2. Growth and Development of the Ruminant Gastro-Intestinal Tract Development of Rumen Papillae   Papillae develop from the lamina propria of the rumen lining Serous membraneMuscular tunicRumen mucosa Contains epithelial layer and lamina propria Cross section of the rumen

3. Growth and Development of the Ruminant Gastro-Intestinal Tract Development of Rumen Papillae   Papillae develop from the lamina propria of the rumen lining Lamina propriaEpithelial layer Cross section of the rumen   Papillae begins as a capillary loop pushing up the lamina propria and the epithelial layer to form the papillae.

4. Growth and Development of the Ruminant Gastro-Intestinal Tract   Reticulorumen growth is delayed (inhibited) by all milk diets. Factors Affecting Rumen Development Rumen from a 6 week old calf fed milk only. Note thin walls of rumen and minimal papillae growth.

5. Growth and Development of the Ruminant Gastro-Intestinal Tract   Hay, forage, fiber stimulates reticulorumen development and growth through increased musculature of the rumen walls and papillae growth.   Addition of concentrates to hay diets increase papillae development due to increased production of VFA’s from microbial fermentation. Factors Affecting Rumen Development Rumen from 12 week old calf fed milk plus hayRumen from 12 week old calf fed milk, hay and concentrate

6. Growth and Development of the Ruminant Gastro-Intestinal Tract Factors Affecting Rumen Development Milk OnlyConcentrateHayHay + Conc. Rumen + Reticulum, g78.7356.1195.9250.5 Omasum, g20.556.130.675.6 Abomasum, g60.548.136.659.4 Volume, ml Rumen + Reticulum7,39430,03737,07128,159 Omasum1858781,1571,781 Abomasum3,2352,5423,7783,105

7. Growth and Development of the Ruminant Gastro-Intestinal Tract   Addition of bulky inert materials to the rumen increases rumen muscular growth and volume, but does not enhance papillae growth because there is no increased fermentation.   Salts of VFA’s introduced directly into the rumen enhance papillary and epithelial development but do not stimulate growth of muscle tissue.   Butyrate is most effective in stimulating papillary growth followed by propionate and acetate.   Butyrate and propionate are most readily absorbed by the rumen epithelium.   Concentrate feeding causes a shift in the microbial population.   Increased microbial production of stronger acids (butyrate and propionate) decreases rumen pH. Factors Affecting Rumen Development

8. Growth and Development of the Ruminant Gastro-Intestinal Tract Study Investigating form of dietary forage (long vs pelleted; pelleted diets were either high fiber or low fiber)   Treatments:   Hay fed in long form   High fiber pellet   Low fiber pellet Factors Affecting Rumen Development Normal tongue like papillae wee present in calves fed long hay.

9. Growth and Development of the Ruminant Gastro-Intestinal Tract Study Investigating form of dietary forage (long vs pelleted; pelleted diets were either high fiber or low fiber)   High fiber pellet Factors Affecting Rumen Development Papillae varied much more in shape with a higher proportion rounded in form and with keratinization of their tips

10. Growth and Development of the Ruminant Gastro-Intestinal Tract Study Investigating form of dietary forage (long vs pelleted; pelleted diets were either high fiber or low fiber)   Low fiber pellet Factors Affecting Rumen Development Papillae were small, nodular, cauliflower shaped with narrow stalks, very dark color, heavily keratinized with ingesta packed between them

11. Growth and Development of the Ruminant Gastro-Intestinal Tract   Establishment of bacteria in the rumen. When the calf is first born there are no bacteria in the rumen. Within days, aerobic bacteria become established. As dry feed is consumed (two weeks), anaerobic bacteria begin to grow and fermentation begins.   Water intake. Anaerobic fermentation requires water. Milk intake through nursing shunts the rumen through the esophageal groove and goes to the abomasum.   Muscular action of the rumen. Rumen contractions, motility and rumination are required to pass digesta through the rumen to the abomasum and lower tract. Factors Required for Rumen Development

12. Growth and Development of the Ruminant Gastro-Intestinal Tract   Absorptive ability of rumen tissue. Varying factors affect rumen wall muscle development vs. development of epithelium and papillae. Primary stimulus to development of epithelium and papillae is presence of VFA’s.   Substrate available in the rumen. Hay and long fiber is needed to develop rumen wall muscle and rumen volume. Concentrates stimulate microbial fermentation and the production of butyrate and propionate and are needed for quick development of rumen epithelium and papillae. Factors Required for Rumen Development Effect on rumen epithelium development MaterialEffect Milk+ Hay++ Grain+++ Inert materials- VFA - acetate++ VFA - propionate+++ VFA – butyrate++++