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Effects of age on fatty acid composition of the hump and abdomen depot fats of the Arabian camel (Camelus dromedarius)
Meat Science 62 (2002) 245–251 www.elsevier.com/locate/meatsci
Effects of age on fatty acid composition of the hump and abdomen depot fats of the Arabian camel (Camelus dromedarius) I.T. Kadim*, O. Mahgoub, R.S. Al-Maqbaly, K. Annamalai, D.S. Al-Ajmi Animal and Veterinary Sciences Department, College of Agriculture, Sultan Qaboos University, PO Box 34, Al-Khoud, 123, Muscat, Sultanate of Oman Received 14 August 2001; received in revised form 12 November 2001; accepted 15 December 2001
Abstract This study aimed to quantify concentrations of fatty acids in the hump and abdomen fats of three different age groups of camel. Hump and abdomen fats were extracted from eight each of one-humped camels (Camelus dromedarius) of three age groups: group 1 (< 1 year old), group 2 (1–3 years old) and group 3 ( > 3 years old). The fatty acid methyl ester concentrations of these fats were determined by gas–liquid chromatography (GLC). The percentage of fat in the hump (H) and abdomen (A) fats was significantly (P < 0.05) lower for group 1 (H 92.0% and A 94.3%) than for group 2 (H 97.4% and A 97.2%) and group 3 (H 97.6% and A 97.5%), on a dry matter basis. Hump and abdomen fats from the three different groups had similar fatty acid patterns with more saturated than unsaturated fatty acids. The saturated fatty acids in the hump fats accounted for 58.3, 67.6, and 63.0% of the total fatty acids for groups 1, 2 and 3, respectively; group 1 had significantly (P<0.05) lower saturated and higher unsaturated fatty acid concentrations than group 2. The iodine numbers were significantly (P< 0.05) higher in group 1 than either group 2 or 3. Palmitic acid (C16:0) was the major fatty acid in hump fat with 32.06, 32.90 and 34.37%, followed by oleic acid (C18:1) 33.65, 21.66 and 28.91.0% and stearic acid (C18:0) 18.85, 24.13 and 20.74% for groups 1, 2 and 3, respectively. Group 1 had significantly higher (P <0.05) oleic acid and lower stearic acid concentrations than group 2. The melting point of both hump and abdomen fats varied between the age groups. This study indicated that age has an effect on the fatty acid composition and the melting point of hump and abdomen fats in one-humped Arabian camels. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Camel; Hump; Abdomen; Fatty acids; Iodine number; Melting point and fat
1. Introduction The camel stores its energy reserves in the form of fat in different depots in their body of which the hump and abdomen depots comprise a considerable amount of the adult body weight, therefore camels can survive long periods without feed. Hump and abdomen fats contain mixtures of fatty acids (Emmanuel & Nahapetian, 1980) and most of these are esterified as triglycerides or phospholipids and vary according to their anatomical location in the body (Duncan & Garton, 1967). In camels, no information is available regarding the relationship between the fatty acid composition and age. It is of interest to determine the types and the composition of fatty acids in the hump and abdomen fats at different * Corresponding author. Tel.: +968-515-232; fax: +968-513-418. E-mail address: [email protected] (I.T. Kadim).
age groups in relationship to fat metabolism. Such information will form the basis for further studies on fat composition of the hump or abdomen and its value for human consumption. Few studies have examined the fatty acid composition of camel hump and abdomen depot fats (Emmanuel, 1981; Emmanuel & Nahapetian, 1980; Mirgani, 1977; Orlov, Servetnik-Chalaia, & Zagibailova, 1985; Rawdah, El-Faer, & Koreish, 1994), and most of these have been conducted in a single group. However, the fatty acid compositions of total fats may vary with age. Mirgani (1977) used thin-layer chromatography to determine the fatty acid composition of hump triglycerides from a single-humped camel (Camelus dromedarius) and found that saturated fatty acids accounted for 74% of the total fatty acids, and Emmanuel (1981), Orlov et al. (1985) and Rawdah, El-Faer, and Koreish (1994) showed that the saturated fatty acid contents in hump
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fats was 64.9, 60.2 and 60.5%, respectively. In the abdomen fat of single humped camels, saturated fatty acids accounted for 63.6% of the total fatty acids (Emmanuel & Nahapetian, 1980). Most information describing the composition of such fats gives only the overall fatty acid composition. This information is important, but other properties such as melting point, saponification and iodine numbers provide further information. The melting point of a fat depends on its fatty acid composition and the concentration of saturated fatty acids gives the best prediction of melting point (Enser, 1984; Wood et al., 1978). Saponification number gives a measure of the average chain length of the fatty acids in the fat and the degree of unsaturation of the fatty acids can be measured by the iodine number. This study compares the fatty acid compositions in the hump and abdomen fat depots of three age groups (less than 1 year old, 1–3 year old and more than 3 year old) of one-humped Arabian camels.
