A survey of California (CA) dairies was performed in spring 2018 to characterize antimicrobial stewardship practices, antimicrobial drug (AMD) use, and health management of adult cows on CA dairies since the implementation of the Veterinary Feed Directive (VFD) and the CA Senate Bill 27 (SB 27). Effective January 1, 2017, the U.S. Food and Drug Administration (FDA) implemented regulatory changes requiring veterinary oversight for therapeutic uses of medically-important antimicrobial drugs (MIADs) administered in feed (VFD) and water (veterinary prescription). Similarly, effective January 1, 2018, the CA legislature enacted California Food and Agricultural Code (FAC) 14400–14408, formerly known as Senate Bill 27 (SB 27) requiring veterinary prescriptions for all other dosage forms of MIADs.
The questionnaire consisted of 43 questions partitioned into three sections to assess herd information, management practices, and AMD use and perspectives. The questionnaire was mailed to 1,282 grade A licensed dairies in CA and 149 responses (11.6%) were collected from 19 counties across the three defined regions of CA: Northern CA (NCA), Northern San Joaquin Valley (NSJV), and Greater Southern CA (GSCA).
Most dairies reported treating all dry cows with intramammary AMD and/or teat sealant at the end of a lactation (87.2%). In 92.3% of dairies, producers relied on the veterinarian for information about AMD used to treat cows. Treatment duration for cows treated with AMD was based on the drug manufacturer’s label and veterinarian’s instructions in most dairies (98.6%). Most respondents to the survey confirmed having a valid veterinarian-client-patient-relationship (VCPR) for their dairies (91.7%), participated in animal welfare audit programs (81.8%) and dairy quality assurance programs (52.9%). Approximately 98.6% respondents were aware that all uses of MIADs in livestock required a veterinary feed directive (VFD) or prescription and are no longer sold over-the-counter (OTC) in CA since January 1, 2018. Multiple factor analysis (MFA) was performed and identified seven components composed of 21 variables (questions) that explained 99.7% of the total variance in the data. Hierarchical cluster analysis on the principal coordinates of the MFA based on conventional dairy survey responses identified two clusters characterized as large conventional dairies (median herd size: 1,265 cows) and mid-sized conventional dairies (median herd size: 715 cows) mostly in GSCA and NSJV. The organic dairies grouped into a single cluster of median herd size of 325 cows mostly in NCA.
The survey results contribute to the knowledge of AMD use and antimicrobial stewardship practices on CA dairies since the implementation of the SB 27 and VFD laws and provide useful information for future evaluation of resistance-related risk in adult cows.
California (CA) is the leading dairy producing state in the United States, with over 1.7 million dairy cows producing 18.5 percent of the nation’s milk supply on 1,331 dairies (
The development of AMR is a complex multifactorial process driven by numerous factors (
Understanding the complex pathways between on-farm AMD use and AMR in the dairy cattle population is key to antimicrobial stewardship and judicious use. In response to the growing concern surrounding AMR, the U.S. Food and Drug Administration (FDA) in June 2015 announced stricter requirements for administering medically important antimicrobial drugs (MIADs) to animals through feed and water. The law, known as the Veterinary Feed Directive (VFD), mandates supervision by a licensed veterinarian for any use of MIADs in animal feed as of January 1st 2017 (
A survey instrument was designed to collect information about AMD use in adult cows on California dairies. The questionnaire was pre-tested using in-person interviews with extension and outreach specialists and veterinarians. The questionnaire consisted of 43 questions partitioned into three sections: herd information, health management, AMD use, practices and perspectives. Of the 43 questions, 40 were multiple choice questions with the option to specify any available additional information, three questions required the respondent to fill in the requested information. An optional section was included to allow respondents to provide contact information if they were interested in participating in a continuation study and to provide feedback about the questionnaire. The study was reviewed by the University of California, Davis Institutional Review Board and was granted exemption approval (IRB Number: 1537295-1).
A list of all 1,282 licensed, grade A dairies in CA in 2017 provided by CDFA served as a sampling frame. A grade A dairy produces milk used in any products intended for consumption in fluid form (also called fluid grade milk or market milk). A confidential identification number was randomly assigned to all dairies on the list. Each dairy was uniquely identified by this number during analysis to maintain confidentiality. Dairies were mailed a survey packet containing a copy of the questionnaire, a postage-paid addressed business reply envelope, and an information cover letter. The cover letter introduced the dairy producers to the survey and provided an explanation that the term antimicrobial included antibiotics, drugs that are naturally produced by other microorganisms and that can kill or inhibit the growth of other microorganisms, and also synthetic chemicals such as sulfonamides. Producers were instructed that for the purpose of this survey questions will refer to all AMDs as antibiotics regardless of their origin. The estimated time for producers to complete the survey was 30 minutes. To improve questionnaire response rate, each dairy was mailed a reminder card two weeks after the initial questionnaire package. A second and third copy of the questionnaire, each followed by a reminder card, were similarly mailed a month and six months later, respectively, to dairies that had not previously responded. All mailings were completed between April and September 2018.
This section focused on gathering baseline information about the responding dairy. Questions included: the respondent’s role on the dairy, the county where the dairy was located, the breeds of milking cows, the number of milking cows (herd size), the annual rolling herd average for milk production (RHA), the previous month’s average bulk tank somatic cell count in the herd (BTSCC), and if the dairy was a USDA certified organic milk producer.
The questions in this section addressed the farms’ dry-off protocols, types of AMD used at dry-off, disease prevention, and vaccinations used in lactating cows. Additional questions highlighted sources of information on AMD used to treat sick cows, who made the decisions on what AMD are stocked or used to treat sick cows, and whether producers had written or computerized animal health protocols or used a drug inventory log on their dairies. Other questions were considered indicators for AMD usage on the dairy, such as how and which AMD treatment information is tracked, if the dairy tracked AMD withdrawal intervals for treated cows, the farm’s disease diagnosis and management practices, and if the dairy had a working relationship with a veterinarian or veterinary practice.
