Resynchrony of previously anoestrous cows and treatment of cows not detected in oestrus that had a palpable corpus luteum with prostaglandin F2𝛂

Relationships between milk protein concentrations at different phases of first to fourth lactation and subsequent calving intervals in Holstein cows

So far, no study has been conducted on the effect of milk protein concentrations (MP%) in different time periods of lactation on subsequent calving intervals (CI). The purpose of this study was to evaluate the association between MP% at different stages of the first to fourth lactations and subsequent calving intervals in primiparous and multiparous Holstein dairy cows. Test day records (3X milking frequency) of milk yield measured on primiparous (n = 503793) and multiparous (n = 389237, 257347, 156035 and 87750 for parity 2, 3 and 4, and 5 respectively) Holstein dairy cows collected during 1984-2019 were obtained from Animal Breeding Center of Iran. To investigate the relationship between MP% at different time intervals of lactation and subsequent calving intervals (up to fifth parity), each lactation was divided into four time periods (≤50d, 50 < d ≤ 100, 100 < d ≤ 200 and 200 < d ≤ 305). At each period, protein concentrations were also divided into three classes: 1-3%, 3-5%, 5-7%. There was a negative relationship between MP% in the first 50 days of first lactation in primiparous and multiparous dairy cows and subsequent calving intervals in a way that calving intervals decreased as MP% increased and the shortest calving intervals were observed for the third class of milk protein concentrations. After the first 50 days of first lactation, the shortest subsequent calving intervals were detected for the second class of MP% and the CI increased non-significantly when MP% increased to 5-7. In general, due to the significant relationship between MP% and subsequent CI, this relationship can be further considered in breeding programs in dairy cattle.

A shortened resynchronization treatment for dairy cows after a nonpregnancy diagnosis

We hypothesized that a shortened version of a modified Ovsynch program (OVS: GnRH-1 - 7 d - PGF_2α-1 - 24 h - PGF_2α-2 - 32 h - GnRH-2 - 16 h - AI) that excluded GnRH-1 to resynchronize ovulation in cows bearing a corpus luteum (CL) after a non-pregnancy diagnosis (NPD) or including progesterone supplementation with the OVS treatment for cows without a CL would produce shorter inter-insemination intervals and pregnancy per AI (P/AI) not different from that of cows treated with the OVS treatment. Of the 1697 lactating Holstein cows enrolled in this experiment, complete data were available for only 1584 cows because the remainder was not treated, inseminated per treatment design, left the herd before pregnancy diagnosis, or some other outcome was missing. Cows were enrolled in the study and assigned to either of three treatments at NPD (32 ± 3 d after AI [Day 0]). Cows with a detected CL were assigned randomly to: (1) a modified Ovsynch (OVS; GnRH-1 - 7 d - PGF_2α-1 - 24 h - PGF_2α-2 - 32 h - GnRH-2 - 16 h - AI) or (2) Short Synch (SS; PGF_2α-1 - 24 h - PGF_2α-2 - 32 h - GnRH-2 - 16 h - AI). Cows with no CL were assigned to OVS plus a progesterone insert (CIDR). Blood was collected at NPD to measure progesterone concentration and determine accuracy of treatment assignment (progesterone ≥ 1 ng/mL for a functional CL). Overall progesterone concentration at NPD was less in OVS + CIDR cows (1.5 ± 0.3 ng/mL) than in OVS (5.2 ± 0.2 ng/mL) or SS cows (3.7 ± 0.3 ng/mL). No differences in luteolytic risk (progesterone < 0.5 ng/mL at 72 h after PGF_2α-1) were detected after PGF_2α (>96.7%) and ovulation risk after GnRH-2 was 93.8, 91.7, and 86.2% for SS, OVS, and OVS + CIDR, respectively. Mean and median inter-insemination interval were less in SS (mean = 34.3 ± 0.05 d [median = 35 d] than OVS cows (40.2 ± 0.05 d [42 d]), but that in OVS cows did not differ from OVS + CIDR cows (41.4 ± 0.05 d [42 d]). Technicians were more accurate in visually detecting a functional CL than a non-functional CL (81.2 vs. 61.1%). Sensitivity of detecting a functional CL by technicians averaged 91.2%, but specificity was 39.8%. Pregnancy per AI at 32 ± 3 d after AI was less for SS (16.5% [n = 115]) than OVS (29.3% [n = 133] when a functional CL was inaccurately detected, but did not differ when a functional CL was detected accurately (27.6% [n = 561] vs 30.3% [508]). Pregnancy per AI did not differ between OVS and OVS + CIDR cows regardless of CL status. Short synch is an alternative to the entire modified Ovsynch program to produce similar P/AI when the CL status was detected accurately, and regardless of functional CL status, SS reduced inter-insemination intervals by 7 d.

