Effects of three management systems on meat quality of dairy breed goat kids

Abstract

The effect of three management systems on meat quality of 61 goat kids was determined. Kids from the extensive management system displayed stronger “pink” meats than animals from intensive systems with natural and artificial rearing management. The type of management system did not affect the pH, chemical composition and sensorial evaluation. Intensive combined with artificial rearing management system meat displayed the lowest capacity to retain water inside the muscle. Intramuscular fat deposits from kids reared under extensive management system showed the lowest percentage of C14:0 fatty acids and the highest percentage of C18:1 fatty acid. A strong influence of physical activity and trough grazing modulated the fatty acid profile in muscle of kids reared under an extensive management system, producing healthier meat relative to intensive with natural and artificial rearing management systems, as reflected by the fact that the lowest atherogenicity index was measured in intramuscular fat from kids reared under extensive management system. An extensive management system produces similar goat kid meat as intensive with natural and artificial rearing management systems, but with a lower atherogenicity index.

Keywords:

• fatty acid
• chemical composition
• atherogenicity index

1. Introduction

Current trends suggest that present day dairy and meat products are losing their market share and that the decline will continue unless there is commercial adaptation to market demands without losing specificity, originality and authenticity (Boyazoglu and Morand-Fehr 2001). However, goat meat is becoming increasingly popular because of the positive environmental image of goat ranching, the meats’ dietetic and health benefits, the cultural tendency of consumers towards natural foods, recent food crises and the association of goat meat with religious celebrations (Dubeuf et al. 2004). Due to the relationship between high-fat diets and heart disease, consumer interest in the fat content and fatty acid composition of foods has grown in recent years (Scollan et al. 2006).

The relationships between dietary fat and the incidence of lifestyle diseases, particularly coronary heart disease, are well established and this has contributed towards the development of specific guidelines from the World Health Organization in relation to fat in the diet (WHO 2003). It is recommended that total fat, saturated fatty acids (SFA), n-6 polyunsaturated fatty acids (PUFA), n-3 PUFA and trans-fatty acids should contribute <15–30%, <10%, <5–8%, <1–2% and <1% of total energy intake, respectively. Reducing the intake of SFA (which are known to raise total and low-density lipoprotein (LDL) cholesterol) and increasing the intake of n-3 PUFA is particularly encouraged. In addition, the atherogenicity index has to be taken into account. The increased levels of C12:0 and C14:0 without an increasing in the total saturated fatty acid content provided an increase in atherogenicity index (Mariniello et al. 2011), and according to Hu et al. (2001) these acids are crucial for high levels of LDL cholesterol and the blood plasma in humans.

Due to the fact that in many European countries goat meat is very poorly valued (Dubeuf et al. 2004), few large-scale goat meat production systems exist, even around the Mediterranean. Due to this marginalisation, there are not many studies on goat products and most of them belong to milk production and especially to milk derivatives. Presently, the economical crisis is affecting the general commerce and alternative sources of added values are in mind of the sector. There is evidence that diet influences human health has promoted a new, blooming market – the functional foods market (Madruga and Bressan 2011). The functional food market is now characterised by bioactive compounds or ingredients. According to Vandendriessche (2008), meat and meat-derived products should incorporate concepts and innovations in order to reduce the fat used in formulae. It could be that meat from kids when consumed could have beneficial effects on health (reducing atherogenicity index, for example). In addition, goats deposit more internal fat and less subcutaneous and intramuscular fat compared with sheep (Colomber-Rocher et al. 1992). Hence, consumers are interested in goat meat as a source of relatively lean meat, especially in developed countries with a high incidence of cardiovascular diseases (Banskalieva et al. 2000).

Thus, the aim of this study was to evaluate the influence of the type of management system on goat kid meat quality as well as to assess the fatty acid profile of the extensive kid meat, dealing with differences in the fatty acid composition (particularly with regard to long chain fatty acids) of the extensive meat with intensive with artificial and natural rearing systems.

