Characteristics and management practices associated with milk production in dairy herds in Ohio enrolled in official Dairy Herd Improvement Association programs

OBJECTIVE: To determine herd characteristics and management practices associated with milk production in dairy herds enrolled in official Dairy Herd Improvement Association (DHIA) programs in Ohio. SAMPLE POPULATION: 186 dairy farms in Ohio. PROCEDURE: All herds in official DHIA programs in 9 counties were invited to participate. Information regarding herd characteristics and management practices was obtained, using a standardized questionnaire. Bulk-tank milk samples were obtained for bacteriologic culture. Official DHIA test-day records were obtained, and associations were identified, using multivariable ANOVA procedures. RESULTS: Of 479 eligible producers, 186 (39%) participated, and consecutive bulk-tank milk samples were available for culture from 172 (36%). Streptococcus agalactiae and Mycoplasma spp were not recovered from bulk-tank milk samples, but Staphylococcus aureus was recovered from 64 (37%) herds. Mean (+/- SD) number of lactating cows in participating herds was 97+/-66, with 123 (66%) herds milking < 100 cows. The RHA was significantly associated with number of cows in milk, estimated percentage of herd detected in estrus, reported annual percentage of heifer calves born alive that died before 8 weeks old, percentage days in milk, use of bovine somatotropin during the preceding 2 years, and sex of the person completing the questionnaire. CONCLUSIONS AND CLINICAL RELEVANCE: In this study, the strongest indicator of milk production was number of cows in milk. However, merely adding cows to a herd should not be considered to guarantee increased milk production, because other management traits could be confounded with increased number of cows in a herd.     

Prevalence of fecal shedding of Salmonella spp in dairy herds

OBJECTIVE: To estimate prevalence of Salmonella spp in Ohio dairy farms and to identify potential risk factors for fecal shedding of salmonellae. DESIGN: Cross-sectional study. SAMPLE POPULATION: 105 Ohio dairy farms. PROCEDURE: Individual fecal samples from all mature cows in study herds were tested for Salmonella spp by use of standard bacteriologic culture procedures. Herds were identified as infected if at least 1 cow was shedding Salmonella spp. Information regarding herd characteristics, management practices, and health history were collected. Potential risk factors for herd-level Salmonella infection were identified. RESULTS: In 31% of the study herds (95% confidence interval, 22 to 40%), at least 1 cow was shedding Salmonella spp. Six percent of 7,776 fecal samples contained Salmonella organisms; prevalence within infected herds ranged from < 1 to 97%. Herd size, use of free stalls for lactating and nonlactating cows, and use of straw bedding in nonlactating cows were significantly associated with fecal shedding of Salmonella spp, as determined by use of univariate analysis. By use of multivariate analysis, large herds were more likely to be infected than smaller herds; however, no other factors were associated with Salmonella infection after adjustment for herd size. CONCLUSIONS AND CLINICAL RELEVANCE: Subclinical shedding of Salmonella spp is common in Ohio dairy herds, although we could not identify specific interventions that may influence the prevalence of Salmonella spp on dairy farms. It appears that large herd size and intensive management may provide an environment conducive to Salmonella shedding and chronic dairy herd infection.     

Herd characteristics and management practices associated with bulk-tank somatic cell counts in herds in official Dairy Herd Improvement Association programs in Ohio

OBJECTIVE: To identify herd characteristics and management practices associated with bulk-tank somatic cell counts (BTSCC) in dairy herds in Ohio enrolled in official Dairy Herd Improvement Association (DHIA) programs. SAMPLE POPULATION: 186 dairies in Ohio. PROCEDURE: All herds in official DHIA programs in 9 counties were asked to participate. Extensive information regarding herd characteristics and management practices was obtained, using a standardized questionnaire. Bulk-tank milk samples were requested from all participating herds for bacterial culture. Official DHIA test-day records for January 1997 were obtained from all herds enrolled in official DHIA programs in the 9 counties. Potential associations were identified, using multivariable ANOVA. RESULTS: Participation was 186 of 479 (39%) herds. Streptococcus agalactiae and Mycoplasma spp were not isolated from bulk-tank milk samples. Staphylococcus aureus was isolated from 64 of 172 (37%) of the herds. The BTSCC were inversely associated with peak daily milk production, postmilking teat disinfection, percentage of eligible cows in the herd detected in estrus, and directly related to the extent to which BTSCC was perceived as a herd problem during the preceding 2 years. Type of housing for nonlactating cows and product used for treatment of nonlactating cows also were significantly associated with BTSCC. CONCLUSIONS AND CLINICAL RELEVANCE: Consideration of herd characteristics and implementation of management practices associated with BTSCC could result in increased milk yield and production of milk with lower BTSCC.     

