Effect of teasing by the ram on the onset of puberty in Romney ewe lambs

Abstract

In two consecutive years (2008 and 2009), ewe lambs that had not attained puberty were allocated to one of two groups (Unteased [n=50 in both years] or Teased [n = 50 in 2008 and n=49 in 2009]) for 17 days (D1 to D17). In 2009, the ovaries of all ewe lambs were examined on D5, D9 and D12 by transrectal ultrasonography. From D18 to D28, crayon-harnessed teaser rams were introduced to both groups each year. In both years a greater proportion (P < 0.05) of Teased than Unteased ewe lambs achieved puberty (based on progesterone concentrations) during D1 to D17 and displayed oestrus during D18 to D28. Teased ewe lambs had larger (P < 0.05) follicle diameters on D9 and D12 compared with the Unteased but differences in corpus luteum sizes were not found (P > 0.05). We have demonstrated that teasing advances the onset of puberty. In ewe lambs that responded to teasing, it appears the response is somewhat delayed in comparison to that observed in mature ewes. © 2012 The Royal Society of New Zealand.