2. Material and methods 2.1. Hump samples Twenty-four hump and abdomen fat samples from Arabian camels were collected from the Municipality slaughterhouse in Muscat (Sultanate of Oman) representing three age groups. Each group consisted of eight camels: group 1 (< 1 year old), group 2 (1–3 years old) and group 3 ( > 3 years old). Soon after slaughter, aliquots of 10 g samples of fat were obtained from middle portions of the hump and abdomen fats, transported to the laboratory and stored at 20 C in sealed plastic bags until analysed. The samples were taken from the same site from each animal. 2.2. Sample analysis Hump and abdomen fat samples from all three groups were analysed for fat content, melting point, iodine number and saponification value (AOAC, 1989). Triplicate samples, each weighing approximately 2 g were freeze-dried for 4 days and then the lipid extracted with petroleum ether in a Soxhlet apparatus. Iodine numbers were determined to assess the saturation levels of the two depots according to the Wijs method. Melting points and saponification numbers were determined according to the Capillary Tube and Titrimetric methods, respectively.The fatty acids were extracted according to the method described in AOAC (1989) with some modifications. Hump or abdomen fat (0.5g) was mixed with 50 ml of 1N KOH and 10 mg of internal standard [Tricosanoic acid (C23)] was added. The mixture was heated for 30 min at 150 C, followed by cooling at
room temperature. The samples were transferred to a 500 ml separating funnel, 150 ml distilled water was added followed by 0.1% methyl orange, drop wise, until the colour changed to yellow. 5N HCl was added until the colour turned to light pink and the solution was then partitioned vigorously for 5 min with 100 ml of diethyl ether. The diethyl ether layer was collected and the coloured aqueous phase re-extracted with a further 100 ml of diethyl ether. The diethyl layer ether extracts were pooled and washed four times with 80 ml of distilled water and subsequently dried over anhydrous Na2SO4. The diethyl ether extract was then concentrated to 2 ml in a rotary vacuum evaporator at less than 40 C and transferred to a screw cap test tube following addition of 2 ml of BF3–methanol reagent (14%). The test tube was heated at 100 C for 15 min in a water bath. After cooling to room temperature, 3 ml of hexane and 5 ml of saturated NaCl was added and the mixture vigorously shaken for 5 min. The hexane layer was then carefully transferred, by a Pasteur pipette, into a screw cap glass vial and stored at 20 C until assayed by gas chromatography mass spectrophotometry. Fatty acid samples were analysed with a Hewlett Packard 5890 Serial II Plus gas chromatograph (GC) coupled with HP5989B mass engine. A 30 m0.25 mm Omega waxTM capillary column (Supeclo Inc., USA) was used for the separation of fatty acids in the GC. Helium was used as carrier gas at a flow rate of 30 cm/ sec. The GC temperature program was 70 C for 1 min then 5 C/min until 260 C, which was maintained for 5 min. The temperatures of injector and detector were 250 and 270 C, respectively. Mass spectrophotometer conditions consisted of optics auto-tuned at 69, 219 and 502 using decafluorotriphenyl phosphate (DFTPP). Mass scan range was set from 40 to 550 amu at 30 thresholds. Fatty acids were identified by comparison of retention time with reference compounds purchased from Supeclo, Inc., USA and further confirmed by comparison with a library of chemical mass spectra (NIST98). Concentration of individual fatty acids was calculated by using tricosanoic acid (C23) as internal standard. 2.3. Data analysis The relationship between fat characteristics and fatty acid composition from hump and abdomen fat depots and the age of camels were analysed using the General Linear Model (GLM) procedure of SAS (1993).
3. Results and discussion Dry matter, lipid, and total fatty acids, saturated and unsaturated fatty acid percentages and the ratio of saturated to unsaturated fatty acids of hump and abdomen
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fat depots from the three age groups are given in Tables 1 and 2. The fatty acid composition of camel hump and abdomen fats for the three age groups are given in Tables 3 and 4, respectively. The hump fat of group 1 had significantly lower (P < 0.05) dry matter percentage (69.5%) than group 2 (87.1%) and group 3 (85.1%). The corresponding values for abdomen fat were significantly lower (53.9%) for group 1 than for group 2 (82.9%) and group 3 (85.2%). Percentage of fats on both a dry matter (DM) and wet basis (g/100 g fat) was significantly (P< 0.05) lower in group 1 than group 2 and group 3 for both hump and abdomen fats. The total fat content of the hump increased significantly (P < 0.05) from 642 mg/g wet weight in group 1 to 848 and 830 mg/g wet weight for groups 2 and 3, respectively (Table 1). The values for the abdomen fats were 508, 806 and 840 mg/g for groups 1, 2 and 3, respectively. Changes in the relative proportions of fat, water and connective tissue occur during growth and have important effects on fat composition and characteristics (Wood, 1984). The values for the total fatty acid (TFA) mg/g total fat (wet basis)
support previous observations made on camel hump (Mirgani, 1977). The difference between the saturated and unsaturated fatty acid percentages varied with age and fat depot. The contents of saturated and unsaturated fatty acids in hump fat, expressed as per 100 g dry matter fatty acids were significantly (P < 0.05) higher in group 1 (58.2%) than group 2 (67.5%), but no significant differences were seen between group 1 and 3 (63.4%) and group 2 and 3 (Table 1). The corresponding values for abdomen fat were 67.5, 69.7 and 67.7%, respectively (Table 2). Camel hump fat is characterized by a high content of saturated fatty acids, 63.0% (average) values, which are in agreement with the findings of Mirgani (1977), Emmanuel (1981), Orlov et al. (1985) and Rawdah, et al. (1994). Hump fats are lower in polyunsaturated fatty acids, 1.89, 2.20 and 1.89% for groups 1, 2 and 3, respectively, in agreement with other investigators (Emmanuel, 1981; Orlov et al., 1985; Rawdah, et al., 1994). The data on saturated fatty acid percentage in abdomen fat support the work of Emmanuel and Nahapetian (1980).
Table 1 Dry matter, fat content, and total fatty acids composition of hump fat from three age groups of one-humped Arabian camel. Least square means within the same row with different letters (a,b) were significantly different (P <0.05, P <0.001). SEM, Standard error of the means Component
Group 1 ( <1 year)
Group 2 (1–3 years)
Group 3 ( >3 years)
SEM
Dry matter% Total lipid% (DM basis) Total lipid% (wet basis) Total lipid weight mg/g (wet basis) Total fatty acids (TFA)% TFA mg/g total fat (wet basis) Saturated fatty acids (SFA)% SFA mg/g TFA (wet basis) Unsaturated fatty acids (USFA)% USFA mg/g TFA (wet basis) SFA: USFA
69.5a 92.0a 64.2a 642a 41.1 276 58.2a 162a 41.8a 114 1.44a
87.1b 97.4b 84.8b 848b 44.6 379 67.5b 254b 32.5b 125 2.41b
