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The objective of this retrospective study was to assess the effect of receiving a single (n = 50,285) or double (n = 4392) artificial insemination (AI), 12 h apart, within a timed artificial insemination protocol on pregnancy per AI (P/AI) in nulliparous heifers (inseminated with either sex-sorted or conventional semen) and pluriparous Holstein cows in a commercial dairy herd. Also, this study aimed to investigate the relationship between temperature-humidity index (THI) and time of the first AI and fertility. Fertility of cows receiving two AI with normothermia (THI <68) was higher (p < .05) than cows receiving a single AI (42.9% vs. 36.4%). P/AI of cows receiving two AI with severe heat stress (THI >85) was higher (p < .05) than cows receiving a single AI (21.0% vs. 12.6%). Regardless of heat stress conditions, applying the first AI in the morning increased (p < .05) P/AI in cows with double AI than in cows whose first AI occurred in the afternoon (38.4 vs. 33.3%). With moderate heat stress, and sexed-sorted semen, P/AI to timed AI was higher (65.0 vs. 51.9%; p < .05) in heifers receiving double AI than those serviced once. It was concluded that double AI, 12 h apart, enhanced fertility at timed AI than herd mates with a single AI, particularly with heat stress at breeding.

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AIM: This study aimed to evaluate the pregnancy rates in hair ewes using an Ovsynch synchronization protocol under a breeding system that combines fixed-time insemination plus a 10-day mating period as an alternative. MATERIALS AND METHODS: Through an experimental study (n=27), ewes were randomly located into one of three treatments: (1) Pre-synch (n=9): Prostaglandin F2α (PGF2α)+Gonadotropin-releasing hormone (GnRH)+PGF2α+GnRH; (2) Ovsynch (n=9): GnRH+PGF2α+GnRH; and (3) control: Ewes bred by natural mating (NM) (n=9). Ewes were fixed-time inseminated (fixed-time artificial insemination [FTAI]) with fresh semen, collected just before the insemination time through vaginoscopy at 16 h after the second GnRH (gonadorelin) injection. Each experimental group was placed separately during 15 days and, after this time, fertile rams were allowed back with ewes for a 10-day mating period. Control group ewes remained with the rest of the herd suitable for breeding and were bred under NM. Pregnancy diagnosis was performed by ultrasound at 28-, 56-, and 84-day post-breeding to differentiate between FTAI and NM pregnancies. Total (FTAI±NM) pregnancy rates at 56-day post-breeding were used to compared Pre-synch, Ovsynch, and control. For this purpose, two-tailed proportions comparison z-test was used with a 95% confidence level, for testing as the null hypothesis whether two proportions were equal. RESULTS: Pregnancy rates were higher in control ewes (66.4%) than FTAI (46.6%). When pregnancy rates after a 10-day mating period (40%) were added, the final rate (86.6%) was significantly (p<0.05) higher in Ovsynch-based protocols. The pregnancy rate was significantly lower in FTAI ewes compared to FTAI +10-day mating group (p<0.05). The overall pregnancy rate was 88.0, 85.7, and 67.0 (p>0.05) for Pre-synch, Ovsynch, and control ewes, respectively. CONCLUSION: These results provide evidence on the benefits of combined FTAI protocols for improving the reproductive efficiency of sheep.

