A study conducted by Teagasc has shown that 53% of triplet lambs are sired by different rams. Research of its kind has never been undertaken previously in any global sheep population.
The phenomenon is called heteropaternal superfecundation (HS), involving separate mating events with two or more rams, leading to the fertilisation and implantation of two or more eggs during the same heat. This results in the birth of two or more sibling lambs sired by different rams.
Sheep are a great example of such a population, as they often bear multiple lambs and are also often mated by more than one ram (mob mated).
HS in Irish sheep
The research looked at the progeny of 685 ewes which were all mob mated:
Of the 539 pairs of twins included in the analysis, 30% were sired by two different rams. Of the 137 sets of triplets included in the analysis, 53% were sired by more than one ram. Of the nine sets of quadruplets, about 90% were sired by more than one ram.The overall incidence of HS among litters was 35%. Given that the incidence of multiple births in these flocks was 65 %, HS is expected to be relatively common in sheep.
/Philip Doyle
Detecting HS in your flock
HS in sheep can be detected if only one ram of each breed was present within the mating mob, and if these breeds were distinctly different.
A Texel ram with a white head and a Suffolk ram with a black head will each produce distinctly different lambs.
DNA information on the lambs provides more concrete proof of HS and is one of the only ways to determine its occurrence when multiple rams from the one breed make up the mob mating team.
Star ratings
Where HS occurs, the extent to which the star ratings of lambs from the same litter can diverge may be large.
The study revealed that the level of genetically identical lambs in a litter is extremely low. Non-identical full siblings are assumed to have a genetic relationship of a half.
If the twins are born from two sires (HS), then the genetic relationship between siblings is expected to be one-quarter or half-siblings.
Hence, where HS occurs, the extent to which the star ratings of lambs from the same litter can diverge may be large.
Read more
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A study conducted by Teagasc has shown that 53% of triplet lambs are sired by different rams. Research of its kind has never been undertaken previously in any global sheep population.
The phenomenon is called heteropaternal superfecundation (HS), involving separate mating events with two or more rams, leading to the fertilisation and implantation of two or more eggs during the same heat. This results in the birth of two or more sibling lambs sired by different rams.
Sheep are a great example of such a population, as they often bear multiple lambs and are also often mated by more than one ram (mob mated).
HS in Irish sheep
The research looked at the progeny of 685 ewes which were all mob mated:
Of the 539 pairs of twins included in the analysis, 30% were sired by two different rams. Of the 137 sets of triplets included in the analysis, 53% were sired by more than one ram. Of the nine sets of quadruplets, about 90% were sired by more than one ram.The overall incidence of HS among litters was 35%. Given that the incidence of multiple births in these flocks was 65 %, HS is expected to be relatively common in sheep.
/Philip Doyle
Detecting HS in your flock
HS in sheep can be detected if only one ram of each breed was present within the mating mob, and if these breeds were distinctly different.
A Texel ram with a white head and a Suffolk ram with a black head will each produce distinctly different lambs.
DNA information on the lambs provides more concrete proof of HS and is one of the only ways to determine its occurrence when multiple rams from the one breed make up the mob mating team.
Star ratings
Where HS occurs, the extent to which the star ratings of lambs from the same litter can diverge may be large.
The study revealed that the level of genetically identical lambs in a litter is extremely low. Non-identical full siblings are assumed to have a genetic relationship of a half.
If the twins are born from two sires (HS), then the genetic relationship between siblings is expected to be one-quarter or half-siblings.
Hence, where HS occurs, the extent to which the star ratings of lambs from the same litter can diverge may be large.
Read more
1% of twin calves are sired by different bulls
Rare twin calves shock Clare farmer
Testing confirms udderless cows had no mammary tissue
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