Comparison of claw horn disruption lesions in four dairy herds using two different trimming techniques: A case study.

Claw disorders are a major problem for health, welfare, and economy in dairy production. This retrospective observational study investigated the association between cow-level prevalence of claw horn disruptive lesions and two different trimming methods - the traditional Danish Method (DAM) and the White Line Atlas Method (WLAM). Trimming records from four herds in Denmark over a 4-year period were analysed. Within each herd, claw trimming was performed with the DAM for the first 2 years, and the WLAM for the next 2 years. The data comprised 3316 claw trimmings of 1027 cows with the WLAM and 3898 claw trimmings of 1080 cows with the DAM. The association between claw trimming method and claw lesions was determined using binominal logistic analysis. There were significant differences between trimming methods for sole haemorrhage (odds ratio = 0.44), sole ulcer (odds ratio = 0.42), and white line separation (odds ratio = 0.64), with a lower prevalence during the period of trimming with the WLAM. No significant difference between trimming methods could be found in the occurrence of white line abscess or double sole. The lower prevalence of claw horn disruption lesions found in this study when cows were trimmed with WLAM justifies and necessitates further experimental studies of claw trimming methods to validate these findings.

Effect of enhanced hygiene on transmission of Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus dysgalactiae in dairy herds with automatic milking systems.

The objective of the study was to evaluate the effect of hygiene measures in automatic milking units on the transmission of 3 mastitis pathogens considered to be mainly or partly transmitted from cow to cow during milking events. Two studies were conducted as within-herd experimental trials in 2 Danish commercial dairy herds (A and B) with automatic milking systems. Interventions to enhance hygiene were implemented on the automatic milking units. The 2 studies evaluated separate interventions. In herd A, the hygiene interventions were manual wash with the Lely foam unit and adjustments on the brush-mediated teat cleaning procedure. In herd B, the hygiene intervention included automatic disinfection spray on the upper surface of the brush motor and daily change of brushes. Composite milk samples were collected longitudinally at 3- or 4-wk intervals from all lactating cows. Additional milk samples were taken from cows entering or leaving the study groups. Milk samples were analyzed with quantitative PCR. A hidden Markov model implemented within a Bayesian framework was used to estimate the transmission probability. For analysis, 701 samples from 156 cows were used for herd A, and 1,349 samples from 390 cows were used for herd B. In the intervention group in herd B, transmission of Streptococcus agalactiae was reduced to 19% (95% posterior credibility interval: 0.00-64%) of the transmission in the control group, whereas transmission of Streptococcus dysgalactiae was reduced to 17% (95% posterior credibility interval: 0.00-85%) of transmission in the control group. This suggests that automatic spray on the upper surface of the brush motor with disinfectant along with daily change of brushes collectively reduced transmission of Strep. agalactiae and Strep. dysgalactiae. Results on Staphylococcus aureus in herd B and results on manual foam cleaning and brush-mediated teat cleaning adjustments in herd A were inconclusive.

Antimicrobial use in organic and conventional dairy herds.

Use of antimicrobials for food-producing animals is a major public concern due to the risk of antimicrobial resistance. Although dairy production has a relatively low usage of antimicrobials, the potential for further reduction should be explored. The objective of the study was to estimate the current differences in antimicrobial use in Danish organic and conventional dairy herds and to describe the differences between them. Based on data from three different sources, 2604 herds (306 organic and 2298 conventional) were identified for the study. These herds had been either organic or conventional for the entire period from 2015 to 2018. Antimicrobial use was calculated as the treatment incidence in Animal Daily Doses (ADDs)/100 animals/day for three age groups: adult cattle, young stock and calves. For adult cattle, the ratio of median treatment incidence between conventional and organic production ranged from 2.8 : 1 to 3.4 : 1, depending on the specific year. For cows, 25% of the organic herds had a higher treatment incidence than the 25% of conventional herds with the lowest treatment incidence. Antimicrobial use for young stock was low and at a similar level in both the organic and conventional production systems. For calves, the median treatment incidence was 1.2 times higher in conventional herds and 1.6 times higher for the 75th percentile. Analyses of treatment incidence in adult cattle showed an overall decrease from 2015 to 2018 in both organic and conventional herds. The decrease was greater for the conventional herds (0.12 ADD/100 animals/day) compared to the organic herds (0.04 ADD/100 animals/day) over the 4-year period. In addition, herd size was an important risk factor for treatment incidence in conventional herds, increasing by 0.07 ADD/100 animals/day per 100 cows, whereas herd size had a minor influence on the treatment incidence in organic herds. The results of this study demonstrate the large variation in antimicrobial use within both organic and conventional herds, suggesting that further reduction is possible. Furthermore, herd size appears to be a risk factor in conventional herds but not in organic herds - an aspect that should be studied in more detail.