The final section posed questions relating to the respondent’s participation in animal welfare audit programs and/or dairy quality assurance programs, the respondent’s familiarity with the FDA’s “medically important antimicrobial drugs (MIADs)” term, and awareness that all MIADs required a prescription and were no longer sold OTC in CA after January 1, 2018. Additional questions addressed differences that may have occurred in the periods before and after January 1, 2018 in: the use of OTC and prescription AMD on the dairy, changes made regarding previously available OTC AMD, and changes in the dairy’s AMD drug costs. Similarly, questions inquired about differences before and after January 1, 2018, in usage of alternatives to AMD (defined as vaccines, vitamins, minerals, herbal remedies or others), any changes in management to prevent a disease outbreak or disease spread, and changes noted in animal health on the dairy. The final questions in this section considered how important survey respondents ranked certain AMD use stewardship practices on the dairy, and their level of agreement on statements relating to AMR.
Data on the counties where the dairies were located were categorized into three regions (
Proportions and their standard error (SE) were computed for categorical and ordinal variables. Mean and SE were computed for continuous variables. Confidence intervals for proportions were calculated using the normal distribution approximation method (
Multiple Factor Analysis (MFA), is a dimensionality reduction approach used for the analysis of several groups of quantitative and/or categorical variables (
A total of 149 (11.6%) survey responses from 19 of the 31 dairy producing counties in CA were received through the three mailings (
Question | Estimate (%) | SE | 95% Confidence limits | ||
---|---|---|---|---|---|
Lower | Upper | ||||
Manager | 28 | 18.9 | 3.2 | 13.3 | 26.1 |
Owner | 95 | 64.1 | 3.9 | 56.0 | 71.5 |
Owner-Manger | 22 | 14.8 | 2.9 | 9.9 | 21.6 |
Veterinarian | 3 | 2.0 | 1.1 | 0.6 | 6.1 |
Northern California (NCA) | 21 | 14.1 | 2.8 | 9.3 | 20.7 |
Northern San Joaquin Valley (NSJV) | 58 | 38.9 | 3.9 | 31.3 | 47.0 |
Greater southern California (GSCA) | 70 | 46.9 | 4.0 | 39.0 | 55.0 |
Certified organic | 16 | 10.8 | 2.5 | 6.3 | 16.9 |
Conventional | 132 | 89.2 | 2.5 | 83.0 | 93.6 |
Holstein | 98 | 66.2 | 3.8 | 58.1 | 73.4 |
Jersey | 7 | 4.7 | 1.7 | 2.2 | 9.6 |
Mixed/Other | 43 | 29.1 | 3.7 | 22.2 | 36.9 |
<1305 | 82 | 55.0 | 4.1 | 46.9 | 62.8 |
1305–3500 | 58 | 38.9 | 3.9 | 31.3 | 47.0 |
>3,500 | 9 | 6.0 | 1.9 | 3.1 | 11.2 |
<10,660 | 56 | 41.5 | 4.2 | 33.1 | 50.2 |
≥10,660 | 79 | 58.5 | 4.2 | 49.7 | 66.9 |
<100,000 | 17 | 11.5 | 2.6 | 7.2 | 17.7 |
100,000–199,999 | 88 | 59.5 | 4.0 | 51.3 | 67.1 |
≥200,000 | 43 | 29.0 | 3.7 | 22.2 | 36.9 |
Overall, 87.2% of the respondents blanket treated cows with intramammary (IMM) AMD and/or teat sealant at dry-off (
Question | Estimate (%) | SE | 95% Confidence limits | ||
---|---|---|---|---|---|
Lower | Upper | ||||
Yes | 130 | 87.2 | 2.7 | 80.8 | 91.7 |
No | 19 | 12.7 | 2.7 | 8.2 | 19.1 |
Intramammary antimicrobial | 63 | 49.6 | 4.4 | 40.9 | 58.3 |
Intramammary antimicrobial + Teat sealant | 56 | 44.1 | 4.4 | 35.6 | 52.9 |
Teat sealant only | 8 | 6.3 | 2.1 | 3.1 | 12.1 |
Yes | 22 | 14.7 | 2.9 | 9.8 | 21.4 |
No | 127 | 85.2 | 2.9 | 78.5 | 90.1 |
Intramammary antimicrobial | 9 | 45.0 | 11.1 | 24.2 | 67.7 |
Intramammary antimicrobial + Teat sealant | 10 | 50.0 | 11.1 | 28.1 | 71.8 |
Teat sealant only | 1 | 5.0 | 4.8 | 0.6 | 31.1 |
Cephalosporins | 65 | 52.0 | 4.4 | 43.1 | 60.6 |
Penicillins | 32 | 25.6 | 3.9 | 18.6 | 34.0 |
Cephalosporins or Penicillins | 10 | 8.0 | 2.4 | 4.3 | 14.3 |
Cephalosporins or Penicillins or Aminoglycosides | 2 | 1.6 | 1.1 | 0.3 | 6.2 |
Penicillins or Aminoglycosides | 16 | 12.8 | 2.9 | 7.9 | 19.9 |
Blanket dry cow treatment = an approach to treat every quarter of every cow at drying-off with antimicrobial Cephalosporins = ceftiofur hydrochloride (Spectramast®), cephapirin benzathine (Tomorrow®) Penicillins = cloxacillin benzathine (Orbenin®, Boviclox®), penicillin G procaine/novobiocin (Albadry®) Penicillins-Aminoglycosides combinations = penicillin G procaine/dihydrostreptomycin (Quartermaster®).
