EFFECT OF DIET ON CONDITION INDICES IN BLACK-TAILED JACKRABBITS Author(s): Scott E. Henke and Stephen Demarais Source: Journal of Wildlife Diseases, 26(1):28-33. Published By: Wildlife Disease Association DOI: http://dx.doi.org/10.7589/0090-3558-26.1.28 URL: http://www.bioone.org/doi/full/10.7589/0090-3558-26.1.28

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Journal

of Wildlife

Di.seases,

EFFECT

OF DIET

ON CONDITION

BLACK-TAILED and

of Range

ABSTRACT:

Stephen and

body

cortisol

in

kidney

best

Estimating

and

fat

Tech

measure

the

nutritional

experimental

experimental

status

study,

objective response

physical

status

to the

of

a

carrying

nor controlled have been

for

Twenty-four

were

to period.

adult

male

black-tailed

in

weight),

and

individually

rabbit cages. to fall through, crude Missouri

ad tuce

A grid

Chow

protein; 63166,

libitum washed

rack

ensuring

Rabbit

Purina

housed

Ralston USA)

during in

an water

allowed

protein

the 2-wk

a sanitary

Complete and

Purina water

was

and

nutritional should

effects feed

status,

not

of the

occur

steel

feces

feed

restriction

was

Rongstad, 1966). to the nearest 0.04

and total measured

body length to the nearest

relationships

outlined

protein Fowler,

=

to

137

Kirkpatrick

this 160

g).

Jackbased (1978).

catabolism

restriction.

al., 1969; weighed

(14.3% St. Louis, provided daily

days.

during

because

were

provided

roughage but added negligible ergy to their diet (Harrison and

of Warren

environment.

period.

mean

22

(30 May to 12 June 1988). placed on 25% feed restriction

Blend Co., were

acclimation

consumption g (range

2

took

chosen

of body

it will

mask

Therefore, based

a upon

to ca25%

of

75% of the running mean for its last 7-day ad hibitum consumption during the acclimation period. Euthanasia was accomplished with a 1.5 ml intraperitoneal injection of T61 euthanasia solution (Taylor Pharmaceuticals, Decatur, Illinois 62525, USA). The time period between initial handling and death was recorded. Jackrabbits

(capture and

±

which

pre-experimental time trials with jackrabbits find the time period directly before body tabolism (S. E. Henke, unpubi. data). The feed restriction for each jackrabbit consisted

two

jackrabbits

urine

feed

148

period were

estimating

jackrab-

in stainless

was

a process

their conit re-

BUN concentrations can reflect moderate feed restrictions of protein and energy (Warren and Kirkpatrick, 1978); however, to be of value in

Lubbock 33#{176}35’N, 101#{176}54’W) from kg

daily

on the results

Lubbock,

County, Texas (USA; 30 April to 8 May 1988. Individual were weighed to the nearest 0.04

mean

2-wk rabbits

AND METHODS

live-trapped

nu-

One jackrabbit died during the acclimation period due to unknown causes. Following the acclimation period, jackrabbits were reweighed to the nearest 0.04 kg (pretrial weight), and randomly assigned to one of two diets, ad libitum or 25% feed restriction for a

black-tailed

californicus) over a 2-wk

period;

period

to quantify urine, and

in

a 7-day

The

evaluareported.

of this study was of selected blood,

MATERIALS

californicus,

were considered adapted when consumption stabilized. Feed was considered stable when within 10% of the 7-day running

mained

et a!., 1974). Although nutrition validations have on cottontail rabbits (Syl(Kirkpatrick and Kibbe, and Kirkpatrick, 1978), nei-

indices

Lepus

study.

nutritional

condition

jackrabbits.

jackrabbit,

the

jackrabbits (Lepus levels of nutrition

bits

these

daily feed sumption

baseline data on jackrabbits

The the

of

black-tailed

capacity of its habitat by using condition indices has been, and continues to be, an important step in the wildlife management process. Quantification of baseline values and the effect of specific nutritional levels are needed to validate condition in-

ther tions

indices in 23 adult male black-tailed and 25% feed restriction were measured restricted jackrabbits had (1) lower postfemur marrow fat, serum bilirubin and (3) depressed immune function. No single

J ackrabbits

relative

USA

79409,

condition

(2) higher width, and

cortex

Texas

Lubbock,

INTRODUCTION

population

dices (LeResche some controlled been conducted vilagusfioridanus) 1971; Warren

University,

physical

indices,

adrenal

Condition,

stress,

Texas

with ad libitum feeding May to 12 June 1988. Feed

and

could

index,

urine

30

and

words:

wildlife

blood,

from

weights

alone

Key tritional

Management,

californicus)

concentrations,

index

Demarais

Wildlife

Changes

jackrabbits (Lepus over a 2 wk period trial

IN

JACKRABBITS

Scott E. Henke Department

INDICES

1990, pp. 28-33 Association 1990

26(1),

Disease

© Wildlife

Letfor

aged

termined. Blood

or en1984). 28

using

samples

eye

lens

weights (Connolly et Jackrabbits were rekg (posttrial weight), (head from hind legs) was 1.0 mm. Weight-length by Bailey (1968) were

were

obtained

by

de-

cardiac

HENKE

puncture

with

needle,

and

ice,

a

allowed

12 to

then

cc

syringe

clot

for

centrifuged

was

miii. Serum

and

at

collected

an

least

1 hr

1,400

rpm

at and

18

ga

on wet for 15

at -23

frozen

C.

