bluuebunny/crossref_metadata_2025 huggingface dataset:
A preliminary study on the effects of jejunocaecostomy in horses
Authors: Bertone A. L. , Stashak T. S. , Ralston S. L. , Bertone J. J. , Hamar D.
Published: June 2010

Ileal bypass by re‐section and jejunocaecostomy is a commonly performed surgery in horses, but has a reportedly lower success rate than other small intestinal surgeries. Lower success rates and chronic problems with diarrhoea, weight loss, protein, sugar and fat malabsorption, and Ca/P imbalance occur in man. The purpose of this study was to investigate changes in bodyweight, nutrient digestion and absorption, and serum and urine composition in horses before and 3, 12 and 27 weeks after ileal resection and side‐to‐side jejunocaecostomy. Four adult, healthy horses had a baseline CBC; serum creatinine, cholesterol, Na, K, Cl, Mg, Ca, P; digestion trial; xylose and fat absorption test; and serum total bile acid test. Digestion of dry matter, crude protein, total plant cell wall, cellulose, hemicellulose, and lignin; and urinary fractional excretions of Na, K, Cl, P and Ca were calculated. A one‐way analysis of variance compared baseline values to those obtained after caeliotomy and jejunocaecostomy (P<0.05). Results include a significant decrease in serum calcium and total protein 27 weeks after surgery and a significant increase in FENa, FECa, and faecal metabolic organic matter 27 weeks after surgery. Bodyweight decreased significantly 3 weeks after surgery, but increased to greater than baseline values at 12 and 27 weeks after surgery. Vitamin A absorption curves were normal (sigmoid) before surgery and linear at all times after surgery. Serum cholesterol was significantly lower 27 weeks after surgery and a trend (P<0.1) for a lower serum cholesterol was observed 3 weeks after surgery. No significant differences were apparent in serum electrolytes, faecal water, protein or fibre digestibility, xylose absorption or serum bile acid measurements. In summary, ileal bypass affected the horses minimally, but derangements of Ca metabolism, fat (fat soluble vitamin) absorption and microbial flora need further study.
Atresia coli in 7 foals (1964–1990)
Authors: Nappert G. , Laverty S. , Drolet R. , Naylor J.
Published: June 2010

Intestinal atresia is uncommon in foals. The occurrence of equine atresia coli was 0.44% in the Veterinary Medical Data Base (VMDB). An occurrence of equine intestinal atresia of 1.3% was found at the Large Animal Hospital, University of Montreal. Five case records from the VMDB and 2 from the University of Montreal were reviewed. The breed distribution of cases was: Appaloosa (N = 2), Morgan (N = 1), Standardbred (N = 1), Throughbred (N = 1), Paint Horse (N / 1) and Quarter Horse (N = 1). Five foals had type III or blind‐end atresias and 2 foals had type II or cord atresias. The pelvic flexure was absent in 2 cases. Clinical signs were progressive abdominal distension, colic, lack of faecal production and lack of response to enema administration. Two cases presented a blind ending rectum on digital palpation. Surgical correction was attempted in 3 foals but was unsuccessful. A grave prognosis should be given when this condition is diagnosed in foals.
Effect of oral omeprazole on basal and pentagastrin‐stimulated gastric secretion in young female horses
Authors: Andrews F. M. , Jenkins Christine C. , Blackford J. T. , Frazier Donita L. , Olovsson S.‐G. , Mattsson H.
Published: June 2010

Omeprazole (0.7 mg/kg bwt), as enteric‐coated pellets in capsules, was administered to 8 horses with chronic gastric cannulae to determine its effect on gastric juice acidity, acid output, pH, and volume. Omeprazole was given via nasogastric tube once daily for 5 days and gastric secretion tests were done on the 1st and 5th day of dosing. Gastric juice samples were collected every 15 mins from the cannula, starting 5 h after the administration of omeprazole. Basal secretion was determined in the first hour of collection followed by a 2‐h determination of pentagastrin (6 μg/kg/h)‐stimulated secretion. Lactose placebo studies were carried out in the same horses for comparison.

Basal and stimulated gastric acid output were inhibited by 69% and 76%, respectively, by the 5th day of dosing, when compared with control values. Basal gastric juice pH increased from 3.2 in placebo‐treated horses to 4.6 by the 5th day of omeprazole treatment. Stimulated gastric juice pH was similarly increased from 1.7 to 4.6 by the 5th day of treatment.

Omeprazole (0.7 mg/kg bwt) given orally once daily significantly inhibited basal and stimulated gastric acid secretion in horses by the 5th day of administration.
Development of cyathostome infection of helminth‐naive foals
Authors: Love S. , Duncan J. L.
Published: June 2010

Three groups of 5 Welsh‐Shetland crossbred pony foals each were infected with 450,000 third stage cyathostome larvae, given as either a single dose of freshly harvested larvae (Group A) or a single dose of larvae that had been cold conditioned for 6 weeks at 4°C (Group B) or as a trickle infection of 18 doses of 25,000 freshly harvested larvae administered on weekdays over 1 month (Group C). The mean pre‐patent periods of Groups A and B were 53 days with shortest and longest individual values of 48 and 62 days. In Group C the mean pre‐patent period was 65 days with a range from 60–77 days. The general patterns of faecal worm egg output were similar in Groups A and B, with rises in mean numbers of faecal worm eggs over about 3 weeks following patency, after which the mean worm egg counts in faeces remained between about 400 and 1,000 eggs/g. The mean faecal worm egg counts of Group C animals, at approximately 200–300 eggs/g, were lower than the mean values of Groups A and B. At post‐mortem examinations 16 weeks post infection, the group mean total and mucosal cyathostome worm counts were: Group A, 60,898–14,806; Group B, 33,592–13,292; Group C, 30,794–14,714. Therefore, the relative proportions of total worm burdens present at mucosal stages were different between groups with values of 24%, 39% and 49% for Groups A, B and C respectively. It was concluded that both larval chilling and trickle larval dosing influenced the development of experimental cyathostome infections.
Lipid peroxidation and antioxidative defences during ischaemia and reperfusion of the equine ascending colon
Authors: Sullivan K. E. , Snyder J. R. , Schiedt M. J. , Harman F. J. , Giri S.N.
Published: June 2010

