Validating the female fertility estimated breeding value in Australian commercial dairy herds

We conducted a retrospective cohort study to validate the efficacy of the Australian multitrait fertility estimated breeding value (EBV). We did this by determining its associations with phenotypic measures of reproductive performance (i.e., submission rate, first service conception rate, and early calving). Our secondary aim was to report the associations between these reproductive outcomes and management and climate-related factors hypothesized to affect fertility. Our study population included 38 pasture-based dairy herds from the northern Victorian irrigation region in Australia. We collected records for 86,974 cows with 219,156 lactations and 438,578 mating events from the date on which managers started herd recording until December 2016, comprising both fertility-related data such as insemination records, calving dates, and pregnancy test results, and systems-related data such as production, herd size, and calving pattern. We also collected hourly data from 2004 to 2017 from the closest available weather station to account for climate-related factors (i.e., temperature humidity index; THI). Multilevel Cox proportional hazard models were used to analyze time-to-event outcomes (days to first service, days to cow calving following the planned herd calving start date), and multilevel logistic regression models for binomial outcomes (conception to first service) in the Holstein-Friesian and Jersey breeds. A 1-unit increase in daughter fertility EBV was associated with a 5.4 and 8.2% increase in the daily hazard of calving in the Holstein-Friesian and Jersey breeds respectively. These are relative increases (i.e., a Holstein-Friesian herd with a 60% 6-wk in-calf rate would see an improvement to 63.2% with a 1-unit increase in herd fertility EBV). Similar results were obtained for submission and conception rate. Associations between 120-d milk yield and reproductive outcome were complicated by interactions with 120-d protein percentage and calving age, depending on the breed and outcome. In general, we found that the reproductive performance of high milk-yielding animals deteriorated faster with age than low milk-yielding animals, and high protein percentage exacerbated the differences between low and high milk-yielding animals. Climate-related factors were also associated with fertility, with a 1-unit increase in maximum THI decreasing first service conception rate by 1.2% for Holstein-Friesians but having no statistically significant association in the Jersey breed. However, THI had a negative association in both breeds on the daily hazard of calving. Our study validates the efficacy of the daughter fertility EBV for improving herd reproductive performance and identifies significant associations between 120-d milk and protein yields and THI on the fertility of Australian dairy cows.

Breed structures in Australian dairy herds

Breed structures of Australian dairy herds over time were described for a large subset of milk-recording herds. The focus for this study was to describe the use of crossbreeding by dairy farmers, specifically proportions of herds using crossbreeding, whether they were using two-breed or three-breed crossbreeding systems, and how herd-breed structures changed over time. The most common breed structure in Australian milk-recording herds between 2000 and 2013 was two-breed crossbreeding (39% of herd-years). The next most common breed structure was purebred (35%). Over the period studied, the proportion of herds that were purebred decreased, while the proportion of herds that were crossbreeding increased (particularly three-breed crossbreeding herds). Herd-breed structures and changes over time varied with region and with the herd's calving system. There were also considerable changes in breed structure within herds, including herds changing breed structure before reverting back to their original breed structure. These results indicate that breed structures in milk-recording dairy herds in Australia are dynamic, and that farmers have commonly employed crossbreeding strategies.

Herd manager attitudes and intentions regarding the selection of high-fertility EBV sires in Australia

