Age- and gender-related variations in hematology, clinical biochemistry, and hormones in Spanish fillies and colts

In order to assess which laboratorial parameters need specific age- and/or gender-related reference values, hematological and biochemical profiles (including hormones) were performed in 205 Spanish foals of 5 groups: A (1-2 months; 20 fillies, 10 colts), B (2-3 months; 24 fillies, 18 colts), C (3-6 months; 25 fillies, 16 colts), D (6-9 months; 20 fillies, 23 colts) and E (9-12 months; 25 fillies, 15 colts). Additionally, 120 adult horses were sampled in order to establish baseline data for this breed in our laboratory. Group E had lower red blood cell number and mean cell volume than B, C and D, and neutrophil count was lower in A. Albumin was lower in A than in D, lactate was higher in B, C and D, CK, AST and K were higher in C. In D and E, cortisol was lower and adrenaline was higher. Urea progressively increases, whereas ALP decreases with age. Packed cell volume was higher in fillies of group A, creatinine was higher in colts of group E and fillies of groups B, C, and D had higher aldosterone than colts. In comparison to Spanish adult horses, mean cell volume, albumin, urea, CK, AST, LDH, and ALP requires specific ranges for foals.     

An investigation of the effect of hesperidin complex and lemon bioflavonoid complex on growth and development of thoroughbred horses

The objective of this study was to determine the effect of Hesperidin Complex and Lemon Bioflavonoid Complex (HC/LBC) on the growth and development of thoroughbred horses. The trial involved twenty-four foals (12 colts, 12 fillies) allotted to treatment shortly after weaning. The study was conducted for a 342-d growing phase and a 153-d training phase, or a total of 495-d. The HC/LBC was included in the test diet at a level calculated to supply the compound at 55 mg X kg body weight-1 X d-1. During the growing phase, average daily gain of colts that received HC/LBC was higher (P less than .05) than gain of control fillies but not different from that of treated and control colts. No differences (P greater than .05) in daily gain due to treatment were observed during the growing phase, training phase, or the data for the combined growing and training phases. Differences between treatments in changes in height at the withers and knees during the growing phase were not significant. In the training phase, average daily height change values for colts was higher (P less than .05) than that of fillies; however, these differences were not related to diet treatment. Radiographs were taken of the epiphyseal plate of the knee initially and at approximately 120-d intervals. No differences (P greater than .05) were noted between diet treatments through d 365 of the trial. Radiographs taken upon termination of the trail (495 d) showed a difference (P less than .05) favoring fillies over colts, but no differences related to diet treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fractures of the distal phalanx of the forelimb in eight foals

Fractures of the distal phalanx of the forelimb were diagnosed in 5 colts and 3 fillies ranging in age from 2 weeks to 5 1/2 months at the time of fracture. Three fractures entered the distal interphalangeal joint and 6 fractures (one foal had bilateral fractures) were nonarticular. All foals with articular fractures became sound with conservative treatment. Four of 5 foals with nonarticular fractures became sound with conservative treatment and 1 foal developed separation of the hoof at the coronary band after application of acrylic around the hoof. On the basis of our observations in these foals, sagittal articular and nonarticular distal phalangeal fractures in foals should be treated conservatively. Foals so treated would have an excellent prognosis for return to soundness.     

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.     

Influence of age and sex on serum osteocalcin concentrations in horses at weaning and during physical conditioning

Three experiments were conducted to evaluate serum osteocalcin concentrations in normal weanling and yearling Quarter Horses. In Experiment 1, jugular blood samples were taken at 3 hr intervals for 24 hr to evaluate diurnal changes in serum osteocalcin concentration of foals (n=3) and yearlings (n=5). In Experiment 2, twelve Quarter Horse foals were weaned at 4 months of age to determine the influence of sex, weaning and method of weaning of serum osteocalcin concentration. The third experiment utilized fifteen yearling Quarter Horses (7 geldings, 8 fillies) in a two-phase trial to evaluate normal peripheral osteocalcin concentration in sedentary and exercising horses. In Experiment 1, there was no detectable variation (P>.05) in serum osteocalcin concentration during the 24 hr sample period in either age group. In Experiment 2, colts had greater (P<.05) osteocalcin concentrations than fillies at weaning. Method of weaning did not alter mean serum osteocalcin concentration (P>.1). Serum osteocalcin concentrations declined (P<.05) in all horses following weaning but returned to preweaning levels within one week. In Experiment 3, sedentary horses had similar (P>.1) osteocalcin concentrations on d 0, 45 and 90. Serum osteocalcin concentrations of sedentary horses were not affected by sex (P>.1). During exercise, fillies had greater (P<.05) osteocalcin concentrations than geldings. Serum osteocalcin concentrations of all horses declined linearly (P<.0001) during the 90 d exercise period. Osteocalcin may be useful as a tool to assess bone metabolism during growth and physical conditioning in horses. However, variability in serum osteocalcin concentrations due to age, sex and level of activity suggest that these factors must also be considered.     