Between-herd prevalence of Mycoplasma bovis in bulk milk in Flanders, Belgium

Mycoplasma bovis (M. bovis) is a highly infectious pathogen of cattle causing pneumonia, polyarthritis, otitis, and less frequently, subcutaneous abscesses, abortions and meningitis. Ineffective drugs treatments, culling of infected cows and loss of milk production can lead to significant economic loss on dairy farms. The early detection of cows excreting M. bovis bacteria to prevent mastitis outbreaks is warranted. Reports suggest that the risk of M. bovis mastitis is higher in larger dairy herds. The objective of this study is to estimate the herd-level prevalence of M. bovis in Flanders, Belgium by culturing bulk tank milk samples taken from dairy farms. Three bulk tank milk samples per dairy herd were taken over four weeks, with collection intervals of two weeks. Culturing was done after pre-incubation using modified Hayflicks media to increase the chances of recovery of bacteria. For the identification of M. bovis, tDNA intergenic spacer PCR was used. In three herds (1.5%) of the 200 herds sampled, M. bovis was isolated from one of the three consecutive bulk tank milk samples. We conclude that in Flanders in 2009 at least 1.5% of the dairy herds had one or more cows excreting M. bovis in the milk. The frequent monitoring of bulk tank milk to detect the presence of M. bovis, especially in expanding herds on farms that often purchase replacement animals, should be encouraged in order to detect the presence of M. bovis and to monitor the success of control procedures following an outbreak of mycoplasmal mastitis in the herd.     

Subclinical laminitis in dairy cows: use of severity of hoof lesions to rank and evaluate herds

Thirteen high-yielding Holstein herds in Ohio were ranked according to the prevalence and severity of lesions associated with subclinical laminitis (pododermatitis aseptica diffusa). One hundred and seventy-three first lactation cows, most of them in their first 100 days of lactation, and 30 pregnant heifers were assessed. The lesions evaluated were yellow waxy discoloration of the sole, haemorrhage of the sole, separation of the white line, and erosion of the heel. Each herd consisted of more than 100 lactating cows and all the herds were producing over 8500 kg of milk per cow on a rolling herd average basis. The lactating cows were housed in cubicles and maintained in concrete yards. The lesions associated with subclinical laminitis were prevalent among the 13 herds, but when each category of lesion was considered independently, significant differences in prevalence and severity were detected among the herds. These differences suggest that it may be possible to make changes in herd management which may influence the prevalence of lesions.     

Herd benefit-to-cost ratio and effects of a bovine mastitis control program that includes blitz treatment of Streptococcus agalactiae

Twelve dairy herds that had participated in the Pennsylvania Dairy Herd Improvement Association (DHIA) program for at least 12 months, that had a 12-month mean DHIA somatic cell count greater than 700,000 cells/ml, and that had greater than 25% of lactating cows infected with Streptococcus agalactiae participated in a herd blitz treatment program. Initially, quarter milk samples for bacteriologic culturing were collected from all lactating cows. Subsequently, all cows identified as infected with Str agalactiae were treated, using a commercial penicillin-novobiocin intramammary infusion product. In addition, a herd mastitis management program of postmilking teat dipping and treatment of all cows at the start of the nonlactating period was instituted. Thirty days after the initial herd visit, samples from all lactating cows were again cultured, and cows infected at that time were treated. Twelve months after the initial herd visit, samples from all lactating cows were again cultured. Mean prevalence of infection with Str agalactiae decreased (P less than 0.05) from 23.0% of quarters and 41.6% of cows initially to 3.4% of quarters and 9.3% of cows at 30 days and 1.6% of quarters and 4.2% of cows at 1 year. Mean herd DHIA somatic cell count decreased (P less than 0.05) from 918,000 cells/ml initially to 439,000 cells/ml at 30 days and 268,000 cells/ml at 1 year.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of paratuberculosis on culling, milk production, and milk quality in dairy herds

