A retrospective study of the causes of morbidity and mortality in farmed elk (Cervus elaphus)

Abstract

A survey of North American farmed elk (Cervus elaphus) producers was performed to determine the causes of sickness and mortality in farmed elk and to estimate mortality rates. Records over a 10-year period from 8 North American veterinary diagnostic pathology laboratories were also examined and summarized. The primary diagnosis for each record was used to classify diseases into categories such as parasitic, infectious, toxicological, and neoplastic. Nonspecific trauma was the most frequently reported known cause of mortality in both sexes and all age classes by elk producers. Ranked on perceived economic importance, producers cited trauma, chronic wasting disease, calf scours, dystocia, pneumonia, winter tick, tuberculosis, and grain overload. One-year mortality rates for adults and yearlings were 2.6% and 2.7%, respectively. Mortality rates for male and female adult animals were 2.4% and 2.7%, respectively. In general, the major findings of the survey matched reported causes for mortality provided by elk producers.

Introduction

In the decade from 1990 to 2000, the number of elk farms in Canada increased from a few hundred to over 1000 (1). Previous disease surveys involved relatively few diagnostic reports from relatively few elk farms (2,3). Expansion of the elk industry provided an opportunity to learn in greater detail about the causes of morbidity and mortality in farmed elk. More detailed knowledge will permit veterinarians and other industry professionals to make science-based recommendations for disease prevention activities and management changes that will improve animal welfare and increase productivity in the elk industry. Industry wide measurements of morbidity and mortality rates provide “benchmark” estimates of these indices. Farmers can compare their own herds against these benchmarks to identify areas of deficiency and develop management programs targeted at improving their herd performance. Scientists can target research efforts towards developing strategies to improve the overall performance of cervid farms.

The purpose of this project was to report the causes of sickness and mortality in farmed elk in Canada and the United States over a 10-year period and to estimate the age and sex specific mortality rates for the 1999 to 2000 production year.

Materials and methods

Producer survey

A set of 35 questions designed to gather observational data about mortality rates and morbidity and reproduction parameters in farmed elk was pretested at 2 industry conventions. Prototype questionnaires and interviews were given to convention participants to ensure that the questions were easily understood and that producers could provide the data requested of them. The survey was then mailed to North American elk producers. To ensure confidentiality, only the name of the state or province where respondents farmed elk was requested.

A random sample of 709 elk producers was selected from a pooled database made from membership lists of national, provincial, state, and regional elk farming associations. After removing duplicate names, the sampling frame contained 1694 producers, who were then grouped by nationality and sampled in proportion to the number of Canadian and US producers in the sampling frame. The number of producers sampled reflected the number needed to detect a disease with a herd prevalence of 2% with 95% confidence, if only 50% of the questionnaires were returned. Producer names were sequentially numbered as they appeared in the database; computer generated randomized numbers were then used to select the sample.

The format of the questionnaire followed Dillman’s recommendations for maximum response to postal questionnaires (4). To maximize the response rate, respondents were made eligible for a lottery draw for 5 L of an anthelmintic (Cydectin; Wyeth Animal Health, Guelph, Ontario). Included with the questionnaire was an explanatory letter introducing the survey and emphasizing the benefits of the study, a lottery entry form, and a stamped self addressed return envelope. Postcard reminders were sent out to all producers 2 and 4 wk later. After approximately 6 wk, a 2nd identical questionnaire package was mailed to nonresponders and postcard reminders were mailed to them 2 and 4 wk later.

To ensure confidentiality, responses were immediately coded after receipt and entered into a database (Microsoft Access; Microsoft Corporation, Mountain View, California, USA) with no association between answers and respondents. Database entries were checked twice against questionnaires for their accuracy, and the internal validity of the database was assessed by comparing the answers to check questions. Database errors resulting from incorrect data entry were corrected in the database.

The at-risk study population was stratified according to age and sex, and mortality rates were calculated for each age and sex class over the 1-year period of the study. Producers were asked to name diseases that caused sickness or mortality on their farms during and before the period of the study. Morbidity and mortality rates were calculated for adults and yearlings over the 1999–2000 production year and expressed as percentages. Cohort specific morbidity and mortality rates for calves born in 2000 were not based on 1-year periods; rather they were based on specific time periods of risk. For example, neonatal mortality rates were calculated as a proportion of those calves born during the 2000 calving year that died within 1 mo after birth.

