We all know now that alpacas are 'induced ovulators'. The physical act of copulation and the stud's ogling noise induces ovulation with the release of an egg from a mature follicle. They do not have an oestrus (sexual receptivity) cycle as most other domestic livestock (cats, rabbits, ferrets, mink and otters are similar) and a sexually mature female is either receptive to mating or non-receptive to mating. We can thus ask our alpacas to mate at any time of the year.
The uterus has a short body with two horns, which lead to the fallopian tubes down which the eggs travel from the two ovaries. Regardless of which ovary ovulates, most pregnancies will implant in the left uterine horn. Twin conceptions are rare, with twin full term births usually resulting in malformed or weak cria.
The most important parts of the ovary are the eggs, follicles and corpus luteum. We need to understand simplistically, their function. Starting with the eggs, under hormonal stimulation some of the cells surrounding them begin to develop and form into what are called follicles. These continue to grow in size, filling with estrogen hormone. The largest one eventually takes over from the smaller ones and becomes dominant. When it has reached a mature size (defined as being greater than 7mm in diameter) and if stimulated by the luteinising hormone (LH) they rupture and release the egg.
The required surge of luteinising hormone, stimulated by copulation, is released from the brain and peaks around 2-4 hours after mating. Ovulation then completes anywhere between 24-48 hours after mating.
Once the egg has been released from the follicle, the cells re-arrange and over a 3 to 6 day period continue to grow into a solid mass called the corpus luteum (CL), the producer of progesterone.
Meanwhile the egg starts its journey down the uterine tube towards the uterus. Sperm swim from the uterus up the uterine tubes and conception hopefully takes place. The fertilized egg completes its journey to the uterus over the next 5 to 7 days. Finally, it takes three to four weeks for the developing embryo to attach itself to the uterine wall and begin to develop its placenta.
Progesterone production is needed throughout the gestation period and any event that causes the CL to shrink will result in foetal abortion.
If ovulation fails to occur then the follicle shrinks and dies back. The growth and then shrinking of the follicle is called a follicular wave and has significance on the sexual receptivity of the female. The typical cycle is 3 to 4 days of growth to reach the mature size of 7mm where it remains mature for another 4 to 6 days, before shrinking back over the next 3 to 4 days. As there are two ovaries and therefore two dominant follicles each with separate waves, we end up with a 2 to 3 day period where the follicles are either too young or too old for a fertile mating to take place, and a 4 to 6 day period with good fertility and receptivity.
A small percentage of females may fail to ovulate after mating because of a LH deficiency. We do not recommend repeated daily matings as no further LH will be available for at least two days after a previous mating.
So how long to we have to wait for the new born cria. A long time is the only real answer. Officially within the range of 315 to 370 days. Yes that is an alarming just over ten months right through to over 12 months. On average though the vast majority will deliver at around 11.5 months. As the mating seasons roll by, your records might well show some consistency of gestation periods for individual alpacas. Some always coming early, some right on the dot and the others that always keep you waiting. (I have read somewhere that there is also some evidence that gestation periods are linked to seasonal mating times with spring matings having longer times than autumn matings)
Finally, at what age do we allow maidens their first experience. Certainly not before 12 months of age. There is some evidence that young pregnancies have higher rates of failure so we will wait for a body weight of at least 100 pounds and at least 12 months of age before we gently try with a not too aggressive male. If the female appears at all under stress or refuses to sit within a short period then we stop. Generally over a few weeks of short sessions we find most girls willingly sit.
Our stud has what is called a fibro-elastic penis and two testicles held in a scrotal sac. He has the alarming ability to be able to move his testicles closer to his body to maintain optimal temperatures. So if you were sure your boy was well endowed when you bought him and then the next time you looked you could see nothing, don't panic !
The prepuce or sac which holds the penis, normally points backwards, but when he is aroused points forward and the penis extends from it. Prior to puberty the penis is attached to the prepuce so no extension is possible. We normally expect sexual maturity at around 2.5 to 3 years of age at which time the penis has become detached, sperm production is in full flow and sexual drive is evident. There are always the exceptions though, so it is wise to keep all entire males away from the girls after 12 months of age, and ideally after weaning.
During mating the penis extends and passes through the cervix up into the uterus. Sperm is ejaculated into both uterine horns as he moves his penis from one to the other. Around 2ml of viscous semen is ejaculated over a period of time which seems to vary from a quick 5 minute session to over 45 minutes, on average 20 minutes seems to do it.
We would normally allow healthy mature males two matings per day, usually in succession, as they are always on the look out for the next girl should she be standing close by. A third mating after a few hours rest seems to work. Young males beginning their stud duties are restrained to one.
First we must decide on whether to use pen or pasture. It is our experience in a stud business that pen mating is the way to go. This facilitates close observation of both alpacas, accurate record keeping for date, length of time and any problems, correct entry into the female and without interference from tail or fleece. We will wrap the females tail to avoid the fleece from interfering with the mating.
Pen mating will require a small secure area perhaps 10 - 14 ft square with a gate on one side. During fine weather small such pens can be easily created within a pasture using portable fencing, but these must be at least four feet high. Best of all, a small stable area with a clean grooved concrete floor for the boy's feet to grip on. Pasture mating will require an area that is new to both the boys and girls. One male can be run with up to a dozen females.
Make sure your stud is halter trained. If you have a rising star that you think might make the grade get the halter out and start the work. If you are looking to purchase your star stud make sure he walks happily on a lead.
And for the girls, fertility starts with good nutrition and a healthy body score. Under nourished or obese alpacas will make it all that much more difficult. When we receive visiting girls for mating that have been on an unspecific nutrition program we will routinely start them with a multivitamin and mineral preparation. Similarly, parasite control is most important , if no firm records can be found on last worming treatment, this will go on the list as well.
Next, is the girl a maiden. If so it is advisable to check for a clear entrance to the uterus. A gloved and lubricated finger gently inserted through the vaginal opening will detect any obstruction. Slight pressure will rupture the hymen. If a persistent obstruction is felt, it is time to call the vet.
And finally, to the rear end. Lift the tail. Look carefully for any evidence of infection at the vulva. An opaque discharge will need treating before you should allow your stud anywhere near. Typically we find Terraourcin LA antibiotic administered at the rate of 1ml/10kg IM does the trick. Leave for seven days after treatment and then check again.
While looking under the tail look at how long the fleece is. Especially under the tail at the base end and around the business area. The last thing needed is for our prize boy to become entangled in long fleece. Such events will certainly force a holiday for him and at worse cause permanent damage. Reach for the clippers and trim her up or wrap the tail.