Between- and within-herd variation in blood and milk biomarkers in Holstein cows in early lactation.

Both blood- and milk-based biomarkers have been analysed for decades in research settings, although often only in one herd, and without focus on the variation in the biomarkers that are specifically related to herd or diet. Biomarkers can be used to detect physiological imbalance and disease risk and may have a role in precision livestock farming (PLF). For use in PLF, it is important to quantify normal variation in specific biomarkers and the source of this variation. The objective of this study was to estimate the between- and within-herd variation in a number of blood metabolites (ß-hydroxybutyrate (BHB), non-esterified fatty acids, glucose and serum IGF-1), milk metabolites (free glucose, glucose-6-phosphate, urea, isocitrate, BHB and uric acid), milk enzymes (lactate dehydrogenase and N-acetyl-ß-D-glucosaminidase (NAGase)) and composite indicators for metabolic imbalances (Physiological Imbalance-index and energy balance), to help facilitate their adoption within PLF. Blood and milk were sampled from 234 Holstein dairy cows from 6 experimental herds, each in a different European country, and offered a total of 10 different diets. Blood was sampled on 2 occasions at approximately 14 days-in-milk (DIM) and 35 DIM. Milk samples were collected twice weekly (in total 2750 samples) from DIM 1 to 50. Multilevel random regression models were used to estimate the variance components and to calculate the intraclass correlations (ICCs). The ICCs for the milk metabolites, when adjusted for parity and DIM at sampling, demonstrated that between 12% (glucose-6-phosphate) and 46% (urea) of the variation in the metabolites' levels could be associated with the herd-diet combination. Intraclass Correlations related to the herd-diet combination were generally higher for blood metabolites, from 17% (cholesterol) to approximately 46% (BHB and urea). The high ICCs for urea suggest that this biomarker can be used for monitoring on herd level. The low variance within cow for NAGase indicates that few samples would be needed to describe the status and potentially a general reference value could be used. The low ICC for most of the biomarkers and larger within cow variation emphasises that multiple samples would be needed - most likely on the individual cows - for making the biomarkers useful for monitoring. The majority of biomarkers were influenced by parity and DIM which indicate that these should be accounted for if the biomarker should be used for monitoring.

Only few benefits from propylene glycol drench in early lactation for cows identified as physiologically imbalanced based on milk spectra analyses.

The main objective of this study was to test the efficiency of a management system combining metabolic clustering of cows based on Fourier-transform mid-infrared (FT-MIR) spectra of milk and targeted treatment of metabolically imbalanced cows with propylene glycol drench. We hypothesized that cows identified in a metabolically imbalanced status during early lactation were associated with subsequent impaired health, reproduction, and production, and that treatment with propylene glycol treatment would improve health, reproduction, and production relatively more in these cows than in control cows. We completed a prospective, randomized controlled trial with 356 early-lactation cows in 2 private dairy herds in Denmark from December 2017 to April 2018. Milk samples of cows were collected before treatment, from 4 to 9 d in milk, and after treatment, from 22 to 27 d in milk. Milk samples were analyzed using FT-MIR spectroscopy. We also measured 4 milk metabolites (ß-hydroxybutyrate, isocitrate, malate, and glutamate) and fat and protein contents. Based on FT-MIR spectra and cluster analyses, cows were clustered into groups of metabolically imbalanced and healthy cows. Within each group, cows were allocated randomly to treatment with propylene glycol (500 mL for 5 d) or no treatment. We analyzed the effect of the treatment on cow-level variables: metabolic cluster, milk metabolites, fat and protein contents, and fat-to-protein ratio at a milk sampling after the treatment. Furthermore, we analyzed daily milk yield, calving to first service interval, and disease occurrence. Results showed only a few effects of propylene glycol treatment and few interactions between treatment and metabolic clusters. We found no significant main effects of propylene glycol treatment in any of these analyses. A negative effect of the imbalanced metabolic cluster was found for the outcome of calving to first service interval for multiparous cows. In conclusion, we found a longer calving to first service interval in metabolically imbalanced cows, but we were not able to demonstrate overall benefits from the applied detection of cows in imbalanced metabolic status in early lactation and follow-up by treatment with propylene glycol.

