Synchronization Methods in Mares Sexual Synchronization in Mares

Synchronization Methods in Mares

Sexual Synchronization in Mares Aims of sexual synchronization in mares are: • Reducing the interval of transition from anestrus to breeding season • Reducing time needed for estrus detection • Decreasing mounting number pregnancy • Allowing use of valuable stallion semen to be used in more mares • Use in situations where mare urine is needed to produce e. CG • To delay estrus in racing or show mares • To reduce early embrionic deaths by leaving more time for involution during early post-partum.

Estrus Synchronization in Mares • • Photoperiod applications Hormone administrations; HCG: is known to enhance follicle development. Progesterone: In cyclic mares there are 2 general approaches 1)oral altrenogest (0. 044 mg/kg bodyweight) 10– 14 days. 2) progesterone and estradiol (P&E) i. m 10 days. In both applications - PGF 2α on the last day (5– 10 mg of dinoprost i. m). It was reported that these applications are successful even if done for a period of 7 -8 days.

Estrus Synchronization in Mares • Gn. RH Analogues: Usually to induce ovulation 1 ml Deslorelin i. m. is administered 48 hours before ovulation. • Oxytocin: Is used in different doses to suppress estrus.

Approaches in Anestrus and Transition Periods Ovarian functions can be stimulated by; • Light applications • Progestagens • PGF 2 a and analogues • HCG

In mares the length of light exposure affect seasonal cyclic functions initiation. • Artificial light applications should be started 810 weeks before breeding season. • Additional light can be applied gradually by 30 minute increases or directly by completing to 16 hours of exposure.

• Current studies show that it is more efficient to apply the daily supplementary artificial light split before and after natural light. • Light treatments help the ovarium function to start within 3060 days and ovulation in 60 -90 days. • For artificial light, at least 10 -12 candles of 100 -200 watt incandescent bulbs are sufficient for rooms of 13 -15 m 2.

• The response time to light applications can be shortened by the combination of a synthetic progesterone, Altrenogest (Allyl trenbolone, Regumate-Hoechst). • After 60 days of artificial light; 20 mg/day progestagen for 10 days, prostoglandin on the last day of progesterone administration and 10 days after this application 2500 IU HCG combination are recommended. • The ovulation occurs about 10 days after the application of Altrenogest. HCG application can also be helpful.

Approaches in Breeding Season As in cows, in cyclic mares, the luteal phase of the sexual cycle can be terminated by PGF 2 a or its analogues. Estrus can be suppressed by short-long term progestagen or by combining with a luteolytic hormone (PG) administration. Ovulation can be stimulated with HCG. 2000 -3300 IU HCG in a single dose can provide ovulation within 24 -48 hours. When 35 mm follicles are detected in ovaries, 2500 IU HCG injections (iv) may provide ovulation within 48 hours.

Use of Prostaglandins Cyclic mares respond to PG injections 5 days after ovulation. Prostaglandins are administered as two injections with 14 -18 day interval. 4 days after second PG injection, 60% of mares; 6 days after second PG injection 75 -80% of mares enter estrus phase. Ovulation occurs 7 -12 days after the second PG injection. By monitoring the synchronization, mating or insemination can be done Daily or once every other day; or insemination or a few matings may be recommended 4 -10 days after the last PG injection.

Estrus Synchronization in Mares Synchronization Method Number of Mares (n) Ones that display heat (n) Rate (%) Start of Heat Ovulation Mares inseminated (n) Pregnant (n) Pregnancy rate (%) PGF 2α twice with 14 day interval 10 6 60 24 -36 hours 5 th day 6 4 66. 7 PGF 2α twice with 14 day interval + HCG after 5 days 10 8 80 24 -36 hours 6. 5 day 8 6 75. 0 PGF 2α 20 th day after parturition 10 8 80 24 -36 hours 5 th day 8 7 87. 0

Use of Progestagens • Can be used as long term application (18 days) or short term application (8 days) combined with PG and short term progestagen + estradiol 17 beta + PG sombination. • Altrenogest, can be applied for 8 -12 days 27 -44 mg/day orally or in intravaginal sponge (0, 5 g) form. • Since the application is short term, possible CL is removed by PG injection on the last day.

• Most mares display estrus 2 -5 days after end of application and ovulate 8 -15 days after. To induce ovulation, a HCG injection may be done 5 -7 days after the applications. This injection causes induction of ovulation on the 4 th day.

Approaches in Early Post-Partum Period While some mares ovulate on the 6 th day postpartum, most mares do not exhibit a mature CL until the 18 th day after parturition. Even though foal heat is a frequently used method to impregnate in breeding, some researchers recommend delaying in order to allow time for involution and decrease early embrionic death rate. For this progesterone is indicated.

• Starting from the parturition day; 200 mg progesterone + 10 mg estradiol 117 beta is administered im for 5 days. With this application foal heat is delayed for 1 -10 days.

Control of Sexual Cycle in Carnivores