Incidence and risk factors for limb fracture in greyhound racing in Western Australia.

Identification of risk factors for race day injury can improve greyhound welfare. Race day fractures are the most significant injury event and have the greatest negative impact on dog welfare and the industry's social license to operate. This study aimed to describe the incidence and risk factors for race-related fractures in greyhounds racing in Western Australia. Electronic extracts describing race level data and race day injuries were provided by Racing and Wagering Western Australia (RWWA). The incidence rate (IR) of fractures for all greyhound race starts in Western Australia from 1 January 2017-31/12/2023 was calculated per 1000 starts. Univariable and multivariable models using Poisson regression were used to calculate the IR ratio of fracture type based on race and greyhound-level factors. There were 198,008 racing starts and 662 (n = 643, 97.1% involving the limbs) fractures resulting in an IR of 3.3 fractures per 1000 starts (95%CI 3.1-3.6). Greyhounds that had an injury in their previous race were 2.3 times (95%CI1.4-4.3) more likely to have a forelimb fracture than greyhounds that did not have an injury (P = 0.013). The risk of tarsal bone fracture was greater in greyhounds older than 30 months and greyhounds that had not raced in the previous 15 days. Risk factors for fractures in the forelimb were associated with trauma after interference or dog collisions, whereas tarsal fractures were associated with strain and cyclic loading from race training/racing. Changes to racing structure, rules and policies based on these risk factors may help to reduce fracture incidence in racing greyhounds.

Risk factors for horse falls in New Zealand Thoroughbred jumps racing.

This study aimed to determine the incidence of, and risk factors for race-day horse falls in Thoroughbred jumps (hurdle and steeplechase) racing in New Zealand. Incidence rates for race-day horse falls in jumps races from 2005/6 - 2018/19 racing seasons (n = 13,648 race day starts) were calculated per 1000 starts. Univariable and multivariable analyses of race-, horse- and jockey-level risk factors for horse falls were conducted using Poisson regression in a generalised linear mixed model. The incidence rate of horse falls in jumps races was 42 (95 % confidence intervals [CI], 39 - 45) per 1000 starts. Horse falls in steeplechase races were 1.6 (95 % CI, 1.4 - 1.9) times more likely than hurdle races. The incidence rate ratio (IRR) for horses falling at the last three jumps in comparison with the first three jumps was 3.1 (95 % CI, 2.8 - 3.5) for hurdle and 4.4 (95 % CI, 3.9 - 5.0) for steeplechase races. Greater jockey (age, P = 0.02) and horse experience (P = 0.001) were associated with a lower IRR of falls (P = 0.05). Longer races (P = 0.02) and those held in autumn compared to winter (IRR 1.4; 95 % CI, 1.0 - 1.8; P = 0.05) were associated with a higher rate of falling in steeplechase races. A regulatory change enhancing discretionary ability of jockeys to pull up 'in-race' was associated with reduced horse falls (IRR 0.65; 95 % CI, 0.51 - 0.82; P = 0.001). Pragmatic rule changes within the industry can have a positive effect on reducing risk and improving equine welfare.

Influence of blanketing and season on vitamin D and parathyroid hormone, calcium, phosphorus, and magnesium concentrations in horses in New Zealand.

The aims of the study were to determine the effect of season and blanketing on vitamin D synthesis in horses and examine the interaction between vitamin D and other analytes involved in calcium homeostasis. Twenty-one healthy horses at pasture were included; 5 were covered with standard horse blankets including neck rugs. Blood samples were collected for 13 mo and analyzed for 25-hydroxyvitamin D2 (25OHD2) and 25-hydroxyvitamin D3 (25OHD3), 1,25-dihydroxyvitamin D (1,25[OH]2D), ionized calcium (iCa), total calcium (tCa), phosphorus (P), total magnesium (tMg), and parathyroid hormone (PTH). Grass and hay samples were collected and analyzed for vitamin D, calcium, phosphorus, and magnesium. Climate data were also collected. The serum concentration of 25OHD3 in horses was either undetectable or below the detection limit of the assay, and the main form of 25OHD was 25OHD2. No differences in serum 25OHD2, 1,25(OH)2D, iCa, tCa, P, tMg, and PTH (P ≥ 0.05) concentrations were seen between the 2 groups. Associations were seen between iCa and PTH (P < 0.05), iCa and tMg (P < 0.05), and dietary vitamin D and 25OHD2 (P < 0.05). A strong seasonal trend was seen in serum 25OHD2 (P < 0.0001), which was higher during spring and summer when the amount of sunshine and UV radiation was higher. Parathyroid hormone and 1,25(OH)2D showed opposing trends with PTH higher in winter whereas 1,25(OH)2D was higher in summer. The results suggest that dietary vitamin D may be necessary for horses to fulfill their vitamin D requirements; however, further research is required to determine the contribution of vitamin D3 synthesis in the skin to the vitamin D status of the horse.

