Evaluation of systematic breeding programs for lactating dairy cows: a review

Review: Some challenges and unrealized opportunities toward widespread use of the in vitro-produced embryo in cattle production

The embryo produced by in vitro oocyte maturation, fertilization, and embryonic development is an important resource for genetic improvement and has the potential to improve female fertility and to be programmed to produce offspring with superior ability for health and production. The cultured embryo is also an important component of several realized and potential technologies such as gene editing, somatic cell nuclear cloning, stem cell technologies and gamete generation in vitro. Full realization of the opportunities afforded by the in vitro-produced embryo will require overcoming some technical obstacles to cost-effective implementation of an embryo transfer program. Among the research goals for improving the penetration of embryo transfer in the cattle industry are development of methods to increase the supply of oocytes from genetically elite females, enhance the proportion of oocytes that become transferrable embryos, improve the fraction of embryos that establish pregnancy after transfer, reduce pregnancy wastage after pregnancy diagnosis, and identify culture conditions to optimize postnatal phenotype.

Ovarian luteal category at the time of exogenous progesterone treatment alters pre-ovulatory follicle size and pregnancy outcome but not initial GnRH treatment in repeat-breeder crossbred dairy heifers submitted to the 7-day fixed-time AI protocol

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Ovarian and fertility outcomes were similar for repeat-breeder crossbred dairy heifers with or without initial GnRH treatment.

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Presence of luteal tissue at the time of progesterone (P4) treatment in infertile heifers resulted in a 68.6% pregnancy rate (PR).

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The likelihood of PR was higher in infertile heifers bearing luteal tissue on the day of exogenous P4 trigger.

Repeat breeding is a substantial problem in heifer and cow breeding leading to greater infertility for female dairy herds. The aim of present study was to investigate the impact of corpus luteum (CL) presence and category and the first gonadotropin-releasing hormone (GnRH) administration concurrent with exogenous progesterone (P4) treatment on the largest follicle (LF) size and pregnancy rate (PR) in repeat-breeder crossbred dairy heifers submitted to the fixed-time artificial insemination (AI) protocol. Heifers (n= 243) were synchronised with (+GnRH) or without (–GnRH) first GnRH in the 7-day P4-GnRH-prostaglandin F2α-based programme. Each GnRH group was divided on presence of CL into two groups (+CL and –CL) in a 2 × 2 factorial arrangement. The PR was similar among –GnRH–CL (20.7%), –GnRH+CL (68.8%), +GnRH–CL (30.4%), and +GnRH+CL (68.3%) groups. However, presence of CL in heifers produced a 43.6% increase in PR compared to PR of heifers without CL (odds ratio = 6.550). Heifers bearing large-sized CL had greater large-sized LF on the day of fixed-time AI and PR. Plasma P4 concentration was positively related with CL diameter (r= 0.845; p < 0.001). The diameter of ovarian LF on the day of fixed-time AI was positively associated with P4 concentrations (r= 0.512; p < 0.001). We highlight that ovarian CL presence and category at the time of exogenous P4 treatment alters pre-ovulatory follicle size and PR but not initial GnRH treatment in repeat-breeder crossbred dairy heifers submitted to service with the 7-day fixed-time AI programme.

Estrus synchronization and artificial insemination in Korean black goat (Capra hircus coreanae) using frozen-thawed semen

Presently, there is an increased demand for livestock products all over the world which has led to more devotion on improving livestock population. Although goats have been bred for a long time in Korea, but there is not much research conducted on traditional Korean black goat (Capra hircus coreanae) compared to other livestock populations. Mutton consumption has been dramatically changing from medicinal use to edible meat and this trend directs the black goat populations declining and also mutton import quantities are increasing consistently. The present study introduced a new estrus synchronizing technique with subsequent artificial insemination (AI) for Korean black goats to enable crossbreeding with non-native breeds for the small or subsistent farmers. Our data highlighted that, the percentage of motile sperm from the electro-ejaculated samples declined significantly after freezing and melting. In addition, the sperm motility significantly declined with regard to sperm incubation period (0, 5, 60, and 120 min at 37°C) and was negatively correlated (64.2 ± 7.9%, 63.3 ± 5.8%, 49.9 ± 6.3%, and 35.9 ± 7.6%, respectively) in frozen-thawed sperm samples. Moreover, the E2 levels were unchanged even 24 h after controlled internal drug releas (CIDR) withdrawal. But, 48 h and 72 h after CIDR removal, E2 levels increased significantly. These data helps us to consider the two time points for AI; CIDR removal after 24 h, at which E2 decreases, and after 48 h, as the time at which progesterone increases. Additionally, the AI after 48 h of CIDR removal group exhibited significantly higher pregnancy and parturition rates (42.9%) compared to AI after 24 h after CIDR removal 28.6% group. In conclusion, these studies will propose an optimal estrus synchronisation process with subsequent timing of AI and also will promote the Korean black goat breeding industry.

Economic benefit in repeat breeder cows using intrauterine infusion of penicillin and estrus synchronization followed by timed artificial insemination

Objective:

Until recently, management of repeat breeding in cattle remains a major problem to dairy farmers. This study was carried out to improve the fertility in cows, those did not conceive after three or more consecutive services.

Materials and methods:

Twenty-three repeat breeding cows were selected from the Central Cattle Breeding Station and Dairy Farm (CCBS & DF), Savar, Dhaka, Bangladesh. Data of another 23 repeat breeding cows that conceived after four or more services were collected from the same farm as controls. The repeat breeders were synchronized for estrus with two injections of PGF_2α 11 days apart and timed AI (TAI) was performed.

Results:

Seventeen of 23 cows had uterine infections. Intrauterine infusion of penicillin daily for three successive days from the following day of the first PGF_2α injection resulted in 94.1% (16/17) recovery. Of 23 treated cows, four with estrus synchronization and TAI, and one with only AI after hormone treatment were detected pregnant by per rectal examination of the genital tract. By this pregnancy, the treated cows have advanced average of 131.6 days calving interval and days open, and thereby saved neat US $3,045.3 in comparison to control cows. Control group cows incurred losses of US $15,134.0 compared with average days open of the treated pregnant cows.

Conclusion:

Intrauterine infusion of penicillin can successfully recover the uterine infections, and estrus synchronization followed by TAI resulted in pregnancy in a proportion of repeat breeder cows with economic benefit that had a uterine infection.

Some effects of post-oestrous hormonal therapies on conception rates and resubmission rates in lactating dairy cows

A range of hormonal therapies has been evaluated to potentially improve the reproductive performance of lactating dairy cows. Early lactation treatments with gonadotrophin releasing hormone (GnRH) or prostaglandin F2∝(PGF) may reduce the interval to first insemination or increase the conception rate to first insemination, but mainly in cows which have had a difficult pueperium or which are in herds with low conception rates. These two hormones, as well as progesterone and oestradiol benzoate (ODB) are commonly used either singly, or in combination (GnRH + PGF; progesterone + ODB + PGF) to synchronise the oestrus preceding first inseminations. None of these synchrony treatments is associated with increased conception rates. Extensive series of trials have been completed to identify post-oestrous or post-insemination hormonal therapies which could increase conception rates to the preceding insemination. The wide variation in results has precluded any being commonly regarded as sufficiently reliable for routine use. Nonetheless, meta-analyses have shown that GnRH treatment at insemination or in late dioestrus (11 to 13 day post-first insemination) can significantly increase “the risk of pregnancy”. Insemination treatments have been most effective with repeat breeders (+22.5%), whereas late dioestrous treatments (10%) may be dose and analogue specific (10 μg buserelin). Although metoestrous supplementation with progesterone can stimulate early embryonic development, the associated reduction in oestrous cycle length also reduces conception rates in heifers. Late dioestrous use of GnRH can prevent both of these negative effects. Early dioestrous supplementation with progesterone may enhance production of interferon tau, but this potentially beneficial effect has not been able to be reliably translated into increased conception rates. Many of these hormonal therapies are associated with altered patterns of ovarian follicle development which are similar to those in some synchrony treatments preceding first insemination. Recent studies have indicated that OBD and progesterone can be used to synchronise returns to service and increase the submission rate for second inseminations made about 3 weeks after first inseminations. This can make the non-return rate a more accurate measure of the response to a hormonal treatment and potentially overcome confusing impressions created when oestrous detection rates may be around 50%. Even if effective hormonal therapies are successfully developed, the results may be compromised by environmental factors such as heat stress, energy balance or energy partitioning for lactation. These factors may reduce oocyte quality, fertilization rates or normal uterine secretion patterns. Reduced conception rates associated with high daily milk yields in early lactation may not be able to be remedied simply with hormonal supplementation or by altering patterns of ovarian follicle development. Under these circumstances, controlling the inter-service interval could reduce the impact of the lowered conception rates.

