The Effect of Growth Intensity and Sex: 2- On the Chemical Composition of Breast and Thigh Meat

Chicks were fattened in pens on deep litter with a stocking density 15.6 chicks/m2, with automatic chained feeders and round automatic waterers.

Lighting program was 24 hours from one to 14 days of age, then decreased to reach 16 hours to the end of the experiment.

At the end of the experiment, chicks were weighed individually, tagged on wings by metal numbers and fasted for 12 hours before slaughtering.

Chemical composition of breast and thigh meat:

The chemical analysis of the thigh and breast meat was as follows:

The breast muscle (m.pectoralis and m.supracoracoideus) and the thigh muscle (m.ilio tibialis posterior) without skin were ground and analyzed by A.O.A.C method to determine the following compounds:

Evaluation of the results was done by using the t-test, analysis of variance, regression analysis (linear and parabolic functions) according to Snedecor and Cochran.

The following table shows that the differences in breast muscles between males and females broiler chicks ,and the differences in the thigh mat without skin between males and females were significantly (p<0.05-p<0.01)affected by sex,including the dry matter, nitrogen and ash conent.The ether extract in both sexes was practically the same. 

Table1: Effect of sex on the chemical composition of breast and thigh meat 1) at 49 days of age

 

The breast meat of female broilers was higher by 1.29% in dry matter, 1.13% in protein (N><6.25) and 0.15% in ash than the thigh meat of males.

From the point of view of the chemical composition, the nutritive value of the meat of females was significantly better than that of the meat of males. These differences in the chemical percentages were due to the fact that female broilers at 49 days of age already had a higher degree of slaughter ripeness with a lower moisture and higher dry matter, nitrogen, ether extract and ash content in the meat, while male broilers were still in intensive growth and because of that the moisture content in the meat was higher. Similar observations were made by Mandak (1985), Pandy (1985) and others. Reddy et al (1986) and others on the contrary, found that female broilers had a significantly higher ether extract percentage than males.

Table 2- Differences in chemical composition between breast and thigh meat within the same sex at 49 days of age

Table 2 shows more dry matter and ether extract, less nitrogen and ash in thigh meat of chicks of both sexes. With the exception of dry matter in females, all the other constituents were significantly (p<0.01) different. Similar observations were made by Trindade et al (1980) and Uhrin(1985) who found highly significant differences in the chemical composition of thigh and breast meat due to the effect of sex. In males the thigh meat, protein content was lower by 4.4% .the ether extract was higher by 5.8% than in breast meat. The corresponding values in females were 4.8, and 5.6% for protein and ether extract, respectively.

From the dietetic point of view, the breast meat is better, while the thigh meat is preferred by some consumers for its higher juiciness related to the higher ether extract content. Similar observations were made by Pandy et al (1985), Reddy et al (1986) ,Uhrin(1985) and others.

The dependence of percentages of dry matter, nitrogen, ether extract and ash (Y) on the live weight of chicks in grams (X) was expressed by regression equations as in tab-3

Table 3: The dependence of chemical composition of meat on the live weight of chicks in grams-regression equations 

With the exception of the ether extract of the thigh meat of males, the regression coefficients in the linear regression equations were not significant.

The parabolic equations were not able to express the dependence better than linear equations with exception of the ether extract content in the thigh meat of males.

With exception of the ether extract in the thigh meat of the males, it may be said that the chemical composition of the breast and thigh meat had no significant relationship with the live weight of the chicks at the same age (49 days).

The ether extract in the thigh meat of males at first decreased to the minimum at 1630 grams of weight and then increased.

Here we notice that no relationship was indicated between the live weight of the males (which varied between 1800 and 2300 grams) and of the females (960 t0 1500 grams) and with the chemical composition of the thigh and breast meat.

Similar observations were made by Reddy et al (1986) ,Seemann (1981) ,Touraille et al(1981) and others.

CONCLUSIONS 

In this experiment found that sex affected the chemical composition of breast and thigh muscles of both sexes. The breast and thigh muscles of females, from the point of view of the chemical composition and nutritively, were significantly better because the breast muscle had a higher content of dry matter (1.29%), protein (1.13%) and ash (0.19%), the thigh muscle had a higher content of dry matter, protein and ash 0.91, 0,75 and 0.15% respectively. From the chemical composition´s point of view, the nutritive value of the females meat was significantly better than that the male meat.

From the dietetic point of view the breast was better, while the thigh meat cut is preferred by some consumers for its better juiciness related to a higher content of ether extract.

In this experiment we followed the effect of sex and live weight of broiler chicks of both sexes at the same age on the chemical composition of the breast and thigh meat.

Chicks of the age 49 days of hybrid combination RX fasted 12 hours before slaughtering were divided according to their live weight into categories differing by 100 grams. The live weight of the females varied from 1000 t0 1300 grams, that of the males from 1500 to 2300 grams.

From each category, 10 chicks were selected for the analysis.

The live weight of the chicks was 1848.0+/-22.87 and 1385.8+/-22.03 grams for males and females, respectively.

No significant differences were reported in the percentage of dry matter ,protein and ash in the muscles in relation to the weight of the chicks before slaughtering.

The percentage of ether extract in the thigh meat of males (Y) increased significantly (p<0.01) with the increasing body weight(X) .The ether extract content in the breast and thigh meat of females appeared to have no relationship with the growth intensity.

The thigh meat had more dry matter and ether extract and less protein and ash than breast muscle, with exception of the dry matter in the females, all the above differences were highly significant (p<0.01).In the thigh meat of females the protein content was lower by 4.6% and the ether extract higher by 5.6%.

With males the thigh meat protein was lower by 4.2%, the ether extract was higher by 5.8% than that of the breast muscle.

Significantly more dry matter, protein and ash was observed in the thigh meat, breast muscle of females than in males.

The ether extract content was virtually the same in both sexes.

From the point of view of dietetic, breast meat is better, while thigh meat will be preferable by some consumers for its higher juiciness related to the higher content of ether extract.

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