2. Material and methods

2.1. Animals and management systems

Sixty one Murciano-Granadina kids (28 females, 33 males) from the herd located in the experimental farm of Diputación de Granada (Granada, Spain) were raised under three different management systems (extensive, intensive with natural rearing and intensive with artificial rearing) from birth to their slaughtering at around 34–38 days old and when they reached 7±1 kg of live weight. The 21 kids (nine females, 12 males) in the extensive management system (E) suckled directly from dams and were raised on a free-range pasture containing mostly wheat (Triticum Sativum Lam. T. Vulgare), oat (Avena sativa) and chickpeas (Cicer arietinum), with no additional feedstuff. At night, they were housed with their dams in a stable. Kids (nine females, 11 males) in the intensive with natural rearing management system (IN) suckled directly from dams and had access to alfalfa hay and cereal straw. The IN kids did not have access to a pasture but could exercise freely. The 20 kids (10 females, 10 males) in the intensive with artificial rearing management system (IA) were separated from dams afterbirth, housed in a nursing parlour, and fed colostrum for the first 2 days, as described by Castro et al. (2005). Subsequently, kids had free access to milk replacer from 9 am to 4 pm (Univet lambs and kids 60, Nutral S.A., Madrid, Spain; ash 6.00%, cellulose 0.04%, protein 24.00% and fat 24.50% on dry matter) that was distributed by a nursing device. This feeding regimen was supplemented with alfalfa hay. Kids from all three systems had free access to water at all times.

2.2. Slaughtering procedure

Animals were slaughtered according to the guidelines of the Council Directive 86/609/EEC (European Communities 1986). They were slaughtered at Los Filabres S.C.A. when their body live weight (BW) reached 7±1 kg. Kids from E and IN took 34 days to reach that BW, and kids from IA took 38 days to reach it. Kids fasted with free access to water during the 24 h before slaughter. The slaughter procedure and carcass definition were as described by Colomer-Rocher et al. (1987). Immediately after dressing, the carcass comprising the body after removing skin, head, forelimb (disjointed at the carpus), hind-limb (disjointed at the tarsus) and viscera was prepared. The kidneys and kidney and pelvic fat were retained in the carcass, and the testes and scrotal fat were removed as described by Colomer-Rocher et al. (1987). After 24 h of chilling (4°C), carcasses were split down the dorsal midline. The left side was divided into five primal cuts (neck, flank, ribs, shoulder and long leg) as described by Colomer-Rocher et al. (1987). Hot (after slaughter) and chilled (after 24 h chilling at 4°C) carcass weight (PCE-HS 50, maximum=50 kg, e=20 g, PCE Group Ibérica, Albacete, Spain) and weights of the head, skin, heart, liver, lungs and trachea, kidney, full and empty gastrointestinal tract (gastrointestinal content was determined as the difference between them) and spleen were recorded using electronic weights (G-310, maximum=15 kg, e=5 g, Dibal S.A., Bilbao, Spain; and Tefal model Gourmet, maximum=5 kg, e=1 g, Groupe SEB Ibérica, Barcelona, Spain). Empty body weight (EBW) was calculated by subtracting the weight of the gastro-100 intestinal contents from fasted body weight (FBW). Dressing carcass percentages were calculated using chilled carcass weight (CCW), hot carcass weight (HCW), FBW and EBW. Samples of longissimus thoracis et lumborum (LTL), triceps brachii (TB) and semimembranosus (SM) muscles were then removed. Intermuscular and subcutaneous fat samples were obtained from the shoulder. All samples were frozen (−20°C) during 7 days until analysis.

2.3. Meat quality attributes

Meat quality traits were measured in different muscles (LTL, TB and SM) because there were not enough muscle samples to carry all of the analysis using just one muscle. Muscle pH was measured in LTL, TB and SM using a Crison 166 pH metre with a combined electrode (Crison instruments S.A., Barcelona, Spain) by inserting into selected muscles immediately after slaughter and 24 h after chilling. Muscle colour was measured at the same time and in the same muscles (LTL, TB and SM) as pH using a Minolta CR200 Chroma-meter (Konica Minolta Sensing, Inc., Osaka, Japan) in the C.I.E. L*a*b* space (C.I.E. 1986), in which L* indicates relative lightness, a* indicates relative redness and b* represents relative yellowness.

The water holding capacity was measured according to Grau and Hamm (1953) on SM muscle. The SM muscle samples were sealed in a vacuum bag and cooked in a water bath at 75°C for 45 min to measure cooking losses. Cooked muscle cores (1×1 cm and at least 3 cm long) were cut parallel to the muscle fibers, and shear force values were recorded using an Instron Universal Testing Machine with a Warner-Bratzler shear force (WBSF) device (Instron, Barcelona, Spain).