The survey showed that 57.7% of respondents provided separate fresh pens, other than the hospital pens, for recently calved cows; 93.9% of the responding dairies’ management included harvesting colostrum from fresh cows to feed newborn calves (
The majority of respondents (92.3%) indicated they relied on a veterinarian or a veterinarian in addition to other sources for information about AMD used to treat their cows (
Approximately one third (38.5%) of dairies included a veterinarian in their decision on which AMD is used to treat sick cows, otherwise, decisions were made by the herd manager (68.4% ± 3.8%), dairy owner (54.3% ± 4.0%), treatment crew (16.1% ± 3.0%), and/or milker (0.7% ± 0.6%), (Note: percentages do not add up to 100% due to multiple selection). For producers who did not include a veterinarian in the decision on which AMD is used to treat sick cows, analysis showed that the majority (91.7% ± 2.9%) had a VCPR for their dairies, while the others had a veterinarian observe or discuss the health of their cows (7.1% ± 2.7%) and served as a source of information about AMD used to treat their cows (1.1% ± 1.1%).
Question | Estimate (%) | SE | 95% Confidence limits | ||
---|---|---|---|---|---|
Lower | Upper | ||||
Veterinarian only | 26 | 18.2 | 3.2 | 12.6 | 25.4 |
Veterinarian + Others | 106 | 74.1 | 3.6 | 66.2 | 80.6 |
Others | 11 | 7.7 | 2.2 | 4.2 | 13.4 |
Include Veterinarian | 69 | 48.9 | 4.2 | 40.4 | 57.5 |
Dairy personnel only | 72 | 51.1 | 4.2 | 42.5 | 59.6 |
Include Veterinarian | 66 | 51.6 | 4.4 | 42.5 | 60.4 |
Dairy personnel only | 62 | 48.4 | 4.4 | 39.5 | 57.4 |
Include Veterinarian | 55 | 38.5 | 4.0 | 30.4 | 46.9 |
Dairy personnel only | 88 | 61.5 | 4.0 | 53.0 | 69.5 |
Yes | 111 | 75.0 | 3.5 | 67.3 | 81.3 |
No | 37 | 25.0 | 3.5 | 18.6 | 32.6 |
Include Veterinarian | 86 | 79.6 | 3.8 | 70.8 | 86.3 |
Dairy personnel only | 22 | 20.4 | 3.8 | 13.7 | 29.1 |
Therapeutic | 83 | 76.1 | 4.0 | 67.1 | 83.2 |
Therapeutic | 26 | 23.9 | 4.0 | 16.7 | 32.8 |
Milk and meat withdrawal interval | 88 | 85.4 | 3.4 | 77.1 | 91.0 |
Milk or meat withdrawal interval | 12 | 11.7 | 3.1 | 6.6 | 19.5 |
No milk or meat withdrawal interval | 3 | 2.9 | 1.6 | 0.9 | 8.7 |
Include Veterinarian | 85 | 77.9 | 3.9 | 69.1 | 84.8 |
Dairy personnel only | 24 | 22.0 | 3.9 | 15.1 | 30.87 |
Yes | 94 | 85.4 | 3.3 | 77.4 | 90.9 |
No | 16 | 14.5 | 3.3 | 9.0 | 22.5 |
Include Veterinarian | 49 | 52.7 | 5.1 | 42.4 | 62.7 |
Dairy personnel only | 44 | 47.3 | 5.1 | 37.2 | 57.5 |
Once to twice a year | 62 | 60.7 | 4.8 | 50.8 | 69.8 |
Every few years | 17 | 16.6 | 3.6 | 10.5 | 25.3 |
When a new product is added | 23 | 22.5 | 4.1 | 15.3 | 31.7 |
Include Veterinarian | 81 | 75.0 | 4.1 | 65.8 | 82.3 |
Dairy personnel only | 27 | 25.0 | 4.1 | 17.6 | 34.1 |
Others = product drug label, drug company material or sales rep, local/national meetings, state/county/university cooperative extension, websites, magazines/industry trade journals, food animal residue avoidance databank, and previous experience with the drug.
Therapeutic = disease specific treatment.
Prophylaxis = vaccination, hoof trimming.
Three quarters (75.0% ± 3.5%) of the respondents indicated having written/computerized animal health protocols (
Approximately 85.4% of the respondents trained their treatment crew members or milkers on treatment protocols for sick cows. A veterinarian was involved in training the treatment crew members or milkers on treatment protocols for sick cows for approximately half (52.7%) of the respondents. Health protocols were reviewed or revised once to twice a year for 60.7% of dairies, when a new product was added for 22.5% of dairies, and every few years for 16.6% of study dairies. Three quarters (75.0%) of the study dairies included veterinarians when reviewing their animal health protocols; the remaining quarter of respondents involved the dairy owner (73.0% ± 4.3%), herd manager (43.2% ± 4.8%), and nutritionist (6.7% ± 2.4%) in protocol review.
Approximately half (50.3%) of the surveyed dairies did not keep a drug inventory log for their dairies (
Question | Estimate (%) | SE | 95% Confidence limits | ||
---|---|---|---|---|---|
Lower | Upper | ||||
Yes | 72 | 49.6 | 4.1 | 41.5 | 57.7 |
No | 73 | 50.3 | 4.1 | 42.2 | 58.4 |
At least two | 17 | 12.4 | 2.8 | 7.8 | 19.1 |
Only one | 53 | 38.6 | 4.1 | 30.8 | 47.1 |
None | 67 | 48.9 | 4.2 | 40.5 | 57.3 |
Veterinarian input | 46 | 32.3 | 3.9 | 25.1 | 40.5 |
No Veterinarian input | 96 | 67.6 | 3.9 | 59.4 | 74.8 |
Drug labels only | 19 | 13.5 | 2.8 | 8.7 | 20.3 |
Drug labels + Veterinarian input | 61 | 43.5 | 4.1 | 35.5 | 51.9 |
Veterinarian input | 58 | 41.4 | 4.1 | 33.5 | 49.8 |
No drug labels/Veterinarian input | 2 | 1.4 | 1.0 | 0.3 | 5.5 |
Pathogen/drug related | 46 | 36.8 | 4.3 | 28.7 | 45.7 |
Veterinarian input | 46 | 36.8 | 4.3 | 28.7 | 45.7 |
Pathogen/drug related + Veterinarian input | 33 | 26.4 | 3.9 | 19.4 | 34.9 |
Milk and meat withdrawal interval + Others | 65 | 45.7 | 4.1 | 37.6 | 54.0 |
Milk or meat withdrawal interval + Others | 49 | 34.5 | 3.9 | 27.0 | 42.7 |
Others | 28 | 19.7 | 3.3 | 13.9 | 27.1 |
Computer + Others | 94 | 64.8 | 3.9 | 56.6 | 72.2 |
No computer | 49 | 33.7 | 3.9 | 26.5 | 41.9 |
Memory | 2 | 1.3 | 0.9 | 0.3 | 5.4 |
Computer + Others | 86 | 61.4 | 4.1 | 53.0 | 69.1 |
No computer | 53 | 37.8 | 4.0 | 30.1 | 46.2 |
Memory | 1 | 0.7 | 0.7 | 0.1 | 4.9 |
Details of drug-related information recorded by dairies farmers include name of drug, cost of drugs, quantity on hand, date of purchase, drug supplier/source, and drug expiration date.