Circadian rhythm of calciotropic hormones, serum calcium, phosphorus and magnesium during the shortest and longest days of the year in horses in New Zealand.

A study was conducted to determine the circadian rhythms and trends of vitamin D metabolites including 25-hydroxyvitamin D3 , 25-hydroxyvitamin D2 , 1,25-dihydroxyvitamin D and parathyroid hormone, in addition to serum calcium, phosphorus and magnesium concentrations in horses over 48 h on the shortest and longest days of the year in 2013. Five healthy adult horses (Equus caballus) were on a constant pasture feeding regimen, and blood samples were collected from each horse every 3 h over a 48-h period, starting at 07:00 PM on day one and finishing at 07:00 PM on day three, for the measurement of calciotropic hormones and electrolytes. There was a significant difference between the serum concentration of calciotropic hormones, iCa, tCa, P and tMg between the shortest (winter) and longest (summer) days of the year in horses. Serum concentration of 25OHD3 was very low and mostly undetectable. Serum iCa, 1,25(OH)2 D and PTH concentrations clearly showed a circadian rhythm on the longest days of the year and serum tCa, P and tMg concentrations showed a diurnal pattern on the longest days (summer) of the year. None of the analytes showed any circadian rhythm on the shortest days (winter) of the year. The result of this study could have significant relevance to equine athletes travelling to international equestrian competitions and facing a huge time and seasonal differences that might affect their ability to adjust their circadian rhythms to new time zones.

Increased sensitivity to kindling in mice lacking TSP1.

The development of a hyperexcitable neuronal network is thought to be a critical event in epilepsy. Thrombospondins (TSPs) regulate synaptogenesis by binding the neuronal α2δ subunit of the voltage-gated calcium channel. TSPs regulate synapse formation during development and in the mature brain following injury. It is unclear if TSPs are involved in hyperexcitability that contributes to the development of epilepsy. Here we explore the development of epilepsy using a pentylenetetrazole (PTZ) kindling model in mice lacking TSP1 and TSP2. Unexpectedly, we found increased sensitivity to PTZ kindling in mice lacking TSP1, while mice lacking TSP2 kindled similar to wild-type. We found that the increased seizure susceptibility in the TSP1 knockout (KO) mice was not due to a compensatory increase in TSP2 mRNA as TSP1/2 KO mice were sensitive to PTZ, similar to the TSP1 KO mice. Furthermore, there were similar levels of TGF-B signal activation during kindling in the TSP1 KO mice compared to wild-type. We observed decreased expression of voltage-dependent calcium channel subunit CACNA2D1 mRNA in TSP1, TSP2, and TSP1/2 KO mice. Decreased CACNA2D2 mRNA was only detected in mice that lacked TSP1 and α2δ-1/2 protein levels in the cortex were lower in the TSP 1/2 KO mice. CACNA2D2 knockout mice have spontaneous seizures and increased PTZ seizure susceptibility. Here we report similar findings, TSP1, and TSP1/2 KO mice have low levels of CACNA2D2 mRNA expression and α2δ-1/2 receptor level in the cortex, and are more susceptible to seizures. CACNA2D2 mutations in mice and humans can cause epilepsy. Our data suggest TSP1 in particular may control CACNA2D2 levels and could be a modifier of seizure susceptibility.

Sub-optimal efficacy of ivermectin against Parascaris equorum in foals on three Thoroughbred stud farms in the Manawatu region of New Zealand.

AIM: To ascertain whether resistance was present in Parascaris equorum to the macrocyclic lactone anthelmintic ivermectin, using faecal egg count reduction tests. METHODS: Thirty-nine foals aged between 11 and 28 weeks on three Thoroughbred stud farms (Farms A; n=20, B; n=5 and C; n=14) were treated with ivermectin (Day 0) and faecal egg counts (FEC) were monitored before and for 21 (Farms A and B) or 14 (Farm C) days after treatment. On Farms A and B, the foals were treated with a macrocyclic lactone/benzimidazole/praziquantel combination on Day 21 and FEC assessed on Day 35. The three farms were all in the Manawatu region in the southern half of New Zealand's North Island. RESULTS: Of the 39 foals, 15 were not shedding P. equorum eggs on the day they were treated with ivermectin, but all 15 did so post-treatment. The FEC on Farms A and B showed no evidence of a reduction at any time between Day 7 and 21; egg output increased steadily over this period. Following combination treatment FEC were reduced by 94% on farm A and 100% on Farm B. On Farm C, there was a 69% reduction in P. equorum FEC on Day 14. Twelve of the 14 foals on Farm C were shedding strongylid eggs on Day 0 and on Day 14 FEC were reduced by 84%. CONCLUSIONS: Without comparison to untreated control animals, these results do not allow a reliable estimation of the exact level of efficacy of ivermectin against P. equorum, but they nevertheless show that, within the farms studied, ivermectin no longer achieved a complete kill of egg-laying adults and that foals treated with this drug may continue to shed considerable numbers of eggs after treatment. The results also indicate that ivermectin had sub-optimal efficacy against strongylid nematodes on one of the farms.

