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Recorded sounds associated with feeding did not affect feeding behavior of lambs
Applied Animal BehaviourScience, 13 (1984/85) 275--281
275
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
RECORDED SOUNDS ASSOCIATED WITH FEEDING AFFECT FEEDING BEHAVIOR OF LAMBS
DID NOT
H. TANIDA, W.D. HOHENBOKEN ~ and L.V. SWANSON
Department of Animal Science, Oregon State University, Corvallis, OR 97331-6702 (U.S.A.) Technical Paper No. 6967, Oregon Agricultural Experiment Station (Accepted for publication 7 June 1984)
ABSTRACT Tanida, H., Hohenboken, W.D. and Swanson, L.V., 1985. Recorded sounds associated with feeding did not affect feeding behavior of lambs. Appl. Anim. Behav. Sci., 13: 275--281. This study was designed to determine whether periodic exposure to pre-recorded sound associated with feed delivery and consumption would alter feed intake or feeding pattern of lambs provided with fresh feed once daily. Thirty cross-bred lambs were randomly assigned to 6 pens. The trial lasted 44 days (30 July to 11 September 1982) and consisted of a 4-day acclimation to test facilities, and then cycles of 4 days without sound stimulation followed by 4 days with sound stimulation. Sound stimulation consisted of 6-min broadcasts, every 3 h, of sounds associated with feed delivery and eating. Lambs were observed continuously for 24 h on 3 days when lambs were subjected to sound stimulation and 3 days when they were not. The recorded sound stimulation affected neither feed intake nor feeding behavior. Lambs largely ignored the recorded sounds, and total feed intakes during 20 sound-stimulated vs. 20 non-sound-stimulated days were 1234 vs. 1240 kg, respectively. There was a rhythmic feeding pattern at 1--2h intervals, synchronously throughout the barn, and this was not affected by the 6 rain of sound stimulation at 3-h intervals. There were no major peaks in feeding activity except after the offering of fresh feed in the morning. Feeding activity did n o t change with sunrise or sunset, and peaks of eating activity were distributed at even time-intervals throughout the 24 h. The overall means per lamb for the total time spent eating, the number of eating bouts (separate eating incidents), the average time eating per bout and the number of drinking episodes across the 6 observation days were 118.8 min, 22.6 times, 5.5 min and 9.6 times, respectively.
INTRODUCTION Sounds associated with feed delivery and feeding have been observed t o m o t i v a t e a n t i c i p a t o r y f e e d i n g b e h a v i o r i n s h e e p w e l l b e f o r e f e e d is a c t u a l ly p r o v i d e d . This led to the q u e s t i o n of w h e t h e r daily feed i n t a k e p a t t e r n s ~Author to whom correspondence should be addressed.
0168-1591/85/$03.30
© 1985 Elsevier Science Publishers B.V.
276 and daily feed intake of lambs being fed ad libitum might be altered by broadcasting, at predetermined intervals, pre-recorded sounds associated with feeding. Attempts to stimulate feeding activity by recorded sound have n o t been reported. Therefore, the present study was designed to examine the effect of recorded feed delivery and feeding sounds on the feeding behavior, feed intake and feeding patterns of lambs fed an ad libitum diet once per day. MATERIALS AND METHODS The experiment was c o n d u c t e d from 30 July to 11 September 1982 at the Oregon State University Sheep Barn. Thirty cross-bred lambs t hat had been raised on hill pasture w i t hout access to processed feed were moved into the barn for the experiment. T he y were approximately 5 m ont hs of age, and the average weight was 36 kg at the beginning of the experiment. Five lambs were r andom l y assigned to each of 6 sawdust-bedded, 7 m X 6 m pens constructed of w o o d e n gates. One sheep per pen was chosen at random to be the subject of individual behavioral observations, which are described later. The 6 pens were adjacent to one anot her in 2 rows of 3 pens each. A feeder (0.3 m X 2.4 m) was placed on one side and a water trough (0.3 m X 0.3 m) on the o t h e r side of each pen. The east side of the barn was open b ut adjacent to another building across a 3.4-m aisle. The west side had a 2.7-m aisle between the pens and a wall with nine 1.2 m X 1 m windows. A standard 200-W incandescent bulb was m o u n t e d 2.4 m above the floor in each of the 3 pens located on the west side of the barn and provided light intensity, 50 cm above the floor, averaging 49 : 2.3 lux during the day and 12 -+ 1.8 lux during the night. The 3 pens located on the open east side of the barn did n o t have artificial lighting but received direct and indirect sunlight during the daylight hours. Light intensity averaged 169 -+ 17.9 lux during the