Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
Topic:Reproduction
Reproduction in horses encompasses the biological processes and mechanisms involved in the breeding and development of equine offspring. This includes the study of reproductive anatomy, physiology, and endocrinology in both mares and stallions. Key areas of interest include the estrous cycle, ovulation, conception, gestation, and parturition. Researchers also examine factors influencing fertility, reproductive technologies such as artificial insemination and embryo transfer, and management practices that impact reproductive success. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, genetic, and environmental aspects of equine reproduction.
Biosynthesis of 3 beta-hydroxy-5,7-pregnadien-20-one by the horse fetal gonad. The production of equilin and the other ring B-unsaturated estrogens by the pregnant mare is anomalous in that they are biosynthesised by a cholesterol-independent pathway. Fetal horse gonads were incubated with tritiated sodium acetate and radiochemically pure 3 beta-hydroxy-5,7-pregnadien-20-one and 3 beta-hydroxy-5,7-androstadien-17-one were isolated. A fetal gonad--placental system is proposed for equilin production, 3 beta-hydroxy-5,7-pregnadien-20-one being a precursor for 3 beta-hydroxy-5,7-androstadien-17-one in the fetal gonad and the latter being the precursor of equilin in the place...
The effect of nutritional stress on the plasma progestagen levels and embryonic mortality in twin pregnancies of mares. Two thoroughbred mares bearing twins as diagnosed by rectal palpation, were subjected to nutritional stress by drastically reducing the daily ration. This resulted in a marked reduction in plasma progestagen levels and the death of either one or both of the twin embryos.
Testosterone effects on mares during synchronization with altrenogest: FSH, LH, estrous duration and pregnancy rate. Twelve mares fed altrenogest for 14 d were used to study the effects of a single injection of testosterone propionate on concentrations of follicle-stimulating hormone (FSH) during diestrus, and to relate the normal and perturbed patterns of FSH secretion to subsequent estrous characteristics and fertility. Seven of 12 mares received testosterone propionate at 200 micrograms/kg of body weight on d 5 of progestogen feeding. Mares were teased and blood samples were drawn daily; all mares were artificially inseminated at the first estrus after progestogen treatment. Testosterone propionate treatm...
Plasma cortisol variations induced in the stallion by mating. Plasma cortisol variations have been determined by radioimmunoassay in 5 stallions during mating and in 2 teasers during oestrous female exposure. In all the animals, cortisol plasma levels consistently increase (71.1 ng/ml vs 44.0 and 63.0 ng/ml vs 35.1, in the stallions and in the teasers, respectively) 7-30 min after female exposure; 120 min after exposure, cortisol concentrations are again low.
Effects of melatonin and thyrotropin releasing hormone on mares during the nonbreeding season. Two hormonal treatments, chosen for their effectiveness in other seasonally breeding species, were tested in mares during the nonbreeding season to determine if they could induce ovarian activity and estrus during the winter. Of 15 functionally anestrous (anovulatory) mares, five received intravaginal, polyurethane sponges containing .75 g of melatonin on December 16; fresh sponges containing melatonin were inserted weekly until February 3. These mares also received daily injections of saline. Five other mares received daily im injections of 100 micrograms of thyrotropin-releasing hormone (TRH...
Effect of intranasal oxygen administration on arterial blood gas and acid base parameters in spontaneously delivered, term induced and induced premature foals. The effect of intranasal administration of oxygen at a flow rate of 10 litres per minute for 10 minutes, was studied in a total of 19 foals (thoroughbred and pony) aged between 0.5 and 12 hours. Arterial blood samples were collected before and after oxygen administration for the determination of paO2, paCO2, pHa and base excess. The foals were divided into three groups: five spontaneously delivered thoroughbred and pony foals (group 1), seven term induced thoroughbred foals (group 2) and seven induced premature pony foals (group 3). To examine the effect of duration of oxygen administration on...
Plasma and endometrial progesterone content following exogenous progesterone administration in mares. Intact and ovariectomized pony mares were treated with either progesterone in-oil or repositol progesterone. Serum progesterone, endometrial progesterone and endometrial histology were examined. There were no differences in serum or tissue progesterone between intact and ovariectomized mares. Serum and tissue progesterone were greater for progesterone in-oil treated mares than for repositol treated mares. Both progesterone in-oil and repositol progesterone initiated endometrial gland proliferation with no difference in response observed between the two preparations.
