Effect of milk yield characteristics, breed, and parity on success of the first insemination in Dutch dairy cows

Application of antioxidants in extender on bull sperm cryopreservation to reduce the male effect in dairy fertility

Because male and female effects on fertility must be considered, it may be difficult to achieve accurate and repeatable fertility predictions using only sperm characteristics given differences in breed, health, and season. Improving sperm quality after cryopreservation may be a method to reduce the male effect on the fertility outcome. This study was conducted using 2 different Certified Semen Service approved extenders, one containing plant-derived antioxidants, to assess cryopreserved sperm quality and determine pregnancy per artificial insemination (P/AI) in a commercial dairy farm. Beef bull ejaculates (n = 24 ejaculates, n = 4 bulls) were split and frozen in egg-yolk-TRIS (EYT) or GameteGuard-FB cryopreservation extenders. Frozen-thawed sperm was evaluated for sperm quality and used for insemination in dairy cows (n = 4856). There was an improvement in total and progressive motility, acrosome integrity, and reduction of DNA fragmentation at 0 and 3 h after thawing in sperm frozen in GameteGuard-FB when compared with the EYT extender. An overall 12.7% improvement in pregnancy per AI (P/AI) was observed when GameteGuard-FB (40.8%) was used for cryopreservation when compared with EYT (36.2%). More importantly, GameteGuard-FB frozen semen increased P/AI for first service by 19.5% (35.9% EYT and 42.9% GameteGuard-FB) and 45.0% was also observed at third service (31.3% EYT and 45.4% GameteGuard-FB). The use of GameteGuard-FB resulted in an average 40% P/AI among bulls. Taken together, the increase in cryopreserved sperm quality using GameteGuard-FB can be used to minimize the male effects on pregnancy outcomes in commercial dairy farms.

Characterization of conception rate after embryo transfer in comparison with that after artificial insemination in dairy cattle

Artificial insemination (AI) and embryo transfer (ET) are important in the reproduction of dairy cows. The conception rate after AI or ET is an essential indicator when selecting appropriate breeding methods. However, information on the environmental factors affecting ET conception rate when compared with AI is limited. We aimed to investigate environmental factors affecting ET conception rate and characterize the differences in environmental factors between AI and ET. Records of the first AI (n = 1,870,143) and ET (n = 29,922) from Holstein nulliparous, primiparous, and multiparous cows in Hokkaido, Japan, were analyzed using separate multivariable logistic regression models. For each breeding method, we grouped primiparous and multiparous cows according to milk yield at peak lactation (PY; < 25, 25-30, 30-35, ≥ 35 kg in primiparous, < 40, 40-45, 45-50, ≥ 50 kg in multiparous) and the interval from calving to first AI or ET (CFI/CFT; < 60, 60-79, 80-99, ≥ 100 d) to evaluate the effects of PY and CFI/CFT on conception rate. AI conception rate decreased with increasing PY in primiparous and multiparous cows, whereas ET conception rate did not decrease significantly. Additionally, the ET conception rate did not decrease even in primiparous and multiparous cows slightly earlier than 60 d in CFI/CFT when compared with those in CFI/CFT after 60 d, which differed from the AI conception rate. Collectively, breeding by ET leads to the avoidance of negative effects of high milk yield and calving on the conception rate, indicating that cows are fertile by ET within 60 d after calving.

Association between body condition profiles, milk production and reproduction performance in Holstein and Normande cows

Body-condition dynamics are known to affect the different steps of reproduction in cattle (cyclicity, estrus expression, fertilization, embryo development). This has led to a widespread idea that there is an ideal-target optimal body condition, but no clear profile has yet been identified. Here we investigated the relationships between body condition score (BCS) profiles and reproductive performance in dairy cows. Data were from Holstein or Normande herds in 6 French experimental farms. In the Holstein breed, we discriminated 4 BCS profiles based on combining BCS at calving (Low: around 2.6 points, or High: around 3.3 points) with BCS loss after calving (Moderate (M): ≤ 1.0 points, or Severe (S): > 1.0 points). The Low-M profile mostly included multiparous cows with higher milk yield and lower reproductive performance than cows in the 3 other profiles. Low-M cows that experienced abnormal ovarian activity had lower reproductive performance than their profile-mates. Moreover, 67% of Low-M cows kept the same profile at the following lactation. The High-S profile mostly included primiparous cows with lower milk yield and higher reproductive performance than cows in other profiles. In High-S cows, higher milk yields correlated to higher risk of failure to calf on first insemination. Moreover, 38% of High-S cows kept the same profile at the following lactation, and none changed to Low-M. The other 2 BCS profiles (Low-S and High-M) were intermediate in terms of milk yield and reproductive performance. In Normande, we discriminated 3 BCS profiles based on combining BCS at calving (Low: around 2.6 points, or High: around 3.5 points) with BCS loss after calving (Flat (F): flat with no loss, Moderate (M): around 0.5 points, or Severe (S): around 1.0 point). The Low-M and High-S profiles included cows with similar performance, even though High-S-profile cows showed better but not significantly different milk yield and reproduction performance. The High-F profile included cows that were more likely to experience abnormal ovarian activity and fail at first insemination than cows in other profiles. More than 50% of Normande cows with 2 successive lactations kept in the same BCS profile at the next lactation. Even though a low BCS at calving combined with severe BCS loss (more than 1 point) after calving was found to increase reproductive failure, there was no evidence of an optimal BCS profile for reproduction in dairy cows, and reproductive success or failure is multifactorial.

