Rumen Development

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
  omasum
• 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

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Rumen Development
Undeveloped Rumen
Developed Rumen
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Size of Ruminant Stomach Compartments
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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
  omasum
• 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

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Nutritional Impact of Rumen By-Pass

• More efficient use of energy and protein
• No methane losses, heat of fermentation or
  ammonia losses
• Dietary requirements (100 kg calf gaining 1
  kg/day)
• 
  Metabolizable Digestible
• 
  energy protein
• 
  (MJ) (gm)
• Preruminant 32.5
  280
• Ruminant 35.1
  290
• Require B vitamins in diet (no microbial
  synthesis)
• Unable to utilize non-protein nitrogen

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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
• 
  

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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

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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

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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

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Digestive Efficiency of Lipids

• Preruminants can make effective use of a variety
  of fats
• 
  Digestibility
• Butterfat
  97
• Coconut oil (cant be fed alone) 95
• Lard 92
• Corn oil 88
• Tallow 87

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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

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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

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Importance of Diet to Rumen Development (6 Weeks
of Age)
Milk only
Milk and grain
Milk and hay
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Importance of Diet to Rumen Development (12 Weeks
of Age)
Milk and hay
Milk, hay and grain
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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
• 
  
  

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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 anaerobic rumen
  bacteria are established
• Regurgitation has been seen as early as 3 days of
  age
• Forage intake is an early instinct in ruminants

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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