Development of the Ruminant Digestive Tract

1
Development of the Ruminant Digestive Tract

• Readings
• Quigley and Drewry 1998. Nutrient and Immunity
  Transfer from Cow to Calf Pre- and Post-Calving.
  J Dairy Sci 812779-2790
•  http//jds.fass.org/cgi/reprint/81/10/2779.pdf
• Quigley et al. 2001 Formulation of Colostrum
  Supplements, Colostrum Replacers and Acquisition
  of Passive Immunity in Neonatal Calves J. Dairy
  Sci 842059-2065
•  http//jds.fass.org/cgi/reprint/84/9/2059.pdf
• Beharka et al. 1998. Effects of Form of the Diet
  on Anatomical, Microbial, and Fermentative
  Development of the Rumen in Neonatal Calves.
  J.Dairy Sci 811946-1955.
• http//jds.fass.org/cgi/reprint/84/9/2059.pdf
• Longenbach and Heinrichs. 1998. A Review of the
  Importance and Physiological Role of Curd
  Formation in the Abomasum of Young Calves. Anim.
  Feed Sci Tech 7385-97.
• ISU Home Page Library Collections
  e-journals Animal Feed Science and Tech.
  ScienceDirect Elsevier Science Journals Volume
  73 Pages 85-97.

2
Transition from birth to functional ruminant

• Phases
• Birth to 3 weeks
• True nonruminant
• 3 weeks to approximately 8 weeks
• Transition
• Length is diet dependent
• Beyond 8 weeks
• Ruminant
• Changes
• Absorption
• Function of the reticular groove
• Enzyme activity of saliva and lower GI tract
• Development of rumen volume and papillae
• Development of rumen microflora

3
Changes in absorption

• Calves born with no maternal gamma-globulins,
  and, therefore, must receive them from colostrum
• Composition Colostrum
  Milk
• Fat, g/kg 36 35
• Non-fat solids, g/kg 185
  86
• Protein, g/kg 143 32
• Immunoglobulins 55-68
  .9
• Lactose 31
  46
• Ash, g/kg 9.7 7.5
• Ca, g/kg 2.6 1.3
• P, g/kg 2.4 1.1
• Mg, g/kg .4 .1
• Carotenoids, ug/g fat 25-45 7
• Vitamin A, ug/g fat 42-48
  8
• Vitamin D, ug/g fat 23-45
  15
• Vitamin E, ug/g fat 100-150 20

4
Factors affecting the concentration of
immunoglobulins in colostrum

• Number of milkings
• Colostrum volume
• Increased ambient temperatures
• Dietary crude protein content during gestation
• No effect on concentration of immunoglobulins in
  colostrum
• Reduces absorption of immunoglobulins by calf.

5
Serum Immunoglobulin concentrations

• 10 g/l serum in calves is recommended
• A 1996 NAHMS study found that 40 of dairy
  heifers had less than the recommended level.
• Reasons for inadequate levels of IgG
• Inadequate colostrum consumption
• Recommended that calf receive 4 L of colostrum
  during first 24 hours after birth.
• Reduced IgG absorption

6
Factors affecting IgG absorption

• Age at first colostrum feeding
• The ability to absorb whole immunoglobulins
  decreases rapidly after birth
• Reasons
• Maturation of the epithelium
• Epithelium is totally replaced in first 24 hours
  after birth
• Development of GI tract proteolytic activity
• Should feed enough colostrum to supply 100 g IgG
  as early as possible
• Sex of calves
• Heifers have higher IgG than bulls
• Cattle breed
• Holsteins have more efficient Antibody Absorption
  Efficiency (AEA) than Ayrshires
• Method of feeding
• Feeding with nipple pail results in higher serum
  antibodies than nursing because
• Nursing calves consume colostrum later than
  nipple-fed calves
• Nursing calves consume less colostrum than
  nipple-fed calves
• Esophageal feeding of colostrum reduces AEA
  because
• Colostrum is retained in the rumen for 2 to 4
  hours
• AEA is greater in calves fed colostrum in 2
  feedings than 1 feeding

7
Factors affecting IgG absorption (Cont.)

• Metabolic or respiratory acidosis reduces AEA
• Causes of metabolic acidosis
• Dystocia
• Low CationAnion balance in diet of dam during
  pregnancy
• Extremely cold ambient temperatures reduce AEA
• Increased plasma glucocorticoids will increase
  AEA
• Increased serum colostrum IgG concentrations will
  increase AEA
• AEA can be improved in low to medium quality
  colostrum by adding bovine serum protein
• Reasons
• Overcome competition with other proteins
• There may be factors in colostrum that stimulate
  closure of the epithelium to antibody absorption

