No abstract

No abstract

Introduction.

No abstract

No abstract

Summary. Large White gilts, 9 to 18 months old, that had exhibited at least two natural oestrous cycles were divided into three groups (phases): unmated pre-ovulatory, unmated post-ovulatory and mated post-ovulatory (n = 16, 20 and 18). Oviductal luminal fluid samples were collected under anaesthesia by micropipette from the ampulla and ampullary\p=n-\isthmicjunction and analysed by an ultramicrofluorometric technique. Glucose concentrations (mmol l \ m=-\ 1, means combining regions; mean \ m=+-\ sem)were significantly higher in blood plasma than in oviductal fluid (4\m=.\56 \ m=+-\0\m=.\20versus 0\m=.\59\ m=+-\0\m=.\16;P < 0\m=.\0001; n = 27), whereas lactate was higher in the oviduct (5\m=.\71\ m=+-\ 0\m=.\53versus 2\m=.\480\m=.\24;P < 0\m=.\0001; n = 27). No significant differences were found between the ampulla and the ampullary\p=n-\isthmicjunction. However, the concentration of glucose was significantly higher (P < 0\m=.\05) in the ampulla of the pre-ovulatory group (0\m=.\97 \m=+-\0\m=.\20;n = 13) compared with the mated group (0\m=.\25 \m=+-\0\m=.\05;n = 14) and its concentration in the ampullary\p=n-\isthmicjunction in the pre-ovulatory group (1\m=.\65\ m=+-\ 0\m=.\63; n = 13) was significantly greater (P < 0\m=.\05) than in the post-ovulatory (0\m=.\43 \ m=+-\0\m=.\11 ; n = 11) or mated groups (0\m=.\17 \ m=+-\ 0\m=.\02; n = 14). Lactate in the ampulla of mated animals was higher than in the pre-ovulatory group (6\m=.\83 \m=+-\0\m=.\70versus 3\m=.\86\ m=+-\0\m=.\38;P < 0\m=.\05;n = 15 and 13), but neither was significantly different from the post-ovulatory group. Furthermore, no change was seen at the ampullary\p=n-\isthmic junction in lactate concentration with phase. Pyruvate concentrations showed no differences with phase, region or with plasma (oviduct 0\m=.\21\ m=+-\ 0\m=.\02;plasma 0\m=.\14\ m=+-\ 0\m=.\01; n = 27 and 26). Glucose concentration within the oviduct decreased at a time when gametes or embryos, with their liberated cumulus cells, were present. Consequently it is evident that the microenvironment of the gametes and embryos is changing and, in the light of these measurements, the composition of the media used for in vitro culture experiments may require modification to reflect the physiological levels more closely.

The incidence of early foetal loss is increasing under intensive management systems for dairy cattle. The aims of the present study were to determine whether there is any peak period of pregnancy loss during the early foetal period and to evaluate possible differences between single and twin pregnancies. The study population consisted of 1442 pregnant cattle from a single herd. Pregnancy was diagnosed by transrectal ultrasonography between 36 and 42 days after insemination, and then weekly until day 90 of gestation or until pregnancy loss. A total of 1310 cows (90.8%) bore single embryos and 132 (9.2%) carried twins. Pregnancy loss was registered in 139 (9.6%) cows before day 90 of pregnancy: 101 (7.7%) in single and 38 (28.8%) in twin pregnancies. The average time of pregnancy loss for all animals was 58.4 +/- 12.6 days and ranged from 45 to 90 days. Seventy-five per cent of the pregnancy losses were registered between 45 and 60 days of gestation. The average time of pregnancy loss for cows with singletons was 52.1 +/- 4.1 days and ranged from 45 to 61 days and that for those with twins was 75.1 +/- 12.4 days and ranged from 46 to 90 days. Seventy-five per cent of the twin pregnancy losses were registered between 68 and 90 days of gestation. Our data show that the foetal loss in singleton pregnancies occurs earlier than in twin pregnancies. Assessment of normal development of gestation on days 60 and 90 after insemination is suggested.

Temperature gradients in female reproductive tissues seem to influence the success of key processes such as ovulation and fertilization. The objective of this study was to investigate whether pre-ovulatory follicles are cooler than neighbouring uterine tissue and deep rectal temperatures in lactating dairy cows under heat stress conditions. Temperatures within the pre-ovulatory follicle, on the uterine adjacent surface and 20 cm deep within rectum, were measured using fine thermistor probes within 45 min after sunrise (dawn). Cows were selected from synchronized groups for fixed-time insemination during the warm period of the year. Five cows under direct sun radiation and 11 cows in the shade were included in the study. None of the cows in the sun area ovulated within 24 hr, whereas 10 of the 11 cows in the sun area ovulated. Four of the 10 ovulating cows became pregnant. In the ovulating cows, follicular temperatures were 0.74 and 1.54°C significantly cooler than uterine surface and rectal temperatures, respectively, whereas temperatures in the uterine area were 0.80°C significantly cooler than rectal temperatures. No significant differences among temperatures were found in non-ovulating cows. Follicular size was similar for ovulating and non-ovulating cows. Environmental temperatures in the shade area were 6.4°C significantly lower than those in the sun area. Results of this study indicate that pre-ovulatory follicles are cooler than neighbouring uterine tissue and deep rectal temperatures and those temperature gradients were not found in cows suffering ovulation failure.