The authors have declared that no competing interests exist.
Group size (GS) and space allowance have major implications for the welfare of production species, however their effects are often confounded. In a previous study we investigated the impact of varying space allowance at constant GS. In the present work we report the consequences of varying GS on pregnant ewes while controlling space allowance. We housed ewes at 6 (GS6) or 12 ewes/enclosure (GS12), while controlling space allowance to 1.5 m2/ewe (3 enclosures/treatment), and necessarily varying enclosure size. Therefore, when indicating GS effects we implicitly reflect a confounding effect with that of enclosure size. Movement, use of space, behaviour, serum cortisol concentration and body condition score (BCS) were collected during the last 12 gestation weeks. Movement, use of space, and behaviour were collected every other week, during 2 days/week, using 10 minute continuous scan samplings. Blood was collected during weeks 10, 13, 17, and 21 of gestation, and BCS during weeks 15 and 21. Data were analysed using repeated measures, generalized linear mixed models, with GS, week, and their interaction as fixed effects, and enclosure as random effect. GS mainly affected movement and use of space. GS12 ewes walked longer distances using longer steps (P<0.001). An interaction GS by week was observed for angular dispersion (P<0.0001), which was smaller for GS12 from week 10 onwards. Initial restlessness levels were lower for GS12, as shown by the reduced frequency of location changes (P<0.0001). Furthest and mean neighbour distances increased with GS (P<0.0001). The effect of GS on behaviour was only evident for eating behaviour as an interaction with gestation week (P<0.05). Changes in behaviour, movement and use of space along the study indicated an activity peak during weeks 3 to 5. Cortisol changes during gestation (P<0.01) also reflected this activity peak, while BCS (P<0.001) reflected normal physical condition changes during pregnancy. Although the separate effects of GS and enclosure size cannot be disentangled, we conclude that if enough space/ewe is given during gestation, larger GS will result in larger effective space, and no major implications for the welfare of ewes should be expected as GS increases. Ewes will adapt their movement patterns and use of space to enclosure size, and no further behavioural, physiological and physical consequences should be expected.
Most animal species form social groups, which represents a trade-off between the costs and opportunities of belonging to a community [
Under production conditions GS is established by farmers, considering aspects mostly related to labour saving and economic profit, with the animal perspective being often overlooked. Large GS may be advantageous for farm animals, since increased social tolerance will lead to a reduction of aggressions [
Dairy sheep have traditionally been reared under extensive conditions characterized, among others, by access to extensive grazing areas [
In addition to behavioural changes, potential stress associated to differences in GS would be expected to trigger the activation of the HPA axis, therefore increasing the concentration of blood circulating glucocorticoids [
In a previous study we investigated the impact of space allowance on the behaviour and use of space of pregnant ewes. In the current study we aimed at determining the impact of GS while maintaining a constant space allowance. It may be anticipated that, if space per ewe remains constant, any potential effect of GS will vary as gestation progresses. In this study we investigated the effect of 2 GS (6 and 12 animals), while controlling for space allowance, on the welfare of pregnant ewes during the last two thirds of gestation. Welfare assessment was carried through a combination of different behavioural, movement patterns, use of space, physiological and physical indicators.
The experiment was approved by the NEIKER-Tecnalia Animal Experimentation Committee (Reference AFA_2011_02), and carried out following the European Directive 86/609/ECC regarding the protection of animals used for experimental and other scientific purposes. The study was designed to detect differences in the behaviour, movement patterns, use of space, serum cortisol concentration, and body condition score of pregnant ewes subjected to 2 GS treatments. Ewes were monitored throughout the whole experiment, and no major health and welfare issues, directly caused by experimental treatments, were observed.