Effect of oxytocin on suppression of oestrus in mares exhibiting normal oestrous cycles.

AIM: To compare the efficacy of oxytocin given once daily, either I/V or I/M, on Days 7-14 post-ovulation, on the expression of oestrus in mares through to 65 days post-ovulation. METHODS: Eighteen mares of various breeds that were displaying normal oestrous cycles were randomly assigned to one of three treatment groups on the day of ovulation (Day 0), detected using transrectal ultrasonography. Mares in the control group (n = 6) were given 1 mL saline I/V; mares in the I/V and I/M groups (n = 6 per group) were injected with 10 IU oxytocin I/V and I/M, respectively. All treatments were given once daily on Days 7-14. Mares were teased by a stallion three times per week, up to 65 days post-ovulation, to detect oestrous or dioestrous behaviour. Ovarian follicular and luteal activity were monitored using transrectal ultrasonography three times weekly, and daily when a follicle >30 mm diameter was present until ovulation. Blood samples were collected weekly for analysis of concentrations of progesterone in serum. Prolonged dioestrus was defined as a period of >30 days of dioestrous behaviour after Day 0, confirmed by detection of corpora lutea and concentrations of progesterone in serum >4 nmol/L. RESULTS: Overall, 8/18 (44%) mares showed prolonged dioestrus. These included 2/6 (33%) mares in the control group, compared with 5/6 (83%) and 1/6 (16%) mares in the I/V and I/M groups, respectively (p = 0.11). The median duration of the first dioestrus was longer for the I/V group (64 (min 16, max 66) days) compared with the control group (18 (min 12, max 64) days) (p = 0.05), but was not different between the control group and the I/M group (16 (min 13, max 65) days) (p = 0.57). For all mares there was strong agreement between teasing behaviours, ultrasonographic assessment of ovarian activity, and concentration of progesterone in serum. CONCLUSIONS AND CLINICAL RELEVANCE: This study found that low doses of oxytocin did not increase the proportion of mares with prolonged dioestrus, compared with controls, although I/V oxytocin did increase the median duration of dioestrus. The results must be interpreted with some caution as group numbers were small, and a variety of breeds were used. Further investigation of oxytocin given I/V may be warranted as a potential method of oestrus suppression in mares exhibiting oestrous cycles that is low cost, safe and well-tolerated, and potentially reversible with prostaglandin.

Multi-drug-resistant Enterococcus spp. as a cause of non-responsive septic synovitis in three horses.

CASE HISTORY: Three Thoroughbred horses, a 6-week-old filly (Case 1), a 15-year-old broodmare (Case 2) and a yearling filly (Case 3), sustained synovial sepsis secondary to trauma. CLINICAL FINDINGS: Case 1 presented with a heel bulb laceration communicating with the distal interphalangeal joint. Arthroscopic lavage was performed and treatment commenced using systemic and local broad spectrum antimicrobial drugs. A pure growth of multi-drug-resistant (MDR) Enterococcus gallinarum was cultured from samples of synovium and joint fluid. Antimicrobial treatment was changed according to the susceptibility results. Response to treatment was poor and despite repeat arthroscopic lavage and intra-osseous regional perfusion of antimicrobials the filly was subject to euthanasia 24 days after the initial injury. Post-mortem examination confirmed septic synovitis, cartilage degeneration and osteomyelitis. Case 2 sustained a full thickness wound to the carpus which was sharply debrided and closed. The wound dehisced with effusion within the tendon sheath. Drainage was established and treatment included systemic broad spectrum antimicrobials, topical lavage with povodine-iodine and manuka honey infusion. A mixed infection including MDR Enterococcus faecalis was cultured from the synovial fluid. Antebrachiocarpal joint effusion developed 21 days after initial injury and joint sepsis was confirmed. Arthroscopic lavage and tendon sheath debridement were performed, followed by treatment with systemic and local antimicrobials. The mare improved and was discharged. Three months later lameness recurred and corticosteroids were administered intra-articularly. The mare became non-weight bearing lame and was subject to euthanasia. Post-mortem examination confirmed joint sepsis of the antebrachiocarpal and intercarpal joint. Case 3 presented with a complete articular open fracture of the tibial crest. Under general anaesthesia the fracture was stabilised and the wounds debrided and closed. Systemic broad-spectrum antimicrobials were administered. Six days later the wound dehisced and a bone fragment was removed. Three weeks post-surgery the wound deteriorated with a purulent discharge. Culture of the discharge revealed a mixed bacterial infection, including a MDR Enterococcus faecalis. Femoropatellar joint involvement was confirmed, and treatment included joint lavage, local and systemic antibiosis, and manuka honey instilled into the wound. The filly initially improved, and then deteriorated such that euthanasia was performed. DIAGNOSIS: All three cases had synovial sepsis with MDR Enterococcus spp. CLINICAL RELEVANCE: Increased awareness of MDR pathogens in equine wound infections is essential. Prompt diagnostic testing, appropriate therapy, infection control strategies and on-going monitoring and management are vital to limit the clinical impact of these organisms.

