Ovarian mass in three mares with regular estrous cycles.

Three mares with regular estrous cycles and a large ovary were examined. In each case, the ovary was composed of a single, fluid-filled cavity with a thick capsule. The ovarian mass was surgically removed from each mare. Histologic diagnosis of each mass was different.     

Apoptosis in the porcine uterine endometrium during the estrous cycle, early pregnancy and post partum

The mammalian uterus changes dramatically during the estrous cycle, pregnancy, and involution post partum. Dynamic changes in the uterine endometrium are a type of homeostasis and proceed with proliferation and exclusion of cells. Homeostasis of the uterus is closely related to apoptosis involving various hormones and cytokines. The objective of the present study was to determine the morphological features and occurrence of apoptosis in the porcine endometrium during the estrous cycle, early pregnancy, and post partum. Cyclic changes in the morphology of the surface epithelium were observed during the estrous cycle. The heights of surface epithelia were significantly high on day 4 of the estrous cycle and the early pregnancy. The heights of the surface epithelium remained low from days 1 to 31 post partum. We then used terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end-labeling (TUNEL) of the 3'-terminal of fragmented DNA, which is effective for detection of apoptosis in various tissues. We found that apoptosis in the porcine endometrium contributed to homeostasis of the endometrium during the estrous cycle through control of cell proliferation and exclusion. Conversely, apoptosis on days 4 and 8 of gestation before the implantation window depended on the plasma estrogen and progesterone levels; however, suppressive homeostasis of apoptosis occurred at the time of implantation on days 15, 18 and 21 of gestation. Our study is the first to demonstrate apoptotic cell death in the porcine endometrium directly by TUNEL method. The results strongly suggest that uterine homeostasis is mainly controlled by apoptosis during the estrous cycle and early pregnancy.     

Thyroxine concentrations are elevated in mares which continue to exhibit estrous cycles during the nonbreeding season

In two successive years, the pattern of secretion of thyroxine was compared in seasonally anestrous mares and a subpopulation of mares that exhibited estrous cycles during the nonbreeding season. Blood samples were collected two or three times per week between October and April from a total of 15 mares that exhibited estrous cycles during the nonbreeding season and 21 anestrous mares. Monthly mean concentrations of thyroxine during the period from October through April were greater (p<0.05) in cycling versus anestrous mares. However, it remains to be determined whether continuation of estrous cycles during the nonbreeding season and elevated concentrations of thyroxine are causally related.     

Surgical results and fertility following correction of vesicovaginal reflux in mares

Objective To evaluate the surgical results and fertility of mares bred at various intervals relative to surgical management of urovagina. Design Sixty-one mares underwent surgery to correct vesicovaginal reflux. Surgery was performed at varying times relative to breeding and postoperative fertility was evaluated. Results Five mares were lost to follow-up and a further four were electively not bred. Of the remaining 52 mares, seasonal pregnancy and live foaling rates were 67% (35/52) and 54% (26/48), respectively. When mares were bred in the same cycle as the surgery, the first cycle following surgery, the second cycle following surgery or the following breeding season after surgery the seasonal pregnancy rates were 89% (8/9), 63% (10/16), 67% (2/3) and 63% (15/24), respectively. After censoring four mares that died of natural causes pre-foaling, the foaling rates were 88% (7/8), 50% (7/14), 0% (0/3), 52% (12/23), respectively. All mares bred in the same cycle as surgery or in the next cycle were bred once only that season, so the pregnancy rate per cycle of 72% (18/25) was identical to the seasonal pregnancy rate. Conclusions Good fertility (comparable to a normal population of mares) was achieved following surgery and the results suggest that delaying breeding until the following breeding season is not necessary. In addition, breeding in the same cycle as surgical repair is a previously unreported technique that should be considered to maintain a yearly foaling interval.     

Onset of luteal activity in foaling and seasonally anoestrous mares treated with artificial light.

Sixty-four mares (27 foaling, 37 barren or maiden), mainly Finnhorses, were subjected to treatment with 14.5 h of light and 9.5 h of darkness, starting at the beginning of December. The onset of cycling in non-foaling mares was estimated by weekly serum progesterone determinations. All of the non-foaling mares cycled in the middle of March. They started to cycle on average in the middle of February, 11.1 weeks after the beginning of the trial. There were statistically significant differences in relation to breed (Finnhorses started to cycle 2 weeks later than warm blooded, p less than 0.02) and in relation to age (brood mares with mean age 10 years, started to cycle 10 days later than those 3 years old, p less than 0.03). However, there was no statistical significant relation to previous lactation, although lactating mares lactating up to the previous autumn started to cycle 7 days later than dry mares (p less than 0.15). Artificial insemination of 14 mares in the 2nd oestrus of the year, in March, resulted in 12 foalings in the subsequent year (86%). The following winter, all pregnant mares (N = 27) were exposed to the same kind of light treatment, starting on 1st December. The 1st mare foaled at the end of January. The time from foaling to 1st post partum ovulation was significantly longer (17.0 days) in foalings taking place within 10 weeks from the beginning of the light treatment period, than in foalings occurring after more than 10 weeks of lighting (12.1 days) (p less than 0.01).     

