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

Reproductive hormone use and its association with herd-level factors on Dutch dairy farms

We studied the use of the 3 commonly used reproductive hormones, namely prostaglandins, GnRH, and progesterone, and associated herd-level factors on 760 Dutch dairy farms from 5 veterinary clinics. From 2017 to 2019 we collected data on the sales of reproductive hormones, converted this data into the number of reproductive hormone doses conducted, and expressed this as the annual number of reproductive hormone doses per 100 adult dairy cows. Additional herd-level information was available for 2019. Due to the excess of zeros in the data set (i.e., a substantial number of farms did not use any hormones), we used a zero-inflated negative binomial model to identify related herd-level factors for the use of reproductive hormones. In the entire study period of 2017 to 2019, 5.8% of the dairy farms did not use any reproductive hormones, with the proportion of nonusers varying between 0.0 and 10.3% per veterinary clinic. This proportion was around 13.5% on an annual basis. Prostaglandins were the most frequently used reproductive hormone in Dutch dairy cows (62.9%), followed by GnRH (33.1%) and progesterone (4.0%). Furthermore, participating in a veterinary herd health management program had a significant effect on reproductive hormone use. These farms used more reproductive hormones than farms that did not participate in a herd health management program and were less represented in the group of nonuser farms. Technologies, such as pedometers and automatic milking systems, also had an effect on reproductive hormone use. The presence of pedometers or activity monitors did not reduce the use of the reproductive hormones but was associated with a greater frequency of users. Farms with an automatic milking system used more reproductive hormones than farms with a conventional milking system. With this study, we have made a first step in achieving transparency in the Dutch dairy industry by providing an objective overview of reproductive hormone use on Dutch dairy farms and identifying associations with some herd-level factors.

Evaluating the cost-effectiveness of diagnosing and treating phantom cows in seasonal-calving dairy herds

The objective of this study was to explore the cost-effectiveness of using a progesterone-based synchrony program to manage phantom cows on seasonal-calving dairy farms. Phantom cows were defined as cows that had been artificially inseminated ≤14 d after mating start date (MSD), were not subsequently detected in estrus, and were diagnosed nonpregnant at a pregnancy diagnosis conducted approximately 49 d after MSD. Decision-tree analysis was applied to data from a previous randomized controlled trial in which phantom cows (n = 378) from spring-calving dairy farms were randomly allocated to an untreated control group or were immediately treated with a 10-d progesterone-based synchrony program with fixed-time artificial insemination. The net economic return of treating all cows presented by the farmer for pregnancy diagnosis that were diagnosed nonpregnant was compared with no intervention. The net return was calculated per cow present at MSD because the decision trees followed all cows present at MSD through to mating end date to account for farmers inadvertently presenting ineligible cows for pregnancy diagnosis and possible treatment. Probabilities, costs, and benefits of reproductive outcomes were based on published data and expert opinion. The effects of key variables on the economic return were tested by sensitivity analysis. Phantom cow intervention delivered a net return of NZ$4.451 (at the time of the study, NZ$1 = US$0.6629) per cow present at MSD. The sensitivity of pregnancy diagnosis, the proportion of ineligible cows presented by the farmer for pregnancy diagnosis, and the prevalence of phantom cows were highly influential on the net economic return from phantom cow intervention. These findings suggest that treatment of phantom cows in seasonal-calving dairy farms using a progesterone-based synchrony program is economically viable based on the current model assumptions. Accurate cow selection and pregnancy diagnosis are essential to success, and veterinarians and animal health advisors can improve the net economic return of intervention by selecting farms likely to have a higher prevalence of phantom cows based on the presence of observable risk factors.

Efficacy of inclusion of equine chorionic gonadotrophin into a treatment protocol for anoestrous dairy cows

AIM

To compare the performance of intravaginal devices containing 1.0 g (DIB) or 1.38 g (CIDR) progesterone and to determine the efficacy of inclusion of equine chorionic gonadotrophin (eCG) into progesterone-based anoestrous cow treatment protocols for New Zealand dairy cows.

