Genetic variability in the humoral immune response to bovine herpesvirus-1 infection in dairy cattle and genetic correlations with performance traits.

Bovine herpesvirus-1 (BoHV-1) is a viral pathogen of global significance that is known to instigate several diseases in cattle, the most notable of which include infectious bovine rhinotracheitis and bovine respiratory disease. The genetic variability in the humoral immune response to BoHV-1 has, to our knowledge, not ever been quantified. Therefore, the objectives of the present study were to estimate the genetic parameters for the humoral immune response to BoHV-1 in Irish female dairy cattle, as well as to investigate the genetic relationship between the humoral immune response to BoHV-1 with milk production performance, fertility performance, and animal mortality. Information on antibody response to BoHV-1 was available to the present study from 2 BoHV-1 sero-prevalence research studies conducted between the years 2010 to 2015, inclusive; after edits, BoHV-1 antibody test results were available on a total of 7,501 female cattle from 58 dairy herds. National records of milk production (i.e., 305-d milk yield, fat yield, protein yield, and somatic cell score; n = 1,211,905 milk-recorded cows), fertility performance (i.e., calving performance, pregnancy diagnosis, and insemination data; n = 2,365,657 cows) together with animal mortality data (i.e., birth, farm movement, death, slaughter, and export events; n = 12,853,257 animals) were also available. Animal linear mixed models were used to quantify variance components for BoHV-1 as well as to estimate genetic correlations among traits. The estimated genetic parameters for the humoral immune response to BoHV-1 in the present study (i.e., heritability range: 0.09 to 0.16) were similar to estimates previously reported for clinical signs of bovine respiratory disease in dairy and beef cattle (i.e., heritability range: 0.05 to 0.11). Results from the present study suggest that breeding for resistance to BoHV-1 infection could reduce the incidence of respiratory disease in cattle while having little or no effect on genetic selection for milk yield or milk constituents (i.e., genetic correlations ranged from -0.13 to 0.17). Moreover, even though standard errors were large, results also suggest that breeding for resistance to BoHV-1 infection may indirectly improve fertility performance while also reducing the incidence of mortality in older animals (i.e., animals >182 d of age). Results can be used to inform breeding programs of potential genetic gains achievable for resistance to BoHV-1 infection in cattle.

Characterization of an X-chromosomal non-mosaic monosomy (59, X0) dairy heifer detected using routinely available single nucleotide polymorphism genotype data.

Evidence exists from a range of species on the impact of karyotype abnormalities on reproductive performance. Despite this, cytogenetic analyses of cattle, especially females, are not routinely undertaken. Genome-wide single nucleotide polymorphism (SNP) genotype data are now, however, routinely being generated in many species globally at a relatively low cost. The objective of the present study was to evaluate the potential of routinely available SNP genotype data to identify sex-chromosome aberrations using X chromosome monosomy 59,X0 as a case study for illustration. A single 2.5-yr old Holstein-Friesian heifer was detected with a mean allelic intensity of SNP on the X chromosome almost 17 standard deviations less than the mean of other genotyped females ( = 103,326). Following cytogenetic analysis (10 replicates by karyotyping and a further 140 by FISH), the female was deduced to be a non-mosaic 59,X0. The female had never produced a calf and, although gross examination revealed no physical abnormalities, she was smaller in size than expected based on her breed and age. Given the age of the animal at slaughter, the uterus and uterine tubes appeared immature and inactive. The oviduct appeared normal while the single ovary present contained a markedly reduced number of follicles. There was, however, some evidence of prior ovulation and formation of corpora lutea. The approach proposed in the present study to identify allosome aneuploidy from routinely available genotype data can be used to screen for such abnormalities at no additional cost to the breeder or producer.

Investigations and implications of associations between mycobacterial purified protein derivative hypersensitivity and MAP-antibody ELISA in Irish dairy cows.

Intradermal testing, involving administration of purified protein derivative (PPD), to elicit a delayed hypersensitivity (DTH) response, is used as a diagnostic tool for bovine tuberculosis (bTB) and to aid in the identification of exposure to Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of Johne's disease (JD). Further research is required to increase the diagnostic value of skin testing for MAP. The aim of this study was to investigate if animals showing DTH reactions to PPD had an associated increase in MAP ELISA response, thereby identifying potential cases of sub-clinical JD. A 139-cow dairy herd was recruited to the study. During the mandatory annual bTB test, skin thickness measurements (mm) were recorded at the site of avian and bovine PPD administration. Cows were categorised based on recording no DTH, DTH at both PPD administration sites and DTH at one PPD site only. Blood samples were collected pre and post bTB testing, and ELISA tested. Generalised estimating equations were performed to identify associations between DTH responses and MAP ELISA results. Significant associations were identified between PPD DTH responses and MAP ELISA readings. Animals with DTH at both avian and bovine PPD sites were most likely to test ELISA positive in the post-PPD period relative to other categories. Further research is required to identify whether skin thickness increases post-PPD and associated increase in ELISA response, identifies animals previously exposed to MAP, or if results are due to cross reactivity.

