Herd-level economic losses associated with Johne's disease on US dairy operations

Johne's disease (‘paratuberculosis') is a chronic, infectious, wasting disease that affects dairy cattle. Estimation of its impact on herd productivity and corresponding economic loss on US dairy operations was part of the USDA National Animal Health Monitoring System's (NAHMS) 1996 national dairy study. Johne's-positive herds experience an economic loss of almost US$ 100 per cow when compared to Johne's-negative herds due to reduced milk production and increased cow-replacement costs. For Johne's-positive herds that reported at least 10% of their cull cows as having clinical signs consistent with Johne's disease, economic losses were over US$ 200 per cow. These high-prevalence herds experienced reduced milk production of over 700 kg per cow, culled more cows but had lower cull-cow revenues, and had greater cow mortality than Johne's-negative herds. Averaged across all herds, Johne's disease costs the US dairy industry, in reduced productivity, US$ 22 to US$ 27 per cow or US$ 200 to US$ 250 million annually.     

Association of herd productivity and bulk-tank somatic cell counts in US dairy herds in 1996

OBJECTIVE: To assess the association of bulk-tank somatic cell counts (BTSCC) and the value of herd productivity (milk produced, calves born, and net costs for cow replacements) in US dairy herds in 1996. DESIGN: Randomized stratified national survey of dairy producers. SAMPLE POPULATION: Records from 1,219 dairy herds in the top 20 dairy states. PROCEDURE: Responses for 1,178 herds had complete information for economic analysis. Per-cow value of production was determined for each herd. Data for herds with high (> or = 400,000 cells/ml) and medium (200,000 to 399,999 cells/ml) BTSCC were compared with values for herds with low BTSCC (< 200,000 cells/ml), using a multivariable regression model. RESULTS: In 1996, milk was priced at $0.287/kg ($13/cwt). Herds with low BTSCC annually generated $103.90/cow more in herd productivity than herds with medium BTSCC and $292.39/cow more than herds with high BTSCC. CONCLUSIONS AND CLINICAL RELEVANCE: Increased BTSCC (> 200,000 cells/ml) were associated with a reduced value of productivity per cow. Thus, dairy producers have a financial incentive to seek out and implement cost-effective management practices that will enable them to decrease their BTSCC to < 200,000 cells/ml and maximize herd productivity.     

Costs associated with selected preventive practices and with episodes of clinical mastitis in nine herds with low somatic cell counts

Nine dairy herds (mean size, 149 cows) with bulk-tank milk somatic cell counts of less than 300,000 cells/ml and greater than 80% of cows with Dairy Herd Improvement Association linear somatic cell counts less than or equal to 4 were selected for study. Each herd was monitored for 12 consecutive months. Duplicate quarter-milk specimens were collected from each cow for bacteriologic culturing at beginning of lactation, cessation of lactation, and at the time of each clinical episode of mastitis. Streptococcus agalactiae was never isolated and Staphylococcus aureus was isolated from less than 1% of all quarters. There were 554 episodes of clinical mastitis. During the year of study, the incidence rate of clinical mastitis varied from 15.6 to 63.7% of cows among the 9 herds. Mean costs per cow per year in herd for mastitis prevention were: $10 for paper towels, $3 for nonlactating cow treatment, and $10 for teat disinfectants. Mean cost associated with clinical mastitis was $107/episode. Approximately 84% ($90) of the costs attributed to a clinical episode were associated with decreased milk production and nonsalable milk. Costs of medication and professional veterinary fees per clinical episode varied significantly among the 9 herds. Three of the herds did not have a veterinarian treat a clinical episode of mastitis during the year of study even though 2 of these herds had the first and third highest incidence rates of clinical mastitis. When calculated on a per cow in herd basis, mean costs of $40/cow/year were attributed to clinical mastitis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Loser cows in Danish dairy herds: definition, prevalence and consequences

During the last few years, many Danish dairy farmers have expressed increasing concerns regarding a group of cows, which we have chosen to term ‘loser cows’. Until now, a loser cow has not been described scientifically. We defined a loser cow on the basis of a clinical examination of the cow. A total of 15,151 clinical examinations were made on 6,451 individual cows from 39 randomly selected, large Danish dairy herds with loose-housing systems using a clinical protocol. Scores for the clinical signs lameness, body condition, hock lesions, other cutaneous lesions, vaginal discharge, condition of hair coat and general condition were converted into a loser cow score. Cows with a loser cow score of 8 or more were classified as loser cows. The overall prevalence of loser cows was 2.15%, 4.50% and 2.98% during the first, second and third round of herd visits, respectively.