OBJECTIVE: To determine the effect of paratuberculosis on culling, milk production, and milk quality in infected dairy herds. DESIGN: Cross-sectional study. ANIMALS: 689 lactating dairy cows in 9 herds. PROCEDURE: Milk, blood, and fecal samples were obtained from all cows. Fecal samples were evaluated via mycobacterial culture. Serum samples were tested with a commercially available ELISA for antibodies against Mycobacterium avium subsp paratuberculosis, and preserved milk samples were tested with an ELISA for antibodies against M paratuberculosis. Mixed effect and proportional hazards models were used to determine the effect of paratuberculosis on 305-day milk, fat, and protein production; somatic cell count linear score; and the risk of culling. RESULTS: Cows with positive results of bacteriologic culture of feces and milk ELISA produced less milk, fat, and protein, compared with herdmates with negative results. No difference in 305-day milk or fat production was detected in cows with positive results of serum ELISA, compared with seronegative cows. The 3 survival analyses revealed that cows with positive results of each test were at higher risk of being culled than cows with negative results. Paratuberculosis status, as determined by use of all 3 diagnostic tests, was not associated with milk somatic cell count linear score. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that for the 9 herds in this study, paratuberculosis significantly decreased milk production and cow longevity.     

Informative Value of an Indirect Enzyme‐Linked Immunosorbent Assay (ELISA) for the Detection of Bovine Viral Diarrhoea Virus (BVDV) Antibodies in Milk

Bulk and individual milk samples from 117 herds located in Brittany (west France) were used to assess: (i) the performance characteristics of an indirect enzyme‐linked immunosorbent assay (ELISA) applied to individual milk for the detection of antibodies to bovine viral diarrhoea virus (BVDV); and (ii) the relationship between the bulk milk result obtained from this test and the within‐herd prevalence of antibody‐positive lactating cows. This ELISA test was based on a monoclonal antibody directed against non‐structural protein NS2‐3 of pestiviruses. At the individual level, based on 1113 matched milk/serum samples, the sensitivity and specificity of this test applied to milk, compared with the virus neutralization test on serum, were 95.0 and 97.7%, respectively. At the herd level, the relationship between the optical density percentage (OD%) of bulk milk and the within‐herd prevalence of antibody‐positive lactating cows was assessed using the receiver operating characteristics (ROC) analysis. Classes of OD% of bulk milk were determined so that they were associated with minimum intraclass and maximum between‐class variances of within‐herd prevalence of antibody‐positive cows. The ROC analysis resulted in two classes of bulk milk results corresponding to different expected levels of within‐herd prevalence. Herds with an OD% of bulk milk <75% and ≥75% had a mean observed prevalence of antibody‐positive cows of 8.9 and 60.6%, respectively. Herds with a bulk milk result <75% were expected to be BVDV free, whereas large variations in prevalence of antibody‐positive cows existed in the herds with OD% ≥75%. The test described in this study is suitable to identify herds likely to have a low prevalence of BVDV antibody‐positive cows.     

Sensitivity of test strategies used in the Voluntary Johne's Disease Herd Status Program for detection of Mycobacterium paratuberculosis infection in dairy cattle herds

OBJECTIVE: To evaluate sensitivities at the herd level of test strategies used in the Voluntary Johne's Disease Herd Status Program (VJDHSP) and alternative test strategies for detecting dairy cattle herds infected with Mycobacterium paratuberculosis. DESIGN: Nonrandom cross-sectional study. SAMPLE POPULATION: 64 dairy herds from Pennsylvania, Minnesota, Colorado, Ohio, and Wisconsin. Fifty-six herds had at least 1 cow shedding M. paratuberculosis in feces; the other 8 herds were free from paratuberculosis. PROCEDURE: For all adult cows in each herd, serum samples were tested for antibodies to M. paratuberculosis with an ELISA, and fecal samples were submitted for bacterial culture for M. paratuberculosis. Sensitivities at the herd level (probability of detecting infected herd) of various testing strategies were then evaluated. RESULTS: Sensitivity at the herd level of the testing strategy used in level 1 of the VJDHSP (use of the ELISA to test samples from 30 cows followed by confirmatory bacterial culture of feces from cows with positive ELISA result) ranged from 33 to 84% for infected herds, depending on percentage of cows in the herd with positive bacterial culture results. If follow-up bacterial culture was not used to confirm positive ELISA results, sensitivity ranged from 70 to 93%, but probability of identifying uninfected herds as infected was 89%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the testing strategy used in the VJDHSP will fail to identify as infected most dairy herds with a low prevalence of paratuberculosis. A higher percentage of infected herds was detected if follow-up bacterial culture was not used, but this test strategy was associated with a high probability of misclassifying uninfected herds.     