Assuming that most trauma arises through animal handling, we attempted to determine the likelihood of an injury resulting from any single handling event, and producers were asked to provide information about their most recent handling session; for example, weaning or tuberculosis testing.

Differences in proportional rates were tested for statistical significance by chi square analysis at a 0.05 significance level. Summary statistics are mostly provided in tabular form. Crude proportions or percentages were calculated by using the number of animals having the element of interest, divided by the number of animals at risk from that element during the study period. Mean proportions or percentages are farm level statistics, that were calculated by summing the crude proportions described above for each farm responding to the question and then dividing by the number of farms.

Pathology laboratory survey

Forty-two veterinary diagnostic pathology laboratories in the United States and Canada were contacted and asked to participate in the study. Of those laboratories willing to participate, 8 were selected for inclusion, based on the number of elk submissions they received over the period from 1990 to 2000 and on their ability to extract useful information from their records. These included laboratories in Alberta, British Columbia, Colorado, Minnesota, North Dakota, Saskatchewan, and South Dakota.

Submissions that included more than 1 dead elk were entered as a single record and each submission was considered 1 disease report without regard to size. Data were extracted from each record and coded into a database (Microsoft Access; Microsoft Corporation). To maintain client confidentiality, submissions for pathologic examination were identified only by an ID number. Keystone information stored for each record included submission date, age, sex, species, and primary cause of mortality. The primary diagnosis for each record was used to classify records into disease categories, such as parasitic, infectious, toxicological, neoplastic, etc. In addition, 3 pathologic diagnoses were recorded for each submission, based on the anatomical location, the pathological change, and the etiology associated with each lesion. Database entries were checked twice against the original records for the accuracy of each entry.

Results

Producer survey

Seven hundred and nine producers responded to the survey. Five questionnaires contained unreliable information and were removed from the study. The overall producer survey response rate was 33.9% (239/704), including 34.3% (148/432) of US and 33.5% (91/272) of Canadian elk producers. The distribution of Canadian respondents was skewed heavily towards the western provinces, with 96% of the responses divided between Alberta (44%) and Saskatchewan (51.8%). The Saskatchewan industry contributed 55.5% (3021/5446) of the total animals in the Canadian database, Alberta contributed 40% (2180/5446). South Dakota had the highest response (54.5%) from a US state, followed by Wisconsin (54.5%) and Kansas (46.2%). However, Minnesota contributed survey information on the most US animals (1393/6497 or 21.4%), followed by Wisconsin (882/6497 or 13.6%), Colorado (759/6497 or 11.7%), and Iowa (656/6497 or 10.1%).

Overall, survey respondents provided information about 11 943 elk. Of the total number, 3748 (31.4%) were live calves, 2116 (17.7%) were yearlings, and 6079 (50.9%) were adult animals. There were 1111 (52.5%) male and 1005 (47.5%) female yearlings, and 2832 (46.6%) male and 3247 (53.4%) female adults.

Producers reported 360 mortalities in elk of all ages (Table 1). Three hundred and five mortalities (84.7%) were attributed to a cause, the remainder were listed as unknown. In 60% of the reports, a veterinarian had been consulted for diagnosis or treatment. One-year mortality rates were similar for adult and yearling elk, 2.6% and 2.7%, respectively. Mortality rates for male and female adult animals were also similar, 2.4% and 2.7%, respectively. The rate for yearling males (3.3%) appeared to be higher than that of yearling females (2.0%), but the difference was not statistically significant (P = 0.10).

Table 1.

