U.S. flag An official website of the United States government
  1. Home
  2. Animal & Veterinary
  3. Products
  4. Animal Food & Feeds
  5. Biological, Chemical, and Physical Contaminants in Animal Food
  6. CVM Issues Assignment to Collect and Analyze Samples of Milk Replacer Products for Salmonella
  1. Animal Food & Feeds

CVM Issues Assignment to Collect and Analyze Samples of Milk Replacer Products for Salmonella

CVM Issues Assignment to Collect and Analyze Samples of Milk Replacer Products for Salmonella


Date: January 29, 2014


  1. To collect 100 official samples of animal milk replacer products and determine the prevalence of Salmonella among the samples collected under this assignment.
  2. To determine the serotype/genetic fingerprint/antimicrobial susceptibilities of Salmonella isolates found in the animal milk replacer products collected under this assignment.


Salmonella-contaminated animal feed can cause illness in animals that consume the feed. Whether Salmonella causes illness in an animal depends on the serotype. Different animal species typically develop disease in response to different serotypes. Salmonella serotypes that cause disease in a particular species are referred to as pathogenic for that animal species.

FDA’s Center for Veterinary Medicine (CVM) is concerned about animal feeds and feed ingredients serving as vehicles for transmitting Salmonella serotypes that are pathogenic to animals that consume the feed. Young animals are generally the most susceptible to Salmonella infections. Salmonella infections in young animals are mainly enteric, but may become symptomatic. Salmonella infections in adult animals, however, are less common and more likely to be enteric and asymptomatic. Salmonella serotypes that cause disease in a particular species are much more likely to cause a more severe, systemic disease in animals.

This assignment will provide information on the prevalence of Salmonella and the serotype/genetic fingerprint/antimicrobial susceptibilities of each Salmonella isolate found in the animal milk replacer products sampled.


Sample Collection

The majority of animal milk replacer products are manufactured for use by calves1 although some milk replacer products are also manufactured for use by orphaned or extra piglets, lambs, and other young animals. Therefore, in this assignment, CVM will use 80% of its resources on milk replacer products for calves, 10% for piglets, and 10% for lambs.

The 100 official samples of animal milk replacer products in dry power form should be aseptically collected from unopened bags or bulk containers or at in-line locations prior to bagging at the manufacturer, distributor, wholesaler, or retailer, and at feed plants supporting integrated operations. The number of milk replacer products to collect is divided among the FDA districts based on states where dairy cattle, swine and sheep production are prominent.

This assignment can include sampling of both medicated and non-medicated animal milk replacer products manufactured in the United States. This assignment does not cover imported products in either import status or domestic import (D/I) status.

Follow the sample collection procedures as described in the FDA Investigators Operations Manual (IOM), Chapter 4 (4.3 and 4.3.6, Aseptic Samples). Investigators are further instructed to make every reasonable effort to collect all interstate documentation, identify the manufacturer, distributor and the shipper of the products, collect labels and labeling materials and report these on the FACTS Collection Report.

Sample Size

For this assignment, the sample size of each official sample should consist of 10 sub-samples with each sub-sample weighing approximately 200 g (7.1 oz). These 10 sub-samples already include the 702(b) portion per 21 CFR 2.10 (b).

Sample Shipment

Refer to IOM subchapter 4.5.5 for sample shipment instructions. Samples are to be shipped by overnight courier to the laboratory identified in the FY 2014 Servicing Laboratory Schedule for your district. The Servicing Laboratory Schedule was distributed to the field with the FY 2014 Work Plan.

Please ensure that samples are packed appropriately to avoid damage to the sample. The servicing laboratory should be notified of the impending shipment. Please make all efforts to collect and send samples so they do not arrive on the weekend without prior approval from your servicing laboratory.

Sample Analysis

ORA servicing laboratories will analyze the 100 official samples of animal milk replacer products for Salmonella. AOAC Official Method 2004.03 [Determination of Salmonella in Foods by VIDAS (SLM) Immunoassay], an enzyme-linked immuno-fluorescent assay, is to be used as the screening method for this assignment. Refer to procedures outlined in the BAM on line, Feb. 2011, chapter 5, Salmonella for the confirmatory method to use in this assignment.

Aseptically weigh approximately 37.5 g (~ 1.3 oz) from each of the 10 sub-samples to form a 375 g (13.2 oz) composite sample for Salmonella analysis.

The servicing laboratory will reserve approximately 75 grams (~ 2.6 oz) or more from each of the 10 sub-samples for use as the 702(b) portion. Each of these 10 sub-samples includes the 702(b) portions so there is no need to collect additional 702(b) portions per 21 CFR 2.10 (b).

If the sample is positive for Salmonella, the servicing lab will send each Salmonella isolate to ARL or DEN-LAB for serotyping, and retain the duplicate Salmonella isolate in the laboratory. All serotyped Salmonella isolates will be sent to DEN-LAB for antimicrobial-susceptibility testing.

PFGE Image(s)

In addition, each servicing laboratory will conduct a pulsed-field gel electrophoresis (PFGE) for each Salmonella isolate under this assignment. The servicing lab will email the PFGE image(s) with FACTS sample numbers to CVM so they can download the PFGE image(s) of the Salmonella isolates found in feed into the CDC PulseNet database.


The District should set up a conference call with CVM’s Division of Compliance and ORA/OFFO/DFFPOI/FFPOB (Food and Feed Program Operations Branch) in cases involving animal milk replacer products that are positive for Salmonella before pursuing further action. CVM will evaluate the information provided in a district's recommendation for advisory/regulatory action.

Daniel G. McChesney, Ph.D.
Director, Office of Surveillance and Compliance

1 The USDA’s National Animal Health Monitoring System, Heifer Calf Health and Management Practices on U.S. Dairy Operations, 2007