Stages of postnatal growth and their hormones Flashcards
Factors affecting growth
Genotype:
- breed
- species
Non-genetic:
- Sex
- Weaning age
Factors affecting post-natal growth
Genetics
Nutrition
Sex
Hormones
Environment
Stages of Post-natal growth
1) Suckling
2) Puberty
3) Adulthood
4) Senescence
Survival of calf at neonatal (Suckling stage)
- expresion of appropriate behaviour of dam
- calf components - stand and suckle within 1-2 hours of birth (delays increase mortality)
- successful suckling depends on - vigor of the calf, teat seeking behaviour and udder or teat conformation
- dystocia, maternal death, poor udder and teat conformation, neonatal infections, dehydration
Weaning (suckling stage)
A major source of stress
- strategies to reduce stress = creep feeding and gradually decrease milk, separation dam and calf with fence but allow to nose-flaps for 1-2 weeks
Puberty
The time at which animals reach a level of sexual development that makes them capable of reproduction
Physiological event at puberty:
- Female - the first estrus with ovulation
- Male - the first ejaculate with fertile sperm
Neither are sexually mature at puberty if:
- Females are to small to bear young
- Males is not capable or fertile enough to breed regularly
Endocrine events associated with onset of puberty in a heifer
1) Decreased negative feedback
2) increased LH pulse frequency
3) Increased follicle growth
4) LH surge
5) Short luteal phase
Adulthood and Senescence
- Generally, we do not understand the naturally aging process in farm animals because once the “productive” life is complete, the animal is removed from the population
- breeding animals only
- peak production at adulthood
- weight and reproductive function decline in late maturity
- senescence is a process by which a cell ages and permanently stops diving but does not die
- IGF-1 and GH decline
Senescence
- the decrease in survival with increasing age
- reduction in muscle mass
- Increased time to repair injuries
- loss of organ functional units
- loss of reproductive capacity
- death
Hormones
- Produce by endocrine (ductles) glands and secrete into the bloodstream
- Hormones may affect a wide array of target cells to produce multiple effects
- Three types:
1) Amino acids-derived hormones (Tyrosine and typtophan derivatives)
2) Peptide hormones
3) Lipid derivatives or Lipid soluble hormones
Cell Signaling types
Endocrine signaling
Paracrine signaling
Autocrine Signaling
Endocrine Signalling
endocrine signalling uses the circulatory system to transport ligands
slower response but long lasting
Paracrine Signalling
A cell target nearby cell
For quick response
Ligand molecules quickly degrade or remove
Autocrine Signalling
Cell target itself
Cell division
Tissue and liver regeneration
Lipid Derived Hormone (Steroid Hormone)
1) steroid hormones enter through the cell membrane and bind to receptors inside of the target cell
2) these hormones may directly stimulate transcription of genes to make certain proteins
3) because steroids by works by triggering gene activity, the response is slower than peptide hormones
