What's the deal with "filler ingredients" in parrot pellets and is there cause for concern?
Spoiler alert: what you think is a filler ingredient likely isn't one. In the pet food industry (parrot pellets included), a filler is typically thought of as an ingredient that adds bulk to the food without adding nutritional value. The only ingredients that really fit this description are fibers, which do not provide direct nutritional benefits but do serve an important role in overall gut health. In general, when most people hear the phrase "filler ingredient," they think of low-quality, cheap ingredients that not only don't add to the nutritional value of the pellet, but even detract from it and/or cause harm to the animal. The reality is that this very concept of a filler ingredient is contrary to the purpose of a pellet. Let's get into it.
Parrot pellets that are formulated by qualified animal nutritionists are designed to provide your bird with sufficient quantities of nutrients that have been identified by avian veterinarians and researchers as necessary to maintain health. There is a ton to say on this topic in and of itself, but I'll save that for another blog post (heck, we might even have to write a book about it). For now, let's just think about what this means for filler ingredients. If the goal of a pellet is to meet the nutritional needs of the average bird, is it productive to add an ingredient that does not add any nutritional value? Generally speaking...nope. When it comes to choosing a pellet, it is far more important to consider the entire nutritional profile (as in the nutrient analysis) of the food than the actual ingredient list. Nonetheless, it is not uncommon to see companies demonize certain ingredients found in other pellets to promote their own product that is free of x, y, or z ingredients. This sends a message that the ingredients (or lack of certain ingredients) used to make pellets is more important than the actual nutrition the pellets provide, which often isn't reported by a full nutrient analysis. This is incredibly problematic and creates unnecessary fears amongst companion parrot owners who are simply trying to do good by their bird. The number of times somebody has messaged me about feeling guilty for feeding their bird a certain brand of pellet, only because somebody or some company told them (without providing any evidence) that a listed ingredient was killing their parrot, is really disturbing. At Nerdy Bird Collective, it is our goal to empower companion parrot owners to make decisions based on credible, evidence-based information, rather than scare tactics. As such, I tried to identify the ingredients that I think are the most commonly called out as fillers in the companion parrot world (corn, soy, peanuts, and even added vitamins and minerals). We're going to break each of these ingredients down to answer the question, "is it a filler?" Let's start from the top.
Probably the single most demonized ingredient in the companion parrot world (dare I say pet food industry in general) is corn. Aside from being highly digestible, corn is one of the best sources of linoleic acid (an essential omega-6 fatty acid), has a good amount of protein with a great amino acid profile, and is a great source of many vitamins and minerals, such as B vitamins, potassium, and magnesium (Refs. 1-3). Furthermore, corn is cheap! And no, this is not a bad thing. Using ingredients that are less expensive helps keep the cost of the finished product down, which can help make pellets more accessible.
Soy has become quite the controversial ingredient owing to the fact that soybeans contain high concentrations of certain phytoestrogens (isoflavones) which have been shown in animal, primarily rat, models to be endocrine disruptors. In humans, the proclaimed negative effects of soy have been thoroughly debunked, and soy has actually been associated with a decreased risk of breast and prostate cancer (Ref. 4). Much of the fear surrounding feeding soy products to parrots in particular seems to have come from a single report in New Zealand that suggested that decreased reproduction and fertility in a flock of parrots was due to consumption of feed with high levels of isoflavones; importantly, these effects have not been directly linked to isoflavones (Refs. 5-6). Research in quail has shown that dietary phytoestrogen does not negatively influence reproductive success, and that during the late laying period, supplementing the diet with soy isoflavone can actually improve egg quality and bone mineralization (Refs 7-8; this has similarly been shown in laying broiler breeder hens, Ref. 9). In another study, researchers did not observe any effect of soy isoflavones on weight gain or feed consumption in immature Japanese quail close to mature body weight, though they did find that testicular development was modestly depressed in growing males (Ref. 10). Few peer-reviewed studies have looked at the effects of dietary phytoestrogens on parrots; however, one study screening foods for the critically endangered kākāpō parrot found that the low levels of estrogenic activity observed in one of three tested commercial chick-raising foods were highly unlikely to be of any physiological or developmental significance (Ref. 11). All in all, if phytoestrogen-containing foods like soy are fine to feed the on-the-brink-of-extinction kākāpō, I personally have zero qualms feeding soy to my own parrot.
You can read all about why peanuts get a bad reputation that they only sometimes deserve in another blog post, but in short, it is largely due to the risk of mycotoxin contamination, a problem that is not unique to peanuts themselves. Further, peanuts are absolutely not a filler ingredient. Peanuts are a great source of antioxidants, are high in protein, low in saturated fats, high in healthy polyunsaturated and monounsaturated fats, and are high in many vitamins and minerals including manganese and copper (Ref. 12). It is also important to realize that peanuts are absolutely not the only food prone to harboring mycobacteria, but they are probably the most picked on. We always advise purchasing pellets from a manufacturer that tests their finished product for mycobacteria, but this is irrespective of whether or not that pellet contains peanuts. If you are unsure if a pellet manufacturer tests their finished product, we recommend checking out their website and/or reaching out to customer service to ask them.
Vitamins and minerals
If a filler ingredient is commonly thought of as an ingredient that does not add nutritional value to the food, I'm really not sure why vitamins and minerals get labeled as such. I think perhaps the thought process is that if pellets were made in a different way or with different ingredients, added vitamins and minerals would not be necessary. It is true that some vitamins can break down during a typical pellet manufacturing process (extrusion), which is in part why we have fortified pellets, but this isn't the only reason why pellets are supplemented with vitamins and minerals. Keep in mind that pellets are designed to be fed as the primary component in the diet, which means that they are formulated to meet all of your bird's basic nutritional needs. The reality is that it's exceptionally difficult to formulate a fully plant-based pellet to meet such requirements. For example, most plants have more phosphorus than they do calcium, but the recommended calcium to phosphorus ratio is between 1:1 and 2:1 (Ref. 13). As a result, calcium (usually in the form of calcium carbonate) is added to achieve a proper balance. Another example is vitamin D3. Most companion parrots do not get enough access to unfiltered sunlight to make their own vitamin D3, and plant matter does not contain nearly enough vitamin D3 by itself, resulting in the need to add vitamin D3 to the pellets. Side note: plants have vitamin D2, but this form of vitamin D is only about 10% as effective as vitamin D3 in birds (Ref. 14).
At the end of the day, you are of course free to feed or not feed your bird whatever you want; our goal is simply to equip you with evidence-based information so that you feel confident in your choices.
Dr. Stephanie Rosenbloom has her Ph.D. from Cornell University and has been caring for parrots her entire life. She believes that we can all benefit from asking more questions, seeking knowledge from reliable sources, and giving others the benefit of the doubt before drawing conclusions. She applies these concepts to her practice as a parrot trainer and behavior consultant.
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