Controlled Breeding Systems for Dairy Cows

The economic consequence of low heat detection rates is the main reason cattle reproduction research programmes continue to focus on developing practical controlled breeding systems for dairy cows. Three approaches can be taken to control the oestrous cycle in cattle: (i) Use of the luteolytic agent prostaglandin F2α alone or one of its potent analogues, (ii) Cycle regulation using short-term progestagen treatments and (Hi) Prior follicle wave synchrony followed by induced luteolysis. Administration of prostaglandin F2α (PGF2α) to cows after about Day 5 of the oestrous cycle causes immediate regression of the CL with progesterone concentrations declining rapidly to basal concentrations within 24 hours. Because PGF2α is only effective in animals between Days 5 and 17 of the oestrous cycle up to 40% of any group of randomly cyclic animals will not respond to a single administration. A number of PGF2α administration regimens have been developed for dairy cows. A two-injection regimen, with an interval of 9-13 days between successive administrations, elicits a higher response, as all animals possess a susceptible CL the time of the second injection. In general, cyclic heifers respond with good precision of heat onset to two PGF2α injections 11 days apart. Fixed-time AI at 72 and 96 hours after the second injection can result in acceptable pregnancy rates. In post partum dairy cows the slower turnover of follicle waves, contribute to the greater variation in oestrus onset, resulting in more variable and generally lower pregnancy rates to fixed-time AI at 72 and 96 hours. Consequently, intensive oestrous detection and AI on the basis of observed oestrus is more appropriate for lactating cows following PGF2α administration. It is generally accepted that fertility of the cyclic heifer after PGF2α treatment is not impaired or may even be higher when compared with untreated control animals inseminated at a natural oestrus. However, in lactating cows, conception rate following PGF2α treatment have been frequently lower (about l0%) than in cows bred following a natural heat. Recently, aprotocol to synchronise follicular development using GnRH and to induce luteal regression using PGF2α was developed In this protocol (Ovsynch), GnRH is administered to cows at random stages of their cycle 7 days before luteolysis is induced with PGF2α; a second GnRH injection at 36-48 hours later induces ovulation. All cows are inseminated once at 16-20 hours after the second GnRH injection. Ovsynch system is not recommended for use in heifers. The development of progestogen delivery devices, such as the PRID, CIDR and Crestar has facilitated the use ofexogenous progestogens for oestrous cycle synchronisation in cattle. Oestradiol is administered at the start of treatment to (i) shorten the life span of the corpus luteum (CL) and (ii) to induce the emergence a new follicle wave. Generally, a high proportion (up to 85%) of the cows that exhibit oestrus after removal of the progestogen do so between 36 and 60hours ofremoval. This allows for either one (54-56 hours) or two fixed-time AIs (48 & 72 hours) after progestogen withdrawal. Alternatively, cows can be observed and inseminated once at a detected oestrus. While fixed-time AI of all treated cows gives 100% submission rate conception rates tend to be lower than when AI is on the basis of observed heat. However, the overall number of cows becoming pregnant (submission x conception rate) is frequently the same, reflecting submission and conception rate differences for the two AI options. Choice of AI option will depend the herdsman 's ability to accurately detect heat, semen costs and labour availability.

Demographics, farm and reproductive management strategies used in Australian automatic milking systems compared with regionally proximal conventional milking systems

OBJECTIVE

To determine the management practices utilised in automatic milking systems (AMS) that affect reproductive management and performance and how these compare with the management practices used in regionally proximal conventional milking systems (CMS).

METHODS

This study examined demographic and management data from AMS and CMS dairy farms through a survey, with a specific focus on reproductive management procedures.

RESULTS

Overall, responses from AMS and CMS dairy farms showed little difference in terms of respondent demographics, farm size, herd structure and most farm management strategies. AMS dairies were more likely to use activity meters or other electronic oestrus detection aids than CMS dairies (P < 0.001) and were also more likely to have changed to electronic recording systems (P = 0.007). Although many respondents indicated that they used key monitoring parameters to assess reproductive performance (e.g. days in milk, conception vs pregnancy rate etc.), the format of responses varied significantly, indicating a relatively widespread (among the respondents) lack of knowledge regarding the meaning and usage of some of these common parameters/terminology.

CONCLUSIONS

Ultimately, reproductive management practices of AMS dairies were largely similar to those of CMS dairies, indicating that such practices can be implemented in a practical sense, even though the resultant reproductive performance is not yet understood. Understanding that the key reproductive management strategies do not need to change vastly is important to ensure that new adoptees are well informed. Further work is needed to objectively measure AMS performance to increase the knowledge base and generate the confidence that will facilitate further adoption of this innovation.

Effects of fixed time AI and AI at detected estrus on conception rate in smallholder zebu and crossbred heifers and cows subjected to double PGF2α administration

The study was conducted to evaluate estrus response, time to the onset of estrus, and conception rate at fixed time AI and AI at detected estrus in local and crossbred heifers and cows subjected to double administration of PGF2α. One hundred twenty local (heifers, n = 27; cows, n = 33) and crossbreds (heifers, n = 21; cows, n = 39) were used for the study. About 63 and 85.7 % of the local and crossbred heifers, respectively, exhibited estrus. Similarly, all crossbred cows and 90.9 % of local cows showed estrus. Most heifers came to estrus between 48 and 72 h while cows exhibited behavioral signs of estrus between 72 and 96 h. AI at detected estrus resulted in higher conception rate than fixed time AI. Pregnancy per artificial insemination was higher in AI at detected estrus than fixed time AI. Accurate estrus detection followed by insemination are crucial factors in maximizing pregnancy, and this study has demonstrated that conception rate in smallholder heifers and cows should be inseminated following estrus detection to maximize the conception rate of the animals.

Impact of thermal stress on the efficiency of ovulation synchronization protocols in Holstein cows

The objective of this study was to evaluate the impact of thermal stress on the efficiency of three different protocols to synchronize time of ovulation in purebred Holstein cows under subtropical Egyptian conditions. The influence of temperature humidity index (THI) on the conception, pregnancy, embryonic loss and early abortion rates were investigated. Conception and pregnancy rates using the CIDRsynch and Presynch (37.5% and 33.9%; 29.5 and 29. 6%, respectively) were significantly greater than that for cows expressing spontaneous estrus (SE) and with use of the Ovsynch (28.5% and 24.3%; 21.6% and 24.6%, respectively) treatment regimen. Conception and pregnancy rates using the Ovsynch protocol were significantly decreased from 31.6% and 26.3% at the lesser THI to 11.5% and 9.9%, respectively than at the greater THI [crude odds ratio (COR) = 0.28 and 0.32; P = 0.001 and 0.004, respectively]. However, conception (P/AI at 28 days) and pregnancy (P/AI at 75 days) rates using the Presynch protocol were significantly reduced at either the lesser or greater THI (COR = 0.47 and 0.42; 0.48 and 0.34, respectively). Embryonic loss rate with the Presynch group was significantly increased from 11.5% at the lesser THI to 22.2% at the greater THI (COR = 2.28; P = 0.039). In contrast, conception, pregnancy and embryonic loss rates did not differ significantly (P > 0.05) with the CIDRsynch protocol at the different THI. Results from the present study indicate that use of the CIDRsynch protocol may provide consistent and satisfactory conception and pregnancy rates in Holstein cows under subtropical environmental conditions.

Use of Stochastic Simulation to Evaluate the Reduction in Methane Emissions and Improvement in Reproductive Efficiency from Routine Hormonal Interventions in Dairy Herds

This study predicts the magnitude and between herd variation in changes of methane emissions and production efficiency associated with interventions to improve reproductive efficiency in dairy cows. Data for 10,000 herds of 200 cows were simulated. Probability of conception was predicted daily from the start of the study (parturition) for each cow up to day 300 of lactation. Four scenarios of differing first insemination management were simulated for each herd using the same theoretical cows: A baseline scenario based on breeding from observed oestrus only, synchronisation of oestrus for pre-set first insemination using 2 methods, and a regime using prostaglandin treatments followed by first insemination to observed oestrus. Cows that did not conceive to first insemination were re-inseminated following detection of oestrus. For cows that conceived, gestation length was 280 days with cessation of milking 60 days before calving. Those cows not pregnant after 300 days of lactation were culled and replaced by a heifer. Daily milk yield was calculated for 730 days from the start of the study for each cow. Change in mean reproductive and economic outputs were summarised for each herd following the 3 interventions. For each scenario, methane emissions were determined by daily forage dry matter intake, forage quality, and cow replacement risk. Linear regression was used to summarise relationships. In some circumstances improvement in reproductive efficiency using the programmes investigated was associated with reduced cost and methane emissions compared to reliance on detection of oestrus. Efficiency of oestrus detection and the time to commencement of breeding after calving influenced variability in changes in cost and methane emissions. For an average UK herd this was a saving of at least £50 per cow and a 3.6% reduction in methane emissions per L of milk when timing of first insemination was pre-set.

