Fatty acid composition of goat muscles and fat depots: a review
V. Banskalieva
a, T. Sahlu
b,*, A.L. Goetsch
c aDepartment of Biochemistry, Institute of Animal Science, 2232 Kostinbrod, Bulgaria bE (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK 73050, USAcDale Bumpers Small Farms Research Center ARS-USDA, 6883 South State Highway 23, Booneville, AR 72927-9214, USA
Received 1 October 1999; accepted 5 January 2000
Abstract
In addition to the fat content of muscle and adipose depots, the fatty acid composition of lipids affects meat quality. Furthermore, relevant reports are dif®cult to use for comparisons, in that samples were collected from muscles and fat depots at various anatomical locations and experiments entailed different objectives, designs, procedures and methodologies. Nonetheless, based on currently available publications, according to a recent classi®cation of meats by concentrations of potentially cholesterol-raising, and neutral, and cholesterol-lowering effects, average values for goat muscles appear better than for beef and lamb. Feeding dry diets seems to increase levels of unsaturated fatty acids and stearic acid in fat depots compared with milk or milk replacer. Increasing concentrate consumption can increase levels of odd-numbered and branched chain fatty acids in subcutaneous fat depots. With increasing age of unweaned kids, the level of stearic acid in fat depots decreases, and with increasing live weight of weaned kids levels of saturated fatty acids increase, and contents of monounsaturated fatty acids decrease in most fat depots. This review of a currently limited database indicates need for further experimentation to characterize interactions among factors such as breed, age and nutritional conditions in the fatty acid
composition of carcass lipids of goats so as to gain a fuller understanding of goat meat quality.#2000 Elsevier Science B.V.
All rights reserved.
Keywords:Goat; Fatty; Acids; Lipids; Meat
1. Introduction
The fatty acid composition of goat meat lipids has received little research attention relative to that given to milk and other meat animals (Parkash and Jenness, 1968; Palmquist and Jenkins, 1980; Haenlein, 1995). Although, there have been some studies which have evaluated the lipid composition of goat meat in single
muscles, different cuts of meat and of the entire carcass. A goal of some of these experiments has been to use lipid composition of goat meat as a determinant of meat quality.
Effects of factors such as breed, age, sex and nutritional conditions on fat deposition in goats have been studied. Goats deposit more internal fat and less subcutaneous and intramuscular fat compared with sheep (Smith et al., 1978; Kirton, 1988; van Niekerk and Casey, 1988; Colomber-Rocher et al., 1992). Hence, consumers are interested in goat meat as a source of relatively lean meat, especially in developed
Small Ruminant Research 37 (2000) 255±268
*Corresponding author. Tel.:1-405-466-3836; fax:1-405-466-3138.
E-mail address: sahlu@mail.luresext.edu (T. Sahlu)
countries with a high incidence of cardiovascular diseases.
The costly deposition of fat besides the effect on product market value represents a waste of dietary energy. The fatty acid composition of fat usually has little in¯uence on market value of the carcass, for which the quantity of fat is of greater importance. However, physical and chemical properties of lipids affect eating and keeping qualities of meat. Meat ¯avor is in¯uenced by fatty acid composition (Melton, 1990). Saturated fatty acids increase hardness of fat and being easily solidi®ed upon cooling in¯uence meat palatability. On the other hand, unsaturated fatty acids increase potential for oxidation which in¯uences shelf life.
Little is known about the fatty acid composition of goat meat. In only a few investigations (Sauvant et al., 1979; Nitsan et al., 1987; Potchoiba et al., 1990; Park and Washington, 1993; Johnson et al., 1995; Matsuoka et al., 1997) has the fatty acid composition of lipids in some goat muscles been studied. Moreover, there is a limited number of publications addressing the fatty acid composition of some fat depots in goats (Duncan et al., 1976; Sauvant et al., 1979; Bas et al., 1982, 1987b, c, 1992, 1996; Casey and van Niekerk, 1985; Gaili and Ali, 1985; Muller et al., 1985; Nitsan et al., 1987; Manfredini et al., 1988; Potchoiba et al., 1990; Zygoyiannis et al., 1992; Rojas et al., 1994; Ham-minga et al., 1996). Furthermore, the available data-base is somewhat fragmentary, such as entailing various muscles and fat depots and being derived from experiments with different designs and breeds. There-fore, the objective of our review was to compile and summarize the available literature concerning the fatty acid composition of muscles and fat depots of goats so as to make comparisons with other meat animals and identify fruitful areas for further research.
2. Muscle lipids
2.1. Species
Data in Table 1 represent means of pooled data for fatty acid composition of total lipids in different muscles of goats in single investigations. Values are sums of fatty acids in phospholipids and neutral lipids (i.e., triacylglycerols plus very small quantities of free
fatty acids). Data are derived from experiments with different designs, such as to investigate effects of diet, breed, sex, age and anatomical location. It should be noted that experimental procedures, methodologies and analytical instruments also differ among experi-ments. Hence, caution should be exercised when considering differences, such as among species, based on relatively small numbers of experiments. Certainly comparisons within experiments of factors like dif-ferent diets have great value, and there is considerable need for conduct of such experiments.
Similar to other livestock species reared for meat production, the major fatty acids in muscle lipids of goats are oleic (C18:1), palmitic (C16:0), stearic (C18:0) and linoleic (C18:2). Saturated fatty acids (SFA) include mainly myristic (C14:0), C16:0 and C18:0; monounsaturated fatty acids (MUFA) are pri-marily palmitoleic (C16:1) and C18:1; and polyunsa-turated fatty acids (PUFA) consist largely of C18:2, linolenic (C18:3) and arachidonic (C20:4; Table 1). Percentages are between 28 and 50 for C18:1; 15 and 31 for C16:0; 6 and 17 for C18:0; and 4 and 15 for C18:2. Other fatty acids present in lower concentra-tions (e.g., C10:0, C12:0, C15:0, C15:1, C17:0, C17:1, C20:1, C20:3,C22:0, C24:0, C22:4, C22:5 and C22:6) are not shown because not all were determined in each study. When values for some of these fatty acids were available, the levels were included in the sum of SFA, MUFA or PUFA for the particular studies. It should be noted that lipids from ruminants contain trans and positional isomers of C18:1 and C18:2 acids, exclu-sively characteristic of these animals, which in the normal course of analysis would be recorded as C18:1 and C18:2 acids (Pearson et al., 1977). Only in the study of Matsuoka et al. (1997) are data presented for the cis-isomer of C18:1.
