Analysis of selected sperm by density gradient centrifugation might aid in the estimation of in vivo fertility of thawed ram spermatozoa

The aim of the present study was to evaluate the effect of selecting a sperm subpopulation by means of a discontinuous density gradient centrifugation (DGC) on the quality of ram thawed semen, and the relationships between sperm parameters assessed in unselected and in selected sperm samples with in vivo fertility after intrauterine artificial insemination (IUI) using unselected sperm samples. Semen samples from twenty males were collected by artificial vagina and cryopreserved following a standard protocol. After thawing, unselected sperm samples were used in an in vivo fertility trial and sperm motility (subjective and objective, assessed by means of CASA) and membrane and acrosomal integrities (microscopy) were evaluated on unselected and selected sperm samples. In addition, plasmalemma integrity (YO-PRO-1/PI), membrane fluidity (Merocyanine 540/YO-PRO-1), mitochondrial activity (Mitotracker Deep Red/YO-PRO-1), and DNA fragmentation index (%DFI) assessed by Sperm Chromatin Structure Assay (SCSA^®) were evaluated by flow cytometry before and after sperm processing using DGC. Results showed that DGC improved all sperm parameters significantly, except the %DFI, which increased after the selection procedure. No relationships were found between sperm parameters evaluated in unselected sperm samples and in vivo fertility. However, we found a positive correlation between spermatozoa with high membrane fluidity within the viable sperm population (VIABMerocyanine+) evaluated in selected sperm samples and in vivo fertility (r = 0.370, P = 0.019). In conclusion, our results suggest that selected spermatozoa represent a sperm subpopulation different to the unselected one that could be related with the in vivo fertility.     

Effect of growth and development during the rearing period on the subsequent fertility of nulliparous Holstein-Friesian heifers

This study investigated the effect of growth parameters and metabolic indices during the rearing period on the fertility of nulliparous Holstein-Friesian heifers managed on 17 UK dairy farms. Growth parameters (body weight [BW], heart girth, height, and crown-rump length) and metabolic indices (insulin-like growth factor-I [IGF-I], insulin, glucose, and urea) were measured at approximately 30, 180, and 450 d of age. Fertility data collected included age at first breeding (AFB), number of services per conception, pregnancy rate to first artificial insemination (AI), and age at first calving (AFC). Of the heifers initially bred (n = 428), 4% failed to conceive. The mean pregnancy rate to first AI for heifers that conceived and calved without suffering reproductive loss (n = 392) was 67%, and 6% required >2 inseminations. The mean AFB and AFC was 473 ± 5 d (range, 357 to 936 d) and 791 ± 6 d (range, 636 to 1529 d), respectively. Increased BW, girth, and IGF-I concentration (at 30, 180, and 450 d) and increased skeletal growth (at 180 and 450 d) was associated with a reduced AFB and AFC (P < 0.05 to 0.001). Heifers calving at <775 d had a mean BW gain of 0.82 ± 0.01 kg from 30 to 180 d. Increased glucose concentration at 180 d was associated with a reduced AFB (P < 0.01), but no associations were found between insulin and urea concentrations and any of the fertility traits recorded (P > 0.1). Suboptimal growth associated with an increased AFC could be alleviated by improved monitoring of replacement heifers during the rearing period.     

Fixation of hybrid sterility genes and favorable alleles of key yield-related genes with dominance contribute to the high yield of the Yongyou series of intersubspecific hybrid rice

In rice, the Yongyou series of Xian-Geng intersubspecific hybrids have excellent production performance, as shown by their extremely high yield. However, the mechanisms underlying the success of these rice hybrids are unclear. In this study, three F₂ populations are generated from three Yongyou hybrids to determine the genetic basis of the extremely high yield of intersubspecific hybrids. Genome constitution analysis reveals that the female and male parental lines belong to the Geng and Xian subspecies, respectively, although introgression of 20% of the Xian ancestry and 14% of the Geng ancestry are observed. Twenty-five percent of the hybrid genomes carries homozygous Xian or Geng fragments, which harbors hybrid sterility genes such as Sd, Sc, f5, and qS12 and favorable alleles of key yield-related genes, including NAL1, Ghd7, and Ghd8. None of the parents carries the S5+ killer of the S5 killer-protector system. Compatible allele combinations of hybrid sterility genes ensure the fertility of these intersubspecific hybrids and overcome the bottleneck in applying intersubspecific hybrids. Additive effects of favorable alleles of yield-related genes fixed in both parents enhances midparent values. Many QTLs for yield and its key component spikelets per panicle shows dominance and the net positive dominant effects lead to heterosis. These factors result in an extremely high yield of the hybrids. These findings will aid in the development of new intersubspecific rice hybrids with diverse genetic backgrounds.     

