Population Of Mares Research Articles

GENETIC PARAMETERS D-SYSTEMS OF BLOOD TYPE IN MARES OF NOVOОLEKSANDRIVSKA HEAVY AND TORI BREEDS

The article presents the results of studies of the immunogenetic structure of mares of the novoоleksandrivska and tory breeds of horses of different farms of Ukraine according to the D-system of blood groups. A comparative analysis of these breeds was carried out, taking into account the fact that the novoоleksandrivska is a weight-carrying breed, and in the Tory breed we singled out only the heavy type. That is, our goal was to find common or different features in their immunogenetic profiles. The population of mares of the novoоleksandrivska heavy breed is characterized by a high frequency of alleles: Ddg (0.225), Dad (0.183), Dd (0.167). Dde (0,162), Dcgm (0,142). The Dbcm (0.039), Dcegm (0.035), and Ddk (0.015) alleles were relatively less frequently detected. Thorians have a high frequency of alleles: Dcgm (0.326), Ddk (0.260), Dd (0.138) Ddg (0.10). The Dde (0.08), Dbcm (0.042), Dcegm (0.020), and Dad (0.014) alleles are less common. The rarest allele in the novoоleksandrivska heavy truck is Ddk (0.015), which is 6.67% less common than Ddg (0.225). Thus, the level of genetic diversity in all studied breeds is at a high level, which indicates a significant reserve of variability and creates the basis for further selection and breeding work. A comparative characterization of the novoоleksandrivska and tory breeds was carried out and it was established that the frequency of occurrence of Dad and Ddg alleles in the novoоleksandrivska heavy hauler is higher than the average for the breed. At the same time, Dсgm and Ddk alleles predominate in the heavy type of the tory breed, which is characteristic of each breed and can serve as a kind of "genetic passport".

Methods for parturition monitoring in the mare - an overview

Various systems are available for birth monitoring in horses, whereby a distinction must be made between methods for more accurate prediction of the date of birth in order to intensify monitoring of the mare in a timely manner as well as methods for detecting individuals that are in labor. Basically, it should be noted that there are almost no studies that compare different methods on the same population of mares. As the time of birth approaches, physiological parameters of mare and fetus change, but their variability is too high to predict the exact parturition time point prospectively. The best method currently available is the detection of a decrease in the pH value and an increase in the calcium concentration of the udder secretions.Continuous camera monitoring is currently the method of choice for the detection of the start of the parturition process. However, the downside of this method is that the recordings have to be evaluated by a human.Recent developments based on the use of artificial intelligence could provide significant improvement. Before these methods are ready for practical use, the combination of camera monitoring and a sensor that is sewn into the vulva and activated during the opening phase of parturition is the safest method.

Evaluation of peritoneal l-lactate concentration in horses in the early post-partum period.

Peritoneal fluid lactate concentration is an important diagnostic tool in horses with abdominal pain. Information on peritoneal lactate concentrations is lacking following parturition in the mare. To compare blood and peritoneal lactate concentrations in a population of mares within 36h post-partum, report a normal reference range and identify any impact of retained foetal membranes (RFMs). This is a retrospective study evaluating healthy mares from which blood and peritoneal samples had been obtained within 36h of parturition. Exclusion criteria included signs of abdominal pain within this period. Data was interrogated for normality using a Shapiro-Wilk test. Wilcoxon signed-rank test and Bland-Altman analysis were used to compare blood and peritoneal lactate concentrations. Linear regression was used to compare age and breed data with peritoneal lactate concentrations. Significance was defined as p<0.05. Forty mares met the inclusion criteria. Mean age was 12.6±4.1 years, and most mares were multiparous (65%). Peritoneal lactate ((1.2 (IQR=0.9-1.6)mmol/L) was increased compared to blood lactate concentration (0.7 (IQR=0-1.1)mmol/L; p<0.001). Plasma total protein (TP) concentrations were 68 (IQR=64-74)g/L and peritoneal protein concentrations 8 (IQR=4-9.7)g/L. Six mares developed RFM. The median fold-increase in peritoneal lactate concentration compared to blood lactate concentration was 0.9 (IQR: 0.01-1.7; range: 0-2.5). The reference range for peritoneal fluid lactate concentration was 0-2.5mmol/L. Peritoneal lactate concentrations in healthy post-partum mares remained within the normal reference range and were not influenced by RFM or parturition. Increased peritoneal lactate in this group warrants further investigation.

