California Dairy Research Articles

The Diagnostic Approach and Public Health Implications of Phorate Poisoning In a California Dairy Herd

Within an hour of the planned feeding of a group of 300 Holstein cattle, a large number of cattle developed tremors, diarrhea, weakness, and paralysis. All cows exposed to the feed, a total of 159, died within 24 hours despite treatment attempts with atropine in approximately 100 animals. An additional 8 exposed animals were culled within a week. A thorough investigation demonstrated the accidental mixing of phorate into the total mixed ration instead of the intended mineral mix. Diagnostics confirming phorate exposure in deceased animals included brain cholinesterase determinations and the analysis of liver, rumen content, milk, and feed for phorate. Phorate is a restricted-use organophosphorus pesticide commonly used in US agriculture because of target pest efficacy, cost, and availability. Even with known human, animal, and ecological risks, organophosphorus pesticides remain the most widely used insecticides in the world today. This necessitates awareness about how to identify pesticide exposure in food animals and the corresponding public health risks for humans, including the potential for meat and milk residues and exposure in children. This report describes a dairy’s catastrophic loss of 167 cows caused by human error and assesses the public health implications therein. Veterinary diagnosticians, public health officials, and veterinarians must be prepared to collaborate in order to advise clients on case work-up, management, and preventive measures.

Risk factors for subclinical intramammary infection in dairy goats in two longitudinal field studies evaluated by Bayesian logistic regression

Identification of risk factors for subclinical intramammary infections (IMI) in dairy goats should contribute to improved udder health. Intramammary infection may be diagnosed by bacteriological culture or by somatic cell count (SCC) of a milk sample. Both bacteriological culture and SCC are imperfect tests, particularly lacking sensitivity, which leads to misclassification and thus to biased estimates of odds ratios in risk factor studies. The objective of this study was to evaluate risk factors for the true (latent) IMI status of major pathogens in dairy goats. We used Bayesian logistic regression models that accounted for imperfect measurement of IMI by both culture and SCC.Udder half milk samples were collected from 530 Dutch and 438 California dairy goats in 10 herds on 3 occasions during lactation. Udder halves were classified as positive or negative for isolation of a major pathogen (mostly Staphylococcus aureus) on bacteriological culture and as positive or negative for SCC (cut-off of 2000×103cells/mL). Potentially controllable risk factors (udder conformation, teat size, teat shape, teat placement, teat-end shape, teat-end callosity thickness, teat-end callosity roughness, caprine arthritis encephalitis-virus infection status, and kidding season), and uncontrollable risk factors (parity, lactation stage, milk yield, pregnancy status, and breed) were measured in the Dutch study, the Californian study or in both studies. Bayesian logistic regression models were constructed in which the true (but latent) infection status was linked to the joint test results, as functions of test sensitivity and specificity. The latent IMI status was the dependent variable in the logistic regression model with risk factors as independent variables and with random herd and goat effects.For the combined data from both studies, the culture-based estimate of apparent prevalence of major pathogens in udder halves was 2.6% (137/5220) and the estimate of the apparent prevalence of high SCC was 11.0% (581/5294). The model was able to estimate the performance characteristics of bacteriological culture and SCC together with the effect of risk factors on the true IMI status. Higher parity, late lactation and low milk yield were significantly related to higher odds of the latent IMI status. The only significant controllable risk factor was an udder base below the hocks.Lack of a perfect reference test is a common problem in veterinary epidemiology and may lead to biased estimates of odds ratios or other measures of association in risk factor studies. The approach described herein can be used to address these problems.

