Pregnancy Rates In Dairy Cows Research Articles

The Effect of Human Chorionic Gonadotropin and Ketoprofen Applications on Pregnancy Rates in Dairy Cows After Artificial Insemination

The aim of the presented study is to investigate the effect of providing progesterone (P4) support for the formation and maintenance of pregnancy or suppressing the luteolysis mechanism during the maternal acceptance process on pregnancy rates. For this purpose, 96 Holstein cows, aged between 2 and 8 years, were synchronized using the Ovsynch protocol to align their estrous cycles. After artificial insemination, the cows were divided into four groups. The group receiving Human Chorionic Gonadotropn (hCG) on the 6th day after artificial insemination (H; n=20), the group receiving Ketoprofen on the evening of the 15th day and the morning of the 16th day after artificial insemination (K; n=24), the group receiving both hCG on the 6th day and Ketoprofen on the 15th day evening and 16th day morning after artificial insemination (HK; n=25), and the control group (C; n=27) that did not receive any post-insemination treatment were established. Pregnancy checks were conducted on the 30th, 45th, and 60th days through rectal and ultrasonographic (USG) examinations. According to the results of the pregnancy examinations, it was determined that 9 out of 20 cows (45.00%) in Group H, 10 out of 24 cows (41.67%) in Group K, 16 out of 25 cows (64.00%) in Group HK, and 12 out of 27 cows (44.44%) in Group C were pregnant. No statistically significant difference (P>0.05) was observed among the groups. Our results suggest that a multi-purpose treatment may be required to reduce pregnancy loss during the early pregnancy period in cows due to an approximately 20% increased pregnancy rate after administering hCG and Ketoprofen. However, further studies, especially involving more cows, are necessary to optimize and use these combined treatments and potentially increase pregnancy rates.

Comparison of synchronisation protocols on pregnancy rate in dairy cows and heifers: A systematic review and network meta-analysis

Estrus synchronisation protocols are used as an essential strategy in the reproductive management of dairy herds, including Ovsynch, Presynch, Selectsynch, Heatsynch, Cosynch, Double-Ovsynch, and some other combinations of these, while the optimal protocol is still uncertain. We performed a network meta-analysis (NMA) to compare the efficacy of the synchronisation protocols in dairy cows and heifers. Pubmed, Scopus, Web of Science, Cabi Direct, and The Cochrane Library were searched up to May 13, 2019. The comparison of synchronisation protocols in terms of pregnancy rate was done by combining direct and indirect evidence. Ranking the synchronisation protocols were conducted by using surface under the cumulative ranking curve (SUCRA). 48 randomized trials involving 9 different protocols were included. Compared with the control group, none of the synchronisation protocols were more effective in pregnancy rate at first insemination. Presynch+Ovsynch was found to be more efficient than Ovsynch (RR=1.21, 95% CI:1.04-1.40), also Presynch+Ovsynch and Presynch+Heatsynch were superior to Presynch+Selectsynch (RR=2.01, 95% CI: 1.03-3.93 and RR=1.91, 95% CI: 1.21-3.01). In conclusion, presynchronisation strategies such as Presynch+Ovsynch increase the effectiveness of pregnancy rate at first insemination related to other synchronisation protocols. Nevertheless, the non-superiority of the synchronisation protocols against not applying any hormonal treatments should be considered in reproductive management in dairy herds.

The Relationship Between Plasma Progesterone Concentration on Day 6 After Artificial Insemination and Pregnancy Rate of Dairy Cows in Vietnam

The study was conducted to determine the relationship between plasma progesterone (P4) concentration on day 6 following artificial insemination (AI) and the pregnancy rate to provide recommendations for measuring P4 concentration before embryo transfer in cows. A total of 85 cows were double AI (day 0) after being detected in natural heat by visual observation. On day 6 after AI, the blood sample was collected from the coccygeal vein to measure plasma P4 concentration by ELISA method. Pregnancy was diagnosed on the 60th day after AI by rectal palpation. The results showed that the plasma P4 concentration at day 6 after AI of the pregnant cow group (4.262±2.195 ng/mL) was significantly higher than that of the non-pregnant cow group (3.146±2.377 ng/mL) (p<0.05). The pregnancy rate was lowest in the group of cows with plasma P4 concentration <2ng/mL, then gradually increased with P4 concentration. The pregnancy rate of cows tended to be stable when P4 concentration ≥4.0 ng/mL. The pregnancy rate of cows was highest when the P4 concentration was from 3-4 ng/mL and 5-6 ng/mL. Additionally, the pregnancy rate of cows is positively correlated with the plasma P4 concentration according to the formula P= 26.356 + 6.612* P4. In conclusion, the plasma concentration of P4 at day 6 after AI has a positive relationship with the pregnancy rate of cows.

