Ja. Skidmore et al., THE OVARIAN FOLLICULAR WAVE PATTERN AND INDUCTION OF OVULATION IN THEMATED AND NON-MATED ONE-HUMPED CAMEL (CAMELUS-DROMEDARIUS), Journal of Reproduction and Fertility, 106(2), 1996, pp. 185-192
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.