Others include date of treatment, dose, and route.
Others include paper records kept in barn or office, markings on the animal, and white/chalk board or other temporary markings.
Selection of a second AMD to treat a sick animal if the first was not successful was based on veterinarian input for approximately two thirds (63.2% ± 4.3%) of the respondents (
A majority, four-fifths, (80.3% ± 3.3%) of the surveyed dairies confirmed tracking/recording milk, meat, or milk and meat withdrawal intervals along with any of: date, dose, and route of AMD treatment (
The statewide mastitis treatment incidence estimated using the survey responses was 2.9 ± 0.3 mastitis cases/100 milking cow months (
The statewide metritis treatment incidence estimated using the survey responses was 1.9 ± 0.2 metritis cases/100 milking cow months (
The statewide lameness treatment incidence estimated using the survey responses was 1.5 ± 0.2 lameness cases/100 milking cow months (
The statewide pneumonia treatment incidence estimated using the survey responses was 0.3 ± 0.1 pneumonia cases/100 milking cow months (
The statewide postoperative care treatment incidence estimated using the survey responses was 0.04 ± 0.01 postoperative care cases/100 milking cow months (
Question | Estimate (%) | SE | 95% Confidence limits | ||
---|---|---|---|---|---|
Lower | Upper | ||||
Yes | 131 | 91.6 | 2.3 | 85.7 | 95.1 |
No | 12 | 8.4 | 2.3 | 4.8 | 14.2 |
Local veterinarian/Clinic | 123 | 94.6 | 1.9 | 89.0 | 97.5 |
Consultant veterinarian | 7 | 5.3 | 1.9 | 2.5 | 10.9 |
Written agreement signed by veterinarian and owner | 85 | 65.3 | 4.1 | 56.7 | 73.1 |
Verbal agreement between veterinarian and owner | 28 | 21.5 | 3.6 | 15.2 | 29.5 |
Not formally discussed but cows receive veterinary care | 17 | 13.0 | 2.9 | 8.2 | 20.1 |
Within a week | 57 | 40.4 | 4.1 | 32.5 | 48.7 |
Forth nightly | 52 | 36.8 | 4.0 | 29.2 | 45.2 |
Monthly | 14 | 9.9 | 2.5 | 5.9 | 16.1 |
As needed | 18 | 12.7 | 2.8 | 8.1 | 19.4 |
Yes | 69 | 47.5 | 4.1 | 39.5 | 55.7 |
No | 71 | 48.9 | 4.1 | 40.8 | 57.1 |
I don’t know | 5 | 3.4 | 1.5 | 1.4 | 8.0 |
Yes | 108 | 73.4 | 3.6 | 65.6 | 80.0 |
No | 36 | 24.4 | 3.5 | 18.1 | 32.1 |
I don’t know | 3 | 2.0 | 1.1 | 0.6 | 6.1 |
Approximately four-fifths (81.8% ± 3.1%) of surveyed dairies participated in animal welfare audit programs (
Question | Estimate (%) | SE | 95% Confidence limits | ||
---|---|---|---|---|---|
Lower | Upper | ||||
Yes | 122 | 81.8 | 3.1 | 74.7 | 87.3 |
No | 27 | 18.1 | 3.1 | 12.6 | 25.2 |
National program | 119 | 97.5 | 1.4 | 92.5 | 99.2 |
Local program | 3 | 2.5 | 1.4 | 0.7 | 7.4 |
Yes | 72 | 52.9 | 4.2 | 44.4 | 61.2 |
No | 64 | 47.0 | 4.2 | 38.7 | 55.5 |
National program | 13 | 31.5 | 7.5 | 18.5 | 48.3 |
Local program | 26 | 68.4 | 7.5 | 51.6 | 81.4 |
Not sure/Not familiar | 44 | 31.9 | 3.9 | 24.5 | 40.1 |
Know MIAD available only via prescription | 94 | 68.1 | 3.9 | 59.8 | 75.4 |
Yes | 141 | 98.6 | 9.8 | 94.5 | 99.6 |
No | 2 | 1.4 | 9.8 | 0.3 | 5.4 |
Both OTC and prescription AMD were used to treat cows | 93 | 65.9 | 3.9 | 57.6 | 73.3 |
Cows were only treated with prescription AMD | 22 | 15.6 | 3.0 | 10.4 | 22.6 |
Cows were only treated with OTC AMD | 5 | 3.5 | 1.5 | 1.4 | 8.2 |
Cows were not treated with OTC AMD | 15 | 10.6 | 2.5 | 6.4 | 16.9 |
Cows were not treated with prescription AMD | 2 | 1.4 | 0.9 | 0.3 | 5.5 |
Cows were neither treated with OTC nor prescription AMD | 4 | 2.8 | 1.3 | 1.0 | 7.3 |
Cows were treated with OTC AMD | 98 | 72.6 | 3.8 | 64.3 | 79.5 |
Cows were not treated with OTC AMD | 37 | 27.4 | 3.8 | 20.4 | 35.6 |
No changes made | 79 | 56.0 | 4.1 | 47.6 | 64.1 |
Some changes made | 62 | 43.9 | 4.1 | 35.9 | 52.3 |
Yes | 38 | 26.5 | 3.6 | 19.9 | 34.4 |
No | 105 | 73.4 | 3.6 | 65.5 | 80.0 |
Yes | 58 | 40.8 | 4.1 | 33.0 | 49.1 |
No | 84 | 59.1 | 4.1 | 50.8 | 66.9 |
Increased | 35 | 24.4 | 3.5 | 18.0 | 32.2 |
Deceased | 41 | 28.6 | 3.7 | 21.8 | 36.6 |
No change | 67 | 46.8 | 4.1 | 38.7 | 55.1 |
Better | 43 | 31.6 | 3.9 | 24.3 | 39.9 |
Worse | 10 | 7.3 | 2.2 | 3.9 | 13.1 |
No change | 83 | 61.0 | 4.1 | 52.5 | 68.9 |
National program = National Dairy FARM Program, Validus Dairy Animal Welfare Review Certification, Certified Humane® Program.