85.1b 97.6b 83.1b 830b 47.1 385 63.4ab 241b 36.6ab 144 1.74ab
2.64 0.79 2.85 28.5 4.94 40.5 2.24 24.5 2.24 18.4 0.320
Table 2 Dry matter, fat content, and total fatty acids composition of abdomen fat from three age groups of one-humped Arabian camels. Least square means within the same row with different letters (a,b) were significantly different (P<0.05). SEM, Standard error of the means Component
Group 1 (<1 year)
Group 2 (1–3 years)
Group 3 ( >3 years)
SEM
Dry matter% Total lipid% (DM basis) Total lipid% (wet basis) Total lipid weight mg/g (wet basis) Total fatty acids (TFA)% TFA mg/g total fat (wet basis) Saturated fatty acids (SFA)% SFA mg/g TFA (wet basis) Unsaturated fatty acids (USFA)% USFA mg/g TFA (wet basis) SFA: USFA
53.9a 94.3a 50.8a 508a 50.1 253a 67. 5 171a 32.6 82 2.07
82.9b 97.2b 80.6b 806b 46.8 374ab 69.7 261b 30.3 113 2.33
85.2b 97.5 b 84.0b 840 b 47.3 398b 67.7 270b 32.3 128 2.29
1.23 1.04 3.78 37.9 5.71 52 1.95 28.6 1.95 25.9 0.18
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Table 3 Fatty acids composition of hump fats from three age groups of one-humped Arabian camels. Least square means within the same row with different letters (a,b) were significantly different (P <0.05). SEM, Standard error of the means Fatty acid%
Group 1 ( <1 year)
Group 2 (1–3 year)
Group 3 ( >3 year)
SEM
Saturated fatty acids 14:0 15:0 16:0 17:0 18:0 19:0 20:0
4.18 1.39a 32.1 1.47 18.9a 0.05 0.20
5.07 2.15b 32.9 2.33 24.1b 0.78 0.19
3.97 2.22b 34.4 1.44a 20.7ab 0.26 0.37
0.633 0.264 1.192 0.432 1.882 0.379 0.097
Mono-unsaturated fatty acids 14:1 15:1 16:1 16:1 w7 18:1 w9
0.75 0.36 1.29 3.86 33.7b
1.01 0.20 1.99 5.39 21.7a
0.55 0.43 1.34 3.59 28.9b
0.178 0.101 0.337 1.004 2.407
Poly-unsaturated fatty acids 18:2 w6
1.89
2.20
1.82
0.310
58.2a 41.8a 40.0b 84.7b
67.5b 32.5b 30.3a 78.7a
63.4ab 36.6ab 34.8ab 84.0b
2.320 2.306 2.306 1.721
Percentage of total fatty acids Saturated Unsaturated Mono-unsaturated C16+C18+C18:1
Table 4 Fatty acids composition of abdomen fats from three age groups of one-humped Arabian camels. SEM, Standard error of the means Fatty acid%
Group 1 ( <1 year)
Group 2 (1–3 years)
Group 3 ( >3 years)
SEM
Saturated fatty acids 14:0 15:0 16:0 17:0 18:0 19:0 20:0
3.45 1.72 31.0 1.51 29.1 0.24 0.48
3.76 1.63 30.2 1.94 31.5 0.25 0.38
4.39 1.57 30.7 1.85 28.6 0.40 0.23
0.493 0.225 0.849 0.183 2.122 0.125 0.108
Mono-unsaturated fatty acids 14:1 15:1 16:1 16:1 w7 18:1 w9
0.79 0.41 1.48 2.54 25.4
0.95 0.44 1.22 2.29 23.5
0.70 0.40 1.18 3.07 25.0
0.144 0.083 0.158 0.718 1.291
Poly-unsaturated fatty acids 18:2 w6
1.98
1.90
1.97
0.184
Percentage of total fatty acids Saturated Unsaturated Mono-unsaturated C16+C18+C18:1
67.5 32.6 30.6 85.4
69.7 30.3 28.4 85.2
67.7 32.3 30.3 84.2
1.846 1.846 1.815 1.125
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Palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1) dominate, but other groups including polyunsaturated acids such as linoleic (C18:2) are seen. The sum of the smaller fractions can exceed 14% for hump and 15% for the abdomen fat of the total fatty acid contents. Age group differences were noted for individual fatty acids in hump fat. For example, pentadecanoic acid (C15:0) was significantly lower in group 1 than group 2 and group 3 and stearic acid (C18:0) in group 1 compared with group 2, but not group 3. Linoleic acid (C18:2) was significantly higher in group 1 (33.7%) than group 2 (21.7%). However, there were no differences between groups 1 and 3. In hump fat, oleic acid (C18:1) is the main fatty acid in group 1 (33.7%) followed by palmitic acid (16:0), 32.1%, and stearic acid (18:0), 18.9%, in groups 2 and 3, palmitic acid (C16:0) is the most abundant followed by stearic acid (18:0) and oleic acid in group 2, while group 3, oleic acid (C18:1) exceeded stearic acid (C18:0). In abdomen fat, palmetic acid (C16:0) is the main fatty acid, followed by stearic acid (C18:0) and then oleic acid (C18:1) in groups 1 and 2, while stearic acid (18:0) is the main fatty acid in group 2, followed by palmetic acid (C16:0) and then oleic acid (C18:1). In one-humped camels reared in temperate climates Mirgani (1977) found that C16:0, C18:0 and C18:1 together accounted for over 81% of the total fatty acids. However, in the present study, the fatty acids in the total fat (triglycerides, phospholipids and cholesterol esters) were analysed, whereas Mirgani only analysed the triglycerides. Similar values were reported by Emmanuel and Nahapetian (1980) and Emmanuel (1981). The mono-unsaturated fatty acids in camel hump account for almost one-third of the total fatty acids (Table 3), group 1 contained significantly (P < 0.05) more (39.9%) than group 2 (30.2%). However, the differences between group 1 and group 3 (34.8%) and between group 2 and group 3 were not significant. No significant differences in mono-unsaturated fatty acid contents were found among abdomen fats from the
three groups. This group of fatty acids is dominated by oleic acid (C18:1) followed by palmitoleic acid (C16:1). The melting points, saponification number and iodine number of the hump and abdomen fats are given in Table 5. The melting point is dependent on the actual content of fatty acids in the triacylgycerols, which account for about 95% of the adipose tissue (Enser, 1984a). In this study, the differences in fatty acid patterns of the hump or abdomen fats from the three age groups resulted in significant differences in melting point. Significant differences of 7.8 and 4.9 C in hump fat melting point between groups 1, 2 and 3, respectively and a significant difference of 3.7 C in abdomen fat melting point between groups 1 and 2, will have a major impact on the consistency of the fats. The mean iodine numbers of the hump fat were significantly higher for group 1 (39.0) than group 2 (35.8) and group 3 (36.0). The differences in iodine numbers are explained by the higher percentages of saturated fatty acids. Gibney and L’Estrange (1975) stated that, whatever the experimental conditions, the decrease in melting points are best explained by a fall in stearic acid (C18:0) content, and not by a fall in total saturated fatty acid content, and by an increase in linoleic acid (C18:2). No significant differences between the three age group in iodine numbers were seen in the abdomen fats, reflecting the similarity in saturated fatty acid contents in the groups. Correlation coefficients between fatty acid composition and the physical properties of hump and abdomen fats are presented in Tables 6 and 7. From Table 6 it can be seen that pentadecanoic acid (C15:0), linoleic acid (C18:2), stearic acid (C18:0), oleic acid (C18:1), saturated fatty acid (SFA):oleic acid (C18:1) ratio, and unsaturated fatty acid (UFA):SFA ratio give the best estimation of the melting point. From Table 6 it can also be concluded that pentadecanoic acid (C15:0), linoelic acid (C18:2), stearic acid (C18:0): oleic acid (C18:1) saturated fatty acid (SFA): oleic acid (C18:1), and unsaturated fatty acid (UFA): SFA give the best estimate of the melting point of adipose tissue.