Reproductive performance in dairy cattle has declined over the last 50 years as an unintended consequence of selection for high milk yield. Since the early 2000s, dairy geneticists have released successive versions of fertility estimated breeding values (EBV) to assist in reversing this trend. At the herd level, fertility EBV can help managers accelerate improvements in reproductive performance by acting as a second selection criteria when used in tandem with a breeding index. However, use of the fertility EBV in sire selection currently varies between herd managers. The aim of this study was to better understand the reasons why herd managers choose or do not choose to select high-fertility EBV sires, using the Theory of Planned Behavior (TPB) as a social research framework. Thirty-five Victorian dairy herd managers were recruited as part of a larger study investigating the daughter fertility Australian Breeding Value and interviewed using a series of questions examining TPB constructs. The interviews were recorded and transcribed using template analysis. A wide range of herd manager types were enrolled into the study, with representation from diverse systems. Out of the 35 herd managers, 27 included fertility in their list of high-priority breeding objectives. A wide variation in results was consistent with previous studies that have demonstrated marked heterogeneity in herd manager attitudes toward bull selection. Herd manager-perceived barriers to selection of sires with high daughter fertility EBV included a lack of high daughter fertility bulls with other desirable traits, a lack of trust in the fertility EBV or in the Australian EBV system, difficulty in interpreting international proofs, information overload, semen prices, low bull reliability, and difficulty in understanding bull catalogs. Not all herd managers found the process problematic, however, particularly if a breeding consultant was employed to select all or most of the sires. Herd manager-perceived barriers for choosing to select daughter fertility as a breeding objective include a lack of awareness of the EBV, a lack of interest in genetics in general, low confidence in the impact of genetic selection for fertility, and a feeling that fertility was not important for their production system. The results of this study suggest that animal geneticists and on-farm service providers need to work together to allow the opportunities arising from appropriate use of fertility EBV to be realized more broadly across the dairy industry.

A cross-sectional pilot study to estimate the prevalence of and risk factors for leptospirosis in South-Western Victorian dairy herds, 2017

Leptospirosis is a zoonosis, found worldwide, affecting many species of animals. We conducted a cross-sectional study to estimate the prevalence of Leptospira borgpetersenii sv Hardjo and Leptospira interrogans sv Pomona in cattle in dairy herds in South-Western Victoria, Australia. Fifty-three herds were enrolled in the study. Urine samples were collected from 15 late-lactation cows in each herd. A questionnaire was provided to herd managers at the time of each herd visit, asking them to describe the methods they used for controlling leptospirosis, including vaccination. Urine samples were pooled at the herd level and tested for leptospira spp. using real time PCR. Urine samples from individual cows within the positive pooled samples were then tested for Leptospira Hardjo and Leptospira Pomona using qPCR. Four of the 53 herds showed positive leptospirosis results giving an apparent prevalence of 8 (95% CI 2-18) leptospira-positive herds per 100 herds at risk. Based on the 53 completed questionnaires, leptospirosis vaccination programs were not compliant with label directions in 36 of the 52 vaccinated herds: 69 (95% CI 55-81) of 100 herd managers that routinely vaccinated for leptospirosis did not comply with label directions. One herd was completely unvaccinated. Based on our findings, we estimate that approximately 10% of dairy farms in South-Western Victoria are likely to be infected with leptospirosis. While most herds are vaccinating for leptospirosis, most are not doing so according to label directions. We conclude that herd managers need to be better educated regarding leptospirosis vaccination programs.

Effect of a second treatment of prostaglandin F2α during the Ovsynch program on fixed-time artificial insemination conception rates and luteolysis in split-calving, pasture-fed dairy cows

OBJECTIVE

To compare fixed-time artificial insemination (FTAI) conception rates and serum progesterone concentrations at the time of FTAI for cows treated with the original Ovsynch program (OV) with those treated with a modified Ovsynch (MO) program.

DESIGN

This was a randomised clinical trial.

METHODS

The study used five split-calving, pasture-based dairy herds in Southwest Victoria, Australia. Controls (n = 851) received the OV program: day 0 gonadotropin-releasing hormone, day 7 prostaglandin F_2α (PGF), day 9 gonadotropin-releasing hormone and FTAI at day 10. The treatment group (n = 852) received a MO program with an additional prostaglandin injection on day 8. Subsets of cows from each group were sampled for blood progesterone at the time of FTAI.

