The effect of initial weight of the ewe on later reproductive effort in domestic sheep (Ovis aries)

Abstract

In ungulates, females typically need to reach a critical threshold body weight in order to reproduce. Females born in`poor' years may lose 1 year of reproduction, as they reach the critical body mass 1 year later. Some studies report also a lasting effect of low initial body weight into prime age, while several other studies have shown that nearly all prime-age females ovulate or are pregnant. However, the quality of the offspring (as measured by offspring body weight) is often not considered. We tested whether female ungulates with an initially low body weight (at around weaning) reach the same reproductive output as females with higher initial weights, and thus whether or not they are able to compensate for their initial low weight. Data on body weight of 123 533 lambs of domestic sheep Ovis aries from 73 299 litters that in turn derived from 32 359 different ewes were used. All ewes and lambs had been free-ranging on outlying pastures in Norway during the entire summer season. Ewes with an initially low body weight produced smaller offspring throughout their lifespan. Ewes with an initially low body weight also produced fewer lambs at ®rst and second parturition, but lifetime number of offspring was not related to ewes' initial weight. We concluded that bigger was better: the smaller offspring of ewes with a low initial weight demonstrate a lasting cost on reproductive effort, with consequences for animal production systems and management of wild ungulates.

The Norwegian sheep breeding scheme: description, genetic and phenotypic change

“…The pattern of trend may indicate that the traits are less heritable than assumed, or that there exists covariances across generations other than genetic, e.g. between the phenotype of the ewe with the permanent environment of the lamb, as proposed in the literature (Eikje, 1975a;Steinheim et al, 2002). This latter effect cannot be estimated by the current model.…”

Asynchronous vegetation phenology enhances winter body condition of a large mobile herbivore

“…The condition of ungulates in winter is an important determinant of future fitness because of its impact on individual body condition at the start of the breeding season (Forchhammer et al 2001;Steinheim et al 2002;Solberg et al 2007;Rodriguez-Hidalgo et al 2010;Taillon et al 2012;Hurley et al 2014). In this paper, we mechanistically link changes in annual weather patterns and variation in the spatial and temporal patterns of plant phenology across landscapes with the winter body condition of adult female mule deer to facilitate understanding of how changing weather patterns may affect this important species.…”

Correlates with body size and mass in yearling brown bears (Ursus arctos)

“…Albon, Clutton-Brock & Guinness, 1987). Additionally, body mass at birth or weaning is reported to be positively correlated with body mass later in life (Schultz & Johnson, 1995;Birgersson & Ekvall, 1997), size as adults (Myers & Master, 1983;Albon et al, 1987;Festa-Bianchet, Jorgenson & Reale, 2000) and lifetime reproductive success (Festa-Bianchet et al, 2000;Steinheim et al, 2002). Thus, conditions experienced during early development can influence growth, survival and later reproduction in birds and mammals (Lindstr¨om, 1999;Solberg et al, 2004).…”