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Circadian behaviour, including thermoregulatory activities, in feedlot lambs
Applied Animal Ethology, 6 (1980) 241-246 o Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
CIRCADIAN ACTIVITIES,
BEHAVIOUR, IN FEEDLOT
CAROL SHREFFLER3 Department
INCLUDING LAMBS1g2
241
THERMOREGULATORY
and WILLIAM HOHENBOKEN
of Animal Science,
Oregon State University,
Corvallis, OR 97331
(U.S.A.)
(Accepted for publication 9 August 1979)
ABSTRACT Shreffler, C. and Hohenboken, W., 1980. Circadian behaviour, including thermoregulatory activities, in feedlot lambs. Appl. Anim. Ethol., 6: 241-246. Fifty-six feeder lambs were observed each half-hour for one day per week for 7 consecutive weeks between July and September, 1973. At each observation period, the number of lambs eating, drinking, standing in an alert state, lying down and standing inactive was counted. The average number of lambs engaged in each activity over the 7 days of observation was plotted against time. Two peaks of eating, drinking and standing active occurred near sunrise and sunset. During the eating peaks, there was frequently competition for space at the self-feeder. At mid-day, lambs were inactive, standing about in groups, shading their heads under the flanks or between the hind legs of adjacent lambs. Later in the afternoon, lambs utilized the shade that became available from the perimeter fence. In both cooling strategies, lambs were particularly keen to shade their heads. All activity declined after sunset, and throughout the hours of darkness the majority of the lambs were lying down.
INTRODUCTION
In modern livestock production systems, animals are displaced from the physical and social environments in which they evolved and in which they were domesticated. Cattle and sheep in feedlots, for example, are constrained to close physical proximity to one another in fairly homogeneous groups based upon size, age and/or sex. Since they are generally provided with a complete, mixed ration the expression of their normal dietary habits and preferences is thwarted. Due to physical and environmental constraints, the scope of their repertoire of behavioural modifications in response to environmental stress may be severely limited. Little is known of the behaviour ’Technical paper No. 5154, Oregon Agricultural Experiment Station. Contribution to North-Central Regional Project NC-111, Increased Efficiency of Lamb Production. ’Please address reprint requests to Dr. Hohenboken at the above address. ’Current address: National Institute of Environmental Health Sciences, 3509 Haworth, Raleigh, NC 27609, U.S.A.
242
of the feedlot lamb or of the relationships between behaviour and lamb performance. The object of this study was to examine circadian patterns of activity and ingestion in feedlot lambs during summer. MATERIALS
AND METHODS
The experiment was conducted at Corvallis, Oregon (latitude 45”N, longitude 123”W) and lasted from 12 July until 17 September 1973. Fifty-six feeder lambs from three separate university flocks were utilized; all were crossbreds of 50% or more Suffolk inheritance. They averaged 32.5 kg liveweight (3.4 kg standard deviation) and were about 5 months of age at the beginning of the trial. All had been reared on pasture with no previous access to harvested or processed feeds or to feeders, except for provision of salt and mineral supplementation. At the initiation of the experiment, lambs were placed in a 6-m by 18-m dirt-surfaced feedlot. Approximately 4 cm water trough and 5.4 cm feeder space were available per lamb. Shade, other than from an adjacent building and the perimeter fence, was not provided. The pen was shaded by the building only to a maximum of 3 h after sunrise. The lambs were self-fed a complete pelleted ration. Air temperature and relative humidity were recorded continuously. During the study, sunrise ranged from 05.51 h to 06.39 h Pacific Daylight Time; the time of sunset ranged from 20.46 h to 19.42 h. Lambs were allowed 2 weeks to become acclimatized to the feedlot environment. Behavioural observations were then recorded every half hour for 27.5 h (18.00 h to 21.30 h the following evening) once per week for 7 consecutive weeks. A low level of artificial lighting was necessary to observe the lambs at night. The measurement criterion at each observation period was the number of sheep engaged in each of five mutually exclusive and exhaustive behaviour categories. The ce+.egories were eating, drinking, standing “active” (i.e. the lamb was judged subjectively to be attentive or alert rather than inattentive or phlegmatic), lying and standing “inactive”. Morning (08.00 to 09.00 h) and afternoon (12.30 to 13.30 h) rectal temperatures and afternoon respiration rates were recorded up to five times per week for 14 of the lambs. To test for circadian patterns for the various behaviours, one-way analyses of variance were performed with time (24-h clock) as the independent variable and the number of lambs engaged in a particular behaviour as the dependent variable. Analyses were run for each of the five behaviours and for “activity”, defined as the total number of lambs per observation period engaged in eating plus drinking plus standing active. Once it was determined that each behaviour varied in frequency over time (P < 0.01 in each case), the average number of lambs per activity was plotted against clock time. Actual points plotted on the curves (Figs. 1 and 2) are moving averages of the immediate previous, the current and the immediate next observation, to smooth the data. Vertical dotted lines in the figures represent ranges for time of sunrise and time of sunset.