8
Change in the function of the reticular groove

• Reticular groove is composed of two lips of
  tissue that run from the cardiac sphincter to the
  reticulo-omasal orifice
• Purpose
• Transport milk directly from the esophagus to the
  abomasum
• Reflex
• Action occurs in two movements
• Contraction of longitudinal muscles that shorten
  the groove
• Inversion of the right lip
• Neural pathway
• Afferent stimulation by the superior laryngeal
  nerves
• Efferent pathway by the dorsal abdominal vagus
  nerve

9
Stimuli for contraction of the reticular groove

• Suckling
• Consumption of milk proteins
• Consumption of glucose solutions
• Consumption of sodium salts
• NaHCO3
• Effective in cattle, but not sheep
• Presence of copper sulfate
• Effective in lambs

10
Effects of age on reticular groove reflex

• Reflex normally equal 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
• Considerable variation
• Advantages of nipple-feeding compared to
  bucket-feeding
• Positioning of calf
• Arched neck
• Rate and pattern of consumption of milk
• Slower and smaller amounts consumed
• Increased saliva flow

11
Nutritional implications of the reticular groove

• More efficient use of energy and protein
• No losses of methane, heat of fermentation or
  ammonia
• Requirements (100 kg gaining 1 kg/day)
• 
  Metabolizable Digestible
• 
  energy protein
• 
  (MJ) (gm)
• Preruminant 32.5
  280
• Ruminant 35.1
  290
• Require B vitamins
• Unable to utilize nonprotein nitrogen

12
Changes in digestive enzymes

• Proteases
• Pepsin
• May or may not be secreted as pepsinogen by
  newborn calf
• HCl secretion is inadequate in newborn calf to
  lower abomasal pH enough for pepsin activity
• Calf born with few parietal cells
• Number of parietal cells increase 10-fold in 72
  hr
• Number of 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
  8 to 9 weeks after birth

13
Effect of age on the volume and composition of
gastric and pancreatic secretion

• 
  Age (days)
• 
  7-10 24-31 63-72
• Estimated apparent secretion
• (Saliva, gastric, and bile)
• Volume (l/12 hr) 2.2
  2.2 2.7
• Cl- minus Na (mmol/l) 95
  140 122
• Pancreatic
• Secretion (ml/l diet) 88
  107 122
• Trypsin activity (mg/l diet) 42
  42 45
• Total protease (g/l diet) .3
  .7 1.0

14

• Rennin
• A protease secreted by the abomasum
• Activity low at birth, but increases rapidly
• Actions
• 
  pH optima
• 
  Rennin Pepsin
• Proteolytic activity
  3.5 2.1
• Curd formation
  6.5 5.3
• Curd formation
• Forms within 3 to 4 minutes
• Slows rate of passage to increase digestion
• Specific for the protein, casein
• Implies that use of proteins other than casein in
  milk replacers may result in digestive upset and
  reduced growth
• Necessity somewhat controversial beyond 3 weeks
  of age

15
Effects of feeding non-milk proteins in milk
replacers

• Less gastric secretion
• Less gastric and pancreatic proteolytic activity
• Less coagulation
• Increased rate of gastric emptying
• Reduced protein digestibility
• Putrefactive scours
• Undigested protein
• Development of Coliform bacteria
• Results
• Damage to intestinal mucosa
• Increased osmotic pressure in digesta from amines
  
• Diarrhea
• Alkaline pH
• Particularly a problem before 3 weeks of age

16
Use of non-milk protein sources in milk replacers

• In 1995, only 11 of milk replacers contained
  only casein because of cost of casein containing
  ingredients
• Substitution levels
  Digestibility Substitution
• 
  CP, (3 wk) for casein
• Whey 40-90
  61-67 Up to 100
• Soy flour 50
  51 20
• Soy protein concentrate 70
  73-89 40 to 100
• Performance of calves fed milk replacers with
  different protein sources
• 
  Daily gain
• Age, wk Casein Soy protein conc
  Whey protein conc
• 0-6 13.8 kg 2.8
  kg
• 4-15 199.1 kg 74.6 kg
• 0-10 -.42 kg/d .09
  kg/d
• 0-6 20.6 kg
  12.5 kg
• 0-9 23.2 kg
  26.5 kg
• 0-9 .54 kg/d
  .56 kg/d
• 0-8 20.4 kg
  20.3 kg
• 0-6 .19 kg/d
  .25 kg/d

