Pregnancy per AI differences between primiparous and multiparous high-yield dairy cows after using Double Ovsynch or G6G synchronization protocols

Selective use of a modified pre-synchronization-Ovsynch and resynchronization reproductive strategy in dairy herds: A field application study

We aimed to evaluate whether a modified pre-synchronization-Ovsynch (MPO) and resynchronization method, adjusted for the timing of biweekly reproductive consulting visits, could be implemented successfully under field conditions in dairy herds. Forty-five days after calving (calving: Day 0), 1,182 cows were assigned randomly to Ovsynch, MPO or control groups. (1) Cows were administered GnRH on Day 65, PGF_2α on Day 72 and GnRH 56 hr later, followed by timed artificial insemination (TAI) 16 hr later (Ovsynch, n = 380). (2) Cows with a CL were administered PGF_2α (n = 204) and cows without were administered GnRH (n = 199) on Day 45. Then, each cow was administered PGF_2α on Day 55 (9 to 12 days later), GnRH on Day 58 and underwent Ovsynch 7 days later (selective MPO [sMPO] n = 403). (3) The remaining cows underwent AI when oestrus was detected (EDAI, n = 399). The probabilities of pregnancy per AI 30 and 45 days after the first AI were higher in the sMPO group (odds ratios 1.99 and 1.92, p < .0001) than in the EDAI group. In addition, the probability of pregnancy by 105 days postpartum tended to be higher (p < .1) in the sMPO group than in the EDAI and Ovsynch groups, which shortened the mean interval from calving to pregnancy in the sMPO group (3.4 and 4.2 days, respectively) than in the EDAI and Ovsynch groups. In the sMPO group, the interval between the first and second treatments during pre-synchronization did not affect the probability of pregnancy per AI after the first AI. The probability of pregnancy per AI after the second AI did not differ between the Ovsynch, sMPO and EDAI groups. In conclusion, the sMPO programme, adjusted for the timing of biweekly reproductive consulting visits, followed by resynchronization, could be successfully adopted in field conditions, and is associated with good reproductive performance in dairy herds.

Treatment of cows that fail to respond to pre-synchronization treatments with a CIDR-Ovsynch regimen improves the overall pregnancy percentage after a double Ovsynch treatment regimen

In this study, there was evaluation of pregnancy per AI (P/AI) as a result of the first postpartum AI following four ovulation-synchronization treatments. Treatment regimens were Ovsynch-56 (OVS, n = 875; GnRH1-7d-PGF_2α-56h-GnRH2-16h-FTAI), CIDR-OVS (n = 1001; OVS plus CIDR inserts between GnRH1 and PGF_2α), Double-Ovsynch (DOVS, n = 663; imposing Pre-OVS followed by breeding-OVS 7 days later), and Modified-DOVS (M-DOVS, n = 1397; imposing Pre-OVS followed either by breeding-OVS or CIDR-OVS based upon the ovarian structure at GnRH1). Cows with a corpus luteum were assigned to a breeding-OVS treatment regimen and those that did not have a corpus luteum were assigned to the CIDR-OVS treatment regimen. Compared with OVS, the P/AI of the cows in the M-DOVS (OR = 1.5, P = 0.001) and CIDR-OVS (OR = 1.4, P = 0.017) was greater at day 30. At day 70, only in the M-DOVS group was there a greater P/AI compared with the OVS group (OR = 1.7, P < 0.001). Pregnancy loss between days 30 and 70 was greater in cows of the CIDR-OVS (OR = 1.9, P = 0.014) compared with those of the OVS group. In cows of the M-DOVS, the dominant ovarian structures (follicle, corpus luteum or cyst) at different time-points of the pre-synchronization period and occurrence of estrus at the end of this period were not associated with P/AI at day 30 post-AI. In conclusion, imposing CIDR-OVS in cows that did not respond to pre-synchronization treatments, resulted in an enhanced pregnancy percentage with the use of the DOVS.

Effect of two prostaglandin injections on days 5 and 6 in a timed AI protocol after estrus expression on pregnancy outcomes in dairy cows during cold or hot seasons of the year

