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PubMed2006

Milking frequency, estradiol cypionate, and somatotropin influence lactation and reproduction in dairy cows.

Our objectives were to determine lactational and reproductive outcomes in response to increased milking frequency (MF), injection of estradiol cypionate (ECP), and treatment with bovine somatotropin (bST). Lactating dairy cows (n = 144) were blocked by lactation number (1 vs. 2+) and assigned randomly to a 2 x 2 x 2 factorial experiment consisting of 8 treatment combinations: 1) MF consisting of 4x daily milking (4x) for the first 30 d in milk (DIM) vs. 2x daily milking (2x), with all cows milked 2x after 30 DIM; 2) 10 mg of ECP given postpartum at 8 +/- 3 DIM versus controls that received ECP diluent (oil); and 3) biweekly bovine somatotropin (bST), starting sometime after 60 DIM, versus no bST. Ovulation before the first artificial insemination was synchronized by using Heatsynch (GnRH injection 7 d before PGF2alpha followed in 24 h by ECP), and cows were artificially inseminated after detected estrus or at 48 h after ECP, whichever came first. Pregnancy was assessed by transrectal ultrasonography 28 to 30 d after artificial insemination. Daily yield and weekly components of milk were measured during the first 90 DIM. Intervals to first and second postpartum ovulation were unaffected by treatment, but cows were in estrus earlier after 2x (24 +/- 4 d) than 4x (41 +/- 4 d) daily MF, and sooner after ECP (25 +/- 3 d) than after oil (39 +/- 4 d) treatment. Pregnancy rates among 4x cows increased for ECP versus oil (52.8 vs. 27.8%) more than for cows with 2x MF treated with ECP versus oil (50.0 vs. 39.4%). Increased MF increased daily milk yields and energy-corrected milk yields during the first 30 DIM. Although milk yields were increased acutely by ECP during the 10 d after its injection, subsequent milk yields were decreased for ECP-treated cows previously milked 4x daily. Treatment with bST increased overall daily milk yields most in cows previously milked 2x daily and treated with oil and those milked 4x daily and treated with ECP. We concluded that early postpartum ECP injection increased pregnancy rates, but generally had detrimental effects on milk yields after 30 DIM for ECP-treated cows previously milked 4x daily, unless those cows also were treated with bST.

Animals↗
PubMed1980

Pubertal adipose tissue: is it necessary for normal sexual maturation? Evidence from the rat and human female.

The high percentage of fat (about 26-28%) in the mature human female may influence reproductive ability directly: 1) as an extragonadal source of estrogen; and 2) by influencing the direction of metabolism of estrogen to the most potent or least potent forms. The slow maturation of the hypothalamus and pituitary up to menarche, or first estrus, is accompanied by a slow maturation of the body, which changes not only in size but in the relative proportion of bone, muscle, and fat. Evidence is presented that a particular ratio of fat to lean mass is normally necessary for puberty and the maintenance of female reproductive ability in the human and rat. The synchronizing signals may be metabolic, relating food intake to core temperature and fat depots.

Adipose Tissue↗
PubMed2002

Stage of the estrous cycle at the time of pregnant mare's serum gonadotropin injection affects pre-implantation embryo development in vitro in the mouse.

The present study aims to analyze in the mouse the effect of the stage of the estrous cycle at the time of pregnant mare's serum gonadotropin (PMSG) injection on fertilization of ovulated cumulus-enclosed oocytes and later embryo development in vitro to the blastocyst stage. Quality of blastocysts was evaluated by staining and counting of total number of nuclei, mitotic index, percentage of apoptotic nuclei, and cell allocation to the inner cell mass (ICM) and trophectoderm (TE) lineage. Superovulation of hybrid (C57Bl/6JIco female x CBA/JIco male) female mice of 4-6 weeks of age was induced by a priming injection of PMSG at different stages of the estrous cycle followed after a 48-hr interval by human chrorionic gonadotropin. Our data indicate that injection of PMSG at the estrus phase gives the best outcome whereas injection of PMSG at the diestrus-1 or diestrus-2 phase provides the worst results. In fact, (1) total number of oocytes ovulated, number of ovulated oocytes enclosed by cumulus cells, and number of TE cells in day-5 blastocysts were significantly lower in diestrus-1 females than in estrus, diestrus-2 and proestrus mice; (2) percentage of day-5 blastocysts and total number of cells in day-5 blastocysts were lower in diestrus-1 and diestrus-2 females than in estrus and proestrus mice; and (3) percentage of apoptotic nuclei in day-5 blastocysts was lower in estrus mice than in diestrus-1, diestrus-2, or proestrus females. These data endorse previous studies suggesting that administration of gonadotropins in mice should be synchronized with the innate estrous cycle of females.

Analysis of Variance↗
PubMed2002

Induction of estrus during the non-breeding season in Egyptian Baladi goats.

