Reduced Conception Rates Research Articles

Stress and the suppression of subordinate reproduction in cooperatively breeding meerkats.

In many animal societies, dominant individuals monopolize reproduction, but the tactics they employ to achieve this are poorly understood. One possibility is that aggressive dominants render their subordinates infertile by inducing chronic physiological "stress." However, this hypothesis has been discarded largely for cooperatively breeding species, where reproductive monopolies are often extreme. Here we provide strong support for the stress-related suppression hypothesis in a cooperative mammal, the meerkat (Suricata suricatta). When pregnant, dominant females subject some subordinate females to escalating aggression, culminating in temporary evictions from the group. While evicted, subordinate females suffer chronic elevation of their glucocorticoid adrenal hormone levels, reproductive down-regulation (reduced pituitary sensitivity to gonadotropin-releasing hormone), reduced conception rates, and increased abortion rates. Rather than constantly harassing all subordinate females, dominants only become aggressive when pregnant themselves (when subordinate reproduction would otherwise conflict with their own) and target those females with whom reproductive conflict is most likely (older, pregnant, and more distantly related females). Our findings suggest that dominant female meerkats employ stressful evictions to suppress reproduction among their probable competitors, when attempting to breed themselves. Given the lack of evidence for stress-related suppression in other cooperative breeders to date, it is clear that social stress alone cannot account for the reproductive failure of subordinates across such societies. However, our findings raise the possibility that, in some cooperative breeders at least, dominants may employ stress-related suppression as a backup mechanism to guard against lapses in reproductive restraint by their subordinates.

Indigenous ecological knowledge of Borana pastoralists in southern Ethiopia and current challenges

Indigenous ecological knowledge (IEK) of Borana pastoralists on strategies of sustainable resource utilization, forage species, ecological interactions, rangeland condition and trend was documented using discussions, a semi-structured questionnaire survey and analytical workshops. Traditional strategies of rangeland and water management were described and the most important forage species identified. Pastoralists' perceptions were compared across age, gender and site. There was a positive correlation between pastoralists' preference ranking of forage species and crude protein content of the species. IEK of men and women was complementary. The process of rangeland degradation was described as shortage of grass and decrease in density and frequency of highly palatable grass species, leading to low milk production and reduced conception rates in cows. The results confirmed that the IEK of these pastoralists could still provide the basis for sustainable resource utilization and rangeland rehabilitation. However, the young generation in the area had not only limited knowledge but also showed less interest to learn and apply the traditional resource management strategies. Therefore, there is high need to perpetuate, document and use this IEK for sustainable development. On the other hand, shortage of forage resources as a result of rangeland shrinkage (leading to rangeland degradation and woody plants encroachment), less application of IEK, the gap between traditional and formal systems, and trends of disobeying traditional rules and regulations were identified as current challenges for the Borana pastoralists.

Economic decision making on prevention and control of clinical lameness in Danish dairy herds

From an economic point of view, clinical lameness is considered to be one of the major health disorders in dairy cattle. The aim of this study was to establish the costs of lameness in different herds and to improve decision-making on prevention and control of clinical lameness. Economically feasible strategies of prevention and control were defined and the potential effects were calculated by a dynamic, stochastic and mechanistic Monte Carlo model, called SimHerd. The modelled risk factors on cow level for lameness were base-risk in the herd, parity, milk yield potential, disease interrelationship, disease recurrence and season. Milk yield reduction, reduced feed intake, weight loss, reduced conception rate and mortality were modeled as effects of lameness. To study the effect of herd differences on the efficacy of the preventive methods, four different herds representing different levels of reproductive management, conception rates and milk production were designed and compared to the default situation. The loss per first case of lameness was found to be €192 in the default herd that represents the modern, average Danish dairy herd. An increase of the margin per cow-year of €22.7 was the result of halving the risk of lameness in the default herd. Implementation of footbaths and rubber flooring increased margin per cow-year by €4.2 and €17, respectively. In a sensitivity analysis, 16 model parameters were changed to their lowest and highest value found in the literature. The model seemed most sensitive to the uncertainty of the effect of lameness on milk yield.