Influence of prostaglandin F₂α analogues on the secretory function of bovine luteal cells and ovarian arterial contractility in vitro

Although prostaglandin (PG) F2α analogues are routinely used for oestrus synchronisation in cattle, their effects on the function of the bovine corpus luteum (CL), and on ovarian arterial contractility, may not reflect the physiological effects of endogenous PGF2α. In the first of two related experiments, the effects of different analogues of PGF2α (aPGF2α) on the secretory function and apoptosis of cultured bovine cells of the CL were assessed. Enzymatically-isolated bovine luteal cells (from between days 8 and 12 of the oestrous cycle), were stimulated for 24h with naturally-occurring PGF2α or aPGF2α (dinoprost, cloprostenol or luprostiol). Secretion of progesterone (P4) was determined and cellular [Ca(2+)]i mobilisation, as well as cell viability and apoptosis were measured. Naturally-occurring PGF2α and dinoprost stimulated P4 secretion (P<0.05), whereas cloprostenol and luprostiol did not influence P4 synthesis. The greatest cytotoxic and pro-apoptotic effects were observed in the luprostiol-treated cells, at 37.3% and 202%, respectively (P<0.001). The greatest effect on [Ca(2+)]i mobilisation in luteal cells was observed post-luprostiol treatment (200%; P<0.001). In a second experiment, the influence of naturally-occurring PGF2α and aPGF2α on ovarian arterial contraction in vitro, were examined. No differences in the effects of dinoprost or naturally-occurring PGF2α were found across the studied parameters. The effects of cloprostenol and luprostiol on luteal cell death, in addition to their effects on ovarian arterial contractility, were much greater than those produced by treatment with naturally-occurring PGF2α.

A five-day progesterone plus eCG-based fixed-time AI protocol improves fertility over spontaneous estrus in high-producing dairy cows under heat stress

This study compared the efficiency of a five-day or standard (nine-day) progesterone-based regimen combined with equine chorionic gonadotrophin (eCG) in a fixed-time AI (FTAI) protocol for dairy cows. The data examined were derived from 3577 inseminations conducted in three dairy herds. Animals with no estrus signs detected over 21 days were randomly assigned to a PRID-9 or PRID-5 group. Cows in each group received a progesterone intravaginal device (PRID) for 9 or 5 days, respectively, PGF(2α) and eCG on PRID removal, and GnRH 48 h later. Fixed-time AI was performed 12 h after the GnRH dose. Cows artificially inseminated following spontaneous estrus during the study period were considered as controls. Based on the odds ratio, the likelihoods of animals in PRID-9 in the warm (conception rate [CR] of 22.3%) and cool (32% CR) periods, and control animals in the warm period (26.6% CR) becoming pregnant were reduced (by factors of 0.6, 0.3 and 0.4, respectively) compared with the control animals in the cool period (CR of 43.7%). The risk of a twin pregnancy was higher (51.4%) for cystic PRID-9 cows (by a factor of 3.6) and lower (9.9%) for cyclic PRID-5 animals (by a factor of 0.4) compared with the PRID-9 cyclic cows. These findings indicate that the proposed protocol achieves similar results during the cool or warm season to those obtained when AI is conducted at spontaneous estrus during the cool season. In addition, PRID-5 reduced twin pregnancy compared with PRID-9.

Effect of acute bull exposure around the time of artificial insemination on serum oxytocin and progesterone concentrations and pregnancy rates in dairy cows

This study examined the effect of acute bull exposure around the time of artificial insemination (AI) on oxytocin and progesterone concentrations, and pregnancy rates in dairy cows. Ninety six dairy cows, stratified according to parity into primiparous and pluriparous, were divided into three groups; short bull exposure (SBE; 10 min, n = 32), long bull exposure (LBE; 4 h, n = 32) or no bull exposure (NBE; n = 32). On day 45 post-partum, all cows were treated with PGF2α on three occasions 11-14 days apart to synchronize oestrus. They were submitted to fixed time AI 80 h after the third PGF2α injection. Cows in the SBE and LBE groups were artificially inseminated 5 min after the introduction of the bull. From a subset of cows (n = 6 per group; three primiparous and three pluriparous), blood samples were collected once every 5 min starting 15 min before AI until 15 min after AI and analysed for oxytocin concentrations. Additional blood samples were collected for measurements of progesterone (P4) concentrations once daily for 4 days starting on the day of AI and once every 3 days thereafter until day 22. The effects of bull exposure, time, parity, difficulty of AI, and pregnancy on oxytocin and P4 concentrations were analysed using the mixed linear model procedure. Mean oxytocin concentrations or change in oxytocin concentrations after bull exposure or AI were not different among groups. Pregnancy rates for the NBE, SBE and LBE groups were 55.5%, 33.3% and 44.4%, respectively, and were not different among groups. In conclusion, acute bull exposure around the time of AI did not affect oxytocin and progesterone concentrations and did not improve pregnancy rates in dairy cattle under these farms conditions.

Dairy cows continuously-housed in tie-stalls failed to manifest activity changes during estrus

Felton, C. A., Colazo, M. G., Ponce-Barajas, P., Bench, C. J. and Ambrose, D. J. 2012. Dairy cows continuously-housed in tie-stalls failed to manifest activity changes during estrus. Can. J. Anim. Sci. 92: 189–196. While pedometers are effective for estrus detection in free-stall herds, their efficacy in tie-stalls is not established. The objectives were to determine if pedometers equipped with a behavior tag for monitoring lying activity (AfiMilk Pedometer Plus Tag system) can accurately record cow activity, and if they can facilitate estrus detection in dairy cows continuously housed in tie-stalls. Nineteen lactating Holstein cows were subjected to estrus induction with prostaglandin F2α, and 18 pregnant cows served as controls. Activity was monitored for 10 d using pedometers and 24-h video recording. Pedometer and video records were compared for 6 d surrounding estrus; stepping (rc=0.85; P<0.01), lying time (rc=0.94; P<0.01), and lying bouts (rc=0.89; P<0.01) were highly correlated. Progesterone concentrations confirmed that 17 of the 19 cows responded to estrus induction; 16 of those 17 cows ovulated. Changes in mean daily activity did not differ (P>0.05) between estrus-induced cows and controls, or in the estrus-induced cows in the 48 to 72 h preceding the day of ovulation. In conclusion, while the pedometers accurately recorded cow activity in lactating cows housed in tie-stalls, they could not facilitate estrus detection because cow activity did not significantly change during estrus.

Bio-economic model to evaluate twinning rate using sexed embryo transfer in dairy herds

A stochastic bio-economic model has been used to determine the effects of new reproductive technologies over a 15-year period. A strategy of using conventional artificial insemination (AI) or embryo transfer (ET) using two sex-controlled embryos at different conception rates (CRs) and herd sizes resulted in a 24 state model. The genetic means of AI population increased over the years, and the genetic means of milk production for all of the embryo strategies were greater than those of AI. In addition, the genetic means of milk yield using different embryo-based scenarios in the expanding herds were greater than those for the fixed herds. The net profit of using sexed ET in the expanding herds was greater (P < 0.05) than that of fixed size herds. In general, there was a roughly consistent trend in net profit per cow for sexed ET strategies in the expanding herds over the years, but there was an increasing trend in net profit per cow for sexed ET strategies in the fixed herds over the years. Medium to high CRs for ET and the use of sex-controlled embryo systems, especially for induction of twin births to produce dairy replacements, will be critical elements of a system that produces significant numbers of female calves. The greater number of female calves produced in the sex-controlled scenarios allows the farmer to select animals with the best genetic potential as dairy replacement heifers; therefore, the rate of genetic gain increased in the dairy herd. Results of sensitivity analyses showed that a significant decrease in the production costs and increase in the ET performance are essential for embryo-based technologies to be profitable.