Table 5 Physical properties of hump and abdomen fats from three age groups of one-humped Arabian camels. Least square means within the same row with different letters (a,b) were significantly different (P <0.05, P <0.001). SEM, Standard error of the means Component
Group 1 ( <1 year)
Group 2 (1–3 years)
Group 3 ( >3 years)
SEM
Hump fat Melting point ( C) Saponification value Iodine number
77.5a 203.2 39.0a
85.3b 202.9 35.8b
82.4b 202.7 36.0b
1.64 3.52 0.97
Abdomen fat Melting point ( C) Saponification value Iodine number
84.5a 196.9 31.9
88.2b 199.0 31.7
86.3ab 198.3 33.9
1.13 2.89 1.69
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Table 6 Simple correlation coefficients between fatty acid composition and physical properties in hump fat of one-humped Arabian camels Item
Melting point Significancea
C14:0 C14:1 C15:0 C15:1 C16:0 C16:1 C16:1 C17:0 C18:0 C18:1 C18:2 C19:0 C20:0 Fat% Total fatty acid Saturated fatty acid (SFA) Unsaturated fatty acid (UFA) C18:0 : C18:1 SFA : C18:1 Polyunsaturated fatty acid UFA : SFA a
Saponification No. R2
NSa NS NS NS NS NS NS NS * NS NS * NS NS NS NS NS * * NS NS
0.30 0.22 0.08 0.11 0.28 0.32 0.01 0.11 0.41 0.31 0.20 0.48 0.35 0.07 0.03 0.30 0.33 0.52 0.39 0.30 0.29
Significancea
Iodine No. R2
*** NS *** ** NS NS NS NS NS NS NS NS * *** NS *** *** NS * NS NS
0.53 0.22 0.85 0.65 0.17 0.14 0.28 0.16 0.20 0.21 0.12 0.22 0.38 0.78 0.25 0.79 0.63 0.06 0.52 0.10 0.81
Significancea *** NS *** *** NS NS NS NS NS NS NS NS NS *** NS *** *** NS * NS ***
R2 0.73 0.33 0.95 0.77 0.08 0.01 0.13 0.04 0.01 0.13 0.01 0.08 0.33 0.80 0.13 0.86 0.68 0.11 0.48 0.11 0.87
NS, not significant; *P<0.05; **=P <0.01; ***=P<0.001.
Table 7 Simple correlation coefficients between fatty acid composition and physical properties in abdomen fat of one-humped Arabian camels Item
Melting point a
Significance C14:0 C14:1 C15:0 C15:1 C16:0 C16:1 C16:1 C17:0 C18:0 C18:1 C18:2 C19:0 C20:0 Fat% Total fatty acid Saturated fatty acid (SFA) Unsaturated fatty acid (UFA) C18:0 : C18:1 SFA : C18:1 Polyunsaturated fatty acid UFA : SFA a
NSa NS NS * NS NS NS NS * * NS NS NS NS * * * ** ** * **
NS, not significant; *P<0.05; **=P <0.01.
saponification No. R
2
Significance
0.03 0.17 0.30 0.49 0.07 0.01 0.35 0.24 0.45 0.48 0.16 0.06 0.04 0.17 0.38 0.52 0.52 0.63 0.66 0.46 0.55
NS NS * NS NS NS NS NS NS NS * NS NS NS NS NS NS NS NS NS NS
a
Iodine No. R
2
Significancea
0.03 0.10 0.44 0.30 0.26 0.25 0.27 0.18 0.20 0.20 0.39 0.23 0.08 0.06 0.03 0.04 0.05 0.30 0.26 0.09 0.12
* NS NS NS NS NS NS NS NS NS NS NS NS NS * * * NS NS NS NS
R2 0.38 0.07 0.11 0.06 0.01 0.11 0.09 0.04 0.05 0.05 0.14 0.28 0.28 0.06 0.38 0.45 0.45 0.06 0.19 0.01 0.36
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In conclusion, the overall results show that hump and abdomen fat have similar fatty acid compositions. Young camels have less total fatty acids (mg/g total wet fat) than older camels in the hump. However, age has little effect on fatty acid composition. References AOAC (1989). Official methods of analysis, (15th ed.). Washington, DC: Association of Official Analytical Chemists. Duncan, W. R. H., & Garton, G. A. (1967). The fatty acid composition and intermolecular structure of triglycerides derived from different sites in the body of the sheep. Journal of the Science of Food and Agriculture, 18, 99–102. Emmanuel, B. (1981). Fatty acid synthesis in camel (Camelus dromedarius) hump and sheep (Ovis aries) tail fat. Comparative Biochemistry Physiology, 68B, 551–554. Emmanuel, B., & Nahapetian, A. (1980). Fatty acid composition of depot fats and rumen wall of the camel (Camelus dromedarius). Comparative Biochemistry Physiology, 67B, 701–704. Enser, M. (1984a). The chemistry, biochemistry and nutritional importance of animal fats. In J. Wiseman (Ed.), Fats in animal nutrition (pp. 23–51). London, UK: Butterworths.