Uroperitoneum in the foal. The case records of 22 foals with uroperitoneum were reviewed. The most common cause was a defect in the urinary bladder. A sex predilection for males was apparent. Clinical signs were tachycardia, tachypnea, and abdominal distention. The history pertaining to micturition was variable. Hyponatremia, hypochloremia, and hyperkalemia were marked. A reliable means of diagnosis was considered to be the demonstration of a wide disparity in serum and peritoneal fluid creatinine values. Surgical repair was successful in 11 of 18 cases, although surgical and anesthetic complications were common. Some o...
Induction of parturition in mares: effect on passive transfer of immunity to foals. Parturition was induced in 11 mares, using a synthetic prostaglandin. Eight mares, not treated, were used as controls. There was no significant difference between the serum immunoglobulin G (IgG) concentrations of the treated and control mares. The concentration of IgG in the colostrum of treated mares compared favorably with that reported for naturally foaling mares. Four foals from treated mares died or were euthanatized because of weakness during the 1st 24 hours after birth. The mean IgG concentration in the surviving foals from treated mares at 24 to 36 hours of age was 1,561 mg/100 ml, w...
Immunochemical demonstration of a new pregnancy protein in the mare. An antiserum against the serum of a pregnant mare was absorbed with stallion serum. This antiserum then gave two precipitates in crossed immunoelectrophoresis with serum from pregnant mares as the antigen. The two precipitates exhibited beta-1 and alpha-2 electrophoretic mobility. Identity was demonstrated between the alpha-2 mobile protein and PMSG. The absorbed antiserum inhibited the biological action of the PMSG preparation when tested in mouse ovarian weight assays. The beta-1 mobile protein was not detected in the serum from non-pregnant mares, stallions or geldings and was detected earl...
Seasonal effects on ovarian follicular development in pony mares. To define ovarian follicular kinetics in the equine ovary during anestrus and the breeding season, the follicular population of pony mares was investigated at mid-anestrus and at the beginning and end of the breeding season. There was a clear effect of season on the exit of reserve (primordial and initiated) follicles since at the beginning of the breeding season we noticed a higher mitotic index for the smaller preantral follicles, leading to an accumulation of small and medium antral follicles. In contrast, the ovaries sampled during anestrus or at the end of the breeding season were very si...
Genetic linkage between the loci for phosphohexose isomerase (PHI) and a serum protein (Xk) in horses. Genetic linkage between the equine loci for phosphohexose isomerase (PHI) and serum Xk protein was demonstrated by means of segregation data from three sire families. The recombination frequency was estimated from pooled data to be 0.23 +/- 0.02; a significant heterogeneity between sires for estimates of the recombination frequency was observed. No indication of linkage was detected between Xk and 14 other blood marker loci. Linkage between the Xk locus and the locus for soluble malic enzyme (ME1) has recently been reported in horses. An equine linkage group designated LG IV comprising the thr...
Reconstitution of primary, severe, combined immunodeficiency in man and horse. Severe combined immunodeficiency disease (SCID) in foals is the only known animal model for the autosomal recessive form of primary SCID in man. A major requirement in the treatment of SCID is the maintenance of the patient in a disease free state until definitive therapy can be undertaken. This paper reviews the current status of prophylactic and definitive therapy in man and the horse. Particular emphasis is placed on the methods of reconstitution available, involving foetal tissues and bone marrow.
Cambendazole for strongyle control in a pony band: selection of a drug-resistant population of small strongyles and teratologic implications. Cambendazole (CBZ) treatments (20 mg/kg) given at 8-week intervals were used for parasite control in a breeding band of ponies (n = 33 to 43) during the period July 1974 to August 1978. Pre- and posttreatment worm egg counts on feces were used to evaluate efficacy of treatments after every 2nd treatment interval by monitoring changes in strongyle egg counts. Initially, effective reductions (expressed as 92% to 96% fewer worm eggs) were lessened to 70% by the 9th treatment (18 months) and to 28% by the 12th treatment, and thereafter, they fluctuated between 0% and 38%. Critical tests on animals...
