A Description of the Dynamics of Fetal Growth in Sheep

Abstract
Two mathematical models which describe the dynamics of fetal growth in ewes were proposed for study. The models are basically of exponential form and take into consideration of the effects of stage of gestation (T), level of nutrition (L), and number of fetuses (N) on the total fetal weight (W). By using a stepwise regression technique, these models were tested against experimental data. It was found that the level of nutrition used in this study did not have a significant effect on the growth rate, however, all other factors are highly significant (P<.01) for both models. Model II closely predicted the total fetal weight for both singles and twins throughout the gestation period while Model I over-predicted the total fetal weight for twins at later stages of gestation. As a result, the following equation is proposed to describe the fetal growth of Targhee ewes at higher than maintenance conditions: An equation of this form should be useful in interpreting prenatal growth data for other breeds and species. Other factors which may influence the dynamics of fetal growth like maternal age or weight could be incorporated into an equation of this type. Copyright © 1975. American Society of Animal Science. Copyright 1975 by American Society of Animal Science.

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