Effects of repeated embryo flushing without PGF2α administration on luteal function, percentage of unwanted pregnancy and subsequent fertility in mares.

PGF2α is commonly given at the end of embryo flushing (EF) to shorten the interval to the next oestrus and ovulation. To determine the effect of repeated EF on plasma progesterone concentration, percentage of mares with endometritis, unwanted pregnancy and subsequent fertility in mares flushed without the use of PGF2α. Controlled experiments. Nine mares were inseminated in seven consecutive cycles (n = 63), to either perform an EF (n = 54) 7-9 days after ovulation or left pregnant (n = 9). PGF2α was not used to induce oestrus. Ultrasound examination and blood sampling were performed just before the EF and 72 h later to determine changes in progesterone concentration and signs of endometritis. The overall percentage of positive EF/pregnancy was 55.5% (30/54) and 66.7% (6/9), respectively. The likelihood of pregnancy/positive EF in the first three cycles was 55.5% (15/29). This was not different (p > 0.1) from the fertility of the last four cycles (69.4%, 25/36). In five EF cycles (9.3%), mares had signs of endometritis and early luteolysis (progesterone <2 ng/mL) 72 h after EF. The reduction in progesterone concentration by 72 h after EF was greater (p < 0.05) for Day 9 (-2.3 ± 0.7 ng/mL) than Day 7 (-1.0 ± 0.8 ng/mL) or Day 8 (-1.3 ± 1.1 ng/mL) cycles. The progesterone concentration in non-flushed mares did not vary significantly during the sampled period (Day 7-12). There were 5 cycles in which the donor mare remained pregnant after the EF, although four were from a single mare. The mare population was limited to barren and maiden mares. The cycle order and operator allocation to each EF were not randomised. EF induces a subtle, but significant reduction in progesterone concentrations compared with non-EF cycles. However, the percentage of mares with EF-induced full luteolysis is low (9.3%). The fertility of mares after repeated EF without administration of PGF2α was unaffected; however, there is a considerable risk of unwanted pregnancy (5/27 = 18.5%) in donors from which an embryo was not recovered.

Effect of mid-diestrus oxytocin treatment on early pregnancy in the mare

Progesterone supplementation in early pregnancy is commonplace in equine reproduction. Recently, there has been some controversy questioning the beneficial effects of routine progesterone administration and rising concerns of medication exposure as an occupational hazard for humans. Although premature luteal regression and resulting low plasma progesterone concentrations are rare in the mare, select cases benefit from luteal support. Duration of luteal function can be prolonged following oxytocin administration during mid-diestrus in the non-pregnant mare (Vanderwall.et.al. Journal of Equine Veterinary Science. 2012; 32:536-541). The aim of this field study was to investigate the effects of oxytocin administration on early pregnancy in the mare. Thoroughbred mares (n = 39; age 5 to 19 years) were enlisted and bred over 55 estrous cycles. Prior to natural breeding, uterine cultures were obtained, and mares were assigned to 1 of 2 groups: Oxytocin treatment (OT); oxytocin 60 units, intramuscularly, once daily, days 7-14 post-ovulation; or Control (CT); no treatment. Mare reproductive cycles were monitored by transrectal palpation and ultrasonography. Ovulation was documented and defined as day 0. Pregnancy diagnosis was performed by transrectal ultrasonography day 14 post-ovulation. If pregnancy was confirmed, a blood sample was collected and assayed for plasma progesterone concentration. Mares that did not conceive were administered prostaglandin F2αanalogue (cloprostenol; 250mcg once intramuscularly) at day 16 post-ovulation. These mares were rebred and treatment was determined by the stage in the study; therefore, some mares underwent the same treatment more than once. Subsequent pregnancy examinations were performed on days 28 and 45 of pregnancy. Data were analyzed using two-tailed Fisher's Exact tests for small counts, with significance defined at p < 0.05. First and per-cycle pregnancy rates for OT and CT were 90.9 and 91.3% and 68.2 and 55.1%, respectively. Median progesterone concentrations for OT were 6.9 and 7.0 ng/ml for CT. There were no differences between OT and CT groups for first (p = 0.165) or per cycle (p = 0.289) pregnancy rates, days 28 and 45 pregnancy rates (p = 1.0), or progesterone concentrations (p = 1.0). In this population of mares, oxytocin administration during mid-diestrus in early pregnancy did not induce a negative effect on pregnancy rate nor a positive effect on progesterone concentration. Whilst the study design did not assess the effect of OT on the inter-ovulatory interval (IOI), the authors’ hypothesize that the IOI would be increased, due to prolonged luteal function, in the non-pregnant OT mare if prostaglandin F2α analogue was not administered. Further investigation in this area may reveal potential beneficial effects of oxytocin administration in early pregnancy.

