Retrospective and statistical analysis of breeding management on the Italian Heavy Draught Horse breed

This study investigated some aspects of breeding management in the Italian Heavy Draught Horse breed, aiming at improving its efficiency at stud farm level. A first aim was to evaluate the risk of unsuccessful reproduction in mares after an early (3 years) or normal (4 years) age at first foaling, in interaction with different stud rearing systems. A second objective was the examination of the mean time length in which young 2-year-old stallions maintain a genetic superiority on older proven stallions, identifying a ‘genetic lifespan’ in which young stallions can be safely used for reducing the cost of services. Reproductive performance at first and second foaling of 1513 mares were used. Mares had a normal first foal at 3 (n = 745) or 4 years of age (n = 768) in stud farms on the basis of stable (n = 488), feral (n = 345) or semi-feral (n = 680) rearing systems. Logistic regression analysis was performed by modeling the risk of unsuccessful reproduction in the subsequent season (i.e., results at second foaling), as affected by the interaction of age at first foaling × rearing system (six classes). Genetic lifespan of young stallions was estimated by regressing the least square means from a mixed model analysis for repeated measures of individual differences in ‘total merit’ estimated breeding values (EBVs) between young stallions (mean no. of 45/year) and the mean EBV of all proven stallions in a given year of genetic evaluation (mean no. of 483/year). Young stallions born between 1999 and 2005 were used, following each generation (i.e., birth year) from 2 to 7 subsequent yearly genetic evaluations. In comparison with the best reproductive success of second foaling at 4 years in stable systems, the greatest risk of unsuccessful reproduction was at 3 years in feral (+167%) and 3 years in semi-feral conditions (+91%). Young stallions showed a 0.50 s.d. greater EBV at the first evaluation than proven stallions, with a mean annual decrease in EBV of 0.07 s.d./year on proven stallions. Optimal breeding management could be obtained in stud farms by limiting foaling at 3 years, particularly in feral and semi-feral rearing systems, and using young stallions for 3 to 4 years to maintain a perceptible selection differential with older proven stallions and to reduce cost of services. Later, the selection differential with proven stallions become less consistent and genetic improvement could be slowed down.     

Immunocontraception in Wild Horses: One Inoculation Provides Two Years of Infertility

ABSTRACT ABSTRACT Previous studies reported one year of contraception associated with a 1-injection porcine zona pellucida (PZP) vaccine. We have subsequently determined contraceptive effectiveness of a presumptive 1-injection, 2-year-duration PZP vaccine in free-roaming wild horses (Equus caballus) in Nevada, USA. In January 2000, we captured, freeze-branded, treated, and subsequently released 96 adult females that received 1) a primary dose of vaccine emulsion consisting of aqueous PZP and Freund's Complete Adjuvant, and 2) booster doses of PZP and adjuvant in controlled-release polymer pellets. We determined PZP release characteristics of pellets in vitro, prior to field use. We determined reproductive success in treated and untreated females through October 2004 via measurement of estrone sulfate and progesterone metabolites in fresh feces collected from the ground and by twice-annual foal counts. Among treated females, annual reproductive success from 2001 though 2004 sequentially was 5.9%, 14.0%, 32.0%, and 47.5%. Untreated females showed average reproductive success of 53.8 ± 1.3% across this period. This study revealed that: 1) PZP acted as an effective contraceptive for 2 years posttreatment; 2) some residual contraceptive effect remained in year 3; and 3) fertility returned to control levels by year 4 posttreatment. It appears that controlled-release technology can replace both the second(1-month) and annual booster injection of PZP vaccine, thereby decreasing cost and increasing efficiency of use of this vaccine in wild horse management.     

