Carcass Characteristics and Chemical Composition of the Longissimus Muscle of Nellore , Caracu and Holstein-friesian Bulls Finished in a Feedlot

This work was carried out to study the carcass characteristics, the chemical composition and the fatty acid profile in Longissimus muscle (LM) of bull breeds Nellore, NEL (11), Caracu, CAR (12) and Holstein-Friesian, HFR (12) finished in a feedlot. The bulls were fed twice a day with corn silage, cotton meal, cracked corn, urea, limestone and mineral salt. NEL and CAR bulls had similar (p>0.05) final weight and hot carcass weight. However, NEL and CAR bulls had higher (p<0.05) final weight and hot carcass weight than HFR bulls. Carcass hot dressing, carcass conformation, cushion thickness, Longissimus muscle area and texture were similar (p>0.05) among NEL, CAR and HFR bulls. NEL and HFR bulls had higher (p<0.05) carcass length in comparison to the CAR breed. Nellore breed had higher (p<0.05) leg length in comparison to CAR and HFR breeds. Leg length was similar (p>0.05) between CAR and HFR breeds. Thickness fat, color and marbling score were lower (p<0.05) in NEL breed in comparison to CAR and HFR breeds. LM of NEL bulls had higher (p<0.05) meat moisture content in comparison to CAR and HFR bulls. In contrast, lipid content was lower (p<0.10) in HFR bulls. LM ash and crude protein contents were similar (p>0.05) among breeds. Saturated fatty acids (SFA) were higher (p<0.10) in HFR animals. Monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), n-6, n-3 and PUFA/SFA ratio were similar (p>0.05) among the different breeds. N-6/n-3 ratio was higher (p<0.05) in CAR animals. (


INTRODUCTION
Brazil has the biggest commercial cattle herd in the world, with approximately 159 million animals and a production of approximately 8.2 millions tons of carcass each year (Anualpec, 2007).Brazil has the great potential to become the highest bovine meat producer and exporter, but, to achieve such position, it is extremely important to control the quality of the commercialized product.
Beef has an excellent nutritional quality because it has proteins of high biological value, it is rich in vitamin contents, especially B-complex, and it is associated to a high mineral content, especially iron, in high bioavailability form (Saucier, 1999).Beef contains all the amino acids in about the right proportions required by humans (Pensel, 1998).
However, beef is considered one of the factors that may lead to the development of human cardiovascular diseases, obesity, hypertension, and cancer, especially due to the presence of saturated fat and cholesterol.Low presence fat contents (less than 5% relative to muscle, Moreira et al., 2003;Prado et al., 2008a;b;c;d) and low cholesterol contents (less than 50 mg/100 g in the muscle) have been observed in beef chemical analyses, ranging from one third to one half of the daily recommended cholesterol intake (Greghi et al., 2003;Padre et al., 2006;Macedo et al., 2007;Padre et al., 2007;Aricetti et al., 2008;Kazama et al., 2008;Prado et al., 2008a;b;c;d;Maggioni et al., 2009).
Breed of cattle is one of the most important factors for fat deposition and composition that needs to be understood because of its genetic transmission.However, the detailed mechanisms of the variation, and whether or how they can be manipulated are not clearly known.British breeds are well-known for their highly marbled meat while the Zebu and Holstein-Friesian breeds contains less fat and more connective tissue (Moreira et al., 2003).In the warm region of the Brazil, adapted breeds of cattle are primarily limited to Bos indicus cattle bred with Brazilian Nellore.
Caracu is a tropically adopted, criollo beef breed to Brazil.Few studies have investigated the meat characteristics of Caracu but focused more on reproductive and performance (Perotto et al., 2000;Gesualdi Jr et al., 2006).Marbling and fatty acid composition of Caracu cattle, especially as compared to other pure breeds and crossbreeding remain few studied.Caracu is a breed with European origin (Bos taurus Taurus, Aquitaine) and it was brought by the initial colonizers.
Beef normally has a low PUFA/SFA ratio compared with pork because of the biohydrogenation of unsaturated fatty acids in rumen (Tamminga et al., 1991).Enser et al. (1996) found that for steaks and chops the mean P/S ratio is 0.11 and 0.58 for beef and pork respectively and is more favorable for pork.However, these mean values may vary largely depending on genetic and feeding factors and should thus not be generalized (Webb, 2006).
This work was carried out to study the carcass characteristics, the chemical composition and the fatty acid profile in Longissimus muscle (LM) of bulls breeds Nellore (11), Caracu (12) and Holstein-Friesian (12) finished in feedlot.