An Interconnection between Elevated SCC Levels in Milk around the First Artificial Insemination and Pregnancy Rate in Dairy Cows

An Interconnection between Elevated SCC Levels in Milk around the First Artificial Insemination and Pregnancy Rate in Dairy Cows

Effect of oestrous expression prior to timed artificial insemination with sexed semen on pregnancy rate in dairy cows.

The objectives of the study were to determine (1) oestrous expression rate and (2) the effect of oestrous expression prior to progesterone-based Ovsynch protocol on pregnancy rate in Holstein cows. All cows (n=917) were subjected to 7-day progesterone-based Ovsynch protocol. In this protocol, cows that expressed oestrus before (HEAT1) the scheduled second GnRH were inseminated 20 h later after the onset of oestrus without GnRH administration. Cows that expressed oestrus after the second GnRH administration (HEAT2) or did not express oestrus (NOHEAT) received fixed-timed AI. Oestrous expression was determined by using activity-rumination monitoring system and all cows were inseminated with sexed semen. Oestrous expression rate prior to FTAI was 40.5% and the majority (p< .01) of oestrous expression were in HEAT2 compared with HEAT1 in both primiparous (71.8 vs. 28.1%) and multiparous cows (69.5 vs. 30.5%). The mean interval from intravaginal device removal to the onset of oestrus was 47.4± 0.9h and 62.9± 0.5 in HEAT1 and HEAT2, respectively. Primiparous cows (47.7%) had a higher (p< .01) expression rate compared with multiparous cows (37.2%). Overall pregnancy rate was 37.4% and there was two-way significant interaction between parity and oestrous expression on pregnancy rate (p< .01). Both primiparous (48.1 vs. 35.8%) and multiparous cows (47.4 vs. 28.4%) that expressed oestrus had greater (p< .01) pregnancy rate compared with cows that did not express oestrus. There was no difference in pregnancy rates of HEAT1 and HEAT2 in both primiparous (44.7 vs. 49.5%) and multiparous cows (47.2 vs. 47.6%). Pregnancy rate was not influenced (p =.21) by milk production (high or low) in both primiparous (47.6 vs. 48.6%) and multiparous (54.9 vs. 42.1%) cows that expressed oestrus, respectively. In conclusion, cows showing oestrus before or after second GnRH of the Ovsynch protocol had greater pregnancy rate than cows not showing oestrus.

Adding equine chorionic gonadotropin to the G6G protocol improves pregnancy rate of dairy cows under heat stress conditions

We studied 663 cyclic lactating Holstein cows in an industrial farm near Qazvin, Iran, from June 2119 to September 2020. We investigated the effects of equine chorionic gonadotropin (eCG) hormone administration 80 h before the implementation of the Ovsynch and fixed-time artificial insemination (OVS + FTAI) program in the form of the G6G protocol on pregnancy rate and reproductive parameters of dairy cows in the first postpartum insemination under heat stress conditions. The cows were randomly assigned to one of the following protocols and received the following treatments: G6G (prostaglandin F2 alpha (PGF2α)-2d-gonadotropin releasing hormone (GnRH)-6d-OVS+FTAI(GnRH(GnRH1)-7d-PGF2α(PG)-56h-GnRH-18h-FTAI, n = 213), 300 international unit (IU) eCG+G6G (300e+G6G) (PGF2α-2d- GnRH-64h-300 IU,eCG-80h-OVS+FTAI, n = 231), and 500 IU eCG+G6G (500e+G6G) (PGF2α-2d-GnRH-64h-500IU,eCG-80h-OVS+FTAI, n = 219). The overall pregnancy rates of cows in the G6G, 300e+G6G, and 500e+G6G protocols were 29.5 ± 0.03%, 33.7 ± 0.03%, and 35.6 ± 0.03%, respectively. The 500e+G6G protocol increased the pregnancy rate of cows with a body condition score (BCS) ≤ 2.5 compared to the G6G protocol (P = 0.04). The 500e+G6G protocol significantly increased the pregnancy rate of cows that produced &gt; 34 kg milk per day compared to the G6G protocol (P = 0.03). In conclusion, using 500 IU, eCG 80 h before the implementation of the OVS+FTAI program in the form of G6G protocol had beneficial effects on increasing the pregnancy rate of cows that had a BCS ≤ 2.5 or produced &gt; 34 kg milk per day compared to the G6G protocol under heat stress conditions.

