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The influence of age at slaughter and litter size on some quality traits of kid meat
Small Ruminant Research 44 (2002) 75–80
The influence of age at slaughter and litter size on some quality traits of kid meat M. Todaroa,*, A. Corraob, C.M.A. Baronec, R. Schinellib, M. Occidented, P. Giacconea a
Department S.En.Fi.Mi.Zo.—Sezione of Animal Production, Universita` di Palermo, viale delle Scienze, 90128 Palermo, Italy b Istituto Zooprofilattico Sperimentale della Sicilia ‘‘A. Mirri’’, via Rocco Dicillo, 4-90129 Palermo, Italy c Department of Scienze Zootecniche e Ispezione degli Alimenti—Sezione T.M. Bettini—Universita` di Napoli Federico II, via Universita`, 100—80055 Portici, Napoli, Italy d Consorzio per la Sperimentazione, Divulgazione e Applicazione di Biotecniche Innovative (ConSDABI), 82020 Circello, BN, Italy Accepted 5 December 2001
Abstract To study variations in the carcass characteristics of Girgentana kids slaughtered at 25 or 35 days of age and litter size (single or twin), 27 male kids were slaughtered and body components, carcass joints, pelvic limb tissue composition, meat fatty acid composition and M. longissimus dorsi (LD) colour were evaluated. Girgentana kids slaughtered at 35 days had greater live weights (6.4 kg versus 5.0 kg; P 0:01), carcass weights (4.5 kg versus 3.6 kg; P 0:01), muscle contents (57.6% versus 54.9%; P 0:01) but similar dressing percentages (70.1% versus 70.6%) as compared to kids slaughtered at 25 days. Twin kids had a higher muscle percentage (57.3% versus 55.2%; P 0:05) and similar fat percentage (5.5% versus 6.0%) but a higher unsaturated/saturated fatty acid ratio (1.17 versus 1.01; P 0:05). Meat colour was not influenced by any factors considered. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Girgentana goat; Capretto kid; Meat quality
1. Introduction The Girgentana goat is originally from the Province of Agrigento in Sicily. Its striking appearance of characteristic long corkscrew horns and its good milk yield helped the breed spread. The numbers of Girgentana goats are presently decreasing (Giaccone et al., 1994). Perceptions of meat quality vary from country to country and among ethnic and age groups. In Italy *
Corresponding author. Tel.: þ39-91-485-181; fax: þ39-91-485-713. E-mail address: [email protected] (M. Todaro).
only ‘‘capretto’’ meat (obtained from suckling kids to produce a carcass weight of 6–10 kg with pink flesh) is highly appreciated by consumers, whereas, in other countries, such as India, the Chevon meat (obtained from older animals with a carcass weight of 16–22 kg) is particularly preferred. Studies concerning chemical composition and meat quality have suggested that kid meat is not inferior to lamb (Babiker et al., 1990). The iron and phosphorus concentrations in the meat, along with its high protein and low fat contents, confirm that it has a high nutritive quality (PopovRaljic et al., 1995). However, it is well known that several factors, such as genetic type (Dhanda et al., 1999), age (Borghese et al., 1990),
0921-4488/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 4 8 8 ( 0 2 ) 0 0 0 3 5 - 4
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M. Todaro et al. / Small Ruminant Research 44 (2002) 75–80
sex (Johnson et al., 1995; Matsuoka et al., 1997) and nutritional conditions (Hadjipanayiotou et al., 1996; Titi et al., 2000) influence meat quality. In Sicily, the market tends to demand meat from a very young goat, often slaughtered at 25–30 days, however, these carcasses have a high bone percentage. The great demand for kid meat is concentrated in the Christmas and Easter holiday periods and only 77% of kid meat utilised is produced in Italy. Several studies (Barbieri et al., 1973; Congiu, 1987) showed that production of kid meat slaughtered at 35 days is more economically favourable than that obtained from kids slaughtered at 25 days, but information about meat quality differences is lacking. To this end, an experiment was conducted to study the carcass characteristics of Girgentana kids slaughtered at 25 or 35 days.