Oxidative damage can occur during ischaemia and reperfusion of the intestine. Malondialdehyde (MDA) concentration can be used to determine the amount of lipid peroxidation that has occurred. Glutathione peroxidase, glucose 6‐phosphate dehydrogenase (G6PD), and superoxide dismutase (SOD) are important elements of cellular defence against reactive oxygen metabolites. Tissue levels of MDA, glutathione peroxidase, G6PD, and SOD were measured in an experimental model of equine ascending colonic ischaemia and reperfusion. Complete segmental colonic ischaemia (3 h) followed by 30 mins of reperfusion was studied in 8 horses. Ischaemia increased the concentration of MDA and decreased the SOD activity; glutathione peroxidase and G6PD remained unchanged. These results indicate that lipid peroxidation occurs during ischaemia of the colon and is associated with a decrease in the cellular defence against free radical attack.
Maturation of the central nervous system: comparison of equine and other species
Authors: SISKEN BETTY F. , ZWICK M. , HYDE J. F. , COTTRILL CAROL M.
Published: June 2010

This review covers the development and maturation of the cerebellum of the horse and compares this developmental sequence with that of man, mouse and chicken. These comparisons attempt to correlate morphological and neurochemical features, developmental time and functional performance necessary for survival at birth. Although there is great disparity between these 3 species, the basic anatomical structures of the cerebellum are present as are specific cellular groups, synapses and neurochemical markers. In addition to this structural homogeneity, other attributes of the cerebellum are its easily identified cellular populations and its well ordered pattern of growth and differentiation.

The cerebella of the developing chick and mouse have been studied in great detail as they are amenable to experimental manipulations. The pattern of cellular differentiation appears to be reproducible from specles to species and differs primarily as it relates to gestational age and functional requirements at birth. For instance, most of the large neurones of the cerebellar cortex differentiate early with small neurones and neuroglia differentiating later. Neurogenesis of the cerebellar cortex is fairly complete in the newborn foal and chick hatchling, but not in the human or rodent newborn.
Foetal endocrine maturation
Authors: CHALLIS J. R. G. , BASSETT NICOLE , BERDUSCO E. T. M. , HAN V. K. M. , LU FENG , RILEY S. C. , YANG KAIPING
Published: June 2010

In domestic ruminants such as the sheep, birth is effected through sequential maturation of the foetal hypothalamic‐pituitary‐adrenal (HPA) axis, leading to the increased output of cortisol. Factors regulating foetal pituitary adrenocorticotrophin (ACTH) secretion have been delineated, and these include corticotrophin releasing hormone (CRH), arginine vasopressin, prostaglandin (PG) E2 and endogenous opioids. The pre‐partum increase in foetal plasma ACTH is associated with a rise in pro‐opiomelanocortin (POMC) mRNA in the foetal pars distalis, and with an altered pattern of POMC post‐translational processing. Foetal adrenal activation results from an increase in ACTH receptors and enhanced coupling through the Gs protein to adenylate cyclase, and increased expression of key steroidogenic enzymes including P450c17. Cortisol modulates the mechanism by which ACTH activates foetal adrenal function, through specific glucocorticoid receptors (GR) in the foetal adrenal cortex. Although the numbers of GR change with gestation, the relative abundance of GR mRNA does not, pointing to post‐translational regulatory mechanisms. Cortisol also stimulates an increase in the concentration of its own high affinity binding protein (corticosteroid binding globulin; CBG) in the foetal circulation, apparently by increasing CBG gene expression in the foetal liver, and by altering the extent of foetal CBG glycosylation in a manner that would be expected to decrease the metabolic clearance of this glycoprotein. Clear evidence for placental CRH and ACTH production is lacking in sheep, but PGE2, produced in increasing amounts by the placenta during late pregnancy, may augment the drive to HPA maturation. Aspects of the maturational pathway of cortisol biosynthesis have been described in other species, including the horse, and some comparison is made with the more detailed information currently available from species such as the sheep.
Retinol‐binding protein in equine endometrium
Authors: McDOWELL KAREN J. , ADAMS MARY H. , SMITH TRACI L. , BAKER C. B.
Published: June 2010

In Exp. 1, endometrial biopsies were collected from normally cycling, unmated mares at Days 0, 4, 8, 10, 12, 14 and 16 and from pregnant mares at Days 10, 12, 14 and 15 after ovulation (2 mares/day) and immediately frozen on solid CO2.

In Exp. 2, biopsies were obtained from acyclic intact mares treated with steroids in regimens designed to simulate an oestrous cycle (oestrogen, low progesterone or high progesterone). Duplicate endometrial samples from each mare were frozen for RNA analysis or pooled within day and incubated in vitro for analysis of proteins secreted into the medium by 2‐D PAGE and fluorography. Fluorograms from all 3 groups revealed proteins with electrophoretic mobility consistent with RBP (Mr 21, 000–22, 000, pI 5–6.5) Identification of these proteins as immunoreactive RBP was confirmed by western blot analysis.

