Oestrus cycle and follicle growth in Djallonké “Mossi” ewes

Abstract

The aim of the present study was to determine the characteristics of the oestrus cycle and follicular growth in Djallonké “Mossi” ewes. Use of a vasectomised ram and plasma progesterone assays showed that the oestrus cycle lasted on an average 18 ± 4 days and the heats 30 ± 7 h. During the dry and the hot season (January to April), there was a significant increase (P < 0.05) in the length of the oestrus cycle (20 ± 6 days), but a decrease in the length of heats (25.7 ± 4.7 h). The total number of follicles with a diameter exceeding 50 µm was 243.1 ± 43.2 per ovary with a significant difference between ovulatory and non ovulatory ovaries (P < 0.05). Numbers of follicles were ranked into 4 groups according to their size: 129.9 ± 27.2 for group I (50 to 118 µm); 95.2 ± 16 for group II (119 to 462 µm); 11.9 ± 2 for group III (463 to 1,284 µm) and 6.1 ± 1.8 for group IV (> 1,284 µm). The number of normal follicles (less than 5 pycnotic follicular cells) was 229 ± 42.2 per ovary and represented 94.3 % of growing follicles. The average number of atretic follicles was 13.9 ± 2 and this number was higher in the ovulatory ovary: 17.8 ± 4.6 against 10 ± 2.1. The average number of follicles in the last growth stage was 9.4 ± 3.3 and 2.6 ± 0.3 of these follicles were normal. The ovulation rate was 1.4 ± 0.2 with 82.6 % ovulations on the right ovary.