day and was negligible during the night, although 0.6 -+ 0.2 lux was recorded at the edge of the lighted pens. At 08.00 daily, the lambs were fed slightly more of a complete pelleted ration than th ey could consume in the ensuing 24 h. Feed intake for lambs in each pen was measured daily. The lambs soon became accustomed to the feeders and feeding schedule. Sounds associated with the offering of fresh feed (buckets rattling, feed cart being moved, pelleted feed striking metal containers and w ooden feeders) and with eating were recorded, edited to 6-min segments and d ub b ed repeatedly o n t o reel-to-reel tape. Two speakers were m o u n t e d 3.5 m apart in the center of the barn and 2.2 m above the barn floor. Following a 4-day acclimation period, lambs were exposed alternately to 4 days sound stimulation followed by 4 days w i t h o u t sound stimulation t h r o u g h o u t the 40-day experimental period. During the 4 days of sound t r e a t m e n t , 6 min sound was played every 3 h, starting at 08.00 on the first day of
277 sound treatment. The sound intensity was approximately 60--65 db throughout the 6 pens. Twenty-four-hour behavioral observations were conducted on the third day of a cycle of no sound treatment and on the third day of a cycle of sound treatment in the first, middle and last part of the experiment. Behavioral observations were conducted from a raised platform from which it was possible to view all lambs in all pens simultaneously. Observers worked 3-h shifts. Every 2 min, the number of sheep out of 5 per pen engaged in eating activity was recorded. The behavior of one lamb per pen was recorded on a continuous basis. Possible activities were eating, drinking or noningestive behavior. These data allowed determination of the proportion of time per lamb devoted to eating, as well as the number of eating bouts (continuous eating activity of at least 4 min duration) and the average duration per eating bout. RESULTS AND DISCUSSION Overall means for feed intake, gain and efficiency t h r o u g h o u t the 40-day experimental period were 82 and 14 kg per lamb and 17% per pen. The pooled variance for dally feed intake per pen of 5 lambs was 1.03 kg. The effect of sound stimulation on feed intake was tested by comparing average pen feed intakes of the first non-sound stimulated 4-day period to average pen feed intakes in the following sound-stimulated 4-day period by paired t-test, and then comparing that sound-stimulated period to the following non-stimulated period, etc., throughout the 40-day experimental period. Differences were not significant, and there was no evidence that sound stimulation led to increased feed intake. In fact, total feed consumption on 20 sound-stimulated days was 1234 kg compared to 1240 kg on 20 non-sound-stimulated days. Rather, the feed intake in each pen increased gradually during the first 2 weeks of the experiment, then stabilized for the remaining time. In agreement with this, Offord et al. (1969) reported that heifers taught to associate machine noise with feeding did not increase their feed intake. There was no apparent tendency, at any time during the experiment, for average pen feed intake to change between the last of 4 non-sound-stimulated days and the first of 4 sound-stimulated days. Also, daily feed intakes within sound-stimulation periods did not vary in a systematic manner. The number of lambs engaged in eating sometime during each 10-rain period of one pen on the second observation day during sound stimulation is presented in Fig. 1A. Feeding patterns for the other 5 pens on that day were very similar in timing and height of peaks, and therefore are not presented. In Fig. 1B, the feeding pattern pooled across all 6 groups Df lambs for the second observation day during sound stimulation is presented. There was a rhythmic feeding pattern at 1--2 h intervals, and this was not affected by the 3-h interval between sound stimulation episodes. In addition,
278 an immediate response of lambs to the sound was not observed during any of the observation days. The lambs totally ignored the stimulus. Even combining all pens, the feeding activity peaks at 1--2-h intervals still existed. This indicates that the feeding activity of all pens was synchronized to some extent, and that a rhythmic pattern existed throughout the barn. This rhythmic feeding pattern persisted throughout the 6-days of 24-h behavioral observation in either sound or no-sound treatments. Social facilitation seems to have occurred with lambs, within and between pens, mutually stimulating feeding activity, as suggested by Craig (1981). Audio-visual stimulus within and between pens and physical contact within pens, rather than the sound treatment, appeared to affect feeding activity.
