DEPENDENCY BETWEEN SOME TRAITS DESCRIBING SLAUGHTER VALUE OF GOAT'S CARCASS

Gruszecki, T.
Szymanowska, A.
Lipecka, Cz.
Patkowski, K.
Junkuszew, A.
Department of Sheep and Goat Breeding
Agricultural University, Lublin, Poland

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ABSTRACT

The aim of our research was the estimation of dependency between some carcass traits and a slaughter value of goats. Thirty-five male kids of a white improved breed, slaughtered at 20 kg body weight, were the investigation material. Statistically significant and positive correlation between carcass content of meat, fat, and bone was found male kid in goats at the slaughter. Meat content in goat's carcass was highly and positively correlated with leg weight (r_xy = 0.989), shoulder weight (r_xy = 0.982) and meat weight in the leg (r_xy = 0.993). Fat content in goat carcasses was highly and positively correlated with breast weight (r_xy = 0.879), saddle (r_xy = 0.838), shank (r_xy = 0.820) and fat weight in the saddle (r_xy = 0.860). Bone content in goat carcasses was highly and positively correlated with both shank weight (r_xy = 0.945), and bone weight in the shank (r_xy = 0.949; r_xy = 0.932). Multiple correlation and determination coefficients indicate that meat, fat and bone contents in carcasses may be estimated on the ground of their content in the leg, shoulder and saddle.

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INTRODUCTION

The increasing interest in goat breeding in Poland results first of all from a milk demand, especially in industrialized regions of the country. There is no doubt that dairy performance becomes the primary direction for these animals. However, features characterizing the meat performance at selection also should be taken into account, due to the need for young male goats and some female goat utilization (Krupa-Zin, 1993).
Precise estimation of this value is possible by means of detailed dissection of carcasses along with meat quality testing. The method, although very accurate, cannot be applied in a wide breeding range because it is labor-consuming and lowers the commercial value of raw material under tests. Thus, it is necessary to elaborate the indirect methods using various interdependent features that would make possible the carcass estimation.
The purpose of this research was to find the interdependencies between some carcass traits and the slaughter value of goats.

MATERIAL AND METHODS

The research results are from experiments carried out in the Bezek Experimental Station belonging to the Agricultural University in Lublin in 1996-1997.
Thirty-five male goats of a white improved breed were the investigation material. All experimental animals were kept with their mothers until about two months of age. Kids were fed with meadow hay - besides the milk - as well as with a cereal mixture. After weaning, young male goats were also supplied with grass and alfalfa green forage.
The animal's body weight was monitored from birth until 20 kg, when the goats were slaughtered. Obtained carcasses were cooled within 24 hours to 4°C and then linear measurements were done. They were divided into general cuts according to IZ methodology elaborated for sheep (Nawara et al., 1963); all cuts - after their weight determination - were dissected into meat, fat and bones.
Results were statistically elaborated (Oktaba, 1996) calculating mean values and standard deviations for particular features. Moreover, the straight correlation coefficients (r_xy) among particular traits characterizing goat's slaughter value were calculated.
After the straight correlation coefficients analysis, multiple correlation (R) and determination coefficients (R²) were calculated for some features.
All results are presented in tables.

RESULTS AND DISCUSSION

Data characterizing the body weight of male goats from birth until slaughter are listed in Table 1. Mean value of this feature at birth amounted to 3.74 kg, and after one month it increased twofold. The described growth rate proves the suitable nutrition and good health of the investigated goats that achieved their slaughter body weight (20.19 kg) at about five months of age.

Table 1. Characteristics of meat kids growth

Dressing percentage estimated on cool carcass weight is one of the most important factors characterizing the slaughter value. At 43.79 percent (Table 2), the value obtained is close to the results of Krupa et al. (1990 and 1992) for young goats with higher slaughter weight, but it is significantly lower than that obtained by Piotrowski and Bidwell-Porbska (1994) in goats of 16kg body weight.
Mean skin weight (Table 2) measured directly after its removal was 1.15 kg, which was 5.69 percent in relation to the body weight at the slaughter. Legs and heads of investigated animals appeared, to be relatively light (about 10 percent of body weight), which was an indicator of small bones in the animals.
Table 2. Meat kids slaughter results

Data characterizing the size of the basic cuts in carcasses are presented in Table 3. It was found that the following cuts were of the highest percentage in carcass: leg (24.09 percent), breast (16.14 percent) and shoulder (15.68 percent); the cuts of lowest percentage: hind and fore-knuckles (5.98 percent and 5.14 percent, respectively).
The percentage of valuable cuts (leg, loin, best end of chump) in goat carcasses under study amounted to about 38 percent, and was consistent with the previous results of Szymanowska et al. (1996), who estimated the slaughter value of young goats of the white improved breed. Slight carcass fatiness was also found since the perirenal fat amount in relation to carcass weight was 0.91 percent.
Results of the detailed dissection (Table 4) showed that the percentage of particular tissues in investigated animal carcasses was as follows: meat - 63.75 percent, fat - 8.89 percent, bones - 27.36 percent. Similar results were obtained for valuable cuts. Data presented are consistent with those of Krupa et al. (1990) which were based on studies of older, pasture-fed goats.
The straight correlation coefficients between kid body weight from birth until the slaughter and carcass measurements, and particular tissue content in carcasses and valuable cuts are presented in Table 5.

