First Ovulation Of Year Research Articles

Preliminary Evaluation of Treatment With Long-Acting Estradiol Cypionate and Sulpiride for Advancing First Ovulation of Year in Postpartum Acyclic Mares

Two preliminary trials were performed to evaluate the efficacy of long-acting estradiol cypionate plus sulpiride treatment for hastening the first ovulation in postpartum acyclic mares. In 2010 (year 1) and 2012 (year 2), mares that had foaled in January or February and that were ≥7 ± 1 day postpartum were teased to a stallion to detect estrus and examined by transrectal ultrasonography 3 times weekly. Mares identified as acyclic were alternately assigned to treatments as follows: year 1—group ECP-SUL (n = 5)—same day intramuscular (IM) injection of 50-mg long-acting estradiol cypionate (ECP) plus 1.5-g long-acting sulpiride (SUL), or CON (n = 5)—control; year 2—ECP-SULX2 (n = 4)—IM injection of 100-mg ECP, followed 2 and 7 days later with IM injection of 1.5-g SUL, or CON (n = 5). When a follicle ≥35 mm in diameter, prominent uterine edema and a relaxed cervix were detected, an ovulation-inducing agent was administered. Examinations continued at 2- to 3-day intervals until ovulation was detected. Median (range) interval to ovulation did not differ in year 1 between SUL-ECP (76 days; 31–90 days) and CON mares (74 days; 35–98 days; P = 1.00), or in year 2 between ECP-SULX2 (48 days; 36–66 days) and CON mares (39 days; 39–71 days; P = .91). The injection of the dopamine antagonist sulpiride in a sustained release form in conjunction with the estrogen ECP failed to shorten the interval to the first ovulation of the year in these two groups of postpartum acyclic mares.

The outcome of the first stages of pregnancy on mares' bloodstream thyroid hormones

The objective of this study was to compare in detail the total and free iodothyronines' pattern of mares from the first ovulation of the year over an extended period of 12 weeks. A total of 20 mares were used in the study. The mares were classified into two groups: mares mated at the ovulation (n = 10) used as observational group and mares unmated at the ovulation (n = 10) used as control group. Serum total and free triiodothyronine (T3, fT3) and thyroxine (T4, fT4) levels were measured in baseline conditions at the first ovulation of year and once a week until 12 weeks later. For the experimental group, the first week of postovulation mating was considered as the first week of gestation. One-way analysis of variance showed a significant effect of time over 12 weeks for T3 (F = 2.44; P = 0.007) in pregnant mares, with the higher levels at the seventh and 12th weeks (P < 0.05) than baseline values, and for fT3 (F = 2.36; P = 0.009), with the higher levels at the 11th week (P < 0.05) than baseline values. Two-way analysis of variance showed a significant pregnancy effect compared with nonpregnancy stage for T3 (F = 15.82; P = 0.009), with the higher levels at the seventh and 12th weeks (P < 0.05) of pregnancy than that in nonpregnant values. Thus, it appears that, under similar environment, management and nutritional regime, the first trimester of pregnancy plays a dynamic role on the thyroid patterns by their anabolic activity; therefore, significant effects of time points on the T3 and fT3 concentrations probably may contribute to the control of early embryonic growth and development, before the onset of fetal thyroid activity. Considerable additional research, outwith the aim of this study, will be required to elucidate the mechanisms by which gestational age affects the physiological thyroid function in mares and/or fetus ratio in the first pregnancy stage.