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Weaning in rats: II. Pup behavior patterns
E Thiels1, J R Alberts, C P Cramer
1Department of Psychology, Indiana University, Bloomington.
Insights
This study tracks rat pup behavior from Day 14 to 35 postpartum. Key findings reveal a three-phase developmental transition from suckling to solid food intake, marked by distinct behavioral shifts.
Area of Science:
- Developmental biology
- Animal behavior
- Mammalian ethology
Background:
- Postnatal development in mammals involves significant behavioral and physiological changes.
- The transition from maternal milk to solid food is a critical developmental milestone.
Purpose of the Study:
- To describe the behavioral changes in rat pups during the postpartum period from Day 14 to Day 35.
- To identify distinct phases in the developmental transition from suckling to solid food intake.
Main Methods:
- Continuous video-monitoring of rat pups and their mothers from Day 14 to Day 35 postpartum.
- Observation and quantification of specific behaviors including suckling, feeding, drinking, grooming, and play-fighting.
Main Results:
- Prior to solid food intake (Day 18), pups primarily suckled.
- Between Days 18-26, feeding, drinking, grooming, and play-fighting increased, while suckling declined.
- By Day 28, intake of solid food and water, and time spent on new behaviors, reached a plateau, though suckling continued until Day 34.
Conclusions:
- The transition to solid food is a complex process involving multiple behavioral changes with specific temporal patterns.
- The developmental period between Day 14 and Day 34 in rat pups can be delineated into three distinct phases based on behavioral changes.
- These findings provide insights into the intricate developmental trajectory of mammalian offspring during weaning.
Abstract:
In this study, litters of rat pups and their mothers were continuously video-monitored from Day 14 to Day 35 postpartum in order to describe the behavioral changes that occur during that period. Prior to the onset of solid food intake (Day 18), pups spent most of their active time suckling. During Days 18 to 26, feeding, drinking, grooming, and play-fighting rapidly became frequent daily activities, while suckling gradually began to decline. By Day 28, pups' food and water intake relative to body weight and time allocated to the new behaviors reached asymptote. Pups nevertheless continued to suckle until Day 34. These results suggest that (1) the transition from milk to solid food is embedded in a multitude of behavioral changes; (2) these behavioral changes have distinct temporal characteristics; and (3) the developmental period between Days 14 and 34 can be divided into three phases.