Associations between early lactation milk protein concentrations and the intervals to calving for Holstein cows of differing parity

High milk protein concentrations (MP%) have been positively associated with the reproductive performance of lactating dairy cows. No studies have measured the effects of this association on subsequent calving dates in multiparous cows, nor assessed whether the underlying causal mechanisms are present in nulliparous heifers. Holstein cows (primiparous = 918; multiparous = 4242) were selected from herds that had seasonally concentrated calving patterns resulting from seasonally restricted breeding periods. In seasonally calving herds, the date of a herd’s planned start of calving (PSC date) is the average gestation length of 282 days after the date that the preceding breeding period commenced, so that the interval from the herd’s PSC date to each cow’s actual calving date (PSC-to-calving interval) primarily reflects the time to conception from the start of the breeding period in the previous year. This measure was used to compare associations between the average MP% during the first 120 days of lactation and time to the calving that initiated that lactation in primiparous and multiparous cows. Early lactation MP% was negatively associated with PSC-to-calving interval. A 1% difference in MP% was associated with an 8-day difference in the average PSC-to-calving interval in primiparous cows and a 31–35-day difference in the average interval in multiparous cows. The observed associations between early lactation MP% and PSC-to-calving interval are likely to involve determinants present during a cow’s breeding period that affect the probability of conception. Some of these determinants are not restricted to early lactation as the association between MP% and PSC-to-calving interval in primiparous cows is a reflection of the reproductive performance in nulliparous heifers at ~15 months of age.

Behavioural, follicular and hormonal characteristics of the oestrous cycle of Mexican Criollo cattle

The objective of the present study was to describe the behavioural, ovarian and hormonal characteristics of the oestrous cycle of Criollo cattle. Twenty-two cycling cows subjected to oestrus synchronisation were used to take blood samples every 4 h, to determine luteinising hormone (LH) until ovulation was detected by ultrasound and then every 24 h until the subsequent naturally occurring ovulation to determine progesterone concentrations. At the onset of synchronised oestrus, ovaries were examined by ultrasound every 8 h to determine dominant follicles until ovulation was detected, and daily afterwards to observe ovarian dynamics until the onset of the subsequent spontaneous behavioural oestrus. Time from oestrus to ovulation was higher in synchronised than in spontaneous oestrus (P < 0.01). Time from LH surge to ovulation was 40.5 h. When two- and three-wave cycles were compared, inter-ovulatory intervals were similar, growth rate of the preovulatory follicle was lower in two-wave cycles, time from onset of ovulatory wave to ovulation was higher in cycles with two waves and time from oestrus to ovulation was higher in three-wave cycles (P < 0.01). Corpus luteum volume averaged 1.3 cm3 and progesterone concentration peaked at an average 6.5 ng/mL. LH peak averaged 33.5 ng/mL during oestrus in all cows. Ovulatory follicle diameter ranged from 8 to 12 mm in either two- or three-wave cycles. Results suggested that overall times from oestrus and LH peak to ovulation are longer in Criollo cows than those in other breeds. This, along with information about growth rate, size and age of ovulatory follicles, may have implications for reviewing the optimum time for artificial insemination and how reproductive technologies are applied to Criollo cattle.

Comparison of diagnostic approaches, and a cost-benefit analysis of different diagnostic approaches and treatments of anoestrous dairy cows

AIM

To compare diagnostic techniques, and to assess the economic effects of diagnosing and treating dairy cows not detected in oestrus before the planned start of mating (PSM).

