COBISS: 1.08 Agris category code: L01
INFLUENCE OF SEX AND AGE AT SLAUGHTER ON GROWTH PERFORMANCE AND CARCASS TRAITS OF BOER KIDS
Ana KAIC Angela CIVIDINI 2, Klemen POTOCNIK 2
ABSTRACT
The aim of the study was to evaluate growth performance and carcass traits of the Boer kids. A total of thirty-four kids were used. The animals were divided into two groups based on sex (17 male and 17 female) and slaughter age (85 ± 10.14 days (Group 1) and 139 ± 17.55 days (Group 2)). In comparison to female kids, male kids had significantly higher average birth weight (3.3 kg : 3.7 kg) and significantly higher average daily gain (163 g : 203 g). Due to greater birth weight and average daily gain, male kids reached higher slaughter weight than female kids. Although mean values of dressing percentage between sexes were not significant (P > 0.05), females (47.1%) had slightly higher values than male kids (45.2%). The increased slaughter weight accompanied the feeding period from 83 to 139 days and, although not significant (P > 0.05), showed slight increase in dressing percentage between groups. Age had positive and significant (P < 0.001) influence on deposition of subcutaneous fatness. Male kids had more developed carcasses than females. Carcass length, hind leg width and shoulder width differed significantly and increased with slaughter age. Sex did not significantly affected proportions of liver, lungs, head and skin. Female kids had higher proportion of hearth (P < 0.05) and spleen (P < 0.001). Proportions of heart, spleen and skin at two different ages at slaughter were not significant.
Key words: goats / breeds / Boer breed / kids / slaughter age / sex / carcass traits / growth
1 INTRODUCTION
The Boer goat is a famous meat purpose breed well known for its rapid growth, excellent meat quality and high fertility (Greyling, 2000; Malan, 2000). The breed originates from South Africa. First animals were imported in Slovenia in 1997 and since then the breed has spread rapidly throughout whole Slovenia. Today, it represents the most numerous Slovenian goat population with a total of 3300 goats (Kompan et al., 2011). The breed is included into breeding programme whose aim is to keep the Boer goat in a meat type and to improve fattening and carcass traits and meat quality (Cividini et al., 2010). Today, when consumer demands are in search of low-fat, low-calorie, healthy and a new meat sources, goat meat has been gaining popularity (Korlie et al., 2000; Carlucci et al., 1998; Potchoiba et al., 1990). The
market of goat meat varies according to the demands of the societies. Meat of the kids slaughtered at very early age (30-65 days old and 6-11 kg live weight; Arias and Alonso, 2002) is favoured in the Mediterranean countries where is considered as a delicacy while meat from mature goats is more accepted in African and South Asian countries (Naude and Hofmeyr, 1981). However, according to Sormunen-Cristian and Kangasmaki (2000) the best goat meat is nearly fatless, light in colour and produced by 3-6 month old kids. A few researches which have studied carcass value of goat kids slaughtered at different body weights/age at slaughter have yielded varying results (Pi-eniak-Lendzion et al., 2010). Therefore, the objective of this study was to evaluate growth performance and carcass traits of male and female Boer kids slaughtered at two different ages.
1	Univ. of Zagreb, Fac. of Agriculture, Dept. of Animal Science and Technology, Svetošimunska c.25, 10 000 Zagreb, Croatia
2	Univ. of Ljubljana, Biotechnical Fac., Dept. of Animal Science, Groblje 3, 1230 Domžale, Slovenia
2 MATERIALS AND METHODS
2.1 ANIMALS
Thirty-four kids (17 male and 17 female) of the Boer breed were used in the study. The kids were chosen from three controlled farms where they were reared with their does and under similar feeding conditions. Apart from doe's milk, the kids had access to commercial concentrate (18% crude protein, 2.2% crude fat, 7.9% crude fibre, 7.8% ash) and hay ad libitum. Water and salt blocks were also available ad libitum. The animals were divided into two Groups according to sex (male and female) and average slaughter age (85 ± 10.14 days and 139 ± 17.55 days). Minimum slaughter age in Group 1 was 64 days and maximum 103 days, while for Group 2 minimum was 115 days and maximum 170 days. The Group 1 comprised of 9 male and 8 female kids and the Group 2 of 8 male and 9 female kids.