173 HINDERING OF CLEAVAGE TIMING IN BOVINE PARTHENOTES DURING THE HOT SEASON

Heat stress is a major contributing factor to low fertility among dairy cattle, as reflected by the dramatic reduction in conception rate during the hot months. The effects of thermal stress on oocyte competence and embryonic development have been well documented. However, timing of embryonic cleavage, which may be considered a parameter for the identification of good-quality embryos, and its association with elevated temperatures have not been studied. Two experiments were performed to examine and characterize seasonal effects (i.e. thermal stress) on cleavage timing of bovine parthenogenetic embryos. Oocytes were aspirated from ovaries collected at the local abattoir in 2 seasons: cold (Dec–Apr) and hot (May–Nov). Matured oocytes were chemically activated (ionomycin followed by 6-DMAP) and cultured in vitro; cleavage timing to the 2- and 4-cell stages was observed and documented. The one-way ANOVA procedure was used for statistical analysis. In the first experiment (n = 5416 oocytes), cleavage was documented at specific time points during development post-activation. The peak in embryonic development to the 2-cell stage was earlier (22 to 27 vs. 27 to 40 h after activation) and the cleavage rate higher (39 vs. 21%; P < 0.0001) during the cold season relative to the hot season, respectively. Similarly, the peak in 4-cell-stage development was also observed earlier (46–52 vs. 52–70 h after activation) and corresponded with a higher proportion of developing embryos (33 vs. 21%; P < 0.0001) during the cold season as compared to the hot season, respectively. These results indicate that embryonic development is delayed and a lower proportion of embryos cleaved during the hot season. To better understand the delay in cleavage timing, a second experiment (n = 308 oocytes) was performed through two consecutive hot seasons. A time-lapse system (EmbryoGuard; IMT, Ltd., Ness-Ziona, Israel) was employed to collect accurate data on the first cleavage division, known to be indicative of embryo quality. The time-lapse system was pre-programmed to take photos at 1-h intervals such that culture dishes did not need to be removed from the incubator. Similar to the pattern noted for the hot season in the first experiment, a wide distribution of cleavage timing (18-40 h after activation) was observed. Further analysis revealed that embryos cleaved in 2 distinct waves: cleavage timing of the first wave (18 to 25 h after activation) was characterized by a time frame similar to that in the cold season, suggesting good-quality embryos; however, the second wave, from 27 to 40 h after activation, presented a delay in cleavage timing, suggesting that these late-cleaving embryos are of inferior quality. Taken together, the results of the 2 experiments lead to the assumption that oocytes harvested from lactating cows during the hot season are of reduced developmental potential, which may be explained, in part, by the pattern of 2 cleavage waves. Furthermore, cleavage timing appears to be a good indicator of embryo potential and may increase the chances of selecting better in vitro-derived embryos during the hot season for embryo transfer.

Age, body weight, and pregnancy loss

T he causes of embryo loss (< 40 days) are both known and speculative.1 Ball (1988) 2 reviewed reported research up to that time. Persistent mating-induced endometritis may be a cause of both lowered conception rate and embryo loss due to bacterial infection or persistence of inflammatory fluids.3,4 An association between multiple pregnancy and embryo size for age with embryo loss has been recently reported.5 There is, however, a percentage of “normal” single pregnancies in healthy young mares which fail for no apparent reason. Studies in other species suggest that levels of nutrition at halfor double-maintenance have adverse effects on embryo survival.6 Observations by breeders and stud managers have suggested that mares, although cyclic, have reduced conception rates when experiencing weight loss and that significant weight loss in early pregnancy is associated with embryo loss. Previous analysis of data from the farm in this study showed that mares losing more than 50 kg were highly likely to lose their pregnancy (unpublished). Various studies have shown the effects of nutrition levels on reproductive function. Guillaume and others (2002)7 restricted diets of ponies over 18 months. The onset of anoestrus was advanced, and the effect of photostimulation was inhibited. Godol and others (2002)8 showed that increasing body condition reduced the parturition to ovulation and the inter-ovulatory intervals. Banach and Evans (1981),9 however, found no adverse effect of a diet restricted in the last 90 days of pregnancy. Mitchell and Allen (1975)10 attributed a 46% embryo loss in yearlings to the effect of nutritional and other stress factors. Van Niekerk (1965)11 also found that se-

