INFLUENCE OF STOCKING DENSITY ON BODY CONFORMATION IN BROILERS

In this experiment the influence of stocking density on the body conformation of broiler carcasses was investigated. One hundred and twenty broiler chickens were divided into three groups; each group comprised 40 chickens. At the end of the first week of the fattening period 20 chickens in each group were marked by random sampling. The first testing group (P1) represented the one with a lower stocking density (12 chickens per square meter); the second one (P2) with a higher stocking density (18 chickens per square meter), while the control group (K) was set in accordance with the technological recommendations (15 chickens per square meter). Breast circumference, drumstick circumference, keel length (crista sterni), breast depth and breast angle were monitored and measured on a weekly basis. Body conformation measures were determined on the carcasses in a horizontal position with their backs placed on the table. The appropriate instruments such as millimetre tape, caliper and ZP-3 protractor were used. In addition, a weekly live weight and feed consumption were measured. Production results (live weight, gain, feed-to-gain ratio and European Production Index (EPI) were calculated. Carcass grades were calculated based on the mass ratio of the cooled carcass and the live body weight before slaughtering. The research findings have confirmed that overcrowding in production facilities is always risky in regard to the expected production results. In contrast, by fully conforming to the production technology requirements, it is possible to achieve better production results.

Stocking density is one of the most important factors in broiler production.It affects the health and well-being of broilers to a large extent in the sense of productivity and behaviour.Definition of the concept of stocking density in poultry production is given on the basis of various criteria.So far, the crucial criteria have been established relating to economic factors, and consequently, the practice has been to place the greatest possible number of chickens per square metre in the final stage of the fattening period.In technical terms it has been expressed as a live weight of chickens per square metre at the end of the fattening period (Broiler Campaign, 2001; Broiler Management Guide Cobb 500, 1998).
Density is an exceptionally important non-genetic factor in regard to successful fattening and it has often been attempted to reconcile the two diametrically opposed views within this determinant.On the one hand, we have productivity goals in terms of the highest possible yield of meat per area unit; while on the other hand, there is a physiological reality and the irrefutable fact that we are dealing with living creatures that cannot be overcrowded in an unacceptable manner.As a result, stocking density is a problem that all producers of commercial hybrids have attempted to resolve for the benefit of animals and the breeding farm as such.
It is a common practice that farmers are trying to maximize the number of chickens per square unit to get the optimal yields.Animal welfare activists have been insisting on humanizing the production process in the fattening period, but also on other segments of poultry breeding with the aim of reducing the stocking density of animals per square unit.According to recommendations of commercial broiler breeders (Cobb, Ross) stocking density depends on many factors, the most important being the manner of breeding and its goals.In open (non controlled environment) poultry houses the calculation of stocking density is dependent on temperature, especially in the summer season, in addition to the type of production facilities.In controlled environment houses for intensive broiler fattening, the maximal stocking density should be up to 34 kg of live weight per one square metre (Broiler Management Guide Cobb 500, 1998).
The increased demand for chicken meat in markets has imposed a challenge for big selection centres to produce broiler chickens with a wide breast circumference and good body conformation.The term "conformation" is of American origin, but it is nowadays used in many countries around the globe to determine form (shape), type and body build of broilers (Pavlovski and Ma{i}, 1983).Determining body conformation in carcasses is vital for any qualitative assessment in research or commercial production.It is done by applying subjective and objective assessment methods (Pavlovski and Ma{i}, 1983;Antonijevi} et al., 1981;Ma{i} et al., 1980;Ma{i}, 1967).
Over the past few years a number of different broiler hybrids have been used in Bosnia and Herzegovina that have remained on the market for a Introduction / Uvod shorter or longer period.Nevertheless, the dominant breeds used in our country today are Ross and Cobb commercial hybrids.Consequently, we conducted our research to examine the influence of this particular factor stocking density on body conformation of broiler chickens in testing and breeding conditions during the fattening period.In addition we also measured their production results such as live body weight, total gain, feed-to-gain ratio and EPI index, as well as the carcass grade.
During the six-week fattening period 120 broiler chickens Cobb 500 were divided into three groups; each group comprised 40 chickens.At the end of the first week 20 chickens in each group were marked by random sampling.The chickens in the first testing group (P 1 ) represented the one with a lower stocking density (12 chickens per square metre); the second one (P 2 ) with a higher stocking density (18 chickens per square metre), while the control group (K) was set in accordance with the technological recommendations (15 chickens per square metre).
Conditions in breeding capacities (such as temperature, humidity and light program) were in accordance with the producer's recommendations relating to floor keeping.Inside the facilities three boxes, differing in size, were set.Each box was adapted to a particular tested group.The manual equipment was installed in the boxes and all production amenities were in conformity with the selector's instructions.Broiler chickens were fed in accordance with nutritional requrements of the Cobb broiler breeds.
During the testing period breast circumference, drumstick circumference, keel length (crista sterni), breast depth and breast angle were monitored and measured on a weekly basis.Body conformation measures were determined on the carcasses in a horizontal position with their backs placed on the table.The appropriate instruments such as millimetre tape, caliper and ZP-3 protractor were used.In addition, a weekly live weight and feed consumption were measured.
Production results (live body weight, total gain, feed-to-gain ratio and European Production Index (EPI) were calculated and presented for the total number (n=40) of the tested broiler chickens.Carcass grades were calculated based on the mass ratio of the cooled carcass and the live body weight before slaughtering.Body conformation measurements were calculated and presented for the marked (n=20) broiler chickens.
The results were analyzed by ANOVA Single factor.If the Fisher's p value proved to be significant (p<0.05), the differences between means were tested by Duncan's multiple range test.The significance was determined at the level of p<0.05.