Longevity and the association with cattle health in Dutch dairy farms

Longevity of a herd is defined as the average age of all cattle over two years old at the moment of death (either natural, by euthanasia or by slaughter), and is increasing since 2018. The aim of this study was to evaluate the association between longevity and cattle health indicators in Dutch dairy herds. Anonymized census data were available for 16,200 Dutch dairy herds (∼98 % of the dairy herds) between 2016 and 2020. All herds were categorized into one of six longevity groups: herds with a high longevity (>seven years old), increasing longevity (mean increase of one year and two months between 2017 and 2020), median longevity (∼five years and eight months, without major fluctuations in longevity), decreasing longevity (mean decrease eight months), low longevity (<four years and ten months) and a varying longevity of ∼five years and eight months, with fluctuation in longevity throughout the study period. Data were aggregated to herd and quarter of the year level. Cattle health parameters were analysed with multivariable population-averaged models with health indicators as dependent variables, and longevity and other management and herd level factors as explanatory variables. Belonging to the group of herds with a high longevity was associated with lower calf- and cow mortality, a higher percentage of cows with a high somatic cell count (HSCC), fewer inseminations per pregnancy for heifers and more inseminations for cows, a higher antibiotic use in adult dairy cows and a lower antibiotic use in calves compared to the average Dutch dairy herd. Further analysis showed that the higher percentage of cows with a HSCC could be explained by the higher share of older cows. Herds with a low longevity had a higher calf- and cow mortality, a lower percentage of cows with a HSCC, more inseminations for heifers and fewer for cows, lower antibiotic use in cows and higher antibiotic use in calves compared to the average Dutch dairy herd. To conclude, there were differences in cattle health between groups of herds with a different longevity.

Pregnancies following Protocols for Repetitive Synchronization of Ovulation in Primiparous Buffaloes in Different Seasons

Simple Summary

Artificial Insemination (AI) is mainly used after estrus synchronization in buffalo, and consecutive synchronization protocols are used to enhance reproductive efficiency. In this study, two different synchronization protocols have been used: Ovsynch vs. a P₄-administration, and their efficiency in primiparous animals has been evaluated in different seasons for up to four cycles of re-synchronization protocols. Results show that the pregnancy rate upon the initial AI tends to be higher in P₄ treated buffaloes, and that AI efficiency after re-synchronization through P₄ is higher than the Ovsynch protocol. In conclusion, synchronization treatments must be selected according to the season of the year. The results derived from this study could be useful for buffalo breeders who want to improve the reproductive efficiency in primiparous animals in commercially managed buffalo herds.

Abstract

Primiparous buffaloes were tested in two periods of the year characterized, by either low or high reproductive efficiency. They were subjected to two protocols for synchronization of ovulation: (i) Ovsynch (OV) and (ii) progesterone based (P₄) treatment. After calving, the animals underwent a series of four cycles of re-synchronization protocols. The season did not affect pregnancy rates when the results of the two treatments were pooled together with regard to the first synchronization protocol, followed by AI. Pregnancy rates were similar during the low breeding season (50.3% vs. 57.4% in OV and P₄, respectively), but different during the high breeding season (50.4% vs. 67.7% in OV and P₄, respectively; p = 0.000). Logistic regression confirmed a significant effect of treatment and season interaction on pregnancy (p = 0.003). Following re-synchronization, a treatment by season interaction was detected during the low breeding season (odds ratio = 2.233), in favor of P₄. Finally, a survival analysis showed a better response of animals subjected to P₄ treatment from the second AI onward. In conclusion, the pooled data of pregnancy rates from both treatments between seasons are not different following AIs. Better results, though, were obtained from the implementation of P₄ treatment, and are recorded in a season-fashioned mode when the comparison is made following first or cumulative AIs.

