AI In Cows Research Articles

Timed artificial insemination in blocks: A new alternative to improve fertility in lactating beef cows

The aim of this study was to evaluate whether changing the interval from CIDR removal to timed artificial insemination (TAI) according to the diameter of the preovulatory follicle (POF) would improve pregnancy per AI in cows. In Study 1, a retrospective analysis of TAI experiments (n=96 cows) was performed to characterize the time of ovulation according to the diameter of the dominant follicle. It was observed that cows with a larger POF had ovulations earlier than cows with smaller POF, according to the equation: y=0.72x2−26.74x+264.54 (R2=0.63; P<0.001). In Study 2, lactating Nelore cows (n=412) were subjected to an EB-CIDR based TAI protocol. On the morning of Day 10 (time of TAI), cows were randomized into Control (n=209) and Block (n=203) groups; (1) Cows in the Control Group were TAI 48h after CIDR removal (08:00am on Day 10), and; (2) Cows in the block group were inseminated once at one of the following time points, according to the diameter of the POF on Day 10: B0 (POF≥15mm, TAI 0h after convetional TAI), B1 (POF 13–14.9mm, TAI 6h later), B2 (POF 10.1–12.9mm, TAI 24h later) and B3 (POF≤10mm, TAI 30h later). The cows of the Block Group had greater pregnancy rates per AI than the Control Group (129/203, 63.5% when compared with 102/209, 48.8%, respectively; P<0.01). In conclusion, results of the present study demonstrate that adjusting the timing of TAI according to the diameter of the POF can be an effective practice for improving fertility of cows in TAI protocols.

Relationships between fertility and postpartum changes in body condition and body weight in lactating dairy cows

The relationship between energy status and fertility in dairy cattle was retrospectively analyzed by comparing fertility with body condition score (BCS) near artificial insemination (AI; experiment 1), early postpartum changes in BCS (experiment 2), and postpartum changes in body weight (BW; experiment 3). To reduce the effect of cyclicity status, all cows were synchronized with Double-Ovsynch protocol before timed AI. In experiment 1, BCS of lactating dairy cows (n=1,103) was evaluated near AI. Most cows (93%) were cycling at initiation of the breeding Ovsynch protocol (first GnRH injection). A lower percentage pregnant to AI (P/AI) was found in cows with lower (≤2.50) versus higher (≥2.75) BCS (40.4 vs. 49.2%). In experiment 2, lactating dairy cows on 2 commercial dairies (n=1,887) were divided by BCS change from calving until the third week postpartum. Overall, P/AI at 70-d pregnancy diagnosis differed dramatically by BCS change and was least for cows that lost BCS, intermediate for cows that maintained BCS, and greatest for cows that gained BCS [22.8% (180/789), 36.0% (243/675), and 78.3% (331/423), respectively]. Surprisingly, a difference existed between farms with BCS change dramatically affecting P/AI on one farm and no effect on the other farm. In experiment 3, lactating dairy cows (n=71) had BW measured weekly from the first to ninth week postpartum and then had superovulation induced using a modified Double-Ovsynch protocol. Cows were divided into quartiles (Q) by percentage of BW change (Q1 = least change; Q4 = most change) from calving until the third week postpartum. No effect was detected of quartile on number of ovulations, total embryos collected, or percentage of oocytes that were fertilized; however, the percentage of fertilized oocytes that were transferable embryos was greater for cows in Q1, Q2, and Q3 than Q4 (83.8, 75.2, 82.6, and 53.2%, respectively). In addition, percentage of degenerated embryos was least for cows in Q1, Q2, and Q3 and greatest for Q4 (9.6, 14.5, 12.6, and 35.2% respectively). In conclusion, for cows synchronized with a Double-Ovsynch protocol, an effect of low BCS (≤2.50) near AI on fertility was detected, but change in BCS during the first 3wk postpartum had a more profound effect on P/AI to first timed AI. This effect could be partially explained by the reduction in embryo quality and increase in degenerate embryos byd 7 after AI in cows that lost more BW from the first to third week postpartum.

19 CHANGES IN PLASMA STEROID CONCENTRATIONS DURING GESTATION IN COWS WITH SPONTANEOUS ABORTION OF SOMATIC CELL CLONED FETUSES

