Statin drugs markedly inhibit testosterone production by rat Leydig cells in vitro: implications for men.

Statin drugs lower blood cholesterol by inhibiting hepatic 3-hydroxy-3-methylglutaryl-Coenzyme-A reductase. Statins are known to inhibit sterol production in the testis, but effect of statins on testosterone production has not been studied critically in vitro and clinical data are controversial. We measured 18-h testosterone production in vitro, using highly purified rat Leydig cells exposed to atorvastatin, mevastatin, or simvastatin and also determined if statin-induced inhibition of testosterone production could be bypassed with substrate distal to cholesterol. Statins had no effect on testosterone production during culture without LH. However, with 10ng/mL LH, testosterone production was ≥12-fold higher and markedly inhibited (-40%) by ≥0.3µM statin. Leydig cells provided sub-saturating pregnenolone or progesterone to bypass the site of statin action, maintained LH-stimulated testosterone production at or above amounts observed with LH stimulation and no statin. Pregnenolone resulted in greater testosterone production, but LH responsiveness was lost. With progesterone, LH responsiveness was maintained.

Impact of genomic selection of AI dairy sires on their likely utilization and methods to estimate fertility: a paradigm shift.

Breeding of dairy cattle is undergoing a paradigm shift to genomic selection of potential sires and dams. This undoubtedly will affect how bulls are managed in an artificial insemination (AI) center and impact methods to estimate their 'fertility'. Our goal is to help decision-makers understand the contents of a straw of semen, current estimates of sire fertility, and how estimates might evolve in a genomic era. Sire fertility is estimated from outcome (pregnant or not) after 300 to > 2,000 inseminations and reported in units (U) as a sire's deviation from a population (> 500 bulls) average pregnancy rate (PR). Too often users do not recognize that imprecision of an estimate encompasses a 3-U range, or more. 'True fertility' of the sire whose semen is inseminated influences outcome far less than 'true fertility' of each female and a myriad of microenvironment and management factors. Further, AI centers discard substandard collections and intentionally adjust number of sperm per straw so that differences in pregnancy rates achieved by different sires are minimized! For > 80% of Holstein bulls, estimated 'sire conception rates' are within a 5.4-U range. In the future, most sires will be 15 to 40 mo old and services will accumulate at > 1,000/mo. Estimated sire conception rates still will be a deviation from the population mean, but should be based on records for the most recent 6 or 12 mo, rather than 48 or 60 mo. Repeated 'snap shots' every 2 mo would allow AI centers to adjust number of sperm per AI straw from genomic-sires in a timely manner, to maintain high pregnancy rates, and to meet market demands with sires producing ∼40% as many sperm as mature 'proven sires' of yesteryear.

Evaluating testis function non-invasively: how epidemiologist-andrologist teams might better approach this task.

Opinions herein focus on epidemiology-based publications using semen to study testis function, but several have broader applicability. 'Opinion 1': authors often fail to write out an explicit question(s) or hypothesis, and to stipulate how measured outcomes will be used to refute or support the hypothesis. Might critical thinking be lax? 'Opinion 2': authors often fail to consider the biology underlying a question or hypothesis, and/or which analytical methods really provide meaningful information or should be rejected. 'Opinion 3': spermatogenesis cannot be evaluated in a meaningful manner via conventional semen attributes. Quantitative evaluation of spermatogenesis requires a 'rate attribute', not provided by number of sperm per milliliter of semen or total number per ejaculate (TSperm). Influence of abstinence interval is under-appreciated. The rate attribute, TSperm per hour of abstinence (TSperm/h), meaningfully estimates sperm production if the abstinence interval is 42-60 h. Most attributes of individual sperm do not reflect quality at spermiation. 'Opinion 4': reliance on a single semen sample per subject might hamper detection of the association sought, because an imprecise value might not establish if a subject's testes were dysfunctional or not. 'Opinion 5': curve-fitting, to adjust quantitative data, for a sample provided after an abstinence interval falling within a broad range, to a standardized abstinence interval, distorts outcomes for many samples provided after approximately 60 h abstinence. TSperm values for individuals with good daily sperm production are artifactually low and those for individuals with poor daily sperm production are artifactually high. Hence, it is important to explain the importance of abstinence interval to participants and censor samples outside an acceptable 37-64 h abstinence range.