Single year^a producer-reported causes of morbidity and mortality for elk of all ages

Disease name	Number of sick	Number of dead	Number of reports	Veterinarianb
Unspecified trauma	9	46	43	13
Unknown	45	55	35	25
Dystocia	5	13	12	7
Pneumonia	15	14	13	13
Tuberculosis	22	118	9	9
Calf scours	19	13	8	5
Dam agalactia	19	13	8	5
Kidney failure	3	4	5	5
Other (38)	91	84	77	44
Total	229	360	210	126

^aMay 1, 1999 to April 30, 2000

^bThe number of incidents in which a veterinarian was consulted for diagnosis or treatment strategies

There were 46 producer-described causes of morbidity, mortality, or both, for elk of all ages. However, 38 of these causes were reported fewer than 5 times over the study period and are grouped in Table 1 as “other” disease. These “other” diseases accounted for 36.7% of the disease reports, which included 40.2% of the morbidity, and 23.3% of the mortalities. Unspecified parasitism (15.3%) and pinkeye (8.7%) accounted for most of the morbidity from this “other” group. Overall, the most frequently reported problem was unspecified trauma, comprising 20.5% of reports. Trauma was usually fatal, resulting in death in 46 animals and recoverable injury in only 9 animals.

Age specific information about the causes of elk mortality is provided in Table 2. Unspecified trauma was the most frequently reported health problem in all age classes of elk and was the 2nd most frequent known cause of mortality in yearlings and adults. Handling related injury and mortality proportions for elk calves, yearlings, and adults are provided in Table 3. Proportions are expressed as the percent of all elk that were injured or died following the last handling event recalled by the producer. Yearling bulls suffered proportionately more injuries (2.1%) than did the other age and sex classes, but the difference was significant only when compared with adult cows (P = 0.003) and calves (P = 0.008).

Table 2.

Single year^a producer-reported causes of morbidity and mortality for elk by age group

Disease name	Number of sick	Number of dead	Number of reports	Veterinarianb
Calves
Unknown	22	36	14	13
Unspecified trauma	2	22	18	5
Dam agalactia/abandoned calf	14	20	10	0
Calf scours	23	16	9	5
Pneumonia	13	9	9	9
Dystocia	3	9	8	3
Stillborn	0	9	5	2
Other (17)	68	26	27	17
Total	145	147	100	54
Yearlings
Unspecified trauma	1	13	12	1
Unknown	16	11	10	5
Tuberculosis	0	16	3	3
Other (10)	6	14	13	7
Total	23	54	38	16
Adults
Unspecified trauma	6	11	13	7
Unknown	7	8	11	7
Tuberculosis	1	102	5	5
Endometritis	3	3	4	3
Dystocia	2	4	4	4
Kidney failure	3	3	4	4
Pneumonia	2	5	4	4
Other	29	24	27	15
Total	53	160	72	49

^aMay 1, 1999 to April 30, 2000

^bThe number of incidents in which a veterinarian was consulted for diagnosis or treatment strategies

Table 3.

Handling specific injury and proportional^a mortality due to handling for elk calves, yearlings, and adults

	Calves	Yearling heifers	Yearling bulls	Adult cows	Adult bulls	Total
Injuries
Number of farms	201	166	161	198	181	227
Number at risk	3008	1147	900	3365	2205	10625
Number injured	28	12	17	25	35	117
Crude % injured	0.9b	1.0	2.1b,c	0.7c	1.6	1.2
Mean % injured	2.2	1.1	3.3	1.3	1.6	2.2
Range	0.0–100.0	0.0–50.0	0.0–100.0	.0–33.3	0.0–50.0	0.0–100.0
Mortality
Number of dead	5	2	0	2	3	12
Crude % mortality	0.2	0.2	0	0.1	0.1	0.1
Mean % mortality	0.8	0.4	0	0.1	0.1	0.7
Range	0.0–100.0	0.0–50.0	0	0.0–14.3	0.0–7.7	0.0–100.0
Case fatality rate
Crude case fatality %	17.2	16.7	0	8.0	8.6	9.8
Mean case fatality %	18.8	25	0	9.1	11.9	14.3
Range	0.0–100.0	0.0–100.0	0	0.0–100.0	0.0–100.0	0.0–100.0

^aProportions are expressed as the percent of all elk that were injured or died following a single handling event during the period May 1, 1999 to April 30, 2000

^b,cStatistically significant difference between groups (P < 0.05)

Calf mortality was calculated over 4 different time periods from birth to 1 y of age: Neonatal mortality (4.9%) was the proportion of all calves born alive that died before July 1st; summer mortality (1.4%) was the proportion of calves alive at July 1st that died before weaning; weaning mortality (0.3%) was the proportion of elk calves alive at weaning that died within 1 mo of weaning; and postweaning mortality was the proportion of calves alive 1 mo postweaning that died by 1 y of age (1.2%). Each period was significantly different from the other (P < 0.0001), except for the summer and postweaning periods (P = 0.90).