Cloning of mammals by nuclear transfer frequently results in gestational failure with a variety of abnormalities that are likely due to inappropriate epigenetic reprogramming. Monitoring the placental function during gestation is important to clarify the cause of abnormalities in cloned animals. Sex steroids are produced in the bovine placenta and their levels in maternal peripheral blood are a useful measure of placentation. The objective of this study was to investigate changes in plasma concentrations of sex steroids during gestation in cows aborting cloned fetuses. Donor cells for nuclear transfer were obtained from subculture of cumulus cells retrieved from ovarian follicles of a Japanese Black cow. Recipient oocytes were derived from ovaries obtained at an abattoir and matured in vitro. Metaphase II oocytes were enucleated and each fused with a donor cell by DC pulses. Nuclear-transferred oocytes were activated and cultured for 7 days. Embryos developed to the blastocyst stage were each transferred into the uterine horn ipsilateral to the ovary bearing the CL of 39 multiparous Japanese Black and Holstein crossbred cows at 7 to 8 days after the day of standing oestrus (day 0). Fourteen recipient cows were diagnosed pregnant on Day 40 by ultrasonography and 7 cows delivered at full term. The other seven miscarried on Day 66, 81, 85, 89, 97, 104 and 211. Blood was collected from these cows at least once a week following the pregnancy diagnosis. Progesterone, estrone, oestradiol-17β and estrone sulfate in the blood plasma were measured by RIA and were compared with those in pregnant AI cows. Statistical differences at stages of gestation were analysed with repeated-measures ANOVA. In all miscarried cows, progesterone concentrations were similar to those in AI cows until several days before abortion and then rapidly decreased to the basal level. Concentrations of all estrogens stayed low until abortion in six cows aborting by day 104, whereas estrone and oestradiol-17β started to increase around Day 80 and estrone sulfate gradually increased from around Day 50 and started to increase drastically around Day 80 in AI cows. In another cow aborting on Day 211, profiles of estrone and oestradiol-17β were similar to those in AI cows until around Day 150. Thereafter, concentrations of these estrogens gradually decreased to the basal levels by Day 160 and stayed low until abortion. In this cow, gradual increase in estrone sulfate during Day 50 to 80 was not observed, but the difference in the concentration was not statistically significant from AI cows. The following profile of estrone sulfate was similar to those in active estrogens. The fetus was still alive on day 160 and fetal death was confirmed on day 180 by ultrasonography. These results suggest the possibility that developmental or functional failure of placenta associated with steroid synthesis may be a cause of mid-term miscarriage of a cloned fetus.

Effects of cloprostenol sodium at final prostaglandin F2α of Ovsynch on complete luteolysis and pregnancy per artificial insemination in lactating dairy cows

Luteolysis is a key event in Ovsynch programs of lactating dairy cows. Studies indicate that as many as 20% of cows treated with a Presynch/Ovsynch program have delayed or incomplete luteolysis using dinoprost tromethamine. Cows must have complete luteolysis to have a chance to become pregnant. Dinoprost tromethamine has a short half-life of approximately 7 to 8min. Cloprostenol sodium is more resistant to endogenous metabolism and is maintained in circulation for a longer time (half-life=3h). The objective was to determine if cloprostenol sodium could increase the percentage of cows with complete luteolysis and subsequent pregnancy per artificial insemination (P/AI) in lactating dairy cows compared with dinoprost tromethamine when administered within a presynchronization plus Ovsynch program for first artificial insemination (n=652) and an Ovsynch resynchronization program for second or later AI (second+; n=394). Blood samples were collected daily for 5 d beginning at the PGF2α of Ovsynch in a subset of cows (n=680) for first and second+ AI to measure circulating concentrations of progesterone (P4) and estradiol (E2). Complete luteolysis was defined as cows with functional corpus luteum (CL) at time of treatment and serum concentrations of P4 <0.5ng/mL at 56, 72, and 96h after treatment. Percentage of cows with functional CL that had complete luteolysis after treatment was not greater for cloprostenol sodium compared with dinoprost tromethamine in first (79 vs. 80%, respectively) or second+ AI (70 vs. 72%, respectively). In addition, mean serum concentrations of P4 were not less for cows treated with cloprostenol sodium following treatment. Pregnancy per AI of cows treated with cloprostenol sodium tended to be greater than dinoprost tromethamine for first (40 vs. 35%; respectively) but not second+ AI (23 vs. 21%, respectively). Cows with greater serum P4 concentrations at time of PGF2α of Ovsynch had a greater probability of undergoing complete luteolysis after PGF2α of Ovsynch and pregnancy at 39 d after timed AI (i.e., 50% pregnant at 8 vs. 28% pregnant at 4ng/mL P4). Serum concentrations of E2 at 56h after PGF2α of Ovsynch were a positive predictor of pregnancy at 39 d after timed AI. In summary, cloprostenol sodium tended to improve P/AI. Cows with greater serum concentrations of P4 at time of PGF2α of Ovsynch had a greater chance of luteolysis and pregnancy.