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2 PM
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Fig. 1. Typical feeding pattern o f lambs in one pen ( A ) and feeding pattern pooled across all 6 groups of lambs (B) fed a complete pelleted ration at 08.00. Lambs were exposed to 6 rnin sound every 3 h starting at 08.00.
A major peak in feeding activity was observed only after the offering of fresh feed in the morning. An increase in feeding activity at the time of feeding has been reported by Vasilatos and Wangsness (1980) and Ray and Roubicek (1971) in cattle. In the present experiment, direct and indirect sunlight entered the open east portion and through the windows in the west side of the barn. Continuous incandescent lighting was provided in the 3 pens located on the west side but not in the 3 pens on the east side of the barn. No change in feeding activity with sunrise or sunset was observed on any of the six 24-h observation days (Fig. 1A,B). Tanida et al. {1984), however, reported that the feeding behavior of Holstein cows subjected to artificial light plus indirect sunlight inside a barn remained synchronized with the natural photoperiod. Outdoor feeding activity coinciding with sunrise and (or) sunset has been reported in grazing sheep (Squires, 1971, 1974; Hulet et
279 a]., 1975; Bueno and Ruckebusch, 1979; Dudziflski and Arnold, 1979), feedlot lambs (Schreffler and Hohenboken, 1980), grazing cattle (O'Donnell and Walton, 1969; Ruckebusch and Bueno, 1978), feedlot cattle (Ray and Roubicek, 1971) and beef cattle in o u t d o o r pens (Wilson and Flynn, 1979; G o n y o u and Stricklin, 1981). Reasons for results differing from these previous studies were hard to elucidate because other environmental influences, such as the temperature and humidity changes, were not measured. Also, there were differences between the current and previous studies in seasons, locations and feeding schedules. There was no apparent decline in feeding activity of lambs during the night; feeding was nearly constant throughout the 24 h. In grazing sheep, however, Bueno and Ruckebusch (1979), Hulet et al. (1975) and Squires (1974) reported that the grazing activity was confined mostly to daylight hours. Shreffler and Hohenboken (1980) found that the majority of feedlot lambs were lying down throughout the hours of darkness. The number of lambs engaged in eating was significantly greater in lambs housed on the east side (open side) than in lambs on the west side of the barn, although the rhythmic feeding pattern was similar. However, there was no significant difference in feed intake between the two groups. This could be explained by the fact that more playful fighting and chasing occurred throughout the 24 h among lambs on the west side which had continuous lighting. These behaviors, however, were not recorded or quantified. Whether the difference in feeding behavior was caused by the difference in lighting or by other environmental factors such as sunlight, temperature or pen location was not possible to determine. The means of three eating activities and of drinking incidents, over the six 24-h observation days for individually observed lambs, are presented in Table I. The results for number of drinking episodes may not be as accurate as the other feeding behaviors because of observational difficulties. There was a significant difference in number of eating bouts between lambs in the west vs. east tiers of pens, and this is consistent with the results for n u m b e r of lambs engaged in eating stated earlier. The overall means per lamb for the total time spent eating, the number of eating bouts, the average time of eating per bout and the number of drinking episodes across the six 24-h observation days were 118.8 min, 22.6 times, 5.5 min and 9.6 times, respectively. The repeatabilities of these four activities on the 6 observation days were 0.28, 0.28, 0.07 and 0.34. Thus, an individual lamb's ingestive behavior on any one day was modestly predictive of its behavior on other days. No significant correlations were found between gain and eating behaviors. The distribution of feeding activities on one observation day with the sound treatment for the 6 individually observed lambs is shown in Fig. 2. Similar patterns existed on the other 5 observation days. This figure emphasizes that lamb feeding activity was synchronized, even though the lambs were selcted randomly from each pen, and that their activities were distributed t h r o u g h o u t 24 h.
280 TABLE I Means and standard errors of feeding activities of randomly selected lambs on 6 observation days
Pen location
Lamb No.
Total time spent eating (min)
Number of (times) eating bouts
Average time spent eating (rain)
West
1 2 3
110.2± 4.4 114.2-+ 9.7 119.9 ± 13.1
18.3± 1.5 19.7± 1.8 19.2 ± 3.1
6.2± 0.5 5.9± 0.5 6.0 ± 0.3
East
4 5 6
117.4 -+ 12.2 155.8 ± 11.2 103.5 ± 8.3
26.2 ± 3.0 31.3 + 4.2 21.0 ± 2.3
4.7 ± 0.6 5.3 ± 0.5 5.1 + 0.5
L
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Fig. 2. Distribution of feeding activities throughout 24 h under sound treatment. Each line indicates the feeding activity of lambs selected randomly from each pen. Asterisks represent sound exposure.