AND DEMARAIS-JACKRABBIT

tributions

marrow

fat,

width

variates. adrenal marrow

and

condition

stained

hr.

with

a Wrights-Giemsa

white

Differential by

conducted

stain

blood 200

counting

cell

within

counts

leukocytes

at

analysis

adrenal

kidney

tested

of the

covariance

adrenal

cose,

blood,

ketone,

leukocytes,

urobilinogen, specific using a Multistix test 46515,

with tested

nitrite,

using

USA).

Kidney

adrenal

for mm

0.025

fat

radius

and pH Elkhart, index

(KFI)

cortex

width

femurs

slight

the

forced

applicator.

2 to 4 mm formalin. 4 tm cross and stained

using

cence light (Instrumentation were

obtained

the

a

wood

a 0.5

to 1.0

reagent-dry

for 1 wk, and

g

assay

were

Ill-plus

Reagents

the

and

manufacturer.

New

Jersey

models

using

the

pretrial

weight

respectively,

as

the

co-

a general

analyzer Mas-

determined

using

Serum

rad ioi mm

lin-

analyzed randomized

feeding

regimens

as

of appropriate Shapiro-Wilk

performed weights

using design

an

treatment residuals test at P

and

a

u noassa

y

on and

unbalanced, with the two

were
0.27)

1). Adrenal weights affected (P> 0.411)

and were

diet

groups.

cortex width the 25% feed

The histology

effects were

of

a low(Table using

body by

weights

diet

(Table

and radius were by diet; however, increased restriction.

changes with

feed-restricted not measured. had a lower (P but had more fat (Table 1).

noted in terms some minimal

integrity in the feed-restricted

of the feed-restricted a mild and patchy

not ad-

(P = 0.016) Spleens ap-

of feed restriction on very mild. Architecturally

liver. Feed restriction IgG concentrations

cortisol

levels.

pretrial body weights for death to occur

central animals.

of chord loss of chords of In only

animals infiltration

fatty

liver

there in

the

comInc.,

1974).

were

(P>

capture, were not

four was

standards

USA)

sample.

and period

The feed-restricted group exhibited er posttrial body weight (P = 0.069) 1). The weight-length relationships

cellular livers

fluores-

Controls

07081,

serum

Capture time

there were differentiation,

thawed

immunoglobulin

Multi-Stat

USA).

jackrabbit

Data completely

were

a

After

and

each trial consisted of two samples (Fisher Scientific,

human

(Abrahams,

butions ing the

the

from

with

Springfield,

was

cortex

linear

peared enlarged in the group, although they were The feed-restricted group = 0.001) kidney fat index, (P = 0.0001) femur marrow

1973).

frozen

02173,

pooled

for

C.

with

scattering microcentrifugal Laboratory, Lexington,

sachusetts analyzed mercial

cavity

using

for bilirubin

analyzed

-23 cracked

estimated

samples,

(IgG)

adrenal

was

at

were the

of marrow and Holland,

Serum and

frozen

femurs from

Fat

sample (Verme

C

were

thawing

marrow

adrenal

indices were tested with analysis of variance.

models

renal with

magnification.

hematoxylin-eosmn. Right

and

Means expressed weight, adrenal fat, and kidney

similar

both kidneys to the nearest of fat and buffered for0.01 mg. Admedial) were

and

at lOx

calipers

the

bilirubin,

Liver tissue slices of approximately thickness were fixed in 10% buffered Liver pathology was evaluated using sections embedded in paraffin blocks with

on

femur

1,000x

a 12 cc for glu-

gravity, protein, (Miles Laboratory,

(Rinev, 1955) was calculated using and their surrounding fat weighed 0.01 g. Both adrenals were cleaned connective tissue, fixed in 10% malin, and weighed to the nearest renal cross sections (transverse and evaluated

of diet

weight,

RESULTS

samples were obtained arid an 18 ga needle and

Indiana

29

a general

radius,

magnification.

Urine syringe

effects

fat

with

INDICES

for posttrial weight, cortex width, femur fat were corrected for the covariate. Effects of diet on the remaining physical characteristics, and blood and urine

ear

were

The

weight,

and

were

and

residuals.

body

Whole blood was drawn into heparinized microcapillary hematacrit tubes at the time of heart puncture and centrifuged at 1,400 rpm for 5 mm. Packed cell volume (PGV) was read on a Damon Micro-capillary Reader (Needham Heights, Massachusetts 02161, USA). Thin blood smears were prepared at the time of collection 24

of

posttrial

CONDITION

us-

Analyses data for dis-

relative

lowered (P

percentages

of

sophils,

and

eosinophils

versely,

feed

restriction

centages

of juvenile

and neutrophils concentrations trations phocyte

ative

(P (P

=

PCV (P 0.0001),

=