Performance, Carcass Traits and Quality of Longissimus lumborum muscle of Santa Inês lambs

Corresponding Author: Fabio Borba Ferrari Department of Technology, São Paulo State UniversityUNESP, Jaboticabal, São Paulo, Brazil Email: fbf_zoo@hotmail.com Abstract: The aim of this research was to evaluate carcass traits and meat quality of finishing lambs in pastures with different leaf area index with or without high protein-mineral supplementation. In this study, forty-eight young Santa Inês rams were used, with an average initial body weight of 13.5 kg and an average age of 4 months. For approximately 10 h a day, the animals had access to pastures comprised of Cynodon spp cultivar Tifton 85. In vivo measurements, including body length, anterior and posterior heights, chest perimeter, rump and thoracic widths, were evaluated. Based on the data in this study, providing supplements for sheep improved the carcass composition as increased hot carcass weight, cold carcass weight, empty body weight, carcass yield, external and internal carcass lengths and thoracic depth. Moreover, supplementation increased slaughter weight, which accounts for the largest portion of the producer’s profitability. Although the use of supplements increases production costs, it also improved quantitative and qualitative characteristics of the meat, which could satisfy the consumer market. The meat from supplemented animals had a lower atherogenicity index compared to the control suggesting the meat from supplemented lambs is healthier to be consumed.


Introduction
The largest share of sheep meat consumers looks for a product derived from young animals, five to six months of age, with carcasses weighing from 13 to 15 kg. A high proportion of muscle and uniform fat coverage is desired which is obtained from the slaughter of animals with 30 to 35 kg body weight (Lage, 2009).
Because of its high-speed growth, the lamb is the animal model that has the greatest production efficiency, resulting in improved carcass dressing and meat quality (Pires et al., 2000). This model, generally associated with feedlot systems, allows maximum weight gain potential during the young age phase. However, the finish lambs utilizing a feedlot can sometimes be a less economical practice because of feed prices, which can represent about 70% of total production costs (Barros, 2013). Therefore, finishing sheep on pasture, combined with the use of multiple supplements, provides satisfactory body weight gains with lower costs.
Pasture management, associated with supplementation strategies, increases animal performance and can reduce the slaughter age, producing younger animals with more desirable meat characteristics.
Grazing time and ingestion rate influence forage intake by grazing animals, which varies depending on the bite size and the bite rate. These two variables are highly correlated with the canopy structure. Larger canopy structure negatively affects intake by the animals, due to the lower availability of leaves in the upper layers. This also decreases bite size due to the increased difficulty of gripping forages with longer stems. Forage intake can also be affected by canopy density, both by vertical and horizontal distribution, as well as by tiller and leaf population density. Forage intake is negatively affected by lower population density of tillers, which directly compromises the size of the bite and is not compensated by an increase in bite rate, therefore reducing intake (Ungar and Noy-Meir, 1988). The individual size of the tillers also negatively affects the bite size, due to the higher proportion of support tissues that the animals avoid while grazing (Flores et al., 1993). Additionally, low leaf density also negatively affects bite size due to the low bite depth (Laca et al., 1992).
The finishing of lambs in Tifton 85 pastures, supplemented with concentrate up to 2% of the body weight on a dry matter basis, improved productive performance and carcass characteristics, providing greater slaughter and warm carcass weights of Santa Inês lambs, as supplementation increased (Carvalho et al., 2007).
Disease, genetics, gender, age, innervation, location, type of muscle, exercise and diet can influence the nature of muscle fibers (Stockdale, 1992;Ono et al., 1993;Macedo et al., 2000;Vestergaard et al., 2000). The pH, color, tenderness and water holding capacity can improve the quality of housing, according to the proportion between the types of muscle fibers (Klont et al., 1998). These factors have more influence in muscle transformation post mortem, suggesting the importance in this study of characteristics and types of muscle fibers in the meat of sheep (Sazili et al., 2005).
Thus, the objective of this research was to evaluate how supplementation and the residual leaf area index can modify or improve the carcass traits and meat quality of lambs.

Experimental Area
Animals were reared and harvested from October 2011 to March 2012 in the Forage Sector at São Paulo State University -FCAV/UNESP, Campus Jaboticabal, São Paulo, Brazil. The physical and chemical analyses were performed at São Paulo State University at the Laboratory of Technology of Animal Products and the classification of Longissimus lumborum muscle fibers were conducted at the Laboratory of Histology and Embryology, Department of Animal Morphology. The Ethics Committee for the Use of Animals from São Paulo State University (Jaboticabal, São Paulo, Brazil) approved and reviewed the trial by protocol number 004633/13.

