Effect of Controlled Environment on the Reproductive Performance of Ewes

Seasonal variations in the cyclic luteal ovarian activity in the Tadmit ewe in Algeria

“…In the same way, in Israel (31°15'N) 80% of Mutton Merino ewes conceived in the months of lengthening daylight (Goot, 1969). Likewise, in south Carolina (33°N) (U.S.A.) the Western Whiteface ewe became anoestrous by early February (Rawlings, Kennedy, Chang, Hill & Henricks, 1977) and commenced cyclic activity in early May (Rawlings et al, 1977) or in early June (Godley, Wilson & Hurst, 1966 (about 45°N) (minimum from April-May to July). Likewise, our own observations showed that in Algeria (36°39'N) the seasonal luteal ovarian activity of the Tadmit ewe started on average during May, when daylength is still increasing.…”

Induction of oestrus and fertility in the anoestrous ewe with hormones and controlled lighting and temperature

“…Exposure to similar light : dark ratios and temperatures was sufficient to induce a high incidence of cycling in anoestrous ewes (Godley et al, 1966). However, the 26 days of exposure to the controlled environment was less (5-110 days) than that reported to induce cycling (Yeates, 1949;Ducker & Bowman, 1972;Palmer et al, 1972) (Dutt, 1963;Thwaites, 1967).…”

“…The use of exogenous hormones generally resulted in a high incidence of both behavioural oestrus and ovulation, but the conception rates for the induced oestrus during mid-anoestrus ranged from 21% (Gordon, 1963a) to 50% (Brunner et al, 1964). Another approach has been to alter environmental stimuli, such as light and temperature, which act via higher nervous centres to modulate the reproductive cycling of sheep (Yeates, 1949; Godley, Wilson & Hurst, 1966;Ducker, Thwaites & Bowman, 1970;Ducker & Bowman, 1972;Palmer, Phillips, Howland & Ibrahim, 1972). This approach has frequently resulted in high conception rates but the length of time required until the onset of oestrus was usually large and variable.…”

A putative effect of ambient temperature during the rut on time of calving in young red deer hinds

“…Another environmental variable is ambient temperature, and its effects on the timing of the onset of the breeding season has been recorded in sheep, cattle, and horses (Dutt & Bush 1955;Dale et al 1959;Godley et al 1966;Lees 1971;Guerin & Wang 1994). While there is apocryphal evidence, indeed a belief commonly held among deer stalkers, that cold nights during the rut result in intense sexual activity in deer (Whitehead 1993), an effect of temperature on red deer reproduction has yet to be documented.…”