2. Materials and methods The 27 male Girgentana kids were raised in the Sicilian interior, on maternal milk and housed indoors in group boxes for 25 or 35 days. After a 12 h fasting, all kids were slaughtered following traditional procedures, and the weight of the warm carcass, dress-off items and gastrointestinal content were recorded. After the carcasses were chilled at 4 8C for 24 h, the right halves of the carcasses were divided into cuts according to the procedure standardised by ASPA (1989). The pelvic limb of each carcass was dissected into muscle, fat, bone and ‘‘other tissue’’. After pelvic limb dissection, the meat was immediately homogenised and lyophilised. Dry matter at 105 8C, fat extracted with petroleum ether in Soxhlet apparatus, ash at 525 8C and protein by the Kjeldhal procedure were determined (AOAC, 1990) in the lyophilised samples. Lipids were determined after extraction, in duplicate, of lyophilised meat samples that were treated with n-hexane at 60 8C for 8–10 h. Methyl esters of the fatty acid component of the neutral triglycerides were prepared according to the transesterification method in a vial at ambient temperature for 30 min by means of m-trifluoromethyl-phenyl-trimethylamonium hydroxide (Meth-Prep II, Alltech) (0.2 N) in methanol. The methyl esters were analysed using a Perkin-Elmer 8500 gas chromatograph equipped
with a flame ionisation detector and an Omegawax 320 fused silica capillary column (30 m 0:32 mm i:d: 0:25 mm film thickness). Following sample injection, the column temperature was kept initially for 4 min at 155 8C, then increased at a rate of 4 8C/ min to 250 8C and maintained at that level until all esters had been eluted. The injector temperature was 250 8C and detector temperature was 270 8C. The carrier gas was nitrogen (15 ml/min). Standards for the fatty acid methyl esters were obtained from Sigma–Aldrich (Sigma, St. Louis, USA). Fatty acids were expressed in both normalised (molar proportion) and gravimetric (milligrams per gram of fresh tissue) formats. The softness index was estimated by dividing the sum of palmitoleic (C16:1) and oleic (C18:1) by the sum of palmitic (C16:0) and stearic (C18:0) content (Leat, 1976). At 24 h after slaughter, samples of M. longissimus dorsi (LD) muscle, taken from the loin, were placed in polyethylene bags, frozen at 20 8C and kept for about 4 months. Then they were thawed for 24 h at 4 8C. The colour was determined using a U 3000 Hitachi spectrophotometer and the CIELAB method (ASPA, 1989), detecting lightness (L), red index (a) and yellow index (b) with the illuminant C, chroma [(a2 þ b2 )1/2, C ¼ 0 grey] and hue (arctg b/a, H ¼ 0 purple red) were also calculated. Data were statistically analysed using the GLM procedure of the SAS package, Version 8.1 (SAS, 1991). Analysis was performed according to the following linear model: Yijk ¼ m þ Ai þ Bj þ eijk where A and B are the effects of age at slaughter (25 or 35 days) and the litter size (single or twin), respectively; the interaction was not significant.
3. Results and discussion Growth performance (Table 1) showed a highly significant effect of age at slaughter; kids slaughtered at 35 days showing a higher slaughter weight than those slaughtered at 25 days (6.4 kg versus 5.0 kg; P 0:01). The kids slaughtered at 35 days of age had heavier live weights (at slaughter), empty body weight and the carcass weight than those slaughtered at 25
M. Todaro et al. / Small Ruminant Research 44 (2002) 75–80
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Table 1 Growth performance, slaughter and dissection data of male Girgentana kids at two different ages (LSM S:E:) Age at slaughtering (days)
Litter size
25 (n ¼ 13)
Single (n ¼ 17)
Slaughter data Slaughter weight (kg) Empty body weight (EBW) (kg) Carcass weight (kg) Dressing percentage (%) Hide (% of EBW) Head (% of EBW) Internal organsa (% of EBW) Limbs (% of EBW)
5.0 4.9 3.6 70.6 11.6 9.5 6.4 2.3
0.3 0.3 0.2 0.5 0.2 0.2 0.1 0.1
Dissection data Right side (RS) (kg) Kidney and Pelvic fat (% of RS) Loin (% of RS) Pelvic limb (% of RS) Shoulder (% of RS) Neck, steaks, brisket (% of RS)
1.3 2.0 5.8 30.4 23.5 37.0
35 (n ¼ 14)
A a A
6.4 6.1 4.5 70.1 11.5 8.7 6.2 2.0
0.3 0.3 0.2 0.5 0.2 0.2 0.1 0.1
0.1 A 0.3 A 0.2 A 0.3 0.3 0.5
1.6 3.18 6.4 29.9 22.9 37.8
A A A
Twin (n ¼ 10)
B b B
5.9 5.6 4.1 70.4 11.5 9.0 6.3 2.1
0.2 0.2 0.2 0.4 0.2 0.2 0.1 0.1
5.6 5.4 3.9 70.4 11.7 9.2 6.3 2.2
0.3 0.3 0.2 0.5 0.2 0.2 0.1 0.1
0.1 B 0.3 B 0.1 B 0.3 0.3 0.5
1.5 2.8 6.3 30.1 23.2 37.5
0.1 0.3 0.1 0.3 0.3 0.5
1.4 2.3 5.9 30.2 23.3 37.2
0.1 0.4 0.2 0.4 0.4 0.6
B B B
On the row (within each factor): different lower case letters are significant at P 0:05; different capital letters are significant at P 0:01; n: number of observations. a Lungs, trachea, heart, liver
Both age at slaughter and litter size influenced the muscle content (Table 2). It was 2.13% higher in the kids slaughtered at 35 days, whereas in twin kids muscle content was higher than single kids (57.3% versus 55.2%; P 0:05). No significant differences were found in meat chemical composition. The principal fatty acids of pelvic limb fat, in decreasing order of proportion in total fat were oleic,
days, but dressing percentages were similar. The slaughter and carcass weights were lower than in other breeds slaughtered at the same age (Terzano et al., 1988). Kids slaughtered at 25 days had significantly heavier heads, internal organs (lungs, trachea, heart, liver) and limbs (percentage of EBW) than kids slaughtered at 35 days. The loin, kidney and pelvic fat were significantly higher for 35 days kids.
