Newborn calves
What is true about newborns calves? and their rumen development?
Abomasum is the largest compartment
Poorly developed rumen - no papillae or microbes
Colostrum - passive transfer of antibodies
Rumen development - neonates begin as monogastrics (milk bypasses rumen), Milk is easily digestible (does not need to be fermented), takes time to develop rumen microbiome
What is the esophageal groove closure?
Also called reticular groove closure
Reflex that lets milk bypass the rumen - esophagus -> groove -> abomasum = omasum is underdeveloped at this point
Milk in pharynx stimulates chemoreceptors (afferent signal sent to brain via cranial nerve IX), brain sends efferent signal back through vagus nerve, contracts muscles in reticulum forming a groove, relaxes omasal orifice
Metabolic changes calves go through?
Pre ruminant - gluconeogenesis is highly regulated, responsive to insulin
Ruminant - more consistent gluconeogenesis from VFA, less responsive to insulin
With a fully developed rumen - absorbed in rumen (VFA, electrolytes, water), digested/absorbed in SI (protein, lipids, vitamins)
Bacteria metabolism aspects?
Protein - can break down AA for energy, transform one AA type into another, can synthesize AA from non-protein nitrogen
Lipids - hydrolyze lipids, biohydrogenate fatty acids, branched chain fatty acids, odd number chain fatty acids
Vitamins - synthesize B vitamins, require cobalt to make vitamin b12
What are carbohydrates good for in the diet?
Structural CHO = cellulose and hemicellulose, lignin and pectin
Non-structural CHO = energy source for the plant, simple sugars (mono and disaccharides), starch (amylose and amylopectin)
What is important about colostrum? specific aspects?
No transfer of antibodies through placenta - take ~2 months to develop after birth
Prevents early infectious disease - sepsis, naval infection, joint infections, scours
Absorption decreases rapidly after birth, first 12 hours is key, abomasum not yet secreting HCl and pepsin, anti-trypsin factor in colostrum, Gut open to antibody absorption, supplement if needed, is also an important source of glucose
What are the signs of the esophageal groove closure?
What does not effect it?
Does bucket feeding have an effect?
Effects = head position, drinking from teat
Bucket feeding - not as much salivary or gastric secretions, groove closure can be erratic
What is the environment that is conducive to growth?
pH 6-7, temp 39, motility (mixing contents and prevents local build up of VFA), substrate and moisture (ingestion of new feed, rumination, drinking and salivation), removal of waste products (absorbed through rumen epithelium, passage to omasum), anerobic (utilized by facultative anaerobes)
Protozoa is?
Smaller number than bacteria, decrease faster with rumen turnover, acquire nutrients from numerous sources (bacteria, starch granules, protein, fat, cellulose and hemicellulose)
Population and species are more variable than bacteria, more sensitive to changes in rumen conditions, optimal pH of 6.2-7.0, free-floating in rumen liquid, good indicator of general rumen health
Fiber is? types?
Slowly digested structural material, cellulose hemicellulose and lignin, essential for rumen fibrous mat
NDF = cellulose + hemicellulose + lignin (determine dry matter intake)
ADF = cellulose + lignin (determines digestibility)
What is the pre-ruminant phase? when is it?
Milk is primary source of nutrients
Consume ~20% of body weight/day
Glucose-based metabolism - not VFAs insulin dependent
Little rumen function
Milk replacer - good quality protein, homogenized fat, simple sugars
The abomasal secretions are? what stimulates them?`
Stimulated by suckling
Secretions contain rennin and HCl (no pepsin)
Rennin = coagulates casein and fat (curd), remaining liquid = whey, curd undergoes slow digestion
The microbial environment in ruminants?
Symbiotic relationship - cows need microbes to break down feed, microbes need cows to provide feed and environment
Different microbes perform different jobs - amylolytic, cellulolytic, methanogens
How do you alter microbial populations - directly adding microbes is not effective long term, more effective to change the environment
Fungi is?
Includes yeast, low mass and low number, anaerobic, ferment - starch, cellulose and hemicellulose, some protein
Non fiber CHO is?
Starches and sugars
take up less space in rumen
completely digested by microbes
rapidly fermented
How does intestinal digestion occur in calves?
Chyme from abomasum gradually enter duodenum
pancreatic enzymes and bile - proteases and lipase
Brush border - lactase hydrolyses lactose, not maltase to digest maltose, and no sucrase to digest sucrose
What is the transitional phase? When?
3-8 weeks
Increasing amount of milk - 20% or more or body weight/day, introduction to solid feed
Salivary glands increasing in size and secretions, rumen development requires solid feed
Development of microbiome, establishment of protozoa required repeated direct contact with other animals, metabolism transitions from glucose to VFA
Bacteria is?
Largest proportion of microbiome, mostly gram-negative, obligate or facultative anaerobes
There are 1 degree bacteria (directly ferment feed material) and 2 degree bacteria (utilize products produced by 1 degree bacteria
Antibiotics affect the rumen how?
Rumen infections generally do not occur
rumen microbes are susceptible to antibiotics
antimicrobials added to feed - ionophores and tylosin
Aspects of starch digestion?
Rumen digestibility - wheat 88-90%, barley 86-88%, corn 75-77%, Oats 88-91%
processing increases digestibility - grinding and rolling, and steam flaking
Sheep and goats can shew whole grain, cattle do not
What are the adverse early GI events?
Ruminal acidosis - milk enters rumen, lactose fermented lactic acid, gas formation rumen distention and fluid splashing
Intestinal bacteria growth - poor milk clot formation, excess milk enters duodenum, rapid proliferation of bacteria, scours
What is the weaning to adult stage? when?
8 weeks and up
Transition to solid feed only, pepsinogen secreted instead of rennin - wean about 8 weeks
Bacteria for CHO metabolism
Amylolytic - starch fermenters = optimal growth at lower pH, rapid proliferation, short life span
Cellulolytic - fiber fermenters = cellulase (extracellular enzyme), Cellulosome, can also ferment starch, optimal growth at higher pH, longer life span
Ionophores help with?
Increases feed efficiency
Helps prevent acute lactic acidosis
helps prevent frothy bloat
helps prevent ketosis in dairy cows
Reduces fecal shedding of M. paratuberculosis
prevents coccidiosis
Volatile fatty acids are?
Short chain fatty acids
Acetate - 2 carbon = 70-80%, energy, fatty acid synthesis
Propionate - 3 carbon = 20-30%, gluconeogenesis
Butyrate - 4 carbon = 10%, ketogenesis
Proportions depend on diets, higher fiber = higher acetate, vs higher concentrate = higher propionate