***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Two experiments examined pregnancy after synchronized ovulation ( Ovsynch ) with or without progesterone ( P4 ) administered via controlled internal drug release ( CIDR ) intravaginal inserts . In experiment 1 , 262 lactating cows in one herd were in 3 treatments : Ovsynch ( n = 91 ) , Ovsynch + CIDR ( n = 91 ) , and control ( n = 80 ) . The Ovsynch protocol included injections of GnRH 7 d before and 48 h after an injection of PGF20 . Timed artificial insemination  ( TAI ; 57 to 77 d postpartum ) was 16 to 20 h after the second GnRH injection . Cows in the Ovsynch + CIDR group also received a CIDR ( 1.9 g of P4 ) insert for 7 d starting at first GnRH injection . Control cows received A-I when estrus was detected using an electronic estrus detection system . Based on serum P4 , 44.1 % of cows were cyclic before Ovsynch . Pregnancy rates at 29 d ( 59.3 vs. 36.3 % ) and 57 d ( 45.1 vs. 19.8 % ) after TAI and embryo survival ( 75.9 vs. 54.5 % ) from 29 to 57 d were greater for Ovsynch + CIDR than for Ovsynch alone . In experiment 2 , 630 cows in 2 herds received TAI at 59 to 79 d postpartum after 6 treatments . Estrous cycles were either presynchronized ( 2 injections of PGF2alpha 14 d apart ; n = 318 ) or not presynchronized ( n = 312 ) . Within those groups , Ovsynch was initiated 12 d after second presynchronization PGF2alpha , and used alone ( n = 318 ) or with CIDR inserts for 7 d ( 1.38 g of P4/insert , n = 124 or 1.9 g of P4/insert , n = 188 ) . Before Ovsynch , 80 % of cows were cyclic . Presynchronization increased pregnancy ( 46.8 vs. 37.5 % ) at 29 d after TAI , but CIDR inserts had no effect on pregnancy in experiment 2 . Overall embryonic survival between 29 and 57 d in experiment 2 was 57.7 % . Use of CIDR inserts with Ovsynch improved conception and embryo survival in experiment 1 but not in experiment 2 , in part due to differing proportions of cyclic cows at the outset . Presynchronization before Ovsynch enhanced pregnancy rate The objective was to determine the effect of exogenous progesterone ( P4 ) in a timed artificial insemination ( TAI ) protocol initiated at 2 different times post-AI on pregnancies per AI ( P/AI ) in lactating dairy cows . Cows ( n=1,982 ) in 5 dairy herds were assigned r and omly at a nonpregnancy diagnosis 32 ± 3 d post-AI to 1 of 4 resynchronization ( RES ) treatments arranged in a 2 × 2 factorial design using the Ovsynch-56 ( GnRH , 7d later PGF2α , 56 h later GnRH , 16 h later TAI ) protocol . Treatments were as follows : cows initiating RES 32 ± 3 d after AI with no supplemental P4 ( d 32 RES-CON ; n=516 ) ; same as d 32 RES-CON plus a controlled internal drug release ( CIDR ) insert containing P4 at the onset of Ovsynch-56 ( d 32 RES-CIDR ; n=503 ) ; cows initiating RES 39 ± 3 d after AI ( d 39 RES-CON ; n=494 ) ; and same as d 39 RES-CON plus a CIDR ( d 39 RES-CIDR ; n=491 ) . Cows were inseminated if observed in estrus before TAI . The P/AI was determined 32 and 60 d after TAI . In a subgroup of cows ( n=1,152 ) , blood sample s were collected and ovarian structures examined by ultrasonography on the days of the first GnRH ( G1 ) and PGF2α of Ovsynch-56 . Percentage of cows with a corpus luteum ( CL ) at G1 was unaffected by timing of treatments , but percentage of cows with a CL at PGF2α was greater for d 32 than for d 39 cows ( 87.9 vs. 79.4 % ) . In addition , percentage of cows with P4 ≥ 1 ng/mL at G1 was unaffected by timing of treatments , but was increased for d 32 compared with d 39 RES cows on the day of the PGF2α of the RES protocol s ( 86.5 vs. 74.3 % ) . Treatment did not affect ovulation to G1 or P/AI 32 d after RES TAI ( d 32 RES-CON=30.1 % , d 32 RES-CIDR=28.8 % , d 39 RES-CON=27.5 % , d 39 RES-CIDR=30.5 % ) . A greater percentage of d 39 RES cows underwent premature luteolysis during the RES protocol compared with d 32 RES cows . An interaction was detected between day of RES initiation and CIDR treatment , in which the CIDR  increased P/AI 60 d after TAI for d 39 ( CON=23.7 % vs. CIDR=28.0 % ) , but not for d 32 ( CON=26.9 % and CIDR=24.2 % ) cows . Pregnancy loss was unaffected by treatment . In addition , cows had improved P/AI 60 d after TAI when they received a CIDR and did not have a CL ( CON-CL=28.2 % , CON-No CL=19.2 % , CIDR-CL=27.0 % , and CIDR-No CL=26.5 % ) or had P4 < 1 ng/mL ( CON-High P4=27.8 % , CON-Low P4=15.0 % , CIDR-High P4=25.0 % , and CIDR-Low P4=29.4 % ) at G1 , but not if a CL was present or P4 was ≥ 1 ng/mL at G1 . In conclusion , addition of a CIDR insert to supplement P4 during the RES protocol increased P/AI for cows initiating RES 39 ± 3 d after AI but not 32 ± 3 d after AI This study evaluated a novel presynchronization method , using Ovsynch prior to the Ovsynch-timed AI protocol ( Double-Ovsynch ) compared to Presynch-Ovsynch .  