Intrauterine infusion of blood serum of dromedary camel improves the uterine health and fertility in high producing dairy cows with subclinical endometritis

The blood serum of dromedary camels contains a unique type of antibodies with a high potency to neutralize toxins and to identify and inactivate some bacterial pathogens. The present study was designed to examine changes in the endometrial histology of cows with no subclinical endometritis (SE) (experiment 1) and changes in the uterine cytology and endometrial mRNA expression of COX2, IL-1β, IL-8, and iNOS following intrauterine administration of DCBS in cows with SE as compared to different common treatments (experiment 2). In addition, the effects of the intrauterine administration of DCBS were examined on the pregnancy rate in dairy cows with SE (experiment 3). DCBS did not induce any histological reactions in the bovine endometrium. The mean ( ± SE) percentage of PMNs after intrauterine infusion of Pen-Strep, DCBS and double DCBS in cows with SE differed as compared to cows treated with PGF2α and no treated cows with SE (1.47 ± 0.87; 1.43 ± 1.08 and 1.31 ± 0.23 vs 3.00 ± 0.43 and 3.5 ± 0.75, P < 0.05, respectively) in experiment 2. The mRNA expression of COX2, IL-1β, and iNOS was reduced (P < 0.05) after treatment with Pen-Strep, DCBS and double DCBS as compared with no treated-cows with SE. The pregnancy rate after the first AI was tended to be higher (49.2 vs 39.0%), while the overall pregnancy rate was greater (P < 0.05) in cows with SE when treated with DCBS as compared to the Pen-Strep group (76.9 vs 61.0%) in experiment 3. In conclusion, serum of dromedary camel, as a non-antibiotic preparation, can improve the uterine health and fertility when used for the treatment of bovine SE.

The negative effects of cold conditions on pregnancy rates in dairy cows

This study was conducted to determine the pregnancy rate in response to two sexual synchronization protocols in 70 healthy multiparous Fleckvieh dairy cows during the cold and warm seasons. After pairing by the actual parturition date [cold seasons (-38 to 0 ºC) (Nov - Feb) vs. warm seasons (0 to 32 ºC) (Mar-Oct)], cows were randomly subjected to either Co-Synch (CoS) or double PGF2α injection (dPG) on d 35 postpartum. Data were subjected to Chi-Square (2) analysis to determine the pregnancy rate at the first service. Overall pregnancy rates (%) at the first service were 57.1 and 40.0 for Groups CoS and dPG, respectively (2 = 2.03, P = 0.15) and 35.0 and 66.7% during cold and warm seasons, respectively (2 = 6.78, P = 0.009). The protocol effect on the pregnancy rate at the first service was insignificant during cold (2 = 1.17, P = 0.28) and warm (2 = 1.62, P = 0.20) season. In summary, the cold conditions negatively affected the pregnancy rate at the first service. The synchronization protocol methods did not differ to improve the pregnancy rate at the first service when cows were exposed to cold conditions.

PSVI-17 Dissimilarities in thyroid profiles and pregnancy rates in dairy cows with different polymorphic variants of the DIO1 gene