Table 2 Tissue composition and meat chemical composition of the pelvic limb, according to age of slaughtering and litter size (LSM S:E:) Age at slaughtering (days) 25
Litter size 35
Single
Twin
Tissue composition (% of pelvic limb) Bone 30.0 Muscle 54.9 Fat 5.6 Other tissues 7.2
0.6 0.7 A 0.5 0.6
28.4 57.6 5.9 6.5
0.6 0.7 B 0.5 0.5
30.0 55.2 6.0 7.3
0.6 0.7 a 0.5 0.5
28.5 0.7 57.3 0.8 b 5.5 0.6 6.5 0.6
Chemical composition (% of DM) Dry matter (DM) Ether extract Protein Ash
0.1 0.3 0.4 0.1
22.8 6.8 89.6 5.3
0.1 0.3 0.4 0.1
22.9 7.2 89.4 5.3
0.1 0.3 0.4 0.1
22.8 6.6 90.0 5.3
22.9 6.9 89.8 5.4
0.1 0.4 0.5 0.1
On the row (within each factor): different lower case letters are significant at P 0:05; different capital letters are significant at P 0:01.
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M. Todaro et al. / Small Ruminant Research 44 (2002) 75–80
Table 3 Fatty acid composition of pelvic limb fat, according to age of slaughtering and litter size (g of fatty acid/100 g of meat fat; LSM S:E:) Fatty acid (g/100 g of fat)
Age at slaughtering (days) 25
Litter size 35
Single
Twin
C8 C10 C12 C14 C14:1 C16 C16:1 C17 C18 C18:1 C18:2 C18:3 C20:4
0.01 0.32 0.39 2.63 0.23 13.31 1.16 0.83 15.48 29.68 4.11 1.16 0.37
0.00 0.03 0.05 0.24 0.02 1.23 A 0.13 0.06 0.90 1.64 0.27 0.07 0.02
0.01 0.25 0.37 3.02 0.18 17.71 1.35 0.77 13.64 27.63 4.39 1.08 0.35
0.00 0.04 0.05 0.25 0.02 1.27 B 0.14 0.07 0.93 1.69 0.28 0.08 0.02
0.01 0.30 0.43 3.18 0.23 16.98 1.41 0.82 15.89 28.94 4.54 1.41 0.37
0.00 0.03 0.04 0.21 a 0.02 1.07 0.12 0.06 0.78 a 1.43 0.24 0.06 0.02
0.01 0.00 0.28 0.04 0.34 0.06 2.47 0.29 b 0.18 0.03 14.05 1.46 1.10 0.16 0.79 0.08 13.24 1.07 b 28.37 1.94 3.96 0.32 1.11 0.09 0.35 0.02
SFA UFA MUFA PUFA UFA/SFA Softness index
32.99 37.60 31.95 5.65 1.18 1.11
1.92 1.90 1.74 0.27 0.05 a 0.06 a
35.77 35.83 30.02 5.82 1.01 0.93
1.98 1.96 1.79 0.28 0.05 b 0.06 b
37.59 37.50 31.45 6.05 1.01 0.93
1.67 a 1.65 1.51 0.24 0.04 a 0.05 a
31.17 2.28 b 35.93 2.25 30.52 2.06 5.42 0.32 1.17 0.06 b 1.11 0.07 b
On the row (within each factor): different lower case letters are significant at P 0:05; different capital letters are significant at P 0:01. SFA: saturated fatty acids; UFA: unsaturated fatty acids; MUFA: mono-unsaturated fatty acids; PUFA: poly-unsaturated fatty acids.