Endometrium which had been frozen at the time of collection was pooled within day (Exp. 1) or within group (Exp. 2), and total RNA was extracted. Northern blot analysis revealed positive hybridisation for RBP at ˜0.9 kb in all samples.

These results demonstrate the presence of mRNA for RBP in equine endometrium during the oestrous cycle and early pregnancy, that equine endometrium synthesises and secretes RBP, and that RBPmRNA and protein concentration may be influenced by the steroid environment. Endometrial RBP probably plays a critical role in successful development of the equine embryo and establishment of pregnancy.
The live foaling rate per cycle in mares
Authors: BAKER C. B. , LITTLE T. V. , McDOWELL KAREN J.
Published: June 2010

The overall live foaling percentage per cycle on 4 Kentucky Thoroughbred farms was 42.0%. The rate varied with mare reproductive status, mare age, cycle number and stallion. The most pronounced effect was associated with mare age. Estimates of the relative importance of embryonic loss as a factor limiting reproductive success for young and old mares. suggest that young mares lose half of their embryos from fertilisation to term, and the loss rate increases with mare age to the point that old mares lose all or nearly all of their embryos.
Age‐associated subfertility before entry of embryos into the uterus in mares
Authors: CARNEVALE E. M. , GRIFFIN P. G. , GINTHER O. J.
Published: June 2010

Age‐associated changes in the fertility of pony mares were studied in 3 experiments. On Days 1.5 and 3 (Day 0=day of ovulation), respectively, the collection rate of ova (cleaved or uncleaved) per ovulation was significantly lower in old mares (>20 years; 11/20 and 6/9) than in young mares (2–10 years; 17/18 and 9/9). The percentage of cleaved ova was significantly lower for old mares (5/11) than for young mares (15/17) on Day 1.5 but was not different on Day 3. Embryos from old mares had significantly more morphological abnormalities and fewer embryonic cells on Day 3. The transfer of embryos from young or old donors into the oviducts of young or old recipients did not significantly alter embryo development between Days 1.5 and 3.5. On Day 11, significantly fewer pregnancies and smaller embryonic vesicles were present in old mares than in young mares. The pregnancy rate on Day 3 was not different from the pregnancy rate on Day 11 within old mares (6/9 versus 4/9) or within young mares (9/9 versus 8/9). The studies indicated that a high incidence of age‐associated defects occurred before the day that an embryo would be expected to enter the uterus.
Interaction between stallion spermatozoa and oviductal epithelial cells in vitro
Authors: LEFEBVRE R. , SAMPER J. C.
Published: June 2010

Oviducts were collected from oestrous, dioestrous and anoestrous mares at the abattoir, and the epithelial cells were incubated in tissue culture medium. Stage of the cycle did not appear to affect significantly the quality of the culture, the ability of sperm cells to attach to the oviduct or prolong the motility of bound spermatozoa. More fresh spermatozoa attached to oviductal tissue than did capacitated, acrosome‐reacted and frozen‐damaged spermatozoa, suggesting that sperm membrane integrity is one of the factors necessary for sperm attachment to the oviductal epithelial cells. Spermatozoa from subfertile stallions had a significantly lower attachment rate to oviductal tissue compared with those of a stallion with normal fertility.
Heparin‐induced capacitation: a comparison between the bull and stallion
Authors: FARLIN M. E. , JASKO D. J. , GRAHAM J. K. , SQUIRES E. L.
Published: June 2010

Spermatozoa were incubated with 0, 10, 50 or 100 μg heparin/ml for 4 h at 37°C (bull) or 39°C (stallion) in 5% CO2. Spermatozoa were then challenged with 10 μM‐calcium ionophore A23187 at 0, 2 and 4 h of incubation for an additional 30 min. Samples were evaluated for the % of motile and acrosome‐reacted spermatozoa. The spermatozoa of both species exhibited a decline in the % of motile spermatozoa during incubation over 4 h, and this decline was similar for heparin and non‐heparin‐treated stallion spermatozoa (P>0.05). Within incubation times the % of acrosome‐reacted stallion spermatozoa during incubation was similar (P<0.05) among heparin and non‐heparin‐treated spermatozoa. As for bull spermatozoa, addition of 10 μM‐A23187 to stallion spermatozoa induced more acrosome‐reactions in heparin‐treated than in non‐heparin‐treated spermatozoa (P<0.05). However, maximal inductions of acrosome reactions following ionophore challenge occurred in stallion spermatozoa after 4 h incubation with ≥50 μg heparin/ml. Bull and stallion spermatozoa incubated with heparin exhibited higher (P<0.05) % of acrosome‐reacted spermatozoa after challenge with A23187 than did non‐heparin‐incubated spermatozoa, suggesting that they may have undergone capacitation during incubation with heparin. Although incubation with 10 μg heparin/ml was sufficient to induce capacitation in bull spermatozoa, stallion spermatozoa required incubation with ≥50 μg heparin/ml.
Transmission electron microscopy of equine embryos cryopreserved by different methods
Authors: e ALVARENGA F. C. LANDIM , ALVARENGA M. A. , MEIRA C.
Published: June 2010