The ontogeny of serum insulin-like growth factor-I concentration in foals: Effects of dam parity,diet, and age at weaning

The effects of dam parity, age at weaning, and preweaning diet were examined in the ontogeny of serum insulin-like growth factor-I (IGF-I) concentrations in foals. Foals born to 13 primiparous and 19 multiparous draft-cross mares were weighed and bled near birth. About one-half of the foals in each group were weaned early (about 13 wk old); the remaining foals were weaned late (about 16 wk of age). Pooled values for serum IGF-I concentrations between birth and 17 wk of age were higher (P < 0.065) for foals born to multiparous (386 ng/ml) than to primiparous mares (237.5 ng/ml). Colts (378 ng/ml) had higher (P < 0.05) serum IGF-I concentrations than fillies (254.5 ng/ml), regardless of dam parity. Colts (173.5 kg) also tended (P = 0.12) to be heavier than fillies (159.2 kg). Weaning, whether at 13 or 16 wk of age, reduced (P < 0.05) growth rates and serum IGF-I concentrations. Serum IGF-I values recovered to preweaning values within 1–3 wk postweaning concurrent to an improved weight gain. Fifteen 1-d-old foals in a second study were fed milk replacer for 7 wk and were compared with five foals that nursed their mares for 8 wk. During the first 2 wk, replacer-fed foals (0.46 kg/d) did not gain as rapidly (P < 0.03) as mare-nursed foals (1.73 kg/d). The associated serum IGF-I values for replacer foals (139.4 ng/ml) were lower (P < 0.0001) than values for mare-nursed foals (317.4 ng/ml). Despite similarity in gains for both groups thereafter, serum IGF-I concentrations of replacer-fed foals were only 36 and 60% of values obtained for mare-nursed foals at 8 (weaning) and 18 wk of age, respectively. The intrinsic differences between mare-nursed and milk-replacer foals in serum IGF-I concentrations persisted to 1 yr of age despite similarities in dietary management and body weight of the foals. At 1 yr of age, the serum IGF-I concentration of mare-nursed foals (1,203 ng/ml) was 48% higher than that of replacer-fed foals (815 ng/ml). These data indicate that dam parity, sex of foal, and preweaning nutrition affect the ontogeny of serum IGF-I concentration in the foal. The chronic, persistent difference in serum IGF-I values created by the early nutritional management of growing animals has implications in the interpretation of longitudinal serum IGF-I studies in all species.     

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.     

Emotional Response of Naive Purebred Arabian Colts and Fillies to Sympathetic and Traditional Training Methods

The aim of this study was to explore the hypothesis that the emotional response of naive purebred Arabian colts and fillies to initial training is lower in the case of sympathetic methods compared with the traditional training methods, and that the response is differentiated with regard to the sex. A group of 32 young purebred Arabian horses was included in the initial training. Half of the group was subjected to a natural training method, and the other 16 horses were trained using a traditional method. Both groups comprised an equal number of colts and fillies. The training lasted a few days, as shortly as possible, with regard to individual horse’s needs. The emotional response of horses to training process was assessed with heart rate measured telemetrically. A horse’s response to sympathetic and traditional training methods depends on its sex. The sympathetic training method modifies the response of colts more than it influences the response of fillies. It is concluded that the natural method is particularly desired in training colts.     