Animals and Treatments
The trial was performed using forty-eight, 120 day old, uncastrated, Santa Inês rams, with an initial body weight of 15 kg. Thirty-two pastures were used (100 m²) which were enclosed and divided by a fence a 1.20 m tall electric fence (5.000 v) with four strands of wire. To protect the animals in the hottest hours of the day mobile shades were placed in the pastures. From 6:00 am to 4:00 pm, all the animals remained in 32 pastures with Tifton-85 (Cynodon spp.), with different residual leaf area index. The pasture management utilized was rotational stocking. The regrowth period varied according to canopy Light Interception (LI). To achieve the desired residual leaf area index (rLAI) over four grazing days, some regulator animals were added.
The chemical composition of Tifton-85 pastures, expressed on a dry matter basis, is presented in Table 1.
The four grazing intensity treatments consisted of rLAI of 0.8, 1.4, 2.0 and 2.6. The animals were transferred to the pasture when 95% Light Interception (LI) had been reached during the resting period and the defined rLAI was observed. The rLAI was measured daily on each pasture.
The analyzer equipment, AccuPAR LP-80 (Decagon Devices, Inc., Pullman, WA, USA) consisting of a bar with light sensors that capture the radiation (at a frequency of 400-700 nm) either above the canopy or on the ground level, was used to determine LAI and the LI. The LI monitoring of the canopy was carried out at the time of removal of the animals from pastures and during the pasture regrowth. The LI measurements were performed weekly until the LI value was close to 95% and then on a daily basis until LI reached 95%. The LAI was monitored daily at the time of entry for animals in pastures (pre-grazing) and during grazing. As rLAI was reached the animals were led to another pasture that had reached the LI target of 95% of during the rest period.
The supplemented animals (24 animals) were kept in individual stalls, receiving 0.7% of body weight of a high protein-energy supplement (Table 2), after 4:00 pm.
The animals were weighed weekly and the color of the conjunctiva of the eye mucosa was monitored by the Famacha® method (Molento et al., 2004).
The twenty-four supplemented animals were allocated to sixteen pastures with different residual leaf area index (0.8, 1.4, 2.0 and 2.6) and the other twentyfour animals from the control group were allocated with the same conditions. There were four pastures per treatment with six animals per pasture. In this trial, the treatments were a cross factorial between rLAI (0.8, 1.4, 2.0 and 2.6) and supplemented or not, totalizing 8 treatments. The slaughter criteria was the age of the animals.
The chemical composition analyzes were performed according to (AOAC, 1990) based on the dry matter as Crude Protein (CP), Neutral Detergent Fiber (NDF) and acid detergent fiber (ADF; Senger et al., 2008) and Lignin (LIG; Silva and Queiroz, 2002). The In Vitro Dry Matter Digestibility (IVDMD) was determined using the method described by (Tilley and Terry, 1963) adapted by (Holden, 1999). Table 3 presents the total forage mass, morphological components, chemical composition and in vitro dry matter digestibility, in pre-and post-grazing of Tifton 85 grasslands managed under four rLAI.

Slaughter, in Vivo and Carcass Traits
The animals were weighed after being fasted for 16 h. Prior to slaughter, the lambs were weighed again to obtain Final Body Weight (FBW) and the biometric measurements were carried out with the animals standing on a flat surface. The Body length (distance between the cervico-thoracic joint and the base of the tail), anterior height (distance between the withers and the distal end of the forelimb), posterior height (distance between the sacral tuberosity and distal end of the hindlimb), chest perimeter (perimeter based on the sternum and withers, passing the tape behind the shoulder), rump width (maximum distance between the trochanter of the femur), chest width (distance between the side faces of the scapularhumeral joint) and body compactness (body weight at slaughter divided by the body length of the animal).
After fasting, weighing and measurements, the animals were electrically stunned (220V for 8 sec) and bled according to the humane slaughter procedures (Monteiro et al., 2000). The carcasses were divided longitudinally and the left half-carcass sectioned in five anatomical regions: neck, shoulder, rib, loin and leg to obtain yield of cuts relative to the half-carcass weight, (Colomer-Rocher et al., 1998).

