Stress and glycemic responses to postprandial interval and feed components in exercising horses

Six Thoroughbred geldings were used in a Latin squaredesign to determine the effects of three feeding regimens and two postprandial intervals on stress parameters during rest, exercise, and recovery. Each horse was randomly assigned to one of six treatments on six sampling days. The three feeding regimens consisted of a fasting regimen in which no feed was offered, or an isoenergetic (4.1 Mcal DE) meal of either corn or alfalfa. One or 4 h after feeding, a standardized exercise test (SET) was imposed on all horses. The SET consisted of three 10-min periods each of saddling, walking to the arena, and warm-up (walking and trotting), followed by three bouts of progressively more intense galloping at heart rates of 130–140 (10 min), 150–160 (10 min), and 170–180 bpm (5 min), respectively. Blood was sampled via jugular catheters from 0630 to 1500, including the 55-min SET. Analysis of variance by repeated measures within either the 1- or 4-h protocol showed no differences between dietary treatments for glucose concentration; differences due to sampling time were shown for concentrations of glucose, lactate, cortisol, α₁-acid glycoproteins (AGP), and the neutrophil to lymphocyte ratio (N:L). In both the 1- and 4-h protocols, glucose concentrations decreased precipitously in cornfed horses at the onset of the SET, but rebounded at the termination of the galloping. Plasma glucose concentrations in fasting and alfalfa-fed horses decreased slightly and then gradually increased throughout the SET. Serum cortisol and plasma lactate concentrations did not differ (P >.05) between dietary treatments, but increased concentrations were detected during the SET in both the 1- and 4-h protocols. The AGP concentration and N:L did not differ (P>.05) due to dietary treatments; however, AGP concentrations marginally increased (P<.10) from prefeeding to early recovery during the 1-h but not the 4-h protocol. The N:L increased (P<.05) in response to exercise; elevated values were detected in early recovery.     

Digestion of soybean meal proteinin the equine small and large intestine at various levels of intake

Four mature pony geldings weighing an average of 134 kg and fitted with ileal cannulas were used in a 4×4 Latin square experiment to determine the digestibility of soybean meal (SBM) protein in different segments of the equine digestive tract at various levels of protein intake. A complete basal corn-based diet was supplemented with SBM to formulate four diets with increasing crude protein. The diets, labeled A (basal), B, C and D, contained 4.9%, 9.5%, 14% and 16.5% crude protein (as fed), and provided nitrogen, per feeding, at approximately 44.8, 84.3, 123.9 and 146.3 mg/kg of body weight, respectively. Chromic oxide was fed to measure ileal flow and fecal excretion. Digestion and absorption of nitrogen was determined from changes in nitrogen: chromium ratios, and true digestion of nitrogen was computed by regression analysis. True total tract digestion of nitrogen was 95.7%. True digestibility of nitrogen in the small intestine over the range of linearity was 72.2%, while true digestibility of nitrogen reaching the large intestine was 89.8%. These data indicate that the protein in SBM was almost completely digested in the equine digestive tract. Furthermore, approximately 75% of the digestible protein was digested prececally when nitrogen intake was less than approximately 125 mg/kg of body weight per feeding.     

Sand colic in a mule: A case report

A 25-year-old mule was showing signs of colic. Clinical examination revealed acute pain, bilateral abdominal distention, stretching out and standing in this position. Rectal palpation revealed a hardened mass in the ventral region of the pelvic inlet. Surgical intervention was accomplished and faecaliths removed by colotomy. The mule died unexpectedly and postmortem examination revealed sand masses within the right ventral and right dorsal colon which caused obstruction of the intestinal tract in sternal and diaphragmatic flexures, respectively. This appears to be the first report of sand colic in a mule in Iran.     

