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Ovulation rate of corriedale ewes at Bahía Blanca, Argentina

Published online by Cambridge University Press:  02 September 2010

H. Irazoqui  and
E. E. Menvielle
H. Irazoqui
Affiliation:
Departamento de Ciencias Agrarias, Universidad Nacional del Sur, Bahía Blanca (8·000), Argentina
E. E. Menvielle
Affiliation:
Departamento de Ciencias Agrarias, Universidad Nacional del Sur, Bahía Blanca (8·000), Argentina
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Abstract

An experiment has been carried out at Bahia Blanca to estimate the trend in ovulation rate throughout the year shown by Corriedale ewes of similar live weight in the south-west district of the Argentinian pampa.

Five groups of 16 animals were each subjected to two 20-day observation periods and the 10 observation periods in the experiment were evenly spaced within a year.

The proportion of ewes showing oestrus and ovulation (OO), the frequency of twin ovulations (TO) and, hence, ovulation rate (OR) were estimated for each period by using vasectomized rams and performing laparatomies.

A significant and periodic relationship was found between each trait and the number of days elapsed from the longest day (×). In turn, changes in the values of ×, arising from the progress of the experiment, were to some extent associated with changes in nutrition and surgical interference. However, it was concluded that these factors could not have affected the similar and remarkable seasonality shown by each trait in this study, and that this seasonality was mainly associated with differences in the natural light regime to which the ewes were exposed before and during their corresponding observation periods.

The predicted maximum values for each parameter were reached 1 month before the shortest day. Prior to and after this date both OO and TO declined, so that the predicted OR values became zero for a period of approximately 2 months before the longest day

Type
Research Article
Information
Animal Production , Volume 35 , Issue 3 , December 1982 , pp. 313 - 320
Copyright
Copyright © British Society of Animal Science 1982

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References

REFERENCES

Allen, D. M. and Lamming, G. E. 1961. Nutrition and reproduction in the ewe. J. agric. Sci., Camb. 56: 69–79.CrossRefGoogle Scholar
Allison, A. J. and Kelly, R. W. 1979. Effects of differential nutrition on the incidence of oestrus and ovulation rate in Booroola × Romney and Romney ewes. Proc. N.Z. Soc. Anim. Prod. 39: 43–49.Google Scholar
Ducker, M. J. and Boyd, J. S. 1974. The effect of daylength and nutrition on the oestrous and ovulatory activity of Greyface ewes. Anim. Prod. 18: 159–167.Google Scholar
Fletcher, I. C. 1971. Effects of nutrition, liveweight, and season on the incidence of twin ovulation in South Australian strong-wool Merino ewes. Aust. J. agric. Res. 22: 321–330.CrossRefGoogle Scholar
Fletcher, I. C. and Geytenbeek, P. E. 1970. Seasonal variation in the ovarian activity of Merino ewes. Aust. J. exp. Agric. Anim. Husb. 10: 267–270.CrossRefGoogle Scholar
Gunn, R. G. and Doney, J. M. 1979. Fertility in Cheviot ewes. 1. The effect of body condition at mating on ovulation rate and early embryo mortality in North and South Country Cheviot ewes. Anim. Prod. 29: 11–16.Google Scholar
Gunn, R. G., Doney, J. M. and Smith, W. F. 1979a. Fertility in Cheviot ewes. 2. The effect of level of premating nutrition on ovulation rate and early embryo mortality in North and South Country Cheviot ewes in moderately-good condition at mating. Anim. Prod. 29: 17–23.Google Scholar
Gunn, R. G., Doney, J. M. and Smith, W. F. 1979b. Fertility in Cheviot ewes. 3. The effect of level of nutrition before and after mating on ovulation rate and early embryo mortality in South Country Cheviot ewes in moderate condition at mating. Anim. Prod. 29: 25–31.Google Scholar
Hafez, E. S. E. 1952. Studies on the breeding season and reproduction of the ewe. J. agric. Soci., Camb. 42: 189–265.CrossRefGoogle Scholar
Hammond, J. Jr, 1944. On the breeding season in the sheep. J. agric. Sci., Camb. 34: 97–105.CrossRefGoogle Scholar
King, C. F. 1976. Seasonal changes in the ovulatory activity of ewes slaughtered in northern Tasmania. Proc. Aust. Soc. Anim. Prod. 11: 121–126.Google Scholar
Little, T. M. and Jackson Hills, F. 1978. Agricultural Experimentation. Design and Analysis. John Wiley, New York.Google Scholar
McDonald, M. F. and Chang, T. S. 1966. Variation in ovarian activity of Romney Marsh ewes. Proc. N.Z. Soc. Anim. Prod. 26: 98–106.Google Scholar
Morley, F. H. W., White, D. H., Kenney, P. A. and Davis, I. F. 1978. Predicting ovulation rate from liveweight in ewes. Agric. Systems. 3: 27–45.CrossRefGoogle Scholar
Radford, H. M. 1959. Variation in the incidence of twin ovulation in Merino ewes on a constant plane of nutrition. Aust. J. agric. Res. 10: 377–386.CrossRefGoogle Scholar
Radford, H. M., Watson, R. H. and Wood, G. F. 1960. A crayon and associated harness for the detection of mating under field conditions. Aust. vet. J. 36: 57–66.CrossRefGoogle Scholar
Steel, R. G. D. and Torrie, J. M. 1960. Principles and Procedures of Statistics. McGraw-Hill, New York.Google Scholar
United States Department of Agriculture. 1975. Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys. Handbk U.S. Dep. Agric, No. 436.Google Scholar
Wheeler, A. G. and Land, R. B. 1977. Seasonal variation in oestrus and ovarian activity of Finnish Landrace, Tasmanian Merino and Scottish Blackface ewes. Anim. Prod. 24: 363–376.Google Scholar
Yeates, N. T. M. 1956. The effect of light on the breeding season, gestation, and birth weight of Merino sheep. Aust. J. agric. Res. 7: 440–446.CrossRefGoogle Scholar