palmitic, stearic, linoleic, miristic and linolenic acid (Table 3), which is in agreement with the literature (Banskalieva et al., 2000). The composition of pelvic limb fat tended to change with age; the palmitic acid (C16) increasing significantly (P 0:01) from 25 to 35 days (Table 3) in accordance with results reported by Zygoyiannis et al. (1992). The oleic acid (C18:1) tended to decrease, although not significantly, so that the kids slaughtered at 25 days showed lower saturated fatty acids (32.99% versus 35.77%) and higher unsaturated fatty acids (37.60% versus 35.83%), than kids slaughtered at 35 days. The unsaturated/saturated fatty acid ratio was significantly higher for kids slaughtered at 25 days (1.18 versus 1.01; P 0:05). The softness index changed with age, showing a decrease from 25 to 35 days (1.11 versus 0.93; P 0:05) in contrast with results reported by Zygoyiannis et al. (1992). Results of fatty acid composition demonstrated a better meat quality obtained from younger kids, in particular from the point of view of health aspects. Litter size (number of kids suckled) influenced some fatty acids; in particular, single kids showed higher miristic (C14) (3.18% versus 2.47%; P 0:05)
and stearic acid (C18) (15.89% versus 13.24%; P 0:05) than twin kids (Table 3). This could be explained by the higher milk availability for the single kids (Todaro et al., 2000), which resulted in significantly higher saturated fatty acids (37.59% versus 31.17%; P 0:05) and a lower unsaturated/saturated fatty acids ratio (1.01% versus 1.17%; P 0:05). The softness index was higher in twin kids than in single kids (1.11 versus 0.93%; P 0:05). The colour of meat is very important to evaluate the Capretto carcasses. In Italy, in fact, the consumer prefers pale or pink meat. In this study, LD colour characteristics (Table 4) were similar to those reported by Dhanda et al. (1999) and Borghese et al. (1990). Girgentana kids showed an a-value lower than other genotypes (Dhanda et al., 1999; Ragni et al., 2001), so that the colour of the LD was paler than that of other kids. Moreover, the Chroma and Hue values indicated that Girgentana kids had a pale and pink meat colour, which is most acceptable to consumers. Age at slaughter and litter size did not significantly influence the muscle colour. Only small differences were found between kids slaughtered at 25 and 35 days, in
M. Todaro et al. / Small Ruminant Research 44 (2002) 75–80
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Table 4 Colorimetric parameters of LD muscle, according to age of slaughtering and litter size (LSM S:E:). Age at slaughtering (days) 25
L a b Chroma Hue
47.76 1.57 13.15 13.31 83.07
Litter size 35
0.85 0.41 0.27 0.29 1.58
46.21 2.30 13.00 13.29 79.93
particular, the kids slaughtered at 35 days of age had lower L*-value and higher a-value than kids slaughtered at 25 days, which show a darker muscle colour.
4. Conclusion This study confirmed that kid meat is of high quality and, probably, on the basis of fatty acid composition, is healthy. Slaughter and dissection data and pelvic limb tissue composition confirmed that production of kid meat slaughtered at 35 days is more favourable than that obtained from kids slaughtered at 25 days. No differences were found on pelvic limb chemical composition. The meat colour did not show significant differences between the two types of kid meat, so that, together with the higher performance, the age at slaughtering could be increased without detrimental effect on meat quality.
Acknowledgements MURST (COFINANZIAMENTO 1999) and CNR (grant no. 99.02336.ST74)
References Association of Official Analytical Chemists, 1990. Official Methods of Analysis, 15th Edition. Association of Official Analytical Chemists, Washington, DC. Associazione Scientifica Produzione Animale, 1989. Methodology relative to slaughtering and evaluation of carcases of livestock animals. Agric. Ric. 11, 39–45. Babiker, S.A., El Khider, I.A., Shafie, S.A., 1990. Chemical composition and quality attributes of goat meat and lamb. Meat Sci. 28, 273–277.
Single
0.84 0.41 0.26 0.29 1.57
46.64 2.41 13.09 13.37 79.68
Twin
0.74 0.36 0.23 0.25 1.38
47.33 0.96 1.46 0.46 13.06 0.30 13.23 0.33 83.32 1.80