Pedigree-Based Description of Three Traditional Hungarian Horse Breeds.

Simple SummaryThe most important purpose of animal conservation programs is to maintain genetic variability. The Furioso-North Star, the Gidran, and the Nonius are indigenous Hungarian horse breeds from the Mezőhegyes Stud. In the last century, the role of the horses was changed, the technical innovations and motorization replaced them, so the population size and the genetic variability of these breeds were reduced. Nowadays these breeds are endangered. The aims of this study were to give information about the current breeding population and support breeder associations during their gene conservation work. The pedigree quality, generation intervals, probability of gene origin, and inbreeding were evaluated. We found that breeds had a large bottleneck effect during breeding history. The level of inbreeding was measured with different methods, such as Ballou’s, Wright’s, and Kalinowski’s coefficient. Most of the current inbreeding coefficient was the result of previously fixed alleles for each breed. Effective population size was also estimated, and the status of the breeds was found to be not critical according to FAO criteria.The Mezőhegyes Stud was founded in 1784 where three different horse breeds were developed: the Furioso-North Star, the Gidran, and the Nonius. These breeds were based on the same mare population, but each breed had different utilization purposes. Our aim was to analyze the pedigree information of these three indigenous breeds. The genealogical information was traced back from the actual breeding population back to the founder animals, and the final database contained more than 47,000 horses. The reference populations were defined as the registered breeding animals in 2019. The complete generation equivalent was 16.45 for the Gidran breed, 15.18 for Furioso-North Star, and 12.64 for Nonius, respectively. Due to the utilization of English Thoroughbred during the breeding history, the average maximum generations were close to 36 generations for each breed. The average relatedness was approximately 4%. The average Wright’s inbreeding coefficient was the highest for the Nonius breed (5.59%). Kalinowski’s decomposition of inbreeding showed that inbreeding is originated mainly from the past; the current fixation of alleles was higher for the Nonius horse breed. There was a reasonable bottleneck effect for each breed. The estimated effective population sizes suggest that there is no problem with the maintaining of Mezőhegyes horse breeds.

Nocardioform placentitis in a sample population of mares foaling in southeastern Pennsylvania and northeastern Maryland in 2020

Nocardioform placentitis (NP) has been associated with mid to late pregnancy loss in mares. To date, disease outbreaks have been described only in central Kentucky, although sporadic, isolated cases have been reported globally. This study describes a series of cases of NP that occurred in a sample population of 299 mares foaling in southeastern Pennsylvania and northeastern Maryland in 2020. These cases coincided with an outbreak of NP that occurred in Kentucky that same year. On farms that reported information on both normal and abnormal foalings, nocardioform organisms/DNA were isolated from 6.3% of placental samples based on aerobic culture and/or PCR. In cases with characteristic gross lesions of the chorion, 41% of cases were positive on aerobic culture and/or PCR. NP was confirmed in 16 mares that had not resided in Kentucky for breeding or any part of gestation. Characteristics of mares confirmed positive for NP, including age, gestation length, and problems during gestation are described. Standardbred mares bred by artificial insemination were less likely to be affected than Thoroughbred mares bred by natural cover. Affected mares had prolonged Stage III labor compared with normal mares. These findings suggest that regional increases in NP may occur outside of Kentucky, potentially in parallel with Kentucky outbreaks.

Quantifying the effect of Warmblood Fragile Foal Syndrome on foaling rates in the German riding horse population.