Cryptorchidism in common eutherian mammals.

Cryptorchidism is failure of one or both testes to descend into the scrotum. Primary fault lies in the testis. We provide a unifying cross-species interpretation of testis descent and urge the use of precise terminology. After differentiation, a testis is relocated to the scrotum in three sequential phases: abdominal translocation, holding a testis near the internal inguinal ring as the abdominal cavity expands away, along with slight downward migration; transinguinal migration, moving a cauda epididymidis and testis through the abdominal wall; and inguinoscrotal migration, moving a s.c. cauda epididymidis and testis to the bottom of the scrotum. The gubernaculum enlarges under stimulation of insulin-like peptide 3, to anchor the testis in place during gradual abdominal translocation. Concurrently, testosterone masculinizes the genitofemoral nerve. Cylindrical downward growth of the peritoneal lining into the gubernaculum forms the vaginal process, cremaster muscle(s) develop within the gubernaculum, and the cranial suspensory ligament regresses (testosterone not obligatory for latter). Transinguinal migration of a testis is rapid, apparently mediated by intra-abdominal pressure. Testosterone is not obligatory for correct inguinoscrotal migration of testes. However, normally testosterone stimulates growth of the vaginal process, secretion of calcitonin gene-related peptide by the genitofemoral nerve to provide directional guidance to the gubernaculum, and then regression of the gubernaculum and constriction of the inguinal canal. Cryptorchidism is more common in companion animals, pigs, or humans (2-12%) than in cattle or sheep (< or =1%). Laboratory animals rarely are cryptorchid. In respect to non-scrotal locations, abdominal testes predominate in cats, dogs, and horses. Inguinal testes predominate in rabbits, are common in horses, and occasionally are found in cats and dogs. S.c. testes are found in cattle, cats and dogs, but are most common in humans.

Sequelae in male rabbits following developmental exposure to p,p'-DDT or a mixture of p,p'-DDT and vinclozolin: cryptorchidism, germ cell atypia, and sexual dysfunction.

Rabbit does (7-9 per group) were treated daily per orum from gestation day 15 through post-natal week 4 to provide per kg body wt 25 micaromol (low) or 250 micromol (high) p,p'-DDT or a mixture of DDT and vinclozolin (12.5 and 125 micromol each). Developmental as well as post-pubertal reproductive sequelae of male progeny were studied. Testicular descent in some pups was impaired by DDT. Serum LH or testosterone was not affected. FSH was lower in mixture- but not in DDT-exposed rabbits. Lack of sexual interest, penile erection and ejaculation were observed in some mixture rabbits. Sperm counts were unaffected, but morphologically normal spermatozoa were fewer; nuclear and acrosomal morphogenesis was disrupted. Atypical germ cells resembling carcinoma in situ were found. Also considering data for vinclozolin [Veeramachaneni DNR, Palmer JS, Amann RP, Kane CM, Higuchi TT, Pau K-YF. Disruption of sexual function, FSH secretion, and spermiogenesis in rabbits following developmental exposure to vinclozolin, a fungicide. Reproduction 2006;131:805-16], we concluded that DDT causes cryptorchidism and germ cell atypia, vinclozolin permanently disrupts FSH secretion and sexual function, and the mixture causes the full spectrum of dysgenesis.

Disruption of sexual function, FSH secretion, and spermiogenesis in rabbits following developmental exposure to vinclozolin, a fungicide.

