Appendix E-3: Acid based products

This draft document was part of the consultation on Acid Based Products, which closed on October 5.

1. Introduction

1.1 Background

Acid Based Products (ABP) and their salts, often referred to as Acidifiers, are products that contain one or more substances with acidic properties and have had a recognized use in feeds to reduce the pH of solid feed when added to a feed matrix, for the acidification of water in areas with alkaline water sources and for use as preservatives in solid and liquid feed, for example, milk replacers. Products with acidifying properties may be intended to act within the animal to prevent disease or target and reduce a particular pathogen, which would be more consistent with a veterinary drug. Historically, a product would be classified as a veterinary drug when referring to the modification of the gut environment. The addition of the Gut Modifier category in feed, allows for the possibility of an ABP in feed to be recognized for its ability to act locally to modify the gut.

1.2 Purpose and scope

The purpose of this appendix is to provide guidance and clarification concerning the classification of ABP intended for oral use in livestock between veterinary drugs, including veterinary health products (VHP1), and livestock feeds. Previously, all feed ABP were registered under the collective term 'Acidifier'. In order to recognize different feed purposes, ABP will be divided into the following 3 categories: pH Adjusters; Preservatives and Mold Inhibitors; and Acidifiers (as Gut Modifiers). Each category is defined below.

ABP with claims related to the disinfection or sanitization of an inanimate object or surface are excluded from the scope of this appendix, as they are not found at the drug-feed interface.

2. Acid based product categories in feed

pH adjusters

These acids are added to livestock feeds including liquid feeds, or water to adjust, or maintain the pH due to its buffering capacity. Feed acidification may significantly reduce the dietary pH, which in turn improves nutrient digestibility of the feed.

Preservatives and mold inhibitors

ABP may be added to feeds before and during processing to decrease the pH to levels that are unfavourable for the growth of spoilage organisms (microbial or fungal) or to prevent other undesirable chemical changes in the feed itself, rather than in the animal.

Acidifiers (as gut modifiers)

These products, when added to livestock feeds or water, elicit their beneficial effects through action in the gastro-intestinal tract (GIT) resulting in an increase in nutrient absorption and digestibility. Acidifiers (as gut modifiers) may be protected (for example, encapsulated) in order to pass through the GIT to the intended target site.

3. Relevant classification criteria

As with any product classification at the drug-feed interface, the criteria outlined in the guidance document should be consulted. The following additional criteria could be useful for consideration in guiding the classification of ABP.

3.1 Characteristics of acids

An essential characteristic of acids is their ability to dissociate and change their charge thereby resulting in differing modes of action and metabolic associations. Hence, a discussion on the molecular formula and the pKA value of the acid could become important criteria for their classification.

In association with the mode of action of the product, the ability of an acid to disassociate can determine its functional suitability.

3.2 Location of action

The location of action is a consideration for classification. Actions in the feed, external to the animal, are likely to reflect a classification as a pH adjuster, a preservative or mould inhibitor. Localized actions within the GIT suggest a potential classification as a Gut modifier. For example, protecting the product through encapsulation allows for targeted action in a particular location in the GIT; this would not be consistent with a pH Adjuster.

A product that includes systemic absorption and a location of action in the animal away from the GIT may indicate an action that is more consistent with a therapeutic or general health purpose and therefore would be better classified as a veterinary drug, which includes VHP. Further classification within the veterinary drug pathway will depend on the mode of action, ingredients and intended purpose.

3.3 Intended purpose and indications (claims)

An indication (or claim) needs to be provided for all ABP, regardless of classification. These claims should be based on a measurable outcome and supported by valid scientific evidence. The proposed claim is a consideration for classification, as follows:

  • therapeutic claims may include the prevention or treatment of a disease condition or state, the mitigation of clinical signs, or disease risk reduction. Products with therapeutic claims are considered drugs and may consist of ABP that claim to target a particular pathogen(s), to reduce pathogen load, or to prevent and/or treat a disease condition
  • nutritional or production/performance claims refer to the provision of nutrients, directly or through their improved availability, and their digestion or absorption. This can be provided by actual modifications in the gut. Products having claims that include the support of maintenance, growth, and improved performance of animals may be associated with livestock feeds
  • general health claims are expected benefits in maintaining or promoting the health and welfare of animals. General health claims may be acceptable for the notification of VHP1 and regulated as veterinary drugs under the Food and Drugs Regulations

Examples of claims are provided in the table that follows.