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Enser, M. (1984b). The relationship between the composition and consistency of pig backfat. In Fat quality in lean pigs (pp. 53–57). Brussels, Belgium: A workshop in the CEC Programme of Coordination of Research on Animal Husbandry. Gibney, M. J., & L’Estrange, J. L. (1975). Effects of dietary unsaturated fat and protein sources on melting point and fatty acid composition of lamb fat. Journal of Agriculture Science, 84, 291–296. Mirgani, T. (1977). Fatty acid composition of hump triglycerides of the camel Camelus dromedaries. Comparative Biochemistry Physiology, 58B, 211–213. Orlov, V. K, Servetnik-Chalaia, G. K., & Zagibailova, N. B. (1985). Fractional and fatty acid composition of the lipids of horse and camel meat. Vopr Pitan, 4, 71–76 (abstract). Rawdah, T. N., El-Faer, M. Z., & Koreish, S. A. (1994). Fatty acid composition of the meat and fat of the one-hump camel (Camelus dromedarius). Meat Science, 37, 149–155. SAS. (1993). Statistical analysis system. Cary, NC: SDS/STDT. User’s guide, Version 6. Wood, J. D. (1984). Fat deposition and the quality of fat tissue in meat animals. In J. W. Wiseman (Ed.), Fats in animal nutrition (pp. 406–435). London: Butterworths. Wood, J. D., Enser, H. B., McFie, H. J. H., Smith, W. C., Chadwick, J. P., Ellis, M., & Laird, R. (1978). Fatty acid composition of back fat in Large White pig selected for low back fat thickness. Meat Science, 2, 289–300.
Effects of age on fatty acid composition of the hump and abdomen depot fats of the Arabian camel (Camelus dromedarius) I.T. Kadim*, O. Mahgoub, R.S. Al-Maqbaly, K. Annamalai, D.S. Al-Ajmi Animal and Veterinary Sciences Department, College of Agriculture, Sultan Qaboos University, PO Box 34, Al-Khoud, 123, Muscat, Sultanate of Oman Received 14 August 2001; received in revised form 12 November 2001; accepted 15 December 2001
Abstract This study aimed to quantify concentrations of fatty acids in the hump and abdomen fats of three different age groups of camel. Hump and abdomen fats were extracted from eight each of one-humped camels (Camelus dromedarius) of three age groups: group 1 (< 1 year old), group 2 (1–3 years old) and group 3 ( > 3 years old). The fatty acid methyl ester concentrations of these fats were determined by gas–liquid chromatography (GLC). The percentage of fat in the hump (H) and abdomen (A) fats was significantly (P < 0.05) lower for group 1 (H 92.0% and A 94.3%) than for group 2 (H 97.4% and A 97.2%) and group 3 (H 97.6% and A 97.5%), on a dry matter basis. Hump and abdomen fats from the three different groups had similar fatty acid patterns with more saturated than unsaturated fatty acids. The saturated fatty acids in the hump fats accounted for 58.3, 67.6, and 63.0% of the total fatty acids for groups 1, 2 and 3, respectively; group 1 had significantly (P<0.05) lower saturated and higher unsaturated fatty acid concentrations than group 2. The iodine numbers were significantly (P< 0.05) higher in group 1 than either group 2 or 3. Palmitic acid (C16:0) was the major fatty acid in hump fat with 32.06, 32.90 and 34.37%, followed by oleic acid (C18:1) 33.65, 21.66 and 28.91.0% and stearic acid (C18:0) 18.85, 24.13 and 20.74% for groups 1, 2 and 3, respectively. Group 1 had significantly higher (P <0.05) oleic acid and lower stearic acid concentrations than group 2. The melting point of both hump and abdomen fats varied between the age groups. This study indicated that age has an effect on the fatty acid composition and the melting point of hump and abdomen fats in one-humped Arabian camels. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Camel; Hump; Abdomen; Fatty acids; Iodine number; Melting point and fat
1. Introduction The camel stores its energy reserves in the form of fat in different depots in their body of which the hump and abdomen depots comprise a considerable amount of the adult body weight, therefore camels can survive long periods without feed. Hump and abdomen fats contain mixtures of fatty acids (Emmanuel & Nahapetian, 1980) and most of these are esterified as triglycerides or phospholipids and vary according to their anatomical location in the body (Duncan & Garton, 1967). In camels, no information is available regarding the relationship between the fatty acid composition and age. It is of interest to determine the types and the composition of fatty acids in the hump and abdomen fats at different * Corresponding author. Tel.: +968-515-232; fax: +968-513-418. E-mail address: [email protected] (I.T. Kadim).
age groups in relationship to fat metabolism. Such information will form the basis for further studies on fat composition of the hump or abdomen and its value for human consumption. Few studies have examined the fatty acid composition of camel hump and abdomen depot fats (Emmanuel, 1981; Emmanuel & Nahapetian, 1980; Mirgani, 1977; Orlov, Servetnik-Chalaia, & Zagibailova, 1985; Rawdah, El-Faer, & Koreish, 1994), and most of these have been conducted in a single group. However, the fatty acid compositions of total fats may vary with age. Mirgani (1977) used thin-layer chromatography to determine the fatty acid composition of hump triglycerides from a single-humped camel (Camelus dromedarius) and found that saturated fatty acids accounted for 74% of the total fatty acids, and Emmanuel (1981), Orlov et al. (1985) and Rawdah, El-Faer, and Koreish (1994) showed that the saturated fatty acid contents in hump
0309-1740/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(01)00254-6
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fats was 64.9, 60.2 and 60.5%, respectively. In the abdomen fat of single humped camels, saturated fatty acids accounted for 63.6% of the total fatty acids (Emmanuel & Nahapetian, 1980). Most information describing the composition of such fats gives only the overall fatty acid composition. This information is important, but other properties such as melting point, saponification and iodine numbers provide further information. The melting point of a fat depends on its fatty acid composition and the concentration of saturated fatty acids gives the best prediction of melting point (Enser, 1984; Wood et al., 1978). Saponification number gives a measure of the average chain length of the fatty acids in the fat and the degree of unsaturation of the fatty acids can be measured by the iodine number. This study compares the fatty acid compositions in the hump and abdomen fat depots of three age groups (less than 1 year old, 1–3 year old and more than 3 year old) of one-humped Arabian camels.