CONCLUSIONS U n d e r the c o n d i t i o n s of this e x p e r i m e n t , s o u n d s t i m u l a t i o n did n o t alter feed intake or feeding behavior patterns. Lambs apparently learned to i g n o r e t h e s t i m u l u s , s i n c e i t was n o t r e i n f o r c e d b y t h e o f f e r i n g o f f r e s h f e e d . O r p e r h a p s t h e f a c t t h a t l a m b s w e r e f e d ad l i b ± t u r n , w i t h f e e d a l w a y s present, rendered the stimulus ineffective.
281
REFERENCES Bueno, L. and Ruckebusch, Y., 1979. Ingestive behaviour in sheep under fieldconditions. Appl. Anita. Ethol., 5: 179--187. Craig, J.V., 1981. Domestic Animal Behavior. Prentice-Hall, Englewood Cliffs, NJ, 364 pp. Dudzifiski, M.L. and Arnold, G.W., 1979. Factors influencing the grazing behaviour of sheep in a Mediterranean climate. Appl. Anita. Ethol., 5: 125--144. Gonyou, H.W. and Stricklin, W.R., 1981. Eating behavior of beef cattle groups fed from a single stall or trough. Appl. Anita. Ethol., 7: 123--133. Hulet, C.V., Alexander, G. and Hafez, E.S.E., 1975. The behavior of sheep. In: E.S.E. Hafez (Editor), The Behavior of Domestic Animals. 3rd edn., Bailli~reTindall, London. O'Donnell, T.G. and Walton, G.A. 1969. Some observations on the behavior and hill pasture utilizationof Irishcattle.J. Br. Grassl. Soc., 24: 128--133. Offord, K.P., Satter, L.D. and Wieckert, D.A., 1969. Study of behavioral conditioning and feed intake in dairy heifers.J. Dairy Sci., 52:918 (abstract). Ray, D.E. and Roubicek, C.B., 1971. Behavior of feedlot cattle during two seasons. J. Anim. Sci., 33: 72--76. Ruckebusch, Y. and Bueno, L., 1978. A n analysis of ingestive behaviour and activity of cattle under field conditions. Appl. Anita. Ethol., 4: 301--313. Shreffler, C. and Hohenboken, W., 1980. Circadian behavior, including thermoregulatory activities,in feedlot lambs. Appl. Anita. Ethol., 6: 241--246. Squires, V.R., 1971. Temporal patterns of activity in a small flock of Merino sheep as determined by an automatic recording technique. Anita. Behav., 19: 657--660. Squires, V.R., 1974. Grazing distribution and activity patterns of Merino sheep on a saltbush community in south-east Australia. Appl. Anita. Ethol., 1: 17--30. Tanida, H., Swanson, L.V. and Hohenboken, W., 1984. Effect of artificialphotoperiod on eating behavior and other behavioral observations of dairy cows. J. Dairy Sci., 67: 585--591. Vasilatos, R. and Wangsness, P.J., 1980. Feeding behavior of lactating dairy cows as measured by time-lapse photography. J. Dairy Sci., 63: 412--416. Wilson, R.K. and F l y n n , A.V., 1979. Feeding behaviour of cattle when offered grass silage in troughs during winter and summer. Appl. Anim. Ethol., 5: 35--41.