METHODS

Cows from 12 herds were defined as anoestrus at Day -9 (where Day 0=PSM) based on presence of tail paint that had been applied at Day -35. The presence of a corpus luteum (CL) was diagnosed by palpation or ultrasonography on Day -9, or by determining the concentration of progesterone (P4) in milk at Days -16 and -9. Cows with concentrations of P4 in milk >1 ng/ml at one or both times were defined as CL+. Cows were randomly assigned to be treated with (a) nothing (Control; n=558); (b) gonadotrophin-releasing hormone (GnRH) on Day -9, prostaglandin F(2alpha) (PGF(2alpha)) on Day -2, and GnRH on Day 0, with set-time artificial insemination (AI) 16-20 h after the second GnRH treatment (Ovsynch; n=553); or (c) as for (b) but with placement of an intravaginal P4-releasing device on Day -9, and removal on Day -2 (Ovsynch+P4; n=551). Cows detected in oestrus between Day -2 and the second GnRH treatment did not receive the second GnRH treatment. Pregnancy diagnosis took place on three occasions, and the date of conception estimated, from which the PSM-to-conception interval was calculated. Agreement between the three diagnostic techniques for CL status was evaluated using Kappa analyses, and sensitivities and specificities were calculated using a Bayesian Monte Carlo approach that does not assume a gold standard. Partial budgets and decision trees were constructed to assess the cost effectiveness of diagnosis and treatment.

RESULTS

The level of agreement was higher between ultrasonography and concentration of P4 in milk (0.64) than for palpation and ultrasonography or concentration of P4 in milk (0.50 and 0.49, respectively). The Ovsynch+P4 treatment had a higher net benefit than Ovsynch relative to no treatment (NZ$80.40 and NZ$47.50/cow treated, respectively) in the absence of diagnosis of CL status. Following diagnosis, the Ovsynch+P4 treatment remained the most cost-effective option for both CL+ and CL- cows. It was concluded that the Ovsynch+P4 treatment without any diagnostic procedure was the most cost-effective option.

CLINICAL RELEVANCE

Treatment of anoestrous cows was more cost-effective than no treatment, with Ovsynch+P4 more cost-effective than Ovsynch in cows with or without a CL. Differentiation of anoestrous cows into CL+ and CL- groups for treatment was not cost-effective.

Use of equine chorionic gonadotrophin in synchronised AI of seasonal-breeding, pasture-based, anoestrous dairy cattle

In seasonally calving dairy areas, a critical index of efficiency and profitability is the ability to maintain a short annual calving spread. In essence, this means that all cows need to conceive within 90 days of calving. Anovulatory anoestrus (AA) is a major barrier to reproductive performance under these conditions and the successful treatment of AA is an important aspect of reproductive intervention. The present paper reviews regimens used to treat AA in New Zealand and reports on a large-scale field trial investigating the effects of equine chorionic gonadotrophin (eCG) within a proven efficacious treatment protocol. The administration of eCG at the time of removal of a progesterone-releasing device in an 8-day, oestradiol benzoate (EB)-based treatment protocol increased the percentage of cows in calf after 7 and 28 days of breeding. The interaction between cow age and treatment with eCG was significant, with cows over 5 years of age having higher conception rates (P = 0.002) and 7 day in-calf rates (P = 0.002) than cows on a standard 8-day treatment protocol without eCG. The addition of eCG to a standard 8-day EB/progesterone protocol can improve reproductive success in seasonally calving AA dairy cows.

Reproductive performance in the subsequent lactation of dairy cows previously treated for failure to be detected in oestrus

AIM

To describe the effect of treatment of cows not detected in oestrus (NDO) with progesterone (P4) and oestradiol benzoate (ODB) in one lactation, on the reproductive and productive performance in the subsequent lactation.

METHODS

Cows (n=770 from nine herds) which were NDO 10 days before the planned start of the seasonal breeding programme (PSM) were blocked by herd, age (2 or >2 years old) and ovarian status (i.e. with or without a palpable corpus luteum; CL), and treated either with an intravaginal progesterone-releasing device and ODB and resynchrony, or were left as untreated controls. In the following lactation, data were collected on the occurrence of endometritis, NDO, breeding dates, pregnancy test results and milk production. The effect of treatment and ovarian status in the previous lactation on the incidence of disease, and the proportions submitted for service, conceived and pregnant in the subsequent lactation were analysed. Calving dates and intervals from start of breeding to first insemination and conception were analysed using Kaplan Meier survival analysis. Additional multivariate analyses were undertaken to include known confounders such as age, breed, herd, calving date and milk production, as well as the cyclic status (i.e. previously cycling, NDO, or "late-calving") in the previous lactation, to examine the potential "carryover" effects of previous status on the reproductive performance in the subsequent lactation.

