Fluid flow and feeding performance in infant mammals: evaluating the impact of nipple design

Infant mammals must suckle in order to acquire food. Many factors, including the design of a nipple, impact suckling, and thus can alter feeding performance. For example, feeding on a bottle nipple that has ducts embedded in silicone requires infants to generate suction to acquire milk, whereas a hollow bottle nipple allows infants to express milk via nipple compression. Furthermore, the design of a nipple impacts milk flow, and likely changes the relationships between suction generation, tongue kinematics and milk flow. In this experiment, we designed two ducted bottle nipples with similar properties and flow rates but with different branching patterns (a nipple with multi-level branching ducts and a nipple with a single central channel), and compared feeding performance with a hollow, cisternic nipple. We also experimentally calculated milk flow using a venturimeter attached to the single ducted nipple, while synchronously recording high-speed biplanar videofluoroscopy and intraoral pressure generation in infant pigs, a validated animal model. We found no significant differences between the ducted nipple types, but infants showed greater suction generation, different tongue kinematics and smaller bolus sizes when feeding from the ducted nipples as compared with a hollow, cisternic nipple. We calculated milk flow and volume per suck using the venturimeter, and saw correlations between milk flow rate and both middle tongue translation and intraoral suction generation. Overall, these data demonstrate that nipple design has a profound impact on the relationship between infant feeding physiology and milk flow.