2. Material and methods 2.1. Hump samples Twenty-four hump and abdomen fat samples from Arabian camels were collected from the Municipality slaughterhouse in Muscat (Sultanate of Oman) representing three age groups. Each group consisted of eight camels: group 1 (< 1 year old), group 2 (1–3 years old) and group 3 ( > 3 years old). Soon after slaughter, aliquots of 10 g samples of fat were obtained from middle portions of the hump and abdomen fats, transported to the laboratory and stored at 20 C in sealed plastic bags until analysed. The samples were taken from the same site from each animal. 2.2. Sample analysis Hump and abdomen fat samples from all three groups were analysed for fat content, melting point, iodine number and saponification value (AOAC, 1989). Triplicate samples, each weighing approximately 2 g were freeze-dried for 4 days and then the lipid extracted with petroleum ether in a Soxhlet apparatus. Iodine numbers were determined to assess the saturation levels of the two depots according to the Wijs method. Melting points and saponification numbers were determined according to the Capillary Tube and Titrimetric methods, respectively.The fatty acids were extracted according to the method described in AOAC (1989) with some modifications. Hump or abdomen fat (0.5g) was mixed with 50 ml of 1N KOH and 10 mg of internal standard [Tricosanoic acid (C23)] was added. The mixture was heated for 30 min at 150 C, followed by cooling at
room temperature. The samples were transferred to a 500 ml separating funnel, 150 ml distilled water was added followed by 0.1% methyl orange, drop wise, until the colour changed to yellow. 5N HCl was added until the colour turned to light pink and the solution was then partitioned vigorously for 5 min with 100 ml of diethyl ether. The diethyl ether layer was collected and the coloured aqueous phase re-extracted with a further 100 ml of diethyl ether. The diethyl layer ether extracts were pooled and washed four times with 80 ml of distilled water and subsequently dried over anhydrous Na2SO4. The diethyl ether extract was then concentrated to 2 ml in a rotary vacuum evaporator at less than 40 C and transferred to a screw cap test tube following addition of 2 ml of BF3–methanol reagent (14%). The test tube was heated at 100 C for 15 min in a water bath. After cooling to room temperature, 3 ml of hexane and 5 ml of saturated NaCl was added and the mixture vigorously shaken for 5 min. The hexane layer was then carefully transferred, by a Pasteur pipette, into a screw cap glass vial and stored at 20 C until assayed by gas chromatography mass spectrophotometry. Fatty acid samples were analysed with a Hewlett Packard 5890 Serial II Plus gas chromatograph (GC) coupled with HP5989B mass engine. A 30 m0.25 mm Omega waxTM capillary column (Supeclo Inc., USA) was used for the separation of fatty acids in the GC. Helium was used as carrier gas at a flow rate of 30 cm/ sec. The GC temperature program was 70 C for 1 min then 5 C/min until 260 C, which was maintained for 5 min. The temperatures of injector and detector were 250 and 270 C, respectively. Mass spectrophotometer conditions consisted of optics auto-tuned at 69, 219 and 502 using decafluorotriphenyl phosphate (DFTPP). Mass scan range was set from 40 to 550 amu at 30 thresholds. Fatty acids were identified by comparison of retention time with reference compounds purchased from Supeclo, Inc., USA and further confirmed by comparison with a library of chemical mass spectra (NIST98). Concentration of individual fatty acids was calculated by using tricosanoic acid (C23) as internal standard. 2.3. Data analysis The relationship between fat characteristics and fatty acid composition from hump and abdomen fat depots and the age of camels were analysed using the General Linear Model (GLM) procedure of SAS (1993).
3. Results and discussion Dry matter, lipid, and total fatty acids, saturated and unsaturated fatty acid percentages and the ratio of saturated to unsaturated fatty acids of hump and abdomen
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fat depots from the three age groups are given in Tables 1 and 2. The fatty acid composition of camel hump and abdomen fats for the three age groups are given in Tables 3 and 4, respectively. The hump fat of group 1 had significantly lower (P < 0.05) dry matter percentage (69.5%) than group 2 (87.1%) and group 3 (85.1%). The corresponding values for abdomen fat were significantly lower (53.9%) for group 1 than for group 2 (82.9%) and group 3 (85.2%). Percentage of fats on both a dry matter (DM) and wet basis (g/100 g fat) was significantly (P< 0.05) lower in group 1 than group 2 and group 3 for both hump and abdomen fats. The total fat content of the hump increased significantly (P < 0.05) from 642 mg/g wet weight in group 1 to 848 and 830 mg/g wet weight for groups 2 and 3, respectively (Table 1). The values for the abdomen fats were 508, 806 and 840 mg/g for groups 1, 2 and 3, respectively. Changes in the relative proportions of fat, water and connective tissue occur during growth and have important effects on fat composition and characteristics (Wood, 1984). The values for the total fatty acid (TFA) mg/g total fat (wet basis)
support previous observations made on camel hump (Mirgani, 1977). The difference between the saturated and unsaturated fatty acid percentages varied with age and fat depot. The contents of saturated and unsaturated fatty acids in hump fat, expressed as per 100 g dry matter fatty acids were significantly (P < 0.05) higher in group 1 (58.2%) than group 2 (67.5%), but no significant differences were seen between group 1 and 3 (63.4%) and group 2 and 3 (Table 1). The corresponding values for abdomen fat were 67.5, 69.7 and 67.7%, respectively (Table 2). Camel hump fat is characterized by a high content of saturated fatty acids, 63.0% (average) values, which are in agreement with the findings of Mirgani (1977), Emmanuel (1981), Orlov et al. (1985) and Rawdah, et al. (1994). Hump fats are lower in polyunsaturated fatty acids, 1.89, 2.20 and 1.89% for groups 1, 2 and 3, respectively, in agreement with other investigators (Emmanuel, 1981; Orlov et al., 1985; Rawdah, et al., 1994). The data on saturated fatty acid percentage in abdomen fat support the work of Emmanuel and Nahapetian (1980).
