Mares In Group Research Articles

Reversibility of the effects of GnRH‐vaccination used to suppress reproductive function in mares

Active immunisation against gonadotrophin-releasing hormone (GnRH) provides a reversible method for control of oestrous behaviour and fertility in mares. Previous reports failed to demonstrate the interval to resumption of cyclic ovarian activity after GnRH-vaccination. Administration of the GnRH-vaccine Improvac in a large group of mares of various ages will result in effective, reliably reversible suppression of ovarian activity within a 2 year period. The mares, subdivided into 3 age categories, were vaccinated twice (with a 35 day interval) using 400 µg Improvac and monitored via blood samples until Day 720 after initial vaccination for serum progesterone concentration determination by radioimmune assay and anti-GnRH antibody titre by enzyme immunoassay. Samples were collected until individuals resumed cyclic ovarian activity. All mares showed suppression of cyclic ovarian activity by clinical examination and serum progesterone concentration (SPC) ≤ 1 nmol/l by Day 70 and 92.2% resumed cyclic activity by SPC at Day 720 with a mean interval = 417.8 days (s.d. ± 23.9; range 232-488 days, median 344 days). A significant age effect (P = 0.028) on the interval, but not on GnRH-antibody titre response, was observed between the youngest (≤ 4 years) and oldest (≥ 11 years) categories. Immunising adult mares of all ages with Improvac resulted in a reversible suppression of cyclic ovarian activity in most mares. An age effect, with the youngest mares showing a longer interval to reversibility, was observed.

Coping in groups of domestic horses – Review from a social and neurobiological perspective

Many sport horses live solitary, with no physical contact to other horses allowed for years, for many different reasons including limiting risk of injuries caused by other horses. Other horses are (semi-) permanently housed in large groups, because their owners perceive this is “natural” and thus good for their horses’ welfare. Indeed, sometimes this leads to increased aggression and individuals who cannot cope with social stress and limited space. However, usually humans determine the social composition of these groups of geldings and mares, possibly leading to other interactions as known from natural equine societies. In this review paper the underlying neurobiological mechanisms of social relationships and social dynamics in modern horses were assessed. Ultimately, it can help to define hypotheses to determine strategies what could be most optimal non-voluntary social compositions of domestic groups and adjust introduction techniques so the individuals can cope optimally, i.e. to show the lowest ethological and physiological stress indicators over both short and long period of time.Based on neurobiological evidence it is shown that indispensable behaviours like exploration and grooming are displayed because of their rewarding properties. Endogenous opioids play a pivotal role in rewarding the individual and motivate it to perform these behaviours, irrespective of the short-term biological success of such indispensable behaviours. Equine allogrooming and play in domestic groups have been addressed to assess whether they fulfilled the four ethological need criteria: (i) performed by all individuals; (ii) self-rewarding; (iii) have a rebound effect and (iv) in absence of a proper substrate (i.e. social partner) chronic stress is induced. Indeed it was assessed whether equine allogrooming and play are ethological needs. Not only in domestic non-voluntarily composed groups but it is evidenced why it is also an ethological need for individually housed sport horses. Summarising: social relationships and interventions especially in relation to preferred partners, have rewarding properties in the brain and seem therefore important for the main coping mechanisms of domestic horses in large groups and most likely also for feral horses.

188 HUMAN FOLLICULAR FLUID IN EQUINE IN VITRO MATURATION MEDIUM SUPPORTS IN VITRO MATURATION AND VIABLE INTRACYTOPLASMIC SPERM INJECTION-BLASTOCYST PREGNANCIES