Prevalence of Michigan dairy herds infected with Mycobacterium avium subspecies paratuberculosis as determined by environmental sampling

A cross-sectional, stratified random survey of Michigan dairy herds was conducted to estimate the prevalence of herds infected with Mycobacterium avium paratuberculosis (MAP), the causative agent of Johne's disease, in Michigan using targeted environmental sampling. One pooled sample each from the primary manure storage area and a high-traffic common cow area from each herd was collected and cultured for MAP using the ESP^® culture system II. A herd was classified as positive if at least one sample was culture positive for MAP. State, agricultural district, and herd size stratum prevalence were calculated. Information on past MAP testing and cattle purchase history was collected, and logistic regression was performed to determine their importance to the MAP status of the herd. One hundred twenty-seven herds were contacted, and 94 agreed to participate in the study. The environment of 38 (40.4%) herds cultured positive for MAP. MAP was found in all herds (n = 15) with greater than 200 lactating cows. Herds that had tested for MAP or purchased cattle in the previous 5 years were 4.6 and 3.1 times, respectively, more likely to be infected than herds that had not. MAP continues to be prevalent on Michigan dairy farms, especially those with greater than 200 lactating cows. The environmental sampling protocol used in this study is an economically attractive alternative for monitoring herd level prevalence and the progress of Johne's disease control programs at the state or national level. Implementation of such a program would aid states in monitoring Johne's control program progress, and guide changes over time.     

Mycoplasmal mastitis in dairy herds.

Mycoplasmal bovine mastitis is potentially a highly contagious disease that can cause severe economic problems in affected herds. The purchase of replacement heifers and cows are frequently the origin of mycoplasmal mastitis outbreaks in previously Mycoplasma-free herds. Purchased cows and heifers should be quarantined and tested for mycoplasmal mastitis before admission to the regular herd. Detection of Mycoplasma-infected cows by culture of milk is straightforward, although there are problems of sensitivity for its detection in milk samples that are inherent to the nature of the disease and laboratory procedures. After detection of infected cows, the best way to protect the herd is to culture all cows in the herd, cows with clinical mastitis, and all heifers and cows after calving and before entering the milking herd. Control of mycoplasmal mastitis requires test and culling from the herd of Mycoplasma-positive cows if possible. When a large number of cows are infected, strict segregation with adequate management is an option; however, animals in this group should never re-enter the Mycoplama-free herd. The functioning of the milking equipment and milking procedures should be evaluated carefully and any flaws corrected. There is no treatment for mycoplasmal mastitis, and vaccination has not proven to be efficacious to prevent, decrease the incidence, or ameliorate the clinical signs of mycoplasmal mastitis. Waste milk should not be fed to calves without pasteurization. M bovis may cause several other pathologies in animals of different ages on a farm, including pneumonia, arthritis, and ear infections. The survival of mycoplasmas in different farm microenvironments needs to be further investigated for its impact on the epidemiology of the disease.     

Reduction in milk yield associated with Mycobacterium avium subspecies paratuberculosis (Map) infection in dairy cows

To assess the profitability of control schemes for Mycobacterium avium subspecies paratuberculosis (Map)-infection implemented in dairy herds, accurate estimates of its production effects are needed. This study aimed at quantifying the variation in milk yield of dairy cows according to their Map-infection status. The cow-status was determined by combining (i) its testing(s)-result(s) (serum ELISA, faecal culture (FC), PCR, Ziehl staining), (ii) the Map-status of its herd, and (iii) its possible vaccination against Map. A total of 15 490 cows in 569 herds located in western France was considered. The effect on test-day milk yield (TDMY) of the cow-status to Map was assessed separately in parity 1, 2 and 3 or more, using mixed linear models, after adjustment for herd-season (random), days in milk and breed. Average TDMY was significantly lower in cows from herds with at least one Map-infected cow (defined as positive herds). Individual TDMY showed a reduction ranging from 1.58 to 3.30, 2.03 to 2.51, 5.36 to 7.20 kg/day (P < 0.001) depending on parity for unvaccinated cows and testing ELISA-positive, PCR- or FC-positive, and Ziehl-positive, respectively, compared to cows in Map-free herds. The loss in milk yield increased with increased parity in ELISA-positive and Ziehl-positive cows. Cows that were both tested ELISA-positive and vaccinated had a smaller loss in TDMY than those that were unvaccinated. The estimates from this study can be used to further assess the economic impact associated with Map-infection in dairy herds or to help in the culling decisions regarding infected cows.     

