Two systems for measuring embryo development in vitro were evaluated. One was a 1-4 scale based on a subjective evaluation of embryo quality (EQ) from microscopic appearance. In addition, a formula for scoring embryo growth rate in vitro was developed. The embryo development rating (EDR) was based on the ratio between the time at which embryos were observed at a particular stage after insemination and the time at which they would be expected to reach that stage in a hypothetical "ideal" growth rate with a cell cycle length of 11.9 hr. Using this scoring system, "normally" growing embryos scored 100. This approach was aimed at partially normalizing the data and allowed all embryos to be analyzed similarly regardless of the time of observation. Analysis of 1539 embryo replacements resulting in 232 clinical pregnancies showed that both EDR and embryo-quality scores were of value in predicting success, with clinical pregnancy most likely to eventuate from a combination of moderate to good EQ scores (2-4) coupled with average or above-average growth rates (EDR scores from 90 to 129). Poor-quality and very slowly or very rapidly growing embryos were underrepresented in cycles that proceeded to pregnancy. These inferences were based on all embryos transferred (mean, 2.73 per transfer cycle), and they were substantiated by an analysis of 33 pregnancies resulting from replacement of a single embryo and from 18 pregnancies in which all embryos scored the same with both systems. EQ and EDR were significantly associated with each other and together provide a valuable guide in predicting pregnancy, in selecting embryos for freezing, and in monitoring day-to-day performance in the in vitro fertilization (IVF) program.

Human mitochondrial DNA polymerase, encoded by POLG, contains a polyglutamine tract encoded by a CAG microsatellite repeat. Analysis of POLG genotypes in different populations identified an association between absence of the common, ten-repeat allele and male infertility typified by a range of sperm quality defects but excluding azoospermia.

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In the present study, we tested the effect of treatment with a slow-release implant containing the gonadotrophin-releasing hormone agonist Deslorelin(TM) (Peptech Animal Health Australia, North Ryde, NSW, Australia) on pituitary and testicular function in mature male dogs. Four dogs were treated with Deslorelin (6-mg implant) and four were used as controls (blank implant). In control dogs, there were no significant changes over the 12 months of the study in plasma concentrations of luteinising hormone (LH) or testosterone, or in testicular volume, semen output or semen quality. In Deslorelin-treated dogs, plasma concentrations of LH and testosterone were undetectable after 21 and 27 days, testicular volume fell to 35% of pretreatment values after 14 weeks and no ejaculates could be obtained after 6 weeks. Concentrations returned to the detectable range for testosterone after 44 weeks and for LH after 51 weeks and both were within the normal range after 52 weeks. Semen characteristics had recovered completely by 60 weeks after implantation. At this time, the testes and prostate glands were similar histologically to those of control dogs. We conclude that a single slow-release implant containing 6 mg Deslorelin has potential as a long-term, reversible antifertility agent for male dogs.