The associations between the loser cow state and milk production, mortality, morbidity, culling and workload for the farmer were evaluated using data from herd visits and from the Danish Cattle Database and a number of different statistical techniques. It was concluded that the loser cow state has significant negative consequences for both the farmer and the cow. On average, loser cows yielded 0.61 to 2.24 kg energy corrected milk less per day than non-loser cows depending on parity. Hazard ratio for death or euthanasia was 5.69 for loser cows compared to non-loser cows. Incidence rate ratio for disease treatments was 0.69 for non-loser cows compared to loser cows. Loser cows were often culled in an ‘unfavourable’ way and generally caused extra workload for the farmer.

A simplified version of the loser cow score was evaluated and is recommended for future research and use in practice.     

Evaluation of production per day of life calculated on cull cows as a comprehensive monitor of dairy herd performance

The primary objective of this study was to determine the contribution of several management variables to average production per day of life (PPDL). A secondary objective was to compare PPDL between two geographic regions in North America and between dairy herds within the two regions. PPDL was determined for animals culled from four ‘large’ dairy farms in Florida, USA (FL), and eight ‘small’ dairy farms in Prince Edward Island, Canada (PEI). Average milk PPDL was calculated by summing the kilograms of milk produced per cow and dividing by the total number of days from birth until culling. PPDL for the four FL herds (9.50 kg day⁻¹) was significantly higher than PPDL for the eight PEI herds (8.64 kg day⁻¹). PPDL increased in a quadratic fashion with number of lactations. PPDL did not differ between the eight PEI herds. Significant differences in PPDL were identified between the four FL dairy farms.

The regression of PPDL on average lactational milk yield (AVGFCM), number of lactations (LACT), age at first calving and average days to conception explained 94.5% and 92.4% of the variation of PPDL for multiparous cows in the PEI and FL herds, respectively. One variable (AVGFCM) accounted for 68% and 55% of the variance in PPDL for PEI and FL, respectively. The addition of LACT to the model explained 87% and 81% of the variance in PPDL for PEI and FL, respectively.     

非洲奶业发展现状及中非合作潜力研究

奶业是非洲居民重要的收入和就业来源,是重要的农业产业。2018年,非洲奶业生产总值171.22 亿美元,占畜牧业总产值的24.0%;奶牛存栏6 752.49 万头,主要集中在东非、北非和西非地区,养殖方式以散养为主,平均存栏仅3 头,部分品种仍以役用为主,牛奶生产仅是副产品,平均单产512.8 kg/头·年,年生鲜乳产量3 462.85 万t;埃及、肯尼亚和南非是主要的乳制品加工国家,加工量占非洲生鲜乳产量的近30%;2019年乳制品消费量折合生鲜乳为5 468.21 万t,鲜奶是最主要的消费品类,占60%以上,其次是奶粉和奶酪,分别占消费量（折合生鲜乳）的16%和15%,人均消费量有所下降,2019年为41.74 kg/人·年;乳制品贸易长期处于净进口趋势,2018年进口量198.72 万t,进口额48.57 亿美元,北非、西非和东非是主要进口地区。非洲奶牛养殖提升空间巨大,乳制品加工前景广阔,乳制品消费增长空间巨大,中国进一步加强与非洲奶业在奶牛养殖、乳制品加工以及奶业贸易等方面的国际合作,推动奶业走出去。     

Review: Cost of Reproductive Diseases and Conditions in Cattle

Based on information from USDA National Animal Health Reporting System early State pilot studies and more recent national studies, the cost of reproductive diseases and conditions was estimated for beef and dairy cattle. We estimate the total yearly cost of female infertility, abortions/stillbirths, dystocia, retained placentas, and metritis/pyometra to be $441 to $502 million for beef producers and $473 to $484 million for dairy producers with an aggregate national total of approximately $1 billion annually. This loss is over six times more costly than that resulting from respiratory diseases. Three-fourths of the cost for reproductive diseases and conditions can be attributed to female infertility and dystocia and the failure to produce a healthy calf that will survive the first 24 h of life. Aggregate national costs are roughly evenly divided between beef and dairy; per cow costs are more than three times greater for dairy cows ($52.60) than for beef cows ($14.00). Approximately equal national costs are attained because there are more than three times more beef cows than dairy cows. One factor contributing to the greater cost for dairy cows is lost milk production associated with dystocia and retained placentas. Lost milk production accounts for one-third of the costs associated with reproductive diseases and conditions in dairy cattle. We conclude from this review and our resulting estimates that focusing on developing strategies to increase the probability of conception, minimize dystocia, and produce a healthy calf that survives beyond the first 24 h of birth must continue to receive high priority in both dairy and beef cattle management and research.     