Horse embryos were preserved with different cooling rates and cryoprotectants. Embryos in Groups I and II were treated with glycerol as cryoprotectant. In Group I the temperature was lowered at 2.5‐4°C/min until seeding (‐6 to ‐7°C) and at 0.3‐0.6°C/min until ‐30°C, followed by direct immersion in liquid nitrogen. Group II embryos were placed in a medium with 20% (v/v) glycerol plus 0.5 M‐sucrose. Cooling was in liquid nitrogen vapour (‐25°C) for 5 min, followed by immersion in liquid nitrogen. Group III embryos were cooled at the same rate as used for Group I, but the cryoprotectant was 1, 2‐propanediol. Group IV embryos were unfrozen. Embryo transfer was done non‐surgically just after thawing. Pregnancy rates were 40%, 0%, 0% and 80% in Groups I, II, III and IV, respectively. Group I embryos survived with most plasma and nuclear membrane intact. Embryos in Groups II and III showed more damage, characterised by cytoplasmic vacuolisation and cellular membrane disruption. Most of the damage appeared to be caused by the freeze‐thaw process, but some morphological changes seen in mitochondria may be caused by glycerol.
Transvaginal ultrasound‐guided follicular aspiration of equine oocytes
Authors: COOK N. L. , SQUIRES E. L. , RAY B. S. , JASKO D. J.
Published: June 2010

Follicular aspiration was performed in 30 cyclic mares during each oestrus and every dioestrus in which >4 follicles 10–15 mm in size were present. During the final oestrous cycle, 15 mares were superovulated with crude equine pituitary extract before aspiration. With the oestrous mares (99 preovulatory follicles yielding 62 (63%) oocytes) 3 follicular aspiration techniques were examined: a 12‐gauge double‐lumen needle, allowing continuous rinsing of the follicle, provided the best oocyte recovery, 36/43 (84%) compared with the single‐lumen needle (24/47; 51%) or the wire‐loop technique (2/9; 22%) (P<0.05). During dioestrus, 71 oocytes were recovered from 323 follicles (22%): oocyte recovery was not affected (P>0.05) by aspiration technique performed (16‐gauge needle with simple or continuous rinsing). Follicles <15 mm in size gave higher (P<0.05) oocyte recovery rates 36/118; 31%) than did follicles >20 mm in size (3/38; 8%). In the superovulated mares 22 oocytes were recovered from 36 preovulatory follicles (61%). We suggest that transvaginal ultrasound‐guided follicular aspiration is a low‐risk, repeatable method for in‐vivo collection of equine oocytes.
The in‐vitro block to development and initiation of transcription in early equine embryos
Authors: BALL B. A. , IGNOTZ G. G. , BRINSKO S. P. , THOMAS P. G. A. , MILLER P. G. , ELLINGTON J. E. , CURRIE W. B.
Published: June 2010

Coculture of early cleavage‐stage equine embryos with other cell types, primarily oviductal epithelial cells, can support development to blastocystsin vitro.Embryos cultured in complex medium without cellular support develop at a significantly poorer rate and appear to undergo a developmental blockin vitro.

In 2 experiments, 1–8‐cell embryos (n= 15) were cultured in Ham's F12: Dulbecco's MEM for 5 days or until morphological degeneration occurred. Embryos were assessed for stage of development and quality score on a daily basis. At the end of culture, embryos were stained to determine the number of nuclei present or were fixed and sectioned for evaluation by light microscopy. Additional embryos (n= 8) collected on Days 2–7 after ovulation were labelled with [3H]uridine and incorporation was determined by autoradiography.

Of 15 embryos cultured without cellular support, 3 reached the morula stage and the remaining 12 embryos cleaved to the 8–16‐cell stage before undergoing morphological degeneration. [3H]uridine was incorporated into embryos at the 8‐cell stage or later, but no incorporation was detected in embryos at the 4‐cell stage. These results indicate that early equine embryos appear to undergo a developmental blockin vitroat the 8–16‐cell stage, relief of which is temporally associated with the onset of embryonic transcription.
Gonadotrophin treatments increase ovulation rate but not embryo production from mares
Authors: PALMER E. , HAJMELI G. , DUCHAMP G.
Published: June 2010

Pony mares were treated with crude equine pituitary extract (CEG) or an FSH‐enriched fraction from the same extract during the anovulatory or ovulatory season. The animals were treated during 2 successive cycles at each season. About 3 follicles achieved the preovulatory stage and ovulated but only 0.6 embryos were obtained after each treatment. There was no influence of season, hormone or treatment cycle on ovulation and embryo rates.

Despite the increased ovulation rate, there was no improvement in embryo production (3.0 follicles, 2.8 ovulations, 0.6 collected embryos in 60 treatment cycles, 1.0 follicle, 1.0 ovulation and 0.6 embryos in 28 untreated cycles). However, the treatment can increase the number of embryos in winter (3.3 ovulations and 0.6 embryos, 30 cycles) compared with no responses in the normally anoestrous mare at this time.
Embryo transfer in anoestrous recipient mares: attempts to reduce altrenogest administration period by treatment with pituitary extract
Authors: LAGNEAUX D. , PALMER E.
Published: June 2010