Molecular Actions of Polyhalogenated Arylhydrocarbons (PAHs) in Female Reproduction

Polyhalogenated aromatic arylhydrocarbons (PAHs) such as polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), the polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent lipophilic pollutants, which affect female fertility resulting in severe reproductive dysregulation, including anovulation, reduced conception rates, abortion, menstrual abnormalities and developmental defects of female reproductive tissues. Many PAHs exert their effects by activating a family of basic helix-loop-helix (bHLH) transcription factors, the arylhydrocarbon receptor (AhR) and the arylhydrocarbon receptor nuclear translocator (ARNT), which result in the expression of AhR target molecules. Complex interactions between PAH-mediated AhR activation and ER signalling pathways have been discovered which may contribute to the developmental malformations, impact on reproductive dysfunctions and promote carcinogenic dedifferentiation of tissues within the female reproductive tract. This review will focus on the multifaceted roles of PAHs in key organs of the female reproductive tract, the ovary, uterus/ endometrium and the mammary gland. The complexity and diversity of actions unleashed by PAHs in these female reproductive tissues identify these environmental pollutants as important endocrine disrupting toxicants impacting on female fertility.

Diet-induced obesity impairs mammary development and lactogenesis in murine mammary gland

We have developed a mouse model of diet-induced obesity that shows numerous abnormalities relating to mammary gland function. Animals ate approximately 40% more calories when offered a high-fat diet and gained weight at three times the rate of controls. They exhibited reduced conception rates, increased peripartum pup mortality, and impaired lactogenesis. The impairment of lactogenesis involved lipid accumulation in the secretory epithelial cells indicative of an absence of copius milk secretion. Expression of mRNAs for beta-casein, whey acid protein, and alpha-lactalbumin were all decreased immediately postpartum but recovered as lactation was established over 2-3 days. Expression of acetyl-CoA carboxylase (ACC)-alpha mRNA was also decreased at parturition as was the total enzyme activity, although there was a compensatory increase in the proportion in the active state. By day 10 of lactation, the proportion of ACC in the active state was also decreased in obese animals, indicative of suppression of de novo fatty acid synthesis resulting from the supply of preformed fatty acids in the diet. Although obese animals consumed more calories in the nonpregnant and early pregnant states, they showed a marked depression in fat intake around day 9 of pregnancy before food intake recovered in later pregnancy. Food intake increased dramatically in both lean and obese animals during lactation although total calories consumed were identical in both groups. Thus, despite access to high-energy diets, the obese animals mobilized even more adipose tissue during lactation than their lean counterparts. Obese animals also exhibited marked abnormalities in alveolar development of the mammary gland, which may partially explain the delay in differentiation evident during lactogenesis.