Clinical observations on changes in concentrations of hormones in plasma of two stallions with thermally-induced testicular degeneration

To investigate effects of thermally-induced testicular degeneration on hormonal and seminal parameters in stallions, the scrotum was insulated for 36 hours in two mature (5-year-old mixed breed and 11-year-old Throughbred) stallions. Semen was collected daily for 10 days (DSO) prior to, and at intervals after, scrotal insulation. When DSO determinations were not being made, semen was collected 3 times weekly. Jugular blood samples were collected at 15-minute intervals for 6 hours from each stallion prior to, and at intervals after, scrotal insulation. A mouse interstitial cell testosterone assay was modified to quantify biologic activity of equine luteinizing hormone (BLH) in plasma samples. Immunoactive luteinizing hormone (ILH) and testosterone (T) concentrations were determined in plasma samples by routine RIA procedures. Percentages of progressively motile and morphologically normal spermatozoa began to decrease by 1 to 2 weeks postinsulation, reached nadir values at 3 to 3-1/2 weeks postinsulation, and returned to preinsulation values by 7 weeks postinsulation. Total number of spermatozoa and total number of progressively motile, morphologically normal spermatozoa in ejaculates at DSO returned to normal by 8 weeks postinsulation in stallion 2 and 12 weeks postinsulation in stallion 1. Concentrations of BLH and ILH increased, and while T concentrations decreased, immediately postinsulation. The increase in ILH concentrations was greater than the increase in BLH concentrations, resulting in a decrease in the BLH:ILH (B:I) ratio. Following the peak in LH secretion immediately postinsulation, LH concentrations gradually decreased while T concentrations increased. The B:I ratio was elevated from 1 to 13 weeks postinsulation compared to immediately postinsulation. In addition to changes in spermatozoal quality in ejaculates, stallion response to scrotal insulation included increased secretion of luteinizing hormone and impaired Leydig cell function (as determined by reduced testosterone concentration in circulating plasma). The proportion of biologically active LH secreted in response to thermal testicular injury increased during the recovery phase.     

The significance of small vs large intestinal digestion of cereal grain and oilseed protein in the equine

Mature ponies fitted with permanent ileal cannulas were used in two 3×3 Latin square experiments to quantify prececal, postileal and total tract digestion of N. In trial 1, corn, oats and sorghum were each fed with coastal Bermuda grass hay in 75:25 ratios. Apparent prececal digestibilities were similar (P>.05) and averaged 46.6%. By-difference procedures were employed to calculate digestibility of the cereal grain N only and apparent prececal N digestibility averaged 57.1%. In trial 2, a basal corn and hay diet was supplemented with cottonseed meal and soybean meal. Apparent total tract N digestibilities were similar (P>.05) across treatments, and prececal digestibility averaged 45.6%. By-difference calculations were used to determine digestibility of SBM and CSM N alone. Apparent prececal digestibility of SBM was 52.5% and was lower (P<.05) than 81.2% for CSM. It is possible that inadequate or excessive heat treatment of SBM affected enzymatic digestion. True digestibility of total rations fed in trial 2 was estimated by linear regression of nitrogen digested on nitrogen intake or N presented to the large intestine. True N digestibility of diets containing SBM and CSM was 54.7% and 69.4%, respectively.     

Thromboelastography: a tool for measuring hypercoagulability, hypocoagulability, and fibrinolysis

Objective: To describe the technique of thromboelastography (TEG) and review the applications of this coagulation test in humans and small animals. Data sources: Data sources included scientific reviews and original research publications. Human data synthesis: TEG in humans has been used for documentation of hypercoagulable and hypocoagulable states and has been shown to be beneficial in patient management. Veterinary data synthesis: Clinical evaluation of TEG in veterinary medicine is limited; however, recent reports have documented evidence of hypercoagulability in dogs with parvovirus and protein‐losing nephropathy. Additionally, many of the research models may be relevant to veterinary patients. Conclusions: TEG provides information about coagulation that is not available through routine coagulation tests. The application of TEG monitoring to veterinary patients shows promise; however, prospective clinical studies are needed.     

