Some carcass traits and physicochemical composition of White Improved breed goat kids slaughtered at 90 and 180 days of age ( Short Communication )

The research aimed at analysing the slaughter value and physicochemical attributes of goat kids slaughtered at 90 and 180 days of age. After weaning at 60 days of age, a balanced mixture containing 18.2 % of protein and 5.63 MJ of net energy was applied as a feed. Some traits of live and slaughtered animal weight attributes were analysed. Moreover, tissue composition of the half carcass and meat physicochemical properties of meat were determined. The carcass of older male kid goats was by 5.08 kg (P≤0.05) heavier and the weight of primal cuts (P≤0.05) including high-priced cuts was by 0.87 kg higher than the young kids. Half carcass tissue composition of older and younger kids was similar: 60.1360.50 % of meat, 25.48-25.37 % of bones, and 14.39-14.13 % of fat. Significant differences (P≤0.05) in fat and bone contents were only found in the leg. Furthermore, physiochemical properties indicated that the meat of older animals was darker and had higher values of chemical parameters.


Introduction
Meat of young goats is a material of full value, which can be utilised in the production of healthy meat.It is characterised by a low intramuscular fat content and a high level of protein and mineral elements (KĘDZIOR et al. 1997, KESAVA RAO et al. 2003, PIENIAK-LENDZION et al. 2003, SEN et al. 2004, SIKORA and BORYS 2006, BRZOSTOWSKI et al. 2008).
Research on goat kids slaughtered at various body weights showed different results.They presented that the content of high-priced cuts and meat tissue in animals slaughtered at higher body weights was higher and the meat was characterised by more favourable physicochemical parameters (KASPRZYK and KRUPA 2000, MIOČ et al. 2001, TSHABALALA et al. 2003).
Intensive feeding increases the slaughter performance of goat kids, therefore it is profitable to fatten them more intensively to obtain heavier animals, cheap food is available and the demand for goat meat is high.The only exception to this is that the goat kids are destined to obtain the so-called (white meat).They are slaughtered at lower body weight and fed mainly on goat milk (KRUPA et al. 1995, KALINOWSKA et al. 1997, LUO et al. 2000, PIENIAK-LENDZION et al. 2005, STANISZ et al. 2005).Kids reared on this feeding system displayed higher growth rates (RINGDORFER 2001), better carcass conformation and fatness than smaller kids (DHANDA et al. 2003, PALA et al. 2005, PEÑA et al. 2007).
The research is aimed to analyse the slaughter value and physiochemical traits of castrated goat kids slaughtered at 90 and 180 days of age.

Material and methods
The experiment was carried out on White Improved breed goat kids, which were raised in tie-stall barns and fattened up to the age of 90 (n=10) and 180 (n=10) days.
After weaning at 60 days of age, a balanced mixture, containing 18.2 % of protein, 88.6 % of dry matter, 5.46 % of fibre and 5.63 MJ of net energy (NE), was applied as a feed.The feeding was supplemented by an addition of meadow hay.The animals were fed ad libitum, castrated and raised in tie-stall barns on deep litter.The slaughtering and analyses were performed in accordance with the methodology for small ruminants used by the Institute of Animal Husbandry (NAWARA et al. 1963).After 24 h cooling at the temperature of 4 °C the division into cuts was carried out.Next the cuts were dissected into meat, fat and bone tissues.
Meat samples of the broadest back (m.longissimus dorsi) were subjected to chemical analyses, including to the contents of dry matter (drier method, 105 °C), protein (Kjeldahl's method) and fat (Soxhelt's method).The muscle was also used to test water-holding capacity by the Grau-Hamm's method, the values of pH were measured after 4 min and 24 h of the slaughter (CP-315 integrated electrode pH-meter), and muscle fibre darkening was analysed (m.semimembranosus) with the Minolta ChromaMeter CR-300.
Statistical analyses of variance were conducted using ANOVA test, and significance of differences between means and groups (90 days and 180 days) were compared by Tuckey's test.
The results were verified statistically by t-test using STATISTICA 6.0 PL software (2002).

Results
The average body weight (Table 1) of the goat kids slaughtered at 180 days of age was significantly higher by 9.86 kg compared with the weight of younger goat kids.Moreover, the weight of cooled carcass obtained from older animals was significantly higher by 5.08 kg and amounted to 14.64 kg in the present study.Carcass weight losses were similar and ranged from 1.64 to 2.17 %.However, the percentage of high-priced cuts in the half carcass was similar in both examined groups and ranged from 36.53 to 36.58 %.It indicates that age did not influence significantly their content in the half carcasses.There were found statistically significant differences (P≤0.05) in the weights of the following primal cuts: chuck, neck, rib, loin, leg, fore shank and shin, in favour of older goat kids, which is an obvious phenomenon due to higher carcass weight (Table 2).Highpriced cut weights in older goat kids were larger by 0.87 kg.The weights of leg, rib and loin were larger by 0.58, 0.14 and 0.15 kg, respectively.The leg content in the half carcass was similar in both groups and it ranged from 24.35 to 24.39 %.Kid carcasses slaughtered at the age of 180 days of life contained significantly (P≤0.05)more kidney fat (3.28 vs. 2.64 %).Dissection results (Table 1) revealed that the fat tissue content in older goat kids was larger by 1.04 % and the bone tissue content was lower by 1.5 % lower.It is an indicator of fat accumulation in legs of older goat kids aged 180 days, which may indicate the slaughter period.No significant differences in the content of individual tissues were found in relation to the whole half carcass.Meat content slightly exceeded 60 % and it was similar in both examined groups.The analysis of tissue composition showed that the culinary meat content in the leg was over 69 %.
Physicochemical traits of meat are shown in Table 3.The contents of dry matter, protein, fat and mineral compounds in meat of goat kids slaughtered at 180 days of age were significantly larger by 1.55, 0.93, 0.69 and 0.04 %, respectively.The W/P (water-protein) index indicates meat maturity and it was significantly higher in the group of goat kids slaughtered at 90 days of age and amounted to 3.98.Among the analysed physical meat traits, significant differences were found only in the case of colour darkness.The values of L* reading for tissue indicate a lighter colour of meat obtained in younger goat kids and the differences between them were highly significant.As far as pH1 measurement is concerned, after 45 min pH1 was higher in the meat of older animals and amounted to 6.03, whereas after 24 h pH2 decreased to 5.66.This phenomenon is a symptom of glycolysis -the process which contributes to meat acidity.