Age-related changes for serum bone metabolism markers in thoroughbred and quarter horse foals

Serum bone specific alkaline phosphatase (BALP) and osteocalcin were measured in 9 Thoroughbred and 4 Quarter Horse (QH) foals. Eight were colts, and 5 were fillies. The first blood sample was collected from foals between 10 and 14 hours after birth on day 1. Blood then was collected on days 3, 6, 9, 12, 15, 18, 21, 28, 35, 42, 49, 56, 70, 84, 98, and 112 between 7:00 and 9:00 am. Serum bone metabolism marker raw data were analyzed with analysis of variance with repeated measures over time with gender and breed in the model. Average serum osteocalcin concentrations were higher for Thoroughbred than QH foals: 152.1 ± 4.6 ng/mL and 131.3 ± 6.3 ng/mL (mean ± standard error), respectively (P = .01). No overall differences were seen for gender (P = .10). However, on day 1, colts had higher osteocalcin than did fillies at 199.6 ± 30.2 ng/mL and 93.8 ± 32.4 ng/mL, respectively (P = .04). Thoroughbred foals had higher average serum BALP concentrations than did QH foals, with average values of 260.8 ± 13.4 U/L and 205.1 ± 18.5 U/L, respectively (P = .02). No gender differences were seen for serum BALP (P = .48). Serum carboxy-terminal propeptide of Type I procollagen (PICP) concentrations could not be measured in this study because the Metra Biosystems assay for PICP could not be validated.

Introduction

Bone synthesis by the osteoblast can be divided into 3 phases: proliferation, matrix development and maturation, and mineralization.¹ Gene expression of type I collagen takes place during the proliferation of the osteoblast cells. The expression of bone specific alkaline phosphatase (BALP) reaches its maximum during matrix maturation and declines as matrix mineralization starts. The osteocalcin gene is expressed during matrix mineralization.When type I collagen is produced as procollagen and released into the extracellular space, the amino and carboxyterminal propeptides of type I procollagen (PINP and PICP, respectively) are cleaved off.² Serum PICP has been shown to be a good marker for bone formation in metabolic bone diseases.³ In Thoroughbred fillies, PICP has an inverse relationship with age, with highest values found in animals less than 1 year of age.⁴ Serum alkaline phosphatase (ALP) has been measured in the young foal and is highest at birth, decreasing to a constant level by 2 months of age.^{5, 6 and 7} Serum BALP constitutes 60% to 92% of the total serum ALP in the horse and is highest in the foal.^{4 and 8} As the foal matures, there is an inverse relationship between age and serum BALP.^{4 and 9} Serum osteocalcin in foals less than 6 months of age has not been reported as having the same age-related pattern as serum BALP.¹⁰However, younger horses have higher serum osteocalcin values than mature horses.^{11, 12 and 13} Davicco et al¹⁴ showed plasma osteocalcin age-related changes for Thoroughbred foals with radioimmunoassay (RIA). Plasma osteocalcin was low at birth, increased to day 8, and then dropped to day 15. The objective of this study was to establish normal ranges and age-related changes in serum BALP, PICP, and osteocalcin in the foal with enzyme-linked immunospecific assays (ELISAs).

Materials and methods

Four Quarter Horse (QH; 2 fillies and 2 colts) and 9 Thoroughbred (3 fillies and 6 colts) foals were included in the study from birth through 112 days of age. Foals were born from February 5 to May 13, 1998. Mares and foals were housed on 40 acres of Bahiagrass (Paspalum notatum) pasture and fed a 15% crude protein (as fed) sweet feed. Body scores were recorded every 28 days on a scale from 1 to 9.¹⁵ Concentrate was fed to each mare at 1.5 kg/100 kg body weight daily and was increased by 20% for each body condition score below 5 and decreased by 20% for each body condition score above 5. Mares were individually fed in 3.6 × 3.6—m stalls twice daily, with foals allowed access to the mares feed. Trace mineral salt blocks were available in the pastures. Water was available at all times.Blood was collected from foals between 10 and 14 hours after birth on day 1. Blood then was collected on days 3, 6, 9, 12, 15, 18, 21, 28, 35, 42, 49, 56, 70, 84, 98, and 112 after morning feedings. Except for day 1, all blood samples were collected between 7:00 and 9:00 am. All blood samples were collected with jugular venipuncture into a glass vacutainer containing no additives or anticoagulants and were allowed to clot. Serum was separated and frozen at −20°C within 4 hours of collection. All samples were analyzed within 6 months of collection.The Alkphase-B immunoassay for the determination of BALP (Metra Biosystems, Mountainview, Calif) and the NovoCalcin immunoassay for determination of osteocalcin (Metra Biosystems), used in this study, have been previously validated in the horse.^{16 and 17} The Prolagen-C immunoassy for determination of the PICP (Metra Biosystems) has not been previously validated in the horse.¹⁷Serum bone metabolism marker raw data were analyzed with analysis of variance with repeated measures over time with gender and breed in the model. Analyses were performed with Statistical Analysis System with proc glm for the analysis of variances.¹⁸