The aim of this study was 2-fold: (1) To determine if altrenogest-treated mares will yield higher numbers of quality in vitro-matured (IVM) oocytes than early pregnant mares and cycling/control mares and (2) if the addition of human follicular fluid (HFF) to IVM medium can support IVM and viable pregnancies from in vitro-produced blastocysts. In this study, 18 mares were assigned to 3 equally sized treatment groups and each mare was subjected to follicle aspiration every 10 to 11 days without monitoring follicular growth. The 3 treatment groups were altrenogest-treated mares (0.044 mg kg–1 of PO daily), early pregnant mares (30–110 days) and control/cycling mares. Using transvaginal ultrasound guidance, all visible follicles were aspirated. Altrenogest-treated mares each yielded more follicles (8.75) per aspiration session when compared with the control mare group (5.75) and the pregnant mare group (3.72), but there was no difference in oocyte recovery rates among the groups (Table 1). A limited number of these oocytes were subjected to in vitro maturation. After heated (38.5°C) transport of oocytes to an off-site laboratory, the oocytes were placed in maturation medium containing 10% HFF obtained from preovulatory follicles after ovulation induction, 20% serum substitute supplement and no hormones for 36 h. This approach yielded a maturation rate of 61.8, 68.8 and 82.0% for the altrenogest, pregnant and control treatment groups, respectively (not significant). Mature oocytes (n = 65) were injected with frozen-thawed sperm using a standard intracytoplasmic sperm injection (ICSI) technique. Four expanding blastocysts (Table 1) were selectively transported back to the embryo transfer facility and transcervically transferred into recipient mares on Day 6 post-ICSI. These 4 transfers resulted in 2 viable, normally progressing pregnancies, ongoing beyond 60 days of gestation. Both pregnancies resulted from the altrenogest-treated aspiration group. In this study we concluded that (1) altrenogest-treated mares provide more follicles and may be a better source of viable immature oocytes for the production of ICSI embryos and foals, but their overall advantage is unclear; (2) addition of HFF to IVM media, in the absence of added gonadotropins, can support oocyte maturation, blastocyst production and viable pregnancies; (3) an aspiration schedule of every 10 to 11 days without ultrasonic monitoring can yield viable immature oocytes, capable of producing ICSI blastocysts, resulting in viable pregnancies. Table 1.Altrenogest-treated mares compared to early pregnant mares and control mares

Persistent Breeding‐Induced Endometritis after Hysteroscopic Insemination in the Mare

Low-dose insemination has been proposed to reduce persistent breeding-induced endometritis (PBIE) in mares with delayed uterine clearance (DUC). Others proposed that hysteroscopic insemination induces an exaggerated inflammatory response and should be avoided in DUC mares. The objectives here were to evaluate presence and severity of PBIE in normal and DUC mares after hysteroscopic insemination with fresh semen, and to determine if hysteroscopy could be used in DUC mares without inducing excessive inflammation. Reproductively normal (n = 4) and DUC (n = 5) mares received four treatments in random order: uterine body insemination (UB, 1 × 10(9) spermatozoa, 20 ml), hysteroscopic insemination (HYST, 5 × 10(6) spermatozoa, 0.5 ml), sham hysteroscopic insemination (SHAM, semen extender, 0.5 ml) and hysteroscopic infusion of seminal plasma (SP, 0.5 ml). Significantly more DUC (50%) mares than normal (14%) mares accumulated intrauterine fluid 24 h post-treatment. The difference in fluid accumulation between DUC (40%) mares and normal (7%) mares was also significant 48 h post-treatment. Fluid scores were not significantly different between treatments in normal mares. However, treatments HYST and SHAM resulted in significantly higher fluid scores 24 h but not 48 h post-treatment in DUC mares. There was no effect of treatment or mare group on the percentage and total number of neutrophils in uterine fluid 48 h post-treatment. Percentage of neutrophils was correlated with duration of hysteroscopy in normal mares, with procedures lasting ≥ 9 min associated with PBIE. There was no effect of mare group, treatment or duration of hysteroscopy on pregnancy rate. Hysteroscopy induces a transient inflammation that is not more severe than that after conventional artificial insemination, suggesting no contraindication to its use in DUC mares.

Relationship Between Sperm Quality Measures of Cooled-Shipped Semen and Fertility.

Features of fresh stallion semen such as sperm concentration, motility, morphology, and DNA quality are routinely evaluated as part of a breeding soundness evaluation and diagnostically to determine the cause of reduced fertility, however, there is limited information about the relationship between these values in cooled-stored semen and stallion fertility. The goals of this study were to determine the relationship of stallion sperm quality features after 24 hr of cooled-storage on fertility. Sperm concentration and viability were determined using a NucleoCounter SP-100, DNA quality by the Sperm Chromatin Structure Assay, sperm motility by phase-contrast microscopy and sperm morphology by differential interference microscopy. Stallion (n=135; age (years)- mean-11; range-3-25) seminal parameters were evaluated during the 2009 breeding season and donor mares (n=204) were bred with cooled-shipped semen at an embryo transfer facility (Royal Vista Southwest, Purcell, OK) either the same day as collection or 24hr after semen collection. Fertility was determined by embryo(s) recovery. The percentage of embryos recovered was higher (65 vs. 51%; P < 0.01) when mares were bred with semen collected from the stallion on the same day compared to mares bred approximately 24 hr after semen collection. Pregnancy data were then compared to each individual seminal parameter in order to determine the relationship between sperm quality and resulting embryo recovery (fertility). Sperm parameters influencing the success of embryo recovery rate were: total sperm motility (P < 0.01), progressive motility (P < 0.077), total sperm number (P < 0.002), total motile sperm (P < 0.003), total progressively motile sperm (P < 0.002), viability (P < 0.004), total viable sperm (P < 0.002), total progressively motile viable sperm (P < 0.0001), %COMP (P < 0.045), morphologically normal sperm (P < 0.001) and total morphologically normal sperm (P < 0.0001). In a large group of mares and stallions this study identifies sperm features that affect fertility as determined by embryo recovery. This information will help horse breeders and researchers determine those sperm quality factors that maximize fertility. (poster)

