THE CONSCIOUS CALF PREPARATION: TECHNICAL ASPECTS 
OF SURGERY, ANIMAL CARE, IMPLANTED INSTRUMENTATION 
AND MONITORING FOR CARDIOVASCULAR DATA ACQUISITION 
K. T. Weber, J. S. Janicki, A. A. Walker' and B. H. Dennison' 
Only recently has the calf been used with any fre- 
quency in the experimental cardiovascular laboratory. 
This growing popularity is in large measure due to the 
following: (1) the animal's docility for chronic experi- 
mentation, (2) its suitability for thoracic surgery, (3) 
availability, and (4) the larger size which greatly en- 
hances its usage for a number of physiological and ana- 
tomical considerations. This presentation is primarily a 
description of the technical, as well as practical, aspects 
of the chronic calf preparation. Particular emphasis is 
placed on the interfacing of the animal and data acquis- 
ition system, the data monitoring equipment itself, and 
pre- and post-operative care. In addition, hemodynamic 
measurements obtained in unanesthetized, resting calves 
and various applications of the preparation are dis- 
cussed. 
INTRODUCTION*** 
In the cardiovascular laboratory, the calf has 
become increasingly popular as an experimental 
animal. This is due in large measure to its car- 
diovascular size and capacity, and to the fact 
that the major vessels are easily accessible and 
capable of v^^ithstanding the trauma of chronic 
instrumentation. Other desirable qualities are 
its docility, which simplifies the task of data 
collection in the conscious state, and availabil- 
ity. Experience with other large animals was 
less encouraging. Large dogs (>60 lbs.) re- 
quired conditioning and training ; furthermore, 
they have a high incidence of Dirofilaria im- 
mitis (heartworms) . In sheep, extreme my- 
ocardial irritability and ventricular fibrillation 
often occurred during manipulation of the 
heart. For chronic data collection, the pig was 
intractible. 
* Department of Medicine, University of Alabama, Birmingham, 
Alabama. 
** Meloy Laboratories, Springfield, Virginia. 
*•* The research upon which this publication is based was per- 
formed pursuant to the Medical Devices Applications Program Con- 
tract PH 43-67-1418 and N.I.H. Grant HE 11,310, National Insti- 
tutes of Health. 
The majority of our experience with calves 
(over 100 animals) was gained while at the Na- 
tional Heart and Lung Institute and in conjunc- 
tion with Meloy Laboratories. Recently, we 
have initiated these experiments in our labora- 
tory here at the University of Alabama Medi- 
cal Center. 
The purpose of this presentation is to 
describe in detail various aspects of our experi- 
mentation with the fully-instrumented, con- 
scious calf preparation. In particular, the sur- 
gery, animal care, components of the total data 
monitoring system and the various applications 
of this preparation are discussed. 
METHODS 
General 
Holstein, Hereford and Charolais calves, 4 to 
12 weeks of age and weighing 50-100 kg, have 
been utilized in the majority of cases. The 
Angus has been less suitable for our purposes 
because of the difficulty in cannulating the fe- 
moral artery which is located deep and posteri- 
omedially. In addition, the short thigh does not 
permit adequate extension and often leads to 
cannula kinking. The calves are housed (both 
pre- and post-operatively) in portable metabolic 
cages* or 3' x 4' stalls with stanchions. We per- 
sonally perfer the cage because of its ease in 
transporting the animal, as well as its suitability 
for maintaining an overall cleaner environ- 
ment for the post-operative animal. In this re- 
gard, we have modified the floor of the cage to 
include a sliding pan for the collection of ex- 
creta. The animals are given grain and water 
pre-operatively (alfalfa has been used ad libe- 
tum) until 24 to 48 hours prior to surgery when 
• Humane Equipment Corporation, Baraboo, Wisconsin 
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