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The motivation of cows to walk as thwarted by tethering¹

INRA, UR1213 Herbivores, Site de Theix, F-63122 Saint-Genès-Champanelle, France

	Abstract

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Cows are often housed in tie-sheds for some part of the year (from 20 to 80% of adult cows in European countries). By contrast, regulations aiming at improving animal welfare generally provide for more opportunity to express behavior and so limit tethering (the European directive for sows). To inform current debate on whether cows should be tethered from an animal welfare point of view, 2 experiments were conducted to determine whether cows were motivated to walk (if their walking motivation was thwarted by tethering) and whether this frustration resulted in acute or chronic stress. In Exp. 1, fifteen cows were housed in tie-stalls for 1, 3, 9, or 27 d or loose-housed in a pen equipped with free-stalls for 27 d according to a Latin square design. On d 28, cows were observed in an 80-m² arena where they could walk or run for 10 min. In Exp. 2, fifteen cows were either loose-housed or tie-housed with or without 1 h of daily access to an exercise area according to a Latin square design (treatment duration of 27 d). On d 28, cows were observed in the test arena for 10 min as in Exp. 1. In addition, in Exp. 2, milk was sampled twice weekly for cortisol concentrations and cows underwent a chronic stress test (challenge with ACTH, followed by blood samples for cortisol concentrations). When they were tied with no access to exercise, cows displayed a greater locomotor activity in the test arena (time spent walking x 1.4 in Exp. 1, P < 0.05; time spent trotting x 5 in Exp. 2, P < 0.05), whatever the duration of tie-housing. Regular exercise caused locomotor activity in the arena test to revert to levels observed when cows were loose-housed. Basal cortisol concentrations in milk decreased with time whatever the housing condition (P < 0.001). This decrease was more marked when cows were tied than when they were loose-housed (P < 0.05). Cortisol responses to ACTH were similar between treatments. Adult cows are motivated to walk, and tethering thwarts this motivation. However, the frustration produced by tethering does not result in either acute or chronic physiological stress responses. We recommend that cows housed in tie-sheds be given regular access to an exercise area.

Key Words: behavior • dairy cow • exercise • housing • welfare

	INTRODUCTION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Cattle are often tied in stalls in many parts of the world. In Europe, between 20 (lowland) to 80% (upland) of cows are tethered at least during the winter. European regulations give animals more freedom to move (Veissier et al., 2008). No directive exists for adult cows, but the acceptability of their tethering is discussed at the Council of Europe.

According to the Lorenz model, expression of some behaviors may be determined by internal motivation building up with time (Jensen and Toates, 1993), and frustration is shown by increased expression of an activity when released from impediment (rebound effect; Mackintosh, 1974). However, the lack of a rebound effect does not preclude a behavioral need. To assess the importance of a behavior for the animal, one needs to know whether expression of the behavior turns off the underlying motivation and whether prevention of the behavior results in suffering (Jensen and Toates, 1993).

A rebound effect on locomotion is observed in calves housed in small crates that performed more trotting, galloping, rear kicking, and buck-kicks when released in a large arena (Dellmeier et al., 1985). This rebound in locomotion is decreased when calves are given daily access to exercise (Jensen, 2001). Preventing animals from expressing certain activities may induce signs of acute or chronic stress. These include increased blood cortisol concentrations, observed in minks denied access to a water pond (Mason et al., 2001), and long-term alterations of the functioning of the hypothalamo-hypophysealadrenal (HPA) axis, in tethered sows and bulls (Ladewig and Smidt, 1989; Janssens et al., 1994).

We aimed to determine whether locomotion is a behavioral need for cows. Therefore, we compared expression of locomotion in cows tethered for various durations and cows housed in a free-shed before release into an exercise area, analyzed the effect of daily exercise on this expression, and determined whether tethering induces acute or chronic stress by measuring basal and ACTH-induced cortisol concentrations.

	MATERIALS AND METHODS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
The scientist in charge of the experiments (I. Veissier) was licensed to perform experiments on animals, and the staff that cared for the animals or applied the experimental procedures had attended a special course approved by the French Ministry of Agriculture.