Awareness of breeders of Warmblood Fragile Foal Syndrome (WFFS) increased after a widely discussed case in the USA in 2018. The hereditary connective tissue disorder, first described by a US research group in 2011 and for which a commercial genetic test exists since 2013, is caused by a point mutation in the PLOD1 gene, inherited autosomal recessively. Extension of molecular genetic testing and reporting of test results of organized horse breeders to their studbooks implies new opportunities for analyses. In Germany, data are centrally accessible through the integrated equine data base allowing comprehensive and population-wide investigation of the role of WFFS. The objective of this study was statistical testing for associations between WFFS and reproductive performance of German riding horses and quantifying possible differences between WFFS carriers and non-carriers, also in respect of performance traits. For this purpose, covering data from 2008 to 2020 were provided by ten German studbooks, so almost 400,000 coverings and resulting foaling rates were available for multiple analyses of variance with general and mixed linear models using procedures GLM, MIXED and HPMIXED of SAS software (version 9.2). Published breeding values of stallions were used for respective comparisons of riding horse performance. Assuming a WFFS carrier frequency of 9.5-15.0% in Warmblood horses, Hardy Weinberg principle implied an expected difference of 2.4-3.7% in the foaling rates of carrier and non-carrier stallions. Our results provided statistical evidence of detrimental effects of WFFS on the reproductive performance of Warmblood horses with about 2.7% lower average foaling rate in carriers of the mutant allele than in WFFS free sires, if mated to an average mare population. Indications of favorable dressage performance of WFFS carriers were found. Reported WFFS cases indicate only the tip of the iceberg and assessing the impact of WFFS on reproduction requires consideration of premature foal losses.

The pattern of breeding and management within the New Zealand Thoroughbred breeding industry 2005–2015. (II) The mare population

Context The New Zealand Thoroughbred breeding industry is heavily focused on producing horses for the export market and there has been a reduction in the number of horses racing in the past 20 years. The impact of these production constraints, and changes in production focus, have not been described at a national herd level. Aim To describe the breeding management, reproductive performance, and careers of the New Zealand Thoroughbred broodmare herd during the 2005/06–2015/16 breeding seasons. Methods The demographics, population structure, reproductive efficiency, breeding management and career descriptors of Thoroughbred mares were examined using descriptive analysis. Gestation length was modelled using a linear mixed effects model. The impact of different variables on breeding career were quantified by calculating odds ratio. Results There was a consistent reduction in the size of the national broodmare herd over the 10 years investigated. Half of the mares not retained for breeding were mares that were breed to low-cost stallions. Despite a short (∼100 days) commercial breeding season few (20%) mares were mated early in the season (September), with most mating (70%) occurring between October and November. The 27 days mean foaling to conception interval (FCI) suggests that FCI was artificially shortened and most pregnancy was achieved within first oestrus cycle post-partum. Mare career length and lifetime productivity was positively associated with the stud fee of the first stallion that the mare was mated to and number of foals registered for racing. Conclusion Mare replacement and loss within the national herd was disproportionately associated with mares that were producing foals for a contracting domestic racing market. There was a constricted breeding season with most mares being mated within the first oestrous cycle post-partum. Mare retention and breeding success were positively associated with the service fee of the sire and progeny that had raced, reflecting the commercial pressure of the industry on mare management. Implication The changes in the broodmare herd and management reflects the increasing proportion of the industry focusing on breeding foals that will appeal to the export market. The economic drivers for early born foals provide management challenges as these are not aligned with the optimal reproductive season of the horse.

