- Email: [email protected]
Physico-chemical characteristics of carcass and meat Manchego-breed suckling lambs slaughtered at different weights
Meat Science 65 (2003) 1085–1093 www.elsevier.com/locate/meatsci
Physico-chemical characteristics of carcass and meat Manchego-breed suckling lambs slaughtered at different weights M.T. Dı´aza, S. Velascoa, C. Pe´rezb, S. Lauzuricab, F. Huidobroc, V. Can˜equea,* a
Instituto Nacional de Investigacio´n y Tecnologı´a Agraria y Alimentaria. Departamento de Tecnologı´a de los Alimentos, Carretera de la Corun˜a, km 7.5, 28040 Madrid, Spain b Universidad Complutense de Madrid. Facultad de Veterinaria, Avenida Puerta de Hierro, s/n. 28040 Madrid, Spain c Instituto Madrilen˜o de Investigacio´n Agraria y Alimentaria, Apartado 127, 28800 Alcala´ de Henares, Madrid, Spain Received 29 April 2002; received in revised form 20 November 2002; accepted 29 November 2002
Abstract Forty-nine Manchego-breed lambs raised exclusively on their dams’ milk until slaughter were used in this study. The effects of gender and slaughter weight (10, 12 and 14 kg) on carcass fatness, meat quality and the fatty acid composition of their fat were studied. Fatness, and in particular dorsal-fat thickness (P40.01), increased with live weight. The effect of gender was even greater (P40.001), as female lambs presented the highest fatness values for all parameters studied. The smallest drop in m. longissimus pH values was seen in the lowest-weight (10 kg) lambs. These same lambs displayed the highest L* value and thus the lightest colour. Fatty acid composition, which was not influenced by live weight, was affected by gender. The subcutaneous fat of female lambs contained more linolenic acid (C18:3) (P40.01) and a greater proportion of polyunsaturated fatty acids than that of male lambs (P40.001). Likewise, the intramuscular fat of female lambs displayed a greater proportion of monounsaturated fatty acids (P40.001) than that of male lambs. # 2003 Elsevier Ltd. All rights reserved. Keywords: Carcass composition; Lamb; Meat quality; Sex; Slaughter weight
1. Introduction Suckling lamb is a typical product of the Mediterranean area. Ewes of the Manchego breed, among others, are milked, and their lambs are weaned early, between 25 and 30 days after birth, and slaughtered at 10–14 kg live weight. Suckling lamb meat is in great consumer demand and reaches high prices, especially at certain times of year (San˜udo, Alfonso, Sanchez, Delfa, & Teixeira, 2000). Suckling lamb carcass quality and price are determined by the fatness score which, in turn, is primarily influenced by slaughter weight (Perez et al., 1994) and gender (Horcada, Beriain, Purroy, Lizaso, & Chasco, 1998). The fat composition of suckling lambs is mainly related to the fat composition of the milk they consume * Corresponding author. Tel.: +34-91-3474038; fax: +34-913572293. E-mail address: [email protected] (V. Can˜eque). 0309-1740/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0309-1740(02)00326-1
(Banskalieva, Shindarska, & Dimov, 1989). Lambs at these slaughter weights have not yet developed a functional rumen with its corresponding microorganisms, for which reason nutrients undergo no ruminal degradation before their absorption (Stokes & Walker, 1970). Few studies on carcass and meat quality of suckling lambs have been published, and those that exist generally refer to a single slaughter weight (San˜udo, Campo, Sierra, Marı´a, Olleta, & Santolaria, 1997). In the present study the authors determine carcass and meat quality characteristics of suckling lambs of both sexes and different slaughter weights.
2. Materials and methods A total of 49 single offspring, Manchego-breed lambs (27 males and 22 females), selected from 110 animals born to previously synchronised ewes, were used in the present study. Average birth weights for lambs of both sexes were similar (4.47 kg in males and 4.44 kg in females).
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1086
Six treatments (both sexes and three slaughter weights (10, 12 and 14 kg) were studied. Lambs were assigned at random to each group (Table 1). Lambs did not receive any kind of feed and were raised exclusively on maternal milk from birth to slaughter. They remained in a drylot while their dams spent the day at pasture. When lambs individually reached their previously determined slaughter weight they were taken from their dams to an experimental abattoir where they were slaughtered and dressed according to the method of Colomer-Rocher, Delfa, and Sierra (1988). Weights of omental and mesenteric fat were obtained and digestive contents were removed to calculate empty live weight (ELW). To obtain the cold carcass weight (CCW), carcasses were weighed after 24 h at 4 C. The weight of kidney knob and channel fat (KKCF) was determined, and dorsal fat thickness was obtained by means of digital calibrator (Mitutoyo UK) at a point 4 cm perpendicular to the carcass midline and 4 cm from the caudal edge of the last rib (Colomer-Rocher et al., 1988), on both the left and right halves of the carcass. Different judges took three measurements from each half-carcass. Fatness was subjectively assessed (SF) using a scoring system that took into account the carcass as a whole (1– 4 points) (EEC Regulation no. 461/93), as well as the quantity of kidney knob and channel fat (1–3 points) (Colomer-Rocher et al., 1988). Carcass pH in the m. longissimus lumborum (Ll) and the m. semitendinossus, was determined at 60 min and 24 h after slaughter by means of a pH-meter equipped with a penetrating electrode and thermometer. The electrode was calibrated to 15 C (slaughter plant ambient temperature). The pH meter automatically corrected pH values, taking into account muscle temperature (Schott-Gera¨te GMBH, Germany). Measurements of meat quality parameters were taken on the m. longissimus thoracis, dissected from the right half-carcass and aged for 72 h at 4 C. Water-holding capacity (WHC) was measured using the pressure method of Grau and Hamm (1953). Meat colour was assessed by the L* a* b* system (Centre International de l’Eclairage, 1976) using a Minolta colorimeter (Chroma Meter CR-200, Minolta Camera Co., Osaka, Japan) to determine the colorimetric indexes of chromaticity and hue. The colour of Table 1 Numbers and age at slaughter of lambs according to the slaughter weights and sex Males
Numbers of lambs Slaughter age (days)
Females
10 kg
12 kg
14 kg
10 kg
12 kg
14 kg
9 19
9 23
9 28
8 22
7 27
7 32
the fat-free surface of the m. longissimus thoracis (between the 12th and 13th ribs), dissected from the right half of the carcass, and the internal face of the rectus abdominis muscle, was evaluated using the mean value of nine colour determinations. After the carcass was split lengthwise down the spine and the tail removed, the left half-carcass was separated in accordance with the Colomer-Rocher, Dumont, and Murillo (1972) method to obtain leg, shoulder, ribs, loin, breast and neck. The dissection method of Fisher and de Boer (1994) was followed to obtain muscle, total fat (subcutaneous, intermuscular, kidney knob and channel fat) and bone. Samples of the m. longissimus thoracis were taken to extract intramuscular fat and evaluate the percentage of the fatty acids contained therein. Fat was extracted using the method of Hanson and Olley (1963) and the technique of Morrison and Smith (1964) was used to prepare fatty acid methyl esters. A Perkin-Elmer gas chromatograph (Perkin-Elmer Corporation, USA; equipped with a split-splitless injector and a flame ionisation detector) with a fused silica capillary column (0.25 mm internal diameter and 25 m long) was used for the chromatographic analysis of the methyl esters. The mobile phase consisted of helium C-50 at a flow of 9 psig. Sigma reference standards were employed to identify and quantify the fatty acids and nonadecanoic acid (C19:0) was used as the internal standard. A PerkinElmer register-integrator (PE Nelson Corporation, USA) was employed for this purpose. Statistical results were obtained by means of analysis of variance, according to the following model: gijk ¼ m þ Gið1::2Þ þ Wjð1::3Þ þ GWij þ ekðijÞ in which m=arithmetic mean; Gi=effect of gender; Wj=effect of slaughter weight (10, 12 and 14 kg); GWij=interaction of genderslaughter weight; ek(ij)= residual experimental error. The Newman–Keuls test was used to analyse differences between means.
3. Results 3.1. Carcass measurements and carcass tissue composition Fatness parameters for lambs of both sexes slaughtered at different weights are presented in Table 2. Slaughter weight significantly affected the subjectively assessed kidney knob and channel fat (KKCF) (P40.05), but not the total amount of KKCF in relation to empty live weight. Gender influenced those parameters (P40.001), as females displayed a higher
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1087
Table 2 Arithmetic means and standard error of the difference of the fatness parameters in lambs of different weights and sex Live weight at slaughter
Slaughter age (days) LWS CCW KKCF (score) Total KKCF/ELW (%) Dorsal-fat thickness (mm) Fatness (score)
Sign.
10 kg (n=17)
12 kg (n=16)
14 kg (n=16)
22.0 10.48a 5.30a 2.12a 1.37 1.87a 1.38a
26.5 12.47b 6.51b 2.30ab 1.59 2.00a 1.55ab
30.8 14.25c 7.49c 2.57b 1.59 2.47b 1.72b
*** *** * NS ** *
S.E.D.
0.306 0.270 0.268 0.275 0.283 0.259
Sex Male (n=27)
Female (n=22)
24.1 12.30 6.32 2.07 1.22 1.66 1.38
28.2 12.50 6.55 2.59 1.81 2.57 1.72
Sign.
S.E.D.
NS NS *** *** *** ***
0.253 0.277 0.226 0.231 0.236 0.219
Sign.: signification; NS: no significant; S.E.D.: standard error of the difference; a, b, c: means with different letters are significantly different (P40.05); LWS: live weight at slaughter; CCW: cold carcass weight; KKCF: kidney knob and channel fat; ELW: empty live weight. * P40.05. ** P40.01. *** P40.001.
proportion of both KKCF values (P40.001) than males. Subcutaneous fat thickness was influenced by slaughter weight; this value was greater in lambs slaughtered at 14 kg (2.47 mm) than in those slaughtered at 12 and 10 kg (2.00 and 1.87 mm, respectively) (P40.01). Lamb gender also influenced this parameter, as females displayed higher dorsal fat values (P40.001) than males (2.57 vs. 1.66) Subjective subcutaneous fatness, determined according to the EU method for lightweight carcasses, was affected by slaughter weight. Significant differences (P40.05) between lambs slaughtered at 10 and 14 kg live weight (1.38 vs. 1.72) were seen. The effect of gender was very significant (P40.001); female lambs obtained a higher subjectively evaluated fatness value than males (1.72 vs. 1.38).
Measurements and analysis of variance of tissue composition, obtained after dissection of the left halfcarcass, are presented in Table 3. Results are expressed as the corrected proportion of the left half-carcass, taking into account the water and tissue losses that occur during dissection. Lamb weight affected carcass composition, this is due to the fact that the proportion of carcass bone tissue dropped as slaughter weight increased (P40.05). Slaughter weight influenced the muscle/total fat (M/TF) (P=0.08) and muscle/bone (M/B) (P=0.06) ratios to a small degree. Lamb gender affected carcass tissue composition; males displayed a higher proportion of muscle (54.64% in males vs. 52.75% in females) (P40.01) and bone (24.56% in males vs. 22.43% in females) (P40.001), while females had a greater proportion of total fat
Table 3 Arithmetic means and standard error of the difference of tissues percentages in the left half of the carcass in lambs of different weights and sex Live weight at slaughter
Components (%) Muscle (M) Bone (B) Total fat (TF) Other tissues Subcutaneous fat (SF) Intermuscular fat (IF) Pelvic fat Renal fat M/TF M/B SF/IF
Sign.