Proximate analysis (moisture, protein, fat, collagen and soluble collagen) was performed on LTL according to AOAC (1984) procedures 24003, 13032 and 2057. Frozen powdered samples (4 g) were heated for 70 min at 77°C in one fourth strength Ringer's solution and separated into supernatant and residue fractions following the procedure of Hill (1966). Each fraction was individually hydrolysed in 6N HC1 for 6 h at 1 atm pressure and 102°C. The hydroxyproline content was determined as outlined by Bergman and Loxley (1963). Collagen content (mg/g, fresh tissue basis) was computed by multiplying the hydroxyproline content of the insoluble portion by 7.25 (Goll et al. 1964) and that of the soluble portion by 7.52 (Cross et al. 1973). The collagen content of the supernatant fraction expressed as a percentage of total collagen constituted percentage soluble collagen as specified by Hill (1966). Fatty acid composition was determined according to Granados (2000).

Fat was extracted from TB and subcutaneous and intermuscular fat as described by Folch et al. (1957). Briefly, fatty acids were separated before derivatisation (ISO Norm 5509, 2000) in a gas chromatograph (Model HP 5890 Series II GC; Hewlett-Packard, Avondale, PA) equipped with a flame ionisation detector and a phenyl-methyl-siloxane (cross-linked at 5%) capillary column (30 m long, 0.25 mm internal diameter, film thickness of 0.25 µm). The detector and the injector were maintained at 280°C. The carried gas was helium at a flow rate of 1 ml/min and a division ratio of 100:1.

The atherogenicity index was calculated using the equation developed by (Ulbricht and Southgate 1991):

where MUFA is monounsaturated fatty acids and PUFA is polyunsaturated fatty acids.

2.4. Sensory panel evaluation

Samples of TB were cooked in plastic bags in a water bath at 75°C for 45 min. Panelists evaluated samples using a five-point descriptive scale for taste (1=very bad, 2=bad, 3=regular, 4=good, 5=very good) according to UNE 87-005-92 (AENOR 1992).

2.5. Statistical analysis

A two-way ANOVA model (Statistical Analysis Software version 5 for Windows 1996) including the fixed effects of the management system and sex was performed and described the interaction between them. A Duncan post-hoc test of mean homogeneity (Statistical Analysis Software version 5 for Windows 1996) was developed to test the individual separation of means. Threshold level of probability to declare the statistical significance of the difference between pairs of means was P<0.05.

3. Results and discussion

The type of management system affected some colour parameters determined in the three different muscles (Table 1). L* values in SM, LTL and TB were not affected by the different management systems (Table 1), and values were in agreement with those established for others dairy goat breeds (Argüello et al. 2005). Statistical analysis showed that SM redness was the lowest with IN, LTL redness was the highest with E, and no system management effects were observed for the TB. SM yellowness was the lowest with IA, and no system management effects were observed on the LTL and on the TB samples. Extensive system dams had free access to pasture during the day, and thus rich Fe pasture intake was greater than in other management systems. Johnson and McGowan (1998) observed the diet/management effects (intensive and semi-intensive) on carcass attributes and meat quality of young goats, and found that lean colour in the LTL was not affected by diet/management, but Schroeder et al. (1980) reported that concentrate feeding of beef produced a lighter lean colour, which could be due to because these beefs had no access to rich Fe pasture intake as a result of not being raised under extensive management. In addition, higher redness values have been correlated with grazing in studies with lambs (Ripoll et al. 2008). Ripoll et al. (2008) reported that increases in physical activity and greater carotenoid intake (characteristic of E) correlate with higher redness values in meat.

Table 1. Effect of management system and sex on physico-chemical quality of semimembranosus (SM), longissimus thoracis et lumborum (LTL) and triceps brachii (TB) muscles and sensorial evaluation on TB muscle.

