Fatty acid profile and cholesterol and retinol contents in different locations of Celta pig breed

R. Domínguez, S. Martínez, J. Carballo and I. Franco*

Área de Tecnología de los Alimentos, Facultad de Ciencias, Universidad de Vigo, 32004 Ourense, Spain

*Corresponding author: inmatec@uvigo.es

 

SUMMARY

The fatty acid profile (total, neutral and polar lipids) and cholesterol and retinol contents of the intramuscular -Longissimus dorsi (LD) and Psoas major (PM)-, adipose -rump, covering Biceps femoris muscle, ventral and dorsal-, perirenal and hepatic fat of the Celta pig breed (Galicia, northwest Spain) were evaluated. Oleic acid was the most abundant fatty acid, except in the polar lipids of the intramuscular fat, where the most abundant fatty acid was linoleic acid. The fatty acid composition of total and neutral lipids was influenced more by the location than the fatty acids of polar lipids. There were some differences only in minor fatty acids of intramuscular and subcutaneous fat between castrated females and castrated males. The fatty acids of neutral lipids were also more influenced by sex than the fatty acids of polar lipids. The cholesterol and retinol contents showed no significant differences by sex. The LD muscle showed a higher content of intramuscular fat than the PM muscle. The greatest cholesterol values were described in the liver. Subcutaneous locations showed higher cholesterol levels than muscles.

 

RESUMEN

Perfil de ácidos grasos y contenidos de colesterol y retinol en diferentes localizaciones del cerdo de raza Celta. Se estudió el perfil de los ácidos grasos y los contenidos en colesterol y retinol en la grasa intramuscular - Longissimus dorsi (LD) y Psoas mayor (PM) -, subcutánea -grupa, ventral, dorsal y la grasa que rodea al músculo Bíceps femoris -, perirrenal y hepática de cerdos de raza Celta (Galicia, noroeste de España). El ácido oleico fue el ácido graso más importante, excepto en los lípidos polares de la grasa intramuscular, donde el ácido graso más abundante fue el ácido linoleico. La composición de ácidos grasos de los lípidos totales y neutros estuvo más influenciada por la localización grasa que los ácidos grasos de los lípidos polares. Se encontraron ligeras diferencias entre hembras y machos castrados en algunos ácidos grasos minoritarios en la grasa intramuscular y subcutánea. Los ácidos grasos de los lípidos neutros fueron más influenciados por el sexo que los ácidos grasos de los lípidos polares. El contenido en colesterol y retinol no mostró diferencias significativas entre sexos. El músculo LD presentó un mayor contenido de grasa intramuscular que el PM. Los mayores valores de colesterol fueron determinados en el hígado. En las localizaciones subcutáneas los contenidos en colesterol fueron más elevados que en la grasa intramuscular.

 

Submitted: 21 January 2014; Accepted: 28 April 2014

Citation/Cómo citar este artículo: Domínguez R, Martínez S, Carballo J, Franco I. 2014. Fatty acid profile and cholesterol and retinol contents in different locations of Celta pig breed. Grasas Aceites 65 (3): e036. doi: http://dx.doi.org/10.3989/gya.0115141.

KEYWORDS: Celta pig; Cholesterol; Fatty acids; Location; Retinol; Sex

PALABRAS CLAVE: Ácidos grasos; Cerdo Celta; Colesterol; Localización; Retinol; Sexo

Copyright: © 2014 CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial (by-nc) Spain 3.0 Licence.


 

CONTENT

1. INTRODUCTIONTOP

The Celta pig is an autochthonous porcine breed raised traditionally in Galicia (northwest of Spain). Because of their poor growth rate, carcass conformation and crossbreeding between local pigs and improved breeds, the Celta breed became extinct during the second half of the 20th century. At the present time, their population is part of a project of recuperation, conservation, and promotion of this breed backed by the Autonomous Regional Government of Galicia (Carril et al., 2001).

The aim of the recovery of the Celta pig breed is not only to obtain high-quality meat, but also to contribute to the environmental preservation and the recovery of traditional practices. Celta pigs can be reared in an intensive, semi-intensive or free-range system. The use of local breed and extensive or semi-extensive feeding systems based on natural feed resources (chestnuts, grass, etc.) could also help to maintain development in the rural populations of northwestern Spain. On the other hand, the recovery of the Celta pig breed also has the objective the producing high-quality dry-cured meat products such as “lacón” (Lorenzo et al., 2014), dry-cured ham (Bermúdez et al., 2012; 2014; Lorenzo et al., 2013) and “chorizo” (Gómez and Lorenzo, 2013).

The carcass quality and meat quality are determined by factors such as breed, sex, rearing system, age at slaughter or physical exercise. Among the compositional traits related to meat quality, the fat is known to be very important. Fat contributes to the texture, flavor and juiciness of the meat. The fatty acid content and its types determine the physical and nutritional characteristics of fat, and they are associated with human health which is why they are of such great interest (Václavková and Bečková, 2007; Wood et al., 2004).

Many studies have reported that the constitutive fatty acids of the fat are influenced by factors such as genotype (Gandemer et al., 1992), types and percentages of feeding (García-Olmo et al., 2002; Rentfrow et al., 2003), age at slaughtering (Bragagnolo and Rodríguez-Amaya, 2002), location in the carcass (Delgado et al., 2002; Vázquez et al., 1996), sex and castration (Cordero et al., 2010; Wood et al., 1989) or slaughter weight (Palanska et al., 1993). However, there are few studies that compare the effects of the anatomical location and sex on fatty acids, cholesterol, retinol and fat contents of the carcass of castrated females and castrated males.

The aim of this research was to study the fatty acid profile (total lipids, neutral lipids and polar lipids), cholesterol and retinol contents of the fat of the Celta pig breed of eight fat deposits in castrated females and castrated males.

2. MATERIALS AND METHODSTOP

2.1. Pigs, samples and dietTOP

In order to carry out this study, 12 castrated Celta pigs (6 males and 6 females) were continuously fed with commercial compound feed. The piglets, which were vaccinated and deparasitized following the usual protocols, were suckled until an age of 40 days. The males were castrated at 75 days of age and the females were castrated at 90 days of age. All pigs were reared and fattened until the age of 16 months in an extensive regime, with a livestock density of 12 animals per hectare.

After slaughtering, and after 24 hours of refrigeration, samples of intramuscular fat (Longissimus dorsi and Psoas major muscles), subcutaneous fat (rump, subcutaneous ventral, subcutaneous dorsal and covering of the Biceps femoris muscle), perirenal fat and liver fat were obtained from each carcass.

The chemical composition, retinol and cholesterol contents and fatty acid composition of the diet are shown in Table 1. The chemical composition analysis of commercial compound feed was carried out according the methods of A.O.A.C. (2000) and fatty acids, retinol and cholesterol analysis were performed according to the methods described below.