Prevalence of abomasal lesions in Danish Holstein cows at the time of slaughter.

Abomasal lesions in cattle are challenging to diagnose because the clinical signs are often subtle and nonspecific. An increasing number of studies suggests that abomasal lesions are commonly found in cattle of all ages, but the number of recent prevalence studies in dairy cows is limited. The main objective of this study was to estimate the prevalence of abomasal lesions in a population of Danish Holstein dairy cattle in Denmark. An abattoir survey of 1,327 dairy cows apparently suitable for slaughter was performed in 2016 and 2017. Abomasal lesions are usually classified using a standardized protocol with the following types: abomasal ulcer type I: erosions and nonperforating ulcers; type II: ulcers with arterial bleeding; type III: perforating ulcer with localized peritonitis; and type IV: perforating ulcer with diffuse peritonitis. A further subdivision of the nonperforating abomasal ulcers type I were classified as subtype Ia: erosions; subtype Ib: small ulcers with localized hemorrhage; subtype Ic: ulcers with a crater-like appearance; and subtype Id: retention of the mucosa due to tissue loss with either radial wrinkles converging at a central point or perforations of the spiral folds. Type I abomasal lesions were found in 84% of the examined cows. No ulcers with arterial bleeding (type II) or perforating ulcers with diffuse peritonitis (type IV) were found, but one perforating abomasal ulcer (type III) was observed. The total number of lesions found was 7,418 and when the lesion subtypes were evaluated individually the majority of subtypes Ia and Ic were found in the pyloric area (85 and 94%, respectively), whereas lesion subtypes Ib and Id dominated the fundus/corpus area (71 and 67%, respectively). When considering lesion subtypes according to parity, there was a high prevalence of subtype Ib across the 3 groups of parity (51, 58, and 55% for parity 1, 2, and ≥3, respectively). The prevalence of lesion subtype Id seemed to increase with increasing parity, and the prevalence of lesion subtype Ia seemed to decrease with increasing parity. The prevalence of abomasal lesions was higher than that shown in similar studies of cattle at the time of slaughter. However, the expectedly most painful cases were rare, with only one perforating and no arterial bleeding ulcers found. The etiology of the different subtype I lesions is still unknown, and further investigations are needed to establish the possible influence these lesions might have on welfare and production.

Evaluation of systematic California Mastitis Tests and vaginal examinations as measures of antimicrobial use in dairy herds.

Antimicrobial use is a commonly applied proxy for animal health and welfare impairment related to disease status in dairy herds. The objective of this study was to estimate the association between antimicrobial use and the results of systematic clinical examinations for metritis and mastitis. Data was collected from 109 Danish dairy herds over a 5-year period. Statistical analysis demonstrated that the results of vaginal examinations and California mastitis tests on fresh cows were poor predictors of antimicrobial use at the herd level and 52% of the variance in the clinical data could be explained by herd-level factors. The results could be explained by the concept of a treatment threshold within each herd. We suggest that antimicrobial use should be categorised as a decision made by the herd manager rather than an approximation of disease status in the herd.

The effect of individual quarter dry-off in management of subclinical mastitis on udder condition and milk production in organic dairy herds: A randomized field trial.

