Omasal ciliated protozoa in cattle, bison, and sheep

Area of Science:

• Rumen microbiology
• Gastrointestinal physiology

Background:

• The omasum's role in microbial populations is not fully understood.
• Ciliated protozoa are key members of the rumen ecosystem.

Purpose of the Study:

• To quantify and characterize ciliated protozoa in the omasal contents of cattle, bison, and sheep.
• To compare omasal protozoan populations with ruminal populations.

Main Methods:

• Omasal contents were collected from slaughtered cattle, bison, and sheep.
• Protozoan numbers and generic distribution were determined.
• Omasal and ruminal dry matter and pH were analyzed.

Main Results:

• Omasal protozoan numbers were lower than ruminal numbers but showed similar genus distribution.
• Highest protozoan counts were observed in sheep omasal contents.
• Omasal dry matter was higher than ruminal dry matter, with higher omasal pH in cattle.

Conclusions:

• The omasum harbors significant populations of ciliated protozoa, particularly in cattle.
• Omasal protozoa are difficult to eliminate and may reinoculate defaunated rumens.
• These findings highlight the omasum as a reservoir for rumen protozoa.