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

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

Monitoring and testing dairy herds for metabolic disease.

Clinical impressions of metabolic disease problems in dairy herds can be corroborated with herd-based metabolic testing. Ruminal pH should be evaluated in herds showing clinical signs associated with SARA (lame cows, thin cows, high herd removals or death loss across all stages of lactation, or milk fat depression). Testing a herd for the prevalence of SCK via blood BHB sampling in early lactation is useful in almost any dairy herd, and particularly if the herd is experiencing a high incidence of displaced abomasum or high removal rates of early lactation cows. If cows are experiencing SCK within the first 3 weeks of lactation, then consider NEFA testing of the prefresh cows to corroborate prefresh negative energy balance. Finally, monitoring cows on the day of calving for parturient hypocalcemia can provide early detection of diet-induced problems in calcium homeostasis. If hypocalcemia problems are present despite supplementing anionic salts before calving, then it may be helpful to evaluate mean urinary pH of a group of the prefresh cows. Quantitative testing strategies based on statistical analyses can be used to establish minimum sample sizes and interpretation guidelines for all of these tests.     

Relationship between herd-level incidence rate of energy-related postpartum diseases,general risk factors and claw lesions in individual dairy cows recorded at maintenance claw trimming

Background

Laminitis and energy-related postpartum diseases share several risk factors, indicating a common etiology. Thus, a herd’s incidence rate of energy-related postpartum diseases, such as displaced abomasum and clinical ketosis, might reflect the likelihood of cows to suffer from laminitis-related claw lesions. The aim of this study was to investigate the association between herd-level incidence rate of displaced abomasum and clinical ketosis, general risk factors, and claw lesions in individual cows recorded at maintenance claw trimming.

Methods

The dataset consisted of 6773 trimmings, performed between 2004 and 2006 by professional trimmers, from 3607 Swedish Red and Swedish Holstein cows in 26 herds. The herds were classified as having a high, inconsistent-high or low incidence rate of energy-related postpartum diseases, based on the number of recorded cases of veterinary-diagnosed displaced abomasum and clinical ketosis in the Swedish national animal disease recording system during 2002 to 2006, and observations and interviews in connections with herd visits. Generalized linear mixed models were used to investigate the association between herd-level incidence rate of energy-related postpartum diseases and laminitis-related lesions including sole ulcer and sole hemorrhage; and hygiene-related lesions including interdigital dermatitis, digital dermatitis, heel-horn erosion, verrucose dermatitis, and interdigital hyperplasia; and absence of any claw lesion. Systematic effects, including first-order interactions, with P < 0.05 were included in the models. Herd classification was forced into the models, and a random effect of herd was included.

Results

In comparison to herds with a high incidence rate of energy-related postpartum diseases, low-incidence herds showed a lower odds ratio (OR; 0.2) for laminitis-related lesions in cows trimmed during the summer months. Low-incidence herds also showed numerically lower OR estimates for laminitis-related lesions in all parity classes and a numerically lower OR for hygiene-related lesions. In addition, low-incidence herds showed tendencies towards a numerically higher OR for absence of any lesion, irrespective of trimming season or parity.

Conclusions

Only a few statistically significant associations were found, but several tendencies pointed towards better claw health in herds with low as compared with high incidence rate of energy-related postpartum diseases.     

Influence of feeding management, concentrate intake and energy intake on the risk of hyperketonæmia in Swedish dairy herds