Table 3. Percentage and weight of basic cuts in carcass

Specification	x (%)	s	x (%)	s
Scrag	7.73	0.94	0.34	0.12
Middle neck	9.77	1.32	0.43	0.12
Shoulder	15.68	0.92	0.69	0.21
Breast	16.14	1.26	0.71	0.22
Hind knuckle	5.91	0.35	0.26	0.06
Fore knuckle	5.00	0.30	0.22	0.06
Best end of chump	6.59	0.78	0.29	0.12
Leg	24.09	0.68	1.06	0.31
Loin	7.27	0.83	0.32	0.08
Kidney	0.91	0.15	0.04	-
Kidney fat	0.91	0.42	0.04	-
Valuable cuts	37.95	1.17	1.67	-
Others	60.23	1.21	2.65	-

Table 4. Tissue composition of carcass and valuable cuts

Specification	Percentage		Weight
	x	s	x	s
Carcass meat	63.75	2.25	2.77	0.86
fat	8.89	1.99	0.39	0.15
bones	27.36	2.11	1.17	0.29
Valuable cuts meat	67.86	3.12	1.14	0.35
fat	7.54	2.40	0.13	0.07
bones	24.6	2.42	0.41	0.10

Coefficient analysis proved that body weight at birth and at the age of one and two months was negatively correlated with the contents of all tissues, both in valuable cuts and the entire carcass. Values of the correlation coefficients calculated ranged from -0.741 to -0.645. The opposite situation was found analysing the interdependence between body weight at the slaughter and tissue content. In this case, correlation coefficients were positive, very high and statistically significant, and their values ranged from 0.832 to 0.956.
Studying the interdependencies between carcass measurements and tissue contents, it was found that - except in three cases - calculated correlation coefficients were statistically significant, positive and highest.
Table 6 presents the values of straight correlation coefficients between the weight of particular cuts and tissue components contents in carcasses and valuable cuts. Cut weight in all studied cases was highly positive and statistically significantly correlated (P < 0.01) with weights of particular tissues. Another situation was noted when analysing the interdependence between basic cut weight and the percentages of particular tissues in them. Regarding meat and fat tissue, coefficients were positive and their values did not exceed 0.496. Correlation coefficients between cut weight and the percentage of bones in it were always negative and statistically significant up to -0.575.
Interdependencies between tissue composition of particular cuts and meat, fat and bones contents in carcasses as well as in valuable cuts was presented in Table 7. The highest straight correlation coefficient value was found between meat weight in carcasses and valuable cuts and its weight in leg (r_xy = 0.993).
A relatively high correlation coefficient was obtained between fat weight in a carcass and its weight in loin (r_xy = 0.860) and leg (r_xy = 0.845).
Fat weight in valuable cuts was the highest correlated with its content in leg (r_xy = 0.952) and loin (r_xy = 0.906).
The bones weight in hind or fore knuckle can serve as a measure for bones weight in entire carcass. Interdependence between bones weight in mentioned cuts and in carcass was expressed with the following correlation coefficients: r_xy = 0.949 and r_xy = 0.923. Correlation between bones weight in leg and shoulder, and the weight of the tissue in carcass was slightly lower (r_xy = 0.925 and r_xy = 0.915, respectively).
In the next stage of investigations there were calculated the multiple correlation and determination coefficients between meat, fat, and bones percentage in carcass, and these tissues percentage in leg, loin and shoulder (Tab. 8).
The highest multiple correlation coefficient (R=0.844) and determination coefficient (R²=0.712) was obtained for bone percentage in the whole carcass. However, it should be emphasized that coefficients calculated for meat and fat percentage in carcass were slightly lower and amounted to: R = 0.725, 0.827; R² = 0.526, 0.684, respectively.
Results obtained point to the possibility of carcass tissue composition prediction only on a base of the content of particular tissues in three discussed cuts.

Table 5. Coefficient of correlation (r_xy) between body weight and carcass measurements and

tissue content in carcass and in valuable cuts

Specification	In carcass (kg)			In valuable cuts (kg)
	meat	fat	bones	meat	fat	bones
Body weight at birth	-0.686	-0.733	-0.667	-0.670	-0.683	-0.705
1st month	-0.664	-0.728	-0.645	-0.651	-0.669	-0.698
2nd month	-0.678	-0.723	-0.664	-0.671	-0.681	-0.741
at the slaughter	0.956	0.833	0.944	0.941	0.832	0.931
Carcass measure length	0.943	0.729	0.881	0.941	0.714	0.859
chest breadth	0.900	0.795	0.863	0.889	0.735	0.830
leg length index	0.817	0.679	0.838	0.800	0.723	0.877
leg depth	0.355*	-	0.290*	0.367*	-	-
leg length	0.965	0.753	0.939	0.959	0.735	0.918
leg circuit	0.921	0.720	0.849	0.919	0.701	0.819
loin fillet	0.906	0.734	0.852	0.901	0.759	0.860

