The effect of repeated follicular aspiration on the onset of puberty and growth rate of winter- or autumn-born lambs

The effects of follicular aspiration for oocyte retrieval on the attainment of puberty and growth rate were studied in winter-born (9 treated and 6 control) and autumn-born (5 treated and 5 control) ewe lambs. In the treated animals (i.e. in which follicular aspiration was performed after ovarian stimulation), laparoscopic oocyte pick-up (OPU) was performed at the age of 12-13, 16-17 and 20-21 weeks. From the 8th until the 57th week of age, serum progesterone concentration was determined in blood samples collected at weekly or bi-weekly intervals. Serum oestradiol concentration was measured in blood samples collected prior to each FSH administration at OPU, and 2 and 24 h thereafter. All lambs were weighed at birth, the 6th and 8th week of age and thereafter at monthly intervals until the 34th (winter-born) or 52nd (autumn-born) week of age. Radiographic images of the right antebrachium and completion of skeletal maturation (radius) were used to assess the growth rate. Serum oestradiol concentration increased in response to FSH administration, but decreased to normal basal values 24h after OPU. Autumn-born ewe lambs attained puberty at a later stage, compared to the winter-born animals. In most OPU-treated winter-born lambs, the first luteal phase was of short duration. This was not observed ill winter-born controls, nor in any of the autumn-born lambs. No differences were detected regarding the age at the onset of puberty between treated and control animals. From the 13th to the 26th week of age, winter-born treated lambs were lighter than the controls (27.3 +/- 1.6 vs 34.3 +/- 1.9 kg at 26 weeks of age, respectively). From the 16th to 34th week of age, radius length differed between the treated and control winter-born lambs, but not between autumn-born lambs. Ossification of the radial growth plate was not complete until the 34th (winter-born labs) or the 52nd (autumn-born lambs) week of age. It is postulated that repeated OPU can be safely applied to prepubertal lambs. with no consequences on the time to onset of puberty, whilst the growth rate of donor animals is also not affected. (C) 2009 Elsevier B.V. All rights reserved