10 kg (n=17)
12 kg (n=16)
14 kg (n=16)
53.18 24.20a 16.78 6.34 7.91 5.66 0.94 2.07 4.19 2.24 1.32
53.78 23.34ab 16.28 6.36 7.41 5.49 0.97 2.47 3.40 2.29 1.38
54.12 22.95b 17.57 5.10 8.45 5.75 0.89 2.56 3.06 2.34 1.50
NS * NS NS NS NS NS NS NS+ NS+ NS
S.E.D.
0.56 0.45 0.82 0.52 0.53 0.36 0.25 0.30 0.44 0.25 0.26
Sex Male (n=27)
Female (n=22)
54.64 24.56 14.05 6.54 6.32 5.03 0.85 1.88 4.25 2.21 1.26
52.75 22.43 19.70 5.32 9.52 6.23 1.00 2.85 2.85 2.37 1.54
Sign.
S.E.D.
** *** *** * *** *** * *** ** ** **
0.44 0.36 0.64 0.42 0.42 0.29 0.22 0.25 0.35 0.21 0.22
Sign.: signification; NS: no significant; S.E.D.: standard error of the difference; a, b: means with different letters are significantly different (P40.05); Other tissues: remaining tissues from dissection; CCW: cold carcass weight. + P40.1. * P40.05. ** P40.01. *** P40.001.
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1088
(19.7% in females vs. 14.05% in males) (P40.001). Female lambs displayed higher proportions of all fat depots than males; the greatest gender difference was observed for subcutaneous fat (9.52% in females as opposed to 6.32% in males) (P40.001). The M/TF ratio (4.25 for males and 2.85 for females, P40.01) also demonstrates that male lamb carcasses were leaner than those of females. Although males displayed more muscle tissue than females, the latter presented a higher M/B ratio (P40.01), as their proportion of bone tissue was also higher. On the other hand, females also displayed a higher subcutaneous fat/intermuscular fat (SF/IF) ratio (P40.01) than males, due to their greater subcutaneous fat depot. 3.2. Meat quality The arithmetic means and analyses of variance of the pH and colour of the longissimus dorsi and semitendinossus muscles, as well as the water-holding capacity of the longissimus dorsi muscle are shown in Table 4. As for the influence of slaughter weight on longissimus dorsi muscle pH values recorded at different times, the highest values were recorded in 14 kg lambs and the greatest differences were observed at 60 min postmortem (P40.05). The drop in pH values between 60 min and 24 h was greater in 14 kg lambs than in those weighing 10 kg (P40.01). Water-holding capacity, expressed as the proportion of liquid expelled, was influenced by gender. WHC was lower in females than in males (P40.05); female lamb meat expelled a higher percentage of liquid than those of males (19.94% vs. 18.54%). Slaughter weight did not affect this parameter.
The colour-related parameters of the m. longissimus dorsi and m. rectus abdominis of lambs of both sexes and the three slaughter weights are shown in Table 5. M. longissimus dorsi colour was affected by slaughter weight. The muscle colour of 10 kg lambs was lighter (L*) than that of 14 kg lambs (47.74 vs. 44.95) (P40.05). Lamb weight also influenced rectus abdominis muscle colour. In animals slaughtered at 10 kg, this muscle displayed greater lightness (L*) (54.83 vs. 52.94 and 52.37 of the 12 and 14 kg lambs, respectively) (P40.01) and a lower redness index (a*) (11.45 as opposed to 12.76 and 12.80 of the other two groups) (P40.05). The yellowness index (b*) was lower in 14 kg lambs than in those weighing 12 kg (P40.05), while hue was greater in the 10 and 12 kg lambs. Gender also affected the colour of the m. rectus abdominis (P40.05); the hue value of male lambs (33.21) was higher than that of females (30.22). The arithmetic means and analyses of variance of the effects of gender and slaughter weight on the total fatty acid composition of subcutaneous rib fat are presented in Table 6. Gender influenced the percentage of chemical fat extracted from the subcutaneous rib depot; this value was 53.53% in females and 45.39% in males (P40.05). With regard to the effect of gender on the fatty acids of subcutaneous rib fat, males presented higher proportions of myristic acid (C14:0) (P40.01), palmitic acid (C16:0) (P40.01) and heptadecenoic acid (C17:1%) (P40.01) than females. On the other hand, females displayed higher percentages of pentadecanoic acid (C15:0) (P40.05), margaric acid (C17:0) (P40.001), linoleic acid (C18:2) (P40.001) and linolenic acid (C18:3) (P40.01) than males.
Table 4 Arithmetic means and standard error of the difference in pH and other parameters related to meat quality (m. longissimus dorsi and m. semitendinossus) in lambs of different weights and sex Live weight at slaughter 10 kg (n=17) pH (Longissimus) pH 60 min pH 24 h PH change 60 min–24 h pH (Semitendinosus) pH 60 min pH 24 h pH change 60 min–24 h WHC (% liquid expelled)
5.87a 5.50a 0.36a
6.02 5.77 0.25 18.54
12 kg (n=16) 6.04a 5.54a 0.49a
5.97 5.66 0.30 19.37
Sign.
S.E.D.
14 kg (n=16) 6.43b 5.67b 0.75b
6.18 5.75 0.43 19.81
Sex Male (n=27)
Sign.
S.E.D.
Female (n=22)
*** * **
0.25 0.25 0.25
6.06 5.57 0.49
6.16 5.58 0.58
NS NS NS
0.22 0.21 0.22
NS NS NS NS
0.25 0.25 0.25 0.69
6.01 5.70 0.30 18.54
6.10 5.76 0.34 19.94
NS NS NS *
0.22 0.22 0.22 0.69
Sign.: significance; NS: no significant; S.E.D.: standard error of the difference; a, b: means with different letters are significantly different (P40.05); WHC: water-holding capacity. * P40.05. ** P40.01. *** P40.001.
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1089
Table 5 Arithmetic means and standard error of the difference of parameters related to meat colours (m. longissimus dorsi and m. rectus abdominis) of different weights and sex Weight 10 kg (n=17)
Sign. 12 kg (n=16)
14 kg (n=16)
Colour (Longissimus) L* 47.74a a* 12.66 b* 6.24 Chroma 14.16 Hue 26.49
46.48ab 13.57 6.49 15.15 26.38
44.95b 14.02 5.96 15.24 23.16
* NS NS NS NS
Colour (Rectus ab.) L* 54.83a a* 11.45a b* 7.91ab Chroma 14.01 Hue 34.38a
52.94b 12.76b 8.26a 15.25 32.75a
52.37b 12.80b 6.81b 14.55 28.01b
** * * NS **
S.E.D.
Sex
Sign.
S.E.D.
Male (n=27)
Female (n=22)
0.78 0.56 0.32 0.50 1.39
46.65 13.42 6.20 14.83 25.05
46.17 13.37 6.25 14.84 25.61
NS NS NS NS NS
0.61 0.45 0.27 0.40 1.08
0.61 0.42 0.47 0.48 1.36
53.57 12.27 8.04 14.73 33.21
53.30 12.41 7.29 14.47 30.22
NS NS NS NS *
0.48 0.34 0.38 0.38 1.05
Sign.: signification; NS: no significant; S.E.D.: standard error of the difference; a, b, c: means with different letters are significantly different (P40.05); colour: L* (lightness), a* (redness index), b* (yellowness index), Chroma: chromaticity (a*2+b*2)1/2; hue=arc tangent b/a57.29. * P40.05. ** P40.01.
Table 6 Arithmetic means and standard error of the difference of the fatty acid composition of subcutaneous fat of the m. longissimus thoracis (proportion by weight of total fatty acids) in lambs under different weights and sex Weight
Sign.
10 kg (n=17)
12 kg (n=16)
14 kg (n=16)
Fatty acids C12:0 C14:0 C14:1 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 C20:0
4.14 14.8 0.78 2.15 34.81 4.32 2.4 0.09 9.3 20.57 2.74 2.78 1.01
3.57 14.09 0.72 2.05 35.36 4.33 2.39 0.12 9.69 20.94 2.67 2.84 1.12
3.47 13.7 0.82 2.11 34.9 4.26 2.42 0.12 9.42 21.27 2.63 2.67 2.02
NS NS NS NS NS NS NS NS NS NS NS NS NS
Sums and ratios OFA SFA MUFA PUFA TUFA PUFA/SFA MUFA/SFA TUFA/SFA n6/n3 DFA
4.69 68.64 25.82 5.52 31.35 0.081 0.37 0.46 0.99 40.65
4.61 68.3 26.17 5.51 31.68 0.08 0.38 0.46 0.95 41.38
4.65 68.2 26.48 5.30 31.79 0.078 0.38 0.46 0.99 41.21
NS NS NS NS NS NS NS NS NS NS
S.E.D.
Sex
Sign.
S.E.D.
Male (n=27)
Female (n=22)
0.36 0.48 0.27 0.26 0.51 0.28 0.25 0.25 0.36 0.68 0.26 0.28 0.41
3.84 14.92 0.75 1.99 35.76 4.30 2.19 0.17 9.18 20.61 2.43 2.51 1.23
3.61 13.5 0.80 2.21 34.33 4.30 2.62 0.04 9.75 21.25 2.93 3.02 1.56
NS ** NS * ** NS *** ** NS NS *** ** NS
0.29 0.38 0.23 0.22 0.40 0.24 0.21 0.21 0.29 0.54 0.23 0.24 0.34
0.29 0.78 0.77 0.34 0.78 0.24 0.24 0.24 0.24 0.85
4.42 69.14 25.9 4.94 30.85 0.071 0.37 0.44 0.98 40.04
4.88 67.62 26.41 5.95 32.37 0.088 0.39 0.48 0.97 42.3
* NS NS *** NS *** NS NS NS *
0.24 0.61 0.60 0.28 0.61 0.21 0.21 0.21 0.21 0.85
Sign.: significance; NS: no significant; S.E.D.: standard error of the difference; OFA: odd fatty acids=15:0+17:0+17:1; DFA: desirable fatty acids=C18:0+TUFA; SFA=saturated fatty acids, MUFA=monounsaturated fatty acids, PUFA=polyunsaturated fatty acids, TUFA=total unsaturated fatty acids; n-6/n-3: (C18:2/C18:3). * P40.05. ** P40.01. *** P40.001.