Granulosa theca cell tumour in a pregnant mare: concentrations of inhibin and testosterone in serum before and after surgery.

CASE HISTORY: A 14-year-old Thoroughbred mare was presented for evaluation of a rapidly enlarging ovary at 73 days gestation. The mare's owner reported behavioural changes in the mare since she returned from stud, notably aggression towards other horses. CLINICAL FINDINGS: Transrectal palpation and ultrasonography of the reproductive tract revealed a viable pregnancy, an enlarged, multiloculated right ovary, and a normal-sized left ovary with a corpus luteum present. Concentrations of inhibin and testosterone in serum were 13.8 ng/mL and 1,150 pg/mL, respectively, being markedly higher than reference ranges. Concentration of progesterone was 4.5 ng/mL, consistent with the presence of functional luteal tissue. A presumptive diagnosis of a granulosa theca cell tumour (GTCT) was made, and the ovary was surgically removed. Histopathological examination of the removed ovary confirmed a benign GTCT. At 31 days after surgery concentrations of inhibin in serum had decreased 18-fold, and testosterone had decreased 10-fold. Pregnancy was reconfirmed at 115 days gestation by rectal palpation and transrectal ultrasonography. DIAGNOSIS: Granulosa theca cell tumour associated with elevated concentrations of inhibin and testosterone in serum. CLINICAL RELEVANCE: While ovarian enlargement and aggressive behaviour may be considered normal in some pregnant mares, a GTCT should be included as a differential diagnosis. Measurement of concentrations of inhibin and testosterone in serum are useful to support a presumptive diagnosis of GTCT in mares.

Gestation length and occurrence of daytime foaling of Standardbred mares on two stud farms in New Zealand.

AIMS: To examine the gestation lengths and occurrence of daytime foaling of Standardbred mares foaling outdoors at stud farms in Southland, New Zealand (latitude 45˚S). METHODS: Data were collected prospectively at two commercial Standardbred stud farms (Farms A and B), during the 2008/9 and 2009/10 breeding seasons (October to February). For each foaling, the identity of the mare, date and time of foaling, gender of foal, time the mare passed the fetal membranes, time the foal stood, and foaling problems including dystocias, were recorded. The effect of farm, season, gender of foal, month of artificial insemination (AI) or foaling, age and parity of mare on gestation length, percentage of mares foaling during daylight hours, and percentage of foalings recorded as dystocia, were examined. RESULTS: A total of 614 foaling records were obtained from 507 mares. For 594 foalings with complete records, mean gestation length was 349 (SE 0.5) days. Mean gestation length was shorter for fillies (347.8 (SE 0.6) days) than colts (350.3 (SE 0.6) days) p = 0.021) and decreased with month of AI, from October to February (p = 0.001). The time of foaling was bimodally distributed with the primary peak around 0200 hours and a secondary smaller peak around 1300 hours. The percentage of mares foaling in daylight was lower on Farm A (69/285 (24%)) than Farm B (128/313 (41%)) (p = 0.001). Colt foals were less likely to be born during the day than fillies (OR = 0.63; (95% CI = 0.44-0.88); p = 0.008), but there was no effect of age or parity of mare or month of foaling (p>0.05). CONCLUSIONS AND CLINICAL RELEVANCE: Mean gestation length of mares in this study was longer than that previously reported from other countries. Longer gestation length decreases the time available for these mares to get back into foal in the same season. It is important that managers take this into account and ensure optimum conditions for conception; breeding at the first postpartum oestrus may be essential. There were more mares foaling in daylight hours on one stud than has previously been reported. Under these conditions mares should be monitored for foaling during daytime as well as at night.

The use of allied health therapies on competition horses in the North Island of New Zealand.

