Maternal behaviour in the ewe: consistency in the expression of maternal behaviour during lactation and the effect of variation in dam and sire breed on the development of offspring

Abstract

Consistency in the expression of maternal care over a single lactation period was investigated using two breeds of ewe, Scottish Blackface and Suffolk. The two breeds showed differences in their initial maternal behaviour with Blackface ewes showing more affiliative and less negative behaviour towards their newborn lambs than Suffolk ewes. These differences in maternal behaviour continued throughout lactation. Whilst both breeds were able to recognise their lambs at three days post­partum, Blackface ewes were more motivated to associate with their lambs in a maternal choice test, suggesting that they had a stronger ewe-lamb bond than Suffolk ewes. During the rest of lactation Blackface ewes had a closer spatial relationship with their lambs, accepted a higher proportion of suck attempts from their lambs and showed more communication with them via the head-up posture, compared to Suffolk ewes. Blackface ewes actively interacted with their lambs, using the head-up posture to control sucking interactions and to encourage their lambs to remain in close proximity. In contrast Suffolk ewes were not proactive in their relationship with their lambs and appeared to react to the behaviour of their lambs, rather than actively communicating with them.

A factor analysis showed that three dimensions, the willingness of the ewe to interact with her lamb throughout lactation, her response to her lamb’s attempts to interact with her and their ewe-lamb bond during later lactation, can be used to describe variation in ovine maternal behaviour. The willingness of the ewe to interact with her lamb accounted for most of the variation between the two breeds, with Blackface ewes showing mostly affiliative behaviour and Suffolk ewes showing more negative behaviour. Within the two breeds variation was mainly due to behaviours associated with the ewe’s response to her lamb’s attempts to interact with her. Individual Blackface ewes showed consistency in their expression of maternal behaviour throughout lactation, but Suffolk ewes did not. This is likely to result in a stable ewe- lamb relationship in Blackface ewes but an unstable relationship in Suffolk ewe.

The different maternal styles were then used to assess the effect of variation in dam and sire breed on the development of offspring. The lambs’ stress response during three tests (social separation, restraint and novel object) and their ability to learn a spatial memory task were assessed. In addition, the ability of day old lambs to recognise their dam, lamb growth rate during lactation and the lambs’ own maternal behaviour was examined to assess traits relevant to sheep production. Lambs raised by Blackface ewes showed an active behavioural response during the stress response tests and were quicker to learn the spatial memory task than lambs raised by Suffolk ewes. Suffolk-raised lambs showed a passive response during the stress response tests. Blackface lambs were better able to recognise their dams at 24 hours old than Suffolk lambs. The willingness of the ewe to interact with her lamb throughout lactation showed a positive association with lamb growth. Ewes and their dams were also found to show similarities in their initial maternal behaviour. Therefore, although it was not possible to rule out the possibility of a genetic influence, maternal behaviour in the ewe appears to have the potential to influence offspring development in a variety of ways.

A study on the early maternal behaviour of mares was also conducted to assess the potential for the sheep study findings to be applied to other domestic species. Compared to the ewes, mares showed much less interaction with their young, in particular grooming, during the immediate post-partum period, but also showed much less negative behaviour. However there did appear to be potential for the findings of the sheep study to be applied to the horse.