18 RELATIONSHIP BETWEEN MULTIPLE OVULATIONS AND CONCEPTION IN LACTATING DAIRY COWS

The relationship between multiple ovulations and various factors involved in conception in lactating Holstein cows was investigated in this study. A total of 53 AI cows housed in a free-stall barn were assigned to this study. They were offered a balanced TMR ad libitum during the experimental period. Cows were milked at 0830 and 1900 h. Milk yields were recorded at each milking. Estrus was detected by radiotelemetric pedometers (Yoshioka et al. 2007 Reprod. Fertil. Dev. 19, 129). The body condition score (BCS) of cows was recorded at estrus. Artificial insemination was performed according to the pedometry data. Pregnancy was diagnosed 42 days post-AI by transrectal ultrasonography. Ovulation was assessed by transrectal ultrasonography of the ovary every 3 h from the end of estrus. Ovulation time was measured from the onset of estrus to ovulation. Milk production of each cow was determined from 14 days before the day of estrus. Blood samples for estradiol-17β (E2) were collected at the peak of estrus, and for progesterone (P4), samples were collected on Days 0, 3, 6, 9, and 12 (estrus = Day 0). The E2 and P4 concentrations were measured by enzyme immunoassay. Preovulatory follicles at estrus and CL on Day 0, 3, 6, 9, and 12 were monitored by transrectal ultrasonography. The overall incidence of multiple ovulations was 28.3% (15/53). There was no difference in duration of estrus between cows with multiple ovulations and cows with single ovulations (10.2 h, n = 15 v. 9.8 h, n = 38). Ovulation time was longer for cows with multiple ovulations than that for cows with single ovulations (30.4 h, n = 10 v. 28.7 h, n = 26; P = 0.0545). In all cases of multiple ovulations, 2 follicles ovulated simultaneously. The milk production of cows with multiple ovulations was higher than that of cows with single ovulations (40.1, n = 15 v. 36.2 kg d–1, n = 38; P = 0.0515); however, BCS showed the opposite results (2.86, n = 15 v. 3.13, n = 38; P &lt; 0.05). There was a significant inverse correlation between milk production and BCS in cows with multiple ovulations (r = –0.768; P &lt; 0.01). The E2 concentrations showed no difference between cows with multiple and single ovulations (9.6 pg mL–1, n = 8 v. 8.2 pg mL–1, n = 23). The diameters of preovulatory dominant follicles and secondary follicles at estrus in cows with multiple ovulations were significantly smaller than those in cows with single ovulations (18.2 and 14.2 mm, n = 14 v. 19.9 mm, n = 38, respectively; P &lt; 0.05). Cows with multiple ovulations showed a significantly higher P4 concentration and a larger CL than those with single ovulations from Day 3 to 12. The conception rate for AI was significantly higher for cows with multiple ovulations than for cows with single ovulations (73.3%, n = 15 v. 36.2%, n = 38; P &lt; 0.05). Our results showed that high conception rates, high levels of milk production, and low BCS were associated with multiple ovulations.

Evaluation of Methods of Resynchronization for Insemination in Cows of Unknown Pregnancy Status

The objectives of this study were to evaluate the effect of 3 methods of resynchronization of estrus and ovulation for lactating dairy cows of unknown pregnancy status on conception rate and time to pregnancy. Holstein cows (n = 495) were randomly assigned to 1 of 3 treatments: 1) control (n = 167), resynchronization with a timed AI protocol upon diagnosis of nonpregnancy on d 31 after preenrollment AI (PAI); 2) CIDR-G (n = 159), use of an intravaginal progesterone insert from d 14 to 21 after AI, with AI at estrus from d 21 to 24 and initiation of a timed AI protocol on d 24 after AI in cows not reinseminated; 3) CIDR-G + ECP (n = 169), the same treatment as CIDR-G but with an injection of 1mg of estradiol cypionate at the time of progesterone insert removal. Cows were continuously reenrolled in the same treatment until diagnosed as pregnant, which resulted in a total of 1,148 AI (495 PAI and 653 resynchronized AI; RAI). Blood was collected from 1,001 cows on d 14, 21, and 24 after each AI for analysis of progesterone, and ovaries were scanned on d 21, 24, and 31 after AI. The presence of an active corpus luteum was presumed based on progesterone ≥1 ng/mL. Pregnancy was diagnosed by ultrasonography on d 31 and 61 after AI. The presence of an active corpus luteum and the incidence of luteolysis were similar for all treatments from d 14 to 24; however, luteolysis increased in the CIDR-G + ECP treatment from d 21 to 24. Conception rates for the PAI and all AI were similar on d 31 and 61 after insemination. Conception rates at 31 and 61 d after the RAI were also similar among treatments. Overall pregnancy loss for the PAI, RAI, and all AI were similar for all treatments. The accuracy of estrous detection, based on progesterone concentration within 2 d of detection of estrus, was similar for all treatments for the RAI and averaged 95.3%. The estrus-detection rate (EDR) decreased for the CIDR-G and CIDR-G + ECP treatments from d 14 to 21, but increased from d 21 to 24 compared with control cows; however, the EDR was smaller for cows in the CIDR-G treatment during the entire resynchronization period compared with those in the CIDR-G + ECP and control groups. The reinsemination interval was reduced in cows receiving the CIDR-G + ECP treatment compared with control cows because of increased EDR after removal of the intravaginal insert; however, the interval from study enrollment to pregnancy was not different among treatments. These results indicate that the reproductive performance of dairy cows did not differ among the 3 resynchronization treatments evaluated.

Maintenance of Pregnancy in Repeat Breeder Dairy Cows by CIDR Administration After Breeding

The aim of this study was to assess the effect of two periods of P4 therapy by CIDR on the 1st service Conception Rate (CR) of repeat breeder dairy cows. The cows were selected on the following basis: absence of dystocia, retained placenta and endometritis after the last parturition. They were inseminated according to the AM/PM rule relative to estrus onset and randomly assigned into 3 groups: (A) CIDR on day 5 after insemination that was removed on day 9 of the cycle (n = 40); (B) CIDR on day 5 after insemination that was removed on day 19 of the cycle (n = 36) and (C) untreated controls (n = 40). Pregnancy diagnosis was conducted by rectal palpation 45-55 days after AI in cows not observed in estrus. The difference in CR among the groups was analyzed by chi square analysis. The CR in groups A, B and C was 55, 41.7 and 30%, respectively and was greater (p<0.05) in treatment (A) cows than in control cows. In conclusion, repeat breeder cows in groups A and B benefited from progesterone supplementation, but significant effects of treatment for improvement of conception rate was seen in short treatment period (4 days treatment).

