Temporary Exposure of Ovine Embryos to an Advanced Uterine Environment Does Not Affect Fetal Weight but Alters Fetal Muscle Development1

Abstract

Embryo transfer techniques may result in fetuses that are heavier at birth and that have been described as highly muscled. The aim of this study was to investigate myogenesis in lambs derived from embryo transfer. Embryos were transferred at Day 3 (estrus = Day 0) to a 3 days-advanced uterine environment, maintained there for 3 days, recovered, and then returned to a synchronous (Day 6) uterus; these fetuses comprised the asynchronous group. Control animals were created by synchronous embryo recovery and single transfer at Day 3. Asynchronous transfer did not affect fetal weight or curved crown-rump length between 46 and 135 days of gestation. No differences were detected between groups at Days 110-135 with respect to muscle mass or protein, RNA, and DNA content. However, total muscle fiber number was significantly increased in plantaris muscles from the asynchronous groups at Day 110 and Day 125, suggestive of prolonged hyperplasia. In addition, the levels of Myf 5 protein and the secondary-to-primary fiber ratio were altered in plantaris muscle from the asynchronous group. The growth data are in contrast to previously reported findings. The results show that fetal myogenesis can be altered by very early events in embryogenesis and suggest that any inferences made solely on the basis of fetal or muscle weight may be fallacious.

The effect of maternal nutrition level during the periconception period on fetal muscle development and plasma hormone concentrations in sheep

“…However, secondary to primary fiber ratio in ST muscle of fetuses from undernourished ewes tended to be lower compared with fetuses from well-fed ewes. Increase or decrease in secondary to primary fiber ratio as the result of nutritional treatments in the present study is compatible with the reported results in response to nutritional manipulations (Maxfield et al, 1998a and1998b;Crosier et al, 2002;Quigley et al 2005).…”

“…Investigation of time points later in gestation, when myogenesis is completed, may reveal whether myogenesis continues longer in fetuses from undernourished ewes, allowing them to attain normal potential for muscle growth. Nevertheless, the evidence indicates that, even after myogenesis is completed, there are still marked differences in muscle fiber characteristics because of nutritional manipulations in sheep suggesting that the early embryonic period may irreversibly program myogenic potential (Maxfield et al, 1998b;Quigley et al, 2005).…”

The monitoring of bovine pregnancies derived from transfer of in vitro produced embryos

“…However, such an approach appears to be more relevant keeping in mind the recently pronounced concept [1][2][3]45] that several diseases encountered during adult life might have their origin during the period of foetal development. The same might be true for physical performance and (re)production in domestic species [37,39,40,48]. In this respect one seems to have forgotten that, within the context of research on growth and production of farm animals, Grahm Everitt already warned in 1968 that "The extent to which events of later life may be modified by factors operating during the formative stages appears insufficiently appreciated"(see Bell [4]).…”

Nutrition in the expression of reproductive potential

“…Another example of the sensitivity of foetal development to the environment of the early embryo is the observation by Maxfield et al (1998) that a temporary 3-day exposure of day 3 sheep embryos to an advanced (day 6) uterine environment increased muscle fibre number and the ratio of secondary to primary fibres in the foetus; it also altered the temporal expression of the myogenic gene, myf 5, implying that this gene is involved in prolongation of foetal myoblast hyperplasia.…”