Abstract

FSH concentrations were examined in 6 FecB FecB (BB) ewe, 3 BB ram and 5 Fec+Fec+ (++) ram full-sibling pairs of Booroola Merino x Romney lambs between 2 and 20 weeks of age. The purpose of this study was to compare variation in FSH profiles within and between prepubertal full-sibling pairs of Booroola ewe and ram lambs, to evaluate their usefulness as control-treatment pairs in endocrinological studies. In ewe lambs, FSH concentrations increased with liveweight and age to reach distinct peaks at 7-12 kg liveweight and at 3-9 weeks of age. Variation between pairs was significantly greater than within pairs for liveweight at all ages, FSH concentrations up to 9 weeks of age, and maximum FSH concentration, but not for age or liveweight at peak FSH. In ram lambs, FSH concentrations were lower than in ewes but followed a similar pattern, with FSH peaks at 12-17 kg liveweight and 5-10 weeks of age. The geometric mean maximum FSH concentrations were 1.44 and 0.81 (LSR 1.78) ng/ml for BB and ++ groups respectively (P<0.05). Between- pair variation was significantly greater than within-pair variation for birth weight, liveweight to 7 weeks of age, peak FSH, and age at peak FSH. Mean FSH concentration and liveweight showed no relationship within or between ram pairs, or between ewe pairs, but the heavier sibling within all six ewe pairs had the higher FSH concentration (P<0.05) most samples up to 7 weeks of age, but not thereafter. The reduced variation in gonadotrophin concentrations within compared with between full-sibling pairs suggests they have considerable value as control-treatment animals in endocrine studies on prepubertal developments.

JC, Pollard, GH Moore, and RP Littlejohn

Proceedings of the New Zealand Society of Animal Production, Volume 51, , 43-46, 1991