The incidence of oestrus (6/46) and ovulation (14/46) in ewes given antisera to androstenedione, oestrone, oestradiol and testosterone either separately or as a mixture of these sera at the time of treatment with progestagen sponges alone or progestagen sponges followed by LH-RH was similar to that of control ewes (2/13 and 6/13 respectively). The number of corpora lutea (CL) recorded for those...

Plasma progesterone concentrations measured by radioimmunoassay in the Natal clinging bat remained below 2.01 ng/ml during lactational anoestrus but increased significantly during the period of delayed implantation. Values peaked at implantation but were followed by a significant decrease thereafter. Concentrations remained low (less than 6.0 ng/ml) during the initial period of fetal developmen...

A seasonal infertility in pig breeding herds is observed in Australia and overseas. It is characterised before mating by an increase in the incidence of anoestrus, delayed puberty in gilts and prolonged wean-to-mate intervals, and after mating by reduced conception rates, delayed returns to service, an increase in sows not-in-pig when due to farrow and possibly by increased abortions. Litter si...

Cape porcupines, Hystrix africaeaustralis, apparently have a wide ecological tolerance and are found extensive­ ly throughout Southern Africa. These fossorial hystrico­ morph rodents are monogamous, live in extended family groups, breed seasonally in summer rainfall areas, and adult pairs produce only a single litter each year. A litter interval ofabout one year is maintained through lactationa...