Euthanasia of Danish dairy cows evaluated in two questionnaire surveys

Background Mortality risk in Danish dairy cows has more than doubled since 1990 (from 2% in 1990 to 5% in 2005). Until now, registrations about dead cows in the Danish Cattle Database have not included information about whether the cow died unassisted or was euthanized. Methods We interviewed a random sample of 196 Danish dairy farmers that had reported a dead cow to the Danish Cattle Database in 2002 and 196 dairy farmers that had reported a dead cow in 2006. Our objectives were to evaluate the proportion of euthanized cows, changes in the behaviour of farmers regarding euthanasia of cows over the years and possible reasons for these changes. Results It seems that the threshold for euthanasia of cows among farmers has changed. Farmers generally reported a lower threshold for euthanasia compared to 5–10 years ago. Conclusion The threshold for euthanasia of cows has, according to the dairy farmers, become lower. This might have positive impacts on animal welfare as more seriously ill cows are euthanized in the herds and not put through a period of suffering associated with disease and treatment or transported to a slaughterhouse in poor condition.


Background
The peer reviewed literature on dairy cow mortality is relatively sparse. In a review on dairy cow mortality, Thomsen and Houe [1] concluded that the number of published studies is surprisingly low, especially seen in relation to the large impact of dairy cow mortality on animal welfare and the farmer's economy.
Mortality risk defined as unassisted death and euthanasia in Danish dairy cows has increased significantly since 1990. The mortality risk has increased from approximately 2% in 1990 to 5% in 2005. This increase is seen for all major dairy breeds and for all parities. There has been only a slight increase in mortality risk during the period 2002 to 2005 (from approximately 4.7% to 4.9%). Throughout the years the mortality risk has been approximately twice as high in older cows (parity 3 or older) as in younger cows [2,3]. At first glance, this development seems very negative, as mortality risk in Danish dairy cows has more than doubled since 1990. The increased mortality can be caused by an increasing number of cows dying unassisted or by an increasing number of euthanized cows (or both). Cows dying unassisted probably often constitute an animal welfare problem, as cows dying unassisted in many cases will suffer from fear or pain before death. The situation concerning euthanasia is, however, more complex. An increase in the number of euthanized cows might be due to an increased number of seriously ill cows. This situation also has negative impacts on animal welfare. If, on the other hand, an increase in the number of euthanized cows is not a consequence of increased morbidity, but caused by an altered threshold for euthanasia of cows among farmers, it might have a positive impact on animal welfare. More seriously ill cows might be euthanized at an early stage and thus not put through a (perhaps long) period of suffering associated with disease and treatment attempts.
The objectives of this study were to examine the proportion of dead Danish dairy cows that had been euthanized in 2002 and 2006, to examine the development over time in the threshold for euthanasia of cows based on interviews with farmers, to evaluate the farmers' perceptions regarding the background of this development and finally to analyse the welfare implications.