	Management system			Sex
Item	E	IN	IA	Male	Female	SEM^1
FBW (kg)	6.78	7.40	7.11	7.19	6.98	0.09
Age at slaughter (days)	33.87^a	33.76^a	38.37^b	35.09^a	46.18^b	1.09
Carcass weights
Hot carcass wt (kg)	3.64^b	4.09^a	3.72^b	3.86	3.76	0.05
Cold carcass wt (kg)	3.47^b	3.92^a	3.59^b	3.72	3.59	0.05
SM muscle
L* (lightness)	52.20	52.12	52.63	53.50	50.92	0.46
a* (redness)	8.79^b	7.14^a	9.04^b	8.16	8.54	0.27
b* (yellowness)	10.51^a	9.89^a	7.90^b	10.45	8.27	0.30
LTL muscle
L*	53.81	54.33	53.07	54.05	53.38	0.52
a*	11.20^b	8.28^a	6.56^a	9.06	8.32	0.37
b*	15.59	12.34	8.31	13.20	10.88	0.44
TB muscle
L*	47.84	50.52	48.58	48.85	49.10	0.54
a*	9.45	10.26	10.18	10.14	9.75	0.26
b*	7.14	7.91	6.42	7.36	6.92	0.27
pH muscle SM
0 hours	6.64	6.76	6.08	6.50	6.49	0.02
24 hours	5.80	5.68	5.72	5.72	5.75	0.04
pH muscle LTL
0 hours	6.56	6.81	6.34	6.54	6.60	0.02
24 hours	5.75	5.70	5.82	5.70	5.81	0.03
pH muscle TB
0 hours	6.36	6.54	6.42	6.48	6.40	0.03
24 hours	5.83	5.63	5.70	5.73	5.71	0.03
SM muscle
Warner-Bratzler shear force (kg/cm^2)	3.17^b	5.37^a	2.72^b	3.15	4.44	0.18
Water holding capacity (%)	13.51^a	13.14^a	15.50^b	13.86	14.25	0.39
Cooking losses (%)	29.27^a	30.22^a	48.73^b	35.88	36.07	0.52
LTL muscle
Moisture (%)	75.74	74.82	75.76	75.33	75.51	0.16
Protein (%)	21.43	22.17	21.59	21.76	21.69	0.63
Collagen (mg/g of dry matter)	1.03	1.08	1.03	1.05	1.04	0.01
Soluble collagen (mg/g of dry)
Matter	1.02	1.02	1.02	1.03	1.01	0.00
Soluble collagen (%)	97.23	93.68	96.56	95.41	96.30	0.73
Fat (%)	1.73	1.97	1.55	1.79	1.70	0.09
Sensorial evaluation on TB muscle^2	3.71	3.50	3.45	3.55	3.57	0.10
^a,bMeans with different superscripts differ significantly (P<0.05).
^1SEM=standard error of the mean.
^2Panelists evaluated samples using a five-point descriptive scale for taste (1=very bad, 2=bad, 3=regular, 4=good, 5=very good) according to UNE 87-005-92.

The pH values measured immediately after slaughter ranged from 6.81 to 6.08, and at 24 h post-slaughter the values ranged from 5.83 to 5.63 (Table 1), which is in agreement with findings by others examining dairy goat kids (Argüello et al. 2005). In our study, the management system type had no effect on meat pH values (Table 1). These results are in agreement with the observations of Kirton et al. (1989) in lambs. In contrast, Solomon et al. (1986) reported a difference in pH in animals with greater glycogen concentrations that were fed high-energy diets. Carrasco et al. (2009) did not report pH differences between grazing and non-grazing lambs. Our results correspond to a normal range ruling out dark-cutting or stress problems, and that might be caused because transport and slaughtering processes were not stressful enough to modify the meat pH in any of the management systems.

The IN meat had the highest WBSF values, and no significant differences were observed between E and IA meat (Table 1). The E and IA meat apparently had less collagen and greater collagen solubility (i.e. characteristics of tender meat) compared with IN meat, although these apparent differences were not statistically significant. Carrasco et al. (2009) reported that effects of the diet on meat toughness are unclear, and thus results from different studies are contradictory. Some authors have reported greater values for shear force and toughness of meat from concentrate-fed lambs than from pasture animals (Santos-Silva et al. 2002), whereas others did not find significant differences (Notter et al. 1991). The results reported for E animals may be related to the relatively greater amount of exercise by kids from E, as suggested by Aalhus et al. (1991) for lambs, who found that muscles from exercised lambs were significantly tenderer than muscles from their indoor counterparts.

The IA kids' meat displayed the lowest capacity to retain water inside the muscle (Table 1). Lower pH values at 24 h and protein muscle percentages have been reported to be related in dry meats, but no differences in pH or muscle protein were observed in the present study. Carrasco et al. (2009) observed that cooking losses were not affected when lambs were fed in pastures rather than receiving commercial feed. Some researchers have compared different diets and observed no differences in cooking losses (Lanza et al. 2001), whereas others reported greater cooking losses for grazing animals (Santos-Silva et al. 2002). Kemp et al. (1976) suggested that cooking losses are mostly due to differences in fatness, but fattier muscles were observed to have lower cooking losses.