Mean age of death and longevity for male scientists of different specialties

The article provides information on the mean age of death (MAD) for 54 256 men professionally involved in research work and assigned to one of the six categories, namely, physics, chemistry, medicine and biology, mathematics, economics, and humanities. In addition, the effect of teaching activity on MAD and longevity has been evaluated for scientists of different specialties. Special attention has been paid to the analysis of MAD of the deceased members of the Russian Academy of Sciences, including members of the USSR Academy of Sciences (1724–2013). The minimum MAD has been found for mathematicians (72.1 ± 0.21 years) and the maximum MAD for scientists in economics (74.6 ± 0.26 years). The relative number of surviving ≥90 years and ≥100 years is minimal for mathematicians (7.59 and 0.37%, respectively), whereas those numbers for economists reveal the maximum values (10.26 and 0.96%, respectively). Indicators of MAD and proportion of centenarians among the scientists who received public recognition strongly depend on the specialty. Similarly, the members of the Russian Academy of Sciences and the USSR Academy of Sciences have the highest MAD in economics (74.7 ± 1.05 years) and the lowest in mathematics (70.6 ± 0.74 years). MAD has proven to be 3.5 years higher for scientists involved in teaching at university or college compared to those who were not involved in teaching. In this case, the “gain” is significant, ranging from 3.1 years for economists and humanitarians to 4.9 years for mathematicians. The results of the study lead to the conclusion that intense scientific work contributes to an increase in life expectancy and longevity.     

Equine frozen semen: freezability and fertility field results

The freezability of stallion semen defined as the number of selected ejaculates/total number of ejaculates frozen from 161 different stallions was analyzed. Of the stallions, 19, 30, 27 and 24% had a freezability of 0%, 0 to 33%, 33 to 66%, over 66%, respectively In 85 different stallions, the correlation of freezability between first and second year was 0.60 (P < 0.001). The relationship between fertility with fresh and frozen semen and freezability was analyzed in 40 stallions whose freezability and fertility information was recorded during 5 years. There was a strong relationship between fertility of fresh semen and semen freezability (P < 0.001). However, the relationship between fertility of frozen semen and freezability was not as marked (P < 0.05). Analysis of the field fertility per cycle results when mares were bred with 300 or 150 x 10(6) total spermatozoa at different frequencies until ovulation indicated that mares that were inseminated 2 times or more per estrus show an improved fertility in comparison with mares inseminated only once (34%, n = 1576 vs 26%, n = 626; P < 0.001). Foaling rate when mares were inseminated with frozen semen (1858 mares during 8 breeding seasons) was mainly influenced by mare age (< 16 years: 54% vs >/= 16 years 42% p < 0.001). Date of first insemination (before May 15: 58% vs after May 15: 37%) also had a significant effect on foaling rate (P < 0.001).     

Absence of effects from immunocontraception on seasonal birth patterns and foal survival among barrier island wild horses

Despite a large body of safety data, concern exists that porcine zonae pellucidae (PZP) immunocontraception--used to manage wild horse populations--may cause out-of-season births with resulting foal mortality. Our study at Assateague, Maryland indicated the effects of immunocontraception on season of birth and foal survival between 1990 and 2002 on wild horses from Assateague Island. Among 91 mares never treated, 69 (75.8%) of foals were born in April, May, and June (in season). Among 77 treated mares, 50 (64.9%) were born in season. Of 29 mares foaling within 1 year after treatment (contraceptive failures), 20 (68.9%) were born in season. Of 48 mares treated for greater than 2 years then withdrawn from treatment, 30 (62.5%) of 48 foals were born in season. There were no significant differences (p <.05) between either treatment group or untreated mares. Survival did not differ significantly among foals born in or out of season or among foals born to treated or untreated mares. Data indicate a lack of effect of PZP contraception on season of birth or foal survival on barrier island habitats.     

A survey of the fertility of Icelandic stallions

Very limited information is available on the breeding performance of Icelandic stallions, let alone the effect that management practices may have had on such performance. As an extensively kept, largely genetically isolated breed of horse it provides a good model for the study of factors that affect reproductive performance without the additional complication of selective breeding, infectious infertility and breed effect. A survey was conducted using 27 Icelandic stallions covering 1590 mares within the normal Icelandic breeding system (May to September). During the season, stallions cover mares within three periods of time, each period being of a similar length (average 35.5 days). During period 1, mares are covered in hand and at pasture. During periods 2 and 3, all mares are covered at pasture. The overall fertility rate for Icelandic stallions was calculated. The effect of a range of variables on fertility was investigated statistically using a number of models in an attempt to minimise the effect of confounding factors. An overall adjusted fertility rate for Icelandic stallions of 67.7% was obtained. The following factors were shown to have a significant effect on fertility: age of mare (P<0.001), training level of stallion (P<0.05) and method of breeding (P<0.05). For some individual stallions reproductive status of the mare also had a significant (P<0.001) effect. Many of these factors have been observed to effect FR in other more intensively managed equine populations. However, the less dramatic detrimental effect of age and the lack of a significant effect of mare reproductive status in most stallions suggests that infertility problems are less evident in Icelandic mares, possibly due to less emphasis on selection for athletic performance and the accepted culling of subfertile stock.     

