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.

Bovine digital dermatitis in Victoria, Australia

AIMS

The objectives of this study were to estimate the prevalence of digital dermatitis (DD) in Victoria, Australia, and to investigate which organisms are consistent with typical DD lesions. The prevalence and causative pathogens of DD are not clear yet in Australia and this paper is one of the first to explore these questions in this country.

METHODS

Examination and sampling of limbs was undertaken at three knackeries in Victoria, Australia. Limbs were classified as normal (N), active DD-lesion (A), dried or chronic DD-lesion (D) or suspected case of DD (S). A total of 823 cows were examined. Six skin biopsies were taken at each knackery, from which DNA was extracted for diversity profiling. Histochemical staining of samples was performed on eight of the skin biopsies.

RESULTS

DD was detected in 29.8% of all cows. The prevalence of DD was significantly higher in dairy cows (32.2%) than in beef cows (10.8%). The differential abundance of Treponema-species was significantly increased in dried lesions, compared with the normal skin biopsies. Actinobacteria, Proteobacteria, Firmicutes and Tenericutes were found to be significantly different in abundance in the DD lesions compared with normal skin biopsies. Silver staining of samples showed only mild inflammation and in two samples organisms with morphology consistent with Spirochaetes were detected.

CONCLUSIONS

The calculated prevalence indicates that DD is present in Victoria, Australia. The results of diversity profiling showed that the presence of Treponema-species was significantly different between the samples of DD lesions and normal skin.

Clinical findings from 104 cases of calving paralysis in dairy cows from Gippsland, Australia

Case History: Dairy cows recumbent following calving on farms in South Gippsland, Australia were examined during two 3-month seasonal calving periods in 2011 and 2012 as part of a larger study of 218 recumbent cows. A cohort of 104 cows diagnosed with calving paralysis following dystocia was derived from the larger group, which were examined with 3 days of becoming recumbent. A thorough medical and musculoskeletal clinical examination was performed on each cow including flexor-withdrawal and patellar reflex tests, and postural assessment in the lifted position, unless the facilities were not available. Cows were diagnosed with one or more neurological syndromes: sciatic, tibial paresis, obturator or femoral, based on clinical findings consistent with damage to these peripheral nerves or their nerve roots. Clinical Findings: Evidence of sciatic syndrome was found in 100/104 (96.2%) cows and 146/172 (84.9%) affected hind limbs either as the sole neuropathy or in combination with tibial paresis, obturator or femoral syndromes. Pelvic damage was also present in 3/104 (2.8%) cows. Obturator syndrome was diagnosed in 30/104 (29%) cows and 45/172 (26.2%) affected hind limbs but not apparently as the sole reason for the recumbency. Femoral syndrome occurred in 16/104 (15.4%) cows and 21/172 (12.2%) affected hind limbs and was the only syndrome recorded in one cow. Clinical Relevance: Sciatic syndrome was the most common neurological syndrome observed in cows with calving paralysis. The other major nerves arising from the lumbo-sacral plexus were also affected and the various syndromes associated with damage to these nerves or their ventral nerve roots occurred in many combinations. Calving paralysis should be thought of as a paresis or paralysis resulting from damage to the ventral nerve roots of the lumbo-sacral plexus as any of the nerves originating from this plexus can be damaged during dystocia either individually or in combination with other nerves from the plexus.

Associations between immune competence, stress responsiveness, and production in Holstein-Friesian and Holstein-Friesian × Jersey heifers reared in a pasture-based production system in Australia

The objectives of this study were to assess antibody and cellular immune responses in first-lactation dairy heifers reared under a pasture-based production system and to investigate associations between immune competence and stress responsiveness, health, and productivity. A commercial vaccine was used to induce antibody and cellular immune responses and, based on measured responses, animals were classified as above average, average, and below average for each trait independently and in combination (overall immune competence). Overall immune competence phenotypic rankings were generated by combining standardized residual values for antibody and cellular responses measured in individual heifers. Cortisol responses to handling and yarding were used to assess stress responsiveness, worm egg counts were used to assess internal parasite burden, somatic cell counts to assess udder health and estimates of total daily milk volume, and milk fat and milk protein contents to assess productivity. A total of 393 Holstein-Friesian and Holstein-Friesian × Jersey crossbred heifers from 2 herds practicing seasonal calving in a pasture-fed production system were enrolled in the study. The immune competence phenotypes of individual heifers were assessed before their first mating and their subsequent performance during their first lactation was monitored. Animals with below-average antibody and cellular immune competence had higher serum cortisol concentrations compared with their counterparts following handling, suggesting they had a reduced ability to cope with management-induced stress. Furthermore, a significant negative (favorable) correlation was observed between antibody responses and stress responsiveness. Similarly, correlations between antibody responses and internal parasite burden were significant and negative (favorable). No correlations were observed between overall immune competence and milk yield, milk fat, and milk protein content.