243
ZOa y
15-
-
EATING
-‘-
DRINKING
.. .
STANDING
-
LYING
*,.
ACTIVITY
-.-
STANDING
INACTIVE
‘, ,’ : ‘+t* ,:, :I :
ACTIVE
,’ z
0
4
6
12 TIME
16 (FIR)
20
24
0
4
6
I2 TIME
16
20
24
(HR.1
Fig. 1. Number of lambs out of a total of 56 engaged in eating, drinking and standing active behaviour categories throughout the day. The vertical dashed lines represent ranges for time of sunrise and sunset. Fig. 2. Number of lambs out of a total of 56 engaged in activity (the sum of lambs eating, drinking and standing active), standing inactive and lying behaviour categories throughout the day. The vertical dashed lines represent ranges for time of sunrise and sunset.
RESULTS
AND DISCUSSION
On five of seven test days, ambient temperature rose above 25.6”C, a temperature above which lambs will generally attempt to dissipate heat by increased respiration rate, shade-seeking and group dispersal (Schein and Hafez, 1969). Rectal temperatures averaged 39.2 and 39.6”C in morning and afternoon, respectively. In the mornings, breathing appeared to be effortless. Afternoon respiration rate averaged 38 inspirations per min, and panting was frequently observed. Nightly low temperatures averaged 10.6”C, a temperature at which lambs will adapt various heat conservation strategies including slower breathing, grouping and seeking protection from the wind (Schein and Hafez, 1969). Greater detail on climatology and behavioural modifications of lambs in the current experiment to ambient temperature changes were provided by Hohenboken and Kistner (1976). The three behavioural categories - eating, drinking and standing active had similar circadian patterns (Fig. 1). The incidence of all three started to rise before, at, or shortly after sunrise, peaked after sunrise and then declined through late afternoon. The lowest level of each occurred about 16.00 h. The incidence of standing active declined more rapidly than the incidence of eating. This may have been due to the limited amount of feeder space provided; only about one quarter of the lambs could be accommodated at the self-feeder at any one time. The incidence of all three
244
behaviours started to rise again prior to sunset, peaked shortly after sunset and then declined, remaining at a fairly low level throughout the remainder of the night. Drinking activity was greatest during or shortly after maximum eating activity and was low in the afternoon, during the hottest part of the day. This conflicts with observations that in feedlot cattle, drinking was most pronounced at 13.00 h and at 20.00 h (Ray and Roubicek, 1971) or between 12.00 h and 15.00 h (Hoffman and Self, 1973). Figure 2 presents the circadian patterns for lying, standing inactive and total activity. Activity is a composite of eating, drinking and standing active behaviours; since each of these had a similar pattern over time, the plot for activity is similar to those shown in Fig. 1. Standing inactive was essentially a daytime behaviour. It peaked in incidence at about 13.00 h when the sun was at maximum elevation and the feedlot was virtually without shade. Nevertheless, it was frequently associated with shade-seeking. Groups of 8-10 lambs would congregate in the middle of the pen, with each lamb shading its head under the flank or between the hind legs of another lamb. Each lamb thus received shade from, and provided shade to, neighboring individuals. Following mid-day, more shade was provided by the perimeter fence, and lambs switched strategies from standing in groups to lying in a line, parallel to and in the shade of the fence, generally positioned so that their heads were in the shade. As the incidence of standing inactive declined after 13.00 h, the incidence of lying increased to peak about 16.00 h. After 16.00 h, both standing inactive and lying declined, as activity increased. As activity declined after sunset, the incidence of lying increased. Throughout the remaining hours of darkness, the majority of lambs were usually lying down. The circadian activity pattern in these feedlot lambs is similar to those reported in grazing sheep (Squires, 1971, 1974; Bechet, 1978), in cattle confined to lots, including lactating cows (Schake and Riggs, 1969), nursing calves (Schake and Riggs, 1970), and feedlot steers (Ray and Roubicek, 1971; Hoffman and Self, 1973; Wilson and Flynn, 1979), and in grazing cattle (Harker et al., 1954, O’Donnell and Watson, 1969; Ruckebusch and Bueno, 1978). Several investigations support the interpretation that two daily activity peaks in cattle and sheep are triggered by sunrise and sunset (O’Donnell and Watson, 1969; Ray and Roubicek, 1971; Squires, 1971, 1974; Ruckebusch and Bueno, 1978; Wilson and Flynn, 1979). In this study, some three quarters of the lambs were lying down at each observation period between midnight and sunrise. Roubicek and Hubbert (1961) reported that approximately 90% of feedlot cattle in a hot climate (Arizona, U.S.A.) during the summer would be found lying down. This observed difference could be due to species, to the physical environment, to climatic conditions or to some combination thereof. Ruckebusch (1972) reported that both cattle and sheep spent most of the hours of darkness in a wakeful state (68% for cattle and 73% for sheep) but that drowsiness predominated over alert wakefulness in cattle (52% of the time) but not in sheep (23% of the time).