Fertility-associated proteins in Nelore bull sperm membranes

The present study was undertaken to evaluate the protein composition of the sperm membranes (SM) of Nelore bulls, assessing protein markers associated with bull fertility, and whether these markers can be used for predicting bull fertility. Samples were obtained of 20 Nelore bulls, with fertility ranked and divided into three groups (greater, normal and least). To rank the bull's fertility weighted classification was used (according to the number of pregnant cows, number of AI cows and number of herds, considering three different breeding seasons), using the PROC GENMOD as a statistical model, with 99% significance. A total of 7897 Nelore cows, randomly distributed among 28 different farms, were considered in the statistical analyses. The bulls were divided into three fertility groups (pregnancy rates): greater (% F > 80), normal (79 < % F > 71) and least (<68% F) with 3, 13 and 4 bulls, respectively. Two-dimensional gel electrophoresis (2DE) of sperm membranes indicated in 27 spots (SM40, SM53, SM69, SM93, SM102, SM111, SM137, SM138, SM189, SM196, SM201, SM202, SM204, SM225, SM236, SM237, SM239, SM241, SM246, SM247, SM275, SM283, SM342, SM346, SM355, SM372, SM391) was prevalent in the higher fertility group, and just one spot (SM244) was prevalent in the lower fertility group. Spots SM244 and SM239 had their identification defined by PMF/MALDI-MS, as BSP-A3 and aSFP, respectively. Both these proteins showed a great potential for predicting bull's fertility. The amount of aSFP was 8.5 times greater in the sperm membrane protein profile of the higher fertility groups of Nelore bulls. Besides that, the BSP-A3 was 2.5 times greater in the lower fertility group. For the other spots potentially associated with fertility not yet identified, additional tests will be necessary, but it is clear that the 2D electrophoresis of the sperm membrane can be used for a new approach to predict Nelore bull fertility.

Comparison of artificial insemination versus embryo transfer in lactating dairy cows

Conception rates (CR) are low in dairy cows and previous research suggests that this could be due to impaired early embryonic development. Therefore, we hypothesized that CR could be improved by embryo transfer (ET) compared with AI. During 365 days, 550 potential breedings were used from 243 lactating Holstein cows (average milk production, 35 kg/day). Cows had their ovulation synchronized (GnRH-7d-PGF 2α-3d-GnRH) and they were randomly assigned for AI immediately after the second GnRH injection (Day 0) or for transfer of one embryo 7 days later. Circulating progesterone concentrations and follicular and luteal size were determined on Days 0 and 7. Pregnancy diagnosis was performed on Days 25 or 32 and pregnant cows were reevaluated on Days 60–66. Single-ovulating cows with synchronized ovarian status had similar CR on Days 25–32 with ET ( n = 176; 40.3%) and AI ( n = 160; 35.6%). Pregnancy loss between Days 25–32 and 60–66 also did not differ ( P = 0.38) between ET (26.2%) and AI (18.6%). When single ( n = 334) and multiple ( n = 57) ovulators were compared, independent of treatment, multiple ovulators had greater ( P < 0.001) circulating progesterone concentrations on Day 7 (2.7 ng/ml versus 1.9 ng/ml) and there was a tendency ( P = 0.10) for a greater CR in multiple ovulators (50.9% versus 38.1%). However, there was no difference in CR between AI and ET cows with multiple ovulations (50.0% versus 51.7%). In single-ovulating cows, CR tended to be lower for AI than ET in cows ovulating smaller follicles (diameter ≤ 15 mm; 23.7% versus 42.3%; P = 0.06) but not average-diameter follicles (16–19 mm; 41.2% versus 37.3%; P = 0.81) or larger (≥20 mm; 34.3 versus 51.0%; P = 0.36) follicles. Thus, although ET did not improve overall CR in lactating cows, follicle diameter and number of ovulating follicles may determine success with these procedures.

In Vitro Embryo Production: Growth Performance, Feed Efficiency, and Hematological, Metabolic, and Endocrine Status in Calves

The potential management benefits of in vitro embryo production have been offset by an increased incidence of health-related problems in resulting calves [increased birth weight, congenital abnormalities, and peri- and postnatal mortality (large-offspring syndrome)] and of recipient cows (prolonged gestation, dystocia, increased hydroallantois, abortion). The aim of the present research was to determine whether relevant metabolic, endocrine, or hematological traits could be related to the causes of enhanced growth performance of in vitro fertilized calves. Growth performance and feed efficiency as well as hematological, metabolic, and endocrine traits studied in calves derived from in vitro-produced embryos (IVP; n=11) and in calves derived from artificial insemination (AI; n=8). Donor cows from which oocytes for in vitro fertilization were obtained had a heterogeneous background, thus excluding genetic maternal influences. On the other hand, semen for in vitro fertilization and for artificial insemination was from the same bull, and recipient cows were held under the same husbandry and feeding conditions as AI cows, thus reducing the variability. Blood samples were collected preprandially on d 1, 2, 3, 4, 7, 14, 28, 56, and 112 of life and every 20min between 0830 and 1630h on d 7 and 112 for the evaluation of growth hormone secretory patterns. Gestation of IVP cows was longer than that of AI cows, but birth weights were similar in both groups. Feed intake, average daily gain, and body length during the experimental period, body weight from wk 8 to 16, and gain/feed ratio during the first month of life were higher in IVP than in AI calves. At birth, potassium, 3,5,3′-triiodothyronine, and thyroxine concentrations were lower in IVP than in AI calves. Concentrations of sodium and potassium on d 7, of triglycerides on d 28, and of albumin on d 56 were higher in IVP than in AI calves. In conclusion, IVP calves had higher feed intake and growth rate during the entire growth period and improved feed efficiency in the first month of life than AI calves, but this was not mirrored by consistent changes of hematological, metabolic, or endocrine traits, whose concentrations were in the normal range. Additional work is needed to study IVP calves under field conditions.