AIM: To obtain data on the use of allied health therapy within competitive equestrian sport in the North Island of New Zealand. METHODS: Data were collected during January 2010 by survey at show jumping and dressage championships in the North Island, and from racing yards in the Central Districts of New Zealand. The survey consisted of 30 open, closed and multiple-choice questions, and was conducted face-to-face, by the same interviewer. Information on the demographics of riders or trainers and horses in each discipline (show jumping, dressage, and Thoroughbred racing), the use of allied health therapy (physiotherapy, chiropractic and equine sports massage) on horses, and knowledge of training and qualifications of the allied health therapists was obtained. Univariable and multivariable logistic regression were used to examine relationships between demographic variables and the use of allied health therapists. RESULTS: In total, 110 riders or trainers participated in the survey. The relative contribution of responses across disciplines was 39/110 (36%), 41/110 (37%) and 30/110 (27%) for show jumping, dressage, and Thoroughbred racing respectively. Allied health therapists were used by 68/110 (62%) respondents to treat their horses. The most common types of allied health therapy used were chiropractic (25/68; 37%) and physiotherapy (16/68; 24%). The main reasons for using allied health therapies were for back pain (22/68; 32%) and lameness (17/68; 25%). Only 5/68 (7%) respondents chose a type of allied health therapy based on veterinary advice, and 49/68 (72%) stated that their veterinarian and allied health therapist did not work together when treating their horses. The final multivariable model for use of allied health therapists included the explanatory variables discipline of the rider or trainer and the number of horses in training per season. CONCLUSIONS AND CLINICAL RELEVANCE: The use of allied health therapies for the treatment of competition and racehorses was widespread. Many riders or trainers perceived allied health therapy to be beneficial, however many therapists and veterinarians do not work together and therefore the integrative treatment approach to rehabilitation is lost.

Transforming growth factor-ß regulates the sphere-initiating stem cell-like feature in breast cancer through miRNA-181 and ATM.

Recent studies indicate that a subset of cancer cells possessing stem cell properties, referred to as cancer-initiating or cancer stem cells (CSCs), have crucial roles in tumor initiation, metastasis and resistance to anticancer therapies. Transforming growth factor (TGF)-ß and their family members have been implicated in both normal (embryonic and somatic) stem cells and CSCs. In this study, we observed that exposure to TGF-ß increased the population of breast cancer (BC) cells that can form mammospheres in suspension, a feature endowed by stem cells. This was mediated by the micro (mi)RNA family miR-181, which was upregulated by TGF-ß at the post-transcriptional level. Levels of the miR-181 family members were elevated in mammospheres grown in undifferentiating conditions, compared with cells grown in two-dimensional conditions. Ataxia telangiectasia mutated (ATM), a target gene of miR-181, exhibited reduced expression in mammospheres and upon TGF-ß treatment. Overexpression of miR-181a/b, or depletion of ATM or its substrate CHK2, was sufficient to induce sphere formation in BC cells. Finally, knockdown of ATM enhanced in vivo tumorigenesis of the MDA361 BC cells. Our results elucidate a novel mechanism through which the TGF-ß pathway regulates the CSC property by interfering with the tumor suppressor ATM, providing insights into the cellular and environmental factors regulating CSCs, which may guide future studies on therapeutic strategies targeting these cells.

A cross-sectional survey of Thoroughbred stud farm management in the North Island of New Zealand.

AIM: To obtain initial baseline data on the management of Thoroughbred stud farms in the North Island of New Zealand. METHODS: Data on the management of Thoroughbred stud farms were collected from a sample of 22 stud farms located in the south Auckland/Waikato region (n=15) and lower North Island (n=7) of New Zealand, using a face-to-face survey. The studmaster provided information on the size, scope and management of the farms during the 2004/2005 breeding season. Analysis was based on the location of the farm and size of the breeding operation (number of resident mares). RESULTS: Effective farm size ranged from 20 to 526 ha and averaged 167 (standard error (SE) 36) and 88 (SE 49) ha in the south Auckland/Waikato and lower North Island areas, respectively. Some farms in the Auckland/Waikato region stood shuttle stallions. The median number of stallions per farm was three (range 0-9), and the median mare-to-stallion ratio was 43 (range 10-250). The farms had a mean of 50 (range 7-180) wet mares and 21 (range 0-100) dry mares. The number of mares per breeding stallion increased with increasing size of breeding operation (p=0.04), being 28 (95% confidence interval (CI) = 10-56) vs 40 (95% CI=16-74) vs 74 (95% CI=44-113) for moderate (or=200 mares in total) operations, respectively. Seventy-one percent of farms aimed to breed dry mares early in the breeding season, and used a combination of lights, hormone therapy, and rising plane of nutrition to achieve this. Foaling took place in foaling paddocks monitored using a night foaling attendant (17/22) or with foaling alarms (5/22). At birth, 17/22 studmasters routinely administered antibiotics, 14/22 administered tetanus antitoxin, 9/22 administered an enema to foals, and 2/22 did not routinely administer prophylactic treatments. Weaning occurred at 5 (range 3.7-7) months of age, and foals were confined to a box for 1-2 weeks on 16/22 farms. Weaned foals were drenched with anthelmintics every 7 (range 4-9) weeks, and were fed 2.9 (range 1-6) kg of concentrate feed while at pasture until intensive management associated with preparation of the horses for auction began 13 (range 6-20) weeks before the yearling sales. Eight farms weighed the weanlings, at least monthly, to monitor growth. CONCLUSIONS AND CLINICAL RELEVANCE: The management of Thoroughbred horses was relatively consistent throughout the regions surveyed. Utilisation of breeding stallions tended to be more efficient on the larger stud farms in the south Auckland/Waikato region. Even though foals are grown at pasture they are often provided with large quantities of concentrate feed.