17
Rationale for efficacy of utilization of non-milk
proteins in milk replacers

• Factors affecting gastric emptying of digesta
• Coagulation of milk proteins
• Fat content of diet
• Fat in duodenum will stimulate cholecystokinin
• Presence of glucose in duodenum
• Presence of amino acids in duodenum
• Processing and compositional factors affecting
  milk replacer protein utilization
• Heating
• Excessive heating inhibits protein coagulation
• Fat content of diet
• Fat (20 of the DM) may improve clotting
• High fat levels may stimulate diarrhea by
  themselves
• Fat processing of diet
• Low temperature dispersion may result in more
  effective protein use than homogenization

18
Changes in digestive enzymes

• Carbohydrases
• Intestinal lactase
• Activity high at birth
• Decrease in activity after birth is diet
  dependent
• In ruminant calves, activity drops to mature
  levels by 8 weeks of age
• In pre-ruminant calves, activity at 8 weeks is
  10x greater than ruminant calves
• Pancreatic amylase
• Activity is low at birth
• Activity increases 26x by 8weeks 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 any sucrase
• Fructose is not absorbed

19
Implications of changes in carbohydrases

• Digestibility
• 
  Digestibility (28 days)
• Lactose
  95
• Maltose
  90
• Starch
  50-80
• Sucrose
  25
• Fermentative scours
• Undigested carbohydrates stimulate excessive
  production of VFAs and lactic acid which cause
  diarrhea
• Feces have an acidic pH
• Causes
• Non-lactose carbohydrates in milk replacers
• Overfeeding lactose as milk or milk-based milk
  replacer

20
Changes in digestive enzymes

• Lipases
• Pregastric esterase
• Secreted in the saliva until 3 months of age
• Activity is dependent on method of feeding and
  composition of feed
• Activity is increased by nipple-feeding
• Activity is greater in calves fed milk than those
  fed hay
• Hydrolytic activity is adapted to milk fat
• Specifically releases C4 to C8 fatty acids from
  triglycerides
• Equal activity to pancreatic amylase for C10 to
  C14 fatty acids
• No activity on longer chain fatty acids
• Although secreted in saliva and the pH optimum of
  PGE is 4.5 to 6, most PGE activity occurs in the
  curd in the abomasum
• 50 of the triglycerides in milk is hydrolyzed
  within 30 minutes
• Importance of PGE is questionable
• Pancreatic lipase
• Secretion is low at birth
• Increases 3x to mature levels by 8 days
• Hydrolyzes both short and long chain fatty acids

21
Implications of the lipase activity in
preruminants

• 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

22
Additional considerations with fats in milk
replacers

• Fat must be emulsified to a particle size less
  than 4 um with lecithin or glycerol monostearate
• Vitamin E and/or antioxidants must be
  supplemented if unsaturated fatty acids present
• Fat is replacers may reduce diarrhea
• Fat reduces concentration of lactose and protein
• Fat reduces rate of passage
• Increasing fat concentration in a replacer may
  increase calf fat reserves for early weaning

23
Metabolic changes occurring as a preruminant
develops into a ruminant

• Energy source
• Energy source
• Fetus Glucose
• Calf Fat
• Cow
  VFAs
• Blood glucose
• 
  Blood glucose, mg
• Calf
  100
• Cow
  60
• Liver enzymes associated with glucose utilization
  decrease
• Enzymes involved in glycolysis
• Fructose-1,6-diphosphate adolase
• Glucose 3 phosphate dehydrogenase
• Enzymes involved in pentose phosphate shunt
• Glucose-6-phosphate dehydrogenase
• 6 phosphogluconate dehydrogenase
• Enzymes involved in fatty acid synthesis from
  glucose
• Citrate lyase
• Liver enzymes associated with gluconeogenisis
  increase

24
Changes in rumen size and papillae

• As a preruminant animal develops, the relative
  size of the reticulorumen and omasum increases
  while that of the abomasum decreases
• 
  Age, wk
• 
  1 3 5 14 Adult
  
  of stomach
  weight
• Reticulorumen 34 48
  65 70 64
• Omasum 10 16 12
  18 25
• Abomasum 56 36
  23 12 11
• Factors affecting development of the ruminant
  stomach
• Age
• Diet

