1. Rumen Development

2. Gut Function After Birth
Digestion and absorption similar to monogastric
Function of the reticular groove
Enzyme activity of saliva, stomach and small intestine different than in adult ruminant
Rumen volume and papillae must develop
Rumen microflora must become established
Length of transition period between “functional non-ruminant” to “fully functional ruminant” is heavily diet-dependent

3. Rumen Development Newborn rumen is nonfunctional
Sterile, small, lack papillae
Reticular groove shunts milk from esophagus to abomasum
Rumen developed by
Exposure to environment & other ruminants
Consumption of solid feed
Consumption of water
Controlled by the producer if animal is separated from dam

4. Rumen Development
Undeveloped Rumen
Developed Rumen

5. Size of Ruminant Stomach Compartments
Adult, %
Newborn, %
Rumen 55 29
Reticulum 7 6
Omasum 24 14
Abomasum 51

6. Reticular Groove
Reticular groove is composed of two lips of tissue that run from the cardiac sphincter to the reticulo-omasal orifice
Transport milk directly from the esophagus to the abomasum
Closure is stimulated by:
Suckling
Consumption of milk proteins
Consumption of glucose solutions
Consumption of sodium salts
NaHCO3
Effective in calves, but not lambs
Presence of copper sulfate
Effective in lambs

7. Reticular Groove Reflex
Reflex similar in bucket-fed and nipple-fed calves until 12 weeks of age
Reflex normally lost in bucket-fed calves by 12 weeks
Reflex normally lost in nipple-fed calves by 16 weeks of age, but effectiveness decreases with age
Considerable variation
Can sometimes be induced in mature animals
Advantages of nipple-feeding compared to bucket-feeding in shunting milk through groove
Positioning of calf
Arched neck
Rate and pattern of consumption of milk
Slower and smaller amounts consumed
Increased saliva flow
Salivary salts stimulate closure
               

8. Site of Digestion in Young Ruminants

9. Nutritional Impact of Rumen By-Pass
More efficient use of energy and protein
No methane losses, heat of fermentation or ammonia losses
Requirements (100 kg calf gaining 1 kg/day)
Metabolizable Digestible
energy protein
(MJ) (gm)
Preruminant
Ruminant
Require B vitamins in diet (no microbial synthesis)
Unable to utilize non-protein nitrogen

10. Rennin in Neonate Produced by gastric mucosa in newborns
Coagulates milk proteins (caseins)
Curd encases whey proteins, fats, and other associated nutrients within minutes
Curd slowly contracts
Formation and contraction of curd allows slow release of nutrients to small intestine, increases digestibility
optimal pH for activity
Rennin Pepsin
Proteolytic activity
Curd formation

11. Enzymes for Protein Digestion
Pepsin
May or may not be secreted as pepsinogen
HCl secretion is inadequate in newborn ruminant to lower abomasal pH enough for pepsin activity
Ruminants born with few parietal cells
Reach mature level in 31 days
Pancreatic proteases
Activity is low at birth
Activity increases rapidly in first days after birth
Mature levels of pancreatic proteases reached at ~2 months of age

12. Enzymes for Carbohydrate Digestion
Intestinal lactase
Activity high at birth
Decrease in activity after birth is diet dependent
Weaning decreases activity – substrate is no longer present
Pancreatic amylase
Activity is low at birth
Activity increases 26-fold by 8 weeks of age
Mature levels not reached until 5 to 6 months of age
Intestinal maltase
Low at birth
Increases to mature levels by 8 to 14 weeks of age independent of diet
Intestinal sucrase – never present in ruminants

13. Enzymes for Lipid Digestion
Pregastric esterase
Secreted in the saliva until 3 months of age
Activity is increased by nipple-feeding
Activity is greater in calves fed milk than those fed hay
Hydrolytic activity is adapted to milk fat
Most activity occurs in the curd in the abomasum
50% of triglycerides in milk are hydrolyzed in 30 minutes
Pancreatic lipase
Secretion is low at birth
Increases 3x to mature levels by 8 days
Hydrolyzes both short and long chain fatty acids

14. Digestive Efficiency of Lipids
Preruminants can make effective use of a variety of fats
Digestibility
Butterfat
Coconut oil (can’t be fed alone) 95
Lard
Corn oil
Tallow

15. Factors Required for Rumen Development
Establishment of bacteria
Water-based environment
Free water intake
Development of muscular tissue
Rumen contractions
Absorptive ability of tissue
Rumen papillae
Substrate availability
Dry feed intake

16. Rumen Development
Rumen epithelium and papillae development stimulated by butyrate (from fermentation of concentrates)
Increase in rumen capacity developed by forage intake
Papillae integrity developed by diet abrasiveness
Prevents papillae clumping and excessive keratin (a wax secreted by rumen epithelium) accumulation on surface of rumen papillae
Increases absorptive function

17. Absorptive Ability of the Rumen
VFA absorption (mg/100 mg/hr)
The ability of the rumen to absorb VFA is thought to depend on production of VFA
Offering dry feed from an early age will promote production of absorptive ability
Increase papillae development, increase surface area, increase absorptive ability
Hay + grain
Milk / grain
Milk

18. Importance of Diet to Rumen Development (6 weeks of age)
Milk only
Milk and grain
Milk and hay

19. Importance of Diet to Rumen Development (12 weeks of age)
Milk, hay and grain
Milk and hay

20. Establishing a Rumen Microflora
Normal microflora established by animal-to-animal contact
Bacteria will still establish if calves are kept separate from mature animals – protozoa will not
Microbes also introduced through environment
Feed sources
Contaminated housing, bedding
Favorable environment for growth:
Presence of substrates
Optimal ruminal pH
Water for fluid environment
Optimal rumen temperature

21. Bacteria in the Rumen At birth the rumen is sterile - NO bacteria
By 24 hr of age there is a large number of bacteria - mostly aerobes
With dry feed intake, typical rumen bacteria are established
Proteolytic
Methanogenic
Cellulolytic
S. bovis

22. Development of Rumen Microflora
1st Appear Reach Peak Type of Organisms
5-8 hours days E. Coli, Clostridium welchii
Streptococcus bovis
½ week weeks Lactobacilli
½ week weeks Lactic-acid utilizing bacteria
½ week weeks Amylolytic bacteria
B. ruminicola – week 6
1 week to 10 weeks Cellulolytic bacteria
Methanogenic bacteria Butyrvibrio – week 1
Ruminococcus – week 3
Fibrobacter succinogenes – week 6
1 week weeks Proteolytic bacteria
3 weeks to 9 weeks Protozoa
to 13 weeks Normal microbial population

23. Outflow from the Rumen Unfermented material must leave the rumen
Muscular action in the rumen begins very early in life (4-6 days) and may depend on establishment of bacteria – associated with onset of feeding grains
Regurgitation has been seen as early as 3 days of age
Forage intake is an early instinct in ruminants

24. Can A Ruminant Survive Without A Rumen???
Rumenectomies (early removal of the rumen) or prolonged milk feeding used to answer this question
Young ruminants will survive for a time without rumen fermentation
Animal viability decreases and sudden death occurs between 6 and 8 months of age
Can be reversed almost immediately by providing food to the rumen!!!
Ruminant animals “hard-wired” metabolically to function as ruminants
Must utilize the end-products of microbial fermentation