(HCW) was defined as a weight of whole carcass with kidney and knob channel fat after bleeding and removing skin, carpal and tarsal joints, head, tail, abdominal and thoracic cavity organs. Dressing percentage (DP) was defined as a ratio of hot carcass weight (HCW) to slaughter weight (SLW). Carcass conformation (1 = low... up to 15 = great) and fatness classes (1 = low... up to 15 = very high) were subjectively scored according to the Slovenian regulation for grading and classifying carcasses of sheep and lambs (Pravilnik ..., 2001), which is in agreement with the European regulations (European Union, 1992, 1994). Carcasses were kept at room temperature for 2 h, and then chilled at 4 °C for 24 h in conventional chiller. After chilling carcass length (CL), hind leg width (HLW) and shoulder width (SW) were measured. CL was measured from anterior edge of the symphysis pubis to the anterior edge of the first rib; HLW and SW were measured at the greatest width of hind leg, i.e. shoulder.
2.2 SLAUGHTERING AND CARCASS CHARACTERISTICS
The kids were weighed on the slaughter day, before transportation to the experimental abattoir at Zootechnical Department of Biotechnical Faculty in Domžale. After fasting for 12 h with free access to water kids were slaughtered and carcasses processed according to standards (Colomer-Rocher et al., 1987). Removed skin, head, liver, lungs, hearth and spleen from carcasses and hot carcass weight (HCW) were determined. Hot carcass weight
2.3 STATISTICAL ANALYSIS
Growth performance and carcass traits were analyzed using MIXED procedures of SAS/STAT software package (SAS Institute, 2008). The analysis was performed according to the following linear model: y..k = p + S. +G. + fk + e..k, where: y..k = dependent variable; p = overall mean; S. = fixed effect of sex (i = male, female); G. = fixed effect of group (j = 1, 2); fk = random effect of farm (k = 1, 2, 3); e..k = residual error. Included random effect of farm was analysed and there were no significant differences found for the parameters evalu-
Table 1: Least-squares means (± SE) of growth performance and carcass traits of Boer kids
Trait	Male (n = 17)	Female (n = 17)	SE	Sig.	Group1 (n = 17)	Group2 (n = 17)	SE	Sig.
BW, kg	3.76	3.31	0.211	**	-	-	-	-
ADG, g	203.90	163.13	14.309	***	181.83	185.20	14.298	ns
SLW, kg	25.50	22.41	0.814	**	18.86	29.04	0.813	***
HCW, kg	12.04	10.96	0.658	**	9.18	13.82	0.657	***
DP, %	45.29	47.19	1.168	ns	45.76	46.72	1.166	ns
CF	8.51	8.24	0.275	ns	8.30	8.46	0.275	ns
IF	8.00	8.29	0.415	ns	7.61	8.68	0.419	ns
SF	7.39	6.89	0.266	ns	6.09	8.18	0.266	***
CL, cm	56.54	54.31	0.835	**	52.17	58.68	0.833	***
HLW, cm	15.38	13.93	0.595	**	13.76	15.55	0.594	***
SW, cm	17.08	15.63	0.767	**	15.11	17.60	0.767	***
Sig.: level of significance, ns: not significant, *P < 0.05, **P < 0.01, ***P < 0.001; BW: birth weight, ADG: average daily gain; SLW: slaughter weight; HCW: hot carcass weight; DP: dressing percentage; CF: carcass conformation; IF: internal fatness; SF: subcutaneous fatness; CL: carcass length; HLW: hind leg width; SW: shoulder width
ated in the present study. Therefore, only the fixed sex and group effects are presented and discussed. Least squares means of growth performance and carcass traits were computed and tested for differences using student's t-test. Differences detected at the 0.05 level or less were considered statistically significant.