Synchronising oestrus with oestradiol benzoate after using a two‐dose prostaglandin treatment to synchronise luteolysis in dairy heifers

To compare the reproductive performance and pattern of onset of oestrus in dairy heifers in which oestrous cycles were synchronised with two doses of prostaglandin (PG) F2alpha and oestrus was synchronised with oestradiol benzoate (ODB). Dairy heifers in two herds (herd A, n = 192; herd B, n = 267) were treated with two doses of an analogue of PGF2alpha (cloprostenol, 375 microg, IM) 12 days apart. Heifers not detected in oestrus 48 h after the last dose of PGF2alpha were either left untreated (No ODB, n = 147) or treated with ODB (0.75 mg IM, n = 126). Onset of oestrus was monitored at 0, 24, 48, 80, 96 and 120 h after the last dose of PGF2alpha Heifers were inseminated on detection of oestrus. After the last dose of PGF2alpha, oestrous detection rates at 80 h (43.5 vs 72.6%, P < 0.001), 96 h (74.1 vs 84.9%, P =0.025) and 120 h (78.2 vs 86.3%, P = 0.082) were less in the No ODB compared to the ODB heifers, respectively. Conception rates (percentage pregnant that were inseminated) were greater in the No ODB compared to the ODB heifers (64.3% vs 47.6%, respectively; P = 0.006), while pregnancy rates (percentage pregnant that were treated) were also greater in the No ODB compared to the ODB heifers, but differences were not significant (50.3% vs 41.1%, respectively; P = 0.068). Administration of ODB to heifers not in oestrus 48 h after a two-dose PGF2alpha treatment increases the percentage of heifers detected in oestrus by 80 h, 96 h and 120 h after treatment, by an estimated 29%, 11% and 8%, respectively. However, administration of ODB decreases conception rates by an estimated 17%, and may decrease pregnancy rates (estimated 9% difference). Results are consistent with the hypothesis that ODB can increase submission rates but reduce conception rates following a two dose treatment with PGF2alpha.

Leptospirosis control on an intensive raising pig farm

Leptospirosis is an infective disease which represents serious health and economic problems in pig raising. The disease is caused by bacteria from genus Leptospira interrogans, which has over 250 serotypes and is isolated from most animal species and also from humans in almost every country in the world. In farm conditions the disease is seldom manifested as a clinically apparent illness. More often is manifested as reduced conception rate increased abortion rate and increased birth of dead and non-vital piglets. The leptospirosis control and eradication program was made for a state owned farm with a capacity of about 1500 sows and over 30000 fattened animals per year. The farm had an on going endemic leptospirosis infection and subsequent progressive economic losses. We detected 29,80% seropositive sows and gilts in which serotypes pomona and icterhaemorrhagiae were isolated. Serologic examination of blood was performed again after program implementation, and no positive animals were found, while production and economic results were improved. The control of leptospirosis and the eradication program for a five-year period were based on detailed quantification of economics losses. Using cost-benefit analysis the necessary inputs and planned outputs were defined, and program evolution was made on the basis of net present value and benefit/cost ratio.

Reproductive consequences of infection with bovine viral diarrhea virus.

Reproductive efficiency is imperative for the maintenance of profitability in both dairy and cow-calf enterprises. Bovine viral diarrhea virus is an important infectious disease agent of cattle that can potentially have a negative effect on all phases of reproduction. Reduced conception rates,early embryonic deaths, abortions, congenital defects, and weak calves have all been associated BVDV infection of susceptible females. In addition, the birth of calves PI with BVDV as a result of in utero fetal exposure is extremely important in the perpetuation of the virus in an infected herd or spread to other susceptible herds. Bulls acutely or PI with BVDV may bea source of viral spread through either natural service or semen used in artificial insemination. Management practices including elimination of PI cattle, biosecurity measures and strategic use of vaccination can be implemented to reduce the risk of BVDV related reproductive losses. Development of vaccines and vaccine strategies capable of providing better protection against fetal infection would be of benefit.

