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Abstract
Data from straightbred Romney and Border Leicester x Romney ewe hoggets, born in the years 1965 to 1967, were used to describe hogget oestrous behaviour, ovulation rate, and live weight. The hoggets were grazed from birth at the Whatawhata Hill Country Research Station.
Oestrous activity extended from late March until late July, with a peak from mid May to mid June. The proportion of hoggets exhibiting oestrus in two Romney and in first-, second-, and third-cross Border Leicester X Romney flocks was 52, 64, 76, 76, and 62% respectively in single-, and 50, 50, 60, 61, and 59% in twin-reared hoggets.
Differences were found in live weights and weight gains after weaning between those hoggets which did and those which did not exhibit oestrus. In April the former were 3.9 kg heavier if born as singles and 3.0 kg heavier if twins. Classification of hoggets by the time period of first oestrus showed large differences in live weights, those which exhibited oestrus earlier being heavier at weaning, and subsequently, than those in which the breeding season commenced later. Age at first oestrus was similarly altered, but weight at first oestrus showed less variation between time periods, being, overall, 34 kg for single-born and 31kg for twin-born hoggets.
Ovulation data at first oestrus were significantly affected by flock and rank, incidence of multiple ovulations being higher in crossbreds than Romneys and higher for single- than for twin-reared hoggets.
Correlations between hogget traits are reported.