Banskalieva, V., Sahlu, T., Goetsch, A.L., 2000. Fatty acid composition of goat muscles and fat depots: a review. Small Rumin. Res. 37, 255–268. Barbieri, V., Minieri, L., Rendina, N., 1973. Ricerche preliminari sulla resa alla macellazione di capretti differentemente alimentati e macellati a diverse eta` (Preliminary studies on meat production of kids feeding with different diets and slaughtered at different age). In: Proceedings of the XXVII Annual Meeting of Veterinary Science. Lodi, Italy, pp. 490–493. Borghese, A., Terzano, G.M., Bartocci, S., 1990. Kid production in intensive rearing. 6. Carcass and meat characteristics in Saanen and Alpine kids at 35 and 50 days of age. Zoot. Nutr. Anim. 16, 167–178. Congiu, F., 1987. La produzione del capretto da latte in allattamento artificiale. Prove di macellazione a 35 giorni d’eta` (Production of Capretto kid fed with replaced milk. Trials of slaughtering at 35 days of age). Agric. Ric. 9 (80), 65–70. Dhanda, J.S., Taylor, D.G., Murray, P.J., McCosker, J.E., 1999. The influence of goat genotype on the production of Capretto and Chevon carcasses. 2. Meat quality. Meat Sci. 52, 363–367. Giaccone, P., Portolano, B., Bonanno, A., Leto, G., 1994. Milk production of Girgentana breed and variability under environmental factors. Tecn. Agric. 46, 3–18. Hadjipanayiotou, M., Koumas, A., Hadjigavriel, G., Antoniou, I., Photiou, A., Theodoridou, M., 1996. Feeding dairy ewes and goats and growing lambs and kids mixtures of protein supplements. Small Rumin. Res. 21, 203–211. Johnson, D.D., Eastridge, J.S., Neubauer, D.R., McGowan, C.H., 1995. Effect of sex class on nutrient content of meat from young goat. J. Anim. Sci. 73, 296–301. Leat, W.M.F., 1976. The control of fat absorption, deposition and mobilization in farm animals. In: Lister, D., Rhodes, D.N., Fouler, V.R., Fuller, M.F. (Eds.), Meat Animals. Plenum Press, New York, pp. 177–193. Matsuoka, A., Furokawa, N., Takahashi, T., 1997. Carcass traits and chemical composition of meat in male and female goats. J. Agric. Sci. 42 (2), 127–135. PopovRaljic, J., Krajinovic, M., KelemenMasic, D., Cvetkovic, T., Dzinic, N., Popov, S., Kunc, V., 1995. Chemical composition of kid meat of the domestic white goat. Acta Vet. Beograd. 45, 303–310. Ragni, M., Vicenti, A., Melodia, L., Caputi Janbrenghi, A., Facciolongo, A.M., Vonghia, G., 2001. o-3 Fatty acid supplementation in bottle feeding for rearing kids. 1. Effects
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on in vivo performances and on the characteristics of carcasses and meat. Zoot. Nutr. Anim. 27, 15–22. SAS, 1991. User’s Guide: Statistics, Version 8.1, 1991 Edition. SAS Institute Inc., Cary, NC. Terzano, G.M., Bartocci, S., Borghese, A., 1988. Kid production in intensive rearing. 4. Data in vita and slaughter in Saanen and Alpine kids at 35 and 50 days of age. Zoot. Nutr. Anim. 15, 495–501. Titi, H.H., Tabbaa, M.J., Amasheh, M.G., Barakeh, F., Daqamseh, B., 2000. Comparative performance of Awassi lambs and black
goat kids on different crude protein levels in Jordan. Small Rumin. Res. 37, 131–135. Todaro, M., Console, A., Giaccone, P., Genna, G., 2000. Preliminary investigation of Girgentana meat kid yielded: living and postmortem data. In Proceedings of the XIV SIPAOC Congress. Vietri sul Mare, Italy, pp. 233–236. Zygoyiannis, D., Kufidis, D., Katsaounis, N., Phillips, P., 1992. Fatty acid composition of carcass fat of indigenous (Capra prisca) suckled Greek kids and milk of their does. Small Rumin. Res. 8, 83–95.
The influence of age at slaughter and litter size on some quality traits of kid meat M. Todaroa,*, A. Corraob, C.M.A. Baronec, R. Schinellib, M. Occidented, P. Giacconea a
Department S.En.Fi.Mi.Zo.—Sezione of Animal Production, Universita` di Palermo, viale delle Scienze, 90128 Palermo, Italy b Istituto Zooprofilattico Sperimentale della Sicilia ‘‘A. Mirri’’, via Rocco Dicillo, 4-90129 Palermo, Italy c Department of Scienze Zootecniche e Ispezione degli Alimenti—Sezione T.M. Bettini—Universita` di Napoli Federico II, via Universita`, 100—80055 Portici, Napoli, Italy d Consorzio per la Sperimentazione, Divulgazione e Applicazione di Biotecniche Innovative (ConSDABI), 82020 Circello, BN, Italy Accepted 5 December 2001
Abstract To study variations in the carcass characteristics of Girgentana kids slaughtered at 25 or 35 days of age and litter size (single or twin), 27 male kids were slaughtered and body components, carcass joints, pelvic limb tissue composition, meat fatty acid composition and M. longissimus dorsi (LD) colour were evaluated. Girgentana kids slaughtered at 35 days had greater live weights (6.4 kg versus 5.0 kg; P 0:01), carcass weights (4.5 kg versus 3.6 kg; P 0:01), muscle contents (57.6% versus 54.9%; P 0:01) but similar dressing percentages (70.1% versus 70.6%) as compared to kids slaughtered at 25 days. Twin kids had a higher muscle percentage (57.3% versus 55.2%; P 0:05) and similar fat percentage (5.5% versus 6.0%) but a higher unsaturated/saturated fatty acid ratio (1.17 versus 1.01; P 0:05). Meat colour was not influenced by any factors considered. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Girgentana goat; Capretto kid; Meat quality
1. Introduction The Girgentana goat is originally from the Province of Agrigento in Sicily. Its striking appearance of characteristic long corkscrew horns and its good milk yield helped the breed spread. The numbers of Girgentana goats are presently decreasing (Giaccone et al., 1994). Perceptions of meat quality vary from country to country and among ethnic and age groups. In Italy *
Corresponding author. Tel.: þ39-91-485-181; fax: þ39-91-485-713. E-mail address: [email protected] (M. Todaro).