245 CONCLUSIONS
Purposeful activity in these feedlot lambs followed a circadian pattern, Activity began prior to sunrise, peaked shortly thereafter, declined during the day to a minimum at about 16.00 h, increased through sunset, peaked shortly thereafter, declined until midnight and remained low throughout the remainder of the night. During the heat of the day, lambs adopted cooling strategies according to the availability of shade. When shade from environmental structures was totally absent, they stood and shaded their heads in the shadow provided by adjacent lambs. When shade was available from the perimeter fence, it was utilized. It is not known whether provision of additional shade would have benefited lamb comfort, gain or health, or, if it had, whether such benefits would have been cost-effective. Lambs spent the majority of the night lying down. At peaks of eating activity, more lambs sought to eat than could be accommodated at the self-feeder. Whether this limited intake and therefore daily gain of some or all lambs is not known.
REFERENCES Bechet, G., 1978. Enregistrement des activites alimentaires et meryciques des ovins au paturage. (Recording of feeding activity and rumination in grazing sheep.) Ann. Zootech., 27: 107-113. Harker, K.W., Taylor, J.I. and Rollinson, D.H.L., 1954. Studies on the habits of zebu cattle. I. Preliminary observations on grazing habits. J. Agric. Sci., Cambridge, 44: 193-198. Hoffman, M.P. and Self, H.L., 1973. Behavioral traits of feedlot steers in Iowa. J. Anim. Sci., 37: 1438-1445. Hohenboken, W. and Kistner, T.P., 1976. Summer water consumption, body temperature and respiration rate in lambs. Can. J. Anim. Sci., 56: 739-744. O’Donnell, T.G. and Watson, G.A., 1969. Some observations on the behavior and hill pasture utilization of Irish cattle. J. Br. Grassl. Sot., 24: 128-133. Ray, D.E. and Roubicek, C.B., 1971. Behavior of feedlot cattle during two seasons. J. Anim. Sci., 33: 72-76. Roubicek, C.B. and Hubbert, F.E., Jr., 1961. Nocturnal behavior of beef cattle in the feedlot during the summer. Proc. West. Sect. Am. Sot. Anim. Prod., 12: LX-1 through LX-3. Ruckebusch, Y., 1972. The relevance of drowsiness in the circadian cycle of farm animals. Anim. Behav., 20: 637-643. Ruckebusch, Y. and Bueno, L., 1978. An analysis of ingestive behavior and activity of cattle under field conditions. Appl. Anim. Ethol., 4: 301-313. Schake, L.M. and Riggs, J.K., 1969. Activities of lactating beef cows in confinement. J. Anim. Sci., 28: 568-572. Schake, L.M. and Riggs, J.K., 1970. Activities of beef calves reared in confinement. J. Anim. Sci., 31: 414-416. Schein, M.W. and Hafez, E.S.E., 1969. The physical environment and behavior. In: E.S.E. Hafez (Editor), The Behavior of Domestic Animals, 2nd edn. Williams and Wilkins, Baltimore, MD, pp. 65-84.
246 Squires, V.R., 1971. Temporal patterns of activity in a small flock of Merino sheep as determined by an automatic recording technique. Anim. 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. Anim. Ethol., 1: 17-30. Wilson, R.K. and Flynn, A.V., 1979. Feeding behavior of cattle when offered grass silage in troughs during winter and summer. Appl. Anim. Ethol., 5: 35-41.
