THE OVARIAN FOLLICULAR WAVE PATTERN AND INDUCTION OF OVULATION IN THEMATED AND NON-MATED ONE-HUMPED CAMEL (CAMELUS-DROMEDARIUS)

Ovarian follicular wave patterns were studied ultrasonographically in three groups of dromedary. Group I camels (n = 20) were teased daily w ith a vasectomized male but mating was prevented; group 2 camels (n = 8) ran freely with a vasectomized male camel for 10 h each day and gro up 3 camels (n = 8) were kept completely separate from any males. In a second experiment (n = 63), when the diameter of the dominant follicl e reached 0.5-0.9 cm, 1.0-1.9 cm, 2.0-2.9 cm or > 3 cm, the camel was given one of three treatments to induce ovulation: (i) natural mating; (ii) 20 mu g of the GnRH analogue, buserelin; or (iii) 3000 iu hCG. T he ovaries were re-scanned regularly to monitor ovulation, and daily b lood samples were assayed for progesterone and oestradiol concentratio ns. The follicular cycle was divisible into a growth phase (10.5 +/- 0 .5 days), a mature phase (7.6 +/- 0.8 days) and a regression phase (11 .9 +/- 0.8 days). The dominant follicle reached a mean +/- SEM maximum diameter of 2.0 +/- 0.1 cm (range 1.5-2.5 cm) in 34 cycles (52%) befo re it began to regress. In the other 32 cycles (48%), however, the dom inant follicle continued to grow to 4.2 +/- 0.2 cm (range 4.0-6.0 cm) before regression commenced. Group 2 camels were mated when their foll icles reached 1.3 +/- 0.1 cm in diameter and the mean interval between successive matings was 13.8 +/- 1.0 days. Mean +/- SEM serum concentr ations of oestradiol reached peak values at 39.0 +/- 1.8 pg ml(-1), wh en the dominant follicle measured 1.7 +/- 0.1 cm and, after ovulation, mean serum concentrations of progesterone reached peak values at 2.6 +/- 0.3 ng ml(-1) on day 8, before decreasing to < 1 ng ml(-1) by day 10 or 11. When the dominant follicle measured 0.5-0.9 cm in diameter, 70%, 60% and 60% of them ovulated in response to mating, or treatment with buserelin or hCG, respectively. These ovulation rates increased t o 85% (mating), 81% (buserelin) and 67% (hCG) when the follicle measur ed 1-1.9 cm, but they decreased again to 12.5% (mating), 29% (busereli n) and 13% (hCG) when the diameter had increased to 2.0-2.9 cm at the time of treatment. No follicles measuring > 3.0 cm ovulated in respons e to any of the treatments. These results indicated that the optimum t ime to mate or attempt to induce ovulation in the female dromedary is when the growing follicle measures 0.9-1.9 cm in diameter.