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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 81:2779-2790

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Development of the Ruminant Digestive Tract

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development of the ruminant digestive tract

Development of the Ruminant Digestive Tract


Quigley and Drewry 1998. Nutrient and Immunity Transfer from Cow to Calf Pre- and Post-Calving. J Dairy Sci 81:2779-2790

Quigley et al. 2001 Formulation of Colostrum Supplements, Colostrum Replacers and Acquisition of Passive Immunity in Neonatal Calves J. Dairy Sci 84:2059-2065

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 81:1946-1955.

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 73:85-97.

Blum, J.W. 2006. Nutritional physiology on neonatal calves. J. Anim. Phys and Anim. Nut. 90:1-11.

transition from birth to functional ruminant
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
changes in absorption
Changes in absorption
  • Calves born with no maternal gamma-globulins, and, therefore, must receive them from colostrum
  • Composition ColostrumMilk

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)

factors affecting the concentration of immunoglobulins in colostrum
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.
serum immunoglobulin concentrations
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
factors affecting igg absorption
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

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
factors affecting igg absorption cont
Factors affecting IgG absorption (Cont.)
  • Metabolic or respiratory acidosis reduces AEA
    • Causes of metabolic acidosis
      • Dystocia
      • Low Cation:Anion 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
change in the function of the reticular groove
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
stimuli for contraction of the reticular groove
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
effects of age on reticular groove reflex
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
nutritional implications of the reticular groove
Nutritional implications of the reticular groove
  • More efficient use of energy and protein
    • No losses of methane, heat of fermentation or ammonia
    • Efficiency


Preruminant 96 86 69

Ruminant (fed starter grain) 88 75 57

  • Require B vitamins
  • Unable to utilize nonprotein nitrogen
changes in digestive enzymes
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
effect of age on the volume and composition of gastric and pancreatic secretion
Effect of age on the volume and composition of gastric and pancreatic secretion

Age (days)


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


Secretion (ml/l diet) 88 107 122

Trypsin activity (mg/l diet) 42 42 45

Total protease (g/l diet) .3 .7 1.0


A protease secreted by the abomasum

Activity low at birth, but increases rapidly


pH optima


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

effects of feeding non milk proteins in milk replacers
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
use of non milk protein sources in milk replacers
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, wkCaseinSoy protein concWhey 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

rationale for efficacy of utilization of non milk proteins in milk replacers
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
changes in digestive enzymes1
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
implications of changes in carbohydrases
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
changes in digestive enzymes2
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
implications of the lipase activity in preruminants
Implications of the lipase activity in preruminants
  • Preruminants can make effective use of a variety of fats


Butterfat 97

Coconut oil (Can’t be fed alone) 95

Lard 92

Corn oil 88

Tallow 87

additional considerations with fats in milk replacers
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
metabolic changes occurring as a preruminant develops into a ruminant
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
    • Glucose-6-phosphatase
    • Fructose diphosphatase
changes in rumen size and papillae
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
effects of diet on development of rumen
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


Chopped hay, kg wet 1.2 .8

% 57.7 42.3

Concentrate, kg wet 2.5 .9

% 74.3 25.7

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
effects of diet on development of rumen1
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


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
Normal epithelial and papillae structure
    • Inadequate long fiber results in:
      • Parakeratosis of rumen epithelium
      • Branched papillae


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


Length, um 2218 1621 1097

Width, um 311 273 280

% Branched 25 16 12



    • Adequate long fiber is necessary in the diet of the growing calf to ensure normal epithelial and papillae growth
development of rumen microflora
Development of rumen microflora
  • At birth, rumen contains no microorganisms
  • Normal development pattern

AppearPeak 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


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

factors affecting development of rumen microbial population
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

25% alfalfa hay:75% grain Age, weeks

  • 246
  • 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