Validation of the Lactate Plus Lactate Meter in the Horse and Its Use in a Conditioning Program

The equine industry has a need for a convenient, rapid, and reliable method of measuring blood lactate concentrations ([LA]). We hypothesized that the handheld Lactate Plus lactate meter (LPlus), developed and tested for use in humans, would provide dependable results when used in horses undergoing an exercise conditioning program and that horse's fitness would improve following individualized conditioning based on each horse's velocity at which [LA] = 4 mmol/L (V_LA4) was reached. Five adult horses underwent a 4-week training program that consisted of 3 exercise bouts/wk. Horses were subjected to an incremental step standardized exercise test (SET) before starting (SET-1) and after the completion of the program (SET-2). Blood samples were collected before each increase in speed until [LA] reached ≥4 mmol/L, and then the SET was terminated. The [LA] sample range in our study was 0–8 mmol/L. Blood was analyzed at the time of collection using a calibrated LPlus, and plasma was collected for [LA] determination using the lactate dehydrogenase–based enzymatic colorimetric method. Although the LPlus tended to significantly underestimate [LA] by 0.39 mmol/L (P < .001), the LPlus proved to be a dependable device for use in horses based on good correlation with the biochemical analysis (r = 0.978) and Bland–Altman limits of agreement and 95% confidence intervals. All horses showed an increase in V_LA4 from SET-1 to SET-2, consistent with improved fitness following our 3 exercise bout/wk training protocol. The LPlus can reliably be used in horses to determine [LA] ranging from 0–8 mmol/L. When determining serial [LA], analytical techniques should not be used interchangeably.     

Adaptation to a Fat-Supplemented Diet by Cutting Horses

In a crossover experiment, eight mature Quarter Horses were exercised by simulated cutting-horse training and fed either a control concentrate (C) or a 10% fat-supplemented concentrate (F) with Bermuda grass hay in a 60:40 ratio. The experiment consisted of two 28-day experimental periods with a 28-day standardization period between treatments. Digestion trials and standardized exercise tests (SET) were conducted every 7 days during experimental periods. Dietary fat had no detrimental effect on digestion of diet constituents, and all digestion coefficients were within expected ranges. Likewise, there was no significant difference in heart rates between treatments or SET days. Plasma lactic acid concentrations did not differ (P > .05) between treatments, however, there was a decline (P < .05) with advancing SET day. When horses were fed fat, there was an increase (P < .05) in muscle glycogen storage from days 0 to 28, but there was no increase (P > .05) in muscle glycogen over time when horses were fed C. On days 7, 14, and 28, muscle glycogen utilization increased (P < .05) from day 0 when horses were fed fat but not C. Pre-exercise data were normalized such that day 0 values equaled zero, due to higher (P < .05) glycogen concentrations for C than F on day 0. Subsequently, muscle glycogen concentrations on day 28 before exercise were higher (P < .05) when horses were fed F than C. The results of this study indicate that Quarter Horses in simulated cutting-horse training can adapt to digestion of a fat-supplemented diet by day 14. However, it may take up to 28 days of adaptation to a fat-supplemented diet to observe increases in glycogen storage and use.     

Relationship of bispectral index to minimum alveolar concentration multiples of sevoflurane in cats

OBJECTIVE: To determine the relationship between bispectral index (BIS) and minimum alveolar concentration (MAC) multiples of sevoflurane in cats. ANIMALS: 8 domestic cats. PROCEDURE: Each cat was anesthetized twice with sevoflurane. First, the MAC of sevoflurane for each cat was determined by use of the tail clamp method. Second, cats were anesthetized with sevoflurane at each of 5 MAC multiples administered in random order. Ventilation was controlled, and after a 15-minute equilibration period at each MAC multiple of sevoflurane, BIS data were collected for 5 minutes and the median value of BIS calculated. RESULTS: The mean (+/- SD) MAC of sevoflurane was 3.3 +/- 0.2%. The BIS values at 0.5 MAC could not be recorded as a result of spontaneous movement in all 8 cats. The BIS values at 2.0 MAC were confounded by burst suppression in all 8 cats. Over the range of 0.8 to 1.5 MAC, BIS values decreased significantly with increasing end-tidal sevoflurane concentrations. Mean (+/- SD) BIS measurements were 30 +/- 3, 21 +/- 3, and 5 +/- 2 at 0.8, 1.0, and 1.5 MAC, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Values of BIS are inversely and linearly related to end-tidal sevoflurane concentrations in anesthetized cats, and BIS may be a useful predictor of CNS depression in this species. The consistently low BIS values recorded in this study suggest that clinical BIS end points used to titrate anesthetic agents in humans may not be applicable to cats.     

Forage mineral concentration, animal performance, and mineral status of heifers grazing cereal pastures fertilized with sulfur.