Determining the heritable component of dairy cattle foot lesions

Lameness and hoof health affect dairy cows as an animal welfare issue, in decreased milk production, and in premature culling. Selection schemes for dairy cattle focus on sire contribution to milk production, with little consideration of the cow’s physical structure or disease probability. On 3 commercial California dairies, 6 phenotypic binary hoof traits that contribute to lameness were recorded: white line disease, sole ulcer, other claw horn lesions, foot rot (interdigital phlegmon), foot warts (digital dermatitis), and other lesions. Monthly lactation records were collected from December 2006 to April 2009 with weekly observations of hoof lesions for lame and dry cows. In addition to hoof lesion information, data on cows (n=5,043) included parentage, birth date, freshening date, lactation number, and date of lameness diagnosis. The prevalence of hoof lesions ranged from a low of 2.2% (foot rot) to a high of 17.1% (foot warts). The farm environment increased the odds ratio depending upon the lesion. Lameness was more common in early lactation and as lactation number increased. Using a threshold model, heritabilities and repeatabilities were estimated for each binary trait. The heritability for risk varied by lesion, with the higher estimates being 0.40 (95% confidence interval: 0.20–0.67) for digital dermatitis and 0.30 (95% confidence interval: 0.08–0.63) for sole ulcer. Including terms to account for cow productivity on either a 305-d mature-equivalent basis or a per-lactation basis had minimal effect on the heritability estimates, suggesting that selection for hoof health is not correlated with response to selection for greater milk production and that improvement could be made for both traits. The genetic component lends support for further genetic studies to identify loci contributing to some of the lesion phenotypes such as foot warts or sole ulcers, 2 of the top 3 causes of lameness in dairy cattle.

Turnover rates are decreasing in California dairies

Dairy employees in the San Joaquin Valley are staying longer in their jobs. Our study in 2009 showed that the average length of employment has increased 250% since 1953 and 40% since 1984. However, tenures among non-Hispanic employees were twice as long as among Hispanic employees, suggesting there are opportunities to further increase workforce stability. The reasons why workers leave dairies are mostly the same as they were 30 and 60 years ago. We also compared our 2009 California interview results with recent studies in the eastern United States, where trends were similar.

Characterization of Endotoxin Collected on California Dairies Using Personal and Area-Based Sampling Methods

Endotoxin, found in the cell wall of gram negative bacteria, is an important contributor to the biological activity of agriculture particulate matter (PM). We analyzed endotoxin in PM collected on 13 California dairies and from the breathing zone of 226 workers during the summer months of 2008. Two particle size fractions were measured: PM2.5 and inhalable PM. Recombinant factor C assays were used to analyze biologically active endotoxin, while gas chromatography coupled with mass spectrometry in tandem was used to quantify total lipopolysaccharide. Biologically active endotoxin concentrations in the inhalable PM size fraction from area-based samples ranged from 11–2095 EU/m3 and from 45–2061 EU/m3 for personal samples. Total endotoxin in the inhalable PM size fraction ranged from 75–10,166 pmol/m3 for area-based samples and 34–11,689 pmol/m3 for personal samples. Area-based geometric mean concentrations for biologically active endotoxin and total endotoxin in PM2.5 and inhalable PM size fractions were 3 EU/m3, 149 EU/m3, 60 pmol/m3, and 515 pmol/m3, respectively. Personal geometric mean concentrations in the inhalable PM size fraction were 334 EU/m3, and 1178 pmol/m3. Biologically active and total endotoxin concentration variation was best explained by meteorological data, wind speed, relative humidity, and dairy waste management practices. Differences in endotoxin concentration and composition were found across locations on the dairy.

Seasonal variation in milk production and culling in California dairy herds

Heat stress influences production and health in dairy herds. The effectiveness of different cooling strategies could potentially be assessed by the degree of seasonal variability on production and health within a herd. The first step to develop an assessment tool is to understand the regional seasonal variation in production and health. The aim of this study was to evaluate the seasonal variation on milk production, peak milk, and early culling in California Holstein herds.

Long-term observations on the dynamics of bovine digital dermatitis lesions on a California dairy after topical treatment with lincomycin HCl

The objective of this study was to observe the dynamics of clinical cure and recurrence of the lesions of bovine digital dermatitis for 11 months after treatment with topical lincomycin HCl. The study was a clinical follow-up of 39 active bovine digital dermatitis lesions (from 29 cows). Cows with active, painful bovine digital dermatitis (BDD) lesions on the interdigital commissure of the rear feet were identified on day 0. On day 1, lesions in all cows were photographed and full-skin thickness 6mm punch biopsies were obtained for histological evaluation. All lesions on all cows were treated with topical lincomycin paste under a light bandage. On days 12 and 23, a subsample of 10 lesions was randomly selected, photographed, and biopsied. On day 37, all lesions on all cows were photographed and biopsied. After day 37, lesions were evaluated on a monthly basis. All lesions were photographed at each observation until day 341 (end of study) but only cows that had macroscopically active lesions were biopsied. Of the 39 lesions treated on day 1, 21 (54%) required re-treatment on at least one occasion before day 341. Macroscopic classification agreed well with histological classification when lesions were small, focal and active (M1 lesions) or large, ulcerative and active (M2), but agreement was variable for lesions that had healed macroscopically (M5) or that were chronic (M4). A transition model showed that M1 and M2 lesions were 27 times more likely to be an M2 lesion on the next observation than to be a healed (M5) lesion.

