Grit, gizzards and good eggs

There are two types of grit that chickens need, and both are essential to the long-term health of your flock (as well as top tier poached eggs).

For chickens, the absence of teeth creates a slight issue with chewing. With a long beak and no teeth, how is food mashed up to move down the digestive tract? That job is cleverly outsourced to the gizzard, a hard, muscular pouch at the top of the intestine. Here, insoluble grit is stored, ready to grind the food up as it travels to the intestine.

Chickens and insoluble grit

Insoluble grit is a collection of gravel and tiny stones that act as a grinding mill. This type of grit doesn’t dissolve in the body or provide any nutritional value. Rather, it tumbles around in the gizzard, breaking down fibrous material consumed by the chicken. A light bashing helps to crack seed coats, insect shells and husks so digestive enzymes can get to work. 

How to feed insoluble grit

Birds who roam outside of their run usually pick up enough tiny stones in the course of a normal day’s foraging. For birds in a run, you may need to supply some.

Soluble grit: It’s about the calcium

Soluble grit dissolves in the digestive system and provides calcium to birds, which is a must for laying hens. To cook up a nice hard eggshell, a layer needs 4–5g of calcium per day as well as a balanced supply of other micro-elements including phosphorus, zinc, magnesium, manganese and vitamin D3. A shortage of calcium can lead to thin-shelled or shell-less eggs, and over time negatively impact the general health of chickens too.

Types of soluble grit for chickens

Soluble grit is most commonly fed to chickens in the form of coarsely ground mussel or oyster shells, separated from their main food so they can help themselves as needed. Some people like to make a DIY soluble grit from dried and crushed eggshells, and limestone chips are another appropriate source of calcium-rich grit for chickens. In powder form limestone is often included in a commercial layer feed. 

Do all chickens need a separate source of soluble grit?

Because a commercial layer feed like Topflite Poultry Pellets already contains the correct amount of calcium and other elements, feeding a separate source of soluble grit is less important for hens who eat only a commercial blend. However, if the chooks are also eating kitchen scraps, extra grains or are free-range foraging in addition to the commercial feed, calcium and other minerals can become diluted. 

If this sounds like your set up, keep a separate dish of grit handy for your chooks. They will eat what they need. Never add extra calcium into a commercial feed as this could result in an imbalance of trace elements, leading to shell problems.

Scratch & Lay, our premium chook mix of whole, New Zealand grown grains and seeds contains Bluff oyster shell grit but it is recommended that chickens have access to a separate dish of grit too.

When should I introduce grit to my chook’s diet?

The most important piece of information to remember is to never give soluble grit, or a layer feed that contains it to chicks less than 18 weeks old. These adolescent chooks have kidneys that are still developing and they cannot handle high calcium levels. If too much calcium is consumed, their kidneys have to excrete the excess as uric acid, which can crystalise and block kidney tubules. The recommended calcium level for birds under 18 weeks is 1% or below and most layer feed contains up to four times that amount.

Chicks eating a starter or grower crumble don't need insoluble grit either, since these feeds are soft enough to digest without it. Once birds transition to seeds or scraps, offering a small amount of fine insoluble grit separately is okay.

What about grit for other bird species?

All adult birds benefit from calcium-grit in their diet. 

Oyster Shell Grit-Fine is best suited to aviary birds, to aid digestion and deliver the calcium appropriate for smaller species. Freshwater canunda shell is another good option for birds due to its 95% soluble calcium and very low salt content, while Cuttlefish are also popular with aviary bird keepers as a calcium source.

As with poultry, aviary birds self-regulate their intake. Supply it separately and let them take what they need.

In a nutshell (or an eggshell) it all comes down to feeding the right grit, at the right time, offered the right way. Keep soluble grit out of reach of young birds, never mix it into their feed, and only introduce grit once your birds have reached the appropriate age.