Trisomics of ryegrass and their transmission

Summary Primary trisomics of perennial ryegrass, Lolium perenne L., were studied for meiotic behaviour, fertility, morphology and trisome transmission. Trisomics differed from each other in mean meiotic association, pollen fertility, seed set and morphology. The combined cytomorphological data suggested that the investigated trisomic plants included trisomes 2 to 7. No pollen transmission of trisomes was detected. Female transmission of trisomes ranged from 12% for tri 3 to 37% for tri 4 with a mean of 24% for the six trisomes. Trisome transmission was not related to either chromosome size or trivalent/univalent frequency, although the larger trisomes formed trivalents more frequently than the smaller trisomes.Part of M.Sc.Agr. Thesis, submitted by senior author to the National University of Ireland, Dublin     

Evaluation of the presence of equine viral herpesvirus 1 (EHV-1) and equine viral herpesvirus 4 (EHV-4) DNA in stallion semen using polymerase chain reaction (PCR)

In the horse, the risk of excretion of two major equine pathogens (equine herpesvirus types 1 (EHV-1) and 4 (EHV-4)) in semen is unknown. The objective of our study was to assess the possible risks for the horizontal transmission of equine rhinopneumonitis herpesviruses via the semen and the effect of the viruses on stallion fertility.Samples of stallion semen (n = 390) were gathered from several different sources. Examination of the semen involved the detection of viral DNA using specific PCR. The mean fertility of the stallions whose sperm tested positive for viral DNA and the mean fertility of stallions whose sperm did not contain viral DNA, were compared using the Student's t-test.EHV-4 viral DNA was not detected in any of the semen samples. EHV-1 DNA was identified in 51 of the 390 samples, (13%). One hundred and eighty-two samples came from 6 studs and there was significant difference (p < 0.05) among the proportion of stallions whose semen tested positive for viral DNA from 0 to 55% between the studs.There was a significant difference (p < 0.014) between the fertility of stallions whose semen tested positive for viral DNA and those whose semen was free from viral DNA. The stallions that excreted the EHV-1 virus in their semen appeared to be more fertile than the non-excretors, but this difference was in fact related to the breeding technique since higher proportion of excretors were found among those whose semen was used fresh rather than preserved by cooling or freezing.In conclusion, this study suggests that the EHV-1 virus may be transmitted via the semen at mating or by artificial insemination as demonstrated with other herpes viruses in other species.     

Ice age: Cryopreservation in assisted reproduction – An update

Since the first reported birth following in vitro fertilization in 1978, further developments in assisted reproductive technology (ART) treatments have produced at least 8 million babies worldwide. Cryopreservation techniques have been central to this treatment revolution, increasing cycle efficacy by allowing the banking of supernumerary embryos for later use, as well as affording the prospective patient more time in cases of anticipated fertility decline. Additionally, these techniques have demonstrated promise in increasing the safety of ART treatments, by reducing complications such as ovarian hyperstimulation, leading to increased support for the introduction of a ‘total freeze’ policy involving deferred embryo transfers. Importantly, the effective cryopreservation of both spermatozoa and oocytes has permitted long-term gamete storage without degradation of quality, facilitating gamete banking for personal use or fertility treatment. Here, we will summarise the indications for applying cryopreservation methods in clinical reproductive medicine, highlighting recent technical advances and examining the evidence base that supports the continued use of cryopreservation in ART.     

Reproductive pattern of three amerindian communities from Costa Rica

The bases of the reproductory models of three indigenous communities from Costa Rica belonging to the same cultural area (Chibcha) but with different social, economical and environmental conditions were studied. In this situation it was observed how the study of the data on fertility and fecundity, analyzed together with other reproductory and social characteristics of women, can precisely determine the reproductory model of the communities to which they belong. A homogeneous fecundity was presented in the studied communities, but one which responded to different reproductory patterns. Starting from the multivariate analysis of the fertility variables, the studied women were divided into two groups. One of the groups presents the highest levels of length of breast feeding period and amenorrhea, together with the near total lack of artificial breast feeding and the early introduction of normal feeding. This model is predominant among the Guaymies. The other one, together with the short period of breast feeding and amenorrhea, shows an early introduction of the bottle and a late one of solid food in the feeding process. It is characteristic of the Huetars. This links a certain reproductory model to an indigenous community and a way of life. The reproductory pattern, a clearly biological model, to an ecological and cultural environment.     

No correlation between chimerism and fertility inCallithrix jacchus (Callithricidae,Primates)

In this study, 40 individuals ofCallithrix jacchus were analyzed in order to investigate the frequency of chimerism and to determine whether the fertility of the colony was in any way affected by chimerism. In the individuals considered the degree of chimerism ranged from 2% to 97% and no correlation was established between the degree of chimerism and fertility of the individuals. Many “good breeders” were chimeric and the best female breeders displayed 84% and 97% chimerism respectively.