only ‘‘capretto’’ meat (obtained from suckling kids to produce a carcass weight of 6–10 kg with pink flesh) is highly appreciated by consumers, whereas, in other countries, such as India, the Chevon meat (obtained from older animals with a carcass weight of 16–22 kg) is particularly preferred. Studies concerning chemical composition and meat quality have suggested that kid meat is not inferior to lamb (Babiker et al., 1990). The iron and phosphorus concentrations in the meat, along with its high protein and low fat contents, confirm that it has a high nutritive quality (PopovRaljic et al., 1995). However, it is well known that several factors, such as genetic type (Dhanda et al., 1999), age (Borghese et al., 1990),
0921-4488/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 4 8 8 ( 0 2 ) 0 0 0 3 5 - 4
76
M. Todaro et al. / Small Ruminant Research 44 (2002) 75–80
sex (Johnson et al., 1995; Matsuoka et al., 1997) and nutritional conditions (Hadjipanayiotou et al., 1996; Titi et al., 2000) influence meat quality. In Sicily, the market tends to demand meat from a very young goat, often slaughtered at 25–30 days, however, these carcasses have a high bone percentage. The great demand for kid meat is concentrated in the Christmas and Easter holiday periods and only 77% of kid meat utilised is produced in Italy. Several studies (Barbieri et al., 1973; Congiu, 1987) showed that production of kid meat slaughtered at 35 days is more economically favourable than that obtained from kids slaughtered at 25 days, but information about meat quality differences is lacking. To this end, an experiment was conducted to study the carcass characteristics of Girgentana kids slaughtered at 25 or 35 days.
2. Materials and methods The 27 male Girgentana kids were raised in the Sicilian interior, on maternal milk and housed indoors in group boxes for 25 or 35 days. After a 12 h fasting, all kids were slaughtered following traditional procedures, and the weight of the warm carcass, dress-off items and gastrointestinal content were recorded. After the carcasses were chilled at 4 8C for 24 h, the right halves of the carcasses were divided into cuts according to the procedure standardised by ASPA (1989). The pelvic limb of each carcass was dissected into muscle, fat, bone and ‘‘other tissue’’. After pelvic limb dissection, the meat was immediately homogenised and lyophilised. Dry matter at 105 8C, fat extracted with petroleum ether in Soxhlet apparatus, ash at 525 8C and protein by the Kjeldhal procedure were determined (AOAC, 1990) in the lyophilised samples. Lipids were determined after extraction, in duplicate, of lyophilised meat samples that were treated with n-hexane at 60 8C for 8–10 h. Methyl esters of the fatty acid component of the neutral triglycerides were prepared according to the transesterification method in a vial at ambient temperature for 30 min by means of m-trifluoromethyl-phenyl-trimethylamonium hydroxide (Meth-Prep II, Alltech) (0.2 N) in methanol. The methyl esters were analysed using a Perkin-Elmer 8500 gas chromatograph equipped
with a flame ionisation detector and an Omegawax 320 fused silica capillary column (30 m 0:32 mm i:d: 0:25 mm film thickness). Following sample injection, the column temperature was kept initially for 4 min at 155 8C, then increased at a rate of 4 8C/ min to 250 8C and maintained at that level until all esters had been eluted. The injector temperature was 250 8C and detector temperature was 270 8C. The carrier gas was nitrogen (15 ml/min). Standards for the fatty acid methyl esters were obtained from Sigma–Aldrich (Sigma, St. Louis, USA). Fatty acids were expressed in both normalised (molar proportion) and gravimetric (milligrams per gram of fresh tissue) formats. The softness index was estimated by dividing the sum of palmitoleic (C16:1) and oleic (C18:1) by the sum of palmitic (C16:0) and stearic (C18:0) content (Leat, 1976). At 24 h after slaughter, samples of M. longissimus dorsi (LD) muscle, taken from the loin, were placed in polyethylene bags, frozen at 20 8C and kept for about 4 months. Then they were thawed for 24 h at 4 8C. The colour was determined using a U 3000 Hitachi spectrophotometer and the CIELAB method (ASPA, 1989), detecting lightness (L), red index (a) and yellow index (b) with the illuminant C, chroma [(a2 þ b2 )1/2, C ¼ 0 grey] and hue (arctg b/a, H ¼ 0 purple red) were also calculated. Data were statistically analysed using the GLM procedure of the SAS package, Version 8.1 (SAS, 1991). Analysis was performed according to the following linear model: Yijk ¼ m þ Ai þ Bj þ eijk where A and B are the effects of age at slaughter (25 or 35 days) and the litter size (single or twin), respectively; the interaction was not significant.
