A note on ovarian measurements in cows with or without a history of twinning

Abstract

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 corpora 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 account 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 ≥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 CL (P < 0.001). Single CL weights averaged 5.6 and 3.2 g in ovaries from 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 herds. 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). Averaging over luteal stages, the largest follicle regardless of side had a diameter of 15.4 mm when there was an ipsilateral CL, compared with 11.8 mm when a CL was absent (P < 0.10). These results showed an effect of CL number on individual CL weights, and the presence of a CL affected the diameter of large follicles.

Keywords:

• twins
• cattle
• follicle numbers
• ovary weight
• corpus luteum