Animal management and sampling
The State University of Maringa animal care and use committee approved the use of animals in this study (CIOMS/OMS, 1985).
This study was carried out at Experimental Farm of Agronomic Institute of Paraná, south Brazil.Thirty five (11 Nellore, 12 Caracu and 12 Holstein-Friesian) bulls with an initial average of 22 months old were used.The meat analyzes were carried out at Chemical Laboratory of State University of Maringa.
After weaning (8 mo old), each breed was kept in a fenced pasture Braquiaria gras (Brachiaria decumbens Stapf) until 18 mo old when they were fed in feedlot.The animals were kept in an exclusive pasture system together from 8 to 18 months old.After 18 months on pasture, they were divided in three breeds groups: NEL, CAR and HFR.The animals were kept separate in individual pen (5 m 2 each animal) for 4 months.The animals were fed twice a day.They were given access to a diet formulated to meet requirements for fattening beef cattle (NRC, 1996).The diet consisted of 50% silage corn, 20% cracked corn, 13% cotton meal, 15% corn germen, 1.0% urea, 0.5% limestone, and 0.5% mineral salt.The animals were weighed in the beginning of feed-lot and each 28 days, and on the day before slaughter after 12-h fasting.

Carcass characteristics
The animals were slaughtered at a commercial slaughterhouse 90 km away from the Experimental Farm of Agronomic Institute of Paraná with the same age (22 months), according to industrial practice in Brazil.After slaughter, the carcass were identified and cooled for 24 h at 4°C.The animals were selected for slaughtered by body weight, according to Brazilian market.
Hot carcass weight (HCW) : It was determined before cooling.
Carcass dressing (CAD) : For an individual animal is defined as hot carcass weight divided by live weight.
Carcass conformation (CAC) : It was evaluated by Müller's point scale (Müller, 1980) in which the highest value indicates the best conformation.The carcass conformation were reported as superior, very good, good, regular, poor, and inferior; ratings may also be reported as plus, mid, and minus.The carcass length was evaluated by measurements taken from the border of the pubis bone until the anterior side of the first rib (Table 1).
Carcass length (CAL) : It is the distance since the anterior board of bone of pubis into the previous side of first rib, measure with a ribbon or a tape line.
Leg length (LEL) : It was evaluated using a wood compass with metallic edges that measures the distance from the anterior border of the pubis bone to a middle point at the tarsus bone.
Cushion thickness (CUT) : It was taken by a wood compass with metallic edges that measures the distance between the lateral face and the median at the superior part of the cushion.The cushion is flat muscle (Biceps femoris).
Fat thickness (FAT) : It was taken by a caliper averaging three points between the 12 th and the 13 th rib but over the LM.
Longissimus muscle area (LMA) : Longissimus area was measured by a tracing made on the right side of carcass, where is made a transversal cut between the 12ª and 13ª ribs, exposing the Longissimus muscle.After this, a compensating planimeter, which is an instrument that measures area of irregularly shaped objects, was used to determine the area.
Color (COL) : Muscle color after 24 h carcass cooling was analyzed.Coloration was evaluated according to a point scale (Table 2) 30 min after a transversal section was made on the Longissimus between the 12 th and 13 th ribs.
Texture (TEX) : Texture was determined through the size of the fascicle (muscle "grain" size) and evaluated subjectively with a point scale (Table 2).
Marbling (MAR) : Intramuscular fat was measured in LM between the 12 th and 13 th ribs according to the scores in Table 3.
After 24 h LM samples (300 g) were taken by complete cross-section between the 12 th and 13 th ribs and were immediately taken to the laboratory.Cover fat was discarded and the muscle portion was frozen at -20°C for later analysis.

Chemical composition
Laboratory analyses of beef were carried out two months after sampling.The samples were thawed at room temperature (20°C), ground, homogenized, and analyzed in triplicate.
Beef moisture and ash percentage were determined according to AOAC (Cunnif, 1998).Crude protein content was obtained through Kjeldahl method (Cunnif, 1998).Total lipids were extracted by the Bligh and Dyer method (1959) with a chloroform/methanol mixture.Fatty acid methyl esters (FAME) were prepared by methylation of fatty acids according to ISO method (1978).
Cholesterol analysis was carried out by the method modified by Rowe (1999).A 60% (w/v) solution of potassium hydroxide was added to the samples in quantities equivalent to 2 ml/h of sample under 1-h reflux.The residue was dissolved again in 2 ml hexane containing 0.2 mg/ml 5-α cholestane internal standard (IS) (Sigma, EUA).