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1090
weight on the total fatty acid composition of intramuscular rib fat. Although fatty acid composition was not affected by slaughter weight, this parameter was influenced by gender. Males displayed a greater proportion of lauric acid (C12:0) (P40.001), margaric acid (C17:0) (P40.01), arachic acid (C20:0) (P40.01) and behenic acid (C22:0) (P40.01) while females presented higher values of palmitoleic acid (C16:1) (P40.001), heptadecenoic acid (C17:1) (P40.05) and oleic acid (C18:1) (P40.01). The sum of the values of fatty acids with odd-number carbon chains (C15:0 +C17:0+C17:1), was influenced by gender (P40.01). Male lambs displayed higher proportions of these fatty acids than females (3.01% vs. 2.69%). As was the case with subcutaneous fat, male lambs displayed a higher proportion of SFA (P40.01). On the other hand, females displayed a greater percentage of MUFA (P40.001) and TUFA (P40.01). Furthermore, female lambs exhibited higher MUFA/SFA and TUFA/
Slaughter weight did not significantly affect the fatty acid composition of subcutaneous rib fat. An average of 4.63% of the fatty acids in the subcutaneous rib fat had odd-number carbon chains (C15:0+C17:0+C17:1). Gender influenced these fatty acids, as females displayed a higher proportion (4.88%) of them than males (4.42%) (P40.05). Slaughter weight and gender did not influence percentages of saturated (SFA), monounsaturated (MUFA) and total polyunsaturated fatty acids (TUFA). In contrast, gender did affect percentages of polyunsaturated fatty acids (PUFA) and the polyunsaturated/ saturated fatty acid ratio (PUFA/SFA); both parameters were higher in females than in males (P40.001). Gender, but not live weight, affected desirable fatty acid (DFA) values, which were higher in female lambs than in males (P40.05). Table 7 presents the arithmetic means and analysis of variance values of the effect of gender and slaughter
Table 7 Arithmetic means and standard error of the difference of the fatty acid composition of intramuscular fat of the m. longissimus thoracis (proportion by weight of total fatty acids), in lambs of different weights and sex Weight 10 kg (n=17) Fat
Sign. 12 kg (n=16)
S.E.D.
14 kg (n=16)
Sex Male (n=27)
Sign.
S.E.D.
Female (n=22)
2.81
2.92
2.67
NS
0.32
2.58
3.03
NS
0.23
Fatty acid C12:0 C14:0 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 C20:0 C20:4 C22:0
1.66 9.35 1.04 31.90 3.68 1.51 0.40 12.07 23.78 4.41 2.31 1.39 3.83 2.6
1.50 8.97 1.003 31.95 3.79 1.48 0.36 12.1 23.8 4.47 2.52 1.34 3.88 2.77
1.32 8.75 0.85 31.44 3.86 1.47 0.44 12.06 24.42 4.67 2.47 1.30 4.2 2.69
NS NS NS NS NS NS NS NS NS NS NS NS NS NS
0.27 0.42 0.42 0.39 0.27 0.25 0.25 0.35 0.67 0.30 0.26 0.27 0.31 0.29
1.77 9.22 9.22 31.65 3.52 1.60 0.35 12.24 22.92 4.50 2.51 1.58 4.02 2.98
1.22 8.82 8.82 31.88 4.03 1.37 0.44 11.92 25.08 4.54 2.36 1.11 3.92 2.39
*** NS NS NS *** ** * NS ** NS NS ** NS **
0.34 0.34 0.32 0.23 0.22 0.22 0.29 0.53 0.25 0.23 0.24 0.26 0.25
Sums and ratios OFA SFA MUFA PUFA TUFA PUFA/SFA MUFA/SFA TUFA/SFA n-6/n-3 DFA
2.95 61.55 27.87 10.57 38.44 0.17 0.45 0.63 3.61 50.52
2.84 61.15 27.95 10.88 38.84 0.17 0.45 0.63 3.39 50.95
2.77 59.91 28.73 11.35 40.09 0.19 0.48 0.67 3.61 52.15
NS NS NS NS NS NS NS NS NS NS
0.26 0.76 0.66 0.46 0.76 0.24 0.24 0.24 0.29 0.88
3.01 62.14 26.8 11.05 37.85 0.17 0.43 0.61 3.45 50.10
2.69 59.6 29.57 10.82 40.39 0.18 0.49 0.68 3.62 52.31
* ** *** NS ** NS ** *** NS *
0.23 0.59 0.52 0.37 0.59 0.21 0.21 0.21 0.24 0.69
Sign.: significance; NS: no significant; S.E.D.: standard error of the difference; OFA: odd fatty acids=15:0+17:0+17:1; DFA: desirable fatty acids=C18:0+TUFA; SFA=saturated fatty acids, MUFA=monounsaturated fatty acids, PUFA=polyunsaturated fatty acids, TUFA=total unsaturated fatty acids; n-6/n-3: (C18:2+C20:4/C18:3). * P40.05. ** P40.01. *** P40.001.
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
SFA ratios (P40.01 and P40.001, respectively) and a greater proportion of DFA (P40.05) than their male counterparts. The n6/n3 ratio was not influenced by either of the factors studied.
4. Discussion 4.1. Carcass measurements and carcass tissue composition In this study, the greatest differences in fatness were seen between 10 and 14 kg lambs. These differences were particularly due to the greater dorsal fat thickness and the higher subjectively evaluated KKCF and SF scores of the 14 kg lambs. Other authors, including Velasco et al. (2000), also found that fatness increased significantly when the live weight of suckling lambs rose from 10 to 12 kg. Adipose tissue development of these lambs had already begun, despite their being very young. Jeremiah, Jones, Tong, and Gibson (1997) report that subcutaneous fat thickness increases as slaughter weight rises. Differences in fatness due to slaughter weight are very important, even for a small weight interval, as they affect abattoir classification of the carcasses (Miguel et al., 2003) and thus carcass price. As for carcass tissue composition, differences in live weight affected only bone tissue, whose proportion dropped as weight increased. Vigneron, Prud’hon, Touraille, Valin, Bouix, & Bibe (1986) also report that the percentage of bone tissue drops as carcass weight rises, as the allometric coefficient of this tissue is lower than 1 (b < 1). Mahgoubt and Lodge (1994) also report that the proportion of fat increases with age, while that of bone decreases. Although the differences observed in our study were not significant, it was possible to detect a tendency towards a higher M/B ratio and a lower M/TF ratio as slaughter weight rose. This confirms that bone tissue is more precocious than muscle, while fat tissue develops later (Hammond, 1932). Mahgoubt and Lodge (1994) and Velasco et al. (2000) also observed that the M/B ratio increases with slaughter weight, that is, the amount of lean tissue increases faster than bone tissue as carcass weight increases. The M/B and M/TF ratios provide valuable information as to carcass tissue composition. Carcasses with a high M/B ratio are more commercial and in greater consumer demand. The M/TF ratio should ensure that the meat offers the tastiness and juiciness demanded by the consumer. Gender had an important effect on objective and subjective fatness parameters, as females displayed higher values than males for all measurements. On the one hand, this is because females display a greater ten-
1091
dency to accumulate fat from a very early age. On the other hand, females were older than males when slaughtered, due to their slower growth rate (282 g/day as compared with 317 g/day in males). Horcada et al. (1998) observed that male and female 11 kg suckling lambs displayed differences with regard to dorsal fat thickness. These authors reported dorsal fat values of 1.6 and 2.1 mm for males and females, respectively. Gender differences were greater for suckling lambs than for heavier lambs. Velasco et al. (2000) found differences between male and female suckling lambs with regard to the quantity and proportion of kidney knob and channel fat. Gender differences in fatness are associated with variations in protein assimilation efficiency and the different composition of weight gain displayed by males and females throughout their growth (Robelin & Theriez, 1981). Males displayed greater nitrogen retention indexes than females and therefore developed proportionally more muscle than adipose tissue (Lobley et al., 1990). The effect of gender on carcass tissue composition was more important. Females matured earlier than males, as reflected in their lower bone and muscle tissue values and their higher percentage of fat. Numerous authors have noted this fact in sheep of various breeds and weight ranges (Mahgoubt & Lodge, 1994; Teixeira, Delfa, & Treacher, 1996; Vergara, Molina, & Gallego, 1999). Female lambs presented more fat tissue than males, mainly due to their greater proportion of subcutaneous fat (9.52% in females as opposed to 6.32% in males). Velasco et al. (2000) obtained similar values (7.20% in males vs. 9.07% in females) in suckling Talaveranabreed lambs. In our study, the M/TF ratio was significantly affected by gender. Males displayed a lower proportion of fat and a higher M/TF ratio (4.25%, as opposed to 2.85% in females). Similarly, Velasco et al. (2000) obtained higher values for this ratio in suckling male lambs than in their female counterparts (2.98 vs. 2.55). The M/B ratio was also influenced by gender. This value was higher in females (2.37 vs. 2.21 in males). Guı´a, Can˜eque, and Lauzurica (1985) also report that at commercial slaughter weights female suckling lambs display greater muscle than bone tissue development. The EU carcass classification system for low-weight lambs is based on carcass fatness. Our study lambs were classified at the bottom end of the scale and considered to be of poor quality due to their low carcass fat content. As they displayed greater fatness at a given weight, female lambs received a better classification than males, and thus a higher sales price. 4.2. Meat quality The low weight (10 kg) lambs displayed lower pH values at 60 min than their high weight (14 kg) counterparts. As
1092
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
a result, pH values at 24 h had dropped less in the former animals than in the latter ones. Due to their lower weight and age, the younger lambs may have suffered greater stress at being separated from their dams (Morgan & Arnold, 1974). These lambs may also be more sensitive to pre-slaughter handling, which produces an antemortem glycogenolysis that depletes part of the muscular glycogen. Gender did not significantly influence pH in the present study; findings similar to our own have been reported by numerous authors (Horcada et al., 1998; Vergara et al., 1999, McGeehin, Sheridan, & Butter, 2001). Although pH is closely related to WHC and differences with regard to pH and the speed of its fall in relation to slaughter weight have been observed, no significant influence of this value on water-holding capacity was found in the present study. The bibliography available offers contradictory information concerning the influence of weight, and therefore slaughter age, on WHC. Some authors report that this parameter is not affected by weight/age (Solomon, Kemp, Moody, Ely, & Fox, 1980), while other studies suggest that higher weight is accompanied by lower (Velasco et al., 2000) or higher (Azia, Ball, Sharpe, & McCutcheon, 1993) water-holding capacity. Gender influenced WHC to a certain degree, as females expelled a greater proportion of liquid, coinciding with the greater (non-significant) fall in their pH values. Velasco et al. (2000) likewise observed that females expelled more liquid than males (15.43% vs. 14.1%). However, no gender related differences were reported by authors studying Lacha-breed suckling lambs (Horcada et al., 1998). In our study, meat colour was influenced by slaughter weight. As slaughter weight rose, L* and b* decreased and a* increased, especially significantly in the rectus abdominis muscle. This confirms to us that in spite of the very small differences observed in slaughter weight, the suckling lambs that weighed least displayed the lightest colour meat. This, in turn, is the meat that consumers value most highly. San˜udo, Sierra, Osorio, Alcalde, Santaolalla, and Alberti (1993) observed in Rasa Aragonesa-breed, 8.5–11.5 kg, lambs that meat darkens as slaughter weight increases, mainly because pigment content increases with age (Lawrie, 1998). Gender hardly influenced meat colour, affecting only hue. Horcada (1996) found no significant differences between male and female Lacha-breed lambs, as the diet, age and weight of animals of both sexes in that study were similar. Likewise, San˜udo, Sanchez, and Alfonso (1998) reported that gender differences are not notable. This author notes however, that females could be darker than males due to their greater precociousness and fatness when comparing both sex at equal slaughter weight. The fatty acid composition of our study lambs was primarily affected by gender. Slaughter weight had
almost no influence on this parameter, mainly because the interval between slaughter weights was small. Female lambs exhibited a greater proportion of MUFA than males in the intramuscular fat depot studied. These MUFA consisted mainly of oleic acid (C18:1) and palmitoleic acid (C16:1). In contrast, male lambs displayed greater fat saturation (SFA) in the same fat depot. The state of fatness, and therefore the amount of fat deposited, affects the fatty acid composition of the different depots studied (Huerta-Leidenz, Cross, Savell, Lunt, Baker, & Smith, 1996). According to Leat (1977) fatness in cattle is accompanied by a higher degree of unsaturation of the fat depots, which is associated with a high palmitoleic acid (C16:1) content. Jackson and Winkler (1970) have reported similar results. The latter authors note that the unsaturation of the fat depots increases with adiposity due to 9 desaturase enzyme activity, responsible for the synthesis of oleic acid (C18:1) from stearic acid (C18:0). In addition, the subcutaneous rib-fat depot of female lambs in our study contained a greater proportion of linolenic acid (C18:3). This, together with the greater percentage of desirable fatty acids (DFA) in both fats studied, indicates that the fat of these female lambs was healthier in terms of human consumption than that of the male lambs (Wood & Enser, 1997). In addition, the subcutaneous fat of male lambs displayed a higher palmitic acid (C16:0) content, which could potentially increase plasma cholesterol levels (Grundy, 1986).