Two experiments were conducted at the INRA experimental farm of Les Monts Dore (Puy-de-Dôme, central France). In Exp. 1 cows were housed in tie-stalls for various durations, from 1 d to 1 mo, or loose-housed. In Exp. 2, cows were either tie- or loose-housed for 1 mo, and some tied cows were given daily access to an exercise area.

Animals, Rearing Conditions, and Experimental Design

The 2 experiments were conducted on a total of 30 Holstein cows. Since birth, they were housed on pasture during summer periods (from May to October), and during winter periods, they were housed indoors in a loose-housing system equipped with free-stalls.

Experiments began when cows were 2 yr old. They were stabled in early October and housed in a pen containing an exercise area (6.3 m²/cow) and as many free-stalls as cows. Free-stalls were 1.24 m wide and 1.86 m long with a 1.02-m passageway in front of them, and they were separated from each other by Euroconfort (Jourdain, Escrennes, France) partitions (Veissier et al., 2004). Cows calved during the second half of October. They were moved to a calving pen before parturition. They stayed in the calving pen for 24 h after parturition. They then returned to the pen equipped with free-stalls. Two weeks (±3 d) after calving, cows were moved on the same day to tie-stalls, located in the same shed, to accustom them to being tethered. They stayed 3 d in the tie-stalls. Tie-stalls were 1.35 m wide and 2.20 m long. Cows were tied using a neck collar and a chain 0.72 m long attached 0.90 m above the floor. No electric restrainer was used. Stalls were covered with a 3-cm-thick rubber mat. Cows were subsequently led back into the cubicle pen until experimental treatments began. Free- and tie-stalls were spread with 500 g of wood shavings per day. Cows were fed at 0930 h ad libitum (on an as-fed basis) a mixed diet (grass silage, corn silage, cocksfoot hay, soybean meal) and supplemented with commercial concentrates (Galaxel Viv, Centraliment, Aurillac, France) adjusted to individual milk production (about 30% of the total regimen).

The experimental observations began 4 wk after cows had gone back to the cubicle pen. We first subjected each cow to the arena test (see below) on 3 consecutive days to accustom them to the test situation. Five groups of 3 cows each were then formed for Exp. 1 and 3 groups of 5 cows each for Exp. 2, with cows chosen to balance calving date and BW at calving between groups. Each group underwent several experimental treatments, each lasting 4 wk, according to a Latin square design.

In Exp. 1, five treatments were applied: loose-housing in the cubicle pen for 27 d (referred to as loose-housing), loose-housing for 26 d then tie-housing for 1 d (1 d of tie-housing), loose for 24 d then tied for 3 d (3 d of tie-housing), loose for 18 d then tied for 9 d (9 d of tie-housing), and tied for 27 d (27 d of tie-housing). The cubicle pen and the tie-stalls were those used before the beginning of the treatments. The order of treatments was as follows: loose-housing, 1 d of tie-housing, 3 d of tie-housing, and 9 d tie-housing for group 1; 1 d of tie-housing, 3 d of tie-housing, 9 d of tie-housing, and loose-housing for group 2, and so on.

In Exp. 2, three treatments were applied: loose in the cubicle pen for 27 d (loose-housing), tied for 27 d (tie-housing), and tied for 27 d plus 1 h of daily exercise (tie-housing plus exercise). For exercise, the 5 cows were untethered and moved together to a 3.65 x 30.0 m area inside the shed. The order of treatments was as follows: loose-housing, tie-housing plus exercise, and tie-housing for group 1; tie-housing plus exercise, tie-housing, and loose-housing for group 2; and tie-housing, loose-housing, and tie-housing plus exercise for group 3.

On d 28 of each treatment, cows underwent an arena test (see below). They were then moved to their next treatment at 1800 h.