Herd management and prevalence of mastitis in dairy herds with high and low somatic cell counts

Thirty-two dairy herds, 16 with low somatic cell counts (LSCC; Dairy Herd Improvement Association 12-month mean herd SCC less than or equal to 150,000 cells/ml) and 16 with high somatic cell counts (HSCC; Dairy Herd Improvement Association 12-month mean herd SCC greater than or equal to 700,000 cells/ml) were evaluated to determine the relationship between the prevalence of mastitis in each herd and each herd's mastitis control and management practices. Once for each herd, duplicate quarter milk samples were collected from the lactating cows, a survey of herd mastitis control, milking hygiene, and management practices of each herd was performed, and milking-machine function was evaluated. Of the 16 herds with LSCC, 2 (12.5%) had Streptococcus agalactiae isolated and 7 (44%) had Staphylococcus aureus isolated. Both organisms were found in all of the herds with HSCC. In herds with LSCC, the mean percentage of quarters infected with Str agalactiae was 0.1%, the mean percentage infected with streptococci other than Str agalactiae was 1.9%, and the mean infected with S aureus was 0.7%. In herds with HSCC, 25.7% of the quarters were infected with Str agalactiae, 3.7% were infected with streptococci other than Str agalactiae, and 7.6% were infected with S aureus. A program of postmilking teat dipping and treatment of all cows at the beginning of the nonlactating period was practiced more frequently in the herds with LSCC (81.3%) than in the herds with HSCC (37.5%). Major differences were not found between the 2 groups of herds in the use of the more common milking hygiene techniques or in the maintenance and functional characteristics of the milking equipment.     

A stochastic model for the simulation of management decisions in dairy herds,with special reference to production,reproduction, culling and income

A stochastic simulation model was developed to study management decisions in dairy herds. The primary purpose of this model is to quantify the economic effects of different culling policies with respect to productive and reproductive failure.Each stimulated herd consists of a fixed number of up to 100 cows (with additional youngstock), individually generated according to various predetermined herd characteristics. Changes in the herd can be followed at 20-day intervals over 15 years. Calculations are repeated 20 times for each alternative, in order to obtain statistically reliable results. Milk production, fat and protein content of the milk, reproductive performance and involuntary disposal are stochastic variables in the model. The major deterministic variables are feed intake, live body weight (including normal carcass value) and number of youngstock.Calculations to test the model's behaviour have been carried out. Results obtained in the basic situation were consistent with averages observed in practice. A sensitivity analysis was used to compare the economic importance of different management issues under identical conditions. Some parameters commonly used as economic indicators, namely 305-day milk production and Fertility Status, were shown to have limited value. Moreover, the results showed again that improvements in fertility traits alone (such as oestrus detection and pregnancy rate) do not affect income greatly. Therefore, a broadening of the content of herd health programs to include other aspects is desirable from an economic point of view. Breeding and culling policy are particularly important. Income decreased considerably when the maximum allowable calving interval was reduced, despite the positive effect on the average calving interval of the herd. Strategic breeding, taking into account the productive capacity of the cows, was the most profitable policy.More precisely defined strategic breeding and culling policies will be evaluated and discussed in a subsequent paper. Meanwhile the present model is being adapted for interactive use in teaching of veterinary and agricultural students.     

