Serological evidence of lack of contact with caprine herpesvirus type 1 and bluetongue virus in goat population in Poland

Investigation into herd-level seroprevalence of caprine herpesvirus type 1 (CpHV-1) and bluetongue virus (BTV) was conducted in 2007 in Poland. It involved the entire population of goats covered by a milk recording program in 2007, which included 49 goat herds. The number of goats examined in each herd was determined statistically in order to detect the presence of at least one seropositive animal in a herd with a 95% probability and simple random method of sampling was applied. No antibodies to CpHV-1 or BTV were detected. Further calculations were carried out to determine the herd-level true seroprevalence, taking into account sensitivity and specificity of the test as well as several other factors. It can be concluded that till the middle of 2007 population of Polish goats covered by the milk recording program remained negative with respect to CpHV-1 and BTV.     

Accuracy and reliability of mastitis detection with electrical conductivity and milk colour measurement in automatic milking

Abstract

Detection of mastitis and reliability of alarms were evaluated in eight herds with automatic milking. Herds were visited once to gather milk samples and the farmers followed up alarms for 15 to 30 days. Sensitivity of detecting quarters with SCC over the threshold value of 200,000 or 1,000,000 cells/ml was 18.0 to 42.9% in Group A, based on electrical conductivity (EC) and 5.5 to13.0% in Group B, based on EC and milk colour. Specificity was over 97.0%. In Group A, 6/17 of the EC alarms were false positives. None of the seven EC alarms in Group B was false positive. On the day that the farmer observed clinical mastitis, more than half of the quarters received alarms, but only milk from some quarters was automatically diverted. In total 58.4% (Group A) and 26.8% (Group B) of cows had alarms based on EC, and 84.1% (<20% true positives) and 12.0% (60–90% true positives) had alarms based on milk yield or milk colour during the follow-up period. The number of alarms was halved in Group A when a running average was applied to the algorithm of EC. The proportion of true positives simultaneously increased from 30% to 60%. In Group B, the number of alarms was almost doubled with algorithm manipulation, but the proportion of true positives declined from >80% to >70%.     

The effect of an outbreak of respiratory disease on herd-level milk production of Norwegian dairy farms

This study was done to evaluate the effect of an outbreak of acute respiratory disease associated with bovine respiratory syncytial virus (BRSV) on the daily milk yield per cow in Norwegian dairy-cattle farms. Retrospective data from 184 dairy herds located in two neighbouring veterinary districts during the study period (December 1994–May 1995, during which an epidemic of acute respiratory disease associated with BRSV occurred in this area) were analysed. Data on the bulk-milk deliveries and the date of the outbreak were collected at herd level, whereas information on calving dates and parity was collected at cow-level. The effect of the herd outbreaks on the daily milk yield was analysed with a repeated-measurement approach. The average daily milk loss was estimated to be 0.70 kg per cow for 7 days after a herd outbreak (compared with the period >1 week prior to an outbreak), adjusted for the herd-level lactation stage, parity and their interaction term. We consider the estimated milk loss associated with a herd outbreak of epidemic respiratory disease to be of minor importance.     

N-acetyl-beta-D-glucosaminidase test for screening milk samples for subclinical mastitis.

The use of the N-acetyl-beta-D-glucosaminidase (NAGase) test for detecting subclinical mastitis was investigated in surveys of milk samples from 20 farms. A milk sample was considered to be mastitic if it had a milk cell count above 400,000 cells/ml, and the NAGase test results were graded accordingly. The test gave an average of 16.6 per cent false positives and 2.0 per cent false negatives per herd. It was concluded that the NAGase test could be used as a rapid screening method for selecting suspect samples for further analysis by standard methods.     