P < 0.01; * - P < 0.05

Table 6. Coefficient of correlation (r_xy) between tissue composition of particular cuts

and that of carcass and valuable cuts

Weight	Content in carcass							Content in valuable cuts
	meat		fat		bones		meat			fat		bones
	kg	%	kg	%	kg	%	kg		%	kg	%	kg	%
Scrag	0.932	-	0.742	-	0.925	-	0.926		-	0.681	-	0.833	-0.446
Middle neck	0.880	-	0.651	-	0.930	-	0.870		-	0.619	-	0.851	-
Shoulder	0.982	0.396	0.777	-	0.908	-0.564	0.978		-	0.710	-	0.864	-0.463
Breast	0.940	-	0.879	0.319*	0.898	-0.575	0.914		-	0.868	0.484	0.888	-0.403
Hind knuckle	0.964	0.282*	0.800	-	0.952	-0.469	0.951		-	0.809	0.369*	0.931	-0.363*
Fore knuckle	0.968	0.287*	0.820	-	0.938	-0.504	0.961		-	0.779	0.344*	0.902	-0.408
Best end of chump	0.956	0.321*	0.700	-	0.946	-0.406	0.954		-	0.713	-	0.930	-0.303*
Loin	0.923	0.296*	0.838	-	0.876	-0.571	0.909		-	0.855	0.496	0.873	-0.411
Leg	0.989	0.354*	0.802	-	0.943	-0.534	0.984		-	0.789	0.335*	0.918	-0.429

P < 0.01; * - P < 0.05
Table 7. Coefficient of correlation ( r_xy ) between tissue composition of particular cuts and

that of carcass and valuable cuts

Specification	Content in carcass				Content in valuable cuts (kg)
	meat	fat	bones	meat		fat	bones
Scrag meat	0.987	0.758	0.929	0.973		0.725	0.875
fat	0.506	0.632	0.487	0.492		0.525	0.456
bones	0.661	0.489	0.749	0.658		0.408	0.586
Middle neck meat	0.938	0.646	0.909	0.932		0.630	0.847
fat	-	0.396	-	-		-	-
bones	0.561	0.393	0.759	0.543		0.394	0.663
Shoulder meat	0.977	0.756	0.900	0.973		0.694	0.865
fat	-	-	-	-		-	-
bones	0.960	0.691	0.915	0.961		0.665	0.870
Hind knuckle meat	0.949	0.792	0.930	0.933		0.814	0.901
fat	0.382	0.565	0.325	0.377*		0.503	0.379*
bones	0.942	0.729	0.949	0.935		0.734	0.926
Fore knuckle meat	0.968	0.726	0.929	0.963		0.693	0.886
fat	0.583	0.828	0.541	0.563		0.787	0.527
bones	0.942	0.793	0.923	0.932		0.749	0.902
Best end of chump meat	0.952	0.642	0.894	0.964		0.615	0.842
fat	0.617	0.815	0.630	0.578		0.899	0.649
bones	0.817	0.540	0.885	0.806		0.588	0.924
Loin meat	0.913	0.670	0.772	0.933		0.614	0.715
fat	0.578	0.860	0.586	0.531		0.906	0.640
bones	0.352	0.411	0.526	0.299*		0.561	0.609
Leg meat	0.993	0.771	0.932	0.993		0.734	0.895
fat	0.793	0.845	0.769	0.765		0.952	0.789
bones	0.917	0.757	0.925	0.906		0.765	0.926

P < 0.05; * - P < 0.01

Table 8. Multiple correlation ( R ) and determination ( R² ) coefficients between meat, fat and

bones contents in the three cuts and these tissues in whole carcass

Content in carcass		Content in leg, loin, shoulder
		meat	Fat	bones
Meat Fat Bones	R R2 R R2 R R2	0.7259 0.5269	0.8271 0.6841	0.8441 0.7124

P _ 0.01

CONCLUSIONS

1. A statistically significant and positive correlation between meat, fat and bones contents in carcasses and goat kids body weight at the slaughter was found.
2. Meat content in carcass was highly and positively correlated with leg weight (r_xy = 0.989), shoulder weight (r_xy = 0.982) and meat weight in leg (r_xy = 0.993).
3. Fat content in carcass was highly and positively correlated with breast weight (r_xy = 0.879), loin (r_xy = 0.838), fore knuckle (r_xy = 0.820) and fat weight in loin (r_xy = 0.860).
4. Bones content in carcass was highly and positively correlated with both knuckles weights (r_xy = about 0.945), bone weight in hind-knuckle (r_xy = 0.949) and in fore-knuckle (r_xy = 0.932).
5. Multiple correlation and determination coefficients calculated indicate that meat, fat and bones contents in the entire carcass may be estimated on a ground of these tissue contents in leg, shoulder and loin.

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