Fertility of high-yielding dairy cows following superovulation and non-surgical recovery of embryos

It was the aim of this investigation to study the combined effect of superovulation and non-surgical recovery on the fertility of the donor animals. Injection of a prostaglandin analogue at the day of collection (days 6–8 after standing heat), significantly shortened the super-ovulatory estrus cycle (21.3 ± 10.0 days), when compared with untreated donor animals (38.7 ± 15.1 days). The prostaglandin treatment, however, also led to more irregular estrous cycles, resulting in a lower pregnancy rate after first insemination (47%) and a need for more inseminations per conception (2.00 ± 1.00), than in animals not treated with prostaglandin analogue (92.3% and 1.06 ± 0.29 AI/conception). For all animals these parameters were 66.6% and 1.60 ± 0.99 AI/conception). The average time from calving to pregnancy was 143.1 ± 34.3 days, slightly longer for prostaglandin treated (148.2 ± 39.4 days) than for untreated animals (137.3 ± 22.8 days). One animal developed endometritis and one had adhesions in the $\text{bursa ovarii}$. It was found that most donors attained normal fertility, and that superovulation was more likely to affect the fertility (abnormal cyclicity, early embryonic mortality e.g.) than the flushing of the uterus. Treatment with a prostaglandin analogue at the day of collection did not improve the subsequent fertility.     

Age-specific fertility rates of the Jeju pony (<Emphasis Type="Italic"> Equus caballus</Emphasis>)

Age-specific fertility is an essential parameter of life history. Here we report age-specific fertility rates, measured as the number of foals per mare per year, for Jeju ponies aged 2–28 years. The total sample consisted of 545 foals produced by 178 mares from 1988 to 2002. The mean fertility rate across all ages of the mares was 0.65 foals/mare per year (±0.24 SD). The fertility rates were above average for the 7- to 8- and 19- to 20-year-old mares, whereas they were relatively low for mares under 4 years old. The fertility rates tended to increase with the age of the stallion, but the relationship was not significant (n =15, P =0.09). The incidence of inter-birth interval was not associated with the age that the mare first reproduced (n =64 mares, P =0.99). However, mares that reproduced later in life tended to have a reduced fertility rate due to an increase in the duration of inter-birth intervals relative to mares that reproduced earlier (n =4 years of first reproduction, P =0.068). The fertility rates of Jeju ponies were lower than for other horses, perhaps because only one stallion was introduced to a relatively large herd every year. We suggest that the introduction of more stallions to the herd each year would increase fertility rates.     

The Anthropomorphic Application of Gender Stereotypes to Horses

ABSTRACT

Gender stereotypes shape human social interaction, often to the detriment of women and those who do not comply with normative expectations of gender. So far, little research has assessed the extent to which people apply gender stereotypes to animals, and the implications this may have for in-dividuals and groups, particularly female animals. The current study investigated survey respondents’ preference for horses to perform in different sport and leisure practices, based solely on ideas about the sex of the animal. An anonymous online survey explored the preferences of riders for mares, geldings, and stallions for dressage, show-jumping, and trail-riding, and reasons for their choice. A total of 1,032 responses were received. Geldings were the preferred choice, being perceived as safe and reliable, followed by stallions who were valued for their supposed power, presence, and good looks. Overall, mares were the least popular choice, and were discussed in ambivalent terms reflecting broad gender stereotypes which depict females as moody, flighty, and unpredictable. Respondents appeared to draw on gender stereotypes to make judgements about horses and justify their choices. The anthropomorphic application of gender stereotypes to animals may have negative consequences for female animals, shaping human–animal interactions and expectations.     

Immunocontraception of captive exotic species. I. Przewalski's horses (Equus przewalskii) and banteng (Bos javanicus)

