Summary. An experiment is described in which spermatozoa were recovered from genital tracts of ewes either at the first oestrus following progestagen synchronization or at a normal oestrus.Recoveries 1, 12, 24, 36 and 48 hr after the insemination of 500\m=x\106 spermatozoa show that synchronization with intravaginal sponges impregnated with the synthetic progestagen 17\g=a\-acetoxy-9\g=a\-fl uoro-11\g=b\\x=req-\ hydroxypregn-4-ene-3,20-dione (Cronolone, Searle) alters the numbers and distribution of spermatozoa throughout the female genital tract at the first oestrus after treatment.One hour after insemination the total numbers of spermatozoa recovered, and their distribution between the various regions of the tract, differed little between progestagen-treated and untreated ewes. Thereafter the numbers recovered from treated ewes were significantly fewer than from untreated, and their distribution differed. Significant differences appeared in the vagina at 12 hr and in the cervix and uterus at 24 hr and thereafter this difference was maintained. The pattern in the Fallopian tubes followed that of the uterus. At 24 hr the mean numbers of tubal spermatozoa recovered were: synchronized\p=m-\900; non-synchronized\p=m-\8200(P< 0\m=.\001).Both transport and survival of spermatozoa may be deleteriously affected in the reproductive tract of the progestagen-treated ewe.

Summary. The oestrous response and subsequent fertility to natural service of 360 cyclic Merino ewes were studied following treatment with intravaginal sponges impregnated with three dose levels of 'Cronolone' (9\g=a\-fluoro-11\g=b\-hydroxy-17\g=a\-acetoxy-progesterone;Searle) and dried either in an oven or at ambient temperature. Sponges were inserted for 8 or 16 days and ninety were assayed for residual steroid after withdrawal.The rate of absorption of Cronolone was a linear function of the amount present at any time, and was affected by the method of drying (oven>air dried;;P<0\m=.\002) and initial dose (10>20>30 mg; P<0\m=.\002).The overall oestrous response with oven-dried sponges was higher than that with air-dried (P<0\m=.\05) but the slight difference in fertility was not significant. There was an additive linear effect of dose of Cronolone (10, 20 and 30 mg) on percentage of ewes in oestrus (75\m=.\8, 81\m=.\7,83\m=.\3;N.S.), oestrous ewes which lambed (61\m=.\5,65\m=.\3,74\m=.\0;N.S.), and total ewes which lambed of ewes treated (46\m=.\7,53\m=.\3,61\m=.\7;P<0\m=.\05).The significant interactions showed the 30-mg oven-dried sponge, which released approximately 13\m=.\4mg Cronolone over a 16-day insertion period, to be highly effective. All of thirty ewes treated were in oestrus within 5 days of cessation, and 22 (73\m=.\3%) lambed as a result of service at that oestrus.

An experiment is described in which the effects of time of mating within the breeding season, farms, and ewe age on patterns of oestrous activity and other reproductive parameters in the New Zealand Romney ewe were examined. The following results were obtained: (i) The patterns of oestrus on each of five farms situated at varying altitudes, over nine 17 day periods of mating from January to June, followed that of a sigmoid curve (P < 0.001). The patterns of oestrous activity on farms 4 and 5 (situated at 1500 and 2000 ft), when compared with the three lower properties, were characterized by a later onset, a shorter period of peak activity, and an earlier decline in the proportion of ewes in oestrus (P < 0.001). The proportion of ewes 1.5 years old which exhibited oestrus was less than in the other three age groups studied: 1.5 years 53.2%, 2.5 years 57.7%, 3.5 years 56.3%, 4.5 years 58.1% (P < 0.01). (ii) The proportion of ewes which returned to service was lower the later the mating (P < 0.001). The incidence of barrenness in ewes which had failed to return to a single service and were therefore considered pregnant increased linearly with time of mating (P < 0.001). (iii) Of the ewes in oestrus, 78.8 % lambed to a single service. There was a significant linear increase in the proportion of ewes lambing to those in oestrus with time of mating (P < 0.001). Further, less ewes lambed to a single service on farms 4 and 5 than on farms 1, 2, and 3 (P < 0.01). (iv) There were significant differences in total and live lamb production with time of mating (0.01 > P > 0.001), between farms (P < 0,001), and between ewe ages (P < 0.001). Multiple births reached a peak at mid-season. Interactions of time of mating with ewe age for multiple births, and with farms for live lamb production, were also significant (P < 0.01). (v) The incidence of perinatal losses to 3 days after birth showed a highly significant difference between farms (P < 0.001). There was also a mid-season rise in lamb losses (P < 0.001) and this accounted for a non-seasonal peak period in live lamb production measured as a ratio either to ewes lambing or to ewes in oestrus. (vi) The performance of maiden ewes (1.5 years) was lower than that of the other three age groups for proportions in oestrus, multiple births, and the ratios of live lambs to both ewes lambing and ewes in oestrus. No significant differences were demonstrated in returns to service, in barren ewes, or in the proportion of dead to total lambs born for this age group.

No abstract

The .results of a survey conducted during 1962-67, which examined the reproductive performance of commercial pure-bred Romney flocks in five geographical areas throughout New Zealand, are given. Within each area, flocks were grouped into one of four property-type classifications: unimproved hill, improved hill, rolling, hill, and intensive flat land. Overall, the reproductive performance of approximately It million ewes was examined.Significant between-area differences were demonstrated in the age structure of flocks, the time and duration of mating, and the percentages of barren ewes, ewes lambing, and ewes which lost all their lambs. Significant linear increases in lamb tailing and weaning percentages were shown from north to south. There were highly significant interactions between areas and property types in the time of mating and the percentages of Iambs tailed and weaned.Significant between-year differences were demonstrated in the age structure and mean size of flocks and in lamb tailing and weaning percentages, which increased linearly from 1962-65 inclusive.