- Email: [email protected]
A non-invasive telemetry system for obtaining heart rate from free-ranging swine
Applied Animal Behaviour Science, 29 ( 1991 ) 3 4 3 - 3 4 8
343
Elsevier Science Publishers B.V., A m s t e r d a m
A non-invasive telemetry system for obtaining heart rate from free-ranging swine* Ted. H. Friend 1, Gisela R. Dellmeier I and Jerry L. Stuart 2 1Department of Animal Science, Texas A&M University, College Station, TX 77843 (U.S.A.) 2j. Stuart Enterprises, 3817 Stanford Drive, Oceanside, CA 92056 (U.S.A.)
ABSTRACT Friend, T.H., Dellmeier, G.R. and Stuart, J.L., 1991. A non-invasive telemetry system for obtaining heart rate from free-ranging swine. Appl. Anita. Behav. Sci., 29: 343-348. A vest made of four-way stretch heavy duty nylon spandex was developed to hold telemetry equipment and permit the use of body surface electrodes for obtaining heart rate data on free-ranging or confined domestic swine (Sus scrofa). The vest was laced on sows with a reinforcing 7.5 cm elastic belt encircling the heartgirth on the posterior edge of the vest. Nylon spandex from the ventral side of the vest with 5 cmX0.7 m elastic tabs sewn on each end extended between the front legs. The tabs were threaded through pockets on the edges of the side panels of the vest and tied together on the back of the sow. Velcro-sealed pockets sewn on the inside of the vest held the heart rate transmitters. The vest protected the equipment and helped maintain contact between the sow and electrodes glued onto her dorsal and ventral sides. The system was much less traumatic to the sow, provided a more rapid turn-around of the telemetry equipment, and was easier to repair, than previously used surgical implantation of the transmitters.
INTRODUCTION
Increasing concern about the welfare and ethical implications of maintaining various species of livestock in housing systems that impose chronic close confinement on the animals has generated a need for methods of evaluating stress in these species. Several types of farrowing systems commonly used in commercial swine production in the United States have been criticized as being unnecessarily stressful. A heart rate telemetry system was needed for use in studies determining the relative amount of arousal or stress displayed by sows (Sus scrofa) farrowing in a variety of housing conditions ranging from crates, which are too narrow to allow sows to turn around, to free-ranging conditions in a complex undeveloped pasture. A telemetry system that does not encumber the subjects was required so that data could be obtained without disturbing the natural behavior of the free-ranging sows. *This p a p e r is technical article No. 23953 o f the Texas Agricultural Experiment Station, Texas A&M University.
0168-1591/91/$03.50
© 1991 - - Elsevier Science Publishers B.V.
344
T.H. FRIEND ET AL.
Heart rate telemetry systems have typically required either implanted electrodes (Essler and Folk, 1962) or total implantation (Essler and Folk, 1962; Follmann et al., 1982) for reliability. Completely external systems for freeranging animals typically have less reliability and may require almost daily attention to maintain the electrodes in contact with the animal, as experienced by Jacobsen and Stuart (1978). The anatomy of swine does not allow the use of standard collars. Tunneling through brush, rubbing on objects and the tendency to wallow in water also complicate external mounting. The difficulty of placing equipment either surgically or externally has severely limited the use of heart rate data in studies of free-ranging swine. The objective of this project was to develop a non-invasive telemetry system for obtaining heart-rate data from free-ranging domestic swine. PROCEDURE
Initially, 4 X 6 X 2 cm heart rate transmitters (Model ECG-1, J. Stuart Enterprises, Oceanside, CA, U.S.A.) with a range of ,-, 100 m were surgically implanted in sows weighing 180-230 kg. The electrodes were run subcutaneously to points on the ventral and dorsal sides of the sows, approximately transecting the heart. Implantation was originally deemed necessary because some of the sows had access to m u d wallows. Though data were successfully collected, surgery was not efficacious owing to trauma to sows, possible effects of surgery and anesthesia on fetuses, labor required, expense, impossibility of repairing broken electrode wires without resorting to additional surgery, and long turn-around time before the equipment could be retrieved and implanted in another sow. Therefore, a non-invasive method of mounting the transmitters was developed. Areas ~ 15 cm in diameter on a ventral side ~ 4 cm forward of the sow's udder, and on her dorsal side just posterior to the shoulder blade and 6-8 cm to the right of her spinal cord were closely clipped to remove the hair and cleaned with 100% alcohol. The alcohol removed oils and dirt and helped dry the skin. Self-adhesive human AgCI electrodes (Adult Pregelled ECG Electrodes, AMED, Doylestown, PA, U.S.A.) were attached to the sow at the clipped sites. Next, the wire that conducts the signal to the transmitter was snapped onto the electrode. A ~ 10 X I 0 cm "patch", made of adhesive tape with livestock "tag" cement (Cattle Back Tag Cement, W.J. Ruscoe Co., Akron, OH, U.S.A. ) added to the perimeter of the adhesive side was then placed over the ventral electrode. The patch helped protect the electrode and served as a point for the rear (7.5-cm wide) elastic of the vest to cross in order to apply pressure on the electrode. The patch also helped prevent the elastic from scraping the electrode off as the elastic moved with the sow. After the second electrode was glued to the sow's back, the vest was placed on the sow to protect the electrodes and to hold the transmitter.
