Postpartum vaginal discharge score is associated with genetic traits, postpartum fertility phenotypes, metabolic status, and overall reproductive performance in seasonal-calving pasture-based dairy cows

The aims of this study were (1) to evaluate potential associations between genetic traits, postpartum phenotypes, cow factors, and postpartum vaginal discharge score (VDS); and (2) to investigate possible associations between postpartum VDS, plasma progesterone (P4) after first service, and reproductive performance. First- and second-parity (n = 2,842) spring-calving lactating dairy cows from 35 dairy herds were enrolled. Farm visits were performed every 2 wk during the postpartum period and weekly during the breeding period. Cows that were at wk 3 and wk 7 postpartum and between 7 and 13 d after first artificial insemination (AI) were examined. Body condition score (BCS) was measured on all farm visits using a 1-to-5 scale (low ≤2.5; target ≥2.75). Transrectal ultrasound examinations were conducted to determine the presence or absence of a corpus luteum (CL). Vaginal discharge score was determined at wk 3 and wk 7 using a Metricheck device (Simcro) and a 1-to-4 scale (1 = clear mucus; 4 = mucopurulent with >50% purulent material ± odor). At wk 3, cows having a VDS ≤2 were considered to have normal reproductive tract health status (RTHS). At wk 7, cows having VDS = 1 were considered to have normal RTHS. Blood samples were collected at each visit, and plasma concentrations of glucose, β-hydroxybutyrate, fatty acids, and progesterone (only during breeding visit) were analyzed. Animals with target BCS at wk 3 and wk 7 had greater odds of having normal RTHS at wk 3 and wk 7, respectively, than cows with low BCS. Cows with a CL at wk 3 and wk 7 had greater prevalence of normal RTHS at wk 3 and wk 7, respectively, compared with cows without a CL. Cows with normal RTHS had a lesser plasma concentration of β-hydroxybutyrate at wk 3 and wk 7 and greater plasma concentration of glucose at wk 3 compared with animals with abnormal RTHS. More cows in the greatest quartiles for the fertility subindex of the Economic Breeding Index and genetic merit for milk production traits (milk kg and milk protein [%]) had normal RTHS at wk 3 and wk 7 compared with the other quartiles. Cows with VDS = 4 at wk 7 postpartum had lesser plasma P4 concentration after first AI (-1.2, -1.1, and -1.0 ng/mL compared with cows with VDS = 1, 2, and 3, respectively). Similarly, cows with VDS = 4 at both wk 3 and wk 7 had lesser pregnancy at first service, lesser cumulative pregnancy rates at wk 3, 6, and 12 during the breeding period, and longer interval from mating start date to conception (+3 d if VDS = 4 at wk 3; +5 d if VDS = 4 at wk 7), compared with cows having other VDS. In conclusion, cows with superior genetic merit for fertility traits and milk production traits, and favorable fertility phenotypes at wk 3 and wk 7, were all associated with greater likelihood of having normal RTHS. In turn, abnormal postpartum RTHS and greater postpartum VDS (score = 4) were associated with lesser odds of successful pregnancy establishment.

The Effect of Month and District on 100-Day In-Calf Rate in Year-Round Calving Dairy Herds