Average percentages of C16:0 and C18:0 in goat muscles are similar to those for other ruminant species (Table 1). The concentration of C18:0 is relatively higher than in pork. The concentration of SFA in goat muscles varied markedly among investigations, from 29 to 54%. The mean concentration of SFA in goats from all studies cited is not different from that in lambs and beef, but it is slightly higher than in pork. 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. Goat muscle lipids are
Table 1
Fatty acid composition (%) of total lipids in different goat, sheep, lamb, beef and pork muscles (mean% of pooled data)a
Fatty acid:muscle/species C10:0
C12:0
C14:0 C14:1 C15:0
C15:1
C16:0 C16:1 C17:0
C17:1
C18:0 C18:1 C18:2 C18:3 C20:4 Others SFA MUFA PUFA Breed (n)b
Age (week)
Goats
Brachii (Sauvant et al., 1979) 1.43 1.20 ± 0.88 15.41 0.39 6.80 14.49 41.66 13.67 ± ± ± 38.76 43.51 13.67 A (Matsuoka et al., 1997) 5±22 Leg (Nitsan et al., 1987) ± 4.85 ± ± 15.60 7.27 2.82 5.92 50.52 11.05 ± 2.05 ± 29.19 57.79 13.10 S (Johnson et al., 1995) 5±10 Rib-LD (Potchoiba et al., 1990) ± 5.05 ± 0.50 31.35 5.65 2.00 14.95 28.00 11.50 1.20 ± ± 53.80 33.65 12.70 A (Nitsan et al., 1987) 20 LD (Park and Washington, 1993) ± 2.93 ± ± 22.30 4.73 ± 16.20 46.20 9.23 ± 3.43 ± 41.43 50.93 12.66 A 20 LD (Park and Washington, 1993) ± 3.58 3.70 ± 23.10 2.40 ± 17.20 36.20 11.80 ± 4.67 ± 43.88 42.30 16.47 N 20 BF (Park and Washington, 1993) ± 2.56 1.40 ± 21.40 1.30 ± 15.90 39.30 15.10 ± 4.52 ± 39.86 42.00 19.62 A 20 BF (Park and Washington, 1993) 1.35 4.76 3.58 ± 24.00 4.50 ± 13.90 38.70 8.06 2.18 3.54 ± 44.01 46.78 13.78 N 20 Leg (Johnson et al., 1995) ± 2.13 ± ± 26.50 4.00 ± 16.77 39.80 4.27 1.43 2.00 3.20 48.50 43.80 7.80 F (Potchoiba et al., 1990) 24±32 LT (Matsuoka et al., 1997) ± 1.97 ± 1.31 20.65 3.00 1.70 11.79 47.86 7.44 0.71 2.15 1.28 35.54 53.04 11.27 JS (Potchoiba et al., 1990) 36±40
Sheep/lamb
Rump (Duncan et al., 1976) ± 2.02 0.20 ± 23.40 3.02 ± 11.10 53.20 1.20 1.40 0.20 ± 36.52 56.60 3.80
LD (Solomon et al., 1991) ± 1.85 0.90 ± 22.71 1.74 ± 16.28 41.75 5.22 0.55 ± 9.84 40.80 43.58 5.77 Potchoiba et al., 1990 SM (Solomon et al., 1991) ± 1.73 0.83 ± 21.81 1.74 ± 15.44 41.67 6.26 0.61 ± 10.66 38.97 43.49 6.87 Potchoiba et al., 1990 TB (Solomon et al., 1991) ± 1.88 0.11 ± 21.63 1.88 ± 14.89 42.28 5.89 0.61 ± 10.49 38.40 44.60 6.49 Potchoiba et al., 1990 LD (Marinova et al., 1992) ± 4.17 ± ± 28..77 2.03 ± 16.13 45.30 3.60 ± ± ± 49.07 47.33 3.60 Potchoiba et al., 1990 Lean (Rhee, 1992) 0.44 3.13 ± ± 22.82 3.58 ± 13.87 42.73 8.05 1.57 1.12 2.68 41.96 47.20 10.74
TB (Enser et al., 1998) ± 3.17 ± ± 19.40 2.05 ± 17.90 36.59 3.43 2.31 1.19 2.51 40.47 38.64 9.41 LD (Enser et al., 1998) ± 3.99 ± ± 20.90 2.19 ± 17.50 35.73 3.24 1.94 1.12 2.25 42.39 37.92 8.55 GB (Enser et al., 1998) ± 3.23 ± ± 20.00 2.09 ± 18.60 35.83 3.28 2.31 1.16 2.44 41.83 37.92 9.19 Lean (Li et al., 1998) ± ± ± ± ± ± ± ± ± 4.90 2.00 1.20 2.10 45.60 44.00 10.20
Beef
Lean (Rhee, 1992) ± 3.16 ± ± 25.96 4.39 ± 13.53 43.88 3.66 0.18 0.54 4.75 44.79 50.45 4.75 TB (Enser et al., 1998) ± 2.07 ± ± 20.95 3.78 ± 13.35 35.76 7.47 1.05 2.63 2.69 36.37 39.54 13.70 LD (Enser et al., 1998) ± 2.40 ± ± 23.75 3.62 ± 14.75 36.48 5.39 0.91 1.69 2.01 40.90 40.10 10.00 GB (Enser et al., 1998) ± 2.04 ± ± 19.80 4.20 ± 13.40 36.48 7.40 1.06 2.71 2.47 35.24 40.68 13.64 GM (Enser et al., 1998) ± 1.77 ± ± 20.60 3.40 ± 14.02 37.02 7.26 1.14 2.48 2.53 36.39 40.42 13.41 Lean (Li et al., 1998) ± ± ± ± ± ± ± ± ± 5.60 1.80 3.00 ± 41.30 42.00 16.60 LDTB (Eichhorn et al., 1986) ± 2.00 ± 0.70 25.60 5.70 ± 14.20 39.80 5.60 0.60 3.50 ± 42.50 45.50 10.70 LD (Rule and Beitz, 1986) ± 4.18 ± 1.15 26.60 4.28 0.95 12.80 37.70 7.66 0.57 ± ± 45.68 41.98 8.23
Pork
Lean (Rhee, 1992) 0.32 1.31 ± ± 24.39 3.44 ± 11.95 45.50 9.66 0.65 1.31 1.48 38.30 50.08 11.62 Lean (Li et al., 1998) ± ± ± ± ± ± ± ± ± 14.40 0.60 3.60 ± 36.20 42.80 21.00 LD (Hernandez et al., 1998) ± 1.21 ± ± 23.80 3.13 ± 11.90 39.60 15.50 0.43 4.52 ± 36.90 42.70 20.40 BF (Hernandez et al., 1998) ± 1.15 ± ± 23.00 2.86 ± 11.30 38.70 17.50 0.52 5.08 ± 35.40 41.50 23.10
a
Goat breeds Ð A: Alpine; F: Florida; N: Nubian; S: Saanen; JS: Japanese Saanen. Muscles Ð BF:biceps femoris; LD:longissimus dorsi; LT:longissimus thoracis; SM:semimembranosus; TB:triceps brachii; GM:gluteus medius; SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids.
b
n: No. of mean% of pooled data;n1 if not speci®ed.