Abstract Thyroid hormones are implicated in regulation of the reproductive function in cattle. In turn, thyroid metabolism is determined by the activity of different types deiodinases. Our research was aimed to compare post-insemination thyroid profiles and pregnancy rates in dairy cows with different SNP genotypes in the deiodinase gene of the first type (DIO1). Thirty lactating Russian Black Pied cows were synchronized using the Ovsynch protocol and artificially inseminated (AI). Blood samples from the cows were collected on Days 0, 7, 14, 21, and 33 after AI. Hormonal levels in the serum were measured by ELISA. Pregnancy was confirmed by progesterone concentrations and ultrasonography. Genetic variants for the DIO1 gene were tested by RT-PCR and polymorphism at position 13149 (NC_037330) was found. The occurrence frequency of cows with genotypes CC, CG, and GG was 43.3, 33.3, and 23.3 %, respectively. A proportion of pregnant cows in the CC group was higher than in the CG group (84.6 vs. 40.0%, P &amp;lt; 0.05) and tended to be higher than in the GG group (42.9%). The concentration of triiodothyronine (T3) in the blood of CC animals did not change during the studied period, whereas that in CG animals decreased between Days 0 and 14 (from 1.60±0.21 to 1.10±0.22 nmol/L, P &amp;lt; 0.05). Concurrently, the T3 concentration on Day 0 was 1.4 times lower (P &amp;lt; 0.05) in the CC group than in the CG group. Furthermore, the level of reverse T3 on Day 7 in the GG group was 1.3 times higher (P &amp;lt; 0.05) than in the CC or CG groups. Thus, cows with DIO1 gene CC genotype have a higher reproductive ability than cows with CG or GG genotypes, which may be due to peculiarities of thyroid profiles during the first two weeks of pregnancy. The study was supported by Russian Ministry of Science and Higher Education (0445-2021-0004).

Effects of injectable trace element and vitamin supplementation during the gestational, peri-parturient, or early lactational periods on neutrophil functions and pregnancy rate in dairy cows

The aim of this study was to evaluate effects of injectable trace element and vitamin combination on phagocytic, oxidative burst activity of neutrophils and reproductive outcomes in dairy cows. Cows were to assigned to the following groups: (1) injectable trace element supplementation (ITES, n = 44, containing zinc, manganese, copper, selenium); (2) injectable vitamin supplementation (VIT, n = 48, containing vitamins A, D3, E); (3) ITES + VIT (n = 46); and (4) control (CON, n = 44). Cows were administered four injections between 230 and 260 days of the gestational period, on day of parturition, and 30 days postpartum. Neutrophil function was assessed at 10 days before and after calving. Phagocytosis was greater in cows of the ITES + VIT group at 10 days prepartum (P < 0.05) while oxidative burst was similar among groups. There were greater non-esterified fatty acid (NEFA) concentrations in cows of the ITES+VIT group at 10 days prepartum (P < 0.05). Cows supplemented with ITES+ VIT had less SOD activity than those supplemented with ITES or vitamin during the pre- to post-partum transition period (P < 0.05). The total odds of pregnancy were greater in cows supplemented with trace element and/or vitamin (P < 0.05). In conclusion, supplementation of ITES and/or VIT resulted in an increased total pregnancy rate. Vitamin or trace element supplementation did not differ with the control group in both the prepartum and postpartum period for immune variables. There, however, was greater phagocytosis in cows supplemented with vitamin and trace elements during the prepartum period that might be related to metabolic-induced inflammation.

LRH-A3 and HCG increase pregnancy rate during timed artificial insemination in dairy cows.

The objective of this study was to use luteinizing hormone-releasing hormone A3 (LRH-A3) and human chorionic gonadotrophin (HCG) to improve pregnancy rate of dairy cows during timed artificial insemination (TAI). In experiment 1, the TAI process (0d, GnRH, 100μg; 7d, PGF2α, 0.4mg; 56hr, GnRH, 100μg; 16hr, AI) was applied to 160 dairy cows on 50th and 60th days after parturition respectively. In experiment 2, 320 postpartum dairy cows were treated with TAI (Group A), TAI+25μg LRH-A3 (Group B), TAI+1,500IU HCG 5days after AI (Group C), and TAI+25μg LRH-A3+1,500IU HCG 5days after AI (Group D). In experiment 3, endometrial cells were treated with HCG. The results showed that TAI did not affect the pregnancy rate, while LRH-A3 and HCG increased the pregnancy rate of the cow. HCG of 5IU/ml and 10IU/ml increased the expressions of leukemia inhibitory factor but decreased those of interleukin-6, epidermal growth factor and vascular endothelial growth factor in endometrial cells. This study provided a plan for the use of LRH-A3 and HCG to increase pregnancy rate during TAI in dairy cows.