Enlargements of the distal third metacarpus and metatarsus in Thoroughbred foals at pasture from birth to 160 days of age.

AIMS: To assess the relationship between the radiographic and microscopic appearance of the physeal regions of the distal third metacarpal (Mc3) and metatarsal (Mt3) bones of Thoroughbred foals at 160 days of age, and to clinically assess changes in contour of the distal Mc3 and Mt3 physeal regions from birth to 160 days of age. To assess relationships between maximum clinical physis scores and age, time of year, foal's sex, condition score, growth rate, copper (Cu) concentration in the liver of the foal, and supplementation of the dam with Cu in late gestation. METHODS: Dams were given Cu (n=5 and n=11, in Years 1 and 2, respectively) or saline (n=5 and n=12, in Years 1 and 2, respectively) injections in late gestation. Liver biopsies were harvested from foals in the first week of life, and the whole liver homogenised after the animals were euthanised at around 160 days of age, to determine Cu concentrations. Pasture samples were collected every 4-8 weeks for analysis of mineral composition. During Year 1, 10 foals were weighed and examined every 2 weeks from birth to 160 days of age for evidence of pain and lameness in the distal Mc3/Mt3. In Year 2, 23 foals were weighed, condition-scored and examined for evidence of pain and lameness weekly for the first 5 weeks of life, then every 2 weeks from birth to 160 days of age, and a clinical physis score for the distal Mc3/Mt3 given. Cabinet radiographs of frontal slices of the physeal region of the distal Mc3/Mt3 at around 160 days of age were given a radiographic physis score. Physes were then examined histologically for evidence of abnormal endochondral ossification. RESULTS: Gross enlargements of the distal Mc3 and Mt3 were observed in all foals in this study, but were not associated with lameness, pain or inflammation. The most severe clinical physis scores occurred over 2 months in late summer/autumn, and were not influenced by the foal's growth rate, sex, or Cu concentration in the liver, or treatment of dams with Cu in late gestation. The clinical physis score was highly correlated to radiographic evidence of shouldering in the forelimb and hindlimb (both p<0.001). Focal disturbances in endochondral ossification were evident radiographically and histologically in the some of the physes at 160 days of age. The mineral composition of pasture was similar in Years 1 and 2, and concentrations of Cu and zinc were below those currently recommended for growing horses. CONCLUSIONS: Gross enlargements of the distal Mc3 and Mt3 were not consistent with previous descriptions of physitis. Results suggest that while many Thoroughbred foals at pasture will have visible boney enlargements of the distal Mc3/Mt3 in the first 5 months of life, few have physeal cartilage abnormalities or significant compromise of endochondral ossification. The importance of these clinical swellings may be overestimated, and they may more appropriately be called physiological enlargements associated with remodelling of bone.

Articular / epiphyseal osteochondrosis in Thoroughbred foals at 5 months of age: influences of growth of the foal and prenatal copper supplementation of the dam.

AIMS: To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dam's age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age. METHODS: Thirty-three Thoroughbred foals, born in two consecutive years, were weighed every 2 weeks from birth. The dams had been supplemented with parenteral Cu or saline during late gestation, and the supplementation regimens were different in each year. Foals had liver biopsies harvested at birth for determination of Cu concentration. Pasture samples were collected every 4-8 weeks for analysis of concentration of Cu and zinc (Zn). At 160 days of age, articular cartilage of long bones was examined. Gross lesions were counted and scored, then sawn and radiographed, and processed for histopathology. Lesions were given radiographic scores and histopathological scores. Maximum scores for each lesion were combined to give a total OC score for each joint and each foal. The fatness of 20 foals (10 each from Years 1 and 2) at 160 days of age was determined chemically. RESULTS: Supplementation of dams with Cu had no significant effect on the concentration of Cu in the liver of foals at birth, or on the frequency or severity of lesions in articular cartilage at 160 days of age. The Cu and Zn concentrations of pasture were similar in Years 1 and 2, and were lower than current recommendations. All foals in Year 2, and 9/10 foals in Year 1 had irregularities in cartilage that was confirmed histologically to be indicative of OC. The average number of lesions per foal was 4.7 (SD 1.1) and 5.7 (SD 1.1) in Years 1 and 2, respectively. However, the severity of the lesions was considered mild, and no foals showed any clinical evidence of OC while alive. The number of lesions in the tarsocrural (TC) joint and the TC OC score at 160 days were positively associated with average daily weight gain (ADG) in the previous 4 weeks (p=0.005 and p=0.001, respectively). There was no significant effect of sex, fatness, birthweight, weight at 160 days of age, or year of birth of the foal on the frequency and severity of OC lesions. CONCLUSIONS: Many of the lesions classified as OC, using classification systems described by other authors, were likely to be normal variations of the process of endochondral ossification. Despite the high frequency of such lesions, they were considered to be of minor significance and none were clinically evident. The distribution of lesions was not typical, and most probably reflected the subtlety of the lesions. These results support the hypothesis that Cu is an over-emphasised factor in the aetiopathogenesis of OC. The relationship between subtle macroscopic lesions and lesions resulting in clinical signs of disease requires further investigation.