The study was conducted at the experimental dairy sheep farm of Neiker-Tecnalia (Arkaute, Spain) between August 2012 and January 2013. One hundred and fifty primiparous and multiparous ewes (
Fifty-three days after AI, positive gestation and number of viable foetuses were determined via ultra-sound methodologies (Ovi-scan 6, BCF, Australia). Ewes were also weighed, and their body condition (BCS) was assessed using a 5-point scoring scale [
Feed was provided in an automatic feeding line, with 8 and 14 individual feeding spaces (48 cm/ewe) for GS6 and GS12 respectively, allowing simultaneous access to feed to all ewes. From gestation week 10 to gestation week 15 ewes were fed silage twice/day, at 08:30 and at 15:00 (about 1.5 kg per ewe and day), complemented with 400–500 g/ewe of a barley and wheat mix during the morning meal, and with
Data collection started during gestation week 10 (64 days after AI, after groups were formed) and lasted for 11 weeks (end of gestation week 20, right before lambing). Live observations were carried out by a single observer every other week. To precisely locate ewes during observations, enclosures were divided into a visual grid (32 and 49 squares for GS6 and GS12, respectively) using an alpha-numerical code written on stickers, which were placed along walls according to enclosure dimensions, as previously described [
Observations were carried out in the morning, during 2 days/week, starting at 09:30 after the morning meal and finishing before the afternoon meal. Two rounds of observations of all enclosures were conducted during each observation day. During each round enclosures were observed consecutively and each enclosure was observed for 10 minutes (total of 240 minutes/week of observations), with 10 scan samplings/enclosure being collected (1 scan/minute). The order of enclosure observations was random for each round. Randomization was carried out by permutations of experimental enclosures, permutation of enclosures and ewes within each enclosure (
Behaviour | Definition | |
---|---|---|
Eat | Standing by the feeder, with the head completely inside one of the feeder holes | |
Explore enclosure | Nose interaction with the enclosure wall of other physical issue | |
Forage | Standing, with the head down, interacting with the floor bedding with the mouth | |
Move | Change position within the enclosure, either walking or running | |
Negative social interaction | Butt | Sudden, strong head contact with another ewe |
Displace from resources | Force another ewe to leave the feeder, drinker, or the mineral resource | |
Push | Press the head against another ewe to force the pass | |
Threaten | Directing the forehead towards another ewe with no physical contact | |
Positive social interaction | Sniff | Smell another ewe without physical contact |
Nose | Slightly contact another ewe with the nose | |
Groom | Clean the wool of another ewe using the mouth | |
Nudge | Slightly, gently push another ewe | |
Lick | Lick any part of another ewe’s body | |
Rest | Lie down on the floor, either ruminating or not | |
Self-groom | Groom, either by self-licking or by rubbing against a physical enclosure object | |
Stand, static | Stand with the four feet on the floor, either ruminating or not |
During data collection, clicking on an
Variable | Definition |
---|---|
Total Distance (cm) | Total distance = |
Net Distance (cm) | Net distance = |
Net to Total distance ratio | Ratio between Net to Total distances. |
Longest step length (cm) |
Longest Euclidean distance between two consecutive locations composing the trajectory of one ewe during one observation period. |
Shortest step length (cm) |
Shortest Euclidean distance between two consecutive locations composing the trajectory of one ewe during one observation period. |
Furthest neighbour distance (cm) | Within the same scan, Euclidean distance between the location of a given ewe and that of the furthest ewe within the enclosure. |
Nearest neighbour distance (cm) | Within the same scan, Euclidean distance between the location of a given ewe and that of the closest ewe within the enclosure. |
Mean neighbour distance (cm) | Within the same scan, mean Euclidean distance between the locations of all the ewes within an enclosure. |
Angular dispersion | For the k consecutive locations composing the trajectory of one ewe during one observation period, angular dispersion = |
Movement activity | Frequency of scans in which the position of a ewe differed from that in the previous scan. |
1: Not to be confounded with a real step taken by the ewe to move that distance between 2 consecutive locations.
