Short- and long-term racing performance of Standardbred pacers and trotters after early surgical intervention for tarsal osteochondrosis.

REASONS FOR PERFORMING STUDY: Osteochondrosis (OC) is commonly diagnosed in young Standardbred racehorses but its effect on performance when surgically treated at a young age is still incompletely understood. This is especially true for Standardbred pacers, which are underrepresented in the existing literature. OBJECTIVE: To characterise the short- (2-year-old) and long-term (through 5-year-old) racing performance in Standardbred pacers and trotters after early surgical intervention (<17 months of age) for tarsal OC. STUDY DESIGN: Retrospective clinical study. METHODS: The study population consisted of related, age-matched Standardbred racehorses (n = 278; 151 pacers, 127 trotters) with (n = 133) or without (n = 145) one or more tarsal OC lesions. All OC-affected horses were treated surgically prior to being sold as yearlings. Data obtained from publicly available race records for each horse included starts, wins, finishes in the top 3 (win, place or show), earnings and fastest time. Comparisons between OC-affected and unaffected horses were made for the entire population and within gaits. A smaller related population (n = 94) had these performance measures evaluated for their 2-5-year-old racing seasons. RESULTS: Osteochondrosis status was associated with few performance measures. Trotters were at higher risk for lesions of the medial malleolus but lower risk for lesions of the distal intermediate ridge of the tibia than were pacers. Horses with bilateral OC lesions and lateral trochlear ridge (LTR) lesions started fewer races at 2 years of age than those with unilateral lesions or without LTR lesions. CONCLUSIONS: Osteochondrosis seemed to have minimal effect on racing performance in this cohort, although horses with bilateral and LTR lesions started fewer races at 2 years. There was evidence for different distribution of OC lesions among pacers and trotters, which should be explored further. Standardbreds undergoing early removal of tarsal OC lesions can be expected to perform equivalently to their unaffected counterparts.

Effect of dental correction on feed digestibility in horses.

To test the hypothesis that routine dental correction (removal only of sharp hooks and points from molars and premolars) would improve digestion of a hay/grain ration whereas performance 'floats' (rounding and smoothing of the dental arcades) would adversely affect digestion, 8 mature horses free from dental correction for over a year were used. Five-day digestion trials were conducted before and 2 and 4 weeks after correction in all horses. Although all horses had sharp points and minor premolar hooks, none had severe dental abnormalities. There were no significant differences found in apparent digestion of dry matter, crude protein, neutral detergent fibre or acid detergent fibre relative to precorrection data or controls (uncorrected horses on same digestion trial). Apparent digestibility of crude protein and fibre, however, was reduced if the occlusal angle of premolar 307 was greater than 80 degrees relative to the vertical axis (flattened). It should be recommended that regular dental correction be continued. However, if only small points and hooks are present, correction will not significantly improve digestion. Performance floating does not adversely affect digestion 2-4 weeks after the procedure is performed. Alterations in molar occlusal surface angle may affect digestibility of protein and fibre.

Diurnal variation and age differences in the biochemical markers of bone turnover in horses.

Biochemical markers of bone turnover provide sensitive, rapid, and noninvasive monitoring of bone resorption and formation. Serum concentrations of osteocalcin (OC) reflect rates of bone formation, and urinary concentrations of the pyridinium crosslinks pyridinoline (Pyd) and deoxypyridinoline (Dpd) are specific and sensitive markers of bone resorption. These markers are age-dependent and are used to detect and monitor changes in the rates of bone turnover in a variety of orthopedic diseases in humans and may prove to have similar application in horses. This study examined age differences and diurnal variation in OC, Pyd, and Dpd in eight adult geldings and seven weanling colts. Blood and urine were collected at regular intervals over 24 h. Serum OC and cortisol, and urinary Pyd and Dpd were analyzed. Mean 24-h concentrations of cortisol and all three markers were higher (P<.003) in weanlings than adults. Significant 24-h variation was observed in adult gelding OC, Pyd, and Dpd concentrations (P< .02). Adult OC concentrations were highest between 2400 and 0900; Pyd and Dpd peaked between 0200 and 0800. Similar patterns of bone turnover were observed in weanling values, but they were not significant (P>.17) owing to greater variability between individuals. Cortisol secretion varied (P<.001) over 24 h in both adults and weanlings and, thus, did not seem to be responsible for greater variability in markers of bone turnover between weanlings. These data demonstrate that diurnal rhythms exist for serum OC and urinary Pyd and Dpd in adult horses, as reported in humans, and that sample timing is an important consideration in future equine studies using these markers.