Linkage disequilibrium between the ELA and the A blood group systems in Standardbred horses. The linkage group formed by the ELA and A blood group system in horses was studied in American Standardbred horses. The distance between the ELA locus and the A blood group locus was measured as 1.61 centimorgans, observing only the haplotypes contributed by the sires. Strong linkage disequilibrium was found in pacing Standardbred horses for ELA-W1 with Aa, ELA-W5 with Ab and ELA-W10 with Ab. Linkage disequilibrium was apparent at both the population and family level. Among trotting Standardbred horses, linkage disequilibrium was found for ELA-W1 with Aa and for ELA-W10 with Ab. It was not pos...
[Topographico-anatomic data on the testicular artery, ductus deferens artery and cremaster artery in the stallion]. To study the vascularization of the testis of stallions we used 96 testes. We examined its topography and anatomy by roentgenography, stereoroentgenography, by the corosive method, and by means of gel and China ink injections. To make the roentgeno-arteriograms we used minimum emulsified in glycerine as contrast medium. The branching off of the Aa. testiculares from the Aorta abdominalis is variable in stallions. We observed also a peculiar age-dependent arrangement of the loops of the convolution. In the adult stallion, the shape of the convolution is either cylindrical or conical, spindle-sh...
Methods for the treatment of twin pregnancy in the mare. Within a group of 130 mares which, in the event, carried twin pregnancies, 29 (22.3 per cent) produced their twins following diagnosis of a single palpable follicle at service and a single pregnancy 42 days later. The whole group of 130 twin-pregnant mares gave birth to only 17 live foals (13 per cent). Breeding results for the following season were available for 102 of these mares, when 38 (37 per cent) produced live foals. Thus over the two seasons an average 23 per cent of this group produced live foals. In a second group, comprising 70 mares, twin pregnancy had been diagnosed in all of the...
Transmission studies with the contagious equine metritis bacterium in albino Swiss mice. Aspects of experimental transmission of the causal bacterium of contagious equine metritis (CEM) to albino Swiss mice were investigated. Whereas infection was established in the majority of female mice, the organism was recovered from only a limited number of male mice after challenge. No clinical evidence of infection was observed in the experimental mice. There was only one instance of presumptive venereal transmission of the CEM bacterium. One third of infected females conceived and had normal litters.
Comparison of glucose, fructose, ascorbic acid and glucosephosphate isomerase enzymatic activity in uterine flushings from nonpregnant and pregnant gilts and pony mares. In Experiment 1, 40 gilts and 30 pony mares were used to characterize changes in glucose, fructose, ascorbic acid and glucosephosphate isomerase (GPI) enzymatic activity in uterine flushings collected either during the estrous cycle or early pregnancy. Total recoverable glucose was greater (P less than 0.01) in uterine flushings from pregnant gilts, but pregnancy status had no effect on total recoverable glucose in pony mare uterine flushings. Fructose was undetectable in uterine flushings from nonpregnant gilts and pony mares and pregnant gilts and pony mares prior to Day 14, but occurred in ...
Hereditary lethal arthrogryposis (“muscle contracture”) in horses. In 4 female foals of the Norwegian horse breed, "Fjord Horse", congenital arthrogryposis of the limbs are described. The disorder was mainly limited to the hind limbs and associated with polydactylia and partly with brachygnathia superior and cleft palate. The defective foals were paternal halfsisters of 4 normal foals (1 female + 3 males), sired by the stallion "Bingo" 1804, which was phenotypically quite normal. The disorder being lethal, is possibly caused by a sex-limited or a strongly sex-influenced dominant gene.
Duration of maternally derived immunity to tetanus and response in newborn foals given tetanus antitoxin. Serum tetanus antitoxin (TAT) concentrations were measured in a group of 30 foals from birth to 4 months of age. Five of 30 foals (16.6%) had serum titers less than 0.01 IU of TAT/ml by 1 month of age. At 2 months of age, 17 of 28 foals (60.7%) had titers less than 0.01 IU/ml. By 3 months of age, 22 of 29 (75.5%) foals tested had titers of less than 0.01 IU/ml. At the age of 4 months, 24 of 29 foals (82.1%) had titers of less than 0.01 IU/ml. The TAT given to foals at birth resulted in an immediate increase in titer when circulating antitoxin was absent or minimal. Titers considered protective...
