http://directory.umm.ac.id/Data%20Elmu/jurnal/A/Animal%20Reproduction%20Science/Vol62.Issue1-3.Aug2000/2028.pdf

Storage of ram semen.

Embryo survival is a major factor affecting production and economic efficiency in all systems of ruminant milk and meat production. For heifers, beef and moderate yielding dairy cows, does and camelids it appears that fertilization generally lies between 90% and 100%. In high-producing dairy cows there is a less substantive body of literature, but it would appear that it is somewhat lower and perhaps more variable. In cattle, the major component of embryo loss occurs before day 16 following breeding with some evidence of greater losses before day 8 in high-producing dairy cows. In cattle late embryo loss, while numerically much smaller than early embryo mortality loss, nevertheless, causes serious economic losses to producers because it is often too late to rebreed females when they repeat. In multiple ovulating small ruminants, the loss rate is positively related to ovulation rate. Systemic concentrations of progesterone, during both the cycle preceding and following insemination, affect embryo survival rate with evidence that too high or indeed too low a concentration being negatively associated with survival rate. Uterine expression of mRNA for progesterone receptor, oestradiol receptor and retinol-binding protein appears to be sensitive to changes in peripheral concentrations of progesterone during the first week after artificial insemination. Energy balance and dry matter intake during 4 weeks after calving are critically important in determining conception rate when cows are inseminated at 70-100 days post-calving. Concentrate supplementation of cows at pasture during the breeding period has minimal effects on conception rates though sudden reductions in dietary intake should be avoided. For all systems of milk production, more balanced breeding strategies with greater emphasis on fertility and feed intake and/or energy balance must be developed. There is sufficient genetic variability within the Holstein breed for fertility traits. Alternative dairy breeds such as the Jersey or Norwegian Red could also be utilized. Genomic technology will not only provide scientists with an improved understanding of the underlying biological processes involved in fertilization and the establishment of pregnancy, but also, in the future, identify genes responsible for improved embryo survival. Its incorporation into breeding objectives would increase the rate of genetic progress for embryo survival.

Embryonic and early foetal losses in cattle and other ruminants.

Current status of embryo technologies in sheep and goat.

Frozen storage of ram semen II. Causes of low fertility after cervical insemination and methods of improvement

State of the art in sheep-goat embryo transfer.

The use of synthetic gonadotropin releasing hormone treatment in the collection of sheep embryos.

Ovulation rate, median time to first ovulation, median time of all ovulations and median time from first to last ovulation were studied by repeated laparoscopy in Merino ewes. Treatments with FSH or PMSG significantly affected ovulation rate (8.4 +/- 0.81 and 7.3 +/- 1.21 respectively, P less than 0.05) and in median time of all ovulations (60 and 54 h respectively after progestagen sponge removal, P less than 0.05). Differences in the median time to first ovulation (60 and 48 h) and median time from first to last ovulation (6 and 6 h) for the respective treatments were not significant. The synchrony of ovulation after both treatments was adversely affected by (1) the occurrence of premature ovulations before the onset of superovulation, (2) variability in the time of commencement of superovulation, and (3) variability in the time from first to last ovulation. Administration of GnRH synchronized the timing of ovulation with both gonadotrophin treatments. This synchrony was due to a reduction in the period during which superovulation began and in the interval from first to last ovulation. The median time of all ovulations was significantly less with FSH + GnRH than with PMSG + GnRH (45 and 48 h after progestagen sponge removal, respectively, P less than 0.05). Administration of GnRH at 16, 20 or 24 h after progestagen sponge removal significantly affected all traits examined except ovulation rate. Administration at 20 and 24 h produced an equally good synchrony of ovulation which was better than that obtained at 16 h. We suggest that the use of GnRH in embryo collection programmes appears justified and is likely to improve embryo yields due to improved rates of fertilization.

/pdf/timing-of-multiple-ovulations-in-the-ewe-after-treatment-3yf21ovxej.pdf

Timing of multiple ovulations in the ewe after treatment with FSH or PMSG with and without GnRH

Real-time ultrasound imaging for predicting ovine fetal age.

Time of ovulation in the South Australian Merino ewe following synchronization of estrus. 1. Variation within and between flocks.

Time of ovulation in the South Australian Merino ewe following synchronization of estrus. 2. Efficacy of GnRH treatment and its relevance to insemination programs utilizing frozen-thawed semen.

D.H. Smith

Papers

The use of synthetic gonadotropin releasing hormone treatment in the collection of sheep embryos.

Timing of multiple ovulations in the ewe after treatment with FSH or PMSG with and without GnRH

Real-time ultrasound imaging for predicting ovine fetal age.

Time of ovulation in the South Australian Merino ewe following synchronization of estrus. 1. Variation within and between flocks.

Time of ovulation in the South Australian Merino ewe following synchronization of estrus. 2. Efficacy of GnRH treatment and its relevance to insemination programs utilizing frozen-thawed semen.