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PubMed2007

Patterns of late embryonic and fetal mortality and association with several factors in sheep.

Embryonic and fetal mortality reduce lambing rates and litter sizes, thus contributing to economic losses in the sheep industry. In the current study, the timing of late embryonic and fetal loss in ewes and the factors with which these losses were associated were examined. Ewes lambing and lambs born were compared with pregnancy diagnosis and counts of embryos by ultrasonography near d 25, 45, 65, or 85 of gestation. Approximately 19.9% of the ewes experienced late embryonic loss, fetal loss, or both; and 21.2% of the embryos or fetuses were lost from d 25 to term. Potential offspring were lost throughout gestation; 3.7% of embryos from d 25 to 45, 4.3% of fetuses from d 45 to 65, 3.3% from d 65 to 85, and 11.5% from d 85 to parturition; thus, approximately 3 to 4% of the potential offspring were lost for each 20-d period of pregnancy beyond d 25. A greater proportion of ewes lost one (36.7%) rather than all (20.5% single; 3.8% multiple) embryos or fetuses. The patterns of loss were similar in ewes mated during the anestrous season and the transitional period and did not vary with service period within breeding season or method of synchronization of estrus. Late embryonic or fetal losses were not related to the temperature-humidity index. Maternal serum collected near d 25, 45, 65, or 85 of gestation was assayed for concentrations of progesterone, estradiol-17beta , and vascular endothelial growth factor (VEGF). The proportions of embryos or fetuses lost were associated with breed type (P < 0.05), as were concentrations of progesterone (P < 0.01), estradiol (P < 0.05), and VEGF (P < 0.01). The relationships of loss or retention of pregnancy to hormonal variables at the 4 stages studied were limited. Complete and partial losses increased rapidly as maternal progesterone at d 25 decreased below 2 ng/mL (P < 0.05). Survival of fetuses within a litter from d 25 to 65 was greater for ewes with medium concentrations of VEGF near d 25 and from d 65 to parturition was greater for ewes with high concentrations of VEGF near d 45 (P < 0.05). In summary, late embryonic or fetal losses occurred from d 25 throughout gestation and varied with breed type and with concentrations of progesterone in maternal serum on d 25.

Abortion, Veterinary↗
PubMed1981

Endogenous hormone response and fertility in dairy heifers treated with norgestomet and estradiol valerate.

Seventy postpuberal dairy heifers were assigned to remain untreated (n = 26) or to receive the Syncro-Mate-B (SMB) treatment (n = 44). Untreated heifers were inseminated at 12 hr after detection of estrus, while SMB-treated heifers were inseminated either at 48 hr after implant removal (group 1) or at 12 hr after detection of estrus (group 2). Jugular blood was collected at regular intervals from four untreated heifers and from 20 SMB heifers. In untreated heifers, estradiol-17 beta (E) was unchanged throughout the estrous cycle. Progesterone (P) reached maximum concentrations during the luteal phase and then declined to less than 2 ng/ml before estrus. Follicle stimulating hormone (FSH) ranged between 50.1 and 100.2 ng/ml during the estrous cycle, then reached a peak (P less than .05) concentration of 516.2 ng/ml coincident with peak luteinizing hormone (LH) concentration at 12 hr after the detection of estrus. In SMB-treated heifers, plasma E increased by 12 hr after injection of estradiol valerate and then declined throughout the rest of the sampling period. P declined to less than 2 ng/ml by 24 hr after administration of the SMB treatment and remained low throughout the sampling period. FSH declined in response to SMB treatment, then reached a peak (P less than .05) concentration coincident with peak LH 40 hr after implant removal. First service pregnancy rates among the untreated, group 1 and group 2 heifers, were 65, 58 and 38%, respectively, and did not differ (P greater than .05). SMB treatment was effective in inducing luteolysis and in suppressing estrus and peak gonadotropin release. Intervals from implant removal until estrus and from implant removal until peak gonadotropin release were highly variable among SMB-treated animals.

Animals↗
PubMed1982

Reproductive response of progestogen-treated sheep in confinement to a single and double insemination.

The reproductive responses to one and two inseminations of fresh extended semen were compared in crossbred sheep housed in confinement. In three trials, ewes in progestogen-induced estrus were inseminated 54 to 56 h after sponge removal. Half the ewes received a second insemination 4 or 5 h later. Resultant fertility, litter size and embryonic mortality indicated no advantage to a double insemination. Conception rates to one and two inseminations according to d 18 plasma progesterone levels were 66 and 63%, 85 and 86% and 74 and 80% in trials 1, 2 and 3, respectively. Corresponding lambing rates were 55 and 56%, 73 and 69% and 67 and 76%. Mean litter sizes were 2.1 and 2.5, while embryonic mortality after the first 2 wk of pregnancy was estimated at 13% for both groups. Single inseminations therefore simplify artificial insemination and double the number of ewes that can be inseminated/ejaculate.

Animals↗
PubMed1983

Influence of supplemental light on sow performance during and after lactation.

