Rumen Development

Question 1

Rumen Development

Answer 1

-neonates begin life as monogastrics as milk bypasses rumen
-milk is easily digestible and does not need to be fermented
-over time with weaning, rumen microbiome must develop

Question 2

Newborn calf (0-24hrs)

Answer 2

-abomasum is largest compartment
-poorly developed rumen (no papillae or microbes)
-colostrum given to allow for passive transfer of antibiotics (first 12-24hrs)

Question 3

Colostrum

Answer 3

-no transfer of antibodies through placenta (takes ~2 months to develop after birth) so need colostrum
-colostrum allows for mothers antibodies to be passed on which prevents early infectious disease

Question 4

What are neonates susceptible to?

Answer 4

-sepsis
-naval infection (omphalophlebitis)
-joint infections (septic arthritis)
-scours (diarrhea)

Question 5

Colostrum absorption

Answer 5

-absorption decreases rapidly after birth (starts to drop off at 12hrs, over by 24hrs)
-Dairy welfare code states need a min of 4L within 4 hrs
-linear (cannot be saturated)

Question 6

Beef cattle colostrum

Answer 6

-colostrum is more concentrated so calves don’t need as much colostrum

Question 7

IgG concentrations

Answer 7

-begins to drop rapidly
-colostrum produced leading up to birth, but as milking occurs, it will rapidly decrease

Question 8

Colostrum replacer

Answer 8

-can be supplemented if needed

Question 9

Colostrums role in glucose

Answer 9

-colostrum also has glucose which is important because newborns have limited liver glycogen

Question 10

Abomasum initially after birth

Answer 10

-Abomasum is not secreting HCl or pepsinogen for first 24hours (no proteolysis)
>anti-trypsin factor in colostrum inhibits protease digestion in SI
-allows for intact IgG absorption across intestinal mucosa through pinocytosis

Question 11

How is transfer of passive immunity assessed?

Answer 11

-plasma IgG is gold standard, but impractical
-instead use plasma total protein via refractometer

Question 12

Pre-ruminant phase (1 day to 3 weeks)

Answer 12

-milk is primary source of nutrients
-glucose-based metabolism (no VFAs, insulin dependent)
-little rumen function

Question 13

Pre-ruminant consumption per day

Answer 13

-animal consumes ~20% of body weight/day (eg. 40-50kg calf=8-10L/day

Question 14

Milk replacer

Answer 14

-good quality protein (milk origin such as casein)
-homogenized fat
-simple sugars (glucose, lactose; no starch or sucrose)

Question 15

Suckling

Answer 15

-6-8 times per day or more OR bottle/bucket feeding 2-3 times/day
-suckling stimulates salivation (more salivation when fed from nipple than drinking from bucket)

Question 16

Saliva importance during suckling

Answer 16

-contains pre-gastric esterase used for lipid digestion

Question 17

Reticular groove closure

Answer 17

-also called esophageal groove closure
-reflex that lets milk bypass the rumen (esophagus to groove to abomasum)
>omasum is underdeveloped at this point

Question 18

Chemoreceptors in esophageal groove

Answer 18

-milk in pharynx stimulates the chemoreceptors (reacts to Na in calves, Cu in lambs)
-afferent signal sent to brain via CN IX
-brain sends efferent signal back through vagus nerve. Resulting in contraction of reticulum muscles forming the groove (allowing movement directly to omasum)
-relaxes omasal orifice (milk flows into abomasum)

Question 19

Signs indicating esophageal groove closure

Answer 19

-head butting
-tail wagging
-enthusiastic to drink

Question 20

What does not effect esophageal groove closure?

Answer 20

-head position (up or down)
-drinking from teat or bottle

Question 21

Bucket feeding effect on groove closure

Answer 21

-bucket feeding results in less salivary or gastric secretion
-can cause the groove closure to be erratic

Question 22

Abomasal secretions

Answer 22

-stimulated by suckling (not bucket drinking)
-secretions contain HCl and rennin (not pepsinogen)

Question 23

Rennin

Answer 23

-coagulates casein and fat forming a hard curd (precipitated Ca caseinate)
> hard curd undergoes slow digestion (12-18 hrs). Lipid component broken down by lipase from mammary gland and pre-gastric esterase from saliva. The caseinate component will be broken down through proteolysis by rennin
> remaining liquid=whey (albumins and globulins) which rapidly move to duodenum

Question 24

Intestinal digestion

Answer 24

1.chyme from abomasum gradually enters duodenum through steady flow (not fast)
2.pancreatic enzymes and bile (proteases and lipase)
3.Brush border enzymes

Question 25

Brush border enzymes

Answer 25

-have lactase which hydrolyses lactose
-no maltase to digest maltose
-no sucrase to digest sucrose

Question 26

Adverse Early GI events

Answer 26

1.ruminal acidosis
2.intestinal bacterial overgrowth

Question 27

Ruminal acidosis

Answer 27

-milk enters rumen by:
>leakage from esophageal groove
>failure to close
>drinking too fast
-lactose fermented to lactic acid
-results in gas formation, rumen distention, fluid splashing

Question 28

Intestinal bacteria overgrowth

Answer 28

-poor milk clot (curd) formation results in excess milk entering the duodenum and the rapid proliferation of bacteria= scours

Question 29

Transitional phase (3-8 weeks)

Answer 29

-increasing amount of milk as animal grows (15% or more of body weight/day)
-introduction to solid feed
>creep feed; but little consumption before 2 weeks although it is beneficial to provide it anyway
>grain and forage mixture
>forage quality is important; chopped straw results in better rumen development

Question 30

Transitional phase-rumen development

Answer 30

-requires solid food
-increases rumen weight and results in development of muscular rumen wall
-rumen motility and rumination begins
>fermentation produces VFAs which stimulates development of papillae and omasal leaves to increase SA for absorption

Question 31

Transitional phase and microbiome

Answer 31

-development of microbiome begins
>establishment of protozoa required repeated direct contact with other animals

Question 32

Transitional phase metabolism

Answer 32

-transitions from glucose to VFA
-less sensitive to insulin

Question 33

Weaning to adult (8 weeks and up)

Answer 33

-transition to exclusively solid feed
-dry matter is more important
-pepsinogen secreted instead of rennin

Question 34

Weaning protocol

Answer 34

-occurs at 8-10 weeks
-eating 2-3kg calf started and ab lib forage
-Step down protocol (gradual reduction in milk provided; 2-3 steps over 2-3weeks)

Question 35

Pre-ruminant metabolism

Answer 35

-liver is more glycolytic
-gluconeogenesis is highly regulated (glucose from diet=less reliance on self-production)
-responsive to insulin

Question 36

Ruminant metabolism

Answer 36

-liver is more glucogenic
-more consistent gluconeogenesis from VFA (from VFA because little glucose in the diet so need to make it from VFA instead)
-less responsive to insulin

Question 37

Fully developed rumen of ruminants

Answer 37

-VFAs, electrolytes, water are absorbed in rumen
-protein (microbial and undigested from feed), lipids (microbial and from feed), vitamins digested/absorbed in small intestine