Dairy Cows Experimentally Infected With Bovine Leukemia Virus Showed an Increased Milk Production in Lactation Numbers 3–4: A 4-Year Longitudinal Study

Bovine leukemia virus (BLV) is widespread in global cattle populations, but the effects of its infection on milk quantity and quality have not been clearly elucidated in animal models. In this study, 30 healthy first-lactation cows were selected from ≈2,988 cows in a BLV-free farm with the same criteria of parity, age, lactation number, as well as milk yield, SCS, and composition (fat, protein, and lactose). Subsequently, these cows were randomly assigned to the intervention (n = 15) or control (n = 15) group, and reared in different cowsheds. Cows in the intervention group were inoculated with 1 × phosphate-buffered solution (PBS) resuspended in peripheral blood mononuclear cells (PBMC) from a BLV-positive cow, while the controls were inoculated with the inactivated PBMC from the same individual. From June 2016 to July 2021, milk weight (kg) was automatically recorded by milk sensors, and milk SCS and composition were originated from monthly performed dairy herd improvement (DHI) testing. Fluorescence resonance energy transfer (FRET)–qPCR and ELISA showed that cows in the intervention group were successfully infected with BLV, while cows in the control group were free of BLV for the entire period. At 45 days post-inoculation (DPI), the numbers of whole blood cells (WBCs) (P = 0.010), lymphocytes (LYMs) (P = 0.002), and monocytes (MNCs) (P = 0.001) and the expression levels of IFN-γ (P = 0.013), IL-10 (P = 0.031), and IL-12p70 (P = 0.008) increased significantly in the BLV infected cows compared to the non-infected. In lactation numbers 2–4, the intervention group had significantly higher overall milk yield (P < 0.001), fat (P = 0.031), and protein (P = 0.050) than the control group, while milk SCS (P = 0.038) and lactose (P = 0.036) decreased significantly. Further analysis indicated that BLV infection was associated with increased milk yield at each lactation stage in lactation numbers 3–4 (P = 0.021 or P < 0.001), but not with SCS and milk composition. Together, this 4-year longitudinal study revealed that artificial inoculation of BLV increased the milk yield in cows in this BLV challenge model.

Success rate of artificial insemination, reproductive performance and economic impact of failure of first service insemination: a retrospective study

Background

A retrospective cohort study using a 10 year artificial insemination (AI) and cow reproductive performance data was conducted to study the success rate of AI; associations between effectiveness of AI and breed, AI season and, number of service per conception, and economic impact of failure of FSC in Dessie town, Dessie zuria and Kutaber districts. A total of 3480 dairy cows’ AI and reproductive performance records which were performed between 2003 and 2013 in the three selected districts of South Wollo were used. The economic losses and costs for cows that failed to conceive at their first AI associated with the larger number of days open were estimated.

Result

The prevalence of conception has a statistically significant difference between breeds of cows (P = 0.019). The non-return rate for first service was 58.54%. The median days to first service (DFS), inter-service interval (ISI) and gestation length (GL) were 126, 30 and 278 days respectively. Whereas, the mean + SD days open, calving interval (CI), number of inseminations (NOI) and number of services per conception (NSPC) were 147.2 ± 60.26, 424.5 ± 60.55, 1.14 ± 0.38 and 1.15 ± 0.39 respectively. Based on AI season there was a significant difference in conception between winter and spring (P = 0.021). There is a 45.04 days extension in the mean calving to conception interval in cows that did not conceive at their first AI but conceived by 2nd and 3rd AI than in cows that did conceive at their first AI. A total of 21,665.3 ETB extra costs was spent on reproductive treatment and other management for cows that failed to conceive at their first AI but conceived by second and third service. In cows that did not conceive totally the owner losses on average 473.7 ETB per cow per day extra costs until the cows will be culled.

Conclusion

Therefore to increase the conception rate and decrease the economic loss the owners of the dairy cows should supervise the cows regularly and should be trained on how to identify cows on estrous, the AI technicians should be trained to conduct the AI service accurately.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03325-1.

Simulation of the lifetime productivity of a dairy herd in Japan according to the number of days to first service of cows

To determine the optimal voluntary waiting period to first service after calving for maximizing the lifetime productivity of cows in a dairy herd, we simulated the changes in lifetime productivity due to increasing the number of days from calving to first service. We also assessed the effects of changes in the maximum number of services within a lactation, maximum number of calvings, and calf sale prices on lifetime productivity. We evaluated lifetime productivity as lifetime average productivity, that is, the sum of daily revenues from milk and calf sales from first calving to culling. The lifetime productivity at ≤65 days to first service was low because of the low conception rate during early lactation. In addition, lifetime productivity at ≥185 days to first service decreased as the number of days to first service increased. The number of days to first service for maximum lifetime productivity decreased as the maximum number of calvings increased. Furthermore, the decrease in lifetime productivity associated with decreasing the maximum number of services within a lactation from five to four was greater than that when the maximum number of calvings was decreased from six to five.