Groups of ovariectomised and anoestrous mares were treated with altrenogest and used as recipients for embryo transfer. Progesterone concentrations in all ovariectomised, pregnant mares increased only after 85 days of pregnancy, but in 2 out of 4 anoestrous pregnant mares progesterone increased between Days 40 and 50 of pregnancy. Follicular growth and luteinised follicles suggested that altrenogest could be withdrawn earlier. To test whether exogenous LH treatment could stimulate earlier onset of ovarian progesterone secretion, anoestrous, recipient pregnant mares treated with altrenogest were treated with LH (25 mg CEG (crude equine gonadotrophin) im daily (N=5). Two of the 4 control mares ovulated at Days 58–60 and plasma progesterone increased. The other 2 mares did not ovulate. In the mares treated with CEG, altrenogest treatment was withdrawn in 3 on Days 45, 50 and 55 respectively. One mare aborted on Day 54 when endogenous progesterone was still very low and there was no indication of ovulation and/or luteinisation in the 5th mare. There was no significant difference in increasing progesterone concentrations between CEG‐treated mares and untreated mares, suggesting that such treatment in anoestrous recipient mares is relatively inefficient.
Special surgical transfers of horse embryos
Authors: MULLER Z. , CUNAT L.
Published: June 2010

Two surgical methods of equine embryo transfer were developed. In Exp. 1, a long needle was used to puncture the vaginal wall and wall of the uterine horn and deposit the embryo: 3 pregnancies from 8 embryo transfers were confirmed at 50 days and 1 embryo was lost between 15 and 30 days.

In Exp. 2, an endoscope was introduced through the flank of the mare into the abdominal cavity. Under the optical control and fixation of the uterine horn by grasping, an embryo was inserted in the lumen of the uterine horn: 3 pregnancies from 7 transfers were confirmed at 50 days of pregnancy.

Surgical and non‐surgical embryo transfers for comparison resulted in 7 pregnancies from 10 surgical transfers and 4 pregnancies and 1 embryo loss from 12 nonsurgical transfers.
Commercial embryo transfer in polo ponies in Argentina
Authors: RIERA F. L. , McDONOUGH J.
Published: June 2010

Different techniques in an embryo transfer programme were studied under field conditions on polo pony mares in Argentina. Comparisons were made between embryo recovery rates from donor mares inseminated before or after ovulation, between two embryo recovery methods and between two embryo transfer methods. In addition, pregnancy rates were compared among recipients that received an embryo on 1, 2 or 3 occasions. Also, embryo recovery and pregnancy rates were compared in mares that underwent successive embryo recovery attempts.

The findings suggest that the success of embryo transfer performed under field conditions is enhanced by inseminating mares before ovulation, recovering embryos with an in‐line filter method and transferring the embryo into the uterine horn instead of the uterine body. Differences in pregnancy rates for recipient mares that had received embryos on 1, 2 or 3 occasions were not significant. Embryo recovery rates and pregnancy rates after transfer were not significantly different in mares in which embryo recovery attempts were performed between 1 and 10 times.
Difficulties in definition of equine osteochondrosis; differentiation of developmental and acquired lesions
Authors: POOL R. R.
Published: June 2010

This paper reviews most of the important clinical syndromes currently considered as examples of articular osteochondroses based on the belief that they arise from a primary lesion in the articular cartilage that produces failure in endochondral ossification. Arguments are made why a number of syndromes are not osteochondroses. Because morphological lesions resembling osteochondrosis can be produced at osteochondral junctions from primary disorders centred in the growth cartilages (dyschondroplasia) or in the capillary bed that replaces the cartilage model during endochondral ossification, the definition of osteochondrosis in horses needs to be reexamined. Because the morphology of an individual lesion of osteochondrosis provides little insight into its fundamental cause, this paper suggests that the pattern of skeletal distribution of the lesions in affected individuals may help distinguish between foals with the idiopathic (constitutional defects in the cartilage model) and acquired forms of osteochondrosis. In foals with acquired osteochondrosis when the cause of the defect in endochondral ossification is known, the cause of the disorder should be included in naming the clinical syndrome, e.g. traumatic osteochondrosis or zinc‐induced osteochondrosis. The search for the key to the pathogenesis of osteochondrosis in horses can only begin after the fundamental mechanisms causing perturbations of endochondral ossification are better understood.
Osteochondrosis/dyschondroplasia: a failure of chondrocyte differentiation
Authors: THORP B. H. , FARQUHARSON C. , KWAN A. P. L. , LOVERIDGE N.
Published: June 2010

Osteochondrosis/dyschondroplasia is a focal disorder of endochondral ossification which occurs in most species and is characterised by retention of epiphyseal or growth plate (physeal) cartilage. Epiphyseal and physeal cartilage in different species is very similar at the molecular and cellular levels. Therefore, the high frequency of lesions, ease of induction and a similar pathology to that found in other species makes avian tibial dyschondroplasia (TD) a useful model for the general study of osteochondrosis. In addition some of the methods successfully applied to the investigation of avian TD may indicate strategies for the investigation of equine OCD/dyschondroplasia.

TD is characterised by an avascular mass of cartilage containing partly hypertrophied (transitional) chondrocytes. Changes occurring during the initiation of a lesion can be obscured by subsequent pathology and caution must be exercised in interpreting results of studies of established lesions. In‐situ biochemistry and immunocytochemistry of chondrocytes in TD indicates that the accumulation of cartilage is not caused by increased chondrocyte proliferation or decreased osteoclast/chondroclast activity. Anaerobic glycolysis is not increased in the transitional chondrocytes, showing that oxygen supply to these cells is not limiting. These initial studies confirmed that TD is the result of a failure of chondrocytes to differentiate fully and are supported by an investigation in which genetic selection for TD resulted in accumulations of transitional chondrocytes.

