Reproduction in flocks selected for and against lamb faecal egg count

W.H. McMillan, D.R.H. Hall, T.G. Watson

AgResearch, Whatawhata Research Centre, Hamilton, New Zealand

Proceedings of the New Zealand Society of Animal Production. 1992, 52: 65-68

Fifty nine mixed age ewes from high (H) and low (L) faecal egg count (FEC) selection lines were used in a MOET programme. Three years of reproductive data were also recorded in 714 ewes from the 2 selection lines and their control line (C). The mean (±SEM) total number of follicles >1.5 mm diameter on the surface of the ovary was high (P<0.05) in L compared with H ewes (13.2 ± 0.9 and 10.9 ± 0.9. Embryo survival rate was 86% in L ewes and 60% in H ewes (P<0.05).

Ewe fertility, litter size, lamb survival and weaning rate in H, C and L ewes were 72%, 73% and 75%; 1.40, 1.43 and 1.47; 71%, 77% and 77%; and 72%, 80% and 84%.

These results demonstrate that some reproductive parameters are higher in L ewes compared with H ewes. There is some direct evidence (from MOET studies) as well as indirect evidence (from flock litter size data) that embryo survival is enhanced in L ewes. It is unlikely that this is a correlated genetic response, but is more likely an effect of the foundation ewes selected.

Keywords: NZSAPAB; Sheep; internal parasites; reproduction; MOET; embryo survival; selection lines; FEC.

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Last Updated 25-01-1997