Validation of a commercial ELISA for the detection of bluetongue virus (BTV)-specific antibodies in individual milk samples of Dutch dairy cows

A recently developed indirect ELISA for the detection of bluetongue virus (BTV)-specific antibodies in bovine milk samples was compared to that of the routinely used competitive ELISA on serum samples. During the bluetongue outbreak in the Netherlands in 2006, caused by BTV serotype 8, coupled serum and milk samples were obtained from 470 individual cows from 10 BTV-infected farms with an average seroprevalence of 57%. In addition, bulk milk samples of the same farms, and historically BT-negative samples were tested. Compared to the ELISA for sera, the relative specificity and sensitivity of the ELISA for milk samples is 96.5% and 98.9%, respectively when using a S/P% cut-off value of 50% as advised by the manufacturer. The optimal cut-off value was found at S/P% of 90% revealing an optimal specificity (99.0%) combined with an optimal sensitivity (98.1%). Titres in positive individual milk samples ranged from 1 to 2048 with a peak titre of 128. Bulk milk samples contained antibodies with titres ranging from 64 to 512. The ELISA for milk samples was found to be a reliable and robust test. This diagnostic tool is very useful, and may replace the ELISA for serum samples as first choice in order to get insight into the status of lactating individual animals and therewith of the entire herd with respect to BTV infection.     

Automatic detection of oestrus and health disorders using data from electronic sow feeders

This article suggests a method for detecting oestrus, lameness and other health disorders for group housed sows fed by electronic sow feeders (ESF). The detection method is based on the measure of the individual eating rank, modeled using a univariate dynamic linear model. Differences between the predicted values of the model and the observations are monitored using a control chart: a V-mask is applied on the cumulative sum of the standardized forecast errors of the model. According to the respective V-mask parameters, alarms are given for each of the three states (oestrus, lameness, others) when the deviations between model predicted values and observations exceed some defined parameters. External information is incorporated into the model to limit the number of false alarms when a subgroup of sows enters and exits a group or both. The detection method was implemented on data collected within three production herds over 12 months. Visual recordings were performed to identify sows in oestrus or with health disorders. The detection method showed a high specificity. For oestrus detection, there was a sensitivity of 59%, 70% and 75% for the three herds as compared to 9% (herd 1) and 20% (herd 2) using lists of sows as alarms. Monitoring lameness results in a sensitivity of 56%, 70% and 41%, vs. 39%, 32% and 22% using the lists; monitoring other health disorders resulted in a sensitivity of 0%, 75% and 39% for the three respective herds, vs. 34% and 16% for herds 2 and 3 using the lists. To limit the number of false alarms, it is suggested to expand the model by including daily feed intake or body activity as other response variables.     

An economic analysis of hyperketonemia testing and propylene glycol treatment strategies in early lactation dairy cattle

The purpose was to develop stochastic economic models which address variation in disease risks and costs in order to evaluate different simulated on-farm testing and propylene glycol (PG) treatment strategies based on herd hyperketonemia (HYK) incidence during the first 30 DIM. Data used in model development concerning the difference in health and production consequences between HYK and non-ketotic cows were based on results from 10 studies representing over 13,000 cows from 833 dairy farms in North America, Canada, and Europe. Inputs for PG associated variables were based on a large field trial using cows from 4 free-stall dairy herds (2 in New York and 2 in Wisconsin). Four simulated on-farm testing and treatment strategies were analyzed at herd HYK incidences ranging from 5% to 80% and included: 1) treating all cows with 5 d of PG starting at 5 DIM, 2) testing all cows for HYK 1 day per week (e.g. Mondays) from 3 to 16 DIM and treating all positive cows with 5 d of oral PG, 3) testing all cows for HYK 2 days per week (e.g. Mondays and Thursdays) from 3 to 9 DIM and treating all positive cows with 5 d of oral PG, and 4) testing all cows for HYK 3 days per week (e.g. Mondays, Wednesdays, and Fridays) from 3 to 16 DIM and treating all positive cows with 5 d of oral PG. Cost-benefit analysis included the costs associated with labor to test cows, β-hydroxybutyrate test strips, labor to treat cows, PG, and the associated gain in milk production, decrease in DA and early removal risks of PG treated HYK positive cows compared to non-treated HYK positive cows. Stochastic models were developed to account for variability in the distribution of input variables. Per 100 fresh cows in a herd with an HYK incidence of 40%, the mean economic benefits of the 4 different strategies were $1088, $744, $1166, and $760, respectively. Testing cows 2 days per week from 3 to 9 DIM was the most cost-effective strategy for herds with HYK incidences between 15% and 50%; above 50%, treating all fresh cows with 5 d of PG was the most cost-effective strategy. These results show that for herds similar to those used in model, when herd HYK incidences rise above 25%, almost any HYK testing and treatment protocol will be economically beneficial for the farm.     

