The importance of the gestation period for welfare of lambs: maternal stressors and lamb vigour and wellbeing

Abstract

The prenatal period is of critical importance in defining how individuals respond to their environment throughout life. Stress experienced by pregnant females has been shown to have detrimental effects on offspring behaviour, health and productivity. The sheep has been used extensively as a model species to inform human studies. However, in the farmed environment, the consequences for the lamb of the imposition of prenatal stresses upon the ewe have received much less attention. The stressors that pregnant ewes are most frequently exposed to include sub-optimal nutrition and those related to housing, husbandry and environment which may be either acute or chronic. A systematic review of the literature was adopted to identify material which had productionrelevant maternal stressors and lamb outcomes. The current review focussed upon the lamb up to weaning around the age of 100 days and the results clearly demonstrate that stressors imposed upon the ewe have implications for offspring welfare and performance. Maternal under-nutrition (UN) in the last third of pregnancy consistently impaired lamb birth-weight and subsequent vigour and performance, while earlier UN had a variable effect on performance. Feeding the ewe above requirements did not have positive effects on lamb performance and welfare. Social and husbandry stressors such as transport, shearing, mixing and physiological treatments designed to mimic acute stress which would be considered disadvantageous for the ewe had positive or neutral effects for the lamb, highlighting a potential conflict between the welfare of the ewe and her lamb. This review also identified considerable gaps in knowledge, particularly in respect of the impact of disease upon the ewe during pregnancy and interactions between different stressors and the responses of ewe and lamb.

Invited review: Improving neonatal survival in small ruminants: science into practice

“…However, the extent to which UN influences mortality through each of these routes has not been thoroughly investigated. Rooke et al (2015) found, across all studies reviewed, that UN consistently reduced birthweight only in the last third of ovine pregnancy with the reduction in birthweight being related both to the length and severity of UN. In the first two-thirds of pregnancy, UN only reduced birthweight in specific circumstances.…”

“…Extensive research (see recent reviews for individual studies; Kenyon and Blair, 2014;Rooke et al, 2015) has described how changes in nutrition, both total and specific nutrient supply, impact on neonatal lamb characteristics relevant to survival. As, in temperate regions, the ewe is a seasonal breeder, and pregnancy in these climatic zones coincides with winter when nutrient availability from grazing is limited, an annual cycle approach to feeding the ewe has long been advised (Russell, 1985; Figure 3).…”

“…Decreased birthweight, however, is only a risk factor for increased lamb mortality. Where both lamb birthweight and mortality were recorded (Rooke et al, 2015), in only half the studies was a decrease in birthweight accompanied by increased mortality. Contributory factors will be how large the decrease in birthweight was, the physical environment and the amount and quality of husbandry.…”

Epigenetics and developmental programming of welfare and production traits in farm animals

“…Numerous studies consistently show that maternal undernutrition of the ewe in late pregnancy (after Day 100) reduces lamb birthweight (for a review, see Rooke et al 2015). Undernutrition before Day 100 has variable effects across different studies: severe early undernutrition has a marked effect on birthweight and mortality (Vincent et al 1985); and moderate undernutrition in early to mid-gestation generally does not affect birthweight, except in young and growing females (Munoz et al 2009) or ewes selected or adapted for a well-fed environment (Burt et al 2007;Rooke et al 2010).…”

Impact of maternal stress and nutrition on behavioural and physiological outcomes in young lambs

“…Arnott et al (2012) employed the systematic review process advocated by Sargeant et al (2006) to minimize systematic and random errors in study selection. Previously, we (Rooke et al 2015) applied the approach of Arnott et al (2012) and identified stressors applied to the ewe during gestation which were practically relevant. In Rooke et al (2015), the subject material was limited (because of the large number of studies)…”