CIRCADIAN ACTIVITIES,
BEHAVIOUR, IN FEEDLOT
CAROL SHREFFLER3 Department
INCLUDING LAMBS1g2
241
THERMOREGULATORY
and WILLIAM HOHENBOKEN
of Animal Science,
Oregon State University,
Corvallis, OR 97331
(U.S.A.)
(Accepted for publication 9 August 1979)
ABSTRACT Shreffler, C. and Hohenboken, W., 1980. Circadian behaviour, including thermoregulatory activities, in feedlot lambs. Appl. Anim. Ethol., 6: 241-246. Fifty-six feeder lambs were observed each half-hour for one day per week for 7 consecutive weeks between July and September, 1973. At each observation period, the number of lambs eating, drinking, standing in an alert state, lying down and standing inactive was counted. The average number of lambs engaged in each activity over the 7 days of observation was plotted against time. Two peaks of eating, drinking and standing active occurred near sunrise and sunset. During the eating peaks, there was frequently competition for space at the self-feeder. At mid-day, lambs were inactive, standing about in groups, shading their heads under the flanks or between the hind legs of adjacent lambs. Later in the afternoon, lambs utilized the shade that became available from the perimeter fence. In both cooling strategies, lambs were particularly keen to shade their heads. All activity declined after sunset, and throughout the hours of darkness the majority of the lambs were lying down.
INTRODUCTION
In modern livestock production systems, animals are displaced from the physical and social environments in which they evolved and in which they were domesticated. Cattle and sheep in feedlots, for example, are constrained to close physical proximity to one another in fairly homogeneous groups based upon size, age and/or sex. Since they are generally provided with a complete, mixed ration the expression of their normal dietary habits and preferences is thwarted. Due to physical and environmental constraints, the scope of their repertoire of behavioural modifications in response to environmental stress may be severely limited. Little is known of the behaviour ’Technical paper No. 5154, Oregon Agricultural Experiment Station. Contribution to North-Central Regional Project NC-111, Increased Efficiency of Lamb Production. ’Please address reprint requests to Dr. Hohenboken at the above address. ’Current address: National Institute of Environmental Health Sciences, 3509 Haworth, Raleigh, NC 27609, U.S.A.
242
of the feedlot lamb or of the relationships between behaviour and lamb performance. The object of this study was to examine circadian patterns of activity and ingestion in feedlot lambs during summer. MATERIALS
AND METHODS
The experiment was conducted at Corvallis, Oregon (latitude 45”N, longitude 123”W) and lasted from 12 July until 17 September 1973. Fifty-six feeder lambs from three separate university flocks were utilized; all were crossbreds of 50% or more Suffolk inheritance. They averaged 32.5 kg liveweight (3.4 kg standard deviation) and were about 5 months of age at the beginning of the trial. All had been reared on pasture with no previous access to harvested or processed feeds or to feeders, except for provision of salt and mineral supplementation. At the initiation of the experiment, lambs were placed in a 6-m by 18-m dirt-surfaced feedlot. Approximately 4 cm water trough and 5.4 cm feeder space were available per lamb. Shade, other than from an adjacent building and the perimeter fence, was not provided. The pen was shaded by the building only to a maximum of 3 h after sunrise. The lambs were self-fed a complete pelleted ration. Air temperature and relative humidity were recorded continuously. During the study, sunrise ranged from 05.51 h to 06.39 h Pacific Daylight Time; the time of sunset ranged from 20.46 h to 19.42 h. Lambs were allowed 2 weeks to become acclimatized to the feedlot environment. Behavioural observations were then recorded every half hour for 27.5 h (18.00 h to 21.30 h the following evening) once per week for 7 consecutive weeks. A low level of artificial lighting was necessary to observe the lambs at night. The measurement criterion at each observation period was the number of sheep engaged in each of five mutually exclusive and exhaustive behaviour categories. The ce+.egories were eating, drinking, standing “active” (i.e. the lamb was judged subjectively to be attentive or alert rather than inattentive or phlegmatic), lying and standing “inactive”. Morning (08.00 to 09.00 h) and afternoon (12.30 to 13.30 h) rectal temperatures and afternoon respiration rates were recorded up to five times per week for 14 of the lambs. To test for circadian patterns for the various behaviours, one-way analyses of variance were performed with time (24-h clock) as the independent variable and the number of lambs engaged in a particular behaviour as the dependent variable. Analyses were run for each of the five behaviours and for “activity”, defined as the total number of lambs per observation period engaged in eating plus drinking plus standing active. Once it was determined that each behaviour varied in frequency over time (P < 0.01 in each case), the average number of lambs per activity was plotted against clock time. Actual points plotted on the curves (Figs. 1 and 2) are moving averages of the immediate previous, the current and the immediate next observation, to smooth the data. Vertical dotted lines in the figures represent ranges for time of sunrise and time of sunset.