Cost-effectiveness of diagnostic strategies to identify Mycobacterium avium subspecies paratuberculosis super-shedder cows in a large dairy herd using antibody enzyme-linked immunosorbent assays, quantitative real-time polymerase chain reaction, and bacterial culture

Diagnostic strategies to detect Mycobacterium avium subsp. paratuberculosis (MAP) super-shedder cows in dairy herds have been minimally studied. The objective of the current study was to compare the cost-effectiveness of strategies for identification of MAP super-shedders on a California dairy herd of 3,577 cows housed in free-stall pens. Eleven strategies that included serum or milk enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qPCR) or culture of environmental samples, pooled or individual cow fecal samples, or combinations thereof were compared. Nineteen super-shedders (0.5%) were identified by qPCR and confirmed by culture as cows shedding ≥ 10,000 colony forming units (CFU)/g feces (median of 30,000 CFU/g feces). A stratified random sample of the study herd based on qPCR results of fecal pools was the most sensitive (74%) strategy and had the highest cost ($5,398/super-shedder). The reference strategy with the lowest cost ($1,230/super-shedder) and sensitivity (47%) included qPCR testing of fecal samples from ELISA-positive lactating (milk) and nonlactating (serum) cows housed in pens with the highest MAP bioburden. The most cost-effective alternative to the reference was to perform qPCR testing of fecal samples from ELISA-positive cows (milk and serum for milking and dry cows, respectively) for a sensitivity of 68% and cost of $2,226/super-shedder. In conclusion, diagnostic strategies varied in their cost-effectiveness depending on the tests, specimen type, and labor costs. Initial qPCR testing of environmental samples from free-stall pens to target cows in pens with the highest MAP bioburden for further testing can improve the cost-effectiveness of strategies for super-shedder identification.

Economic sustainability of a biomass energy project located at a dairy in California, USA

Previous experience has demonstrated the tenuous nature of biomass energy projects located at livestock facilities in the U.S. In response, the economic sustainability of a 710kW combined heat and power biomass energy system located on a dairy farm in California was evaluated. This biomass energy facility is unique in that a complete-mix anaerobic digester was used for treatment of manure collected in a flush-water system, co-digestates were used as additional digester feedstocks (whey, waste feed, and plant biomass), and the power plant is operating under strict regulatory requirements for stack gas emissions. Electricity was produced and sold wholesale, and cost savings resulted from the use of waste heat to offset propane demand. The impact of various operational factors was considered in the economic analysis, indicating that the system is economically viable as constructed but could benefit from introduction of additional substrates to increase methane and electricity production, additional utilization of waste heat, sale of digested solids, and possibly pursuing greenhouse gas credits. Use of technology for nitrogen oxide (NOx) removal had a minimal effect on economic sustainability.

Estimate of colostral immunoglobulin G concentration using refractometry without or with caprylic acid fractionation