Treatment of Endometritis Caused by Different Types of Bacteria by Cefoperazone Antibiotic and its Effect on the Days Open and Pregnancy Rate in Dairy Cows (Field Study)

Treatment of Endometritis Caused by Different Types of Bacteria by Cefoperazone Antibiotic and its Effect on the Days Open and Pregnancy Rate in Dairy Cows (Field Study)

Comparative Study of Pregnancy Rate of Dairy Cows Inseminated with Fresh or Frozen-Thawed Semen

The aim of this study was to investigate conception rates (CR) achieved with artificial insemination of Holstein cows using fresh or frozen insemination doses (ID). The synchronization protocols (Double-Ovsynch, Ovsynch, ReSynch) and pedometers were used to secure proper timing of artificial inseminations (AI). Total of 3979 inseminations data were recorded. Statistical analysis was performed using the SAS 9.3 package. For the evaluation of a CR, the effects of ID type, season, year, sire breed, lactation number and oestrus detection type, were analysed. Cows inseminated with fresh ID performed higher CR (+4.86%; P &lt; 0.05). Best pregnancy per artificial insemination (P/AI) success was observed during the winter season (+11.82%; P &lt; 0.01). Parity affected P/AI with primiparous having a greater P/AI than multiparous cows (P &lt; 0.01). The least likelihood of pregnancy success matched up with ReSynch and the highest with Ovsynch protocol (+7.7%; P &lt; 0.05). In conclusion, fresh ID manifested superior CR over frozen-thawed semen under common conditions of Czech dairy farming. Similar or better P/AI was achieved when an automated activity monitoring were used rather than timed AI based on Ovsynch protocol, indicating a possible reduction in hormonal treatment applications without affecting fertility of high producing dairy cows.

Penggunaan kombinasi Gonadotropin untuk pengobatan hipofungsi ovarium pada sapi perah

This case report aims to determine the response of estrus and pregnancy rates in dairy cows with ovarian hypofunction by administering a combination of gonadotropin hormones. The sample used was ten dairy cows that had been calving, were not pregnant, showed no signs of estrus for more than 60 days after the last calving and had ovarian hypofunction based on rectal palpation. All dairy cows were injected 300 IU PG-600, then divided into two groups, each injected with 100 and 300 IU hCG respectively for first group and second group, intramuscularly at the time of insemination. The results showed that the estrus response occurred in all cows, in 6-8 (6.8 ± 0.84) days (first group), and 6-7 (6.2 ± 0.45) days (second group). Trans-rectal palpation pregnancy diagnosis 60 days after artificial insemination showed that all dairy cows in both groups were pregnant. It could be concluded that the treatment of dairy cows suffering from ovarian hypofunction with a combination of 300 IU PG-600 and 100 IU hCG was sufficient to induce 100% estrus rates and 100% pregnancy rates.

Pregnancy rate in dairy cows treated with human chorionic gonadotropin five days after insemination

espanolRESUMEN: Este estudio evaluo si la administracion de hCG cinco dias despues de la inseminacion incrementa la concentracion de progesterona y la tasa de prenez (TP) en vacas lecheras. Se utilizaron 989 vacas Holstein de diferente numero de parto y servicio. Las vacas se inseminaron despues de la deteccion del estro o a tiempo fijo. El dia cinco postinseminacion las vacas se asignaron aleatoriamente a dos tratamientos: hCG (n=482), donde recibieron 3500 UI de hCG via im; y control (n=507), donde no recibieron tratamiento. Se diagnostico la gestacion mediante ecografia el dia 30 posinseminacion y se confirmo el dia 60 por palpacion transrectal. En 15 vacas de cada tratamiento se determino la concentracion plasmatica de progesterona los dias 5, 11 y 15 postinseminacion. Se analizo la TP mediante regresion logistica y la concentracion de progesterona mediante analisis de varianza. La concentracion de progesterona fue mas alta los dias 11 y 15 en las vacas tratadas con hCG que en las control (P0.1). Se concluye que la inyeccion de hCG cinco dias despues de la inseminacion incrementa la concentracion de progesterona y la tasa de prenez en vacas lecheras. EnglishABSTRACT: This study tested whether the administration of hCG five days after insemination increased progesterone concentration and pregnancy rate (PR) in dairy cows. A total of 989 lactating Holstein cows with different parity and number of prior services were used. Cows were inseminated after overt estrus or at a fixed-time. Five days post-insemination, cows were randomly assigned to two treatment groups: hCG (n=482), which received 3500 IU of hCG by intramuscular injection; and the control group (n=507), which did not receive any treatment. Pregnancy was diagnosed by ultrasound on day 30 post-insemination, and gestation was confirmed on day 60 post-insemination by rectal palpation. In 15 cows from each treatment group, plasma progesterone concentration was determined on days 5, 11, and 15 post-insemination. Pregnancy rate was analysed using logistic regression. Variations in progesterone concentration between treatments were tested by ANOVA for repeated measurements. Progesterone concentration was higher on days 11 and 15 in cows treated with hCG, compared to the control group (P0.1). We conclude that injection of hCG five days after insemination increased progesterone concentration and pregnancy rate in dairy cows.