Discussion
The average body weight of the kids slaughtered was similar to the results obtained in earlier studies by the authors (PIENIAK-LENDZION et al. 2005) and the research results, concerning different period of goat kid slaughter, by other researchers (SEN et al. 2004, STANISZ and GUT 2005, KOYUNCU et al. 2007).In the studies carried out on 5-month goat kids with the Boer breed genes, STANISZ and GUT (2005) obtained the content of highpriced cuts and leg amounting to 35.63 and 23.14 %, respectively.A higher percentage of leg and lion in the half carcass was found by SEN et al. (2004), the respective values were 28.19 % and 13.43 %.TSHABALALA et al. (2003) obtained congruent results in relation to the meat tissue content in half carcasses of the goat kids.They obtained larger values of meat tissue (76.19-78.06%) and bone tissue (20.16-22.74%) in legs of castrated kids in relation to the breed than in the presented study.On the other hand, LUO et al. (2000) recorded a lower content of meat tissue (57.1 %) and higher fat and bone fibre percentage (20.2and 20.6 %, respectively) in goat kids slaughtered at 50 weeks of age.Kid carcasses of Florida breed were characterized by different content of cuts according to the slaughtering weight (PEÑA et al. 2007).The slaughtering weight did not significantly affect the long leg content (30-33 %), back content (18-19 %) and neck content (8-10 %); however, it affected rib content (23-25 %).The carcasses contained 57-58 % of muscles, 20-25 % of bone, 5-6 % subcutaneous fat and 9-12 % of intramuscular fat.
The effect of castration of Turkish hair kids (weaning at 160-216 days) had no significant effect on the content of priminal cuts in the whole carcasses (57.29-57.42%), excluding the long leg and ribs.The bone (9.56 vs. 7.09 %) and muscle (52.05 vs. 56.50%) contents of carcasses differed significantly between intact males and castrated (KOYUNCU et al. 2007).The content of culinary meat in the leg was similar to the values obtained by KĘDZIOR et al. (1997) as well as earlier studies by PIENIAK-LENDZION et al. (2003).On the contrary, SEN et al. (2004) recorded 76.77 % of meat tissue and 6.93 % of fat tissue in the leg.
The results obtained in relation to dry matter and protein contents, were similar to the earlier studies on the Polish White Improved bread (23.53 and 20.21 %, respectively) (PIENIAK-LENDZION et al. 2005) and the research on the Alpine and Saan breeds (23.74 and 19.64 %;21.96 and 20.65 %, respectively) (MIOČ et al. 2001).The higher fat content in meat at the age of 180 days (1.99 %) was also reported by GRUSZECKI et al. (2006) in lambs of 35 kg of body weight.The value of the W/ B index calculated by KESAVA RAO et al. (2003) was within the limits of 3.10-3.87according to the protein content in the ration.The higher the protein content was the higher value of W/ B index obtained.Meat of French Alpine kids compared to meat of French Alpine × Boer crossbreed contained higher (P≤0.05)index W/P (4.18), and lower dry matter content (22.21 %) and crude protein content (19.44 %) (BRZOSTOWSKI et al. 2008).
In conclusion, the current study had confirmed that prolonged fattening of goat kids up to 180 days of age with the same balance mixture enabled the authors to obtain higher values of parameters for most analysed slaughtering traits.In spite of the fact that the weight of high-priced cuts was higher, their contents in the half carcass were similar in both analysed groups (36.53-36.58 %).Significantly higher percentage of fat and bone tissue were recorded in the group of older goat kids but the meat tissue content in the whole half carcass was alike.The adequate physicochemical composition of goat kid meat determined its dietary as well as culinary value.It should be stressed that the meat of goat kids slaughtered at 180 days of age contained more dry matter, protein, fat and mineral compounds and it was of a darker colour.

Table 1
Body weight goat kids, slaughter value and tissue composition in half-carcass Körpergewicht der Kitzen, Schlachtwert und Gewebezusammensetzung der Schlachthälften a,b P≤0.05, A,B P≤0.01, SE standard deviation

Table 2
The composition of cuts half-carcass Anteile der Teilstücke a,b P≤0.05, A,B P≤0.01, SE standard deviation a,b P≤0.05, A,B P≤0.01, SE standard deviation