During the last two decades, it was shown that some specific nutrients play an important role in growth, reproduction and immunity. Among of these nutrients, BC (β-carotene) is required not only for maintaining vitality of the tissues in the reproductive tract but also for keeping the body in good health in general. Also there is a possible role of β-carotene as protective nutrient against cancer has been reported. As well other studies reported that β-carotene protects against lung cancer and probably against stomach cancer and it may also be protective against cancers of ovary, cervix, breast and other cancers except the cancers of colon or rectum. Feed of sheep is mainly poor in vitamin A, simply because of deficient BC in roughages, cereal stubble wheat straw, stored alfalfa hay and barely grain. Although green forages are the major source of carotenoids including β-carotene (BC), but they are not available throughout the year. This means that BC should be taken from exogenous sources in order to cover the deficiency of vitamin A from one side and to fill the tissue vitamin A reserves from the other side. Therefore, the aim of this study was to investigate the long-term effect of BC on LBW, age at puberty, number and percentage of estrus coming post-puberty, types of estrous cycle following puberty and P4 and E2 profiles at puberty and pre-and post- puberty in Farafra ewe lambs. The study contained 48 ewe lambs with mean body weight 13.25 ± 0.43 kg and divided into two equal groups (24 per each), the first group was injected i.m. with arachis oil (peanut oil) and considered control for the other treated group because it can be metabolized easily in the body, the second group was injected i.m. 0.1 mg/kg by BC loaded on arachis oil 2 times a week for 4 months starting from weaning period to age at puberty. Beside detection of estrus by a ram, P4 value was taken as a marker in determining age at puberty. Olive oil can not be used for long time because of its destruction of the tissues. All ewe lambs were fed maintenance ration and housed in semi-open pens under Upper-Egypt environment conditions, El-Minia Governorate. P4 Blood samples (10 ml/animal) were withdrawn from 6 animals per each group (control and treatment) by jugular vein puncture into tubes without anticoagulant.After clotting blood samples were centrifuged at 3,000×g for 10 min to separate the sera, which was stored at −20°C until P4 and E2 assay. Both BC and vit. A were assayed by colorimetric method.