Behavioral Measurements

In both experiments, an arena test was performed at the end of each treatment period. The arena was 8 x 10 m (the short side corresponded to more than 4 times the diagonal length of the cows, 1.8 m). The arena was thus assumed to offer good opportunity for locomotion. The arena had solid walls on 3 sides and a large gate on the fourth side. The floor was concrete and marked with white lines to delimit 12 rectangles (2.7 x 2.5 m). The arena was located about 60 m from the tie-stalls and 50 m from the cubicle pen. Tests took place between 1000 and 1600 h. Each cow was individually led to the test arena and left there for 10 min before being led back to its pen or stall. When the cow walked to the arena, the handler walked 2 m behind it. If the cow stopped moving, the handler approached it and if necessary touched its back to prompt it to move. The cow was also allowed to trot or gallop to the arena. We measured the time taken to walk to the arena, divided by the exact distance from the pen or stall and the arena. The cow was left for 10 min in the arena where it was free to move. To distinguish between general walking activity and tendency to explore, a traffic cone was placed in a corner of the arena at the end of the 10 min in Exp. 2, and the cow was observed for a further 2 min. In the arena, we recorded the behavior of the cow on a hand-held computer (Psion Workabout, Psion PLC, London, UK) with Observer (Observer Video Pro, Noldus, the Netherlands). The following states were taken into account: the position of the cow in the arena (the rectangle on which it stood), whether the cow was immobile, walking (at least taking 2 steps, at any time 3 hoofs touching the floor), or trotting (moving with diagonally synchronized leg movements). No galloping and no bucking (as defined in Jensen, 1999) occurred, and cows never slipped in the arena. Sniffing of the traffic cone (neck extended and nose 10 cm or less from the cone) was recorded as an event. We then calculated the time the cow spent walking or trotting and the frequency of sniffing the cone, and we estimated the distance covered by the cow by multiplying the frequency of position changes by the average distance between rectangles.

Physiological Measurements

Milk samples were collected at morning and evening milking for 2 d before the beginning of the experimental treatments on all the animals and then every 3 or 4 d (twice weekly) when cows underwent 27 d of tie-housing in Exp. 1, and whatever the treatment in Exp. 2. The milk was immediately frozen at –20°C before cortisol assay.

In Exp. 2, a test combining blockade and then stimulation of the HPA axis was performed 3 wk after the beginning of each treatment (Veissier and Le Neindre, 1988). This test required cows to be kept still to take blood samples. To acclimatize cows to the handling procedures, loose cows were headlocked at the feeding barrier for 2 h on the 3 d preceding the test. We then administered 0.02 mg/kg of BW i.m. of dexamethasone acetate (Dexalone, Alcyon, Lyon, France) to each cow between 1700 and 1800 h. The next morning, we administered 1 IU/kg of metabolic weight (BW^0.75) of ACTH (Synacthene Immediat, Novartis Pharma, Rueil-Malmaison, France) i.v. to each cow. Blood samples (5 mL) were collected by venipuncture of a jugular vein or a caudal vein for the last samples before injection of dexamethasone, before ACTH injection, and then 30, 120, and 180 min after injection. During the injection of dexamethasone and for the entire period of blood sampling when ACTH was injected, loose cows remained headlocked at the feeding barrier. Samples were centrifuged at 3,000 x g for 5 min and were immediately frozen at –20°C before cortisol assay.

Milk samples were defrosted at room temperature, then defatted by centrifugation (2,400 x g for 20 min; 4°C). Corticosteroids were extracted from skimmed milk with ethyl acetate. The cortisol concentrations were determined by RIA with an antibody produced by Cognié and Poulin (INRA, Tours, France; Boissy, 1990). The detection limit was 0.02 ng/mL, and the within- and between-assays CV were 11 and 22% for low controls (4 ng/mL) and 7 and 14% for high controls (32 ng/mL).