5. Conclusions Female lamb carcasses displayed greater fatness than their male counterparts for all the parameters studied, despite the fact that all the animals were young. This meant that the former received a better classification and were more highly valued than their male counterparts. Slaughter weight affected the pH value 24 h after slaughter; the lowest values were found in the m. longissimus of the lowest weight lambs, which in addition, exhibited the lightest colour. Fatty acid composition was influenced by gender. Subcutaneous fat of the female lambs contained more linolenic acid as well as a higher proportion of polyunsaturated fatty acids. In addition, the intramuscular fat of the females displayed a lower proportion of saturated fatty acids than that of the male lambs. From the nutritional point of view, and assuming that all the fat of these lambs is consumed, consumers may consider the fat of female lambs healthier than that of males.
References Azia, N. N., Ball, R. O., Sharpe, P. H., & McCutcheon, B. (1993). Growth, carcass composition and meat quality of crossbred lambs
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093 at different slaughter weights. In 39th International Congress of Meat Science and Technology. INRA-ITOVIC, Paris. Banskalieva, V., Shindarska, Z., & Dimov, V. (1989). Fatty acid composition of various depot fats of lamb. In Proceeding. 35th International Congress on Meat Science and Technology 3; pp. 1222– 1229, Copenhagen. Centre International de l’Eclairage (1976). De´finition d’un space de colour por deux cordones de cromaticite´ et la luminosite´. Supplement no. 2 to CIE, publication no. 15 (E-1.3.1) 1971/(TC-1-3). Centre Internationale de L’Eclairage, Paris. Colomer-Rocher, F., Dumont, B. L., & Murillo, N. L. (1972). Descripcio´n del despiece ovino Aragone´s y definicio´n de un despiece de referencia normalizado. Anales del INIA. Serie.: Produccion Animal, 3, 79–108. Colomer-Rocher, F., Delfa, R., & Sierra, I. (1988). Me´todo normalizado para el estudio de los caracteres cuantitativos y cualitativos de las canales ovinas producidas en el a´rea mediterra´nea segu´n los sistemas de produccio´n. Cuadernos INIA, 17, 19–41. Fisher, A. V., & de Boer, H. (1994). The EAAP standard method of sheep carcass assessment. Carcass measurements and dissection procedures. Livestock Production Science, 38, 149–159. Grau, R., & Hamm, R. (1953). Eine einfache Methode zur bestimmung der Wasserbindurng in Muskel. Naturwissenschaften, 40, 29–30. Grundy, S. M. (1986). Comparison of monounsaturated fatty acids in carbohydrates for lowering plasma cholesterol. The New England Journal of Medicine, 314, 745–748. Guı´a, E., Can˜eque, V., & Lauzurica, S. (1985). Estudio de la aptitud ca´rnica de la raza Talaverana. In ITEA (Vol. Extra n 5, pp. 256– 258) Zaragoza. Hammond, J. (1932). Growth and development of mutton qualities. In O. Y. Boyd, Ed., The sheep. Edinburgh and London. Hanson, S. W. F., & Olley, J. (1963). Application of the Bligh and Dyer method of lipid extraction to tissue homogenates. Biochemical Journal, 89, 101–102. Horcada, A. (1996). Calidad de la carne de los corderos de las razas Lacha y Rasa Aragonesa. Tesis Doctoral, Universidad Pu´blica de Navarra. Pamplona. Horcada, A., Beriain, M. J., Purroy, A., Lizaso, G., & Chasco, J. (1998). Effect of sex on meat quality of Spanish lamb breeds (Lacha and Rasa Aragonesa). Animal Science, 67, 541–547. Huerta-Leidenz, N. O., Cross, H. R., Savell, J. W., Lunt, D. K., Baker, J. F., & Smith, S. B. (1996). Fatty acid composition of subcutaneous adipose tissue from male calves at different stages of growth. Journal Animal Science, 74, 1256–1264. Jackson, H. D., & Winkler, V. W. (1970). Effects of saturation on the fatty acid composition of adipose tissue and plasma lipids of sheep. Journal of Nutrition, 100, 201–207. Jeremiah, L. E., Jones, S. D. M., Tong, A. K. W., & Gibson, L. L. (1997). The influence of lamb chronological age, slaughter weight and gender on carcass measurements. Sheep and Goat Research Journal, 13, 87–95. Lawrie, R. A. (1998). Meat Science (6th ed). Abinton, Cambridge, England: Woodhead Publishing Ltd. Leat, W. M. F. (1977). Depot fatty acids of Aberdeen Angus and Friesian reared on hop and barley. Journal of Agricultural Science Camb, 89, 575–582. Lobley, G. E., Connell, A., Milne, E., Burchan, V., Galder, A. G., Anderson, S. E., & Vint, H. (1990). Muscle protein synthesis in response to testosterone administration in wether lambs. British Journal of Nutrition, 64, 691–704. Mahgoubt, O., & Lodge, G. A. (1994). Growth and body composition of Omani local sheep. 1. Live-weight growth and carcass and noncarcass characteristics. Animal Production, 58, 365–372.
1093
McGeehin, B., Sheridan, J. J., & Butter, F. (2001). Factors affecting the pH decline in lamb after slaughter. Meat Science, 58, 79–84. Miguel, E., Onega, E., Can˜eque, V., Velasco, S., Dı´az, M. T., Lauzurica, S., Perez, C., Bla´zquez, B., & Ruiz de Huidobro, F. (2003). Carcass classification in suckling lambs. Discrimination ability of the European Union scale. Meat Science, 1, 107–117. Morgan, P. D., & Arnold, G. E. (1974). Behavioural relationships between merino ewes and lambs during the four weeks after birth. Animal Production, 19, 169–176. Morrison, W. R., & Smith, L. M. (1964). Preparation of fatty acid methyl esters and dimethyl acetals from lipids with boron fluoridemethanol. Journal of Lipid Research, 5, 600–608. Perez, J. I., Gallego, L., Gomez, V., Osorio, M. T., San˜udo, C., Otal, J., Bernabeu, R., & Molina, A. (1994). Influencia del tipo de destete, tipo de parto, sexo y peso de la canal frı´a en la composicio´n tisular de la canal en corderos de raza Manchega. In XVIII Jornadas Cientı´ficas de la Sociedad Espan˜ola de Ovinote´cnia y Caprinotecnia, pp. 623–627, Albacete. Robelin, J., & Theriez, M. (1981). Fixation de proteı´nes les rumiants: e´volution en fonction du poids des animaux et variation selon la race, le sexe on le niveau des apports alimentaires. Reproduction Nutrition Development, 21, 335–353. San˜udo, C., Alfonso, M., Sanchez, A., Delfa, R., & Teixeira, A. (2000). Carcass and meat quality in light lambs from different fat classes in the EU carcass classidication system. Meat Science, 56, 89–94. San˜udo, C., Campo, M. M., Sierra, I., Marı´a, G. A., Olleta, J. L., & Santolaria, P. (1997). Breed effect on carcase and meat quality of suckling lambs. Meat Science, 46(4), 357–365. San˜udo, C. Sanchez, A., & Alfonso, M. (1998). Small ruminant prouction systems and factores affectin lamb meat quality. 44th International Congress of Meat Science and Technology. Barcelona. Spain, 22–47. San˜udo, C., Sierra, I., Osorio, M. T., Alcalde, M. J., Santaolalla, Pl., & Alberti, P. (1993). Variation of meat quality in light lamb depending on weight increase of the carcass (7,4–15,4 kg). Proceedings of the 39th international congress of meat science and technology. Alberta Canada, p 86. Solomon, M. B., Kemp, J. D., Moody, W. G., Ely, D. G. A., & Fox, J. D. (1980). Effect of breed and salughter weight on physical, chemical and organoleptic properties of lamb carcasses. Journal Animal Science, 51, 1102–1107. Stokes, G. B., & Walker, D. M. (1970). The nutritive value of fat in the diet of the milk-fed lamb. British Journal of Nutrition, 24, 435– 440. Teixeira, A., Delfa, R., & Treacher, T. (1996). Carcass composition and body fat depots of Galego Braganc¸ano and crossbred lambs by Suffolk and Merino Precoce sire breeds. Animal Science, 63, 389–394. Velasco, S., Lauzurica, S., Can˜eque, V., Perez, C., Ruiz De Huidobro, F., Manzanares, C., & Diaz, M. T. (2000). Carcass and meat quality of Talaverana breed sucking lambs in relation to gender and slaughter weight. Animal Science, 70, 253–263. Vergara, H., Molina, A., & Gallego, L. (1999). Influence of sex and slaughter weight on carcass and meat quality in light and medium weight lambs produced in intensive systems. Meat Science, 52, 221–226. Vigneron, P., Prud’hon, M., Touraille, C., Valin, C., Bouix, J., & Bibe, B. (1986). Croissance des agneaux. Types da fibres musculaires et qualite´ de la viande. Muscles indicateurs. In 11e´me Journe´es de la Recherche Ovine et Caprine. Qualite´ des Produits chez les Ovins et les Caprins (Ed INRA), pp. 49–73, Versailles. Wood, J. D., & Enser, M. (1997). Factors influencing fatty acids in meat and the role of antioxidants in improving meat quality. British Journal of Nutrition, 78(Suppl. I), 549–560.