Two hundred and forty respondents answered the question: Have you ever had 1 of the following diseases in your elk? Of the 17 disease conditions presented in the question, winter tick was most commonly mentioned (23.8%), followed by calf scours (22.1%), grain overload (14.2%), and pneumonia (12.1%). Other parasitic diseases reported were lungworm (7.1%), liver fluke (6.7%), and meningeal worm (1.3%). Pinkeye was mentioned by 4.6% of respondents and 4.6% claimed that they had experienced bloat on their farm.

From a list of 21 diseases, respondents were asked to choose a) the single disease they thought was most economically important to individual elk farming operations and b) the one they considered the most economically important to the elk industry. Diseases were ranked according to the number of respondents selecting each disease as most important. With regard to individual operations, trauma (nonspecific) was cited most often from 142 responses, followed in descending order of frequency by chronic wasting disease (CWD), calf scours, dystocia, pneumonia, and winter tick. Tuberculosis and grain overload were ranked 7th and intestinal parasites, 8th. Liver fluke was 9th and capture myopathy, lungworm, and nutritional disease were mentioned 10th most often. Another 8 diseases shared the remaining votes equally.

One hundred and ninety respondents ranked diseases according to their importance to the overall industry. Chronic wasting disease was mentioned most often, followed by tuberculosis, Johne’s disease, calf scours, and intestinal parasitism in that order. Capture myopathy, liver fluke, and winter tick were the 6th most frequently mentioned diseases. The remainder of 1st place votes were divided equally among babesiosis, blackleg, brucellosis, bluetongue, and dystocia.

Pathology laboratory survey

The pathology laboratory survey yielded 1077 submissions. There were 314 (29.1%) female and 258 (24%) male elk submitted, and there was 501 (46.9%) submissions where the sex was not recorded. Twenty-nine (2.7%) submissions were less than term fetuses and 49 (4.5%) were animals less than 24 h old. One hundred and seventy-five (16.3%) submissions were older than 24 h but younger than 30 d of age. There were 145 submissions (13.5%) from animals > 30 d but < 1 y, and 473 submissions (44.1%) from animals > 1 y; 206 submissions (19.1%) were of unknown age.

In general, the major findings of the pathologic survey matched reported causes for mortality provided by elk producers. Primary diagnoses of pathology laboratory submissions for all ages of elk are summarized in Table 4. There were 94 diagnoses identified in the data set, but many causes had only 1 or 2 submissions, so primary diagnoses with less than 10 submissions are identified as “other.” The most common nonspecific primary diagnosis for the cause of death was either no diagnosis or emaciation. Emaciation was listed as a cause of mortality when the carcass was emaciated, but no cause for the emaciation could be found by the pathologist. The 2nd most common cause of mortality in the pathology records was trauma. Unknown and trauma were also the 2 most common causes of mortality reported by elk producers.

Table 4.

Primary diagnosis of submissions^a for all ages of elk to pathology laboratories

Disease	Cases
No diagnosis	144
Trauma	119
Pneumonia	88
Enteritis/diarrhea	70
Emaciation	61
Septicemia	55
Abscess	40
Kidney disease	37
Liver disease	33
Parasitism	28
Liver flukes	25
Abortion	23
Grain overload	18
Encephalitis	17
Dystocia	16
Cardiac disease	15
Stillborn	14
Neoplasia	13
Johne’s disease	13
Peritonitis	13
Meningitis	13
Copper deficiency	10
Other	212
Total submissions	1077