3 RESULTS AND DISCUSSION
Growth performance and carcass traits of male and female Boer kids slaughtered at two different ages are presented in Table 1. The male kids had significantly higher (P < 0.01) average birth weight than females for 0.4 kg. Higher birth weight of male kids and significant effect of sex has also been reported by Koratkar et al. (1998) of Osmanabadi kids and Karna et al. (2001) of Cheghu kids. This could be explained with the fact that the male foetus grows faster during prenatal development (Soundarara-jan and Sivakumar, 2011). In the present study male kids had significantly higher (P < 0.001) average daily gain than female kids (203 g : 163 g). Significant influence of sex on the average daily gain was also reported by ^agra§ et al. (1999) of Saanen kids, Browning et al. (2004) of Boer and Kiko kids, and Ugur et al. (2004) of Turkish Saanen kids. Although older animals (Group 2) had slightly higher average daily gain than the younger ones (Group 1), these differences were not significant. Due to greater birth weight and average daily gain male kids reached higher slaughter weight than female kids (Table 1). Mioc et al. (2011) also reported that kids with higher birth weight had significantly higher average daily gain, what is in agreement with our results. Due to the higher slaughter weights male kids had also significantly (P < 0.01) higher hot carcass weights in comparison to female kids. As we expected, an average values for slaughter weight of kids in Group 1 and Group 2 were significantly different (P < 0.001). Consequently these differences influenced on the average values for hot carcass weights (Table 1). Literature reports indicated that dressing per-
centage in goats varies between 38 and 56% and it dependents on breed, sex, age, weight and conformation (Anjaneyulu and Joshi, 1995; El Hag and El Shargi, 1996; Dhanda et al., 1999a; Getahun, 2001). According to the above mentioned an average values for dressing percentage in our study were within range for goats. Although mean values of dressing percentage between sexes were not significant, female kids (47.1%) had slightly higher values than male kids (45.2%) which could be explained by their tendency to have a higher fat deposition in the carcasses. The increased slaughter weight accompanied the feeding period from 83 to 139 days and, although not significant, showed slight increase in dressing percentage between groups. These results are in agreement with results of Mayi and Alkass (2010) of Meriz and Black goat kids who pointed out that dressing percentage of goat increased with body weight and age. Differences in conformation, internal fatness and subcutaneous fatness between male and female kids were not significant. These results are in agreement with Peña et al. (1994) who found a significant effect of slaughter weight on fatness but not of sex. Contrary to these results, Bonvillani et al. (2010a) found higher mean scores for subcutaneous and internal fatness in female kids. Although older animals had slightly higher values for conformation and internal fatness they were not significantly different (Table 1). As expected, goat carcasses had a thin subcutaneous fat cover, which increased significantly (P < 0.001) with the progress of age. These results are in agreement with Bonvillani et al. (2010b) of Criollo Cordobes and Anglonu-bian kids who reported that conformation, internal and subcutaneous fatness increased with slaughter weight and age. Compared fatness (internal fatness vs. subcutaneous fatness) degree it could be concluded that with increase in age and slaughter weight kids in our research tends to store a slightly higher portion of their fat internally, rather than in subcutaneous sites. These results are in agreement with ones reported by Gibb et al. (1993) of British Saanen and Anglo-Nubian kids and Boer x British Saanen crossbreeds, and Dhanda et al. (1999b) of Boer x
Table 2: Least-squares	means (± SE) of.	non-carcass	components (% on empty body			weight) of Boer	kids		
	Male	Female				Group1	Group2		
Trait	(n = 17)	(n = 17)	SE		Sig.	(n = 17)	(n = 17)	SE	Sig.
Liver	4.02	4.28	0.123		ns	4.40	3.89	0.123	**
Lungs	2.74	2.92	0.146		ns	3.06	2.61	0.145	**
Hearth	0.89	0.97	0.029		*	0.95	0.92	0.029	ns
Spleen	0.36	0.48	0.028		***	0.43	0.41	0.028	ns
Head	13.46	12.13	0.527		ns	13.78	11.81	0.537	*
Skin	15.12	16.04	0.333		ns	15.37	15.78	0.334	ns
Sig.: level of significance, ns: not significant,*P < 0.05, **P < 0.01, ***P < 0.001
Angora, Boer x Saanen, Feral x Feral, Saanen x Angora and Saanen x Feral crossbreed kids. Male kids had more developed carcasses than females (Table 1). The carcasses derived from male kids were longer and had higher hind leg and shoulder width than those derived from female kids. Contrary to these results, Bonvillani et al. (2010a) reported no differences in carcass measurements between male and female Criollo Cordobés kids. Peña et al.
(2007),	although at lower slaughter age, also did not find significant differences between male and female Florida goat kids. Carcass length, hind leg width and shoulder width increased with progression of slaughter age (Table 1) which is consistent with reports of Zimerman et al.
(2008).
Proportions of non carcass components of male and female Boer kids slaughtered at two different ages are presented in Table 2. Sex did not significantly affected proportions of liver, lungs, head and skin. Female kids had higher proportion of hearth (P < 0.05) and spleen (P < 0.001). A significant decrease in the proportions of liver, lungs and head at higher slaughter age was found. These results are partially in agreement with the ones reported by Marichal et al. (2003) and Peña et al. (2007) where a significant decrease in the proportions of non-carcass components and internal organs with increase of age and weight at slaughter was found. In the present study proportions of heart, spleen and skin at different age at slaughter were not significant.