72 EFFECT OF PROGESTERONE SUPPLEMENTATION ON DAY 4 AFTER TIMED ARTIFICIAL INSEMINATION ON PREGNANCY RATE OF LACTATING DAIRY COWS

Progesterone plays an important role in the maintenance of pregnancy. It is hypothesised that insufficient progesterone early in pregnancy may result in embryonic loss, and that supplemental progesterone would decrease pregnancy loss in dairy cows. The aim of this study was to compare the effect of progesterone supplementation after timed AI on pregnancy rate of dairy cows. The experiment was conducted in a single commercial herd, in Sao Paulo State (Brazil), during a period of 1 year (January–December 2016). The cows were assigned at a nonpregnancy diagnosis 32 ± 3 days after AI to 1 to 6 resynchronization treatments. They were submitted to the same fixed time AI protocol: Day 0, 0.1 mg of gonadorelin, 2 mg of oestradiol benzoate, and an intravaginal device of 1.9 g of progesterone; Day 7, 25 mg of dinoprost tromethamine; Day 8, 25 mg of dinoprost tromethamine, 1 mg of oestradiol cipionate, and device withdrawal; Day 10, AI. At Day 14, the cows were alternately arranged in 2 groups. Group 1 received a 900-mg progesterone supplementation IM injection, and Group 2 did not receive progesterone supplementation. Then, 32 ± 3 days after insemination, pregnancy diagnosis was performed by transrectal ultrasonography, and the data were tabulated. Full statistical analysis will be done at the end of the study, when more than 500 cows will be allocated to the 2 groups. From January until April 2016, 230 lactating dairy cows were submitted to the experiment. Both groups had similar average days in lactation (166), average number of lactations (1.95), and average number of inseminations (4.3). Group 1 had a pregnancy rate of 25% (29/116), and group 2 had a pregnancy rate of 15.8% (18/114) (P = 0.01, one-way ANOVA). Based on these preliminary data, pregnancy rates of lactating dairy cows may be improved with progesterone supplementation on Day 4 after insemination. These results need to be confirmed on larger numbers of cows.

Effectiveness of a recombinant human follicle stimulating hormone on the ovarian follicles, peripheral progesterone, estradiol-17β, and pregnancy rate of dairy cows.

Aims:This study aimed at elucidating the effects of recombinant human follicle stimulating hormone (r-hFSH) on the ovarian follicular dynamics, progesterone, estradiol-17β profiles, and pregnancy of dairy cows.Materials and Methods:Three groups (G, n=5 cows) of multiparous dairy cows were used. G1 (C) control cows were given controlled internal drug release (CIDR) and prostaglandin F2α; G2 (L) cows were given low dose (525 IU and G3 (H) cows were given high dose (1800 IU) of r-hFSH on twice daily basis at the last 3 days before CIDR removal. All cows were ultrasonically scanned for follicular growth and dynamics, and blood samples were collected every other day for two consecutive estrus cycles for the determination of estradiol-17β and progesterone.Results:Estrus was observed in all C and L but not in H cows. Dominant follicle was bigger in L compared to C and H cows. Dominant follicle in C (16.00±2.5 mm) and L cows (17.40±2.3 mm) disappeared at 72 h after CIDR removal. However, in H cows, no ovulation has occurred during 7 days post-CIDR removal. Progesterone was not different (p>0.10) among groups, whereas estradiol-17β revealed significant (p<0.01) reduction in H (15.96±2.5 pg/ml) cows compared to C (112.26±26.1 pg/ml) and L (97.49±15.9 pg/ml) cows. Pregnancy rate was higher in L cows (60%) compared with C cows (20%). However, H cows were not artificially inseminated due to non-ovulation. Only a cow of C group has calved one calf, however, 2 of the L cows gave birth of twins and a cow gave single calf.Conclusion:Administration of a low dose (525 IU) of r-hFSH resulted in an optimal size of dominant follicle, normal values of progesterone and estradiol-17β, and 40% twinning rate, howeverusing 1800 IU of r-hFSH, have adverse effects on ovarian follicular dynamics and hormonal profiles with non-pregnancy of dairy cows raised under hot climate.