^a1990 to 2000

The primary laboratory diagnoses by age group are summarized in Table 5. Among elk aged < 30 d there were 39 different diagnoses identified in the data set, but diagnoses with fewer than 3 submissions were reported as “other.” The most common primary diagnoses were enteritis (21.2%), septicemia (12.8%), and pneumonia (8.0%). Causes of enteritis in elk included Escherichia coli, Rotavirus, Nematodirus spp., Clostridium perfringens, and cryptosporidia infections. The most important reported cause of septicemia was E. coli infection. Other, less important causes included infection by Clostridium spp., Salmonella spp., and Arcanobacterium pyogenes. The most important reported cause of pneumonia was infection by A. pyogenes, followed by Pasteurella spp., E.coli, Aspergillus spp., and Mycobacterium spp.

Table 5.

Primary diagnosis of elk submissions^a to pathology laboratories by age group^b

Disease	Cases
Less than 30 days of agec
Enteritis/diarrhea	48
Septicemia	29
No diagnosis	28
Pneumonia	18
Still born	14
Emaciation	13
Trauma	10
Dystocia	7
Liver disease	7
Kidney disease	6
Omphalophlebitis	5
Cardiac disease	3
Enteritis, necrotic	3
Myopathy	3
Non viable neonate	3
Abomasitis	2
Other (23)	25
Total submissions	224
30 to 365 days of age
Pneumonia	20
No diagnosis	15
Trauma	13
Parasitism	10
Emaciation	9
Septicemia	7
Abscess	7
Enteritis/diarrhea	5
Meningitis	5
Johne’s	4
Grain overload	4
Encephalitis	3
Cardiac disease	2
Listeriosis	2
Coccidiosis	2
Copper deficiency	2
Other (27)	35
Total submissions	145
Older than 1 year of age
Trauma	77
No diagnosis	70
Pneumonia	35
Kidney disease	31
Emaciation	23
Abscess	19
Liver disease	16
Enteritis/diarrhea	14
Encephalitis	13
Grain overload	13
Neoplasia	12
Dystocia	9
Liver flukes	9
Peritonitis	9
Johne’s	8
Septicemia	8
Cardiac disease	7
Copper deficiency	7
Capture myopathy	6
Liver flukes	6
Arthritis	5
Locoweed poisoning	5
Other (37)	71
Total submissions	473

^a1990 to 2000

^bExcluding cases with unrecorded age (n = 206)

^cIncluding animals < 24 h old but not less than term fetuses (n = 29)

There were 43 different diagnoses identified for elk between 30 and 365 d of age. Diagnoses with fewer than 3 submissions were reported as “other.” The exceptions were listeriosis, coccidiosis, and copper deficiency, which were included for their relevance to other species. Pneumonia was the most common primary diagnosis (13.9%) and unspecified trauma was the 2nd (9.0%). Other important primary diagnoses were unspecified parasitism (6.9%) and septicemia (4.9%).

The data set for elk > 1 y contained 59 diagnoses, but those associated with less than 5 submissions were reported as “other.” The most common primary diagnoses of elk pathology submissions in this age group were trauma (16.2%), followed by pneumonia (7.4%). Other important primary diagnoses for elk > 1 y were kidney disease (6.5%), abscesses (4.0%), liver disease (3.4%), and enteritis (2.9%).

Of the 133 morphologic diagnoses for mortalities with lesions in the respiratory tract, the most common was pneumonia (88/133 or 66.2%). Most frequently the etiology for the pneumonia was “unknown” (36/88 or 40.9%). Of the known etiologies, A. pyogenes was the most common (17%), followed by Pasteurella spp. (6.8%). Pulmonary edema was an important primary diagnosis of respiratory tract lesions, but in none of these submissions was an etiology reported.

The most common morphologic diagnosis of 186 elk pathology submissions with gastrointestinal lesions was enteritis (81/186 or 43.6%). The most common etiological agents associated with enteritis were E. coli (20/81 or 24.7%), Rotavirus (7.4%) and Clostridia spp. (8.6%). Parasitic enteritis etiologies included coccidia, Trichostrongylus sp., Strongyloides sp., Nematodirus sp., Haemonchus sp., and Trichurus sp. The 2nd most common etiology associated with gastrointestinal lesions was grain overload (9.7%). Johne’s disease was also important in causing morbidity in elk (7.0%).