The type of management system did not affect meat composition, and results were closer to the often-quoted standard composition of normal adult mammalian muscle (Lawrie 1998), which is 75% water, 19% protein, 2.5% fat and 0.65% minerals. Argüello et al. (2005) reported no differences in meat composition due to diet (goat milk versus milk replacer) in dairy bred goat kids with a similar fasted BW (FBW).

Sensorial evaluation was not affected by the type of management system (Table 1). Similarly, Walshe et al. (2006) reported no sensorial differences between organically and conventionally reared steers.

Sex did not affect meat quality traits in the current study (Table 1), as similarly reported by Todaro et al. (2004) for Nebrodi kids. Although there were no statistical differences in WBSF due to sex, Hogg et al. (1992) and Johnson et al. (1995) found that WBSF values for female goats were significantly lower than castrated or intact male goats. The low fasted body weight (FBW) observed in the current study (Table 1) may have prevented significant differences between the sexes. Sex did not affect sensorial evaluation.

Fatty acid profile in intramuscular (TB muscle), subcutaneous, and intermuscular fat deposits are shown in Tables 2–4, respectively. The saturated fatty acids (SFA) percentages ranged from 45.23% to 63.91%, which are consistent with those reported by Bañón et al. (2006) and García-Navarro et al. (2008) in goats, and were mainly contributed by C14:0, C16:0 and C18:0. SFA percentage is studied because it increases the concentration of blood cholesterol, although the different SFA have different effects on cholesterol concentration. For example, lauric (C12:0), myristic (C14:0) and palmitic (C16:0) fatty acids raise the plasma cholesterol level (Denke and Grundy 1992; Derr et al. 1993; Sundram et al. 1994), whereas, stearic acid (C18:0) does not appear to have such an effect and is considered ‘neutral’ (Denke and Grundy 1992; Derr et al. 1993). While it is clear that C14:0 and C16:0 are responsible for increasing the total plasma and LDL (low density lipoprotein) cholesterol concentration, the other major SFA, i.e. C18:0, is not hypercholesterolaemic and does not increase the total cholesterol or LDL cholesterol concentration (Williams 2000). High dietary levels of long-chain SFA increase plasma cholesterol level compared with high levels of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA; Grundy and Denke 1990).

Table 2. Effect of management system and sex on fatty acid composition (% of total fatty acids) of triceps brachii muscle intramuscular fat.

	Management system			Sex
Fatty acid composition (%)	E	IN	IA	Male	Female	SEM^1
C6:0	0.01	0.15	0.02	0.01	0.12	0.05
C8:0	0.87	0.48	1.90	0.22^a	1.93^b	0.35
C10:0	0.07	0.37	0.43	0.15	0.41	0.13
C11:0	ND	ND^2	0.02	0.01	ND	0.00
C12:0	0.36	0.83	1.67	1.12	0.55	0.30
C13:0	5.52	3.92	4.74	5.00	4.46	0.42
C14:0	12.31^b	19.27^a	21.29^a	17.53	16.48	1.37
C14:1	0.03	0.01	0.61	0.27	0.05	0.12
C15:0	0.29^ab	0.06^b	0.63^a	0.21	0.39	0.08
C15:1	0.06^a	ND	0.17^b	0.05	0.09	0.02
C16:0	25.31^a	23.02^ab	21.27^b	24.01	22.82	0.64
C16:1	0.43	0.27	0.63	0.31	0.56	0.09
C16:2	1.09	0.99	0.60	0.95	0.91	0.11
C16:3	0.36^b	0.09^a	0.23^ab	0.21	0.26	0.03
C16:4	0.06	ND	0.10	0.03	0.08	0.01
C17:1	0.14^a	0.02^a	1.38^b	0.04	0.87	0.22
C18:0	12.81	13.26	11.51	12.34	13.00	0.51
C18:1	36.66^b	29.85^a	28.35^a	32.87	31.25	1.24
C18:2	1.61^b	4.93^a	2.29^b	3.13	2.67	0.63
C18:3	0.10^ab	0.01^a	0.27^b	0.07	0.16	0.03
C18:4	0.03	0.02	0.05	0.01	0.06	0.01
C20:0	0.23	0.05	0.09	0.17	0.08	0.05
C20:1	0.04	0.04	0.1	0.02	0.09	0.01
C20:3	ND	ND	0.01	0.00	ND	0.00
C20:4	0.57	0.79	0.83	0.50	0.98	0.20
C20:5	0.03	ND	0.12	0.04	0.04	0.02
C22:0	0.01	0.07	0.00	0.03	0.03	0.01
C22:2	0.18	0.24	0.30	0.16	0.32	0.06
C23:0	0.73	1.15	0.21	0.42	1.15	0.23
C24:0	0.01^b	0.38^a	0.12^ab	0.13	0.22	0.05
C24:4	0.10	ND	0.00	0.07	ND	0.03
C26:6	0.00	ND	0.05	0.03	ND	0.01
All SFA	58.52	63.01	63.91	61.34	61.63	1.11
All MUFA	37.36^b	30.19^a	31.23^a	33.57	32.90	1.13
All PUFA	4.12	6.81	4.86	5.08	5.47	0.73
Atherogenicity index^3	1.81^b	2.73^a	3.00^a	2.46	2.32	0.25
^a,bMeans with different superscripts differ significantly (P<0.05).
^1SEM=standard error of the mean.
^2ND=not detected.
^3Atherogenicity index=(C12:0+(4×C14:0) + C16:0)/(MUFA + PUFA), Ulbricht and Southgate (1991).