Production and related variables in bovine leukaemia virus-infected cows

A newly developed milk dot blot test was used to detect anti-bovine leukaemia virus (BLV) antibody in milk samples from 2079 lactating adult cows from among 61 herds. The milk dot blot test was highly repeatable; the concordance rate, compared with the agar gel immunodiffusion test performed on serum, was 83.5%. All herds contained BLV-positive cows; the prevalence rate was 36%. BLV-positive cows tended to come from larger herds and were older and more often later in lactation. Fourteen production and related variables (herd size, age, days open, days in milk, milk somatic cell count, milk, fat, and protein produced in the current lactation, projected production of milk, fat, and protein, and breed class average deviations for milk, fat, and protein) were compared between BLV-positive and BLV-negative cows. Although somatic cell count, milk produced, and projected production of milk and protein were related significantly to BLV status using simple tests of association, once the variables herd size, age and days in milk were controlled, these differences were removed. Further analyses using logistic (outcome: individual cow BLV status) and least-squares regression (outcome:herd proportion of BLV-positive cows) failed to show an association between any of the measured production or related variables and BLV-positivity. We concluded that the effect of BLV on production and related variables in dairy cows was below the sensitivity of our analytical techniques or was non-existent.Abbreviations ABCA herd average breed class average for milk, fat, and protein production - AVGAGE average age of the herd - ADIM herd average for days in milk - AGID agar gel immunodiffusion - AVGSCC herd average milk somatic cell count - BCA breed class average, a milk, fat and protein production index calculated by comparing a cow's actual 305-day lactation production to the corresponding BCA standard for the same breed, age, and month of calving - BLV bovine leukaemia virus - CALVINT calving interval - COWAGE cow age - DBCA breed class average deviation for milk, fat, and protein production, the difference between an individual cow's BCA and the herd average - DIM days in milk - HS herd size corresponding to the number of lactating cows in a herd - LACT actual amount of milk, fat, and protein produced in a cow's lactation - ODHIC Ontario Dairy Herd Improvement Corporation - PCTPOS percentage of herd that is BLV-positive - PROJ projected 305-day production for milk, fat, and protein by fitting to a standard lactation curve adjusted for days in milk and age at calving - RHBCA rolling herd average for breed class average for milk, fat, and protein production, the average for all cows that completed a lactation (cows must have completed a 305-day lactation) during the previous 12 months - SCC milk somatic cell count     

Reproductive performance and milk production of Israeli-Holstein cows with different supplementation during the dry period]

In three field trials comprising 602 Israeli-Holstein dairy cows, the effect of the dry period ration on reproductive performance, culling rate and milk production was investigated. The cows were fed in groups. The basic dry period rations consisted for two herds of medium quality cereal hay and for one herd of corn straw, which were fed ad libitum. In each herd dry cows were assigned to an experimental and control group. Cows of the experimental group were supplemented with 1.5 to 3 kg of lactating cows mixed ration (LMR), whereas in the control group the amount of supplement was increased by the factor two or 3.3. In the experimental group the amount of the supplement was calculated to achieve levels of net energy and of crude protein close to NRC requirements; in the control group the level of net energy and protein was 12 to 18% higher as compared to the experimental group. The amount of LMR supplement in the experimental group of herds A, B, C were 1.5 kg, 1.9 kg, and 3 kg, respectively. In the control groups these amounts were 5 kg, 3.8 kg, and 6 kg, respectively. The groups fed moderate amounts of LMR supplement had a higher conception rate at first insemination, a higher percentage of cows conceiving and fewer cows culled in the consecutive lactation than cows fed increased amounts of LMR supplement. The lactational incidence of reproductive disorders and the milk production were not affected by the differences in feeding during the dry period. Reproductive performance and culling rate appeared to be more favorable for cows fed moderate amounts of supplement during the entire dry period or during the last 3 to 4 weeks of the dry period.     

Association between anti-F. hepatica antibody levels in milk and production losses in dairy cows

This study was conducted to determine: (1) the associations between anti-Fasciola hepatica antibody levels in milk and some productive and reproductive parameters in dairy cattle, and (2) the threshold antibody level associated with loss of productivity, at both herd and individual level. Anti-F. hepatica antibodies were analysed by MM3-SERO ELISA in milk samples from the bulk tanks of 490 dairy farms and from 686 lactating cows. The results of general linear model analysis revealed a significant (P<0.05) negative association between the F. hepatica infection status at herd level, determined by analysis of specific antibodies in bulk tank milk, and the average herd milk production. Highly positive herds (MM3-SERO ELISA result>0.405) produced an average of 1.5 kg milk/cow per day less than the negative herds. At cow-level, the mixed model analysis also revealed a significant (P<0.05) association between anti-F. hepatica antibody levels and milk yield. A significant (P<0.05) average reduction of 2 kg milk/day was observed in cows with highly positive ELISA results (>0.762) in relation to cows with negative results. The results of the study led us to conclude that MM3-SERO ELISA is a powerful tool that can be successfully applied, if appropriate "economic thresholds" are established, to identify herds and cows suffering from milk production losses associated with natural infection by F. hepatica.     