Qualitative Muscle Traits
The color traits were determined using a portable Minolta CR-400 colorimeter (Konica Minolta Sensing Inc., Osaka, Japan; diffuse illumination/0º angle of viewing, illuminant D65). The measures were performed in three different positions of the longissimus lumborum muscle after deboning. This device gauges the changes of lightness (L*), intensity of red (a*) and yellow (b*), according to CIELab scale. Three measures were made in different places of the surface.
The fat color was taken at one point on the external fat coverage of the ribeye region located in the portion between the 11th and 12th ribs.
The meat pH was determined in triplicate using a digital pH meter (Testo® brand, model 230, Testo Inc., Sparta, NJ, USA), equipped with a glass penetration electrode for direct measurement from within the samples. The final pH value was considered as the average of all measures taken in the sample.
The Water Holding Capacity (WHC) was determined by the method proposed by (Hamm, 1977). The cooking loss was determined by the method proposed by (Wheeler et al., 1990). The Shear Force (SF) was determined by the method proposed by (Wheeler et al., 1990), using a texturometer (Texture Analyzer TA, XT2i) coupled to a Warner-Bratzler blade that was 1.016 mm thick. The results were expressed in Newton (N). Analyses of chemical composition comprising protein, ether extract, moisture and ash were performed according to (AOAC, 1995).
The total collagen was quantified by determining the amino acid hydroxyproline according to the methodology proposed by (AOAC, 1995).

Muscle Fibre Structure Analysis
The identification of fiber types was determined by the method proposed by (Dubowitz and Brooke, 1973).
The classification of muscle fibers was obtained by the techniques and it was possible to distinguish three types of muscle fibers and rank them by Slow Oxidative (SO), Fast Oxidative Glycolytic (FOG) and Fast Glycolytic (FG) using the color as a parameter, shown in Table 4.

Statistical Analysis
Data were analyzed by analysis of variance, using the Mixed procedure of SAS (2002), with statistical models that included the fixed effects of Leaf Area Index (LAI) (0.8; 1.4; 2.0; 2.8) and supplemented or not (zero and 0.7%). For significant effects, the means were compared using a Tukey test at 5% significance.