The objective of this study was to test whether prostaglandin (PG) injection on day 30 postpartum (pp) and detection of estrus can affect the efficacy of injecting PG on days 5 and 6 in the timed artificial insemination (TAI) protocol on pregnancy rate in a large dairy herd in hot or cold seasons. Out of 2235 cows, 1998 received an injection of PG at 30±3 d pp and estrus was observed. Cows that displayed estrus during the estrous observation period after PG injection were classified as estrus (E), while those that did not show estrus were classified as nonestrus (NE). Cows in each group were assigned to two treatments: CO-72 (control treatment) (ECO-72 and NECO-72) (day 44 GnRH, day 51 PGF2α, day 54 GnRH+TAI) or PG–PG (EPG–PG and NEPG–PG) (day 44 GnRH, day 49 PGF2α, day 50 PGF2α, day 52 GnRH+TAI). Pregnancy was diagnosed on days 33 and 47 after artificial insemination (AI). The proportion of cows in estrus on the day of TAI was higher (P≤0.05) for cows that received two PG than for cows that received one PG. Pregnancies per AI (P/AI) on days 33 and 47 for cows inseminated during and after a voluntary waiting period in the NEPG–PG treatment had higher rates than for cows in the EPG–PG, ECO-72 and NECO-72 treatments. Moreover, P/AI were significantly (P≤0.05) affected by parity. Primiparous had higher P/AI (37.0 %) than multiparous cows (31.6 %). Cows inseminated in cold months had higher P/AI and reduced PL (35.6 % and 20.8 %) than cows inseminated in hot months (29.1 % and 30.6 %, respectively). In conclusion, treatments with PG on days 5 and 6 after the first GnRH injection increased P/AI. Estrus detection before the beginning of TAI protocol did not affect fertility. To maximize P/AI cows exhibiting heat at any time during the synchronization protocol should be inseminated.

A simple and practical short-term timed artificial insemination protocol using estradiol benzoate with prostaglandin F2α in lactating dairy cows

To minimize costs and labor for short-term ovulation synchronization protocol, we developed one wherein each treatment-drug administration and timed artificial insemination (TAI)-was performed 24 h apart. The objective of the present study was to evaluate this short-term ovulation synchronization protocol in lactating dairy cows. Data were derived from 133 inseminations performed in 120 cows (32 primiparous and 88 multiparous), and the ovaries of these cows were scanned using ultrasound. The cows detected to have a functional corpus luteum (CL) received prostaglandin F2α (PGF) as a luteolytic agent. The cows were randomly assigned to two treatment groups: (1) treatment with estradiol benzoate (EB) 24 h after PGF treatment, and TAI 24-28 h after EB treatment (EB group); and (2) treatment with gonadotropin-releasing hormone agonist (GnRH) 56 h after PGF treatment, and TAI 16-20 h after GnRH treatment (GnRH group). As a luteolytic agent, either dinoprost (DP; 25 mg) or D-cloprostenol (DCLP; 0.15 mg) was administered intramuscularly in each treatment group. Pregnancy per AI (P/AI) was significantly higher in the DP- or DCLP-treated cows in the EB group when compared with their counterparts in the GnRH group (64.5% vs. 33.3%, P = 0.03 in the DP-treated cows and 51.1% vs. 27.3%, P = 0.04 in the DCLP-treated cows, respectively). Regarding parity, multiparous cows had greater P/AI in the EB group than in the GnRH group (52.8% vs. 26.7%, P = 0.01), whereas primiparous cows showed no significant intergroup difference (65.2% vs. 41.7%, P = 0.28). To conclude, the use of a convenient synchronization protocol comprising the administration of PGF and EB 24 h apart, rather than PGF and GnRH 56 h apart, has greater potential to improve pregnancy rates after TAI in lactating dairy cows given that a functional CL was accurately detected. This beneficial effect of the protocol using EB was clearly demonstrated in multiparous cows.

Effect of presynchronization prior to Ovsynch on ovulatory response to first GnRH, ovulatory follicle diameter and pregnancy per AI in multiparous Holstein cows during summer in Iran

The aim was to evaluate the effect of presynchronization with GnRH and PGF2α prior to Ovsynch on ovulatory response to first GnRH, diameter of largest follicle at TAI and pregnancy per AI (P/AI) in multiparous dairy cows during summer. Cows (n=1069) were randomly assigned to one of three timed-AI (TAI) protocols. The TAI protocols were: 1) Ovsynch (O; n=425), GnRH- 7d-PGF2α-56h-GnRH-16h-TAI), 2) double-Ovsynch (DO; n=302), GnRH-7d-PGF2α-3d-GnRH and Ovsynch was initiated 7 days later, and 3) G7G-Ovsynch (G7G; n=342), PGF2α-2d-GnRH and Ovsynch was initiated 7 days later. Ovarian examinations were performed by transrectal ultrasonography during Ovsynch to determine ovulatory response to first GnRH and diameter of largest follicle at TAI. Presynchronization increased ovulatory response after first GnRH of Ovsynch (P=0.001), which was greater in DO (74.0%) and G7G (76.0%) groups compared to O group (50.0%). Means (±SEM) diameter (mm) of largest follicle at TAI was smaller in cows presynchronized before Ovsynch (DO and G7G, overall 15.7±0.3) compared to that in cows subjected to a standard Ovsynch without presynchronization (18.5±0.42). P/AI at 32 d after Al was greater (P=0.001) in G7G (32.7%) and DO (31.1%) groups compared to Ovsynch (19.7%) group. Presynchronization prior to Ovsynch also affected P/AI at 60 and 150 d after AI (P<0.05). In conclusion, DO and G7G protocols resulted in greater ovulatory response to first GnRH, smaller ovulatory follicles and greater P/AI compared to a standard Ovsynch protocol. Therefore, TAI protocols that include a presynchronization with GnRH and PGF2α prior to Ovsynch should be used in multiparous cows during summer to achieve acceptable reproductive performance.

