Both male and female alpacas suffer from heat stress, but it is more of a problem with the stud males, because the heat stress destroys their sperm, and can make them permanently sterile. Seriously. We have known this happen.
The testicles can be very swollen and solid when a Stud is suffering from heat stress.
In Peru the temperature rarely goes above 20C, and almost always freezes at night, and so I believe there is not a problem with heat stress sterility there. However, we have found that when we have hot weather in UK, the males can become sterile for 6-8 weeks if they become heat stressed. We think this is due to the very dense coats that our alpacas have now and that usually when we get hot weather it comes as a drastic change not a gradual one. In recent years we have found heat stress in some heavily-fleeced stud males even in April before shearing. To lose fertility in a male due to heat stress can really throw a spanner in the works for a breeding programme. This is not good, as we want to have crias born in Spring and early summer, when they grow much better. We have found crias born during August and later in the year do not grow as quickly as the crias born earlier in the year. (See the article “Weaning”.) Even when we feed the females and crias extra all through the winter they still do not grow as well and it takes them longer to catch up.
The female suffers trauma in her vulva, cervix and uterus every time she is mated by a male. So we need to keep the number of matings to a minimum. If the male is sterile for any reason, including heat stress, then he will mate the female many times without results. This can damage the female. There is also a higher probability of introducing dirt and disease inside the female, which can lead to endemetritis and sterility in the female. So it is important to make sure the male is fertile when mating with the females.
Mating a particular female should take place as little as possible and should happen only once a week and a female should take after very few matings. Ideally spit offs should occur at exactly 7 day intervals to confirm firstly that the female has ovulated, and then that she is pregnant. We require 3 spit offs and then we are content the female is pregnant and we will confirm this at a 60 day scan. If an ultrasound scan is not possible, another spit-off 6 weeks after mating, and again the following Spring will check that she is retaining her pregnancy. Spit-offs are not infallible to confirm pregnancy, as they may in some cases mean that there is just a retained CL (corpus luteum) instead. So we always do an ultrasound scan, with fetus seen, before we confirm any pregnancy.
We have several ways to deal with heat stress for the stud males.
1. We shear them as early as possible in the Spring. We start shearing the middle of April and are finished by the 2nd week of May. Our studs are some of the first to be sheared.
2. We give them a field with a large amount of shade from trees and hedges.
3. During hot weather we only mate them with the females in the morning when it is cool.
4. In very hot weather we bring the Studs into a cool barn during the daytime, or pen them in the shade so they don’t have the option to sun themselves. (plus 30C)
In addition, we generally use the stud males only twice a day (occasionally 3 times), and visiting females always have the first mating of any day. Our studs have several days rest every week, as alpacas are dribble ejaculators, and do not produce copious amounts of sperm.