3. Results and discussion Growth performance (Table 1) showed a highly significant effect of age at slaughter; kids slaughtered at 35 days showing a higher slaughter weight than those slaughtered at 25 days (6.4 kg versus 5.0 kg; P 0:01). The kids slaughtered at 35 days of age had heavier live weights (at slaughter), empty body weight and the carcass weight than those slaughtered at 25
M. Todaro et al. / Small Ruminant Research 44 (2002) 75–80
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Table 1 Growth performance, slaughter and dissection data of male Girgentana kids at two different ages (LSM S:E:) Age at slaughtering (days)
Litter size
25 (n ¼ 13)
Single (n ¼ 17)
Slaughter data Slaughter weight (kg) Empty body weight (EBW) (kg) Carcass weight (kg) Dressing percentage (%) Hide (% of EBW) Head (% of EBW) Internal organsa (% of EBW) Limbs (% of EBW)
5.0 4.9 3.6 70.6 11.6 9.5 6.4 2.3
0.3 0.3 0.2 0.5 0.2 0.2 0.1 0.1
Dissection data Right side (RS) (kg) Kidney and Pelvic fat (% of RS) Loin (% of RS) Pelvic limb (% of RS) Shoulder (% of RS) Neck, steaks, brisket (% of RS)
1.3 2.0 5.8 30.4 23.5 37.0
35 (n ¼ 14)
A a A
6.4 6.1 4.5 70.1 11.5 8.7 6.2 2.0
0.3 0.3 0.2 0.5 0.2 0.2 0.1 0.1
0.1 A 0.3 A 0.2 A 0.3 0.3 0.5
1.6 3.18 6.4 29.9 22.9 37.8
A A A
Twin (n ¼ 10)
B b B
5.9 5.6 4.1 70.4 11.5 9.0 6.3 2.1
0.2 0.2 0.2 0.4 0.2 0.2 0.1 0.1
5.6 5.4 3.9 70.4 11.7 9.2 6.3 2.2
0.3 0.3 0.2 0.5 0.2 0.2 0.1 0.1
0.1 B 0.3 B 0.1 B 0.3 0.3 0.5
1.5 2.8 6.3 30.1 23.2 37.5
0.1 0.3 0.1 0.3 0.3 0.5
1.4 2.3 5.9 30.2 23.3 37.2
0.1 0.4 0.2 0.4 0.4 0.6
B B B
On the row (within each factor): different lower case letters are significant at P 0:05; different capital letters are significant at P 0:01; n: number of observations. a Lungs, trachea, heart, liver
Both age at slaughter and litter size influenced the muscle content (Table 2). It was 2.13% higher in the kids slaughtered at 35 days, whereas in twin kids muscle content was higher than single kids (57.3% versus 55.2%; P 0:05). No significant differences were found in meat chemical composition. The principal fatty acids of pelvic limb fat, in decreasing order of proportion in total fat were oleic,
days, but dressing percentages were similar. The slaughter and carcass weights were lower than in other breeds slaughtered at the same age (Terzano et al., 1988). Kids slaughtered at 25 days had significantly heavier heads, internal organs (lungs, trachea, heart, liver) and limbs (percentage of EBW) than kids slaughtered at 35 days. The loin, kidney and pelvic fat were significantly higher for 35 days kids.
Table 2 Tissue composition and meat chemical composition of the pelvic limb, according to age of slaughtering and litter size (LSM S:E:) Age at slaughtering (days) 25
Litter size 35
Single
Twin
Tissue composition (% of pelvic limb) Bone 30.0 Muscle 54.9 Fat 5.6 Other tissues 7.2
0.6 0.7 A 0.5 0.6
28.4 57.6 5.9 6.5
0.6 0.7 B 0.5 0.5
30.0 55.2 6.0 7.3
0.6 0.7 a 0.5 0.5
28.5 0.7 57.3 0.8 b 5.5 0.6 6.5 0.6
Chemical composition (% of DM) Dry matter (DM) Ether extract Protein Ash
0.1 0.3 0.4 0.1
22.8 6.8 89.6 5.3
0.1 0.3 0.4 0.1
22.9 7.2 89.4 5.3
0.1 0.3 0.4 0.1
22.8 6.6 90.0 5.3
22.9 6.9 89.8 5.4
0.1 0.4 0.5 0.1
On the row (within each factor): different lower case letters are significant at P 0:05; different capital letters are significant at P 0:01.