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higher in PUFA (i.e., C18:2, C18:3 and C20:4) than noted in lamb and beef but lower compared with pork. For the individual PUFA, the species rankings are C18:2: pork>goats>beef>lamb; C18:3: goatslamb> beef>pork; and C20:4: pork>goatsbeef>lamb.
Sinclair and O'Dea (1987) found that low intra-muscular lipid in bovine muscle was characterized by low proportions of SFA and MUFA and a high propor-tion of PUFA (Table 1). Park and Washington (1993) found similar results with goats, but only with two muscles (m. longissimus dorsiandm. biceps femoris). Also, data from Alpine and Nubian goats were pooled in this study. Breed differences in fatty acid composi-tion were observed, but lipid contents of each muscle were not presented for both breeds.
It is generally accepted that plasma cholesterol concentration is in¯uenced by the fatty acid composi-tion of dietary fat. High dietary levels of long-chain SFA increase plasma cholesterol level compared with high levels of MUFA and PUFA (Grundy and Denke, 1990). However, not all SFA have equivalent effects. Lauric (C12:0), C14:0 and C16:0 raise the plasma cholesterol level (Denke and Grundy, 1992; Derr et al., 1993; Sundram et al., 1994; Tholstrup et al., 1994; Zock et al., 1994); whereas, C18:0 does not appear to have such an effect and is considered `neutral' (Bona-nome and Grundy, 1988; Denke and Grundy, 1992; Derr et al., 1993). Salter et al. (1998) found that even in low cholesterol diets, C16:0 and C14:0 exert differ-ential, dose-dependent effects on cholesterol and lipo-protein metabolism. Evidence is now growing that the molecular structure of dietary triacylglycerols plays an important role in the development of atherosclero-sis (Patsch, 1994), because triacylglycerols, enriched with SFA at the sn-2-position, exhibit different meta-bolic behavior than triacylglycerols with SFA at sn-1 and sn-3 positions (Redgrave et al., 1988; Tuten et al., 1993; Carnielli et al., 1995). Unfortunately, no data are available concerning goat meat lipids in this respect, and no attention has been given to C16:0 and C14:0 as possible factors that increase cholesterol level.
Table 2 contains PUFA:SFA and (C18:0C18:1):
C16:0 ratios. Also included is the sum of desirable fatty acids (DFA) according the health classi®cation of Rhee (1992), with DFA being all unsaturated fatty acids and C18:0. Nonetheless, in most studies where the fatty acid composition of meat or muscle lipids was determined, the PUFA:SFA ratio is presented
because of impacts of all SFA on the cholesterol level. Goats are closer to beef than lamb in the PUFA:SFA ratio. Conversely, the PUFA:SFA ratio in goats is lower compared with pork. The PUFA:SFA ratio is lower in ruminants than nonruminants because of biohydrogenation of dietary unsaturated fatty acids by ruminal microorganisms.
Rhee (1992) classi®ed some meats (pork, beef, lamb, veal and chicken) by the concentrations of undesirable fatty acids (potentially cholesterol-rais-ing) and DFA (those considered to have either neutral or cholesterol-lowering effects) in separable lean. Following this classi®cation, data presented in Table 2 show that average percentages of DFA in goats are between 61 and 80, relatively higher than values for beef and lamb and similar to levels for lean pork.
Bonanome and Grundy (1988) suggested that only C16:0 increases blood cholesterol, whereas C18:0 has no effect and C18:1 decreases blood cholesterol con-tent. Because these fatty acids represent the majority of fatty acids, the ratio of (C18:0C18:1):C16:0 could perhaps better describe possible health effects of different types of lipids. Data in Table 2 show that for all species this ratio is between 2 and 3, except in studies of Sauvant et al. (1979) and Nitsan et al. (1987) with a ratio above 3, and of Rule and Beitz (1986) and Potchoiba et al. (1990) where it was less than 2.
Although ruminant meats normally have a low ratio of PUFA:SFA, muscles contain a range of PUFA, both n-6 and n-3 series, that have potential signi®cance in human nutrition. However, information about the amounts of these fatty acids in muscles of goats is limited. Data presented in Table 1 show that the contents of C18:3 and C20:4 were determined with goats in only a few instances. Johnson et al. (1995) presented the content of C20:3 (0.1%), and Matsuoka et al. (1997) determined amounts of C20:2 (0.16%), C20:3 (0.11±0.18%), C22:4 (0.13±0.17%), C22:5 (0.37±0.56%) and C22:6 (0.12%) as well. Matsuoka et al. (1997) did not present the ratio n-6:n-3 PUFA, but calculations based on their data suggest that the ratio n-6:n-3 PUFA for male goats is similar to that for bulls (Enser et al., 1998).
Although PUFA may have bene®cial effects on blood cholesterol, there is concern that some meats may have an excessively high ratio of n-6:n-3 PUFA (James et al., 1992). In accordance, a diet high in such
meat could lead to a tissue membrane imbalance in the ratio of n-6:n-3 PUFA. C20:4 is an essential fatty acid, which can be derived either from C18:2 or directly from the diet. It is the precursor of a multitude of vasoactive eicosanoids and increases in vivo platelet aggregation. Goat muscles contain nearly twice as much C18:2 as lamb muscles and have more C20:4 as well, but there are no data available concerning all n-6 or n-3 series of PUFA (Table 1).