A comparison of subjective and quantitative methods for detection of physitis in Thoroughbred foals.

AIM: To compare subjective and quantitative methods of assessing physeal swelling of the distal third metacarpal (Mc3) and metatarsal (Mt3) bones of Thoroughbred foals. METHODS: The fetlocks of 16 Thoroughbred foals were filmed on five occasions over a period of 5 months and the video images were transferred to computer and digitised. The rate of change of each of the medial and lateral contours of the distal Mc3 and Mt3 bones was determined by calculating values for the second derivative of the contour. The degree of physeal swelling at the same site was subjectively assessed and allocated a grade based on an ordinal scale of severity. The maximum value for the second derivative was compared with the grade of physeal swelling. RESULTS: The second derivative values for sites with slight to distinct physeal swelling (Grade >/=1.5) were significantly higher (p=0.001) than the second derivative values for sites with no apparent physeal swelling (Grade 0). CONCLUSION: This finding indicates that the value of the second derivative of the contour of a limb has potential as a diagnostic tool for quantitative detection of physitis.

Feeding value of pastures for horses.

The feeding value of fresh pasture grazed in situ is determined by animal performance or productivity and could be relatively easily established for growing and lactating horses. Despite this, there is a lack of published information on the relative feeding value of different pastures and forages grazed by horses in New Zealand and the world. In addition, for adult breeding or non-breeding and young or adult sport or performance horses, the definition of feeding value and its determination remain problematic. Limited information suggests that the feeding value of perennial ryegrass-based pasture in New Zealand for young growing horses is high, and growth rates for Thoroughbred horses fed solely on pasture in New Zealand are similar to those reported from the Northern Hemisphere where grain-based supplements are fed in addition to pasture or other forages. Attempts to assess the ability of fresh pastures to meet the nutrient requirements of horses are hampered by problems associated with determination of feed intake by grazing horses and lack of knowledge of the digestibility and utilisation of digested nutrients, including the relative bioavailability of macro- and micro-minerals in pasture. A further challenge for future research is to determine the effect of herbage allowance and grazing behaviour, including pasture species preferences, on voluntary feed intake by grazing horses. Grazing pasture has benefits for equine health and well-being including reduced risk of some nutrition-related disorders and reduced prevalence of stereotypic behaviour. Pastured horses have greater freedom for expression of natural behaviours including social interaction and exercise. However, grazing pasture is also associated with animal health problems, particularly parasitism and diseases related to pasture-associated toxins.

The effect of two different weaning procedures on the growth of pasture-reared Thoroughbred foals in New Zealand.

AIM: To identify if there was a significant difference in the average daily liveweight gain (ADG) between Thoroughbred foals weaned using two weaning protocols commonly used in New Zealand. METHODS: Sixteen Thoroughbred foals were blocked for sex and age, randomly allocated into progressive (187, SD 33 days; three colts, five fillies) or abrupt (182, SD 28 days; four colts, four fillies) weaning groups, and weighed every second day for 2 weeks either side of weaning, then fortnightly from birth to 480 (SD 31) days old. ADG was calculated to examine the short-term (10 days before weaning, 5 and 10 days post weaning) and long-term (0-6 and 6-16 months of age) effect of the two weaning treatments. RESULTS: ADG was 1.10 (SD 0.091) kg/day before weaning (0-6 months of age) and 0.59 (SD 0.06) kg/day from weaning to 480 (SD 31) days old. At the start of weaning, liveweights of the progressive and abrupt weaning groups were 276.5 (SD 40.3) kg and 257 (SD 15) kg, respectively (p=0.23). For the 5-day period during weaning, irrespective of treatment, there was a significant decrease in ADG of -0.29 (SD 0.49) kg/day and -0.15 (SD 0.30) kg/day for progressive and abrupt weaning, respectively. There was no significant difference in ADG between weaning methods at any measurement period (short or long term) during and after weaning. However, there was large variation between foals in ADG in the 10 days after the weaning process, which may indicate variation in individual foals' responses to being weaned, rather than the weaning treatment. CONCLUSIONS: Weaning, irrespective of method, was associated with a decrease in ADG in the first week after weaning. The method of weaning had no effect on post-weaning ADG either short term, 10 days after weaning, or long term up to 480 days of age. Practically, it may be more important to consider maturity and liveweight as criteria for weaning foals rather than age alone.

