EFFECTS OF NUTRITION IN-UTERO AND IN EARLY-LIFE ON THE SUBSEQUENT LIFETIME REPRODUCTIVE-PERFORMANCE OF SCOTTISH BLACKFACE EWES IN 2 MANAGEMENT-SYSTEMS

Over 3 years, a flock of scottish Blackface ewes was managed so that o ne-third of the ewes received a high level of nutrition during the las t 100 days of pregnancy (P), one-third received a high level of nutrit ion during the first 100 days of lactation (L) and one-third received a low level of nutrition as derived from a hill grazing over the same two periods (C). From these ewes, 496 ewe lambs were retained at weani ng (19 to 22 weeks of age), balanced for treatment, year and birth typ e. At 6 months of age half of the lambs, similarly balanced, were tran sferred to an upland grazing system (U) for three breeding years. The other half was retained on the same hill grazing as their mothers for the same period (H). At the end of the study, all ewes were fed to red uce the range in body condition at a synchronized mating and ovulation rates were determined at slaughter. Differences in live weight of ewe s due to treatment between groups P, L and C had disappeared by 18 mon ths. There were no pre-mating differences between treatments in live w eight or body condition score except that ewes in group P had higher l ive weights than those in group C at condition scores greater than 2.7 5. There was little effect of grazing system on the differences betwee n treatments in live weight or body condition score at 30 and 42 month s but H ewes were heavier and fatter at 18 months of age. Ewe mortalit y was consistently less in group L than in groups P and C and on syste m H than on system U, although the differences were not statistically significant. Group L had fewer barren ewes than groups P and C, and ba rrenness was significantly greater in the U than the H system. Group C had proportionally more single than multiple births than either group s P or L. At the end of the study there were no differences between th e treatments in the proportion of ewes successfully mated at the final mating nor in their ovulation rates in relation to pre-mating body co ndition. It is concluded that nutrition during either the lactation pe riod ol late pregnancy period can influence subsequent lifetime reprod uctive performance and that this was expressed through an effect on em bryo or foetal loss since there were neither residual differences appa rent in live weight or condition score nor in ovulation rate potential .