Data in Table 1 also show that there are differences in fatty acid composition among the various muscles of goats. The lowest content of PUFA in muscles is in
m.longissimus thoracis(Matsuoka et al., 1997), and the highest is in m. biceps femoris of Alpine goats (Park and Washington, 1993). However, there is a difference between Alpine and Nubian breeds in the level of PUFA in m. biceps femoris (Park and Washington, 1993), as well as in the PUFA content
Table 2
PUFA:SFA and (C18:0C18:1):C16:0 ratios and contents of desirable fatty acids (by Rhee, 1992) in different musclesa
Species/muscle PUFA:SFA (C18:0C18:1):
C16:0
Desirable fatty acids (Rhee, 1992)
Goats
Brachii (Sauvant et al., 1979) 0.35 3.64 71.67
Leg (Nitsan et al., 1987) 0.45 3.62 76.81
Rib±LD (Potchoiba et al., 1990) 0.24 1.37 61.30
LD (Park and Washington, 1993) 0.31 2.80 79.79
LD (Park and Washington, 1993) 0.37 2.31 75.97
BF (Park and Washington, 1993) 0.49 2.58 74.52
BF (Park and Washington, 1993) 0.31 2.19 74.46
Leg (Johnson et al., 1995) 0.16 2.13 68.37
LT (Matsuoka et al., 1997) 0.32 2.88 76.17
Sheep/lamb
Rump (Duncan et al., 1976) 0.10 2.75 71.50
LD (Solomon et al., 1991) 0.14 2.56 65.63
SM (Solomon et al., 1991) 0.18 2.62 65.80
TB (Solomon et al., 1991) 0.17 2.64 65.98
LD (Marinova et al., 1992) 0.07 2.13 67.06
Lean (Rhee, 1992) 0.26 2.48 71.81
TB (Enser et al., 1998) 0.23 2.81 65.98
LD (Enser et al., 1998) 0.20 2.55 63.97
GB (Enser et al., 1998) 0.22 2.72 65.71
Lean (Li et al., 1998) 0.22 ± ±
Beef
Lean (Rhee, 1992) 0.11 2.21 68.73
TB (Enser et al., 1998) 0.38 2.34 66.59
LD (Enser et al., 1998) 0.24 2.16 63.45
GB (Enser et al., 1998) 0.39 2.52 67.72
GM (Enser et al., 1998) 0.38 2.48 67.85
Lean (Li et al., 1998) 0.40 ± ±
LDTB (Eichhorn et al., 1986) 0.25 2.11 70.40
LD (Rule and Beitz, 1986) 0.18 1.90 63.01
Pork
Lean (Rhee, 1992) 0.30 2.35 73.65
Lean (Li et al., 1998) 0.58 ± ±
LD (Hernandez et al., 1998) 0.55 2.16 75.00
TB (Hernandez et al., 1998) 0.65 2.17 75.90
aMuscles Ð BF:biceps femoris; LD: longissimus dorsi; LT:longissimus thoracis; SM:semimembranosus; TB:triceps brachii; GM: gluteus medius. SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids.
inm. longissimus dorsiin the different experiments with goats. Turkki and Cambell (1967) noted a high phospholipid concentration in red oxidative muscle ®bers. Enser et al. (1998) found that relatively white
m.longissimus dorsiin beef was generally lower in PUFA compared with the hindlimb muscle gluteus medius. The m. semimembranosus and m. triceps brachiiin lambs contained 12±19% more PUFA than
m.longissimus dorsi (Solomon et al., 1991).
2.2. Diet
The effect of different diets on the fatty acid com-position of total lipids in different muscles was studied in experiments of Sauvant et al. (1979) and Potchoiba et al. (1990) with Alpine goats, and in the experiment of Nitsan et al. (1987) with Saanen kids. Sauvant et al. (1979) found that an elevated dietary level of milk replacer before and after weaning increased C18:0 and C18:1 levels, respectively, inm.brachii. Similar dif-ferences were observed in leg muscle lipids between goats fed milk replacer versus concentrates (Nitsan et al., 1987) and in them.longissimus dorsiof kids receiving milk versus a starter diet (Potchoiba et al., 1990). By the classi®cation of Rhee (1992), results of these studies indicate that dry diets increase level of DFA. However, in the experiments of Sauvant et al. (1979) and Potchoiba et al. (1990), feeding of dry diets also increased the concentration of `undesirable' C16:0. The fatty acid composition of ruminant tissues is generally less affected by diet composition compared with nonruminants. However, numerous studies with ruminants (Marmer et al., 1984; Eichhorn et al., 1986; Larick and Turner, 1989; Melton, 1990; Solomon et al., 1991; Enser et al., 1998; Mandel et al., 1998) show that different nutritional conditions can change muscle lipid fatty acid composition, PUFA level and the n-3:n-6 PUFA ratio. For example, Enser et al. (1998) increased the content of C20:4 in beef muscles by feeding concentrate diets. This higher level of C20:4 together with the increased concentration of 18:2 increased the ratio n-6:n-3. In the three experiments with goats mentioned above, the C18:2 level was increased, but except for the study of Nitsan et al. (1987) there are no data for C20:4. The results from experiments with goats show that, similar to other ruminants, diet can affect fatty acid composition of muscle lipids. However, there are no data available
examining interactions between diet, muscle type, age, live weight or breed of goats.
2.3. Breed
Data presented in Tables 1 and 2 show considerable differences among breeds in contents of SFA, MUFA and PUFA and in PUFA:SFA (C18:0C18:1):C16:0 ratios. The lowest content of SFA and highest of MUFA were noted for Saanen kids in the experiment of Nitsan et al. (1987). Opposite of these data are results for Alpine kids from the experiment of Potch-oiba et al. (1990). Data for the other breeds are between these two extremes. The muscle PUFA con-centration for Florida goats (Johnson et al., 1995) was low, resulting in the lowest PUFA:SFA ratio among breeds. In fact, the PUFA:SFA ratio for Florida kids was three times less than that in Alpine kids (Park and Washington, 1993), although data of Johnson et al. (1995) are for cooked meat. The lowest ratio of (C18:0C18:1):C16:0 is for Alpine kids from the experiment of Potchoiba et al. (1990). Lipids from
m. longissimus dorsi in Alpine kids (Park and Washington, 1993) are characterized by a high quan-tity of DFA. Differences in the fatty acid composition of muscle lipids among animals of the same breed (Alpine) have been observed in numerous experiments (Sauvant et al., 1979; Potchoiba et al., 1990; Park and Washington, 1993). Ch'ang et al. (1980) in experi-ments with lambs hypothesized that carbon length is probably an important factor, which is responsible for phenotypic variation.
The fatty acid composition of the same muscle (m.
longissimus dorsi) was examined in two experiments with Alpine kids reared on concentrate-based diets (Potchoiba et al., 1990; Park and Washington, 1993). Muscle lipids for the second experiment were higher in concentration of C18:1 (46.2 versus 28.0%) but lower in C16:0 (22.3 versus 31.3%) and C18:2 (9.2 versus 11.5%) than for the ®rst experiment. The total amount of MUFA was also higher for the second experiment than for the ®rst (50.9 versus 33.6%), contrary to the difference in SFA for the second experiment versus the ®rst (41.4 versus 53.8%). The PUFA:SFA and (18:018:1)/16:0 ratios and the sum of DFA were higher inm.longissimus dorsiof Alpine kids in the experiment of Park and Washington (1993) than that of Potchoiba et al. (1990).
