Luridiana S, Tilloca G. Productive performance and meat quality of Mouflon x Sarda and Sarda x Sarda suckling lambs. Meat Sci 2008; 80:326-34.         [ Links ]

Warner RD, Greenwood PL, Pethick DW, Ferguson DM. Genetic and environmental effects on meat quality. Meat Sci 2010; 86:171-83.         [ Links ]

Webb EC, Casey NH, Simela L. Goat meat quality. Small Ruminant Res 2005; 60:153-66.         [ Links ]

Wood JD, Enser M, Fisher AV, Nute GR, Sheard PR, Richardson RI, Hughes SI, Whittington FM. Fat deposition, fatty acid composition and meat quality: a review. Meat Sci 2008; 78, 343-58.         [ Links ]