Genetic parameters for both a liver damage phenotype caused by and antibody response to phenotype in dairy and beef cattle.

is a helminth parasite of economic importance to the global cattle industry, with documented high international herd prevalence. The objective of the present study was to generate the first published genetic parameter estimates for liver damage caused by as well as antibody response to in cattle. Abattoir data on the presence of live , or -damaged livers, were available between the years 2012 and 2015, inclusive. A second data set was available on cows from 68 selected dairy herds with a blood ELISA test for antibody response to in autumn 2015. Animals were identified as exposed by using herd mate phenotype, and only exposed animals were retained for analysis. The abattoir data set consisted of 20,481 dairy cows and 75,041 young dairy and beef animals, whereas the study herd data set consisted of 6,912 dairy cows. (Co)variance components for phenotypes in both data sets were estimated using animal linear mixed models. Fixed effects included in the model for both data sets were contemporary group, heterosis coefficient, recombination loss coefficient, parity, age relative to parity/age group, and stage of lactation. An additional fixed effect of abattoir by date of slaughter was included in the model for the analysis of the abattoir data. Direct additive genetic effects and a residual effect were included as random effects for all analyses. After data edits, the prevalence of liver damage caused by in cows and young cattle was 47% and 20%, respectively. The prevalence of a positive antibody response to in cows from the study herd data was 36% after data edits. The heritability of as a binary trait for dairy cows in abattoir data and study herd data was 0.03 ± 0.01 and 0.09 ± 0.02, respectively; heritability in young cattle was 0.01 ± 0.005. The additive genetic SD of as a binary trait was 0.069 and 0.050 for cows and young cattle from the abattoir data, respectively, and 0.112 from the study herd cows. The genetic correlation between liver damage caused by in young cattle and cows from the abattoir data was 0.94 ± 0.312 and the genetic correlation between liver damage caused by in cows and positive antibody response to in cows in the study herd data was 0.37 ± 0.283.

Six-year longitudinal study of Fasciola hepatica bulk milk antibody ELISA in the dairy dense region of the Republic Ireland.

Completion of the F. hepatica lifecycle is dependent on suitable climatic conditions for development of immature stages of the parasite, and its snail intermediate host. Few investigations have been conducted regarding temporal variations in F. hepatica status in Irish dairy herds. The current study aimed to conduct a longitudinal study examining annual and seasonal trends in bulk milk seropositivity over six years, while also investigating associations with soil temperature, rainfall and flukicide treatment. Monthly bulk milk samples (BTM) were submitted by 28 herds between March 2009 and December 2014. In all, 1337 samples were analysed using a Cathepsin L1 ELISA. Soil temperature, rainfall and management data were obtained for general estimating equation and regression analyses. A general decrease in milk seropositivity was observed over the six year study period and was associated with an increased likelihood of treating for liver fluke (OR range=2.73-6.96). Annual and seasonal analyses of rainfall and F. hepatica BTM status yielded conflicting results. Higher annual rainfall (>1150mm) yielded a lower likelihood of being BTM positive than annual rainfall of <1000mm (OR=0.47; P=0.036). This was most likely due to farmers being more proactive in treating for F. hepatica in wetter years, although a 'wash effect' by high rainfall of the free living stages and snails cannot be ruled out. Higher seasonal rainfall (>120mm), however, was associated with increased ELISA S/P% values (Coefficient=9.63S/P%; P=0.001). Soil temperature was not found to influence F. hepatica to the same extent as rainfall and may reflect the lack of severe temperature fluctuations in Ireland. Flukicides active against both immature and mature F. hepatica were approximately half as likely to record a positive F. hepatica herd BTM status than a flukicide active against only the mature stage of the parasite (OR≅0.45; P<0.01). This study highlights the importance of examining both annual and seasonal F. hepatica data, which can vary significantly. Additionally, it highlights the progress that can be achieved in fluke control by application of a continuous BTM monitoring program.

Analysis of Johne's disease ELISA status and associated performance parameters in Irish dairy cows.