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The objective was to compare the fertility of dairy cows using a presynchronization protocol by induction of a largest follicle using a progesterone intravaginal device prior to an Ovsynch protocol (P4synch) with the Double-Ovsynch in lactating dairy cows. Lactating Bos indicus x Bos taurus crossbred cows (n = 440) were randomly allocated to one of two treatments: (I) Double-Ov (n = 228), GnRH (D-17), PGF2α 7 days later (D-10) and GnRH 3 days later (D-7) followed by an Ovsynch protocol 7 days later (GnRH on D0, PGF on D7, GnRH on D9); (II) P4synch (n = 212), insertion of a sustained release progesterone intravaginal device (D-10), 10 days later (D0) an Ovsynch protocol was initiated (GnRH on D0, PGF on D7, GnRH on D9) with progesterone device withdrawal on Day 7. All cows were artificially inseminated (TAI) 16 h after the second GnRH of the Ovsynch protocol and pregnancy diagnosis was performed by transrectal ultrasonography 30 and 60 days after TAI. A subset of cows (n = 52 for Double-Ov and n = 50 for P4synch) ultrasonography was performed on days 0, 7, 9 and 24 of the experimental period. There were no differences among treatments on presynchronization rate [presence of a follicle>12 mm on D0, Double-Ov 94.2% (49/52) and P4synch 92.0% (46/50); P = 0.66], follicular diameter on the 1st GnRH (Double-Ov 17.2 ±â€¯0.7 mm e P4synch 18.6 ±â€¯0.9 mm; P = 0.28), ovulation rate to the 1st GnRH [Double-Ov 86.3% (44/51) and P4synch 81.2% (39/48); P = 0.50], synchronization rate [presence of a follicle>12 mm on D9; Double-Ov 84.6% (44/52) and P4synch 86.0% (43/50); P = 0.84], follicular diameter on the 2nd GnRH (Double-Ov 17.5 ±â€¯0.6 mm and P4synch 18.0 ±â€¯0.5 mm; P = 0.48), ovulation rate to the 2nd GnRH [Double-Ov 90.9% (40/44) and P4synch 86.0% (37/43); P = 0.48] and CL diameter on D24 (Double-Ov 27.9 ±â€¯0.7 mm and P4synch 29.4 ±â€¯0.9 mm; P = 0.19). Corpus luteum presence on D0 was different (P = 0.03) among treatments [Double-Ov 57.7% (30/52) and P4synch 36.0% (18/50)]. There was no difference (P = 0.85) among the pregnancy per AI on day 30 [Double-Ov 39.0% (89/228) and P4synch 40.1% (85/212)], on day 60 [Double-Ov 34.8% (79/227) and P4synch 38.7% (82/212); P = 0.41] and pregnancy loss [Double-Ov 10.2% (9/88) and P4synch 3.5% (3/85); P = 0.08]. The presynchronization by induction of a largest follicle using a sustained release progesterone device prior to Ovsynch yielded similar results compared with the Double Ovsynch protocol on follicular development patterns and on the fertility of lactating dairy cows.

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The aim of this study was to investigate the effects of low and moderate blood β-hydroxybutyric acid (BHBA) levels in primiparous cows during the early postpartum period on follicle development and pregnancy rate after the Ovsynch protocol. Holstein primiparous cows with low (n = 85) and moderate (n = 71) BHBA concentrations were used as experimental animals. At 7- 8 weeks postpartum, blood samples were collected and the Ovsynch protocol was performed on the same day. Ultrasonographic examination was performed to determine the dominant follicle (DF) diameter and presence of corpus luteum on the day of the first and second gonadotropin releasing hormone (GnRH1 and GnRH2) injections and prostaglandin F2 alpha (PGF2α) injection as well as 24 and 48 h after the GnRH1 and PGF2α injections. The ovulatory response to GnRH1 and pregnancy rate at day 30 and day 60 post insemination were also evaluated. No significant differences were observed between groups in the DF diameter on the day of GnRH1 and PGF2α injections, and at 24 and 48 h after these injections, as well as in the ovulation and atresia response to GnRH1 (P > 0.05). Significant differences were observed between groups in DF diameter (low-BHBA group, 13.8 ± 0.2 mm; moderate-BHBA group, 13.2 ± 0.2 mm; P = 0.039) at the time of insemination, and in pregnancy rates at 30 days (low-BHBA group, 38.82%; moderate-BHBA group, 21.13%, P = 0.017) and 60 days after insemination (37.6 and 18.3%, respectively; P = 0.008). Our findings suggest that moderate blood levels of BHBA (0.80-1.19 mmol/L) in primiparous cows during the early postpartum period affect the response to the Ovsynch protocol.(AU)