Table 1. Chemical composition (expressed as g·100 g−1) and fatty acids of commercial compound feed
Moisture 10.5
Crude protein 15.3
Eter extract 3.9
Crude fiber 4.6
Starch 39.7
Ash 6.3
Cholesterol (mg·100 g−1) 32.3
Retinol (μg·100 g−1) 180
Fatty acids
C12:0 5.56±0.06
C14:0 41.70±0.19
C14:1 0.17±0.02
C15:0 4.87±0.00
C15:1 0.97±0.03
C16:0 873.46±0.37
C16:1 n7 57.13±0.26
C17:0 12.98±0.24
C17:1 7.19±0.08
C18:0 361.43±0.08
C18:1 c n9 1048.48±0.57
C18:2 n6 1012.74±3.37
C18:3 n6 2.12±0.08
C18:3 n3 97.54±0.24
C20:0 4.98±0.04
C20:1 n9 15.11±0.09
C20:2 n6 5.10±0.34
C20:3 n6 1.50±0.06
C20:4 n6 3.73±0.20
C20:3 n3 1.71±0.31
C20:5 n3 1.66±0.05
C22:0 5.89±0.07
C22:1 n9 3.84±1.09
C22:2 n6 306.69±4.63
C23:0 20.65±0.27
C24:0 1.82±1.57
C24:1 n9 1.01±0.36
SFA 1333.33±0.33
UFA 2566.67±0.33
MUFA 1133.89±1.60
PUFA 1432.78±1.93
SFA: sum of saturated fatty acids; UFA: sum of unsaturated fatty acids;
PUFA: sum of polyunsaturated fatty acids; MUFA: sum of monounsaturated fatty acids.

2.2. Fat and fatty acid analysesTOP

The intramuscular and hepatic fats were extracted following the procedure described by Folch et al. (1957) and the subcutaneous and perirenal fats were extracted following the procedure described by De Pedro et al. (1997).

In order to determine if there are significant differences between the two methods of fat extraction, fat was extracted in triplicate from two different locations with both methods, and the lipid profile was analyzed. There were no significant differences (P<0.05) in the fatty acid profile between the two extraction methods.

Intramuscular fat content (IMF) was quantified according to the ISO 1443:1979.

The neutral and polar lipids from muscles, perirenal, subcutaneous and liver samples were obtained according to the procedure developed by Kaluzny et al. (1985). Fat extracts were methylated and the fatty acid profile of both lipids were determined using the procedure described by Franco et al. (2006).

Fatty acid methyl esters were analyzed by Gas Chromatography using a Thermo Finnigan Trace GC (Thermo Finnigan, Austin, TX, USA). The separation of the different fatty acids was carried out in an Innowax column: 30 m; 0.25 mm ID; 0.25 μm film thickness (Agilent Technologies, Palo Alto, CA, USA). The temperature of the detector was 250 °C and that of the injector 230 °C. The chromatographic conditions used in the determination of the fatty acids were: initial oven temperature: 50 °C for 1 minute; ramp 1: 5 °C·min−1 to 248 °C; ramp 2: 248 °C for 6 minutes.

The gasses used were air (350 mL·min−1), hydrogen (335 mL·min−1) and helium (30 mL·min−1).

Each fatty acid was expressed as a percentage of the total fatty acids. The indices for the activities of Δ9, Δ6 and Δ5 desaturase and the elongase activity were determined as described by Ntawubizi et al. (2009). The thioesterase index was calculated according to Zhang et al. (2007).

2.3. Cholesterol and retinol analysesTOP

Tissue samples and commercial compound feed were saponified according to the procedure described by Saldanha et al. (2006), the unsaponifiable material was extracted by the procedure of López-Cervantes et al. (2006) and cholesterol and retinol contents were quantified by high performance liquid chromatography (HPLC), using a Thermo Finnigan HPLC (Thermo Finnigan, Rodano, Italy) equipped with an on-line solvent degasser (model Spectrasystem SCM1000), solvent delivery system (model Spectrasystem P4000), autosampler with a column oven (model Spectrasystem AS3000), rheodyne injector with a 100 μL loop, photodiode array detector (model Spectrasystem UV6000LP) and a system controller ChromQuest 4.1. The analytical column was Ultrasphere ODS (250 mm×4.6 mm I.D.) with a particle size 5 μm (Beckman, Fullerton, USA).

The HPLC conditions were as follows: mobile phase 68:28:4 (v/v/v) methanol:acetonitrile:water; a flow rate of 2 mL·min−1; column temperature 36 °C. The detection was operated using two channels of a diode-array spectrophotometer, 325 nm for retinol and 208 nm for cholesterol. Retinol and cholesterol in the non-saponifiable fractions of the lipid fraction were identified by the comparison of retention times and UV absorption spectra with those obtained for corresponding standards (Sigma Chemical Co., Saint Louis, MO, USA). Results are expressed as mg·100g−1 of sample for cholesterol and μg·g−1 of sample for retinol.

All samples and patterns of fatty acids, cholesterol and retinol were injected at least in duplicate. Repeatability tests were performed injecting a pattern and a sample consecutively six times in a day. Reproducibility tests were also carried out, injecting the pattern and the sample twice a day for 3 days, under the same experimental conditions. Significant differences were not found among the results obtained in any of the tests.

2.4. Statistical analysisTOP

Mean and standard error of the mean values were determined for all the parameters and the results were expressed as mean and standard error of the mean for six samples in each group. Analysis of variance (ANOVA) was carried out in order to compare the value of each parameter and the significance is given as P<0.05, P<0.01 and P<0.001. Means were compared by the least-square difference test (LSD), using the computer programme Statistica© 7 for Windows (Statsoft Inc., Tulsa, OK, USA).

3. RESULTSTOP

Table 2 shows the fatty acid composition of total, neutral and polar lipids, cholesterol and intramuscular fat content from the Longissimus dorsi–LD- and Psoas major-PM- muscles.

Table 2. Fatty acid composition (as a percentage of total fatty acids), cholesterol (mg·100 g−1 of muscle), fat content (g·100 g−1 of muscle) and standard error of the mean (SEM) of total, neutral and polar lipids from Longissimus dorsi and Psoas major muscles

The intramuscular fat of Celta pigs had a high concentration of saturated (SFA) and monounsaturated (MUFA) fatty acids and a lower concentration of polyunsaturated (PUFA) fatty acids. Oleic acid (C18:1 c n-9) was the most abundant fatty acid in the total and neutral lipids and linoleic acid (C18:2 n-6) in the polar lipids. In polar lipids, the arachidonic acid (C20:4 n-6) content was higher than in total and neutral lipids.

A statistical analysis of the results showed that the total amount of SFA, unsaturated fatty acids (UFA), MUFA and PUFA in the intramuscular fat was affected by the type of muscle. LD showed higher levels of UFA and MUFA and lower levels of SFA and PUFA than the PM intramuscular fat. These differences were a result of the effect on individual fatty acids. For example, palmitoleic (C16:1 n-7), margaric (C17:0), C18:1 c n-9, C18:2 n-6, α-linolenic (C18:3 n-3), arachidic (C20:0), eicosatrienoic (C20:3 n-6), C20:4 n-6, behenic (C22:0) or lignoceric (C24:0) acids showed significant differences (P<0.001) in the total lipids of the intramuscular fat.