Evaluation of transrectal real-time ultrasound for use in identifying sources of reproductive failure in weaned sows

Real-time ultrasound (RTU) may aid in identifying sources of reproductive failure. In the month prior to observation, a commercial 2500-sow unit experienced an increase in the wean-to-estrus interval and reduced conception rates. A subpopulation of 52 sows was examined using RTU once daily on days 4, 5, and 6 postweaning. Transrectal RTU of the ovaries and uterus, performed following estrus detection, required 3.5 minutes per sow. To identify sources of reproductive failure, measures of follicle size, cysts, and time of ovulation were analyzed with sow records. Only 38 of the 52 sows expressed estrus within 7 days of weaning (73%), and only 29 sows ovulated (56%). Nine of the 23 sows that failed to ovulate (24%) were detected standing. Cystic ovaries were observed in four sows that failed to ovulate (17%) and in two sows that ovulated (7%). Of the 14 sows not detected in estrus, none ovulated (0%). The average estrus-to-ovulation interval, which was 39 hours, was influenced by the wean-to-estrus interval. Characterization of the reproductive tract may be used to evaluate the adequacy of estrus detection and artificial insemination procedures and the incidence of pathological conditions.

Associations between the manipulation of patterns of follicular development and fertility in cattle

The wave-like patterns of ovarian follicular development in cattle can be manipulated by shortening the luteal phase with prostaglandin F 2α (PGF), lengthening the period of follicle dominance with progesterone or curtailing follicle development with GnRH or oestradiol as 17β, benzoate or cypionate. These hormones can also be used to synchronise ovulation allowing timed inseminations without detected oestrus. Progesterone, PGF, GnRH and oestradiol benzoate have each been used to increase conception rates in some situations, but their use has reduced them in others. For example, inseminations made within 96 h of a single injection of PGF administered during the luteal phase were associated with increased conception rates in dairy cows whereas double injection protocols reduced conception rates. The three forms of oestradiol and GnRH have greater effects on follicular development following divergence and dominance than following wave emergence. This can mean that follicles of differing maturity will be present about 7 days later and can result in varied intervals to the onset of oestrus following a PGF injection. The consequent variation in ovulation time can be reduced by injecting GnRH or an oestradiol during pro-oestrus. This means that some less mature follicles will ovulate, forming corpus luteum (CL) associated with a slower rise in plasma progesterone and lower mid-luteal concentrations. The lower conception rates recorded with single timed inseminations with synchronised ovulations have been associated with increased prevalences of short cycles in lactating dairy cows (with GnRH), with long luteal phases in cows and heifers (with oestradiol benzoate) and with embryo loss following positive pregnancy diagnosis (as with Ovsynch in lactating Holstein cows). Extensive Canadian studies have demonstrated that these same hormones can be successfully used without these limitations and reliably obtaining conception rates over 50% and up to 70% in beef cattle that have been supplemented with a progestin during the period of ovarian follicle synchronisation. The inherently lower fertility of Holstein cows during early lactation may be contributing to the reduced effectiveness of hormonal treatments for synchronised follicle development and ovulation. The role of reduced dose rates of GnRH in compromising this effectiveness needs to be determined if the potential of these treatments realised with beef cattle is to be achieved with lactating Holstein cows.

Expression of lysyl oxidase and effect of copper chloride and ammonium tetrathiomolybdate on bovine ovarian follicle granulosa cells cultured in serum-free media

