1. Horse and Cattle Digestion

2. Horse oddities Unable to vomit Lack a gallbladder Stomach  Esophageal region of stomach- nonglandular  Margo plicatus

3. Horse-large intestine Hindgut fermenters-ferment feedstuffs in Large intestine Cecum- via ileocecal orifice Ventral colon- via cecocolic orifice Dorsal colon Small colon=descending colon

4. Horse-large colon Flexures-”turns” in the colon; named for where they are in the abdomen  Sternal flexure  Pelvic flexure**  Diaphragmatic flexure ** Sites of impactions or twists-leads to colic

5. A=ileum B=Cecum C=right ventral colon D=left ventral colon E=pelvic flexure F=left dorsal colon G=right dorsal colon H=transverse colon I=descending colon Caudal Cranial right left

6. Horses-carbohydrate digestion Carbohydrates-poorly digested in small intestines  Needed to feed the microbes in hindgut  Excess carbs-highly fermented, leads to gas production---BAD!

7. http://www.wcds.afns.ualberta.ca/Proceedings/1996/figures/wc96-058.gif

8. Horses-protein digestion Efficiently digested in small intestines Microbes in the hindgut need proteins Liver secretes urea-helps feed microbes

9. Horses- Microbes produce Volatile Fatty Acids (VFA’s) that are absorbed for energy (other animals-what is the primary energy source??)  Acetic acid, Proprionic acid, Butyric acids Acids in the colon still need to be buffered  Bicarbonate secreted in colon  Cows where is bicarb from???

10. http://eduforum.ugent.be/vakgroep/fysiologie/theorie/LasMinuteTheo2de2006.htm

11. Horses-small colon Absorb electrolytes, water, VFAs

12. Other nonruminant hindgut fermenters? Guinea pigs Rats Rabbits Swine

13. Ruminant digestion Ruminate their food-  Swallow  Regurgitate  Chew their “cud”=remastication Breaks down large plant fibers Increase surface area for microbes  Swallow again Cattle, sheep, and goats are ruminants

14. Rumination

15. Ruminant digestion Prestomach vs. True stomach  Prestomach Reticulum Rumen Omasum  True stomach Abomasum

16. Reticulum “Honeycomb” Cranial most chamber Ruminoreticular folds Coordinated contractions with rumen “Hardware Disease”  magnet

17. Rumen Fermentation Vat L. side of the cow Muscular pillars with separate chambers within rumen for mixing Ruminoreticular contraction-  Regurgitation  Eructation-escape of CO 2 and methane Bloat

19. Control of Rumen Vagus nerve Other factors-rate and strength of contractions  pH  Presence of VFAs ( )  Consistency of feedstuffs  Stretch receptors

20. Fermentative Digestion = protozoal and bacterial action on remasticated plant material  Enzymes from microbes!  Mammals do not have cellulase! (complex carbohydrate) Simple sugars (glucose)-  Microbes utilize  Convert to VFAs Absorbed – liver converts to glucose Microbes also provide Vitamin B and K

21. Protein digestion Proteins eaten  Microbe converts to peptides, then amino acids  Used by microbes, then converted to: Ammonia –used by other microbes for protein production VFAs-absorbed by animal So where do cows get protein????  Liver converts ammonia to urea  Bug bodies!!  Bypass proteins

22. Delicate balance Fermentation balances:  Substrate used by microbes (glucose and peptides)  Microbe number  Amount of microbes product (VFAs and ammonia No rapid changes in diet!!!

23. Omasum The “book” Break down food particles further VFA absorption Remove bicarbonate ions Water absorption

24. Abomasum “True stomach” Similar function as simple stomach animals Left displaced abomasum (LDA), RDA

25. Calf digestion Do calves eat fermentable material?? Rumen/reticulum small and nonfunctional Reticular groove (esophageal groove)- esophagus to omasum

27. Ruminants-hindgut Spiral colon  Modification of ascending colon  Some fermentation in hindgut!

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