Materials and methods / Materijal i metode rada
The means of production results are shown in Table 1.The highest final body weight of 2.36 kg and highest total gain of 2.32 kg were achieved in Group K.The best feed-to-gain ratio (1.78 kg) was also achieved by the chickens from the same group as well as the highest EPI index (317).The highest carcass weight and carcass grade was confirmed in Group K, but were not significantly different compared to the other two groups (Table 2).
Means of body conformation measurements of broiler carcasses are presented in Table 3.The highest value of the breast circumference was found in Group K wich was significantly higher than in Group P 2 , but not in Group P 1 .Drumstick circumference and keel length were essentialy the same in all tested groups.Breast depth was the highest in Group P 1 and the lowest in Group K, and breast angle was also highest in Group P 1 .

316
Vet. glasnik 61 (5)(6)  We could not confirm any important influence of stocking density on production results, which is absolutely in conformity with the results obtained by Thomas et al. (2004) who report that the stocking density of 10, 15 and 20 chickens per square metre did not significantly influence the achieved production results.

Carcass weight and carcass grade / Te`ina i ocena trupova
After slaughtering and processing the weight of the carcasses in broiler chickens from the control group amounted to 1.70 kg with a carcass grade of 72.03 %.At the same time, these were by far the best expected results based on the selector's recommendations and breeding conditions as such (Broiler Growth Cobb 500, 1998; Broiler Performance Cobb 500, 1998).The weight of the processed carcasses and the carcass grade appeared to be better, and as such it could elicit some doubts.This outcome was hinted at by the production results of live broiler chickens, and in spite of the fact that chickens from this group had a somewhat larger living space, it did not result in irrational use of food energy for movement and did not influence the gain.On the contrary, the chickens from the group that had a reduced living space, or the least capacity for movement, did not use the feed rationally, and thus, they achieved the poorest pre-slaughter results.In production circumstances these results may have been caused by difficult access to water and feed, which was not a case in our experiment.Therefore, the causes should be looked for in a wide range of factors relating to high stocking density, but generally, they can be summed up under the notion of a disrupted well-being of individual chickens.In this respect, our research results are similar to those of authors who reported etological factors as serious causes of production failures in intensive poultry breeding conditions (Spinu et al., 2003 1962).Otherwise, the slaughter-related results that we obtained for the control and the first testing group are similar to those of other authors (Kavazovi} et al., 2004;Alibegovi}-Ze~i} et al., 2003;Pavlovski et al., 2003;Feddes et al., 2002;Supi} et al., 2000;Alibegovi}-Ze~i}, 1999;Mitrovi}, 1996;Petrovi}, 1981), but they are even better than the results obtained by others (^aklovica et al., 1991;Pav-lovski et al., 1980).The reasons could be related to different broiler strains used in their experiments (^aklovica et al., 1991), or a different experiment design aimed at establishing the influence of various feed brands on the fattening results (Pavlovski et al., 1980), but not the housing conditions.
Body conformation of broiler caracass / Telesna konformacija trupova pili}a Body conformation is a crucial indicator in assessing the quality of chicken carcasses.The measures of body conformation of broiler carcasses, expressed as the index of body weight before slaughtering and the observed measures on the carcasses themselves, aimed at reducing the effect of the body weight and accentuating the importance of the applied treatment, are also considered to be the important indicators of the carcass quality.We could not find data in the available literature for some tested parameters because of the nature of our experiment design.Consequently, in such conditions we tried to compare our results related to body conformation measures with available results from other authors, being fully aware that the results of the latter were most commonly influenced by other factors, namely, by other experiment designs.