Results

Average serum osteocalcin concentration for the testing period was higher for Thoroughbred than QH foals: 152.1 ± 4.6 and 131.3 ± 6.3 ng/mL (mean ± standard error), respectively (P = .01). No overall differences were seen for gender (P = .10). However, on day 1, colts had higher osteocalcin concentrations than did fillies at 199.6 ± 30.2 ng/mL and 93.8 ± 32.4 ng/mL (P = .04; Fig 1).

Total and free iodothyronine levels of growing Thoroughbred foals: Effects of weaning and gender

The aim of this study was investigate the effect of growing associated with different gender on circulating total and free iodothyronine concentrations during the first 13 mo of age in foals. In addition, we investigated the evolution of circulating concentrations of thyroid hormones during the first 3 d of weaning. Blood was collected from 13 clinically healthy Thoroughbred foals every month. All foals were weaned at the 4 mo and blood samples were taken also at 24, 48 and 72 h after weaning. The results obtained showed growing effects for tri-iodothyronine (T₃), thyroxine (T₄), free tri-iodothyronine (fT₃) and free thyroxine (fT₄) values (P < .001).

Serum T₃ concentrations averaged respectively 2.89 and 0.29 nmol/L at 7 and 9 mo. Serum T₄ concentrations averaged respectively 100.17 and 21.77 nmol/L at 1 and at 10 mo. Serum fT₃ concentrations averaged respectively 6.96 and 1.50 pmol/L at 1 and 4 mo. Serum fT₄ concentrations averaged respectively 31.40 and 4.93 pmol/L at 1 and 9 mo. Significant correlations between T₃, T₄, fT₃ and fT₄ with body weight (BW) and between T₃, T₄ and fT₄ with age were observed.

Weaning effects (P < .001) were shown for T₃ and fT₄ levels. No differences (P > .05) in T₄ and fT₃ levels were observed over the 3-day period. Gender effects (P < .001) were shown for T₃, T₄, fT₃, and fT₄ levels. Significant correlations between T₄ and fT₄ with BW and age were observed in colts and fillies. T₃ concentrations were correlated with age only in colts and fT₃ with BW only in colts. The results obtained seem to lend support to the recognized effects of growing and weaning in modulating the thyroid function of Thoroughbred foals. In fact, significant and differentiated effects of growing and weaning on total and free iodothyronine levels have been demonstrated.     

Emotional Response to Novelty and to Expectation of Novelty in Young Race Horses

The aim of this study was to estimate the emotional response to novelty and to expectation of novelty in young race horses. The novelty in this study was the first training on an automated horse walker at a new training center. To estimate the level of emotionality in horses, the telemetric measurement of heart rate (HR) was used. A hypothesis was developed that expectation of novelty can be as exciting for horses as a novelty test. In this study, 40 horses were studied just before and then during their first walk on an automated horse walker. They were divided into four groups, with 10 horses in each group. These groups were as follows: (1) 1.5-year-old Thoroughbred colts, (2) 1.5-year-old Thoroughbred fillies, (3) 2.5-year-old Purebred Arabian colts, and (4) 2.5-year-old Purebred Arabian fillies. HR was measured at rest before exercise, during handling and moving the horse from the stable, while walking on the automated horse walker for about 20 minutes, while moving the horse from the walker to the stable, and at rest after exercise. HR response to the anticipation of novelty was higher in colts than in fillies, particularly in the group of Thoroughbreds.     