The most common parasites reported in 75 submissions where the primary cause of mortality was parasitism were liver flukes (26/75 or 34.7%), including F. magna and D. dendriticum. Other parasites reported included coccidia (5/75), Trichostrongylus sp. (4/75), Trichuris sp. (3/75), Babesia sp. (2/75), Nematodirus sp. (2/75), tapeworm (3/75), Haemonchus sp. (1/75), Sarcocystis sp. (1/75), Cephenemyia sp. (1/75), and ticks (1/75).

Encephalitis was the most common (17/45 or 37.8%) morphologic diagnosis for 45 pathology submissions showing central nervous system lesions, followed by meningitis (12/45 or 26.7%). Etiologies were often not reported for encephalitis (12/45), but those that were included infection by E. coli and A. pyogenes, and parasitism by Elaeophora schneiderii. Causes of meningitis were likewise infrequently recorded, but E.coli (4/12) and P. multocida (1/12) were found. Other important primary diagnoses associated with central nervous system lesions were locoweed poisoning (8/45) and spongi-form encephalopathy (3/45).

Of the 280 primary diagnoses associated with infectious disease, septicemia (55/280 or 19.6%), followed by pneumonia (43/280 or 15.4%), enteritis (45/280 or 16.1%), and abscesses (38/280 or 13.6%) were the most common. Etiologies associated with septicemia were largely unrecorded (24/550) but included most commonly E. coli (17/55), followed by Clostridium spp. (4/55), A. pyogenes (2/55), Salmonella spp. (2/55), and Listeria spp. (2/55). Pneumonia was most commonly associated with A. pyogenes (15/43), unidentified bacteria (7/43), Pasteurella spp., Aspergillis spp. (6/43), Mycobacterium spp. (2/43), Streptococcus spp. (1/43), Aeromonas hydrophilia (1/43), and E. coli (1/43). Abscesses were mostly not attributed an etiology (24/38). Those that were were attributed most commonly to A. pyogenes (9/38), followed by unspecified bacteria and fungal agents. Infectious enteritis was most frequently associated with E. coli (20/45), followed by Rotavirus (7/45), C. perfringens (5/45), and unidentified viruses (6/45) or bacteria (5/45).

Discussion

Producer survey

The response rate and the proportional numbers of elk represented from Alberta and Saskatchewan accurately reflect the distribution of farmed elk in Canada in 1999 to 2000. Canadian inventory records for the year 2000 show that Alberta had 47.9% of Canada’s elk herd and Saskatchewan had 41.9% (1). Elk in Saskatchewan are somewhat over represented at 55% of the surveyed Canadian elk, but in the authors’ opinion, management techniques and feeding practices do not differ appreciably between the 2 provinces. The US samples were also selected proportionately, but they can be assumed to reflect a wider range of geographic influences on morbidity and mortality, such as climate and feed type, than did the Canadian samples. However, major industry problems, such as handling-related trauma, are largely independent of regional influences on the incidence of infectious disease, such as climate.

The cause of most mortality was unknown or due to unspecified trauma (Table 1). Similar findings regarding the importance of trauma as a cause of mortality have been reported elsewhere (3). However, in our survey, trauma was associated with the most individual mortalities, only in calves (Table 2). Aside from tuberculosis, the cause of most producer reported mortalities was unknown. There may have been several reasons why producers did not know the cause of their elk mortalities, including failing to employ a veterinarian to perform a postmortem diagnosis on dead animals. The use of veterinarians was highly variable among individual elk producers, but veterinarians were consulted for 60% of disease occurrences. Nine outbreaks of tuberculosis involving 118 mortalities were reported, making this disease the primary cause of producer reported individual elk mortality in North America in 2000. This finding was not supported by our pathology records survey results, although this may be because submissions that included more than 1 dead elk were entered as a single record into the laboratory database and each submission was considered 1 disease incident without regard to size.