Park and Washington (1993) reared two breeds under the same experimental conditions and noted that SFA in m. longissimus dorsi and m. brachii femoriswere higher for Nubian than for Alpine goats, and the opposite was true for MUFA levels in m.
longissimus dorsi and PUFA in m. biceps femoris. Malau-Aduli et al. (1998) found breed differences in the fatty acid composition of lipids in adipose tissue as well as in phospholipids in m. triceps brachiiin cattle subjected to the same experimental conditions. Differences were even greater in phos-pholipids. Signi®cant breed effects on tissue fatty acid composition have also been reported for lambs (Boylan et al., 1976; Wise, 1977; Zygoyiannis et al., 1985; Webb and Casey, 1995). The only available data for goat muscle phospholipid fatty acid composition are those of Matsuoka et al. (1997) for Japanese Saanen goats. The fatty acid composition of phospholipids (especially PUFA) can have a signi®cant effect not only on human health, but also on animal metabolism and growth. Phospholipid fatty acids play a signi®cant role in reproductive and skeletal tissues (Simopoulous, 1994) and affect cell and anabolic processes (Scott and Asches, 1993).
2.4. Sex
In the studies of Johnson et al. (1995) and Matsuoka et al. (1997), despite use of different breeds and tested meat (i.e., cooked and raw), the total muscle lipid content was lower and the PUFA level and the PUFA:SFA ratio were greater in male animals compared with females. The concentration of PUFA in females was similar between Japanese Saanen and Florida goat breeds, but Japanese Saanen males contained more PUFA. Also, female goats had a higher percentage of C18:1 and lower levels of C14:0 and C18:0, 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. Sex differences in fatty acid composition in the literature have been inconsistent. Other studies (Terrel et al., 1968) with cattle have shown that sex effects were associated with the neutral rather than phospholipid fraction of fatty acids. The results of Matsuoka et al. (1997) for Japanese Saanen goats
show that sex differences in fatty acid composition are more pronounced in phospholipids than in neutral lipids.
3. Other fat depots
3.1. Species
Tables 3 and 4 present the fatty acid composition of total lipids (i.e., mainly triacylglycerols and small amounts of free fatty acids) for different fat depots for goats and for sheep, lamb and beef, respectively. The results represent mean values of pooled data and come from different experiments, where effects of factors such as diet, live weight, age and anatomical location were studied. Relatively more data are avail-able for internal and subcutaneous fat depots than for intermuscular lipids.
The main fatty acids of goat fat depots, regardless of the location of the adipose tissues in the body, are C18:1, C18:0 and C16:0, followed by C14:0, C16:1, C17:0 and C18:2 (Table 3). Levels are lowest for C10:0, C12:0, C14:1, C15:0, C17:1 and C18:3. How-ever, minor fatty acids were not quanti®ed in all cited studies. Goat depot lipids consist mainly of SFA (30± 71%) and MUFA (20±57%). The PUFA (i.e., the sum of C18:2 and C18:3) are less than 6% in some fat depots. The contents of SFA, MUFA and PUFA vary depending on anatomical location.
In general, the fatty acid composition of fat depots in goats (Table 3) appears in the range typical for ruminants (Table 4). Goat kidney fat is higher in C18:0 and lower in C14:0, C16:1, MUFA and PUFA compared with lambs. The C16:0 concentration in kidney fat is similar between goats and lambs, but lower for goats compared with beef. Opposite to kidney fat, subcutaneous fat depots in goats are less saturated, relatively higher in MUFA and contain less C18:2, C18:3 compared with sheep. Hilditch and Williams (1964) noted that land animals tend to have a relatively constant amount of palmitic acid in fat depots. Gaili and Ali (1985) compared three fat depots (subcutaneous, kidney and intermus-cular) in fattening sheep and goats and found that goat depots contained more C18:1. Our compiled data show this to be true for the subcutaneous fat depots, but in contrast goat kidney fat was higher
Table 3
Fatty acid composition (%) of different goat fat depot lipids (mean% of pooled data)a
Fatty acid: Fat depot C10:0
C12:0
C14:0 C14:1 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 Others SFA MUFA PUFA Breed (n)b Age or