Expression of cell cycle proteins in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced mouse lung tumors.

Cyclin D1 dysregulation and differential inactivation of p16INK4a and Rb have been observed in human lung cancer. In chemically induced mouse lung tumors, the p16INK4a gene is a target of inactivation, and Rb is reduced at the mRNA level (Northern blot) although similar at the protein level (Western blot) when compared to normal lung tissues. The expression of cyclin D1, cdk4, p16INK4a, and Rb protein was examined by immunohistochemistry in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced mouse lung tumors. Immunohistochemical staining revealed exclusive nuclear staining of both cyclin D1 and cdk4 that was light to moderate in normal mouse lung tissues, but intense in lung adenomas and adenocarcinomas. Western blot analysis confirmed the increased expression of cyclin D1 and cdk4 in lung tumors compared to normal lung. Immunohistochemical analyses of lung tumors showed focal areas which lacked p16INK4a staining. Expression of p16INK4a, as determined by RT-PCR, was variable in lung tumors. Mutations in p16INK4a were not found by SSCP analysis. Immunohistochemical analyses of normal lung tissues showed intense staining for Rb protein in alveolar epithelial cells and in other lung cell types; however, in the lung tumors the staining intensity was reduced and the distribution was altered. Expression of Rb was detected in normal lung tissues but was barely detectable by Northern blot hybridization in lung tumors. Western blot analysis indicated the presence of both hypophosphorylated and hyperphosphorylated Rb protein in lung tumors and in normal lung tissues. These results suggest that alterations in the cell cycle proteins, cyclin D1, cdk4, p16INK4a, and Rb, may play a role in the acquisition of autonomous growth by adenomas. Furthermore, they demonstrate the importance of immunohistochemical studies to examine expression in tissues that contain multiple cell types, such as the lung, and in tumors that by nature are heterogeneous.

Stereoselective activation of dibenzo[a,l]pyrene and its trans-11,12-dihydrodiol to fjord region 11,12-diol 13,14-epoxides in a human mammary carcinoma MCF-7 cell-mediated V79 cell mutation assay.

Dibenzo[a,l]pyrene (DB[a,l]P) represents the most potent carcinogenic polycyclic aromatic hydrocarbon (PAH) yet discovered. Like other PAHs, DB[a,l]P requires metabolic activation to exert its mutagenic and/or carcinogenic activity. In the human mammary carcinoma cell line MCF-7, DB[a,l]P is stereoselectively metabolized to the (-)-anti- and (+)-syn-DB[a,l]P-11,12-diol 13,14-epoxides (DB[a,l]PDE) which both bind extensively to deoxyadenosine residues in DNA. To further characterize the underlying mechanism of its strong carcinogenicity, the relationship between DNA binding and mutagenicity of DB[a,l]P was determined. Racemic DB[a,l]P-11,12-dihydrodiol and the two individual (+)- and (-)-enantiomers, the metabolic precursors of the stereoisomeric fjord region dihydrodiol epoxides, were also investigated. Induction of mutations at the HPRT locus was measured in a MCF-7 cell-mediated Chinese hamster V79 cell mutation assay. The parent hydrocarbon, (+/-)-DB[a,l]P-11,12-dihydrodiol, and (-)-DB[a,l]P-11,12-dihydrodiol were highly mutagenic under the assay conditions. In contrast, (+)-DB[a,l]P-(11S,12S)-dihydrodiol was not mutagenic using MCF-7 cells as the metabolic activating system. Analysis of DNA adducts in the same experiments revealed that MCF-7 cells treated with (-)-DB[a,l]P-11,12-dihydrodiol formed exclusively (-)-anti-DB[a,l]-PDE adducts whereas cells treated with (+)-DB[a,l]P-11,12-dihydrodiol did not contain detectable levels of DNA adducts. These results suggest that specific cytochrome P450 enzymes may have high stereoselectivity for activation of the two DB[a,l]P-11,12-dihydrodiol enantiomers, and this may play an important role in the metabolic activation of the strong carcinogen DB[a,l]P in human cells.