Reproductive performance of anoestrous high-producing dairy cows improved by adding equine chorionic gonadotrophin to a progesterone-based oestrous synchronizing protocol

This study sought to improve the reproductive performance of anoestrous high-producing dairy cows by including equine chorionic gonadotrophin (eCG) after progesterone-releasing intravaginal device (PRID) removal. In Experiment I, 806 cows at 51-57 days post-partum were randomly assigned to a PRID (treated with PRID), PRID-500 (treated with PRID plus 500 IU of eCG) or PRID-750 (treated with PRID plus 750 IU of eCG) group. In Experiment II, 422 cows showing a long anoestrus period (animals with no oestrus signs nor luteal tissue 35 days before treatment) were randomly assigned to the PRID, PRID-500 or PRID-750 groups. The dependent variables considered in binary logistic regression analyses for both experiments were the rates of oestrus, ovulation and conception after treatment, the cumulative conception rate on Day 120 post-partum and pregnancy loss. In Experiment I, interaction between treatment and season showed a significant effect on the oestrous response. Thus, during the warm season, PRID group cows were 8.9 times more likely to express oestrus than the remaining cows. Moreover, inseminated cows with two or more corpora lutea 8-14 days after treatment were more likely to become pregnant (by a factor of 2.4) than cows with a single corpus luteum. Finally, cows without luteal structures treated with PRID were 0.4 less likely to be pregnant on Day 120 post-partum, compared with the remaining cows. In Experiment II, cows in the PRID group treated during the warm or cool season were less likely to exhibit oestrus (by a factor of 0.06 or 0.2, respectively) or ovulate (by a factor of 0.004 or 0.14, respectively) than the remaining cows. In conclusion, in anoestrous cows in both experiments, the addition of eCG to the use of an intravaginal progesterone device to induce oestrus was beneficial. The recommended dose of eCG is 500 IU.

Hormonal and antimicrobial therapy in theriogenology practice: currently approved drugs in the USA and possible future directions

Hormonal and antimicrobial therapies are essential to regulate and maintain healthy reproduction in domestic animals. The appropriate and legal use of these compounds is ultimately the responsibility of the veterinarian and other users, with a primary mission to directly protect and promote the health of animals, and indirectly the health of people. The appropriate use of these products is defined by the Federal Food, Drug, and Cosmetic Act, 21 United States of America § 301 et seq and implementing regulations in the Code of Federal Regulations. In the past, use of a drug in an animal for an unapproved use violated this Act. However, passage of the Animal Medicinal Drug Use Clarification Act 1994 legalized the extra-label use of certain animal and human drugs in veterinary practice for treating diseases. This manuscript reviews currently approved hormonal and antimicrobial drugs for use in theriogenology. Considering the ever increasing knowledge in the area of veterinary reproduction, particularly in the treatment and control of reproduction using antimicrobials and hormones, it would be beneficial to widen the therapeutic options in these categories. The potential for widening the therapeutic options is also discussed in this review, by providing a non-exhaustive but essential list of potential new drugs for use in clinical animal reproduction (theriogenology).

Embryonic genotype and inbreeding affect preimplantation development in cattle

Infertility in cattle herds is a growing problem with multifactorial causes. Embryonic genotype and level of inbreeding are among the many factors that can play a role on reproductive efficiency. To investigate this issue, we produced purebred and crossbred bovine embryos by in vitro techniques from Holstein oocytes and Holstein or Brown Swiss semen and analyzed several cellular and molecular features. In the first experiment, purebred and crossbred embryos, obtained from abattoir oocytes, were analyzed for cleavage, development to morula/blastocyst stages, amino acid metabolism and gene expression of developmentally important genes. The results indicated significant differences in the percentage of compacted morulae, in the expression of three genes at the blastocyst stage (MNSOD, GP130 and FGF4) and in the utilization of serine, asparagine, methionine and tryptophan in day 6 embryos. In the second experiment, bovine oocytes were collected by ovum pick up from ten Holstein donors and fertilized with the semen of the respective Holstein sires or with Brown Swiss semen. The derived embryos were grown in vitro up to day 7, and were then transferred to synchronized recipients and recovered on day 12. We found that purebred/inbred embryos had lower blastocyst rate on days 7-8, were smaller on day 12 and had lower expression of the trophoblast gene PLAC8. Overall, these results indicate reduced and delayed development of purebred embryos compared with crossbred embryos. In conclusion, this study provides evidence that embryo genotype and high inbreeding can affect amino acid metabolism, gene expression, preimplantation development and therefore fertility in cattle.

Comparison of Two Different Programmes of Ovulation Synchronization in the Treatment of Ovarian Cysts in Dairy Cows

It was the aim of this field study to evaluate two different protocols of ovulation synchronization for the treatment of ovarian cysts and their effect on reproductive performance in dairy cows. In addition, factors with a possible influence on treatment success and pregnancy outcome as well as costs per pregnancy were analysed. The study was performed with 130 German Holsteins with ovarian cysts diagnosed on days 55 to 60 postpartum. Cows belonging to group 1 (n = 65) received a modified ovsynch protocol [day 0: 0.15 mg cloprostenol (PGF) + 0.02 mg buserelin acetate (GnRH); day 14: PGF; day 16: GnRH]. Group 2 (n = 65) was treated with the conventional ovsynch protocol (day 0: GnRH; day 7: PGF; day 9: GnRH). Timed artificial insemination was performed 20 to 24 h later. Cows without ovarian cysts served as controls. Treatment success (disappearance of the ovarian cyst) after the first ovsynch cycle was higher in group 1 (66.2%) than in group 2 (23.1%, p < 0.05). Reproductive measures in group 1 were comparable with those of the control group and, compared with group 2, were conspicuously better (66.2%, 76.9%, 83.1%, 59.5% vs. 40.0%, 50.7%, 60.0%, 27.5% for cumulative pregnancy rate after treatment cycle 1 to 3 and second service conception rate, respectively, p < 0.05). Overconditioned cows and cows with larger ovarian cysts showed a diminished treatment and pregnancy success. In group 1, costs per pregnancy were only slightly higher than in the control group (group 1: €352.44, group 2: €484.59, control group: €333.77). In conclusion, our results suggest that ovsynch protocols can be used in the treatment of ovarian cysts. The modified ovsynch protocol led to a better cure rate as well as a better reproductive performance, and was economically beneficial compared with a conventional ovsynch protocol.

Economic analysis of reproductive management strategies on US commercial dairy farms

Reproductive management has received increased attention in recent years as new technologies and programs have been developed to aid dairy managers in efficiently breeding cows and heifers. Efficient breeding of cows and heifers has become increasingly difficult as fertility has decreased because of a correlated negative response with milk yield. Dairy farm survey results were used to parameterize the economic analyses of reproductive management programs. Reproductive management program costs and the levels of reproductive performance achieved with such programs varied significantly among farms and were especially sensitive to on-farm labor costs. For example, visual heat detection requires more hours of labor per cow than use of an estrus synchronization program. Therefore, visual heat detection programs were relatively more sensitive to labor costs than synchronization programs. In addition, past reproductive performance was found to affect the determination of which reproductive program was optimal. Farms that had attained high levels of labor efficiency for visual heat detection in the past had less incentive to adopt a synchronization program than farms with less efficient visual heat detection.