Physico-chemical characteristics of carcass and meat Manchego-breed suckling lambs slaughtered at different weights M.T. Dı´aza, S. Velascoa, C. Pe´rezb, S. Lauzuricab, F. Huidobroc, V. Can˜equea,* a
Instituto Nacional de Investigacio´n y Tecnologı´a Agraria y Alimentaria. Departamento de Tecnologı´a de los Alimentos, Carretera de la Corun˜a, km 7.5, 28040 Madrid, Spain b Universidad Complutense de Madrid. Facultad de Veterinaria, Avenida Puerta de Hierro, s/n. 28040 Madrid, Spain c Instituto Madrilen˜o de Investigacio´n Agraria y Alimentaria, Apartado 127, 28800 Alcala´ de Henares, Madrid, Spain Received 29 April 2002; received in revised form 20 November 2002; accepted 29 November 2002
Abstract Forty-nine Manchego-breed lambs raised exclusively on their dams’ milk until slaughter were used in this study. The effects of gender and slaughter weight (10, 12 and 14 kg) on carcass fatness, meat quality and the fatty acid composition of their fat were studied. Fatness, and in particular dorsal-fat thickness (P40.01), increased with live weight. The effect of gender was even greater (P40.001), as female lambs presented the highest fatness values for all parameters studied. The smallest drop in m. longissimus pH values was seen in the lowest-weight (10 kg) lambs. These same lambs displayed the highest L* value and thus the lightest colour. Fatty acid composition, which was not influenced by live weight, was affected by gender. The subcutaneous fat of female lambs contained more linolenic acid (C18:3) (P40.01) and a greater proportion of polyunsaturated fatty acids than that of male lambs (P40.001). Likewise, the intramuscular fat of female lambs displayed a greater proportion of monounsaturated fatty acids (P40.001) than that of male lambs. # 2003 Elsevier Ltd. All rights reserved. Keywords: Carcass composition; Lamb; Meat quality; Sex; Slaughter weight
1. Introduction Suckling lamb is a typical product of the Mediterranean area. Ewes of the Manchego breed, among others, are milked, and their lambs are weaned early, between 25 and 30 days after birth, and slaughtered at 10–14 kg live weight. Suckling lamb meat is in great consumer demand and reaches high prices, especially at certain times of year (San˜udo, Alfonso, Sanchez, Delfa, & Teixeira, 2000). Suckling lamb carcass quality and price are determined by the fatness score which, in turn, is primarily influenced by slaughter weight (Perez et al., 1994) and gender (Horcada, Beriain, Purroy, Lizaso, & Chasco, 1998). The fat composition of suckling lambs is mainly related to the fat composition of the milk they consume * Corresponding author. Tel.: +34-91-3474038; fax: +34-913572293. E-mail address: [email protected] (V. Can˜eque). 0309-1740/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0309-1740(02)00326-1
(Banskalieva, Shindarska, & Dimov, 1989). Lambs at these slaughter weights have not yet developed a functional rumen with its corresponding microorganisms, for which reason nutrients undergo no ruminal degradation before their absorption (Stokes & Walker, 1970). Few studies on carcass and meat quality of suckling lambs have been published, and those that exist generally refer to a single slaughter weight (San˜udo, Campo, Sierra, Marı´a, Olleta, & Santolaria, 1997). In the present study the authors determine carcass and meat quality characteristics of suckling lambs of both sexes and different slaughter weights.
2. Materials and methods A total of 49 single offspring, Manchego-breed lambs (27 males and 22 females), selected from 110 animals born to previously synchronised ewes, were used in the present study. Average birth weights for lambs of both sexes were similar (4.47 kg in males and 4.44 kg in females).
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1086
Six treatments (both sexes and three slaughter weights (10, 12 and 14 kg) were studied. Lambs were assigned at random to each group (Table 1). Lambs did not receive any kind of feed and were raised exclusively on maternal milk from birth to slaughter. They remained in a drylot while their dams spent the day at pasture. When lambs individually reached their previously determined slaughter weight they were taken from their dams to an experimental abattoir where they were slaughtered and dressed according to the method of Colomer-Rocher, Delfa, and Sierra (1988). Weights of omental and mesenteric fat were obtained and digestive contents were removed to calculate empty live weight (ELW). To obtain the cold carcass weight (CCW), carcasses were weighed after 24 h at 4 C. The weight of kidney knob and channel fat (KKCF) was determined, and dorsal fat thickness was obtained by means of digital calibrator (Mitutoyo UK) at a point 4 cm perpendicular to the carcass midline and 4 cm from the caudal edge of the last rib (Colomer-Rocher et al., 1988), on both the left and right halves of the carcass. Different judges took three measurements from each half-carcass. Fatness was subjectively assessed (SF) using a scoring system that took into account the carcass as a whole (1– 4 points) (EEC Regulation no. 461/93), as well as the quantity of kidney knob and channel fat (1–3 points) (Colomer-Rocher et al., 1988). Carcass pH in the m. longissimus lumborum (Ll) and the m. semitendinossus, was determined at 60 min and 24 h after slaughter by means of a pH-meter equipped with a penetrating electrode and thermometer. The electrode was calibrated to 15 C (slaughter plant ambient temperature). The pH meter automatically corrected pH values, taking into account muscle temperature (Schott-Gera¨te GMBH, Germany). Measurements of meat quality parameters were taken on the m. longissimus thoracis, dissected from the right half-carcass and aged for 72 h at 4 C. Water-holding capacity (WHC) was measured using the pressure method of Grau and Hamm (1953). Meat colour was assessed by the L* a* b* system (Centre International de l’Eclairage, 1976) using a Minolta colorimeter (Chroma Meter CR-200, Minolta Camera Co., Osaka, Japan) to determine the colorimetric indexes of chromaticity and hue. The colour of Table 1 Numbers and age at slaughter of lambs according to the slaughter weights and sex Males
Numbers of lambs Slaughter age (days)
Females
10 kg
12 kg
14 kg
10 kg
12 kg
14 kg
9 19
9 23
9 28
8 22
7 27
7 32
the fat-free surface of the m. longissimus thoracis (between the 12th and 13th ribs), dissected from the right half of the carcass, and the internal face of the rectus abdominis muscle, was evaluated using the mean value of nine colour determinations. After the carcass was split lengthwise down the spine and the tail removed, the left half-carcass was separated in accordance with the Colomer-Rocher, Dumont, and Murillo (1972) method to obtain leg, shoulder, ribs, loin, breast and neck. The dissection method of Fisher and de Boer (1994) was followed to obtain muscle, total fat (subcutaneous, intermuscular, kidney knob and channel fat) and bone. Samples of the m. longissimus thoracis were taken to extract intramuscular fat and evaluate the percentage of the fatty acids contained therein. Fat was extracted using the method of Hanson and Olley (1963) and the technique of Morrison and Smith (1964) was used to prepare fatty acid methyl esters. A Perkin-Elmer gas chromatograph (Perkin-Elmer Corporation, USA; equipped with a split-splitless injector and a flame ionisation detector) with a fused silica capillary column (0.25 mm internal diameter and 25 m long) was used for the chromatographic analysis of the methyl esters. The mobile phase consisted of helium C-50 at a flow of 9 psig. Sigma reference standards were employed to identify and quantify the fatty acids and nonadecanoic acid (C19:0) was used as the internal standard. A PerkinElmer register-integrator (PE Nelson Corporation, USA) was employed for this purpose. Statistical results were obtained by means of analysis of variance, according to the following model: gijk ¼ m þ Gið1::2Þ þ Wjð1::3Þ þ GWij þ ekðijÞ in which m=arithmetic mean; Gi=effect of gender; Wj=effect of slaughter weight (10, 12 and 14 kg); GWij=interaction of genderslaughter weight; ek(ij)= residual experimental error. The Newman–Keuls test was used to analyse differences between means.
3. Results 3.1. Carcass measurements and carcass tissue composition Fatness parameters for lambs of both sexes slaughtered at different weights are presented in Table 2. Slaughter weight significantly affected the subjectively assessed kidney knob and channel fat (KKCF) (P40.05), but not the total amount of KKCF in relation to empty live weight. Gender influenced those parameters (P40.001), as females displayed a higher
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1087
Table 2 Arithmetic means and standard error of the difference of the fatness parameters in lambs of different weights and sex Live weight at slaughter
Slaughter age (days) LWS CCW KKCF (score) Total KKCF/ELW (%) Dorsal-fat thickness (mm) Fatness (score)
Sign.
10 kg (n=17)
12 kg (n=16)
14 kg (n=16)
22.0 10.48a 5.30a 2.12a 1.37 1.87a 1.38a
26.5 12.47b 6.51b 2.30ab 1.59 2.00a 1.55ab
30.8 14.25c 7.49c 2.57b 1.59 2.47b 1.72b
*** *** * NS ** *
S.E.D.
0.306 0.270 0.268 0.275 0.283 0.259
Sex Male (n=27)
Female (n=22)
24.1 12.30 6.32 2.07 1.22 1.66 1.38
28.2 12.50 6.55 2.59 1.81 2.57 1.72
Sign.
S.E.D.
NS NS *** *** *** ***
0.253 0.277 0.226 0.231 0.236 0.219
Sign.: signification; NS: no significant; S.E.D.: standard error of the difference; a, b, c: means with different letters are significantly different (P40.05); LWS: live weight at slaughter; CCW: cold carcass weight; KKCF: kidney knob and channel fat; ELW: empty live weight. * P40.05. ** P40.01. *** P40.001.
proportion of both KKCF values (P40.001) than males. Subcutaneous fat thickness was influenced by slaughter weight; this value was greater in lambs slaughtered at 14 kg (2.47 mm) than in those slaughtered at 12 and 10 kg (2.00 and 1.87 mm, respectively) (P40.01). Lamb gender also influenced this parameter, as females displayed higher dorsal fat values (P40.001) than males (2.57 vs. 1.66) Subjective subcutaneous fatness, determined according to the EU method for lightweight carcasses, was affected by slaughter weight. Significant differences (P40.05) between lambs slaughtered at 10 and 14 kg live weight (1.38 vs. 1.72) were seen. The effect of gender was very significant (P40.001); female lambs obtained a higher subjectively evaluated fatness value than males (1.72 vs. 1.38).
Measurements and analysis of variance of tissue composition, obtained after dissection of the left halfcarcass, are presented in Table 3. Results are expressed as the corrected proportion of the left half-carcass, taking into account the water and tissue losses that occur during dissection. Lamb weight affected carcass composition, this is due to the fact that the proportion of carcass bone tissue dropped as slaughter weight increased (P40.05). Slaughter weight influenced the muscle/total fat (M/TF) (P=0.08) and muscle/bone (M/B) (P=0.06) ratios to a small degree. Lamb gender affected carcass tissue composition; males displayed a higher proportion of muscle (54.64% in males vs. 52.75% in females) (P40.01) and bone (24.56% in males vs. 22.43% in females) (P40.001), while females had a greater proportion of total fat
Table 3 Arithmetic means and standard error of the difference of tissues percentages in the left half of the carcass in lambs of different weights and sex Live weight at slaughter
Components (%) Muscle (M) Bone (B) Total fat (TF) Other tissues Subcutaneous fat (SF) Intermuscular fat (IF) Pelvic fat Renal fat M/TF M/B SF/IF
Sign.