Fifty-six days after AI 4 ewes/enclosure were randomly selected for the determination of pre-experiment serum cortisol concentration through 10 ml blood collection. Blood samples from these ewes were also collected during gestation weeks 10, 13, 17, and 21. Blood sampling started at 11:30 in the morning, with the enclosure order, and ewes within each enclosure order, being random. Samples were collected into non-coated, evacuated tubes (Vacutainer® Rapid Serum Tubes, BD, New Jersey, USA), through jugular venepuncture for determination of pre-experiment serum cortisol concentration. Blood sampling was carried out within the enclosure, with the whole sampling process taking about 1 minute/ewe (that is, no more than 4 minutes/enclosure in total), therefore minimizing any potential effect of handling. Blood samples were stored on ice during collection, and were processed immediately after. They were centrifuged at 4°C during 15 minutes at 4000 rpm/2486
Mean values of all variables per enclosure and gestation week were calculated. Normality and variance homoscedasticity of data were confirmed and, accordingly, movement and use of space variables were analysed considering a Gaussian distribution. Frequencies of behaviours were analysed considering a binomial distribution except for negative social behaviours in which case, given their low occurrence, a Poisson distribution was chosen. Serum cortisol concentration and BCS were analysed using a lognormal distribution. The effects of GS (DF = 1), gestation week (DF = 6 for movement, use of space, and behaviour variables; DF = 3 for serum cortisol concentration; DF = 1 for BCS), and their interaction on all variables were estimated using a repeated measures, mixed model ANOVA. In the models gestation week was included as the repeated measures unit, and enclosure within GS was included as a random effect. In the models for cortisol and BCS the pre-experiment values were included as covariates. A first order autoregressive covariance structure was assumed for all variables to account for any linear dependence of measured variables over time, except for BCS in which case a variance component structure was assumed. Least square means were computed in case of statistically significant effects (
The effects of GS on movement and use of space are shown in
Variables | GS6 | GS12 | |||||
---|---|---|---|---|---|---|---|
Movement and use of space | Mean | SE | Mean | SE | F1, 24 | ||
Total distance (cm) | 288.4b | 38.5 | 544.1a | 38.5 | 22.06 | < 0.0001 | |
Net distance (cm) | 84.7b | 8.7 | 144.2a | 8.7 | 23.36 | < 0.0001 | |
Net/total distance | 0.31 | 0.01 | 0.29 | 0.01 | 0.61 | 0.4406 | |
Longest step length (cm) | 97.1b | 9.3 | 188.7a | 9.3 | 48.33 | < 0.0001 | |
Shortest step length (cm) | 1.7b | 0.7 | 4.2a | 0.7 | 6.12 | 0.0208 | |
Furthest neighbour distance (cm) | 223.7b | 5.6 | 381.7a | 5.6 | 392.24 | <0.0001 | |
Nearest neighbour distance (cm) | 78.8b | 1.9 | 83.5a | 1.9 | 3.02 | 0.0951 | |
Mean neighbour distance (cm) | 150.2b | 4.1 | 231.7a | 4.1 | 198.37 | < 0.0001 | |
Angular dispersion | 0.55a | 0.01 | 0.52b | 0.01 | 14.87 | 0.0025 | |
Movement activity (%) | 81.4 | 0.6 | 83.0 | 0.6 | 3.52 | 0.0729 | |
Behaviour | |||||||
Eat (% of observations) | 0.5 | 15.5 | 0.4 | 5.1 | 0.00 | 0.9925 | |
Explore enclosure (% of observations) | 1.3 | 0.4 | 0.9 | 0.2 | 0.57 | 0.4563 | |
Forage (% of observations) | 4.1 | 1.6 | 4.8 | 0.8 | 0.14 | 0.7109 | |
Negative social interactions (number of observations) | 0.2 | 41.4 | 0.3 | 67.4 | 0.00 | 0.9991 | |
Positive social interactions (% of observations) | 0.5 | 0.2 | 0.6 | 0.2 | 0.02 | 0.8865 | |
Rest (% of observations) | 36.4 | 10.6 | 44.3 | 10.8 | 0.27 | 0.6080 | |
Self-groom (% of observations) | 1.2 | 0.2 | 1.2 | 0.1 | 0.02 | 0.8946 | |
Stand (% of observations) | 38.2 | 7.7 | 34.1 | 7.1 | 0.15 | 0.6982 |
Within each row, different letters (a, b) indicate statistically significant differences (
Movement activity (
Interaction between group size (GS) and gestation week on the movement activity (A) and the angular dispersion (B) of gestating ewes. Within each week, (*) indicates significant differences between GS (
Regarding changes observed through gestation, total and net distances, and net to total distance ratio were shorter after group formation as compared to weeks 12 and 14, with distances decreasing afterwards for total and net distances (