The effects of the type of muscle on the polar lipids from the intramuscular fat were minor. The highest differences between LD and PM muscles were observed for stearic acid (C18:0) and C18:1 c n-9.

Fatty acid contents were influenced more by type of muscle than by sex. In the case of total lipid content in the intramuscular fat, only C17:0 showed highly significant (P<0.001) sex effects.

The neutral lipids of the intramuscular fat showed significant differences for pentadecanoic acid (C15:0), cis-10 heptadecanoic acid (C17:1), C17:0, C18:1 c n-9, C18:3 n-3 and cis- 11, 14, 17 eicosatrienoic acid (C20:3 n-3) among males and females.

The effect of sex on the polar lipids of the intramuscular fat was minor, and there were significant differences between male and female animals only concerning the nervonic acid (C24:1 n-9). An interaction between type of muscle and sex was observed for C18:0 in the polar lipids.

The fatty acid composition of total lipids, cholesterol and retinol contents from the subcutaneous fat (rump, dorsal, ventral and covering the Biceps femoris muscle) are shown in Table 3 and the fatty acid composition of neutral and polar lipids, are shown in Tables 4 and 5, respectively.

Table 3. Fatty acid composition (as a percentage of total fatty acids), cholesterol (mg·100 g−1 of sample), retinol (μg·g−1 of sample) and standard error of the mean (SEM) of total lipids from subcutaneous fat
Fatty acids Rump Sub. Biceps femoris Subcutaneous dorsal Subcutaneous ventral Significance
Male Fem. SEM Male Fem. SEM Male Fem. SEM Male Fem. SEM S L SxL
C10:0 0.01 0.02 0.002 0.01 0.01 0.002 0.01 0.01 0.001 0.01 0.01 0.002 ns ns ns
C12:0 0.04 0.04 0.0021 0.04 0.04 0.0011 0.04 0.03 0.0011 0.06a 0.05b 0.0032 ** *** ns
C14:0 1.19 1.12 0.0281 1.16 1.11 0.0241 1.11 1.05 0.0201 1.32 1.25 0.0352 * *** ns
C14:1 0.01 0.01 0.001 0.01 0.01 0.001 0.01 0.01 0.001 0.01 0.01 0.001 * ** ns
C15:0 0.04a 0.03b 0.0011 0.03 0.03 0.0011 0.04a 0.04b 0.0022 0.05a 0.04b 0.0022 *** *** ns
C16:0 22.25 21.79 0.2961 21.93 21.44 0.1871 22.58 21.80 0.2731 25.27 24.44 0.4012 * *** ns
C16:1 n7 1.72 1.60 0.0541 2.09 2.09 0.1452 1.73 1.57 0.0591 2.12 2.20 0.1072 ns *** ns
C17:0 0.26 0.23 0.00912 0.23 0.22 0.0092 0.30 0.26 0.0131 0.31a 0.24b 0.0161 ** ** ns
C17:1 0.26a 0.21b 0.013 0.28 0.25 0.010 0.27 0.22 0.018 0.26 0.23 0.010 ** ns ns
C18:0 11.92 11.92 0.1991 11.45 11.34 0.2561 11.89 12.24 0.3121 13.92 12.67 0.4862 ns ** ns
C18:1 c n9 43.98 44.68 0.4791 46.36 46.29 0.3932 43.02 43.71 0.5461 39.45 41.76 0.8173 ns *** ns
C18:1 c n7 2.13 2.19 0.0771 2.48 2.45 0.0982 2.15 2.16 0.0581 2.20 2.45 0.10712 ns ns ns
C18:2 n6 12.32 12.43 0.1191 10.74 11.49 0.2352 13.16 13.06 0.2811 11.79 11.26 0.3512 ns ** ns
C18:3 n6 0.02a 0.01b 0.002 0.02 0.02 0.001 0.03a 0.02b 0.002 0.02 0.02 0.002 ** ns ns
C18:3 n3 0.64 0.59 0.017 0.61 0.63 0.017 0.66 0.64 0.028 0.61 0.56 0.024 ns ns ns
C20:0 0.22 0.20 0.01012 0.17 0.15 0.0082 0.23 0.21 0.0211 0.21 0.17 0.01312 ns * ns
C20:1 n9 1.31 1.36 0.0401 1.06 1.09 0.0202 1.25 1.35 0.0711 1.02 0.99 0.0452 ns *** ns
C20:2 n6 0.85 0.85 0.0251 0.62 0.65 0.0182 0.83 0.81 0.0301 0.56 0.54 0.0373 ns *** ns
C20:3 n6 0.07 0.06 0.004 0.07 0.07 0.004 0.07 0.07 0.004 0.07 0.07 0.005 ns ns ns
C20:4 n6 0.12 0.11 0.0061 0.16 0.16 0.0082 0.12 0.12 0.0081 0.19 0.18 0.0113 ns *** ns
C20:3 n3 0.18 0.16 0.0091 0.12 0.11 0.0042 0.15 0.15 0.0063 0.10 0.09 0.0062 ns *** ns
C22:2 n6 0.43 0.36 0.062 0.31 0.30 0.054 0.31 0.45 0.058 0.38 0.39 0.066 ns ns ns
C24:0 0.03 0.03 0.0031 0.05 0.04 0.00412 0.04 0.03 0.0031 0.05 0.05 0.0042 ns ** ns
C24:1 n9 nd 0.01 0.002 0.01 0.01 0.002 nd 0.01 0.002 0.01 0.01 0.001 * ns ns
SFA 35.96 35.38 0.4361 35.07 34.38 0.2761 36.24 35.68 0.4941 41.19a 38.92b 0.8082 ns *** ns
UFA 64.04 64.62 0.4361 64.93 65.62 0.2761 63.76 64.32 0.4941 58.81 60.75 0.7532 ns *** ns
MUFA 49.41 50.06 0.4101 52.29 52.19 0.4002 48.43 49.02 0.5851 45.08a 47.64b 0.9183 ns *** ns
PUFA 14.63 14.57 0.1271 12.64 13.43 0.2712 15.33 15.30 0.3251 13.73 13.11 0.4332 ns *** ns