In our producer survey, adult tuberculosis accounts for almost 10 times as many mortalities as trauma. Interestingly, tuberculosis was also reported to have caused the most yearling deaths. It is uncertain whether deaths attributed by producers to tuberculosis were actually caused by disease or were, in fact, postmortem findings subsequent to tuberculosis control slaughter programs. Although tuberculosis is certainly an important cause of disease in elk, it tends to cluster within herds and in some years, it may be infrequently reported, depending on surveillance activity.

Age specific injury and mortality rates indicate that yearling bulls are most at risk from injury during handling episodes and injure themselves more than twice as often as yearling heifers (Table 3). However these injuries were apparently not as likely to be fatal and males were not more likely to die as a result of handling than females. No handling fatalities were reported for yearling males, which is perhaps surprising given their disposition to panic and flight when handled. Recall that overall mortality rates for yearling males (3.3%) is higher than for any other age or sex class, and although in this study the difference is not statistically significant, it makes empirical sense to those who handle elk frequently.

Since trauma associated with handling farmed elk was identified as an important known cause of mortality, research aimed at improving handling systems would be beneficial. Improved understanding of elk behavior in both a confined setting and during handling or processing activities is needed. Basic principles for handling elk should be developed, so that paddocks and handling facilities that are less likely to cause injuries could be designed.

Neonatal mortalities were highest during the 1st month after birth compared with those during the summer months, at weaning, and after weaning to 1 y of age (P < 0.0001). Pople et al (5) found that 36.9% of neonatal mortalities during the 1st month of life were from infectious disease. Our survey of laboratory records shows that diarrhea, septicemia, and pneumonia alone were responsible for 42.4% of mortalities in that age group (Table 5). The rates dropped over the summer and at weaning but increased again for the period from 1 mo after weaning to 1 y of age. This increase may not have resulted from a truly higher rate but rather because this period was longer than the previous 2.

Diarrhea, septicemia, and pneumonia are common disease syndromes associated with neonatal mortality in other farmed species, as well as elk. The syndromes are precipitated by a collage of risk factors including infectious agents, nutrition, weather, genetics, behavioral characteristics of the dam, and management conditions. The information about risk factors for these diseases in other farmed species should be used to establish causal associations between the risk factors and disease syndromes in elk. For example, previous studies in deer have identified behavioral characteristics of the dam, such as mismothering and calf abandonment, as important to neonatal mortality (5,6). Information about dehydration, starvation, and emaciation problems indirectly related to inadequate maternal care was not captured in our survey. Dam agalactia or calf abandonment was held responsible for 9.7% of calf morbidity and 13.6% of calf mortality (Table 2), but we suspect that elk calves dying indirectly from factors like calf abandonment may have been mis-classified as “unknown cause,” thereby underestimating the importance of management-related factors in fawn mortality.

To compare the overall mortality experienced between farmed cervids, a 1-year age and sex standardized mortality rate for elk, white-tailed, fallow, and red deer was calculated from the results of similar surveys by the authors. The rates of mortality for each age and sex class of each species was standardized against the combined population of elk and white-tailed, red, and fallow deer. Although the populations of the 4 species in this study had slightly different age and sex structures, white-tailed deer had the highest mortality rate at 13.9%. It was 5.2 times higher than red deer (2.7%), 2.7 times higher than fallow deer (5.2%), and 3.0 times higher than elk (4.6%). This standardized mortality rate for elk is larger than the 2.6% crude mortality rate reported for adult elk in our study and should only be used to compare mortality among species.

Producer derived information about on-farm morbidity focused largely on parasitic disease. Winter tick (Dermacentor albipictus) was identified by a large proportion of elk producers and presumably it caused large problems. The life cycle of this one-host tick is such that most of the larval developmental stages occur on the animal (7). Not all stages are feeding at the time of systemic treatment with avermectins and not all stages are susceptible to currently available acaricides. These factors and practical considerations, such as application of water-based treatments at subzero temperatures, can make effective treatment difficult. Environmental management of the parasite may be the best alternative to current treatments (7).

Other diseases mentioned by producers, such as grain overload, are management-based. The practice of strategic feed supplementation to optimize performance in antler growth or reproduction and lactation can be problematic, if producers do not understand the hierarchical nature of elk herd structure. The most socially aggressive animals are often at risk from supplementation practices, unless consideration is given to factors such as adequate feeder space, feeding frequency, and gradual onset of supplementation.

