Norwegian Cold-blooded Trotters Research Articles

Effect of dietary krill oil supplementation on horse red blood cell membrane fatty acid composition and blood parameters.

Supplementation with marine-derived n-3 long-chain polyunsaturated fatty acids (LC PUFAs), eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) is linked to beneficial health effects in both humans and horses. Krill oil (KO), which is extracted from the Antarctic krill (Euphausia superba), is well documented as a safe and biologically available dietary supplement in humans and several animal species, but there is a lack of documentation regarding its effect as a dietary ingredient for horses. The objective of this study was to test whether KO as a dietary supplement had the ability to raise horse red blood cell (RBC) membrane EPA and DHA, expressed as the n-3 index. Five nonworking Norwegian cold-blooded trotter horse geldings (body weight [BW]: 567 ± 38 kg) were supplemented with KO (10 mL/100 kg BW) for 35 days in a longitudinal study. Blood samples were analysed for RBC membrane fatty acid (FA) profile, haematology and serum biochemistry every 7th day. KO was well accepted by all horses, and no adverse health effects were observed during the 35-day trial period. KO supplementation affected the RBC membrane FA profile by increasing the n-3 index from Day 0 to 35 (Day 0: 0.53% vs. Day 35: 4.05% of total RBC FAs). The observed increase in the sum of EPA and DHA (p < 0.001), total n-3 FAs (p < 0.001) and the reduction of n-6 FAs (p < 0.044) resulted in a lower n-6:n-3 ratio (p < 0.001) by Day 35 of KO supplementation. In conclusion, the RBC n-3 index was increased and the general n-6:n-3 ratio was decreased in horses receiving 35-day dietary KO supplementation.

182 Feed intake and metabolic responses in horses in transition from haylage feeding to pasture grazing

The transition from winter-feeding to pasture involves a considerable diet change that might compromise health of horses, and info on the metabolic responses in horses on pasture are scarce. The objective of the study was to investigate how the transition from haylage feeding to strip grazing affected feed intake (FI) and metabolic responses (blood glucose (GLU)-insulin (INS) and cecal pH). Four cecum-cannulated Norwegian cold-blooded trotter geldings were used in a longitudinal study consisting of 3 periods: 1) haylage only (d 0 to 8) reflecting winter-feeding, 2) transition (d 9 to 20) reflecting a diet where the proportion of forage decreased and grazing increased (0 min to 2 × 3 h per d), and 3) grazing only (d 21 to 28) reflecting horses on pasture (2 × 3 h per d). Strip grazing was used to control and measure daily FI in period 2 and 3. From d 9 to 28 the horses were allowed access to a new strip of grass for a specified time-period. The remaining grass was cut each day after grazing, collected, weighed, and compared with the amount of grass from a strip of ungrazed pasture. It was possible to estimate FI for all horses and calculate an average FI per horse. Haylage and grass samples from every 4th d were analyzed for nutritional composition (neutral detergent fiber excluding residual ash (aNDFom), water soluble carbohydrates (WSC), and crude protein (CP)) and used to estimate dry matter (DM) and nutrientintake. On d 8 and 28, blood and cecal samples were collected before and each h after feeding (2 kg haylage as fed vs. 3 h of grazing) for 8 h. ?Area under the curve (AUC) of GLU and INS were calculated using GraphPad Prism. The effect of d on nutrient content, FI, body weight (BW), AUC and peak GLU and INS, and minimum pH were compared using PROC mixed in SAS and considered different if P < 0.05. Grass yield increased (P < 0.001) over time as the grass matured (0.32 to 0.54 kg DM/m2). Plant maturity of the grass affected the nutrient content (P < 0.001) as aNDFom increased (545 to 636 g/kg DM), and CP decreased (158 to 101 g/kg DM). The WSC content varied (P < 0.001) over time (73 to 128 g/kg DM). Similar BW was measured on d 8 and 28 (568 ± 31 kg). The DM intake was 1.62 kg (0.29% of BW) on d 8 and estimated to be 3.7 kg (0.65% of BW) on d 28. There was no effect of d on AUC and peak GLU and INS, but cecal pH was higher (P < 0.001) when feeding haylage (6.89) on d 8 than pasture (6.57) on d 28. In conclusion, FI was controlled by strip grazing, BW was maintained, and metabolic responses were within the expected ranges. However, a longer grazing time would probably result in increased FI and undesired BW gain.