P/S 0.41 0.41 0.0071 0.36 0.39 0.0082 0.42 0.43 0.0111 0.33 0.34 0.0113 ns *** ns
Cholesterol 68.72 73.74 5.120 71.33 61.30 4.307 82.77 74.61 7.144 85.27 85.27 3.470 ns ns ns
Retinol 1.41 1.67 0.107 1.07 1.12 0.065 1.57 1.67 0.142 1.25 1.44 0.100 ns ns ns
SFA: sum of saturated fatty acids; UFA: sum of unsaturated fatty acids; PUFA: sum of polyunsaturated fatty acids; MUFA: sum of monounsaturated fatty acids; P/S: the ratio of total PUFA to total SFA; Fem: female; S: significantly different values as influenced by sex *(P<0.05); **(P<0.01); ***(P<0.001); ns: no significant difference; L: significantly different values as influenced by location *(P<0.05); **(P<0.01); ***(P<0.001); SxL: interaction of sex and location *(P<0.05); **(P<0.01); ***(P<0.001); a–b Means within the same row not followed by the same letter differ significantly (influence of sex) (P<0.05); 1–3 SEM within the same row not followed by the same letter differ significantly (influence of location) (P<0.05).
Table 4. Fatty acid composition (as a percentage of total fatty acids) and standard error of the mean (SEM) of neutral lipids from subcutaneous fat
Fatty acids Rump Sub. Biceps femoris Subcutaneous dorsal Subcutaneous ventral Significance
Male Fem. SEM Male Fem. SEM Male Fem. SEM Male Fem. SEM S L SxL
C10:0 0.01 0.02 0.002 0.01 0.02 0.003 0.01 0.02 0.002 0.01 0.02 0.002 * ns ns
C12:0 0.05 0.04 0.0021 0.05 0.04 0.0021 0.04 0.04 0.0011 0.06 0.05 0.0012 * *** ns
C14:0 1.24 1.18 0.0271 1.22 1.18 0.0211 1.18 1.12 0.0201 1.36 1.37 0.0202 ns *** ns
C14:1 0.02 0.01 0.003 0.02 0.01 0.003 0.01 0.01 0.003 0.02 0.01 0.003 * ns ns
C15:0 0.04 0.05 0.008 0.03 0.03 0.001 0.04a 0.03b 0.002 0.04a 0.03b 0.002 ns ns ns
C16:0 22.32 21.85 0.2811 22.15 21.82 0.1601 22.75 21.91 0.3121 25.34a 24.15b 0.3122 * *** ns
C16:1 n7 2.40 2.18 0.0861 2.81 2.68 0.0962 2.43 2.24 0.0621 2.90 3.03 0.0622 ns *** ns
C17:0 0.26 0.23 0.00912 0.23 0.22 0.0081 0.29 0.26 0.0132 0.30a 0.24b 0.0132 ** ** ns
C17:1 0.25a 0.20b 0.013 0.26 0.23 0.010 0.25 0.21 0.018 0.24 0.21 0.018 ** ns ns
C18:0 12.36 13.22 0.3721 10.90 10.71 0.2612 11.83 11.74 0.2693 13.33a 11.87b 0.26913 ns *** ns
C18:1 c n9 43.13 43.20 0.5081 46.23 46.29 0.4172 42.49 43.87 0.4881 39.59a 42.70b 0.4883 ns *** ns
C18:1 c n7 2.06 2.03 0.0861 2.38 2.42 0.1052 1.96 1.98 0.1081 2.28 2.41 0.1082 ns ** ns
C18:2 n6 12.49 12.44 0.1621 10.93 11.56 0.2292 13.34 13.24 0.2933 11.78 11.30 0.2932 ns *** ns
C18:3 n6 0.01 0.02 0.005 0.01 0.01 0.002 0.02 0.02 0.006 0.02 0.02 0.006 ns ns ns
C18:3 n3 0.65 0.60 0.02012 0.62 0.62 0.01312 0.68 0.64 0.0281 0.62 0.57 0.0282 ns ns ns
C20:0 0.19 0.20 0.00913 0.15 0.13 0.00723 0.22 0.20 0.0191 0.18 0.16 0.0193 ns ** ns
C20:1 n9 1.21 1.31 0.0401 0.96 0.98 0.0242 1.18 1.28 0.0711 0.89 0.95 0.0712 ns *** ns
C20:2 n6 0.82 0.81 0.0221 0.60 0.60 0.0132 0.80 0.81 0.0151 0.54 0.51 0.0153 ns *** ns
C20:3 n6 0.06 0.06 0.006 0.06 0.07 0.004 0.06 0.05 0.005 0.06 0.06 0.005 ns ns ns
C20:4 n6 0.11 0.11 0.0091 0.15 0.14 0.0082 0.11 0.10 0.0071 0.17 0.16 0.0072 ns *** ns
C20:3 n3 0.17 0.15 0.0081 0.10 0.10 0.0042 0.12 0.14 0.0133 0.09 0.08 0.0133 ns *** ns
C22:2 n6 0.10 0.07 0.016 0.09 0.06 0.013 0.14a 0.05b 0.032 0.15a 0.06b 0.032 ** ns ns
C24:0 0.03 0.03 0.0011 0.03 0.04 0.0032 0.03 0.03 0.00312 0.04 0.04 0.0032 ns * ns
C24:1 n9 0.01 0.01 0.004 0.02 0.01 0.004 0.01 0.01 0.002 0.01 0.02 0.002 ns ns ns
SFA 36.51 36.81 0.4541 34.77 34.19 0.3462 36.40 35.34 0.50712 40.66a 37.94b 0.5073 ns *** ns
UFA 63.49 63.19 0.4541 65.23 65.81 0.3462 63.60 64.66 0.50712 59.34a 62.06b 0.5073 ns *** ns
MUFA 49.08 48.94 0.4651 52.67 52.64 0.4282 48.33 49.60 0.5301 45.92a 49.31b 0.5301 ns *** ns
PUFA 14.42 14.25 0.1861 12.55 13.17 0.2492 15.27 15.06 0.3191 13.42 12.75 0.3192 ns *** ns
P/S 0.40 0.39 0.0071 0.36 0.39 0.0081 0.42 0.43 0.0122 0.33 0.34 0.0122 ns *** ns