Heterosis effects in a black and white dairy cattle population under different production environments

The effect of the environmental level of production (ENV) on the expression of heterosis for 305-day milk, fat, protein, and fat plus protein (FP) yields, lactation average somatic cell score (LSCS), and age at first calving (AFC) was investigated in first lactation Black and White dairy cows in the Netherlands, and officially enrolled in the Dutch herd-book. Holstein Friesian (HF), Dutch Friesian (DF), and first generation (F₁) crosses obtained from the mating of HF sires and DF dams (HD) were involved in the study, and data from animals with a calving date between 1990 and 2000 were used. A total of 22,930 cows with production and AFC information distributed in 3549 herds and 11,055 cows with LSCS information distributed in 2071 herds, were available. Adjusted lactation yield of milk for each herd was obtained using a model that accounted for fixed effects of herd, year and month of calving, genotype, and AFC. The overall mean of all adjusted data was computed, and 3 ENV were defined on the basis of the overall mean ± 0.5 standard deviations. Once ENV was defined, traits were analysed with a model that included fixed effects of ENV, herd nested within ENV, AFC (only production traits and LSCS), year and month of calving, genotype, and the interaction between ENV and genotype. Least squares means for the interaction effect were used to estimate heterosis and to evaluate its magnitude across ENV. Holstein Friesian achieved higher productions than DF. First generation crosses showed productions close to HF, especially in the low ENV. Estimates of heterosis for yield traits ranged from 2.4% (milk) in the high to 5.3% (fat) in the low ENV, and reduced with increasing ENV. Estimates for LSCS and AFC were low, with the exception of LSCS in the high ENV. Results suggest that the highest non-additive genetic effects for yield traits and LSCS were expressed in the most stressful ENV, i.e., the low one for production and the high one for LSCS.     

Foot lameness in dairy goats

An outbreak of foot lameness in a dairy herd of 170 goats is described. The herd, that was kept mostly indoors, was attended between December 2006 and November 2007. During this period, 15% of the goats showed lameness with foot lesions and 24% of the goats showed lameness without foot lesions. The foot lesions consisted of cracks and erosions on the horn of the bulbs of the heel that in most cases extended along the internal side of the axial hoof wall. The clinical diagnosis was interdigital dermatitis. Annual milk production was lower in lame goats compared to those that were not lame (P < 0.05). Furthermore, annual milk yield was significantly affected by the type of foot disease present and was significantly lower in cases with foot lesions than in the animals that were not lame (P < 0.05) and also in the lame goats without foot lesions (P < 0.05).     

Trends in the reproductive performance of Holstein dairy cows in Iran

The study was undertaken to determine the trends in the reproductive performance of Holstein dairy cows in Iran during 1994 to 2008. Reproductive performance data for 528,034 lactations of 246,132 cows in 1,822 Holstein dairy herds of Iran were used. The potential effect of calving season, herd, parity, calving year, as well as herd size and 305-day milk production on reproductive performance traits was investigated using multiple regression models. The least squares means of age at first calving decreased by 3.1 (±0.06) days per year from 806.5 (±96.3) days in 1994 to 788 (±89.9) days in 2008. The least squares means of calving interval increased 1.02 (±0.03) days per year from 394.1 (±65) days in 1994 to 413.2 (±81) days in 2008. Greater 305-day milk production was associated with an average increase of 6.55 (±0.08) days in calving interval per 1,000-kg increase in milk yield. Larger herd size was associated with an average decrease of 0.22 (±0.02) days in calving interval per 50 cows per herd. The mean number of days dry was 88.6 (±51.3) days and increased by 0.82 (±0.02) days per year. In conclusion, reproductive performance in Holstein dairy herds has generally decreased, whereas herd size and milk production have increased over time. Producers may make significant improvements in herd reproduction by reviewing management strategies including the sire selection, reproductive management, inseminator training and techniques, and improved estrous detection. Moreover, it may be advisable for the fertility traits to be included in the genetic selection indices to reduce the rate of reproductive decline.     

