Kerala, India
Sexual activity in sheep is predominantly controlled by the daylight to darkness ratio. Estrus becomes more frequent as day length decreases. Generally, fertility is highest and most efficient when ewes are bred in September, October, or November; ewes bred during this timeframe typically produce the highest percentage of multiple births.
Elevated temperatures are detrimental to fertility, embryo survival, and fetal development. This represents the primary disadvantage to fall lamb production. High breeding temperatures can decrease conception rates. Heat stress during gestation impairs fetal development and can result in significantly smaller lambs at birth.
Psychological Stimulation
Introducing a ram near the anestrous period’s end appears to psychologically stimulate ewes. It triggers earlier ovulation and estrual activity. The ram can be either fertile or surgically sterilized. Rams should remain with ewes for approximately 10 to 14 days and be removed from the flock before breeding commences. Then, at breeding season onset, rested fertile rams intended to sire the lamb crop can be introduced. The stimulation does not occur when rams are placed with ewes earlier, or when rams simply remain with ewes continuously.
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