Natural casings from pig, sheep and cattle — types, calibres and use
How to distinguish between the raw materials you work with every day
When you stand at the sorting table the first thing you must be able to read on a casing is which animal species it comes from and what caliber it has. It's not just about knowing the difference — it determines which batch the casing goes into and thereby what sausage type it later ends as a skin for. The three basic types you work with in the trade are pig casing sheep casing and beef casing (also called bung) and each has its own characteristics.
§Pig intestine — the workhorse of the range
Pig intestine is the most common natural casing in production and typically lies in the calibre range 30-38 mm, sold in intervals such as 30-32 mm and 32-34 mm. The thinnest pig intestines are often used for bratwurst-type sausages, while the thicker calibres are used for coarser products like cooked sausages. Pig intestine is relatively robust to work with compared to the two other types, which makes it a good casing to practise your handiwork on as new to the trade.
§Sheep intestine — the thin and delicate one
Sheep intestine is the thinnest of the three natural casings and typically falls in the 18-28 mm range, divided into finer sizes like 18-20, 20-22, and up to 26-28 mm. The thinner the caliber, the more delicate the casing, and the thinnest sheep casings are classically used for wieners. Because sheep casing is so thin it requires more care during cleaning and turning than pig casing — it can simply burst if you use too much force or wrong technique.
§Beef intestine (casing) — the thick and curved
Beef intestine, often called casing, is the strongest of the three and typically ranges from around 37 mm and upwards, sorted into groups such as 37-40 mm and 40-43 mm. It is so distinctly curved in its natural form that it is almost only suitable for sausages shaped as rings, for example Christmas sausages and coarse aged sausage types. The coarse structure also makes it more robust to rough handling than sheep intestine, but it in turn requires a different turning technique because of the curvature.
| Type | Typical calibre | Typical application |
|---|---|---|
| Sheep intestine | 18-28 mm | Wiener sausages and other thin sausages |
| Pig intestine | 30-38 mm | Bratwurst type and coarser cooked sausages |
| Beef intestine (casing) | 37-43 mm and upwards | Christmas sausages and coarse ring sausages |
§Calibre is not just a number
Calibration is about measuring the casing's diameter so precisely that the customer – typically a sausage factory – can count on a batch giving a uniform sausage size throughout. If the calibre is too spread within the same batch the customer's production gets uneven sausages and that's a quality fault that can send the goods back. Therefore a steady hand and a trained eye for thickness is some of what sets an experienced casing technician apart from a newcomer.
- 01Sheep intestine: thinnest and most delicate — requires the gentlest handling.
- 02Pig intestine: medium-thick and robust — the most common working material.
- 03Beef intestine/casing: strongest and distinctly curved — typically used for ring-shaped sausages.
- 04Calibration: diameter measurement that determines which batch and which customer the casing fits.
- 05Uniformity within the same batch is a quality factor in itself.
§Quality grades and sorting
Beyond type and calibre intestines are also sorted into quality grades. At the sorting table you assess the intestine for visible damage — holes thin or discoloured areas and places where cleaning has not fully succeeded. An intestine with too many defects or too much variation in thickness is sorted into a lower quality group or rejected entirely while a uniform whole and properly calibrated intestine goes into the best quality group. It is this step that ultimately determines which price and which customer a batch can be sold to.
Part of the Danish bowel trade is organized into large, specialized companies that clean, sort and export natural casings on a large scale to sausage producers in many countries. Whether you end up in a small intestine cleaning company or a large export company, it is the same basic skills — knowing the types, measuring calibre correctly and assessing quality honestly — that underpin the work.
Over time, you learn to read type and calibre almost by intuition, before you even get the measuring tape out. This is the kind of experience that makes you valuable in a trade where the raw material varies from animal to animal, and where it is your hands that ensure the finished product is consistent.