A multilevel model with clustered management practices differentiating dairy herd environments in southeastern Sicily

Herd environments constitute productivity potentials, or aggregate opportunity outcomes, resulting from management actions taken with the available inputs. Management outcomes from cow nutrition, udder health and milking practices were quantified with the help of surveys of 254 dairy producers in southeastern Sicily. Objectives were to disentangle environmental opportunities by disaggregating herd effects into causal inputs. Average ME milk production was 8640 kg/lactation for the 183 Friesian herds containing 35 lactating cows and 10 dry cows. Seventy-one Brown Swiss herds averaged 6443 kg ME milk from 25 lactating and 10 dry cows. For Friesian (Brown Swiss) herds 10 (11) management practices affected milking performance and 9 (8) practices influenced somatic cell concentration (P<0.05). Multilevel analysis and herd clustering procedures differentiated low from high opportunity herd environments but altering relative weightings among management practices did not further discriminate them. This clustering methodology helps ensure unbiased estimation of management input effects and could help target priority management substitutions and technical support priorities in dairy extension programs.     

Technical and Economic Effects of Culling and Reproduction Strategies in Dairy Cattle Herds Estimated by Stochastic Simulation

Abstract

The objective of this study was to create operational replacement guidelines under various conditions concerning reproductive performance, supply of replacement heifers and individual milk yield. Nine culling strategies were defined by three average insemination periods and by three discrimination policies between high- and low-yield cows. The effect of the nine culling strategies was analysed with combinations of heat detection rate and time of initiation of breeding after calving under two replacement heifer purchase policies: purchase (open herd) and no purchase (closed herd). The strategies were evaluated using a stochastic simulation model that simulated production and reproductive status in herds composed of dual-purpose cattle with additional young stock. The evaluation of the strategies was made in a situation without a milk quota under typical Danish conditions in 1993. Results showed that discriminating between high- and low-yield cows improved net revenue significantly in open herds but not in closed herds. Irrespective of the purchase policy, using longer insemination periods increased net revenue significantly in herds with poor reproductive performance; whereas net revenue in herds with good reproductive performance tended to increase by using shorter insemination periods. The culling rate is a poor figure when evaluating culling strategies and culling strategies should be assessed at herd level rather than per cow.     

Association between milk production, somatic cell count and bacterial dermatoses in three dairy cattle herds

OBJECTIVE: To determine the correlations between three bacterial dermatoses in cattle, milk production and bulk-milk somatic cell count (BMSCC). DESIGN: Field observations in three dairy cattle herds. METHODS: Milk production, BMSCC, fertility and all herd diseases were recorded by computerised dairy management systems. Each herd was visited twice weekly and the clinical signs, course of diseases and morbidity and culling rates were noted. Bulk-tank milk was sampled twice monthly and analysed for somatic cell count. Bacteriological and histological examinations were carried out from samples collected from affected animals in the respective herds. RESULTS: The acute exudative form of dermatophilosis was diagnosed only in first-calving cows. The morbidity rate was 53% and the culling rate was 16% of the affected animals. The BMSCC increased by a factor of 2.4 times, and there was an average loss of milk production of 30%/cow/day in affected animals. Ulcerative lymphangitis was diagnosed in first-calving cows (22%) and older cows (15%). The culling rate was 28%. The BMSCC increased by a factor of 17.3 times, and the average loss of milk production was 5.5%/affected animal/day. Papillomatous digital dermatitis (PDD) was diagnosed in first-calving cows (25%) and in older cows (18%). The culling rate was 8%. The BMSCC increased by a factor of two times, and the average loss of milk production was 1.7%/affected animal/day. CONCLUSIONS: The correlations between three skin diseases (ulcerative lymphangitis, dermatophilosis, papillomatous digital dermatitis), milk production and BMSCC have been found to be unfavourable.