The risk of hyperketonaemia (clinical and subclinical ketosis) and how it is influenced by feeding and management routines was analyzed in 291–354 dairy herds over a 3 year period. The overall frequencies of cows with milk acetone ≥ 0.40 mM ranged between 4.2 and 6.2% in Parity 1 and 12.7 and 13.8% in Parity 2+. The incidence was probably underestimated, as samples were taken once per 30 day period. The risk of hyperketonæmia was higher at low than at high feeding frequencies; most odds ratios (OR) were in the range of 1.0–2.7 for two versus four meals per day. The effect of feeding frequency was most evident on high concentrate rations. A larger amount of concentrate in early lactation was deemed to increase the risk of hyperketonæmia, but not consistently so; OR ranged between 0.4 and 2.7, with highest risks for the Swedish Red and White breed. Feeding forage before concentrate and feeding the cows a meal close to milking time reduced the risk of hyperketonæmia, but the results were inconsistent. Hyperketonæmia occurred more often in herds with feeding barriers than in short stall without feeding barrier. Our findings suggest that a high feeding frequency and a cautious feeding strategy of concentrate early in lactation are important factors in the prevention of subclinical or clinical ketosis.     

An epidemiologic study of disease in 32 registered Holstein dairy herds in British Columbia.

Data recorded in a herd health management system were obtained from 32 registered Holstein dairy herds from British Columbia. Frequencies of disease were described, and the effect of herd, age, year, season, and the interrelationships between diseases within a lactation on the occurrence of disease were evaluated. Lactational incidence rates were computed for diseases with a short period of risk (ie, udder edema, milk fever, retained placenta, metritis, displaced abomasum, and ketosis), whereas for diseases with a longer period of risk (ie, cystic ovaries, mastitis and stable footrot), incidence densities were calculated. Overall, the disease incidence was low and showed an increase in frequency by year, which we attributed to more observing and complete recording by the owner, rather than an actual increase in disease incidence. Most diseases occurred early in lactation and their frequency increased with lactation number; the exception was udder edema, which occurred mainly during the first 2 lactations. An informal path model of disease interrelationships was made conditional on herd. Based on the results we inferred 2 independent pathways: one started by udder edema, and the other by milk fever. Udder edema was directly associated with mastitis occurrence from 0 to 30 d in lactation, metritis, and cystic ovaries. Mastitis from 0-30 d in lactation increased the risk of both mastitis from 31-150 d in lactation and cystic ovaries. Both of these increased the risk of late lactation mastitis. Milk fever was directly related with displaced abomasum, which increased the risk of footrot. In general, diseases that occurred in early lactation tended to increase the risk of other diseases later in lactation.     

Relationship among blood indicators of lipomobilization and hepatic function during early lactation in high-yielding dairy cows

Blood indicators are used as a tool to diagnose metabolic disorders. The present work was conducted to study the relationships among blood indicators of lipomobilization and hepatic function in high-yielding dairy cows. Two groups of Holstein cows were studied: 27 early lactation cows and 14 mid lactation cows from four different herds with similar husbandry characteristics in Galicia, Spain. Blood samples were obtained to measure beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), triglycerides (TG), and the activity of aspartate transaminase (AST) and gamma-glutamyl transferase. Cows in early lactation had higher levels of BHB and NEFA than mid lactation cows. High lipomobilization (NEFA > 400 µmol/L) was detected in 67% and 7% of early lactation and mid lactation cows, respectively, while subclinical ketosis (BHB > 1.2 mmol/L) was detected in 41% and 28% of the early lactation and lactation cows, respectively. TG concentrations were low in all cows suffering subclinical ketosis and in 61% of the cows with high lipomobilization. During early lactation, 30% of cows suffered hepatic lipidosis as detected by levels of AST. Compromised hepatic function was observed in early lactation cows as shown by lower concentrations of glucose, total protein, and urea.     