Environmental effects on progesterone profile measures of dairy cow fertility

Environmental effects on fertility measures early in lactation, such as the interval from calving to first luteal activity (CLA), proportion of samples with luteal activity during the first 60 days after calving (PLA) and interval to first ovulatory oestrus (OOE) were studied. In addition, traditional measurements of fertility, such as pregnancy to first insemination, number of inseminations per service period and interval from first to last insemination were studied as well as associations between the early and late measurements. Data were collected from an experimental herd during 15 years and included 1106 post-partum periods from 191 Swedish Holsteins and 325 Swedish Red and White dairy cows. Individual milk progesterone samples were taken twice a week until cyclicity and thereafter less frequently. First parity cows had 14.8 and 18.1 days longer CLA (LS-means difference) than second parity cows and older cows, respectively. Moreover, CLA was 10.5 days longer for cows that calved during the winter season compared with the summer season and 7.5 days longer for cows in tie-stalls than cows in loose-housing system. Cows treated for mastitis and lameness had 8.4 and 18.0 days longer CLA, respectively, compared with healthy cows. OOE was affected in the same way as CLA by the different environmental factors. PLA was a good indicator of CLA, and there was a high correlation (−0.69) between these two measurements. Treatment for lameness had a significant influence on all late fertility measurements, whereas housing was significant only for pregnancy to first insemination. All fertility traits were unfavourably associated with increased milk production. Regression of late fertility measurements on early fertility measurements had only a minor association with conception at first AI and interval from first to last AI for cows with conventional calving intervals, i.e. a 22 days later, CLA increased the interval from first to last insemination by 3.4 days. Early measurements had repeatabilities of 0.14–0.16, indicating a higher influence by the cow itself compared with late measurements, which had repeatabilities of 0.09–0.10. Our study shows that early fertility measurements have a possibility to be used in breeding for better fertility. To improve the early fertility of the cow, there are a number of important factors that have to be taken into account.

Fertility following fixed-time AI or insemination at observed estrus in Ovsynch and Heatsynch programs in lactating dairy cows

The objective of this study was to compare the conception rate for fixed-timed artificial insemination (FTAI) and observed heat artificial insemination (HAI) prior to the scheduled FTAI in Ovsynch and Heatsynch synchronization protocols. In Experiment 1, lactating dairy cows ( n = 535) received two set-up injections of 25 mg prostaglandin F 2α (PGF 2α) i.m., 14 days apart starting at 36 ± 3 days in milk (DIM). Cows were blocked by parity and were randomly allocated to either Ovsynch or Heatsynch groups. All cows received 100 μg of GnRH i.m. 14 days after the second set-up injection of PGF 2α, followed by a third injection of 25 mg PGF 2α i.m., 7 days later. In the Ovsynch group, HAI cows ( n = 29) were bred on standing estrus after the third PGF 2α before the scheduled second GnRH, whereas FTAI cows ( n = 218) that were not observed in estrus, received a second injection of 100 μg of GnRH i.m., 48 h after the third PGF 2α and received TAI 8 h after the second GnRH. In the Heatsynch group, all cows ( n = 288) received 0.5 mg of estradiol cypionate (ECP) 24 h after third PGF 2α and HAI cows ( n = 172) were bred on standing estrus and FTAI cows ( n = 116) that were not observed in estrus, received TAI 72 h after the third PGF 2α. In Experiment 2, repeat breeder cows ( n = 186) were randomly assigned to either Ovsynch or Heatsynch groups. The FTAI and HAI cows were inseminated similar to Experiment 1. All cows were observed for estrus three times daily. The associations with the conception rate were modeled with logistic regression separately for Experiments 1 and 2. Of all the variables included in the model in Experiment 1, type of AI (HAI versus FTAI, P = 0.0003) and parity (primiparous versus multiparous, P = 0.05) influenced the first service conception rate. Over-all conception rate and first service conception rate for HAI cows were higher compared to FTAI cows (33.8% versus 21.3%, and 35.3% versus 21.0%; P = 0.001). In the Heatsynch group, cows that received HAI had significantly higher over-all conception rate and first service conception rate compared to FTAI (35.2% versus 17.3% and 36.0% versus 15.5%; P = 0.0001). The conception rates in repeat breeder cows for HAI and FTAI (30.1% versus 22.3%) were not different ( P > 0.1). In conclusion, it was recommended to include AI at observed estrus and fixed-time AI for cows not observed in estrus in order to improve the conception rate in synchronization protocols.