SWINE HEART RATE BY A NONqNVASIVE TELEMETRY SYSTEM
345
The use of an elastic belt that fit around the sow's heartgirth and had sewnon electrodes with a liberal application (2-3 ml) of electrode gel was also evaluated. This belt required more frequent service because of its tendency to rotate and did not have the water resistance of the glued-on electrodes. Non-stretch and two-way stretch material proved unsatisfactory, especially for the sows on pasture. Non-stretch material provided little support for the electrodes, became very tight when sows assumed certain postures and collected large amounts of m u d when the sows wallowed. A well tailored, snug fitting vest was then designed. A vest (Fig. 1 ) made of heavy duty, four-way stretch spandex (No. 40 cloth, Russel Athletic Co., Alexandria City, AL, U.S.A. ) proved to be relatively efficacious. Detailed instructions and patterns for vest construction are available from the authors. Pockets to hold the transmitters were sewn on the inside of the vest just below the lacing or top. The pockets appear as dark squares in Fig. 1A. Velcro (Velcro USA Inc., Manchester, NH, U.S.A.) strips along the flap of each pocket were very successful in keeping the transmitters secure. The forward 1-m-long elastic belt had previously been threaded through a pocket along the edge of the chest piece until it was half-way through. The elastic was then loosely sewn to the chest piece to hold it in place. After the rear belt was passed around the sow, the elastic and bib were passed through the sow's legs. The front elastic belt was then run forward of the sow's legs and threaded through pockets in the side pieces (Fig. 1B).This system eliminated the need for requiring a sow to pick up her front feet and place them through leg holes in the vest; a problem with one of the earlier models. The sows appeared not to be irritated by the vests and made no attempt to remove them by rubbing on objects or chewing them offother sows. However, the sows used in this study were within 48 h of scheduled farrowing when the vests were placed on them. Impending parturition and the presence of their piglets post-partum may have created a diversion, an advantage unavailable for bored sows or swine of other ages or physical states. Care must be taken in tightening the forward elastic band of the vest so that it does not abraid the sow's forelegs. Though the stretch material and lacing allows one vest to fit a considerable variation in sizes of sow, designing different-sized vests to fit sows at approximately 25 kg intervals ensures a better fit and improves the vest's effectiveness in protecting the electrodes and maintaining them in position. Velcro, heavy-duty snaps, and buttons were used for fastening parts of the vest in early prototypes, but they proved insecure, limited the adjustments that could be made, or j a m m e d when covered with sand and mud. Lacing the vests and using square knots to secure the forward and rear elastic proved to be the most desirable m e t h o d (Fig. 1C). The knots were easy to untie and readjust owing to the width of the elastic The only restraint usually needed while placing the vest on a sow was to keep her standing in one place. The sows on pasture were initially equipped
346
T.H. FRIEND ET AL.
while in their feeding stalls; sows housed indoors were equipped while in their respective housing treatments. The electrodes usually required replacement every 2-3 days; however, ~ 30% of sows did not require electrode replacement for the duration of a 5-day trial in spite of much time spent wallowing in mud and water. Signals from the transmitters were picked up by omnidirectional antennae and relayed via RG 58 A / U or other cable to a TR-2 receiver (Telonics, Mesa, AZ, U.S.A. ) controlled by an Apple IIe computer equipped with DATACOL (J. Stuart Enterprises, Oceanside, CA, U.S.A. ) hardware and software. The
Fig. I.
SWINE HEART RATE BY A NON-INVASIVE TELEMETRY SYSTEM
347
computer automatically scanned and sampled all the transmitters in use at programed intervals, recorded the heart rate and time and stored the data on floppy disks for later analysis. The DATACOL system is described in detail in Stuart and Friend ( 1990 ).