Carcass weights and management system did affect significantly the SFA percentages in TB muscle, subcutaneous and intermuscular shoulder fat (Tables 2–4). Cifuni et al. (2000) found that the C16:0 percentage increased as carcass weight increased but C15:0, C14:0 and C24:0 percentages were not influenced. In the TB muscle, E had the lowest C14:0 percentages and the highest C16:0 percentages, and IN and IA showed similar percentages. In subcutaneous and intermuscular shoulder fat (Tables 3 and 4), the lowest C18:0 percentages were found in the IN samples, and those values were in agreement with a previous report (García-Navarro et al. 2008), but in the intermuscular shoulder fat samples, the highest C12:0 and C13:0 percentages were found in the IN samples. The C14:0 intramuscular percentage was the lowest in organic extensive meat. Although average percentages of C14:0 in TB muscle were lower than in sheep and beef (Banskalieva et al. 2000), the average percentages of C16:0 and C18:0 in the same muscle were similar. In rabbits, Hougham and Cramer (1980) demonstrated that muscle lipids in animals with high-activity metabolic profiles have larger amounts of 18-carbon fatty acids at the expense of 14- and 16-carbon fatty acids. This could explain the lower myristic fatty acid intramuscular percentage observed in organic extensive animals. In the current study, 18-carbon fatty acids (mainly oleic acid) were elevated at the expense of myristic fatty acid.

The MUFA percentages (Tables 2–4) were mainly due to oleic acid (C18:1), which is considered hypolipidaemic as it reduces cholesterol in plasma and triglycerides (Lee et al. 1998). The C18:1 concentration (mainly determining total MUFA) in goats is similar to that in other species, but the mean concentration of C16:1 in goat muscles is higher compared with lambs (Banskalieva et al. 2000).

The type of management system did not affect the percentage of C18:1 in subcutaneous or intermuscular deposits (Tables 3 and 4). In contrast, this percentage was greater in the TB muscle samples from the E carcasses (Table 2). As reported previously, the relatively high muscular activity of E animals causes a reduction in C14:0 content with a concomitant rise in the abundance of 18 carbon fatty acids (Hougham and Cramer 1980). Angood et al. (2008) did not observe that any management system affects the relative abundance of C18:1 in lambs. The lambs in that study were older than the kids in our current study, which may explain the contrasting results observed in the two studies. It has been reported that increasing age of slaughter of weaned kids receiving a concentrate-based diet decreases the MUFA level in subcutaneous adipose tissues (Bas et al. 1987). Bas et al. (1982) pointed out those levels of branched chain fatty acids (saturated C14, C15 and C16) in subcutaneous fat were higher in intact than castrated kids. In our study, sex did not have an effect on MUFA percentages and it was probably due to the fact that the animals were slaughtered too young.

Table 3. Effect of management system and sex on the fatty acid composition (% of total fatty acids) of subcutaneous shoulder fat.