RESULTS

Treatment of NDO cows resulted in an earlier calving date (Julian calving date 214, 95% CI=207-221, vs 224, 95% CI=220-228; p=0.005), more female calves reared (31.4% vs 23.3%; p=0.01), and reduced risk of being NDO (33.9% vs 46.1%; p=0.002) in the subsequent lactation compared with controls. There were no differences in the incidence of peripartum disease, or the proportion of cows submitted, conceived or pregnant between the Treatment and Control groups in the subsequent lactation (p>0.2). Previously CL-positive (+ve) NDO cows were less likely to produce a female calf that was reared (19.0% vs 29.9%; p=0.005), more likely to be treated as NDO (26.4% vs 18.6%; p=0.02), less likely to conceive by the end of the subsequent lactation's breeding programme (82.2% vs 87.8%; p=0.09), and took longer to conceive (41 vs 33 days from the PSM to conception) than cows that were NDO-CL-negative (-ve) in the previous lactation. There was no interaction between ovarian status and treatment for any of the outcome variables (p>0.05). Cows that were NDO or late-calving in the previous lactation were more likely to be NDO (p<0.005), treated as NDO (p<0.005), and have longer PSM to conception intervals (p<0.005) in the subsequent lactation than cycling herdmates, despite inclusion of factors known to confound reproductive performance in analyses.

CONCLUSIONS

Treatment of NDO cows resulted in more female calves reared, earlier calving and a reduced risk of being NDO in the subsequent lactation. Status (i.e. NDO-CL+ve or NDO-CL-ve) affected some reproductive measures in the subsequent lactation, and the effect of treatment in the subsequent lactation differed between the two groups for some measures. Reproductive performance in the subsequent lactation was not improved despite the earlier calving date and longer calving to PSM intervals. Additionally, the previous season's status was still important in the subsequent season's reproductive performance, despite adjusting for known confounders of fertility.

CLINICAL RELEVANCE

The economic benefits from treatment of NDO cows are likely limited to effects of an earlier calving date and potential for longer lactation and increased milk yield, increased number of calves derived from artificial insemination and from a reduced number of NDO cows in the subsequent lactation. Effects of improved reproductive performance in the subsequent lactation were not demonstrated and hence should not be included in any economic analysis of therapy of NDO cows.

A comparison of performance of the Ovsynch treatment program between cycling and non-cycling cows within seasonally-calving dairy herds

OBJECTIVE

To compare performance of the Ovsynch program on reproductive performance between cycling and non cycling cows in seasonally-calving herds.

PROCEDURE

An Ovsynch mating program (100 mg Gonadorelin on day 1 and day 9, 500 mg of Cloprostenol on day 7 with fixed time artificial insemination on day 10) was administered to 3,559 cows from 14 herds in Australia and New Zealand. Cycling status before planned start of mating was determined. All cows were treated and artificial insemination continued for at least 25 days after fixed time artificial insemination. Pregnancy testing was performed 75 to 100 days after fixed time artificial insemination. Multivariable modelling examined the impact of the Ovsynch program and other risk factors upon reproductive performance.

RESULTS

Thirty percent of cows were classified as no visible oestrous (NVO). Odds of being NVO increased significantly for cows that were young, recently calved, and in low body condition. The fixed time artificial insemination conception rate was 35.7% and 33.2%, 21-day pregnancy rate was 54.5% and 48.4% and 42-day pregnancy rate was 69.7% and 62.6% for cycling and NVO cows respectively. Odds of pregnancy increased significantly for cows calved more than 40 days by planned start of mating, in greater body condition, and cycling, and there was a significant interaction between body condition and cycling status in both models. The return-to-service rates by 24-days were 67.6% and 55.9% and by the end of the AI period were 86.9% and 81.5% for cycling and NVO cows respectively. Odds of return to service increased significantly for cows in greater condition score in both models. Odds of return were increased for cycling cows in the 24-day multivariable model.