243
ZOa y
15-
-
EATING
-‘-
DRINKING
.. .
STANDING
-
LYING
*,.
ACTIVITY
-.-
STANDING
INACTIVE
‘, ,’ : ‘+t* ,:, :I :
ACTIVE
,’ z
0
4
6
12 TIME
16 (FIR)
20
24
0
4
6
I2 TIME
16
20
24
(HR.1
Fig. 1. Number of lambs out of a total of 56 engaged in eating, drinking and standing active behaviour categories throughout the day. The vertical dashed lines represent ranges for time of sunrise and sunset. Fig. 2. Number of lambs out of a total of 56 engaged in activity (the sum of lambs eating, drinking and standing active), standing inactive and lying behaviour categories throughout the day. The vertical dashed lines represent ranges for time of sunrise and sunset.
RESULTS
AND DISCUSSION
On five of seven test days, ambient temperature rose above 25.6”C, a temperature above which lambs will generally attempt to dissipate heat by increased respiration rate, shade-seeking and group dispersal (Schein and Hafez, 1969). Rectal temperatures averaged 39.2 and 39.6”C in morning and afternoon, respectively. In the mornings, breathing appeared to be effortless. Afternoon respiration rate averaged 38 inspirations per min, and panting was frequently observed. Nightly low temperatures averaged 10.6”C, a temperature at which lambs will adapt various heat conservation strategies including slower breathing, grouping and seeking protection from the wind (Schein and Hafez, 1969). Greater detail on climatology and behavioural modifications of lambs in the current experiment to ambient temperature changes were provided by Hohenboken and Kistner (1976). The three behavioural categories - eating, drinking and standing active had similar circadian patterns (Fig. 1). The incidence of all three started to rise before, at, or shortly after sunrise, peaked after sunrise and then declined through late afternoon. The lowest level of each occurred about 16.00 h. The incidence of standing active declined more rapidly than the incidence of eating. This may have been due to the limited amount of feeder space provided; only about one quarter of the lambs could be accommodated at the self-feeder at any one time. The incidence of all three
244
behaviours started to rise again prior to sunset, peaked shortly after sunset and then declined, remaining at a fairly low level throughout the remainder of the night. Drinking activity was greatest during or shortly after maximum eating activity and was low in the afternoon, during the hottest part of the day. This conflicts with observations that in feedlot cattle, drinking was most pronounced at 13.00 h and at 20.00 h (Ray and Roubicek, 1971) or between 12.00 h and 15.00 h (Hoffman and Self, 1973). Figure 2 presents the circadian patterns for lying, standing inactive and total activity. Activity is a composite of eating, drinking and standing active behaviours; since each of these had a similar pattern over time, the plot for activity is similar to those shown in Fig. 1. Standing inactive was essentially a daytime behaviour. It peaked in incidence at about 13.00 h when the sun was at maximum elevation and the feedlot was virtually without shade. Nevertheless, it was frequently associated with shade-seeking. Groups of 8-10 lambs would congregate in the middle of the pen, with each lamb shading its head under the flank or between the hind legs of another lamb. Each lamb thus received shade from, and provided shade to, neighboring individuals. Following mid-day, more shade was provided by the perimeter fence, and lambs switched strategies from standing in groups to lying in a line, parallel to and in the shade of the fence, generally positioned so that their heads were in the shade. As the incidence of standing inactive declined after 13.00 h, the incidence of lying increased to peak about 16.00 h. After 16.00 h, both standing inactive and lying declined, as activity increased. As activity declined after sunset, the incidence of lying increased. Throughout the remaining hours of darkness, the majority of lambs were usually lying down. The circadian activity pattern in these feedlot lambs is similar to those reported in grazing sheep (Squires, 1971, 1974; Bechet, 1978), in cattle confined to lots, including lactating cows (Schake and Riggs, 1969), nursing calves (Schake and Riggs, 1970), and feedlot steers (Ray and Roubicek, 1971; Hoffman and Self, 1973; Wilson and Flynn, 1979), and in grazing cattle (Harker et al., 1954, O’Donnell and Watson, 1969; Ruckebusch and Bueno, 1978). Several investigations support the interpretation that two daily activity peaks in cattle and sheep are triggered by sunrise and sunset (O’Donnell and Watson, 1969; Ray and Roubicek, 1971; Squires, 1971, 1974; Ruckebusch and Bueno, 1978; Wilson and Flynn, 1979). In this study, some three quarters of the lambs were lying down at each observation period between midnight and sunrise. Roubicek and Hubbert (1961) reported that approximately 90% of feedlot cattle in a hot climate (Arizona, U.S.A.) during the summer would be found lying down. This observed difference could be due to species, to the physical environment, to climatic conditions or to some combination thereof. Ruckebusch (1972) reported that both cattle and sheep spent most of the hours of darkness in a wakeful state (68% for cattle and 73% for sheep) but that drowsiness predominated over alert wakefulness in cattle (52% of the time) but not in sheep (23% of the time).