Subfertility that will respond to appropriate copper supplementation is a widespread problem in the UK dairy herd and, although characterized by reduced or absent oestrus and reduced conception rates, the exact cause remains unknown. The aim of this study was to investigate the expression of mRNA for the copper-dependent enzyme, lysyl oxidase, and the effect of copper and/or copper chelating thiomolybdates on FSH-induced differentiation of bovine granulosa cells cultured in serum-free media. Expression of lysyl oxidase mRNA was investigated using bovine specific primers and RT-PCR on cell lysates obtained from bovine granulosa cells cultured under optimum conditions for 0, 16, 24, 48, 96, 144 and 192 h. The effect of thiomolybdates and copper were investigated by supplementing optimized granulosa cell culture media with ammonium tetrathiomolybdate at 0, 0.1, 1, 10, 100 and 1000 micro g ml(-1), copper chloride at equimolar concentrations (0, 0.0516, 0.516, 5.16, 51.6, 516 micro g ml(-1)) or equimolar combinations of both media. Lysyl oxidase mRNA was expressed by the granulosa cells throughout the 192 h of culture. Thiomolybdate depressed oestradiol production in a dose-dependent manner at doses > 1 micro g ml(-1) and prevented the characteristic clumped appearance of granulosa cells in this serum-free system. Although the supplementation of copper alone had no effect at physiological doses, the use of the equimolar copper and thiomolybdate media ameliorated the effect of tetrathiomolybdates on both oestradiol production and cellular morphology. In conclusion, the results of the present study indicate that lysyl oxidase is expressed by granulosa cells, that thiomolybdates can prevent FSH-induced differentiation of bovine granulosa cells in vitro and that these effects can be reversed by copper supplementation. Overall, these data support the hypothesis that copper-responsive subfertility results from perturbation of the normal pattern of ovulatory follicle growth and development, an effect that may be mediated, at least in part, via lysyl oxidase activity.

Expression of lysyl oxidase and effect of copper chloride and ammonium tetrathiomolybdate on bovine ovarian follicle granulosa cells cultured in serum-free media

Subfertility that will respond to appropriate copper supplementation is a widespread problem in the UK dairy herd and, although characterized by reduced or absent oestrus and reduced conception rates, the exact cause remains unknown. The aim of this study was to investigate the expression of mRNA for the copper-dependent enzyme, lysyl oxidase, and the effect of copper and/or copper chelating thiomolybdates on FSH-induced differentiation of bovine granulosa cells cultured in serum-free media. Expression of lysyl oxidase mRNA was investigated using bovine specific primers and RT-PCR on cell lysates obtained from bovine granulosa cells cultured under optimum conditions for 0, 16, 24, 48, 96, 144 and 192 h. The effect of thiomolybdates and copper were investigated by supplementing optimized granulosa cell culture media with ammonium tetrathiomolybdate at 0, 0.1, 1, 10, 100 and 1000 micro g ml(-1), copper chloride at equimolar concentrations (0, 0.0516, 0.516, 5.16, 51.6, 516 micro g ml(-1)) or equimolar combinations of both media. Lysyl oxidase mRNA was expressed by the granulosa cells throughout the 192 h of culture. Thiomolybdate depressed oestradiol production in a dose-dependent manner at doses > 1 micro g ml(-1) and prevented the characteristic clumped appearance of granulosa cells in this serum-free system. Although the supplementation of copper alone had no effect at physiological doses, the use of the equimolar copper and thiomolybdate media ameliorated the effect of tetrathiomolybdates on both oestradiol production and cellular morphology. In conclusion, the results of the present study indicate that lysyl oxidase is expressed by granulosa cells, that thiomolybdates can prevent FSH-induced differentiation of bovine granulosa cells in vitro and that these effects can be reversed by copper supplementation. Overall, these data support the hypothesis that copper-responsive subfertility results from perturbation of the normal pattern of ovulatory follicle growth and development, an effect that may be mediated, at least in part, via lysyl oxidase activity.

Type of Cottonseed and Level of Gossypol in Diets of Lactating Dairy Cows: Plasma Gossypol, Health, and Reproductive Performance