Chromatographic analysis and cholesterol quantification
Cholesterol content was analyzed in a 14-A gas chromatograph (Shimadzu, Japan), equipped with a flame ionization detector and a fused silica capillary column (25 m long, 0.25-mm internal diameter, and 0.20 μm Ohio Valley-30).Injector, column, and detector temperatures were 260, 280, and 280°C, respectively.Ultra-pure gas fluxes (White Martins) of 1.5 ml/min H 2 as carrier gas, 30 ml/min N 2 as make-up gas, 300 ml/min synthetic gas, and 30 ml/min N 2 for flame were used.The sample injection split mode was: 1:150.Peak integration was carried out with CG-300 computing integrator (CG Instruments, Brazil) and cholesterol was identified by comparison with standards from Sigma (EUA).Sample cholesterol quantification was carried out after verification of the method linearity.Standard cholesterol solutions (Sigma, USA) were prepared with concentrations 0.0; 0.4; 0.8; 1.6, and 2.0 mg/ml, all containing 0.20 mg/ml 5-α cholestane (Sigma, USA), and analyzed.The ratio of the areas of cholesterol and 5-α cholestane was plotted against the cholesterol concentration for injected volumes of 0.0; 2.0; 3.0; 4.0, and 5.0 μl.The curve obtained was used for cholesterol analysis in mg/100 g (Rowe et al., 1999;Milinsk et al., 2005).

Analysis of fatty acid methyl esters
The fatty acids methyl esters (FAMEs) were analyzed in a gas chromatograph (Varian, USA) equipped with a flame ionization detector and a fused silica capillary column CP-7420 (100 m, 0.25 mm and 0.39 μm o.d., Varian, USA) Select Fame.Column temperature was programmed at 165°C for 18 min, 180°C (30°C/min) for 22 min, and 240°C (15°C/min) for 30 min, with 45-psi pressure.The injector and detector were kept at 220°C and 245°C, respectively.The gas fluxes (White Martins) used was: 1.4 ml/min for the carrier gas (H 2 ); 30 ml/min for the make-up gas (N 2 ) and 30 ml/min and 300 ml/min for H 2 and the synthetic flame gas, respectively.Sample injection split mode was 1/80.Fatty acids were identified by comparing the relative retention times of FAME peaks of the samples with fatty acids methyl esters standards from Sigma (USA) by spiking samples with standard.The peak areas were determined by  Star software (Varian).The data were expressed as percentages of the normalized area of total fatty acids.

Experiment design and statistical analysis
The experimental design consisted of 3 treatments: 11 NEL, 12 CAR and 12 HFR bulls.The data were submitted to an analysis of variance, and the averages (when different) were compared using the Tukey test at 10, 5 and 1% significance levels, using SAS statistical software (2000).

Carcass characteristics
Table 4 shows the carcass characteristics of NEL, CAR and HFR bulls finished in feedlot.NEL and CAR bulls had similar (p>0.05)final weight (FWE) and hot carcass weight (HCW), which were greater (p<0.05)than the FWE and HCW of HFR bulls.The higher FWE and HCW observed to NEL and CAR breeds is due the higher average day gain during of the life (Perotto et al., 2000).The higher FWE observed to NEL and CAR breeds is due their ability to production of meat.In the other hand, animals HFR have higher ability to production of milk, as they have lower average daily gain.
NEL and HFR breeds were longer (p<0.05)leg length (LEL) in comparison to that CAR breed, but the LEL was similar (p>0.05) between NEL and HFR breeds (Table 3).The lower leg length for CAR breed is due the selection work that animals were submitted for many years (selection for major muscle and fatty deposition in the body).
NEL breed was higher (p<0.01)carcass length (CAL) in comparison to that of CAR and HFR breeds.CAL was similar (p>0.01) between CAR and HFR breeds.The zebu breeds has major development of the carcass than the British and Caracu breeds, because the Zebus breeds had a selection for the animals may walk along in the tropical region looking for pasture.
On the contrary, fat thickness (FAT), color (COL) and marbling (MAR) score were lower (p<0.05) in NEL breed in comparison to that CAR and HFR breeds.Zebu breed was known for low fat deposition.The Nellore's muscle is considered leaner than others breeds because this animal has less marbling (Moreira et al., 2003) so presents less risk to human (Saucier, 1999).The result of marbling score can be due fat deposition.