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     

Vesicular stomatitis epidemic in colorado: Clinical observations and financial losses reported by dairymen

The financial impact and clinical expression of vesicular stomatitis in Colorado dairy herds was studied during the 1982 epidemic. A non-random sample of 15 dairy herds was surveyed, 13 of which had clinical cases in lactating cows. These 13 herds represented 2404 cows among which were 378 clinical cases. The dairymen reported a distribution of lesions among the cases as follows: 262 (69.3%) oral only; 87 (23.0%) teat only; 22 (5.8%) both oral and teat and 7 (1.9%) with foot lesions. Herds experiencing primarily oral lesions had an attack rate of 19.8% with an average clinical course of 23.8 days. The attack rate in 2 of the 4 herds with teat lesions was 55.8% and 1.6% in the other 2 herds. Mastitis complicated 72% of the cases with teat lesions.The direct costs resulting from 378 cases of vesticular stomatitis reported by 13 dairymen totaled $95 752, which is an average cost of $253.31 per clinical case. The average cost per case with oral lesions is estimated to be $174.06 in contrast to $568.22 average for cases with teat lesions. The greatest loss was due to cows culled, 36.6% of the total direct costs. Decreased milk production was second with 30.3% of the total.The average decrease in milk production per clinical case was 261.3 kg (576 lbs). Deaths accounted for 11.3% of the loss and the combined costs of drugs, extra labour, veterinary service, weight loss and extra ectoparasite control accounted for 11.9% of the $95 752 total.     

Advancing parity is associated with high milk production at the cost of body condition and increased periparturient disorders in dairy herds

The objectives of this study were to determine the effects of parity on milk production, body condition change, periparturient health, and culling in Korean dairy herds. The data utilized included; milk yield, body condition score, cow parity, calving condition, periparturient disorders, culling, and reproductive status, which were recorded from 1290 calvings in eight dairy herds. The mean milk yield in cows over 305 days increased with increasing parity (p < 0.01). Cows with parities of 3, 4, and 5 or higher lost more body condition than those with a parity of 1 during month 1 of lactation (p < 0.01), and body condition recovery by cows with parities of 4 and 5 or higher was slower (p < 0.01) than recovery by cows with parities of 1, 2, or 3 until month 3 of lactation. The risk of retained placenta, metabolic disorder, and endometritis also increased with advancing parity (p < 0.05). Moreover, the incidence of ovarian cysts was lower in cows with a parity of one than in cows with greater parities (p < 0.01). Culling rate due to reproductive failure also increased with advancing parity (p < 0.01). These results suggest that parity increases milk yield, body condition loss during early lactation, the risk of periparturient disorders, and culling due to reproductive failure in dairy herds.     

Milk Production Effect of a Morantel Tartrate Treatment at Calving in Dairy Cows with Subclinical Parasitism

A field trial involving 217 dairy cows from 13 herds located in four different areas of Quebec was conducted to determine the level of subclinical parasitism. The effect on milk production was evaluated on 116 cows following a single anthelmintic treatment with morantel tartrate administered at freshening. The results showed that this treatment increased milk production in nine herds, which was statistically significant at P ≤ 0.05 in one of the herds and decreased yields in four herds. Overall, this treatment increased milk production by an average of 255 kg per cow for the official 305 day production period. This increase was found to be not statistically significant (P>0.05).     

Association between exposure to Neospora caninum and milk production in dairy cows

OBJECTIVE: To determine association between exposure to Neospora caninum and milk production in dairy cows. DESIGN: Prospective observational study. Animals: 565 Holstein cows. PROCEDURE: Cows were classified as seropositive or seronegative to N. caninum within 7 days after calving by use of a kinetic ELISA. Milk production was compared between seropositive and seronegative cows. RESULTS: On the basis of 305-day mature equivalent milk production data, seropositive cows produced less milk (2.8 lb/cow per day) than did seronegative cows. In addition, analysis of results throughout the first 300 days of lactation revealed that after adjusting for effects of lactation number, calving season, clinical mastitis, and lameness, milk weight of seropositive cows was 2.5 lb/cow per day less than that of seronegative cows. CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to N. caninum was associated with a 3 to 4% decrease in milk production. A decrease in milk production of 800 lb/cow for a typical 305-day lactation represents a loss of $128/cow.     