275
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
RECORDED SOUNDS ASSOCIATED WITH FEEDING AFFECT FEEDING BEHAVIOR OF LAMBS
DID NOT
H. TANIDA, W.D. HOHENBOKEN ~ and L.V. SWANSON
Department of Animal Science, Oregon State University, Corvallis, OR 97331-6702 (U.S.A.) Technical Paper No. 6967, Oregon Agricultural Experiment Station (Accepted for publication 7 June 1984)
ABSTRACT Tanida, H., Hohenboken, W.D. and Swanson, L.V., 1985. Recorded sounds associated with feeding did not affect feeding behavior of lambs. Appl. Anim. Behav. Sci., 13: 275--281. This study was designed to determine whether periodic exposure to pre-recorded sound associated with feed delivery and consumption would alter feed intake or feeding pattern of lambs provided with fresh feed once daily. Thirty cross-bred lambs were randomly assigned to 6 pens. The trial lasted 44 days (30 July to 11 September 1982) and consisted of a 4-day acclimation to test facilities, and then cycles of 4 days without sound stimulation followed by 4 days with sound stimulation. Sound stimulation consisted of 6-min broadcasts, every 3 h, of sounds associated with feed delivery and eating. Lambs were observed continuously for 24 h on 3 days when lambs were subjected to sound stimulation and 3 days when they were not. The recorded sound stimulation affected neither feed intake nor feeding behavior. Lambs largely ignored the recorded sounds, and total feed intakes during 20 sound-stimulated vs. 20 non-sound-stimulated days were 1234 vs. 1240 kg, respectively. There was a rhythmic feeding pattern at 1--2h intervals, synchronously throughout the barn, and this was not affected by the 6 rain of sound stimulation at 3-h intervals. There were no major peaks in feeding activity except after the offering of fresh feed in the morning. Feeding activity did n o t change with sunrise or sunset, and peaks of eating activity were distributed at even time-intervals throughout the 24 h. The overall means per lamb for the total time spent eating, the number of eating bouts (separate eating incidents), the average time eating per bout and the number of drinking episodes across the 6 observation days were 118.8 min, 22.6 times, 5.5 min and 9.6 times, respectively.
INTRODUCTION Sounds associated with feed delivery and feeding have been observed t o m o t i v a t e a n t i c i p a t o r y f e e d i n g b e h a v i o r i n s h e e p w e l l b e f o r e f e e d is a c t u a l ly p r o v i d e d . This led to the q u e s t i o n of w h e t h e r daily feed i n t a k e p a t t e r n s ~Author to whom correspondence should be addressed.
0168-1591/85/$03.30
© 1985 Elsevier Science Publishers B.V.
276 and daily feed intake of lambs being fed ad libitum might be altered by broadcasting, at predetermined intervals, pre-recorded sounds associated with feeding. Attempts to stimulate feeding activity by recorded sound have n o t been reported. Therefore, the present study was designed to examine the effect of recorded feed delivery and feeding sounds on the feeding behavior, feed intake and feeding patterns of lambs fed an ad libitum diet once per day. MATERIALS AND METHODS The experiment was c o n d u c t e d from 30 July to 11 September 1982 at the Oregon State University Sheep Barn. Thirty cross-bred lambs t hat had been raised on hill pasture w i t hout access to processed feed were moved into the barn for the experiment. T he y were approximately 5 m ont hs of age, and the average weight was 36 kg at the beginning of the experiment. Five lambs were r andom l y assigned to each of 6 sawdust-bedded, 7 m X 6 m pens constructed of w o o d e n gates. One sheep per pen was chosen at random to be the subject of individual behavioral observations, which are described later. The 6 pens were adjacent to one anot her in 2 rows of 3 pens each. A feeder (0.3 m X 2.4 m) was placed on one side and a water trough (0.3 m X 0.3 m) on the o t h e r side of each pen. The east side of the barn was open b ut adjacent to another building across a 3.4-m aisle. The west side had a 2.7-m aisle between the pens and a wall with nine 1.2 m X 1 m windows. A standard 200-W incandescent bulb was m o u n t e d 2.4 m above the floor in each of the 3 pens located on the west side of the barn and provided light intensity, 50 cm above the floor, averaging 49 : 2.3 lux during the day and 12 -+ 1.8 lux during the night. The 3 pens located on the open east side of the barn did n o t have artificial lighting but received direct and indirect sunlight during the daylight hours. Light intensity averaged 169 -+ 17.9 lux during the day and was negligible during the night, although 0.6 -+ 0.2 lux was recorded at the edge of the lighted pens. At 08.00 daily, the lambs were fed slightly more of a complete pelleted ration than th ey could consume in the ensuing 24 h. Feed intake