Progesterone, follicular, and estrual responses to progesterone-based estrus and ovulation synchronization protocols at five stages of the estrous cycle

The objective was to monitor changes in ovarian status in heifers exposed to a progesterone insert with or without concurrent GnRH injection. Estrus was manipulated in 283 heifers (31 breeding clusters) by administering GnRH, progesterone, and PGF(2alpha) at 5 stages of the estrous cycle. Estrus was presynchronized with a progesterone insert (CIDR) for 7 d before PGF(2alpha) was administered 24 h before insert removal. Successive clusters of heifers were assigned to treatments (2 heifers per treatment) on cycle d 2, 5, 10, 15, and 18. Treatments consisted of a progesterone insert (d 0) for 7 d plus: 1) PGF(2alpha) on d 6, 24 h before insert removal (early PGF); 2) GnRH on d 0 + early PGF(2alpha) (GnRH + early PGF); 3) PGF(2alpha) at insert removal (late PGF); and 4) GnRH on d 0 + late PGF (GnRH + late PGF). Controls received GnRH on d 0 and PGF(2alpha) on d 7. Ovaries were scanned by transrectal ultrasonography on d 0, 2, 7, 9, and 11 to assess follicle diameters and ovulation. Blood was collected on d 0, 2, 6, 7, 8, and 9 to quantify serum concentrations of progesterone. Insemination occurred after detected estrus or by timed artificial insemination (TAI) at 64 h after insert removal. Only 25% of 141 GnRH-treated heifers ovulated by d 2; twice as many ovulated when treatment was initiated on d 5 (46.4%) than on other cycle days (20.3%). Diameters of the largest follicle exposed to GnRH on d 0, 2, 7, or 9 did not differ regardless of whether ovulation occurred. Small treatment and stage of cycle differences in diameter of the largest follicle were detected on d 2, 7, and 9. Compared with controls, progesterone concentration was greater in all progesterone-treated heifers on d 2 and 6. Early- vs. late-PGF treatment resulted in less progesterone on d 7 and 8. Pregnancies per AI were less after TAI (44%) than after detected estrus (56%) and were less in controls than in all progesterone treatments. Heifers in which treatments were initiated on d 10 of the cycle had the most consistent (estrus vs. TAI) pregnancies per AI (65.4%) compared with other cycle days. Compared with controls, more progesterone-treated heifers ovulated by 96 h after insert removal. Application of the progesterone insert reduced variance of the interval to estrus after insert removal (or PGF(2alpha) injection in controls) by 1.6-fold compared with controls. These results do not support the use of GnRH in a progesterone-based synchronization protocol.

Timed artificial insemination of two consecutive services in dairy cows using prostaglandin F2alpha and gonadotropin-releasing hormone

Timed artificial insemination (TAI) protocols use PGF(2alpha) and GnRH injections to synchronize ovulation. The objective was to evaluate the PGPG protocol (d 0, PGF(2alpha); d 3, GnRH; d 11, PGF(2alpha); d 13, GnRH and TAI) for first TAI and also examine methods for second TAI in nonpregnant cows. A factorial test of the first PGF(2alpha) and first GnRH injections within the PGPG protocol was performed (the last PGF(2alpha) and GnRH injections were deemed essential to the TAI). Lactating dairy cows (n = 804) in a commercial herd were assigned to 1 of 5 first-TAI treatments, which were PGPG, GPG (d 0, no treatment; d 3, GnRH; d 11, PGF(2alpha); d 13, GnRH and TAI), PPG (d 0, PGF(2alpha); d 3, no treatment; d 11, PGF(2alpha); d 13, GnRH and TAI), and PG (d 0, no treatment; d 3, no treatment; d 11, PGF(2alpha); d 13, GnRH and TAI); the Ovsynch protocol (GnRH, 7 d, PGF(2alpha), 2 d, GnRH and TAI) was the positive control. For resynchronization, cows received either GnRH or the control (no injection) on d 22 after TAI. Nonpregnant cows on d 28 were then treated with PGF(2alpha) on d 29, GnRH on d 31, and TAI [i.e., resynchronization treatments of ReGPG (received GnRH on d 22) and RePG (did not receive GnRH on d 22)]. Pregnancy rates for PGPG, GPG, PPG, PG, and Ovsynch were similar at d 28 after first TAI. Analyses of multiple explanatory factors by logistic regression detected an effect of uterine or ovarian abnormality on the d-28 pregnancy rate (normal more likely to be pregnant). Day-42 pregnancy rates were affected by uterine or ovarian abnormality (normal more likely to be pregnant), postpartum disease occurrence (healthy cows more likely to be pregnant), milk production, and days in milk. Treatment was not significant for the d-42 pregnancy rate. Effects of postpartum disease, milk production, and days in milk on the d-42 pregnancy rate were apparently manifested through their effects on embryonic loss between d 28 and 42 of pregnancy. High-producing cows that received TAI early postpartum were most likely to experience embryonic loss. Day-42 pregnancy rates after the resynchronization treatment were affected by an interaction of the first synchronization treatment with the resynchronization treatment. We concluded that although PGPG can be used for TAI, a simpler TAI protocol that includes the last 2 injections (PGF(2alpha), 2 d; GnRH and TAI) would be equally effective.

Conception rates and serum progesterone concentration in dairy cattle administered gonadotropin releasing hormone 5 days after artificial insemination

The objectives of this study were to determine the effect of administration of exogenous GnRH 5days after artificial insemination (AI) on ovarian structures, serum progesterone concentration, and conception rates in lactating dairy cows. In experiment 1, 23 Holstein cows were synchronized using the Ovsynch protocol. Five days after AI (day 0) cows were assigned randomly to receive either saline (saline; n=11) or 100microg GnRH (GnRH; n=12). To examine ovarian structures, ultrasonography was performed on day 1 and every other day beginning on day 5 until day 13. On days 5 and 13 blood samples were obtained to measure serum progesterone concentrations. All cows in the GnRH-treated group developed an accessory corpus luteum (CL), whereas cows in the saline group did not. Mean serum progesterone concentrations did not differ between GnRH and saline groups on day 5 (1.64+/-0.46ng/ml versus 2.04+/-0.48ng/ml). On day 13 serum progesterone concentrations were greater (P<0.05) in the GnRH group compared with saline (5.22+/-0.46ng/ml versus 3.36+/-0.48ng/ml). In experiment 2, 542 lactating cows, at two different commercial dairies, were used to test the effect of administering GnRH 5 days after AI on conception rates. Cows were synchronized and detected for estrus according to tail chalk removal. Cows detected in estrus received AI within 1h after detection of estrus. Five days after AI, cows were assigned randomly to receive either GnRH (n=266) or saline (n=276). Pregnancy status was determined by palpation per rectum of uterine contents approximately 40 days after AI. There was no effect of farm on conception rate. There was no effect of treatment as conception rates did not differ between GnRH and saline groups (26.7% GnRH versus 24.3% saline). Regardless of treatment, days in milk, parity, milk yield, and number of services had no effect on the odds ratio of pregnancy. In summary, the results of this study indicated that GnRH administered 5 days after AI increased serum progesterone by developing an accessory CL but did not improve conception rates in dairy cattle.

Timing of follicular phase events and the postovulatory progesterone rise following synchronisation of oestrus in cows

In cows the timing of both ovulation and the subsequent postovulatory progesterone rise are critical to successful fertilisation and early embryo development. The aim of this study was to determine the degree of variability in the timing of ovulation relative to other follicular phase events and to determine how variations in the timing of follicular phase events contribute to the timing of the postovulatory progesterone rise. Plasma concentrations of progesterone, oestradiol and luteinising hormone (LH) and the timing of oestrus and ovulation were determined following induction of luteolysis were determined in 18 mature, non-lactating Holstein-Friesian cows. Four cows were excluded on the basis of abnormal reproductive function. In the remaining 14 cows oestrus occurred at 57.4+/-4.3h and the LH surge at 54.6+/-4.0h following luteolysis (progesterone <1ngmL(-1)) followed by a fall in circulating oestradiol concentration at 64.6+/-4.4h. Cows ovulated at 88.0+/-4.7h with the postovulatory progesterone rise (to >1ngmL(-1)) occurring 159+/-7.2h after luteolysis. There was considerable variation in the timing of ovulation following luteolysis (range 64-136h) onset of oestrus (range 24-40h) and onset of the LH surge (range 24-44h). Cows were then split on the basis of interval from progesterone fall to progesterone rise giving groups (n=7 per group) with intervals of 180.6+/-6.7 and 138.3+/-5.7h (P<0.001). Between groups, both the intervals from luteolysis to ovulation (98.3+/-6.9 vs 77.7+/-3.4h; P<0.05) and ovulation to progesterone rise (82.3+/-4.2 vs. 60.6+/-5.5h; P<0.01) were longer in late rise cows. There was no difference between groups in the interval from oestrus or LH surge to ovulation. In conclusion the results of this study further highlight the high variability that exists in the timing and interrelationships of follicular phase events in the modern dairy cow, reemphasising the challenges that exist in optimising mating strategies. However, the data do suggest that in cows with poor post ovulatory progesterone secretion, the key problem appears to be poor post ovulatory development rather than a delay in ovulation.