Calving Management: A Questionnaire Survey of Veterinary Subject Matter Experts and Non-Experts

Simple Summary

We designed a questionnaire and asked two groups of veterinarians: (1) subject matter experts, who had published on calving management and (2) veterinary practitioners) for their opinion about aspects of calving management. Participants recommended to differentiate between the two stages of parturition and emphasized signs of imminent parturition, such as “restlessness” and “visibility of fetal parts”. There was no consensus on the right time to move the cow to the maternity pen. Almost half of the respondents recommended a 6-h observation interval for prepartum cows in the maternity pen. The two veterinary groups differed little in their knowledge of calving management.

Abstract

Accurate detection of the onset of parturition is a key factor in the prevention of dystocia. In order to establish current best practice recommendations for calving management, we asked subject matter experts (SME) who had published on calving management (by online survey, n = 80) and non-SMEs, veterinary practitioners (by workshop survey, n = 24) for their opinions. For this, we designed a questionnaire on the significance of signs of imminent parturition (SIP), the frequency of calving observation, and influencing factors for the timing of cow movement to a maternity pen. The response rate was 67.5% in the online survey and 100% in the workshop survey. The majority (89.7%) of all respondents agreed that it is beneficial for successful calving management to differentiate between stage I and II of parturition. Of 12 signs of imminent parturition (for stage I and II), “restlessness” and “visibility of fetal parts in vulva” were cited by 56.5% and 73.3% of SME and non-SME respondents, respectively. There was no consensus on the right time to move the cow to the maternity pen; recommendations varied from one to over 21 days. Almost half of the respondents (45.7%) recommended a 6-h observation interval for prepartum cows in the maternity pen. This study identified a strong consensus on the SIP and how and when to observe cows prior to parturition. SMEs and non-SMEs provided broadly similar recommendations, while the SMEs and the non-SMEs differed significantly in the number of publications on calving they authored, they differed little in their knowledge of calving management.

The Use of Artificial Neural Networks and a General Discriminant Analysis for Predicting Culling Reasons in Holstein-Friesian Cows Based on First-Lactation Performance Records

The aim of the present study was to verify whether artificial neural networks (ANN) may be an effective tool for predicting the culling reasons in cows based on routinely collected first-lactation records. Data on Holstein-Friesian cows culled in Poland between 2017 and 2018 were used in the present study. A general discriminant analysis (GDA) was applied as a reference method for ANN. Considering all predictive performance measures, ANN were the most effective in predicting the culling of cows due to old age (99.76-99.88% of correctly classified cases). In addition, a very high correct classification rate (99.24-99.98%) was obtained for culling the animals due to reproductive problems. It is significant because infertility is one of the conditions that are the most difficult to eliminate in dairy herds. The correct classification rate for individual culling reasons obtained with GDA (0.00-97.63%) was, in general, lower than that for multilayer perceptrons (MLP). The obtained results indicated that, in order to effectively predict the previously mentioned culling reasons, the following first-lactation parameters should be used: calving age, calving difficulty, and the characteristics of the lactation curve based on Wood's model parameters.

Fatores de influência sobre o desempenho reprodutivo em vacas leiteiras

RESUMO O objetivo deste estudo foi avaliar os efeitos das estações do parto e da inseminação, da retenção de placenta, da natimortalidade e da ordem de parto sobre o desempenho reprodutivo de vacas leiteiras. Utilizou-se a regressão logística, em que as variáveis dependentes foram concepção à primeira inseminação pós-parto e percentual de vacas prenhes no rebanho aos 100, 150 ou 200 DEL e as variáveis independentes foram a estação do parto e a estação da inseminação, a retenção de placenta, a natimortalidade e a ordem de parto. A estação do parto e a estação da inseminação influenciaram o desempenho reprodutivo, reduzindo a fertilidade das vacas nas estações quentes do ano. O atraso na primeira inseminação aumentou a concepção na primeira inseminação, mas reduziu o percentual de vacas prenhes ao longo da lactação. O desempenho reprodutivo da vaca leiteira foi afetado por vários fatores, relacionados à vaca, ao ambiente e ao manejo a ela imposto.

Primiparous and multiparous Friesland, Jersey, and crossbred cows' behavior around parturition time at the pasture-based system in South Africa

OBJECTIVE

The objective of the study was to assess the behavioral attributes of primiparous and multiparous Friesland, Jersey, and Crossbred cows around calving time in a pasture-based dairy system.