Statistical Analyses

Data were transformed to fit conditions for ANOVA. Cortisol concentrations, distance covered in the arena, and frequency of sniffing the cone were log-transformed because data were left-truncated (no values below 0). Time duration and percentages were transformed into arcsines. Statistical analyses were performed with SAS v.8.1 (SAS Inst. Inc., Cary, NC). Analyses of variance for repeated data were conducted using PROC MIXED of SAS assuming a compound symmetry of the correlation matrix or an unstructured matrix when more appropriate. The following factors were included in the model: animal (random factor), housing (the treatments being tie-housing with no exercise for 1, 3, 9, 27 d or loose-housing for 27 d in Exp. 1 and tie-housing with or without exercise for 27 d, or loose-housing for 27 d in Exp. 2), and group (5 groups in Exp. 1 and 3 in Exp. 2, taken as the repeated factor). In addition, data collected before the beginning of experimental treatments were included as covariates to analyze the same type of variates during the experimental period. To this aim, the frequency and duration of each behavior over the second and third exposures to the test arena were included in the statistical model to account for variations in the same behaviors during the treatments. Similarly, milk cortisol content before the beginning of the treatments was included in the analysis to account for variations in milk cortisol concentration during the treatments. Finally, time effects were included to analyze cortisol concentrations determined in milk repeatedly throughout the experiment and in blood at several intervals after ACTH administration. Post hoc comparisons were performed with the least squares means procedure, and probabilities were estimated with the Tukey-Kramer arrangement.

We report on significant differences (P < 0.05) and tendencies (P < 0.10) between housing treatments. In most cases, we observed that the covariate included in the model had a significant effect (cows that moved more than others in the arena during pretesting continued to move more during testing, and those who had greater cortisol concentrations before the treatments began continued to do so thereafter). However, this was not the focus of the study. Group effects were generally not observed and will not be reported.

	RESULTS

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Exp. 1

Behavior. In Exp. 1, when the cows were led to the arena, cows walked at the same speed (about 1 m/s) whatever their housing conditions (Table 1). Once in the arena, cows spent more time walking (P = 0.03) and covered a longer distance (P = 0.004) when they had been tied rather than loose. These differences were already significant after 1 d of tie-housing but not after 9 d for time spent walking and 3 and 9 d for distance covered. Time spent trotting in the arena did not differ (P = 0.25) between housing treatments.

Exp. 2

Behavior. In Exp. 2, cows tended to cover a longer distance in the arena (P = 0.10) when they had been tie-housed without exercise than when they had been loose or tied with some daily exercise (Table 2). No difference in the time spent walking (P = 0.28) in the arena was observed, but cows spent more time trotting (P = 0.05) when they had been tied without exercise than when they were loose or tied with some exercise.

View larger version (11K): [in this window] [in a new window]   Figure 1. Exp. 2, changes in milk cortisol with time when cows are tied, with or without 1 h of daily access to an exercise area, or loose-housed in a pen equipped with free-stalls (SEM = 0.24).

	DISCUSSION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
In this study, locomotion of cows that were accustomed to loose-housing was increased after a period of tie-housing except when tied cows had access daily to an exercise area for 1 h. No stress response was observed under tie-housing.

When cows were released into an arena, we observed an increased locomotion in cows that had been tie-housed with no exercise for some time. Time spent walking or trotting was less in Exp. 2 than in Exp. 1, possibly due to lower temperatures during Exp. 2. Nevertheless, similar effects were observed within each experiment. In Exp. 1, after only 1 d of tie-housing, time spent walking and distance covered in the arena increased by 40% (±9%) and 50% (±7%), respectively, on average between 1 to 27 d of tie-housing. In Exp. 2, similar increases were observed, but the increase in time spent walking was not significant, and only a tendency was observed in distance covered. Cows also spent more time trotting when they had been tied before the arena test. This time was doubled (115% ± 21%) in Exp. 1 and increased 5-fold in Exp. 2 when loose and tied cows are compared. This time remained small (less than 1%), but the difference between loose and tied cows was nevertheless significant in Exp. 2.