Activities of matrix metalloproteinase-2 and -9 in amniotic fluid at parturition in mares with normal and high-risk pregnancy

The matrix metalloproteinases (MMPs) are a family of enzymes involved in extracellular matrix remodeling. MMPs are secreted in a latent form and activated by local and infiltrating cells. MMP-2 and -9 are the most studied in reproduction and have been detected in bovine, ovine, equine and human placenta. There is only one study on MMPs in the equine amniotic fluid (AF) reporting a decrease in the activity of MMP-2 in case of premature delivery. The aim of this study was focused on MMP-2 and -9 activity in AF collected at parturition from mares with normal or high-risk pregnancy. High-risk pregnancy was defined as a history of premature udder development/lactation, increase of combined thickness of the uterus and placenta, vulvar discharge and/or mare's systemic illness. The diagnosis of placental insufficiency was confirmed retrospectively after macroscopic and histopatologic examination of the placenta. AF was collected by needle puncture of the amnion within 5 min after its appearance through the vulva. The activity of MMP-2 and -9 was analyzed by in-gel zymography allowing the evaluation of both latent and active forms. Twenty mares with normal pregnancy (group 1) and 8 mares with high-risk pregnancy (group 2) were included. All mares in group 2 had a high-risk pregnancy with a diagnosis of placental insufficiency associated with placental villous hypoplasia, placentitis or placental edema. The bands relative to latent and active forms of MMP-2 were clearly visible in both groups and the activity of latent (P = 0.010) and active (P = 0.004) forms was lower in the AF samples of group 2. The band of the latent form of MMP-9 was visible in 17/20 samples of group 1, while it was completely absent in all samples of group 2. In contrast, the band of the active form was clearly visible and with a greater activity in AF samples of group 2 (P = 0.002). Placental dysfunction seems to induce a lower MMP-2 activity and a higher MMP-9 activity through the release of pro-inflammatory cytokines. Because fetal pulmonary secretions are a likely source of gelatinases in AF during late gestation, the increased MMP-9 activity could be related to fetal distress. These data provide a starting point to better understand the role of MMPs in equine pregnancy, although it should be confirmed in a larger and more homogeneous population of mares with high-risk pregnancy.

The Effects of Treatment with N-Acetyl Cysteine on Clinical Signs in Persistent Breeding-Induced Endometritis Susceptible Mares

Persistent breeding-induced endometritis (PBIE) is a major cause of infertility in mares. Endometrial inflammation that persists until embryonic descent ultimately results in early embryonic death. A poor endometrial biopsy grade (IIb or III) has been identified as a risk factor for PBIE. Intrauterine fluid accumulation (>2 cm in depth), pathologic endometrial edema, and elevated intrauterine neutrophil levels are all clinical features of PBIE. Commonly applied treatment options include uterine lavage and oxytocin therapy. N-acetyl cysteine (NAC), a mucolytic used to treat bacterial endometritis in mares, has anti-inflammatory properties and was investigated as a potential treatment for PBIE. A randomized, blinded, cross-over design clinical trial used NAC before breeding in PBIE-susceptible mares (n = 9). Intrauterine infusion of 3.3% NAC was performed 12 hours before insemination, and endometrial cytology and endometrial biopsy samples were obtained at 12 and 60 hours after insemination. Endometrial biopsies were evaluated for the degree of inflammation present. Clinical signs of endometrial edema and intrauterine fluid volumes were assessed by transrectal ultrasound at 12 and then every 24 hours after breeding. Data were analyzed using repeated measures analysis of variance and a Mann Whitney Wilcoxon Test. Treatment with NAC did not improve clinical signs in PBIE-affected mares. However, endometrial biopsies from mares treated with NAC displayed more diffuse and severe neutrophil infiltration than control cycles. Further research using a larger population of mares is required to evaluate the effects of NAC treatment on the endometrium of PBIE-susceptible mares.

PSXVI-33 Evaluation of the microbiome of mares’ milk through lactation.

Classically, the nutrients in milk have been studied as critical components to support growth. Recently, other factors have been identified for their role in supporting neonatal nutrition. Once thought to be sterile, milk is known to be populated by numerous microbes, an important factor related to the development of the foals’ gastrointestinal microbiome. It is believed that the initial inoculum comes as the foal passes through the vaginal canal and continues as the foal interacts with its environment, and consumes milk. The objective of this study was to evaluate the bacterial population of mares’ milk. Samples were evaluated and bacterial population data was correlated to the age, BW, and BCS of the mare, days of lactation, offspring gender, and physiological growth measurements of the foal. Eight multiparous Quarter Horse mares foaled naturally and milk samples were obtained aseptically at 36 hr, 70 d, and 136 d post foaling. Mares were offered 8 lb of concentrate (Purina® Ultium Growth®) 2x/d and 18 lb of hay with free choice access to water and salt. Microbial DNA was extracted and PCR amplified prior to sequencing utilizing an Illumina® MiSeq® platform. Bacterial diversities were determined based on OTU assignment between and within samples. Data were analyzed via ANOVA using the MIXED procedure of SAS. 94.57% of reads were mapped to SILVA (V4) database. No differences existed in alpha or beta diversity. The predominant phyla were Firmicutes. Staphylococcus were the predominant genera. The small sample size may have resulted in the lack of observed differences. With the absence of any differences observed when analyzing the metadata, this study provides insights into the bacterial population of mares’ milk through lactation. In the future, this data can be utilized to examine the early colonizers of the foal gastrointestinal tract and identify targets for probiotic or prebiotic supplementation.