BW
SC (Duncan et al., 1976) ± 3.50 ± ± 21.00 3.50 ± ± 14.50 41.00 1.50 ± 14.00 53.00 44.50 1.50 (Sauvant et al., 1979)
(Pericardic (Sauvant et al., 1979) 0.48 2.27 0.14 1.33 17.70 0.62 6.34 1.23 22.69 41.62 3.74 ± ± 50.81 43.63 3.74 A (Nitsan et al., 1987) 5±22 wk Kidney (Sauvant et al., 1979) 0.55 1.97 0.29 1.36 17.33 0.69 6.47 1.17 23.87 39.81 4.44 ± ± 51.55 41.96 4.44 A (Nitsan et al., 1987) 5±22 wk Omental (Sauvant et al., 1979) 0.56 2.09 0.24 1.20 17.09 0.59 6.13 1.38 21.19 42.07 3.92 ± ± 48.26 44.27 3.92 A (Nitsan et al., 1987) 5±22 wk Pericostal (Sauvant et al., 1979) 0.60 2.38 ± 1.53 18.52 0.49 7.09 1.89 10.01 52.39 2.89 ± ± 40.13 54.77 2.89 A (Nitsan et al., 1987) 5±22 wk Susternal (Sauvant et al., 1979) 0.65 2.90 1.82 2.60 16.98 1.68 9.45 3.29 5.77 49.01 1.69 ± ± 38.35 55.80 1.69 A (Nitsan et al., 1987) 5±22 wk Inguinal (Sauvant et al., 1979) 0.61 2.66 2.11 3.67 17.73 1.59 8.44 2.41 12.11 43.32 3.04 ± ± 45.20 49.43 3.04 A (Nitsan et al., 1987) 5±22 wk Kidney (Casey and van Niekerk, 1985) ± 3.39 ± ± 26.97 1.17 2.06 0.54 32.09 25.16 0.99 ± ± 64.51 26.87 0.99 B (Muller et al., 1985) 15 wk SC (Casey and van Niekerk, 1985) ± 2.99 ± ± 23.91 3.21 1.72 1.57 15.26 42.95 0.95 ± ± 43.88 47.70 0.95 B (Muller et al., 1985) 15 wk Kidney (Gaili and Ali, 1985) ± ± ± 9.90 32.00 ± ± ± 27.50 28.10 1.80 ± ± 69.40 28.10 1.80 SD 22 kg SC (Gaili and Ali, 1985) ± ± ± 8.30 32.20 ± ± ± 28.90 28.70 1.90 ± ± 69.40 28.70 1.90 SD 22 kg IM (Gaili and Ali, 1985) ± ± ± 10.70 32.10 ± ± ± 28.00 28.20 2.00 ± ± 70.80 28.20 2.00 SD 22 kg Kidney (Muller et al., 1985) 1.46 7.69 0.29 0.49 24.92 2.67 1.18 0.52 19.14 34.79 3.80 0.45 0.66 55.23 38.58 4.25 GG (Casey and van Niekerk, 1985) SC (Muller et al., 1985) 0.89 7.02 0.48 0.53 23.78 3.86 1.06 0.90 12.13 41.96 3.74 0.52 0.81 45.95 47.47 4.26 GG (Casey and van Niekerk, 1985) Kidney (Nitsan et al., 1987) 4.77 12.20 ± ± 21.85 4.17 1.06 0.53 16.27 34.77 4.60 ± ± 56.15 39.47 4.60 S (Gaili and Ali, 1985) 5±10 wk Mesenteric (Nitsan et al., 1987) 4.00 10.34 ± ± 19.35 5.82 0.56 0.70 12.07 42.22 4.42 ± ± 46.36 48.74 4.50 S (Gaili and Ali, 1985) 5±10 wk Omental (Bas et al., 1987b) ± ± ± ± 29.90 ± ± ± 27.60 25.60 ± ± ± 57.50 25.60 ± A 5±22 wk Perirenal (Bas et al., 1987b) ± ± ± ± 32.10 ± ± ± 30.70 19.60 ± ± ± 62.80 19.60 ± A 5±22 wk Mesenteric (Bas et al., 1987b) ± ± ± ± 29.00 ± ± ± 32.60 20.70 ± ± ± 61.60 20.70 ± A 5±22 wk Periranal (Bas et al., 1987c) ± ± ± ± 18.15 1.60 2.45 ± 27.45 38.30 ± ± 1.60 49.65 39.90 ± A (Nitsan et al., 1987) 4±8 wk Sternal (Bas et al., 1987c) ± ± ± ± 15.85 3.30 3.60 ± 5.80 50.75 ± ± 5.85 31.10 54.05 ± A 4±8 wk Inguinal (Manfredini et al., 1988) 2.03 7.53 0.87 0.52 20.85 4.92 1.08 1.28 11.41 43.44 2.99 0.99 ± 43.42 50.51 3.96 A (Casey and van Niekerk, 1985) 12±19 wk Sternal (Manfredini et al., 1988) 1.71 6.90 1.05 0.56 20.44 5.62 1.08 1.62 8.64 45.64 3.53 1.22 ± 39.33 53.93 4.75 A (Casey and van Niekerk, 1985) 12±19 wk Sacral (Potchoiba et al., 1990) ± 6.30 ± 0.70 30.00 3.40 2.10 ± 23.30 28.70 5.35 0.60 ± 62.55 32.10 5.9 A (Sauvant et al., 1979) 20 wk Kidney (Zygoyiannis et al., 1992) 1.59 7.89 ± ± 27.00 2.38 ± ± 23.80 30.10 4.53 0.55 2.13 62.41 32.48 5.08 G (Sauvant et al., 1979) 5±9 wk SC (Zygoyiannis et al., 1992) 1.38 8.51 ± ± 26.85 3.63 ± ± 13.90 38.00 4.45 0.60 2.83 53.47 41.63 5.05 G (Sauvant et al., 1979) 5±9 wk Omental (Bas et al., 1992) ± 3.00 ± ± 29.90 1.20 2.20 0.60 27.60 27.90 0.90 ± ± 62.70 30.00 0.90
Kidney (Rojas et al., 1994) 2.82 9.85 ± 0.56 24.46 3.01 0.93 0.61 13,80 35.34 4.32 ± 4.30 52.43 38.96 4.30 V (Bas et al., 1987c) 7 wk
Kidney (Bas et al., 1996) ± ± ± ± ± ± ± ± ± ± ± ± ± 62.50 33.80 ± 17 wk
Omental (Bas et al., 1996) ± ± ± ± ± ± ± ± ± ± ± ± ± 54.10 39.40 ± 17 wk
IM (Bas et al., 1996) ± ± ± ± ± ± ± ± ± ± ± ± ± 48.20 45.50 ± 17 wk
Caudal (Bas et al., 1996) ± ± ± ± ± ± ± ± ± ± ± ± ± 34.00 50.60 ± 17 wk
Sternal (Bas et al., 1996) ± ± ± ± ± ± ± ± ± ± ± ± ± 29.80 57.30 ± 17 wk
Kidney (Hamminga et al., 1996) ± 2.87 1.40 ± 26.28 3.52 ± ± 31.82 25.67 2.36 0.33 ± 60.97 30.59 2.69 WAD 120 wk Intestinal (Hamminga et al., 1996) ± 2.80 1.28 ± 22.52 3.37 ± ± 29.01 29.58 2.74 0.78 ± 54.33 34.23 3.52 WAD 160 wk
aBreeds Ð A: Alpine; B: Boer; G: Greek; GG: improved German; S: Saanen; SD: Sudan desert; V: Verata; WAD: West African Dwarf.; SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids; SC:
subcutaneous; IM: intermuscular.