We studied sequelae of prenatal plus infantile exposure of male rabbits to vinclozolin, because it is ingested by women and children. Female Dutch-Belted rabbits (7-10/group) were treated daily per orum from gestation day 15 through post-natal week 4 to provide 0, 7.2, or 72 mg vinclozolin/kg dam's body weight/day. Vinclozolin had no effect on maintenance of pregnancy, growth of pups, age at testicular descent or weight of organs. Concentrations of serum LH or testosterone at 6, 12, or 24 weeks of age were unaffected. However, FSH was lower (P < 0.05) in both vinclozolin groups at all three ages. Following injection of GnRH at 12 or 24 weeks, the increase in FSH was less (P < 0.05) in both vinclozolin groups, as was testosterone at 12 weeks of age. After full sexual maturity, 2 of 7 low dose rabbits were uninterested in female or male teasers and never achieved erection or ejaculation. Overall, rates of ejaculation failure were: control 0% (0/48), low dose 29% (12/42), and high dose 5% (3/60). Daily sperm production per gram of testis and total number of sperm per ejaculate in both vinclozolin groups were similar (P > 0.1) to controls. However, semen from vinclozolin rabbits contained over two times more (P < 0.05) morphologically abnormal spermatozoa, mostly nuclear and acrosomal defects, than semen from controls. Seminiferous tubules with degenerative changes were more frequent (P < 0.05) in vinclozolin rabbits than in controls. Lesions included syncytia of spherical spermatids and desquamation of germ cells. Hence, developmental exposure to vinclozolin caused presumably permanent changes in copulatory ability, secretion of FSH, and spermiogenesis.

Long-term effects on male reproduction of early exposure to common chemical contaminants in drinking water.

We evaluated sequelae to early exposure of male rabbits to drinking water containing chemicals typical of ground water near hazardous waste sites. The mixture (p.p.m. at 1x) was 7.75 arsenic, 1.75 chromium, 9.25 lead, 12.5 benzene, 3.75 chloroform, 8.5 phenol and 9.5 trichloroethylene. Dutch-Belted does received mixture at 0x (deionized water; control), 1x or 3x as drinking water from day 20 pregnancy through weaning. Exposure of individual males (7-9/treatment) continued until 15 weeks (adolescence); then, all males received deionized water. At 57-61 weeks of age, ejaculatory capability and seminal, testicular, epididymal and endocrine characteristics were evaluated. At 10 opportunities with a female teaser, all seven control males ejaculated every time, but 12 of the 17 treated males failed to express interest, achieve erection and/or ejaculate on one to five occasions; four of the 12 accomplished ejaculation with a second male teaser. Total spermatozoa/ejaculate and daily sperm production were unaffected. However, treatment caused (P < 0.03) acrosomal dysgenesis and nuclear malformations. Baseline serum concentrations of LH were lower, but with borderline significance (P = 0.05). Testosterone secretion after exogenous human chorionic gonadotrophin (P < 0.04) was low. Thus, even at 45 weeks after last exposure to drinking water pollutants, mating desire/ability, sperm quality, and Leydig cell function were subnormal.

A fragment of prosaposin (SGP-1) from rooster sperm promotes sperm-egg binding and improves fertility in chickens.

A protein isolated from the supernatant of cryopreserved rooster sperm was found to increase the capability of cryopreserved rooster sperm to bind in vitro to the perivitelline membrane of a chicken egg and substantially raise fertility after artificial insemination (AI). That activity was partially purified and termed universal primary sperm-egg binding protein (UPSEBP). Insufficient protein remained from 6 x 10(11) sperm, despite retention of bioactivity, to allow sequencing. We deduced that the protein may be related to prosaposin (also termed SGP-1, for sulfated glycoprotein-1), and we used published amino acid sequences of prosaposin as a guide for synthesis of peptides. Certain peptides were found to increase in vitro sperm-egg binding and increase fertility of frozen-thawed or fresh rooster sperm, in a manner similar to semipurified UPSEBP. Active epitopes were in a 60 amino acid sequence, reflecting the intervening sequence between saposins A and B, plus short extensions into saposins A and B. Highest activity was found when this synthetic peptide was oxidized to form a disulfide bond between terminal cysteines. Antibody against a synthetic peptide consisting of 58 of these 60 amino acids bound to a 7-9 kilodalton protein in UPSEBP. Collectively, the data support the conclusion that UPSEBP is a fragment of prosaposin. Because prosaposin is in semen in humans and animals, these observations have broad implications for possible cause and therapy of one type of subfertility.