	Management system			Sex
Fatty acid composition (%)	E	IN	IA	Male	Female	SEM^1
C6:0	0.00	0.00	0.04	0.00	0.03	0.01
C8:0	0.27	0.08	0.07	0.16	0.11	0.07
C10:0	0.16	0.27	0.24	0.12	0.32	0.07
C11:0	0.00	0.00	0.07	0.00	0.05	0.02
C12:0	0.61	1.59	1.40	1.15	1.23	0.36
C13:0	1.26	1.44	0.71	1.43	0.80	0.16
C14:0	8.98	9.51	8.65	9.23	8.78	0.51
C14:1	0.15	0.06	0.17	0.09	0.17	0.02
C15:0	0.69	0.07	0.61	0.57	0.43	0.12
C15:1	0.17^ab	0.01^a	0.28^b	0.12	0.22	0.04
C16:0	28.27	29.37	28.75	29.14	28.42	0.83
C16:1	1.00	0.66	1.07	1.05	0.84	0.16
C16:2	0.95	0.65	0.76	0.61	0.96	0.16
C16:3	0.62^b	0.14^a	0.46^b	0.40	0.45	0.05
C16:4	0.22^b	0.02^a	0.03^a	0.10	0.08	0.03
C17:1	0.12^a	0.03^a	0.37^b	0.11	0.27	0.05
C18:0	14.66^b	9.22^a	14.05^b	12.67	13.22	0.64
C18:1	40.43	44.77	40.81	41.36	42.08	0.96
C18:2	1.36	2.09	1.05	1.37	1.49	0.19
C18:3	0.00	ND^2	0.02	ND	0.01	0.01
C18:4	ND	0.00	0.07	0.04	0.02	0.01
C20:1	0.01	0.02	0.01	0.01	0.02	0.01
C22:2	0.01	ND	0.29	0.25	0.01	0.10
C23:0	0.03	0.00	0.00	0.02	0.01	0.01
C24:0	0.01	0.00	0.00	0.00	0.00	0.00
All SFA	54.94	51.55	54.58	54.48	53.38	0.98
All MUFA	41.89	45.55	42.72	42.75	43.59	0.94
All PUFA	3.17	2.90	2.69	2.77	3.02	0.17
Atherogenicity index^3	1.44	1.42	1.43	1.48	1.39	0.21
^a,bMeans with different superscripts differ significantly (P<0.05).
^1SEM=standard error of the mean.
^2ND=not detected.
^3Atherogenicity index=(C12:0+(4×C14:0) + C16:0)/(MUFA + PUFA), Ulbricht and Southgate (1991).

Table 4. Effect of management system and sex on fatty acid composition (% of total fatty acids) of intermuscular shoulder fat.

	Management system			Sex
Fatty acid composition (%)	E	IN	IA	Male	Female	SEM^1
C8:0	ND^2	0.14	0.11	0.06	0.09	0.05
C10:0	0.08	0.20	0.20	0.12	0.19	0.06
C12:0	0.14^b	1.43^a	0.50^ab	0.60	0.55	0.19
C13:0	0.35^b	1.99^a	1.06^ab	0.81	1.18	0.23
C14:0	5.55	5.72	6.65	4.77	7.17	0.89
C14:1	4.33	4.28	4.02	4.80	3.65	1.08
C15:0	0.29	0.20	0.92	0.15	0.88	0.22
C15:1	0.07	1.88	0.16	0.04	0.89	0.39
C16:0	33.44	30.11	31.29	31.66	31.93	1.15
C16:1	0.76	0.97	1.05	0.78	1.06	0.18
C16:2	0.73	0.42	0.88	0.68	0.77	0.16
C16:3	0.32	0.16	0.42	0.17	0.47	0.06
C16:4	ND	ND	0.01	ND	0.01	0.00
C17:1	0.17	0.06	0.17	0.11	0.18	0.04
C18:0	10.78^b	5.33^a	10.41^b	8.98	9.87	0.97
C18:1	41.93	44.48	41.00	43.36	38.36	0.99
C18:2	0.61^b	2.44^a	0.70^b	0.83	1.24	0.25
C18:3	ND	0.01	0.04	0.02	0.02	0.00
C18:4	ND	0.03	0.03	0.00	0.04	0.01
C20:0	ND	0.08	0.14	0.12	0.04	0.03
C20:1	ND	0.02	0.05	0.04	0.01	0.01
C20:4	ND	0.00	0.01	0.01	0.00	0.00
C22:2	0.01	0.02	0.13	0.04	0.08	0.03
C23:0	ND	0.01	0.01	0.01	0.01	0.01
C26:6	ND	0.00	0.01	0.00	0.00	0.00
All SFA	52.60	45.23	51.32	47.28	53.24	1.71
All MUFA	45.73	51.69	46.46	51.00	44.13	1.80
All PUFA	1.67	3.08	2.22	1.72	2.63	0.29
Atherogenicity index^3	1.17	0.99	1.19	0.97	1.30	0.23
^a,bMeans with different superscripts differ significantly (P<0.05).
^1SEM=standard error of the mean.
^2ND=not detected.
^3Atherogenicity index=(C12:0+(4×C14:0) + C16:0)/(MUFA + PUFA), Ulbricht and Southgate (1991).