4 CONCLUSIONS
The birth weight, average daily gain, slaughter weight, hot carcass weight and carcass measurements were higher in male kids indicating that males grow faster and had more developed carcasses than females. As expected, subcutaneous fatness, slaughter weight and consequently hot carcass weight increased significantly with the progress of age. Considering the above mentioned and the fact that dressing percentage was not influenced by sex and age it could be concluded that the Boer kids could be better used also at higher slaughter ages. The findings of this study also suggest that it is necessary to conduct more detailed studies and investigate influence of longer fattening time on meat quality traits, sensory evaluation of goat meat and their acceptance by consumers.
5 REFERENCES
Anjaneyulu A.S.R., Joshi H.B. 1995. Carcass characteristics and composition of goat meat in Indian breeds - an overview.
In: National Symposium on Production and Marketing of Goat Meat, CIRG and ISSGPU, India Arias M., Alonso A. 2002. Estudio sobre sistemas caprinos del norte de la provincia de Córdoba, Argentina (study in goat production systems in the north of Córdoba province, Argentine). Archivos de Zootecnia, 51: 341-349 Bonvillani A., Peña F., de Gea G., Gómez G., Petryna A., Perea J. 2010a. Carcass characteristics of Criollo Cordobés kid goats under an extensive management system: Effects of gender and live weight at slaughter. Meat Science, 86: 651-659 Bonvillani A., Peña F., Domenech V., Polvillo O., García P.T., Casal J.J. 2010b. Meat quality of Criollo Cordobes goat kids produced under extensive feeding conditions. Effects of sex and age/weight at slaughter. Spanish Journal of Agricultural Research, 8, 1: 116-125 Browning Jr. R., Kebe S.H., Byars M. 2004. Preliminary assessment of Boer and Kiko does as maternal lines for kid performance under humid, subtropical conditions. South African Journal of Animal Science, 34, Suppl. 1 ^agra§ 1., Óz^elik M., Ugur F., Karabayir A. 1999. Farkli iki sürede sütten kesilen saanen oglaklarinin büyüme ózel-likleri. Uluslararasi Hayvancilik'99 Kongresi, Izmir: 789792
Carlucci A., Girolami A., Napolitano F., Monteleone E. 1998. Sensory evaluation of young goat meat. Meat Science, 50: 131-136
Cividini A., Birtič D., Bojkovski D., Čepon M., Drašler D., Gor-janc G., Kastelic M., Klopčič M., Kompan D., Komprej A., Krsnik J., Potočnik K., Simčič M., Zajc P., Žan Lotrič M. 2010. Rejski program za bursko pasmo koz. Domžale, Biotehniška fakulteta, Oddelek za zootehniko, Zveza društev rejcev drobnice Slovenije Colomer-Rocher F., Morand-Fehr P., Kirton A.H. 1987. Standard methods and procedures for goat carcass evaluation, jointing and tissue separation. Livestock Production Science, 17: 149-159 Dhanda J.S., Taylor D.G., McCosker J.E., Murray P.J. 1999a. The influence of goat genotype on the production of Capretto and Chevon carcasses. 3. Dissected carcass composition. Meat Science, 52: 369-374 Dhanda J.S., Taylor D.G., Murray P. J., McCosker J.E. 1999b. The influence of goat genotype on the production of Capretto and Chevon carcasses. 1. Growth and carcass characteristics. Meat Science, 52: 355-361 El Hag M.G., El Shargi K.M. 1996. Feedlot performance and carcass characteristics of local (Dhofari) and exotic (Cashmere) goats fed on a high-fibre by-products diet supplemented with fish sardine. Asian-Australasian Journal of Animal Science, 9: 398-396 European Union. 1992. Council Regulation (EEC) No 2137/92 of 23 July 1992 concerning the Community scale for the classification of carcasses of ovine animals and determining the Community standard quality of fresh or chilled sheep carcasses and extending Regulation (EEC) No 338/91. Official Journal L 214, 30/07/1992, p. 1-5 European Union. 1994. Council Regulation (EEC) No 1278/94 of 30 May 1994 modifying Council Regulation No 2137/92, determining the Community scale for the classification of ovine carcasses. Official Journal L 140, 03/06/1994, p. 5
Getahun L. 2001. Growth pattern and carcass characteristics of Somali and Mid-rift valley goats. MSc thesis. Alemaya Univesity, Ethiopia Gibb M.J., Cook J.E., Treacher T.T. 1993. Performance of British Saanen, Boer x British Saanen and Anglo-Nubian castrated male kids from 8 weeks to slaughter at 28, 33 or 38 kg live weight. Animal Production, 57: 263-271 Greyling J.P.C. 2000. Reproduction traits in the Boer goat doe.
