Avian Crop Function – A Review

The aim of this review is to present and discuss the anatomy and physiology of crop in different avian species. The avian crop (ingluvies) present in most omnivorous and herbivorous bird species, plays a major role in feed storage and moistening, as well as functional barrier for pathogens through decreasing pH value by microbial fermentation. Moreover, recent data suggest that this gastrointestinal tract segment may play an important role in the regulation of the innate immune system of birds. In some avian species ingluvies secretes “crop milk” which provides high nutrients and energy content for nestlings growth. The crop has a crucial role in enhancing exogenous enzymes efficiency (for instance phytase and microbial amylase, β-glucanase), as well as the activity of bacteriocins. Thus, ingluvies may have a significant impact on bird performance and health status during all stages of rearing. Efficient use of the crop in case of digesta retention time is essential for birds’ growth performance. Thus, a functionality of the crop is dependent on a number of factors, including age, dietary factors, infections as well as flock management. It is important to expand knowledge about the crop functions to use them effectively in poultry production. Furthermore, more scientific data is needed in the scope of immunological function of the crop as well as its microecosystem for a better understanding of the avian immune system and enhancing the health of the birds.