Effect of indoor management systems for pregnant ewes on maternal behaviour expressed after parturition
Md Yusof, Nur Nadiah
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The survival of newborn lambs is highly dependent on the successful partnership between ewes and their offspring. High lamb mortality before one week of age is largely due to hypothermia, mismothering and starvation, which are indirectly consequences of poor establishment of a maternal bond between a ewe and her lambs. Maternal behaviour displayed by ewes towards their lambs is therefore crucial in ensuring the survival of the newborn lamb. However, maternal behaviour can be affected by many factors including the social environment, nutrition and husbandry routines. It is common in the UK for sheep to be kept indoors during winter from mid gestation until lambing to protect ewes and lambs from adverse conditions. Keeping the ewes indoor nonetheless, has its own challenges as the animals may have to be mixed with unfamiliar conspecifics, have limited floor and feeding space, changes to the diet and increased handling by humans. Therefore, the main objective of this study was to investigate the effect of housing systems experienced by ewes during gestation on mother-offspring interactions after parturition. The impact of different housing conditions were assessed by recording body weight, body condition score (BCS), behaviour, faecal glucocorticoid metabolite (FGM) concentrations and haematology parameters. After parturition, maternal behaviour was then assessed. Parity and the temperament of the ewes were also taken into account in assessing all parameters during gestation and after parturition. In the first experiment the effect of an indoor housing system on the behaviour and physiology of 41 primiparous and 36 multiparous ewes from 11 until 18 weeks of gestation was assessed. The ewes were divided into two groups: Control and RS-Mix (Restricted-Space and Mixed) where the RS-Mix ewes were allocated half the amount of space and feedface allowance given to Control group and were also subjected to three social mixing events. No significant treatment effects on physiology or behaviour during gestation were found except for higher aggression in RS-Mix ewes during the first week of observation which gradually declined to the same level as Control ewes at the end of experiment. RS-Mix ewes also displayed significantly higher ruminating behaviour at week 18 of gestation compared to Control ewes. However, primiparous ewes were more affected than multiparous ewes regardless of treatment group, with lower weight gain and higher FGM concentrations compared to multiparous ewes. In this study, the difference in housing system did not seem to have a lasting impact on the physiology and behaviour of pregnant ewes. The maternal behaviour of these ewes during parturition and lactation was investigated. RS-Mix ewes were significantly more likely to give birth to Lamb 2 (L2) while standing, compared to Control ewes and also more likely to give birth during the day whereas Control ewes were equally likely to give birth during the day or night. Grooming behaviour of these ewes was not affected by pregnancy treatment but RS-Mix ewes displayed significantly higher avoidance when the lambs reached the udder to suck compared to Controls. During tests of lamb recognition, primiparous ewes from RS-Mix group took longer to approach their own lambs and during lactation on the field, they kept the greatest distance from their neighbouring ewes, compared to all other groups. This suggests that maternal behaviour in RS-Mix ewes may have been affected by the stress experienced from the space restriction, regrouping and remixing during pregnancy. In the first experiment Control ewes as well as RS-Mix ewes displayed aggressive behaviour at the feedface during concentrate feeding. This implies that Control ewes may also experience competition at feeding which might explain the few behavioural effects of treatment. Therefore, in the next study two new housing treatments were set up: Alternative and Negative. Alternative ewes were provided with a larger space allowance of 4.57m2/ewe and 66cm/ewe of feedface allowance and had ad libitum access to food (grass silage) throughout the experiment. Negative ewes were provided with the same space and feedface allowance (1.28m2/ewe and 33cm/ewe respectively) as Control ewes from the first experiment but they were subjected to additional stressors, such as exposure to dogs and delayed feeding. The Control group in this experiment was as the RS-Mix group from the previous study but without the occurrence of social mixing. Surprisingly, Alternative ewes were found to be the most affected by the treatment. The BCS of Alternative ewes decreased significantly from week 15 to week 17 of gestation and this group had the least weight gain throughout gestation compared to Control and Negative ewes. FGM concentration in Alternative ewes was also the highest compared to other treatment groups from week 13 until week 17 of gestation, and at 12 hours postpartum. Interestingly however, the concentrations of beta-hydroxybutyrate and neutrophil-lymphocyte ratio in Alternative ewes were significantly lower than other groups. Alternative ewes also took a longer time to groom their lambs, spent less time grooming and were less cooperative with the lambs sucking attempts than other groups. This study found only minor evidence that housing systems, which mimicked commercial conditions, caused significant stress in pregnant ewes, although short-term aggression at feeding was observed in both Control and Negative groups. An alternative system, which was designed to reduce competition and aggression at feeding, by allowing continual access to feed, did reduce aggression but had other effects on the ewes, such as loss of body condition, which suggested this feeding system was not providing the ewes with their full requirements, perhaps because the ewes did not find the feed palatable. It was apparent, however, that primiparous ewes may have more difficulties in adjusting to the new environment than older and more experienced ewes, and this may contribute to greater stress in this group. Even though the behaviour and physiological parameters recorded during gestation were insufficient to verify the existence of stress, the alteration of certain aspects of maternal behaviour recorded after parturition suggested that management systems in indoor housing could cause stress to the ewes. Exposure to undernutrition during pregnancy was also shown to affect maternal behaviour in ewes. Therefore, special attention should be taken to provide the ewes with adequate housing condition and fulfil the nutrition requirements of gestating ewes in order to ensure the establishment of stronger ewe-lamb interaction which will eventually improve the survivability of newborn lambs.