139 In sacco and in vivo digestibility of silages in horses

The gold standard method for measuring digestibility of feedstuffs is by total collection of feces. An alternative method is the in sacco technique which provide information on both digestibility and digestion kinetics of a feed. The in sacco technique is commonly used in feedstuff evaluation systems for ruminants. Only few studies have used the technique in horses, but further validation against in vivo studies is needed. The objective of the study was to determine if the in sacco technique can be used to measure digestibility in horses. Five cecum cannulated Norwegian coldblooded trotters (body weight 550 ± 75 kg) were used in a 22 d study consisting of 18 d of diet adaptation followed by 4 d of total collection of feces. Horses were fed 24.3 kg of a late harvested silage (LHS, dry matter (DM) 31.0%, neutral detergent fiber (NDF) 59.6% of DM) fed in 3 equal meals at 0800, 1400 and 2000 h. The apparent total-tract digestibility (ATTD) of LHS was estimated by total collection of feces over 4 consecutive days. Before the collection period, in sacco digestibility was estimated of the LHS and an early harvested silage (EHS, DM 26.0%, NDF 28.6% of DM) using the in sacco technique (bag size 6 × 15 cm, 5.13 mg feed/cm 2 , pore size of 36 μm). The EHS and LHS were dried, ground to 1 mm and 1 g was added to in sacco bags. Two bags of each feedstuff were fastened to a 78 cm long string with rubber bands and incubated in the cecum for 0, 2, 4, 8, 16 and 24 h, then washed, dried for 48 h and weighed to determine DM loss after incubation. The in sacco digestibility was modeled in SAS according to D = A tB (e −Ct ) , where D is the digestibility through time t, A is the soluble fraction of the feedstuff and curve interception, B is the potential digestibility of the insoluble fraction, and C is the digestion rate of B. The potential digestibility (A+B) of the LHS was compared with EHS and to the ATTD of LHS in SAS using a paired t -test and considered significant if P < 0.05. The ATTD of DM for LHS (57.0% ± 0.49) was not different ( P = 0.22) from the potential digestibility (58.4% ± 2.16) measured with the in sacco technique. The A, B and C values were 33.6, 24.8 and 0.096 for the LHS and 64.2, 28.6 and 0.178 for the EHS. The potential digestibility for EHS (92.8% ± 0.42) was higher ( P < 0.001) than the LHS as expected and show that the technique can differentiate between feedstuffs. In conclusion, the in sacco technique resulted in similar results as in vivo ATTD of LHS and it is a promising technique for estimating digestibility of individual feedstuffs in horses. However, the technique needs to be developed further and validated using other feedstuffs and mixed diets.

Clustering the relationship matrix as a supportive tool to maintain genetic diversity in the Scandinavian cold-blooded trotter

ABSTRACTIn the joint breeding population of the Norwegian and North-Swedish cold-blooded trotters, formerly suggested actions concerning sire selection strategies due to reduced genetic variation have not been implemented. The aim of this study was therefore to update the status regarding genetic variation and to explore the cluster structure and evaluate if such a tool could give an immediate action to maintain the diversity. This study reports that the joint population is approaching a bottleneck, and clustering of the additive relationship matrix of one year-class showed that some smaller clusters existed, mainly in the Swedish part of the joint population. Through active recruitment of sires in these clusters, there is a potential for maintaining the genetic variation. Development of an interactive mating tool is essential, realizing real-time subscription of mares to sires on basis of knowledge of the cluster structure, which would give an immediate, practical solution close to minimum coancestry mating.