Thirty yearling Santa Gertrudis-sired heifers (average initial weight 238 kg) were continuously grazed (five heifers/pasture) on six 2-ha oat-wheat small grain pastures for 112 d to determine the effect of fertilization of pastures with urea (U) vs ammonium sulfate (AS) on mineral status and performance of heifers. Pastures were fertilized with either U, at 200 kg/ha, or AS, at 438 kg/ha, to provide 92 kg of N/ha in November 1987 and March 1988. Ammonium sulfate provided 107 kg of S/ha. Forage samples were collected during each month. Heifers were initially weighed following an overnight fast and at the end of four consecutive 28-d intervals (Periods 1 to 4). Serum and ruminal fluid were collected on d 56 and 112. Pastures fertilized with AS had a greater (P less than .10) in vitro dry matter disappearance during Periods 2 and 3. Ammonium sulfate-fertilized pastures had greater than (P less than .05) S concentrations from January 29 through termination of the trial. There were no differences in ADG (P less than .28) or gain/ha (GPH; P less than .43) over 112 d; however, heifer ADG was greater (P less than .08) in Period 3 and tended to be greater (P less than .16) in Period 2 for those animals grazing U-fertilized pastures. Pastures receiving AS produced less (P less than .04) GPH during Period 2. Ammonium sulfate fertilization in this trial had no effect on forage K, Ca, P, Mg, Cu, or Mo mineral concentrations or on serum mineral and ruminal VFA concentrations, but it did result in an increase in IVDMD and a trend for decreased ADG apparently associated with a decrease in forage intake.     

Effect of transport stress on respiratory disease, serum antioxidant status, and serum concentrations of lipid peroxidation biomarkers in beef cattle

OBJECTIVE: To determine the effect of transportation stress on serum concentrations of oxidative stress biomarkers of calves. ANIMALS: 105 crossbred beef steer calves (mean [+/-SD] body weight, 207 +/- 21.2 kg). PROCEDURE: Calves were assembled at 1 location in Tennessee, and pretransit (day -3) blood samples were collected. Calves were allotted randomly by body weight into 2 groups. Calves were transported 1,930 miles to a feedlot in Texas, and 1 group received tilmicosin phosphate (33 microg/kg, s.c.) upon arrival. Calves were weighed and blood samples collected on the day of arrival (day 1) and on days 15, 22, and 28. Calves were scored daily for signs of bovine respiratory disease (BRD). Serum total antioxidant capacity (TACA) and serum malondialdehyde (MDA) concentrations were determined. RESULTS: Transportation stress significantly decreased mean serum TACA concentrations (from 147 +/- 31.2 U/mL to 133 +/- 20.1 U/mL) and significantly increased serum MDA concentrations (from 10.9 +/- 18.3 microg/mL to 30.2 +/- 50.5 microg/mL). Calves that died had a 43% increase in serum MDA concentration on day 1, compared with calves that lived (42.2 +/- 67.0 microg/mL vs 29.4 +/- 49.4 microg/mL, respectively). Calves that had > or =3 episodes of BRD had 2-fold higher serum MDA concentrations on day 1 than healthy calves. Tilmicosin-treated calves had a 20.8% significantly greater average daily gain and significantly greater serum TACA concentration than nontreated calves on day 28. CONCLUSIONS AND CLINICAL RELEVANCE: Transportation stress increases serum concentrations of oxidative stress biomarkers that are related to episodes of BRD and mortality in calves.     

Effects of dietary monensin and potassium on apparent absorption of magnesium and other macroelements in sheep

Twelve ruminally cannulated lambs (average weight, 31.1 kg) were used to determine the effects of monensin and K on apparent absorption of Mg in lambs. Lambs were assigned randomly to two groups and fed a basal high concentrate diet containing .44% K with or without 20 mg/kg monensin for 19 d of dietary adjustment. During adjustment, lambs were housed by treatment group and given ad libitum access to their diets. Following dietary adjustment, lambs were placed in individual metabolism stalls and fed 450 g of their respective diet twice daily. Within each monensin group, lambs were infused ruminally with 0, 7.6 or 31.6 g K/d (equal amounts at each feeding in 158 ml of distilled-deionized water) during three periods in a 3 X 3 Latin-square arrangement of K treatments. Each period consisted of a 10-d preliminary phase and a 7-d collection phase followed by a 3-d D2O infusion phase to determine water turnover. Addition of monensin to the diet decreased (P less than .05) fecal Mg excretion 15.9%. Apparent absorption and retention of Mg were increased (P less than .05) with the addition of monensin. Increasing K level increased (P less than .05) fecal Mg excretion. Apparent absorption of Mg decreased (P less than .05) from .93 to .80 g/d when either level of K was infused into the rumen. Monensin decreased the acetate:propionate (A:P) ratio. There was a significant interaction between monensin and K level for acetate and propionate (molar %), and A:P ratio. In the presence of higher K concentrations, monensin appears to be more effective in decreasing the A:P ratio.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical Feline Toxoplasmosis

Clinical toxoplasmosis was diagnosed in 15 cats by correlating serologic evidence of infection and clinical signs to either response to therapy or histopathologic demonstration of the organism. Ophthalmic manifestations, primarily involving the anterior segment, were common. Other common physical examination abnormalities included muscle hyperesthesia, fever, and weight loss. Response to therapy was variable, but administration of clindamycin hydrochloride resulted in resolution of all clinical signs not involving the eyes in surviving animals. This drug, alone or in combination with corticosteroids, led to total resolution of clinical signs in four of four cats with active retinochoroiditis and in six of nine cats with anterior uveitis. Four of the 15 cats had concurrent infection with feline immunodeficiency virus (FIV). Feline leukemia virus antigen or antibodies to feline infectious peritonitis virus were not detected.