A NOTE ON OVARIAN MEASUREMENTS IN COWS WITH OR WITHOUT A HISTORY OF TWINNING

Ovaries were recovered at slaughter from 30 cows in either a twinning (T; n = 16) or control (C; n = 14) herd. Weights of ovaries and corpor a lutea (CL) and records of follicle numbers and their diameters were obtained. Mean CL numbers/cow were 1.38 +/- 0.12 and 1.07 +/- 0.07 in the T and C cows respectively (P < 0.10). The objective was to compare the herds for ovary weights, CL weights, and follicle data, taking ac count of ovary side (left or right), luteal stage (Days 4-8, 9-13, 14- 18, where oestrus = Day 0), and numbers of CLs on each ovary (0 or gre ater-than-or-equal-to 1). Ovary weights were not affected by herd, and averaged 15.0 g when a CL was present compared with 9.1 g without a C L (P < 0.001). Single CL weights averaged 5.6 and 3.2 g in ovaries fro m cows which had produced single or double CLs respectively (P < 0.05) . Total CL weight/cow was not significantly different in T and C herds . Numbers of ovarian follicles of given size were similar in the two h erds. The diameters of the largest follicle on the right ovary and of the largest follicle overall were affected by the presence of a CL. On the right ovary, the presence of a CL was associated with a 4.5 +/- 1 .7 mm larger follicle diameter than when a CL was absent (P < 0.05). A veraging over luteal stages, the largest follicle regardless of side h ad a diameter of 15.4 mm when there was an ipsilateral CL, compared wi th 11.8 mm when a CL was absent (P < 0.10). These results showed an ef fect of CL number on individual CL weights, and the presence of a CL a ffected the diameter of large follicles.