Bovine Subclinical Ketosis in Dairy Herds in Iran

Subclinical ketosis (SCK) is defined as elevated concentrations of ketone bodies in the absence of clinical signs of ketosis. It is an important metabolic disease in dairy cattle during early lactation and is associated with losses in milk production and several other periparturient diseases. Limited information is available regarding the prevalence of SCK in dairy herds in Iran. The objectives of this study were (i) to determine the incidence of SCK in the dairy herds in Kerman province of Iran using serum beta-hydroxybutyrate (BHB) concentrations, and (ii) to investigate the relationship between serum concentrations of BHB and glucose of cows with SCK. In the present study, 90 multiparous Holstein cows (4-6 years old) from 11 commercial dairy herds were evaluated 3-4 weeks after calving. The distribution of blood BHB concentrations seemed to suggest a cut-off point of 1200 micromol/L between cows with and without SCK. At this cut-off point, 14.4% of tested cows (13/90) were classified as subclinically ketotic, with the prevalence rate within herd ranging from 10% to 20%. Cows with SCK were detected in all the investigated dairies except one. Blood glucose concentrations in cows with SCK were significantly lower (p < or = 0.05) than in cows without SCK, and serum BHB and glucose concentration were inversely correlated (r = -0.43, p < or = 0.05). The results suggest that, using a cut-off of 1200 micromol/L, BHB concentrations can be used during early lactation for diagnosis and to make management decisions for prevention and treatment.     

Disease, production and culling in Holstein-Friesian cows I. The data

A two-and-a-half-year study was undertaken in 32 commercial dairy herds within a 50-mile radius of Guelph, Ontario, in order to provide a comprehensive evaluation of relationships amongst diseases, production parameters and risk of removal in Holstein-Friesian cows. Diseases consisted of common clinical diseases as well as two subclinical diseases (mastitis and ketosis).

The data set consisted of a total of 2875 lactation records from 2008 cows. The means and standard deviations of some of the production parameters were: age 4.9 ± 2.5 year, breed class average for milk 140 ± 26 BCM units, milk production per day of life 18.0 ± 3.8 kg and days to conception 118 ± 60 days. Lactational incidence rates of the more common diseases were: reproductive tract infections 0.182, mastitis 0.168, cystic ovaries 0.104, subclinical ketosis 0.096, retained placenta 0.086 and ketosis 0.074. The average lactation mean log somatic cell count was 179 000 cells/ml. The times postpartum to the first diagnosis of all disease conditions are presented.     

The relationship between herd level disease incidence and a return over feed index in Ontario dairy herds

The objective of the current research was to examine the association of herd level disease incidence with the return over feed (ROF) (milk income minus feed cost) herd profit index offered through Canwest Dairy Herd Improvement. The lactational incidence risks (LIR) for displaced abomasum, retained placenta, clinical mastitis, milk fever, clinical ketosis, and lameness submitted by producers (n = 48) were similar to previous reports. However, there was no negative association of clinical disease LIR's with ROE Subclinical ketosis and subclinical mastitis cumulative incidence were determined during the early postpartum period by using a cow-side test for betahydroxybutyrate in milk and the California Mastitis Test, respectively. Subclinical mastitis was not associated with ROE However, a unit increase in the cumulative incidence of subclinical ketosis was associated with a decrease of dollars 0.015/cow/day in the ROE The results highlight the economic significance that subclinical ketosis may have in Ontario dairy herds.     

The association between Mycobacterium avium subsp. paratuberculosis fecal shedding or clinical Johne's disease and lactation performance on two Minnesota, USA dairy farms

Lactation performance of cows infected with Mycobacterium avium subsp. paratuberculosis (Map) was previously studied using only serum ELISA as a diagnostic method. This study evaluated on two dairy farms in Minnesota, USA the lactation performance (measures of health, production, reproduction, and survival) of cows shedding Map in feces before calving and of cows culled with clinical signs consistent with Johne's disease (JD) during the subsequent lactation. Fecal samples were collected from 1052 cows within 21 day before calving and tested for Map with bacterial culture. Producers’ observed signs of clinical disease (milk fever, retained placenta, metritis, ketosis, displaced abomasum, lameness, mastitis, pneumonia, and JD) and production and reproduction data were recorded for each cow. The association between fecal shedding or clinical JD and lactation performance was evaluated. Logistic regression was used to evaluate the association with any clinical and subclinical diseases as the outcome. General linear model was used to evaluate the association with milk production, and survival analysis techniques were used to evaluate the association with days in the study before culling and days from calving to conception. In 84 cows (8% of 1052 cows) fecal samples were positive for Map (46% light, 26% moderate, and 28% heavy shedders). In multivariable analysis, light, moderate, and heavy fecal shedding cows produced on average 537, 1403, and 1534 kg, respectively, less milk per lactation and 1.4, 5.2, and 7.5 kg, respectively, less milk per day than fecal negative cows. Fecal culture positive cows were less likely to be bred and conceive. In the multivariable analysis the 56 cows culled with presumed JD produced approximately 1500 kg/lactation or 5 kg/day less than all other cows. The negative economic impact implied by decreased lactation performance in cows shedding Map or with clinical JD may motivate producers to implement programs to control Map infection and subsequent JD.     

