The date of onset of puberty in ewe lambs as an indicator of the ability to breed out-of-season

J.F. Smith, J. Parr, D.L. Johnson, D.M. Duganzich

AgResearch, Ruakura Agriculture Centre, Private Bag 3123, Hamilton, New Zealand

Proceedings of the New Zealand Society of Animal Production. 1993, 53: 299-302

The breeding values for date of lambing (BV) for these animals were calculated from a pedigree and performance database. Multiple regression analysis were performed to determine the value of factors associated with hogget oestrus for predicting BV. While all the factors analysed, date of puberty, age and weight at puberty and number of subsequent oestrus cycles, had significant effects, none were as useful a predictor as date of birth(Bday). Season of birth (autumn vs spring) also exerted considerable influence on date of first tup and number of cycles. The results indicate that the best method of selection at present is that based on date of birth. Further research is needed to understand the interaction between season of birth and BV as they influence the onset of puberty.

Keywords: NZSAPAB; Puberty; ewe lambs; out-of-season breeding; breeding values.