The induction of estrus during the non-breeding season was investigated in 100 Egyptian Baladi goats (Capra hircus). All animals assigned to treatments had low progesterone concentrations (<0.5 ng/ml) tested 2 times 10 days apart to confirm anestrous condition. Animals were assigned to three experimental groups. A group of animals received subcutaneous norgestomet ear implant for 11 days and a single i.m. injection of PGF2alpha 24 hr before implant removal (group I; n=40). Second group of animals received subcutaneous norgestomet ear implant for 11 days and a single i.m. injection of PGF2alpha 24 hr before implant removal and gonadotropin releasing hormone 24 hr after implant removal (group II; n=40). Third group of animals received no treatment (control group; n=20). The percentage of goats that showed estrous behavior during the first 72 hr after implant removal was 77.5, 85.0% and 10.0% in group I, group II and control group, respectively. The fertility rate was 57.5, 70.0% and 10.0% in group I, group II and control group, respectively. In conclusion, estrus can be induced in seasonally anestrous Egyptian Baladi goats using norgestomet and PGF2alpha and the injection of GnRH 24 hr after norgestomet implant removal synchronized ovulation in a higher percentage of goats.

Animals↗
PubMedDate not supplied

Effects of in-phase and out-of-phase ovulation induction on early mouse embryos.

The effects of ovulation induction on pre-implantation embryos (day 4 of gestation) were studied in mature cycling mice (the Jcl:ICR strain) using relatively small doses of pregnant mare's serum (PMS)/human chorionic gonadotropin (HCG) (2.5 or 5 IU each) given at two different stages (in-phase or out-of-phase to the estrous cycle). The proportion of degenerated embryos was increased and the development of the embryos was retarded in the treated groups, especially in the out-of-phase subgroups. Therefore, we propose that the use of PMS/HCG for ovulation induction should be more restricted in mouse reproductive experiments when mature females are used, and that, even when ovulation induction is used, a treatment synchronized to the spontaneous estrous cycle should be elected.

Animals↗
PubMed1996

Prolonged dominance of follicles and reduced viability of bovine oocytes.

Prolonging the lifespan of bovine follicles is known to result in reduced fertility after ovulation and insemination. In this study, the effect of prolonged development of follicles on oocyte viability was examined. In Expt 1, six cows in the aspirated-prolonged-follicle group received a vaginal progesterone releasing device on day 4 of the oestrous cycle (day 1 = ovulation) and prostaglandin F2 alpha (40 mg) on day 6. Ultrasound-guided follicular aspiration was performed on day 13. Six cows in the aspirated-growing-follicle group received prostaglandin F2 alpha on day 6, and follicular aspiration on day 7. In Expt 2, all cows were stimulated with 36 mg FSH-P to develop multiple large follicles for study. Three cows in the prolonged-multiple-follicle group received the same treatment as did cows in Expt 1, but were ovariectomized on day 13. Three cows in the growing-multiple-follicle group received prostaglandin F2 alpha on day 6 and were ovariectomized on day 7. Oocytes recovered in both experiments were stained to reveal the stage of nuclear development. All oocytes from aspirated-prolonged and prolonged-multiple follicles showed expanded cumulus cells and condensed chromatin dispersed in the ooplasm, with possible germinal vesicle breakdown. Oocytes from aspirated-growing and growing-multiple follicles showed compact cumulus cells and an intact germinal vesicle. Plasma concentrations of oestradiol in both growing follicle groups increased until oocyte recovery. Oestradiol in the aspirated-prolonged-follicle group increased after luteolysis on day 6 and remained high until follicular aspiration. In contrast, in the FSH-stimulated prolonged-multiple-follicle group, oestradiol fell to trace amounts on day 8 and remained low. Oestradiol concentrations in follicular fluid were consistent with plasma concentrations for all groups. Bovine oocytes from prolonged dominant follicles undergo premature maturation in vivo, which perhaps accounts for the poor fertility observed in other studies when oestrous synchronization with progestins prolongs follicle lifespan.

Animals↗
PubMed1988

Effect of insemination timing on the fertilizing capacity of frozen/thawed equine spermatozoa.

A breeding trial was conducted to evaluate the effect of insemination timing on the fertility of mares bred with frozen/thawed equine semen. One stallion and 60 reproductively sound, estrous-synchronized mares were included in the study. Mares were assigned to one of three groups (n = 20): 1) insemination with fresh semen every other day during estrus from detection of a 35-mm follicle until ovulation, 2) insemination with frozen/thawed semen every day during estrus from detection of a 35-mm follicle until ovulation or 3) insemination with frozen/thawed semen once, within 6 h after ovulation. Single-cycle 18-d pregnancy rates resulting from insemination with fresh semen (70%), preovulation insemination with frozen/thawed semen (60%) and postovulation insemination with frozen/thawed semen (55%) were not different (P > 0.05). Possibly, equivalent pregnancy rates could be achieved with frozen/thawed semen using either daily inseminations until ovulation occurs or frequent ovarian palpations with a single post-ovulation insemination. Further studies regarding the effect of insemination timing on stallion fertility are needed since the present investigation included only one stallion and a small number of mares.

Journal Article↗