How innate is locomotion in precocial animals? A study on the early development of spatio-temporal gait variables and gait symmetry in piglets

Abstract

Locomotion is one of the most important ecological functions in animals. Precocial animals, such as pigs, are capable of independent locomotion shortly after birth. This raises the question whether coordinated movement patterns and the underlying muscular control in these animals is fully innate or whether there still exists a rapid maturation. We addressed this question by studying gait development in neonatal pigs through the analysis of spatio-temporal gait characteristics during locomotion at self-selected speed. To this end, we made video recordings of piglets walking along a corridor at several time points (from 0 h to 96 h). After digitization of the footfalls, we analysed self-selected speed and spatio-temporal characteristics (e.g. stride and step lengths, stride frequency and duty factor) to study dynamic similarity, intralimb coordination and interlimb coordination. To assess the variability of the gait pattern, left-right asymmetry was studied. To distinguish neuromotor maturation from effects caused by growth, both absolute and normalized data (according to the dynamic similarity concept) were included in the analysis. All normalized spatiotemporal variables reached stable values within 4 h of birth, with most of them showing little change after the age of 2 h. Most asymmetry indices showed stable values, hovering around 10%, within 8 h of birth. These results indicate that coordinated movement patterns are not entirely innate, but that a rapid neuromotor maturation, potentially also the result of the rearrangement or recombination of existing motor modules, takes place in these precocial animals.

Does intrauterine crowding affect locomotor development? A comparative study of motor performance, neuromotor maturation and gait variability among piglets that differ in birth weight and vitality

“…As argued in our previous study [ 32 ], spatio-temporal characteristics can be considered the most basic collective output emerging from the entire underlying neuro-mechanical system (musculo-skeletal system and its control), with relative phasing of the limbs revealing aspects of interlimb coordination and single limb behavior (during stance and swing) as a collective measure of intralimb coordination. However, in order to attribute changes in spatio-temporal gait characteristics to neuromotor maturation, one needs to be able to distinguish between maturation on the one hand and growth or postural changes on the other hand.…”

“…To this end, normalization according to the dynamic similarity principle [ 33 ] is applied (cf. [ 32 ]). If the dynamics of the motor task do not change during development, we assume no underlying neuromotor maturation.…”

“…Our earlier study [ 32 ] showed that N piglets undergo a very rapid (within a few hours after birth) neuromotor maturation, with a rapidly decreasing variability of the gait pattern (within 8 hours after birth). We expect that L piglets show a lower level of neuromotor skill at birth and afterwards show a differential/slower neuromotor maturation, compared to N piglets.…”

“…This question entails three hypotheses, which can be answered by studying different aspects of spatio-temporal coordination. Is voluntary locomotion for L piglets at u dynamically similar to N piglets after a few hours [ 32 ] and is, in that case, the locomotion of both groups identical? We hypothesize that normalized walking at birth is different for L piglets compared to N piglets and that this is followed by a slower maturation.…”

“…For this purpose we will normalize u and its components ( f and l stride ) according to the dynamic similarity principle, generating u’ , f’ , l stride ’ (cf. [ 32 , 33 ]). We checked for differences in the development of u’ , f’ and l stride ’ between L and N piglets.…”