METHODS

Anoestrous cows (n = 1,906) from 12 herds were randomly assigned to four treatments: 100 μg gonadorelin (GnRH) at Day -10; 500 μg cloprostenol at Day -3; 100 μg GnRH at Day -1 and fixed time artificial insemination (FTAI) on Day 0 (gonadotrophin-prostaglandin-gonadotrophin [GPG] group, n = 475); GPG with CIDR device (1.38 g progesterone) inserted between Day -10 and Day -3 (CIDR group, n = 477); GPG with DIB device (1.0 g progesterone) inserted between Day -10 and Day -3 (DIB group, n = 477); and DIB with 400 IU eCG at Day -3 (DIB + eCG group, n = 477). Conception rates to FTAI and pregnancy at Day 28 were analysed using generalised estimating equations (GEE). Time to conception and time to return to oestrus were analysed using Kaplan-Meier survival analysis and Cox's proportional hazards regression.

RESULTS

The proportion of cows conceiving to FTAI was 0.34 (95%CI = 0.29-0.37), 0.38 (95%CI = 0.34-0.43), 0.38 (95%CI = 0.33-0.42) and 0.41 (95%CI = 0.37-0.46) for GPG, CIDR, DIB and DIB + eCG groups, respectively. The proportion of cows pregnant by Day 28 was 0.55 (95%CI = 0.51-0.60), 0.57 (95%CI = 0.52-0.61), 0.56 (95%CI = 0.52-0.60) and 0.63 (95%CI = 0.59-0.67) for GPG, CIDR, DIB and DIB + eCG groups, respectively. There was an interaction between treatment and number of days calved (p < 0.05). Cows more than 60 days calved and treated with DIB + eCG had higher FTAI conception and 28-day pregnancy rates than cows treated with GPG (p < 0.001). Median interval to conception did not differ between treatments (p > 0.05). There were no differences between DIB and CIDR groups for any parameter (p > 0.05). The range of the relative risk distribution among herds comparing DIB + eCG to DIB groups was greater than that comparing CIDR to DIB groups for conception to FTAI and pregnancy at Day 28.

CONCLUSIONS

The inclusion of eCG into progesterone-based anoestrous cow treatment protocols improves conception to FTAI and 28-day pregnancy rates in cows >60 days calved at treatment compared with a GPG protocol. There was no difference in clinical performance between DIB and CIDR devices.

CLINICAL RELEVANCE

The combination of a low payload (1.0 g) progesterone releasing intravaginal device with eCG treatment at device removal within a GPG treatment is a clinically effective treatment for anoestrous in New Zealand dairy cows.

Recent advances in the synchronization of estrus and ovulation in dairy cows

Synchronization programs have become standard components in the current breeding management of cows in the dairy herds of most dairy industries. Many are based on protocols that allow timed inseminations (TAI) so as to circumvent the practical difficulties associated with estrus detection. These difficulties are exacerbated in modern herds of high producing cows either because of increasing herd size in which individual animal monitoring is difficult and often subjective, or because small intensively managed herds are milked in robotic systems that minimize animal: staff interactions. Additional reasons arise from high producing cows having less obvious symptoms of estrus, partly because of housing systems combined with intensive feeding and milking, partly because of higher metabolic clearance rates of reproductive hormones like estradiol and partly because of the increasing prevalence of prolonged post-partum anestrus and reproductive tract pathology. The most recently developed programs include protocols for resynchronization following first or subsequent inseminations. These re-synchronization protocols may involve selected forms of hormonal intervention during the diestrous and pro-estrous periods following TAI, or following pregnancy diagnosis by ultrasound from 28 days after TAI. The latter form of re-synchronization has become increasingly important with the recognition that late embryonic/early foetal death has become a major factor compromising the reproductive performance of high producing Holstein cows in many dairy industries. Although cows detected in estrus without any hormonal treatment before insemination have higher conception rates than those inseminated following synchronization and TAI, the low detection rates combined with embryonic death means that intervals from calving to conception (days open) are usually less when synchronization programs have been successfully implemented. One of the significant factors affecting a program's success is the compliance rate that may sometimes be less than 70%. Almost all programs involve strategically timed injections of prostaglandin F2alpha (PGF) and gonadotropin releasing hormone (GnRH). Injections of an estradiol ester and progesterone supplementation per vaginum may be included in some programs. The basic program is the "Ovsynch" regimen. Numerous variations have been tested and developed. Many involve increasingly complex protocols that increase the risk of non-compliance, none has consistently achieved conception rates that exceed 40% and few have reduced the incidence of embryonic death. These synchronization programs are the best that are currently available. They have not been able to overcome the consequences of lowered fertility associated with high levels of milk yield, forms of nutrition and environmental factors like heat stress that have profound effects on the physiology and metabolism of the high producing dairy cow.

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.