A contraceptive vaccine made of porcine zonae pellucidae (PZP) was tested in three Przewalski's mares and five banteng cows. The vaccine antigen consisted of the complete family of glycoproteins of the porcine zona pellucida, including the sperm receptor ZP3. All mares and three of five banteng were inoculated with 2 or 3 i.m. injections of approximately 65 μg of antigen given over a 6 week period. Two other banteng received inoculations of only 35 μg of antigen on the same schedule. Two of the three mares and three of five banteng cows were pregnant at the time of inoculation. No new pregnancies, as a result of postinoculation breedings, occurred among either the mares 36 months after 65 μg antigen inoculations or among the banteng for 24 months after 65 μg inoculations. One postinoculation pregnancy resulted among the two banteng receiving only 35 μg of antigen. Differences in fertility between treated and control mares and between preinoculation and postinoculation reproductive performance of the banteng were significant (P < 0.05). Urinary ovarian steroid metabolites and behavioral observations indicated follicular development and ovulations were occurring among treated mares during the year following PZP inoculations. PZP immunization produced progressively elevated anti-PZP antibodies in both species, which provided contraceptive protection. PZP immunization appears to be an effective form of contraception in both species. © 1995 Wiley-Liss, Inc.     

The effects of age, season and fertility status on plasma and intratesticular insulin-like growth factor I concentration in stallions

The purposes of this study were to establish the basal plasma and testicular insulin-like growth factor-I (IGF-I) values for stallions ranging in age from 6 months to 23 years and to determine if IGF-I could be used as a marker for declining fertility. Blood and testes were obtained from 28 light horse stallions and colts. Of the 28 stallions, 22 were considered fertile and were categorized by age (<2 y, 5 to 10 y, 11 to 15 y, and 16 to 23 y); 12 age-matched stallions were grouped as to fertility status (fertile, subfertile, infertile); and all 28 stallions were grouped as to season of castration (breeding season vs. non-breeding season). In colts less than 2 years of age, IGF-I concentrations in plasma and testicular extracts were higher (P < 0.01) than in the other age groups and were higher in the breeding season than in the non-breeding season (P < 0.01). No significant differences in plasma or testicular extract concentrations of IGF-I were found among fertility groups. The results of this study demonstrate that plasma and testicular IGF-I levels are high in stallions younger than 2 years of age and then decline and plateau in stallions older than 5 years of age, suggesting that IGF-I may be involved in testicular development. The results allude to a possible seasonal effect on IGF-I production. However, it is difficult to separate true seasonality and the effect of age as only those stallions less than 2 years old exhibited variation between seasons. The IGF-I does not appear to have a direct relationship with declined fertility in the stallions tested, suggesting that IGF-I may not be a reliable biomarker for the diagnosis of subfertility and infertility.     

Capacitation, acrosome function and chromatin structure in stallion sperm

In general, fertility in breeding stallions is lower and more variable than in the other farm animal species, primarily because selection is based on pedigree, looks and/or athletic performance, with little consideration of fertility or fertility potential. Moreover, because the average stallion breeds only a limited number of mares per year and in-field fertility is influenced significantly by non-stallion factors such as management and mare fertility, meaningful fertility data are hard to come-by. Unfortunately, generating usable figures would involve impractically high costs, time and numbers of mares. Instead, a breeding soundness examination (BSE), based on assessments of sperm number, motility and morphological normality and of mating ability, is often carried out with the ostensible aim of identifying animals with the "potential for good fertility". In fact, the BSE generally succeeds only in ruling out those stallions with a very clear reason for sub-fertility, and still fails to identify some seriously sub-fertile animals. Thus, the routine BSE has very limited use as a predictor of subsequent fertility. This paper reviews assays developed for identifying capacitated, acrosome-reacted and DNA-damaged sperm, and assesses their utility for improving our ability to predict a stallion's fertility prior to the onset of his breeding career.     

Influence of Age and Hypertension Treatment-time on Ambulatory Blood Pressure in Hypertensive Patients

