The influence of progesterone and nutrition on the sheep embryo.

Abstract

Proc. Aust. Soc. Anim. Prod. (1978) 12: 257 THE INFLUENCE OF PROGESTERONE AND NUTRITION ON THE SHEEP EMBRYO R.A. PARR*, I.A. CUMMING*, R.A.S. LAWSON*, D.J. KERTON* and A.M. HARRIS* Undernutrition during early pregnancy can cause embryo loss in the ewe (Edey 1966). Cumming et al. (1971) found that progesterone levels in mperipheral plasma were either elevated or reduced in ewes fed either a 25% or 200% maintenance ration respectively. This paper reports a study of the relationships between embryo growth and survival, progesterone and the ewe's level of nutrition. I Three hundred and sixty mature Merino ewes were randomly allotted to a control group and five treatment gro ups receiving progesterone at levels of 5, 10, 15, 20 or 25 mg/day as twice dai ly inject ions in arachis oil after ovariectomy at Day. 4 post coitus'(p.c.). The animals were further allotted to sub-groups receiving either 25% or 100% of a maintenance ration from Day 1 p-c. until embryo 'recovery at either Day 11 p-c. or Day 2l.p.c. Embryos were assessed for survival and their sizedetermined. Ewes inxe control group underwent a sham operation. Ewes with multiple ovulations were discarded from this analysis due to insufficient numbers. Analysis of the data on embryo survival and size gave only one significant interaction, that of nutrition by progesterone treatment on embryo size at Day 11 p-c. This interaction was largely accounted for within the ewes on a mxtenance ration receiving 10 mg/day progesterone. This group had only four embryos (mean size, 1.45 (log x + l)mm of which three had entered the exponential growth phase. Nutrition did not affect either embryo size or survival at Day 11 or 21 p-c. However, there were significant effects of progesterone treatment -on each of these parameters (Table 1, Data analysed by Least Squares Analysis of Variance). . Detailed studies of growth and development of these embryos may identify meaningful treatment effects. While recognizing difficulties involved in the experimental design, the results suggest that nutrition did not have a direct effect upon the embryo. Progesterone treatment lowered embryo survival at the lowest treatment levels. Certainly high levels of progesterone had no detrimental influence on embryo survival. EDEY, T.N. (1966). J. Agric. Sci.; Camb. 52: 287: CuMMING, I-A., MOLE, B.J., OBST, J,, BLOCKEY, M.A. de B, WINFIELD, C.G., GODING, J;R. (1971). J. Reprod. Fert. zi: 146. *Animal Research Institute, Department of Agriculture, Werribee 3030. 257. ' :