Pregnancy rate in dairy cows treated with progesterone for six days during estrus synchronization with PGF2α

The present study evaluated the effect of progesterone supplementation during a double PGF2α injection synchronization protocol on pregnancy per artificial insemination (P/AI) and on the incidence of twin births. Seven hundred and eighty three dairy cows were synchronized with two injections of PGF2α 14 days apart, starting on day 35 postpartum for their first postpartum insemination. Six days before the second PGF2α injection, cows were treated either with a progesterone-releasing intravaginal device (PRID-Delta) and an intramuscular injection of 500mg of progesterone (n=387) or served as control (n=396) and did not receive progesterone treatment. Cows were inseminated 12h after being detected in estrus. Pregnancy was diagnosed 40–45 days later by transrectal palpation. Progesterone administration improved (P<0.05) the percentage of cows detected in estrus in multiparous [(192/255) 75% vs (161/267) 60%], but not in primiparous cows [93/132 (70%) vs 90/129 (70%)]. Progesterone treatment increased P/AI in multiparous [53/192 (28%) vs 27/161 (17%)] but not in primiparous cows [25/93 (27%) vs 29/90 (32%)]. The incidence of twin births tended to be lower (P=0.09) in cows treated with progesterone [1/74 (1%)] than in the control group [4/53 (7%)]. It is concluded that progesterone administration during estrus synchronization with two PGF2α injections in dairy cows improves estral response and increases P/AI in multiparous, but not in primiparous cows, and tended to decrease the incidence of twin births.

The effect of ovulatory follicle size at the time of insemination onpregnancy rate in lactating dairy cows

The aims of this study were to determine the factors that affect follicle size at the time of artificial insemination (AI) and to detect the relationship between ovulatory follicle size at the time of AI and pregnancy rate in dairy cows. A total of 1428 follicle size measurements were obtained from Holstein-Friesian (HF) and Swedish Red (SR) cows that were inseminated with the fixed-timed AI protocols used in this study. Follicle size was affected by breed (P = 0.0001), milk production (P = 0.01), parity (P = 0.05), and season (P = 0.04). Follicle size was greater (P = 0.0001) in the HF (15.55 mm) than the SR cows (14.88 mm). Multiparous cows had larger (P = 0.04) follicles (15.35 mm) than the primiparous cows (15.07 mm). Cows with follicle sizes between 13.5 and 17.5 mm were more likely to be pregnant than cows with other sizes follicles (P < 0.01). Embryonic loss was lower (P < 0.01) in cows with follicle sizes between 13.5 and 16.5 mm. Thus, the follicle size was affected by breed, milk production, parity, and season. Pregnancy and embryonic loss in lactating dairy cows were significantly related to follicle size.

Inducing ovulation with oestradiol cypionate allows flexibility in the timing of insemination and removes the need for gonadotrophin-releasing hormone in timed AI protocols for dairy cows.

The effects of addition of gonadotrophin-releasing hormone (GnRH) to a progesterone plus oestradiol-based protocol and timing of insemination in Holstein cows treated for timed AI (TAI) were evaluated. Cows (n=481) received a progesterone device and 2mg oestradiol benzoate. After 8 days, the device was removed and 25mg dinoprost was administered. Cows were allocated to one of three (Study 1; n=57) or four (Study 2; n=424) groups, accordingly to ovulation inducer alone (Study 1; oestradiol cypionate (EC), GnRH or both) or ovulation inducer (EC alone or combined with GnRH) and timing of insemination (48 or 54h after device removal; Study 2). In Study 1, the diameter of the ovulatory follicle was greater for GnRH than EC. Oestrus and ovulation rates were similar regardless of ovulatory stimuli. However, time to ovulation was delayed when GnRH only was used. In Study 2, cows treated with GnRH or not had similar pregnancy per AI (P/AI) 30 days (41.5% vs 37.3%; P=0.28) and 60 days (35.9% vs 33.0%; P=0.61) after TAI. TAI 48 and 54h after device removal resulted similar P/AI at 30 days (40.3% vs 38.5%; P=0.63) and 60 days (33.8% vs 35.1%; P=0.72). Thus, adding GnRH at TAI does not improve pregnancy rates in dairy cows receiving EC. The flexibility of time to insemination enables TAI of a large number of cows using the same protocol and splitting the time of AI.