SFA: sum of saturated fatty acids; UFA: sum of unsaturated fatty acids; PUFA: sum of polyunsaturated fatty acids; MUFA: sum of monounsaturated fatty acids; P/S: the ratio of total PUFA to total SFA; Fem: female; S: significantly different values as influenced by sex *(P<0.05); **(P<0.01); ***(P<0.001); L: significantly different values as influenced by location *(P<0.05); **(P<0.01); ***(P<0.001); ns: no significant difference; SxL: interaction of sex and location *(P<0.05); **(P<0.01); ***(P<0.001); a–b Means within the same row not followed by the same letter differ significantly (influence of sex) (P<0.05); 1–3 SEM within the same row not followed by the same letter differ significantly (influence of location) (P<0.05).
Table 5. Fatty acid composition (as a percentage of total fatty acids) and standard error of the mean (SEM) of polar lipids in subcutaneous fat
Fatty acids Rump Sub. Biceps femoris Subcutaneous dorsal Subcutaneous ventral Significance
Male Fem. SEM Male Fem. SEM Male Fem. SEM Male Fem. SEM S L SxL
C10:0 0.04 0.04 0.008 0.05 0.03 0.010 0.05 0.07 0.016 0.06 0.05 0.016 ns ns ns
C12:0 0.04 0.05 0.006 0.06 0.05 0.007 0.06 0.07 0.007 0.06 0.08 0.010 ns ns ns
C14:0 1.29 1.35 0.0501 1.29 1.31 0.0381 1.27 1.34 0.0461 1.51 1.48 0.0712 ns * ns
C14:1 0.02 0.03 0.006 0.02 0.02 0.004 0.02a 0.04b 0.007 0.03 0.03 0.005 ns ns ns
C15:0 0.02a 0.03b 0.004 0.03 0.03 0.003 0.09 0.05 0.026 0.03 0.04 0.005 ns ns ns
C16:0 23.74 24.62 0.3891 23.26a 25.27b 0.5111 25.27 26.87 0.5662 27.55 25.90 0.7042 ns ** ns
C16:1 n7 1.83 1.60 0.0631 2.08 1.85 0.0632 1.77a 1.51b 0.0621 1.98 2.09 0.0832 * *** ns
C17:0 0.26 0.26 0.008 0.24 0.25 0.012 0.29 0.29 0.021 0.31 0.26 0.018 ns ns ns
C17:1 0.20a 0.15b 0.01012 0.21 0.19 0.0091 0.19a 0.14b 0.0152 0.18 0.16 0.0082 *** * ns
C18:0 12.93 13.90 0.3041 12.29 12.66 0.2461 14.40 15.33 0.6622 15.17a 13.34b 0.4712 ns ** ns
C18:1 c n9 40.08 39.72 0.5611 42.65 40.52 0.6061 37.04 35.81 0.7952 35.81a 39.11b 0.9792 ns *** ns
C18:1 c n7 2.66 2.61 0.1071 3.00 3.03 0.1312 2.54 2.61 0.1381 2.56 3.03 0.14912 ns ns ns
C18:2 n6 12.87a 12.11b 0.1721 11.35 11.20 0.2722 13.00 12.16 0.3491 11.25 11.07 0.2822 ns *** ns
C18:3 n6 0.05 0.03 0.008 0.02 0.02 0.004 0.02 0.04 0.008 0.02 0.03 0.005 ns ns ns
C18:3 n3 0.61 0.52 0.026 0.57 0.55 0.020 0.58 0.52 0.027 0.52 0.46 0.035 * ns ns
C20:0 0.17 0.18 0.0091 0.14 0.15 0.0082 0.19 0.20 0.0091 0.17 0.17 0.01212 ns * ns
C20:1 n9 1.07 1.01 0.0331 0.92 0.88 0.0222 1.01 0.99 0.0401 0.86 0.81 0.0452 ns *** ns
C20:2 n6 0.75 0.72 0.0201 0.58 0.56 0.0172 0.67 0.65 0.0303 0.51 0.49 0.0264 ns *** ns
C20:3 n6 0.12 0.18 0.019 0.11 0.15 0.012 0.15 0.20 0.029 0.16 0.15 0.022 ns ns ns
C20:4 n6 0.39 0.34 0.050 0.49 0.32 0.067 0.49 0.34 0.071 0.39 0.48 0.051 ns ns ns
C20:3 n3 0.14 0.10 0.0111 0.09 0.07 0.0072 0.10 0.09 0.01312 0.10 0.07 0.0142 * ns ns
C22:2 n6 0.65 0.33 0.085 0.44 0.70 0.108 0.69 0.56 0.091 0.66 0.59 0.085 ns ns ns
C24:0 0.06 0.07 0.009 0.07 0.11 0.020 0.08 0.09 0.010 0.09 0.09 0.007 ns ns ns
C24:1 n9 0.03 0.04 0.010 0.03 0.06 0.018 0.04 0.04 0.008 0.03 0.04 0.008 ns ns ns
SFA 38.55 40.49 0.6411 37.43 39.87 0.6981 41.69 44.30 1.1002 44.94a 41.41b 1.1352 ns *** *
UFA 61.45 59.51 0.6411 62.57 60.13 0.6981 58.31 55.70 1.1002 55.06a 58.59b 1.1352 ns *** *
MUFA 45.89 45.18 0.5451 48.92a 46.55b 0.6051 42.62 41.14 0.8952 41.45a 45.26b 1.07012 ns *** *
PUFA 15.56a 14.33b 0.2671 13.66 13.58 0.3672 15.70 14.56 0.4231 13.61 13.33 0.3412 ns ** ns
P/S 0.40a 0.36b 0.0111 0.37 0.34 0.01412 0.38 0.33 0.0171 0.30 0.33 0.01312 ns * ns
SFA: sum of saturated fatty acids; UFA: sum of unsaturated fatty acids; PUFA: sum of polyunsaturated fatty acids; MUFA: sum of monounsaturated fatty acids; P/S: the ratio of total PUFA to total SFA; Fem: female; S: significantly different values as influenced by sex *(P<0.05); **(P<0.01); ***(P<0.001); ns: no significant difference; L: significantly different values as influenced by location *(P<0.05); **(P<0.01); ***(P<0.001); SxL: interaction of sex and location *(P<0.05); **(P<0.01); ***(P<0.001); a–b Means within the same row not followed by the same letter differ significantly (influence of sex) (P<0.05); 1–4 SEM within the same row not followed by the same letter differ significantly (influence of location) (P<0.05).