Infection of peripheral blood mononuclear cells with neuropathogenic equine herpesvirus type-1 strain Ab4 reveals intact interferon-α induction and induces suppression of anti-inflammatory interleukin-10 responses in comparison to other viral strains

The recent increase in incidence, morbidity, and mortality of neurological disease induced by equine herpesvirus type 1 (EHV-1) has suggested a change of virulence of the virus. The exact mechanisms by which EHV-1 induces neurologic disease are not known. Environmental, viral, and host risk factors might contribute to neurological manifestation. Here, we investigated innate interferon-α (IFN-α), interleukin-10 (IL-10) and IL-4 responses after infection of equine peripheral blood mononuclear cells (PBMC) with EHV-1 using an available cytokine multiplex assay. Three viral strains representing an older isolate (RacL11), a recent abortigenic (NY03) and a neuropathogenic isolate (Ab4) were compared to identify differences in cytokine induction that might explain the increased pathogenicity of Ab4. Cytokine concentrations were also compared between foals, mares after birth, pregnant and non-pregnant mares to investigate whether immune responses to EHV-1infection are influenced by age or pregnancy status. PBMC from all groups secreted high concentrations of anti-viral IFN-α in response to EHV-1. A reduced response was observed in foals compared to non-pregnant mares. EHV-1 infection induced moderate IL-10 and overall low IL-4 secretion. Ab4 infection resulted in a significant reduction of IL-10 responses in adult horses. IL-10 and IL-4 responses were lower in foals than in most mare groups. These data suggested that EHV-1 induces robust IFN-α secretion without major differences between viral strains. However, anti-inflammatory IL-10 production was significantly reduced after infection with neuropathogenic Ab4. The ability of this EHV-1 isolate to down-regulate IL-10 production might contribute to increased local inflammation and a higher risk for neurological manifestation of the disease after infection with Ab4.

Stallion Mate Choice and Mare Sexual Behaviour in a Herd of Sorraia Horses (Equus caballus)

We examined the relationship between male mate choice, female sexual behaviour, and individual factors in a managed group of Sorraia horses. The herd comprised 9–11 adult mares and their foals. Two stallions were introduced into the mare group in different years for pasture breeding. Mare receptivity during oestrus was poorly correlated with individual factors. Stallions did not prefer to mate with mares that showed the greatest behavioural receptivity during oestrus. The older and more experienced stallion preferred to mate with the older, higher-ranking, or barren oestrous mares. The younger stallion preferred to mate with the more genetically related mares and showed higher oestrus discrimination of mares to who he kept proximity during oestrus. Mate choice was not associated with probability of foaling in the following year. The differential influence of individual factors on mate choice between the stallions could stem from differences in breeding experience and familiarity with the mares.

Health and behaviour consequences of feral horse relocation

Despite ongoing projects involving the breeding and release of equids into semi-wild and wild environments, insufficient information is available in the literature that describes strategies used by equids to adapt and survive in a novel environment. The aim of this study was to assess the ability of naïve, feral Equus caballus (horse) mares to cope in a novel feral horse environment and investigate possible reasons why some may not survive this challenge. Four mares taken from a semi-arid desert environment remained in good health but significantly changed their movement behaviour pattern when surrounded by prime grazing habitat in a mesic temperate grassland. Three of the four mares captured from the prime grazing habitat and released in the semi-arid desert habitat died, apparently due to stress and/or starvation, within 8 weeks of release. The fourth mare survived 4 months but lost considerable weight. The group of mares relocated to the semi-arid desert environment had difficulty adapting to relocation and did not take up the movement behaviour strategy of local horses, which required long distance treks from a central water hole to distant feeding areas at least 15 km away. The movement behaviour, range use and health consequences of relocating equids may be of interest to wildlife ecologists, animal behaviourists and horse welfare groups. The observations may be used to guide those intending on relocating managed domestic and native horses to novel habitats.