An epidemiological study of hyperketonaemia in Swedish dairy cows; Determinants and the relation to fertility

In a study based on 3078 Swedish dairy cows from 126 herds, milk acetone was measured at the first 3 monthly production tests after calving. The values were assessed together with data from the official milk recording system, artificial insemination records and the computerised recording system for veterinary treatments. Milk acetone concentrations above 0.40 mmol 1^?1 were considered to indicate hyperketonaemia. The prevalence of hyperketonaemia was 8.9, 4.7 and 1.1%, respectively, at the first 3 monthly production tests. A significant influence on milk acetone was found for herd mean production, breed, herd, lactation number, cow, week of lactation, season and the interaction between lactation number and week of lactation. The highest individual milk yield and highest individual acetone value were significantly positively correlated. Test-day milk yield and milk acetone on the same day were significantly negatively correlated. The recorded incidence of clinical ketosis and ovarian cysts increased with increasing highest milk acetone concentration. Significant correlations were found between the prevalence of hyperketonaemia and herd means of the intervals from calving to first and last service. No significant correlations were found between milk acetone and fertility traits when calculated on an individual cow basis.     

A stochastic predictive model for the natural spread of bluetongue

In recent years the vector-borne diseases (VBD) are (re)-emerging and spreading across the world having a profound impact on human and veterinary health, ecology, socio-economics and disease management. Arguably the best-documented example of veterinary importance is the recent twofold invasion of bluetongue (BT) in Europe. Much attention has been devoted to derive presence-absence habitat distribution models and to model transmission through direct contact. Limited research has focused on the dynamic modelling of wind mediated BT spread. This paper shows the results of a stochastic predictive model used to assess the spread of bluetongue by vectors considering both wind-independent and wind-mediated movement of the vectors. The model was parameterised using epidemiological knowledge from the BTV8 epidemic in 2006/2007 and the BTV1 epidemic in 2008 in South-France. The model correctly reflects the total surface of the infected zone (overall accuracy=0.77; sensitivity=0.94; specificity=0.65) whilst slightly overestimating spatial case density. The model was used operationally in spring 2009 to predict further spread of BTV1. This allowed veterinary officers in Belgium to decide whether there was a risk of introduction of BTV1 from France into Belgium and thus, whether there was a need for vaccination. Given the far distance from the predicted infected zone to the Belgian border, it was decided not to vaccinate against BTV1 in 2009 in Belgium.     

Evaluation of bluetongue virus diagnostic tests in free-ranging bighorn sheep

Five bluetongue virus (BTV) diagnostic tests were evaluated for use in free-ranging bighorn sheep. We sampled one bighorn sheep population four times between 1989 and 1995. The tests evaluated included virus isolation (VI), polymerase-chain reaction (PCR), serum neutralization (SN), agar-gel immunodiffusion (AGID), and competitive enzyme-linked immunosorbent assay (c-ELISA). The c-ELISA, AGID and SN tests had high levels of agreement in determining serogroup exposure in bighorn sheep. We used maximum-likelihood algorithms to estimate the parameters of each diagnostic test used. Although the c-ELISA and AGID had high sensitivity and specificity, the SN had perfect specificity but lower apparent sensitivity. Due to the potential of cross-reactions among multiple serotypes, results of the SN must be interpreted with caution when assessing serotype exposure in an area where multiple serotypes are endemic. The PCR assay delineated convalescent antibody titers from more-recent infections, and consequently, was pivotal in distinguishing a different exposure pattern between the bighorn sheep and cattle in an adjacent herd. Based on an increasing seroprevalence (50% to 100%), BTV circulated through this bighorn sheep population between 1989 and 1993. This increase in seroprevalence coincided with a bighorn die-off due to BTV infection in June, 1991. An adjacent cattle herd was sampled in 1995 for comparison. The bighorn sheep and adjacent cattle had different patterns of exposure to BTV between 1994 and 1995. There was no evidence that BTV circulated through the bighorn sheep population from 1994 to 1995. In 1995, seroprevalence to BTV decreased to 72%, none of yearling bighorn was seropositive, and all of the 39 bighorn sheep were PCR-negative. In contrast, all adult cattle were seropositive to BTV by c-ELISA and SN, and 4 of the calves were seropositive; 11 of the 24 cattle were PCR-positive, including all five calves. Overall, the pattern of temporal herd immunity in the bighorn sheep appeared to follow a classic epidemic curve, with the appearance and subsequent disappearance of herd immunity coinciding with the 1991 die-off in this population. As low levels of herd immunity and high proportions of susceptible animals are key factors in the development of epidemics, this population of bighorn sheep may be at increased risk for a BTV epidemic in the future.     