RESULTS

The treatment group demonstrated FTAI conception rates that were 7% (95% confidence interval 2%-12%) greater than the control group. After adjusting for the effect of age, days in milk at Mating Start Date and herd, the odds of conception using FTAI was 1.36 (95% confidence interval 1.12-1.66) times greater for treatment group cows compared with control group cows. The variability of serum progesterone concentrations at the time of FTAI was significantly less for treatment group cows compared with control group cows.

CONCLUSION

For Holstein-Friesian and Holstein-Friesian cross-bred cows managed in pasture-based dairy herds in southern Australia, a MO protocol, including a second injection of prostaglandin F_2α on day 8, increased FTAI conception rates compared with cows receiving the OV protocol.

Scrotal circumference, bodyweight and semen characteristics in growing dairy-breed natural-service bulls in Tasmania, Australia

AIMS

To provide herd managers with a set of decision rules allowing them to predict the likelihood that a juvenile bull is ready for Bull Breeding Soundness Evaluation (BBSE), or breeding, if bodyweight and scrotal circumference are known.

METHODS

This was a longitudinal study following two groups of young pasture-fed Holstein and Jersey bulls from northwest Tasmania, Australia. Individual scrotal circumference, bodyweight and semen characteristics were recorded at 6-8 weekly intervals, from 6-18 months of age. Classification and regression tree analyses were used to predict the probability that a bull had ≥70% normal sperm morphology based on scrotal circumference and bodyweight measurements.

RESULTS

Overall 1,661 scrotal circumference and bodyweight measurements were obtained, and 518 semen samples from 356 bulls were assessed for sperm morphology, from 16 examination sessions that took place between 29 May 2015 and 17 August 2016. Classification and regression tree analyses generated a decision tree for Holstein bulls with four node endpoints, and for Jersey bulls with three node endpoints. Diagnostic test performance showed that for Holstein bulls, using the node endpoints of scrotal circumference ≥27 cm and bodyweight ≥349 kg, 98% had ≥70% normal sperm (positive likelihood ratio 10.4; 95% CI = 2.7-41), and using the node endpoints of scrotal circumference ≥27 cm and bodyweight between 282-349 kg, 89% had ≥70% normal sperm (positive likelihood ratio 1.6; 95% CI = 0.9-2.6). For Jersey bulls, using the node endpoints of bodyweight ≥259 kg and scrotal circumference ≥29 cm, 88% had ≥70% normal sperm (positive likelihood ratio 3.4; 95% CI = 1.6-7.0).

CONCLUSIONS

This study provides a set of relatively simple decision rules based on bodyweight and scrotal circumference measurements that allows herd managers to assess the likelihood that juvenile bulls are ready for BBSE or breeding.

ABBREVIATIONS

BBSE: Bull breeding soundness evaluation; BRT: Boosted regression tree.

A survey of northern Victorian dairy farmers to investigate dairy calf management: calf-rearing practices

OBJECTIVES

To describe the calf-rearing practices carried out in northern Victorian dairy herds and to identify weaknesses that may affect calf health and welfare by comparing the results with current industry recommendations.

METHODS

Survey of dairy farms from Rochester and the surrounding farming area.

RESULTS

The response rate was 39% (58/150). Many dairy producers were not meeting the current industry recommendations in the following areas: (1) delayed access to pellets and roughage, (2) failing to provide access to water from birth, (3) delayed disbudding of calves, (4) delayed timing of booster vaccinations, (5) weaning based on age alone, (6) failing to isolate sick calves and (7) early sale age of excess calves.

CONCLUSION

The results from this survey highlight the need for greater awareness of industry standards for calf husbandry and weaning.

A survey of northern Victorian dairy farmers to investigate dairy calf management: colostrum feeding and management

Objectives

To describe colostrum management practices carried out in northern Victorian dairy herds and to identify weaknesses in these areas that may affect calf health and welfare by comparing the results with the current industry recommendations

Methods

A questionnaire to obtain information about colostrum management and calf‐rearing practices was sent to commercial dairy farming clients of Rochester Veterinary Practice between June and September 2013. The questionnaire consisted of a general herd overview and colostrum harvesting practices.

