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Báo cáo sinh học: "Sources of variation and genetic profile of spontaneous, out-of-season ovulatory activity in the Chios sheep"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học thế giới đề tài: Sources of variation and genetic profile of spontaneous, out-of-season ovulatory activity in the Chios sheep | 65 Genet Sei. Evol. 35 2003 65-76 INRA EDP Sciences 2003 DOI 10.1051 gse 2002036 Original article Sources of variation and genetic profile of spontaneous out-of-season ovulatory activity in the Chios sheep Melpomeni Avdia Georgios Banosb Athanasios Kouttosa Loys Bodinc Philippe Chemineaud a FacultY of Agriculture Aristotle UniversitY of Thessaloniki 54124 Thessaloniki Greece b FacultY of VeterinarY Medicine Aristotle UniversitY of Thessaloniki 54124 Thessaloniki Greece c Inra 31326 Castanet-Tolosan France d Inra 37380 NouzillY France Received 11 FebruarY 2002 accepted 13 August 2002 Abstract - Organising the breeding plan of a seasonally breeding species such as sheep presents a challenge to farmers and the industry as a whole since both economical and biological considerations need to be carefully balanced. Understanding the breeding activity of individual animals becomes a prerequisite for a successful breeding program. This study set out to investigate the sources of variation and the genetic profile of the spontaneous out-of-season ovulatory activity of ewes of the Chios dairy sheep breed in Greece. The definition of the trait was based on blood progesterone levels measured before exposing the ewes to rams which marks the onset of the usual breeding season. Data were 707 records taken over two consecutive years of 435 ewes kept at the Agricultural Research Station of Chalkidiki in northern Greece. When all available pedigree was included the total number of animals involved was 1068. On average 29 of all ewes exhibited spontaneous out-of-season ovulatory activity with no substantial variation between the years. Significant sources of systematic variation were the ewe age and live weight and the month of previous lambing. Older heavier ewes that had lambed early the previous autumn exhibited more frequent activity. Heritability estimates were 0.216 0.084 with a linear and 0.291 with a threshold model. The latter better accounts for the categorical nature of the