Results and Discussion
Tables 5 and 6 present the in vivo characteristics and lamb carcass measurements finished at different leaf area index LAI, with or without supplementation.
There was no significant effect (p≥0.05) of LAI on the quantitative in vivo characteristics. However, supplementation increased EBW, chest circumference and width compared to the control group (p≤0.05). The EBW were 22.65 and 18.53 kg, for the supplemented and control group animals, respectively. These results can be explained by greater daily energy intake in the diet of the supplemented lambs, compared to those kept in pasture without supplementation, providing greater weight gain and final slaughter weight (Carvalho et al., 2007). In this study, the supplemented animals consumed about 7% more TDN (Total Digestible Nutrients) than the control group, contributing to improved performance of supplemented animals.
Despite the additional costs, supplementation is one of the alternatives to improve production indices, which ensures the animal better physiological conditions to combat the adversities that may occur during animal production, thus contributing to obtaining younger animals for slaughter. This fact, can be explained by the trial performed by (Silva, 2014). In this trial, the authors observed 9.5% increase in daily average gain, 21% in average gain per area. Thus, the supplementation is a strategic way to increase the profitability of the property and shorten the production cycle with low investment.
Evaluating the effects of supplementation, it was observed that the supplemented animals had greater hot carcass weight, cold carcass weight and empty body weight compared to control group animals (p<0.05). There was no effect of LAI on quantitative carcass characteristics. The greater carcass weight can be considered as a consequence of the greater slaughter weight and the empty body weight due to the lower amount of gastrointestinal content. According to (Martinez et al., 2001), carcass dressing depends mainly on the digestive tract content and fat deposition degree.
Carcass Dressing (CD) is important information as it represents the profitability of the edible portion and is the main parameter for producer compensation. The mean value for CD in this study was within the standard expected for lambs, ranging from 40 to 50%. This variable is influenced by intrinsic (breed, sex, body condition and weight at slaughter), extrinsic factors (feed management and finishing system) and how it is calculated (Silva Sobrinho, 2001). True carcass dressing considers the weight of the empty gastrointestinal tract, so ranges from 53-56% Yamamoto et al., 2005;Zundt et al., 2006). The results obtained in this study for hot carcass corroborate with the cited authors (between 40 and 50%) and are also close to true values (53%).
In Table 6, the residual leaf area index had no effect on the parameters evaluated, but the supplementation increased depth of the chest and the external and internal carcass lengths. The variable length of the leg was not influenced by LAI or supplementation. This can be explained by the greater slaughter weight of animals receiving supplementation, which is consistent with the study by (Carvalho et al., 2007) that found greater internal carcass lengths in Ile de France × Corriedale animals slaughtered at 32 kg compared to 28 kg.
Forage intake was negatively affected by increases in canopy structure residual Leaf Area Index (rLAI) -0.8 to 2.6). The animals in pastures with greater rLAI (2.6), had greater difficulty in harvesting the leaf forage due to lower availability of leaves in the upper layers, which decreases the size of the bite. With high rLAI the canopy density decreases which decrease the density of tillers and leaves which lead to reduced intake and is not compensated by bite size or bite rate (Ungar and Noy-Meir, 1988). On the other hand, animals in pastures with lower rLAI (0.8), had no difficulty in harvesting the forage. Pastures with rLAI (0.8) have high availability of leaves in the upper layers, high canopy density and population of tillers and leaves. These animals can compensate lower rLAI with large bite size and higher bite rate.
These results are consistent with those found by (Dantas et al., 2008), that studied the carcass characteristics of lambs finished on pasture receiving three supplementation levels in the diet (0.0, 1.0 and 1.5% BW). In their trial, they found longer carcasses for animals supplemented with 1.5% of BW compared to the control group. According to the author, it can be explained by the levels of protein and energy in the diet, resulting in higher deposition of muscle and adipose tissue.
Tables 7 shows the data for the weight (kg) of regional carcass cuts of lambs finished on pasture with different LAI with supplementation or not. Supplementation increased the weight of cuts. This result can be explained by the fact that supplementation provided higher carcass weight, which may be related to the greater amount of muscle tissue in the supplemented treatment, confirming order of priority for tissue deposition; initially depositing bone followed by muscle and lastly, fat (Boggs et al., 1998). Similar results were reported by (Gonzaga Neto et al., 2006), when evaluating different concentrate levels (Silva Sobrinho, 2001;Ulbricht and Southgate, 1991 and 60%) in the diets of lambs, where the authors observed a linear effect for weight of cuts as the concentrate inclusion increased in the diet. The differences obtained for cuts between treatments reflect, mainly, the increased growth of muscles for the supplemented animals.
Pointed out that animals slaughtered at heavier weights have heavier cuts than lighter animals, indicating increased deposition of muscle and adipose tissue, probably as a result of increased supply of nutrients. However, there were no effects of LAI on the weight of cuts (Silva Sobrinho, 2001).
The parameters of chemical composition were conducted on the Longissimus lumborum muscle of supplemented lambs finished in different LAI (Table 8)        The chemical composition of lamb meat presents average values of 75% moisture, 19% protein, 4% fat, 1.1% mineral matter and less than 1% of carbohydrates. Except for the ether extract values, other values obtained in this study were similar to those cited by the author (Prata, 1999). The ether extract content of lamb meat has large variation, mainly due to the diet, weight and age at slaughter, breed, sex and muscle deposition (Madruga et al., 2005).
The chemical composition of meat can be influenced by different factors such as breed, sex, nutrition and slaughter weight. Gaili et al. (1972) studied the Longissimus lumborum muscle of goats and lambs, slaughtered at different ages and observed that younger animals had higher protein, ash and fat content than older animals. Thus, the data obtained in this study can be explained by the young age of slaughter (7-8 months), because the accumulation of subcutaneous and intramuscular fat is lower in young animals (Lawrie, 2005;Zapata et al., 2003). For (Berg and Butterfield, 1976), maturity is reflected by an increase in the proportion of fat, accompanied by a decrease in the proportion of water and protein in the body.