Stereoselective activation of dibenzo[a,l]pyrene to (-)-anti (11R,12S,13S,14R)- and (+)-syn(11S,12R,13S,14R)-11,12-diol-13,14-epoxides which bind extensively to deoxyadenosine residues of DNA in the human mammary carcinoma cell line MCF-7.

Dibenzo[a,l]pyrene (DB[a,l]P) is an environmental contaminant and a very potent carcinogen. DB[a,l]P exceeds the carcinogenic potency of both benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene in rodent bioassays. Previous studies demonstrated that DB[a,l]P is metabolized to DB[a,l]P-11,12-diol-13,14-epoxide (DB[a,l]PDE) in the human mammary carcinoma cell line MCF-7. In the present study the major DNA adducts formed in DB[a,l]P-treated MCF-7 cells have been identified through the use of 33P-postlabeling. TLC and HPLC. DB[a,l]P is metabolically activated in MCF-7 cells to form large amounts of three major DNA adducts and smaller amounts of three other adducts. The three major DNA adducts are with deoxyadenosine: two are formed by reaction of (+)-syn-DB[a,l]PDE (11S,12R,13S,14R), the third by reaction of (-)-anti-DB[a,l]PDE (11R,12S,13S,14R). The results demonstrate that DB[a,l] is stereoselectively metabolized in MCF-7 cells to form one enantiomer of each diol epoxide diastereomer; (+)-syn-DB[a,l]PDE and (-)-anti-DB[a,l]PDE. The high extent of binding of these diol epoxides to deoxyadenosine in DNA of MCF-7 cells may help to explain the very high carcinogenic potency of DB[a,l]P and suggests that DB[a,l]P could also pose a carcinogenic threat to humans.

Effects of shortening the steeplechase phase (phase B) of a 3-day-event.

Thirty-four horses competing in the Endurance Test of a 3-day-event were divided into 3 groups: horses in Group 1 (n = 15) competing in a 3.5 min steeplechase phase; horses in Group 2 (n = 13) in a 3 min steeplechase phase (Phase B) and horses in Group 3 (n = 6) in a 2.5 min steeplechase phase. The shortening of Phase B was associated with a lengthening of Phase C so that the total distance of the event for all horses was 14,940 m. Bodyweight (BW) was measured and total body water (TBW) and water loss estimated. Blood samples were collected from the horses prior to the Endurance Test, at the end of Phase B, the 4 km marker on Phase C (C4K), the end of Phase C, and 20 min after the completion of Phase D for measurement of packed cell volume (PCV), total plasma protein [TPP], lactate, ionised calcium, pH, sodium, potassium, chloride, total calcium and glucose concentrations, and aspartate aminotransferase, creatine kinase and lactate dehydrogenase activities. Mean +/- s.d. ambient environmental temperature during the Endurance Test was 25.3 +/- 1 degrees C (range 20.3 degrees C-29.7 degrees C). Mean relative humidity was 43.8 +/- 2.4% (range 39%-48.6%) and the average 'comfort index' (CI) was 121. There were no significant differences between the groups competing in the Endurance Test, despite the shorter Phase B. However, there were significant decreases in BW, TBW, net exchangeable cations, chloride, ionised calcium, and pH. The sodium and total calcium concentrations remained at near pre-event values. The PCV, TPP, lactate, potassium, glucose, aspartate aminotransferase, and lactate dehydrogenase activity increased during the Endurance Test, when compared to pre-event values. Horses competing in this competition experienced significant fluid and electrolyte losses, reduced glomerular filtration, increased glycogenolysis and had significant leakage of enzymes from working muscles during competition. These changes could not be reduced by shortening Phase B and lengthening Phase C.

Weight, water, and cation losses in horses competing in a three-day event.