Metabolic parameters and blood leukocyte profiles in cows from herds with high or low mastitis incidence

The objective of this study was to determine whether there were differences in metabolic parameters and blood leukocyte profiles between cows in herds with high or low yearly mastitis incidence. In this study, 271 cows from 20 high yielding dairy herds were examined. According to the selection criteria, all herds had low somatic cell counts. Ten of the selected herds represented low mastitis treatment incidence (LMI) and ten herds had high mastitis treatment incidence (HMI). The farms were visited once and blood samples were taken from each cow that was in the interval from three weeks before to 15 weeks after parturition. The eosinophil count was significantly lower among cows from the HMI herds in the period from four weeks to 15 weeks after parturition. The plasma concentrations of beta-hydroxybutyrate, glucose, insulin and urea did not differ between groups, but the concentration of nonesterified fatty acids was significantly higher among HMI cows during the period three weeks after parturition. The concentration of the amino acid tryptophan in plasma was significantly lower among the HMI cows prior to parturition. Glutamine was significantly lower in cows from HMI herds during the first three weeks after parturition. Arginine was consistently lower in HMI cows, although the decrease was only significant during the period from four to fifteen weeks after parturition. The results suggest that there were differences in the metabolism and immune status between herds with high or low yearly mastitis treatment incidence indicating an increased metabolic stress in HMI cows.     

Subclinical ketosis: prevalence and associations with production and disease.

Cows in 32 southern Ontario Holstein herds were monitored for subclinical ketosis for a period of two and one half years. Milk samples were routinely collected and the level of milk ketone bodies determined by the use of a commercial nitroprusside based test powder (reactions scored as negative, +1 or +2). Approximately 92% of positive reactions were observed in the first 65 days of lactation and for that time period the prevalence of ketosis was 12.1%. Based on this prevalence, the minimum possible duration of subclinical ketosis would be 7.9 days and the minimum possible lactational incidence rate would be 12.1%. The prevalence during the first 65 days of lactation in individual herds ranged from 0 to 33.9%. Subclinical ketosis was more likely to be found in cows experiencing metritis than in unaffected cows. Detection of elevated levels of milk ketones also indicated that the cow had a significantly higher risk of having clinical ketosis, metritis or cystic ovaries diagnosed within the following four days. Milk ketone scores of +1 and +2 were found to be associated with a reduction in daily milk production of 1.0 and 1.4 kg of milk respectively.     

Cross-sectional study of the association of abomasal displacement or volvulus with serum electrolyte and mineral concentrations in dairy cows

The objective of this study was to evaluate serum mineral and electrolyte concentrations at the time of on-farm diagnosis of left displaced abomasum, right displaced abomasum, or abomasal volvulus in dairy cows. Data were collected from 104 affected cows and 96 control cows matched with cases, based on herd, parity, and stage of lactation. Cows with abomasal displacement or volvulus had significantly lower calcium, phosphorous, magnesium, potassium, and chloride concentrations and increased anion gap at the time of diagnosis compared with control cows from the same herds. The percentages of cases and controls with total serum calcium concentrations below the lower limit of the laboratory reference range (2.08 mmol/L [8.3 mg/dL]) were 70% and 23%, respectively. Based on the large percentage of cases with hypocalcemia, administering calcium salts at the time of treatment of field cases of abomasal displacement or volvulus may be beneficial.     