The difference of total cholesterol between the nonsupplemented or supplemented animals, can be explained by the difference in the elongase enzyme activity. The supplemented animals showed lower average activity of the enzyme elongase compared 21 control group animals, 69.69 and 71.17, respectively. This enzyme increases the number of carbons in the carbon chain, participating in the formation of polyunsaturated fatty acids and total cholesterol (Sargent, 1997). Spritz and Misual (1969) reported that diet has more influence on the amount of cholesterol of the meat than breed or genetic group. The amount of cholesterol increases as unsaturated fatty acids decrease.
Atherogenicity index were greater for the control group in comparison to the supplemented animals. This fact makes the meat of these animals more likely to cause problems for human health, increasing the incidence of atheromas or even death. Some trials showed that in meat and dairy products the predominance of saturated fat is associated with increased blood cholesterol, which increases the risk of clogged arteries and may lead to coronary heart disease and even death (Taubes, 2001). Ulbricht and Southgate (1991) proposed that an ideal atherogenicity index would be lower than 1.27. Using this information, the consumption of meat from either supplemented or control group animals would not cause any health problems to the consumer. However, consuming meat from supplemented animals may be healthier considering the lower atherogenicity index.
The average cholesterol levels obtained in this study were lower compared to those obtained by (Rowe et al., 1999), who found values of 62.03 and 57.76 mg/100 g in samples of lamb finished on pasture or confined, respectively. In contrast, Madruga et al. (2005) found cholesterol values closer to those obtained in this study, with 44.10 mg/100 g in meat of Santa Inês lamb finished with 60% roughage diets.
The participation of collagen in meat tenderness is related to the total collagen content and its solubility (Young and Braggins, 1993;Ramos and Gomide, 2005). It can be quantified by hydroxyproline content, which is an amino acid present almost exclusively in collagen and is directly related to the thermal stability (Gaili et al., 1972). Soluble collagen content influences the tenderness of the meat in animals of different ages, while the total content predicts differences in tenderness between muscles (Ramos and Gomide, 2005). With increasing age of the animals, the collagen is modified by number of cross-linkages, making it more resistant to cutting. Animals in this study were a similar age, therefore significant differences in shear force and total collagen content could not be detected. Díaz et al. (2002) evaluated the meat quality of lambs in different production systems and obtained collagen levels higher than those found in this study for animals finished on pasture, 2.47 mg per gram of muscle. Table 9 shows the averages for L*, a*, b*, pH 45 min after slaughter and pH 24 h after slaughter, along with CL, WHC and shear force in the Longissimus lumborum muscle, according to the LAI being supplemented or not. The parameters were not influenced the different treatments.
Faria et al. (2001) described meat trait values from 31.36 to 38.0 for L*, 12.27 to 18.01 for a* and 3.34 to 5.65 for b*. In the present experiment, the values of a* and b* are within these ranges, but the L* values were greater. The results of this study are similar to those found by (Sañudo et al., 1992), who studied the quality of lamb meat with different carcass weights and found means for L* between 45.61 and 48.15, a* between 13.94 and 16.95 and b* between 5.90 and 6.02. According to (Boggs et al., 1998), observing a drop in meat pH suggests that other quality parameters such as WHC, tenderness and color, will present good results, because they are influenced by pH.
The average values of CL were close to those found by (Lloyd et al., 1981) and (Kadim et al., 1993), being 25.95 and 16.12%, respectively. However, these values were lower than 36.48% obtained by (Bonagurio, 2001) in Santa Inês lambs. Rota et al. (2004) reported values above 73%. However, values observed in this study indicate that the meat presented no exudative problems and was within the range considered normal for lambs (Rota et al., 2004).
The values obtained for shear force characterize the meat of the present study as medium softness because according to (Cezar and Sousa, 2004), ovine meat that exhibit SF values lower than 22.26 N; from 22.36 to 35.60 N; from 35.69 N to 53.34 N and above 53.34 N, can be classified as soft, medium soft, hard and extremely hard, respectively. Grazziotin et al. (2002), studied the effect of the pasture availability and breed on carcass and meat characteristics of lambs and found values for shear force between 31.18 and 32.36 N, similar to those obtained in the present experiment.
There was no difference on the frequency in the area (µm²) and total relative area (µm²) for SO, FOG and FG of muscular fibers from lambs submitted to different LAI being supplemented or not. This result shows that diet had no influence on these parameters. The proportion of the types of muscle fibers can be related to meat tenderness. Calkins et al. (1981) found a significant correlation between the oxidative muscle fibers (SO and FOG) and marbling rate, consequently, affecting the tenderness of the meat. Moody et al. (1980) and (Ockerman et al., 1984) found a significant positive correlation between the red fibers (SO and FOG) and the tenderness of the meat. In this study, the tenderness showed a positive and significant correlation (p<0.05) with CL, reflecting the importance of evaluating the qualitative parameters that influence the quality of the meat product. In this study, a low and negative correlation (-0.21) between SF and frequency of FG fiber in longissimus Lumborum muscle of Santa Inês lambs was also observed. It is evident that there are numerous effects that can interfere with tenderness of the longissimus muscle. Among these important effects are antemortem factors (diet and pre-slaughter management) and post-mortem factors (cooling, handling and packaging). Given the above, researchers not only have to take into account breeding systems, but also feed management and all the points that can compromise the quality of the meat. Koohmaraie et al. (2003) reported that if considering the same breed regardless of the species, 30% of the tenderness and or meat quality can be attributed to the genotype of the animal. The other 70% can be attributed to environmental factors that can directly influence the meat quality ultimately consumed by the consumer.

Conclusion
Providing supplements for sheep improves the carcass composition such as hot carcass weight, cold carcass weight, empty body weight, carcass dressing, external and internal carcass lengths and thoracic depth. Additionally, supplementation improves the slaughter weight, which is the most important parameter for the producer's profitability. Although the use of supplements involves the increase of production costs, it provides quantitative and qualitative characteristics favorable to the product, aiming to satisfy the consumer market. The meat from supplemented animals is healthier to be consumed compared to control group animals, due to the low atherogenicity index.