Fig. 1.A. The vest prior to being placed on a sow. The forward or top elastic is 5-cm wide and is drawn through casings sewn onto the side pieces. The pockets, on the inside of the vest and appearing as black rectangles, are closed with velcro on the flaps. An encapsulated transmitter with electrodes is in front of the vest. B. The forward 5-cm-wide elastic is being drawn through the casings, thus avoiding the necessity of having the sow step into the vest. C. The rear 7.5-cmwide, and the forward 5-cm-wide elastic have been tied in a square knot. D. A fully dressed sow.
348
T.H. FRIEND ET AL.
T h e n o n - i n v a s i v e t e l e m e t r y s y s t e m d e s c r i b e d in this p a p e r has p r o v e n itself to be an efficacious m e t h o d o f o b t a i n i n g h e a r t rate d a t a on free ranging sows. W h e n c o n d i t i o n s p e r m i t , it has d e f i n i t e a d v a n t a g e s o v e r surgically i m p l a n t e d telemetry equipment. ACKNOWLEDGMENTS This study was partially s u p p o r t e d b y H u m a n e I n f o r m a t i o n Services, St. Petersburg, FL, U.S.A. a n d R a l s t o n P u r i n a Inc., St. Louis, M O , U.S.A. T h e a u t h o r s t h a n k G l a d y s D. F r i e n d for assembling the vests.
REFERENCES Essler, W.O. and Folk, Jr., G.E., 1962. A method of determining true resting heart rates of unrestrained mammals by radio telemetry. Anim. Behav., 10: 168-170. Follmann, E.H., Manning, A.E. and Stuart, J.L., 1982. A long-range implantable heart rate lransmitter for free-ranging animals. Biotelem. Patient Monit., 9:205-212. Jacobsen, N.K. and Stuart, J.L., 1978. Telemetered heart rates as indices of physiological and behavioral status of deer. In: Proceedings of the PECORA IV Symposium: Application of Remote Sensing Data to Wildlife Management, Sioux Falls, SD, I0-12 October 1978, National Wildlife Federation, Washington, DC, pp. 248-255. Stuart, J i . and Friend, T.H., 1990. An automated telemetry data collection system for physiological studies of swine farrowing. In: C.J. Amlaner (Editor), Proceedings of the 10th International Symposium on Biotelemetry, 31 July-5 August 1988, Fayetteville, AR. University of Arkansas, Fayetteville/London, pp. 406-410.
343
Elsevier Science Publishers B.V., A m s t e r d a m
A non-invasive telemetry system for obtaining heart rate from free-ranging swine* Ted. H. Friend 1, Gisela R. Dellmeier I and Jerry L. Stuart 2 1Department of Animal Science, Texas A&M University, College Station, TX 77843 (U.S.A.) 2j. Stuart Enterprises, 3817 Stanford Drive, Oceanside, CA 92056 (U.S.A.)
ABSTRACT Friend, T.H., Dellmeier, G.R. and Stuart, J.L., 1991. A non-invasive telemetry system for obtaining heart rate from free-ranging swine. Appl. Anita. Behav. Sci., 29: 343-348. A vest made of four-way stretch heavy duty nylon spandex was developed to hold telemetry equipment and permit the use of body surface electrodes for obtaining heart rate data on free-ranging or confined domestic swine (Sus scrofa). The vest was laced on sows with a reinforcing 7.5 cm elastic belt encircling the heartgirth on the posterior edge of the vest. Nylon spandex from the ventral side of the vest with 5 cmX0.7 m elastic tabs sewn on each end extended between the front legs. The tabs were threaded through pockets on the edges of the side panels of the vest and tied together on the back of the sow. Velcro-sealed pockets sewn on the inside of the vest held the heart rate transmitters. The vest protected the equipment and helped maintain contact between the sow and electrodes glued onto her dorsal and ventral sides. The system was much less traumatic to the sow, provided a more rapid turn-around of the telemetry equipment, and was easier to repair, than previously used surgical implantation of the transmitters.
INTRODUCTION
Increasing concern about the welfare and ethical implications of maintaining various species of livestock in housing systems that impose chronic close confinement on the animals has generated a need for methods of evaluating stress in these species. Several types of farrowing systems commonly used in commercial swine production in the United States have been criticized as being unnecessarily stressful. A heart rate telemetry system was needed for use in studies determining the relative amount of arousal or stress displayed by sows (Sus scrofa) farrowing in a variety of housing conditions ranging from crates, which are too narrow to allow sows to turn around, to free-ranging conditions in a complex undeveloped pasture. A telemetry system that does not encumber the subjects was required so that data could be obtained without disturbing the natural behavior of the free-ranging sows. *This p a p e r is technical article No. 23953 o f the Texas Agricultural Experiment Station, Texas A&M University.
