Link to this article: http://journals.cambridge.org/abstract_S0003356100000453How to cite this article: A. M. Hamra and M. J. Bryant (1982). The effects of level of feeding during rearing and early pregnancy upon reproduction in young female sheep.ABSTRACT Two hundred and forty Suffolk x (Cadzow Improver x Scottish Blackface) female sheep were housed at 4 months of age and average live weight (+ s.d.) of 30-6 + 501 kg, and divided into four equal treatment groups: HH, HL, LH and LL. They were group-fed such that HH and HL sheep were 39-7 + 5-27 kg, and LH and LL were 35-6 ± 4-64 kg, at puberty, which was recorded in all sheep. There were no differences in average date at puberty.After puberty the sheep were gradually transferred to different levels of feeding by the time of mating with fertile rams at the second oestrus such that HH and LH were group-fed 1-50, and HL and LL 0-75 of maintenance requirement. The sheep were slaughtered at return or 25 + 3 days after mating.The proportion of sheep with live embryos was 0-48,0-40,0-50 and 0-41 for HH, HL, LH and LL groups respectively (NS). Ova wastage was 0-59, 0-68, 0-51 and 0-59 for the treatments, with statistically significant differences in losses between treatments in sheep with two corpora lutea (P<0-05). Ovulation rate also differed between treatments (HH > HL, P < 0-01; HH > LH and LL, P < 0-05). Differences occurred between treatments in the proportion of multiple cycles between first and second oestrus (P<0-05), and HL sheep had a greater proportion of sheep failing to return to service but without embryos (HH>HL, P<0-05). The pooled results showed that pregnant sheep were heavier at 4 months of age (P < 0-05), but not at mating, than non-pregnant sheep. Sheep with two corpora lutea were more likely to be pregnant than sheep with one corpus luteum (P < 0-05).