LUTEOTROPIC HORMONE

1
LUTEOTROPIC HORMONE

• Proteinaeous gonadotropic hormone produced in
  the pars distalis of the anterior pituitary.
• From the hypothalamus there are two different
  releasing hormones produced that affect the
  release or non-release of LTH.
• These are PRH and PIH.

2
LTH CONTINUED

• Prolactin releasing hormone (PRH) from the
  hypothalamus stimulates a release of prolactin or
  LTH which acts on the corpus luteum to stimulate
  progesterone production and release.
• As LTH rises in the blood and hits its preset
  threshold, PIH or prolactin inhibiting hormone is
  released from the hypothalamus.

3
LTH CONTINUED

• PIH inhibits the release of LTH from the pars
  distalis and thus reduces the level of
  progesterone in the blood.
• Thus, in concert the two hormones from the
  hypothalamus moderate or keep the level of
  progesterone at a constant level in the blood by
  means of progesterone feeding back to the
  hypothalamus.

4
LTH CONTINUED

• As long as progesterone remains in the blood
  because of LH maintenance of the CL and LTH
  stimulation of the CL the levels of progesterone
  will be maintained at a constant level.
• As a side effect, LTH inhibits the release of
  GnRH by the hypothalamus. Remember, LTH high, no
  GnRH, no FSH, no cycle.

5
LTH CONTINUED

• LTH is also known as prolactin. This terminology
  is due to the fact that prolactin is responsible
  for the alveolar cells of the mammary gland
  producing milk in mammals and stimulating the
  crop sac in birds.
• However, after parturition there is no CL on the
  ovary and thus no progesterone is produced.

6
LTH CONTINUED

• An alternative control of prolactin is in place
  for the non-pregnant lactating female.
• Prolactin is released as long as the mammary
  gland is empty or only partially full. When the
  udder is full then PIH is released and prolactin
  declines. It stays low until the udder has some
  release of milk.

7
LTH CONTINUED

• In most mammalian species, the young when first
  born suckle often thus keeping the udder only
  partially full. Thus, LTH is always high in the
  blood to manufacture more milk. REMEMBER.
• This causes what is termed postpartum anestus
  which will last until the young is weaned or
  becomes mature enough to gain nourishment from
  outside sources.

8
APPLICATION

• Objective is to have females pregnant as quickly
  as possible.
• Hormones are against this objective.
• Manage against these hormones without hurting the
  young on the ground.

9
APPLICATION

• Early weaning
• 48 hour calf removal
• Synchromate B treatment-Norgestamid for 9 days as
  an implant. One time injection of norgestamid
  plus estradiol valerate at time of implant.
  Remove implant.
• Shang treatment- Synchromate B plus 48 hour calf
  removal.

10
APPLICATION

• Swine do not cycle until their piglets are weaned
  at 3 to 8 weeks of age.
• Beef cattle do not cycle until 45 to 65 days
  postpartum depending on parity. This may be even
  longer in case of low energy in the diet.
• Dairy cattle have shorter ppi due to 2X or 3X a
  day milkings.