In January 2014, the USDA’s National Animal Health Monitoring System (NAHMS) launched its sixth national dairy study. As with all NAHMS national studies, objectives for the Dairy 2014 study were identified through focus groups and a needs assessment survey completed by various stakeholders in the U.S. dairy industry.

Over the coming months, NAHMS researchers will release a series of reports highlighting different components of the study. Some preliminary results have already been presented at the recent American Dairy Science Association and American Association of Bovine Practitioners (AABP) conferences. This article summarizes some of the preliminary results presented at the conferences.

Data collection

Study data were collected from 1,261 dairy operations from the nation’s top 17 dairy states. These states represented approximately 80 percent of U.S. dairy operations and dairy cows in 2013. To analyze study results, the NAHMS research team used statistical software to provide estimates reflective of the U.S. population of dairy producers.

Use of veterinarians

One objective of the Dairy 2014 study was to determine the percentage of U.S. dairies that used veterinarians, how frequently veterinarians visited the dairies and the types of services veterinarians provided. To collect this information, a portion of the survey was developed in tandem with the AABP’s Veterinarian-Client-Patient Relationship Best Management Practices Task Force and focused on how veterinarians are used in the dairy industry. 

For the past 15 to 20 years, veterinarians have focused on reproduction management on dairy operations; however, the introduction of relatively inexpensive pregnancy tests could supplant veterinarians from this role. In addition, many larger dairies are hiring non-veterinarians to perform pregnancy exams and surgeries, skills traditionally provided by veterinarians.

Conversely, the use of antimicrobials and other drugs in livestock is coming under increasing scrutiny, and veterinarians will have more oversight and responsibility in this area in the future.

Almost 94 percent of dairy producers had worked or consulted with a veterinarian in 2013, and about 65 percent had a veterinarian on the operation at least monthly.  Of the 6 percent of producers that did not work with or consult a veterinarian, more than two-thirds indicated that they did not need a veterinarian at their operation. Only 3 percent of the 6 percent indicated that a veterinarian was not available in their area, while 30 percent of the 6 percent reported that veterinarians were too expensive.

More than 80 percent of producers reported that their veterinarian was very good or excellent in terms of availability, knowledge of dairy cattle, and performing procedures and tasks. The top six services provided to dairies were:

·         Emergency services (91 percent of operations).

·         Reproductive management (86 percent).

·         Disease diagnosis and treatment (85 percent).

·         Drug sales (85 percent).

·         Left displaced abomasal surgery (65 percent).

·         Vaccination (53 percent).

Reproductive management was one of the most important services provided by a veterinarian on 71 percent of dairy operations. Less than 20 percent of dairies used their veterinarian for biosecurity for new herd additions, facility design, nutrition services or employee training. More than 30 percent of dairies consulted with their veterinarian when developing protocols for reproductive management, disease diagnosis and treatment, and vaccinations.

Prescription veterinary drugs were purchased directly from the dairies’ primary veterinarian on 76 percent of operations, while non-prescription drugs were purchased from the primary veterinarian on 32 percent of operations. Overall, 38 percent of operations purchased non-prescription drugs directly from a farm/ranch or feed store.

Our results show that the majority of dairies use veterinarians for traditional veterinary services such as reproductive management; however, based on current trends, the percentage of operations that use a veterinarian for these traditional services will likely decrease in the future. The good news for dairy veterinarians is that there are a number of non-traditional services that veterinarians already provide to dairies, and the percentage of dairies requesting or needing these non-traditional services will likely increase in the future.

Antibiotic use on U.S. dairy operations

As the primary health providers and consultants on most dairy operations, veterinarians are usually involved in the selection and use of antibiotics, implementing management strategies to prevent drug residues in milk and meat, and applying guidelines for judicious use of antibiotics. The use of antibiotics in livestock agriculture is coming under increased scrutiny because of the focus on reducing antibiotic resistance. Beginning in 2017, policy changes from the Food and Drug Administration (FDA) will ban the use of certain antibiotics (those medically important to humans) used in feed and water to increase animal performance, such as weight gain. These antibiotics may still be used for therapeutic purposes, with veterinarian oversight.  

Several questions from the study’s questionnaire focused on antibiotic use during 2013 in preweaned, weaned, pregnant and adult cattle. 

Ionophores were fed to weaned heifers on 51 percent of operations and fed to 63 percent of all weaned heifers. Similarly, 39 percent of operations fed ionophores to pregnant heifers, representing 47 percent of all pregnant heifers. Cows were fed ionophores on 37 percent of operations, with a higher percentage of medium and large operations (100-499 and 500 or more cows, respectively) feeding ionophores to cows (56 and 63 percent, respectively) than very small and small operations (fewer than 30 and 30-99 cows, respectively) at 20 and 28 percent, respectively.

Most antibiotics that are not administered in feed or water are used for dry-cow therapy; 89 percent of operations dry-treated all cows and 93 percent of all cows were dry-treated. For dry-cow therapy, beta lactams were the predominant drugs used, and 22 percent of dry-treated cows received third-generation cephalosporins.