Effect of timing of first clinical mastitis occurrence on lactational and reproductive performance of Holstein dairy cows

Objectives of this study were to determine the influence of timing of first clinical mastitis case occurrence on lactational and reproductive performance in high producing lactating dairy cows during the first 320 days in milk (DIM). Holstein cows, 1001, from two commercial dairy farms in California were retrospectively divided into four treatment groups according to timing of first clinical mastitis case caused by environmental pathogens: control with no recorded clinical cases of mastitis (C; n=501); first clinical mastitis prior to first postpartum AI (MG1; n=250); first clinical mastitis between first postpartum AI and pregnancy diagnosis (MG2; n=147); and first clinical mastitis after diagnosed pregnant (MG3; n=103). Clinical cases of mastitis were identified at every milking by the herd personnel based on abnormal milk or swelling of the mammary gland. A fore sample of milk was aseptically collected from every clinical case for microbiological culture. Mastitis decreased yields of milk, 3.5% fat-corrected milk, and milk components, but the effect was only observed for MG1 and MG2. Cows in the control group had lower linear somatic cell count (SCC) score throughout the lactation. Culling was increased by mastitis, and cows in the mastitis groups left the study earlier than controls. Conception rate at first postpartum AI and pregnancy rate at the end of the study were both decreased by mastitis prior to or after first AI, and MG1 and MG2 cows had extended days open. Furthermore, cows experiencing mastitis during lactation had a higher incidence of abortions. The negative effects of mastitis on reproduction were observed regardless of clinical case being caused by either Gram positive or negative bacteria. Mastitis either prior to or after first postpartum AI impairs lactation performance, increases culling, and decreases reproductive efficiency in high producing Holstein dairy cows.

Is fertility declining in dairy cattle?: A retrospective study in northeastern Spain

The past few decades have seen a dramatic increase in infertility and reproductive disorders associated with a rising milk yield. Herein, we present a 10-year (from 1991 to 2000) retrospective survey of these factors using data from a reproductive management program performed on high-yielding dairy herds in north-east Spain. The data series included 12,711 lactations. The year was divided into warm and cool periods. Data were obtained from cows first inseminated or examined 45–70 days postpartum. The reproductive tract of each animal was examined by palpation per rectum within 43–48 days postpartum. Cows were then weekly examined until insemination or until postpartum Day 70. Cows with a corpus luteum were synchronized for estrus and timed AI. Cows showing natural estrus in the same period were also inseminated. All inseminations were pooled as a single group and inseminated cows were considered cyclic. Inactive ovaries and ovarian cysts were recorded as ovarian disorders. Incomplete uterine involution, endometritis and pyometra were grouped as uterine disorders. Overall cyclicity and pregnancy rates of all AI cows, and cyclicity and pregnancy rates corresponding to the warm period significantly decreased over the 10-year period, yet remained practically constant during the cool period. The incidence of inactive ovaries in the entire population and that corresponding only to cows examined during the warm period significantly increased with time but was similar during the cool period. Ovarian cysts were more frequent during the warm (12.3%) than during the cool (2.4%) period, though these proportions were maintained throughout the study. The incidence of uterine disorders significantly decreased with time and did not differ between cool and warm periods. Milk yield per cow and year increased from 7800 kg in 1991 to 10,200 kg in 2000. Regression analysis revealed that, for all cows and those inseminated or examined in the warm period respectively, each 1000 kg increase in average milk yield was related to decreases of 3.2 and 6% in pregnancy rate, 4.4 and 7.6% in cyclicity, and to increase of 4.6 and 8% in the incidence of inactive ovaries. The rate of uterine disorders decreased 1.1% regardless of season. Our overall results clearly reflect the increased infertility and incidence of reproductive disorders over the study period. This occurred simultaneous to increasing average milk yield. Nevertheless, under our study conditions, a cool environment appears to preserve fertility and reduce the risk of reproductive disorders irrespective of the milk yield. These findings prompt the need to improve management practices by attempting to reduce the effects of factors provoking stress.

乳牛におけるGnRHとPGF&lt;SUB&gt;2α&lt;/SUB&gt;およびhCG投与による排卵同期化および定時人工授精の検討

The present study was carried out to determine the efficacy of replacing the second GnRH with hCG (GnRHPGF2αhCG) in Ovsynch used for timed AI in cows. In the firstexperiment, Holstein cows were divided into 3 groups according to post-estrus day: day 5-6, day 10-11, and day 15-16 (n = 5 for each group). In each group, ovulation was highly synchronized in cows treated with GnRH-PGF2α-hCG (hCG: 3, 000 IU). In thesecond experiment, Holstein cows were randomly divided into 2 groups and each cow was treated with either GnRHPGF2α-hCG (n=42) or Ovsynch (n=41). Conception rates were 52.4% for cows treated with GnRH-PGF2α-hCG and 51.2% for cows treated with Ovsynch. It was estimated that replacisng GnRH with hCG for ovulation synchronization saved \703 per cow and Y1, 533 per conception. These results show that ovulation synchronization and timed AI for dairy cows can be performed without conception-rate reduction and at lower costs by replacing the second GnRH with hCG in Ovsynch.