Exposure of turkey sperm to a synthetic peptide before insemination increases fertility.

Effects on fertility and hatch of eggs laid by hens inseminated with sperm exposed to a synthetic peptide were studied. Pooled semen from 40 randomly selected toms was split and held in vitro for 0 or 24 h before use. Just before insemination, sperm (at 8.33x10(9) sperm/mL) were exposed for 5 min to 0.0, 0.05, 0.25, or 0.50 microM peptide. Hens (28 per group) were inseminated within less than 30 min with 250x10(6) in 30 microL. Two inseminations 24 h before onset of lay were followed by weekly inseminations through 22 or 20 wk. For sperm that was fresh or held 24 h, peptide treatment (P<0.02 or 0.01) and week of lay (P<0.01) affected fertility and hatch of total eggs set. There was no effect of peptide treatment on hatchability of fertile eggs. For fresh sperm, use of 0.25 microM peptide, but not 0.05 or 5.0 microM peptide, increased (P<0.05) fertility and hatch of total eggs set compared with the control (0 microM). Values for fertility were 94 vs. 90% and for hatch were 84 vs. 80%. Increases in hatch were especially evident for fresh sperm after approximately 13 wk of lay.

Fertilizing potential in vitro of semen from young beef bulls containing a high or low percentage of sperm with a proximal droplet.

Fertilizing potential of semen containing a high percentage of sperm with a proximal droplet was evaluated using IVF. Design criteria: (a) specified semen with >100 x 10(6) sperm/mL with >40% progressively motile spermatozoa, after collection via electro-stimulation; (b) designated a droplet group, bulls whose semen contained >30% spermatozoa with a proximal droplet and <25% with other morphological abnormalities, and a control group, with <25% abnormalities of any type; and (c) stipulated evaluations at 11 to 13 mo of age and again -4 wk later. At the initial evaluation, when a bull was assigned to the droplet group, the next bull meeting control criteria was designated his pair; 15 pairs in four herds were studied. Semen was extended in egg-yolk citrate, cooled to 5 degrees C over approximately 2.5 h, and held at 5 degrees C. After 20 to 44 h, spermatozoa were processed by swimup, incubated with heparin, and co-cultured with oocytes (35 to 56 oocytes/sample; 18 h). Ova were observed for cleavage approximately 42 h after co-culture, and further development was evaluated on day 8. At first evaluation, cleavage rates were 18 and 46% for droplet and control groups (P < 0.01); semen had 34 to 70% and 0 to 12% droplet spermatozoa. For 10 of 15 droplet bulls, <10% of ova were cleaved whereas cleavage rate was >15% for all control bulls. At second evaluation, only three droplet bulls still had >30% of spermatozoa with a proximal droplet. Cleavage rates increased accordingly; only four droplet bulls had <10% cleaved ova and 10 had >34% cleaved ova. Three control bulls had <10% cleaved ova and nine had > or = 34% cleaved ova. Considering all 60 ejaculates, correlation between percentage of spermatozoa with a proximal droplet and percentage of cleaved ova was -0.49 (P < 0.0 1). Correlations between percentages of motile or normal spermatozoa in field evaluations and outcome in IVF were 0.28 and 0.52. Laboratory evaluations of spermatozoa concomitant with preparation for IVF revealed that only incidence of proximal droplets appeared related to outcome in IVF. We concluded: (a) semen from most yearling beef bulls with a high incidence of proximal droplet spermatozoa had severely compromised IVF fertility; (b) as these bulls matured, the incidence of proximal droplets decreased, and IVF fertilizing potential increased; and (c) semen containing >30% spermatozoa with a proximal droplet is strong evidence that fertilizing potential of the bull will be low until the incidence decreases.