Significant differences were also observed among the fatty acid composition of the subcutaneous fat locations. The fatty acids of total and neutral lipids were affected more by location than polar lipids. The subcutaneous ventral fat showed a higher SFA content and lower UFA, MUFA and PUFA than the subcutaneous dorsal fat, subcutaneous fat from the rump and the fat covering the B. femoris muscle. In addition, the polar lipids of the subcutaneous fat showed higher levels of MUFA than in other locations.

Sex affected the fatty acids of the subcutaneous fat. However, in total lipids, there were significant differences for lauric acid (C12:0), C15:0, C17:0, C17:1 and C18:3 n-6 among males and females. In the neutral lipids of the subcutaneous fat, males had a higher content of C12:0, myristoleic acid (C14:1), palmitic acid (C16:0), C17:0, C17:1 and cis-13, 16-docosadienoic acid (C22:2 n-6) than females.

An interaction between location and sex was observed for SFA, UFA and MUFA in polar lipids. In polar lipids, the males showed higher contents of C16:1 n-7, C17:1, C18:3 n-3 and C20:3 n-3 than the females.

The fatty acid composition of total, neutral and polar lipids, cholesterol and retinol contents from perirenal and hepatic fat are presented in Table 6.

Table 6. Fatty acid composition (as a percentage of total fatty acids), cholesterol (mg·100 g−1 of sample), retinol (μg·g−1 of sample) and standard error of the mean (SEM) of total, neutral and polar lipids from hepatic and perirenal fat
Fatty acids Liver fat Perirenal fat
TOTAL LIPIDS S NEUTRAL LIPIDS S POLAR LIPIDS S TOTAL LIPIDS NEUTRAL LIPIDS POLAR LIPIDS
Male Fem. SEM Male Fem. SEM Male Fem. SEM Male Fem. SEM S Male Fem. SEM S Male Fem. SEM S
C10:0 0.09a 0.04b 0.030 ns 0.08a 0.04b 0.017 ns 0.01 0.01 0.002 ns 0.01 0.02 0.002 ns 0.01 0.02 0.003 ns 0.05 0.04 0.007 ns
C12:0 0.05 0.09 0.031 ns 0.03 0.03 0.006 ns 0.01 0.01 0.002 ns 0.05 0.05 0.002 ns 0.06 0.05 0.002 ns 0.05 0.07 0.007 ns
C14:0 0.45 0.55 0.035 ns 0.27 0.34 0.032 ns 0.41 0.36 0.049 ns 1.24 1.23 0.023 ns 1.30 1.32 0.022 ns 1.36 1.39 0.039 ns
C14:1 0.06 0.03 0.006 * 0.04 0.04 0.007 ns 0.05 0.05 0.005 ns 0.01 nd 0.000 ns 0.02 0.01 0.004 ns 0.02 0.04 0.004 ns
C15:0 0.04 0.05 0.007 ns 0.05 0.06 0.006 ns 0.07 0.07 0.006 ns 0.04 0.04 0.002 ns 0.04 0.04 0.002 ns 0.05 0.04 0.004 ns
C16:0 17.22 17.63 0.422 ns 14.31a 15.85b 0.538 ns 20.92 20.06 0.723 ns 27.11 27.16 0.128 ns 27.12 27.06 0.167 ns 28.41 29.46 0.482 ns
C16:1 n7 0.80a 1.24b 0.155 ns 0.90 1.03 0.154 ns 0.87 0.84 0.079 ns 1.39 1.38 0.052 ns 2.16 2.20 0.063 ns 1.52 1.42 0.043 ns
C17:0 0.34 0.41 0.045 ns 0.34 0.35 0.047 ns 0.46 0.48 0.058 ns 0.33 0.30 0.014 ns 0.33 0.29 0.015 ns 0.34 0.31 0.018 ns
C17:1 0.11 0.15 0.014 ns 0.16 0.14 0.019 ns 0.17 0.15 0.011 ns 0.19 0.16 0.011 ns 0.16 0.14 0.007 ns 0.14 0.11 0.008 ns
C18:0 20.12 20.92 0.847 ns 20.41 18.93 1.146 ns 24.06 24.94 0.744 ns 18.56 18.47 0.351 ns 18.52 18.43 0.431 ns 19.02 19.77 0.491 ns
C18:1 c n9 20.77 21.10 0.760 ns 19.87 21.66 1.205 ns 15.49 16.85 0.584 ns 33.76 33.11 0.404 ns 33.07 33.52 0.447 ns 31.43 29.88 0.891 ns
C18:1 c n7 2.36 2.49 0.234 ns 2.12 2.17 0.105 ns 1.52 1.61 0.155 ns 1.52 1.73 0.066 ns 1.52 1.60 0.007 ns 1.87 2.14 0.012 ns
C18:2 n6 16.37 15.65 0.395 ns 17.98 16.98 0.577 ns 17.57 16.63 0.745 ns 12.90 13.20 0.201 ns 13.21 12.82 0.371 ns 12.43 12.09 0.434 ns
C18:3 n6 0.30 0.26 0.053 ns 0.39 0.35 0.006 ns 0.40 0.33 0.075 ns 0.03 0.02 0.002 ns 0.01 0.02 0.004 ns 0.02 0.04 0.006 ns
C18:3 n3 0.61 0.54 0.048 ns 0.69 0.63 0.062 ns 0.51 0.44 0.004 ns 0.72 0.67 0.022 ns 0.72 0.67 0.021 ns 0.63a 0.52b 0.032 ns
C20:0 0.05 0.06 0.009 ns 0.04 0.03 0.008 ns 0.01 0.02 0.004 ns 0.22 0.26 0.021 ns 0.21 0.24 0.018 ns 0.19 0.21 0.017 ns
C20:1 n9 0.24 0.32 0.025 ns 0.34 0.36 0.017 ns 0.12 0.14 0.013 ns 0.71 0.88 0.058 ns 0.64 0.73 0.035 ns 0.65 0.65 0.003 ns
C20:2 n6 0.38 0.32 0.033 ns 0.39a 0.26b 0.034 ns 0.32 0.31 0.019 ns 0.48 0.51 0.020 ns 0.46 0.46 0.027 ns 0.45 0.40 0.018 ns
C20:3 n6 0.34 0.32 0.039 ns 0.61a 0.45b 0.058 ns 0.46 0.50 0.049 ns 0.05 0.06 0.004 ns 0.04 0.05 0.003 ns 0.12 0.14 0.013 ns
C20:4 n6 15.07a 13.43b 0.712 ns 18.13 17.72 0.846 ns 13.50 12.72 0.704 ns 0.16 0.15 0.009 ns 0.15 0.14 0.008 ns 0.31 0.48 0.048 ns
C20:3 n3 0.04 0.07 0.017 ns 0.38a 0.28b 0.042 ns 0.12 0.11 0.012 ns 0.08 0.08 0.003 ns 0.07 0.07 0.003 ns 0.05 0.06 0.007 ns
C22:0 0.49 0.43 0.049 ns 0.62 0.54 0.065 ns 0.54 0.54 0.008 ns nd nd nd nd nd nd nd nd nd
C22:2 n6 1.32 1.29 0.199 ns 0.11 0.13 0.015 ns 0.13 0.09 0.024 ns 0.37 0.48 0.061 ns 0.14 0.08 0.026 ns 0.79 0.66 0.142 ns
C24:0 1.28 1.40 0.092 ns 1.70 1.59 0.012 ns 1.24 1.39 0.105 ns 0.04 0.04 0.005 ns 0.04 0.04 0.003 ns 0.06 0.05 0.005 ns
C24:1 n9 1.11 1.25 0.128 ns 0.05 0.05 0.005 ns 1.06a 1.36b 0.156 ns 0.01 0.02 0.003 ns 0.01 0.02 0.002 ns 0.03 0.03 0.009 ns
SFA 40.12 41.57 0.769 ns 37.84 37.76 0.941 ns 47.73 47.87 0.908 ns 47.62 47.56 0.338 ns 47.62 47.49 0.471 ns 49.52 51.33 0.962 ns
UFA 59.88 58.44 0.771 ns 62.16 62.24 0.941 ns 52.27 52.13 0.908 ns 52.38 52.44 0.338 ns 52.38 52.51 0.471 ns 50.48 48.67 0.962 ns
MUFA 25.45 26.56 0.935 ns 23.48 25.44 1.394 ns 19.27 21.01 0.726 ns 37.58 37.28 0.446 ns 37.58 38.20 0.490 ns 35.66 34.27 0.954 ns
PUFA 34.43a 31.88b 0.831 ns 38.68a 36.79b 0.917 ns 33.00 31.13 1.436 ns 14.80 15.16 0.278 ns 14.80 14.31 0.424 ns 14.82 14.39 0.566 ns
P/S 0.86a 0.77b 0.028 ns 1.03 0.98 0.033 ns 0.70 0.66 0.045 ns 0.31 0.32 0.006 ns 0.31 0.30 0.001 ns 0.30 0.28 0.014 ns
Cholesterol 313.05 317.52 10.184 ns _ _ _ _ 63.60 82.27 7.932 _ _ _ _
Retinol 777.21 735.03 20.362 * _ _ _ _ 1.07 1.37 0.102 _ _ _ _
SFA: sum of saturated fatty acids; UFA: sum of unsaturated fatty acids; PUFA: sum of polyunsaturated fatty acids; MUFA: sum of monounsaturated fatty acids; P/S: the ratio of total PUFA to total SFA; Fem: female; S: significantly different values as influenced by sex *(P<0.05); **(P<0.01); ***(P<0.001); ns: no significant difference; a-b Means within the same row not followed by the same letter differ significantly (influence of sex) (P<0.05).