Compliance with recommended drug withdrawal requirements for dairy cows sent to market in Michigan

By examination of computerized individual cow records from January 1981 through June 1985, compliance with premarketing drug withdrawal times was investigated in 23 dairy herds. During this period, 877 cows were culled from 23 herds; 33 cows from 12 herds were in violation of premarketing drug withdrawal times. Six herds had 1 violation, 2 herds had 2 violations, 2 herds had 3 and 4 violations, and 2 herds had 7 and 9 violations. Fifty drugs had been used; 15 drugs were used in violation of drug withdrawal times before cows were sent to market. The most commonly used drugs in violation were oxytetracycline, gentamicin, chloramphenicol, and a combination of lincomycin/spectinomycin. Significant differences between cows in violation and cows not in violation were not observed for age, lactation number, milk production, herd size, or month of culling. However, the 12 herds in violation of premarket drug withdrawal times had significantly (P less than 0.05) more cows culled within 30 days for retained placenta and milk fever, and more cows culled within 30 and 100 days for mastitis, metritis, and displaced abomasum. Although not significant, the 2 herds with 7 and 9 violations had more hired vs family labor than did the other herds with violations.     

Use of every ten-day criteria for metabolic profile test after calving and dry off in dairy herds

The traditional metabolic profile test cannot be applied to peripartum dairy cows, because these cows are in a state of physiological abnormality making it difficult to interpret their blood components. This study aimed at establishing and evaluating the practicability of interpreting a metabolic profile test every 10 days (Ten-day criteria) during the dry and lactation periods in herds with high and no incidence of peripartum diseases. Data from 29,043 cows in 1,130 commercial dairy herds were used to establish standard values every 10 days, mean +/- 1.0 standard deviation for the metabolic profile test. The practicability of these criteria was evaluated in herds with peripartum diseases. In the ten-day criteria, the body condition score, albumin, blood urea nitrogen, glucose, total cholesterol, nonesterified fatty acids, gamma-glutamyl transpeptidase and aspartate aminotransferase, fluctuated during the dry and early lactation periods and there were very big changes in packed cell volume, blood urea nitrogen, total cholesterol and magnesium just after calving. The ten-day criteria were able to detect overconditioned cows, low levels of albumin, total cholesterol and magnesium, and high nonesterified fatty acids in herds with a high incidence of peripartum diseases. In conclusion, the ten-day criteria can be successfully applied to peripartum cows, and is recommended because it is able to detect metabolic abnormalities not only in the herd, but also in individual cows.     

Risk factors associated with the incidence of veterinary-treated clinical mastitis in Swedish dairy herds with a high milk yield and a low prevalence of subclinical mastitis

We conducted a case-control study to investigate factors associated with the incidence rate of veterinary-treated clinical cases of mastitis (IRVTCM) in Swedish dairy herds with the overall objective to reduce the incidence of clinical mastitis (CM) and excessive use of antibiotics. Herds with documented high milk yield, low prevalence of subclinical mastitis and high (27.3-67.5 cases/100-cow years=case) or low (0.0-10.8 cases/100-cow years=control) IRVTCM were selected for this study. One hundred and fifty-eight herds participated. Logistic-regression models were used to assess statistically significant risk factors associated with a high or low IRVTCM. HI-herd farmers more often contacted a veterinarian for treatment of a cow with CM as soon as the milk appearance was altered, compared to LO-herd farmers that more often waited until the general condition of a cow was altered. HI-herd farmers also treated more cows due to high somatic-cell counts during lactation and/or at drying off. There were more high-yielding cows with dirty lower hind-legs, a higher percentage of first-parity cows and a higher incidence of veterinary-treated teat injuries in HI-herds. HI-herd farmers had their cows claw-trimmed more than once per year, compared to LO-herd farmers that had their cows claw-trimmed only once per year, and the condition of silage storage at HI-farms more often had one or more remarks. LO-herds consisted more often of cows of the Swedish Red and White breed, and their roughage diet was more often complemented with only commercial concentrates compared to HI-herds that more often fed grain in combination with commercial concentrates. The herds participating in this study were all well managed herds, and the attitude towards treatment and production seemed to influence the IRVTCM more than environmental factors.     