Methods
In Denmark, farmers are required by law to report all deaths in cows to the Danish Cattle Database. Registration is based on the mandatory identification by ear tags and a central computerized tracking system. Consequently, a registration rate very close to 100% is achieved. Until now, these registrations have not distinguished between cows dying unassisted and cows being euthanized on the farm. They were all simply recorded as 'dead'. Until recently, it was therefore unknown how many cows died unassisted and how many were euthanized and whether there has been a change in the prevalence of euthanized cows over the years. Over the course of 7 weeks in 2002, and again in 2006, we randomly identified four cows on a daily basis that had been reported as 'dead' to the Danish Cattle Database. The random samples in each of the two years were independent. Dead cows included unassisted dead and euthanized cows, but not cows slaughtered. As all Danish dairy farmers are required by law to report dead cows to the Danish Cattle Database, the sample population for the study was all Danish dairy cows/ herds. The 196 farmers who had reported the selected dead cows were asked to participate in a questionnaire survey that was part of a larger study on dairy cow mortality [2] (data from the 2002 questionnaire survey has previously been presented in [2]). The number of farmers participating in each questionnaire survey was determined based on a sample size calculation that is presented in [2]. The sampling protocol guaranteed that an equal number of cows, which had died every day of the week, were sampled. Only cows of dairy breeds and currently in commercial milk-producing herds were included. Cows from herds where all cows were euthanized because of occurrence of bovine spongiform encephalopathy (BSE) were not included (until July 2008, a total of 14 Danish herds have been infected with BSE [4]). Cows from educational or experimental herds were also excluded from the study. Immediately following the daily sampling protocol, a letter of introduction was sent to the farmers. The letter explained the background and purpose of the study and guaranteed confidentiality. To minimize recall bias, farmers were contacted by telephone 2 to 7 days following the mailing of the letter. If the farmer was not reached by phone, we attempted calling each subsequent day up to a maximum of four days. The farmer was censored if we failed to make contact. If farmers were excluded from the study an additional dead cow was identified from the database and the owner contacted in the same manner as described above. The resulting data set contained 196 dead cows and the corresponding interview from the 196 owners of these animals in each of the two years sampled (in total 392 farmers interviews).
The farmers were asked whether the cow died unassisted or was euthanized (closed question). Additionally, the farmers were asked their opinion regarding changes in their practice concerning euthanasia over the past 5 years using a closed question. The possible answers were: 1) I have lowered my threshold for euthanasia compared to 5 years ago, 2) my threshold is unchanged compared to 5 years ago, and 3) my threshold has increased compared to 5 years ago. If the farmer had started his/her operation less than 5 years ago the question was classified as 'not relevant'.
In the 2006 questionnaire survey the new sample of farmers were interviewed in exactly the same manner as described above. Additionally, they were interviewed about the reasons behind possible changes in their practice concerning euthanasia using an open question. Trends in prices of live dairy cows and beef meat over time were compiled from public statistics and used in the discussion of possible changes in the practice concerning euthanasia.   Percent of farmers that they had the same threshold and therefore euthanized the same relative number of cows as 5 years earlier.

Results and discussion
In 2006, 54% reported a lower threshold and therefore performed euthanasia relatively more frequent than 5 years earlier, 33% reported unchanged threshold and performed euthanasia at the same level as previously and 10% reported higher threshold and euthanized relatively fewer cows than 5 years earlier. Additionally, many farmers stated that changes in the practice concerning the veterinary inspection at the Danish slaughterhouses have affected their behaviour. A cow that was considered fit for transport a few years ago, is now often considered unfit for transport. If a farmer chooses to send such a cow for slaughter, the case may be considered as a violation of animal protection laws and consequently result in a fine to the farmer. To avoid this situation, many farmers therefore probably choose to euthanize cows whose fitness for transport is questionable. Some of the cows that are currently euthanized in the  1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year Meat Live cows herds would probably have been sent to slaughter a few years ago. Besides a relatively new law against the slaughter of cows in the last tenth of pregnancy, these changes at the slaughterhouses are not caused by changes in any laws or regulations [7], but are most likely a result of a generally increased debate about and focus on the welfare of animals being transported for slaughter in Denmark in recent years [8]. This debate on animal welfare might have affected the awareness of veterinarians at the slaughterhouses and caused them to lower their threshold between what is acceptable and not when it comes to the transportation of animals.
We have no evidence indicating whether the number of seriously ill cows has increased during the last decade and therefore we are not able to quantify to what extent an increasing prevalence of euthanized cows might also have been affected by an increasing number of seriously ill cows. The number of recorded disease treatments in Danish dairy cows has, however, not changed significantly during the last 10-15 years [9]. It should be noted that the number of recorded disease treatments is not necessarily a good indicator of the 'true' disease status in the population. There are a number of steps from a cow being sick to a treatment record. If the farmer does not observe that the cow is sick, no treatment is initialised and hence no treatment is recorded. If the farmer observers that the cow is sick, he/she might for different reasons decide not to treat the cow [10]. Again, no treatment is recorded. And finally, if the farmer observes a sick cow and decides to treat her, the treatment might not be recorded correctly.
As a consequence of the findings from this study, as of the end of 2007, farmers are required to report to the Danish Cattle Database whether a dead cow died unassisted or was euthanized thus allowing differentiation between unassisted dead and euthanized cows in the future and evaluation of the welfare implications of possible changes in the proportion of euthanized cows.

Conclusion
Other studies have shown that mortality risk in Danish dairy cows has increased significantly since 1990. Results from interviews with farmers, however, indicate that the threshold for euthanasia of cows among farmers has lowered. This situation might have a positive impact on animal welfare as more seriously ill cows are euthanized in the herds and not put through a period of suffering associated with disease and treatment or transport to a slaughterhouse in poor condition.