b
Table 4
Fatty acid composition (%) of different fat depot lipids of sheep, lambs and beef (mean% of pooled data)a
Fatty acid: fat depot C10:0
C12:0
C14:0 C14:1 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 Others SFA MUFA PUFA Breed (n)b
Sheep/lamb
Kidney (Gaili and Ali, 1985) ± ± ± 9.60 32.90 ± ± ± 28.10 27.70 1.70 ± ± 70.60 27.70 1.70 SD SC (Gaili and Ali, 1985) ± ± ± 7.70 32.20 ± ± ± 30.10 28.20 1.80 ± ± 70.00 28.20 1.80 SD IM (Gaili and Ali, 1985) ± ± ± 10.900 33.20 ± ± ± 28.90 27.80 1.90 ± ± 73.00 27.80 1.90 SD Kidney (Zygoyiannis et al., 1985) 2.00 9.10 ± ± 25.00 3.40 ± ± 17.60 33.80 4.20 1.10 3.60 57.30 37.20 5.30 S Kidney (Zygoyiannis et al., 1985) 1.50 7.50 ± ± 24.00 3.40 ± ± 19.30 35.20 3.20 1.30 4.20 56.50 38.60 5.50 K Kidney (Zygoyiannis et al., 1985) 1.60 7.80 ± ± 25.10 3.20 ± ± 17.50 36.20 3.20 1.20 4.30 56.30 39.40 4.40 Ch SC (Zygoyiannis et al., 1985) 2.10 9.50 ± ± 26.50 4.40 ± ± 11.40 36.90 4.40 1.40 3.30 52.804 41.30 5.80 S SC (Zygoyiannis et al., 1985) 1.60 7.60 ± ± 24.60 4.90 ± ± 11.30 40.00 3.50 1.50 4.90 50.00 44.90 5.00 K SC (Zygoyiannis et al., 1985) 1.50 8.10 ± ± 25.80 4.20 ± ± 11.60 39.10 3.40 1.40 4.80 51.80 43.30 4.80 Ch Separable fat (Rhee, 1992) 0.84 4.79 ± ± 24.90 3.17 ± ± 15.70 40.71 6.07 2.08 0.19 46.23 45.42 8.35 SC (Webb and Casey, 1995) ± 4.79 ± 0.63 21.25 2.40 2.49 0.88 22.01 39.05 3.99 0.93 0.22 51.45 42.35 4.91 D (2) SC (Webb and Casey, 1995) ± 5.09 ± 0.62 22.05 2.42 2.12 0.65 22.84 36.96 4.10 0.81 0.22 52.95 40.04 4.90 S (2) Kidney (Banskalieva, 1996) ± 5.75 ± ± 22.70 2.00 ± ± 26.75 37.50 5.75 ± ± 55.20 39.05 5.75 B (3) SC (Banskalieva, 1996) ± 10.07 ± ± 27.10 2.75 ± ± 16.90 38.72 4.40 ± ± 54.07 41.47 4.40 B (3) Breast (Banskalieva, 1996) ± 8.70 ± ± 25.80 4.95 ± ± 11.55 45.00 4.20 ± ± 45.50 49.95 4.02 B (3)
Beef
Separable fat (Rhee, 1992) 0.82 3.80 ± ± 28.17 6.16 ± ± 14.00 42.81 2.37 1.70 0.17 46.78 49.15 4.07 LD (Bock et al., 1991) ± 4.59 ± ± 31.35 4.07 ± ± 17.91 42.03 0.46 0.42 ± 53.85 46.10 0.88 H (3) SM (Perry et al., 1998) ± 3.76 2.13 0.33 24.85 5.68 0.99 1.13 14.58 42.88 2.14 1.49 ± 44.51 51.84 3.63 H (3)
aBreeds Ð B: local Bulgarian sheep; K, Ch, S: local Greek sheep; D, S :South African sheep; SD: Sudan Desert sheep; H: Hereford steers.; LD: over m.longissimus dorsi; SM: overm.semimembranosus; SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids; SC: subcutaneous; IM: intermuscular.
bn: No. of mean% of pooled data;n1 if not speci®ed.
V
.
Banskalie
va
et
al.
/
Small
Ruminan
t
Resear
ch
37
(2000)
255±268
in C18:0 and relatively lower in C18:1 compared with lambs. Comparing subcutaneous and kidney fat in kids and lambs slaughtered at similar age, Zygoyiannis et al. (1985, 1992) concluded that kid fat is harder because of a higher content of SFA, mainly C18:0. Webb and Casey (1995) indicated that subcutaneous adipose tissue of lambs is high in C18:0. Data pre-sented in Tables 3 and 4 show that the mean percen-tage of C18:0 in subcutaneous adipose tissue of goats is similar to that of lambs.
In contrast to the investigations with muscle lipids (except for the studies of Matsuoka et al., 1997 and Sauvant et al., 1979), a few investigations of depot fat have considered positional or geometrical isomers of some fatty acids as well as odd-numbered (C15:0, C17:0 and C17:1) and branched chain (iso- or anteiso fatty acids with a middle carbon chain, mainly satu-rated as C12:0, C14:0, C15:0, C16:0 and C17:0, and monoenic C16:1) fatty acids (Duncan et al., 1976; Sauvant et al., 1979; Bas et al., 1987a,c, 1992, 1996; Hamminga et al., 1996; Matsuoka et al., 1997). For example, Duncan et al. (1976) and Bas et al. (1987a) noted that levels of branched chain and odd-numbered fatty acids in subcutaneous adipose tissue were high in goats and that concentrations of C14:1 and C15:1 were very low.
Oleic acid is the main fatty acid in both goat muscles and fat depot (Tables 1 and 3) and the average percentage from all subcutaneous fat depots studied is similar, but that from kidney fat is lower than for muscle lipids. On the contrary, the average percentage of C18:0 is higher in kidney fat depots than in muscles. Depot lipids also contain more other SFA, such as C10:0, C12:0, C15:0 and C17:0, but less C18:2. Data for SFA and MUFA percentages of some fat depots are to some extent close to average levels of SFA and MUFA in muscle lipids.
Comparisons of the fatty acid composition among fat depots (consisting mainly of triacylglycerols) and of muscle lipids (containing relatively larger amounts of phospholipids) should be done with caution. Only in the study of Matsuoka et al. (1997) were data presented separately for the muscle phospholipid frac-tion and for neutral lipids (mainly triacylglycerols). Levels of C18:1, C18:0 and C16:0 indicate that neutral lipids in muscles of Japanese Saanen goats are close to those of the pericostal fat depot of Alpine goats (Sauvant et al., 1979).
3.2. Anatomical location
The numbers and locations of the fat depots studied in goats vary among experiments. In some, one or two depots have been investigated (Duncan et al., 1976; Casey and van Niekerk, 1985; Bas et al., 1987b; Manfredini et al., 1988; Potchoiba et al., 1990; Zygoyiannis et al., 1992; Rojas et al., 1994; Ham-minga et al., 1996), although in others more have been considered (Sauvant et al., 1979; Gaili and Ali, 1985; Muller et al., 1985; Bas et al., 1987a,b). Results are also presented from different locations of subcuta-neous adipose tissue (Sauvant et al., 1979; Bas et al., 1987c), as well as from different sites of the same adipose tissue such as omental adipose tissue (Bas et al., 1992).