The effect of diet and exercise on plasma metabolite and hormone concentrations in horses measured before and after exercise

Exercise influences different endocrine and metabolic parameters, and information in the literature is sparse for some of these hormones and metabolites in the exercising horse. The aim of the present experiment was to study the metabolic response to exercise when feeding diets with varying carbohydrate composition (fibre and starch) under experimental conditions where diet and exercise were standardised and controlled. The response was investigated in a 4×4 Latin square design experiment using four Norwegian Coldblooded trotter horses. The dietary treatments were two fibre based diets, hay only and hay (85% of dry matter intake (DMI)) supplemented with molassed sugar beet pulp (mSBP) (15% of DMI), or two starch based diets of hay (68% of DMI) and barley (32% of DMI), and hay (68% of DMI), barley (26% of DMI) and mSBP (6% of DMI). Each diet was fed for 28 days; 16 days of adaptation followed by 12 days of data collection. 4 h after the morning feeding at 06:00 the horses performed a standardised exercise test (SET) lasting 45 min. Blood samples were taken before feeding the morning meal at 06:00, before the SET (10:00), after the SET (10:45) and after recovery from exercise (15:00), and plasma samples were analysed for relevant metabolites and hormones. Plasma leptin concentrations increased after exercise but were not affected by diet, whereas diet and exercise had no effect on the plasma concentrations of ghrelin and insulin like growth factor 1 (IGF-1). Furthermore, diet influenced the plasma concentrations of short-chained fatty acids (SCFA) more than exercise. The results provide important comparative information that can be useful in studies where diet and exercise cannot be controlled, e.g. in field studies.

The effect of feeding barley or hay alone or in combination with molassed sugar beet pulp on the metabolic responses in plasma and caecum of horses

Highly fermentable fibre sources like sugar beet pulp (SBP) might be fed as an alternative to starch rich concentrate to horses. However, including soluble fibre from SBP in a meal of concentrate might delay gastric emptying and increase viscosity in the small intestine, altering or impairing glucose absorption, hence affect the metabolic responses measured in plasma and the hindgut. Four diets with different carbohydrate composition were investigated in a 4×4 Latin square design experiment in four periods using four caecum cannulated Norwegian coldblooded trotter horses. The diets were hay only (HAY), hay and molassed SBP (HAY+SBP), hay and pelleted barley (BAR), and hay, pelleted barley and molassed SBP (BAR+SBP). The amount of barley (2g starch/kg body weight (BW)) fed in the test meals was similar for the BAR and BAR+SBP diets. Each diet was fed for 16days followed by data collection, then each horse changed to a new diet in the next period. Caecum pH and short-chain fatty acid (SCFA) profiles and the metabolic responses measured in plasma at rest were followed for 9h after the test meal. Caecum pH decreased more (P<0.001) after feeding BAR and BAR+SBP than after HAY and HAY+SBP. Diet also affected the proportions of acetate (P<0.001) and propionate (P<0.001) with less acetate and more propionate measured on the BAR and BAR+SBP diets than on the HAY and HAY+SBP diets, reflecting differences in the substrates fermented by the caecal microbes. Feeding barley resulted in a postprandial increase in plasma glucose (P=0.030) and insulin (P<0.001) whereas these values remained almost stable when the fibre-based diets were fed. The total SCFA concentration in the caecum was greater (P<0.001) on the BAR and BAR+SBP diets than on the HAY and HAY+SBP diets. However, the plasma concentrations of SCFA were differently affected with greater (P<0.001) levels of SCFA (mainly acetate) in horses fed the HAY and HAY+SBP diets than in the BAR and BAR+SBP fed horses, reflecting a shift in the provision of carbohydrate derived nutrients from the small to the large intestine in response to the dietary carbohydrate composition. In conclusion, there was no effect of adding molassed SBP to a meal of barley compared to feeding barley alone, and fluctuations in plasma and caecal variables were more stable when feeding hay and molassed SBP than feeding barley.

A retrospective cohort study on fertility in the Norwegian Coldblooded trotter after artificial insemination with cooled, shipped versus fresh extended semen.