Monitoring 100-day in-calf rate (100DICR) is an integral part of the assessment of reproductive performance in year-round calving dairy herds. The objective of this study was to investigate the effect of month on 100DICR in year-round calving herds in New South Wales (NSW), Australia and determine whether a fluctuating 100DICR target is an appropriate alternative to a constant 100DICR target. The 100DICR is defined as the percentage of all current lactating cows over 100 days in milk (DIM) that conceive on or before 100 DIM. As dairy cows are typically dried off 7 months after conception, 100DICR was an approximate 7-month rolling average. Mean monthly 100DICRs were calculated with a generalised linear model for six NSW north coast herds located 15-140 km from the coast and four NSW south coast herds located less than 10 km from the coast, over a two-year period. The mean 100DICR was lowest in May at 28.62% (95%CI 28.31-28.93) and increased during winter and spring, peaking in December at 34.74% (95%CI 34.32-35.15). The observed trend was similar for north and south coast herds, although north coast herds experienced a greater change in 100DICR from the peak to a nadir of 27.58% (95%CI 27.18-27.98), a 7.15-point difference, compared to south coast herds with a nadir of 30.18% (95%CI 29.69-30.67), a 4.67-point difference between the peak and nadir. In conclusion, 100DICR is affected by month with the lowest 100DICRs observed in late autumn and the highest 100DICRs observed in late spring and early summer. Therefore, a fluctuating target 100DICR is an appropriate alternative to a constant target when assessing reproductive performance in year-round calving herds. While the district does not affect mean 100DICR per se, the district does affect the difference between peak and nadir 100DICR.

Key Performance Indicators Used by Dairy Consultants During the Evaluation of Reproductive Performance in a First Visit

Reproduction plays a fundamental role in the profitability of dairy farms. Consultants use key performance indicators (KPI) to monitor the reproductive performance of the farms. They must decipher between the most suitable ones to face two different scenarios that may need the analysis of different parameters: (1) approach in a first visit, and (2) routine visits. Forty-nine consultants specialized in dairy reproduction from 21 countries responded to an online survey conducted to determine the most suitable parameters in a first visit approach. The survey was comprised of 190 questions, 178 of them rated from 0 (irrelevant) to 10 (maximum importance) points. The questions were divided into 5 sections: (1) consultant and farm model, (2) general data of the farm, (3) cow reproduction, (4) postpartum and metabolic disease, and (5) heifer reproduction. The median, interquartile range, minimum and maximum values, and 95% confidence interval (CI) were determined for each question. Afterward, a multivariate analysis, using between-group linkage via Ward's hierarchical clustering was conducted to generate clusters of consultants according to their response pattern. Lastly, a Chi-square test was conducted to assess the association between the years of experience of the consultant and farm size within the clusters generated in each section of the questionnaire. Most of the consultants considered 27 parameters to be highly important to analyze during the first visit. Consultants use several KPIs (in variable quantitative range) to evaluate any of the presented sections. Moreover, consultants preferred parameters focused on heat detection, fertility, and pregnancy achievement regarding the production cycle of a dairy cow. Consultants also showed high interest in obtaining a general overview of milk production, farming efficiency, and the heifer rearing process; but the farm size and the years of experience of the consultant influenced the type and number of parameters chosen as KPI. The parameters rated with the highest importance (rate 10) that could be considered for an easy, fast, and universal first visit to assess the reproductive status were: first service conception rate, overall pregnancy rate, and 21d pregnancy rate for cows, and age at first calving for heifers.

Reproductive Performance and Partial Budget Analysis of a Prostaglandin or a Modified Ovsynch Protocol in Autumn Calving Dairy Herds

Simple Summary

In autumn calving dairy herds cattle must conceive within a restricted timeframe to maintain the seasonality of calving. Cattle not observed in estrus prior to the mating start date are frequently treated with a single prostaglandin injection even though its relative effectiveness is unknown. The perceived cost of other treatments, such as a modified Ovsynch protocol, may be a reason why they are less favored. This study compares the reproductive and economic outcomes associated with treating cows not observed in estrus prior to breeding with a modified Ovsynch protocol, in comparison to a single prostaglandin injection. The main inputs influencing profitability are identified, and differences in dry-off strategy are considered. From the analyses, cows treated with a modified Ovsynch protocol had a greater likelihood of conception at the beginning of, and throughout, the breeding season. Differences in barren rate and the amount of milk produced were the main variables affecting profitability, the latter strongly influenced by drying-off policy. Farmers and advisors should consider the relative performance of their breeding strategies as well as their own management policies to optimize reproductive and economic performance.