25
Effects of diet on development of rumen

• Chemical effect
• Volatile fatty acids produced during carbohydrate
  fermentation cause development of rumen
  epithelium and papillae
• Mechanism
• Volatile fatty acid metabolism in the epithelium
• Metabolism of butyrate to acetoacetate and
  Beta-OH-butyrate causes hypoxia which stimulates
  blood flow and nutrient transport
• Volatile fatty acids stimulates insulin secretion
• Insulin stimulates DNA synthesis
• Moderate levels of volatile fatty acids
  stimulates mitosis
• Increased volatile fatty acids in the epithelium
  increases osmotic pressure in cells
• Effect (20 wk old calves)
  Tissue
• Diet
  Epithelium Muscle
• Chopped hay, kg wet
  1.2 .8
• 
  57.7 42.3
• Concentrate, kg wet
  2.5 .9
• 
  74.3 25.7

26

• Implications of the effects of volatile fatty
  acids on epithelial development
• For early weaning programs, a starter concentrate
  should be offered as early as possible
• Calves should not be weaned until they are
  consuming 1 lb starter/day

27
Effects of diet on development of rumen

• Physical form of diet
• Volume
• Addition of bulk or fiber stimulates the rate of
  increase in stomach volume
• 
  Volume, l
• 
  Reticulorumen Omasum Abomasum
• Newborn
  1.5 .1 2.1
• 13 weeks
• Milk only
  7.4 .2 3.2
• Concentrates
  30.0 .9 2.5
• Hay
  37.1 1.2 3.8
• Mixed hay-concentrate 28.2
  1.8 3.1
• Presence of fiber in the diet does not affect
  mature volume

28

• Normal epithelial and papillae structure
• Inadequate long fiber results in
• Parakeratosis of rumen epithelium
• Branched papillae
• 
  Hay
• 
  Fine Intermediate Course
• Empty weight, g
• Reticulorumen
  994 904 931
• Omasum
  338 225 211
• Abomasum
  386 422 296
• Mucosal layers, um
• Keratin
  16 11 6
• Total epithelium
  53 79 75
• Muscle layers, um
• Inner
  933 1005 1062
• Outer
  688 799 736
• Papillae
• Length, um
  2218 1621 1097
• Width, um
  311 273 280

29
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30

• Implication
• Adequate long fiber is necessary in the diet of
  the growing calf to ensure normal epithelial and
  papillae growth

31
Development of rumen microflora

• At birth, rumen contains no microorganisms
• Normal development pattern
• Appear Peak
  Organisms
• 5-8 hours 4 days E.
  Coli, Clostridium welchii
• 
  Streptococcus bovis
• ½ week 3 weeks
  Lactobacilli
• ½ week 5 weeks
  Lactic-acid utilizing bacteria
• ½ week 6 weeks
  Amylolytic bacteria
• 
  B. ruminicola week 6
• 1 week 6 to 10 weeks
  Cellulolytic and Methanogenic
• 
  bacteria
• Butyrvibrio week 1
• 
  Ruminococcus week 3
• 
  Fibrobacter succinogenes week 6
  
• 1 week 12 weeks
  Proteolytic bacteria
• 3 weeks 5 to 9 weeks Protozoa
• - 9 to 13 weeks Normal
  microbial population

32
Factors affecting development of rumen microbial
population

• Presence of the organisms
• Normal population of bacteria and protozoa is
  established by animal-to-animal contact between
  ruminant and preruminant animals
• Bacteria will still establish if calves are kept
  separate from mature animals.
• Protozoa will not
• Favorable environment for growth
• Presence of substrates
• Includes intermediate substrates
• CO2
• Ammonia
• H2
• Branched-chain VFA
• Aromatic growth factors
• Phenylpropanoic acid
• B vitamins
• Increased ruminal pH
• Digesta turnover
• 
  
  

33
25 alfalfa hay75 grain Age,
weeks
2 4 6

Rumen pH Fine
6.25 5.35
5.6 Chopped
6.65 5.70 6.0
Amylolytic
bacteria, x 1010 /gm DM Fine
1.05 1.2
1.3 Chopped
.2 1.1 1.2

Cellulolytic bacteria, x 106/gm DM Fine
.09
.3 30 Chopped
.18 2.0
100