Producer ranking of diseases important to themselves and the elk industry demonstrated an awareness of existing problems, as well as potential disease threats. By acknowledging that handling trauma is a current problem on their farms, producers have taken the first step towards developing welfare friendly handling and restraint techniques and systems. Naming CWD, calf scours, pneumonia, and parasitism as important diseases accurately reflects the general disease syndromes found in North American pathologic surveys (1,2,8). Producers accurately predicted that CWD, bovine tuberculosis, and Johne’s disease (Mycobacterium paratuberculosis infection) would be problems to the industry. The surveys were conducted in 2000, prior to the discovery of widespread CWD in wild cervids, and before an appreciation of the magnitude of mycobacterial disease in wild cervids in Michigan (9) and Manitoba (10).

Pathology laboratory survey

An attempt was made to include only those records that could be determined to have originated from farmed elk. Although many of the laboratories did not provide information clearly stating that submissions originated from farmed elk, there was often information within the body of the record that allowed submissions to be classified as to their origin. Records of elk heads submitted from hunter-killed elk for CWD testing, as well as from those submitted from clients who were fish and game officers or from those that contained information indicating that an elk was shot with a rifle, were excluded from the database. It was not possible, however, to determine the origin of all submissions and the database must be considered to contain some submissions from free ranging elk.

Submissions comprising more than 1 dead elk were entered as 1 disease incident, because we felt that farmers and veterinarians would be reluctant to submit all dead elk from an outbreak for laboratory analysis due to the cost of laboratory diagnosis. Rather, they would submit only as many mortalities as they felt were necessary to firmly establish a cause of death. Therefore, the number of elk submitted in each disease incident was considered to be a poor estimate of the mortality rate in an outbreak. Any inferences about the relative importance of specific diseases obtained from this portion of the study must relate to the number of disease incidents, rather than to overall mortality associated with the disease.

The most common nonspecific cause of death was either no diagnosis or emaciation. To some extent, the ability of a diagnostic pathologist to determine cause of death is dictated by the adequacy of case history information and the financial resources available to pursue laboratory investigations. One could speculate that submission with an improved case history and more laboratory testing might have reclassified many of the emaciation cases.

Analysis of laboratory reported calf mortality (Table 5) suggests that disease, for example, enteritis and septicemia, rather than management or other factors, such as mismothering, were responsible for most mortalities in calves < 30 d of age. As noted elsewhere in this discussion, some studies in deer have identified environmental-or management-related factors, such as mismothering and abandonment resulting in a diagnosis of dehydration and emaciation, as being at least as important as disease in causing neonatal deaths (5,6). Data were accumulated from summary reports provided by participating laboratories rather than close examination of case report contents. Because of this, we feel that information helpful in identifying a lack of maternal care or environmental causes of morbidity and mortality was not collected, leading to a default diagnosis of unknown cause of death. The effect of this would be the relative overreporting of disease issues and underreporting of management related issues in neonatal mortality.

No effort was made to separate mortality diagnoses by pathology laboratory, perhaps giving some indication of regional importance of diseases, such as pneumonia. It is now understood that early cases of CWD were mis-classified because the presenting signs were that of an aspiration pneumonia or nonspecific emaciation. Impaired vagus nerve function in CWD results in swallowing problems, often leading to secondary aspiration pneumonia (11). Histological examination of brain is time consuming and costly, so animals classified as pneumonia or nonspecific emaciation may have, in fact, been CWD cases, but there is no practical way to confirm this.

In summary, the highest mortality rates in farmed elk occurred in the neonatal period from birth to 1 mo of age and resulted from a variety of conditions precipitated by risk factors, including environment, management, and nutrition. Epidemiological research targeted at determining causally associated risk factors could help to reduce the incidence of these diseases in the 1st mo of life. Elk farm productivity is also strongly influenced by post weaning mortality, a large proportion of which is due to handling associated trauma and, therefore, preventable. Improved facilities and the use of appropriate handling practices would be of great benefit.