Proceedings of the New Zealand Society of Animal Production. 1995,
55: 154-156
Proceedings of the New Zealand Society of Animal Production. 1995,
55: 154-156
In each year the early lambing (BV-) hoggets had an earlier (P<0.05) mean date of onset of oestrus than the hoggets from the late-lambing (BV+) line. In 1992 and 1993 this effect was confounded by the season of birth such that nearly all the BV- animals were autumn born (AB) and the BV+ animals born in the spring (SB). In 1993 animals from both lines were produced in both seasons. Their mean day of first oestrus in 1994 (expressed as day of year ± standard error) were AB BV-81 ± 3; AB BV+ 100 ± 7; SB BV- 122 ± 5 and SB BV+ 148± 5. This indicates significant effects of both season (P<0.05) and selection line (P<0.05). A greater proportion of the BV+ animals did not cycle in 1993 (18% v 2%; P<0.05) and 1994 (40% v 18%; P<0.01).
These data confirm that selection for date of lambing has a significant effect on the date of first hogget oestrus, which could be used as a screening aid in the selection process. The effect of season of birth independent of genotype is of considerable interest to the evaluation of underlying mechanisms.
Keywords: NZSAPAB; hogget oestrus; out-of-season lambing; selection lines