Peripartum back fat thickness of multiparous Holstein-Friesian cows with displacement of the abomasum or ketosis

To establish a method to predict postpartum diseases using prepartum back fat thickness (BFT), the peripartum BFTs of 54 healthy multiparous cows before calving, which were diagnosed with postpartum displacement of the abomasum (DA), clinical ketosis or subclinical ketosis were compared with those of healthy cows from 8 weeks before the expected calving date to 8 weeks after calving. The peripartum BFTs of the cows with DA or clinical ketosis were significantly higher than those of healthy cows. The peripartum BFTs of the cows with subclinical ketosis were not significantly higher than those of the healthy cows.     

A study of the role of genetic factors in the etiology of left abomasal displacement.

The ancestry of 69 cows having left displaced abomasum was compared with that of 69 cows (matched for age, farm and lactation) not having experienced left displaced abomasum. A variety of tests were used to ascertain if certain bulls or families of bulls produced daughters with an increased risk of developing left displaced abomasum. However, there were no significant differences between the pedigrees of the affected and nonaffected cows.     

The level of serum ionised calcium, aspartate aminotransferase, insulin, glucose, betahydroxybutyrate concentrations and blood gas parameters in cows with left displacement of abomasum

The purpose of this study was to determine concentrations of serum glucose, aspartate aminotransferase (AST), insulin, beta-hydroxybutyrate (BOH) and ionised calcium (Ica) in dairy cows with left displaced abomasum (LDA) and to compare these parameters before and after surgical correction of LDA. Eighteen Swiss-Holstein dairy cows with LDA were used in this study. Clinically healthy post parturient cows (n: 10) from a local dairy farm were used as control group. Blood samples were collected from the jugular vein from all the cows. Surgery was performed in cows with LDA. Blood samples from cows with LDA were collected 24 hours after surgery. The abomasum was repositioned followed by an omentopexy. Six of the 18 cows with LDA had clinical ketosis as detected with urine dipstick. The mean concentrations of insulin, BOH, glucose and AST in cows with LDA at admission time were increased compared with the healthy cows. But the mean concentration of ICa at admission time was slightly decreased compared with healthy cows. The mean BOH concentration was decreased 24 hours following surgery compared with values on admission time. However, the mean serum AST levels were increased both at admission time and 24 hours after surgery compared with healthy cows. The levels of blood gas parameters in cows with LDA were not significantly different in comparison with healthy cows, although hyperbasemia in six of 18 cows with LDA was determined. In conclusion, the results of this study indicated that serum insulin, glucose, AST and BOH levels were increased in dairy cows with LDA. Serum BOH and ICa levels were decreased 24 hours after surgery compared with values on admission time. All cows with LDA used in this study had subclinical/clinical ketosis. We could say that ketosis might be a risk factor for the displacement of the abomasum.     

Ketosis treatment and milk yield in dairy cows related to milk acetoacetate levels

Milk yield and milk acetoacetate (M-acac) were measured weekly for the first 6 weeks of lactation in 5 herds with a ketosis problem. Ketosis treatments and the corresponding ketotest score, were also recorded. The treatment rate was highest 7-16 days after calving. Most of these early cases were associated with low ketone levels in milk, whereas the treatment rate for cows with high ketone levels was highest 17-31 days after calving. Nearly half of the treated cows were low-ketone animals. They were classified as ketosis cases in the cow health card records, although probably suffering from other post partum disturbances in many instances. About 40% of the cows with high ketone levels recovered spontaneously. Reduction in milk yield associated with peak M-acac levels was transient and moderate. It was concluded that health card statistics overestimates the severity of the ketosis problem in Norway.