Manipulation and control of the estrous cycle in pasture-based dairy cows

Treatments designed to synchronize luteolysis, preovulatory follicular development, and ovulation, and resynchronize estrus after a first AI have improved responses to synchronization treatments. Protocols based only on the use of PGF result in variable onset of estrus. Concentrations of progesterone prior to administering PGF have affected submission rates and fertility while administration of estradiol benzoate (EB) after inducing luteolysis has improved the synchrony of estrus and ovulation in some studies. In pasture-based dairy cows, GnRH-based protocols have generally resulted in one-third of both anestrous and cycling cows conceiving following synchronization of ovulation and timed AI. Protocols which use intravaginal progesterone releasing inserts (IVP4) are effective in inducing estrus in over 90% of treated dairy cows. Resynchronization of estrus after reinsertion of an IVP4 also improves the synchrony of returns to estrus, but pregnancy rates to the first AI have been reduced in some studies, and submission rates at a resynchronized estrus are less than at the first synchronized estrus. Administration of EB can be used to synchronize follicle wave emergence in resynchronized cows with intervals to new wave emergence comparable to that in cows synchronized for a first AI, but plasma concentrations of progesterone following treatment may be reduced. Synchronization of estrus and ovulation can be enhanced by administration of EB or GnRH during proestrus, but dose, timing and stage of follicular development at the time of treatment can affect outcomes.

JSAR Innovative Technology Award. Development of ovulation synchronization and fixed time artificial insemination in dairy cows

Recently, reproductive management has become more difficult as a result of increased herd size. Problems with missing estrous signs and decrease in conception rate by artificial insemination (AI) performed at wrong timing have caused low AI conception rates. In 1995, ovulation synchronization and fixed-time AI (Ovsynch/TAI) was developed in the USA as a new reproductive technology, which was accepted as an useful reproductive management tool in many countries. However, no information on the use of Ovsynch/TAI was available in Japan. It was, therefore, warranted to show the ovulation rate and conception rate after Ovsynch/TAI using gonadotropin releasing hormone analogue (GnRH-A, fertirelin acetate) and prostaglandin F2alpha (PGF2alpha)-THAM, both were commercially available in this country. The conception rate after Ovsynch/TAI has been known to vary among different herds and individuals. Investigation and analysis of factors affecting the conception rate was also warranted to improve the conception rate. A series of experiments were carried out to establish Ovsynch/TAI using domestically produced GnRH-A and PGF2alpha and to study factors affecting conception rate after Ovsynch protocol. Ovsynch using 100 microg GnRH-A and 25 mg PGF2alpha were observed using ultrasonography. As a result, a high synchronization rate of ovulation at 16 to 20 h after the second GnRH injection was confirmed. The conception rate after Ovsynch/TAI was compared in 87 cows with the conception rate after AI at estrus induced by PGF2alpha (139 cows). Conception rate after Ovsynch/TAI was higher than the figure after AI at induced estrus (59.1% vs 20.9%, P<0.05). The dose of GnRH-A was also studied and a practical dose of GnRH-A was found to be 50 microg per cow. To clarify some factors affecting the conception rate after Ovsynch/TAI, 1,558 cows were investigated for the state of their ovaries, days after calving, parity, season, ovarian cyclicity postpartum and nutritional state at the day of Ovsynch. The overall conception rate after Ovsynch/TAI was 51.5%. Fifty-six cows (3.6%) showed estrus at 6 to 7 d after the first injection of GnRH-A. The conception rate after Ovsynch/TAI was low in cows that were 40 to 60 d postpartum, those in their 5th lactation or more, those bred in July to August, and those recovering ovarian cyclicity later than 56 d postpartum. The conception rate after Ovsynch/TAI was high in cows in which body condition score (BCS) was 3.75 at dry period and 3.0 at the day of Ovsynch. In conclusion, Ovsynch/TAI is an effective tool for the reproductive management of dairy cows. A steady and sufficient conception rate after Ovsynch/TAI could be expected by taking the factors affecting the conception rate into the consideration.

Pregnancy Rates After Timed AI of Heifers Following Removal of Intravaginal Progesterone Inserts

Reproductive performance of dairy heifers was compared for each of 2 synchronization protocols: The first group of 54 heifers was synchronized using intravaginal progesterone inserts (CIDR) plus estradiol cypionate (ECP) on d 0, PGF(2alpha) on d 7, and ECP again on d 8 (CIDR-ECP); a second group of 56 heifers was synchronized using CIDR and ECP on d 0, PGF(2alpha) on d 7, and GnRH on d 9 (CIDR-GnRH). All heifers received timed artificial insemination (TAI) at 48, 56, or 72 h after CIDR removal on d 7. Pregnancy diagnosis was conducted by ultrasonography 32 +/- 1 d post AI to confirm pregnancy and at 60 +/- 1 d post AI to determine embryo survival. Ovaries were monitored by ultrasonography daily from d 0 to 7 and twice daily from d 8 to ovulation to examine emergence of a new wave of follicles, size of the ovulatory follicle, and timing of ovulation on 15 heifers per protocol. New follicular development was detected 3.7 +/- 0.2 d after CIDR insertion. Heifers receiving CIDR-ECP had a shorter interval from CIDR removal to ovulation than heifers receiving CIDR-GnRH (63.8 +/- 3.0 vs. 71.6 +/- 2.3 h, respectively); however, ovulation occurred 39.8 +/- 3.0 h after ECP or 23.6 +/- 2.3 h after GnRH. Diameters of ovulatory follicles did not differ between treatments. Overall pregnancy rate for synchronized heifers was 60.1%, and embryo survival was 98%. Pregnancy rate for heifers synchronized with CIDR-ECP was 63.0% and similar to that in heifers synchronized with CIDR-GnRH (57.1%). Pregnancy rate was affected by time of AI for heifers synchronized using CIDR-ECP but not for those synchronized with CIDR-GnRH. Heifers in the CIDR-ECP group that were inseminated 56 h after CIDR removal had a higher pregnancy rate (81.0%) compared with heifers inseminated 48 (66.7%) or 72 h (50.0%) after CIDR removal. Either ECP or GnRH used in a CIDR-based TAI program in dairy heifers can achieve acceptable reproductive performance.

Recent Developments in Oestrous Synchronization of Postpartum Dairy Cows with and without Ovarian Disorders

This report reviews the most recent developments in prostaglandin-based oestrous synchronization programmes for postpartum dairy cows and addresses the efficiency of controlled breeding protocols based on such developments for cows with abnormal ovarian conditions. A double prostaglandin protocol applied 11-14 days apart seems to be capable of bringing most cows to oestrus. Because of varying oestrus onset times, improved conception rates are obtained following artificial insemination (AI) at detected oestrus rather than fixed-time AI in prostaglandin-treated cows. The administration of oestradiol or human chorionic gonadotrophin, or both these hormones, after prostaglandin treatment, improves the synchrony of oestrus yet does not enhance the conception rate. Progesterone-based treatments for oestrous synchronization are considered the most appropriate for non-cyclic or anoestrous postpartum dairy cows; prostaglandin alone being ineffective because of the absence of a mature corpus luteum in these cows. Improved oestrus synchrony and fertility rate have been reported using short-term progesterone treatment regimes (7-9 days) with or without oestradiol benzoate combined with the use of a luteolytic agent given 1 day before, or at the time of, progesterone withdrawal. The ovulation synchronization (Ovsynch) protocol, based on the use of gonadotrophin releasing hormone and prostaglandin, was developed to coordinate follicular recruitment, CL regression and the time of ovulation. This protocol allows fixed time insemination and has proved effective in improving reproductive management in postpartum dairy cows. However, timed AI following Ovsynch seems to have no beneficial effects in heifers, because of an inconsistent follicle wave pattern, and in anoestrous cows, given their lack of prostaglandin responsive CL. To date, there are several prostaglandin based, fixed-time insemination oestrous synchronization protocols for use in early postpartum dairy cows with ovarian disorders such as ovarian cysts and acyclicity.

Pregnancy Rate after Timed Artificial Insemination in Early Post-partum Dairy Cows after Ovsynch or Specific Synchronization Protocols

The present study was designed to compare the reproductive performance of pre-synchronized post-partum dairy cows subjected, either to the Ovsynch protocol without screening for ovarian status (control group), or to a specific oestrous synchronization protocol applied according to their ovarian status, as determined by transrectal ultrasound (experimental group). The study was conducted on 428 lactating dairy cows. Cows in the Ovsynch group (n = 205) were synchronized and time inseminated after receiving the Ovsynch protocol treatment. Cows in the specific synchronization (Ssynch) group (n = 223) were weekly subjected to transrectal ultrasound exams for 4 weeks, or until AI or starting treatment, and divided into four subgroups according to their ovarian status: (i). corpus luteum (CL) subgroup (n = 130), cows with a CL; (ii). natural oestrus (NE) subgroup (n = 58), cows showing NE; (iii). anovulatory follicles (AF) subgroup (n = 26), cows considered to have AF; and (iv). ovarian cysts (OC) subgroup (n = 9), cows with OC. Cows in the Ssynch group were synchronized and time inseminated following a specific oestrous synchronization protocol, or inseminated at NE. Logistic regression analysis was carried out for the dependent variables ovulation and pregnancy rates to first and to second AI (second AI: first AI + return AI). Cows subjected to Ssynch were 2.1 times more likely to become pregnant at first and at second AI compared with those synchronized using the Ovsynch protocol (P < 0.0001). Our results show that the response of post-partum pre-synchronized cows to a specific oestrous synchronization protocol applied according to their ovarian status is more effective than the response to the Ovsynch protocol applied without taking into account the ovarian status of the animals.