The objective of the study was to evaluate the effect of individual quarter dry-off in management of subclinical mastitis on clinical development, behavior during milking, and short-term production loss. The study was conducted as a controlled randomized trial in 5 commercial organic dairy herds. Seventy cows meeting the inclusion criteria were randomly allocated to 1 of 2 treatments: individual quarter dry-off (QDO) or continued milking. The inclusion criteria constituted an increase in somatic cell count from below to above 400,000 cells/mL at milk recording and identification of a quarter scoring of at least 3 and higher than the remaining quarters at California mastitis testing (scale 1-5). Quarters were evaluated clinically for atrophy, swelling, firmness, signs of pain, and milk leakage, and rectal temperature of the cows was measured. Behavior during milking was assessed as average frequency of hind limb tripping and kicking during milking obtained by registrations on video recordings. Milk production loss was estimated based on average daily milk yield for 19 d subsequent to treatment start, with reference to average daily milk yield in 19 d before treatment. The QDO treatment was associated with quarter swelling and increased quarter firmness around d 10 from treatment start and with quarter atrophy around d 40 from treatment start. However, around d 40 from treatment start 35% of the dried-off quarters remained nonatrophic and only 6% of the quarters were completely dry. The QDO was associated with signs of pain related to the dried-off quarter. No obvious effects on behavior during milking of QDO treatment was observed. On average the production loss associated with QDO was 4.1 kg/d (95% confidence interval: 3.1-5.0) greater than for continued milking. The production loss depended on parity, days in milk, and prior yield on the quarter subjected to dry-off (Q1). The production loss increased with increasing prior yield on Q1. For the majority of cows the increase in production loss was below 1 kg of milk/d when the prior yield on Q1 increased by 1 kg of milk/d, demonstrating a compensatory production potential of the nontreated quarters. Early lactation multiparous cows showed the greatest compensatory potential. Further studies into the effect on welfare, cure rates, and transmission are needed to determine the feasibility of individual quarter dry-off.

Sow level risk factors for early piglet mortality and crushing in organic outdoor production.

Piglet mortality is a major problem in organic pig production affecting both farm economy and animal welfare. Knowledge is scarce on the risk factors of piglet mortality in Danish commercial organic pig production. The objectives of this study were to evaluate season, litter size, parity, sow body condition and stillborn littermates as risk factors for early piglet mortality and crushing of liveborn piglets from parturition until castration at day 3 to 5 postpartum (pp). The study was conducted over a 1-year period in nine commercial Danish organic pig herds practicing outdoor farrowing all year round. Data included recordings on 3393 farrowings with 50 284 liveborn piglets of which 14.8% died before castration. A subset of the dead piglets were collected and necropsied to identify crushed piglets. The average number of liveborn piglets per litter was 14.8 (SD=3.7) and the average time from parturition until castration was 4.1 (SD=1.7) days. A negative binomial regression analysis was used to model the effect of the predictive variables on the early piglet mortality accounting for different time periods from parturition to castration. An increase in maternal body condition score (BCS) and parity significantly increased the risk of dying between parturition and castration. Early mortality was found to be lowest during spring (March to May) and highest during summer (June to August). Being born into a litter with one or more stillborn littermates increased the risk of early mortality. The risk factors for crushing of piglets were evaluated using a logistic analysis. A significant effect of parity and litter size was found where the odds of at least one piglet in a litter with mortality was diagnosed as crushed increased with increasing parity and litter size. In conclusion, being born during summer (June to August), high parity and maternal BCS and stillborn littermates were found to be risk factors for piglet mortality between parturition and castration. In addition, parity and increasing litter size were found to be risk factors for crushing of piglets in litters with mortality.

Sow-level risk factors for stillbirth of piglets in organic sow herds.