Table 1 Dry matter, fat content, and total fatty acids composition of hump fat from three age groups of one-humped Arabian camel. Least square means within the same row with different letters (a,b) were significantly different (P <0.05, P <0.001). SEM, Standard error of the means Component
Group 1 ( <1 year)
Group 2 (1–3 years)
Group 3 ( >3 years)
SEM
Dry matter% Total lipid% (DM basis) Total lipid% (wet basis) Total lipid weight mg/g (wet basis) Total fatty acids (TFA)% TFA mg/g total fat (wet basis) Saturated fatty acids (SFA)% SFA mg/g TFA (wet basis) Unsaturated fatty acids (USFA)% USFA mg/g TFA (wet basis) SFA: USFA
69.5a 92.0a 64.2a 642a 41.1 276 58.2a 162a 41.8a 114 1.44a
87.1b 97.4b 84.8b 848b 44.6 379 67.5b 254b 32.5b 125 2.41b
85.1b 97.6b 83.1b 830b 47.1 385 63.4ab 241b 36.6ab 144 1.74ab
2.64 0.79 2.85 28.5 4.94 40.5 2.24 24.5 2.24 18.4 0.320
Table 2 Dry matter, fat content, and total fatty acids composition of abdomen fat from three age groups of one-humped Arabian camels. Least square means within the same row with different letters (a,b) were significantly different (P<0.05). SEM, Standard error of the means Component
Group 1 (<1 year)
Group 2 (1–3 years)
Group 3 ( >3 years)
SEM
Dry matter% Total lipid% (DM basis) Total lipid% (wet basis) Total lipid weight mg/g (wet basis) Total fatty acids (TFA)% TFA mg/g total fat (wet basis) Saturated fatty acids (SFA)% SFA mg/g TFA (wet basis) Unsaturated fatty acids (USFA)% USFA mg/g TFA (wet basis) SFA: USFA
53.9a 94.3a 50.8a 508a 50.1 253a 67. 5 171a 32.6 82 2.07
82.9b 97.2b 80.6b 806b 46.8 374ab 69.7 261b 30.3 113 2.33
85.2b 97.5 b 84.0b 840 b 47.3 398b 67.7 270b 32.3 128 2.29
1.23 1.04 3.78 37.9 5.71 52 1.95 28.6 1.95 25.9 0.18
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Table 3 Fatty acids composition of hump fats from three age groups of one-humped Arabian camels. Least square means within the same row with different letters (a,b) were significantly different (P <0.05). SEM, Standard error of the means Fatty acid%
Group 1 ( <1 year)
Group 2 (1–3 year)
Group 3 ( >3 year)
SEM
Saturated fatty acids 14:0 15:0 16:0 17:0 18:0 19:0 20:0
4.18 1.39a 32.1 1.47 18.9a 0.05 0.20
5.07 2.15b 32.9 2.33 24.1b 0.78 0.19
3.97 2.22b 34.4 1.44a 20.7ab 0.26 0.37
0.633 0.264 1.192 0.432 1.882 0.379 0.097
Mono-unsaturated fatty acids 14:1 15:1 16:1 16:1 w7 18:1 w9
0.75 0.36 1.29 3.86 33.7b
1.01 0.20 1.99 5.39 21.7a
0.55 0.43 1.34 3.59 28.9b
0.178 0.101 0.337 1.004 2.407
Poly-unsaturated fatty acids 18:2 w6
1.89
2.20
1.82
0.310
58.2a 41.8a 40.0b 84.7b
67.5b 32.5b 30.3a 78.7a
63.4ab 36.6ab 34.8ab 84.0b
2.320 2.306 2.306 1.721
Percentage of total fatty acids Saturated Unsaturated Mono-unsaturated C16+C18+C18:1
Table 4 Fatty acids composition of abdomen fats from three age groups of one-humped Arabian camels. SEM, Standard error of the means Fatty acid%
Group 1 ( <1 year)
Group 2 (1–3 years)
Group 3 ( >3 years)
SEM
Saturated fatty acids 14:0 15:0 16:0 17:0 18:0 19:0 20:0
3.45 1.72 31.0 1.51 29.1 0.24 0.48
3.76 1.63 30.2 1.94 31.5 0.25 0.38
4.39 1.57 30.7 1.85 28.6 0.40 0.23
0.493 0.225 0.849 0.183 2.122 0.125 0.108
Mono-unsaturated fatty acids 14:1 15:1 16:1 16:1 w7 18:1 w9
0.79 0.41 1.48 2.54 25.4
0.95 0.44 1.22 2.29 23.5
0.70 0.40 1.18 3.07 25.0
0.144 0.083 0.158 0.718 1.291
Poly-unsaturated fatty acids 18:2 w6
1.98
1.90
1.97
0.184
Percentage of total fatty acids Saturated Unsaturated Mono-unsaturated C16+C18+C18:1
67.5 32.6 30.6 85.4
69.7 30.3 28.4 85.2
67.7 32.3 30.3 84.2
1.846 1.846 1.815 1.125
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Palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1) dominate, but other groups including polyunsaturated acids such as linoleic (C18:2) are seen. The sum of the smaller fractions can exceed 14% for hump and 15% for the abdomen fat of the total fatty acid contents. Age group differences were noted for individual fatty acids in hump fat. For example, pentadecanoic acid (C15:0) was significantly lower in group 1 than group 2 and group 3 and stearic acid (C18:0) in group 1 compared with group 2, but not group 3. Linoleic acid (C18:2) was significantly higher in group 1 (33.7%) than group 2 (21.7%). However, there were no differences between groups 1 and 3. In hump fat, oleic acid (C18:1) is the main fatty acid in group 1 (33.7%) followed by palmitic acid (16:0), 32.1%, and stearic acid (18:0), 18.9%, in groups 2 and 3, palmitic acid (C16:0) is the most abundant followed by stearic acid (18:0) and oleic acid in group 2, while group 3, oleic acid (C18:1) exceeded stearic acid (C18:0). In abdomen fat, palmetic acid (C16:0) is the main fatty acid, followed by stearic acid (C18:0) and then oleic acid (C18:1) in groups 1 and 2, while stearic acid (18:0) is the main fatty acid in group 2, followed by palmetic acid (C16:0) and then oleic acid (C18:1). In one-humped camels reared in temperate climates Mirgani (1977) found that C16:0, C18:0 and C18:1 together accounted for over 81% of the total fatty acids. However, in the present study, the fatty acids in the total fat (triglycerides, phospholipids and cholesterol esters) were analysed, whereas Mirgani only analysed the triglycerides. Similar values were reported by Emmanuel and Nahapetian (1980) and Emmanuel (1981). The mono-unsaturated fatty acids in camel hump account for almost one-third of the total fatty acids (Table 3), group 1 contained significantly (P < 0.05) more (39.9%) than group 2 (30.2%). However, the differences between group 1 and group 3 (34.8%) and between group 2 and group 3 were not significant. No significant differences in mono-unsaturated fatty acid contents were found among abdomen fats from the
three groups. This group of fatty acids is dominated by oleic acid (C18:1) followed by palmitoleic acid (C16:1). The melting points, saponification number and iodine number of the hump and abdomen fats are given in Table 5. The melting point is dependent on the actual content of fatty acids in the triacylgycerols, which account for about 95% of the adipose tissue (Enser, 1984a). In this study, the differences in fatty acid patterns of the hump or abdomen fats from the three age groups resulted in significant differences in melting point. Significant differences of 7.8 and 4.9 C in hump fat melting point between groups 1, 2 and 3, respectively and a significant difference of 3.7 C in abdomen fat melting point between groups 1 and 2, will have a major impact on the consistency of the fats. The mean iodine numbers of the hump fat were significantly higher for group 1 (39.0) than group 2 (35.8) and group 3 (36.0). The differences in iodine numbers are explained by the higher percentages of saturated fatty acids. Gibney and L’Estrange (1975) stated that, whatever the experimental conditions, the decrease in melting points are best explained by a fall in stearic acid (C18:0) content, and not by a fall in total saturated fatty acid content, and by an increase in linoleic acid (C18:2). No significant differences between the three age group in iodine numbers were seen in the abdomen fats, reflecting the similarity in saturated fatty acid contents in the groups. Correlation coefficients between fatty acid composition and the physical properties of hump and abdomen fats are presented in Tables 6 and 7. From Table 6 it can be seen that pentadecanoic acid (C15:0), linoleic acid (C18:2), stearic acid (C18:0), oleic acid (C18:1), saturated fatty acid (SFA):oleic acid (C18:1) ratio, and unsaturated fatty acid (UFA):SFA ratio give the best estimation of the melting point. From Table 6 it can also be concluded that pentadecanoic acid (C15:0), linoelic acid (C18:2), stearic acid (C18:0): oleic acid (C18:1) saturated fatty acid (SFA): oleic acid (C18:1), and unsaturated fatty acid (UFA): SFA give the best estimate of the melting point of adipose tissue.