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The aim of this study was to investigate the effects of low and moderate blood β-hydroxybutyric acid (BHBA) levels in primiparous cows during the early postpartum period on follicle development and pregnancy rate after the Ovsynch protocol. Holstein primiparous cows with low (n = 85) and moderate (n = 71) BHBA concentrations were used as experimental animals. At 7- 8 weeks postpartum, blood samples were collected and the Ovsynch protocol was performed on the same day. Ultrasonographic examination was performed to determine the dominant follicle (DF) diameter and presence of corpus luteum on the day of the first and second gonadotropin releasing hormone (GnRH1 and GnRH2) injections and prostaglandin F2 alpha (PGF2α) injection as well as 24 and 48 h after the GnRH1 and PGF2α injections. The ovulatory response to GnRH1 and pregnancy rate at day 30 and day 60 post insemination were also evaluated. No significant differences were observed between groups in the DF diameter on the day of GnRH1 and PGF2α injections, and at 24 and 48 h after these injections, as well as in the ovulation and atresia response to GnRH1 (P > 0.05). Significant differences were observed between groups in DF diameter (low-BHBA group, 13.8 ± 0.2 mm; moderate-BHBA group, 13.2 ± 0.2 mm; P = 0.039) at the time of insemination, and in pregnancy rates at 30 days (low-BHBA group, 38.82%; moderate-BHBA group, 21.13%, P = 0.017) and 60 days after insemination (37.6 and 18.3%, respectively; P = 0.008). Our findings suggest that moderate blood levels of BHBA (0.80-1.19 mmol/L) in primiparous cows during the early postpartum period affect the response to the Ovsynch protocol.

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Lactating dairy cows have unique reproductive responses compared to when they were heifers that result in distinctly different reproductive measurements and pregnancy outcomes that can be partially overcome with pharmacological strategies. These parameters include circulating progesterone and estradiol concentrations, ovulatory follicle and corpus luteum diameter, incidence of anovulation and double ovulations, time in estrus, pregnancies per artificial insemination and pregnancy losses. Circulating concentrations of progesterone during diestrus are approximately half that in cows compared with heifers. This marked difference in progesterone is likely the explanation for an increased size in diameter of the ovulatory follicle and incidence of double ovulations in cows compared with heifers. Differences in diameter of the ovulatory follicle may explain why cows have greater corpora lutea diameters compared to heifers. The increase in double ovulations appears to be a key driver in the increase in twinning and pregnancy loss as dairy heifers transition to primi- and multiparous cows. Reduced estradiol concentrations in cows at time of estrus helps to explain the decreased duration of estrus in cows compared with heifers...(AU)

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Lactating dairy cows have unique reproductive responses compared to when they were heifers that result in distinctly different reproductive measurements and pregnancy outcomes that can be partially overcome with pharmacological strategies. These parameters include circulating progesterone and estradiol concentrations, ovulatory follicle and corpus luteum diameter, incidence of anovulation and double ovulations, time in estrus, pregnancies per artificial insemination and pregnancy losses. Circulating concentrations of progesterone during diestrus are approximately half that in cows compared with heifers. This marked difference in progesterone is likely the explanation for an increased size in diameter of the ovulatory follicle and incidence of double ovulations in cows compared with heifers. Differences in diameter of the ovulatory follicle may explain why cows have greater corpora lutea diameters compared to heifers. The increase in double ovulations appears to be a key driver in the increase in twinning and pregnancy loss as dairy heifers transition to primi- and multiparous cows. Reduced estradiol concentrations in cows at time of estrus helps to explain the decreased duration of estrus in cows compared with heifers...