Comparison of Timed AI After Synchronized Ovulation to AI at Estrus: Reproductive and Economic Considerations

A timed artificial insemination (TAI) protocol using OvSynch was compared to artificial insemination (AI) at detected estrus in 2 large dairy herds differing in reproductive management. Cows were synchronized for TAI starting at 62 and 42 d in milk in herds 1 and 2, respectively. The OvSynch regimen included: GnRH (buserelin) at 0.02 mg (i.m.) on d 0; PGF2alpha (tiaprost) at 0.75 mg (i.m.) on d 7; buserelin at 0.02 mg (i.m.) on d 9; and TAI 16 to 20 h later. After TAI, cows seen in estrus received AI, whereas cows diagnosed not pregnant were resynchronized for TAI. Control cows received AI based on detected estrus after voluntary waiting periods of 72 d in herd 1 and 50 d in herd 2. An economic analysis included costs associated with days open, culling, AI, synchrony products, treatment, and examinations. A sensitivity analysis of those variables determined effects on total costs per pregnancy. Use of OvSynch reduced intervals to first AI and days open in both herds and reduced culling for infertility in herd 2. Conception rates for first AI at detected estrus were significantly higher compared to TAI in both herds and for overall AI at estrus in herd 2. For groups assigned to AI at estrus, mean 21-d submission rates over 200 d for AI were higher in herd 1 than in herd 2 (55.6 vs. 28.6%). Days open and culling were the major cost factors. Although OvSynch improved reproduction in both herds, AI based on detected estrus was economically superior in herd 1, whereas OvSynch was superior in herd 2. This was consistent across ranges of cost factors evaluated. Evaluation of synchrony protocols should include reproductive performance along with appropriate costs associated with treatments. Such costs may offset benefits to reproduction in herds with good estrous detection rates.

Luteal activity at the onset of a timed insemination protocol affects reproductive outcome in early postpartum dairy cows

This study was designed to compare two timed insemination protocols, in which progesterone, GnRH and PGF2alpha were combined, with the Ovsynch protocol in presynchronized, early postpartum dairy cows. Reproductive performance was also evaluated according to whether cows showed high or low plasma progesterone concentration, at the onset of treatment. One hundred and six early postpartum dairy cows were presynchronized with two cloprostenol treatments given 14 days apart, and then assigned to one of the three treatment groups. Treatments for the synchronization of estrus in all three groups started 7 days after the second cloprostenol injection, which was considered Day 0 of the actual treatment regime. Cows in the control group (Ovsynch, n=30) were treated with GnRH on Day 0, PGF2alpha on Day 7, and were given a second dose of GnRH 32 h later. Cows in group PRID (n=45) were fitted with a progesterone releasing intravaginal device (PRID) for 9 days, and were given GnRH at the time of PRID insertion and PGF2alpha on Day 7. In group PRID/GnRH (n=31), cows received the same treatment as in the PRID group, but were given an additional GnRH injection 36 h after PRID removal. Cows were inseminated 16-20 h after the administration of the second GnRH dose in the Ovsynch group, and 56 h after PRID removal in the PRID and PRID/GnRH groups. Ovulation rate was determined on Day 11 postinsemination by detecting the presence of a corpus luteum in the ovaries. Lactation number, milk production, body condition at the onset of treatment and treatment regime were included as potential factors influencing ovulation and pregnancy after synchronization. Logistic regression analysis for cows with high and low progesterone concentration on treatment Day 0 revealed that none of the factors included in the models, except the interaction between progesterone and treatment regime, influenced the risk of ovulation and pregnancy significantly. In cows with high progesterone concentration at treatment onset, Ovsynch treatment resulted in a significantly improved pregnancy rate over values obtained following PRID or PRID/GnRH treatment. In cows with low progesterone concentration, PRID or PRID/GnRH treatment led to markedly increased ovulation and pregnancy rates with respect to Ovsynch treatment. These findings suggest the importance of establishing ovarian status in early postpartum dairy cows before starting a timed AI protocol, in terms of luteal activity assessed by blood progesterone.

Comparison of effects of GnRH and prostaglandin in combination, and prostaglandin on conception rates and time to conception in dairy cows

OBJECTIVE

To assess the effectiveness of a gonadotrophin-releasing hormone (GnRH) / prostaglandin program (GnRH-PG-GnRH, Ovsynch) on conception rates and time to conception of lactating dairy cows compared with a PG program (double prostaglandin injection).

DESIGN

A randomised multi-centre cohort study was conducted with 778 cows from nine dairy herds. Cows at different stages of lactation were randomly assigned, after matching for days open at the time of treatment, to either the PG or Ovsynch program.

PROCEDURE

Cows on the PG program received two intramuscular injections of prostaglandin (2 mL, Prosolvin) 11 days apart. The Ovsynch program consisted of two intramuscular injections of GnRH (1 mL, Fertagyl) 9 days apart, separated by one injection of prostaglandin 40 h before the second GnRH injection. Milk samples were taken at the time of artificial insemination and assayed for progesterone by radioimmunoassay.

RESULTS

The Ovsynch program was not significantly different to PG in achieving conception, with overall conception rates of 37.6% and 41.4%, respectively, for each program. There was, however, a significant interaction between the effects of parity and treatment (P = 0.03), because conception rates were higher in older cows (parity 5 or more) on the PG program than for older cows on the Ovsynch program. There was no significant effect of treatment (P > 0.5) on time to conception after treatment, but older cows were slower to conceive (P < 0.0001). Conception rates differed (P < 0.0001) among herds.

CONCLUSION

The median days to conception for both groups was 22 and mean days from treatment to conception were 36.3 +/- 3.3 and 31.6 +/- 2.7 for the Ovsynch and PG programs respectively, indicating that reproductive performance of cows was not significantly different with Ovsynch program or PG program. There appears to be a need to evaluate causes of reproductive failure in older cows.

Conception rates after AI in Swedish red and white dairy heifers: relationship with progesterone concentrations at AI

Blood samples were collected from 211 dairy heifers at the time of field insemination [artificial insemination (AI)]. Heifers were defined as either first-service heifers (n = 91) or third to eigth-service heifers [presumed (third AI, n = 60)] or well-defined repeat breeders (greater than the fourth AI, n = 60). Plasma progesterone concentrations at AI were evaluated in relation to oestrous behaviour at AI and conception rates post-AI. Conception rates after third AI were good, but conception rates decreased markedly after fourth AI and onwards. Those heifers that did not become pregnant after AI had significantly higher basal progesterone concentrations (>0.5 nmol/l) at AI, so-called suprabasal concentrations, compared with those which conceived after AI (irrespective of the number of AI practised). Relative risk for repeat breeding was 58% after AI performed at suprabasal progesterone concentrations, while it was 42% at basal (0.5) progesterone concentrations. Results from this field study confirm results obtained in earlier controlled studies of repeat-breeder heifers (RBH), indicating that the current definition of repeat breeding should be retained. Analysis of suprabasal progesterone concentrations could be considered as a tool for identification of RBH, provided that heat detection and AI timing are optimal. Besides considering the direct costs involved in repeat breeding, it remains to be determined whether it would be economically beneficial to identify and exclude RBH from the breeding population.