Our objectives were to evaluate the use of refractometry as a means of estimating immunoglobulin G (IgG) concentration of bovine maternal colostrum (MC) and determine if fractionation of MC using caprylic acid (CA) improved estimates of IgG. Samples (n=85) of MC were collected from a single dairy in California and used to determine the method of CA fraction that produced the best prediction of IgG based on CA fractionation followed by refractometry. Subsequently, samples of MC (n=827) were collected from 67 farms in 12 states to compare refractometry with or without CA fractionation as methods to estimate IgG concentration. Samples were collected from the feeding pool and consisted of fresh (n=196), previously frozen (n=479), or refrigerated (n=152) MC. Samples were further classified by the number freeze-thaw cycles before analysis. Fractionation with CA was conducted by adding 1mL of MC to a tube containing 75μL of CA and 1mL of 0.06 M acetic acid. The tube was shaken and allowed to react for 1min. Refractive index of the IgG-rich supernatant (nDf) was determined using a digital refractometer. Whole, nonfractionated MC was analyzed for IgG by radial immunodiffusion (RID) and refractive index (nDw). The relationship between nDf and IgG (r=0.53; n=805) was weak, whereas that between nDw and IgG was stronger (r=0.73; n=823). Fresh samples analyzed by refractometry that subsequently went through 1 freeze-thaw cycle before RID analysis resulted in the strongest relationship between IgG and nDf or nDw (r=0.93 and 0.90, respectively). The MC samples collected fresh on the farm but frozen 2 or more times before analysis by refractometry or RID had low correlations between IgG and nDf and nDw (r=0.09 and 0.01). Samples refrigerated or frozen on the farm before analysis had weaker relationships between RID and nDf or nDw (r=0.38 to 0.80), regardless of the number of freeze-thaw cycles. Breed and lactation number did not affect the accuracy of either test. These results indicated that refractometry, without or with CA fractionation, was an accurate and rapid method to determine IgG concentration when samples of MC were not previously stored before refractometry and frozen only once before RID analysis.

Occupational exposure to particulate matter and endotoxin for California dairy workers

Occupational exposure of dairy workers to particulate matter (PM) and endotoxin has been considered by some to be of potential concern. This paper reports personal exposure concentrations of PM (μg/m3) and endotoxin (EU/m3) for 226 workers from 13 California dairies. Arithmetic mean personal concentrations for PM2.5, inhalable PM and endotoxin were 48 μg/m3 (N = 222), 987 μg/m3 (N = 225) and 453 EU/m3 (N = 225), respectively. Using mixed effects models, time spent re-bedding of freestall barns versus any other job conducted on a dairy led to the highest exposure for PM2.5, inhalable PM, and endotoxin. Personal exposure concentrations were found to be greater than those reported for ambient area based concentrations at the same dairies. A pseudo R-square approach revealed that one area based measure combined with time spent performing tasks explained a significant portion of variation in personal exposure concentrations.

The combination of abundance and infection rates of Culicoides sonorensis estimates risk of subsequent bluetongue virus infection of sentinel cattle on California dairy farms

Bluetongue (BT) is an important viral disease of ruminants that is transmitted by hematophagous Culicoides midges. We examined the seasonal patterns of abundance and infection of Culicoides sonorensis at four dairy farms in the northern Central Valley of California to develop estimates of risk for bluetongue virus (BTV) transmission to cattle at each farm. These four farms were selected because of their similar meteorological conditions but varying levels of vector abundance and BTV infection of cattle. C. sonorensis midges were collected weekly at each farm during the seasonal transmission period, using three different trapping methods: traps baited with either carbon dioxide (CO2) alone or traps with CO2 and UV light, and by direct aspiration of midges from sentinel cattle. Analysis of BTV-infected midges using group and serotype-specific quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) assays confirmed that BTV serotypes 10, 11, 13 and 17 are all present in the region, but that midge infection rates and the number of BTV serotypes circulating differed markedly among the individual farms. Furthermore, more serotypes of BTV were present in midges than in sentinel cattle at individual farms where BTV circulated, and the virus was detected at each farm in midges prior to detection in cattle. BTV infection rates were remarkably lower among female C. sonorensis midges collected by CO2 traps with UV light than among midges collected by either animal-baited aspirations or in CO2 traps without light. A subsample of female midges examined from each collection method showed no overall differences in the proportion of female midges that had previously fed on a host. Findings from this study confirm the importance of using sensitive surveillance methods for both midge collection and virus detection in epidemiological studies of BTV infection, which is especially critical if the data are to be used for development of mathematical models to predict the occurrence of BTV infection of livestock.

Apparent Prevalence of Congenital Infections in Calves Born on a Single California Dairy Herd

The placenta in cattle prevents in utero transfer of maternal immunoglobulins and leukocytes to the fetus. The fetal immune system, on the other hand, can be exposed to pathogens that cross the placental barrier and mount an immune response to bovine leukosis virus (BLV), infectious bovine rhinotracheitis (IBR), bovine viral diarrhea (BVD) types 1 and 2, Neospora caninum (NC), Leptospira hardjo (LH), and Leptospira Pomona (LP). The objective of this study was to determine the apparent prevalence of congenital infections to common infectious pathogens in calves.