Some studies based on ambulatory blood pressure (BP) monitoring (ABPM) have reported a reduction in sleep-time relative BP decline towards a more non-dipping pattern in the elderly, but rarely have past studies included a proper comparison with younger subjects, and no previous report has evaluated the potential role of hypertension treatment time on nighttime BP regulation in the elderly. Accordingly, we evaluated the influence of age and time-of-day of hypertension treatment on the circadian BP pattern assessed by 48-h ABPM. This cross-sectional study involved 6147 hypertensive patients (3108 men/3039 women), 54.0?±?13.7 (mean?±?SD) yrs of age, with 2137 (978 men/1159 women) being ≥60 yrs of age. At the time of study, 1809 patients were newly diagnosed and untreated, and 4338 were treated with hypertension medications. Among the later, 2641 ingested all their prescribed BP-lowering medications upon awakening, whereas 1697 ingested the full daily dose of ≥1 hypertension medications at bedtime. Diagnosis of hypertension in untreated patients was based on ABPM criteria, specifically an awake systolic (SBP)/diastolic (DBP) BP mean ≥135/85?mm Hg and/or an asleep SBP/DBP mean ≥120/70?mm Hg. Collectively, older in comparison with younger patients were more likely to have diagnoses of microalbuminuria, chronic kidney disease, obstructive sleep apnea, metabolic syndrome, anemia, and/or obesity. In addition, the group of older vs. younger patients had higher glucose, creatinine, uric acid, triglycerides, and fibrinogen, but lower cholesterol, hemoglobin, and estimated glomerular filtration rate. In older compared with younger patients, ambulatory SBP was significantly higher and DBP significantly lower (p?<?.001), mainly during the hours of nighttime sleep and initial hours after morning awakening. The prevalence of non-dipping was significantly higher in older than younger patients (63.1% vs. 41.1%; p?<?.001). The largest difference between the age groups was in the prevalence of a riser BP pattern, i.e., asleep SBP mean greater than awake SBP mean (19.9% vs. 4.9% in older vs. younger patients, respectively; p?<?.001). The sleep-time relative SBP decline was mainly unchanged until ～40 yrs of age, and then significantly and progressively decreasing with increasing age at a rate of .28%/yr (p?<?.001), reaching a minimum value of 4.38%?±?.47% for patients ≥75 yrs of age. Treated compared with untreated patients showed lower awake and asleep SBP means, although the predictable changes of SBP and DBP with age were equivalent in both groups. As a consequence, there were no significant differences between untreated and treated patients in the changes of the sleep-time relative SBP and DBP declines with age. Additionally, the asleep SBP and DBP means were significantly lower and the sleep-time relative SBP and DBP declines significantly higher at all ages in patients ingesting ≥1 BP-lowering medications at bedtime as compared with those ingesting all medications upon awakening. Our findings document a significantly elevated prevalence of a blunted nighttime BP decline with increasing age ≥40 yrs. The prevalence of a riser BP pattern, associated with highest cardiovascular risk among all possible BP patterns, was 4 times more prevalent in patients ≥60 yrs of age than those <60 yr of age. Most important, there was an attenuated prevalence of a blunted nighttime BP decline at all ages when ≥1 hypertension medications were ingested at bedtime as compared with when all of them were ingested upon awakening. These findings indicate that older age should be included among the conditions for which ABPM is recommended for proper cardiovascular risk assessment. (Author correspondence: rhermida@uvigo.es)     

Sexual behavior following introduction of a stallion into a group of mares

A rested stallion was introduced daily for 30 days into each of three herds of 20 mares. Observations of sexual and mating behavior were made for one hour. The stallion remained with a herd until another stallion was introduced the following day. Other mares were isolated from stallions and were bred by artificial insemination. The diameter or growth rate of the preovulatory follicle for the six days preceding ovulation and the length of the interovulatory interval for mares which did not become pregnant were not affected significantly by the presence of a stallion. The number of breedings per hour of observation (2.4 ±0.2) and the length of the interval from introduction of a stallion into the herd of mares to first breeding (12 ±1 min) were significantly different among stallions, but the length of the interval between breedings (17 ±2 min) was not. The mean number of breedings per stallion per hour was not affected significantly by the number of posturing (estrous) mares. The number of times that the stallion rebred the same mare when more than one mare postured during the observation hour (49%) was greater (P<0.01) than what would be expected to occur by chance (30%). The hypothesis that breeding occurs preferentially in those estrous mares that are closest to ovulation was not supported, except for significantly lower breeding activity in posturing mares on days 8 and 7 before ovulation and on days 0 (day of ovulation) and ?1 (26% bred) than on days 6 to 1 (52%).     

Fertility control using intrauterine devices: an alternative for population control in wild horses

The purpose of this study was to develop a contraceptive method for feral horses. The feral horse population has increased significantly in recent years despite attempts to control numbers. As in most wild animal population control programs, contraceptive methods must be easy to apply, cause minimal disruption to the social structure and be fully reversible. In the present study, we tested the effectiveness of an intrauterine device (IUD) for fertility control in mares. Six mares were fitted with a silastic O-ring-shaped IUD on July 1 of Year 1. The IUD-treated mares were turned out with 12 nontreated mares and a fertile stallion in a large pasture until October 20 (112 d). None of the IUD-treated mares and all the nontreated mares became pregnant. The IUD-treated mares were maintained separately from the stallion during the winter. Following removal of the IUD on April 27 of Year 2, the mares were again introduced to the pasture with the stallion together with 6 nontreated mares. For the 6 mares previously treated with an IUD, the mean interval from introduction to the stallion to conception was 17.5 +/- 5 d or 1.3 cycles per pregnancy, and all mares produced a normal foal at term. Subsequently, 19 recorded mare breeding seasons resulted in 18 foals. Uterine cytology and histopathology indicate that the IUD causes mild chronic endometritis without permanent changes in the endometrium. We conclude that based on our observations, the O-ring-shaped IUD is an effective, safe and practical contraceptive method for mares.     