Application of timed artificial insemination protocols to grazing Japanese black cattle with long open period

To investigate the viability of timed artificial insemination (TAI) protocols in grazing Japanese Black cattle with long open period, ovarian status and progesterone and estradiol-17 beta profiles of the animals during the protocol were monitored. In 1998, prosta-glandin F(2a) (PG) was administered to 36 animals seven days after GnRH injection. Three out of the 36 animals were inseminated after detection of estrus and did not receive further treatment. The second GnRH was injected to the remaining 33 animals 48 hr after the PG injection and TAI was performed 24 hr later. In 1999, PG was injected to 25 animals six days after GnRH, the second GnRH was injected to 22 animals 48 hr after PG, and TAI was performed 16 hr later (The other three animals were inseminated before the time of TAI). The percentage of the animals with at least one functional corpus luteum and one follicle equal to or greater than 10 mm in diameter at PG injection was similar between the groups in 1998 and 1999. Likewise, the hormonal profiles were similar between the two groups. Pregnancy rates (PR) after the TAI protocols and natural mating in 1998 and 1999 were 75.0% and 88.0%, respectively. These figures were comparable to the PR obtained by conventional estrus synchronization protocols using PG (in 1995; 69.4%) or CIDR (in 1996; 59.1%). In conclusion, the TAI protocol can be applicable into grazing Japanese Black cattle with long open period.

Effects of Body Condition Score in Cows Peripartum on the Onset of Postpartum Ovarian Cyclicity and Conception Rates after Ovulation Synchronization/Fixed-Time Artificial Insemination

The aim of this study was to examine whether the nutritional state of cows peripartum was associated with the recovery of ovarian function and conception rates after synchronization of ovulation and fixed-time artificial insemination (OVSYNCH/TAI). The effect of the interval in days from calving to the first ovulation on conception rates after OVSYNCH/TAI was also investigated. Conception rates of cows after OVSYNCH/TAI (n=39) were 43.6%. The conception rates of cows with a body condition score (BCS) of 2.75-3.25 at 30 d postpartum and on the day of OVSYNCH treatment were significantly higher than in cows with a BCS < or =2.5 (P<0.05). The percentage of cows establishing ovarian cyclicity before 55 d postpartum in cows with a BCS of 2.75-3.25 at 30 d postpartum and on the day of OVSYNCH treatment were significantly higher than in cows with a BCS < or =2.5 (P<0.05). The conception rates after OVSYNCH/TAI in cows which recovered ovarian cyclicity within 34 d postpartum were significantly higher than in cows with first ovulation > or =56 d (P<0.05). These results indicated that the nutritional state in cows peripartum influenced the conception rates after OVSYNCH/TAI and the postpartum ovarian cyclicity and also suggested that the conception rates after OVSYNCH/TAI decreased in cows with delayed recovery of ovarian cyclicity.

Influence of GnRH analogue (fertirelin acetate) doses on synchronization of ovulation and fixed-time artificial insemination in lactating dairy cows

The effect of using a dose of 50 micro g rather than 100 micro g fertirelin in an ovulation/fixed-time insemination protocol for Holstein-Friesian dairy cows was investigated in three experiments. In each experiment, fertirelin was administered at the beginning of the protocol followed 7 days later by 500 micro g cloprosterol. Two days later, a second dose of fertirelin was given and AI performed 16-19 h later regardless of the incidence of behavioral oestrus. The effect on conception rate was studied in experiment 1 using 114 postpartum anoestrus cows. There was no significant difference in the age, parity or number of days after parturition in each treatment groups. The conception rate did not differ between the 50 micro g fertirelin group (61.1%; n=72) and the 100 micro g group (59.5%; n=42; NS). In experiment 2, a further 12 cows at 40-60 days postpartum were treated with 100 or 50 micro g fertirelin (n=6 per dose) with treatment commencing in the follicular or luteal phase of the oestrous cycle. The plasma concentration of luteinizing hormone (LH) reached similar peaks of over 5 ng/ml 120 min after the intramuscular administration of fertirelin in both groups. There were no significant differences in LH levels between treatments or phase of the oestrous cycle when treatment commenced. Doses of 50 and 100 micro g fertirelin were compared in experiment 3 using 17 cows to study follicular wave development and synchronization by transrectal ultrasonography, conception rate and corpus luteum function. There were no significant differences between treatments for these factors. It was concluded that using a dose of 50 micro g fertirelin enabled the drug costs to be reduced without affecting the efficiency of a synchronization of ovulation/fixed-time AI protocol for dairy cows.

Exogenous hormonal manipulation of ovarian activity in cattle

To achieve precise control of the oestrous cycle in cattle it is necessary to control both the life span of the corpus luteum and the follicle wave status at the end of the treatment. Antral follicle growth in cattle occurs in distinct wavelike patterns during the ovarian cycle and the postpartum anoestrous period. The emergence of each new wave is stimulated by a transient increase in FSH. Each follicle wave has an inherent life span of 7-10 days as it progresses through the different stages of development, viz., emergence, selection, dominance and atresia or ovulation. The dominant follicle (DF) is distinguishable from other subordinate follicles by its enhanced capacity to produce oestradiol, maintenance of low intrafollicular concentrations of insulin-like growth factor binding proteins-2, -4 and -5 and follistatin and an increase in free intrafollicular concentrations of IGF-I as well as an increase in size. Three approaches can be taken to control ovarian activity and regulate the oestrous cycle in cattle: (i) use of the luteolytic agent prostaglandin F2alpha (PGF2alpha) alone or one of its potent analogues, (ii) administration of exogenous progesterone-progestagen treatments combined with the use of exogenous oestradiol or gonadotrophin releasing hormone (GnRH) to control new follicle wave emergence and shorten the life span of the corpus luteum, and (iii) prior follicle wave synchrony followed by induced luteolysis. A number of different oestrous synchronisation regimens, viz., PGF2alpha-based only, short-term progesterone with prior follicle wave synchrony using oestradiol or GnRH have been developed but the problem of obtaining good follicle wave synchrony and CL regression limit their widespread application. GnRH-prostaglandin-GnRH regimens have recently been developed for beef and dairy cows. However, their success is variable. A better understanding of the hormonal control of follicle growth is a prerequisite in order to obtain more precise control the oestrous cycle allowing one AI at a predetermined time giving high pregnancy rates without recourse to detection of oestrus.

The relationship between estrous behavioral score and time of ovulation in dairy cattle

One of the major contributors to poor fertility of a dairy herd is ineffective detection of estrus. Recently, it has become evident that cow factors contribute largely to low detection rates. Until now, standing behavior has been the symptom used to determine the right moment for insemination. However, standing behavior is not observed in over 50% of the cows in estrus in a number of herds, and no data are available to relate the moment of ovulation to other estrous symptoms. Therefore, in the present study, cows were observed for a number of visual signs of estrus, twice per day for 30 min, and the moment of ovulation was estimated by transrectal ultrasonographic scanning of the ovaries. In this study, 100 cows were detected in estrus visually, using a scoring system. Standing behavior was observed in 50% of those cows, although there was more than one cow in estrus at a time in most (85%) cases. There was no correlation between follicular size and ovulation time or estrous behavior score. Levels of 305-d milk yield and parity were also not correlated with estrous behavior scores. However, a significant correlation (0.31) was found between detection score and day of ovulation. A retrospective analysis revealed that cows that ovulated 0 to 24 h after artificial insemination (AD) scored almost three times the number of estrous behavior points compared to the ones that ovulated 24 to 48 h after AI. Ovulation more than 48 h after AI resulted in pregnancy in only 15% of the cows.

Comparison of two timed artificial insemination (TAI) protocols for management of first insemination postpartum

Two estrus-synchronization programs were compared and factors influencing their success over a year were evaluated. All cows received a setup injection of PGF2alpha at 39 +/- 3 d postpartum. Fourteen days later they received GnRH, followed in 7 d by a second injection of PGF2alpha. Cows (n = 523) assigned to treatment 1 (modified targeted breeding) were inseminated based on visual signs of estrus at 24, 48, or 72 h after the second PGF2alpha injection. Any cow not observed in estrus was inseminated at 72 h. Cows (n = 440) assigned to treatment 2 received a second GnRH injection 48 h after the second PGF2alpha, and all were inseminated 24 h later. Treatment, season of calving, multiple birth, estrual status at insemination, number of occurrences of estrus before second PGF2alpha, prophylactic use of PGF2alpha, retained fetal membranes, and occurrence of estrus following the setup PGF2alpha influenced success. Conception rate was 31.2% (treatment 1) and 29.1% (treatment 2). A significant interaction occurred between protocol and estrual status at insemination. Cows in estrus at insemination had a 45.8% (treatment 1) or 35.4% (treatment 2) conception rate. The conception rate for cows not expressing estrus at insemination was 19.2% (treatment 1) and 27.7% (treatment 2). Provided good estrous detection exists, modified targeted breeding can be as successful as other timed artificial insemination programs. Nutritional, environmental, and management strategies to reduce postpartum disorders and to minimize the duration of postpartum anestrus are critical if synchronization schemes are used to program first insemination after the voluntary waiting period.