245 CONCLUSIONS
Purposeful activity in these feedlot lambs followed a circadian pattern, Activity began prior to sunrise, peaked shortly thereafter, declined during the day to a minimum at about 16.00 h, increased through sunset, peaked shortly thereafter, declined until midnight and remained low throughout the remainder of the night. During the heat of the day, lambs adopted cooling strategies according to the availability of shade. When shade from environmental structures was totally absent, they stood and shaded their heads in the shadow provided by adjacent lambs. When shade was available from the perimeter fence, it was utilized. It is not known whether provision of additional shade would have benefited lamb comfort, gain or health, or, if it had, whether such benefits would have been cost-effective. Lambs spent the majority of the night lying down. At peaks of eating activity, more lambs sought to eat than could be accommodated at the self-feeder. Whether this limited intake and therefore daily gain of some or all lambs is not known.
REFERENCES Bechet, G., 1978. Enregistrement des activites alimentaires et meryciques des ovins au paturage. (Recording of feeding activity and rumination in grazing sheep.) Ann. Zootech., 27: 107-113. Harker, K.W., Taylor, J.I. and Rollinson, D.H.L., 1954. Studies on the habits of zebu cattle. I. Preliminary observations on grazing habits. J. Agric. Sci., Cambridge, 44: 193-198. Hoffman, M.P. and Self, H.L., 1973. Behavioral traits of feedlot steers in Iowa. J. Anim. Sci., 37: 1438-1445. Hohenboken, W. and Kistner, T.P., 1976. Summer water consumption, body temperature and respiration rate in lambs. Can. J. Anim. Sci., 56: 739-744. O’Donnell, T.G. and Watson, G.A., 1969. Some observations on the behavior and hill pasture utilization of Irish cattle. J. Br. Grassl. Sot., 24: 128-133. Ray, D.E. and Roubicek, C.B., 1971. Behavior of feedlot cattle during two seasons. J. Anim. Sci., 33: 72-76. Roubicek, C.B. and Hubbert, F.E., Jr., 1961. Nocturnal behavior of beef cattle in the feedlot during the summer. Proc. West. Sect. Am. Sot. Anim. Prod., 12: LX-1 through LX-3. Ruckebusch, Y., 1972. The relevance of drowsiness in the circadian cycle of farm animals. Anim. Behav., 20: 637-643. Ruckebusch, Y. and Bueno, L., 1978. An analysis of ingestive behavior and activity of cattle under field conditions. Appl. Anim. Ethol., 4: 301-313. Schake, L.M. and Riggs, J.K., 1969. Activities of lactating beef cows in confinement. J. Anim. Sci., 28: 568-572. Schake, L.M. and Riggs, J.K., 1970. Activities of beef calves reared in confinement. J. Anim. Sci., 31: 414-416. Schein, M.W. and Hafez, E.S.E., 1969. The physical environment and behavior. In: E.S.E. Hafez (Editor), The Behavior of Domestic Animals, 2nd edn. Williams and Wilkins, Baltimore, MD, pp. 65-84.
246 Squires, V.R., 1971. Temporal patterns of activity in a small flock of Merino sheep as determined by an automatic recording technique. Anim. 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. Anim. Ethol., 1: 17-30. Wilson, R.K. and Flynn, A.V., 1979. Feeding behavior of cattle when offered grass silage in troughs during winter and summer. Appl. Anim. Ethol., 5: 35-41.