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7/27/2019 Partus & Lactation
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Metabolic load
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Sudden metabolic load placed on mother as
compared to providing nutrients to fetuses
Tend to focus on the mammary gland
Lactation requires the integrated and
orchestrated activities of most of the organs
and tissues in the body.
Recall that the mammary gland evolved
after all the endocrine organs haddeveloped.
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Metabolic adaptations associated with
onset of lactation
Milk synthesis
-increased used of nutrients
mammary gland
- energy budget 2-3X in some species,larger than any other time in life cycle.
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Metabolic adaptations associated with
onset of lactation (cont.)
Intake and digestion
-increased food and water consumption
-hypertrophy of digestive tract
-increased capacity for nutrient absorption
central nervous system most important,
but other factors will be listed-all segments of digestive tract
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Metabolic adaptations associated with
onset of lactation (cont.)
Lipid metabolism
-Increased lipolysis
-decreased lipogenesis
adipose tissue
- major difference among species
- seals stay on land, eat nothing
- body fat stores massively mobilized
- litter bearers rats, mice
- food intake about 300%
- woman + 25% max.
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Metabolic adaptations associated
with onset of lactation (cont.)
Glucose metabolism
-increased gluconeogenesis, increasedglycogenolysis
liverenlarges in some species and health ofthis organ is vital to whole animal heath status.
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Metabolic adaptations associated
with onset of lactation (cont.)
Protein metabolism
-mobilization of protein reserves
muscle and other body tissues
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Metabolic adaptations associated
with onset of lactation (cont.)
Mineral metabolism
-increased absorption and mobilization of
reserves- Ca, P, Mg
gut, bone, kidney, liver
- downer cow syndrome, milk fever, muscleweakness
- hormonal control- PTH, CT, E2
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Metabolic adaptations associated
with onset of lactation (cont.)
Water metabolism
-increased absorption and expansion of
plasma volume
gut, kidney, central nervous system
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Appetite Regulation
1. Palatability - important primaryconstraint
2. Physical capacity - distension of rumen or
stomach
3. Chemical signals - blood glucose levels
- fatty acids (NEFA in bloodstream)
- rumen function- intake during mobilization
obesity - NEFA
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4. Hormonal Signals
- insulin
- cholecystokinin satiety signals
- gastrin
- opiates -- stimulate feeding
- endorphins
Appetite Regulation (cont.)
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A previous world record cow >19 gal/day
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Important factors on milk yield
1. Genetics- species and breed differences.
2. Nutrition- nutrient availability.
Diet formulation- milk composition
3. Age- growth requirements limit nutrients
for milk production in 1st or 2nd parity vs.
older mature animal.
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4. Pregnancy- nutrition of fetus in latepregnancy milk yield due to energy demand.Also pregnancy hormones have an effect onappetite.
5. Environment- cold & heat stress- watermetabolism, maintenance requirements (fig.)
6. Disease- ketosis- incomplete oxidation of fattyacids when glucose is lacking.
--mastitis- inflammation reducesmammary secretion.
Important factors on milk yield-2
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Lactation delays reproduction
Effects of negative energy balance during high milkyield- inhibits reproduction- expect poorest
reproduction in highest producing females. TABLE
NEB (undernutr i tion in ear ly lactation) suppresses LH
pulse generator resulting in delay of ovarian
cycles. FIGURE
Mobilization of body reserves is related to delayed
ovarian activity. How does LH neuroendocrinesystem monitor body composition? LEPTIN??
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Milk Yield Kg Conception Rate %
8640 38.5
Spring and Fall 39.0Summer 55.0
Winter 17.0
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High milk production
Negative energy balance-
Mobilization of body reserves
LH pulses
Delay of ovarian cyclesLower fertility due
to fewer cycles
Lactation and reproduction
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Lactation delays reproduction
Effects of negative energy balance during high milkyield- inhibits reproduction- expect poorest
reproduction in highest producing females.TABLE
NEB (undernutr i tion in ear ly lactation) suppresses LH
pulse generator resulting in delay of ovarian
cycles. FIGURE
Mobilization of body reserves is related to delayed
ovarian activity. How does LH neuroendocrinesystem monitor body composition? LEPTIN??
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Lactation delays reproduction-2
Energy costs of lactation-- low glucoseand insulin?
Effects ofsuckling stimulus- overlapping
effects on the ovarian control system- LHsecretion is depressed.
Most important mechanism may be
opiate inhibition of LH.
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Suckling PRL via opiate pathway(endorphins)
LH prolonged interval to ovulation Lactational anovulation leads into seasonal
anestrous in some species.
Overall combination of energy andmetabolic demands coupled with sucklingresults in reduced reproductive capability.
Lactation delays reproduction-3
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Darwin, 1859 and 1868
hard living retards the period at
which animals conceive amount of food affects the fertility
it is difficult to fatten a cow that is
lactating
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