MATERIAL AND METHODS

A total of 120 pregnant cows were used in the study, comprising of 40 cows per genotype in different parities [A-primiparous (n = 10), B-2 to 4 (n = 10), C-5 and 6 (n = 10), and D-7 and 8 (n = 10)] and kept in a maternity paddock. Five observers monitored cows from the onset of parturition until the calves were fully expelled, recording the frequency and duration of lying, standing, and walking bouts, calf licking, and suckling.

RESULTS

There were differences (p < 0.05) observed in the behavioral patterns around the time of calving. Jersey multiparous cows spent (p < 0.05) significantly most of their time (20.50 ± 3.10) in lying position as compared to the other genotypes. The Jersey cows also spent most (p < 0.05) of their time (48.00 ± 0.34) in a standing position during the calving period. Friesland cows spent (p < 0.05) most of their time (12.00 ± 1.19) exhibiting either stepping or walking attributes as compared to Jersey and Crossbred cows. The Jersey genotype spent significantly (p < 0.05) more time (123.00 ± 10.43) in expelling their calves compared to the other genotypes. There was a significant (p < 0.05) interaction between genotypes and parity on time spent by cows on licking their calves. There was a significant difference (p < 0.05) observed between the genotypes of the primiparous cow.

CONCLUSION

The primiparous cows spent most of their time in standing and the least amount of time in other activities throughout the trial due to the lack of maternal experience. The current study revealed that behavioral activities differ according to genotype and parity.

Effects of Extruded Linseed and Soybean Dietary Supplementation on Lactation Performance, First-Service Conception Rate, and Mastitis Incidence in Holstein Dairy Cows

This study quantifies the effects of extruded linseed and soybean (ELS) dietary supplementation on milk yield, composition, and fatty acid profiles, as well as first-service conception rate in Holstein dairy cows. Seventy-eight open Holstein dairy cows were divided into two groups: (1) a control, which received a basal diet; and (2) a test group, which received a basal diet supplemented with the ELS (650 g/kg of extruded linseed and 150 g/kg of extruded soybean) at a rate of 100 g/kg. In the ELS group, milk yield per day and solid not fat (SNF) yield increased by 3.26% and 0.88%, respectively, in relation to the control. Percentage milk fat decreased significantly by 1.4% in the ELS group when compared with the control. The ELS supplement resulted in a decrease in saturated fatty acids (SFAs) and an increase in monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs) in milk. In conclusion, the supplementation of dairy cow feed with 100 g/kg of ELS increases milk yield and milk unsaturated fatty acids (especially MUFAs and PUFAs). ELS supplementation also causes a decrease in percentage fat and SFA levels but does not affect the first-service conception rate or the incidence rate of mastitis.

Assessment of associations between transition diseases and reproductive performance of dairy cows using survival analysis and decision tree algorithms

This study aimed to evaluate the associations between transition cow conditions and diseases TD with fertility in Holstein cows, and to compare analytic methods for doing so. Kaplan-Meier, Cox proportional hazard, and decision tree models were used to analyze the associations of TD with the pregnancy risk at 120 and 210 DIM from a 1-year cohort with 1946 calvings from one farm. The association between TD and fertility was evaluated as follows: 1 cows with TD whether complicated with another TD or not TD-all, versus healthy cows, and 2 cows with uncomplicated TD TD-single, versus cows with multiple TD TD+; complicated cases, versus healthy cows. The occurrence of twins, milk fever, retained placenta, metritis, ketosis, displaced abomasum, and clinical mastitis were recorded. Using Kaplan-Meier models, in primiparous cows the 120 DIM pregnancy risk was 62% (95% CI: 57-67 %) for healthy animals. This was not significantly different for TD-single (58%; 95% CI: 51-66 %) but was reduced for TD+ (45%; 95% CI: 33-60 %). Among healthy primiparous cows, 80% (95% CI: 75-84 %) were pregnant by 210 DIM, but pregnancy risk at that time was reduced for primiparous cows with TD-single (72%; 95% CI: 65-79 %) and TD+ (62%; 95% CI: 49-75 %). In healthy multiparous cows, the 120 DIM pregnancy risk was 53% (95% CI: 49-56 %), which was reduced for TD-single (36%; 95% CI: 31-42 %) and TD+ (30%; 95% CI: 24-38 %). The 210 DIM pregnancy risk for healthy multiparous cows was 70% (95% CI: 67-72 %), being higher than the 210 DIM pregnancy risk for multiparous cows with TD-single (47%; 95% CI: 42-53 %) or TD+ (46%; 95% CI: 38-54 %). Cows with TD-all presented similar pregnancy risk estimates as for TD + . Cox proportional hazards regressions provided similar magnitudes of effects as the Kaplan-Meier estimates. Survival analysis and decision tree models identified parity as the most influential variable affecting fertility. Both modeling techniques concurred that TD + had a greater effect than TD-single on the probability of pregnancy at 120 and 210 DIM. Decision trees for individual TD identified that displaced abomasum affected fertility at 120 DIM in primiparous while metritis was the most influential TD at 120 and 210 DIM for multiparous cows. The data were too sparse to assess multiple interactions in multivariable Cox proportional hazard models for individual TD. Machine learning helped to explore interactions between individual TD to study their hierarchical effect on fertility, identifying conditional relationships that merit further investigation.