Diarrhea was the most common disease in preweaned heifers, with 21 percent of all heifers affected with diarrhea and 16 percent of all heifers treated with antibiotics for diarrhea. The primary antibiotics given for diarrhea were third-generation cephalosporins (28 percent of treated preweaned heifers), trimethoprim/sulfa (19 percent) and aminoglycosides (15 percent).

Respiratory disease affected 8 percent of weaned heifers. The primary antibiotics used for respiratory disease were florfenicol (32 percent of treated weaned heifers) and macrolides (30 percent).

Overall, 21 percent of cows received antibiotics for mastitis, 8 percent for reproductive diseases, 4 percent for lameness, 3 percent for respiratory problems and 1 percent for digestive diseases. On operations that treated cows, 51 percent of cows received third-generation cephalosporins for mastitis, 60 percent for lameness, 78 percent for respiratory disease and 62 percent for digestive problems.

Ionophores are frequently used as feed additives on dairy operations, but this class of antibiotics is not listed as “medically important” by the FDA and, thus, is not affected by the recent FDA policy changes. Third-generation cephalosporins, trimethoprim/sulfa and macrolides are all considered critically important for use in humans. In the dairy industry, these drugs are primarily used for disease treatment, and relatively few cattle are treated with the drugs.

Calf health

Another objective of Dairy 2014 was to evaluate heifer-calf health from birth to weaning. To address this objective, NAHMS convened a group of international experts in calf health to help design the calf component of the study. In addition to collecting disease-incidence data, the group also wanted to determine the impact of other factors on the health of calves, including dystocia, colostrum management, housing, etc.

Researchers asked approximately 300 dairy operations participating in the study to volunteer to take part in the calf component. Participation in this component required that each operation enroll two to four heifer calves at birth per month for 12 months (24-48 calves) and monitor them through weaning. Information was collected on morbidity, mortality, birthing parameters, serum IgG and treatments administered in preweaned dairy heifers.

As of July 2015, data have been collected from approximately 1,700 calves on 97 farms in 13 of the nation’s top dairy states. These results from the interim analysis are based on approximately 70 percent of the total number of calves expected to be enrolled in the study.

Of enrolled calves, 35 percent experienced at least one disease event, and 7 percent had more than one disease event. The maximum number of disease events reported was six. Clinical signs of morbidity were classified as dull, dehydrated, gastrointestinal, respiratory, lameness and neurological. Gastrointestinal signs were observed in 53 percent of sick calves; dullness was reported in 37 percent of sick calves; and respiratory problems were observed in 32 percent of sick calves. Of the 35 percent of calves with clinical signs, 92 percent received treatment. Medications, including antibiotics, were administered to 80 percent of sick calves, and electrolytes were administered to 35 percent of sick calves.

Interestingly, of the 5 percent of calves that died, 29 percent died without any clinical signs being reported before death. The average age at death was 22.3 days, with a range of 3 to 78 days. Birthing parameters, including calving-ease score, number of calves born and disinfection of the navel, were not associated with morbidity or mortality.

The study also evaluated colostrum quality at the time of administration. The mean colostrum IgG level was 74.6 g/L, with 68.4 percent of samples having IgG levels above 50 g/L. The highest per­centage of calves (53 percent) received colostrum from their dam. Pasteurized colostrum was fed to 7 percent of calves. On average, colostrum was fed within 3.1 hours following birth. The mean volume of colostrum fed at first feeding was 3.1 L, and the mean volume of colostrum fed in the first 24 hours of life was 4.7 L. The highest percentage of calves (63 percent) were fed colostrum by bottle, while 3 percent were fed colostrum by esophageal feeder.

The mean serum IgG level was 22.1 g/L. Overall, 73 percent of calves were classified as having excellent passive transfer at serum levels of ≥ 15.0 g/L; 13 percent were classified as fair at 10.0-14.9 g/L; and 14 percent had passive transfer failure at < 10.0 g/L. Calves with fair passive transfer had higher levels of morbidity (44 percent) compared with calves with excellent passive transfer (30 percent). Serum IgG categories were not associated with mortality. High serum IgG levels were associated with decreased morbidity. Digestive and respiratory diseases were the two most common causes of morbidity in preweaned heifer calves.

A statistical model selection was used to determine which colostrum management factors were most impor­tant for determining serum IgG levels. The model includes grams of total colostrum fed at the first feeding, dam lactation, breed, pasteurization status of colostrum, the number of hours following birth that calves received their first colostrum feeding, the age at the time of blood draw, the source of colostrum and the calves’ birthweight. Serum IgG from calves that received colostrum from first-lactation heifers was higher than second- or higher-lactation cows.  Jerseys had higher serum IgG than all other breeds.  Serum IgG was lower for calves that received commercial colostrum replacer compared with all other sources of colostrum.  Calves that received pasteurized colostrum had higher serum IgG compared with calves that received unpasteurized colostrum.    

Serum IgG increased when grams of total colostrum fed at first feeding increased.  Serum IgG decreased as the number of hours following birth to first feeding increased, the age at blood draw increased and as birthweights increased. These results show that feeding appropriate amounts of high-quality colostrum shortly following birth is crucial to the passive-transfer status of dairy calves.

A follow-up article in the next issue of Bovine Veterinarian will summarize results relating to lameness, factors affecting animal welfare and other management issues on dairy operations.