This study reports the results of the first cross breeding of Romney ewes with Wiltshire rams as part of a grading-up transition. Romney mixed-age ewes were bred to either Romney (n=200) or Wiltshire rams (n=349) in March 2020. Ewe breeding pattern (cycle bred), reproductive performance (pregnancy and fecundity rates) and lambing performance (lambing rate, lamb birth and weaning live weight and lamb survival) were recorded. The reproductive performance of ewes bred to either Romney or Wiltshire rams showed few differences. There were no differences (P>0.05) in pregnancy, fecundity or lambing rates of ewes bred to either Romney or Wiltshire rams although minor differences (P<0.05) in the breeding pattern were observed. Lamb live weights at birth and in mid-lactation did not differ (P>0.05) among single, twin and triplet lambs sired by either Romney or Wiltshire rams, however at weaning Romney-sired triplet lambs were heavier than Wiltshire triplets (P<0.05). At weaning, a small percentage (1.6%) of Wiltshire lambs showed early signs of fleece shedding. Combined, these results suggest that in this flock there was little impact of introducing Wiltshire rams to a mixed-age Romney ewe flock on ewe reproductive performance and the growth of the F1 progeny to weaning. Keywords: Wiltshire; Romney; reproduction; growth; shedding

RA, Corner-Thomas, AL Ridler, PR Kenyon, HT Blair, and ST Morris

New Zealand Journal of Animal Science and Production, Volume 81, Online, 136-140, 2021
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