Exp. Geront. Vol. 1, pp. 193-199. Pergamon Press 1965. Printed in Great Britain

SURVIVAL OF BEAGLES UNDER NATURAL AND LABORATORY CONDITIONS*

A. C. ANDERSEN AND L. S. ROSENBLATT

Radiobiology Laboratory, University of California, Davis, California, U.S.A.

(Received 3 June 1965)

INTRODUCTION

CONCOMITANT with a life-span study of control and irradiated Beagles, 220 pups were released to private owners. Records of deaths of the two groups, experimental and field dogs, have been kept since 1952. This report deals with the causes of death and probability of survival to the x-th year of life for the two groups.

MATERIALS AND METHODS

A breeding colony consisting of 12 males and 82 females was assembled in 1951-52. These dogs were Beagles registered with the American Kennel Club and purchased from kennels and individuals throughout the United States. Breeding procedures and care of the pups to weaning age have been described (Andersen, 1957). At weaning, two or more litters were placed in a large outdoor pen until 2 to 4 months old, when they were assigned to various groups. The experimental group consisted of female Beagles, and only male Beagles in excess of experimental demands were released to private owners throughout California. Most of the released dogs were sibs of the control group.

The fifty-seven experimental control dogs used in this study were randomly placed in outdoor pens with X-irradiated pen mates. Kennel facilities and care of the experi- mental dogs have been described in detail elsewhere (Andersen and Hart, 1955). These dogs were kept under 24 hr surveillance seven days a week, and veterinary care was available at all times. Approximately one-half of the experimental group was bred between 2 and 4 years of age, and whelped two litters. Whenever a dog died, gross autopsy was performed as soon as possible, and representative tissue samples from each organ, organ system, and lesion were placed in Bouin's fixative, sectioned in tissuemat, and stained by hematoxylin and eosin. The cause of death was determined from review of the clinical history, autopsy record, and histological preparations. The cause and age at death were punched in IBM cards for analyses.

The release procedure of Beagles from the kennel and a survey of deaths to 3 years of age have been reported (Andersen, 1958). In brief, at 2 to 4 months old the dogs were released to private owners, and each owner agreed to report on the well-being of his dog by replying to a questionnaire. A returnable postcard questionnaire was sent annually to each owner. Of the 220 dogs released, 215 could be accounted for through 1964. Since these dogs were whelped in the kennel, litter records were available for calculating the probability of survival from birth as well as after their release.

* Supported by USAEC Contract AT(04-3)-472.

193

194 A. C. ANDERSEN AND L. S. ROSENBLATT

Data accumulated f rom the experimental and field groups of Beagles between 1952 and 1964 were analyzed according to technique described by Cutler and Ederer (1958). This method utilized data f rom all individuals until information no longer became available. The experimental group (controls) required 4 to 5 years to assemble, and the dogs entered the experiment at one year of age. Similarly the field group was released over a 5-year period, but some of these dogs were lost, stolen, or given away (i.e. lost to the follow-up). Hence, computat ions on the field dogs were made including and excluding these uncontrollable factors. T h e statistics computed were probabili ty of survival to the x-th year of life (P , ) and the standard error of Px(Sac). These statistics will be presented as percentages.

R E S U L T S

Survival and causes of death for the experimental group are listed in Tables 1 and 2. I t will be noted that the 50 per cent survival of control experimental Beagles has not yet been reached. At the t ime these computat ions were made, the average age of living experimental dogs was 10-6 years (range 8-14 years).

TABLE 1. PROBABILITY OF SURVIVAL OF EXPERIMENTAL CONTROL BEAGLES

Age (years )* P x -k S . Age (years )* P a ~ S~

1-2 100 ~ 0 7 8 79 4- 5 2-3 95 ~ 3 8 9 75 ~ 6 3-4 93 ::i:: 3 9-10 75 :]- 6 4-5 91 -c 4 10-11 65 ~:: 6 5-6 86 .+ 5 11-12 58 -L 7 6-7 81 :~: 5 12-13 58 ~ 7

* Fifty-seven Beagles entered experiment at 1 year old.