Table 5 Physical properties of hump and abdomen fats from three age groups of one-humped Arabian camels. Least square means within the same row with different letters (a,b) were significantly different (P <0.05, P <0.001). SEM, Standard error of the means Component
Group 1 ( <1 year)
Group 2 (1–3 years)
Group 3 ( >3 years)
SEM
Hump fat Melting point ( C) Saponification value Iodine number
77.5a 203.2 39.0a
85.3b 202.9 35.8b
82.4b 202.7 36.0b
1.64 3.52 0.97
Abdomen fat Melting point ( C) Saponification value Iodine number
84.5a 196.9 31.9
88.2b 199.0 31.7
86.3ab 198.3 33.9
1.13 2.89 1.69
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Table 6 Simple correlation coefficients between fatty acid composition and physical properties in hump fat of one-humped Arabian camels Item
Melting point Significancea
C14:0 C14:1 C15:0 C15:1 C16:0 C16:1 C16:1 C17:0 C18:0 C18:1 C18:2 C19:0 C20:0 Fat% Total fatty acid Saturated fatty acid (SFA) Unsaturated fatty acid (UFA) C18:0 : C18:1 SFA : C18:1 Polyunsaturated fatty acid UFA : SFA a
Saponification No. R2
NSa NS NS NS NS NS NS NS * NS NS * NS NS NS NS NS * * NS NS
0.30 0.22 0.08 0.11 0.28 0.32 0.01 0.11 0.41 0.31 0.20 0.48 0.35 0.07 0.03 0.30 0.33 0.52 0.39 0.30 0.29
Significancea
Iodine No. R2
*** NS *** ** NS NS NS NS NS NS NS NS * *** NS *** *** NS * NS NS
0.53 0.22 0.85 0.65 0.17 0.14 0.28 0.16 0.20 0.21 0.12 0.22 0.38 0.78 0.25 0.79 0.63 0.06 0.52 0.10 0.81
Significancea *** NS *** *** NS NS NS NS NS NS NS NS NS *** NS *** *** NS * NS ***
R2 0.73 0.33 0.95 0.77 0.08 0.01 0.13 0.04 0.01 0.13 0.01 0.08 0.33 0.80 0.13 0.86 0.68 0.11 0.48 0.11 0.87
NS, not significant; *P<0.05; **=P <0.01; ***=P<0.001.
Table 7 Simple correlation coefficients between fatty acid composition and physical properties in abdomen fat of one-humped Arabian camels Item
Melting point a
Significance C14:0 C14:1 C15:0 C15:1 C16:0 C16:1 C16:1 C17:0 C18:0 C18:1 C18:2 C19:0 C20:0 Fat% Total fatty acid Saturated fatty acid (SFA) Unsaturated fatty acid (UFA) C18:0 : C18:1 SFA : C18:1 Polyunsaturated fatty acid UFA : SFA a
NSa NS NS * NS NS NS NS * * NS NS NS NS * * * ** ** * **
NS, not significant; *P<0.05; **=P <0.01.
saponification No. R
2
Significance
0.03 0.17 0.30 0.49 0.07 0.01 0.35 0.24 0.45 0.48 0.16 0.06 0.04 0.17 0.38 0.52 0.52 0.63 0.66 0.46 0.55
NS NS * NS NS NS NS NS NS NS * NS NS NS NS NS NS NS NS NS NS
a
Iodine No. R
2
Significancea
0.03 0.10 0.44 0.30 0.26 0.25 0.27 0.18 0.20 0.20 0.39 0.23 0.08 0.06 0.03 0.04 0.05 0.30 0.26 0.09 0.12
* NS NS NS NS NS NS NS NS NS NS NS NS NS * * * NS NS NS NS
R2 0.38 0.07 0.11 0.06 0.01 0.11 0.09 0.04 0.05 0.05 0.14 0.28 0.28 0.06 0.38 0.45 0.45 0.06 0.19 0.01 0.36
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In conclusion, the overall results show that hump and abdomen fat have similar fatty acid compositions. Young camels have less total fatty acids (mg/g total wet fat) than older camels in the hump. However, age has little effect on fatty acid composition. References AOAC (1989). Official methods of analysis, (15th ed.). Washington, DC: Association of Official Analytical Chemists. Duncan, W. R. H., & Garton, G. A. (1967). The fatty acid composition and intermolecular structure of triglycerides derived from different sites in the body of the sheep. Journal of the Science of Food and Agriculture, 18, 99–102. Emmanuel, B. (1981). Fatty acid synthesis in camel (Camelus dromedarius) hump and sheep (Ovis aries) tail fat. Comparative Biochemistry Physiology, 68B, 551–554. Emmanuel, B., & Nahapetian, A. (1980). Fatty acid composition of depot fats and rumen wall of the camel (Camelus dromedarius). Comparative Biochemistry Physiology, 67B, 701–704. Enser, M. (1984a). The chemistry, biochemistry and nutritional importance of animal fats. In J. Wiseman (Ed.), Fats in animal nutrition (pp. 23–51). London, UK: Butterworths.
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