10 kg (n=17)
12 kg (n=16)
14 kg (n=16)
53.18 24.20a 16.78 6.34 7.91 5.66 0.94 2.07 4.19 2.24 1.32
53.78 23.34ab 16.28 6.36 7.41 5.49 0.97 2.47 3.40 2.29 1.38
54.12 22.95b 17.57 5.10 8.45 5.75 0.89 2.56 3.06 2.34 1.50
NS * NS NS NS NS NS NS NS+ NS+ NS
S.E.D.
0.56 0.45 0.82 0.52 0.53 0.36 0.25 0.30 0.44 0.25 0.26
Sex Male (n=27)
Female (n=22)
54.64 24.56 14.05 6.54 6.32 5.03 0.85 1.88 4.25 2.21 1.26
52.75 22.43 19.70 5.32 9.52 6.23 1.00 2.85 2.85 2.37 1.54
Sign.
S.E.D.
** *** *** * *** *** * *** ** ** **
0.44 0.36 0.64 0.42 0.42 0.29 0.22 0.25 0.35 0.21 0.22
Sign.: signification; NS: no significant; S.E.D.: standard error of the difference; a, b: means with different letters are significantly different (P40.05); Other tissues: remaining tissues from dissection; CCW: cold carcass weight. + P40.1. * P40.05. ** P40.01. *** P40.001.
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1088
(19.7% in females vs. 14.05% in males) (P40.001). Female lambs displayed higher proportions of all fat depots than males; the greatest gender difference was observed for subcutaneous fat (9.52% in females as opposed to 6.32% in males) (P40.001). The M/TF ratio (4.25 for males and 2.85 for females, P40.01) also demonstrates that male lamb carcasses were leaner than those of females. Although males displayed more muscle tissue than females, the latter presented a higher M/B ratio (P40.01), as their proportion of bone tissue was also higher. On the other hand, females also displayed a higher subcutaneous fat/intermuscular fat (SF/IF) ratio (P40.01) than males, due to their greater subcutaneous fat depot. 3.2. Meat quality The arithmetic means and analyses of variance of the pH and colour of the longissimus dorsi and semitendinossus muscles, as well as the water-holding capacity of the longissimus dorsi muscle are shown in Table 4. As for the influence of slaughter weight on longissimus dorsi muscle pH values recorded at different times, the highest values were recorded in 14 kg lambs and the greatest differences were observed at 60 min postmortem (P40.05). The drop in pH values between 60 min and 24 h was greater in 14 kg lambs than in those weighing 10 kg (P40.01). Water-holding capacity, expressed as the proportion of liquid expelled, was influenced by gender. WHC was lower in females than in males (P40.05); female lamb meat expelled a higher percentage of liquid than those of males (19.94% vs. 18.54%). Slaughter weight did not affect this parameter.
The colour-related parameters of the m. longissimus dorsi and m. rectus abdominis of lambs of both sexes and the three slaughter weights are shown in Table 5. M. longissimus dorsi colour was affected by slaughter weight. The muscle colour of 10 kg lambs was lighter (L*) than that of 14 kg lambs (47.74 vs. 44.95) (P40.05). Lamb weight also influenced rectus abdominis muscle colour. In animals slaughtered at 10 kg, this muscle displayed greater lightness (L*) (54.83 vs. 52.94 and 52.37 of the 12 and 14 kg lambs, respectively) (P40.01) and a lower redness index (a*) (11.45 as opposed to 12.76 and 12.80 of the other two groups) (P40.05). The yellowness index (b*) was lower in 14 kg lambs than in those weighing 12 kg (P40.05), while hue was greater in the 10 and 12 kg lambs. Gender also affected the colour of the m. rectus abdominis (P40.05); the hue value of male lambs (33.21) was higher than that of females (30.22). The arithmetic means and analyses of variance of the effects of gender and slaughter weight on the total fatty acid composition of subcutaneous rib fat are presented in Table 6. Gender influenced the percentage of chemical fat extracted from the subcutaneous rib depot; this value was 53.53% in females and 45.39% in males (P40.05). With regard to the effect of gender on the fatty acids of subcutaneous rib fat, males presented higher proportions of myristic acid (C14:0) (P40.01), palmitic acid (C16:0) (P40.01) and heptadecenoic acid (C17:1%) (P40.01) than females. On the other hand, females displayed higher percentages of pentadecanoic acid (C15:0) (P40.05), margaric acid (C17:0) (P40.001), linoleic acid (C18:2) (P40.001) and linolenic acid (C18:3) (P40.01) than males.
Table 4 Arithmetic means and standard error of the difference in pH and other parameters related to meat quality (m. longissimus dorsi and m. semitendinossus) in lambs of different weights and sex Live weight at slaughter 10 kg (n=17) pH (Longissimus) pH 60 min pH 24 h PH change 60 min–24 h pH (Semitendinosus) pH 60 min pH 24 h pH change 60 min–24 h WHC (% liquid expelled)
5.87a 5.50a 0.36a
6.02 5.77 0.25 18.54
12 kg (n=16) 6.04a 5.54a 0.49a
5.97 5.66 0.30 19.37
Sign.
S.E.D.
14 kg (n=16) 6.43b 5.67b 0.75b
6.18 5.75 0.43 19.81
Sex Male (n=27)
Sign.
S.E.D.
Female (n=22)
*** * **
0.25 0.25 0.25
6.06 5.57 0.49
6.16 5.58 0.58
NS NS NS
0.22 0.21 0.22
NS NS NS NS
0.25 0.25 0.25 0.69
6.01 5.70 0.30 18.54
6.10 5.76 0.34 19.94
NS NS NS *
0.22 0.22 0.22 0.69
Sign.: significance; NS: no significant; S.E.D.: standard error of the difference; a, b: means with different letters are significantly different (P40.05); WHC: water-holding capacity. * P40.05. ** P40.01. *** P40.001.
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1089
Table 5 Arithmetic means and standard error of the difference of parameters related to meat colours (m. longissimus dorsi and m. rectus abdominis) of different weights and sex Weight 10 kg (n=17)
Sign. 12 kg (n=16)
14 kg (n=16)
Colour (Longissimus) L* 47.74a a* 12.66 b* 6.24 Chroma 14.16 Hue 26.49
46.48ab 13.57 6.49 15.15 26.38
44.95b 14.02 5.96 15.24 23.16
* NS NS NS NS
Colour (Rectus ab.) L* 54.83a a* 11.45a b* 7.91ab Chroma 14.01 Hue 34.38a
52.94b 12.76b 8.26a 15.25 32.75a
52.37b 12.80b 6.81b 14.55 28.01b
** * * NS **
S.E.D.
Sex
Sign.
S.E.D.
Male (n=27)
Female (n=22)
0.78 0.56 0.32 0.50 1.39
46.65 13.42 6.20 14.83 25.05
46.17 13.37 6.25 14.84 25.61
NS NS NS NS NS
0.61 0.45 0.27 0.40 1.08
0.61 0.42 0.47 0.48 1.36
53.57 12.27 8.04 14.73 33.21
53.30 12.41 7.29 14.47 30.22
NS NS NS NS *
0.48 0.34 0.38 0.38 1.05
Sign.: signification; NS: no significant; S.E.D.: standard error of the difference; a, b, c: means with different letters are significantly different (P40.05); colour: L* (lightness), a* (redness index), b* (yellowness index), Chroma: chromaticity (a*2+b*2)1/2; hue=arc tangent b/a57.29. * P40.05. ** P40.01.
Table 6 Arithmetic means and standard error of the difference of the fatty acid composition of subcutaneous fat of the m. longissimus thoracis (proportion by weight of total fatty acids) in lambs under different weights and sex Weight
Sign.
10 kg (n=17)
12 kg (n=16)
14 kg (n=16)
Fatty acids C12:0 C14:0 C14:1 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 C20:0
4.14 14.8 0.78 2.15 34.81 4.32 2.4 0.09 9.3 20.57 2.74 2.78 1.01
3.57 14.09 0.72 2.05 35.36 4.33 2.39 0.12 9.69 20.94 2.67 2.84 1.12
3.47 13.7 0.82 2.11 34.9 4.26 2.42 0.12 9.42 21.27 2.63 2.67 2.02
NS NS NS NS NS NS NS NS NS NS NS NS NS
Sums and ratios OFA SFA MUFA PUFA TUFA PUFA/SFA MUFA/SFA TUFA/SFA n6/n3 DFA
4.69 68.64 25.82 5.52 31.35 0.081 0.37 0.46 0.99 40.65
4.61 68.3 26.17 5.51 31.68 0.08 0.38 0.46 0.95 41.38
4.65 68.2 26.48 5.30 31.79 0.078 0.38 0.46 0.99 41.21
NS NS NS NS NS NS NS NS NS NS
S.E.D.
Sex
Sign.
S.E.D.
Male (n=27)
Female (n=22)
0.36 0.48 0.27 0.26 0.51 0.28 0.25 0.25 0.36 0.68 0.26 0.28 0.41
3.84 14.92 0.75 1.99 35.76 4.30 2.19 0.17 9.18 20.61 2.43 2.51 1.23
3.61 13.5 0.80 2.21 34.33 4.30 2.62 0.04 9.75 21.25 2.93 3.02 1.56
NS ** NS * ** NS *** ** NS NS *** ** NS
0.29 0.38 0.23 0.22 0.40 0.24 0.21 0.21 0.29 0.54 0.23 0.24 0.34
0.29 0.78 0.77 0.34 0.78 0.24 0.24 0.24 0.24 0.85
4.42 69.14 25.9 4.94 30.85 0.071 0.37 0.44 0.98 40.04
4.88 67.62 26.41 5.95 32.37 0.088 0.39 0.48 0.97 42.3
* NS NS *** NS *** NS NS NS *
0.24 0.61 0.60 0.28 0.61 0.21 0.21 0.21 0.21 0.85
Sign.: significance; NS: no significant; S.E.D.: standard error of the difference; OFA: odd fatty acids=15:0+17:0+17:1; DFA: desirable fatty acids=C18:0+TUFA; SFA=saturated fatty acids, MUFA=monounsaturated fatty acids, PUFA=polyunsaturated fatty acids, TUFA=total unsaturated fatty acids; n-6/n-3: (C18:2/C18:3). * P40.05. ** P40.01. *** P40.001.