BACKGROUND: Infection with Mycobacterium avium subspecies paratuberculosis (MAP) has been associated with reductions in milk production in dairy cows and sub optimal fertility. The aim of this study was to highlight the production losses associated with testing MAP ELISA positive in Irish dairy cows. Secondary objectives included investigation of risk factors associated with testing MAP ELISA positive. A survey of management practices on study farms was also conducted, with examination of associations between management practices and herd MAP status. Blood samples were collected from 4188 breeding animals on 22 farms. Samples were ELISA tested using the ID Screen Paratuberculosis Indirect Screening Test. Production parameters examined included milk yield, milk fat, milk protein, somatic cell count, and calving interval. The association between MAP ELISA status and production data was investigated using multi-level mixed models. Logistic regression was used to identify risk factors for testing JD blood ELISA positive at individual cow level and to identify associations between farm management practices and herd MAP status. RESULTS: Data were available for 3528 cows. The apparent prevalence recorded was 7.4%. Mixed model analysis revealed no statistically significant association between testing MAP ELISA positive and dairy cow production parameters. Risk factors associated with testing positive included larger sized herds being over twice more likely to test positive than smaller herds (OR 2.4 P = <0.001). Friesians were less likely to test positive relative to other breeds. A number of study farmers were engaged in management practices that have previously been identified as high risk for MAP transmission e.g., 73.1% pooled colostrum and 84.6% of study farmers used the calving area to house sick animals throughout the year. No significant associations however, were identified between farm management practices and herd MAP status. CONCLUSION: No production losses were identified; however an apparent prevalence of 7.4% was recorded. With the abolition of EU milk quotas herd size in Ireland is expanding, as herds included in this study were larger than the national average, results may be indicative of future JD levels if no JD control programmes are implemented to minimise transmission.

Prevalence of exposure to bovine viral diarrhoea virus (BVDV) and bovine herpesvirus-1 (BoHV-1) in Irish dairy herds.

Bovine viral diarrhoea virus (BVDV) and bovine herpesvirus 1 (BoHV-1) are contagious bovine viral agents. The objectives of this study were to use quarterly bulk milk and 'spot' testing of unvaccinated youngstock to establish the national prevalence of exposure to BVDV and/or BoHV-1 in Irish dairy herds. Seasonality of bulk milk ELISA results was also examined. From a geographically representative population of 305 dairy herds, 88% and 80% of herds yielded mean annual positive bulk milk readings for BVDV and BoHV-1, respectively. Of these, 61% were vaccinated against BVDV and 12% against BoHV-1. A total of 2171 serum samples from weanlings having a mean age of 291 days yielded 543 (25%) seropositive for BVDV, and 117 (5.4%) seropositive for BoHV-1. A significant seasonal trend in bulk milk antibody ELISA readings and herd status was recorded for BVDV, with more herds categorised as positive in the latter half of the year.

A survey of biosecurity-related practices, opinions and communications across dairy farm veterinarians and advisors.

Biosecurity at farm-level can often be poorly implemented, and lack of information has been cited by many studies as a potential explanation. Veterinary practitioners (VPs) and dairy advisors (DAs) play a central role in the provision of animal health and management services to dairy farmers. The objective of this study was to document and compare biosecurity-related practices and opinions across VPs and DAs in Ireland. A selection of veterinary experts (VEs) from outside of Ireland was also surveyed. Questionnaires were completed and response rates of 47% (VPs), 97% (DAs), and 65% (VEs) were achieved. Significant differences were identified in the promotion and implementation of biosecurity between VPs and DAs, with a higher proportion of VPs regularly receiving requests from (P = 0.004), and dispensing advice to (P < 0.0001), their farm clients. Communication between DAs and VPs was sub-optimal with over 60% of each group not in regular communication with each other. With regard to the main farmer motivation for biosecurity implementation, the majority of VPs (62%) prioritised external factors such as 'economic benefit' and 'mandatory obligation', while the majority of DAs prioritised health/animal-related factors (69%), which were similar to those of farmers (83.1%), although they remained significantly less likely (OR = 1.8) than farmers to choose such motivators (P = 0.005). Inconsistencies in the implementation of, and in opinions relating to, farm biosecurity were highlighted across all the groups surveyed emphasising the need for standardised information and improved communication.

Implementing biosecurity measures on dairy farms in Ireland.

Dairy farms in Ireland are expanding in preparation for a new era of unrestricted milk production with the elimination of the European Union (EU) production quotas in 2015. Countries experiencing a changing agricultural demographic, including farm expansion, can benefit from documenting the implementation of on-farm biosecurity. The objectives of this study were to document and describe influences on biosecurity practices and related opinions on dairy farms. A representative response rate of 64% was achieved to a nationwide telesurvey of farmers. A 20% discrepancy was found between self-declared and truly 'closed' herds indicating a lack of understanding of the closed herd concept. Although >72% of farmers surveyed considered biosecurity to be important, 53% stated that a lack of information might prevent them from improving their biosecurity. Logistic regression highlighted regional, age, and farm-size related differences in biosecurity practices and opinions towards its implementation. Farmers in the most dairy cattle dense region were three times more likely to quarantine purchased stock than were their equivalents in regions where dairy production was less intense (P=0.012). Younger farmers in general were over twice as likely as middle-aged farmers to implement biosecurity guidelines (P=0.026). The owners of large enterprises were almost five times more likely to join a voluntary animal health scheme (P=0.003), and were over three times more likely to pay a premium price for health accredited animals (P=0.02) than were those farming small holdings. The baseline data recorded in this survey will form the basis for more detailed sociological and demographic research which will facilitate the targeting of future training of the farming community in biosecurity.