0168-1591/91/$03.50
© 1991 - - Elsevier Science Publishers B.V.
344
T.H. FRIEND ET AL.
Heart rate telemetry systems have typically required either implanted electrodes (Essler and Folk, 1962) or total implantation (Essler and Folk, 1962; Follmann et al., 1982) for reliability. Completely external systems for freeranging animals typically have less reliability and may require almost daily attention to maintain the electrodes in contact with the animal, as experienced by Jacobsen and Stuart (1978). The anatomy of swine does not allow the use of standard collars. Tunneling through brush, rubbing on objects and the tendency to wallow in water also complicate external mounting. The difficulty of placing equipment either surgically or externally has severely limited the use of heart rate data in studies of free-ranging swine. The objective of this project was to develop a non-invasive telemetry system for obtaining heart-rate data from free-ranging domestic swine. PROCEDURE
Initially, 4 X 6 X 2 cm heart rate transmitters (Model ECG-1, J. Stuart Enterprises, Oceanside, CA, U.S.A.) with a range of ,-, 100 m were surgically implanted in sows weighing 180-230 kg. The electrodes were run subcutaneously to points on the ventral and dorsal sides of the sows, approximately transecting the heart. Implantation was originally deemed necessary because some of the sows had access to m u d wallows. Though data were successfully collected, surgery was not efficacious owing to trauma to sows, possible effects of surgery and anesthesia on fetuses, labor required, expense, impossibility of repairing broken electrode wires without resorting to additional surgery, and long turn-around time before the equipment could be retrieved and implanted in another sow. Therefore, a non-invasive method of mounting the transmitters was developed. Areas ~ 15 cm in diameter on a ventral side ~ 4 cm forward of the sow's udder, and on her dorsal side just posterior to the shoulder blade and 6-8 cm to the right of her spinal cord were closely clipped to remove the hair and cleaned with 100% alcohol. The alcohol removed oils and dirt and helped dry the skin. Self-adhesive human AgCI electrodes (Adult Pregelled ECG Electrodes, AMED, Doylestown, PA, U.S.A.) were attached to the sow at the clipped sites. Next, the wire that conducts the signal to the transmitter was snapped onto the electrode. A ~ 10 X I 0 cm "patch", made of adhesive tape with livestock "tag" cement (Cattle Back Tag Cement, W.J. Ruscoe Co., Akron, OH, U.S.A. ) added to the perimeter of the adhesive side was then placed over the ventral electrode. The patch helped protect the electrode and served as a point for the rear (7.5-cm wide) elastic of the vest to cross in order to apply pressure on the electrode. The patch also helped prevent the elastic from scraping the electrode off as the elastic moved with the sow. After the second electrode was glued to the sow's back, the vest was placed on the sow to protect the electrodes and to hold the transmitter.
SWINE HEART RATE BY A NONqNVASIVE TELEMETRY SYSTEM
345
The use of an elastic belt that fit around the sow's heartgirth and had sewnon electrodes with a liberal application (2-3 ml) of electrode gel was also evaluated. This belt required more frequent service because of its tendency to rotate and did not have the water resistance of the glued-on electrodes. Non-stretch and two-way stretch material proved unsatisfactory, especially for the sows on pasture. Non-stretch material provided little support for the electrodes, became very tight when sows assumed certain postures and collected large amounts of m u d when the sows wallowed. A well tailored, snug fitting vest was then designed. A vest (Fig. 1 ) made of heavy duty, four-way stretch spandex (No. 40 cloth, Russel Athletic Co., Alexandria City, AL, U.S.A. ) proved to be relatively efficacious. Detailed instructions and patterns for vest construction are available from the authors. Pockets to hold the transmitters were sewn on the inside of the vest just below the lacing or top. The pockets appear as dark squares in Fig. 1A. Velcro (Velcro USA Inc., Manchester, NH, U.S.A.) strips along the flap of each pocket were very successful in keeping the transmitters secure. The forward 1-m-long elastic belt had previously been threaded through a pocket along the edge of the chest piece until it was half-way through. The elastic was then loosely sewn to the chest piece to hold it in place. After the rear belt was passed around the sow, the elastic and bib were passed through the sow's legs. The front elastic belt was then run forward of the sow's legs and threaded through pockets in the side pieces (Fig. 1B).This system eliminated the need for requiring a sow to pick up her front feet and place them through leg holes in the vest; a problem with one of the earlier models. The sows appeared not to be irritated by the vests and made no attempt to remove them by rubbing on objects or chewing them offother sows. However, the sows used in this study were within 48 h of scheduled farrowing when the vests were placed on them. Impending parturition and the presence of their piglets post-partum may have created a diversion, an advantage unavailable for bored sows or swine of other ages or physical states. Care must be taken in tightening the forward elastic band of the vest so that it does not abraid the sow's forelegs. Though the stretch material and lacing allows one vest to fit a considerable variation in sizes of sow, designing different-sized vests to fit sows at approximately 25 kg intervals ensures a better fit and improves the vest's effectiveness in protecting the electrodes and maintaining them in position. Velcro, heavy-duty snaps, and buttons were used for fastening parts of the vest in early prototypes, but they proved insecure, limited the adjustments that could be made, or j a m m e d when covered with sand and mud. Lacing the vests and using square knots to secure the forward and rear elastic proved to be the most desirable m e t h o d (Fig. 1C). The knots were easy to untie and readjust owing to the width of the elastic The only restraint usually needed while placing the vest on a sow was to keep her standing in one place. The sows on pasture were initially equipped
346
T.H. FRIEND ET AL.