Hypocalcemia in a critically ill patient

Objective: To present a case of clinical hypocalcemia in a critically ill septic dog. Case summary: A 12‐year old, female spayed English sheepdog presented in septic shock 5 days following hemilaminectomy surgery. Streptococcus canis was cultured from the incision site. Seven days after surgery, muscle tremors were noted and a subsequent low serum ionized calcium level was measured and treated. Intensive monitoring, fluid therapy, and antibiotic treatment were continued because of the sepsis and hypocalcemia, but the dog was euthanized 2 weeks after surgery. New or unique information provided: Low serum ionized calcium levels are a common finding in critically ill human patients, especially in cases of sepsis, pancreatitis, and rhabdomyolysis. In veterinary patients, sepsis or streptococcal infections are not commonly thought of as a contributing factor for hypocalcemia. Potential mechanisms of low serum ionized calcium levels in critically ill patients include intracellular accumulation of calcium ions, altered sensitivity and function of the parathyroid gland, alterations in Vitamin D levels or activity, renal loss of calcium, and severe hypomagnesemia. Pro‐inflammatory cytokines and calcitonin have also been proposed to contribute to low ionized calcium in the critically ill. Many veterinarians rely on total calcium levels instead of serum ionized calcium levels to assess critical patients and may be missing the development of hypocalcemia. Serum ionized calcium levels are recommended over total calcium levels to evaluate critically ill veterinary patients.     

Assessment of changes in blood volume in response to resuscitative fluid administration in dogs

Objective: To determine the continuous changes in blood volume in response to fluid administration using an in‐line hematocrit monitor. Design: Prospective study. Setting: Research laboratory. Animals: Four healthy dogs. Interventions: Each dog received intravenous boluses of 80 mL/kg of 0.9% saline (S), 4 mL/kg of 7.5% saline (HS), 20 mL/kg of dextran 70 (D), 20 mL/kg of hetastarch (HES), or no fluids (control, C) on separate occasions. Fluids were administered at 150 mL/min in the S, D, and HES groups, and at 1 mL/kg/min in the HS group. Measurements and main results: Blood volume changes were measured every 20 seconds for 240 minutes using an in‐line hematocrit monitor. There was a rapid rise in blood volume during all infusions. Immediately after the administration of crystalloid fluids, the rapid rise in blood volume ceased. Subsequently, there was a steep decline in blood volume for 10 minutes, and a slower decline thereafter. In contrast, the rise in blood volume continued for at least 10 minutes after the infusion of the colloids was complete, and a plateau was observed for the remainder of the experiment. The blood volume effect, as measured by area under the curve, was significantly greater in the saline group than the other groups during the infusion time and for the 0–240 minutes time period. The areas under the curve for the two colloid solutions were not significantly different from each other during any time periods. The percent increase in blood volume immediately following the infusions was 76.4±10.0 in the S group, 17.1±3.2 in the HS group, 23.0±10.5 in the D group, and 27.2±6.4 in the HES group. At 30 minutes from the start of the infusion, the mean percent increases in blood volumes were 35.2±9.3 in the S group, 12.3±0.9 in the HS group, 35.9±7.3 in the D group, and 36.8±6.5 in the HES group. At 240 h post‐infusion, the mean percent increases in blood volume were 18.0±9.7 in the S group, 2.9±6.1 in the HS group, 25.6±16.1 in the D group, and 26.6±8.6 in the HES group. The C group had a mean percent change in blood volume of ?3.7±3.4 at the end of the experiment. Conclusions: This study indicates that the rapid administration of saline at clinically relevant doses leads to the largest immediate increase in blood volume, although this change is transient because of rapid redistribution of the fluid. Despite a brief increase in blood volume that was almost 3 times the volume administered, hypertonic saline led to the smallest increase in blood volume post‐infusion. The synthetic colloid solutions increased the blood volume by an amount greater than that infused and the effect was sustained for a longer period of time than seen following crystalloid administration, but the maximum increase in blood volume was significantly less than saline. The measurement of continuous changes in blood volume, using an in‐line hematocrit monitor, was a useful means of assessing the dynamic effects of fluid administration in dogs in a research setting.     

EXCRETORY UROGRAPHY BY INTRAOSSEOUS INJECTION OF CONTRAST MEDIA IN A RABBIT MODEL

There are many indications for an intravenous excretory urogram. However, where intravenous access is not available, the intraosseous route to the circulation may be an alternative. We found that safe and diagnostic excretory urograms could be obtained in rabbits following the injection of different contrast media via the intraosseous route. In fact, these excretory urograms were indistinguishable from ones obtained by the conventional intravenous route. While the rabbits did not develop any abnormal clinical signs following the procedure, there were postmortem histologic lesions of osteochondrosis in 5 of 22 (22.7%) tibias receiving an intraosseous needle, but in none of the 14 tibias that did not receive an intraosseous needle. Further, the use of diatrizoate was associated with the development of osteochondrosis while the use of iopamidol was not.