P BB.15 - EN
Motor abilities of juvenile laboratory rats from litters of different sizes
Susann Meyer, Heiko Rödel
Lehrstuhl Tierphysiologie, Universität Bayreuth
Litter size of most small mammal species is highly variable. Offspring from larger litters usually receive a lower share of milk leading to lower pre-weaning growth, which may influence the physical capabilities of the young shortly after weaning. On the other hand, a higher number of siblings may positively affect the motor development of the juveniles by higher rates of behavioural interactions with their litter mates. We tested the motor skills and strengths of juvenile laboratory rats from litters of different sizes (3 to 17 pups/litter) around and shortly after weaning by behavioural tests.The latency time of jumping down from an elevated platform or out of their opened home cage was positively correlated with litter size. Furthermore, we found a non-linear effect of litter size on the juveniles’ strength in relation to their body mass, tested by the time they managed to stay attached to an elevated vertical wooden bar. Generally, young rats from large litters fell down earlier from the bar than the ones with less siblings, whereas juveniles from very small litters of 3 or 4 pups also fell down very fast, most likely due to their very high body masses. In conclusion, our study shows that juveniles from smaller litters had better motor skills and strength, most probably due to their better physical development. However, a very high body mass, as it occurs in juveniles from extremely small litters, might negatively affect their physical capabilities shortly after weaning.