Plasma levels of cortisol in zero-weaned and lactating sows during the first two weeks post partum

The object of this investigation was to study the plasma levels of cortisol during the day of parturition and the first two weeks post partum in primiparous zero-weaned (weaned within 12 hr after birth) and lactating sows. Fourteen primiparous sows were used. They were grouped as follows: group A, (3 sows) zero-weaned, ovulating; group B, (4 sows) zero-weaned, anovulatory; group C, (4 sows) lactating with normal litter size; group D, (3 sows) lactating with small litter size. The peripheral plasma levels of cortisol were determined by radioimmunoassay throughout the experimental period,The peripheral plasma levels of cortisol were significantly higher in the anovulatory than in the normally ovulating sows. The lactating sows had almost the same levels of cortisol as the zero-weaned sows with anovulatory estrus. There was no difference in cortisol levels between sows nursing small or normal litters.It may be concluded that elevated plasma levels of cortisol might be one of several factors inhibiting the LH surge during the first estrus after zero-weaning. No relationship was found between cortisol levels and number of suckling piglets.     

Progesterone therapy in mares with abnormal oestrous cycles

In two studies in Holland and France a total of 41 mares found either to be in anoestrus or showing continuous oestrous behaviour during the early part of the covering season were treated with a progesterone releasing intravaginal device. Of the 32 mares in the first study, 24 ovulated after treatment and 11 became pregnant to a covering at the induced oestrus. In the second study all but one of the nine mares showed oestrus, seven ovulated and six became pregnant at the post treatment oestrus. By the end of the covering season 15 of the 21 mares treated for anoestrus and seven of the 11 mares treated for persistent oestrus were found to be in foal.     

Cervimetry and ultrasonographic observations of the cervix regression in dairy cows during the first 10 days post partum

The aim of this study was to describe the involution process of the bovine cervix during the first 10 days post partum by using an intracervically introduced gauge and transrectal ultrasonography. Twenty-five pluriparous Holstein Friesian cows were included, which were randomized into three groups: group 1 (n = 10): transrectal ultrasonographic presentation of the formation of cervical folds; group 2 (n = 10): measurement of the reduction of the canalis cervicalis using an intracervically introduced gauge. The examinations were performed directly after expulsion and 2, 4, 6, 8, 12, 16, 18 and 24 h post partum, and in intervals of 24 h up to the tenth day. The involution process can be divided into four phases: 1: fast reduction up to the sixth hour; 2: protracted reduction up to the second day without constant formation of folds; 3: protracted reduction up to the seventh day with constant formation of folds; 4: re-opening of the canalis cervicalis maintaining the structure of the folds. The reduction process (phase 1- phase 3) can be shown as the sum of two exponential functions with different grading coefficients: y = reduction 1 x e(-b1 x t) + reduction 2 x e(-b2 x t). Reduction 1 is reduction in cm during the first phase and reduction 2 is reduction in cm during the second and the third phase. Group 3 (n = 5): to exclude an influence of the high frequency of examinations on the involution process the cows were examined immediately after parturition and on the fifth and tenth day postpartum using the same method as in groups 1 and 2. In conclusion, the involution process of the bovine cervix guarantees a fast protection of the cavum uteri and a drainage of the lochia at the end of the early puerperium. The re-opening phase after the seventh day has not yet been described in any other species and can be interpreted as the adaptation to the exsudative puerperium in the cow.     

Effects of the intensity of a post partum examination on the fertility performance of high yielding dairy cows

Two methods for a scheduled post partum examination were compared on a commercial dairy farm. In Group 1, all cows (n = 601) were examined by rectal palpation between day 20 and 26 post partum for signs of endometritis (vaginal discharge, enlarged uterus). In Group 2, all cows (n = 652) were examined by external inspection for vaginal discharge as a sign for endometritis. In both groups all cows with endometritis were treated twice with prostaglandin F2 alpha (25 mg of dinoprost) in a 14-day interval. The proportion of cows with signs of endometritis was 33.3% and 17.2% in Group 1 and Group 2, respectively (p < 0.05). In Group 1, the conception rate (39.0% vs 49.3%) and the proportion of cows pregnant (60.5% vs 72.6%) were lower for cows with endometritis than for cows without endometritis. In Group 2, no significant differences were found in reproductive performance for cows with and without signs of endometritis. No significant differences in reproductive performance were found for cows with endometritis between the two groups. Also, for cows without endometritis no significant differences in reproductive performance were found between the groups. It is concluded that the post partum examination by rectal palpation was more sensitive in finding cows with endometritis. However, with regard to the reproductive performance the more sensitive method was not more effective than the method based on systematic external inspection.