Results

The response rate was 39% (58/150). Many dairy producers were not meeting the current industry recommendations in the following areas: (1) time of removal calf from the dam, (2) relying on calf suckling colostrum from the dam to achieve adequate passive transfer, (3) failing to supplement calves with colostrum, (4) feeding inadequate volumes of colostrum, (5) delayed colostrum harvesting, (6) pooling of colostrum, (7) failing to objectively assess colostrum quality or relying on visual assessment and (8) storing colostrum for a prolonged periods of time at ambient temperatures.

Conclusion

The results from this survey highlight the need for greater awareness of industry standards for colostrum management and feeding hygiene.

Factors associated with colostrum immunoglobulin G concentration in northern-Victorian dairy cows

OBJECTIVES

To determine the proportion of first-milking colostrum samples produced on four northern-Victorian dairy farms that meet industry standards in terms of immunoglobulin G (IgG) concentration and to identify risk factors that affect colostrum quality.

METHODS

Colostrum IgG concentrations from 442 dairy cows on four farms were estimated using a Brix refractometer and risk factors for colostrum IgG concentration were determined using multivariable logistic regression.

RESULTS

Only 39% of samples met the definition of high quality. The strongest predictor for colostrum quality was the interval from calving to colostrum harvesting. Colostrum harvested from cows within 12 h of calving was 6-fold more likely to be high quality compared with colostrum harvested later. Colostrum from cows in ≥ 4th lactation was nearly twice as likely to be high quality compared with cows entering their 1st lactation. If the calf was not allowed to suckle from the dam prior to colostrum harvesting, the odds of producing high-quality colostrum were nearly 4-fold greater. If the cow had not leaked colostrum prior to harvesting, it was more than 3-fold more likely to produce high-quality colostrum.

CONCLUSIONS

The majority of samples assessed were below industry standard. Herd, lactation number, calf suckling or cow leaking colostrum prior to harvesting and time between calving and colostrum harvesting were factors that influenced colostrum IgG concentration. The results support current industry recommendations of harvesting colostrum shortly after parturition (ideally within 12 h of calving) and testing the quality of all colostrum prior to feeding to dairy calves.

Short communication: Milking order consistency of dairy cows in large Australian herds

We used on-farm records from dairy infrastructure to examine the consistency of the milking order over 150 d in 5 Australian dairy herds that were milking more than 500 cows as a single group. Within a single day the difference in milking order rank position was less than 20 percentage points for 72% of cows. The correlation coefficient comparing milking rank position in the morning and afternoon was 0.72, with the position of cows at the beginning and end of the milking order being more consistent than cows toward the middle of the milking order. Over a period of 150 d, cows with a mean position in the first and last 20% of the milking order maintained their position more consistently than cows in the middle of the milking order. Milking position of cows between one month and the next was highly correlated (r = 0.88). In large herds, subpopulations of cows are regularly milked toward the beginning and the end of the milking order. It is common for cows to be collected from the paddock as a group, to wait as a group in the dairy yard to be milked, and to return individually to the paddock or feed pad immediately after they have been milked. Thus, cows milked later in the milking order are likely to be away from the paddock for several hours longer than cows milked earlier in the milking order. This may affect their welfare though differences in time available for lying down, equality of pasture eaten, and time spent standing in the dairy yard.

Postpartum anoestrus in five seasonally-calving dairy farms in Victoria, Australia

OBJECTIVE

A cross-sectional study of seasonally-calving dairy cows in south-western Victoria to quantify the prevalence of anoestrus and to assess the effect of body condition score (BCS), days in milk (DIM) at mating start date (MSD) and age on the likelihood of being diagnosed as anoestrus.

