Transcript Transition from birth to functional ruminant

Rumen Development
Gut Function After Birth
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Digestion and absorption similar to monogastric
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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 nonruminant” to “fully functional ruminant” is heavily
diet-dependent
Rumen Development
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Newborn rumen is nonfunctional
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Reticular groove shunts milk from esophagus
to abomasum
Rumen developed by
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Sterile, small, lack papillae
Exposure to environment & other ruminants
Consumption of solid feed
Consumption of water
Controlled by the producer if animal is
separated from dam
Rumen Development
Undeveloped Rumen
Developed Rumen
Size of Ruminant Stomach
Compartments
Compartment
Adult, %
Newborn, %
Rumen
55
29
Reticulum
7
6
Omasum
24
14
Abomasum
14
51
Reticular Groove
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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:
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Suckling
Consumption of milk proteins
Consumption of glucose solutions
Consumption of sodium salts
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NaHCO3
Effective in calves, but not lambs
Presence of copper sulfate
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Effective in lambs
Reticular Groove Reflex
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Reflex similar in bucket-fed and nipple-fed calves
until 12 weeks of age
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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
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Considerable variation
Can sometimes be induced in mature animals
Advantages of nipple-feeding compared to bucketfeeding in shunting milk through groove
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Positioning of calf
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Rate and pattern of consumption of milk
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Arched neck
Slower and smaller amounts consumed
Increased saliva flow
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Salivary salts stimulate closure
Site of Digestion in Young
Ruminants
100
95.1
Rumen
Sm. intest.
Lg. intest.
75
Feces
%
49
47
50
33
25
25
25
13
3
1
2
7
1
0
Milk
Milk+Conc
Concentrate
Nutritional Impact of Rumen By-Pass
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More efficient use of energy and protein
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No methane losses, heat of fermentation or ammonia losses
Requirements (100 kg calf gaining 1 kg/day)
Metabolizable
energy
(MJ)
Preruminant
Ruminant
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32.5
35.1
Digestible
protein
(gm)
280
290
Require B vitamins in diet (no microbial synthesis)
Unable to utilize non-protein nitrogen
Rennin in Neonate
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Produced by gastric mucosa in newborns
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Coagulates milk proteins (caseins)
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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
3.5
6.5
2.1
5.3
Enzymes for Protein Digestion
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Pepsin
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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
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Reach mature level in 31 days
Pancreatic proteases
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Activity is low at birth
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Activity increases rapidly in first days after birth
Mature levels of pancreatic proteases reached at
~2 months of age
Enzymes for Carbohydrate Digestion
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Intestinal lactase
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Activity high at birth
Decrease in activity after birth is diet dependent
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Pancreatic amylase
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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
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Weaning decreases activity – substrate is no longer present
Low at birth
Increases to mature levels by 8 to 14 weeks of age
independent of diet
Intestinal sucrase – never present in ruminants
Enzymes for Lipid Digestion
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Pregastric esterase
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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
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50% of triglycerides in milk are hydrolyzed in 30 minutes
Pancreatic lipase
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Secretion is low at birth
Increases 3x to mature levels by 8 days
Hydrolyzes both short and long chain fatty acids
Digestive Efficiency of Lipids
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Preruminants can make effective use of a variety
of fats
Digestibility
Butterfat
97
Coconut oil (can’t be fed alone)
95
Lard
92
Corn oil
88
Tallow
87
Factors Required for Rumen
Development
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Establishment of bacteria
Water-based environment
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Development of muscular tissue
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Rumen contractions
Absorptive ability of tissue
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Free water intake
Rumen papillae
Substrate availability
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Dry feed intake
Rumen Development
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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
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Prevents papillae clumping and excessive keratin (a
wax secreted by rumen epithelium) accumulation on
surface of rumen papillae
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Increases absorptive function
Absorptive Ability of the Rumen
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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
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Increase papillae
development, increase
surface area, increase
absorptive ability
VFA absorption (mg/100 mg/hr)
500
400
Hay + grain
300
200
Milk / grain
100
Milk
0
0
7
14
21
Week of age
28
Importance of Diet to Rumen
Development (6 weeks of age)
Milk only
Milk and grain
Milk and hay
Importance of Diet to Rumen
Development (12 weeks of age)
Milk, hay and grain
Milk and hay
Establishing a Rumen Microflora
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Normal microflora established by animal-to-animal
contact
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Microbes also introduced through environment
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Bacteria will still establish if calves are kept separate from
mature animals – protozoa will not
Feed sources
Contaminated housing, bedding
Favorable environment for growth:
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Presence of substrates
Optimal ruminal pH
Water for fluid environment
Optimal rumen temperature
Bacteria in the Rumen
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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
#/g
1E+08
Proteolytic
1E+06
Methanogenic
1E+04
Cellulolytic
1E+02
S. bovis
1E+00
0
2
4
Age (wk)
6
8
Development of Rumen Microflora
1st Appear
Reach Peak
5-8 hours
4 days
½ week
½ week
½ week
3 weeks
5 weeks
6 weeks
1 week
6 to 10 weeks
1 week
3 weeks
-
12 weeks
5 to 9 weeks
5 to 13 weeks
Type of Organisms
E. Coli, Clostridium welchii
Streptococcus bovis
Lactobacilli
Lactic-acid utilizing bacteria
Amylolytic bacteria
B. ruminicola – week 6
Cellulolytic bacteria
Methanogenic bacteria
Butyrvibrio – week 1
Ruminococcus – week 3
Fibrobacter succinogenes – week 6
Proteolytic bacteria
Protozoa
Normal microbial population
Outflow from the Rumen
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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
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Forage intake is an early
instinct in ruminants
Can A Ruminant Survive
Without A Rumen???
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Rumenectomies (early removal of the rumen)
or prolonged milk feeding used to answer this
question
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Young ruminants will survive for a time without
rumen fermentation
Animal viability decreases and sudden death
occurs between 6 and 8 months of age
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Can be reversed almost immediately by providing food to
the rumen!!!
Ruminant animals “hard-wired” metabolically
to function as ruminants
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Must utilize the end-products of microbial
fermentation