ZWIĄZEK POLIMORFIZMU GENU LEPTYNY ZE WSKAŹNIKAMI ROZRODU KLACZY RASY POLSKI KOŃ ZIMNOKRWISTY

The objective of the research was to analyze the relationship between leptin genotypes and reproduction indices in cold blood mares. The statistical analysis was conducted on 65 mares from a stud farm in Nowe Jankowice. Based on reproductive outcomes we calculated basic reproduction indices. The leptin polymorphism was determined using the PCR-RFLP method. In the examined population, A and B allele frequencies were identical (0.50). Three genotypic forms of the leptin gene were found to occur: AB, AA, and BB. The most frequently noted form was heterozygotic AB (frequency of 0.47), whereas homozygotic AA and BB occurred with equal frequency of 0.26. The most favourable results for the majority of the other reproduction indices were observed in the AB heterozygotic mare group, whereas the least favourable in the AA mares. The said differences were not statistically significant. No significant effect of the leptin genotype on the reproduction traits in mares was found.

Embryo Recovery in Mares Treated with Systemic Dexamethasone.

Post-breeding endometritis in mares is related to inflammatory process, which is stimulated by the presence of sperm cells inside the uterus. However, when this inflammatory response takes the persistent form, it becomes one of the most frequent causes of sub-fertility and this persistent form usually occurs in mares older than 14 years of age. With the efficiency shown by nonsteroidal anti-inflammatory drugs in immunomodulation of uterine inflammation and the possibility of increasing the productivity of these affected animals, this study aimed to evaluate the impact of the dexamethasone systemically administered in the rate of embryo recovery from mares resistant and susceptible to persistent post-breeding endometritis. This study comprised 30 mares which were divided into two groups: 15 mares between 14 and 18 years of age with a history of intra-uterine fluid accumulation after mating determined by ultrasound, low fertility rate, poor perineal conformation and uterus in the abdominal cavity designed. The remaining 15 mares selected to compose the group of resistant mares ranged from 4 to 8 years old, had no history of intra-uterine fluid accumulation, decrease in fertility rate or anatomical changes cited above. These 30 mares had 2 consecutive estrous cycles accompanied by rectal palpation and ultrasonography, and when a follicle with at least 35 millimeters of diameter and a compatible uterine edema were detected, the mares underwent induction of ovulation with 1 milligram of deslorelin acetate (Intra-Muscular). In the interval between 1 and 2 hours prior to artificial insemination 40 milligrams of dexamethasone was administered intravenously. Fertility was measured by the rate of embryo recovery on the eighth day after ovulation confirmation. Estrous cycles with a unique artificial insemination were used in this study. Due to the small number of animals in the experiment, the rates of embryo recovery did not differ between resistant (Control group: 73.33%; Treated group: 80%) and susceptible mares (Control group: 33.33%; Treated group: 69.23 %) regardless of treatment (p> 0.05). However, systemic treatment doubled the number of embryos recovered per cycle when compared to the control group for the mares susceptible to PPBE. Thus, further studies should be conducted using a larger number of subjects so that the results of this work are better understood. Financial support: FAPESP. (poster)

Administration of RRR-α-tocopherol to pregnant mares stimulates maternal IgG and IgM production in colostrum and enhances vitamin E and IgM status in foals