Can ovariectomy be justified on grounds of behaviour?

Can ovariectomy be justified on grounds of behaviour?

113 PRELIMINARY CHARACTERIZATION OF OXYTOCINASE IN EQUINE SERUM

Oxytocinase/insulin regulated aminopeptidase (IRAP) or leucyl-cystinyl aminopeptidase (LNPEP) is an enzyme that is involved in the regulation of hormones such as oxytocin, vasopressin, and angiotensin in both humans and sheep. Historically, very low levels of this aminopeptidase were reported in monthly samples obtained from cycling and pregnant mares using an enzymatic colourimetric method. The regulation of oxytocin in horses is of interest because of its central role in uterine clearance, luteal maintenance, parturition, passage of fetal membranes, maternal foal bonding, and milk let-down. A preliminary study was performed with the objective of re-examining the level of serum oxytocinase in nonpregnant control (n = 3 mares sampled every other day; EOD of the oestrous cycle), and n = 5 mares sampled Day 12 to 15; oxytocin-treated (n = 2 mares sampled Day 12 to 15), and early pregnant mares (n = 6 mares sampled EOD), using more sensitive ELISA methodology. Mares were examined daily in oestrus until ovulation (Day 0) and from Days 10 to 21, using transrectal ultrasonography of the reproductive tract. Palpable changes in uterine and cervical tone, ultrasound measurement of dominant follicles, oedema scores (0 to 4 with 4 being maximal oedema), and changes in luteal echotexture and size were recorded. Pregnant mares were bred using AI (&gt;200 million motile and normal sperm) from a proven stallion while in oestrus until ovulation, beginning when the dominant follicle was &gt;35 mm. Oxytocin-treated mares were administered 60 IU IM oxytocin SID from Day 7 to 14. Blood was collected to obtain serum. Changes in serum oxytocinase levels were measured using a commercially available ELISA kit for Horse LNPEP according to the manufacturer's instructions (MyBioSource, San Diego, CA, USA) and validated for use in our laboratory using serial dilutions of pooled serum with an intra-assay and inter-assay CV &lt;15%. The lowest standard of the assay was 31.2 ng mL–1. Preliminary results of this pilot study demonstrated in control cycles median serum oxytocinase levels below the lowest standard (2.0 to 30.1 ng mL–1). Oxytocin-treated mares had median serum oxytocinase levels from 39 to 61 ng mL–1 on Days 12 to 15. Early pregnant mares had detectable levels from Day 8 to 21 (medians ranging from 40 to 89 ng mL–1). We concluded that serum oxytocinase levels were below the lowest standard in diestrus, and were low but detectable in oxytocin-treated mares. The highest oxytocinase levels were measured during early pregnancy. Further studies of serum oxytocinase in a larger population of mares, along with studies of tissue mRNA levels of oxytocinase, are required to better understand the regulation of oxytocin in horses. Research was supported by the Natural Sciences and Engineering Research Council of Canada (Ottawa, ON, Canada) and the Equine Health Research Fund (University of Saskatchewan, SK, Canada).