Seroprevalence of infection with Mycobacterium avium subspecies paratuberculosis, bovine leukemia virus, and bovine viral diarrhea virus in maritime Canada dairy cattle

The purpose of this study was to survey the seroprevalence of infection with the agents of production-limiting diseases in dairy cattle in New Brunswick, Nova Scotia, and Prince Edward Island. In 30 randomly selected herds per province, 30 cattle per herd were randomly selected and tested for antibodies to bovine leukemia virus (BLV) and Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis), while 5 unvaccinated cattle over 6 months of age were tested for antibodies to bovine viral diarrhea virus (BVDV). For BLV, 20.8% (15.8% to 27.0%) of cows were positive, and 70.0% (60.3% to 79.7%) of herds had at least one positive cow. In BLV-positive herds, the average BLV prevalence was 30.9% (24.8% to 37.2%). For M. paratuberculosis, 2.6% (1.8% to 3.9%) of cows were positive, and 16.7% (8.8% to 24.5%) of herds had at least 2 M. paratuberculosis-positive cows. In M. paratuberculosis-positive herds, the average M. paratuberculosis prevalence was 8.5% (6.9% to 10.1%). For BVDV, 46.1% (35.5% to 56.7%) of herds had at least 1 BVDV-positive animal with a titer greater than or equal to 1:64.     

Paratuberculosis sero-status and milk production,SCC and calving interval in Irish dairy herds

The objective of this study was to investigate the impact of paratuberculosis sero-status on milk yield, fat, protein, somatic cell count and calving interval in Irish dairy herds. Serum from all animals over 12 months of age (n = 2,602) in 34 dairy herds was tested for antibodies to Mycobacterium avium subsp. paratuberculosis using an ELISA. Herds were categorised by sero-status into positive, non-negative and negative, where a positive herd contained two or more positive cows, a non-negative herd contained only one positive cow and a negative herd contained no positive cows. Data at animal, parity and herd-level were analysed by multiple regression using general linear models. Positive herds (mean herd size = 129 cows) and non-negative herds (81 cows) were larger than negative herds (72 cows) (P < 0.01). Negative herds had the highest economic breeding index (EBI), while positive herds had the highest estimated breeding value (EBV) for milk yield. There was no significant effect of paratuberculosis sero-status at animal, parity or herd-level on milk yield, milk fat or protein production, somatic cell count score (SCCS) or calving interval. Negative herds tended to have a lower SCCS than positive and nonnegative herds (P = 0.087). This study only examined the effects of paratuberculosis sero-status but did not examine the clinical effects of Johne's disease at the farm or dairy industry levels.     

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.     

A comparison of production and management between Wisconsin organic and conventional dairy herds

An observational study was conducted in Wisconsin to compare production and management on organic and conventional dairy farms. Thirty organic dairy herds, where antimicrobials are rarely used for calves and never used for cows, were compared with 30 neighboring conventional dairy farms on which antimicrobials were routinely used for animals of all ages. A seven-page questionnaire regarding milk production, milking practices, housing, incidence of the major dairy diseases and medical treatments was used to assess management and production during 2000-2001. Body condition scores (BCS) of lactating cows and environmental and animal sanitation scores (EASS) were also collected on each of two occasions. The organic herds had significantly fewer cattle than did the conventional herds (P=0.017). The average daily milk production per cow in organic dairy herds (20.2 kg/day) was lower than that of conventional herds (23.7 kg/day). The incidence of clinical mastitis (CM) on organic farms (28 cases per 100 cow-years at risk) was not statistically different from that of on conventional farms (32 cases per 100 cow-years at risk). No significant difference in bulk tank somatic cell count (BTSCC) was observed between organic farms (262,000 cells/ml) and conventional farms (285,000 cells/ml). The average annual cull rate was 18.0 cases per 100 cow-years for the conventional farms and 17.2 for the organic farms (P=0.426). Our paired t-test results indicated significantly higher parasite burden on organic dairy farms; however, no significant difference between the two farm types when controlling for season (March and September), grazing intensity (no grazing, little grazing, grazing with access to housing and grazing only) and herd average milk production per cow. There was little evidence of other fundamental differences between the two farm types in other management and production parameters.     

Effects of bovine leukemia virus infection on production and reproduction in dairy cattle.