Chemical composition
Table 5 shows the chemical composition results of Longissimus muscle (LM) of NEL, CAR and HFR bulls.NEL bulls LM had higher (p<0.05)moisture contents in comparison to that of CAR and HFR bulls, but the moisture contents between CAR and HFR was similar (p>0.05).Meat moisture content is inversely related to its lipid content because the fat has low water content.
The ash content and crude protein content were similar (p>0.05)among breeds.The protein and ashes contents change very little in Longissimus muscle of cattle finished in feedlot (Greghi et al., 2003;Abrahão et al., 2005).
Total lipids was higher (p<0.10) in CAR breed in comparison to HFR breed and NEL breed (Table 5).Total lipids were lower (p<0.10) in HFR breed.
The animals HFR show low lipids contents because this animals did not select to fat deposition (Greghi et al., 2003).In the other hand, animals as NEL and CAR that were selected for meat production show the high muscle and fat deposition (Abrahão et al., 2005).
LM cholesterol content was lower (p<0.01) in CAR breed (34.1 mg/100 g muscle) to that HFR breed (55.3 mg/100 g muscle).LM cholesterol content in NEL (44.1 mg/100 g muscle) was similar (p>0.01) in comparison to that CAR and HFR.These values can be considered low in comparison to cholesterol levels cited in literature (Greghi et al., 2003;Moreira et al., 2003;Padre et al., 2006).
The variations observed among treatments can be explained by the age (22 months old).
However, the cholesterol content observed was 44.5 mg/100 g of muscle less than 50.0 mg/100 g of muscle have been reported in literature as been badly for human health (Saucier, 1999).

Fatty acid profile
The proportion of fatty acids in LM intramuscular fat is shown in Table 6.On the contrary observed in pork (Enser et al., 1996) the fatty acid composition in cattle change little in function with the diet (Greghi et al., 2003;Abrahão et al., 2005;Padre et al., 2007;Aricetti et al., 2008;Macedo et al., 2008;Prado et al., 2008a;b;c;d).Fatty acids diversity in cattle is partly explained by the biohidrogenation that occurs in the rumen (Tamminga et al., 1991).
The miristic acid (C 14:0), (C 14:1 n-7) and docosahexaenoic acid (C 22:6 n-3) content were higher (p<0.05) in the NEL and CAR breeds.On the contrary, the arachidonic acid (C 20:4 n-6) was lower (p<0.05) in the The anti-iso (C 17:0) and cis-vaccenic acid (C 18:1 n-7) content was higher (p<0.01) in NEL and HFR breeds.This fatty acid is an important intermediate produced by microorganisms in the rumen.After it is absorption, this acid can be transformed into CLA (C 18:2 c-9, t-11rumenic acid) in the tissue of ruminants (Bauman et al., 1999).The CLA content was higher (p<0.10) in NEL and HFR breeds.
As ruminant diets contain low fat concentration, the majority the adipose tissue is synthesized from lipogenisis.Fatty acids are elongated up to C 18:0 and are converted into C 18:1 by desaturation (Rule et al., 1997).As the adipose tissue increases, the deposition of C 18:1 content increases also and of C 18:0 content is reduced.
Oleic acid increases human HDL-cholesterol (High Density Lipoprotein) and decreases LDL-cholesterol (Low Density Lipoprotein) concentrations in blood (Katan et al., 1994).Studies have demonstrated a strong relationship between LDL-cholesterol levels and human cardiovascular diseases and that HDL-cholesterol has an inverse relation with the risk of cardiovascular diseases (Kwiterovich, 1997).
Saturated fatty acids (SFA) content was similar (p<0.10) in CAR and in HFR breeds.However, SFA content was lower (p<0.10) in NEL to than HFR breed (Table 7).
Although the animal diet contained high levels of PUFA, the meat presents high values of SFA due to biohydrogenation in the rumen.PUFA/SFA fatty acids have important roles in reducing the risk of coronary heart disease; however, the optimal balance between these two classes of fatty acids is still a matter of debate (Hu, 2001).
The n-6/n-3 ratio was higher (p<0.05) in CAR breed in comparison the NEL and HFR breeds.Nevertheless, did not have difference (p>0.05) between NEL and HFR.The n-6/n-3 ratio must be 4 to 10.In this manner, all the breeds showed very great ratio for quality food to human health.

IMPLICATIONS
The animal's genetic status has influence on carcass characteristics, chemical composition and fatty acid profile.However, the carcass characteristics change show magnitude little to meat quality.

Table 2 .
Scale of points for meat texture and color evaluation

Table 4 .
Means (±SE)showing the effect of breed on carcass characteristics of bulls finished in a feedlot Nellore. 2 Caracu. 3Holtein-Friesian.NS = No significant difference among means.Means with different letters, in the same line, are different by Tukey test. 1

Table 5 .
Means (±SE)showing the effect of breed on chemical composition in Longissimus muscle of bulls finished in a feedlot

Table 6 .
Means (±SE)showing the effect of breed on fatty acids profile (% of total of fatty acids) of Longissimus muscle of bulls finished in a feedlot

Table 7 .
Means (±SE)showing the effect of breed on saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, n-6, n 3, PUFA/SFA and n-6/n-3 ratio of Longissimus muscle of bulls finished in a feedlot