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- Title
Effect of FecX<sup>R</sup> polymorphism in the BMP15 gene on natural or eCG-induced ovulation rate and litter size in Rasa aragonesa ewes and implications for on-farm application.
- Authors
Lahoz, B.; Alabart, J. L.; Jurado, J. J.; Calvo, J. H.; Martínez-Royo, A.; Fantova, E.; Folch, J.
- Abstract
A new mutation in the bone morphogenetic protein 15 (BMP15) gene (FecXR allele) causing increased prolificacy in heterozygous (R+) and sterility in homozygous ewes has been recently described in Rasa aragonesa, a low-prolificacy Mediterranean breed. The current study determined, firstly, the effect of this polymorphism on natural and eCG-induced ovulation rate (OR) and the effect of eCG dose on reproductive performance; and secondly, its effect on prolificacy and its interaction with progestagen + eCG treatment on farms, which have not been reported to date. The FecXR allele increased OR by 0.44 and 0.63 ovulations in young (n = 91) and adult (n = 84) R+ ewes, respectively (both, P < 0.01), increments lower than reported in prolific breeds carrying other mutations in BMP15. When the standard dose of eCG used on farms (480 IU) was applied to R+ ewes (n = 36), an extremely high OR (3.95) was recorded, which was accompanied by a high partial failure of multiple ovulations (PFMO). On the contrary, OR using 240 IU in R+ ewes (2.90; n = 35) was similar to 480 IU in wildtype (++) ewes (2.82; n = 48; both P < 0.01 when compared with 480 IU in R+ ewes). No differences were found in the birth weight of the offspring between R+ and ++ eCG-stimulated ewes within the same litter size (LS). To validate the genealogy identification on farms, PCR genotyping was carried out in 1,667 ewes from 4 elite flocks, resulting in a negligible misclassification of R+ ewes, which demonstrated that identification by genealogy is a reliable tool to identify FecXR ewes within the breeding program. In recorded farms, the natural LS of ++ ewes (1.34, n = 599,160 lambing records) was increased due to the FecXR allele by 0.35 lambs (P < 0.0001, n = 6,593 lambing records). A similar increase (0.30) was observed when comparing ++ and R+ ewes treated with 480 IU of eCG (P < 0.0001, n = 62,055 and n = 866; respectively). When applying 480 IU of eCG to R+ ewes, the increase in prolificacy was only due to increased percentages of triplets (P < 0.001) and quadruplets (P < 0.0001), but not of twin births. In conclusion, the favorable reproductive performance of R+ ewes, with 0.63 extra ovulations and 0.35 extra lambs per lambing ewe, is responsible for the increased interest in the use of this polymorphism. Nevertheless, care must be taken in the application of eCG to R+ ewes, with the current results showing that the standard dose increases prolificacy by only increasing triple and higher-order births.
- Subjects
BONE morphogenetic proteins; OVULATION; ANIMAL litters; ARAGONESE sheep; SHEEP; MAMMAL reproduction
- Publication
Journal of Animal Science, 2011, Vol 89, Issue 11, p3522
- ISSN
0021-8812
- Publication type
Article
- DOI
10.2527/jas.2010-3828