TABLE 2. MAJOR CAUSES OF DEATH AMONG EXPERIMENTAL CONTROL BEAGLES*

Av. age at dea th Causes of dea th Per cent (days)

Acute disease 13"5 1452 Chronic disease 18-2 2147 Dystocia 4"6 1465 Heat exhaustion 9" 1 2173 Heart failure 9" 1 3404 Neoplasms 36-4 3685 Others 9' 1 2145

* Twenty- two deaths out of 57 dogs.

Data on the number of Beagles released to private owners and the causes of death are listed in Tables 3 and 4. T h e principal cause of death was accidents, of which 52 per cent were due to motor vehicles. Remaining causes of accidental deaths varied grea t ly- -mul t ip le bee stings, beaten by a neighbor, electrocution, etc. I t should be ment ioned that the natural causes of field dog deaths are somewhat ambiguous, because autopsies were performed on only nine cases, of which four were performed by the senior author.

SURVIVAL OF BEAGLES UNDER NATURAL AND LABORATORY CONDITIONS

TABLE 3. NUMBER OF FIELD BEAGLES AND FATE ~'

195

Year released No. dogs Deaths Lost/Stolen No reply No. alive

1952 3~ 1 0 0 1 1953 15 8 3 1 3 1954 71 40 10 6 15 1955 99 42 30 6 21 1956 32 11 8 8 5

Totals 220 102 51 21 45

* As of December 1964. One dog returned to project.

TABLE 4. MAJOR CAUSES OF DEATH FOR FIELD BEAGLES

Av. age at death Cause Per cent (days)

Accidental Motor vehicles 52 874 Poison 2 1783 Misc. 11 1227

Natural Acute 15 622 Chronic disease 11 2250 Reproduction 1 1584 Neoplasms 2 2046 Unknown 5 1577

I n f o r m a t i o n on survival of released dogs f rom bi r th is s u m m a r i z e d in T a b l e 5.

F r o m the 542 pups whe lped , 82 per cent su rv ived wean ing age, Surv iva l to one year

of age was 70 per cent, wi th a 95 per cent conf idence interval of 64 to 76 per cent

( P . - - S . ) .

TABLE 5. PROBABILITY OF SURVIVAL FOR FIELD BEAGLES FROM BIRTH ~

Age (months) P~ _ Sx Age (years) P~ !: S .

0-1 84 -5:1 1-2 63 L 3 1-2 82 ~ 2 2-3 58 ± 3 2-3 82 :~ 1 3-4 55 -[: 3 3-4 81 ~ 2 4--5 47 ± 3 4-5 80 :~ 2 5-6 44 ~ 3 5-6 79 -t: 2 6-7 42 ± 3 6-7 77 ~ 2 7-8 38 -tz 3 7-8 75 ± 2 8-9 37 -5:3 8-9 73 ::[: 2 9-10 32 ~ 4 9-10 72 ~ 2 10-11 27 ~ 4

10-11 71 -L 2 11-12 27 :~ 4 11-12 70 :]_ 3

* Based on 542 pups whelped from 104 litters.

196 A. C. ANDERSEN AND L. S. ROSENBLATT

Survival of field dogs f rom the t ime of release is listed in co lumn A, Tab le 4. T h e 50 per cent probabi l i ty of survival was about 71 years, however, if the uncer ta in events (lost, stolen, given away) are el iminated the 50 per cent survival occurred at about 4½ years old. I n an a t t empt to compare field and experimental groups, the probabi l i ty of survival for released dogs after one year old was calculated for all deaths (column C, Tab le 6), and only natural deaths (co lumn D, Tab le 6).