A completely randomized block experiment with two treatments was designed to investigate the effect of supplemental light on sow performance during and after lactation. Crossbred multi- and primiparous sows were exposed to either limited (control, n = 164) or 16 h (n = 163) timer-controlled supplemental light beginning 3 to 9 d before expected farrowing. Overhead illumination (32 to 266 lux) was furnished by seven fixtures (two tubes each) of cool white fluorescent light at twice-daily feedings in control rooms (less than 1 h/d) and for 16 h/d in supplementally lighted rooms (16 h). Litter size was equalized within 48 h postpartum (10 +/- .1 pigs/litter; X +/- SE) in each of five identical rooms that served alternately as control or 16-h treatments during 10 consecutive weekly farrowings (September 24 to November 26, 1981). Litters were heavier (P less than .05) at weaning (26 +/- .1 d) for 16-h than for control sows (57.8 +/- 1 vs 54.3 +/- 1 kg) while pigs weaned (9.2 +/- .1 vs 9.1 +/- .1), piglet survival (90 vs 91%) and days to mating (5.9 +/- .4 vs 5.5 +/- .3) were similar (P greater than .05). However, more (P less than .01) 16-h than control sows (83 vs 68%) were mated by 5 d postweaning. Multiparous sows weaned heavier (P less than .05) litters than primiparous sows (57.9 +/- 1 vs 50.1 +/- 1 kg) while overall litter weight increased (P less than .05) 141 +/- 6 g for each 10 lux increase in light intensity. We concluded that litter weight is increased and return to postweaning estrus more synchronous when sows are exposed to 16 h supplemental ligh/d during a 4-wk lactation.

Animals↗
PubMed1985

Increased ovulation rate of adult ewes treated with anti-bovine LH antiserum during the normal breeding season.

Adult Suffolk ewes (n = 14) were treated on d 10 of the estrous cycle with anti-bovine luteinizing hormone (LH) antiserum. Control ewes (n = 10) were treated with normal horse serum. Estrous behavior and the number of corpora lutea and ovarian follicles were examined at the subsequent estrous cycle. Daily plasma concentrations of progesterone (P4), follicle stimulating hormone (FSH) and estradiol were determined before and after treatment. Ewes treated with antiserum had a higher (P less than .05) ovulation rate (2.7 +/- .2) than did controls (2.1 +/- .1). No differences were found in the numbers of large (greater than 5 mm) or small (less than 5 mm) follicles between treatment groups. Estrus was delayed (P less than .025) approximately .6 d/in ewes treated with antisera. Immunoreactive FSH increased (P less than .05) within 1 d after treatment and remained higher than the controls for 5 d. Peak estradiol concentrations occurred on d 17 for treated ewes compared with peak concentrations on d 15 or 16 for control ewes. The P4 concentrations were generally less (P less than .025) in treated ewes throughout the luteal phase of the treatment cycle. These data demonstrate that ovulation rate is increased in ewes treated with LH antiserum. The marked increase in plasma FSH suggests a possible mechanism whereby ovulation rate is enhanced.

Animals↗
PubMed1989

Induction of fertile estrus in prepuberal gilts by treatment with a combination of pregnant mare's serum gonadotropin and human chorionic gonadotropin.

Ten trials involving 678 presumed prepuberal gilts (5.5 to 7.5 mo old) were conducted in North Carolina, Illinois and Missouri to evaluate the reproductive performance of gilts given a combination of 400 IU of pregnant mare's serum gonadotropin and 200 IU of human chorionic gonadotropin (P. G. 600). Gilts that were presumed to be prepuberal received P. G. 600 or no treatment (control) on the day of movement from finishing facilities to pens for breeding. Detection of estrus, with the aid of mature boars, was conducted daily for 28 d; gilts in estrus were mated naturally. Treatment with P. G. 600 increased the percentage in estrus within 7 (57.5 vs 40.9%) or 28 d (72.9 vs 59.5%); average interval to estrus was reduced (P less than .05) from 10.4 to 7.5 d. Farrowing rate (78.5 +/- 3.1%), number of pigs born alive (8.6 +/- .2) or dead (.26 +/- .06) and number of pigs weaned (8.0 +/- .2) were unaffected by treatment. Gilts that were heavier than the median for each farm were in heat sooner and more were detected in heat, but no other reproductive traits differed between heavy and light gilts. Overall, the results reveal that P. G. 600 was useful for induction of fertile estrus in prepuberal gilts.

Analysis of Variance↗
PubMed1989

Conception rates in early postpartum ewes bred naturally or by intrauterine insemination.