for lambs in each pen was measured daily. The lambs soon became accustomed to the feeders and feeding schedule. Sounds associated with the offering of fresh feed (buckets rattling, feed cart being moved, pelleted feed striking metal containers and w ooden feeders) and with eating were recorded, edited to 6-min segments and d ub b ed repeatedly o n t o reel-to-reel tape. Two speakers were m o u n t e d 3.5 m apart in the center of the barn and 2.2 m above the barn floor. Following a 4-day acclimation period, lambs were exposed alternately to 4 days sound stimulation followed by 4 days w i t h o u t sound stimulation t h r o u g h o u t the 40-day experimental period. During the 4 days of sound t r e a t m e n t , 6 min sound was played every 3 h, starting at 08.00 on the first day of
277 sound treatment. The sound intensity was approximately 60--65 db throughout the 6 pens. Twenty-four-hour behavioral observations were conducted on the third day of a cycle of no sound treatment and on the third day of a cycle of sound treatment in the first, middle and last part of the experiment. Behavioral observations were conducted from a raised platform from which it was possible to view all lambs in all pens simultaneously. Observers worked 3-h shifts. Every 2 min, the number of sheep out of 5 per pen engaged in eating activity was recorded. The behavior of one lamb per pen was recorded on a continuous basis. Possible activities were eating, drinking or noningestive behavior. These data allowed determination of the proportion of time per lamb devoted to eating, as well as the number of eating bouts (continuous eating activity of at least 4 min duration) and the average duration per eating bout. RESULTS AND DISCUSSION Overall means for feed intake, gain and efficiency t h r o u g h o u t the 40-day experimental period were 82 and 14 kg per lamb and 17% per pen. The pooled variance for dally feed intake per pen of 5 lambs was 1.03 kg. The effect of sound stimulation on feed intake was tested by comparing average pen feed intakes of the first non-sound stimulated 4-day period to average pen feed intakes in the following sound-stimulated 4-day period by paired t-test, and then comparing that sound-stimulated period to the following non-stimulated period, etc., throughout the 40-day experimental period. Differences were not significant, and there was no evidence that sound stimulation led to increased feed intake. In fact, total feed consumption on 20 sound-stimulated days was 1234 kg compared to 1240 kg on 20 non-sound-stimulated days. Rather, the feed intake in each pen increased gradually during the first 2 weeks of the experiment, then stabilized for the remaining time. In agreement with this, Offord et al. (1969) reported that heifers taught to associate machine noise with feeding did not increase their feed intake. There was no apparent tendency, at any time during the experiment, for average pen feed intake to change between the last of 4 non-sound-stimulated days and the first of 4 sound-stimulated days. Also, daily feed intakes within sound-stimulation periods did not vary in a systematic manner. The number of lambs engaged in eating sometime during each 10-rain period of one pen on the second observation day during sound stimulation is presented in Fig. 1A. Feeding patterns for the other 5 pens on that day were very similar in timing and height of peaks, and therefore are not presented. In Fig. 1B, the feeding pattern pooled across all 6 groups Df lambs for the second observation day during sound stimulation is presented. There was a rhythmic feeding pattern at 1--2 h intervals, and this was not affected by the 3-h interval between sound stimulation episodes. In addition,
278 an immediate response of lambs to the sound was not observed during any of the observation days. The lambs totally ignored the stimulus. Even combining all pens, the feeding activity peaks at 1--2-h intervals still existed. This indicates that the feeding activity of all pens was synchronized to some extent, and that a rhythmic pattern existed throughout the barn. This rhythmic feeding pattern persisted throughout the 6-days of 24-h behavioral observation in either sound or no-sound treatments. Social facilitation seems to have occurred with lambs, within and between pens, mutually stimulating feeding activity, as suggested by Craig (1981). Audio-visual stimulus within and between pens and physical contact within pens, rather than the sound treatment, appeared to affect feeding activity.
2°t A ©
1
t
(-9
z 5~-~oo UJ 7 Lu ~
B
80
©©6ocrl
4o
Z
20 0
8 AM
II
2 PM
5
8
It
2 AM
5
8
Fig. 1. Typical feeding pattern o f lambs in one pen ( A ) and feeding pattern pooled across all 6 groups of lambs (B) fed a complete pelleted ration at 08.00. Lambs were exposed to 6 rnin sound every 3 h starting at 08.00.