while in their feeding stalls; sows housed indoors were equipped while in their respective housing treatments. The electrodes usually required replacement every 2-3 days; however, ~ 30% of sows did not require electrode replacement for the duration of a 5-day trial in spite of much time spent wallowing in mud and water. Signals from the transmitters were picked up by omnidirectional antennae and relayed via RG 58 A / U or other cable to a TR-2 receiver (Telonics, Mesa, AZ, U.S.A. ) controlled by an Apple IIe computer equipped with DATACOL (J. Stuart Enterprises, Oceanside, CA, U.S.A. ) hardware and software. The
Fig. I.
SWINE HEART RATE BY A NON-INVASIVE TELEMETRY SYSTEM
347
computer automatically scanned and sampled all the transmitters in use at programed intervals, recorded the heart rate and time and stored the data on floppy disks for later analysis. The DATACOL system is described in detail in Stuart and Friend ( 1990 ).
Fig. 1.A. The vest prior to being placed on a sow. The forward or top elastic is 5-cm wide and is drawn through casings sewn onto the side pieces. The pockets, on the inside of the vest and appearing as black rectangles, are closed with velcro on the flaps. An encapsulated transmitter with electrodes is in front of the vest. B. The forward 5-cm-wide elastic is being drawn through the casings, thus avoiding the necessity of having the sow step into the vest. C. The rear 7.5-cmwide, and the forward 5-cm-wide elastic have been tied in a square knot. D. A fully dressed sow.
348
T.H. FRIEND ET AL.
T h e n o n - i n v a s i v e t e l e m e t r y s y s t e m d e s c r i b e d in this p a p e r has p r o v e n itself to be an efficacious m e t h o d o f o b t a i n i n g h e a r t rate d a t a on free ranging sows. W h e n c o n d i t i o n s p e r m i t , it has d e f i n i t e a d v a n t a g e s o v e r surgically i m p l a n t e d telemetry equipment. ACKNOWLEDGMENTS This study was partially s u p p o r t e d b y H u m a n e I n f o r m a t i o n Services, St. Petersburg, FL, U.S.A. a n d R a l s t o n P u r i n a Inc., St. Louis, M O , U.S.A. T h e a u t h o r s t h a n k G l a d y s D. F r i e n d for assembling the vests.
REFERENCES Essler, W.O. and Folk, Jr., G.E., 1962. A method of determining true resting heart rates of unrestrained mammals by radio telemetry. Anim. Behav., 10: 168-170. Follmann, E.H., Manning, A.E. and Stuart, J.L., 1982. A long-range implantable heart rate lransmitter for free-ranging animals. Biotelem. Patient Monit., 9:205-212. Jacobsen, N.K. and Stuart, J.L., 1978. Telemetered heart rates as indices of physiological and behavioral status of deer. In: Proceedings of the PECORA IV Symposium: Application of Remote Sensing Data to Wildlife Management, Sioux Falls, SD, I0-12 October 1978, National Wildlife Federation, Washington, DC, pp. 248-255. Stuart, J i . and Friend, T.H., 1990. An automated telemetry data collection system for physiological studies of swine farrowing. In: C.J. Amlaner (Editor), Proceedings of the 10th International Symposium on Biotelemetry, 31 July-5 August 1988, Fayetteville, AR. University of Arkansas, Fayetteville/London, pp. 406-410.