Abstract:
Animal Production in Australia THE COMPARISON OF BIOLOGICAL ACTIVITY OF EQUINE CHORIONIC GONADOTROPHIN (eCG, PMSG) IN TWO BIOASSAY SYSTEMS, THE SHEEP AND THE RAT T.STELMASIAK*, I.D.KILLEEN ** , S.T.DAWE ** and N.E.JOHNSTON* Increasing use of PMSG in controlled breeding programmes and embryo transfer techniques in sheep has revealed high variability in the response of animals to the hormone. The variations in biological effects of commercial preparations of PMSG could be caused by differences in the estimates of biological activity resulting from different laboratory techniques employed by manufacturers or could reflect the differences between various species of animals in their recognition of the hormone. To test this latter possibility we compared the compatability of two bioassay systems; the rat and the sheep, both based on quantitative ovarian response to the hormone. In the first part of the experiment we established biological activity and relative potency of two commercially available PMSG preparations (Folligon, Batch 2900; Pregnecol, Batch 5/6) in the rat ovarian bioassay (Cole and Erway, 1941) In the second part of the against the II International Standard of PMSG. experiment both commercial preparations of PMSG were tested in the sheep ovarian bioassay using Folligon, Batch 2900 as a standard. The PMSG preparations were tested in both bioassay systems using seven to 10 animals at each of the four dose levels. In rats the weight of the ovaries and in sheep the numbers of corpora lutea (CL) and follicles larger than 10 mm were recorded. Sheep were synchronized with MAP sponges (Repromap, Upjohn) prior to the injection of PMSG and ovaries examined by laparoscopy eight days later. Statistical validity of the assays and potency estimates were calculated according to Borth (19m). TABLE 1. Biological activity and relative potency of two different PMSG preparations tested in the rat bioassay The results indicate that a good correlation exists between both bioassay systems and that the rat ovarian bioassay is an accurate indicator of the biological activity of PMSG in sheep. BORTH, R. (1960). Acta Endocr. 2: 454. COLE, H.H. and ERWAY, J. (1941). Endocrinology 2: 514. * Dept of Agriculture, 'Attwood' Vet Res Laboratory, Westmeadows, Vic. 3047. ** Dept of Agriculture, Agricultural Research Station, Leeton, N.S.W. 2705. 647