Transitional chondrocytes contain high concentrations of TGF‐b and the product of the proto‐oncogene, c‐myc. In TD these cells are deficient in TGF‐β and c‐myc. Alkaline phosphatase and Type X collagen mRNA are increased but a lower concentration of collagen X within the matrix indicates a defect in its secretion or incorporation within the matrix. Type II collagen expression remains unchanged in dyschondroplasia. These data enable the point at which the arrest of chondrocyte differentiation occurs to be identified more precisely.

These methodologies are starting to reveal the sequence of events which results in the initiation of dyschondroplasia in domestic poultry. Strategies developed, tested and applied in the investigation of TD can be applied to studies of osteochondrosis/dyschondroplasia in other species including equids.
A review of possible metabolic relationships of copper to equine bone disease
Authors: CYMBALUK NADIA F. , SMART MARION E.
Published: June 2010

Copper (Cu) deficiency is a putative cause of equine bone disease. A review of the literature describing Cu metabolism and presumptive Cu deficiency in the horse is presented. The clinical and pathological consequences of primary and secondary Cu deficiency in equids are discussed with special reference to skeletal abnormality. Diagnostic criteria and recommendations for supplementation are provided.
Inferences from referred clinical cases of osteochondritis dissecans
Authors: McILWRAITH C. W.
Published: June 2010

This report relates to cases of osteochondritis dissecans from my surgical case records. Two categories of OCD were recognised: (1) those showing clinical and radiographic signs, and (2) those showing clinical without radiographic (but arthroscopic) signs. Case material examined included OCD in 318 tarsocrural joints in 225 horses, 261 femoropatellar joints in 161 horses, 170 fetlock joints in 71 horses, and 49 shoulder joints in 43 horses. In 64 tarsocrural joints, other lesions accompanied the OCD lesion including articular cartilage fibrillation (31 joints) and degenerate or eroded articular cartilage (24 joints). In 13 joints, lesions of OCD were present at arthroscopy without being identified by radiographic examination. There was discrepancy in the radiographic demonstration of lateral trochlear ridge lesions and their arthroscopic manifestations. Lesions in femoropatellar joints were divided into three grades and it was common for the arthroscopic lesion to be of a higher grade than the radiographic lesion. Lesions on the medial trochlear ridge with no radiographic manifestations and where the separated articular cartilage was the same thickness as normal articular cartilage were recognised commonly. In the shoulder, the humeral head alone was involved in 12 joints, the glenoid alone in 11 and both humeral head and glenoid were involved in 26 joints. Osteochondritis dissecans of the dorsal aspect of the distal metacarpus and metatarsus was divided into type I, II and III lesions. Type I lesions usually resolved with conservative treatment but type II lesions did not. Based on the arthroscopic findings of these cases, it is noted that instances do occur where there is no thickening of the cartilage, which is inconsistent with previous statements regarding pathogenesis. Breed predispositions were apparent (Standardbred in the hocks, Thoroughbred in the femoropatellar, and metacarpophalangeal/ metatarsophalangeal joints, Quarter Horse and Thoroughbred in the shoulder). The consistent location of lesions within the joint (very close to the limits of articulation) suggests that physical factors may be involved in the pathogenesis. The frequent bilateral nature of lesions in the femoropatellar and tarsocrural joints (and quadrilateral nature in the fetlock joint) while infrequently involving different joints is consistent with a ‘window of vulnerability’ in the endochondral ossification of that specific joint when an environmental insult occurs.
Osteochondrosis in the tarsocrural joint and osteochondral fragments in the fetlock joints in Standardbred trotters. I. Epidemiology
Authors: Sandgren B. , Dalin G. , Carlsten J.
Published: June 2010

Radiographic examinations of the tarsocrural and metacarpo/metatarsophalangeal joints were made in two groups of 1.5‐year‐old Standardbreds. One group comprised 674 horses drawn at random from the Swedish population of Standardbred trotters to provide an estimate of the incidence of tarsocrural joint osteochondrosis and osteochondral fragments in the fetlock joints. An additional 119 progeny of 4 stallions which themselves had osteochondrosis or fetlock fragments were included for the study of the distribution of lesions and the characteristics of affected animals, i.e. a total of 793 animals. The radiographic views were chosen to detect osteochondrosis in the tarsocrural joints (OC) and palmar/plantar osteochondral fragments (POF), ununited palmar/plantar eminences (UPE) and dorsal fragments (DF) in the fetlock joints.

The incidence of tarsocrural joint OC was estimated as 10.5% while palmar/plantar osteochondral fragments in the fetlock joints were present in 21.5% of the 674 animals.

In the group of 793 animals, tarsocrural joint OC was seen in 11.5% of the horses and was found bilaterally in 45% of the affected animals. In the fetlock joints, POF was found in 22.4%, UPE in 4.2% and DF in 4.4% of the horses. One or several of the lesions were found in 35.9% of the 793 horses. There were no significant sex differences in the incidence of OC and POF, but when all lesions were considered males were significantly more often affected than females (40.5%vs31.2%).

Of the OC lesions in the tarsocrural joint, 95% were found at the intermediate ridge of the tibia and 5% were seen at the lateral trochlea of the talus. POF and UPE mainly occurred in the hindlimbs. In 75% of the POF cases, the findings were located in the medial part of the joint while UPE findings almost exclusively were found laterally. Horses with UPE had a significantly higher incidence of POF.