Ewes were treated with a medroxyprogesterone acetate (MAP) sponge for 8 d followed, at sponge removal, with 500 IU pregnant mare serum gonadotropin (PMSG) at d 30, 40 or 50 (d 0 = lambing) to induce estrus. Dry and lactating ewes were divided into equal numbers at each postpartum day and bred at estrus. Conception rates and number of accessory sperm were determined by flushing the oviducts 3 d after mating and examining the recovered ova. There was no effect (P greater than .05) of lactational status on conception rates. Conception rates increased (P less than .05) from d 30 (10%) to d 40 (45%) and from d 40 to d 50 (80%). There were fewer (P less than .05) ova with accessory sperm (5/26) in d-30 ewes compared with d-40 (10/27) or d-50 (12/24) ewes. In Exp. 2, ewes were assigned to two groups after receiving PMSG on d 30: 1) mated naturally or 2) inseminated during laparotomy near the uterotubal junction (UTJ). Dry and lactating ewes were divided evenly within each of the two treatments. Oviducts were flushed and ova were examined for cleavage. The conception rate was 60% in ewes that were inseminated in the UTJ vs 10% in ewes mated to rams (P less than .05). Lactational status had no effect on results. In conclusion, conception rates in postpartum ewes treated with MAP sponge and PMSG increased from postpartum d 30 to d 50 with natural breeding, and d-30 conception rates were increased over natural mating by insemination into the uterine horn near the UTJ.

Administration, Intravaginal↗
PubMed2001

Stage of cycle, incidence, and timing of ovulation, and pregnancy rates in dairy cattle after three timed breeding protocols.

In experiment 1, 705 cows were assigned to three treatments: 1) the Ovsynch protocol (a GnRH injection given 7 d before and another 48 h after one PGF2alpha injection); 2) PGF2alpha + Ovsynch (one PGF2alpha injection given 12 d (d -22) before initiating Ovsynch (d -10); and 3) 2xPG12 (two PGF2alpha injections 12 d apart; d -15 and -3, followed 48 h later by a GnRH injection. All cows were inseminated (d 0) 16 to 20 h after the GnRH injection on d -1. Cyclic status was estimated by serum progesterone. More cows were in early diestrus at d -10 for PGF2alpha + Ovsynch (36%) and 2 x PG12 (29%) versus Ovsynch (19%). Multiparous cows receiving PGF2alpha + Ovsynch had greater pregnancy rates via ultrasonography at d 28 after AI (42%) than contemporaries after Ovsynch (28%) or 2xPG12 (27%) but did not differ significantly at palpation 10 to 30 d later (28, 19, and 17%, respectively). Pregnancy of first-parity cows was similar across treatments at 28 d (41%) or at palpation (33%). Pregnancy rates for 128 anestrous cows were lower, regardless of treatment. Overall embryo survival from d 28 until palpation was 72% but was only 44% in 2xPG12 cows that were anestrus through d -10. Experiment 2 included the three treatments above plus controls (one GnRH injection 7 d before PGF2alpha and AI after estrus). Preovulatory follicles were 6 to 11% larger near estrus in controls than on d -1 in cows receiving GnRH. More controls ovulated by 32 h after onset of estrus than were treated cows by 32 h after GnRH, but percentages (79 to 94%) were similar by 40 h. In multiparous cows, PGF2alpha before Ovsynch increased pregnancy rates, whereas the 2xPG12 protocol produced similar pregnancy rates as Ovsynch across parities. Ovulation was effectively induced by 40 h after GnRH.

Animals↗
PubMed2004

A modified presynchronization protocol improves fertility to timed artificial insemination in lactating dairy cows.

To compare 2 hormonal protocols for submission of lactating dairy cows for timed artificial insemination (TAI), nonpregnant lactating Holstein cows (n = 269) >60 d in milk were randomly assigned to each of 2 treatments to receive TAI (TAI = d 0). Cows assigned to the first treatment (Ovsynch, n = 134) received 50 microg of GnRH (d -10), 25 mg of PGF2alpha (d -3), and 50 microg of GnRH (d -1) beginning at a random stage of the estrous cycle. Cows assigned to the second treatment (Presynch, n = 135) received Ovsynch but with the addition of 2 PGF2alpha (25 mg) injections administered 14 d apart beginning 28 d (d -38 and -24) before initiation of Ovsynch. All cows received TAI 16 to 18 h after the second GnRH injection. Ovulatory response after each GnRH injection for a subset of cows (n = 109) and pregnancy status 42 d after TAI for all cows were assessed using transrectal ultrasonography. Based on serum progesterone (P4) profiles determined for a subset of cows (n = 109), P4 concentrations decreased for Presynch cows after the first 2 PGF2alpha injections, and Presynch cows had greater P4 concentrations at the PGF2alpha injection on d -3 compared with Ovsynch cows. Although the proportion of cows ovulating after the first and second GnRH injections did not differ statistically between treatments (41.1 and 69.6% vs. 35.9 and 81.1% for Ovsynch vs. Presynch, respectively), pregnancy rate per artificial insemination (PR/AI) at 42 d post TAI was greater for Presynch than for Ovsynch cows (49.6 vs. 37.3%). Parity, DIM, and body condition score (BCS) at TAI did not affect PR/AI to TAI. These data support use of this presynchronization protocol to increase PR/ AI of lactating dairy cows receiving TAI compared with Ovsynch.

Animals↗