It is unlikely that the greater locomotion in tied cows was due to a greater tendency to explore the environment. As a matter of fact, the arena was known to the cows, which had been exposed to it on 3 occasions before the experimental housing conditions began. In addition, when an object was added to the arena, the investigation of this object was unrelated to the previous housing conditions. Therefore, the increased activity observed in tied cows is not explained by increased motivation to explore. One hypothesis could be that cows moved because the concrete floor of the arena was not comfortable enough to lie on. However, in cows, decreased lying down is likely to be compensated by more time spent standing immobile and not by increased walking (Veissier et al., 2004). In addition, there is no reason to think that the putative uncomfortable floor would have affected one treatment rather than another. Therefore, we conclude that the motivation of cows to move is prevented by tie-housing and is expressed by increased locomotion when tied cows are released. This finding supports a limitation of tie-housing in cows, already advocated by the CIGR (1994).

Galloping and bucking are frequent in young cattle. Jensen (1999) reported that unconfined calves spend nearly 1% of the time in these activities in a 10-min open-field test. The occurrence of these activities is greater after confinement in calves and heifers, whereas walking and trotting remain unaffected (de Passillé and Rushen, 1995; Jensen, 1999). Only Dellmeier et al. (1985) found that trotting is increased in calves after confinement, in addition to galloping and bucking. Galloping and bucking were not observed in our experiment, presumably due to the age of our experimental animals (2.5 yr). It is likely that the motivation for locomotion varies with age of cattle, galloping and bucking being more specific for young animals and walking and trotting more specific in adults.

Confinement of very young calves seems to decrease their ability to move, because the more they are confined, the less they walk or trot when released in an arena (Sisto and Friend, 2001). A lack of housing effect on walking speed in our experiment (about 1 m/s for all cows when led to the test arena) suggests that walking capacity was unaffected by housing in the present study. Similarly, once in the arena, cows walked at the same speed, with no differences between treatments.

The behavior of tied cows that were led to an exercise area for 1 h/d was very similar to that of loose-housed cows. They spent the same amount of time walking or trotting and covered the same distance in the arena. Similarly, Loberg et al. (2004) reported that the time spent walking or trotting by tied cows released in an outdoor paddock for 1 h decreases when the cows have access to that paddock once daily as opposed to twice or once weekly (from 15 to 20 to 21% of the time). However, no statistical analyses were performed in this study. The present findings confirm the impression given by Loberg et al. (2004). The expression of locomotion is thus likely to exert a negative feedback on the underlying motivation. According to the Jensen and Toates (1993) model of control of behaviors, this negative feedback supports the hypothesis that locomotion is a behavioral need in cows. From a practical point of view, it suggests that 1 h of daily exercise is sufficient to fulfill the motivation of cows to perform locomotion.

In addition, lameness is more common in tie-stalls than in loose-housing systems, specially because of more frequent hock lesions and hoof disorders (sole disorders or heel erosions, Regula et al., 2004; Bielfeldt et al., 2005; Keil et al., 2006). Such disorders are decreased by regular access to an exercise yard or pasture (Regula et al., 2004; Bielfeldt et al., 2005; Keil et al., 2006). The benefit of exercise seems to vary with its duration but inversely with its frequency. Keil et al. (2006) recommend at least 50 h of exercise per month with a long period of exercise (several hours) rather that frequent short ones. By contrast, our results suggest that cows should have access to exercise every day, because some effects of behavioral frustration are observed after only 1 d of tethering. Therefore, it is likely that cows need more than 1 h of exercise a day to both fulfill their behavioral needs and stay in good health. Whether this exercise should take place inside or outdoors (e.g., at pasture) must be specified, because we do not know at present if access to an indoor area of exercise, with a concrete floor, results in a reduction of lameness.