Small Ruminant Research, 36: 171-177 Karna D.K., Koul G.L., Bisht G.S. 2001. Birth weight, morphometry and relative gain in body weight in Cheghu kids. Indian Journal of Animal Sciences, 71: 180-182 Kompan D., Šalehar A., Bojkovski D., Žan Lotrič M., Holcman A.,Kovač M., Dovč P., Malovrh Š., Čepon M., Potočnik K., Cividini A., Simčič M., Gorjanc G., Razpet A., Terčič D. 2011. Program varstva biotske raznovrstnosti v slovenski živinoreji - Poročilo za leto 2010. Domžale, Biotehniška fakulteta, Oddelek za zootehniko Koratkar D.P., Bhoite U.Y. and Deshmukh A.K. 1998. Factors affecting birth weight in Osmanabadi kids. Indian Journal of Small Ruminants, 4: 31-33 Korlie M.S., Banskalieva V., Sahlu T., Goetsch A.L. 2000. Fatty acid composition of goat muscles and fat depots: a review. Small Ruminant Research, 37: 255-268 Malan S.W. 2000. The improved Boer goat. Small Ruminant Research, 36: 165-170 Marichal A., Castro N., Capote J., Zamorano M.J., Arguello A. 2003. Effects of live weight at slaughter (6, 10 and 25 kg) on kid carcass and meat quality. Livestock Production Science, 83: 247-256
Mayi E.J.T., Alkass J.E. 2010. Effect of fattening period on growth rate and carcass characteristics of Meriz and Black goats. In: 3rd International Scientific Conference on Small Ruminant Development, Hurghada, Egypt, 12-15 April,
2010.	Egyptian Journal of Sheep & Goat, 5, 1: 221-232 Mioč B., Sušic V., Antunovic Z., Prpic Z., Vnučec I., Kasap A.
2011.	Study on birth weight and pre-weaning growth of Croatian multicolored goat kids. Veterinarski arhiv, 81, 3: 339-347
Naude R.T, Hofmeyr H.S. 1981. Meat production. In: Goat production. Gall C. (ed.)., London, Academic Press: 285-307 Peña F., Gutiérrez M.J., Herrera M., Rodero E. 1994. Clasificación de canales de cabritos de raza Florida Sevillana. Archivos de Zootecnia, 43: 43-45 Peña F., Perea J., García A., Acero R. 2007. Effects of weight at slaughter and sex on the carcass characteristics of Florida suckling kids. Meat Science, 75: 543-550 Pieniak-Lendzion K., Niedziólka R., Horoszewicz E., Lukasiewicz M. 2010. Quality traits of meat from goat kids fed a diet with 10% flaxseeds. Annals of Animal Science, 10, 1: 75-82
Potchoiba M.J., Lu C.D., Pinkerton R., Sahlu T. 1990. Effects of all-milk diet on weight gain, organ development, carcass characteristics and tissue composition, including fatty acids and cholesterol contents, of growing male goats. Small Ruminant Research, 3: 583-592 Pravilnik o ocenjevanju in razvrščanju trupov ovc jagnjet in
sesnih jagnjet na klavni liniji. Ur.l. RS 28/2001 SAS Institute. 2008. The SAS System. Version 8. Cary, SAS Institute
Sormunen-Cristian R., Kangasmaki T. 2000. Performance of Finnish Landrace goat kids and lambs raised under stallfeeding conditions in Finland. Small Ruminant Research, 38, 7: 109-114
Soundararajan C., Sivakumar T. 2011. Factors affecting birth weight of Kanni kids and sex ratio of Boer x Kanni crossbred goats. Tamilnadu Journal of Veterinary & Animal Sciences, 7, 3: 144-149 Ugur F., Savas T., Dosay M., Karabayir A., Atasogly C. 2004. Growth and behavioural traits of Turkish Saanen kids weaned at 45 and 60 days. Small Ruminant Research, 52, 1-2: 179-184
Zimerman M., Domingo E., Lanari M.R. 2008. Carcass characteristics of Neuquén Criollo kids in Patagonia region, Argentina. Meat Science, 79: 453-457