The effect of presynchronization with prostaglandin F2α and gonadotropin-releasing hormone simultaneously, 7 d before Ovsynch, compared with Presynch-10/Ovsynch on luteal function and first-service pregnancies per artificial insemination

Pregnancy per artificial insemination (P/AI) following Ovsynch is optimized when cows ovulate to the first GnRH of Ovsynch. Fertility programs are designed to presynchronize cows to d 6 or 7 of the estrous cycle to increase the chances of ovulation of a first-wave dominant follicle to the first GnRH of Ovsynch. The hypothesis of this experiment was that simplification of a presynchronization program through the combination of PGF_2α and GnRH on the same day, 7 d before Ovsynch, would allow for similar P/AI compared with Presynch-10. Lactating dairy cows (n = 432) 41 to 47 d in milk (DIM) were randomly assigned to 2 treatments within parities for first service. Control cows received Presynch-10/Ovsynch consisting of the following: PGF_2α-14 d-PGF_2α-10 d-GnRH-7 d-PGF_2α-56 h-GnRH-16 h-AI. Treated cows received PGF_2α and GnRH-7 d-GnRH-7 d-PGF_2α-56 h-GnRH-16 h-AI. All cows received a supplemental injection of PGF_2α 24 h after the PGF_2α of Ovsynch to enhance complete luteolysis. All cows received timed AI between 75 and 81 DIM. Blood was collected to assess circulating concentrations of progesterone (P4), and the number and size of corpora lutea (CL) were recorded using ultrasonography on day of PGF_2α of Ovsynch. The administration of PGF_2α simultaneously with GnRH and 7 d before Ovsynch (PG+G) had similar P/AI at 28 (46 vs. 48%), 35 (43 vs. 43%), 49 (39 vs. 39%), and 77 d post-AI (38 vs. 39%) compared with Presynch-10. No differences were observed in P/AI in primiparous versus multiparous cows at 28 (52 vs. 45%), 35 (48 vs. 41%), 49 (45 vs. 37%), and 77 d post-AI (43 vs. 36%). No difference existed between treatments in percentage of cows with functional CL at PGF_2α of Ovsynch, total luteal area (mm²), or serum concentrations of P4 at time of PGF_2α of Ovsynch, regardless of parity. Number of CL had a tendency to be greater for multiparous PG+G vs. Presynch-10 cows (2.34 ± 0.09 vs. 2.15 ± 0.08) but not in primiparous cows (1.95 ± 0.10 vs. 1.98 ± 0.11). In summary, administering both PGF_2α and GnRH on the same day, 7 d before the start of Ovsynch, appears to be a simple and effective alternative to Presynch-10 Ovsynch.

Early postpartum administration of equine chorionic gonadotropin to dairy cows calved during the hot season: Effects on fertility after first artificial insemination

Heat stress reduces fertility of high-producing dairy cows, and early administration of equine chorionic gonadotropin (eCG) may improve it. Here, 401 heat-stressed, high-producing dairy cows on a single commercial farm were given eCG (500 UI, n = 214) or saline (n = 187) on days 11-17 after calving, and the effects on fertility after the first artificial insemination (AI) were assessed. On post-partum day 96.34 ± 9.88, all cows were inseminated after a "double short Cosynch" synchronization protocol. Ovarian activity and uterine status were checked by ultrasound on the day of eCG administration and every 7 days thereafter for a total of 3 weeks; checks were also performed during synchronization, and 7 days after AI. On post-partum day 30, cytobrush uterine cytology was performed to check for subclinical endometritis. Pregnancy status was checked on days 30 and 60 after AI. The eCG and control groups did not differ significantly in terms of average lactations per cow (2.33 ± 1.34), days in milk at first AI (96.33 ± 9.88), average milk yield at AI (41.38 ± 7.74 L), or the particular inseminator or bull used for AI. The eCG and control groups showed increasing ovarian activity with time, with approximately 75% of cows in both groups showing a corpus luteum at the beginning of the synchronization protocol. On post-partum day 30, 17.4% of eCG cows and 22.9% of control cows showed subclinical endometritis. Cows treated with eCG showed a tendency toward lower hyperecogenic intraluminal content (16.8 vs. 21.4%, P = 0.15), but ovarian activity during the synchronization protocol was similar between eCG and control groups, with 91% of animals in both groups showing luteolysis after prostaglandin application and 88% showing ovulation after the last administration of gonadotropin-releasing hormone. Fertility was similar between the two groups at both time points after AI (30 days, 34.9 vs. 31.8%; 60 days, 30.6 vs. 28.5%; P > 0.2). These results suggest that early postpartum eCG administration does not improve fertility of heat-stressed dairy cows as long as 60 days after AI. Other strategies may be more effective at mitigating the ability of post-partum heat stress to reduce fertility of high-producing dairy cows.

