Stiftung Tierärztliche Hochschule Hannover Die ontogenetische ...

Studie II: Shift of the CoM in growing dogs
3.4. Animals and Methods
Dogs
Six male Beagle siblings (Canis lupus familiaris, Linnaeus 1758) from the same
litter were used in this longitudinal study. The dogs were from a breeding colony of
the University of Veterinary Medicine Hannover (Germany) and came to the Small
Animal Clinic at the age of 9 weeks (i.e., PW9). During the study period, all dogs
underwent two standard orthopedic exams, one at PW14 and one at PW50, which
confirmed that the dogs were sound. For the gait analysis, the puppies were gently
introduced to ambulating on the treadmill when they were 9 weeks old. All
experiments were carried out in accordance with the German Animal Welfare
guidelines and notice was given to the Ethics committee of Lower Saxony
(Germany).
Data collection
GRF measurements started at PW9 and continued until PW51. Data were
collected weekly up to PW20, fortnightly up to PW32 and monthly henceforth.
Additionally to the GRF recordings, various morphometric measurements (e.g.,
segment and limb lengths) were taken for a related study (Helmsmüller et al., subm.)
and the dogs were photographed in lateral perspective standing as balanced and
square as possible (Fig. 1). From all recordings, data from PW11, 13, 19, 22, 26, 30,
43 and 51 were selected for further analysis. Two dogs could not participate in the
data collection at PW19 and were therefore measured the following week (i.e.,
PW20).
During GRF data collection, the dogs trotted on a horizontal treadmill with four
separate belts and integrated force plates underneath each belt (Model 4060-08,
Bertec Corporation, Columbus, OH, USA). Because of their small body size, the
puppies trotted on one side of the treadmill allowing the forces exerted by the foreand
the hindlimbs to be recorded separately (sample rate 1,000 Hz). Separate force
curves for the left and the right limbs were nevertheless obtained because the duty
factor was less than 0.5 during all recordings. To identify whether the right or the left
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