Body weight of 48 horses competing in a 3-day event was measured the day before the event (baseline), following the dressage phase of the event (day 1), after the endurance phases of the event (day 2), and 18 to 24 hours after the endurance phases (day 3). Plasma sodium and potassium concentrations were measured the evening before, immediately after, and 10 minutes after the endurance phases. Total body water, water loss, and net exchangeable cation loss were then calculated. Body weight and total body water were significantly decreased, compared with baseline values, at all times during the event, and significant water loss was detected. The largest changes were recorded after the endurance phases of the event. Water deficits were still detected 18 to 24 hours after the endurance phases of the event. Mean plasma sodium concentration was significantly increased immediately after the endurance phases of the event, compared with concentration measured the evening before, and remained increased after the 10-minute recovery period, presumably because of dehydration. Mean plasma potassium concentration was significantly increased immediately after the endurance phases of the event, compared with concentration measured the evening before, but was not increased after the 10-minute recovery period.

The potent carcinogen dibenzo[a,l]pyrene is metabolically activated to fjord-region 11,12-diol 13,14-epoxides in human mammary carcinoma MCF-7 cell cultures.

Dibenzo[a,l]pyrene (DB[a,l]P), an environmental hydrocarbon and very potent carcinogen in rodent bioassays, could be activated to DNA-binding intermediates in cells through formation of three different regioisomeric bay- or fjord-region diol-epoxides or other more highly oxidized metabolites. The mechanism of metabolic activation of DB[a,l]P in the human mammary carcinoma cell line MCF-7 was elucidated by analyzing the DB[a,l]P-DNA adducts formed by [35S]phosphorothioate postlabeling, immobilized boronate chromatography, and high-performance liquid chromatography. Six DB[a,l]P-DNA adducts were detected. Comparison with those formed in cells by DB[a,l]P-11,12-diol and by reaction of DNA with syn- and anti-(benzylic hydroxyl and epoxide oxygen cis and trans, respectively) DB[a,l]P-11,12-diol-13,14-epoxide (DB[a,l]PDE) demonstrated that all DB[a,l]P-DNA adducts in MCF-7 cells were formed by these diol-epoxide isomers. Cellular DNA contained large amounts of two syn- and one anti-DB[a,l]PDE-DNA adducts and small amounts of one syn- and two anti-DB[a,l]PDE-DNA adducts. The ability of human cells to activate DB-[a,l]P to its fjord-region 11,12-diol 13,14-epoxides suggests that environmental exposure to DB[a,l]P could pose a risk for humans.

Serum chemistry and lipid profiles in neonatal beagle puppies fed homemade milk replacer formulas.

Milk replacer formulas based on cow's milk and egg yolks are frequently recommended for use in neonatal puppies. These formulas are lower in protein, kilocalories, calcium, and phosphorus than bitch's milk. In addition, the cholesterol content is greater than bitch's milk. The effect of feeding these formulas on serum chemistry profiles, lipid profiles, and alkaline phosphatase isoenzyme profiles of 5-week-old beagle puppies was studied. Three groups of beagle puppies were fed bitch's milk (control) (n = 18), a homemade milk-egg-oil formula (Formula 1) (n = 18), or a homemade milk-egg-oil formula supplemented with additional calcium and phosphorous (Formula 2) (n = 18). Concentrations of serum urea nitrogen, albumin, and total CO2 were lower (P < 0.05), and concentrations of serum phosphorus, globulins, sodium, chloride, and cholesterol were higher (P < 0.05) in formula-fed puppies than bitch-fed puppies. Serum potassium concentration was lower in the puppies fed Formula 1 than in the control puppies (P < 0.05), and serum potassium concentration in the puppies fed Formula 2 was not significantly different from that in puppies fed Formula 1 or the control puppies. Total triglyceride (TG) and high density lipoprotein2 cholesterol (HDL2) concentrations were similar in all three groups of puppies but the combined high density lipoprotein1 (HDL1) plus low density lipoprotein (LDL) cholesterol fraction was higher (P < 0.05) in the formula-fed puppies and accounted for the majority of the increase in cholesterol. There were no differences (P < 0.05) in total serum alkaline phosphatase (ALP) or bone-derived ALP (BALP) concentrations among the groups, however there was a higher (P < 0.05) serum concentration of liver-derived ALP (LALP) in the Formula 1-fed puppies. Feeding homemade egg and cow's milk-based puppy replacement formulas is not recommended for long term use.