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.

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.

High-quality care improves outcome in recumbent dairy cattle

OBJECTIVE

To investigate the influence of the quality of care on outcome and occurrence of secondary damage in recumbent dairy cows.

METHODS

Recumbent dairy cows were monitored during their recumbency under field conditions in South Gippsland, Victoria, Australia. The cause of the original recumbency of 218 downer cows was determined and any secondary damage, day 7 status, final outcome and the nursing conditions of the cows were recorded. A four-tiered grading system describing nursing quality was developed to allow analysis of its influence on outcome and on the occurrence of secondary damage.

RESULTS

Day 7 outcome, final outcome and occurrence of important secondary damage were very strongly associated with the level of overall care provided to the recumbent cows. There was a decrease in the percentage of cows recovering by day 7 from 33% to 0%, a decrease from 45% to 0% of cows eventually recovering and an increase from 68% to 100% of cows with clinically important secondary damage as overall care decreased.

CONCLUSION

Management of recumbent cattle is potentially a significant animal welfare issue for the dairy industry and their care is a very important but often under-appreciated aspect of their management. Recovery is positively influenced by high-quality care by improving the chances of recovery from the initial cause of recumbency and by reducing the occurrence of secondary damage. Recumbent cows must either be nursed at a high level of care or euthanased promptly.

An assessment of immune and stress responsiveness in Holstein-Friesian cows selected for high and low feed conversion efficiency

The objective of this study was to assess the immune and stress responsiveness of cows identified as extremely high and low feed conversion efficiency phenotypes. The study utilised 16 Holstein-Friesian cows in their third to fourth lactation, and identified as having either extremely high (n = 8) or extremely low (n = 8) feed conversion efficiency. A commercial vaccine was used to induce measurable antibody- and cell-mediated adaptive immune responses and assess general immune responsiveness. Stress responsiveness was assessed by measuring changes in plasma cortisol concentrations in response to yarding and handling. No significant differences in antibody- or cell-mediated immune responsiveness were observed between the extreme high and low feed conversion efficiency phenotypes (P = 0.343 and 0.546, respectively). However, results suggested that plasma cortisol concentrations trended higher in the low feed conversion efficiency phenotype cows than their high feed conversion efficiency counterparts (P = 0.079) 48 h post-yarding and handling. A significant negative correlation was observed between antibody-mediated immune responsiveness and stress responsiveness (r = –0.44, P = 0.043) but not with cell-mediated immune responsiveness (r = 0.135, P = 0.309). This study provides preliminary evidence that cows selected for feed conversion efficiency may have improved stress-coping abilities and immune responsiveness.

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.

Assessing adaptive immune response phenotypes in Australian Holstein-Friesian heifers in a pasture-based production system

The objective of this study was to determine the repeatability of ranking Holstein-Friesian heifers reared in an Australian pasture-based production system for immune responses (IR) when ranking was based on secondary versus tertiary IR. Further objectives were to investigate associations between IR and stress responsiveness, ADG and resistance to internal parasites. A total of 100 heifers were IR phenotyped at 5 to 6 mo of age and again at 12 to 13 mo of age using commercial vaccine antigens to induce measurable IR. Antibody production to tetanus toxoid (TT) was used to assess antibody-mediated IR (AMIR), and delayed-type hypersensitivity reactions to vaccine antigens were used to assess cell-mediated IR (CMIR). Changes in serum cortisol and haptoglobin were used to assess stress responsiveness and fecal egg counts used as a measure of resistance to internal parasites. Based on testing, animals were categorized as either average to above-average (High) or low responders for IR. Secondary and tertiary AMIR were well correlated (r = 0.651, adjusted R(2) = 0.418, P < 0.0001), whereas correlations between secondary and tertiary CMIR were poor (r = 0.078, R(2) = –0.004, P = 0.450). A Cohen kappa (κ) test of agreement was used to test the consistency of ranking of individual animal for IR and, therefore, the ability to consistently identify low immune responder animals within the herd across test periods. The consistency of ranking (High versus low) was moderately high for AMIR (κ = 0.445), poor for CMIR (κ = –0.055), and fair to moderate for combined IR (κ = 0.395). High AMIR phenotype animals had significantly higher serum cortisol concentrations than their low immune responder counterparts (P = 0.045). A similar relationship was observed in heifers categorized for CMIR, with High CMIR responders having higher serum cortisol concentrations than their low responder counterparts (P = 0.008). High AMIR calves had a higher ADG compared with low AMIR calves (0.72 ± 0.02 versus 0.66 ± 0.06 kg/d; P = 0.009). Serum haptoglobin concentrations and worm egg counts were very low and could not be used to investigate associations with immune responsiveness. It is concluded that secondary and tertiary antibody responses to TT were well correlated in the Holstein-Friesian heifers in this study and that by using the testing procedure described here, low antibody responders were able to be consistently identified in the herd.