The purpose of this study was to determine the effects of bovine leukemia virus (BLV) infection on production, reproduction and longevity in dairy cattle. The study population was a commercial Holstein dairy herd of approximately 400 milking cows. Cattle were tested for antibodies to BLV at least annually for three years and when culled. Four groups of culled cows were compared: seronegative cows (n = 79), seropositive cows without lymphocytosis (n = 176), seropositive cows with lymphocytosis (> or = 9,000 lymphocytes/microliter) (n = 74), and seropositive cows with lymphosarcoma (n = 29). Seropositive groups of cows were bred more times and had longer calving intervals than seronegative cows. The seropositive groups had greater 305-day ME (mature equivalent) FCM (3.5% fat-corrected milk) per lactation and were older when culled than seronegative cows. However, the percent fat per lactation was greater in seronegative cows. In the last complete lactation, differences in 305-day ME FCM, days open and cull age between groups were reduced and none were significant (p > 0.05). In the cull lactation, only cows with lymphocytosis had reduced milk production relative to seronegative cows, although this difference was not significant. After adjustment for initial production and reproductive values, only seropositive nonlymphocytotic cows were culled at a significantly older age than seronegative cattle. Lymphocytotic cows were culled four months younger on average than nonlymphocytotic seropositive cows. Hence, BLV infected cows had greater milk production on average than uninfected cows. Adverse effects of BLV infection were primarily limited to lymphocytotic cows which were culled earlier and had reduced milk production in the cull lactation.     

Distribution and environmental risk factors for paratuberculosis in dairy cattle herds in Michigan.

OBJECTIVE: To determine prevalence of paratuberculosis among dairy cattle herds and to identify associated soil-related risk factors. SAMPLE POPULATION: Serum and soil samples for 121 Michigan dairy herds. PROCEDURE: Blood samples were collected from cows at each farm and tested for Mycobacterium paratuberculosis, using an antibody ELISA. Soil samples were collected from pastures and exercise lots; pH and available iron content were determined. A questionnaire was administered to collect data regarding farm management practices and productivity. RESULTS: 55% of the herds tested had > or = 2 M paratuberculosis-positive cattle. Adjusting sample prevalence for distribution of herd size strata yielded a statewide herd prevalence of 54%. Of 3,886 cattle tested, 267 had positive results. Prevalence of test-positive cattle was 6.9%. For every part per million (ppm) increase in soil iron content, there was a 1.4% increase in the risk of a herd being test-positive. An increase in soil pH of 0.1 was associated with a 5% decrease and an increase in soil iron content of 10 ppm was associated with a 4% increase in the number of test-positive cattle. Application of lime to pasture areas was associated with a herd being only 10% as likely to be paratuberculosis positive and with a 72% reduction in number of test-positive cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Prevalence of paratuberculosis-positive dairy herds in Michigan (54%) was greater than expected, but prevalence of paratuberculosis-positive cattle (6.9%) was within anticipated values. These prevalences were associated positively with acidic soil and increased soil iron content. Application of lime to pasture areas was associated with reduced risk of paratuberculosis.     

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.     

Herd-level economic analysis of the impact of paratuberculosis on dairy herds

OBJECTIVE: To perform a herd-level analysis of economic losses associated with paratuberculosis in dairy herds. DESIGN: Cross-sectional study. SAMPLE POPULATION: A multistage stratified random sample of 121 dairy herds in Michigan. PROCEDURE: A 2-part questionnaire was used to gather data on management practices, herd productivity, labor use, and expenditures. Blood samples were collected from a random sample of cows > or = 2 years old in each herd and tested for antibodies to Mycobacterium paratuberculosis. A herd was considered negative for paratuberculosis if results for all cows tested were negative. Multivariable linear regression was used to evaluate the data. RESULTS: A 10% increase in proportion of cows positive for paratuberculosis was associated with a 33.4 kg (73.5 lb) decrease in mean weight of culled cows. Mortality rate among herds positive for paratuberculosis was 3% higher than rate among herds negative for paratuberculosis. Herds positive for paratuberculosis did not have a significantly higher annual number of hours of labor per cow than did herds negative for paratuberculosis. CLINICAL IMPLICATIONS: For a herd of average size and cull rate, the reduction in mean weight of culled cows attributable to paratuberculosis represented a loss of approximately $1,150 annually for each 10% increase in herd prevalence of paratuberculosis. The increased mortality rate attributable to paratuberculosis represented a loss of between $1,607 and $4,400 on the basis of lost slaughter value and cost of replacement heifers.