Are respiratory decrements associated with exposure to particles including endotoxins on large California dairies?

ObjectivesTo determine whether exposure to particulate matter (PM) including endotoxins on large California dairies is associated with decreased cross-shift respiratory function.MethodsMale workers at 13 dairies and one control facility wore...

Survey of dairy housing and manure management practices in California

In 2007, a descriptive survey was mailed to all dairies in Glenn (G) and Tulare (T) Counties to identify current and future opportunities of manure management practices on California dairies. The purpose was to provide baseline information for development of outreach curriculum and a decision support tool to quantify potential benefits of various N management options on dairy farms. Such baseline information is valuable to staff regulating dairy facilities (e.g., San Joaquin Valley Unified Air Pollution Control District and Central Valley Regional Water Quality Control Board), dairy trade association representatives, and technology vendors. Response rates for each county were similar at 29.7% (n=19; G) and 26.7% (n=88; T). Mean milking herd size averaged 570 (range 50 to 3,000) cows in G and 1,800 (range 196 to 9,286) cows in T. Survey data are reported by location due to differences between counties in herd size, housing facilities, and climate. Freestalls are common housing facilities (63.2%, G; 38.6%, T) and separated solids and corral scrapings are commonly used as bedding in freestalls (81.8% G and 79.4% T). The most common methods of manure collection were flushing and scraping (18.8%, G; 44.7%, T), only flushing (43.8%, G; 34.1%, T), or only scraping daily or less frequently than daily (37.5%, G; 20.0%, T). Most dairy farms in G (63.2%) and T (70.5%) used some method of separating solids from liquids. However, mechanical separation systems alone were used by 5.3% G and 11.4% T of dairy farms. Storage or treatment ponds were found on 95.9% of dairies. Respondents identified existing manure management practices and did not indicate any new technologies were in use or being considered for manure management. Survey results were used to describe the 2 predominant manure management pathways of manure collection, storage, treatment, and utilization. Survey results will be used to develop and disseminate targeted information on manure treatment technologies, and on-farm evaluation of implemented technologies related to anaerobic digesters, solid liquid separation, and pond additives.

Evaluation of Surveillance Methods for Monitoring House Fly Abundance and Activity on Large Commercial Dairy Operations

Relative house fly, Musca domestica L., activity at three large dairies in central California was monitored during the peak fly activity period from June to August 2005 by using spot cards, fly tapes, bait traps, and Alsynite traps. Counts for all monitoring methods were significantly related at two of three dairies; with spot card counts significantly related to fly tape counts recorded the same week, and both spot card counts and fly tape counts significantly related to bait trap counts 1-2 wk later. Mean fly counts differed significantly between dairies, but a significant interaction between dairies sampled and monitoring methods used demonstrates that between-dairy comparisons are unwise. Estimate precision was determined by the coefficient of variability (CV) (or SE/mean). Using a CV = 0.15 as a desired level of estimate precision and assuming an integrate pest management (IPM) action threshold near the peak house fly activity measured by each monitoring method, house fly monitoring at a large dairy would require 12 spot cards placed in midafternoon shaded fly resting sites near cattle or seven bait traps placed in open areas near cattle. Software (FlySpotter; http://ucanr.org/ sites/FlySpotter/download/) using computer vision technology was developed to count fly spots on a scanned image of a spot card to dramatically reduce time invested in monitoring house flies. Counts provided by the FlySpotter software were highly correlated to visual counts. The use of spot cards for monitoring house flies is recommended for dairy IPM programs.

Rural Cooperatives Magazine, March/April 2011

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Adult House Fly (Diptera: Muscidae) Activity and Age of Females Near Varying Levels of (<I>Z</I>)-9-Tricosene on a Southern California Dairy

The number of adult male and female house flies, Musca domestica L. (Diptera: Muscidae), near varying levels of (Z)-9-tricosene alone (5, 50, or 100 micdrol) or combined (50 microl) with sugar was determined using conical screened traps on a dairy in southern California. Overall, significantly more males than females were collected in the traps. Significantly more flies (male and female) were collected in traps with (Z)-9-tricosene. There were no significant differences among doses of (Z)-9-tricosene alone, but numbers of both sexes were significantly higher in traps baited with (Z)-9-tricosene and sugar compared with the 5- and 50-microl doses without sugar. The age of female flies collected in traps was determined by pterin analysis. Mean female ages ranged from 94.7 to 99.6 degree-days (6.3-6.8 d of age) and did not differ significantly among treatments. Dissections of a subset of females from each treatment determined that collected females were primarily nongravid (86.3%). Proportions of gravid females that were collected did not differ among treatments.