Abstract

In autumn calving dairy herds, treatment of cattle not observed in estrus prior to the breeding season is common. Routinely, a single prostaglandin or a modified Ovsynch (MOFT) protocol are used—without evidence of their relative effectiveness. This study compares the effects on conception, associated timing, and profitability of administering cows with prostaglandin or MOFT treatment. A hundred and ninety-two Holstein-Friesian cows from three herds without an observed estrus within 28-days before mating start date were randomly treated with d-cloprostenol (PGOD) or an 8-day MOFT protocol. The association of treatment and calving-breeding start-date interval (CBSI) on the risk of conception were investigated. Partial budget, sensitivity analysis, and Monte Carlo simulation was used to assess economic performance, identify critical input variables, and explore the effects of input uncertainties on model output. There was a significant association between MOFT treatment and conception during 21 and 84 days after mating start date, compared to PGOD. MOFT treatment was associated with a mean net benefit of £58.21 (sd £19.42) and £27.29 (sd £17.75) per cow for herds with a fixed or variable dry-off date, respectively. The relative profitability of an MOFT protocol is dependent on its effects on barren rate and herd dry-off strategy.

The effect of participation in a regular reproductive herd health program on 80-day submission rate and 100-day in-calf rate in year-round calving dairy farms

Herd health management programs are commonly implemented on dairy farms to improve farm reproductive performance. In year-round calving systems, herd health programs can be supported by extension programs such as InCalf, which focus on improving the 100-day in-calf rate (100DICR) as a key reproductive performance indicator. The effect of implementing a herd health program was evaluated by analysing the 80-day submission rate (80DSR) and 100DICR during the initial 18-month period following commencement of regular herd health visits at 11 year-round calving dairy farms. The mean 80DSR and 100DICR was calculated for each of six consecutive three-month intervals following the initial herd health visit at 11 dairy farms distributed across the north and south coasts of New South Wales (NSW). On the 11 study farms 80DSR increased from 36.9% (95% confidence interval [CI] 36.7-37.2) at 0-3 months to 61.9% (95% CI 61.4-62.4) and 100DICR increased from 19.1% (95% CI 18.9-19.3) at 0-3 months to 28.5% (95% CI 28.0-29.0) at 15-18 months. 80DSR increased at similar rates on north coast farms compared to south coast farms; however, north coast farms had a lower 100DICR at 0-3 months which increased at a greater rate compared to south coast farms. 100DICR on north coast farms increased from 12.8% (95% CI 12.5-13.2) at 0-3 months to 27.6% (95% CI 26.8-28.4) at 15-18 months, whereas 100DICR on south coast farms increased from 26.7% (95% CI 26.3-27.0) at 0-3 months to 29.6% (95% CI 28.8-30.5) at 15-18 months. Participation in a regular herd health program resulted in an increased 80DSR and 100DICR.

A comparison of machine learning and logistic regression in modelling the association of body condition score and submission rate

The effect of body condition score (BCS) on reproductive outcomes is complex, dynamic and non-linear with interaction and confounding. The flexibility inherent in machine learning algorithms makes them attractive for analysing complex data. This study was designed to compare the ability of a range of machine learning techniques in estimating the probability of service within 21 days of the planned start of mating. We hypothesised that if there were complex and unknown interactions or non-linearity in the data, some machine learning algorithms would result in superior model performance compared to regression models. For a period of six months from the planned start of calving, BCS was visually assessed once a month for 6127 cows on 8 commercial New Zealand dairy farms by a trained veterinarian using the DairyNZ 10-point range for every cow in the herd. Cow, lactation and reproductive data was extracted from the national herd database. This data was used to predict probability of service within 21 days of planned start of mating (PSM) using mixed multivariable logistic regression and decision tree, k-nearest neighbour, random forest and neural network analysis. Models were adjusted for herd, cow age, breed, days in milk, BCS at calving, BCS change between calving and mating, BCS change after mating, volume adjusted milk protein and fat concentration pre-mating. Models were constructed on a training data set using 10-fold cross validation repeated 10 times and evaluated on a test data set using discrimination and calibration techniques. In all models, days calved at PSM was the most important variable for predicting submission rate, followed by BCS at PSM. Factors associated with an increased probability of insemination were calving at a BCS of 5.0, losing less BCS after calving, having a higher BCS at nadir, losing BCS rapidly after calving, nadir occurring before PSM and calving early. All the models except for the decision tree had an area under the receiver operating characteristic curve (AUC) in the range 0.68-0.73 indicating good overall discriminatory power, but calibration analysis suggested all models were better at predicting cows that got inseminated than correctly identifying animals that did not get inseminated. Overall, the machine learning techniques were no better than a generalised logistic regression model. These results highlight the importance of BCS targets at calving and indicate BCS loss, milk characteristics and days calves may be useful indicators identifying cows at risk of poor reproductive outcomes.

