Effects of mating behaviour and the ovarian follicular state of female alpacas on conception.
OBJECTIVE
To determine relationships between mating behaviour, ovarian follicular state and successful conception in receptive female alpacas.


METHODS
Seventy pen matings were observed at a commercial alpaca stud in south-western Victoria. The behaviours observed included time taken to assume sternal recumbency, mating duration, and evidence of nonreceptive behaviour such as spitting, kicking and vocalisation. Ovarian follicular state was determined by ultrasonography, which was complemented by measuring plasma concentrations of oestradiol and progesterone. Pregnancies were confirmed by transabdominal ultrasonography between days 45 and 80 after mating.


RESULTS
There were no significant differences between receptive females that conceived and those that failed to conceive in the time taken to adopt the copulation position of sternal recumbency, mating duration, or maximum follicle diameter. There was no significant relationship between time taken to assume sternal recumbency (log10) and maximum follicle diameter or plasma oestradiol (log10). However, there was a significant quadratic relationship between plasma oestradiol concentration (log10) and follicle diameter, and the probability of pregnancy increased as the plasma concentration of oestradiol (log10) at the time of mating increased. Females were sexually receptive most of the time in the absence of a corpus luteum, and regardless of size of the largest follicle or plasma concentration of oestradiol. Breed (Huacaya vs Suri), site of the dominant follicle (left or right ovary), lactation state, number of matings by the male (1 or 2), or interval between parturition and mating, did not affect pregnancy outcome. Follicles with a diameter less than 7 mm were able to ovulate in response to mating. This was smaller than previously reported. Thirty-four pregnancies (49% pregnancy rate) resulted in 30 (88%) births with a gestation length of 343 days (SEM +/- 2, range 316-367 days). There were 4 (12%) abortions between days 45 and 80 of gestation and full term.


CONCLUSIONS
It was not possible to correlate mating behaviour and ovarian state with conception. To optimise pregnancy rates in receptive alpacas, matings need to occur in the presence of an oestrogenic follicle that is capable of ovulation in response to mating. A simple method of detecting alpacas with follicles in this state is not currently available and treatments that control ovarian follicular growth should therefore be investigated.
Vaughan
J L
JL
Animal Sciences and Production Group, Central Queensland University, Rockhampton, Queensland 4702.
Macmillan
K L
KL
Anderson
G A
GA
D'Occhio
M J
MJ
D000818:Animals; D002161:Camelids, New World / Q000097:blood / Q000502:physiology*; D004958:Estradiol / Q000097:blood; D005260:Female; D008297:Male; D006080:Ovarian Follicle / Q000502:physiology*; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000097:blood; D012726:Sexual Behavior, Animal; D014739:Victoria / Q000453:epidemiology
D011374:Progesterone; D004958:Estradiol