Physiological response to a breed evaluation field test in Icelandic horses

This study examined the response in terms of heart rate (HR), respiratory rate (RR), haematocrit (Htc), rectal temperature (RT), and some plasma variables in Icelandic horses of different sexes and ages performing the riding assessment in a breed evaluation field test (BEFT). The study was conducted in Iceland on 266 horses (180 mares and 86 stallions, divided into four age groups; 4, 5, 6 and ⩾7 years old). RT and RR were recorded and blood samples were taken before the warm-up and after the riding assessment. Horse HR, velocity and distance were recorded during the warm-up, the riding assessment and a 5-min recovery period. The distance covered in the BEFT was 2.9±0.4 km (range: 1.8 to 3.8 km, n=248), the duration was 9:37±1:22 min:s (range: 5:07 to 15:32 min:s, n=260) and the average speed was 17.8±1.4 km/h (range: 13.2 to 21.3 km/h, n=248). Average HR was 184±13 b.p.m. (range: 138 to 210 b.p.m., n=102) and peak HR 224±9 b.p.m. (range: 195 to 238 b.p.m., n=102), and 36% of the BEFT was performed at HR ⩾200 b.p.m. Post-exercise plasma lactate concentration (Lac) was 18.0±6.5 mmol/l (range: 2.1 to 34.4 mmol/l, n=266), and there was an increase in total plasma protein, plasma creatine kinase and aspartate amino transferase concentration, as well as RR, RT and Htc. Stallions covered a longer total distance (in the warm-up and BEFT) (P<0.05), at a faster speed during BEFT (P<0.001) than mares and had higher Htc and lower HR and post-exercise Lac values. There were few effects of age, but the 4- and 5-year-old horses had lower Htc than older horses and 4-year-old horses had higher post-exercise RR than older horses, although they were ridden for a shorter distance, shorter duration and at lower peak velocity (P<0.1). The results showed that the riding assessment in the BEFT is a high-intensity exercise. The results also showed that aerobic fitness was higher in stallions and that age had a limited effect on the physiological response. It is suggested that these results should be used as a guide for the development of training programmes and fitness tests in Icelandic horses that would improve both performance and welfare of the horse.     

Reproductive efficiency of Thoroughbred mares under Indian subtropical conditions: A retrospective survey over 7 years

Service records of 253 mares (1181 mare-years) spanning over 7 consecutive years, from nine organized Thoroughbred stud farms, situated in the subtropical northwestern India were retrospectively analyzed to assess their reproductive performance. The overall per cycle pregnancy rate at Day 16 and overall foaling rates were 50.30% and 68.95%, respectively, and were significantly higher in mares aged 3–7 years than ≥18 years old mares. The late embryonic losses (9.86%) that occurred between Days 16 and 39 post-ovulation contributed more than 50% of the overall detected pregnancy losses (19.11%). The overall percent detected pregnancy losses were lower in mares at ages 3–7 years compared to those at ages ≥18 years (14.78% vs. 46.43%, respectively; P < 0.0001). Chronic barren and habitual aborter mares tended to affect reproductive efficiency of mares. Fifty percent of the mares that experienced ≥2 consecutive abortions or barren years, again stayed aborted or barren in the next seasons, respectively. No effect of numbers of matings per oestrus was observed on overall fertility. Neither the induction of oestrus nor ovulation by exogenous hormonal treatment had any effect on most of the analyzed reproductive parameters. Regarding breeding month or years, the reproductive efficiency did not differ significantly. The incidence of multiple pregnancies was 5.40% and percent late embryonic loses were higher (P = 0.0016) in twin (21.98%) than singleton (8.64%) pregnancies. In conclusion, comparatively lower fertility rates were recorded in Thoroughbred mares bred under Indian subtropical climatic conditions than those reported from temperate regions that might be due to difference in breeding management rather than prevailing environment.     