Presynchronization of lactating dairy cows with PGF2α and GnRH simultaneously, 7 days before Ovsynch have similar outcomes compared to G6G

The overarching objective of this study was to develop an alternative strategy for first and greater services that will improve fertility in lactating dairy cows for dairy operations limited by labor or other logistical constraints that make it difficult to use Presynch-11, G6G, or Double-Ovsynch. Our overall hypothesis was that simplification of a Presynch program through the combination of PGF2α and GnRH on the same day (PG + G), 7 days before the first GnRH of Ovsynch, would allow for similar ovulation and luteolysis rate and pregnancies per AI (P/AI) compared with G6G. Lactating dairy cows 58 to 64 days in milk (first service; n = 114), and cows diagnosed not pregnant 39 days after previous AI (second + service; n = 122) were blocked by parity and service and randomly assigned to control or PG + G. Control cows received G6G (n = 116) that consisted of PGF2α, 2-day GnRH, 6-day GnRH, 7-day PGF2α, 56-hour GnRH, and 16-hour AI. Treated cows (PG + G; n = 121) received PGF2α and GnRH, 7-day GnRH, 7-day PGF2α, 56-hour GnRH, and 16-hour AI. All cows received a second PGF2α 24 hours after the PGF2α of Ovsynch. First service cows received AI between 76 and 82 days in milk and second + service received AI 57 days after previous AI. Pregnancies/AI (n = 230) were similar in controls compared with treated cows on Day 35 (57 vs. 50%; P = 0.27) and Day 49 (54 vs. 47%; P = 0.33), respectively. Percent of cows ovulating after GnRH of the presynchronization was greater (P = 0.002) for controls vs. treated (80 vs. 58%); however, ovulation after first GnRH of Ovsynch was similar (67 vs. 68%; P = 0.86). Serum concentrations of progesterone were similar (P = 0.78) at the time of first GnRH of Ovsynch for control and treated cows (2.22 vs. 2.14 ng/mL). However, serum progesterone at the time of PGF2α of Ovsynch was greater (P = 0.002) for control cows compared with treated cows (5.75 vs. 4.64 ng/mL). In summary, administering both PGF2α and GnRH on the same day, 7 days before the start of Ovsynch, appears to be a simple alternative that results in acceptable P/AI but potentially less progesterone during the growth of the ovulatory follicle.

Maternal aging affects life performance of progeny in a Holstein dairy cow model

The development and life performance of 404 high-producing Holstein dairy cows was studied from birth onwards and during two lactations. The management, environment and parental genetics of the cows were known in detail. Cluster analysis identified four performance ‘types’: high-yielding (HY) cows and persistently high-yielding (PHY) cows, which accounted for 33% of the animals; medium-yielding (MY) cows, 41%; and low-yielding (LY) cows, 26%. Prenatal determinants of the life performance of the progeny were analyzed. Developmental and environmental factors were excluded as determinants of performance (including birth weight, level of passive immunity transfer, growth rate, age at first parturition and reproductive efficiency). Life performance did show minor seasonal effects, with more HY cows but less PHY being born during the cold season (90.1% in HY; 58.3% in PHY v. 81.5%). Instead, the single most important factor influencing life performance of daughters was maternal age. HY cows were born from the youngest mothers (1.89±1.14 parturitions, 3.12±1.42-year old), whereas LY cows were born from the oldest (2.72±1.80 parturitions, 3.97±2.01-year old; P<0.001). Life performance of the dams did not differ among clusters. In addition, metabolic parameters (fat and protein yield) were found to correlate significantly with yields between the first and second lactations (milk yield: r=0.357; fat yield: r=0.211; protein yield: r=0.277; P<0.0001), suggesting the influence of the individual. These results suggest that under optimal health, nutritional and environmental conditions, maternal aging is an important determinant of the life performance of progeny and argue for the need to identify conditions that contribute to health and disease in progeny according to the Developmental Origin of Health and Disease or DOHaD concept. Our findings may help the development of novel management guidelines for dairy farms.