In vitro sperm-binding assay to distinguish differences in populations of human sperm or damage to sperm resulting from cryopreservation.

Annually, >1.3 million men are members of couples seeking help because of infertility. Semen from many of these men contains reasonable numbers of motile and normal sperm, but for a subset of individuals, many sperm are deficient in ability to bind to the zona pellucida during in vitro fertilization. Diagnosis of this defect has been hampered by lack of a low-cost test. Molecular similarity exists between the perivitelline membrane of a hen's egg and the mammalian zona pellucida. These facts and some preliminary data led to evaluation of binding of human sperm during incubation for 60 minutes at 37 degrees C to an extract of chicken perivitelline membrane coated in microwell assay plates. The sperm-binding assay had inter- and intraassay plate variations of 21 and 12%, respectively, using washed fresh sperm. All seminal samples were normal, except a few that had 36 to 50% motile sperm with a low rate of sperm movement (if there is a low rate of movement, World Health Organization [WHO] criterion for normalcy is >50% motile). Nevertheless, this sperm-binding assay detected differences among individuals in percentage of sperm bound. Based on data for two to four ejaculates from each of eight occasional sperm donors, the coefficient of variation for ejaculates within donor averaged 31%, and means for the donors differed (P < 0.02). Percentage of sperm bound ranged from <1 to 38% for fresh semen from 57 men and from <1 to 13% for frozen-thawed semen from 34 men. Percentage of motile sperm accounted for <30% of the variation in percentage of sperm bound. In a direct comparison based on 17 ejaculates, aliquots evaluated fresh averaged 13% sperm bound, versus 2% for frozen-thawed aliquots. We concluded that the egg membrane substrate used in these microwell assay plates might serve as the basis for a diagnostic assay. However, it remains to be established whether samples of human semen with a low percentage of sperm binding indeed have relatively low fertilizing potential.

Increased in vitro binding of fresh and frozen-thawed human sperm exposed to a synthetic peptide.

Prosaposin is a well-characterized, approximately 68-kDa protein found in many tissues and as a normal component of human semen. A fragment of prosaposin apparently is involved in primary sperm-egg binding. We hypothesized that binding of sperm from some men to egg investments would be increased by in vitro exposure of their sperm to a synthetic fragment of human prosaposin (FertPlus peptide). Hence, we evaluated samples of washed fresh or frozen-thawed human sperm after a 10-minute exposure to synthetic FertPlus peptide at 0 (control), 80, 160, 320, 640, or 1280 pM, followed by 1:50 dilution for evaluation of binding. The criterion of response was mean percentage of sperm bound to a substrate prepared from chicken egg membranes after sperm were incubated for 60 minutes at 37 degrees C in substrate-coated wells of a sperm-binding assay plate. For each seminal sample, data were normalized against the percentage of sperm bound for control aliquots, providing values for relative binding. With fresh sperm, relative binding was increased (P < 0.01) by exposure of sperm to peptide, and the effect was especially obvious at 1280 pM. Higher doses were not tested. Collectively at three study sites, exposure of fresh sperm to 1280 pM peptide substantially increased (above 99% confidence interval; on the basis of duplicate control samples) percentage of sperm bound for 25 of 74 (34%) samples. For frozen-thawed sperm, exposure to 1280 pM peptide increased binding for 29 of 65 (45%) samples. We concluded that for >30% of men, exposure of their sperm to this synthetic fragment of prosaposin at 1280 pM increased binding of sperm to an egg membrane substrate similar to that offered by the zona pellucida.

Identifying potentially subfertile toms via a sperm-binding assay.