Group formation | Week 10 | Week 12 | Week 14 | Week 16 | Week 18 | Week 20 | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Movement and use of space | Mean | SE | Mean | SE | Mean | SE | Mean | SE | Mean | SE | Mean | SE | Mean | SE | F6, 24 | ||
Total distance (cm) | 215.1c | 59.5 | 407.7abc | 59.5 | 594.6ab | 59.5 | 648.8a | 59.5 | 338.6bc | 59.5 | 347.4bc | 59.5 | 361.2bc | 59.5 | 6.43 | 0.0004 | |
Net distance (cm) | 82.6c | 12.8 | 113.0abc | 12.8 | 147.7ab | 12.8 | 152.1a | 12.8 | 90.0c | 12.8 | 97.0bc | 12.8 | 118.7abc | 12.8 | 5.18 | 0.0015 | |
Net/total distance | 0.40a | 0.03 | 0.28ab | 0.03 | 0.27b | 0.03 | 0.25b | 0.03 | 0.27ab | 0.03 | 0.28ab | 0.03 | 0.35ab | 0.03 | 3.70 | 0.0096 | |
Longest step length (cm) | 91.6c | 15.9 | 141.0abc | 15.9 | 184.1ab | 15.9 | 197.0a | 15.9 | 122.2bc | 15.9 | 124.5bc | 15.9 | 142.0abc | 15.9 | 5.15 | 0.0016 | |
Shortest step length (cm) | 3.9 | 1.2 | 1.7 | 1.2 | 5.6 | 1.2 | 5.2 | 1.2 | 0.9 | 1.2 | 2.4 | 1.2 | 1.0 | 1.2 | 2.86 | 0.0302 | |
Furthest neighbour distance (cm) | 266.2b | 8.2 | 302.0a | 8.2 | 311.3a | 8.2 | 313.5a | 8.2 | 306.2a | 8.2 | 314.4a | 8.2 | 305.5a | 8.2 | 4.28 | 0.0045 | |
Nearest neighbour distance (cm) | 71.1b | 2.8 | 78.7ab | 2.8 | 79.5ab | 2.8 | 82.7ab | 2.8 | 85.7a | 2.8 | 86.3a | 2.8 | 83.9a | 2.8 | 3.11 | 0.0213 | |
Mean neighbour distance (cm) | 167.5b | 5.6 | 191.8ab | 5.6 | 193.5a | 5.6 | 198.2a | 5.6 | 193.9a | 5.6 | 199.3a | 5.6 | 192.7ab | 5.6 | 4.06 | 0.0060 | |
Angular dispersion | 0.54 | 0.01 | 0.52 | 0.01 | 0.53 | 0.01 | 0.54 | 0.01 | 0.54 | 0.01 | 0.53 | 0.01 | 0.53 | 0.01 | 0.34 | 0.9112 | |
Movement activity (%) | 81.2ab | 1.1 | 84.8a | 1.1 | 84.7a | 1.1 | 84.1ab | 1.1 | 80.0b | 1.1 | 80.0b | 1.1 | 80.6ab | 1.1 | 5.13 | 0.0016 | |
Behaviour | |||||||||||||||||
Eat (% of observations) | 0.0ab | 0.0 | 5.3a | 1.2 | 1.6ab | 0.6 | 1.9ab | 0.6 | 1.8ab | 0.6 | 1.3b | 0.5 | 2.8ab | 0.8 | 3.36 | 0.0150 | |
Explore enclosure (% of observations) | 0.6ab | 0.4 | 1.7ab | 0.4 | 2.1ab | 0.5 | 2.6a | 0.5 | 0.7ab | 0.3 | 0.8ab | 0.3 | 0.6b | 0.2 | 4.12 | 0.0055 | |
Forage (% of observations) | 21.6a | 3.5 | 4.4b | 1.2 | 10.8ab | 1.8 | 7.3b | 1.5 | 3.6b | 1.1 | 3.2b | 1.0 | 0.3b | 0.4 | 10.33 | < 0.0001 | |
Negative social interactions (number of observations) | 0.0 | 0.4 | 2.0 | 0.7 | 4.3 | 1.1 | 3.3 | 1.0 | 1.7 | 0.7 | 0.0 | 0.5 | 1.7 | 0.7 | 1.22 | 0.3297 | |
Positive social interactions (% of observations) | 0.6 | 0.3 | 0.7 | 0.2 | 0.9 | 0.3 | 0.7 | 0.3 | 0.3 | 0.2 | 0.7 | 0.2 | 0.2 | 0.1 | 1.63 | 0.1812 | |
Rest (% of observations) | 50.0ab | 12.3 | 28.5b | 8.5 | 19.2b | 7.1 | 22.1b | 7.4 | 64.7a | 9.5 | 62.1a | 9.6 | 44.0ab | 10.0 | 6.92 | 0.0002 | |
Self-groom (% of observations) | 0.6 | 0.3 | 2.0 | 0.3 | 1.7 | 0.3 | 0.8 | 0.2 | 1.1 | 0.3 | 1.4 | 0.3 | 1.6 | 0.3 | 2.23 | 0.0751 | |
Stand (% of observations) | 22.3ab | 7.7 | 47.3a | 7.5 | 48.6a | 7.5 | 52.2a | 7.5 | 22.6b | 5.9 | 23.5b | 5.9 | 43.3ab | 7.4 | 5.40 | 0.0012 |
Within each row, different letters (a-c) indicate statistically significant differences (
Behavioural analysis detected no main effects of GS (
Within each week, (*) indicates significant differences between GS treatments (
Somewhat more interesting were the effects of gestation week on behaviour, with the highest enclosure exploration frequencies detected for week 14, and highest foraging frequencies after group formation (
No effect of GS was detected on BCS (
The aim of this study was to determine the effect of GS on the welfare of pregnant ewes during the last two thirds of gestation. Two experimental GS treatments, GS6 and GS12, were used while space allowance (1.5 m2/ewe) remained constant. Welfare assessment was carried out through a combination of different behavioural, movement patterns, use of space, physiological and physical indicators. It is essential to remark that varying GS while controlling for space allowance unavoidably leads to confusion between group and enclosure sizes, as there is no alternative to control for both space allowance and enclosure size. This problem has been experimentally addressed and discussed in a number of papers [