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
1090
weight on the total fatty acid composition of intramuscular rib fat. Although fatty acid composition was not affected by slaughter weight, this parameter was influenced by gender. Males displayed a greater proportion of lauric acid (C12:0) (P40.001), margaric acid (C17:0) (P40.01), arachic acid (C20:0) (P40.01) and behenic acid (C22:0) (P40.01) while females presented higher values of palmitoleic acid (C16:1) (P40.001), heptadecenoic acid (C17:1) (P40.05) and oleic acid (C18:1) (P40.01). The sum of the values of fatty acids with odd-number carbon chains (C15:0 +C17:0+C17:1), was influenced by gender (P40.01). Male lambs displayed higher proportions of these fatty acids than females (3.01% vs. 2.69%). As was the case with subcutaneous fat, male lambs displayed a higher proportion of SFA (P40.01). On the other hand, females displayed a greater percentage of MUFA (P40.001) and TUFA (P40.01). Furthermore, female lambs exhibited higher MUFA/SFA and TUFA/
Slaughter weight did not significantly affect the fatty acid composition of subcutaneous rib fat. An average of 4.63% of the fatty acids in the subcutaneous rib fat had odd-number carbon chains (C15:0+C17:0+C17:1). Gender influenced these fatty acids, as females displayed a higher proportion (4.88%) of them than males (4.42%) (P40.05). Slaughter weight and gender did not influence percentages of saturated (SFA), monounsaturated (MUFA) and total polyunsaturated fatty acids (TUFA). In contrast, gender did affect percentages of polyunsaturated fatty acids (PUFA) and the polyunsaturated/ saturated fatty acid ratio (PUFA/SFA); both parameters were higher in females than in males (P40.001). Gender, but not live weight, affected desirable fatty acid (DFA) values, which were higher in female lambs than in males (P40.05). Table 7 presents the arithmetic means and analysis of variance values of the effect of gender and slaughter
Table 7 Arithmetic means and standard error of the difference of the fatty acid composition of intramuscular fat of the m. longissimus thoracis (proportion by weight of total fatty acids), in lambs of different weights and sex Weight 10 kg (n=17) Fat
Sign. 12 kg (n=16)
S.E.D.
14 kg (n=16)
Sex Male (n=27)
Sign.
S.E.D.
Female (n=22)
2.81
2.92
2.67
NS
0.32
2.58
3.03
NS
0.23
Fatty acid C12:0 C14:0 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 C20:0 C20:4 C22:0
1.66 9.35 1.04 31.90 3.68 1.51 0.40 12.07 23.78 4.41 2.31 1.39 3.83 2.6
1.50 8.97 1.003 31.95 3.79 1.48 0.36 12.1 23.8 4.47 2.52 1.34 3.88 2.77
1.32 8.75 0.85 31.44 3.86 1.47 0.44 12.06 24.42 4.67 2.47 1.30 4.2 2.69
NS NS NS NS NS NS NS NS NS NS NS NS NS NS
0.27 0.42 0.42 0.39 0.27 0.25 0.25 0.35 0.67 0.30 0.26 0.27 0.31 0.29
1.77 9.22 9.22 31.65 3.52 1.60 0.35 12.24 22.92 4.50 2.51 1.58 4.02 2.98
1.22 8.82 8.82 31.88 4.03 1.37 0.44 11.92 25.08 4.54 2.36 1.11 3.92 2.39
*** NS NS NS *** ** * NS ** NS NS ** NS **
0.34 0.34 0.32 0.23 0.22 0.22 0.29 0.53 0.25 0.23 0.24 0.26 0.25
Sums and ratios OFA SFA MUFA PUFA TUFA PUFA/SFA MUFA/SFA TUFA/SFA n-6/n-3 DFA
2.95 61.55 27.87 10.57 38.44 0.17 0.45 0.63 3.61 50.52
2.84 61.15 27.95 10.88 38.84 0.17 0.45 0.63 3.39 50.95
2.77 59.91 28.73 11.35 40.09 0.19 0.48 0.67 3.61 52.15
NS NS NS NS NS NS NS NS NS NS
0.26 0.76 0.66 0.46 0.76 0.24 0.24 0.24 0.29 0.88
3.01 62.14 26.8 11.05 37.85 0.17 0.43 0.61 3.45 50.10
2.69 59.6 29.57 10.82 40.39 0.18 0.49 0.68 3.62 52.31
* ** *** NS ** NS ** *** NS *
0.23 0.59 0.52 0.37 0.59 0.21 0.21 0.21 0.24 0.69
Sign.: significance; NS: no significant; S.E.D.: standard error of the difference; OFA: odd fatty acids=15:0+17:0+17:1; DFA: desirable fatty acids=C18:0+TUFA; SFA=saturated fatty acids, MUFA=monounsaturated fatty acids, PUFA=polyunsaturated fatty acids, TUFA=total unsaturated fatty acids; n-6/n-3: (C18:2+C20:4/C18:3). * P40.05. ** P40.01. *** P40.001.
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
SFA ratios (P40.01 and P40.001, respectively) and a greater proportion of DFA (P40.05) than their male counterparts. The n6/n3 ratio was not influenced by either of the factors studied.
4. Discussion 4.1. Carcass measurements and carcass tissue composition In this study, the greatest differences in fatness were seen between 10 and 14 kg lambs. These differences were particularly due to the greater dorsal fat thickness and the higher subjectively evaluated KKCF and SF scores of the 14 kg lambs. Other authors, including Velasco et al. (2000), also found that fatness increased significantly when the live weight of suckling lambs rose from 10 to 12 kg. Adipose tissue development of these lambs had already begun, despite their being very young. Jeremiah, Jones, Tong, and Gibson (1997) report that subcutaneous fat thickness increases as slaughter weight rises. Differences in fatness due to slaughter weight are very important, even for a small weight interval, as they affect abattoir classification of the carcasses (Miguel et al., 2003) and thus carcass price. As for carcass tissue composition, differences in live weight affected only bone tissue, whose proportion dropped as weight increased. Vigneron, Prud’hon, Touraille, Valin, Bouix, & Bibe (1986) also report that the percentage of bone tissue drops as carcass weight rises, as the allometric coefficient of this tissue is lower than 1 (b < 1). Mahgoubt and Lodge (1994) also report that the proportion of fat increases with age, while that of bone decreases. Although the differences observed in our study were not significant, it was possible to detect a tendency towards a higher M/B ratio and a lower M/TF ratio as slaughter weight rose. This confirms that bone tissue is more precocious than muscle, while fat tissue develops later (Hammond, 1932). Mahgoubt and Lodge (1994) and Velasco et al. (2000) also observed that the M/B ratio increases with slaughter weight, that is, the amount of lean tissue increases faster than bone tissue as carcass weight increases. The M/B and M/TF ratios provide valuable information as to carcass tissue composition. Carcasses with a high M/B ratio are more commercial and in greater consumer demand. The M/TF ratio should ensure that the meat offers the tastiness and juiciness demanded by the consumer. Gender had an important effect on objective and subjective fatness parameters, as females displayed higher values than males for all measurements. On the one hand, this is because females display a greater ten-
1091
dency to accumulate fat from a very early age. On the other hand, females were older than males when slaughtered, due to their slower growth rate (282 g/day as compared with 317 g/day in males). Horcada et al. (1998) observed that male and female 11 kg suckling lambs displayed differences with regard to dorsal fat thickness. These authors reported dorsal fat values of 1.6 and 2.1 mm for males and females, respectively. Gender differences were greater for suckling lambs than for heavier lambs. Velasco et al. (2000) found differences between male and female suckling lambs with regard to the quantity and proportion of kidney knob and channel fat. Gender differences in fatness are associated with variations in protein assimilation efficiency and the different composition of weight gain displayed by males and females throughout their growth (Robelin & Theriez, 1981). Males displayed greater nitrogen retention indexes than females and therefore developed proportionally more muscle than adipose tissue (Lobley et al., 1990). The effect of gender on carcass tissue composition was more important. Females matured earlier than males, as reflected in their lower bone and muscle tissue values and their higher percentage of fat. Numerous authors have noted this fact in sheep of various breeds and weight ranges (Mahgoubt & Lodge, 1994; Teixeira, Delfa, & Treacher, 1996; Vergara, Molina, & Gallego, 1999). Female lambs presented more fat tissue than males, mainly due to their greater proportion of subcutaneous fat (9.52% in females as opposed to 6.32% in males). Velasco et al. (2000) obtained similar values (7.20% in males vs. 9.07% in females) in suckling Talaveranabreed lambs. In our study, the M/TF ratio was significantly affected by gender. Males displayed a lower proportion of fat and a higher M/TF ratio (4.25%, as opposed to 2.85% in females). Similarly, Velasco et al. (2000) obtained higher values for this ratio in suckling male lambs than in their female counterparts (2.98 vs. 2.55). The M/B ratio was also influenced by gender. This value was higher in females (2.37 vs. 2.21 in males). Guı´a, Can˜eque, and Lauzurica (1985) also report that at commercial slaughter weights female suckling lambs display greater muscle than bone tissue development. The EU carcass classification system for low-weight lambs is based on carcass fatness. Our study lambs were classified at the bottom end of the scale and considered to be of poor quality due to their low carcass fat content. As they displayed greater fatness at a given weight, female lambs received a better classification than males, and thus a higher sales price. 4.2. Meat quality The low weight (10 kg) lambs displayed lower pH values at 60 min than their high weight (14 kg) counterparts. As
1092
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093
a result, pH values at 24 h had dropped less in the former animals than in the latter ones. Due to their lower weight and age, the younger lambs may have suffered greater stress at being separated from their dams (Morgan & Arnold, 1974). These lambs may also be more sensitive to pre-slaughter handling, which produces an antemortem glycogenolysis that depletes part of the muscular glycogen. Gender did not significantly influence pH in the present study; findings similar to our own have been reported by numerous authors (Horcada et al., 1998; Vergara et al., 1999, McGeehin, Sheridan, & Butter, 2001). Although pH is closely related to WHC and differences with regard to pH and the speed of its fall in relation to slaughter weight have been observed, no significant influence of this value on water-holding capacity was found in the present study. The bibliography available offers contradictory information concerning the influence of weight, and therefore slaughter age, on WHC. Some authors report that this parameter is not affected by weight/age (Solomon, Kemp, Moody, Ely, & Fox, 1980), while other studies suggest that higher weight is accompanied by lower (Velasco et al., 2000) or higher (Azia, Ball, Sharpe, & McCutcheon, 1993) water-holding capacity. Gender influenced WHC to a certain degree, as females expelled a greater proportion of liquid, coinciding with the greater (non-significant) fall in their pH values. Velasco et al. (2000) likewise observed that females expelled more liquid than males (15.43% vs. 14.1%). However, no gender related differences were reported by authors studying Lacha-breed suckling lambs (Horcada et al., 1998). In our study, meat colour was influenced by slaughter weight. As slaughter weight rose, L* and b* decreased and a* increased, especially significantly in the rectus abdominis muscle. This confirms to us that in spite of the very small differences observed in slaughter weight, the suckling lambs that weighed least displayed the lightest colour meat. This, in turn, is the meat that consumers value most highly. San˜udo, Sierra, Osorio, Alcalde, Santaolalla, and Alberti (1993) observed in Rasa Aragonesa-breed, 8.5–11.5 kg, lambs that meat darkens as slaughter weight increases, mainly because pigment content increases with age (Lawrie, 1998). Gender hardly influenced meat colour, affecting only hue. Horcada (1996) found no significant differences between male and female Lacha-breed lambs, as the diet, age and weight of animals of both sexes in that study were similar. Likewise, San˜udo, Sanchez, and Alfonso (1998) reported that gender differences are not notable. This author notes however, that females could be darker than males due to their greater precociousness and fatness when comparing both sex at equal slaughter weight. The fatty acid composition of our study lambs was primarily affected by gender. Slaughter weight had
almost no influence on this parameter, mainly because the interval between slaughter weights was small. Female lambs exhibited a greater proportion of MUFA than males in the intramuscular fat depot studied. These MUFA consisted mainly of oleic acid (C18:1) and palmitoleic acid (C16:1). In contrast, male lambs displayed greater fat saturation (SFA) in the same fat depot. The state of fatness, and therefore the amount of fat deposited, affects the fatty acid composition of the different depots studied (Huerta-Leidenz, Cross, Savell, Lunt, Baker, & Smith, 1996). According to Leat (1977) fatness in cattle is accompanied by a higher degree of unsaturation of the fat depots, which is associated with a high palmitoleic acid (C16:1) content. Jackson and Winkler (1970) have reported similar results. The latter authors note that the unsaturation of the fat depots increases with adiposity due to 9 desaturase enzyme activity, responsible for the synthesis of oleic acid (C18:1) from stearic acid (C18:0). In addition, the subcutaneous rib-fat depot of female lambs in our study contained a greater proportion of linolenic acid (C18:3). This, together with the greater percentage of desirable fatty acids (DFA) in both fats studied, indicates that the fat of these female lambs was healthier in terms of human consumption than that of the male lambs (Wood & Enser, 1997). In addition, the subcutaneous fat of male lambs displayed a higher palmitic acid (C16:0) content, which could potentially increase plasma cholesterol levels (Grundy, 1986).
