Beyond Digestion: Can Animals Shape the Landscape According to Their Species–Specific Salivary Secretions?

Maria Grazia Cappai,Sabine Aboling,Cecilia Dall’Aglio

doi:10.3390/agriculture11090817

Maria Grazia Cappai, Sabine Aboling + Show 1 more

Open Access

https://doi.org/10.3390/agriculture11090817

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Abstract

Several functions are acknowledged for saliva secretion in different animal species following prehension and mastication of feed. Most of such are linked to the specific role of lubrication and softening of the bolus to allow taste perception and easy swallowing. Moreover, enzymatic components are produced in the saliva, some of which are destined to contribute to the digestion of different nutrients (to various extents according to animal species) and to exert antimicrobial activity (lysozyme). In addition, the buffering power and the virtuous recycle of water, electrolytes, and other metabolites are of particular importance for proper digestion and for nutrition–related aspects. Moreover, salivation appears to be involved in a number of other functions. Recent studies on salivary production and roles point to salivary glands as target organs of neuroendocrine regulation in response to many external stimuli coming from the outer world, for which feed still represents the chief external stimulus. Various animal species establish an adaptive strategy when coming into contact with different feeding stuffs and/or dietary substances by modifying both the composition and amount of saliva produced. In the light of recent updates, this review provides a focus on the functional roles of saliva secretions, showing the broad involvement of salivary response in several mechanisms beyond the digestive function and influencing feed selection.

Highlights

Saliva is the product of salivary glands, which pour into the mouth, exhibiting different volumes and compositions of their secretion, following specific internal and external stimuli
In the light of recent updates, this review provides a focus on the functional roles of saliva secretions, showing the broad involvement of salivary response in several mechanisms beyond the digestive function and influencing feed selection
Salivation plays a pivotal role in bridging animal feeding habits with natural feeding sources available in the environment

Summary

Introduction

Saliva is the product of salivary glands, which pour into the mouth, exhibiting different volumes and compositions of their secretion, following specific internal and external stimuli. External stimuli (exteroception), alongside conditioned reflexes and proprioceptive stimuli (from internal stimuli), can lead to different salivary secretion responses by an animal, either varying in amount or composition of secretions or both. BBeeyyoonndd tthhee ddiiffffeerreenntt ddiissttrriibbuuttiioonnss,, ssaalliivvaarryy ggllaannddss aallssoo pprroodduuccee ssaalliivvaa wwiitthh ddiiffffeerreenntt ccoommppoossiittiioonnss ((TTaabbllee 11)). Under normal conditions, the progression of ingesta follows normal swallowing in order to reach the stomach, where food, saliva, and microbes can be found. Such modulation differently engages the salivary glands according to the type and level of secretion

Autonomic Control of Salivary Secretion

Response to External Stimuli

Dynamics of Interaction between Natural Feeding Sources and Animals

Conclusions