The trend of breast circumference increase on carcasses of the broiler chickens bred in conditions in conformity with the recommended technical standards proved to be statistically different compared to the carcasses of two other testing groups.Nevertheless, the best mean value of breast circumference in our experiment was lower than that reported by Latshaw and Bishop (2001).It must here be mentioned that the authors in their experiment on broiler chickens, which were divided according to sex, used another set of instruments for measuring breast circumference.On the other hand, our values regarding the breast circumference of all the three groups are higher in comparison with the results obtained by Antonijevi} et al. (1981) who conducted their experiments on broad-breasted broiler chickens of the Hubbard breed.
Drumstick meat, along with white breast meat, is classified as the topquality part of the chicken carcass.Taking into consideration the fact that drumstick circumference is bigger in broiler chickens with full, rounded drumsticks, our results for all the tested groups are better than those reported by other authors (Luki}, 2001;Hopi}, 1996;Pavlovski and Ma{i}, 1983;Pavlovski et al., 1980).
The lower index value of the drumstick is an indicator of a more favourable body conformation factor (Pavlovski and Ma{i}, 1983;Ma{i}, 1973).In accordance with the said criterion the most favourable body conformation was observed in broiler chickens bred in conditions of a higher stocking density, although the total values for all the three groups were very similar.The keel length index can be observed from two points.The longer the keel means the more space is provided for breast musculature, but the breast roundness in this case is smaller, and as a result, the carcass appears less compact.When priority is given to carcass meatiness, it is understood that longer-keel carcasses have an advantage.Therefore, a lower index value indicates a more favourable body conforma-tion.The broiler chickens from the control group achieved the best results although statistically they did not differ from the other two groups.Our results for all the three groups are approximately the same as those of other authors (Hopi},1996;Pavlovski and Ma{i}, 1983), but considerably lower than the results reported by Pavlovski et al. (2003).It must be emphasized that the latter authors used several broiler breeds in their study, and chickens were divided according to sex.
Selection, aimed at improving body conformation and slaugtherrelated parameters of broiler chickens, was focused on the breast part of the carcass.Bearing in mind that a higher index of breast depth indicates a more favourable body conformation, the results we obtained in this respect were also better in comparison with other research results (Pavlovski et al., 1980;Luki}, 2001).Although breast meatiness and roundness need not always be in correlation, our results have also proven that, apart from selection, the limited movement of broiler chickens is an indispensable prerequisite of a better body conformation.However, this does not mean that the factor of limited movement should be used indiscriminately because other research findings in the present study appear to be against a higher stocking density of broiler chickens in the fattening period.
The best results were achieved by the broiler chickens from the control group that were fattened in conformity with the recommended stocking density of 15 individual broilers per one square metre.The research findings have confirmed that overcrowding in production facilities is always risky in regard to the expected production results.Fully conforming to the production technology requirements is needed for the achievement of the best production results.

Table 3 .
Means of body conformation measurements of broiler carcasses / Tabela 3. Srednje vrednosti merenja telesne konformacije trupova pili}a u tovu Ze~i} et al., 2003; Pavlovski et al., 2003; Pejin et al., 1980), but they are attributable to a different test design and the use of other broiler breeds in it.