BackgroundPregnancy rates with cooled equine semen can be unsatisfactory and show great variation. Information about first cycle pregnancy rates and pregnancy rates per cycle are often lacking from publicly available records. This retrospective cohort study was performed to evaluate the fertility of the Norwegian Coldblooded trotter. The aim of the study was to compare the breeding results after insemination with fresh, extended with those of cooled, shipped semen among Norwegian Coldblooded trotter mares. First cycle pregnancy rate was the main parameter used to measure fertility. Stud-books were collected from four studs from the years 2006–2010. Statistical analyses were done in Stata using Chi square test and multivariable analyses where different models were compared based on Akaike’s information criterion.ResultsFirst cycle pregnancy rate, seasonal pregnancy rate and foaling rate all showed significant differences (P < 0.0001) when comparing mares inseminated at stud with mares inseminated with cooled, shipped semen, favoring artificial insemination (AI) at stud. First cycle pregnancy rate was 55.1 % for mares inseminated at stud with fresh extended semen and 42.2 % for mares inseminated with cooled shipped semen. The overall pregnancy rate per cycle was 84.4 % for AI at stud and 66.9 % for cooled, shipped semen. The parameters stud, mare age, number of inseminations within an estrus cycle and individual stallion were also investigated for influence on fertility.ConclusionsFew retrospective studies include the parameter of first cycle pregnancy rates. Our study does not differ dramatically when comparing seasonal pregnancy rates and foaling rates with similar studies. Fertility parameters for the Norwegian Coldblooded trotter do not differ significantly from most other studies of Coldblooded mares and other mare breeds around the world. But the difference in fertility parameters between AI at stud to AI with cooled semen between our study and others, indicates that higher pregnancy rates in Norwegian Coldblooded trotter may be possible.

Ossification of ungular cartilages in front feet of cold-blooded trotters--a clinical radiographic evaluation of development over time.

BackgroundIt has not yet been shown that ossification of ungular cartilages (OUC) is a pathological condition. Beside heredity, factors such as sex, age, repeated concussion, local trauma, hoof and body size have been suggested as contributing factors for OUC development. By comparing radiographs of front hooves from cold-blooded trotters with different age we wanted to evaluate when development of OUC in cold-blooded trotters occurs and if and when it stabilizes in relation to age and workload. Diagnosis and grading of OUC were based on radiological field examinations of 649 Swedish and Norwegian cold-blooded trotters’ front hooves. A hundred and forty-seven of the horses were re-examined 3-13 years (mean age 9, median 8 years) after the first occasion. All radiographs were evaluated blind, using two different grading systems for OUC. Work load, in form of number of races completed, and body size score were collected from official data. Four statistical ordinal regression models were used, compared and evaluated.ResultsWe identified a breakpoint at 2.8 ± 0.38 years of age when ossification ends and proposed a simpler grading system with more consistent results. There was no significant correlation between body size and grade of OUC. Comparison of different statistical methods for evaluation of ordinal data revealed a piecewise linear regression model as most suitable.ConclusionsIndividuals with OUC developed this condition during the stage of life when their hooves develop in size. Results from this study can assist equine practitioners when examining and for understanding this condition in their clinical work and is also beneficial for the Scandinavian equine industry when devising breeding programs.

The effect of dietary carbohydrate composition on apparent total tract digestibility, feed mean retention time, nitrogen and water balance in horses

A total of four diets with different carbohydrate composition were investigated in a 4×4 Latin square design experiment with four Norwegian Coldblooded trotter horses. The objective of the present study was to increase the fermentable fibre content and reduce the starch intake of the total ration obtained by partly substituting mature hay and barley with sugar beet pulp (SBP), a soluble fibre source. The diets investigated were hay only (HAY), hay (85% of dry matter intake (DMI)) and molassed SBP (15% of DMI) (SBP), hay (68% of DMI) and barley (32% of DMI) (BAR), and hay (68% of DMI), barley (26% of DMI) and SBP (6% of DMI) (BAR+SBP). The feeding level was 18.5, 17.3, 15.7 and 15.7 g DM/kg BW per day for the HAY, SBP, BAR and BAR+SBP diets, respectively. Each diet was fed for 18 days followed by 10 days of data collection, where apparent total tract digestibility (ATTD), total mean retention time (TMRT) of ytterbium-labelled hay, water balance, digestible energy (DE) intake and nitrogen balance were measured. An enzymatic chemical dietary fibre (DF) method was used to get detailed information on the composition and ATTD of the fibre fraction. Inclusion of SBP in the diet increased the ATTD of the constituent sugars galactose and arabinose (P<0.01). Feeding the HAY and SBP diets resulted in a lower TMRT owing to a higher DF intake than the BAR and BAR+SBP diets (P<0.01). There was no difference in water intake between HAY and SBP, but faecal dry matter was lower for HAY than the other diets (P=0.017), indicating that water was more tightly bound to fibre in the HAY diet. The diets were iso-energetic and provided enough DE and protein for light to moderate exercise for a 550 kg horse. In conclusion, this study showed that the DF intake had a larger effect on TMRT than partly substituting hay or barley with SBP, and that highly fermentable pectin-rich soluble DF from SBP maintains high nutrient utilization in horses.