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A total of 332 postpartum (pp) lactating Friesia n cows allocated in two treatment groups at a commercial dairy farm were used to study the effect of a modified Ovsynch protocol supplemented with exogenous estradiol (E2) on fertility in lactating dairy cows during the summer season. All cows were injecte d with gonadotrophin releasing hormone (GnRH), followed 7 d ays later by an injection of prostaglandin (PGF 2 α ). Then cows were randomly assigned to receive GnRH and TAI 72 h after PGF 2 α ( CO - 72; control group) or E2 , GnRH and TAI at 48, 56 and 72 h , respecti vely after PGF2 α (OV - 56+ E2). Estrus response for cows in the OV - 56+E2 ( 59.8 %) group was higher (P < 0.0 5 ) than for cows in the CO - 72 ( 40.2 %) group. Pregnancy per insemination ( P/AI ) at two diagnoses ( days 30 to 35 and confirmed at days 45 to 50 after AI ) w ere similar between the two treatment group s , but were higher ( P < 0.05) for cows that showed estrus (59.8 and 41.2% , respectively ) than for cows that did not show estrus (45.5 and 7.9% , respectively ) . Moreover, P /AI at the two diagnoses were higher (P < 0 .05) for cows with a body condition score (BCS ) >2.5 (60.1 and 36.4 %, respectively) compared to those with BCS < 2.5 (44.3 and 16.5%, respectively). Pregnancy losses were higher (P < 0.05) for cows that did not show estrus (82.6%) or with BCS < 2.5 (62.8%) t han for cows that showed estrus (31.0%) or with a BCS >2.5 (39.5%). No differences were observed in P/AI or pregnancy losses between primiparous and multiparous cows . Results indicate that the OV - 56+ E2 synchronization protocol resulted in a higher expressi on of estrus than the CO - 72 without improving fertility as measured by P /AI and pregnancy losses. However , cows with high BCS had higher estrus expression, pregnancy rates, and lower pregnancy losses than cows with low BCS during the summer season.(AU)

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A total of 332 postpartum (pp) lactating Friesia n cows allocated in two treatment groups at a commercial dairy farm were used to study the effect of a modified Ovsynch protocol supplemented with exogenous estradiol (E2) on fertility in lactating dairy cows during the summer season. All cows were injecte d with gonadotrophin releasing hormone (GnRH), followed 7 d ays later by an injection of prostaglandin (PGF 2 α ). Then cows were randomly assigned to receive GnRH and TAI 72 h after PGF 2 α ( CO - 72; control group) or E2 , GnRH and TAI at 48, 56 and 72 h , respecti vely after PGF2 α (OV - 56+ E2). Estrus response for cows in the OV - 56+E2 ( 59.8 %) group was higher (P 2.5 (60.1 and 36.4 %, respectively) compared to those with BCS 2.5 (39.5%). No differences were observed in P/AI or pregnancy losses between primiparous and multiparous cows . Results indicate that the OV - 56+ E2 synchronization protocol resulted in a higher expressi on of estrus than the CO - 72 without improving fertility as measured by P /AI and pregnancy losses. However , cows with high BCS had higher estrus expression, pregnancy rates, and lower pregnancy losses than cows with low BCS during the summer season.

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Los días abiertos en el hato lechero dependen de muchos factores, dentro de los cuales se debe considerar, la preparación de la vaca preparto incluyendo el manejo dietario pre y postparto. Factores como la hipocalcemia y la condición corporal son determinantes en la presentación de patologías puerperales y en el inicio de la ciclicidad. Adicional a este manejo, se debe considerar la utilización de protocolos de inseminación a tiempo fijo que incrementa el número de animales servidos cerca del tiempo voluntario de espera y genera un incremento en las tasas de preñez. La presente revisión discutirá temas relacionados con la condición corporal y la presentación de hipocalcemia puerperal que afectan la fertilidad posparto de la vaca, así como alternativas para mejorar las tasa de preñez y reducir los días abiertos.

In dairy herds, the interval between calving and pregnancy depend on many factors including preparation of the cow for calving, dietary management before and after calving. Factors such as hypocalcemia and body condition are determinant in the presentation of postpartum pathologies and ovarian activity resumption. Additionally, management of the dairy cattle should include fixed time artificial insemination protocols to increase the number of animals bred close to the voluntary waiting period and pregnancy rates. The following review will address topics related with cattle body condition and puerperal hypocalcemia that affect negatively postpartum reproductive performance and also will, address management alternatives to improve pregnancy rates y to reduce days open.

