Exam 4 (Lecture 48) - Foregut Fermentation II Flashcards
Define rumination.
Remastication (cud chewing)
Time spent ruminating depends on the ______.
Type of diet
Rumination time: What type of diet would cause an increase in rumination time? __________ also influences the amount of rumination time.
High forage diets
Feed intake level
Briefly describe the steps of rumination.
Step 1: Regurgitation; Step 2: Remastication (cud chewing)
Regurgitation:
- There is an extra contraction of the reticulum (takes place just before the regular biphasic reticular contr)
- Simultaneously, the cardia relaxes and there is an inspiratory excursion of ribs with glottis closed
- This creates a negative pressure within the thorax favoring movement of ingesta into esophagus
- Reverse peristaltic wave propels material cranially into the oral cavity
- Excess water is expressed by action of tongue
- Water is swallowed
- Remastication begins
Remastication:
- Increases surface area
- Exposes additional fermentable substrates not exposed to previous microbial action
- Assists with particle separation process
- Separates small particles from large particles (water and small particles are expressed from bolus)
- Small particles sink into the reticulum when re-swallowed (then are subject to passage into omasum)
- Larger particles are ejected back into the cranial part of the rumen when swallowed after remastication
Briefly describe the process of rumen water flow. Transit rate of ________ must be considerably greater than the transit of _______ through the rumen.
Liquid must constantly wash through all sections of the rumen and then move through the reticulo-omasal oriface to the omasum.
Water; particulate matter
Dorsal vagal nucleus of the brainstem > __________ nerve > rumen and reticulum
Vagus
Important _______________ come from the lumen of the reticulorumen. What conditions are monitored?
Afferent signals
1) Distention
2) Ingesta consistency
3) pH
4) VFA concentration
5) Osmolality (ionic strength)
What do the chemoreceptors in the walls of the rumen and reticulum monitor?
1) pH
2) VFA
3) Osmolality
What suppresses rumen motility?
Increasing VFAs or decreasing pH
What is the function of the omasum?
Absorption
- Removes residual VFAs and HCO3- from ingesta before material is transported to the abomasum
Briefly describe omasal transport failure (vagal indigestion).
Caused by traumatic injury and severe adhesions of the reticulum and omasum to the body wall
- Causes damage to Vagal fibers entering the omasum
Ability to move food out of the fore stomach and into the abomasum is severely impaired
Rumen becomes greatly distended with finely comminuted feed and the entire rumen becomes a slurry zone
Animals eventually suffer severe exhaustion due to lack of nutrients