Table E-3.1 – Example claims
Food and Drugs Act and Regulations Food and Drugs Act and Regulations Feeds Act and Regulations
Therapeutic claims – New drug (Drug Identification Number) General health claims – VHP Table Note 1 (notification number) Feed claims – Feed (registration number)

Prevention/Treatment of disease:

  • Reduces the incidence of post-weaning diarrhea in piglets
  • For the prevention and/or treatment of diarrhea caused by E. coli
  • Reduction in the incidence/severity of necrotic enteritis in broiler chickens

Pathogen reduction

  • Limiting the spread of disease through the reduction in the shedding of Salmonella spp.
  • Reduces shedding of E. coli in feces reducing the risk of carcass contamination at harvest


  • Decrease morbidity/mortality rate
  • Promotes a healthy gut flora
  • For good intestinal health
  • Maintains balance of healthy microflora
  • Provides friendly bacteria that play an important role in basic digestion, proper metabolism and overall well-being
  • Supports the function of the immune system
  • Promotes healthy intestinal microbiota

Gut modifier:

  • Replenishes (or maintains) intestinal flora after a physiological event Table Note 2
  • Increases surface area/length of intestinal microvilli for nutrient absorption
  • Stimulates intestinal development in neonatal piglets
  • Reduces the pH in the gastro-intestinal tract

Production and performance:

  • Improves feed intake/Improves palatability
  • Improves feed efficiency/Conversion
  • Improves daily weight gain
  • Improves live weight gain


  • Improves the digestibility of nutrients

Preservative or mold inhibitor:

  • Inhibits growth of spoilage microbes such as bacteria/fungi/yeasts/molds in feeds
  • Reduces the growth of bacteria in feeds, including Salmonella
  • Feed preservative
  • Prevents feed spoilage or contamination
  • Prolongs the shelf-life and storage of feeds

pH adjuster:

  • Acidify feeds
  • Acidity regulator of feed or water
  • Improves buffering capacity of diets


  • As an aid in odour control

Note: This table is for illustrative purposes only and should not be considered as an exhaustive and complete list. If a product's claim or indication is not listed above, please contact Veterinary Drugs Directorate (as a single-window access for classification) for further assessment.

3.4 Dosage forms

Consistent with the guidance document, dosage forms that require forcible administration (for example, boluses and tablets) are regulated under the Food and Drug Regulations. Oral dosage forms that do not require forcible administration may be regulated under either the Food and Drug Regulations or the Feed Regulations depending on other classification criteria. To ensure consistent regulatory oversight and application of standards in safety, efficacy and quality, products in oral dosage form will be regulated as illustrated in Table E-3.2.

Table E-3.2: Potential regulatory pathways of ABPs in oral dosage forms separated based on the governing regulations and regulatory approval processes.
Food and Drugs Act; Food and Drug Regulations Food and Drugs Act; Food and Drug Regulations Feeds Act; Feed Regulations
Therapeutic claims – New drug (Drug Identification Number) General health claims – VHP1 (notification number) Feed claims – Feed (registration number)
Forcible administration
(for example, bolus, tablet, drench)
Yes Yes No
Mixed in feed Yes No Table Note 3 Yes
Top-dressed on feed Yes Yes Yes
In-water Yes Yes Yes

For further information on VHPs and the VHP notification pathway:

4. Other considerations

It is important to note that the type of acid (for example, citric, acetic, or formic acid) does not determine the product's classification. Products that contain similar acids (and/or their salts) may have different purposes, concentrations or formulations which may change the respective classification or feed categorization.