The Effect of Abnormal Reproductive Tract Discharge on the Calving to Conception Interval of Dairy Cows

Prolonged calving-to-conception interval (CCI) can increase economic loss in cattle. We investigated the effect of post-calving abnormal reproductive tract discharge (ARTD) on CCI in dairy cows and quantified the relationship of ARTD and associated risk factors with CCI. The source population was dairy cows that calved in the study period on three pasture-based, year-round calving farms in the Riverina, NSW, Australia. Farm records and records from veterinarians' visits were analyzed. ARTD was defined as the presence of reproductive tract discharge according to the following classification: per vaginum purulent discharge ≥21 days post-calving or mucopurulent discharge >26 days post-calving. The incidence of ARTD was calculated. A Kaplan-Meier survivor function was used to estimate median time to conception post-calving dependent on the presence or absence of ARTD. Mixed effects Cox-proportional hazard models were used to estimate the direct and indirect effects of ARTD, and other potential risk factors on CCI such as body condition score (BCS), ambient temperature, and milk yield. Model structures were guided by a directed acyclic graph of potential risk factors for ARTD. The incidence of ARTD in lactations was 16% (95% CI 13.8–18.5%) and did not differ significantly between the three farms (P > 0.05). The median CCI was 176 and 118 days for lactations with and without ARTD, respectively (P < 0.01). The rate of pregnancy following calving in cows with ARTD was significantly decreased relative to the rate of pregnancy in cows without (total effect hazard ratio = 0.62, se = 0.18, P = 0.01). High peak milk yield (>32 L) and parity >2 also significantly extended CCI. We did not observe an effect of BCS or ambient temperature on CCI. The incidence of ARTD in the current study was consistent with clinical endometritis (considered a major source of ARTD) reported in other studies. In contrast—and despite regular veterinary assessment and treatment of on the farms in this study—ARTD extended CCI. Evaluation of the economic impact of ARTD on dairy farms in this region is warranted, and methods to identify high risk cows and develop effective interventions are required.

A Holstein-Friesian dairy farm survey of postparturient factors influencing the days to first AI and days open in Hungary

The authors monitored the postpartum period during the first seven weeks after calving at a Holstein-Friesian dairy farm in Hungary. Calvings occurred between 2013 and 2015 in three periods from June to November each year (n = 314). Data were collected from the farm record and ultrasonographic examinations were performed between 22 to 28 and 43 to 49 days in milk (DIM), respectively. The animals were followed until successful artificial insemination (AI), i.e. until becoming pregnant or until culling, but at most at 365 DIM. The prevalence of dystocia, twin calving, stillbirth rate and retained fetal membranes (RFM) was 23.2%, 3.8%, 3.5%, and 34.4%, respectively. Altogether 38.9% of the cows (n = 122) had bacterial complications of involution in the first 49 DIM. The prevalence of Grade 2 clinical (puerperal) metritis (CM) was 20.1% within 5 DIM, 10.5% between 6 to 10 DIM and 13.1% from 11 to 20 DIM, while 9.9% of the cows had clinical endometritis (CEM) between 21 and 28 DIM and 1.3% of the cows between 42 and 49 DIM, respectively. Pyometra was diagnosed in 1% of the cows between 21 and 28 DIM and 0.3% between 42 to 49 DIM, respectively. About 80% (80.6%) of the cows were inseminated at least once (n = 253). The success rate of the first AI was 26.9% (n = 68). Dystocia, twin calving, RFM, CM, CEM and cyclicity had no significant effect on the days between calving and first AI, however, according to the Kaplan-Meier analysis stillbirth significantly increased the number of days from calving to first AI (P = 0.039). According to the Kaplan- Meier analysis dystocia, twin calving, stillbirth, RFM, and cyclicity had no effect on the days open. In cows with CM developed within 5 DIM or with CEM diagnosed between 21 and 28 DIM the number of days open significantly decreased (P = 0.009 and P = 0.007, respectively), which confirms the importance of early diagnosis and treatment of uterine diseases. Similar surveys should be conducted to discover the risk factors for reproductive diseases in order to decrease the reproductive losses in dairy farms.

