02353naa a2200301 a 450000100080000000500110000800800410001910000180006024501050007826000090018352015210019265000240171365000200173765000170175765000100177465000160178465000210180065000110182165000170183265000100184965000100185965000170186965300240188665300200191065300180193065300140194877300890196215205452023-06-13       1972    bl uuuu     u00u1 u    #d1 aCLARKE, J. N.  aCurrent levels of performance in the Ruakura fertility flock of Romney sheep.h[electronic resource]  c1972  aAbstract: Data are presented for a flock of mixed-age Romney sheep established in 1948 as a long-term two-way selection experiment comprising animals selected for a high incidence of multiple births (H line), a low incidence of multiple births (L line) and a control (C line). The average reproductive performance of 2 to 4 year old ewes in the H line has shown a gradual but erratic increase relsative to the C line at an average annual rate of round 13/4 !ambs born and 11/2 lambs docked per 100 ewes mated. By contrast, there has been little consistent change in overall reproductive performance in the L line relative to the C line. Over the period 1967-70, respect.ive reproductive performance averaged for 2- to 4-year-old-ewes in the H, C and L lines was: 0.93, 0.89 and 0.84 for the ratio of ewes lambing per ewe present at lambing; 1.62, 1.22 and 1.13 for the ratio of lambs born per ewe lambing (litter size); and 0.78, 0.78 and 0.88 for the ratio of lambs docked per lamb born. Thus, relative to the C line, litter size made the greatest contribution ,to the superior overall reproductive performance of the H line, while for the L line, improved lamb survival was compensated for by a small increase in barrenness and a small decrease in litter size. Data on the growth and wool production of ewe hoggets born over the period 1965-8 are indicative of a small positive correlated response in liveweight at 14 to 16 months of age and a small negative correlated response in lamb and hogget wool production.  aGenetic improvement  aMultiple births  aReproduction  aSheep  aCrescimento  aGenética Animal  aManejo  aMelhoramento  aOvino  aRaça  aReprodução  aDesperdício animal  aEscore corporal  aPeso corporal  aPeso vivo  tProceedings of the New Zealand Society of Animal Productiongv. 32, p. 99-111, 1972.