CONCLUSION

The Ovsynch program may provide a useful treatment option for NVO cows within seasonally-calving pasture-based dairy herds.

The sensitivity and specificity of single manual examination tests for detection of corpora lutea in the ovaries of non-cycling cows

OBJECTIVE

To evaluate the sensitivity and specificity of single manual examination of ovarian surface structures and of ovarian size as tests for the detection of corpora lutea in non-cycling cows

DESIGN

Non cycling cows were dichotomously classified for the presence of palpable corpora lutea and for ovarian size. The performance characteristics of the palpable corpus luteum test and the ovarian size test were estimated using Bayesian analysis. Previously published information on prevalence and test performance was combined with observed data using the Gibbs Sampler to derive posterior distributions for prevalence and test parameters.

RESULTS

Prior distributions for the prevalence of corpora lutea in cows not detected on heat before mating within seasonal herds were centred on 25%, and for the corpus luteum test sensitivity were centred on 70%. No prior assumptions for any other test parameter were made. From a total of 650 cows, 144 were found to have at least one corpus luteum, and 156 were found to have two small ovaries. The posterior estimate obtained for prevalence was 0.30 (95% Cl 0.22 to 0.43), for corpus luteum test sensitivity was 0.71 (95% Cl 0.49 to 0.93), and for corpus luteum test specificity was 0.98 (95% Cl 0.49 to 1.00). For the ovarian size test, the posterior estimate for size test sensitivity was 0.98 (95% Cl 0.95 to 1.00) and for size test specificity was 0.34 (95% CI 0.28 to 0.43). Sensitivity analysis indicated that corpus luteum test sensitivity ranged from 0.60 to 0.70 in most herds.

CONCLUSIONS

Errors associated with pre-mating heat detection are likely to result in between 15 to 30% of cycling cows not detected in oestrous before mating, resulting in the inclusion of cycling cows within the population of non-cycling cows. This mixed population of cows is then subjected to manual examination by veterinarians in order to assign cows to treatment groups. The corpus luteum test has modest sensitivity and high specificity and the size test has high sensitivity and low specificity. Therefore the use of a single examination of the ovaries of cows not detected on heat before the mating period, in order to classify them as anovulatory anoestrous cows with or without a corpus luteum, is not sufficient to accurately classify them and thus to recommend treatment.

Reproductive Performance of Anestrous Dairy Cows Treated with Progesterone and Estradiol Benzoate

Anestrus is a major reproduction problem in pasture-based dairy operations that results in poorer reproductive outcomes than herdmates detected in estrus before the start of the seasonal breeding program. The objective of the current study was to assess a combined progesterone and estradiol benzoate treatment program including resynchrony with no treatment. Anestrous pasture-fed dairy cattle (n = 756) in 9 herds were blocked by herd and age and assigned within sequentially presented pairs of cows to be treated with an intravaginal progesterone-releasing insert for 8 d plus 2 mg of estradiol benzoate injected i.m. at insert insertion and 1 mg of estradiol benzoate injected 1 d after insert removal (d -1). Those cows detected in estrus from 0 to 3 d had a used progester-one-releasing insert reinserted for 6 d commencing on d 16 with 0.5 mg of estradiol benzoate injected i.m. 1 d after insert removal (treatment). The other cow within the pair was left as an untreated control (control). Treatment increased the risk of insemination and pregnancy by 28 d into the breeding program and resulted in conception 15 d earlier compared with controls. In contrast, treatment did not increase the risk of pregnancy after 56 d into the breeding program or at the end of the breeding season. It is concluded that treatment of anestrous dairy cattle with progesterone and estradiol benzoate combined with reinsertion of the progesterone insert resulted in earlier conception, but no difference in the final pregnancy rate compared with no treatment.