TABLE 6. PROBABILITY OF SURVIVAL FOR FIELD BEAGLES

A B C D Age (years) (P . ~ S . ) (P . ~7_ S. ) (P . -4- S . ) (P . ~ S~)

0-1 93 ~ 2 9 0 ~ - 3 1-2 77 :to 3 68 ~ 4 91 :{- 2 99 -~_- 1 2-3 70 - ! :3 6 0 ~ 4 83 ~ 3 9 4 i 2 3-4 66 3 56 q_ 4 78 ": 3 92 - 2 4-5 57 ~ 4 46 ~ 4 67 ~- 4 87 _~_ 3 5-6 53 7~ 4 43 ~ 4 63 ::~- 4 86 ! 3 6-7 51 -!:4 41 I 4 60: :~4 83 • 4 7-8 46 4~4 3 7 T 4 5 4 T 4 7 9 ~ 4 8-9 45 7 -4 36 ~ 4 53 ~-5 79:r__4 9-10 38 ~ 4 30 -- 4 45 -- 5 69 :]- 6

10-11 33 ~: 5 26 ~ 4 39 ~ 6 69 i : 6 11-12 33 -- 5 26 ~ 4 19 ~_ 6 69 _!- 6

A--Two hundred and fifteen dogs Dora time of release. B--Includes only those dogs with accurate record, i.e. lost, stolen, and no-reply dogs deleted, 102

deaths and 45 living as of December 1964. C--Includes 172 dogs surviving 1 year of age. D--Includes 172 dogs surviving 1 year of age and dying of natural causes, i.e. accidental deaths were

deleted.

D I S C U S S I O N

In conduc t ing a field s tudy, uncontrol lable events such as lost, stolen, given-away, and no- rep ly are of concern in interpretat ion. One- th i rd of the 220 Beagles released to private owners were accounted for by these events (Table 3). I t is remarkable that approximate ly 90 per cent of the owners coopera ted in this s tudy, hence, accurate records were obtained on almost 200 Beagles in the field. Data obtained enabled a compar i son of Beagles in natural and kennel envi ronments . T h e selected me thod of analyses utilizes all in format ion until the dog was lost to the study, irrespective of cause.

Since litter records were available on field dogs, the probabili t ies of survival could be calculated f rom birth. Survival of 542 pups whelped f rom 104 litters is shown in Fig. 1. Losses to the weaning age (2 months) were 18 per cent ; this was 10 per cent lower than repor ted in other studies (Andersen, 1957; Andersen et al., 1962). T h e decrease in survival of field dogs f rom 4 to 12 mon ths old was due pr imari ly to acute infectious diseases and mo to r vehicles. F i f ty - two per cent of deaths, largely occur r ing at puber ty , were at t r ibutable to mo to r vehicles (Andersen, 1958). T h e 50 per cent survival of Beagles f rom bir th was about 41 years.

SURVIVAL OF BEAGLES UNDER NATURAL AND LABORATORY CONDITIONS 197

Ioo

8o

6 0 -

u_ 50~

0 4 0 ~

F- ~o- -5 ' ~ "

2 0 r < 03 IoL o

AGE (YEARS)

FIG. 1. Probability of survival from birth for field Beagles.

12

The survival of field dogs from the time of release is shown on Fig. 2. The solid line represents the entire group except for five dogs on whom no information was received after their release. The remaining 215 Beagles were used in the calculations until they died or further information was unavailable. The dotted line on Fig. 2 includes the 147 dogs on whom definite information was available, and the 50 per cent survival in the field was 4} years old.

tu (D c~

co

~0C

90

8O

7O

6O

5O

4O

3 0

I

• ~ ALL(215) DOGS \ \ _ _ _ 102 DEATHS ond 45

LIVING

AGE (YEARS)

FIG. 2. Probability of survival for field Beagles.