Local program = Dairy Farmers of America.
National program = National Dairy FARM Program (Validus, Dairy Animal Welfare Review Certification, California Dairy Quality Assurance Program).
Local program = Creamery, On-farm training, Cooperate extension.
FDA = U.S. Food and Drug Administration.
MIAD = Medically Important Antimicrobial Drugs.
OTC = Over-the-counter.
Cows were treated with OTC AMD group comprised dairies that used both OTC and prescription AMD to treat cows and dairies that treated cows with only OTC AMD.
Cows were not treated with OTC AMD group comprised dairies that did not treat cows with OTC AMD and dairies that treated cows with only prescription AMD.
The majority (85.2% ± 2.9%) of survey respondents confirmed the use of OTC and/or prescription AMD on their dairies prior to January 1, 2018. Approximately half (56.0% ± 4.1%) of the studied dairies had not made any changes since January 1, 2018 compared to 2017 with regard to injectable and/or IMM AMD that were previously available OTC. Approximately 43.9% ± 4.1% made changes which included: treating fewer animals with AMD (69.3% ± 5.8%); discontinued one or more AMD (43.5% ± 6.2%); use same AMD but the dosage and duration decreased (19.3% ± 5.0%) or increased (3.2% ± 2.2%); added one or more AMD (1.6% ± 1.5%). No respondents indicated treating more animals with AMD after January 1, 2018 compared to 2017. A quarter (26.5% ± 3.6%) of the study dairies confirmed usage or increased use of alternatives to AMD (vitamins (66.6% ± 8.2%), minerals (60.6% ± 8.5%), herbal remedies (36.3% ± 8.3%), and vaccines (36.3% ± 8.3%)) since January 2018. Approximately 40.8% ± 4.1% confirmed making changes in management to prevent disease outbreaks or spread since January 2018; specifically, these changes included: improvements in vaccination programs to prevent disease (83.0% ± 5.1%); quarantine purchased/returning animals from offsite locations (e.g. fairs, shows, calf ranch) (20.7% ± 5.5%); improved biosecurity (e.g. restricted traffic on operation; better isolation of sick animals, or designated separate equipment for feed and manure handling) (11.3% ± 4.3%); and pre-purchase testing of animals before adding to the herd (5.6% ± 3.1%). More than a quarter (28.6% ± 3.7%) of surveyed dairies confirmed decreased AMD costs on their dairies since January 2018 compared to 2017 and earlier. Additionally, 24.4% ± 3.5% and 46.8% ± 4.1% of the dairies confirmed an increase, and no change, respectively, in costs of AMD on their dairies since January 2018 compared to 2017 and earlier. Furthermore, a third (31.6% ± 3.9%) of the surveyed dairies confirmed better animal health on their dairies since January 2018 compared to 2017 and earlier. Only 7.3% ± 2.2% confirmed worse animal health, while 61.0% ± 4.1% confirmed no change in animal health since January 2018 compared to 2017 and earlier.
The percentage of respondents that blanket treated cows with IMM AMD and/or teat sealant at dry-off were comparable across herd sizes; however, respondents whose average number of milking cows were 3,500 or more exclusively blanket treated cows at dry-off (
The first two principal component dimensions of the MFA explained approximately 14.02% of variability in the survey responses, 9.59% for the first dimension and 4.43% for the second. Seven components with correlation coefficient ≥ 0.4 were identified and retained (
Identified components | Variation proportion (%) | Component variables | Correlation |
---|---|---|---|
35.1 | |||
Mastitis: Basis for treatment decision | 0.576 | ||
Mastitis: Treat with intramammary AMD infusion | 0.695 | ||
Mastitis: Treat with intramammary and oral/injectable AMD | 0.694 | ||
Metritis: Basis for treatment decision | 0.522 | ||
Metritis: Treat with intrauterine/oral/injectable AMD | 0.609 | ||
Lameness: Basis for treatment decision | 0.483 | ||
Lameness: Hoof treatment (wrap/spray/bath), or oral/injectable | 0.504 | ||
Pneumonia: Treatment bolus/injectable treatment | 0.505 | ||
AMD use stewardship practices | 15.6 | Administration of appropriate AMD, dose, route and duration | 0.430 |
Good record keeping on treatments and treatment dates | 0.456 | ||
Having a current veterinarian-client-patient-relationship (VCPR) | 0.415 | ||
Observing withdrawal periods and drug residue avoidance | 0.491 | ||
Using alternatives to AMD (vaccines, minerals, vitamins, herbal remedies) | 0.426 | ||
Familiar with FDA | 14.1 | Use of OTC | 0.502 |
Herd demography | 13.5 | Conventional vs. certified organic dairies | 0.609 |
Annual rolling herd average for milk production | 0.612 | ||
Producer perceptions of AMD on dairies | 13.4 | AMD use in livestock does not cause problems in humans | 0.415 |
Any use of AMD may result in infections that are more difficult to treat in the future | 0.400 | ||
AMD usage information | 7.8 | How do you track AMD treatments given to cows? | 0.476 |
How do you track AMD withdrawal for treated cows? | 0.557 | ||
Dry-off protocols | 6.3 | Classes of AMD used at dry-off | 0.446 |
FDA = U.S. Food and Drug Administration.
