The reproductive hormones are produced from the pituitary gland at the base of hypothalamus once the heifer is mature at the age of 15-16 months the hypothalamus succeeds releasing factor, which is known as GnRH, of which synthetic version is available in the market by the name of Receptal. This one releasing factor releases FSH and LH both, when it is given 2.5 ml it works as LH for releasing the ova and when given 5 ml (double dose) it works as FSH.
At puberty the higher amount of GnRH is released so the pituitary gland secretes follicular stimulating hormones which goes to ovary and stimulate follicular development. Now at the peak of follicular development there is the sharp rise in the luteinizing hormone (LH), which in turn causes ovulation. At high temperature and nutritional deficiency ovulation does not take place and there is blood in the discharge. This is due to higher accumulation of estrogen in the follicle. The ovary may become cystic. The details of cystic ovary are given in the chapter of ovarian diseases.
There is a feedback inhibition of FSH an LH estrogen gives feedback to release of FSH and progesterone gives feedback to LH release. This has been in shown in the diagram, also on my YouTube channel.
There is one follicle is not developing there is a wave of follicular development and during the estrus cycle, the first wave lasts for 10 days, then the follicle become astatic. Second wave starts on 10th day onwards in this also several thousand follicle developed out of which only one ovulate. In multiple ovulation with FSH many ova’s can be shed and can be used in embryo transfer. In case of heifer, at the start of puberty there are so many luteal cycles in which there is no ovulation. So for practical purpose mating for conception mating should not carried out in first few heat cycles and after calving also.
For controlled breeding in place of LH for ovulation HCG (Human chorionic gonadotropin) which is available in the market by the name if Chorulon, but with the introduction of GnRH it is no longer in use, its use is prohibited because of two reasons. Previously MSD was supplying PMSG whch is sa sustiture for fsh the folligon PMSG is no longer supplied. However, Stimufol is supplied by Minitube.
- It is a foreign protein so it can cause the allergy reactions (anaphylactic reactions).
- Its long term use will meant production of antibodies thus it cannot be used repeatedly.
In place of follicular stimulating hormone, for induction of estrus PMSG (follegon) (pregnant mare serum) had been used. But now the GnRH is a substitute for it, so it is no longer used.
The cow and buffalo in breeding season comes in heat or estrus six or seven times whereas, the exotic cow exhibit heat for 15 times.
However, there is prostaglandin of which the synthetic form denoprost or cloprostenol is available in market if it is injected on the hip side on which the corpus luteum is present after seventh day of estrus the cow will come in estrus in 48 hours. Thus this prostaglandin invented in 1980’s from the prostate gland extract is very handy in following situations.
- Synchronisation of estrus
- Post-partum induction of ovulation
- Pseudo Pregnancy (retained corpus luteum)
- Macerated foetus.
- Mummified foetus.
- Inhibition of lactation
- In early lactation
- Treatment of Pyometra
- Treatment of Metritis
- Retention of placenta while calving
Caution: This prostaglandin should not be given to pregnant animal, and not to be injected accidentally in human, it can cause serious allergy, and can abort pregnant women, and it should be used only by veterinarians. If it is used in pregnant animals it can cause abortion.
GnRH (Gonadotropin Releasing Hormone)
It is also used in prolapse of vagina, from my experience I can tell that 2.5 ml of Receptal intramuscular on hips seems to work satisfactorily in prolapse of vagina. The logic behind this use is that in the pregnant animals there is the follicular activity the follicles, estrogens which in turn results in prolapse. I’ve been using it along with the Bioplex (MSD). In combination with the Receptal this Bioplex bolus is given then it got us the synergistic effect. The prolapse of uterus is a big problem, the veterinarian are requested to test it further and convey me with the feedback. Because this will be a great service to the cases of buffalo prolapse.