Attenuation of premature estrous behavior in postpartum beef cows synchronized to estrus using GnRH and PGF 2α

The efficacy of GnRH and PGF 2α (7-day injection interval) for estrus synchronization is diminished by estrous expression before PGF 2α (premature estrus; PE). Effects of modifications to GnRH-PGF 2α protocols on the incidence of PE and other indicators of reproductive performance were evaluated. In Experiment 1, Angus-based crossbred cows (n=51) received 25 mg of PGF 2α im on Day 0. Animals were randomly assigned by parity and interval postpartum to receive GnRH 100 μg im on either Day −7 or Day −6. Estrous detection and AI were conducted from Day −3 to Day 5. Treatment had no effect on the incidence of PE, estrous response, conception rate per AI or synchronized pregnancy rate (6- vs. 7-day interval; 8 vs. 15%; 92 vs. 93%; 77 vs. 76%; 71 vs. 70%, respectively). In Experiment 2, Angus cows (n = 150) received GnRH 100 μg im on Day −7 and 25 mg PGF 2α im on Day 0. Animals were randomly assigned by parity, interval postpartum, and body condition score to receive either no further treatment (Control) or 0.5 mg melengestrol acetate/hd/d from Day −7 to Day −1 (MGA). Estrous detection and AI were conducted from Day −2 to Day 7. Fewer (P < 0.05) MGA-treated cows were detected in PE (0%) compared to controls (7%). Treatment had no effect on estrous response or synchronized pregnancy rates (Control vs. MGA; 78 vs. 84%; 52 vs. 60%, respectively). Conception rate per AI of cows ≥60 days postpartum were not affected by treatment (Control vs. MGA; 79 vs. 73%) however, control cows <60 days postpartum tended (P < 0.10) to have lower conception rates per AI (39%) than did their MGA-treated counterparts (69%). In summary, 6- and 7-day GnRH-PGF 2α injection intervals resulted in similar synchronized reproductive performance. Inclusion of MGA feeding between GnRH and PGF 2α injections eliminated the occurrence of premature estrus and improved conception rate per AI of late-calving cows.

Synchronization rate, size of the ovulatory follicle, and pregnancy rate after synchronization of ovulation beginning on different days of the estrous cycle in lactating dairy cows

Recently a protocol was developed that precisely synchronizes the time of ovulation in lactating dairy cows (Ovsynch; GnRH-7d-PGF 2α-2d-GnRH). We evaluated whether initiation of Ovsynch on different days of the estrous cycle altered the effectiveness of this protocol. The percentage of cows (n=156) ovulating to the first GnRH was 64% and varied (P<0.01) by stage of estrous cycle. Treatment with PGF 2α was effective, with 93% of cows having low progesterone at second GnRH. The overall percentage of cows that ovulated after second GnRH (synchronization rate) was 87% and varied by response to first GnRH (92% if ovulation to first GnRH vs 79% if no ovulation; P<0.05). There were 6% of cows that ovulated before the second injection of GnRH and 7% with no detectable ovulation by 48 h after second GnRH. Maximal diameter of the ovulatory follicle varied by stage of estrous cycle, with cows in which Ovsynch was initiated at midcycle having the smallest follicles. In addition, milk production and serum progesterone concentration on the day of PGF 2α affected (P<0.05) size of the ovulatory follicle. Using these results we analyzed pregnancy rate at Days 28 and 98 after AI for cows (n=404) in which Ovsynch was initiated on known days of the estrous cycle. Pregnancy rate was lower for cows expected to ovulate larger follicles than those expected to ovulate smaller follicles (P<0.05; 32 vs 42%). Thus, although overall synchronization rate with Ovsynch was above 85%, there were clear differences in response according to day of protocol initiation. Cows in which Ovsynch was initiated near midcycle had smaller ovulatory follicles and greater pregnancy rates.

Reproductive performance of lactating dairy cows following estrus synchronization regimens with PGF2α and progesterone

The objective of this study was to evaluate the reproductive performance of lactating cows in seasonal dairy herds after estrus synchronization with PGF2α (PG) with or without supplementation with progesterone (P4). In Trial 1, synchronized cows (S1; n = 521) were compared with untreated control cows (C; n = 518) in 5 herds. Estrus of cows in the S1 group was synchronized with 2 treatments of PG (Lutalyse) 13 d apart. The breeding season started 2 d after the second PG. Cows were first bred by AI for 7 wk and then herd sires were used. Compared with C cows, estrus synchronization in the treated cows reduced the conception rate to first AI (61.1 vs 70.5%; P < 0.01) and the intervals from start of the breeding season to conception for cows conceiving to AI (11.0 vs 14.6 d; P < 0.05) or to both AI and natural mating (16.5 vs 18.4 d; P < 0.05). There was no effect on conception rate to second AI (68.8%), on pregnancy rate by Day 24 (72.3%) or Day 49 (86.3%) of the breeding season, or on the percentage of cows not pregnant at end of the breeding season (5.0%). In Trial 2, effects of P4 supplementation before the second PG on reproductive performance were evaluated in 4 herds. Estrus of each cyclic cow was synchronized with PG as in Trial 1. Half of the cows in each herd were treated with an intravaginal P4 device (CIDR) for 5 d before the second PG (S2+P4, n = 608), whereas the remaining half received no CIDR treatment (S2, n = 593). Compared with S2 cows, P4 treatment increased the estrous response rate to the second PG (89.6 vs 82.9%; P < 0.01), the conception rate to first AI (65.1 vs 59.7%; P = 0.07), the pregnancy rate by Day 6 of the breeding season (59.3 vs 49.0%; P < 0.001), and reduced the intervals from start of the breeding season to conception for cows conceiving to AI (8.6 vs 10.4 d; P < 0.10) or to both AI and natural mating (12.7 vs 16.4 d; P < 0.01). Treatment with a used CIDR from Days 16 to 21 after start of breeding to resynchronize returns to service had no effect on conception rate to first or second AI but may decrease the conception rate to second AI in cows previously treated with CIDR. In conclusion, estrus synchronization with the double PG system can reduce fertility, while P4 supplementation for 5 d before the second PG can improve estrous response and overall reproductive performance. Stage of the estrous cycle at the time of the second PG can affect fertility following synchronization.