Clinical nutrition of adult horses.

Horses suffering from trauma, sepsis, and severe burns need 12% to 16% of protein (dry matter basis) in their diet. Since reduced appetite may be a problem, relatively energy dense (greater than 2 Mcal DE/kg) feeds should be offered. In hepatic failure, maintenance protein requirements (8% on a dry matter basis for adult horses) should be met with feeds that are high in short branched-chain amino acids and arginine but low in aromatic amino acids and tryptophan (for example, milo, corn, soybean, or linseed meal) in addition to grass hay. Vitamins A, C, and E should also be supplemented. In cases with renal failure, protein, calcium, and phosphorus should be restricted to maintenance or lower levels. Grass hay and corn are the best feeds for horses with reduced renal function. Do not offer free-choice salt to horses with dependent edema from uncompensated chronic heart failure. Following gastrointestinal resection, legume hay and grain mixtures are the feeds of choice. Horses with diarrhea should not be deprived or oral or enteral alimentation for prolonged periods of time. Liquid formulas may be used if bulk or gastrointestinal motility are a problem. Apple cider vinegar and a high grain diet may reduce the incidence of enteroliths in horses prone to this problem. Pelleted feeds will reduce fecal volume and produce softer feces for horses that have had rectovaginal lacerations or surgery. Horses with small intestinal dysfunction or resection should be offered low residue diets initially, but long-term maintenance requires diets that promote large intestinal digestion (alfalfa hay, vegetable oil, restricted grain). Geriatric horses (greater than 20 years old need diets similar to those recommended for horses 6 to 18 months old.

Effects of transportation on early embryonic death in mares.

Incidence of early embryonic death (EED) and associated changes in serum cortisol, progesterone and plasma ascorbic acid (AA) in transported mares were investigated. Mares were transported for 472 km (9 h) during either d 16 to 22 (T-3 wk, n = 15) or d 32 to 38 (T-5 wk, n = 15) of gestation. Blood samples were drawn from control, nontransported mares (NT-3 wk, NT-5 wk, n = 24) and transported mares pre-trip, midtrip, and at 0, 12, 24, 48 and 72 h post-transport and daily for the next 2 wk. Incidence of EED between transported and nontransported mares was not different (P greater than .05). Serum cortisol in all transported mares increased (P less than .05) relative to pre-trip values at midtrip and 0 h post-transport. Relative to NT mares, serum cortisol was higher (P less than .05) at midtrip in T-3 wk mares and 0 h post-transport in T-5 wk mares. Serum progesterone in all T mares increased (P less than .05) at midtrip relative to pre-trip values and was higher (P less than .05) in T-3 wk mares than in NT-3 wk mares at midtrip and 0 h post-transport. Post-transport decreases (P less than .05) in concentrations of progesterone were observed in mares that aborted. Plasma AA in transported mares increased (P less than .05) at midtrip in T-5 wk mares and decreased (P less than .05) relative to pre-trip values at 24 and 48 h post-transport (T-3 wk and T-5 wk mares, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of transportation on the estrous cycle and concentrations of hormones in mares.

Effect of transportation on estrous behavior, duration of the estrous cycle, ovulation, pregnancy rates and concentrations of serum cortisol, plasma ascorbic acid (AA), LH, estradiol and progesterone in mares was investigated. Fifteen mares were transported for 792 km (12 h) during the preovulatory stage of estrus. Transported mares were bled immediately before transport (baseline), at midtrip and 0, 12, 24, 48 and 72 h post-transport and twice daily from d 1 before transport to d 1 (estrogen) or 3 (LH) post-ovulation. Blood samples also were taken for progesterone on d 0, 2, 6, 10, 15, 16, 17, 18, 19 and 20 post-ovulation. Nontransported control mares (n = 15) were bled on the same schedule as transported mares. There was no difference (P greater than .05) in number of mares ovulating, estrous behavior, duration of the estrous cycle or pregnancy rate between groups. Cortisol in transported mares increased to concentrations greater (P less than .05) than those in control mares at midtrip and 0 h post-transport. Concentrations of AA in transported mares also increased (P less than .05) at midtrip, then decreased (P less than .05) below baseline at 24 h post-transport. Concentrations of LH and estradiol increased (P less than .05) above baseline throughout the blood-sampling period. Increases apparently were due to preovulatory surges of these hormones. Increase in LH concentrations in transported mares, however, was greater (P less than .05) than that in control mares at 0 h post-transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Large intestinal capacity, retention times, and turnover rates of particulate ingesta associated with extensive large-colon resection in horses.