MIAD = Medically Important Antimicrobial Drugs.
OTC = over-the-counter.
The profiles of the conventional dairy clusters are described in
Components | Characteristics | Cluster C1 | Cluster C2 |
---|---|---|---|
Herd demography | |||
Northern California | 6.6 ± 2.2a | 0.0 ± 0.0a | |
Northern San Joaquin Valley | 43.4 ± 4.4a | 40.0 ± 15.4a | |
Greater Southern California | 50.0 ± 4.5a | 60.0 ± 15.4a | |
Other | 26.4 ± 4.0a | 30.0 ± 14.4a | |
Hostein | 69.4 ± 4.1a | 70.0 ± 14.4a | |
Jersey | 4.1 ± 1.8a | 0.0 ± 0.0a | |
Herd size (median) | 1,265.0a | 715.0a | |
Rolling herd average (median) | 11,339.8a | 10,092.4b | |
Dry-off protocol | |||
No | 4.9 ± 1.9a | 20.0 ± 12.6b | |
Yes | 95.1 ± 1.9a | 80.0 ± 12.6b | |
Cephalosporins | 50.9 ± 4.6a | 66.7 ± 15.7a | |
Penicillins | 27.1 ± 4.1a | 0.0 ± 0.0b | |
Cephalosporins or Penicillins | 10.5 ± 2.8a | 0.0 ± 0.0a | |
Penicillins or Aminoglycosides | 11.4 ± 2.9a | 33.3 ± 15.7b | |
Disease management | |||
Findings of abnormal milk | 34.5 ± 4.3a | 100.0 ± 0.0b | |
Abnormal milk + Lab testing | 25.2 ± 3.9a | 0.0 ± 00a | |
Abnormal milk + Lab testing + Treat pending test result | 40.3 ± 4.4a | 0.0 ± 0.0b | |
No | 1.6 ± 1.1a | 25.0 ± 15.3b | |
Yes | 98.4 ± 1.1a | 75.0 ± 15.3b | |
Bolus/Injectables | 75.2 ± 3.9a | 100.0 ± 0.0a | |
Intrauterine | 6.8 ± 2.3a | 0.0 ± 0.0a | |
Intrauterine + Bolus/Injectables | 17.9 ± 3.5a | 0.0 ± 0.0a | |
Hoof treatment (antibiotic wrap, heel spray, foot bath) | 28.4 ± 4.3a | 66.7 ± 27.2a | |
Bolus/Injectables | 14.7 ± 3.3a | 0.0 ± 0.0a | |
Hoof treatment + Bolus/Injectables | 56.8 ± 4.7a | 33.3 ± 27.2a | |
Antimicrobial stewardship | |||
Computer + Others | 69.7 ± 4.1a | 40.0 ± 15.4b | |
No computer | 30.3 ± 4.1a | 60.0 ± 15.4b | |
Computer + Others | 66.4 ± 4.2a | 22.2 ± 13.8b | |
No computer | 33.6 ± 4.2a | 77.8 ± 13.8b | |
Very important | 97.5 ± 1.4a | 80.0 ± 17.8b | |
Some importance | 2.5 ± 1.4a | 20.0 ± 17.8b | |
Not important | 0.0 ± 0.0a | 0.0 ± 0.0a | |
Antimicrobial use on dairies | |||
Cows were treated with OTC AMD | 72.3 ± 4.1a | 66.7 ± 27.2a | |
Cows were not treated with OTC AMD | 27.7 ± 4.1a | 33.3 ± 27.2a | |
Producer perceptions of AMD on dairies | |||
Strongly agree/agree | 11.6 ± 2.9a | 40.0 ± 21.9b | |
Neutral | 30.6 ± 4.2a | 20.0 ± 17.8a | |
Strongly disagree/disagree | 57.9 ± 4.5a | 40.0 ± 21.9a |
Blanket dry cow treatment = an approach to treat every quarter of every cow at drying-off with antimicrobial.
AMD = Antimicrobial drug.
Others = markings on the animal, paper records kept in barn or office, white/chalk board or other temporary marking.
OTC = over-the-counter.
Most of the cluster C1 dairies (95.1%) implemented blanket treatment of dry cows with IMM AMD and teat sealant, compared to dairies in cluster C2 (80.0%). Notably, dairies in cluster C1 used multiple AMD classes (cephalosporins, penicillins, and aminoglycosides) for dry cow treatment, dairies in cluster C2 used mainly cephalosporins. Approximately two thirds of the dairies in cluster C1 tracked both AMD treatments given to cows (69.7%) and withdrawal periods for AMD treated cows (66.4%) using a computer, in addition to other methods. The reverse was true for dairies in cluster C2, approximately two fifths (60.0%) do not track AMD treatments and two thirds (77.8%) do not track AMD withdrawal periods using a computer.
For mastitis treatment, dairies in cluster C1 relied mostly on clinical signs and laboratory testing, and tended to treat cows while culture results, if any, were pending. Dairies in cluster C2 relied mostly on clinical signs. Most C1 dairies (98.4%) treat mastitis with AMD, compared to 75.0% in C2. For metritis treatment, dairies in cluster C2 totally relied on oral/injectable AMD, while cluster C1 relied on both oral/injectable AMD and intrauterine treatment. Similarly, dairies in cluster C2 managed lameness in adult cattle using mostly hoof treatment and less of oral/injectable AMD compared to dairies in C1.
