Seasonal reproduction in ewes selected on seasonal changes in wool growth. 1987

G W Montgomery, and H Hawker

Romney and Perendale ewes were selected on the amplitude of seasonal wool growth. The ewes were fed a constant plane of nutrition and run with vasectomized rams. Ovarian activity was recorded by laparoscopy during 11 months. Ewes with a low amplitude of seasonal wool growth (Group L) had a 68% higher wool growth rate in winter and a 17% lower wool growth rate in summer compared with ewes with a high amplitude (Group H). There was no difference between the groups in the date of the first mating mark. Ewes in Group L entered anoestrus significantly later than did ewes in Group H; the difference was 11 days in the mean date of the last mating mark and 17 days in the mean date of the last ovulation. A significantly higher proportion of ewes in Group L ovulated during July to November. In addition, ewes in Group L had a significantly higher proportion of multiple ovulations throughout the experiment: on average the difference between the groups was 0.21. These results show that phenotypic selection for a low amplitude of seasonal wool growth resulted in a delay in the end of the breeding season associated with an increase in ovulation rate, suggesting independent effects on the beginning and end of the breeding season.

UI MeSH Term Description Entries
D010060 Ovulation The discharge of an OVUM from a rupturing follicle in the OVARY. Ovulations
D010641 Phenotype The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment. Phenotypes
D012098 Reproduction The total process by which organisms produce offspring. (Stedman, 25th ed) Human Reproductive Index,Human Reproductive Indexes,Reproductive Period,Human Reproductive Indices,Index, Human Reproductive,Indexes, Human Reproductive,Indices, Human Reproductive,Period, Reproductive,Periods, Reproductive,Reproductive Index, Human,Reproductive Indices, Human,Reproductive Periods
D005260 Female Females
D000780 Anestrus A state of sexual inactivity in female animals exhibiting no ESTROUS CYCLE. Causes of anestrus include pregnancy, presence of offspring, season, stress, and pathology.
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012621 Seasons Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Seasonal Variation,Season,Seasonal Variations,Variation, Seasonal,Variations, Seasonal
D012756 Sheep Any of the ruminant mammals with curved horns in the genus Ovis, family Bovidae. They possess lachrymal grooves and interdigital glands, which are absent in GOATS. Ovis,Sheep, Dall,Dall Sheep,Ovis dalli
D014935 Wool The hair of SHEEP or other animals that is used for weaving or felting.

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