Lactating Holstein ( n=337 ) cows , were assigned to two treatment groups : ( 1 ) Presynch ( n=180 ) , two injections of PGF 14 d apart , followed by the Ovsynch-timed AI protocol 12 d later ; ( 2 ) Double-Ovsynch ( n=157 ) , received GnRH , PGF 7 d later , and GnRH 3 d later , followed by the Ovsynch-timed AI protocol 7 d later . All cows received the same Ovsynch-timed AI protocol : GnRH ( G1 ) at 68+/-3 DIM ( mean+/-SEM ) , PGF 7 d later , GnRH ( G2 ) 56h after PGF , and AI 16 to 20h later . Pregnancy was diagnosed 39 - 45 d after timed AI . Double-Ovsynch increased the pregnancies per AI ( P/AI ) compared to Presynch-Ovsynch ( 49.7 % vs 41.7 % , P=0.03 ) . Surprisingly , Double-Ovsynch increased P/AI only in primiparous ( 65.2 % vs 45.2 % ; P=0.02 ) and not multiparous ( 37.5 % vs 39.3 % ) cows . In a subset of 87 cows , ovarian ultrasonography and progesterone ( P4 ) measurements were performed at G1 and 7 d later . Double-Ovsynch decreased the percentage of cows with low P4 ( < 1ng/mL ) at G1 ( 9.4 % vs 33.3 % ) and increased the percentage of cows with high P4 ( > or = 3ng/mL ) at PGF ( 78.1 % vs 52.3 % ) . Thus , presynchronization of cows with Double-Ovsynch increased  fertility in primiparous cows compared to a st and ard Presynch protocol , perhaps due to induction of ovulation in non-cycling cows and improved synchronization of cycling cows . Future studies are needed , with a larger number of cows , to further test the hypothesis of higher fertility with Double-Ovsynch , and to eluci date the physiological mechanisms that underlie apparent changes in fertility with this protocol Lactating Holstein cows ( n = 711 ) on a commercial dairy farm in Wisconsin received a hormonal synchronization protocol to initiate first timed artificial insemination ( TAI ) on the following postpartum schedule : two injections of 25 mg PGF2alpha at 32 + /- 3 d and 46 + /- 3 d ( Presynch ) ; 100 microg GnRH at 60 + /- 3 d ; 25 mg PGF2alpha at 67 + /- 3 d ; and 100 microg GnRH + TAI at 69 + /- 3 d ( Ovsynch ) . At first TAI , cows were r and omly assigned to initiate the first GnRH injection of a hormonal protocol for resynchronization of ovulation ( Resynch ; 100 microg GnRH , d 0 , 25 mg PGF2alpha , d 7 , 100 microg GnRH + TAI , d 9 ) at 19 ( D19 ) , 26 ( D26 ) , or 33 d ( D33 ) after first TAI to set up a second TAI service for cows failing to conceive to Ovsynch . Overall pregnancy rate per artificial insemination ( PR/AI ) to Ovsynch assessed 68 d after TAI was 31 % and did not differ among treatment groups . For Resynch , PR/AI was assessed 26 d after TAI for D19 and D26 cows and 33 d after TAI for D33 cows . Overall PR/AI to Resynch was 32 % . However , the PR/AI for D26 ( 34 % ) and D33 ( 38 % ) cows to Resynch was greater than for D19 cows ( 23 % ) . Cows with a CL at the PGF2alpha injection ( D19 cows ) or at the first GnRH injection ( D26 + D33 cows ) of Resynch exhibited greater PR/AI to Resynch compared with cows without a CL . Survival analysis ( failure time ) of cows in the D26 and D33 treatment groups across the first three TAI services did not differ statistically . Although administration of GnRH to pregnant cows 19 d after first TAI service did not appear to induce iatrogenic embryonic loss , initiation of Resynch 19 d after first TAI service result ed in a lower PR/AI compared with initiation of Resynch 26 or 33 d after first TAI service Objectives were to determine the effect of progesterone ( P4 ) concentration on fertility of lactating dairy cows induced to ovulate follicles of the first follicular wave . Lactating dairy cows ( n=989 ) at 38±3d postpartum were balanced by parity and body condition score and r and omly assigned to 3 treatments : first follicular wave ( FFW ) , first follicular wave with exogenous P4 ( FFWP ) , or second follicular wave ( SFW ) . All cows had their estrous cycle presynchronized with 2 injections of prostagl and in ( PG ) F(2α ) given 14 d apart . Cows in the FFW and FFWP treatments started the ovulation synchronization protocol 3 d after the last PGF(2α ) of the presynchronization protocol , whereas SFW cows received a GnRH injection ( 100 μg of gonadorelin diacetate ; Cystorelin , Merial Ltd. , Duluth , GA ) 3 d after the last PGF(2α ) of the presynchronization protocol and started the synchronization protocol 7 d later . The synchronization protocol consisted of GnRH on d -10 , PGF(2α ) on d -3 , and GnRH concurrent with timed artificial insemination ( AI ) on d 0 . Cows in the FFWP treatment received 2 controlled internal drug release inserts containing 1.38 g of P4 from d -8 to -3 . Progesterone concentration was determined on d -10 , -8 , -6 , -3 , and 0 from all cows and at 7 , 14 , and 21 d after AI from a sub sample of cows ( n=170 ) . Cows ( n=715 ) had their ovaries scanned by ultrasound on d -10 , -3 , and 7 d. Pregnancy was diagnosed at 38 and 
    Output:
    
Service number and presynchronization did not influence the effect of progesterone supplementation on fertility .
In summary , progesterone supplementation using a single intravaginal insert during the timed AI program increased P/AI mostly in cows without CL and reduced the risk of pregnancy loss in lactating dairy cows .
Insemination of cows in estrus during the synchronization protocol eliminated the benefit of supplemental progesterone on P/AI