METHODS

Age, DIM and BCS details were collected from 1795 cycling and 1399 cows diagnosed as anoestrus in five seasonally-calving dairy herds in Victoria. Multivariable logistic regression was used to quantify the association between BCS, DIM and age and the probability of being diagnosed as anoestrus.

RESULTS

The apparent prevalence of anoestrus in cows that took part in the study was 44% (95% confidence interval (CI) 42-46%). The risk of anoestrus increased with decreases in DIM and BCS. There was a significant interaction between BCS and DIM. For cows >90 DIM at MSD (the reference category) the odds of anoestrus in cows with BCS <4.00 was 8.05-fold (95% CI 3.2-20.2) that of cows of BCS ≥4.50. The risk of anoestrus decreased with increases in cow age. Cows aged 2 and 3-5 years had 2.4-fold (95% CI 1.79-3.22) and 1.4 (95% CI 1.11-1.77) odds of anoestrus, respectively, compared with cows aged ≥6 years.

CONCLUSION

Reproductive management to maximise the number of days calved at MSD and nutritional management to ensure cows are in BCS >4.5 at mating will reduce the prevalence of anoestrus in Victorian dairy herds.

Anthelmintic resistance in gastrointestinal nematodes of dairy cattle in the Macalister Irrigation District of Victoria

OBJECTIVE

To report anthelmintic resistance in gastrointestinal nematode parasites of cattle on commercial dairy farms in the Macalister Irrigation District of Gippsland, Victoria.

METHODS

Faecal egg count reduction tests (FECRTs) were used to assess anthelmintic resistance on 20 Macalister Irrigation District dairy farms between May 2013 and June 2014. All three currently available anthelmintic classes for cattle nematodes in Australia were tested. Faecal samples were collected 10-14 days post-treatment for individual faecal egg counts (FEC) and larval differentiation. The arithmetic mean FEC for each treatment group was compared with an untreated control post-treatment. Resistance was defined as <95% reduction in FEC, with a lower 95% confidence interval <90% when the mean FEC of the control group, differentiated by genus, was greater than 25 eggs/g.

RESULTS

Anthelmintic resistance was present on all 20 dairy farms involved in this study. Resistance to doramectin in at least one species was detected on 15/20 (70%) farms, fenbendazole on 16/20 (80%) farms and levamisole on 5/20 (25%) farms. On three farms, resistance by Ostertagia ostertagi to all three anthelmintic classes was detected.

CONCLUSION

This is the first report of anthelmintic-resistant O. ostertagi on Australian dairy farms. Resistance to all three available anthelmintic classes is of concern, given the high pathogenicity of this species. The study highlights the need for veterinarians and dairy farmers to be aware of the risks posed by anthelmintic resistance.

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.

Infectious reproductive disease pathogens in dairy herd bulls

OBJECTIVE

Investigate the presence of infectious reproductive disease pathogens in dairy herd bulls in south-west Victoria, Australia, using a cross-sectional study.

METHODS

Dairy herd bulls from 32 herds were sampled for bovine viral diarrhoea virus (BVDV: 256 bulls, 32 herds) prior to the natural mating period, bovine herpes virus-1 prior to (10 bulls, 5 herds) and after (118 bulls, 19 herds) the natural mating period, and for Campylobacter fetus spp. and Tritrichomonas foetus after the natural mating period (61 bulls, 7 herds). BVDV was detected from an ear-notch sample using a commercially available rapid assay ELISA, bovine herpes virus-1 and T. foetus were screened for by PCR from a penile swab and preputial sample respectively, and C. fetus spp. were screened for by culture of preputial samples.

RESULTS

None of the bulls tested positive for BVDV antigen. Campylobacter fetus venerealis (or C. fetus fetus) was cultured in 6.6% (4/61) of bulls, representing 2 of the 7 (28.6%) farms that were not vaccinating bulls against bovine genital campylobacteriosis. Bovine herpes virus-1 was identified in 7.8% (10/128) bulls sampled; T. foetus was not identified in any samples.