Evaluation of alternative strategies to treat anoestrous dairy cows and implications for reproductive performance in pasture-based seasonal calving herds: A pilot study

The objective of the present study was to assess the effects on ovulation and reproductive performance of a single injection of either GnRH or hCG applied 9 days before the start of the seasonal breeding period in anovulatory anoestrus cows compared with a 7-day progesterone-Ovsynch protocol. The study was conducted on four grass-based seasonal calving dairy herds in Ireland. The total number of cows in the herds was 2112, of which 488 were diagnosed as anoestrus based on absence of behavioural oestrus during a 30 day period. Ovarian structures and the uterus were examined by transrectal ultrasound on all 488 presumptive anestrus cows 9 days before mating start date (MSD). The number of corpora lutea (CL), number of large follicles (≥10 mm) and uterine reproductive tract score were recorded. Only cows that had no CL, ultrasound reproductive tract score ≤2 and were ≥30 days in milk (DIM) were enrolled in the study (n = 214). Cows were blocked by parity, DIM and body condition score and randomly assigned to one of four treatments: i.m. injection of gonadotropin releasing hormone analogue [GnRH; (n = 57)], i.m. injection of human chorionic gonadotropin [hCG; (n = 48)], 7-day Progesterone-Ovsynch protocol [P4OV; (n = 60)] and Control (no hormonal intervention, n = 49). A second ultrasound examination was performed 7 days after treatment to determine ovulatory response. There was a treatment effect on ovulation rate (P < 0.0001), whereby Control cows had a lesser ovulation rate compared with GnRH-, hCG- and P4OV-treated cows. Submission rate during the first 21 days of the breeding period [SR21; (P = 0.74)], pregnant to first service [P/AI1; (P = 0.24)], pregnant within 42 days after the onset of breeding [P42; (P = 0.73)], and pregnant within 84 days after the onset of breeding were not affected by treatment. A tendency was observed (P = 0.07) for greater likelihood of pregnancy within 21 days after the onset of breeding (P21) for P4OV and Control cows compared with GnRH- and hCG-treated cows. GnRH- and hCG-treated cows tended (P = 0.10) to have greater P/AI1 when first service events occurred after day 21 of the breeding period compared with Control cows. P4OV cows had shorter MSD to first service interval (P = 0.0001) and shorter MSD to conception interval (P = 0.02) compared with Control, GnRH- and hCG-treated cows. In conclusion, treatment of anestrous cows with GnRH or hCG resulted in an increase in ovulation rate compared with untreated Control cows, but did not improve reproductive performance during the first 21 days of the breeding season. The best reproductive performance results were obtained with the P4OV treatment, but this treatment has the greatest cost, and has the greatest number of interventions. The observation of good P/AI1 in hCG- and GnRH- treated cows when the first insemination occurred later than day 21 after MSD warrants further investigation, and suggests that these interventions should be applied earlier than 9 days before the farm MSD.