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O objetivo desse estudo foi avaliar a liberação de LH durante os protocolos de sincronização da ovulação em bubalinos. Para tanto, quinze búfalas multíparas receberam 25 mg de Lecirelina no Dia 0, e150 mg de D-Cloprostenol no Dia 7. No Dia 8, foi aplicado benzoato de estradiol nas búfalas do Grupo 1 (0,5 mg, n = 5) e do Grupo 2 (1,0mg, n = 5). No Dia 9, os animais receberam 25mg de Lecirelina (Controle, n = 5). Para mensuração das concentrações plasmáticas de LH foram colhidas amostras de sangue da veia jugular no Dia 7, e em seguida em intervalos de 3 horas até completar 72 horas após a aplicação de PGF2a. Para avaliação da liberação de LH foram comparados os momentos de ocorrência do pico LH em relação à PGF2a, as durações, as amplitudes e a área sob o pico de pré-ovulatório de LH. As búfalas dos Grupos Controle, 1 e 2 apresentaram picos pré-ovulatórios de LH em 51 + 0,0 horas, 47,3 + 2,7 horas e 47,0 + 3,8 horas após a aplicação da PGF2a, respectivamente (P>0,05). A duração do pico de LH foi menor no Controle (7,8 + 1,5 horas) do que nos Grupos 1 e 2 (10,5 + 1,5 horas vs. 10,8 + 2,4 horas, respectivamente; P < 0,05). A amplitude média dos picos pré-ovulatórios de LH foram de 4,5 + 0,4ng/mL, 4,0 + 0,4 ng/mL e 4,3 + 0,8 ng/mL para os Grupos Controle, 1 e 2, respectivamente (P > 0,05). A área sob o pico de LH no Controle (4,8 ± 0,7) foi menor do que as áreas dos Grupos 1 e 2 (8,8 ± 2,5 vs.8,7 ± 2,2, respectivamente; P < 0,05). Em resumo, a aplicação de benzoato de estradiol proporcionou maior duração e área do pico pré-ovulatório de LH do que a administração de GnRH em protocolos Ovsynch em bubalinos.(AU)

The objective of this study was to evaluate the LH surge after last hormonal injection of synchronization of ovulation protocols in buffalo. Fifteen multiparous buffaloes received 25 mg of Lecirelin in Day 0, and 150 mg of D-Cloprostenol on Day 7. On Day 8, estradiol benzoate was injected in Group 1 (0.5 mg, n = 5) and Group 2 (1.0mg, n = 5). On Day 9, five buffaloes received 25 mg of Lecirelin (Control). Blood samples were collected for measure the LH concentrations on Day 7 and then every 3 hours until 72 hours after the PGF2a injection. For evaluation of LH surge were compared the interval between PGF2a injection to LH surge, duration, amplitude and area under the LH peak. The LH surge occurred 51.0 + 0.0 hours, 47.3 + 2.7 hours and 47.0 + 3.8 hours after PGF2a injection for Control, Group 1 and Group 2, respectively (P > 0.05). The duration of LH peak in Control (7.8 + 1.5 hours) was shorter than Groups 1 and 2 (10.5 + 1.5 hours vs. 10.8 + 2.4 hours, respectively; P < 0.05). The amplitudes of LH peak were 4.5 + 0.4 ng/mL, 4.0 + 0.4 ng/mL and 4.3 + 0.8 ng/mL for Control, Group 1 and Group 2, respectively (P> 0.05). The area under LH peak for Control (4.8 ± 0.7) was smaller than the areas of the Groups 1 and 2 (8.8 ± 2.5 vs. 8.7 2.2, respectively; P < 0.05). In summary, the estradiol benzoate injection provided higher duration and area of LH peak than GnRH injection in Ovsynch protocol in buffalo.(AU)

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