Relative prevalence of upper respiratory tract obstructive disorders in two breeds of harness racehorses (185 cases: 1998–2006)

Two genetically and phenotypically distinct horse breeds are used for harness racing in Scandinavia: the Standardbred (SB) and Coldblooded Trotter. These racehorses have identical environmental, management and racing conditions. Therefore, this study was undertaken to identify and compare the relative prevalence of upper respiratory tract (URT) obstructive disorders in these 2 breeds. To determine whether these 2 phenotypically different breeds of harness racehorses have different predispositions for URT disorders. Retrospective study of 88 Norwegian Coldblooded Trotters (NCT) and 97 SBs referred to this hospital for URT evaluation between 1998 and 2006. Case records of all horses diagnosed with an URT disorder during resting endoscopy, and all horses undergoing high-speed treadmill videoendoscopy (HSTV) with one or more periods of induced poll flexion were evaluated. The relative prevalence of URT disorders between the 2 breeds was analysed using a Fisher's exact test. There was a significant (P<0.05) breed predisposition regarding 6 URT disorders. Bilateral dynamic laryngeal collapse associated with poll flexion and flaccid epiglottis was significantly more frequent in the NCT. Alar fold collapse and nasopharyngeal collapse were significantly more frequent in SBs. Epiglottic entrapment and nasal flutter were only diagnosed in the SBs. Dynamic disorders were more common than resting disorders in both breeds. URT obstructive disorders (dynamic laryngeal collapse associated with poll flexion, flaccid epiglottis, pharyngeal collapse, alar fold collapse, nasal flutter and epiglottic entrapment) are breed related, indicating an anatomic or functional cause. Periods of induced poll flexion during HSTV was essential to declare harness racehorses free of URT disorders. Further anatomic or physiological studies comparing these breeds could potentially provide insight into the pathogenesis of certain URT obstructive disorders. Induced poll flexion should be included in routine HSTV examinations of all harness racehorses.

A novel treatment for dynamic laryngeal collapse associated with poll flexion: The modified checkrein

Dynamic laryngeal collapse (DLC) associated with poll flexion is a performance limiting dynamic upper airway disorder commonly diagnosed in Coldblooded trotters. An inspiratory obstruction occurs when affected horses are driven with tension on the reins, inducing poll flexion. To date, surgical treatment and conservative management have failed to improve racing performance in affected horses. To test the efficacy of an external device, the modified checkrein, in limiting poll flexion, diminishing laryngeal collapse and improving airway mechanics when horses are driven on a treadmill with tension on the reins and test the hypothesis that the modified checkrein will limit poll flexion thereby improving endoscopic appearance of the larynx and reduce airway obstruction in harness racehorses affected with DLC. Fourteen Norwegian Coldblooded trotter (NCT) racehorses previously diagnosed with DLC associated with poll flexion exercised on a high-speed treadmill at speeds that resulted in heart rate >200 beats/min. Upper airway videoendoscopy recordings, tracheal pressures and video recordings of the head and neck position were collected while horses exercised with the conventional checkrein on Day 1 and the modified checkrein on Day 2. The modified checkrein successfully limited poll flexion as measured by no change in head position parameters between phases of no rein tension and phases of rein tension. Endoscopic scores were significantly improved (arytenoids cartilage collapse P<0.0001; vocal fold collapse P<0.0001) and tracheal peak inspiratory pressures were significantly less negative (P = 0.0162) when horses were fitted with the modified checkrein compared to the conventional checkrein. The modified checkrein successfully limited poll flexion and also prevented upper airway obstruction in NCT horses affected with DLC associated with poll flexion. The modified checkrein seems promising in offering a method of conservative management in harness racehorses affected with this disorder.