Effect of reproductive methods and GnRH administration on long-term protocol in Santa Ines ewes

This study aimed to determine whether reproductive performance of ewes submitted to laparoscopic timed artificial insemination (TAI) would be similar to ante meridiem (AM)/post meridiem (PM) rule and assisted natural mating (NM), and whether GnRH may enhance the pregnancy rate in TAI. In experiment I, 191 non-lactating ewes were synchronized, then TAI was performed either 48 h after progesterone (P4) removal (TAI-48 h) or 12 h after estrus detection (AM/PM); moreover, some ewes were submitted to NM (NM) as control treatment. In experiment II, 247 non-lactating ewes were allocated in five treatments, a control (no-GnRH on protocol) and four treatments arranged in a factorial design 2 × 2. The factors were time and dose of GnRH: ewes that received either 10 μg (TAI-10 μg-36 h) or 25 μg of GnRH (TAI-25 μg-36 h) 36 h after P4 removal and ewes that received either 10 μg (TAI-10 μg-48 h) or 25 μg of GnRH (TAI-25 μg-48 h) at time of insemination, 48 h after P4 removal. In experiment I, pregnancy rate in TAI-48 h was lower (P = 0.03) than AM/PM and NM. Moreover, the probability of pregnancy in TAI-48 h was higher (P = 0.06) in ewes detected in estrus early. In experiment II, the use of GnRH in TAI protocols increased (P < 0.01) pregnancy rate at synchronization, and TAI-25 μ-48 h and TAI-10 μg-36 h treatments increased (P = 0.02) pregnancy rate compered to TAI-10 μg-48 h. We conclude that TAI decreased pregnancy rate compered to NM and AM/PM, which may be improved by GnRH use in TAI to synchronize ovulation.

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.

An assessment of dairy herd bulls in southern Australia: 2. Analysis of bull- and herd-level risk factors and their associations with pre- and postmating breeding soundness results

In pasture-based, seasonally calving dairy herds of southern Australia, the mating period usually consists of an initial artificial insemination period followed by a period of natural service using herd bulls. The primary objective of this study was to identify associations between individual bull- and herd-level management factors and bull fertility as measured by a pre- and postmating bull breeding soundness evaluation (BBSE). Multivariable mixed effects logistic regression models were used to identify factors associated with bulls being classified as high risk of reduced fertility at the premating and postmating BBSE. Bulls older than 4 yr of age at the premating BBSE were more likely to be classified high risk compared with bulls less than 4 yr of age. Bulls that were in herds in which concentrates were fed before mating were more likely to be classified as high risk at the postmating BBSE compared with bulls that were in herds where concentrates were not fed. Univariable analyses also identified areas in need of further research, including breed differences between dairy bulls, leg conformation and joint abnormalities, preventative hoof blocking for bulls, and mating ratios.

Periparturient immunosuppression and strategies to improve dairy cow health during the periparturient period

Common health problems observed during peripartum include milk fever, mastitis, fatty liver disease, ketosis, dystocia, retained placenta, metritis, hypomagnesaemia and abomasal displacements. The increased incidence of health problems observed during the periparturient period can be partly attributed to suboptimal immune responses. Factors contributing to decreased periparturient immunity include the act of parturition itself, impaired leukocytic activity, effects of colostrogenesis and lactogenesis, and associated hypocalcemia and negative energy balance. Nutritional and other management strategies represent a relevant short-term strategy aimed at improving the health and welfare of the transitioning cow. Additionally, it is important to consider improving the health of dairy herds through the genetic selection of animals with enhanced robustness by identifying those with superior disease resistance or resilience in the face of infection. As a consequence these animals are better able to cope with the production and environmental stresses. These may provide long-term selection strategies for improving the health and welfare of the transitioning cow particularly when combined with sound management practices, allowing dairy cattle to reach their full genetic potential.

Reproductive performance of seasonal-calving, pasture-based dairy herds in four regions of New Zealand

AIMS

The primary objective of this study was to describe the reproductive performance of a selection of New Zealand dairy herds in 2009/10 and 2010/11. A secondary objective was to explore associations between a number of biophysical and socio-demographic herd-level variables and herd-level reproductive outcomes.

