Reproduction in ewe lambs and its effect on 2‐year‐old performance

Abstract

Abstract Reproductive performance was studied in 1‐ and 2‐year‐old Romney and Border Leicester x Romney ewes. Control lambs were joined with vasectomised rams, and the remainder were joined with entire rams for 5 weeks. Fertility, growth rate, and weaning rate were higher in crossbred ewe lambs, and birth rank effects were small. Conception rate to first service was negatively related to liveweight gain over joining. Weaning rate (57% lambs weaned/ewe joined) was lower than normally expected from adult ewes. Lamb survival was improved in previously lambed 2‐year‐old ewes, whereas oestrous and ovarian activity, fertility, fecundity, and lamb growth were unaffected. Ewe liveweight and fleece weights were temporarily reduced. It is concluded that lambing in l‐year‐old ewes can enhance their reproductive performance as 2‐year‐olds.