Reproductive performance in anestrous dairy cows following treatment with two protocols and two doses of progesterone

The objectives of this study were to evaluate the effect using two doses of progesterone (P4) releasing devices in two different programs on reproductive performance of anestrous dairy cows. Cows (n = 1555) not detected in estrus by 10 d before the planned start of the seasonal breeding program and in which no CL was palpable were treated with an intravaginal P4-releasing device ('Single'; approximately 1.56 g of P4) or a modified device with triple the normal P4 dose ('Triple'; approximately 4.7 g of P4). The devices were in place for either 6 d ('Short') or 8 d ('Long'), with 1mg estradiol benzoate (EB) given 24 h after device removal. The 'Long' program also included treatment with 2 mg EB at device insertion. The Long program resulted in a higher first service conception rate (RR = 1.18 (95% CI = 1.03-1.33); P = 0.02), but had no effect on the 28-d, 56-d or final pregnancy rate compared to the Short program. There were no effects of dose of P4 on any outcome. In conclusion, the Long compared to the Short program, but not the dose of P4, improved first service conception rates in anestrous cows.

Comparison of two estrus synchronization and resynchronization treatments in lactating dairy cows

Reproductive performance in cows following synchronization of estrus with intravaginal progesterone releasing devices (IVD) has varied with the length of treatment, cyclic status and prolonged return to estrus intervals in some cows following first AI. The objective of this study was to compare two methods of synchronizing and resynchronizing estrus on the reproductive performance of lactating dairy cows. Cows were treated with an IVD (Day 0) for 7 days (n = 350) or 8 days (n = 350), cloprostenol (0.5 mg i.m.) at the time of device removal and estradiol benzoate (EB) at the time of device insertion (1.5mg i.m.), and again 9 days later (1.0 mg i.m.). Cows were also resynchronized starting on Days 23 and 46 by reinsertion of IVDs for either 7 or 8 days and treatment with EB (1mg i.m.) at the time of device insertion and again 9 days later. Cows were inseminated on detection of estrus for 4 days after removal of devices at each of the synchronized estrous cycles. No significant differences in reproductive performance were detected between each treatment throughout the study period. Synchrony of estrus was more precise at the first and second estrus after treatment with an IVD for 8 days compared to 7 days. Cows classified as anestrous had lower reproductive performance than cows classified as cycling and had longer intervals to estrus at the second (P < 0.001) and third estrus (P < 0.06), but not at the first estrus (P = 0.09). Mean time to onset of estrus after IVD removal was less in cows treated with an IVD for 8 days compared to 7 days at each synchronized estrus (P < 0.01). More Holstein-Friesian cows were classified as non-pregnant and not detected in estrus than crossbreed cows (15.7%, 54/343 versus 9.0%, 24/266; [P < 0.05). The results of the study suggested that the main effects of the treatments that were used to synchronize and resynchronize estrus were to alter the timing and synchrony of estrus without affecting fertility.

The use of hormonal treatments to improve the reproductive performance of lactating dairy cows in feedlot or pasture-based management systems

Hormonal interventions have been used to increase the probability of estrous detection and insemination, and to increase pregnancy rates of dairy cattle under a variety of management systems. The present review addresses the basic principles of hormonal intervention and presents typical examples that illustrate the methodology. The hormones used to control the estrous cycle mimic the reproductive hormones found within the normal cow. Most estrous synchronization systems employ a method for controlling follicular wave development, promoting ovulation in anestrous cows, regressing the corpus luteum in cyclic cows, and synchronizing estrus and (or) ovulation at the end of treatment. A wide range of reproductive systems are in place on dairy farms. In most herds, a non-intervention period is practiced where postpartum cows are observed estrus estrus. Cows not observed in estrus are then treated. A number of studies in pasture-based and confinement systems have demonstrated net benefits of whole-herd synchronization. Despite the advantages of whole-herd reproductive programs, their uptake has been inconsistent globally. The benefits of a timed artificial insemination (AI) system increase under conditions of poor estrous detection rate and poor conception rate. The unpopular nature of timed AI programs in pasture-fed cows relates to high rates of estrous detection and conception for pasture-based dairying. Regardless of production system, some cows must be re-inseminated because they are not pregnant after first insemination. The presence of "phantom cows" (non-pregnant cows that do not return to estrus) creates a serious reproductive challenge for both pasture-based and confinement-style operations. Early pregnancy diagnosis and second insemination timed AI may reduce the effects of phantom cows on dairy herds. Fundamental research into anestrous, the hormonal control of the estrous cycle, and early pregnancy detection should elucidate new methods that can be used to strengthen reproductive programs on dairy farms.