The Impact of Group Size on Welfare Indicators of Ewes during Pregnancy

Abstract

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.

¿Cómo afecta la disponibilidad de espacio y el tamaño de grupo al bienestar de los animales de granja?

“…La disponibilidad de espacio es un aspecto relevante para las prácticas de manejo, debido a las consecuencias mencionadas anteriormente sobre el bienestar, el comportamiento productivo de los animales y sus implicaciones económicas (Estevez et al, 2007;Averós et al, 2014). Bajo condiciones comerciales de producción, los productores son quienes establecen el espacio disponible o el tamaño de grupo, basándose en aspectos relacionados con el ahorro de mano de obra y el beneficio económico, principalmente, aunque desde el punto de vista del animal, las necesidades de espacio se pasen por alto (Averós et al, 2016;Dawkins, 2017;Muñoz-Osorio et al, 2019). Al respecto, Muñoz-Osorio et al (2015) encontraron, en un estudio descriptivo de sistemas intensivos de engorda de corderos, diferencias significativas en cuanto al área del corral y a la disponibilidad de espacio, destacando un menor espacio por animal en corrales elevados con piso de rejilla en comparación con los corrales a nivel del suelo.…”

“…Las ovejas lecheras alojadas en interiores durante la gestación presentaron restricciones en el movimiento y en el uso de espacio. Las distancias caminadas por las ovejas, en grupos de seis, fueron significativamente más cortas que las de las ovejas en grupos de 12, mientras que la relación de distancia neta no se vio afectada, indistintamente del tamaño de grupo (Averós et al, 2016). Las ovejas alojadas en espacios reducidos (1 m 2 /oveja), pasaron menos tiempo moviéndose y corriendo en comparación con las ovejas alojadas en espacios de mayor tamaño (3 m 2 /oveja) (Averós et al, 2014).…”

Available space in feeders for housed sheep: social behavior and performance

“…Brazilian livestock practices of domestic sheep (Ovis aries) can differ greatly, ranging from extensive pasture to intensive indoor system, differing in quantity and quality of space, which largely determine sheep behavior (Sevi et al, 1999;Estevez et al, 2007;Stafford and Gregory, 2008). Sufficient available space is essential to assure welfare of livestock species (Averós et al, 2014;Averós et al, 2016).…”