Objectives were to determine effects of altering gossypol intake by feeding whole linted Upland (WUP) or a 1:2 blend of WUP and cracked Pima (BUPCP) cottonseed on plasma gossypol (PG) concentrations, reproduction, and health of Holstein cows. Cows, 813, on three dairy farms were assigned to one of two diets starting at 13±11 d in milk for a 170-d experiment. Diets contained 717 and 951mg of free gossypol/kg of dry matter from WUP and BUPCP, respectively. Concentrations of PG, as well as the proportion of total gossypol (TG) as the minus isomer were higher for cows fed BUPCP vs cows fed WUP. Conception rate at the first postpartum artificial insemination did not differ between treatments. However, cows consuming the higher gossypol diet had reduced subsequent conception rates and a lower pregnancy rate. Incidence of abortions increased in the higher gossypol diet, and cows that aborted or remained open had higher PG concentrations. Increasing PG concentrations resulted in reduced conception rates and extended days open. The probability of conception after the first artificial insemination declined at a decreasing rate as the plasma TG increased. Incidence of health disorders were unaffected by gossypol intake and PG concentrations. Similarly, gossypol intake and PG concentrations had no effect on culling or mortality. Six cows died in each diet, and none had postmortem signs compatible with gossypol toxicity. Consumption of a high gossypol diet for 170 d had no effect on health of lactating dairy cows, but it increased PG concentrations and impaired reproductive performance.

Effect of Immunization of Gilts with Zona Pellucida Antigen on Conception Rate and Litter Size

Twenty gilts of the Large White breed were selected and divided into two groups of 10. One group was immunized with porcine zonae pellucidae isolated from ovaries collected from the slaughterhouse. The gilts, control and immunized, were bred. Immunization significantly reduced conception rate, 100% compared to 30% (P

Effects of lactation length and an exogenous progesterone and estradiol-17β regimen during embryo attachment on endogenous steroid concentrations and embryo survival in sows

The hypotheses that short lactation lengths increase embryo mortality by altering endogenous post-weaning steroid concentrations, and that an exogenous steroid regimen during embryo attachment might increase embryo survival were tested using 36 s parity sows assigned randomly to a 2×2 factorial. Sows were subjected to either a short lactation (SL, 13.0 days, n=25) or a long lactation (LL, 31.5 days, n=11), artificially inseminated at first estrus and treated daily with 2 ml i.m. of either 25 mg progesterone (P 4) and 1.25 μg estradiol-17β (E 2) (steroid treatment, ST, n=17) or the vehicle alone (control treatment, CT, n=17) on Days 14–20 post-insemination. Blood samples were collected by jugular venipuncture from weaning to 24 days post-insemination on alternate days. Sows subjected to the SL compared to the LL tended to have a longer weaning-to-estrus interval (WEI) (5.3 versus 4.6 days; P<0.10), but did not have a significantly reduced conception rate (CR) (71 versus 90%; P>0.10). The SL and LL sows had a similar ovulation rate (19.9 versus 21.3 corpora lutea, CL; P>0.05), but SL sows had fewer viable embryos than LL sows (11.5 versus 15.3; P<0.05) when reproductive tracts were recovered 28–32 days post-insemination. In addition, even after correction for the difference in number of embryos between groups, viable embryos from the SL versus the LL group weighed less (1.63 versus 1.79 g; P<0.05), had a decreased amnion volume (1.02 versus 1.22 ml; P<0.05) and apparently produced less estrogens since estrone sulfate concentration was decreased at 24 days post-insemination in SL versus LL sows (4.3 versus 6.3 ng/ml; P<0.05). Embryo survival (percentage of CL represented by a viable embryo) however, was not different between SL and LL sows (60 versus 74%; P>0.05) and no differences in post-weaning P 4 or E 2 concentrations were apparent. Sows that received the ST only tended to have increased P 4 concentrations at 16 days post-insemination compared to CT sows and neither the number of viable embryos, nor embryo survival, was increased in ST versus CT sows (14.7 versus 12.2; P>0.05 and 66 versus 68%; P>0.05, respectively). These data suggest that short lactations do not increase embryo mortality by inducing aberrant endogenous post-weaning P 4 or E 2 concentrations. It is unclear whether or not small, repeated doses of exogenous P 4 and E 2 during attachment can increase embryo survival.