Estimation of the economic value of herd‐life length based on simulated changes in survival rate

Functional traits are an important aspect of long‐term breeding strategies for dairy cattle. In this regard, it is necessary to develop simple methods for estimating the economic value of herd life. In this study, the economic daily value of herd life was estimated when survival rate varied between ?0.05 and 0.05 from the basal survival rate. The extension days per survival rate were 26.5 days in Hokkaido and 20.3 days in other regions. The increases in values of annual income per day of herd life were 95.18 yen in Hokkaido and 101.80 yen in other regions. The relative economic weights of milk yield to herd life per genetic standard deviation were 0.668 in Hokkaido and 1.03 in other regions. Estimated increments in yearly profits based on young sire selection for herd life were 963 yen in Hokkaido and 1,030 yen in other regions. The estimated increments in annual profits based on young sire selection for milk yield were 1,268 yen in Hokkaido and 2,097 yen in other regions. Given that economic value was linearly correlated with herd‐life length, the linear regression coefficients between these factors could be used to estimate the economic value of herd‐life length.     

The effects of liveweight loss and milk production on the risk of lameness in a seasonally calving,pasture fed dairy herd in New Zealand

Dairy herd managers have attempted to increase and maintain profits by selectively breeding dairy cattle for high production. Selection for milk production may have resulted in a tendency for greater liveweight (LW) loss postpartum. This study aimed to: (1) determine if excessive LW loss and milk yield in the first 50 days in milk (DIM) was associated with the development of lameness after 50 DIM, and (2) estimate the incidence risk of lameness in this herd attributable to excessive liveweight loss. The dataset comprised details from 564 mixed age cows from a single, seasonally calving, pasture fed dairy herd in New Zealand.     

The consequences of risk-based surveillance: Developing output-based standards for surveillance to demonstrate freedom from disease

Risk factors associated with high or low long-term incidence of displaced abomasum (DA) or clinical ketosis were studied in 60 Swedish dairy herds, using multivariable logistic regression modelling. Forty high-incidence herds were included as cases and 20 low-incidence herds as controls. Incidence rates were calculated based on veterinary records of clinical diagnoses. During the 3-year period preceding the herd classification, herds with a high incidence had a disease incidence of DA or clinical ketosis above the 3rd quartile in a national database for disease recordings. Control herds had no cows with DA or clinical ketosis. All herds were visited during the housing period and herdsmen were interviewed about management routines, housing, feeding, milk yield, and herd health. Target groups were heifers in late gestation, dry cows, and cows in early lactation. Univariable logistic regression was used to screen for factors associated with being a high-incidence herd. A multivariable logistic regression model was built using stepwise regression. A higher maximum daily milk yield in multiparous cows and a large herd size (p = 0.054 and p = 0.066, respectively) tended to be associated with being a high-incidence herd. Not cleaning the heifer feeding platform daily increased the odds of having a high-incidence herd twelvefold (p < 0.01). Keeping cows in only one group in the dry period increased the odds of having a high incidence herd eightfold (p = 0.03). Herd size was confounded with housing system. Housing system was therefore added to the final logistic regression model. In conclusion, a large herd size, a high maximum daily milk yield, keeping dry cows in one group, and not cleaning the feeding platform daily appear to be important risk factors for a high incidence of DA or clinical ketosis in Swedish dairy herds. These results confirm the importance of housing, management and feeding in the prevention of metabolic disorders in dairy cows around parturition and in early lactation.     

Influence of long-term vaccination of a breeding herd of pigs against PCV2 on reproductive parameters

