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.
• Blum, J.W. 2006. Nutritional physiology on
  neonatal calves. J. Anim. Phys and Anim. Nut.
  901-11.

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
• Non-nutritive biogenic substances (Insulin,
  IGFs, Growth hormone, thyroxine, glucagon,
  prolactin, cytokines)

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 a minimum of 3 to
  3.8 L of good quality colostrum within 1 hour
  after birth.
• Supply 100 g IgG
• 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
• Result of gene activation and vascularization
• Modulation
• Ingested nutrients
• Regulatory substances produced and acting
  within GIT
• Development of GI tract proteolytic activity
• Should feed enough colostrum to supply 100 g IgG
  as early as possible

7

• 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

8
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

9
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

10
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

11
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

12
Nutritional implications of the reticular groove

• More efficient use of energy and protein
• No losses of methane, heat of fermentation or
  ammonia
• Efficiency
• 
  DE-ME ME-NEm ME-NEg
• Preruminant 96
  86 69
• Ruminant (fed starter grain) 88
  75 57
• Require B vitamins
• Unable to utilize nonprotein nitrogen

13
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

14
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

15

• 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
• Low temperature ultrafiltration processing has
  produced acceptable whey protein concentrates

16
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

17
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

18
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 (40 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

19
MILK REPLACER PROTEIN SOURCES
Preferred Acceptable as partial substitute Marginal
Dried whey protein concentrate Soy protein isolate Soy flour
Dried skimmilk Protein modified soy flour Modified potato protein
Casein Soy protein concentrate
Dried whey Animal plasma
Dried whey product Egg protein
Modified wheat protein
20
Changes in digestive enzymes

• Carbohydrases
• Intestinal lactase
• Activity high at birth
• Stimulated by feeding IGF-1
• 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

21
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

22
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 lipase 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

23
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

24
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 in 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

25
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

26
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

27
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

28

• 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

29
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

30

• 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

31
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32

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

33
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

34
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
• 
  
  

35
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