Seasonal reproduction in ewes selected on seasonal changes in wool growth.

Romney and Perendale ewes were selected on the amplitude of seasonal wool growth. The ewes were fed a constant plane of nutrition and run with vasectomized rams. Ovarian activity was recorded by laparoscopy during 11 months. Ewes with a low amplitude of seasonal wool growth (Group L) had a 68% higher wool growth rate in winter and a 17% lower wool growth rate in summer compared with ewes with a high amplitude (Group H). There was no difference between the groups in the date of the first mating mark. Ewes in Group L entered anoestrus significantly later than did ewes in Group H; the difference was 11 days in the mean date of the last mating mark and 17 days in the mean date of the last ovulation. A significantly higher proportion of ewes in Group L ovulated during July to November. In addition, ewes in Group L had a significantly higher proportion of multiple ovulations throughout the experiment: on average the difference between the groups was 0.21. These results show that phenotypic selection for a low amplitude of seasonal wool growth resulted in a delay in the end of the breeding season associated with an increase in ovulation rate, suggesting independent effects on the beginning and end of the breeding season.

Haematological factors associated with avascular necrosis of the femoral head in homozygous sickle cell disease.

The haematological indices in 50 patients with homozygous sickle cell (SS) disease and avascular necrosis of the femoral head and in 180 patients with SS disease without this complication have been compared. Avascular necrosis of the femoral head was significantly associated with high total haemoglobin levels and with low fetal haemoglobin levels. Low fetal haemoglobin levels are associated with increased intravascular sickling. These results suggest that both intravascular sickling and the increased viscosity associated with high haemoglobin levels are related to the development of avascular necrosis of the femoral head in SS disease.

Haematological factors associated with avascular necrosis of the femoral head in homozygous sickle cell disease

The haematological indices in 50 patients with homozygous sickle cell (SS) disease and avascular necrosis of the femoral head and in 180 patients with SS disease without this complication have been compared. Avascular necrosis of the femoral head was significantly associated with high total levels and with low fetal haemoglobin levels. Low fetal haemoglobin levels are associated with increased intravascular sickling. These results suggest that both intravascular sickling and the increased viscosity associated with high haemoglobin levels are related to the development of avascular necrosis of the femoral head in SS disease. (AU)