Effect of type of grain and feed processing on gastrointestinal retention times in horses1

Gastrointestinal retention time may affect digestive processes in the horse. To evaluate the effect of processing of grains on mean retention time in different segments of the gastrointestinal tract, 4 Norwegian Cold-blooded trotters (cecally cannulated, approximately 500 kg of BW) were used. Barley, maize, and wheat were all ground, pelleted, extruded, and micronized to create a total of 12 processed grains. After an adaptation period of 5 d, each horse was given 0.2 kg of Yb-mordanted grain together with their morning meal, which consisted of 2 kg of hay and 1 kg of one of the grains. Fecal samples were collected 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 48, and 52 h after administration of the marker dose. The samples were analyzed for Yb, and values were used for a 2-compartment nonlinear passage model to calculate the retention times in different segments of the gastrointestinal tract for each type of grain and each processing method. Among grains, maize had a longer retention time in the time-dependent compartment (believed to be cecum) than barley and wheat (P < 0.05) and hence a decreased passage rate out of this compartment (P < 0.05). For the feed processing treatment, ground grains had a longer compartmental retention time than those grains processed with the high temperature (extruded and micronized; P < 0.05), but the total mean retention time was not affected by treatments. In conclusion, feed processing affected passage rates and compartmental retention times, but did not affect the overall retention time in the gastrointestinal tract of the horse.

Effect of poll flexion and dynamic laryngeal collapse on tracheal pressure in Norwegian Coldblooded Trotter racehorses

Dynamic laryngeal collapse (DLC) associated with poll flexion is a newly diagnosed upper respiratory tract obstructive disorder that causes poor racing performance. To determine if Norwegian Coldblooded Trotters (NCTs) affected with DLC associated with poll flexion differ from normal, elite NCTs based on simple airway mechanics measurements. Five normal elite NCTs and 6 NCTs diagnosed previously with DLC underwent treadmill videoendoscopy while tracheal pressures were measured continuously. Alternating head positions were used such that horses were exercised with free head carriage and induced poll flexion at heart rates >200 beats/min. Peak inspiratory tracheal pressures were significantly more negative for horses with DLC compared to the elite horses. This difference was only significant during the exercise phases when the poll region was flexed, P = 0.0015. Head position significantly affected peak inspiratory pressure for both elite and affected horses, P < 0.0001. Induced poll flexion significantly affected peak inspiratory pressure (PIP) in all horses; however, PIPs were significantly more negative in those affected with DLC. Based upon the tracheal pressure measurements recorded in this study, DLC in NCTs is a severe obstructive upper respiratory tract disorder that is induced by poll flexion.

Surgical and Conservative Management of Bilateral Dynamic Laryngeal Collapse Associated with Poll Flexion in Harness Race Horses

To test the hypothesis that in bilateral dynamic laryngeal collapse associated with poll flexion, vocal fold collapse (VFC) is the initial abnormal event that induces further laryngeal collapse, and that racing performance would therefore be substantially improved after bilateral ventriculocordectomy in affected individuals. Retrospective study. Twenty-six horses. Medical records (1998-2006) of harness racehorses admitted for high-speed treadmill videoendoscopy (HSTV) that had bilateral dynamic laryngeal collapse associated with poll flexion were reviewed. Race records, owner interviews, and follow-up HSTV were used to evaluate outcome after either surgical treatment including bilateral ventriculocordectomy or conservative management. Bilateral dynamic laryngeal collapse, defined as bilateral VFC with concurrent arytenoid cartilage collapse (ACC), was identified in 26 horses. Norwegian Coldblooded Trotters (NCT) were overrepresented. Sixteen horses had surgical treatment and 10 were treated conservatively. Return to racing and racing performance was not improved within or between groups after the treatment. On follow-up HSTV of 6 surgically treated horses, there was no residual soft tissue collapse in the ventral portion of the rima glottidis; however, ACC and other abnormalities were still evident. Bilateral ventriculocordectomy resolved VFC, but failed to stabilize the arytenoid cartilages or to significantly improve racing performance. Bilateral dynamic laryngeal collapse associated with poll flexion is a serious performance-limiting upper respiratory tract disorder that is overrepresented in NCT racehorses. Our results suggest that VFC is not the initiating event in this complex obstructive airway disorder for which there is currently no consistently effective treatment.

