Ewe reproductive performance and growth rate of suckling-lambs on endophyte-infected perennial ryegrass pasture

Abstract

Two groups (n=39) of Romney breeding ewes were maintained under the same grazing management on either endophyte-infected (E+) or endophytefree (E-) perennial ryegrass pasture for two years (1997-1998) following a one-year equilibration period. The ewes were naturally mated in March each year and ovulation rate at 1st mating was measured, and conception and the number of lambs born and weaned were recorded. All ewes were weighed monthly and lamb growth rates were determined between birth and weaning. Mean mating date was delayed by 1.8 days (P<0.05) in the E+ ewes. There were no significant differences in any of the other reproductive parameters measured in either year. Grazing endophyte-infected pasture had a significant (P<0.001) negative effect on ewe liveweight, which appeared to be a result of reduced feed intake by the E+ ewes. Growth rate of twin- and single-lambs suckling ewes grazing E+ pasture were significantly (P<0.01) reduced in the second year of the trial but not in the first year. Differences in lamb growth rate may have been due to differences in ewe milk production. Ergovaline and lolitrem B levels in the E+ pasture were significantly higher in 1998 than they had been in 1997. Ewe and lamb performance in relation to endophyte toxin levels in the pasture is also discussed. Keywords: endophyte, ewe, lamb growth rate, Neotyphodium lolii, perennial ryegrass, reproductive performance