The incidence of OC in the tarsocrural joint was related to the date of birth and the incidence was higher in the later than in the early part of the foaling season. The incidence of OC findings was also related to body size. Horses affected were taller at the withers and had a greater circumference of the carpus. Synovial effusions of the tarsocrural joint were significantly more pronounced in horses with radiographic signs of OC. In horses with POF and UPE, synovial effusions of the fetlock joints were not more frequent or severe.
Development of osteochondrosis in the tarsocrural joint and osteochondral fragments in the fetlock joints of Standardbred trotters. I. A radiological survey
Authors: Carlsten J. , Sandgren B. , Dalin G.
Published: June 2010

In a longitudinal study 77 Standardbred foals were examined 6 times from birth to the age of 16 months. The radiological examination included 9 views, selected to demonstrate the time of occurrence and the appearance of early radiographic signs of osteochondrosis in the tarsocrural joints (OC), palmar/plantar osteochondral fragments in the fetlock joints (POF) and ununited proximal palmar/plantar eminences of the proximal phalanx (UPE). Subchondral bone defects with a diameter >5 mm and/or osseous fragments were considered significant radiographic findings and were correlated to clinical signs.

Eight horses (10.4%) showed OC in the tarsocrural joints at the age of 12 months. All 8 horses showed radiographic changes indicating early OC lesions that were detectable before the age of 3 months. In 4 of these horses subchondral bone defects and/or fragments at the intermediate ridge of the distal tibia were visible before 1 month of age. Eleven horses showed radiographic changes first detected between 1 and 3 months of age that reverted to normal appearance at 8 months of age. In no case was a significant radiographic finding first detected between the age of 8 and 16 months. The radiographic findings of permanent hock OC were significantly correlated with the presence of tarsocrural joint effusions but did not correlate with lameness.

At the age of 12 months, 11 horses (14.3%) showed significant radiographic changes with defects and/or osseous fragments in the metacarpo‐ and metatarsophalangeal (fetlock) joints. In all of these horses early indications of these changes were detected before the age of 5 months. In 7 horses early radiographic signs of abnormal ossification reverted to a normal appearance before the age of 8 months. No additional significant radiographic findings were detected after the age of 8 months. There was no correlation between radiographic findings and fetlock joint synovial effusion or lameness.

Osteochondrosis of the tarsocrural joints and palmar/plantar intraarticular fragments in the fetlock joints develop very early in life and can be regarded as being permanent if present at 1 year of age.
Development of osteochondrosis in the tarsocrural joint and osteochondral fragments in the fetlock joints of Standardbred trotters. II. Body measurements and clinical findings
Authors: Sandgren B. , Dalin G. , Carlsten J. , Lundeheim N.
Published: June 2010

In a stud survey, 77 Standardbred foals (35 colts, 42 fillies) were examined 6 times from birth to the age of 16 months. In addition to the radiographic examination of the tarsocrural and fetlock joint areas, the horses were measured for height at the withers and at the croup, the circumference of the girth, carpus and cannon, and the length of cannon, and their conformation assessed according to a standardised protocol. The examination was completed by clinical examination, including thorough palpation of the extremities. All examinations were done by the same person. The foals were weighed each month. The metric observations were precorrected according to a model including the effects of sex, year of birth and the regression on individual recording age.

Eight foals (4 colts, 4 fillies) that developed radiographic signs of tarsocrural joint osteochondrosis (OC) had a higher body weight at birth (54.0 kgvs51.0 kg) and continued to be heavier and have a significantly higher average daily weight gain than did unaffected foals (12 months 337.8 kgvs316.8 kg, 0.80 kg/dayvs0.74 kg/day). They also had a larger frame than did horses without tarsocrural OC, including a greater height at the withers and at the croup, and had a markedly larger circumference of the carpus and cannon.

From 5 months of age onwards, there was a significantly higher incidence and more severe degree of synovial effusion in the hock joint in horses with OC. Enlargement of the distal physeal region of the metacarpus was more common and more pronounced between 3 and 8 months of age in horses with tarsocrural joint OC.

Eleven foals (3 colts, 8 fillies) with fetlock findings, palmar/plantar osteochondral fragments (POF) and/or ununited palmar/plantar eminences (UPE), were slightly lighter (birth weight 50.8 kgvs52.0 kg, 12 months 316.3 kgvs321.6 kg). The average daily weight gain, as well as the different body measurements, were similar in affected and in unaffected horses. There was no relation between radiological findings of POF or UPE and the degree of synovial effusion or other clinical signs in the fetlock area, including the distal physeal region.

The early radiological signs of OC and the observed difference in body size at birth indicate that the pregnancy period and the first months in the foal's life are of major importance for the development of OC. The differences in body weights, body measurements and clinical signs between horses affected by tarsocrural OC and fetlock POF or UPE are indications that the pathogenesis of these lesions differs.
Natural history of femoropatellar osteochondrosis in three crops of Thoroughbreds
Authors: McIntosh S. C. , McIlwraith C. W.
Published: June 2010