Cortisol content of milk was around 0.7 ng/mL, which corresponds to a plasma content of 7 ng/mL according to Mormède et al. (2007). This is consistent with concentrations reported in the literature (Tucker and Schwalm, 1977; Butler and Des Bordes, 1980; Verkerk et al., 1996). Milk cortisol content decreased regularly with time in all cows (–0.01 ng/mL daily as measured in Exp. 2). In ruminants, release of cortisol in blood is linked to metabolic balance, with increased cortisol concentrations when needs exceed energy intake (Simonetta et al., 1991; Ward et al., 1992; Samuelsson et al., 1996). The metabolic imbalance is generally marked at the beginning of lactation, due to cows not eating enough to meet their lactation needs. The imbalance decreases after the lactation peak. At the end of lactation, cows generally eat more than they need, and cortisol concentration decreases (Tucker and Schwalm, 1977). We observed a similar decrease in the cortisol concentration of milk in the 2 experiments, probably due to a progressive decrease in metabolic needs, because the cows were observed immediately after their lactation peak (from wk 6 to 30 after calving in Exp. 1 and from wk 6 to 24 after calving in Exp. 2). The decrease in cortisol production was more marked when cows were tied with no possibility of exercise (–0.024 ng/mL daily). Loose-housed cows spent about 2% of their time walking (personal observation in the cubicle pen used in the present experiment), and walking increases energy expenditure (Lachica and Aguilera, 2005). Cortisol content may decrease more rapidly in tied cows because of a progressive reduction of metabolic rate due to lower needs. Therefore, it seems that in dairy cows, cortisol release in blood is closely linked to metabolic needs due to milk yield or walking.

In contrast to Ladewig and Smidt (1989) but similarly to Sisto and Friend (2001), we did not observe an increase in cortisol release after tethering. On the contrary, tied cows that had access to exercise had less cortisol content in milk than loose-housed cows. One could argue that these cows benefited both from a calm environment (being alone in their tie-stall) and the possibility to express their motivation to walk. However, this assumption is very speculative, and more investigations are necessary to understand why these cows had lower milk cortisol content.

Our cows had been tethered for 3 d before the experimental treatments began, whereas Ladewig and Smidt (1989) observed bulls when they were tethered for the first time. These authors observed a much lower cortisol release after 4 to 5 d of tethering than after 2 to 3 d. Therefore, it might be that cortisol responses to tethering are essentially due to the novelty of the situation. This needs to be supported by more detailed observations of stress responses, such as indices of the activation of the autonomic nervous system (e.g., through heart rate), by observing cattle that have always been tethered on the first days after they are moved to loose-housing, or by assessing the potential aversiveness of the 2 housing conditions (tie vs. loose) in conditioning paradigms, as done in sheep for aversiveness of handling (Rushen, 1986).

Finally, we did not detect any difference in cortisol responses to blockade by dexamethasone or stimulation by ACTH of the HPA axis. It is generally assumed that chronic stress can induce a deficient suppression of HPA activity by dexamethasone and at the same time an increased sensitivity of the axis to ACTH, as in pigs and calves maintained on a very small space allowance (Friend et al., 1985; Meunier-Salaun et al., 1987). By contrast, Ladewig and Smidt (1989) observed less adrenocortical reactivity in bulls after 4 wk of tethering and concluded that the bulls were under chronic stress. No such effects were observed in our experiment. Hence, there is no evidence of any chronic stress induced by tethering in adult cows. This may be because tethering is less constraining than overcrowding. Nevertheless, this finding should be confirmed on prolonged periods of tethering, because cows can be tied for several months (during the whole winter period).

In conclusion, adult cows are motivated to walk and trot. The motivation to perform locomotion cannot be expressed under tethering, whereas it is fulfilled by regular exercise. Absence of an increase in cortisol concentrations suggests that the lack of locomotion due to tethering does not result in either acute or chronic stress in diary cows. Cows may nevertheless suffer more frequently from lameness when they do not exercise. Taken together, results show that cattle have a behavioral need for locomotion. We recommend that cows housed in tie-sheds be given regular access to an exercise area. When these cows are milked in a milking parlor, as is common for tied cows in some countries, this exercise could be given around milking times in order not to increase the workload of farmers.

	Footnotes

 
¹ We are grateful to the staff from the INRA experimental farm of Les Monts Dore for taking care of the animals and handling them during the behavioral and physiological tests, E. Delval for organizing the behavioral observations, and C. Ravel for her contribution to cortisol assays.

² Corresponding author: veissier{at}clermont.inra.fr

Received for publication March 9, 2008. Accepted for publication May 28, 2008.

	LITERATURE CITED

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 


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