Lamb Slaughter: From Kill to ChillSteven Brankle, Tom Finney, Summer Heyerly

This is the sheep waiting in the handling facility. The area must be free of protruding objects that could injure the sheep during handling. There must be a constant water source up to the point of slaughter. It needs to be a low stress environment to prevent the degradation of meat quality.

Pre-Slaughter Handling Facility

Acquiring the Live Weight

The sheep is weighed immediately before slaughter. The lamb may have 1-2% shrink from stress of transport and excessive handling before slaughter.

The live weight can help in estimating the dressing percentage which is used to calculate the whole carcass value.

The dressing percentage adjusts for the inedible parts of the animal that are discarded. These parts have no value, but must be accounted for during slaughter. These include: hide, head, feet, viscera, etc.

Captive-bolt Stunning

The lamb is handled gently into the kill area. A captive-bolt gun is used to render the lamb unconscious before exsanguination, or bleeding of the lamb. This process is meant to be as painless for the animal as possible. This also prevents meat quality from decreasing during the slaughtering process due to extreme stress.

Exsanguination

Immediately after stunning the lamb, the carotid arteries are cut to drain the animal of as much blood as possible. The animal is allowed to bleed out for at least five minutes to prevent blood spotting in the meat. The animal’s heart still beats a few minutes immediately following exsanguination, which helps pump as much blood out of the body as possible.

Removing the Hide from the Animal

The hide must be removed with careful attention not to puncture or damage the carcass. A lot of time is taken during this part of the process due to the amount care needed to maintain the meat quality and conformation.

Hide Removal (continued)

The head and feet are also removed at this time along with the hide. If you remember, these are all inedible and directly influence the dressing percentage.

Determining the Physiological AgeIn determining the approximate age, the radius and ulna must be broken. If the foot separates at the actual joint, or spool joint, then the lamb is considered old and will receive a lower quality grade.

If the bone breaks at the growth plate, at the epiphyseal plate, then the lamb is considered young and can receive a choice or prime quality grade. The picture here shows a break joint on a lamb.

Removal of the Viscera

AfterAfter the hide is removed, the hind legs are tied together, and then hung from a hook on the rail.

The sternum, or rib cage, is cut open with a saw. The cut is taken further with a knife to the groin area. This allows the viscera to be cut out carefully. Caution is taken not to puncture any of the organs and risk contaminating the meat with fecal material.

USDA Inspection

The viscera is inspected by State USDA Inspector. The inspector will be looking for any tumors, inflammations, or other abnormalities in the viscera. If none are found, parts like the heart and liver can be sold, but the rest is discarded.

Washing the Carcass

The carcass must be washed thoroughly to remove any kind of fecal material or any other inedible material remaining in the carcass. Each carcass must be verified of being free of any of the mentioned contaminants per USDA regulations.

Hot Carcass Weight is Recorded and Carcass is Labeled

After washing, a hot weight is taken of the carcass. A tag is made containing the live and hot weight, along with the date and tag number of the lamb. The tag remains on the carcass until the carcass is broken down. All of this information is also kept in the business office to have on hand for quality assurance.

Final USDA Inspection

The State Health Inspector performs a final inspection of the carcass. He searches for wool, fecal material, or other foreign materials on the carcass. If unacceptable, the carcass must be rewashed and problem areas must be trimmed, or cut out of the carcass. Once approved, the carcass is stamped with a USDA seal and moved to the cooler.

Carcass Chilling

The carcass is chilled to a temperature of 30-35 °F. The lamb carcasses are allowed to hang until the onset of rigor. They can safely be stored in the cooler for 5-14 days depending on how soon they need to be processed. The longer the carcass remains in the cooler, the more tender the product will be for the consumer. If the carcass was not put in the cooler at this specific temperature, meat quality issues would occur including freeze rigor, heat rigor, microbial growth, etc. These issues will all decrease the quality of the final product and are minimized at this temperature.

Following chilling, the carcass is broken down into retail cuts and sold.

Please see the Carcass Breaking Project for more information.

All pictures were taken by Tom Finney in the Purdue Meat Lab (Butcher Block)