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    DIE BEDEUTUNG DER LAUFAKTIVITÄT UND DER GEWICHTSENTWICKLUNG BEI DER ENTSTEHUNG VON BEINSCHÄDEN BEIM MASTGEFLÜGEL
    (2006) Djukic, Mirjana; Bessei, Werner
    Within the last 50 years, an intensive selection took place in broilers on high growth and therefore there exists a clear reduction of the age at slaughter. Side effects of the selection of faster and higher growth are leg disorders. RUTTEN et al. (2002) tried to reveal the causal relations between weight load, activity and leg disorders by reducing the weight load on legs of fast growing broilers (FB) by a special device. The weight reduced FB showed higher locomotor activity and better bone quality. However, the harness used for the reduction of weight load on the legs impaired the growth rate. In the present study, the experiment of RUTTEN et al (2002) was repeated with an improved device for reduction of weight load of FB. In addition, slow growing broilers (SB) were used, and were brought to the same weight load as weight reduced FB by additional load. In total three experiment were carried out. The first experiment was split in two parts (1a and 1b) so as to incrase the number of replicates. For each experiment, 24 male broilers were used: 12 FG (ROSS 308) and 12 SB (ISA S 257). Load reduced birds weared a harness which was connected to the load reducing device. The load increase of SB weared the same harness with small pieces of led. The chicks of the groups were treated as follows: one with harness and suspension (HS), one with a harness and without suspension ? control bird 1 (C1) and a control bird with no harness and no suspension ? control bird 2 (C2). The load of FB was reduced to the average weight of SB-C2 and FB C2. The load of the SB was increased to the same average value. The following parameters were recorded: body weight, food consumption, weight of breast muscle, thigh, tibiotarsus, femur; length of tibiotarsus and femur; angular deformity of distal femur, distal and proximal tibiotarsus; torsional deformity of femur and tibiotarsus, total area, total density, Corticalis area, Corticalis density, SSI, walking, sitting, standing, eating and ?other behavior?. The weight load reduction in FB led to a significant increase of the locomotor activity. Both the torsional and angular deformities of the Tibiotarsus were clearly reduced, while total area, total density, Corticalis area and SSI were increased. It can be assumed that this was caused by the higher locomotor activity of load reduced FB. The increase of load in the SB diminished the locomotor activity but bone characteristics were not deteriorated. The improvement in the bone conditions of the FB was obviously caused by the increase in activity. In order to determine the influence of decreased load in FB and of increased load in SB the opportunity to move was restricted by reduction of the length of the compartments from 2 to .45 meters. All other experimental conditions remained the same as in experiment 1. Despite the restricted space there was a significant increase in locomotor activity of the load reduced FB. The torsion and angular deformity of the proximal and distal angular deformities of the Tibiotarsus were reduced. There was no significant effect of the increase and decrease of load on the CT-criteria. As in experiment 1, the weight load in the SB diminished the locomotor activity, but the bone characteristics were not influenced significantly. In the third experiment the gait of the load increased SB and load decreased FB was analyzed by a foot print program. For this purpose the length and width of the steps were measured at 4, 5 and 6 weeks of age. The same breeds and the same technique of the modification of the load were used. The load treated birds were kept individually and could use the full length of the test pens. In contrast to the previous experiments the control birds were kept in pens of 1 m² floor space (1 x 1 m). Only the birds without harness (C2) were kept as control. The results of the morphometric and CT- criteria confirmed the results. The FB control birds showed higher step length and greater step width than SB controls. The step length of FB was increased through the load reduction, and decreased through load increase in SB. The treatment had no influence on the step width. SB broilers showed problems to keep their balance under increased weight load. As indicated in the low width of the foot prints the load increased SB broilers tried to place their feet, as usual, under the point of gravity of their body. This seems to impair the stability of gait under increased weight load. FB in contrast, move their centre of gravity above the supporting leg which allows a stable gait under high load. FB did not change the width of their foot prints when the load was decreased, and only the length of the steps increased. The results underline the importance of locomotor activity on the leg conditions of FB. They clearly show that low activity of FB is not caused by lack of motivation but by the high weight load.