Despite the difficulties in interpretation, the results from our study are relevant as management practices and potential legislation are normally decided according to an established space allowance. In this sense, the results of this study clearly showed that, even when space allowance remains constant, maintaining larger groups in larger enclosures is advantageous from a welfare perspective, as compared to smaller groups in smaller enclosures, as it allows a greater freedom of movement to pregnant ewes, while no negative behavioural incidences were detected. In fact, the effects of the experimental treatments were almost restricted to effects on movement and use of space patterns. Ewes in GS12 walked longer distances, and their movement trajectories were composed of longer steps; neighbour distances were larger, and their trajectories were more tortuous. Group size also influenced the variation in eating frequencies. In a previous study with pregnant ewes, in which GS remained constant while space allowance varied [
It is generally assumed that, for a given space allowance, the amount of space is the same for all individuals, and does not depend on GS. However in practice, and as previously proposed [
The experimental treatments also had an impact on movement activity and angular dispersion after group formation, with ewes in GS6 changing location more frequently and also described more tortuous trajectories. This suggests a differential response to the novel environment, with initial restlessness levels being higher when GS was smaller. In our previous study (GS kept constant at 6 ewes) an initial adaptation period also occurred, mainly characterized by higher movement activity irrespective of space allowance [
Despite the large differences found in regard to movement patterns, the experimental treatments showed a surprisingly limited effect on the behaviour of the ewes. The interaction between GS and gestation week was significant only for eating behaviour, and would to some extent agree with the reported increase in the percentage of time eating in larger groups (36 ewes vs. 9 ewes) [
Negative and positive social interactions were not affected by GS either. This would confirm previous results [
Whilst it must be accepted that the HPA axis responsiveness is decreased during pregnancy [
In conclusion, the effects of GS on pregnant ewes appeared to be mainly caused by the largest effective space available as GS, and therefore enclosure size, was larger in order to maintain space allowance constant. Effects were majorly restricted to movement and use of space parameters, with GS12 ewes walking longer distances composed of longer steps. They described more sinuous trajectories due to a more prevalent barrier effect caused by the presence of a higher number of individuals in the enclosure. Inter-individual distances increased with GS, indicating adjustments in the group dynamics as enclosure size got larger. Initial restlessness levels were smaller for GS12 ewes, changing less frequently in location and describing less sinuous trajectories after group formation. The absence of treatment differences in the frequency of social interactions, particularly negative social interactions, suggests that increasing the number of individuals in the group does not translate into differences in their welfare status from a social perspective. Otherwise, behaviour changes during the study can be attributed to normal changes caused by the progression of gestation. The lack of an effect of GS on serum cortisol concentrations and BCS indicates that movement and use of space adjustments sufficed and made the activation of further behavioural and physiological coping mechanisms unnecessary. Their changes along the study reflected normal adaptations as gestation progressed.
The authors gratefully acknowledge the European Union financial support for conducting the experiments and the salary for X. Averós under the Seventh Framework Programme for Research, Technological Development and Demonstration Activities, of the Project Animal Welfare Indicators (AWIN; FP7-KBBE-2010-4). The authors are grateful to Josune Arranz for her invaluable help in the preparation of the experimental setup, and to Imanol Etxebarria and Juan Carlos Ochoa de Zuazola for the excellent care of ewes during the study.