We evaluated the utility of the commercial version of a new sperm-egg binding assay for detection of differences in sperm quality in samples of turkey semen from individual toms. Each sample had a swirl of 2 or more on a scale of 0 to 4. For assays conducted with fresh semen at 4 x 10(6) sperm per well, values ranged from 0.11 to 12% sperm bound to an extract of perivitelline membrane. Within-male variation averaged 0.17 percentage units, based on three ejaculates per male evaluated. Two experiments compared fertility and hatch for hens after weekly insemination with pooled semen from subpopulations of toms classified as having sperm with LOW or HIGH binding. Average fertility and hatch were lower (P < 0.05) for eggs laid by hens inseminated with semen from LOW toms in one experiment. In another experiment, hen fertility was not different between treatments after insemination during Weeks 32 to 39; however, a sharp decline in hatch was observed only for hens inseminated with semen from LOW toms after 40 wk of age. With semen from HIGH toms, hatch remained at > or = 80%. For these experiments, approximately 7% more poults were obtained from hens inseminated with semen from HIGH toms. We demonstrated that the sperm-egg binding assay detects differences in sperm quality between individuals, and these differences influence fertility.

Exposure of thawed frozen bull sperm to a synthetic peptide before artificial insemination increases fertility.

We evaluated the effect on fertility of in vitro exposure of thawed frozen bull sperm to synthetic FertPlus peptide prior to artificial insemination (AI). The peptide represented a 60-amino acid sequence within rat prosaposin. Commercial cryopreserved semen was from three Holstein bulls. Onset of estrus in groups of Holstein nulliparous heifers was synchronized via injection of prostaglandin F2-alpha, and heifers were scheduled for AI 8-24 hours after estrus was detected. Semen was thawed, diluted to 2.4 x 10(6) sperm/ml with buffer, and split to provide control and exposed aliquots (0 or 30 microM peptide) that were incubated at 37 degrees C for 10 minutes and then were held at 32 degrees C. The two aliquots of semen then were used on an alternate basis 2-65 minutes later to inseminate females. Each AI (one per female) involved the deposit of approximately 250,000 sperm into each uterine horn. This procedure for AI was used to reduce the pregnancy rate with control semen to below the maximum value for a given bull and to facilitate detection of any beneficial effect of the peptide. For each bull, approximately 32 heifers were inseminated with control semen, and approximately 32 heifers were inseminated with peptide-exposed semen. Pregnancy was evaluated ultrasonically approximately 60 days after AI. After excluding one group of heifers with unusually low fertility, averaged across all animals, a 29% increase in pregnancy rate resulted from exposure of sperm to peptide (P < 0.04; one-tailed chi-square test; means were 48 vs. 62%). Pregnancy rates for the three bulls for control and peptide-exposed semen, respectively, were 42 and 62%, 44 and 64%, and 56 and 61%; means in the first two pairs of values tended to differ (P approximately equal to 0.10). These observations should be confirmed with sperm from other bulls used in a more conventional manner. However, with insemination of a limiting number of cryopreserved sperm, brief exposure of the thawed bull sperm to FertPlus peptide appeared to improve fertility dramatically.

Exposure of human, boar, or bull sperm to a synthetic peptide increases binding to an egg-membrane substrate.