5. Conclusions Female lamb carcasses displayed greater fatness than their male counterparts for all the parameters studied, despite the fact that all the animals were young. This meant that the former received a better classification and were more highly valued than their male counterparts. Slaughter weight affected the pH value 24 h after slaughter; the lowest values were found in the m. longissimus of the lowest weight lambs, which in addition, exhibited the lightest colour. Fatty acid composition was influenced by gender. Subcutaneous fat of the female lambs contained more linolenic acid as well as a higher proportion of polyunsaturated fatty acids. In addition, the intramuscular fat of the females displayed a lower proportion of saturated fatty acids than that of the male lambs. From the nutritional point of view, and assuming that all the fat of these lambs is consumed, consumers may consider the fat of female lambs healthier than that of males.
References Azia, N. N., Ball, R. O., Sharpe, P. H., & McCutcheon, B. (1993). Growth, carcass composition and meat quality of crossbred lambs
M.T. Di´az et al. / Meat Science 65 (2003) 1085–1093 at different slaughter weights. In 39th International Congress of Meat Science and Technology. INRA-ITOVIC, Paris. Banskalieva, V., Shindarska, Z., & Dimov, V. (1989). Fatty acid composition of various depot fats of lamb. In Proceeding. 35th International Congress on Meat Science and Technology 3; pp. 1222– 1229, Copenhagen. Centre International de l’Eclairage (1976). De´finition d’un space de colour por deux cordones de cromaticite´ et la luminosite´. Supplement no. 2 to CIE, publication no. 15 (E-1.3.1) 1971/(TC-1-3). Centre Internationale de L’Eclairage, Paris. Colomer-Rocher, F., Dumont, B. L., & Murillo, N. L. (1972). Descripcio´n del despiece ovino Aragone´s y definicio´n de un despiece de referencia normalizado. Anales del INIA. Serie.: Produccion Animal, 3, 79–108. Colomer-Rocher, F., Delfa, R., & Sierra, I. (1988). Me´todo normalizado para el estudio de los caracteres cuantitativos y cualitativos de las canales ovinas producidas en el a´rea mediterra´nea segu´n los sistemas de produccio´n. Cuadernos INIA, 17, 19–41. Fisher, A. V., & de Boer, H. (1994). The EAAP standard method of sheep carcass assessment. Carcass measurements and dissection procedures. Livestock Production Science, 38, 149–159. Grau, R., & Hamm, R. (1953). Eine einfache Methode zur bestimmung der Wasserbindurng in Muskel. Naturwissenschaften, 40, 29–30. Grundy, S. M. (1986). Comparison of monounsaturated fatty acids in carbohydrates for lowering plasma cholesterol. The New England Journal of Medicine, 314, 745–748. Guı´a, E., Can˜eque, V., & Lauzurica, S. (1985). Estudio de la aptitud ca´rnica de la raza Talaverana. In ITEA (Vol. Extra n 5, pp. 256– 258) Zaragoza. Hammond, J. (1932). Growth and development of mutton qualities. In O. Y. Boyd, Ed., The sheep. Edinburgh and London. Hanson, S. W. F., & Olley, J. (1963). Application of the Bligh and Dyer method of lipid extraction to tissue homogenates. Biochemical Journal, 89, 101–102. Horcada, A. (1996). Calidad de la carne de los corderos de las razas Lacha y Rasa Aragonesa. Tesis Doctoral, Universidad Pu´blica de Navarra. Pamplona. Horcada, A., Beriain, M. J., Purroy, A., Lizaso, G., & Chasco, J. (1998). Effect of sex on meat quality of Spanish lamb breeds (Lacha and Rasa Aragonesa). Animal Science, 67, 541–547. Huerta-Leidenz, N. O., Cross, H. R., Savell, J. W., Lunt, D. K., Baker, J. F., & Smith, S. B. (1996). Fatty acid composition of subcutaneous adipose tissue from male calves at different stages of growth. Journal Animal Science, 74, 1256–1264. Jackson, H. D., & Winkler, V. W. (1970). Effects of saturation on the fatty acid composition of adipose tissue and plasma lipids of sheep. Journal of Nutrition, 100, 201–207. Jeremiah, L. E., Jones, S. D. M., Tong, A. K. W., & Gibson, L. L. (1997). The influence of lamb chronological age, slaughter weight and gender on carcass measurements. Sheep and Goat Research Journal, 13, 87–95. Lawrie, R. A. (1998). Meat Science (6th ed). Abinton, Cambridge, England: Woodhead Publishing Ltd. Leat, W. M. F. (1977). Depot fatty acids of Aberdeen Angus and Friesian reared on hop and barley. Journal of Agricultural Science Camb, 89, 575–582. Lobley, G. E., Connell, A., Milne, E., Burchan, V., Galder, A. G., Anderson, S. E., & Vint, H. (1990). Muscle protein synthesis in response to testosterone administration in wether lambs. British Journal of Nutrition, 64, 691–704. Mahgoubt, O., & Lodge, G. A. (1994). Growth and body composition of Omani local sheep. 1. Live-weight growth and carcass and noncarcass characteristics. Animal Production, 58, 365–372.
1093
McGeehin, B., Sheridan, J. J., & Butter, F. (2001). Factors affecting the pH decline in lamb after slaughter. Meat Science, 58, 79–84. Miguel, E., Onega, E., Can˜eque, V., Velasco, S., Dı´az, M. T., Lauzurica, S., Perez, C., Bla´zquez, B., & Ruiz de Huidobro, F. (2003). Carcass classification in suckling lambs. Discrimination ability of the European Union scale. Meat Science, 1, 107–117. Morgan, P. D., & Arnold, G. E. (1974). Behavioural relationships between merino ewes and lambs during the four weeks after birth. Animal Production, 19, 169–176. Morrison, W. R., & Smith, L. M. (1964). Preparation of fatty acid methyl esters and dimethyl acetals from lipids with boron fluoridemethanol. Journal of Lipid Research, 5, 600–608. Perez, J. I., Gallego, L., Gomez, V., Osorio, M. T., San˜udo, C., Otal, J., Bernabeu, R., & Molina, A. (1994). Influencia del tipo de destete, tipo de parto, sexo y peso de la canal frı´a en la composicio´n tisular de la canal en corderos de raza Manchega. In XVIII Jornadas Cientı´ficas de la Sociedad Espan˜ola de Ovinote´cnia y Caprinotecnia, pp. 623–627, Albacete. Robelin, J., & Theriez, M. (1981). Fixation de proteı´nes les rumiants: e´volution en fonction du poids des animaux et variation selon la race, le sexe on le niveau des apports alimentaires. Reproduction Nutrition Development, 21, 335–353. San˜udo, C., Alfonso, M., Sanchez, A., Delfa, R., & Teixeira, A. (2000). Carcass and meat quality in light lambs from different fat classes in the EU carcass classidication system. Meat Science, 56, 89–94. San˜udo, C., Campo, M. M., Sierra, I., Marı´a, G. A., Olleta, J. L., & Santolaria, P. (1997). Breed effect on carcase and meat quality of suckling lambs. Meat Science, 46(4), 357–365. San˜udo, C. Sanchez, A., & Alfonso, M. (1998). Small ruminant prouction systems and factores affectin lamb meat quality. 44th International Congress of Meat Science and Technology. Barcelona. Spain, 22–47. San˜udo, C., Sierra, I., Osorio, M. T., Alcalde, M. J., Santaolalla, Pl., & Alberti, P. (1993). Variation of meat quality in light lamb depending on weight increase of the carcass (7,4–15,4 kg). Proceedings of the 39th international congress of meat science and technology. Alberta Canada, p 86. Solomon, M. B., Kemp, J. D., Moody, W. G., Ely, D. G. A., & Fox, J. D. (1980). Effect of breed and salughter weight on physical, chemical and organoleptic properties of lamb carcasses. Journal Animal Science, 51, 1102–1107. Stokes, G. B., & Walker, D. M. (1970). The nutritive value of fat in the diet of the milk-fed lamb. British Journal of Nutrition, 24, 435– 440. Teixeira, A., Delfa, R., & Treacher, T. (1996). Carcass composition and body fat depots of Galego Braganc¸ano and crossbred lambs by Suffolk and Merino Precoce sire breeds. Animal Science, 63, 389–394. Velasco, S., Lauzurica, S., Can˜eque, V., Perez, C., Ruiz De Huidobro, F., Manzanares, C., & Diaz, M. T. (2000). Carcass and meat quality of Talaverana breed sucking lambs in relation to gender and slaughter weight. Animal Science, 70, 253–263. Vergara, H., Molina, A., & Gallego, L. (1999). Influence of sex and slaughter weight on carcass and meat quality in light and medium weight lambs produced in intensive systems. Meat Science, 52, 221–226. Vigneron, P., Prud’hon, M., Touraille, C., Valin, C., Bouix, J., & Bibe, B. (1986). Croissance des agneaux. Types da fibres musculaires et qualite´ de la viande. Muscles indicateurs. In 11e´me Journe´es de la Recherche Ovine et Caprine. Qualite´ des Produits chez les Ovins et les Caprins (Ed INRA), pp. 49–73, Versailles. Wood, J. D., & Enser, M. (1997). Factors influencing fatty acids in meat and the role of antioxidants in improving meat quality. British Journal of Nutrition, 78(Suppl. I), 549–560.