During my endeavour to learn about optimal nutrition, I have been hunting for any possible links between nutrition/diet and tear staining (chromodacryorrhea), commonly referred to as eye rust.

This link became of particular interest after seeing many comments in online forums linking particular brands to causing rust, but there doesn’t seem to be any available science or studies supporting such theories or anecdotes. What the science has found, however, is just as interesting… (and there is nutritional support available, but…)


Stress seems to be the leading exacerbator of tear staining, so much so, that studies around the world are indicating that tear staining could be used as a tool for welfare assessment on swine farms. But our mini pigs aren’t the subjected to those harsh, crowded living conditions, so why is it so common amongst our beloved “little” minis? Eye rust is fairly normal for pigs anyways, but it’s the severe, prolonged, or persistent cases that are indicative of something else going on.

There are many factors contributing to stress in pigs, and even though we love them unconditionally, and they might act tough or pushy, they truly are sensitive animals.

You can help reduce stressors by evaluating their living conditions and social groups. Common stressors include:

1) Changing feeds too quickly – not all commercial brand pellets are made equally, or even with similar ingredients in some cases, so it is very important to gradually transition between feeds, mixing them for as long as a week or more before the change is complete
* Perhaps this, and not the feed itself, is why some brands are being blamed – hard to know with so many potential variables.

2) Isolation, or being alone for prolonged periods.

3) Social hierarchy – particularly if they are lower in the pecking order, or around other animals that may bully or chase them.

4) Separation or weaning – it’s always stressful when they are separated from friends, and especially their mother, so being able to provide some consistencies or alternate familiar companionship will ease the transition.

5) Boredom – adding as much enrichment as you can to your pig’s environment, such as hay or a hay box to encourage rooting behaviours, puzzle feeders, etc, and companionship will help reduce boredom.

6) Travel

Nutritional Support for Stress

If you’re worried about your pig going through a stressful transition in life (ie: new home, sickness, surgery, a new pet/child), take a close look at their B vitamins. They are water soluble vitamins, and since some of the best healthy food sources are low in calories, you can safely beef up their greens and forages.

Niacin (vitamin B3) helps regulate hormones associated with coping with stress. While 13-55 mg is the recommended daily amount for healthy maintenance, supplementation of up to 750 mg has been studied in pigs for beneficial effect.

Some niacin rich food includes nuts, seeds, legumes, bananas, broccoli, spinach, sweet potatoes.

Stress can deplete B vitamins from the body, so niacin isn’t the only one to worry about. Luckily, grass and forages often have adequate to high levels of B vitamins, and if it’s winter or where consistent foraging might not be able to be accommodated, such as indoor pigs, B complex vitamins are readily available (for people) to supplement your piggy.

There was also an interesting study with L-glutamine, an amino acid, that demonstrated marked and consistent improvements, decreasing stress and behaviours attributed to stress with as little as 0.2% as fed.

For the love of pigs!