We evaluated the effects of in vitro exposure of sperm to synthetic FertPlus peptide, which represents a 60-amino acid sequence within rat prosaposin, using a microwell sperm-binding assay (SBA), in which an extract of hen's egg served as the binding substrate. Sperm suspensions were incubated with FertPlus peptide (six to eight concentrations; 0 and 20-1,280 pM) at 37 degrees C for 10 minutes, diluted > or = 20 times, and placed onto SBA plates. After 60 minutes at 37 degrees C, unbound sperm were washed away and the DNA of bound sperm was quantified. Percentage of sperm bound was independent of the percentage of motile sperm, but immotile sperm did not bind. For fresh human sperm (25 ejaculates), the percentage of sperm bound was increased by exposure to 640 pM peptide (P < 0.01). For 11 of 25 samples, the percentage of sperm bound for the aliquot exposed to 640 pM peptide was > or = 1.4 times the value for a 0 pM control aliquot. With frozen-thawed human sperm, for six of seven samples, binding was > or = 1.4 times greater after exposure to 640 pM peptide. For boar sperm held for approximately 24 hours at approximately 18 degrees C before use (28 ejaculates), there was a higher percentage of sperm bound for aliquots previously exposed to 1,280 pM peptide than there was for control aliquots (P < 0.01). For 16 of 28 samples, exposure to peptide increased the percentage of sperm bound by > or = 1.4 times. For frozen-thawed bull sperm, percentage of sperm bound was > or = 1.4 times greater for 4 of 10 samples that were briefly exposed to 160 pM peptide. Clearly, human, boar, and bull sperm were beneficially modified by brief in vitro exposure to FertPlus peptide, so that for many samples a greater percentage of sperm was bound in vitro. As presented in an accompanying paper, fertility of bull sperm was increased by brief exposure to FertPlus peptide.

Lessons for the poultry industry gleaned from experiences with other commodity species.

Do breeders really know how well or poorly they are managing reproduction? Poultry breeders could benefit from application of proven concepts of reproductive management used to exploit elite mammalian males, via selection for reproductive traits and extensive use of AI. Use of elite males could dramatically increase the impact of genes of economic importance transferred to the producer level. Testes weight has up to a 35-fold range among males within most lines of poultry, as does number of sperm that can be harvested from a male. These observations should not be ignored. Males with small testes will provide few sperm and they should be culled. Similarly, identification and elimination of males whose sperm are likely to have low fertilizing potential should be beneficial. Approaches to maximize harvest of those sperm produced by an elite male and minimize wastage of these valuable cells are emphasized. To this end, semen should be extended to allow insemination of a minimal volume containing just sufficient sperm consistent with the breeder's goal. Presumably, the goal should be obtaining the maximum number of offspring from a unique male or great-grandparent family, while minimizing cost of producing each chick. This goal might not require maximizing "fertility". A 10-fold increase in dissemination of DNA from elite males to the next generation is realistic. Over three generations, this increase equals a 1,000-fold increase in the number of birds with the desirable traits! Appropriate biotechnology is available. Will decision makers evaluate new (to them) approaches and progress into the next millennium using modern technology, when cost-effective, or will they continue to manage reproduction with methods more than 50 yr old? Those who choose the latter path may risk extinction.

Issues affecting commercialization of sexed sperm.

A decision tree for genetics or sperm-sexing entities considering sales of sexed sperm is discussed in terms of: (a) how best to avoid harm; (b) how best to do good; (c) needed synergy with other assisted reproductive technologies; (d) constraints on biotechnology; and (e) costs with current and likely technologies versus potential benefits to producers. The sexed-sperm industry might wish to take a pro-active stance on societal issues potentially affecting use of sexed sperm. For most sales in animal agriculture, cost of added value must be < 50% of benefit. Cost is less important for emotionally-driven uses with horses and human beings. Current procedures for flow-sorting allow most sperm to retain their fertilizing potential. Added cost to produce and package 2 x 10(6) sperm is estimated at US $30 to US $46 with flow sorted sperm. Estimating cost of any alternative technology is premature. For IVF/embryo transfer (ET), cost and numbers of flow-sorted sexed sperm are appropriate for commercial use. For use in low-dose AI, however, added cost to supply one insemination dose must be near US $12. Flow-sorting instruments with higher throughput and lower purchase and operating costs are obligatory for economic application in most AI situations. Developers of antibody-based separations also will face issues of retention of fertilizing potential while minimizing cell loss, separation of living from dead sperm concurrent with sperm sexing, output, and cost. To benefit producers and consumers in a changing world, genetics and sperm-sexing companies will have to collaborate and interface to provide funding for needed research and development and to recover these costs, using mechanisms not yet obvious.