Pedigree analysis of Thoroughbred horses in Slovakia

DOI: 10.15414/afz.2014.17.04.122–126 Received 14. April 2014 ǀ Accepted 17. July 2014 ǀ Available online 24. November 2014 The aim of this paper was to evaluate the breeding population of Thoroughbreds in Slovakia by means of pedigree analysis. Examined population consisted of 123 mares and 10 stallions registered in Slovak Stud Book. Three stallions linked to Nasrullah line (30%) and 2 stallions linked to Northern Dancer (20%) and Native Dancer (20%) lines. Over a half of mares were represented by Northern Dancer line (50.41%). The 64 mares had Slovak rating mark, 21 mares had German GAG, 3 mares had Swiss GAG, 3 mares had Czech GAG and 1 mare had Austrian GAG. The 31 mares had no own performance results. The average Slovak rating was 61.51 kg. There were 10 animals (15.63%) with underaverage performance, 43 animals (67.18%) with average performance and 11 animals (17.19%) with above-average performance in population of mares with Slovak rating. The average inbreeding coefficient was 0.86% in whole reference population (133 individuals) and increase in inbreeding per generation was 0.17%, in stallions 0.25%. The number of founders in investigated population was 949. The effective number of founders was 202, while the effective number of ancestors was 67. These results point out unbalanced contributing of founders and ancestors into reference population as well as the bottleneck effect occurance. The Northern Dancer (CAN) was the most important ancestor in investigated population with individual contribution IC=7.88%. Keywords: genetic diversity, inbreeeding, pedigree analysis, racing, Thoroughbred

Short communication. Mitochondrial DNA diversity of the founder populations of the Asturcón pony

A 380 bp fragment of the horse D-loop region was analysed in 42 founder mare samples of the bay-coated Asturcón pony obtained in three different and reproductively isolated mountainous areas of Western Asturias: range of “La Bobia” (20), range of “Carondio” (13) and range of “El Aguión” (9). These sequences were compared with the information provided by 37 founder matrilines of black-coated Asturcón assigned to the range of “Sueve” (26) and the “out-of-Sueve” (11) founder populations. The aim of this research was to ascertain the differences in founder mtDNA diversity between the two strains of the Asturcón pony and if such differences have geographical consistency. The 79 sequences analysed gave 16 different haplotypes defined by 33 polymorphic sites. The two Asturcón strains shared eight haplotypes that gathered 76% and 81% of the samples available in bay-coated and black-coated Asturcón, respectively. Both haplotypic (0.027 ± 0.006) and nucleotide (0.021 ± 0.011) diversity were higher in the bay-coated than in the black-coated Asturcón (0.024 ± 0.005 and 0.016 ± 0.009, respectively). AMOVA analyses failed in assessing any statistically differentiation among Asturcón geographical populations or strains. Most genetic variability is due to the individuals (estimates varying from 96.34% to 99.81%). Differentiation among strains or population took low and non-significant values. Differentiation between Asturcón pony strains using mtDNA marker would not have clear support. The two strains of the Asturcón pony breed likely derive from the same ancestral mare population.

Factors Influencing the Frequency of Pregnancy Loss among Thoroughbred Mares in Hidaka, Japan

Pregnancy loss in mares is thought to be a main problem associated with reproductive efficiency. To clarify the situation of pregnancy loss in Thoroughbred mares in Japan, the occurrence of pregnancy loss before and after 35 days of gestation was investigated with 1,476 Thoroughbred mares in Hidaka, Japan, from 2007 to 2009. Pregnancy loss on days 17-35 was determined by ultrasound examination between 17 and 35 days after the last mating. Follow-up surveys were conducted between 35 days and foaling to determine pregnancy loss on day 35 until foaling in 843 of these mares. Using multiple logistic regression analysis, we assessed the influence of mare age, reproductive status, twin pregnancy reduction, body condition score (BCS), estrus type in foaling mares (foal heat or not), progesterone therapy, and endometrial cysts on pregnancy loss rates on days 17-35 and on day 35 until foaling in this population of mares. The pregnancy loss rates on days 17-35 and on day 35 until foaling were 5.8% and 8.7%, respectively. The overall pregnancy loss rate (day 17 until foaling, including parturient losses) was 14.7%. Risk factors for pregnancy loss included decrease in BCS between 17 and 35 days, <5 BCS at day 35, mating during foal heat, and endometrial cysts. In all, 14.7% of pregnancies were lost between day 17 and birth, contributing significantly to reduced reproductive efficiency in Thoroughbred mares in Japan. These observations indicate that mares should be maintained at high BCS and should be prevented from mating in foal heat to decrease the pregnancy loss rates.