To compare field and experimental Beagles, the two groups were normalized to one year of age, and the results are shown in Fig. 3. In the field group, 172 were alive at one year of age, and if accidental deaths were deleted from the field dogs, the probability of survival for the two groups compared favorably (Fig. 3). That is, under "protected" conditions the 50 per cent survival of Beagles can be projected to

198 A . C . A N D E R S E N A N D L . S . R O S E N B L A T T

be 12 to 13 years of age. Since the two groups compare favorably in this analysis, no sex difference in survival is apparent; it will be recalled that the field group was males, and the experimental group females. The major cause of death among the experimental Beagles was neoplasms (Table 2), and the most common primary sites were the mammary gland, ovary and lung (Andersen, 1965).

I O 0 ~ v ~ - , ~ r - , + , , . . . . . v - - - -

+01

"z' 8° I "" ~..-\ ,\ i - ~ - . - ~ . + - ...... .

E X P E R I M E N T A L \ ~ \

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0 . . . . . F rELD DOGS-ACCIDENTS D E L E T E D ,>_ 3C F-

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m I0

Q _ i i i i i t

AGE ( Y E A R S )

FIG. 3. Probability of survival--experimental and field Beagles.

12

REFERENCES

ANDERSEN, A. C. (1957) Puppy production to the weaning age. J. Am. vet. reed. Ass. 130, 151.

ANDERSEN, A. C. (1958) A comparison of Beagles released for private ownership with those maintained under kennel conditions. J. Amer. vet. reed. Ass. 132, 95.

ANDERSEN, A. C. (1965) Long Term Effects of X-Irradiation on the Beagle. U C D 472-111. ANDERSEN, A. C. and HART, G. H. (1955) Kennel construction and management in relation to

longevity studies in the dog. J. Ant. vet. reed. Ass. 126, 366. ANDERSEN, A. C., McKELVIE, D. H. and PHEMISTER, R. (1962) Reproductive fitness of the female

Beagle. J. Am. vet. reed. Ass. 141, 1451. CUTLER, S. J. and EDERER, F. (1958) Maximum utilization of the life table method in analysing

survival. J. chron. Dis. 8, 699.

S u m m a r y - - L i f e - s p a n data obtained in this study indicate that the 50 per cent survival of Beagles from birth and kept under natural (field) conditions was 4,~ years. Survival of 215 Beagles from time of release (post-weaned) was 7,~ years. When Beagles were kept under a "protected" environment, the 50 per cent survival approximated 12 to 13 years of age. No sex difference in survival was observed in this study.

R 6 s u m 6 - - L e s donn6es sur la long6vit6, obtenues de cette 6tude, indiquent que 50 pour cent de la survivance de bigles, gard6s dans des conditions naturelles (champs), ~ partir de leur naissance, rut de 4 ans et demie. 215 bigles surv6curent 7 ans et demie fi partir de leur liberation (aprbs-sevrage). Avec des bigles gard6s dans un milieu 'prot6g6', 50 pour cent de la survivance fur d'approx. 12 & 13 ans. Aucune influence de la diff6rence de sexe n'a 6t6 observ6e dans cette 6tude.

SURVIVAL OF BEAGLES UNDER NATURAL AND LABORATORY CONDITIONS

Z u s a m m e n f a s s u n g - - D i e Lebensdauerangaben welche in diesem S tud ium erhal ten wurden u n d die un te r natf ir l ichen (Bereich) Verh~iltnissen gehalten wurden , zeigen, das die 50 prozent ige l~ber lebung yon Sp i i rhunden 4½ Jahre, von G ebu r t war. Die l~ber lebung von 215 Sp t i rhunden seit der Loslassungszei t (Nachen tw6hnung) war 7½ Jahre. W e n n die Sp i i rhunde unte r einer "geschi i tz ten" U m g e b u n g gehalten wurden , war die 50 prozent ige l~ber lebung zu e inem anni ihernden Alter yon 12 bis 13 Jahren. Keine Geschlechtsuntersch iede in der ~ b e r l e b u n g wurden in diesem S tud ium beobachted .

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199