M. Ristic
Federal Centre for Meat Research,
Institute for Meat Production and Market Research,
Kulmbach, Germany
In a study from 5 test series (n = 7.864) broiler were held under ecological conditions and compared with a control group. Thereby the fattening duration varied from 35 (control group) to 80 days. Following broiler genotypes were used: Ross 308 (control group), ISA J 457/ISA J 257, ISA JA 57, RedBro (Shaver) as well as Sena (double Breast) and Ross (Mini).
For the registration of the carcass and meat quality 380 broilers were investigated in the laboratory. The investigations led to following results: large differences are to be found in the composition of the carcass, particularly the tissue proportions of the joints breast and thighs; the chemical composition of the breast-and thigh meat was subject to the influence of the production process; there was no significant improvement in the sensory characteristics of breast -and thigh meat through the ecological production in comparison to the conventional one; the influence of the fattening age and the breed was statistically demonstrable.
Introduction
The EU regulation on organic production [Regulation (EC) No. 1804/1999] prescribes the conditions of the production. Furthermore, following demands on the organic production are put in the guidelines of ecological associations in Germany (Bioland, Naturland): slowly growing breeds are to be used, grain share in the ration should be at least 65 %, also the rearing duration, trimming density and open yard size are set.
Material and methods
At an animal material of broilers from 5 test series (n = 7864) the animals were held under controlled ecological conditions and compared with a (conventional) control group. The rearing duration varied from 35 (control group) to 80 days. Thereby following breeds were included: Ross 308 as control group, rearing duration 35 days (n = 4000); Sena, rearing duration 60 days (n = 864); ISA J 457 brown feathered broiler as well as ISA J 257 white feathered broiler with 77 days (n = 2000) and also slowly growing hybrids ISA JA 57 and RedBro (Shaver) and quickly growing breeds Sena and Ross with a rearing duration of 80 days (n = 1000).
The comprehensive data about feeding and keeping can be taken from Ristic and Damme (1996, 1999, 2002). The growing performance of the animals was determined too. A total of 380 carcasses were analyzed on their carcass composition and meat quality. The used methods are described by Ristic et al. (1994), and Ristic and Freudenreich (2000). The statistical evaluation occurred with a SAS -and SPSS (ANOVA)-program package using a fixed model. The multiple median value comparison was accomplished with the help of the Tukey-test (p ≤ 0.05).
Results and discussion
The development of the weight was determined first of all by the duration of the rearing period (Table 1). In each growing period another breed was represented. A clear delimitation resulted at equal fattening age after 70 days between slowly- and fast growing broiler lines (ISA, RedBro to Sena, Ross). Thereby a difference of 1325 g was found in favour of the breeds Sena and Ross and the feed utilisation was more favourable by 120 g.
The slaughter weight of chickens from the traditional production was approximately of. 1200 g, while that from the ecological production ranged from 1800 to approx. 3000 g (Table 2). The share of the valuable joints was between 27 and 31 % (breast) and between 30 and 32 % (thigh). The fattiness of the carcass by means of the abdominal fat ranged between 2.3 and 4 %. The lowest significant difference was 0.8 %.
The supreme meat quantity of the both valuable joints had the Sena and Ross broiler, as well as the broiler from the conventional production (Table 3). The highest total amount of fat, calculated from the tissue dissection of the parts breast and thighs summed up with abdominal fat was found to be 7.4%, after 77-day or rearing period for ISA–broilers.
The lipid content of the breast meat of broilers from the conventional production was 0.9 % (Table 4). The lipid value of broilers from ecological production was for the most cases lower with one exception of the ISA - broiler after 77-day of rearing (1.03 %). Despite that the water, protein and ash content values of the breast meat showed statistically significant differences, it was noticeable that these values were in a narrow range.
For the sensory evaluation of the breast meat, the duration of the rearing was always significant (Table 5). Larger differences appeared for juiciness and tenderness between the different growing duration and thus between the examined breeds. The best scores in juiciness were for the Ross - broiler after a 35-day rearing period, followed by Sena - broilers after a growing duration of 60 days, which achieved at the same time also higher notes for tenderness with 5.4. For flavour and overall impression of the breast meat there was a similar tendency as for the scores of juiciness and tenderness.
After a short fattening period of 32, 35 and 39 days average final weights of 1590 g, 1775 g and 2206 g were achieved respectively, at breeds from the German market (Damme and Rychlik, 2001; Simon, 2001). The feed conversion index was 1:1.519, 1.618 and 1.705, respectively.
A clear difference existed for the live weight of the different breeding products, like e.g. Ross 308 to ISA S 657 (Grashorn and Clostermann, 2002). By using regression analysis it was demonstrated, that the slowly growing breeds must be reared 10 to 32 days longer, to reach a live weight of 2000 g, as the breed Ross 308 on the 42nd day.
In the present investigation this development was demonstrated. The abdominal fat content was for the broilers from the traditional production as well as for slowly growing breeds (ISA, RedBro) lower than for the other breeds. After a rearing period of 70 and 84 days, a similar tendency was found by Grashorn and Clostermann (2002).
The proportion of the valuable joints breast and thighs grows in principle with the age (Havenstein et al., 1994; Lewis, et al., 1997; Ristic, 1991, 1992, 1994, 2002). For slow growing breeds it is not always the case (Grashorn and Clostermann, 2002). Similar observation was made in the present investigation, because ISA J 457/J 257 as well as ISA JA 57 had a lower proportion of the joints breast and thighs. The slowly growing breeds had a higher thigh percentage than that of the fast growing breeds (Lewis at al., 1997). Slow growing breeds have a lower breast meat percentage than fast growing breeds (Lewis et al., 1997; Havenstein et al., 1997).
The nutrient content of the meat, particularly in the thigh muscles changed also with age. The water and protein contents decreased while the fat content increased. The fat content of the breast meat from the traditional production is approx. 0.5 %. The corresponding value from the biological production is of the same level. With the organic feeding, the fat content of the thigh meat has grown dramatically but with no effects on the sensory characteristics (Ristic, 2000). According to Culioli et al. (1990) it is supposed, that a higher fat content in the muscle tissue lead to better flavour characteristics of the meat in slow growing broiler. With increasing rearing duration, the sensory properties (juiciness, tenderness) were improved in from 5 to 8 weeks in commercial production conditions (Ristic, 1994). An improvement appeared also at the breed "Landkornhähnchen" with 46 days, which had an intramuscular fat content of 0.17 % in the breast meat. The juiciness and tenderness scores of the breast meat, in comparison with chickens from the traditional production, were significantly higher of about 0.7 points (4.0:4.7) and 0.4 points (4.9:5.3) respectively (n = 110). The sensory scores of the commercial group in the present investigation were superior when compared with the data from the biological production of the slow growing lines. The fast growing lines obtained better results.
References
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VERORDNUNG (EG) Nr. 1804/1999 des Rates vom 19. Juli 1999: Zur Einbeziehung der tierischen Erzeugung in den Geltungsbereich der VO (EWG) Nr. 2092/91 über den ökologischen Landbau und die entsprechende Kennzeichnung der landwirtschaftlichen Erzeugnisse und Lebensmittel. Amtsblatt der Europäischen Gemeinschaften L 222/1-28
From Proceedings of the "XVI European Symposium on the Quality of Poultry Meat" and the "X European Symposium on the Quality of Eggs and Egg Products", Saint-Brieuc Ploufragan, France.
