In October of 2021, we had Graeme Martin on the HeadShepherd Podcast to talk about teasing, and the biology behind it.
Graeme has a long and distinguishedcareer in sheep reproduction. He worked in France and Scotland and thenreturned to WA, Australia, in the mid 80's as Lecturer in Animal Science (TheUniversity of WA) and Research Scientist (CSIRO Division of Animal Production),specialising in the "Male effect", throughout his career.
Graeme takes us through the scienceof the sheep's brain when it comes to reproduction.
“The sheep is much cleverer than mostpeople give it credit for. It effectively spends its whole day measuring itsenvironment. It measures the length of the night, it measures the amount offood that's available, it measures its body reserves, but also and, inparticular, it measures its social surroundings- basically by usingsmell."
"And so the sense of smell in thefemale sheep responds to an odour from a male sheep, and this switches on thereproductive system."
"Now there are limitations tothis- it is most effective when the animals are not cycling normally. Thatmeans, for example, in the period between September and January, for Merinosheep in Australia."
"We are lucky that we have got somany merinos in Australia because they really are the best animals for the rameffect and teasing. "
"And so what happens is that thefemale sheep is just wandering around the place and then suddenly she smells anew male."
"And this is something we'vediscovered quite recently that it needs to be a new male- a novel male,something she hasn't smelled before. Or maybe she has, but she's forgottenbecause it was two or so months ago. "
"And so when she smells thesmell, her brain switches on, which is within seconds."
"Two days later, she willovulate. She won't come on heat with that first ovulation. So she'll go througha cycle and then on the second ovulation she will show heat and can bemated."
"And that is roughly 19 daysafter teaser/novel male introduction."
"There is a little bit of a catchhere in that after that first ovulation in the first two days, about half ofthe animals seem to have a short cycle of only about six or seven days insteadof 17 days. And they have the second ovulation, therefore at around nine days.And there's no oestrogen there, either so it's another silent ovulation."
"The first two ovulations inthose animals are silent and then they have the third ovulation at about day21, and then they come on heat."
"That's why the recommendation isa 14-day tease because nothing will be back cycling before that. You shouldhave got rid of both those two silent oestruses after a 14 day teasing and thenyou should have the entire rams in before that next round of ovulationstarts."
“You've got sort of peak of activityof sexual behavior between days 19 and 25 in that period of time. If you have agood percentage of rams, you'll get 70 or 80% of the animals pregnant, whichyou can then verify later on an ultrasound."
"This gives you a nice,concentrated lambing.”
"There's a debate about whether you should have therams present after the second cycle. That's an individual decision. After thesecond cycle, we don't get much benefit and so it's probably better to pullthem out and just keep it concentrated lambing in a nice cohort coming throughto the market.”
We all have in our heads this 17day cycle, and that's obviously an average, not the rule. What is the range andtempo of ovulation?
“15 to 18 days is the range, butyou'll get most of the animals on 16 and 17. It is quite reliable compared toother species.”
"So day length decreases,spontaneous ovulation starts kicking in and then teasing is less effective orhas zero effect."
“Once the animals are all cycling,you're wasting your time. There are effects going on in the body in terms ofhormones, but you won't have any synchronisation or induction ofovulation."
"So if you were a Merino breederthen you might expect the normal seasonal cycles to begin sometime in January,which means that teasing is really only effective up until the middle ofJanuary."
You said merinos are the mostresponsive, but a Romney or a Composite, they are later when their spontaneousovulation starts kicking in- does teasing have an effect on them too, just notas strong?
"Sheep become more resistant tothe teasing effect as they become more seasonal. They become less and lessresistant as they get closer to the start of the season."
"So, if you're using a compositewith some British genes in there, you can expect the breeding season to bedelayed until March. If you go into the end of February, you likely might havea good result with it."
What about mating ewe lambs at12/13 months. Is it the same sort of process?
"There you've got a sort ofstrange interaction between the season and the onset of puberty."
"So teasing can induce an earlypuberty if the animals are sufficiently mature in terms of the body mass andthe body weight and the condition and age. And if you're getting close topuberty, then it's easy to induce early puberty, which is exactly the sameexperience as you see in the adult ewes. "
"Basically, you can help out theprocess by using teasing and gain some traction in terms of getting an earlierfirst pregnancy there."
How long does it take for them toforget a male?
"We don't really know. Basically,we think it's a couple of months."
"It is an interesting bit ofbiology because what happens is the female smells a novel of male, and then inher brain, she gets some cell division happening in the memory stems. These newcells make new memories. And then after a while, these cells die. We just don'tknow how fast they die and therefore how fast the memory disappears. "
"And it's exactly the sameprocess that a female sheep goes through when she smells a newborn lamb."
"So this process is somethingthat is quite poorly understood. But if you want to be conservative, it wouldbe a few months."
Best practice to keep in mind in this period, is that ifyou want to use the teasing effect, you want to keep all males in the propertywell away from where the ewes are. Is one ram providing pheromones enough or isthere a percentage that you need?
"The more smell, the better. Butgenerally speaking, you're looking at just a couple of percent, because theywander all over the place."
"When it comes to putting theentire males in, that’s when you’ve got to be careful."
"If you're mating during thenormal breeding season, then the ram is going to see one ewe in seventeencoming into oestrus every day."
"That's 6% of the flock coming onheat every day, on average. That's pretty easy for the average ram to keep upwith."
"What happens when you’reteasing, is that you’re going to get three, maybe four times as many per day inthat period between the first day 14 and day 26 or 28. So in that period,things are really concentrated and if your ram percentage is too small, theyjust won't be able to get it all done."
"You’ll need to bump up your rampower percentage to something like three or four percent."
If you're teasing and then single siremating, you have to be really careful with your numbers. They're not going tocover the numbers they would in a normal mating.
We have clients putting rams out inNovember in Australia could you just put the Rams in two weeks earlier becausethey shouldn't be spontaneously ovulating?
The risk is that there's always goingto be a few percentage of the flock that are going to be cycling and they'llget pregnant.
It's a bit dangerous, which is whyteasers have that advantage, being sterile males.