A major peak in feeding activity was observed only after the offering of fresh feed in the morning. An increase in feeding activity at the time of feeding has been reported by Vasilatos and Wangsness (1980) and Ray and Roubicek (1971) in cattle. In the present experiment, direct and indirect sunlight entered the open east portion and through the windows in the west side of the barn. Continuous incandescent lighting was provided in the 3 pens located on the west side but not in the 3 pens on the east side of the barn. No change in feeding activity with sunrise or sunset was observed on any of the six 24-h observation days (Fig. 1A,B). Tanida et al. {1984), however, reported that the feeding behavior of Holstein cows subjected to artificial light plus indirect sunlight inside a barn remained synchronized with the natural photoperiod. Outdoor feeding activity coinciding with sunrise and (or) sunset has been reported in grazing sheep (Squires, 1971, 1974; Hulet et
279 a]., 1975; Bueno and Ruckebusch, 1979; Dudziflski and Arnold, 1979), feedlot lambs (Schreffler and Hohenboken, 1980), grazing cattle (O'Donnell and Walton, 1969; Ruckebusch and Bueno, 1978), feedlot cattle (Ray and Roubicek, 1971) and beef cattle in o u t d o o r pens (Wilson and Flynn, 1979; G o n y o u and Stricklin, 1981). Reasons for results differing from these previous studies were hard to elucidate because other environmental influences, such as the temperature and humidity changes, were not measured. Also, there were differences between the current and previous studies in seasons, locations and feeding schedules. There was no apparent decline in feeding activity of lambs during the night; feeding was nearly constant throughout the 24 h. In grazing sheep, however, Bueno and Ruckebusch (1979), Hulet et al. (1975) and Squires (1974) reported that the grazing activity was confined mostly to daylight hours. Shreffler and Hohenboken (1980) found that the majority of feedlot lambs were lying down throughout the hours of darkness. The number of lambs engaged in eating was significantly greater in lambs housed on the east side (open side) than in lambs on the west side of the barn, although the rhythmic feeding pattern was similar. However, there was no significant difference in feed intake between the two groups. This could be explained by the fact that more playful fighting and chasing occurred throughout the 24 h among lambs on the west side which had continuous lighting. These behaviors, however, were not recorded or quantified. Whether the difference in feeding behavior was caused by the difference in lighting or by other environmental factors such as sunlight, temperature or pen location was not possible to determine. The means of three eating activities and of drinking incidents, over the six 24-h observation days for individually observed lambs, are presented in Table I. The results for number of drinking episodes may not be as accurate as the other feeding behaviors because of observational difficulties. There was a significant difference in number of eating bouts between lambs in the west vs. east tiers of pens, and this is consistent with the results for n u m b e r of lambs engaged in eating stated earlier. The overall means per lamb for the total time spent eating, the number of eating bouts, the average time of eating per bout and the number of drinking episodes across the six 24-h observation days were 118.8 min, 22.6 times, 5.5 min and 9.6 times, respectively. The repeatabilities of these four activities on the 6 observation days were 0.28, 0.28, 0.07 and 0.34. Thus, an individual lamb's ingestive behavior on any one day was modestly predictive of its behavior on other days. No significant correlations were found between gain and eating behaviors. The distribution of feeding activities on one observation day with the sound treatment for the 6 individually observed lambs is shown in Fig. 2. Similar patterns existed on the other 5 observation days. This figure emphasizes that lamb feeding activity was synchronized, even though the lambs were selcted randomly from each pen, and that their activities were distributed t h r o u g h o u t 24 h.
280 TABLE I Means and standard errors of feeding activities of randomly selected lambs on 6 observation days
Pen location
Lamb No.
Total time spent eating (min)
Number of (times) eating bouts
Average time spent eating (rain)
West
1 2 3
110.2± 4.4 114.2-+ 9.7 119.9 ± 13.1
18.3± 1.5 19.7± 1.8 19.2 ± 3.1
6.2± 0.5 5.9± 0.5 6.0 ± 0.3
East
4 5 6
117.4 -+ 12.2 155.8 ± 11.2 103.5 ± 8.3
26.2 ± 3.0 31.3 + 4.2 21.0 ± 2.3
4.7 ± 0.6 5.3 ± 0.5 5.1 + 0.5
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Fig. 2. Distribution of feeding activities throughout 24 h under sound treatment. Each line indicates the feeding activity of lambs selected randomly from each pen. Asterisks represent sound exposure.
CONCLUSIONS U n d e r the c o n d i t i o n s of this e x p e r i m e n t , s o u n d s t i m u l a t i o n did n o t alter feed intake or feeding behavior patterns. Lambs apparently learned to i g n o r e t h e s t i m u l u s , s i n c e i t was n o t r e i n f o r c e d b y t h e o f f e r i n g o f f r e s h f e e d . O r p e r h a p s t h e f a c t t h a t l a m b s w e r e f e d ad l i b ± t u r n , w i t h f e e d a l w a y s present, rendered the stimulus ineffective.
281
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