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Ontogeny of feeding controls in suckling and weanling rats
Insights
Fasting rat pups
Area of Science:
- Animal behavior
- Developmental biology
- Physiology
Background:
- Conflicting literature data on rat pup attachment behavior.
- Importance of nutritional status and environmental conditions on early development.
Purpose of the Study:
- Investigate the effect of fasting and environmental conditions on rat pup nipple attachment latency.
- Determine the relationship between nutritional status and feeding behavior at different postnatal ages.
Main Methods:
- Studied attachment latencies of fed and fasted rat pups at various ages (10, 14, and 17 days).
- Manipulated fasting conditions: incubator temperature (30°C vs. 34°C) and foster mother presence.
- Controlled for maternal deprivation and body temperature maintenance.
Main Results:
- At 10 and 14 days, fasting in a 30°C incubator shortened attachment latency; other fasting conditions showed no difference from fed pups.
- Body temperature maintenance is crucial; maternal deprivation influences attachment latency.
- From 17 days onward, fasted pups showed shorter latencies than fed pups, irrespective of fasting conditions.
- Appetitive behavior emerged around the third postnatal week, correlating with weaning onset.
Conclusions:
- Early rat pup feeding behavior (10-14 days) is not solely dependent on nutritional status but is influenced by environmental factors like temperature.
- Later in development (from 17 days), nutritional status becomes a significant driver of feeding behavior, coinciding with the onset of weaning.
- Environmental control is critical for accurate assessment of nutritional effects on attachment behavior in young rat pups.
Abstract:
To rationalize conflicting data in the literature, the latency of attachment of fed and fasted rat pups to the nipples of their anesthetized mother has been studied at various postnatal ages. At 10 and 14 days of age, the mode of fasting had a critical effect on the results: pups fasted in a 30 degrees C incubator had shorter attachment latencies than fed pups, whereas when pups were fasted in a 34 degrees C incubator or with a nonlactating foster mother at room temperature, their latencies were no different from those of fed pups. Thus maternal deprivation has an important influence on attachment latencies, unless other steps are taken to maintain the body temperature of fasted pups. When this variable is controlled, it is apparent that at 10 and 14 days of age, the feeding behavior of rat pups is not related to nutritional status. In contrast, from 17 days onward, latencies of fed pups were significantly longer than those of faster pups, regardless of the mode of fasting. This appearance of appetitive behavior during the 3rd postnatal wk was shown to have a temporal correlation with the beginning of weaning, as measured by the appearance of chow in the stomachs.