Fecal excretion of a particulate marker, ytterbium (Yb), was evaluated in 9 horses before surgery and 3 weeks, 3 months, and 6 months (4 trials) after sham-operation (group 1; n = 3) or extensive large colon resection (group 2; n = 6). Fecal excretion curves of total Yb excretion, loge Yb excretion, % Yb excretion, loge % Yb excretion, and cumulative % Yb excretion were evaluated, and kinetic analysis was performed on the loge Yb excretion curves to detect mixing pools and to calculate the fractional rate of particulate passage, turnover rate, and pool size. Calculations were performed to determined transit time, mean overall retention time, adjusted mean retention time, peak time, and disappearance time. Values were statistically analyzed to determine differences between groups and among trials (P less than 0.05). Group-2 horses had significantly shorter transit, peak, and mean overall retention times, compared with preoperative values and with values for group-1 horses. Two mixing pools were identified: a slower emptying pool of 5.7% hour-1 (k1) and a faster emptying pool of 12.3% hour-1 (k2). The rate of passage from the first pool (k1) was not altered by colon resection, and was interpreted as being most influenced by the cecum. In further support of this interpretation, the capacity of the k1 pool approximated the capacity of the cecum (17 L). The capacity of the k1 pool significantly expanded by 6 months in the resected horses. the rate of passage from the second pool (k2) significantly increased initially after colon resection (3 weeks and 3 months), but returned to preoperative values by 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Fiber digestion and voluntary intake in horses after adaptation to extensive large-colon resection.

Each of 3 digestion trials (3 forage diets) was performed on 2 groups of horses 6 to 12 months after sham operation (group 1; n = 3) or large-colon resection (group 2; n = 5). Diets were alfalfa pellets, alfalfa hay, and grass hay. Feed and fecal analyses were performed to determine apparent digestion of dry matter, organic matter, and crude protein and true digestion of dry matter, organic matter, crude protein, total plant cell wall, hemicellulose, cellulose, and lignin. Additional fecal and metabolic variables determined were percentage of fecal water, total fecal water, metabolic organic matter, metabolic crude protein, and metabolic nitrogen. Large-colon resection decreased the digestion of plant cell wall because of decreased digestion of cellulose in alfalfa pellet and grass hay diets, but not in alfalfa hay diet. Insufficient digestible energy and/or protein from grass hay was obtained by horses with colon resection, and significant (P less than 0.05) weight loss was observed. Voluntary intake was significantly (P less than 0.05) increased by horses with colon resection. Of the diets studied, alfalfa hay was the most appropriate forage diet, compared with average grass hay and alfalfa pellet diet, for horses after extensive large-colon resection. Additionally, horses with colon resection may have higher levels of feed intake than do horses without colon resection.

Differences in diagnostic test results and hematologic data between aged and young horses.

Hematologic data and results of diagnostic tests were compared between aged (greater than or equal to 20 years old) and young (less than or equal to 5 years old) horses to identify hematologic and metabolic changes associated with aging. Initial data were obtained from 8 aged and 6 young mares (group 1). Similar data were collected from a second group of aged (3 mares and 3 geldings) and young (1 mare and 5 geldings) horses (group 2). Dexamethasone suppression tests (DST) and necropsies were performed on 6 additional mares and mare 8 from group 1 (group 3). Complete blood counts and serum biochemical profiles were compared between young and aged horses of groups 1 and 2. Mean corpuscular volume was higher (P less than 0.05) in aged horses. Oral glucose tolerance and insulin response to orally administered glucose were measured in 13 aged horses (groups 1 and 2) and 6 young mares of group 1. In group 1, plasma ascorbic acid values were lower (P less than 0.05) in aged horses than in young horses maintained under the same conditions and feeding regimens. An apparent age-related hyperinsulinemic response to orally administered glucose identified in group-1 mares was probably a result of a high occurrence of subclinical hypophyseal and/or thyroid adenomas. Of 13 aged horses necropsied (groups 2 and 3), 10 had hypophyseal and/or thyroid adenomas that, in group 2, were consistently associated (P less than 0.05) with hyperinsulinemic responses to orally administered glucose. All horses in groups 2 and 3 were given a 24-hour DST.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutritional management of horses competing in 160 km races.