Chemical body composition of 20 Thoroughbred foals at 160 days of age, and preliminary investigation of techniques used to predict body fatness.

AIMS: To determine the chemical body composition of Thoroughbred foals born in two consecutive years, and to investigate several techniques used to predict body composition in foals born in the second year, with particular reference to fat. METHODS: The chemical composition of 20 foals at around 160 days of age, born in two years, was determined. In vivo techniques to predict body composition were assessed in 23 foals born in Year 2, before and after euthanasia; 10 of these foals were used for chemical body composition analysis. Techniques to assess body composition in vivo included liveweight (LW), overall and regional condition scores, ultrasonic fat thickness measurements over the ribs and rump, linear measurements and bioelectrical impedance analysis. Correlations were determined between ultrasonic fat thickness, and bioelectrical impedance analysis, before and after euthanasia. Stepwise regression analysis was used to determine the relationships between in vivo techniques used to assess body composition and the chemical body composition of 10 animals. RESULTS: Foals used for analysis of chemical composition weighed between 220.5 and 260.0 kg before euthanasia. Fat content ranged from 5.5-13.0% of the partial empty bodyweight (LW less head, gastrointestinal contents, distal limbs and skin). Fillies had significantly more fat mass and percentage fat than colts (p=0.031 for both measurements). The mean chemical composition of the fat-free partial empty body was 73.2% (SD 0.6) water, 22.7% (SD 0.9) protein, and 4.1% (SD 0.4) ash. Most of the variation in the concentration of empty body water was associated with variation in the concentration of fat (p<0.001). The live animal overall condition scores were correlated with fat mass and concentration (p=0.006 and p=0.013, respectively; n=10). Condition score over the rib region was highly correlated with fat mass and fat concentration (p=0.004 and p<0.001; n=10). Ultrasound measurements taken 10 cm cranial to the tailhead and 4 cm from midline, used to assess the thickness of rump fat, were correlated with condition score (p=0.001), and explained 71% of the variation in body fat mass (p=0.002; n=10).Nearly 50% of the variation in fat-free mass and partial empty body water mass were associated with variation in the impedance indices calculated from length and bioelectrical impedance analysis measurements (p=0.023 and p=0.026, respectively; n=10). CONCLUSIONS: At around 42% of expected mature weight, fillies were significantly more fat than colts. Condition scores were correlated with partial empty body fat mass, and there was a trend for higher scores in fillies compared to colts. Much of the variation in water or protein mass of the partial empty body could be explained by variations in LW. CLINICAL RELEVANCE: Measurements of LW, rump fat and condition score are useful predictors of the chemical composition of foals at 5 months of age.

Digestible energy intake, dry matter digestibility and mineral status of grazing New Zealand Thoroughbred yearlings.

AIM: To measure the nutritive value of pasture in terms of digestible energy intake (DEI) and dry matter (DM) digestibility, and to determine the effect of Ca, P, Cu, Zn, and Se supplementation on growth rate and degree of physeal swelling in Thoroughbred yearlings grazed on pasture. METHODS: Fourteen yearling horses were randomly allocated to 1 of 2 groups and rotationally grazed on a ryegrass/white clover pasture for 7 months. One group was supplemented daily with a mineral mix. Liveweight changes were recorded at fortnightly intervals and pasture mineral composition determined at monthly intervals. The DM intake (DMI) was determined from daily faecal DM outputs divided by the indigestible DM fraction (1 - digestible DM) determined from a digestibility study. The DEI was determined from the difference between the gross energy intake and the gross energy faecal output. The DM, gross energy content, crude protein (CP), soluble carbohydrate, acid detergent fibre (ADF), neutral detergent fibre (NDF), lipid and mineral composition of pasture offered and faeces were analysed and their digestibility or apparent absorption calculated. RESULTS: The DM digestibility of pasture averaged 0.64 while the daily DMI and DEI of a 350 kg yearling, gaining 0.6 kg liveweight/day, averaged 6.9 kg DM/day and 78 MJ DE/day, respectively. The mineral supplement had no significant effect on the growth of yearlings grazing pasture that had a mineral composition of (g/kg DM) Na 0.17, K 32.8, Ca 3.6, P 3.4, Mg 2.1, S 3.0, and (mg/kg DM) Cu 7.9, Fe 177, Mn 83, Zn 28 and Se 0.016. Plasma Se was elevated (e.g. 40-218 microg/l) by Se supplementation while Cu supplementation had no effect on plasma and liver Cu concentrations. Physeal swelling was observed in all horses, regardless of treatment. CONCLUSION: Good quality ryegrass/white clover pasture that had a DE content of 11.3 MJ/kg DM and adequate mineral composition (as observed in this study, with the possible exception of Se) will provide an adequate intake of nutrients to ensure good growth in yearling horses.