In total and neutral lipids, the hepatic fat showed higher levels of PUFA and lower levels of MUFA than the subcutaneous or intramuscular fats. These differences are a direct consequence of higher amounts of some fatty acids such as C18:2 n-6 or C20:4 n-6 in the hepatic fat and lower amounts of C18:1 c n-9, vaccenic acid (C18:1 c n-7) or cis-11-eicosenoic acid (C20:1 n-9). In polar lipids, hepatic fat showed higher levels of PUFA than the subcutaneous fat but lower than the intramuscular fat.

The sex had no significant influence on the composition of the hepatic fat.

The SFA (mainly C16:0 and C18:0) and C18:3 n-3 contents were higher in the perirenal fat compared to the other fat depots.

Desaturase and elongase activity indices are given in Table 7. Δ6 desaturase index and C18:0/C16:0 elongase index were not significantly influenced by the location or the sex in LD and PM. However, significant differences (P<0.01) were observed between males and females in the rump.

Table 7. Desaturase and elongase activity indices

A significant effect (P<0.001) of location and sex was observed for the Δ5 desaturase index in LD and PM. PM presented a higher Δ5 desaturase index than LD in females than in males. In subcutaneous fat, differences were determined only by the location in the Δ5 desaturase index.

The Δ9 desaturase index was higher in LD than in PM, showing that the conversion of palmitic acid to palmitoleic acid and stearic acid to oleic acid is higher in LD. This index was also higher in fat covering the Biceps femoris muscle than in other locations of subcutaneous fat. This index did not differ between the two sexes.

Elongase activity did not show differences between females and males in LD and PM. However, the elongase index, which provided an estimate of C16:1 n-7 to C18:1 c n-7 fatty acid elongase activity, was higher in PM than in LD. In the subcutaneous fat, significant differences were observed between sex (P<0.05) and locations (P<0.001). Finally, the thioesterase index did not differ among locations or sexes in intramuscular fat. In this case, differences between locations were observed concerning subcutaneous fat.

In LD muscle significantly higher values (P<0.05) of intramuscular fat than in the PM muscle were obsereved (Table 2). In our study, the retinol content in muscles was not detectable.

Cholesterol contents from the subcutaneous and perirenal fat was superior to that described in intramuscular fat. The cholesterol and retinol contents of the subcutaneous locations were not strongly influenced by location. The ventral subcutaneous fat had the greatest (P<0.05) cholesterol values.

The retinol and cholesterol contents from the hepatic fat were much higher than those observed in other locations.

The percentage of intramuscular fat and cholesterol contents in the muscles and retinol and cholesterol contents in the subcutaneous and perirrenal fat showed no significant differences between males and females. However, there appears to be a greater deposition (P<0.05) of retinol in the liver of males than in females.

4. DISCUSSIONTOP

The statistical analysis showed some differences in the contents of some fatty acids of the studied locations. However, the fatty acid profile was very similar in the deposits of fat studied. These results are in agreement with previous findings by other authors in different fat locations (Cava et al., 2003; Franco et al., 2006).

The studied Celta pigs were fed with commercial compound feed (Table 1). These have high contents of carbohydrates and low contents of fat. Their fatty acid composition is characterized by high levels of C18:1 c n-9 and C18:2 n-6. The carbohydrates may serve as substrate in the synthesis of fat, synthesizing C16:0. Also, the dietary retinol may have a direct effect on the deposition of fatty acids such as C16:0 and C18:0 (Olivares et al., 2009a). On the other hand, the enzyme Δ-9 desaturase would be very active in Celta hogs, as it is favored by the carbohydrates and the MUFA, which would explain in part the high content of MUFA and especially of C18:1 c n-9 (Franco et al., 2006).

The SFA content was higher in hepatic and perirenal fat than in other deposits. C18:1 c n-9 and UFA contents were higher from intramuscular and subcutaneous fat than for the hepatic and perirenal fat. Oleic acid is synthesized by Δ9-desaturase (stearoyl-CoA-desaturase). Thompson and Allen (1969) observed that the activity of this enzyme was higher in the subcutaneous adipose tissue than in the perirenal fat, which may explain the higher oleic acid content in the subcutaneous fat.

However, the percentage of C20:4 n-6 and PUFA content was significantly higher in hepatic fat than in other anatomical locations.

Total lipids and neutral lipids, except for the ones in the liver, showed similar fatty acid composition, as the neutral lipid represented the greatest percentage of total lipids.

The fatty acid composition of total and neutral lipids is more influenced by location than the fatty acids of polar lipids. The proportion of PUFA in the polar lipids from the intramuscular fat was significantly higher than those of the total and neutral lipids. These differences were a consequence of a higher content of some individual fatty acids in the polar lipids such as C18:2 n-6 and C20:4 n-6.

The type of fibers and their cellular metabolism determines the fatty acid composition in the muscle (Andrés et al., 2001; Leseigneur-Meynier and Gandemer, 1991). PM is a predominantly oxidative muscle, showing higher levels of PUFA than LD in both lipid classes, which has been described as a predominantly glucolitic muscle in the scientific literature.

The differences observed in the fatty acids from different locations could also be explained as a function of the amount of neutral lipids and phospholipids that they contain (Cava et al., 2003; Franco et al., 2006).

On the other hand, in monogastric animals such as the pig, the fatty acid composition of different fat deposits is affected by the diet (Viera-Alcaide et al., 2007) and some fatty acids of the diet are absorbed and deposited directly into the fat deposits. Tissue fatty acid composition is not modified to the same extent in the different locations. C18:2 n-6 and C18:3 n-3 are directly accumulated from the diet, while C20:4 n-6 is derived from dietary C18:2 n-6. The studied Celta pigs were fed with commercial feed, which was rich in C18:2 n-6 (Table 1).