A survey was taken of dietary management and training schedules of 54 horses competing in two 160 km endurance races. A total of 52 owners, representing 54 horses, responded to a questionnaire distributed prior to the races. Diet and training schedules were compared between horses that successfully completed the races and those that were eliminated for metabolic reasons. Horses that completed the races were 11.5 +/- 4 years old, weighed 429 +/- 4.5 kg and were ridden 61 +/- 32 km a week when training. Feed intake was reported as "free choice hay or pasture" by 34 of the respondents. Dry matter (DM) hay intake in these horses was estimated to be 3% body weight (kg) minus the kg DM of grain fed, assuming a maximum intake. They were fed 12.3 +/- 2.3 kg feed per day consisting of 10 +/- 2.3 kg hay and 2.3 +/- 1.4 kg of grain. Most had free access to salt and were fed 1 +/- 1 vitamin/mineral supplement per day. Based on Nutritional Research Council (NRC) values for nutrient content of the reported feeds, diets contained 60 +/- 5% total digestible nutrients (TDN), 12 +/- 2% crude protein, 27 +/- 4% crude fiber, 0.72 +/- 0.4% calcium and 0.29 +/- 0.06% phosphorus. Maximum caloric intake was estimated to be 31.9 Mcal per day. Ratios of nutrients fed per kilometer trained were: kg TDN/km = .14 +/- .08, kg crude protein/km trained = .03 +/- .02, and kg crude fiber/km trained = .06 +/- .04.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental large colon resection at the cecocolic ligament in the horse.

Ten normal horses had approximately 95% of the length of the large colon resected with a side-to-side anastomosis between right ventral and right dorsal colon performed with surgical stapling equipment. Four horses died shortly after surgery of colitis (1 horse) or failure of the TA 90 transection staple line (3 horses). Another horse died 4 months after surgery from disseminated streptococcal infection but had recovered well from the colon resection. Five horses survived long term (18 months) with no clinical evidence of adverse effects of the resection. Surviving horses had weight loss and soft fecal consistency for 3 to 12 weeks after surgery but returned to preoperative values within 12 months. At a second surgery 1 year later (5 horses) or at necropsy 4 months later (1 horse), fibrous omental adhesions were present over the transection staple line in four horses and over the anastomotic staple line in two horses. Omental adhesions to the everted staple line were moderate but not associated with any clinical sequellae. An incisional hernia was present in one horse. The anastomotic stomata measured between 8 and 9 cm, which was 60% of the size of the original surgically created stomata. Failure of the transection staple line occurred in the first three of five horses in which the procedure was attempted due to improper configuration of the staples or crushing of the tissue between the staples. Experience corrected this complication.

Feeding behavior.

Problems related to feeding behavior in horses fall into three main categories: underconsumption, overconsumption, and abnormal consumption. Anorexia may be caused by a variety of diseases and overcome by removing the underlying causes (pain, fever), and physical or chemical stimulation of appetite. "Hypophagia" may be caused by poor dentition, disease, or stress. Again, removal of the cause or stimulation by physical or chemical means may improve intakes. Acute and chronic overconsumption of feeds are reflections of the normal controls (or lack thereof) of feeding in the horse. The only reliable prevention is to limit access to feeds. Abnormal eating behaviors such as pica or coprophagy are usually caused by a dietary imbalance or boredom. Coprophagey, however, is a normal behavior in young foals. Drinking disorders are rare, the only common one being the avoidance of "strange" water. Masking water at home with specific flavors such as peppermint or vinegar may encourage the horse to drink water from other sources to which the "home" flavor has been added.