In Danish organic pig production, one-third of total born piglets die before weaning, and stillbirth has previously crudely been estimated to account for 27% of the total preweaning mortality. The objective of this study was to evaluate season, litter size, parity and body condition of the sow as risk factors for stillbirth in nine commercial Danish organic pig herds. The study was conducted over a 1-year period, and the data included registrations on 5170 farrowings with 82 906 total born piglets. The average number of total born piglets per litter was 16.0, and the number of stillborn piglets per litter was 1.1. A significant effect of season was seen with an odds ratio for stillbirth of 1.15 during summer (May to August) compared with the remaining part of the year. A non-linear effect of litter size was seen where an increase in litter size from 11 to 16 resulted in an odds ratio of stillbirth of 1.11. An increase in litter size from 16 to 21 resulted in an odds ratio of stillbirth of 1.45. A significant interaction between body condition and parity was present. In first parity sows, an increase in body condition score from 2 (thin) to 3 (moderate) and from 3 to 4 (fat) increased the probability of stillbirth with an odds ratio of 1.23 and 1.36, respectively. In sows with parity above 4, an increase in body condition score from 2 to 3 and from 3 to 4 decreases the probability of stillbirth with an odds ratio of 0.68 and 0.79, respectively. In conclusion, increasing litter size and being born during the summer months of May to August were found to be risk factors for stillbirth. Furthermore, an interaction between body condition and parity showed that thin sows with parity above 4 had a substantially increased risk of stillbirth compared with normal and fat sows with parity above 4. In contrast, for parity 1 sows risk of stillbirth was increased in fat sows.

Evaluation of effects of metritis management in a complex dairy herd health management program.

Evaluating the effects of all interventions in a dairy herd, including the effects of various herd health management programs (HHMP), is highly relevant. A traditional randomized controlled trial is the gold standard but is likely practically impossible or prohibitively expensive to use for a general evaluation of a HHMP. Generalizability may also be poor because of the dynamics of the production contexts. In this study, we demonstrate an approach for evaluating the effects of an HHMP in the field, specifying an intervention theory for an ongoing HHMP in the context of the Danish dairy industry. As an example, we suggest one coherent analytical approach for studying the possible effects on milk production of systematic postpartum examinations of vaginal discharge, which is supposed to improve detection and treatment of metritis or endometritis. This routine is one component of the HHMP. The data consisted of 121 herds and 76,953 lactations over a 15-yr period. For parity group 1, the negative effects of metritis (despite treatment) on 305-d milk production after a normal calving were reduced by 116 kg of energy-corrected milk after enrollment in the HHMP. For parity group 2 and parity group >2, enrollment in the HHMP resulted in a 129-kg and an 80-kg energy-corrected milk yield increase in milk production, respectively. The results indicate that effects of the HHMP existed, which were mediated through improved metritis detection. This study demonstrates the importance of a clear-cut intervention theory, although even with a theory, the research question can be too herd and context specific. In such a case, a within-herd randomized controlled trial study design seems to be the only way to achieve a valid result for a given herd, and acquiring valid results from an observational multi-herd study will be very difficult.

Latent class evaluation of a milk test, a urine test, and the fat-to-protein percentage ratio in milk to diagnose ketosis in dairy cows.

In this study, 3 commonly used tests to diagnose ketosis were evaluated with a latent class model to avoid the assumption of an available perfect test. The 3 tests were the KetoLac BHB (Sanwa Kagaku Kenkyusho Co. Ltd., Nagoya, Japan) test strip that tests milk for ß-hydroxybutyrate, the KetoStix (Bayer Diagnostics Europe Ltd., Dublin, Ireland) test strip that tests urine for acetoacetate, and the fat-to-protein percentage ratio (FPR) in milk. A total of 8,902 cows were included in the analysis. The cows were considered to be a random sample from the population of Danish dairy cattle under intensive management, thus representing a natural spectrum of ketosis as a disease. All cows had a recorded FPR between 7 and 21 d postpartum. The KetoLac BHB recordings were available from 2,257 cows and 6,645 cows had a KetoStix recording. The recordings were analyzed with a modified Hui-Walter model, in a Bayesian framework. The specificity of the KetoLac BHB test and the KetoStix test were both high [0.99 (0.97-0.99)], whereas the specificity of FPR was somewhat lower [0.79 (0.77-0.81)]. The best sensitivity was for the KetoStix test [0.78 (0.55-0.98)], followed by the FPR [0.63 (0.58-0.71)] and KetoLac BHB test [0.58 (0.35-0.93)].

