Natural and induced ovulation rate of Finnish Landrace and other breeds of sheep

Abstract

Ewes of seven breeds (Oxford Down, Border Leicester, Finnish Landrace, Southdown, Welsh Mountain, Tasmanian Merino and Soay) were treated with progestagen-treated sponges to synchronize oestrus for an egg-transfer experiment. Ewes of five of the breeds were treated with superovulating doses of pregnant mare serum gonadotropin (PMSG). Mean body weight ranged from 89 kg for Oxford Downs to 20 kg for Soays. Interval from sponge withdrawal to oestrus differed significantly between breeds, ranging from 1-83 days in Finnish Landrace to 3-00 days for Soays, but was not consistently related to ewe weight. Treatment with PMSG prior to sponge removal reduced the interval to oestrus; fertilization rate at the first synchronized oestrus was low. There were marked differences among breeds in proportion of ewes showing oestrus following PMSG treatment, total follicular response, and proportion of follicles ovulated. Ewes of the Finnish Landrace breed, with the highest natural fertility, were equal or superior to the other breeds in every component of response, and yielded more than double the number of fertilized eggs per ewe of the next best breed. Finnish Landrace females 6 to 9 months old made very satisfactory donors. Natural ovulation rates of adult recipient ewes were as follows: Welsh Mountain (23 ewes)-1-43; Border Leicester (15 ewes)-2-00; Finnish Landrace (26 ewes)-3-31.

Major genes control hormone-induced ovulation rate in mice

“…1 led to the discovery of a tremendous amount of genetic variation in this trait. The 5-fold genetic differences in hormone-induced ovulation rate between A/J and SJL/J mice and 6-fold genetic differences in hormone-induced ovulation rate between A/J and C57BL/6J mice are considerably larger than the genetic differences previously reported for hormone-induced ovulation rate of mice (Fowler & Edwards, 1957;Falconer et ., 1961;Bradford, 1969;Land & Falconer, 1969;Wolfe, 1971;Land et al, 1974;Bindon & Pennycuik, 1974;Durrant et al, 1980), sheep (Bradford et al, 1971) and cattle (Chupín et al, 1985). Nevertheless, screening widely divergent genotypes in other mammalian species may also reveal a magnitude of genetic variation in hormone-induced ovulation rate similar to that found in the present study.…”

“…The genetic differences in hormone-induced ovulation rate observed in the present study are likely to be indicative ofthe kinds of genetic variation in ovarian function present in other mammalian species. Striking differences in the ovarian response to exogenous gonadotrophins have also been found within sheep, cattle and human populations (Bradford et al, 1971;Jones, 1984). Unfortunately, well defined genetic models for examining hormone-induced ovulation rate are not available for many mammalian species.…”

“…Laboratory and farm animal species show a considerable amount of genetic variation in the ovarian responsiveness to exogenous gonadotrophins (Fowler & Edwards, 1957;McLaren, 1962;Bradford, 1969;Land & Falconer, 1969;Bradford et al, 1971; Bindon & Pennycuik, 1974;Durrant et al, 1980;Spearow, 1980;Spearow & Bradford, 1983). Unfortunately, the magnitude and nature of genetic variation in hormone-induced ovulation rate are not completely understood.…”

Genetic Control of Hormone-Induced Ovulation Rate in Mice1

“…Even when these physiological factors are held constant, ovarian responsiveness to gonadotropins often differs 5-to 50-fold between individual females from the same population. Much of this variability is genetic as demonstrated by the differences in ovarian responsiveness to gonadotropins between breeds, strains, or lines of laboratory and domestic animals [1][2][3][4][5][6][7][8][9][10].…”

A note on ovulation rate and embryonic survival in D'man ewes

“…Furthermore, the present experiment was conducted during a season (April/May) when sexual activity is zero for other Moroccan breeds (Marie and Lahlou-Kassi, 1977). Comparing D'man with European prolific breeds, the ovulation rate for ewes of the same age was lower than for Finnish Landrace (2-96 to 411) (Bradford, Quirke and Hart, 1971;Land, Russell and Donald, 1974;Hanrahan and Quirke, 1975), nearly identical to Romanov (2-27 to 2-86) (Land, Pelletier, Thimonier and Mauleon, 1973;Ricordeau, 1975), and markedly higher than Blackface (1-33 to 1-86) (Griffiths, Gunn and Doney, 1970;Land, 1970).…”