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M. Todaro et al. / Small Ruminant Research 44 (2002) 75–80
Table 3 Fatty acid composition of pelvic limb fat, according to age of slaughtering and litter size (g of fatty acid/100 g of meat fat; LSM S:E:) Fatty acid (g/100 g of fat)
Age at slaughtering (days) 25
Litter size 35
Single
Twin
C8 C10 C12 C14 C14:1 C16 C16:1 C17 C18 C18:1 C18:2 C18:3 C20:4
0.01 0.32 0.39 2.63 0.23 13.31 1.16 0.83 15.48 29.68 4.11 1.16 0.37
0.00 0.03 0.05 0.24 0.02 1.23 A 0.13 0.06 0.90 1.64 0.27 0.07 0.02
0.01 0.25 0.37 3.02 0.18 17.71 1.35 0.77 13.64 27.63 4.39 1.08 0.35
0.00 0.04 0.05 0.25 0.02 1.27 B 0.14 0.07 0.93 1.69 0.28 0.08 0.02
0.01 0.30 0.43 3.18 0.23 16.98 1.41 0.82 15.89 28.94 4.54 1.41 0.37
0.00 0.03 0.04 0.21 a 0.02 1.07 0.12 0.06 0.78 a 1.43 0.24 0.06 0.02
0.01 0.00 0.28 0.04 0.34 0.06 2.47 0.29 b 0.18 0.03 14.05 1.46 1.10 0.16 0.79 0.08 13.24 1.07 b 28.37 1.94 3.96 0.32 1.11 0.09 0.35 0.02
SFA UFA MUFA PUFA UFA/SFA Softness index
32.99 37.60 31.95 5.65 1.18 1.11
1.92 1.90 1.74 0.27 0.05 a 0.06 a
35.77 35.83 30.02 5.82 1.01 0.93
1.98 1.96 1.79 0.28 0.05 b 0.06 b
37.59 37.50 31.45 6.05 1.01 0.93
1.67 a 1.65 1.51 0.24 0.04 a 0.05 a
31.17 2.28 b 35.93 2.25 30.52 2.06 5.42 0.32 1.17 0.06 b 1.11 0.07 b
On the row (within each factor): different lower case letters are significant at P 0:05; different capital letters are significant at P 0:01. SFA: saturated fatty acids; UFA: unsaturated fatty acids; MUFA: mono-unsaturated fatty acids; PUFA: poly-unsaturated fatty acids.
palmitic, stearic, linoleic, miristic and linolenic acid (Table 3), which is in agreement with the literature (Banskalieva et al., 2000). The composition of pelvic limb fat tended to change with age; the palmitic acid (C16) increasing significantly (P 0:01) from 25 to 35 days (Table 3) in accordance with results reported by Zygoyiannis et al. (1992). The oleic acid (C18:1) tended to decrease, although not significantly, so that the kids slaughtered at 25 days showed lower saturated fatty acids (32.99% versus 35.77%) and higher unsaturated fatty acids (37.60% versus 35.83%), than kids slaughtered at 35 days. The unsaturated/saturated fatty acid ratio was significantly higher for kids slaughtered at 25 days (1.18 versus 1.01; P 0:05). The softness index changed with age, showing a decrease from 25 to 35 days (1.11 versus 0.93; P 0:05) in contrast with results reported by Zygoyiannis et al. (1992). Results of fatty acid composition demonstrated a better meat quality obtained from younger kids, in particular from the point of view of health aspects. Litter size (number of kids suckled) influenced some fatty acids; in particular, single kids showed higher miristic (C14) (3.18% versus 2.47%; P 0:05)
and stearic acid (C18) (15.89% versus 13.24%; P 0:05) than twin kids (Table 3). This could be explained by the higher milk availability for the single kids (Todaro et al., 2000), which resulted in significantly higher saturated fatty acids (37.59% versus 31.17%; P 0:05) and a lower unsaturated/saturated fatty acids ratio (1.01% versus 1.17%; P 0:05). The softness index was higher in twin kids than in single kids (1.11 versus 0.93%; P 0:05). The colour of meat is very important to evaluate the Capretto carcasses. In Italy, in fact, the consumer prefers pale or pink meat. In this study, LD colour characteristics (Table 4) were similar to those reported by Dhanda et al. (1999) and Borghese et al. (1990). Girgentana kids showed an a-value lower than other genotypes (Dhanda et al., 1999; Ragni et al., 2001), so that the colour of the LD was paler than that of other kids. Moreover, the Chroma and Hue values indicated that Girgentana kids had a pale and pink meat colour, which is most acceptable to consumers. Age at slaughter and litter size did not significantly influence the muscle colour. Only small differences were found between kids slaughtered at 25 and 35 days, in
M. Todaro et al. / Small Ruminant Research 44 (2002) 75–80
79
Table 4 Colorimetric parameters of LD muscle, according to age of slaughtering and litter size (LSM S:E:). Age at slaughtering (days) 25
L a b Chroma Hue
47.76 1.57 13.15 13.31 83.07
Litter size 35
0.85 0.41 0.27 0.29 1.58
46.21 2.30 13.00 13.29 79.93
particular, the kids slaughtered at 35 days of age had lower L*-value and higher a-value than kids slaughtered at 25 days, which show a darker muscle colour.
4. Conclusion This study confirmed that kid meat is of high quality and, probably, on the basis of fatty acid composition, is healthy. Slaughter and dissection data and pelvic limb tissue composition confirmed that production of kid meat slaughtered at 35 days is more favourable than that obtained from kids slaughtered at 25 days. No differences were found on pelvic limb chemical composition. The meat colour did not show significant differences between the two types of kid meat, so that, together with the higher performance, the age at slaughtering could be increased without detrimental effect on meat quality.
Acknowledgements MURST (COFINANZIAMENTO 1999) and CNR (grant no. 99.02336.ST74)
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