This paper reports the incidence of radiographic lesions of osteochondritis dissecans (OCD) of the femoropatellar joint relative to the development of clinical symptoms in the 1989 foal crop, and the clinical symptoms, radiographic features and outcome of the 1990 and 1991 foal crops affected with OCD at the same Thoroughbred farm. In the 1989 foal crop, 23 of 96 yearlings were identified with clinical and/or radiographic signs of OCD. They had an average age of 12.6 months at identification. Eighteen cases had clinical and radiographic signs of osteochondrosis, 3 had clinical signs in the stifles without radiographic signs and 2 had radiographic signs of osteochondrosis but no clinical signs (one eventually became symptomatic). Of the cases with clinical signs but no radiographic signs, one subsequently developed radiographic signs and the other 2 had bilateral clinical signs and unilateral radiographic signs. Seven horses had surgery at the time of clinical and radiographic diagnosis; 5 subsequently raced, 1 is in training and 1 has persistent problems. Of 11 cases not operated initially, 6 raced, 3 had no follow‐up, 1 became a jumper and 1 was operated later. In the 1990 foal crop, 13 of 120 foals were diagnosed with femoropatellar OCD. The average age at diagnosis was 9 months. Nine of the foals had radiographic lesions, 3 had equivocal radiographic lesions (1 progressed to an obvious lesion) and 1 had no radiographic lesions of the femoropatellar joint (but did have them in the fetlocks). All but one horse were treated conservatively. Of the horses with radiographic lesions initially, 2 have raced, 2 are still unraced, 3 have lameness and 2 were used for non‐racing careers. One horse had equivocal lesions initially but these progressed. In the 1991 foal crop, there were 16 cases of femoropatellar OCD diagnosed out of 125 foals. The average age at clinical recognition was 6 months. Ten horses had radiographic lesions at the time of initial diagnosis, 5 had no radiographic lesions initially but subsequently developed them, and 1 never had a radiographic lesion. Four horses were sold as yearlings reportedly without synovial effusion or lameness, 1 died of unrelated causes, 10 are currently racing or training and 1 subsequently developed OCD of the metatarsophalangeal joints.
Correlative study of defective cartilage and bone growth in foals fed a low‐copper diet
Authors: Hurtig M. , Green Sherril L. , Dobson H. , Mikuni‐Takagaki Y. , Choi J.
Published: June 2010

A blind randomised study using two groups of age‐ and sex‐matched Quarter Horse foals was conducted by feeding a low copper diet containing 8 ppm of copper (Cu) and a control diet containing 25 ppm. Foals in the low‐Cu group had declining liver Cu values and developed osteochondritis (OCD), epiphysitis and limb deformities over a 6‐month period. Erosion and separation of cartilage from the subchondral bone in the dorsal facets of the cervical spine were the most consistent post‐mortem lesions. Foals fed the high‐Cu diet had no significant musculoskeletal lesions. Scoring of standing lateral cervical radiographs was a moderately sensitive (0.68) and specific (0.70) test and had moderate agreement with post‐mortem findings (κ = 0.35). Technetium scintigraphy of the limbs and cervical spine failed to detect occult or known lesions in the limbs and cervical spine. Microscopic examination of growth plates and metaphyseal bone from affected foals showed that fractures disrupted or displaced the normal growth plate architecture and interfered with orderly bone growth, similar to Cu deficiency in cattle. Bone morphometry indicated there was less subchondral bone volume in the distal cannon bone (P<0.005). Similarly, there were fewer newly formed trabeculae in the primary spongiosa (P<0.02) and metaphysis (P<0.07) of the distal tibia in the Cu‐deficient foals. Biochemical studies were limited to 4 control and 6 low‐Cu foals. Of the 6 low‐Cu foals, 4 were severely affected with multiple lesions. These assays showed significantly reduced collagen cross‐linking in the cartilage and bone articular cartilage of severely affected foals. The control group foals had articular and growth plate cartilage explants in tissue culture released increased amounts of gelatinase and proteoglycanase, reflecting increased matrix remodelling. Traditional concepts of osteochondritis have implicated a non‐specific defect in endochondral ossification. This study proposes a relationship between low copper intakes in fast‐growing horses, inferior collagen quality, biomechanically weak cartilage and OCD lesions. While all foals in the low‐Cu group were affected, only 5 of the 9 developed clinically significant lesions. This indicates that factors other than nutrition, such as individual variation in growth rate or genetic potential, still influence the expression of this syndrome.
Effects of dietary energy and protein on induction of dyschondroplasia in foals
Authors: Savage C. J. , McCarthy R. N. , Jeffcott L. B.
Published: June 2010

Thirty mixed‐bred foals aged 2.5–6.5 months (mean 4.6 ± 1.0 months) with no clinical or radiographic signs of dyschondroplasia (DCP) were fed one of four diets for 16–18 weeks. Twelve foals were fed a Control diet which comprised ˜100% of the NRC recommendations for dietary energy (DE) and crude protein (CP). Six were fed a diet with ˜126% of NRC levels for CP and 12 foals were fed a diet with 129% of NRC levels for DE. The diets comprised 3 different formulations of rice‐based pellets with added maize oil for the High DE diet, and oaten chaff.

Average daily gain, humeral length and wither height were slighly, but not significantly, different in the foals on the High DE diet than in those fed the Control or High CP diet. Clinical and radiographic signs of DCP were seen in 6 out of 12 foals fed the High DE diet. Not one of the foals fed High CP or Control diets showed any clinical and radiographical signs of DCP. The number and severity of DCP lesions found at post‐mortem examination were much greater in the High DE foals than in the Control and High CP foals. Multiple lesions of DCP were detected in 11 foals fed the High DE diet, in 1 foal fed the High CP diet and in 1 foal fed the Control diet. Histological lesions of DCP were confirmed in 18 foals; in all 12 of the High DE foals, 4 of the 6 High CP foals and 2 of the 12 Control foals. The number of histological lesions of DCP were significantly greater in the High DE foals than in the Control group (P < 0.0001). The incidence of lesions of DCP in the foals fed High CP was not significantly different from that in the Control foals (P = 0.11).