METHODS

Seasonal-calving, pasture-based herds from the Waikato (n=16), Taranaki (n=16), North Canterbury (n=17) and South Canterbury (n=14) regions of New Zealand were enrolled as part of a larger study. Submission, conception and pregnancy risks ("in-calf risks") were calculated for 2009/10 and 2010/11 based on cow-level records and from the results of strategically timed pregnancy diagnoses. Additional herd-level information was collected during interviews with the herd key decision maker (KDM). Associations between independent variables and reproductive performance were examined using univariable and multivariable generalised linear models.

RESULTS

Mean 6-week in-calf risk of the herds over both study years was 67 (min 46, max 86)%, mean 3-week submission risk was 81 (min 44, max 95)% and mean probability of pregnancy at first insemination was 48 (min 25, max 71)%. On univariable analyses, the herd's 6-week in-calf risk in the year before enrollment (2008/09) was the strongest identified predictor of each of submission risk, probability of pregnancy at first insemination and 6-week in-calf risk (all p<0.01), while other predictor variables considered were non-significant. From multivariable modelling, herds using extensive production systems had better reproductive performance than more intensively managed systems. Higher 3-week submission risks were achieved in herds where the KDM were farm managers rather than owner operators, and where the predominant breed was Jersey rather than Friesian.

CONCLUSIONS

The New Zealand dairy industry has set a target for a mean 6-week in-calf risk of 78%, with minimal hormonal intervention, by 2016. Achieving this target appears unlikely unless there are substantial increases in both submission risks and pregnancy at first inseminations. The mean 6-week in-calf risk of New Zealand dairy herd does not appear to have changed in the last decade. However the large differences between herds indicate that better reproductive performance is currently possible in many herds. The herd's 6-week in-calf risk in the year before enrollment (2008/09) was the strongest identified predictor of current 6-week in-calf risk, suggesting that rate of improvement in reproductive performance would be slow within current management systems unless substantial changes are introduced.

Timed artificial insemination early in the breeding season improves the reproductive performance of suckled beef cows

The objective was to compare reproductive performance of breeding programs that used natural service (NS), AI after estrus detection (ED), and timed AI (TAI). In experiment 1, 597 suckled beef cows were randomly allocated to one of four groups. Cows in the TAI+NS group (N = 150) were bred by TAI at 11 days after the onset of the breeding season (BS). Bulls were placed with cows 10 days after TAI and remained together until the end of the 90-day BS. Cows in the TAI+ED+NS group (N = 148) received TAI, then AI based on ED for the next 45 days, and finally NS for the last 45 days of the BS. Cows in the ED+NS group (N = 147) received AI based on ED during the first 45 days of the BS, followed by NS for the last 45 days of the BS. Cows in the NS group (N = 149) were bred by NS for the entire 90-day BS. Cows in the ED+NS or NS groups had a decreased (P < 0.001) hazard of pregnancy compared with cows in the two groups bred by TAI at the onset of BS. Also, cows bred by TAI (TAI+NS = 92.7%; and TAI+ED+NS = 91.9%) had higher (P < 0.01) pregnancy rates at the end of the BS compared with cows not bred by TAI (ED+NS = 85.0%; NS = 83.2%). In experiment 2, 507 suckled beef cows were randomly assigned to one of two groups at the onset of a 90-day BS. The NS group (N = 255) received only NS during the entire BS, and the TAI+NS group (N = 252) received TAI at the onset of the BS, followed by NS until the end of BS. Cows in the TAI+NS group had 63% higher hazard of pregnancy (P < 0.001) compared with cows in the NS group, and reduced the median days to pregnancy by 44 (11 vs. 55 days). However, there was no difference (P = 0.31) in proportion of pregnant cows at the end of the BS (TAI+NS = 77.0% vs. NS = 71.0%). Therefore, incorporation of TAI programs early in the BS increased reproductive performance of suckled beef cows.