Studies offer scientific appraisal of tail docking effects in dairy cattle

"The prevalence of (bovine) tail docking has exploded. Ten years ago, there weren't very many people docking tails," Dr. Pamela Ruegg began during a presentation at the dairy session of the AABP conference, Sept. 26-28 in Madison, Wis.

"As the perception of improved milking hygiene and improvements in operator comfort have become more widespread, there's been wide adoption of this practice."

Dr. Ruegg, who is with the Department of Dairy Science at the University of Wisconsin-Madison, said that some have concerns about this practice. The pain associated with tail removal is one issue, and the effects on behavior, another. Animal behaviorists and researchers such as Temple Grandin, PhD, are concerned about the ability of cows with docked tails to express normal behavioral signaling to other cows. In the United Kingdom, where tail docking is considered animal mutilation, Dr. Ruegg said, the practice is banned.

To study the behavioral and physiologic effects of tail docking, including subsequent tail atrophy, she and her team, including graduate student Daniel Shriner, conducted experiments in preparturient heifers, with and without use of epidural anesthesia. A secondary objective was to determine the effects that tail banding has on the behavior of calves seven to 42 days of age.

The reason Dr. Ruegg's team conducted that research on the behavioral and physiologic effects of tail docking was so that the university's animal care and use committee would allow them to proceed with a second study—the effects of tail docking on milk quality and cow cleanliness. The committee wanted investigators to show that the tail docking process wasn't harmful to the animals.

Behavioral, physiologic effects study
At least a week before they began the initial study, the researchers went to one of their experimental herds and trimmed the switches off the 20- to 25-month-old heifers prior to application of tail bands three to four inches below the vulva. They were vaccinated against tetanus 21 days before treatment and again the day the bands were applied. All hair was clipped from their tails five days prior to treatment.

"Anecdotally, I wish we had done behavioral observation after we had clipped the hair from the tails," Dr. Ruegg said, "because one of the biggest behavioral effects came when we shaved the switches—the heifers spent the next hour switching their tails and looking at their hindquarters."

The 24 heifers were randomly allocated to one of four groups: two groups whose tails were docked, using an elastrator band (the calves in one group were given epidurals); and two control groups, one given epidurals.

Trained observers recorded the animals' behavior for six weeks, using standardized definitions of behavior, recorded formats, and time periods.

Experiments in calves involved 40 Holstein calves aged one to six weeks. They were divided into two groups: 22 preweaned calves aged seven to 21 days, and 18 preweaned calves aged 21 to 42 days. Each group included animals whose tails were docked by application of a rubber ring, and control animals. No epidurals were given.

The results: in the preparturient heifers, the investigators observed no significant behavioral, hematologic, or physiologic differences attributable to tail docking, with or without an epidural or in the process of tail atrophy.

Cortisol values in the heifers were comparable to values others have collected for nonstressed animals. Hematologic values for the heifers were within normal limits, except for neutrophils, which were slightly outside the reference range for all the heifers. Heart rate and body temperature did not differ significantly.

There was a significant behavioral difference among the calves, however. Those aged 21 to 42 days were observed to be more restless after application of rubber banding than were the control calves. The tail-docked calves also had a tendency toward more frequent rear visualization than the control calves.

"The older calves—the calves that were 21 to 42 days of age—were more playful and they had more restlessness than the younger calves, and that was statistically significant," Dr. Ruegg reported.

The banded tails in the calves and heifers demonstrated progressive atrophy, and five detached spontaneously between days 25 and 42. The investigators removed the remaining seven tails on day 42.

Milk quality, cow cleanliness study
The objective of this study was to determine the effects of tail docking on somatic cell count, intramammary infections, and udder and limb cleanliness in commercial dairy herds.

"Premilking udder hygiene ... is a very important point of exposure to environmental mastitis pathogens," Dr. Ruegg said.

The team enrolled 1,250 lactating dairy cows in eight commercial free-stall operations in Wisconsin.

All cows received two doses of Clostridium vaccine. Each cow received either a rubber ring on its tail, or the second dose of the vaccine and nothing more.

The investigators collected sterile, composite milk samples on the day of treatment and four more times, bimonthly.

"At the end of the study, there was no significant difference in the culling of animals between the docked and control groups."

The prevalence of intramammary infection did not differ significantly between the animals with docked tails and the control animals, for any pathogen, including environmental pathogens and minor pathogens.

Udder hygiene scores for tail-docked and control cows were similar. Limb hygiene scores were slightly lower for tail-docked compared with control cows, but Dr. Ruegg questions the biological relevance of that statistic because the difference was less than 0.3.