People ask me all the time: “Do cattle and pigs know they are going to slaughter?” When I started my career back in the 1970’s, I had to answer this question, so I went back and forth, comparing animal behaviors at feedlots and large meat plants. To my surprise I discovered that the behavior of the animals moving through the chute was the same in both places. If the cattle knew they were going to slaughter, I expected them to act wilder and be more difficult to drive in the slaughter chute. It was obvious that they did not know the difference between a chute that led to vaccinations from a chute that led to the stunner.

In very small meat plants, it is normal commercial practice to move pigs and sheep through the cattle stun box and stun them in groups in the shackling area. When one animal is stunned, the other pigs and sheep are standing next to them and observe stunning, hoisting and bleeding. When pigs are stunned in groups of five or six animals, does the last animal in the group become more stressed than the first one or two animals?

Research by Colorado State Univ. graduate research assistant Morgan Schaeperkoetter, who was studying livestock animal behavior and welfare, showed that the last pig in a group of five pigs was less stressed and had lower lactate levels compared to the first pig. Lactate is an easy-to-use blood test for measuring short-term handling stress. Her research was conducted in a small commercial plant during normal operation. To our surprise, the pigs that were stunned with a captive bolt and bled near the end of each group also had calmer behavior. They were more likely to spend more time rooting and exploring the shackling area, compared to the first pig. Watching the other pigs get stunned and bled had no effect on them. Stunning and bleeding of each group of pigs took 15 to 20 minutes.

One of the reasons the first one or two pigs were more stressed was due to being moved through a chute designed for cattle. The pigs became jammed beside each other and wedged in the chute. This occurred because a cattle chute is too wide for pigs. It is likely that the last few pigs in each group had time to calm down. One can conclude that getting jammed in a cattle chute was much more stressful than watching another pig get stunned and bled.

Other species

Sheep had the opposite results when handled, stunned and bled using the same methods. Each lamb was shot with a captive bolt and bled where other sheep could observe it. The sheep moved easily through the cattle chute. The lactate test showed that the sheep at the end of a group of 8 to 12 were definitely more stressed. The last one or two sheep were also more likely to run around the shackle pen and attempt to jump out. It is likely that the sheep were reacting to being separated from the other sheep. They have a strong flocking instinct, and one or two lambs isolated alone will often become highly stressed. It was likely that the sheep were reacting to isolation stress and not to observing stunning. To reduce stress from being isolated, it is recommended to stun the last two or three lambs in rapid succession to avoid having isolated animals.

The pigs acted as if they had no idea that their herd mate was being killed. Anecdotal evidence has shown that as long as the animal is still intact, there is little reaction. People who have made the mistake of removing the head in front of another animal sometimes observed a violent reaction. At this point, the animal discovers that something is really wrong.

The pigs and sheep in the experiment always observed a fully intact animal being hoisted, stunned and bled. I strongly recommend avoiding letting the animals observe the head being removed. From my observations, seeing skinned carcasses has little effect because they don’t know what they are. In most cases, they seem to be reacting to movement of the carcasses on the rail.