Models for estimating digesta passage kinetics in the gastrointestinal tract of the horse

Fecal samples were collected to evaluate mathematical models to describe the kinetics of digesta passage in the segments of the equine gastrointestinal tract and to compare the passage kinetics of hay and oats. Four Norwegian Cold-blooded trotters (cecally cannulated, approximately 500 kg of BW) were fed Cr-mordanted hay and Yb-marked oats with their morning meal. The meal consisted of 2 kg of hay and 1 kg of oats processed as ground, pelleted, extruded, or micronized. Each horse was fed each type of oats on different days of collection, after a 5-d adaptation period, in a 4 x 4 Latin square design. Fecal samples were collected 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 48, and 52 h after administration of the marker dose. The samples were analyzed for Cr and Yb, and values were plotted using 1- and 2-compartment nonlinear passage models and an algebraic model. The 1-compartment G4 model and the 2-compartment G4G1 model showed an equally good fit to the observed excretion curves, based on low mean square error and SE. The excretion curves for hay (Cr) and oats (Yb) showed a striking similarity, and there seemed to be no difference in retention time between hay and oats in the horse. The mixing compartments in the horse are believed to be the cecum or both the cecum and the right ventral and dorsal segments of the colon, but further research in this area is needed to make a final conclusion.

Electroencephalographic and cardiovascular variables as nociceptive indicators in isoflurane-anaesthetized horses

ObjectiveTo evaluate Fourier-transformed electroencephalographic (EEG) variables, mean arterial blood pressure (MAP) and pulse rate as nociceptive indicators in isoflurane-anaesthetized horses. AnimalsFive standardbred and three Norwegian cold-blooded trotter stallions undergoing castration, aged 2–4 years, mass 378–538 kg. Materials and methodsAll horses received intravenous (IV) detomidine (10 μg kg−1 IV) and butorphanol (0.01 mg kg−1 IV). Additional detomidine (4 μg kg−1 IV) was administered in the induction area. Anaesthesia was induced with ketamine (2.5 mg kg−1 IV) and diazepam (40 μg kg−1 IV), and maintained for 30 minutes with isoflurane (end-tidal concentration of 1.4%) vaporized in oxygen. The electroencephalogram, MAP and pulse rate were recorded for 15 minutes, beginning 5 minutes before skin incision. Differences between the mean values of recordings taken before, and during surgery were calculated and tested for significant differences using a two-sided Student's t-test. ResultsA significant rise in MAP and a fall in pulse rate were found. No significant change was found in any EEG variable. Conclusion/clinical relevanceOf the variables evaluated, MAP seems to be the most sensitive and reliable indicator of nociception in isoflurane-anaesthetized horses.

Dynamic bilateral arytenoid and vocal fold collapse associated with head flexion in 5 Norwegian Coldblooded Trotter racehorses

Dynamic obstruction of the upper airway is a common cause of poor performance in racehorses, often associated with abnormal respiratory noise during exercise (Morris and Seeherman 1991; Kannegieter and Dore 1995). Welldocumented upper respiratory tract disorders diagnosed using traditional resting upper airway endoscopy include left laryngeal hemiplegia (LLH), dorsal displacement of the soft palate (DDSP), epiglottic entrapment, subepiglottic cyst, epiglottic hypoplasia, pharyngeal lymphoid hyperplasia, arytenoid chondritis and rostral displacement of the palatopharyngeal arch. High-speed treadmill (HST) videoendoscopy has improved our ability to appreciate previously unrecognised forms of dynamic airway obstruction (King et al. 2001). Recently described forms of upper airway obstruction diagnosed using HST videoendoscopy are dynamic collapse of the roof of the nasopharynx (Strand and Staempfli 1993), epiglottic retroversion (Holcombe et al. 1997; Parente et al. 1998), intermittent epiglottic entrapment (Weishaupt et al. 1998) and axial deviation of the aryepiglottic folds (King et al. 2001). This report describes 5 cases of upper airway obstruction due to dynamic bilateral collapse of the vocal folds and arytenoid cartilages in Norwegian Coldblooded Trotter (NCT) racehorses, diagnosed by use of slowmotion playback of HST videoendoscopic recordings.