Risk factors limiting first service conception rate in dairy cows and their economic impact

OBJECTIVE

We determined the risk factors limiting first service conception (FSC) rate in dairy cows and their economic impact.

METHODS

Data were collected from 790 lactations regarding cow parity, peri- and postpartum disorders, body condition score (BCS), reproductive performance, and expenses associated with reproductive management (treatment, culling, and others). Initially, we identified the risk factors limiting FSC rate in dairy cows. Various biological and environmental factors, such as herd, cow parity, BCS at 1 month postpartum and first artificial insemination (AI), resumption of cyclicity within 1 month of calving, year, AI season, insemination at detected estrus or timed AI, peri- and postpartum disorders, and calving to first AI interval, were evaluated. Next, we evaluated the economic impact of the success or failure of FSC by comparing the expense associated with reproductive management until conception between cows that did or did not conceive at their first service.

RESULTS

Cows with BCS <3.0 had a lower probability of conceiving at first insemination (odds ratio [OR] = 0.64, p<0.05) than cows with BCS ≥3.0. Cows inseminated during summer were less likely to conceive (OR = 0.44, p<0.001) than cows inseminated during spring. Cows with peri- or postpartum disorders were less likely to conceive (OR = 0.55, p<0.001) than cows without disorders. Survival curves generated using MedCalc showed an 81 day extension in the mean interval between calving and conception in cows that failed to conceive over those that did conceive at first insemination. Cows failing conceive required additional expenditure on reproductive treatment ($55.40) and other management ($567.00) than cows that conceived at first insemination.

CONCLUSION

Lower BCS, hot weather at first insemination, and peri- and postpartum disorders are risk factors limiting FSC, which result in an economic loss of $622.40 per dairy cow.

Cytological endometritis at artificial insemination in dairy cows: Prevalence and effect on pregnancy outcome

The aims of our field study in dairy cows were (1) to consolidate cytotape (CT) as a valid technique to diagnose cytological endometritis (CYTO) during artificial insemination (AI); (2) to establish a cutoff point concerning the polymorphonuclear cells (PMN) proportion to diagnose CYTO at AI; (3) to assess the prevalence of CYTO at AI; and (4) to evaluate the effect of CYTO on the pregnancy outcome of that AI. The investigation was performed using 1,625 AI-CT samples harvested from 873 Holstein-Friesian cows from 18 dairy farms in the Flemish region of Belgium. The CT device consisted of adapting a 1.5-cm piece of paper tape on the top of a conventional AI catheter covered with a double guard sheet, allowing an endometrial cytology sample to be taken when performing an AI. A receiving operator characteristic curve was built to assess the threshold level above which the PMN proportion significantly affected the AI success. Multilevel generalized mixed-effect models were built to identify factors affecting the pregnancy outcome of the AI under investigation. Only 7 samples (0.4%) harvested in 5 cows were discarded because of low-quality parameters. The cutoff point for CYTO at AI was set at ≥1% PMN (sensitivity=33.8%, specificity=88.6%). Prevalence of CYTO at AI was 27.8%. The conception rate for CYTO-positive samples was 32.7%, whereas it was 47% for CYTO-negative samples. A CYTO-negative AI had 1.8 [odds ratio (OR)] more chances to become pregnant than a CYTO-positive one. Other factors identified as detrimental for the pregnancy outcome were body condition score ≤1.5 (OR=0.6), relative 305-d milk yield (OR=0.9), dystocia (OR=0.3), parity ≥2 (OR=0.7), and warm months of the year. In conclusion, CT is a consolidated technique to diagnose CYTO at AI, PMN 1% is the threshold level to diagnose CYTO at AI, around one-quarter of inseminated uteri suffer from CYTO, and affected uteri having a significantly lower chance to become pregnant from that insemination.

A cow-level association of ruminal pH on body condition score, serum beta-hydroxybutyrate and postpartum disorders in Thai dairy cattle

Subacute ruminal acidosis in dairy cows occurs when ruminal pH is below about 5.5. However, the exact threshold level of ruminal pH affecting cow health is still in debate. This investigation was carried out in 505 cows within 31 farms. The postpartum disorders, including dystocia, retained placenta, anestrus, cystic ovary, metritis, clinical mastitis and lameness, were analyzed. Ruminal pH, serum beta-hydroxy butyrate (SBHB), serum urea nitrogen and body condition score (BCS) were measured once during the 3 to 6 weeks postpartum, while BCS was determined once more at 1 week before calving. Ruminal pH was determined by ruminocentesis technique. The ruminal pH was evaluated to study the association with BCS, SBHB and postpartum disorders using linear regression in a generalized linear mixed model with farm as a random effect. The results show that low ruminal pH was associated with dystocia, metritis and lameness. Moreover, a low ruminal pH can be found in cows with a high loss of BCS after calving and also in cows with low SBHB postpartum. These findings confirmed the feasibility of the ruminocentesis technique and the association of low ruminal pH on various postpartum disorders at the individual cow level. However, the consequences of low ruminal pH on dairy cow health still needs more exploration for a better understanding of the physiological mechanisms.