CONCLUSION

Bovine genital campylobacteriosis is present in south-western Victoria, despite longstanding recommendations to vaccinate bulls. Screening bulls for persistent infection with BVDV is probably justified, despite the absence of persistently infected bulls in this study. Further research is warranted to investigate the potential reproductive implications of BHV-1, and the presence of T. foetus.

Pilot study--parenteral treatment of recently acquired subclinical mastitis during lactation

OBJECTIVE

To conduct a pilot study to investigate the effect of parenteral antibiotic treatment with penethamate hydriodide on recently acquired sub-clinical mastitis.

DESIGN

Sixty-nine cows from five Western Victorian dairy farms were enrolled in a pilot trial. Cows that had an Individual Cow Cell Count (ICCC) of greater than 250,000 cells per mL in their milk at their first or second herd test were enrolled in the trial if they were in their first lactation, or if they had a history of ICCCs below 250,000 cells per mL at all herd tests during the previous lactation. These criteria were used in an effort to exclude cows with chronic subclinical mastitis and include cows with recently acquired subclinical mastitis.

PROCEDURE

Cows were divided into control and treatment groups on the basis of having an odd or even ear tag number. The treatment group was treated with penethamate hydriodide shortly after the first or second herd test; the control group was left untreated. The ICCCs of subsequent herd tests were recorded for the remainder of lactation.

RESULTS

In 58% of the treatment group, and 25% of the control group, all subsequent ICCCs for that lactation were less than 250,000 cells per mL (p < 0.05). If only first and second lactation cows were considered, 72% of the treatment group, and 11% of the control group, had subsequent ICCCs less than 250,000 cells per mL (p < 0.05).

CONCLUSION

An ICCC of greater than 250,000 cells per mL is a good predictor for more high ICCCs at subsequent herd tests. This effect was significantly altered in our trial by treatment with penethamate hydriodide at or near the first or second herd test. Whilst in general treatment of high ICCC cows during lactation is considered to be unrewarding, this pilot study suggests that treatment of cows and heifers appropriately selected on the basis of a previous history of low ICCCs can lead to sustained reductions in cell counts. These results support the case for further study into this area.

Compliance of Victorian dairy farmers with current calf rearing recommendations for control of Johne's disease

Questionnaires were posted to 800 randomly selected registered Victorian dairy farmers in 1996. Five hundred and thirty-four responses were received and analysed. Johne's disease (JD) had been diagnosed on the farm of 13.2% of respondents in the last 5 years. JD was rated second only to neonatal diarrhoea in importance as a disease of calves, even though other diseases occurred more frequently. However, there was a low level of compliance with JD control recommendations by the respondents. There was no significant difference in the number of JD control recommendations adopted by farmers between the three major Victorian regions. There was a significant difference in compliance between farms having had a diagnosed case of JD and those that had not. Although there is awareness among dairy farmers of the importance of JD, there appears to be a poor implementation of measures by farmers to prevent the spread of the disease. Current JD control recommendations and the method of information transfer to Victorian dairy farms should be reassessed to ensure that dairy heifers are reared with minimal risk of transmission of JD.

Renal cell carcinoma in pregnancy: report of three cases and review of the literature

BACKGROUND

Renal cell carcinoma is a potentially fatal tumor that occasionally presents during pregnancy. Based on our experience with three patients and a review of the recent cases in the literature, we believe there has been a change in presentation of this lesion over that described in previous reviews.

CASES

Two of three women with renal cell carcinoma found during pregnancy had symptoms suggesting recurrent urinary tract infection. The renal tumors were all discovered by ultrasound. In addition, magnetic resonance imaging was used for preoperative, intragestational staging of one patient.

CONCLUSION

Renal cell carcinoma should be considered in women of childbearing age who present with recurrent or refractory urinary tract symptoms, flank pain, or a palpable flank mass. Ultrasound appears to be the imaging procedure of choice for evaluating the urinary system in pregnant women.