The influence of exercise during growth on ultrasonographic parameters of the superficial digital flexor tendon of young Thoroughbred horses

REASON FOR PERFORMING STUDY: Conditioning by early training may influence the composition of certain musculoskeletal tissues, but very few data exist on its effect during growth on tendon structure and function. OBJECTIVES: To investigate whether conditioning exercise in young foals would lead to any ultrasonographically detectable damage to the superficial digital flexor tendon or an increase in cross-sectional area (CSA). METHODS: Thirty-three Thoroughbred foals reared at pasture were allocated to 2 groups: control (PASTEX) allowed exercise freely at pasture; and CONDEX, also at pasture, began conditioning exercise from mean age 21 days over 1030 m on a purpose-built oval grass track, for 5 days/week until mean age 18 months. Foals were observed daily, and underwent orthopaedic examination monthly. Ultrasonographic images of the superficial digital flexor tendon (SDFT) at the mid-metacarpal level of both forelimbs were obtained in all foals at ages 5, 8, 12, 15 and 18 months. CSA was validated (r(2) = 0.89) by determining CSA from digital photographs of the transected SDFT surface from 12 of the horses necropsied at age 17.1 months. RESULTS: here was no clinical or ultrasonographic evidence of tendonopathy in either group and the greatest increase in mean CSA in both groups occurred between age 5 and 8 months. Across all age categories, there was no significant difference in mean CSA between the left and right limbs, or colts and fillies; there was a trend towards a larger CSA in the CONDEX group (P = 0.058). CONCLUSIONS: There was no conclusive evidence for a structural adaptive hypertrophy of the SDFT, probably because the regimen was insufficiently rigorous or because spontaneous pasture exercise may induce maximal development of energy storing tendons. POTENTIAL RELEVANCE: A moderate amount of early conditioning exercise against a background of constant exercise at pasture is not harmful to the development of the flexor tendons.     

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.     

Retrospective analysis of 50 cases of guttural pouch tympany in foals

Between 1994 and 2001, guttural pouch tympany was diagnosed in 51 foals; there were approximately three times as many fillies as colts, of Arabian, different German warmblood breeds and Western horse breeds. There were significantly more Arabian and paint horse foals than expected in comparison with the breed distribution of the foals hospitalised at the Clinic for Horses. The foals' breed and sex did not influence the age of onset, the type and severity of the clinical signs or the recurrence rate. A surgical laser technique was used on 50 of the foals; in 35 cases only one surgical treatment was necessary, in seven cases a second operation was required during the foal's initial period of hospitalisation, and in eight cases a second operation was performed during a second period of hospitalisation. Long-term follow-up information was obtained for 44 of the 50 treated horses; 24 of them were under two years of age and 20 were over two years of age. In six horses, no follow-up information was available. Four horses were euthanased for reasons unrelated to the condition or its treatment. The horses over two years of age were in training or were being used for competitions in dressage or jumping or for breeding purposes, and in only one of them was an adventitious respiratory noise reported. All the horses up to two years of age were reported to be healthy.     

Developmental Changes During the First Year of Life in Plasma Tryptophan Concentration of the Foal

Circulating tryptophan (TRP) levels can influence protein synthesis in various tissues during early stages of life. It is important to investigate factors that influence TRP dynamics to evaluate results of TRP use in equines. Previous studies have demonstrated that plasma TRP levels in the first periods of life are indicative of brain serotonin synthesis and that in horses there may be breed differences in the behavioral response to TRP administration. Current research has investigated the pattern of plasma TRP concentration in growing foals of two different breeds: Anglo-Arabian (AA) and Sicilian Oriental Purebred (PSO). Blood samples were collected from 10 clinically healthy colts, ages 1 to 12 months old. Plasma TRP concentrations were determined by high-performance liquid chromatography. Two-way analysis of variance showed age- and breed-related differences. A positive significant correlation was found between age and TRP concentration (r = 0.6, P < .001). After weaning (7th month of age) TRP levels were significantly higher than in previous months. PSO colt foals had TRP levels significantly higher than AA colt foals in the 1st, 2nd, and 12th months of life. These findings suggest that plasma TRP dynamics in growing horses are influenced by age and breed and should be taken into consideration for TRP experiments in equines.     

