Theme 4:Introduction and NEB

AK

Lactation

Combined process of milk secretion and milk removal

mammals

Lactation gives a varieyt of evolutionary benefits to mammals

moisture

antimicrobials

nutrients

pormoting immune development (specieis specific)

promotinng endocrine development (species specific)

behaviuoral development (bonding)

hygienic process

Milk synthesis in the mammary epitahlial cells

raw materials are tranferred via the blood stream

proteins

• synthesized in the secretory cell → mammry epithelial cell

• from amino acids

lipids

• short chain fatty acids c4-c14 are syntheiszed in the cells

• from volatile fatty acids of rumen orien (dairy cow) (other psecies fermentation int he gut)

• longer fatty acids >c16 are preformed (orignate from diet or body fat)

lactose

• synthesized in the secretory cell

• from glucose or glucogenic precursors

• controls the volume of milk secreted

Milk compostion: variation among species

Why differences in milk composition across species

Genetic background

Nursing intervals

Growth rate infants

Developmental stage infants (associated with lactation stage)

• nutrient requirements infants

available nutrients for milk synthesis

• diet composition

• mobilisation of body reserves

Stages of lactation

1. mammogenesis: growth of the mamary gland

2. lactogenens: functional change of the mammary gland so that is can produce milk

   1. colostrogenesis (till birht)

   2. milk secretion (starts at birth)

3. galactopoiesis: maintenance of lactation

4. involution: cessation of laction

all stages are predominanlty controlled by the endocrine system

all stages are affected by management/environment

Galactopioesis: maintance of lactation

important factors

galactopietic hormones (prolactin, growth hormone)

removal of acuumated milk

removal of milk is key to continue lactation

by stimulation of blood flow

role for local mammary factors?

• veolii, nutritioon

role for prolactin in maintenance and function of mamamry epithelial cell

removal is needed, otherwise stoppng of production

lactation cycle of a dairy cow - traditional schematic overview

Lactation curve of a dairy cow

gradual involution

• stages not clearly separated (overlap)

Start of lactation is related with a lot of transitions

From pregnancy to lactation

• hormonal changes

• changes in fat, protein, carbohydrate and mineral metabolism

diet transitions

group and housing transitios

lack of adaptation to a new lactation is related with an increased risk for disease

Increase in milk production per cow per lactation during the last decades

Negative energy balance

Energy balance = energy intake - energy requirements

for lactating and pregnant cows

• enegy balance = energy intke - energy for maintenance - milk - prgnancy

negative enrgy balance = energy itnake < energy requirements

NEB = body weight loss

• 74% body fat

• 6% body protein

negative energy balance - example of how it looks like

Indicatos for energy balance

Body weight change

Body fat thickness (muscle thickness, sows)

Body codition score (BCS) (change in)

Efeed intake - E milk - E maintenance

plasma variables (non-esterfieid fatty acids)

disadvantages/limitations

• minitue to mminute variabtion (body weight change)

• assumptions for Emaintenance

• local measurements (BCSA, fat/muscle thickness)

• affected by diet composition (NEFA)

• between-person variability (BCS)

indirect calorimetry in climate respiration chambers as golden standard

climate respiratin chambers when:

want to control the climate

measure complete energy exchange or gas echange

relevant for experiments focusing on: e.g. heat stress, energy balance, methane emission

Negative energy balance - metabolizable energy intake

ME= GE - Efaeces, urine - E methance

Negative energy balance - energy in milk

Negative enrgy balance - overview

N

Negative enrgy balance - protein balance

Negative energy balance - fat balance

Why a NEB in early lactation

Dairy cattle: increase in milk production, increase in feed intake → cannot compromise

peripartum feed intaske depression

selectyion for milk yield = seleection for priority for the cow’s current calf

How does the cow organize the energetic priority for milk production

Genetic selection for milk production has decreased plasma insulin in early lactation

low insulin resulsts in lipolysis (body fat mobilization)

low insulin facilitates glucose uptake by the mammary galnd

insulin-independent glucose transporters in the mammary gland (GLUT1)

Why a NEB and health consequencesin early laction

1. Major adaptive changes occur around parturition

• hormonal: dry period - parturition - lactation

• nutritional: increase in demandL: glucose, amino acids and fatty acids

• environmental: housing, regrouping

2. selection on priority for lactation

• selection of animals for their current offspring (as a consequence of future offspring)

• selection for partitioning of nutrient (enegy) towards milk (as a consequence of body reserves

selection for milk yield is associated with metabolic load

yes, transition from pregnancy to lactation is associated with healthproblems 0 metabolic stress

Healht consequences of a NEB

Increase in metabolic disorders

• fatty liver

• ketosis

increase in infectious diseases

• mastitis

• laminitis

decrease in reproductive performance

increase in veterinary costs and reduced animal welfare

lack of adaptation

What could explain this relation between engative energy balance and metabolc disorders

energy metabolism of dairy cattle with energy balance = 0 orbelow

Energy metabolism in non-lactating dairy cows (EB=0)

Energy metabolism of dairy cows n a NEB (EB<0)

Health consequences of a NEB

ketosis

Health consequences of aNEB

Fatty liver

Health cnsequences of a NEB

infectious diseases

multifactorial origin

Laminitis associated with early lactation

High concentrate intake/low feed intake

-more fermentable carbohydrates/less fiber

saliva production and rumination time decrease

ruminal ph decrease (rumen acidosis)

rumen bacteria change, may even die

endotoxin release in the rumen, whic enters the bloodstream

vasodilation

damage to blood vessels in the hoof

Health consequenes of a NEB

Mastitis

start of lactation

• open teat canal

• intrammamry pressure (oedema) milk leakage

• loss of protective effect of preventice antibiotics and presence of environmental pathogens

reduced immune competence

ketosis

excess prouction (acetate, bhb, aceto-acetate) of ketone bodies in the liver

fatty liver

hepatic tri-acyl glyceride accumulation