Comparison of the capacitation-like state of cooled boar spermatozoa with true capacitation

Cryopreserved spermatozoa demonstrate reduced conception rates compared with fresh spermatozoa when used for artificial insemination. The preliminary stage of cryopreservation of spermatozoa involves cooling to 5 degrees C, during which spermatozoa experience a capacitation-like change, which may be partially responsible for the reduced conception rate observed. The aim of this study was to determine the nature of these capacitation-like changes and how much this process resembles true capacitation. Boar spermatozoa, cooled to 5 degrees C and re-warmed to physiological temperatures (39 degrees C), were compared with spermatozoa capacitated in Tyrode's complete medium (TALP) for 2 h at 39 degrees C. Fluorescent probes, and SDS-PAGE and western blotting were used to visualize events known to occur during capacitation in vitro. Chlortetracycline staining of membrane domains and Fluo-3 detection of changes in intracellular free calcium by flow cytometry in cooled and re-warmed spermatozoa showed similarities to those of capacitated spermatozoa. Alterations to lipid bilayer fluidity assessed by merocyanine fluorescence staining and intracellular signalling pathways detected by tyrosine phosphorylation of cooled and re-warmed spermatozoa, did not completely reflect the changes detected during capacitation in vitro. Thus, cooling spermatozoa to 5 degrees C results in a similar endpoint to that observed in capacitated cells in terms of reactive membranes and changes in intracellular ion concentrations, which may account for their comparable functionality. However, these modifications are not completely analogous and should not be considered true capacitation, but rather a by-passing of the capacitation process.

Comparison of the capacitation-like state of cooled boar spermatozoa with true capacitation

Cryopreserved spermatozoa demonstrate reduced conception rates compared with fresh spermatozoa when used for artificial insemination. The preliminary stage of cryopreservation of spermatozoa involves cooling to 5 degrees C, during which spermatozoa experience a capacitation-like change, which may be partially responsible for the reduced conception rate observed. The aim of this study was to determine the nature of these capacitation-like changes and how much this process resembles true capacitation. Boar spermatozoa, cooled to 5 degrees C and re-warmed to physiological temperatures (39 degrees C), were compared with spermatozoa capacitated in Tyrode's complete medium (TALP) for 2 h at 39 degrees C. Fluorescent probes, and SDS-PAGE and western blotting were used to visualize events known to occur during capacitation in vitro. Chlortetracycline staining of membrane domains and Fluo-3 detection of changes in intracellular free calcium by flow cytometry in cooled and re-warmed spermatozoa showed similarities to those of capacitated spermatozoa. Alterations to lipid bilayer fluidity assessed by merocyanine fluorescence staining and intracellular signalling pathways detected by tyrosine phosphorylation of cooled and re-warmed spermatozoa, did not completely reflect the changes detected during capacitation in vitro. Thus, cooling spermatozoa to 5 degrees C results in a similar endpoint to that observed in capacitated cells in terms of reactive membranes and changes in intracellular ion concentrations, which may account for their comparable functionality. However, these modifications are not completely analogous and should not be considered true capacitation, but rather a by-passing of the capacitation process.

Dramatic declines in saiga antelope populations

AbstractWe present new data on the size of all the saiga antelope populations; three populations of the subspecies Saiga tatarica tatarica in Kazakhstan, one of S. t. tatarica in Kalmykia, Russia, and two of S. t. mongolica in Mongolia. The data suggest that three populations are under severe threat from poaching and have been declining at an increasing rate for the last 2–3 years. The Ustiurt population in Kazakhstan was relatively secure but is now also under threat. There is evidence of much reduced conception rates in Kalmykia, probably because of selective hunting of adult males. The Mongolian subspecies shows no evidence of recent decline, but is of concern because of the population's small size. The cause of the population declines appears to be poaching for meat and horns, which is a result of economic collapse in the rural areas of Kazakhstan and Kalmykia. We suggest that full aerial surveys be carried out on the Betpak-dala (Kazakhstan) and Mongolian populations, and that funding is urgently required for the control of poaching in all parts of the saiga range.