Relationships between conception rate in Holstein heifers and cows and milk yield at various stages of lactation

We investigated the relationships between conception rates (CRs) at first service in Japanese Holstein heifers (i.e. animals that had not yet had their first calf) and cows and their test-day (TD) milk yields. Data included records of artificial insemination (AI) for heifers and cows that had calved for the first time between 2000 and 2008 and their TD milk yields at 6 through 305 days in milk (DIM) from first through third lactations. CR was defined as a binary trait for which first AI was a failure or success. A threshold-linear animal model was applied to estimate genetic correlations between CRs of heifers or cows and TD milk yield at various lactation stages. Two-trait genetic analyses were performed for every combination of CR and TD milk yield by using the Bayesian method with Gibbs sampling. The posterior means of the heritabilities of CR were 0.031 for heifers, 0.034 for first-lactation cows and 0.028 for second-lactation cows. Heritabilities for TD milk yield increased from 0.324 to 0.433 with increasing DIM but decreased slightly after 210 DIM during first lactation. These heritabilities from the second and third lactations were higher during late stages of lactation than during early stages. Posterior means of the genetic correlations between heifer CR and all TD yields were positive (range, 0.082 to 0.287), but those between CR of cows and milk yields during first or second lactation were negative (range, -0.121 to -0.250). Therefore, during every stage of lactation, selection in the direction of increasing milk yield may reduce CR in cows. The genetic relationships between CR and lactation curve shape were quite weak, because the genetic correlations between CR and TD milk yield were constant during the lactation period.

The association of ruminal pH and some metabolic parameters with conception rate at first artificial insemination in Thai dairy cows

The objective of this study was to determine the association of metabolic parameters and cow associated factors with the conception rate at first insemination (FCR) in Thai dairy cows. The investigation was performed with 529 lactations from 32 smallholder dairy farms. At 3-6 weeks after parturition, blood samples and ruminal fluid were collected. Body condition scores (BCS) of cows were scored 1 week before expected calving date and at blood sampling date. Ruminal pH was measured at 2-4 h after morning feeding in ruminal fluid collected by ruminocentesis. Serum beta-hydroxybutyrate and serum urea nitrogen were measured by kinetic enzyme method. Cows with first insemination (AI) between 41 and 114 days postpartum were identified after pregnancy diagnosis for FCR. Breed, parity, interval from calving to first AI, BCS before calving, BCS after calving, loss in BCS after calving, SBHB, SUN, ruminal pH, and postpartum problems were selected as independent variables for a model with FCR as a dependent variable. A multivariable logistic regression model was used with farm as a random effect. Overall FCR was 27.2 %. The FCR depended on interval from calving to first AI, BCS before calving, and ruminal pH. The FCR between 69 and 91 days postpartum was significantly highest (45 %). Before calving, a cow with high BCS (≥ 3.5) had significantly greater FCR than a cow with low BCS (≤ 3.25; P<0.01). An increased ruminal pH raised significantly FCR (OR=2.53; P=0.03).

Changes of endoplasmic reticulum and mitochondria in mammary epithelial cells during mammogenesis in Chinese Holstein dairy cows

The objective of the research was to study the changes of the major organelles, endoplasmic reticulum (ER) and mitochondria, in mammary epithelial cells of the Chinese Holstein dairy cow during mammogenesis. For this purpose, a mammary epithelial cell bank was established from 9 selected Chinese Holstein dairy cows using collagenase I digestion and attachment culture biotechniques. This cell bank included 9 samples at stages of pregnancy, lactation and involution. The changes of ER and mitochondria in the mammary cells were observed at the subcellular level using living cell fluorescent labeling and laser confocal microscopy. Subsequently, the area of integrated optical density of each sample was calculated to determine changes of ER and mitochondria in the mammary epithelial cells. The results showed clear differences in the epithelial major organelles during the various mammary gland development stages. The ER and mitochondria, as an indicator of lactogenic activity of alveolar secretory cells, increased in number from pregnancy to lactation by an average 37.32% and 18.44%, respectively, which was followed by a reduction at involution by an average 38.04% and 22.91% compared to lactation. Our study shows that the stages of mammogenesis are accompanied by changes in activity of the major organelles of the mammary epithelial cells.