Population genetics of Great Basin feral horses

The genetic make-up of Great Basin wild (feral) horses was investigated by blood typing studies. Blood samples of 975 feral horses from seven trap sites in Nevada and Oregon were tested by serological and electrophoretic techniques for genetic markers at 19 polymorphic loci. The average number of variants for the seven feral populations [72·1 ± 3·2 (SEM), range 62–85] was not significantly different from that of 16 domestic breeds (75·0 ± 11·5, range 58–105). The expected average frequency of heterozygotes per locus (average heterozygosity) for the feral populations (0·402 ± 0·009, range 0·368–0·442) was not significantly different from the domestic breeds (0·389 ± 0·045, range 0·295–0·443). Dendrograms constructed using pairwise comparisons of Nei's distance measurements substantiated anecdotal accounts of the origins of Great Basin horses from Iberian, American saddle horse and draft horse breeds.     

Acceleration and Timing of Fertile Ovulation in Cyclic Mares with a Deslorelin Implant

In a blinded trial, the effectiveness and safety of 2.2 mg of the GnRH analog deslorelin acetate, administered in a short–term implant (STI) to normally cycling mares in estrus with a dominant ovarian follicle of 30 mm in diameter or larger, were evaluated, using a placebo implant as a negative control. A total of 39 mares received treatments at admittance with pre–randomized implants containing either 2.2 mg or 0 mg deslorelin. Mares were teased daily and examined rectally with ultrasound at 24 h intervals to determine time to Ovulation and duration of estrus. The number of breedings and the pregnancy rate at 18 (±3) and 38 (±3) days were recorded, as were systemic side effects and local reactions at the implantation sites. Pregnancies resulting from breedings during the treatment estrus and/or from breedings during the next estrus were followed and the early and late pregnancy loss rate, the number of pregnancies going to term and of live–born foals was recorded. Mean follicle diameter at treatment was not significantly different between the deslorelin and placebo treatment group with 41.6 mm and 40.8 mm, respectively. Treatment with deslorelin STI reduced the time interval to Ovulation significantly from 69.5±25.48 h to 42.7±12.35 h (p<0.001). The percentage of mares having ovulated within 48 h rose from 26.3% to 95.0%, respectively, for placebo and deslorelin STI (p<0.001). As a consequence, the duration of estrus in days and the percent of animals requiring more than 1 breeding were significantly reduced in deslorelin treated animals from 5.4 days to 4.6 days, and from 55.6% to 5.0%, respectively (p=0.009 and =0.001). The percent of mares pregnant from breedings at the treatment estrus (65.0% versus 44.4%) or the next estrus (83.3% versus 92.3%) was satisfactory and similar for deslorelin and placebo treated mares (p>0.005), and in 70.0% and 66.7% of these once or twice bred mares did pregnancies go to term and live foals were born. kw|Keywords|k]GnRH     

Economic Benefit of Fertility Control in Wild Horse Populations

ABSTRACT I projected costs for several contraceptive treatments that could be used by the Bureau of Land Management (BLM) to manage 4 wild horse (Equus caballus) populations. Potential management alternatives included existing roundup and selective removal methods combined with contraceptives of different duration and effectiveness. I projected costs for a 20-year economic life using the WinEquus© wild horse population model and state-by-state cost estimates reflecting BLM's operational expenses. Findings revealed that 1) currently available 2-year contraceptives in most situations are capable of reducing variable operating costs by 15%, 2) experimental 3-year contraceptives may be capable of reducing costs by 18%, and 3) combining contraceptives with modest changes to herd sex ratio (e.g., 55–60% M) could trim costs by 30%. Predicted savings can increase when contraception is applied in conjunction with a removal policy that targets horses aged 0–4 years instead of 0–5 years. However, reductions in herd size result in greater variation in annual operating expenses. Because the horse program's variable operating costs make up about half of the total program costs (which include other fixed costs), contraceptive application and management can only reduce total costs by 14%, saving about $6.1 million per year. None of the contraceptive options I examined eliminated the need for long-term holding facilities over the 20-year period simulated, but the number of horses held may be reduced by about 17% with contraceptive treatment. Cost estimates were most sensitive to the oldest age adoptable and per-day holding costs. The BLM will experience significant cost savings as carefully designed contraceptive programs become widespread in the wild horse herds it manages.