Most dairies in cluster C1 (97.5%) strongly agreed that administration of appropriate AMD, dose, route and duration are important AMD stewardship practices compared to less in C2 (80.0%). However, responding to questions relating to AMD resistance, more dairies in cluster C2 (40.0%) strongly agreed with the statement “
All the survey’s organic dairies formed a single cluster characterized by multiple breeds with Holstein and Jersey making up 37.5% and 12.5%, respectively and the remaining majority being other breeds. The dairies in the cluster were predominantly in NCA (81.2%) with three respondent in GSCA (18.8%), had a median herd size of 325 milking cows, and a median annual rolling herd average of 8,235 kg per cow. Two organic dairy (12.5%) reported use of blanket treatment of dry-cows depending on the season with an external teat sealant, one organic dairy (6.3%) reported use of blanket treatment of dry-cows with organic intramammary infusion (Phyto-Mast, Bovin-ity Health LLC, Narvon, PA). One organic dairy (6.3%) reported use of selective dry-cow treatment with an organic intramammary infusion (Phyto-Mast), and one other dairy reported use of selective dry-cow treatment with external teat sealant depending on season and mastitis history. Approximately two thirds (60.0%) of the organic dairies reported use of abnormal milk and sample testing at a milk quality laboratory as basis for mastitis treatment decisions, the remaining relied on abnormal milk findings only. Of the organic dairy respondents, 18.8% indicated treatment of mastitis with AMD, while 50% reported treatment of metritis with intrauterine bolus, and 100% reported treatment of lameness with bolus or injection of AMD and hoof treatment. Few organic dairies in the cluster used computers to track AMD treatments (41.7%) and withdrawal periods (37.5%). Three fifths (60.0%) of the survey’s organic dairies indicated use of OTC AMD, or OTC and prescription AMD prior to January 1st 2018. The remaining organic dairy responses (40.0%) indicated no OTC AMD, prescription but no OTC AMD, neither OTC nor prescription, or no response.
Most of the organic respondents (76.9%) identified the following AMD stewardship practices as very important: administration of the appropriate dose, route and duration of AMD; good record keeping of treatments and treatment dates; and observing withdrawal periods and drug residue avoidance. However, on a statement that any use of AMD may result in infections more difficult to treat in future, 38.5% of the survey’s organic dairies agreed or strongly agreed, 38.5% disagreed or strongly disagreed, while 23.0% were neutral.
The purpose of the current study was to explore the antimicrobial stewardship practices, AMD use and health management practices in adult cows on CA dairies following the passage of California SB 27 and FDA’s VFD rules on the judicious use of MIADs in food producing animals. While the current survey achieved an 11.6% response rate, the responses represented 19 (61%) of the dairy producing counties in CA, responsible for over 94.9% of total CA milk production. Producers who participated in our survey were distributed across the three milk sheds in CA, specifically 14% in NCA, 39% in NSJV, and 47% in GSCA. The survey respondent’s distribution was similar to the distribution of dairy operations across CA published by the CDFA, California Dairy Statistics 2017 (
Additional survey findings categorized CA dairy producers into three clusters characterized by demographic parameters, dry-off protocol, disease management, and AMD stewardship practices. Our findings identified important management practices, such as dry cow treatment practices, cow health protocols and treatment practices, where extension and outreach efforts should focus on improving antimicrobial stewardship. One of the goals of such extension education is to introduce and reinforce preventive measures that may reduce the use of AMDs on dairies, including vaccines, supplements, and preventive measures, such as internal teat sealants at dry-off and hoof trimming (
Our findings indicated that the majority of surveyed dairies (93.7%) treated all end-of-lactation cows presenting for dry-off with IMM AMD and/or teat sealants. About half (49.6%) of the respondents used IMM AMD, 44.1% used both IMM AMD and teat sealant, while 6.3% used only teat sealant at dry-off. The USDA-National Animal Health Monitoring System 2014 Dairy Study, (
Most dairy producers in the survey vaccinated lactating cows to prevent mastitis due to coliform bacteria (85.6%), respiratory disease (87.0%), and abortion and infertility (73.0%). Furthermore, 95.3% of the study dairies administered at least one type of vaccine to lactating cows for disease prevention. This percentage is higher than the 73.8% of dairy operations that administered any vaccine to cows for disease prevention reported by
Overall, 92.3% of the study dairy producers relied on a veterinarian only or veterinarian and other sources for information regarding AMD to use for treatment of adult cows. Half (49.3%) of the dairies included a veterinarian in their decision on which oral and injectable AMD are purchased and stocked, while 37.9% included a veterinarian in their decision on which AMD is used to treat sick cows. These proportions are consistent with the
In our study, 75.0% of dairies confirmed having written/computerized animal health protocols for cows, mainly developed with veterinarian inputs for both treatment and preventative therapeutic uses. In a 2007 study aimed at determining South Carolina (SC) dairy farmers’ knowledge on the importance of prudent antibiotic use on dairy cows,
Drug inventory and treatment records help dairy producers track drug use and treated cows. Approximately half of the surveyed dairies reported not keeping a drug inventory log on their dairies, information which otherwise may help the producers monitor drug use on the dairy over time, track availability and stocking of drugs to avoid shortages or waste due to their expiration, and prevent accidental administration of expired drugs. A survey of dairies in Pennsylvania found only 50% of the dairies kept written or computerized records of antibiotic treatment that could be verified (
At least 36.8% of our survey respondents relied on bacterial culture and antibiotic sensitivity results in choosing a second antibiotic drug to treat a sick animal if the first was not successful. In addition to consulting with a veterinarian, laboratory testing may be a better approach after a treatment failure to confirm the bacterial etiology or its antimicrobial sensitivity if the diagnosis was correct.