The proportion of fatty acids is also determined by endogenous synthesis. Previous studies showed that the activity of the enzymes involved in the lipogenesis is tissue specific (Buller and Enser, 1986; Narváez-Rivas et al., 2009). Our results show that desaturase and elongase activity is significantly different (P<0.001) in LD and PM muscles.

Traditionally, male and female Celta pigs are castrated to reduce the negative effect of oestrous on growth, to improve meat quality and to facilitate management. The effect of castration on lipid content and fatty acid composition has been previously described (Cai et al., 2010; Högberg et al., 2004; Ntawubizi et al., 2009; Razmaite et al., 2008). In most cases, these studies are carried out on entire males, females or castrated males. However, little is known about the effect of castration on the females.

Our results showed that the sex exerted less influence than the anatomical location on fatty acid contents. However, there were differences in some fatty acids of the intramuscular and subcutaneous fat between castrated females and castrated males. The fatty acids of neutral lipids were also more influenced by sex than the fatty acids of polar lipids.

Results reported in the literature about the effect of sex on fatty acids show that the most important differences between sexes in fatty acid composition are caused by a difference in metabolism between females and males or between castrated and uncastrated pigs. However, most of these sex differences are eliminated by the castration of males and females because the castration causes a removal of hormones that affects the fatty acid metabolism (Högberg, 2002).

In addition, the age of castration has an influence on the effect of sex on meat quality. In the case of castrated animals at a young age, the sexual hormones have little influence on growth (Mayoral et al., 1999). The differences observed in the literature could also, at least in part, be due to the different ages of castration.

Our results showed differences among some fatty acids in castrated females and castrated males. For example, C17:0 in the total lipid contents from the intramuscular fat, C15:0 in total lipids and C17:1 in polar lipids from the subcutaneous fat showed significant effects of the sex. In contrast to our results, Ramírez and Cava (2008) did not find differences in fatty acid compositions in subcutaneous and intramuscular fat from LD and Biceps femoris muscles between castrated females and castrated males. Serrano et al. (2008) did neither observe any difference in the fatty acid contents of the subcutaneous fat of castrated females and castrated males. Cordero et al. (2010) did not find any difference in the fatty acid composition of the intramuscular fat from LD between castrated females and castrated males in the Iberian×Duroc pig. However, these authors found differences in C18:1 c n-9, SFA and the MUFA of the subcutaneous fat between sexes.

Peinado et al. (2008) did not observe differences between the fatty acids of subcutaneous fat of intact females, castrated females and castrated males, except for the C18:2 n-6 content, which was higher for intact females than for castrated females and castrated males.

On the contrary, a significant effect (P<0.001) of location and sex was observed for the Δ5 desaturase index. PM presented a higher Δ5 desaturase index than LD in females than in males. Δ-5 desaturase activity, which is an indicator of the stearoyl-CoA desaturase influence on the conversion of C20:3 n-6 to C20:4 n-6, was higher in castrated females than in castrated males.

Hasty et al. (2002) showed that fatty acid metabolism follows a different course according to sex. Cordero et al. (2010) observed that the subcutaneous fat from castrated males had lower MUFA/SFA and C18:1 c n-9/C18:0 ratios than those from castrated females. However, Zhang et al. (2007) did not observe any differences in the indices of Δ9-desaturase, thioesterase, or elongase between males and females.

The cholesterol contents of muscles coincided with those described by Bragagnolo and Rodríguez-Amaya (2002) and Salvatori et al. (2008). The fact that the PM muscle presented a higher cholesterol content (P>0.05) than the LD muscle could be due to that oxidative muscles are richer in phospholipids than glycolytic muscles, and as a result, they are richer in cholesterol (Alasnier et al., 1996; Chizzolini et al., 1999).

Intramuscular fat content also affects the amount of cholesterol, since the muscles with high content of intramuscular fat present proportionately less membrane polar lipids and therefore lower amounts of the cholesterol associated with these membranes (Alasnier et al., 1996). This would explain, in part, the fact that the LD muscle has a lower cholesterol content than the PM muscle.

Bragagnolo and Rodríguez-Amaya (2002) found that cholesterol contents decreased significantly with increasing age at slaughter. In turn, Salvatori et al. (2008) found a significant relationship between carcass weight and cholesterol content, the last one decreased as the weight of the carcass increased. This may explain, in part, the low-cholesterol in Celta pig muscles, as these pigs were slaughtered at an older age (16 months), presenting a high carcass weight and high percentage of intramuscular fat. So, despite not being significant, we found that there was an inverse correlation between carcass weight and cholesterol content.

Several authors suggest that castration causes increased intramuscular fat deposition (Latorre et al., 2003; Mersmann, 1984; Mourot et al., 1999; Peinado et al., 2008), because the pigs have greater energy, resulting in an increased fat storage (Gandemer et al., 1979; Kolstad et al., 1996). These differences were not noted in our study, as both males and females were castrated.

There are few studies that describe the content of retinol in pig muscles. Högberg et al. (2002) and Olivares et al. (2009a) described a retinol content of approximately 0.03 and 0.04 μg·g−1 of pork loin samples, respectively, showing that the retinol content from muscles is very low.

The retinol and cholesterol contents from hepatic fat were much higher than those observed in other locations. This is mainly due to the fact that liver synthesized and accumulated these substances, which explains their high contents in relation with the other locations. The retinol content present in the Celta pork liver was above the one described by Olivares et al. (2009a, 2009b) possibly due to a higher content of vitamin A in the diet of the Celta pig (Table 1).

The percentage of intramuscular fat and cholesterol contents in muscles and the retinol and cholesterol contents in the subcutaneous and perirrenal fat showed no significant differences between males and females. However, there appears to be a greater deposition (P<0.05) of retinol in the liver of males compared to females.

The absence of significant differences in the content of cholesterol and retinol due to sex can be due to the fact that castration removed hormones that affect cholesterol and retinol metabolism and, as noted above, differentiate males from females.

5. CONCLUSIONSTOP

The effects of gender and location on the fatty acid profile were less intense in polar lipids than in total and neutral lipids. The differences determined by the location could be due to the different activity of the elongase and desaturase enzymes. In turn, the cholesterol content decreased with increasing age of slaughter, weight, and amount of intramuscular fat.

Castration removed hormones that differentiate sexes, so as both male and female pigs were castrated, only significant differences could be seen in some minor fatty acids. Cholesterol, retinol and intramuscular fat contents showed no significant differences between sexes.

ACKNOWLEDGEMENTTOP

This work was financially supported by the Spanish Ministry of Science and Innovation (Grant AGL2008-0574-C02-01/ALI). The authors also wish to thank to the “Instituto Orensano de Desarrollo (INORDE)” for its valuable collaboration in the rearing of the pigs.

 

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