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.

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.

The effects on ruminal pH and serum haptoglobin after feeding a grain-based supplement to grazing dairy cows as a partial mixed ration or during milking

Ruminal pH and serum concentrations of haptoglobin (Hp) were measured in order to assess the risk of subacute ruminal acidosis (SARA) in grazing cows offered rolled wheat grain twice daily in the dairy at milking (Control group; n= 64), or as a partial mixed ration (PMR group; n= 64) on a feedpad. Cows were allocated various levels of the supplement (8, 10, 12 or 14 kg dry matter/day). Ruminal pH was measured in 16 rumen-fistulated cows (eight PMR and eight Control group cows), using indwelling pH meters, recording every 10 min for 14 days. Serum Hp was analysed in samples collected from 125 cows. No differences in ruminal pH or serum Hp concentration were found between treatment groups, or levels of feeding. It was concluded that, using ruminal pH patterns and Hp as markers of SARA at the feeding levels used in this study, there were no differences between grazing cows fed the supplement either as grain in the dairy or as a PMR fed on a feedpad.

Comparison of bandaging and elevation of the claw for the treatment of foot lameness in dairy cows

OBJECTIVE

To compare the effectiveness of three treatments for sole injuries in dairy cows and to evaluate the ease and speed of applying the treatments.

DESIGN

A randomised clinical trial.

PROCEDURE

The three forms of treatment were elevating the affected claw of a lame cow with a wooden block glued to the unaffected claw (39 cows), elevating the affected claw with a rubberised shoe glued to the unaffected claw (42 cows) or applying a padded bandage to the whole foot of a lame cow (31 cows).

RESULTS

The percentages of cows that recovered from lameness at 3 and 7 days after treatment were significantly higher for cows treated with wooden blocks (P = 0.013 and P = 0.008) or rubberised shoes (P = 0.026 and P = 0.0003) than padded bandages. Cows treated with blocks had a recovery rate of 48.7% at day three and 65.8% at day seven, and cows treated with rubberised shoes, rates of 45.2% and 76.2%, respectively. Cows which had a bandage applied to the foot had recovery rates of 19.4% at day three and 32.3% at day seven. However, by day 14, there was no significant difference in recovery rate between the three treatments. Rubberised shoes were shown to offer a number of advantages over wooden blocks. The shoes were significantly quicker to attach than blocks (median of 9.5 minutes compared with 14.0 minutes, P < 0.0001) and remained on the claw longer (57.1% of rubberised shoes remained at 30 days compared to 30.8% of blocks, P = 0.025). The rubberised shoes also offered an advantage over wooden blocks for operator safety and health by reducing contact between the potentially hazardous adhesive used to attach both devices and the skin of the person applying the device.

CONCLUSIONS

Rubberised shoes are a superior method of elevating an affected claw in conditions of lameness likely to respond to removal of weightbearing forces.

Anthelmintic resistance in nematode parasites of goats

Cases of anthelmintic resistance on 3 goat farms in Gippsland were investigated. On the first farm Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia (Teladorsagia) circumcincta were found to be resistant to fenbendazole, but the first 2 species were fully susceptible to levamisole. On the second farm a population of T. colubriformis, resistant to concurrent full doses of levamisole and a benzimidazole, was found to retain this resistance when transferred to sheep. On the third farm, heavy mortality due to Ostertagia and Trichostrongylus spp burdens was arrested only by the use of concurrent full doses of levamisole and oxfendazole; no single anthelmintic was found to be effective. A disturbing rise in the incidence of clinical helminthiosis, often accompanied by anthelmintic resistance, occurred on goat farms in Gippsland early in 1984.