Time to the occurrence of a decline in milk production in cows with various paratuberculosis antibody profiles.

Infection with Mycobacterium avium ssp. paratuberculosis (MAP) in dairy cattle often results in reduced milk production and premature culling. Some test-positive animals can live for years without being affected by infection, whereas others are test negative when they die from the infection. Our objective was to describe the deviation in milk production of cows with various MAP antibody profiles compared with their repeatedly test-negative herdmates in the same parity. Data were obtained from herds participating in the Danish control program on paratuberculosis, for which 4 annual MAP antibody ELISA of individual cows were performed per herd per year. A total of 136,489 ELISA results from 38,998 dairy cows in 64 herds were used along with 484,285 test-day records on energy-corrected milk (ECM) yield. Cows were divided into 6 antibody groups based on their repeated milk ELISA results: A0) repeated ELISA negative; A1) ELISA negative, but only once; A2) ELISA negative on the last 3 tests, but with 1 previous positive result; A3) ELISA negative on the last test, but with 1 or more previous positive results; A4) last sample was ELISA positive, but all previous were negative; and A5) at least the last 2 samples were ELISA positive. The expected test-day kilograms of ECM by herd and parity were estimated for cows in antibody group A0. Deviations from expected milk production were then assessed for cows in the other antibody groups relative to the time of the first test-positive ELISA result (D 0). Cows in groups A2, A3, and A5 produced approximately 0.5 kg of ECM/d more than cows in group A0 at 300 d before D 0. Cows in group A4 had a decline in milk production from d 300 before D 0, with daily milk production reduced by 5 kg of ECM at 200 d after D 0. Milk production of cows in group A5 was reduced by 2.5 kg of ECM at 300 d after D 0 compared with 300 d before D 0, whereas cows in groups A2 and A3 produced 0.5 kg of ECM more than cows in group A0. The conclusions of the study were that 1) increasing the number ELISA tests increases the predictive value of ELISA for inference on milk production losses, 2) a combination of ELISA with assessment of observed milk production may be a valuable tool for decisions on culling, and 3) the declines in milk production attributable to MAP occurred over a long time period, and may not be realized by the herd manager without more advanced management tools such as the model proposed here.

Technical indicators of financial performance in the dairy herd.

Monte Carlo simulation was used to predict the long-term financial performance related to the technical performance of dairy herds. The indicators addressed were derived from data collected routinely in the herd. They indicated technical performance that can be affected by the farmer or the consultant, and they were derived from expected cause-effect relations between technical performance and financial performance at the herd level. The study included the indicators shape of lactation curve, reproduction efficiency, heifer management, variation between cows in lactation curve persistency, mortality in cows and calves, dynamics of body condition, and somatic cell counts. Each indicator was defined by 2 or 3 levels, and 2- and 3-factor interactions were included in the simulation experiment, which included 72 scenarios. Each scenario was replicated 200 times, and the resulting gross margin per cow was analyzed as the measure of financial performance. The potential effects of the selected indicators on the gross margin were estimated by means of an ANOVA. The final model allowed estimation of the financial value of specific changes within the key performance indicators. This study indicated that improving the shape of the herd-level lactation curve by 1 quartile was associated with an increase in gross margin of euro 227 per cow year. This represents 53% of the additional available gross margin associated with all the management changes included in the study. The improved herd-level lactation curve increased the gross margin 2.6 times more than improved reproduction efficiency, which again increased the gross margin 2.6 to 5.9 times more than improved management related to heifers, body condition score, mortality, and somatic cell counts. These results were implemented in a simple "metamodel" that used data extracted from ordinary management software to predict herd-specific financial performance related to major management changes. The metamodel was derived from systematic experiments with a complex simulation model that was used directly for advanced herd-specific decision support. We demonstrated the use of these key performance indicators to forecast the financial consequences of different "what-if" herd management options, with emphasis on herd health economics.