Emissions of volatile fatty acids from feed at dairy facilities

Abstract Recent studies suggest that dairy operations may be a major source of non-methane volatile organic compounds in dairy-intensive regions such as Central California, with short chain carboxylic acids (volatile fatty acids or VFAs) as the major components. Emissions of four VFAs (acetic acid, propanoic acid, butanoic acid and hexanoic acid) were measured from two feed sources (silage and total mixed rations (TMR)) at six Central California Dairies over a fifteen-month period. Measurements were made using a combination of flux chambers, solid phase micro-extraction fibers coupled to gas chromatography mass spectrometry (SPME/GC–MS) and infra-red photoaccoustic detection (IR-PAD for acetic acid only). The relationship between acetic acid emissions, source surface temperature and four sample composition factors (acetic acid content, ammonia-nitrogen content, water content and pH) was also investigated. As observed previously, acetic acid dominates the VFA emissions. Fluxes measured by IR-PAD were systematically lower than SPME/GC–MS measurements by a factor of two. High signals in field blanks prevented emissions from animal waste sources (flush lane, bedding, open lot) from being quantified. Acetic acid emissions from feed sources are positively correlated with surface temperature and acetic acid content. The measurements were used to derive a relationship between surface temperature, acetic acid content and the acetic acid flux. The equation derived from SPME/GC–MS measurements predicts estimated annual average acetic acid emissions of (0.7 + 1/−0.4) g m −2 h −1 from silage and (0.2 + 0.3/−0.1) g m −2 h −1 from TMR using annually averaged acetic acid content and meteorological data. However, during the summer months, fluxes may be several times higher than these values.

Effects of feeding a ruminally protected lysine product, with or without isoleucine, valine and histidine, to lactating dairy cows on their productive performance and plasma amino acid profiles

The literature on post-ruminal lysine supplementation to diets of lactating dairy cows shows generally small negative responses to supplemental intestinally absorbable lysine, and our recent metabolic modeling of California dairy rations predicted other amino acid (AA) that could become co-limiting if supplies of intestinally absorbable lysine were met. The objectives of this study were to estimate the rumen escape potential of a ruminally protected (RP) lysine (RPL) product, and an RPL product also containing isoleucine, valine and histidine (RPAA), to determine effects of feeding these products on performance and plasma AA profiles of high producing dairy cows. Three pens of about 310 multiparous early lactation cows were used in a 3 × 3 Latin square design with 28 day experimental periods in which the basal total mixed ration (TMR) was the same for all groups except for the RP products which were added to the treatment pens at a level designed to deliver an equal amount of intestinally absorbable l-lysine to both RP groups. However rumen stability was slightly higher for the RPL versus the RPAA, and the RPL was calculated to deliver ∼13.2 g/d of intestinally absorbable lysine and the RPAA calculated to deliver ∼10.6, 5.4, 2.2 and 1.6 g/d of intestinally absorbable lysine, isoleucine, histidine and valine respectively. Only milk protein proportion was increased when RPL was fed. However, replacement of the RPL with the RPAA increased milk and milk lactose yields, while milk protein and energy outputs tended to increase. Plasma levels of both non-essential and essential AA, including lysine, were not impacted by feeding the RPL or RPAA. Overall, feeding the RPL alone was judged to cause a generally reduced productive performance, which could be interpreted to suggest that lysine was not supplied in sufficient quantity or that it was not required. Feeding the RPAA versus the RPL increased productive performance of the cows overall, which could support an overall hypothesis that lysine alone resulted in an imbalance and/or deficiency of isoleucine, histidine and/or valine which was alleviated by their supplementation. Overall treatment differences, regardless of their statistical significance, were small and of very limited practical application. Nevertheless, feeding a complex of RPAA was beneficial beyond supplementation of RP lysine alone, but more research on AA imbalances will be required in order to determine effects of supplementation of RP amino acids.