Evaluation of the bispectral index as an indicator of degree of central nervous system depression in isoflurane-anesthetized horses.

To determine whether the bispectral index (BIS) can be used as an indicator of degree of CNS depression in isoflurane-anesthetized horses. 10 Standardbred and 6 Norwegian cold-blooded trotter stallions admitted for routine castration. A 2-channel referential electrode configuration was used to record EEG for calculation of BIS by the EEG monitor. The BIS was calculated before (awake) and after (sedated) administration of detomidine (0.01 mg/kg of body weight, IV) and butorphanol (0.01 mg/kg, IV). Anesthesia was induced with ketamine hydrochloride (2.5 mg/kg, IV) and diazepam (0.04 mg/kg, IV) and maintained with isoflurane delivered in oxygen. The BIS was calculated after 30 minutes of equilibration at an end-tidal isoflurane concentration of 1.4% (n = 8) or 1.9% (8) and recorded continuously during surgery. Bispectral index was significantly less in sedated and anesthetized horses, compared with awake horses. However, BIS was not significantly different between sedated and anesthetized horses. Mean BIS in horses anesthetized at 1.9% isoflurane was significantly greater, compared with horses anesthetized at an end-tidal concentration of 1.4%. Four horses in the 1.4% group moved during surgery, and BIS increased immediately prior to movement in 2 of these horses. BIS is not a precise indicator of degree of CNS depression in isoflurane-anesthetized horses. Thus, determination of BIS may not be a useful technique for monitoring anesthetic depth in isoflurane-anesthetized horses.

Stochastic simulation of sire selection strategies in North-Swedish and Norwegian cold-blooded trotters

Static selection rules relevant for selecting North-Swedish and Norwegian cold-blooded trotters on annually calculated animal model breeding values for racing performance were sought by stochastic simulation. A closed population keeping 1480 animals born per year was modelled. Selection was on accumulated, transformed and standardised earnings among 3- and 4-year-old trotters with a heritability of 0.2. Sires ranging 5 to 29 year of age were selected and mated at random to females, however, full-sib, sire–daughter or mother–son matings were not allowed. At a fixed two-year mating quota, repeated selection of sires generated larger gain than strategies selecting sires twice according to a progeny testing design or once as for young sire selection. Under repeated selection, marginal improvement in gain, at a large expense in rate of inbreeding, was resulting from going beyond 120 mares per sire over two years. At this mating quota, moderate restrictions on both number of reselection rounds (max. 5) and number of selected sons per sire (max. 6) reduced the rates of inbreeding and gain to, respectively, 50 and 91% of the corresponding unrestricted results. The resulting effective population size was 95 and in accordance with the 100 considered necessary for natural selection to counterbalance the existing inbreeding depression of fitness traits.

Conformational Traits of Norwegian Cold-blooded Trotters: Heritability and the Relationship with Performance

Four body measurements and 18 (forelimb), 20 (hindlimb) and 35 (hoof) subjectively scored conformation traits were investigated on 508 Norwegian cold-blooded trotters. The heritabilities of the body measurements ranged from 0.27-0.73. Several conformational traits showed heritabilities comparable to those of body measurements, and only six had heritabilities approaching zero. Of four faults of conformation that enhanced the prevalence of arthritis in the carpal joint, only calf knees showed significant heritability, which might justify use of the trait for indirect selection against the disease. Increased height at withers and decreased girth circumference significantly increased performance. Base narrow behind, straight hocks and curby hocks were associated with reduced start status and earnings, while cow hocks negatively affected start status only. Conformation was responsible for 10% of the variation in start status and 12% of the variation in earnings, demonstrating the importance of direct selection on breeding values for racing performance.