This study assessed the effect of a vitamin E supplement given to pregnant mares on immunoglobulins (Ig) levels in foals. In addition, the fatty acid (FA) content and composition of the mares' milk was assessed. Milk α-tocopherol concentrations were compared between pregnant Danish Warmblood mares (n = 17) given a daily oral supplement of 2500 international units (IU) RRR-α-tocopherol in the last 4 weeks of pregnancy and a group of unsupplemented mares (n = 17) receiving 170-320 IU vitamin E daily originating from the feed. Milk α-tocopherol was higher in supplemented mares (36.7, 12.4 and 9.8 μmol/l respectively) in relation to control mares (13.1, 6.4 and 5.8 μmol/l on days 1, 2 and 3 respectively; p < 0.001). Milk IgG was higher on days 2 and 3 post-partum (PP) in supplemented mares (1.03 and 0.73 mg/ml respectively) in relation to control mares (0.79 and 0.56 mg/ml respectively; p < 0.05). Milk IgM was higher on days 2 and 3 post-partum (PP) in supplemented mares (0.19 and 0.17 mg/ml) in relation to control mares (0.13 and 0.11 mg/ml respectively; p < 0.05). Plasma α-tocopherol in foals was higher from supplemented mares on days 1, 2 and 3 (5.7, 14.8 and 19.2 μmol/l respectively) in relation to foals from control mares (3.6, 6.1 and 7.6 respectively; p < 0.001). Foal plasma IgM was higher from supplemented mares on day 3 (0.50 mg/ml) in relation to foals from control mares (0.32 mg/ml; p < 0.001). The total FA content in milk was highest on day 1 (21.6 g FA/kg milk) in relation to days 2 and 3 (13.6 and 13.5 g FA/kg milk respectively; p < 0.001). In conclusion, a daily oral supplement of 2500 IU RRR-α-tocopherol increased α-tocopherol content in mare milk and foal plasma, IgG and IgM in mare milk and IgM in foal plasma.

The reversibility of GnRH vaccination to suppress ovarian activity in a large group of mares over a two-year period

The reversibility of GnRH vaccination to suppress ovarian activity in a large group of mares over a two-year period

64,XX, SRY-, and ZFY-Negative Icelandic Horse Likely to Be True Hermaphrodite

A 4-year-old Icelandic horse, considered to be a mare, showed stallion-like behavior in a group of mares. On clinical examination, the horse turned out to have an enlarged erectable phallic clitoris. Ultrasound examination showed a normal-sized left ovary covered with numerous small follicular cysts and a compact testis-like tissue in place of the right ovary. The karyotype was normal for a mare (64,XX), and the horse was found to be negative for the Y chromosome–specific markers SRY, ZFY, and EIF1AY. This case indicates that the intersexual phenotype may be caused by autosomal recessive mutation, resulting in defects in cortisol biosynthesis rather than transferal of Y chromosome male–specific genes. This is the first report of an intersexual phenotype in an Icelandic horse that is likely to be a true hermaphrodite because of female sex chromosomes and a mixture of female and male gonads and external genitals.

Effect of mare's breed on the fatty acid composition of milk fat

Gas chromatography and IDF Standard method (1999) were used to analyze the fatty acid composition of milk fat of mares originating from the following breeds: 10 of Wielkopolska breed, 10 Konik Polski Horses, and 9 Polish Cold-blooded Horses. Eighty-seven mare’s milk samples were collected in the years 2000–2002. Unsaturated fatty acids were shown to prevail in the milk fat of mares of Wielkopolska breed (61.32%) and of Konik Polski mares (52.58%) whereas saturated acids prevailed in the milk fat of Cold Blooded mares (54.95%). The study revealed that the fatty acid composition of the investigated groups of mares was breed-specific. Of course, the impact of other uncontrolled factors such as nutrition is not excluded, either.

Enrofloxacin-based therapeutic strategy for the prevention of endometritis in susceptible mares

Enrofloxacin (EFX) is often used empirically to prevent uterine infections in mares in order to improve efficiency on Commercial Embryo Transfer Farms. This study investigated the uterine distribution of EFX and its metabolite ciprofloxacin (CFX) in mares and assessed the minimal inhibitory concentrations (MIC) of EFX against various common pathogens as a basis for establishing a rational dosing schedule. Plasma and uterine pharmacokinetic (PK) studies were performed in two groups (n = 5) of healthy mares following intravenous (i.v.) administration of EFX at either 2.5 and at 5 mg/kg bodyweight. Plasma and endometrial tissue samples, taken before for up to 48 h after treatment were analysed by Reverse Phase HPLC. MIC values for wild strains of Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive bacteria (beta-haemolytic streptococci) ranged from 0.25-2 and 1.5-3.0 microg/mL respectively. In terms of tissue distribution, the sum of the endometrial concentrations of the parent drug (EFX) and its active metabolite (CFX) (in terms of AUC), exceeded those in plasma by 249% and 941% following administration of EFX at 2.5 and 5 mg/kg respectively. After i.v. treatment with EFX at 5 mg/kg, endometrial concentrations of EFX and CFX above the MIC value were detected for 36-48 and 22-43 h posttreatment for Gram-negative and -positive isolates respectively. Concentrations above MIC were maintained for much shorter periods at the lower (2.5 mg/kg) treatment dose. Based on these results, a conventional dose (5 mg/kg) of EFX given prebreeding followed by two further doses at 36-48 h postbreeding are proposed as a rational strategy for using of EFX as a preventative therapy against a variety of common bacterial strains associated with equine endometritis.