Coprophagy by foals: effect of age and possible functions

In colts and fillies observed from birth to 24 weeks old, coprophagy occurred from Weeks 1 to 19. Its frequency was greatest during the first two months. Coprophagy was rarely observed in mares and stallions. Foals usually ate the faeces of their mother but were observed to eat their own and those of a stallion and another unrelated mare. Urination by the foal occurred before, during or after 26 per cent of the coprophagy incidents. It is hypothesised that foals may consume faeces in response to a maternal pheromone which signals the presence of deoxycholic acid or other acids which the foal may be deficient in and which it may require for gut immuno-competence myelination of the nervous system. Such a pheromone may also serve to accelerate growth and sexual maturation. Coprophagy may also provide nutrients and introduce normal bacterial flora to the gut.     

Inheritance of recurrent exertional rhabdomyolysis in thoroughbreds

OBJECTIVE: To develop a diagnostic test for recurrent exertional rhabdomyolysis (RER) in Thoroughbreds that relied on in vitro contracture of muscle biopsy specimens and determine whether the inheritance pattern of RER diagnosed on the basis of this contracture test was consistent with an autosomal dominant trait. DESIGN: Clinical trial. ANIMALS: 8 adult horses with RER and 16 control adult horses for development of the contracture test; 23 foals for inheritance of RER. PROCEDURE: External intercostal muscle biopsy specimens from the 24 adult horses were tested for contracture in response to halothane and caffeine, and criteria for a positive test result were determined. These criteria were then applied to results for the 23 foals to determine whether they had RER. Simple segregation analysis was performed to determine whether results were consistent with a dominant pattern of inheritance. RESULTS: Results of the contracture test were positive for 5 of the 12 colts and 4 of the 11 fillies. Results of segregation analysis were consistent with an auto-. somal dominant pattern of inheritance. Two sires with RER produced colts with RER, supporting the hypothesis that RER had an autosomal, rather than an X-linked, inheritance pattern. In addition, in 1 instance, an unaffected colt was produced by 2 affected parents, which was not consistent with a recessive mode of inheritance. CONCLUSIONS AND CLINICAL RELEVANCE: Although the expression of the RER trait is influenced by sex, temperament, and diet, among other factors, results from the in vitro muscle contracture test and this breeding trial suggest that RER in Thoroughbreds can be modeled as a genetic trait with an autosomal dominant pattern of inheritance.     

Distances between thoracic spinous processes in Warmblood foals: A radiographic study

Reason for performing study: The aetiological factors behind impinged or overriding of dorsal spinous processes (‘kissing spine syndrome’, KSS) are not clearly understood. Back conformation, breed, age, training and gender may play important roles in this condition. Radiographic changes vary and abnormalities are seen in many clinically normal horses, but the conclusion of previous studies in mature horses is that interspinous spaces <4 mm are considered too narrow and potentially indicative of KSS. Objectives: To evaluate whether narrowing of the interspinous space was present in a population of normal Warmblood foals. Materials and methods: The mean interspinous space width in the area of T10–L1 was measured on radiographs from 25 Warmblood foals aged 9–88 days. Results: Mean ± s.d. interspinous space width was found to be between 5.9 ± 1.2 and 8.9 ± 2.6 mm with the narrowest space in the area T16–T17 and the widest space in T10–T12. No interspinous spaces were <4 mm wide. Gender and location of the interspinous space significantly affected the width of the distance between the spinous processes. Conclusions and potential relevance: In this study none of the interspinous spaces were <4 mm and therefore none of the foals showed signs of impinged or overriding of dorsal spinous processes known as KSS based on the current definitions. Consequently, in this population, there did not appear to be a congenital narrowing of the interspinous space. However, long‐term follow‐up studies, including detailed information on imposed factors such as training, are needed in order to further elucidate a possible congenital component in the aetiology of KSS.     

Small colon stenosis secondary to ulcerative colitis in three Standardbred foals

Three Standardbred foals, a colt approximately one month old and 2 fillies approximately 4.5 months old, from the same farm, presented to University of Pennsylvania's New Bolton Centre over the course of 3 months for further evaluation due to acute onset of colic. All foals had a history of diarrhoea prior to presentation. On presentation, the foals had abdominal distension, dull demeanour and repeatedly lay down and rolled. Exploratory celiotomy revealed a segment of stenotic (lumen diameter 1–4 mm) small colon with marked distension of the colon proximal to the stenotic segment. Post mortem examination of the foals confirmed stenosis of the small colon with a segment of ulcerative colitis associated with the stenotic region. An aetiological agent was not identified.