The effect of liveweight and liveweight gain of ewes immediately post-weaning on the liveweight and survival of subsequent lambs

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Thirteen-hundred and sixty-seven Romney mixed-aged ewes were randomly allocated to one of two liveweight gain treatments (high vs maintenance) from weaning of one litter of lambs until 71 days before the subsequent breeding (a period of 42 days). The aims of this study were first to determine whether ewe liveweight or liveweight gain treatment before rebreeding affected the number and liveweight of lambs produced and reared in the following season, and second, to identify whether the birth rank of the dam or the grand-dam affected the number, survival or liveweight of their lambs. Liveweight gain during the 42-day treatment period was greater (P < 0.05) in the high than maintenance treatment (87 ± 6 vs 4 ± 6 g/day, respectively), although it did not influence (P > 0.05) number of fetuses, lambs born or reared per ewe or total weight of lambs born or weaned per ewe. Ewe liveweight at weaning (113 days before rebreeding), and liveweight gain between the weaning and rebreeding, explained only a minor proportion of the variation in lamb liveweight at birth and weaning in the following season. Birth rank of the ewe or of the ewe’s dam did not (P > 0.05) influence liveweight or number of lambs born or weaned. In conclusion, this experiment indicated that liveweight and liveweight gain from weaning until rebreeding in the flock investigated had only a very minor influence on lamb production. Therefore, there appears to be little advantage in specifically managing ewes during this period to gain considerable amounts of liveweight.