As reported by Banskalieva et al. (2000), PUFA percentages were mainly due to linoleic (C18:2), linoleic (C18:3) and arachidonic (C20:4) fatty acid (Tables 2–4). The percentage of C18:2 in intermuscular and intramuscular depots (Tables 2 and 3) in carcasses from IN and IA management systems, which were the heaviest, was significantly greater than in carcasses from the E. A similar trend was observed in subcutaneous deposits (Table 4), although the difference was not statistically significant. Banskalieva et al. (2000) found that the content of the level of MUFA in all deposits decreased with increasing live weight. The feedstuff for the IN dams was prepared with sunflower meal, and Eknaes et al. (2009) recently demonstrated that the inclusion of sunflower in goat feed increases the C18:2 in milk. This increase may have resulted in the observed increase in this acid in IN fat deposits. In addition, the diet for E dams did not include any sunflower, and the percentage of C18:2 in intensive milk replacer were very low (approximately 3%, data provided by manufacturer). It is well established that docosanoic acid and eicosapentaenoic acid (EPA) are beneficial to human health (Horrocks and Yeo 1999), but meat and meat products generally do not contain substantial levels of these fatty acids. Fortunately, goat meat from the IA showed high levels of the mentioned fatty acids. The highest concentration of long chain n-3 PUFA was found in the TB samples from the IA. In fact, the consumption of goat meat from IA with increased n-3 fatty acid concentration can contribute to human requirements for these fatty acids, especially alpha linoleic acid (C18:3n-3), EPA (eicosapentaenoic acid), DPA (docosapentaenoic acid) and DHA (docosahexanoic acid). Meat, milk and eggs are the only sources of long chain n-3 PUFA in the diet of people who do not consume fish. Long chain n-3 PUFA like EPA and DHA play an important role in the development of cerebral and retinal tissues and in the prevention of heart diseases and some cancers (Simopoulos 2002).

The results reported in Tables 2–4 support the notion that DHA and EPA are indeed present in goat kid meat, suggesting that the consumption of this meat may have health benefits in a general sense.

Sex did not affect the SFA, MFA or PUFA percentages in any fat depot (Tables 2–4), but it must be said that sex differences in fatty acid composition in the literature have been inconsistent. For example, Banskalieva et al. (2000) reported that female goats had lower levels of C14:0 and C18:0, and that was similar to results for heifers and steers of Marchello et al. (1967) and Waldman et al. (1968). Opposite results have been reported by Malau-Aduli et al. (1998) with heifers and steers.

The atherogenicity index (Ulbricht and Southgate 1991) values in subcutaneous and intermuscular fat deposits (Tables 3 and 4) were not affected by the type of management system. In contrast, the intramuscular fat deposit (Table 2) was affected by the type of management system, with E samples showing the lowest atherogenicity index. The reason for these differences is probably the low C14:0 percentage and high C18:0 percentage in the E muscle fat deposit because both percentages are modulated by grazing-related muscular activity. Fehily et al. (1994) reported that an increase of 0.2 in the atherogenicity index is associated with an increase in plasma cholesterol of 1.93 mg/dL in consumers. Although further should be performed, the consumption of E kid meat may have greater health benefits compared with consumption of conventional kid meat. The sex did not affect the atherogenicity index of any fat depot.

4. Conclusions

Extensive system produces goat kid meat that is similar to meat produced by intensive with natural and artificial rearing system with respect to physical characteristics and the proximal chemical composition. However, fatty acid composition is influenced by the managements system, with the meat from the extensive system the one with the highest oleic fatty acid content and lowest saturated fatty acids content, as well as the lowest atherogenicity index. Although further studies are required, our results suggest that meat from extensive system is truly unique and could provide more health benefits than meat from intensive with natural and artificial rearing systems.

Acknowledgements

The authors thank Diputación de Granada, Murciano-Granadina National Breeders Association and Los Filabres SCA for financial support for this study.