Reproductive and financial impact of a do-it-yourself artificial insemination programme compared with keeping a bull.

The fertility of five dairy herds was studied for three years while they initiated a programme of do-it-yourself artificial insemination (DIY AI) and kept a herd bull, and the financial impact of the new programme was assessed. The herds of approximately 100 cows were all Friesian pedigree, changing to Friesian/Holstein. The DIY inseminators each operated within one herd and were all trained at the same centre. Within a herd, each cow inseminated by a bull was paired with a cow inseminated by AI. The paired cows calved during the same week and were of the same lactation number and genetic type. Each year 20 matched pairs, that is 40 cows per herd, were used, giving a total of 600 cow records. During the first two years, in the majority of herds the calving interval decreased in both the cows inseminated by DIY AI and by the bull. There was a higher culling rate for all cows in the first year, resulting in an improved Fertex score and improved profitability in the second year compared with the first. However, in the five herds combined it was only by the third year that the calving interval for the DIY AI cows was shorter (by 17.9 days) than for cows inseminated by the bull (P < 0.05). The first year of the DIY AI programme was a financial strain for the farmers, but the second and third years showed enough improvement to recover the losses incurred in initiating DIY AI, that is, the capital investment and learning period.

Levels of bPSPB throughout single and twin pregnancies after AI or transfer of IVM/IVF cattle embryos

Blood plasma measurements of bovine pregnancy-specific protein B (bPSPB) during gestation in Alentejano beef cows were used to characterize twin pregnancies resulting from transfer of in vitro fertilized embryos (TWIN IVF; n = 25, beef crosses), single pregnancies resulting from transfer of similar embryos (SING IVF; n = 35, beef crosses) and single gestations resulting from artificial insemination (SING AI; n = 36, pure breed), as well as late embryonic mortality associated (HS; n = 10) or not associated (EM; n = 16) with heat stress. Blood samples were collected monthly starting at 40 days of pregnancy. Levels of bPSPB at 40 days were significantly lower in cows with EM (0.56 ± 0.18 ng ml −1) and HS (0.15 ± 0.09 ng ml −1) than in cows finally calving twins (3.63 ± 0.43 ng ml −1) or singletons (1.87 ± 0.14 ng ml −1) . In six out of ten cows of the HS group, levels of bPSPB rose above the detection limit only at 70 days after estrus, while in the EM group only 1 of 16 cows presented the same pattern ( P ⪕ 0.035). PSPB concentrations in TWIN IVF cows were significantly higher than those of SING IVF cows at 40 and 240 days of pregnancy (3.85 ± 0.30 vs. 2.04 ± 0.26 ng ml −1, and 715 ± 63 vs. 415 ± 58 ng ml −1, respectively; P < 0.001). The TWIN IVF group of cows presented significantly higher concentrations of bPSPB than SING AI cows at all stages of gestation, except at 180 days. In the single pregnancy groups, cows carrying fetuses originated by IVF embryos, when compared with cows carrying fetuses originated by AI, presented significantly higher concentrations of bPSPB from 100 to 210 days of pregnancy and at calving. The rate of increase in bPSPB from 40 to 240 days of gestation, taken from the slope of multiplicative regressions, was significantly higher in SING IVF than in TWIN IVF and SING AI groups of cows (3.284 ± 0.085 vs. 2.750 ± 0.101 and 2.852 ± 0.086, respectively; P < 0.0001). After spontaneous calvings, calves born from the SING IVF cows were significantly heavier than those born from either SING AI or TWIN IVF cows (58 ± 3 vs. 42 ± 2 and 39 ± 2 kg, respectively; P < 0.0001). Twin gestations were 8 days shorter than single ones ( P < 0.0001). In conclusion, bPSPB measurements at 40 and 70 days of gestation are useful to diagnose embryo losses occurring later then 21 days of gestation. Heat-stressed cows with embryo losses presented a retarded pattern of bPSPB production, suggesting an impaired metabolic function of the trophoblast until near 70 days of gestation. Significantly higher amounts of bPSPB are produced at 40 days in twin pregnancies. A larger variation and higher bPSPB production were observed in cows carrying crossbred fetuses derived from IVF techniques than in purebred AI'ed cows. These results suggest that there is a relationship between fetal growth rate and PSPB increase during pregnancy in cattle.