Most (80.3%) of the dairies in our survey confirmed tracking/recording milk, meat, or milk and meat withdrawal intervals. According to NAHMS, more than 90.0% of U.S. dairy operations administered drugs that required a milk withdrawal period or a milk and meat withdrawal period (
According to the survey, the number one reason for AMD use on CA dairies was for mastitis treatment, followed by metritis, lameness, pneumonia, and postoperative care; similar to the report by
According to NAHMS 2014 dairy study (
The basic elements of a VCPR are that the veterinarian agreed to assume the responsibility for the animal’s health and the producer agreed to comply with the veterinarian’s instructions; the veterinarian has sufficient knowledge of the animals to make a general diagnosis and assumes responsibility for follow-up care, including adverse reactions and/or treatment failures; and the veterinarian maintains all animal records (16 CCR 2032.1). Most dairies (92%) in our survey confirmed having a valid VCPR for their dairies. Further analysis of the survey questions revealed that the 8.0% (12/143) of producers who said they do not have a VCPR for their dairies may have either misunderstood the question, were not familiar with the term, or mistakenly selected the incorrect answer, as their responses to other questions relating to cow health on their farms showed direct involvement of a veterinarian in cow health care decisions. Specifically, of the 12 producers who indicated not having a VCPR, 10 included veterinarians as one of the sources they relied on for information about AMD used to treat cows. The remaining two dairies had either submitted non-routine samples for infectious disease diagnosis or had used other on-farm diagnostic techniques to guide treatment decisions with AMD for cows; both diagnostic activities were most likely associated with a veterinarian. Hence, continued education of dairy producers is necessary to update their understanding of the requirements of the current law and what a valid VCPR entails.
Animal welfare audit programs are designed to improve welfare standards in livestock operations by ensuring animals are humanely raised. Dairy quality assurance programs, on the other hand, are designed to improve product quality through assessments and monitoring, thereby promoting consumer health, environmental health, and dairy cattle health and welfare. Most dairies in our survey participated in welfare (97.5%) and quality assurance programs (52.9%) in the previous year, highlighting the dedication of CA producers to maintaining high standards of animal welfare and product quality. Based on the NAHMS 2014 dairy study, approximately 45.9% of all dairy operations nationwide participated in a quality assurance program, with higher participation by operations in Western US (66.8%) compared to in the Eastern US (43.9%) (
The MFA identified seven components that accounted for 99.7% of the variation in the data. The seven components identified the important questions that could be considered for a risk assessment tool for AMD use and AMR on CA dairies in future studies, similar to the approaches adopted for bovine respiratory disease (
Cluster C1 consisted of large-scale conventional dairies (median herd size: 1,265 cows; median RHA: 11,340 kg/cow) situated mainly in the GSCA and NSJV region. Dairies in this cluster were characterized by their AMD usage in dry cow management (blanket treatment of all dry cows) at the end of each lactation, and in the management of disease conditions such as mastitis, metritis, and lameness in adult cows. The cluster can be linked with good knowledge of AMD stewardship practices as evident by the high frequency of AMD treatment and withdrawal tracking, most often using a computer, and overall agreement to statements regarding drug use stewardship practices and AMR in their dairy operations.
Cluster C2 consisted of mid-sized conventional dairies (median herd size: 715 cows; median RHA: 10,092 kg/cow) located in NSJV and GSCA regions. Producers in this cluster could be linked with some knowledge of AMD use stewardship practices as characterized by their high level of agreement (100%) to statements regarding AMD use stewardship practices. They tend to show more agreement regarding AMR issues raised in the study compared to dairies in clusters C1. Producers in this cluster could benefit from outreach and education relating to use of computer in record keeping, AMD use stewardship practices and their impact on AMR in dairy operations.
The organic cluster consisted of small-sized dairies mainly located in NCA and reported little or no usage of AMD in their dairy operations. Organic dairies do not use AMD amongst other prohibited chemicals (such as pesticides, hormones with exception of oxytocin) unless sick animals require antibiotics. Emergency AMD treatments to maintain the welfare of the sick animals are allowed on organic dairies; however, such animals have to be segregated from the organic herd and sold to a non-organic market in addition to strict documentation and reporting requirements (
The current study data were collected based on voluntary participation, in accordance with the SB 27 from CA licensed grade A dairy producers. The mean dairy herd size in our survey was 1,550 cows per herd, which was greater than a 2017 estimate of average herd size of 1,304 cows per herd (
The current study provided a description of the current AMD use, treatments, and AMD stewardship practices that may influence AMR on CA dairies. The majority of the current practices reported by respondent CA dairy producers are in line with the provisions of the SB 27 and VFD regulations. The purpose of such regulations is to protect human and animal health through the judicious use of MIADs in food-producing animals, which has the potential to slow or prevent the development of bacterial resistance to AMDs. Support for producers in understanding and enhancing their VCPRs is likely to enhance judicious use of antimicrobial drugs. Producers and veterinarians may want to consider implementation of selective dry cow therapy, increased use of alternatives to AMDs, and adoption of electronic record-keeping as means to further implement antimicrobial stewardship.
a BVD = Bovine viral disease; b SRP = siderophore receptor and porin
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a DA = displaced abomasum; b C-Section = Cesarean section
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The authors are grateful for California’s dairy industry responses to the survey mailings including the state’s dairy producers, herd managers and veterinarians.
Sharif Aly is an Academic Editor for PeerJ. Edith Marshall is an employee of the California Department of Food and Agriculture.
The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):
The study was reviewed by the University of California, Davis Institutional Review Board and was granted exemption approval (IRB Number: 1537295-1).
The following information was supplied regarding data availability:
While the raw data was available for peer review, this study was sponsored by the California Department of Food and Agriculture and is subject to California Food and Agriculture Code (FAC) Sections 14400 to 14408. FAC section 14407 requires that data collected be held confidential to prevent individual identification of a farm or business; as such, raw data from this study is not able to be shared.