The objective of the study was to evaluate an efficacy of sows vaccination protocols in the herd with serious problems affecting efficacy of reproduction. The study was performed in a large pig herd with about 1200 sows. Before vaccination against PCV2, farrowing rate in this farm was about 65%. Sows, boar and replacement gilts were immunized using Circovac vaccine (Merial, France) according to producer's recommendations. Parameters of production were analyzed since 2007 until 2010 in selected batches of sows inseminated at the same weeks of the year (17th, 18th, 19th and 20th) to eliminate seasonal variability. In total, 940 sows were subjected to the study. No significant changes in management during these years were introduced. The applied protocol of sow herd long-term vaccination proved to be very efficient. All measured production parameters: reproduction rate, number of piglets born alive, birth weight of piglets and number of piglets weaned per a litter improved after implementation of immunization program. Moreover, further improvement was observed with vaccination in the following reproduction cycles. The most spectacular effect of vaccination regarded average farrowing rate that increased from 64.76% in control group to 86.93% after basic vaccination. Two years after implementation of vaccination program this parameter reached 93.6%. Number of piglets weaned per sow per a litter improved from 10.31 to 11.74 after one year of vaccination and remained relatively stable through the following year. Simultaneously, the percentage of newborn piglets with birth weight < 1 kg decreased significantly (p < 0.05). To summarize, vaccination against PCV2 influenced positively the insemination rate, number of piglets born alive and weaned per litter as well as birth body weight and percentage of piglets weighing < 1 kg.     

Disease, production and culling in Holstein-Friesian cows: IV. Effects of disease on production

The effects of common clinical and two subclinical disease conditions (mastitis and ketosis) on milk production and reproductive performance in Holstein-Friesian cows were investigated in a two and a half year study. The data used were from 1315 lactation records and results from tests performed on 6241 composite milk samples.

Path analyses were used to estimate the direct and indirect impact of disease on days to conception, milk production in a standard 305 day lactation and milk production per day. Indirect effects accounted for a large percentage of the total effect of some diseases on production. The path coefficients were quite sensitive to the units used to measure production, with deviation from the herd average being the preferable measure. These units controlled confounding due to herd level variables. Effects identified by the path analyses were substantially different from those determined on the basis of unconditional associations between diseases and production parameters.

Subclinical mastitis and the reproductive diseases (most of which were subclinical in nature) were found to have the greatest detrimental impact on milk production per day. Several disease conditions had a beneficial effect on milk production and this was attributed to the therapy provided to cows affected with these conditions. All conditions related to reproductive performance had a detrimental effect on days to conception.     

Estimation of genetic parameters for functional longevity in the South African Holstein cattle using a piecewise Weibull proportional hazards model

Non‐genetic factors influencing functional longevity and the heritability of the trait were estimated in South African Holsteins using a piecewise Weibull proportional hazards model. Data consisted of records of 161,222 of daughters of 2,051 sires calving between 1995 and 2013. The reference model included fixed time‐independent age at first calving and time‐dependent interactions involving lactation number, region, season and age of calving, within‐herd class of milk production, fat and protein content, class of annual variation in herd size and the random herd–year effect. Random sire and maternal grandsire effects were added to the model to estimate genetic parameters. The within‐lactation Weibull baseline hazards were assumed to change at 0, 270, 380 days and at drying date. Within‐herd milk production class had the largest contribution to the relative risk of culling. Relative culling risk increased with lower protein and fat per cent production classes and late age at first calving. Cows in large shrinking herds also had high relative risk of culling. The estimate of the sire genetic variance was 0.0472 ± 0.0017 giving a theoretical heritability estimate of 0.11 in the complete absence of censoring. Genetic trends indicated an overall decrease in functional longevity of 0.014 standard deviation from 1995 to 2007. There are opportunities for including the trait in the breeding objective for South African Holstein cattle.     

Comparison of methods to evaluate the energy supply in dairy herds

Different methods to evaluate the nutritional and metabolic status in dairy herds are available. The aim of this study was to evaluate three different methods to assess the energy status of the herd: 1) the calculation of the energy balance of the herd with a new method based on the Swiss standard calculations, 2) the "efficiency of the feeding management" based on milk yield and milk protein content (%) obtained from DHI data, and 3) the percentage of cows per herd with an average milk yield (16-25 kg/day), but a low milk protein (< 3.2 %). The study included data from 47 farms enrolled in the herd reproduction survey program of the University of Berne, with a total of 653 cows included in one winter period. A correlation could only be seen between methods two and three. It is concluded that it is insufficient only to calculate the ration as an estimation of the energy status of the herd. A rough calculation of the ration is necessary to have an idea on the energy density. But the calculated ration seems to be considerably different from the amount of energy and nutrients of the diet finally absorbed by the cow. As the ingested ration is relevant for milk production and animal health, the relationship between milk yield and milk protein content as well as the percentage of cows with milk protein < 3.2% are considered to provide good information about the efficiency of the feeding management in dairy herds.