SYNCHRONIZATION OF ESTRUS IN FARM ANIMALS

BY-

1. L.Kipjen Singh^a* and K. Merina Devi^b

^a Animal Reproduction Gynaecology and Obstetrics Division, ICAR-National Dairy Research Institute, Karnal-132001,

^b Department of Livestock Farm Complex, COVSc & A.H.,CAU, Jalukie, Nagaland-797110,

*Corresponding author:laishramkipjen04@gmail.com

What is synchronization of estrus?

Synchronization of estrus implies the manipulation of the estrous cycle or induction of estrus to bring all females into estrus at a predetermined time with a reasonable accuracy.

Approaches or methods of estrus synchronization

Hormonal method

• Extending the luteal phase (using exogenous progesterone)
• Shortening the luteal phase (using prostaglandin and its analogs)

Non-hormonal method

• Male effect
• Artificial lighting
• Weaning

Advantages of estrus synchronization

• Allows fixing of breeding time within a short predefined period
• Can schedule the parturition time at the most favorable season
• Produces more uniformity of calves at weaning.
• Enables wider use of artificial insemination or through natural selection of superior sires.
• Reduced time and workload for heat detection
• Provides more economic returns by improving animal production efficiency
• Silent estrus and anestrous are handled effectively

Disadvantage of estrus synchronization

• Expensive of drug and labor under field conditions
• Difficulties in small animal holders
• Prostaglandins only act in cyclic animals

Synchronization of estrus in cattle:

Two shot prostaglandin

• Prostaglandin acts as a luteolytic agent (regression of corpus luteum in cyclic animals). It is classified as natural and synthetic prostaglandin.

*Estrus rate: 80% in non-descript and 100% in crossbred cows

Progesterone treatment

• Progesterone exerts negative feedback on LH (Luteinizing hormone) secretion after the regression of corpus luteum. Administration of progesterone can be done through a vaginal sponge i.e., CIDR (Controlled internal drug release) and PRID (Progesterone releasing intra-vaginal device).

*Synchronization rate~ 30% and pregnancy rate~20% in anestrous and cyclic females

Ovsynch Protocol (GPG Protocol)

• Gonadotropin-releasing hormone (GnRH) affects follicular growth by causing either ovulation or luteinization of the largest follicle and prevents estrus until after the prostaglandin injection, which causes the corpus luteum or luteinized follicle to regress.

*Synchronizes the estrous cycles of 70-80% cyclic cows

GnRH– PG System (Select-synch)

Synchronization of estrus in sheep and Goats:

Two shot prostaglandin

*Estrus behavior in goats: 95-100%, Estrus response in sheep: 100%

Progestogen and eCG combination

Sheep

Goat

The male effect

• The introduction of male animals to isolated anoestrus female animals during breeding and non-breeding season at least for three weeks leads to luteolysis and ovulation (Ram effect in sheep and Buck effect in goat). The physiological basis for this response is due to its smell and sight. The female animals showed estrus within 72-144 hrs.

Artificial Lighting

• Alteration of day length by artificial lighting i.e., 8hrs light followed by 16 hrs of darkness can increase the breeding efficiency of sheep.

Melatonin

• Subcutaneous implants of melatonin (18mg) for 30-40 days in seasonally anoestrus sheep during early or transition period will return to normal cyclicity in ewes.

Synchronization of estrus in horse:

Prostaglandin

• A single injection of prostaglandin (natural-10mg, synthetic-250 mcg) i/m during the diestrous in mares will exhibit estrus at 3-5 days.

Progesterone

• Feeding of altrenogest (0.44mg/kg/day) for 15 days in mare will exhibit estrus at about 3 days after altrenogest withdrawal.

Synchronization of estrus in swine:

Prostaglandin

• Prostaglandin is not effective for synchronizing estrus as corpus luteum does not respond first 12-13 days of the estrus cycle.

Weaning of piglets

Removal of litters from sows at the same time will induce estrus in pigs.

Progesterone

• Feeding of altrenogest (15-20mg/day) for 14-20 days in swine will induce estrus at about 4-7 days.

Reference

Hafez, E.S.E. and Hafez, B. eds., 2013. Reproduction in farm animals. John Wiley & Sons.