Steroid hormone receptors ERα and PR characterised by immunohistochemistry in the mare adrenal gland

BackgroundSex steroid hormone receptors have been identified in the adrenal gland of rat, sheep and rhesus monkey, indicating a direct effect of sex steroids on adrenal gland function.MethodsIn the present study, immunohistochemistry using two different mouse monoclonal antibodies was employed to determine the presence of oestrogen receptor alpha (ERalpha) and progesterone receptor (PR) in the mare adrenal gland. Adrenal glands from intact (n = 5) and ovariectomised (OVX) (n = 5) mares, as well as uterine tissue (n = 9), were collected after euthanasia. Three of the OVX mares were treated with a single intramuscular injection of oestradiol benzoate (2.5 mg) 18 – 22 hours prior to euthanasia and tissue collection (OVX+Oe). Uterine tissue was used as a positive control and showed positive staining for both ERalpha and PR.ResultsERalpha staining was detected in the adrenal zona glomerulosa, fasciculata and reticularis of all mare groups. Ovariectomy increased cortical ERalpha staining intensity. In OVX mares and one intact mare, positive ERalpha staining was also detected in adrenal medullary cells. PR staining of weak intensity was present in a low proportion of cells in the zona fasciculata and reticularis of all mare groups. Weak PR staining was also found in a high proportion of adrenal medullary cells. In contrast to staining in the adrenal cortex, which was always located within the cell nuclei, medullary staining for both ERalpha and PR was observed only in the cell cytoplasm.ConclusionThe present results show the presence of ERalpha in the adrenal cortex, indicating oestradiol may have a direct effect on mare adrenal function. However, further studies are needed to confirm the presence of PR as staining in the present study was only weak and/or minor. Also, any possible effect of oestradiol treatment on the levels of steroid receptors cannot be determined by the present study, as treatment time was of a too short duration.

Grouping horses according to gender—Effects on aggression, spacing and injuries

Many horse owners tend to group horses according to gender, in an attempt to reduce aggressive interactions and the risk of injuries. The aim of our experiment was to test the effects of such gender separation on injuries, social interactions and individual distance in domestic horses. A total of 66 horses were recruited from 4 different farms in Norway and Denmark and divided into six batches. Within each batch, horses were allotted into one mare group, one gelding group and one mixed gender group, with most groups consisting of three or four animals. After 4–6 weeks of acclimatisation, a trained observer recorded all social interactions using direct, continuous observation 1 h in the morning and 1 h in the afternoon for three consecutive days. Recordings of the nearest neighbour of each horse were performed using instantaneous sampling every 10 min. The horses were inspected for injuries before grouping, day 1 after grouping and after 4–6 weeks. No significant effect of gender composition was found on social interactions ( P > 0.05), spacing ( P > 0.07) or injuries ( P > 0.23). Eighty percent of all aggressive interactions recorded were threats, not involving physical contact. Horses with the smallest space allowance showed the highest mean number of aggressive interactions (28.6 ± 6.1 interactions per 6 h) compared to the mean of all the other batches (8.3 ± 1.0 interactions per 6 h). Very few injuries were found and most were superficial. In conclusion, gender composition does not seem to have any effect on aggression level, spacing or injuries. However, the early social experience of horses, management of feeding and space allowance probably represents more important factors for successful group housing of domestic horses.

Follicle suppression of circulating follicle-stimulating hormone and luteinizing hormone before versus after emergence of the ovulatory wave in mares