In general, internal fat depots in goats are more saturated than subcutaneous fat (Table 3), similar to results for lambs (Marchello et al., 1967; L'Estrange and Mulvihill, 1975; Kemp et al., 1981; Zygoyiannis et al., 1985; Banskalieva, 1996; Table 4). Leat (1976) and Belibasakis et al. (1990) concluded that subcuta-neous fat in sheep, cattle and pigs is softer (i.e., more unsaturated) than internal depot fat. Likewise, our compiled data suggest that some internal fat depots in kids are less saturated than other subcutaneous fat depots. Kidney fat from nine different investigations (Table 3) varies from 17 to 32, 16±32 and 20±40% in C16:0, C18:0 and C18:1, respectively. The results of Bas et al. (1987a), involving ®ve visceral adipose tissues and six subcutaneous fat depots of Alpine goats between Weeks 35 and 39 of lactation, depict highly variable fatty acid composition among tissues. The ranking of SFA in visceral sites was: perine-phric>pericardic>mesenteric>great omentum>minus omentum. Various locations of subcutaneous adipose tissue differ in fatty acid composition as well (Sauvant et al., 1979; Bas et al., 1987a; Manfredini et al., 1988). The ranking in the extent of saturation for subcuta-neous fat depots was: inguinal>udder>loin>costal>-caudal>sternal. There were also substantial differences in saturation among the same locations of subcutaneous fat depots noted by Zygoyiannis et al. (1992) and Bas et al. (1996).
Bas et al. (1987a) found that pericardic fat tissue in Alpine goats between Weeks 35 and 39 of lactation was highest in C18:0, whereas caudal and sternal fat was low in C18:0, C17:0 and C18:1n-6 but high in
C16:1n-7, C17:1n-8, C18:1n-7, C18:n-9 and branched chain fatty acids. The last two depots listed had the lowest lipid content compared with other subcuta-neous fat depots as well as with internal depots. These results are in agreement with those of Sinclair and O'Dea (1987), in that a lower lipid content is accom-panied by a higher level of MUFA. However, in another study with pregnant Alpine goats, Bas et al. (1987b) reported that the omental adipose tissue, which was higher in lipid content, contained more C18:1 than mesenteric fat depot. Bas et al. (1992) also found differences in fatty acid composition of 11 samples taken from different sites of omental fat in dry Alpine goats.
3.3. Diet
During milk feeding the fatty acid composition of adipose tissue of kids depends on the fatty acid composition of milk fat (Sauvant et al., 1979; Muller et al., 1985; Kuhne et al., 1986). In the investigations of Duncan et al. (1976); Sauvant et al. (1979); Casey and van Niekerk (1985); Muller et al. (1985); Nitsan et al. (1987); Potchoiba et al. (1990) and Rojas et al. (1994), carried out with different breeds of goats (Alpine, Boer, improved German, Saanen and Verata), effects of diet composition were examined. Use of higher amounts of milk replacer or concentrates, feeding of milk replacer versus milk and use of concentrates compared with milk or milk replacer resulted in lower contents of C14:0 and C16:0 and greater levels of C18:1 and C18:2 in fat depots studied (internal or subcutaneous). Although, magnitudes of difference varied with the type of fat depot. A common result from these experiments is that lipids in depots studied were softer, with an increase in the content of MUFA and PUFA. Also there is tissue dependence, in that various fat depots react differently to the type of diet. It was found that increasing concentrate con-sumption leads to accumulation of more odd-num-bered (C15:0, C17:0 and C17:1) and branched fatty acids (saturated C14, C15 and C16) in subcutaneous fat depots, and also a high intake of milk replacer increases the proportions of some minor fatty acids (e.g., C20:1). Comparing data from two experiments with goats of the same breed (Sauvant et al., 1979; Manfredini et al., 1988), a substantial effect of diet is evident. Use of a concentrate diet (Manfredini et al.,
1988) compared with use of milk replacer (Sauvant et al., 1979) led to a higher level of unsaturated fatty acids (MUFA and PUFA) in sternal (59.7 versus 48.2) and inguinal fat (56.0 versus 45.4).
3.4. Age and sex
In the studies of Bas et al. (1987c) and Zygoyiannis et al. (1992) with increasing age at slaughter of unweaned kids the composition of fat depots changed with a decreasing proportion of stearic acid but increasing proportions of all other acids. As a result of these changes the melting point of fat depots decreased, although there were signi®cant effects of age on the softness index (Zygoyiannis et al., 1992). Increasing age of slaughter of weaned kids receiving a concentrate-based diet decreases the MUFA level in kidney and subcutaneous adipose tissues (Bas et al., 1987b). Bas et al. (1982) pointed out that levels of branched chain fatty acids (saturated C14, C15 and C16) in subcutaneous fat were higher in intact than castrated kids. Rojas et al. (1994) did not ®nd any effect of sex on the fatty acid composition of kidney fat. Animal physiological state, such as dry versus pregnant, had similar total lipid concentration and fatty acid composition of omental fat (Bas et al., 1987b, 1992).
3.5. Live weight
Sauvant et al. (1979) compared the fatty acid com-position of different fat depots for unweaned (8±9 kg live weight) and weaned (average 27 kg live weight) Alpine kids. In older kids, fat depots except sternal and inguinal fat increased in stearic acid concentration with increasing live weight, and in all depots the content of SFA increased and the level of MUFA decreased.
In the experiment of Manfredini et al. (1988), with Alpine kids receiving milk replacer and concentrates and slaughtered at 12, 16 or 19 kg of live weight, in both inguinal and sternal adipose tissues there was a constant decrease in the ratio of SFA to unsaturated fatty acids as live weight increased. Similar results have been noted by Webb and Casey (1995) and Banskalieva (1996) for subcutaneous and perirenal adipose tissues of lambs slaughtered at different live weights.
4. Conclusions
There have been relatively few studies on the fatty acid composition of lipids in muscles and fat depots of goats. The present reports available are dif®cult to use for comparisons, in that samples were collected from muscles and fat depots at various anatomical locations and experiments entailed different designs, and pro-cedures and methodologies differ among experiments as well. Interactions among diet, age, live weight, breed and rearing conditions in the fatty acid compo-sition of lipids in different types of muscles and fat depots in goats have not been extensively studied, and little attention has been given to the characteristic of goats to deposit high levels of internal fat. The goat is known to produce relatively lean meat, yet there have been only a few incomplete reports on the mono- and polyunsaturated fatty acid concentration in muscle (being of importance for human health). For example, currently conjugated linoleic acid, as an anticarcino-genic factor, is the subject of a large number of investigations with ruminants, but not yet with goats. Thus, goat meat fatty acid composition deserves more research attention, especially now when different systems of nutrition and breeding are being tested for improving goat meat production.
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