Neosporose equina: ocorrência de anticorpos anti-Neospora spp. e associação entre status sorológico de éguas e de suas crias

Os protozoários Neospora caninum e N. hughesi infectam os equinos e podem provocar diferentes sinais clínicos associados a problemas reprodutivos ou a distúrbios neurológicos, respectivamente. A patogenia da neosporose é pouco conhecida nos equinos, bem como as fontes de infecção horizontal de N. hughesi. Além disso, há dúvidas quanto ao papel da transmissão vertical de Neospora spp. na sua manutenção em populações equinas. Neste estudo avaliaram-se: (1) a ocorrência da infecção por Neospora spp. na população de éguas em idade reprodutiva em um haras de cavalos da raça Crioula; e (2) a possível associação entre o status sorológico destas éguas com o de suas crias, como meio de investigar, indiretamente, a relevância da transmissão transplacentária na ocorrência da infecção por Neospora spp. nestes animais. A associação entre o status sorológico das éguas e o de suas crias foi altamente significativa. Os animais descendentes de éguas soropositivas tiveram maior ocorrência de anticorpos anti-Neospora spp. do que os descendentes de éguas soronegativas, embora expostos aos mesmos fatores de risco ambientais. A associação entre parentesco em primeiro grau e status sorológico indica a influência da infecção vertical (transplacentária) na ocorrência de Neospora spp. na população equina estudada.

Subclinical infection and periodic shedding of equid herpesvirus 3

The temporary disruption of reproductive activities due to equine coital exanthema (ECE), caused by equid herpesvirus 3 (EHV-3), at thoroughbred breeding facilities and embryo transfer centres, has an appreciable economic impact. The aim of the present study was to estimate the prevalence of excretion of EHV-3 in mares without clinical symptoms under field conditions and the re-excretion patterns of the virus in two seropositive (presumably latently infected) mares maintained in isolation for 11 mo. The EHV-3 virus was detected in perineal-vaginal swabs by real time PCR in 14 (6%) of 220 thoroughbred mares without clinical symptoms at the time of breeding. In the two isolated mares, re-excretion of EHV-3 was demonstrated on two occasions, 3 mo apart (each for a 3 d interval) in one mare, and on only 1 d in the other mare. Antibodies against EHV-3 were identified by seroneutralization in 105 (48%) of the thoroughbred mares, and during the entire period in the two isolated mares. Therefore, the present study provided evidence of EHV-3 shedders in a healthy mare population under both field and isolation conditions. Furthermore, at least two periods of spontaneous EHV-3 reactivation and re-excretion in the presence of serum antibodies occurred in one mare in an 11 mo interval. These findings could assist in the design and implementation of measures to minimize the spread of EHV-3 and control ECE outbreaks.

Risk Factors for the Development of Haemorrhagic Anovulatory Follicles in the Mare

Haemorrhage into the dominant follicle during the reproductive season is a subtle but definitive cause of infertility in the mare population. This condition however can be of high relevance for an individual in which its incidence is abnormally high. Little is known about the nature and factors affecting the incidence of haemorrhagic anovulatory follicles (HAFs) in the mare. The objectives of the study were to define and characterize the ultrasonographic development and incidence of HAFs and to investigate possible risk factors influencing its occurrence. Detailed reproductive and ultrasound records of seven mares studied during their entire reproductive lives (>10 years and 612 oestrous cycles) were analysed retrospectively and computed into a statistical mixed model. Of all animal studied, two mares were found to have an unusually high incidence of HAFs of approximately 25%. Time of season and use of induction treatments (Cloprostenol) were found to influence its incidence. It appears that early-enhanced stimulatory effect of LH on an ovary with the presence of small and immature follicles might increase the risk of ovulatory failure of those follicles later in the cycle. Mares during the months of highest follicular activity (May to August) and after treatment with hormones to induce oestrus and ovulation are at greater risk to develop HAFs. The potential relevance of this study is two folds: clinical relevance for the practitioner to better understand this condition and so improve reproductive management of mares with abnormally high incidence; and to provide useful insights for researchers willing to further investigate the nature of this phenomenon.