The effect of the ovarian follicles on plasma concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) before versus after the expected emergence of the ovulatory follicular wave was studied on Days 0 to 18 (Day 0 = ovulation) in four groups of mares (n = 6/group). In addition to a control group, all follicles ≥6 mm in diameter were ablated on Days 0.5, 6.5, or 12.5 in a herd of mares with reported emergence at 6 mm of the future ovulatory follicle on mean Day 10.5. Concentrations of FSH were not different between the Day-0.5 or Day-6.5 ablation groups and the corresponding controls. However, ablation on Day 12.5 resulted in an immediate FSH increase (group-by-day interaction, P < 0.003). For LH, ablation on Day 0.5 resulted in an interaction (P < 0.02), partially from lower (P < 0.05) concentrations on each of Days 15.5 to 18.0 than that in the controls, whereas ablation on Days 6.5 or 12.5 did not result in a significant group effect or interaction. Testosterone concentration, but not progesterone or estradiol concentration, was lower (P < 0.04) on Day 2 in the Day-0.5 ablation group than that in the controls. We inferred that follicles did not contain adequate FSH suppressors on Days 0.5 and 6.5 and that they were present only in the Day-12.5 ablation group or after the expected emergence of the ovulatory wave. The hypothesis of an association between low postovulatory concentrations of an ovarian steroid and low concentrations of LH after Day 15 was supported.

Morphological characterization and meiotic competence of oocytes collected from filly ovaries

The effect of filly age on morphology of the ovaries, collected oocytes and their capacity for in vitro maturation (IVM) was examined. The ovaries of slaughtered fillies were classified into three groups, according to filly age: (I) <10 month old (<10MF); (II) approximately 1 year old (1YF); and (III) approximately 1.5 year old (1.5YF). The ovaries of mares were used as a control group. Ovarian morphology and collected oocytes were evaluated. Only oocytes with expanded (Ex) and compact (Cm) cumuli were used for IVM. In <10MF, 1YF, 1.5YF and mare groups, corpora lutea were found in the ovaries of 9.3%, 36.7%, 59.6% and 80.9% females, respectively ( P < 0.001). Based on this observation, we found that about 37% of fillies reach puberty at approximately 12 months of age. No relationship was found between filly age and morphology of the oocytes obtained. In comparison to mares, fewer ( P < 0.05) Cm oocytes were collected from filly ovaries. Among Cm groups, fewer filly (28.4–35.5%) than mare oocytes (50.0%) reached metaphase II stage, but the difference was only significant when compared to oocytes of the <10MF group ( P < 0.05). In the Ex groups, a similar proportion of oocytes of fillies (40.8–51.1%) and mares (48.4%) attained the metaphase II stage. In conclusion, in the culture conditions applied, Cm oocytes of fillies younger than 10 months showed lower meiotic competence than mare oocytes. Oocytes of older fillies showed meiotic competence similar ( P > 0.05) to mare oocytes. Both filly and mare oocytes with expanded cumuli displayed the same capacity for IVM.

Calendar of Events

Fifty-six mares of lighthorse breeding were utilized in a controlled management scheme for induced daytime foaling. All mares had pre-foaling mammary secretions sampled for evaluation of water hardness (ppm) or calcium carbonate content (ppm). Sampling began 10 days prior to expected foaling date for each mare and was performed once daily for 3 days followed by twice daily until foaling occurred. Samples were diluted 1:6 in distilled water and tested by each of 3 methods: Sofchek™ Test Strips4, Predict-A-Foal™ Test Kit5 and Titrets™ Calcium Hardness Test Kit6. Mares were then either induced (i) to foal (no.= 33) according to a decision point of readiness for birth as indicated by pre-foaling mammary secretion testing (≥250 ppm water hardness by Sofchek™ test, ≥ 250 ppm calcium carbonate content by Titrets test, ≥ 4 color bar changes by Predict-A-Foal test), or allowed to foal spontaneously (s) (no.=23). There were no differences (p>0.05) in the mean pre-foaling mammary secretion test values (μi=293ppm, μs=329ppm; μi=4.1, μs=4.2; and μi=281ppm, μs=298ppm; for Sofchek, Predict-A-Foal and Titrets, respectively) between mare groups at the time of foaling (time=0) for any of the 3 testing methods employed. Mean intervals to foaling after reaching decision points of readiness for birth were different (p<0.05) between Sofchek and Titrets test for both mare groups, but only in the induced-to-foal group between Sofchek and Predict-A-Foal tests. Probabilities of 79%, 53% and 59% were calculated for mares foaling spontaneously within 24 hours of reaching the decision points used in this trial of readiness for birth on the initial occasion for Sofchek, Predict-A-Foal and Titrets™ tests, respectively. Each test was determined to have the ability to predict readiness of approaching parturition and found to be easily applicable to field use. The Titrets test was found to be least variable in its response to measurement of pre-foaling mammary secretion hardness changes both within and between mares.