Question

Primary contraction cycle of bovine start with

• A. Monophasic contraction of rumen
• B. Monophasic contraction of reticulum
• C. Biphasic contraction of rumen
• D. Biphasic contraction of reticulum

Hint:

Remember: The primary (mixing) cycle starts with a biphasic reticular contraction, whereas the secondary (eructation) cycle is reticulo-independent and restricted to the rumen.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Ruminant forestomach motility is critical for the mixing, fermentation, and transit of ingesta.
The motility pattern consists of two distinct cycles: the primary (mixing) cycle and the secondary (eructation) cycle.
The primary cycle is highly coordinated and responsible for mixing the reticulorumen contents.
Detailed Explanation:
The primary contraction cycle occurs approximately once per minute in a normal, resting bovine.
This cycle always starts with a characteristic biphasic contraction of the reticulum.
The first phase of this reticular contraction is a partial, rapid contraction that forces coarser, freshly ingested fibrous material into the cranial sac of the rumen.
The reticulum then relaxes slightly before immediately undergoing a second, more powerful contraction that empties smaller, well-fermented particles and liquid into the omasum through the reticulo-omasal orifice.
Following this biphasic reticular contraction, the contraction wave propagates caudally over the rumen, involving the cranial sac, dorsal sac, and finally the ventral sac of the rumen.
Secondary cycles, on the other hand, do not involve the reticulum and are primarily concerned with the eructation of fermentation gases from the dorsal rumen sac.

Step 2: Final Answer:
The primary contraction cycle begins with a biphasic contraction of the reticulum.