VTechWorks Repository :: Browsing by Author "Lawrence, Larry A."

Browsing by Author "Lawrence, Larry A."

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Acid-base regulation during sprint exercise in horses fed lecithin
Taylor, Lynn Elizabeth (Virginia Tech, 1995)
The effects of exercise, training, and a supplemental lecithin/corn oil diet on acid-base homeostasis and blood gases in arterial and central venous blood were examined during repeated sprint exercise in horses. Differences between temperature measurement sites for the adjustment of pH and blood gases during exercise was also investigated. The independent variables, strong ion difference (SID), total weak electrolytes ([A_tot]), and pCO₂, had different effects on the dependent variables, [H⁺] and [HCO₃⁻], and these influences changed depending on blood sampling site (arterial or central venous), and exercise intensity. Data supporting the involvement of the chloride shift during repeated sprint exercise in the horse was observed for the first time. Training resulted in increased plasma [Na⁺], [K⁺], [SID], albumin, free fatty acids, and beta~-hydroxybutyrate concentrations, and decreased blood lactate ([Lac⁻]), plasma [Cl⁻], [H⁺], cholesterol, and heart rate during exercise. Horses consuming the corn oil/lecithin supplemented diet had a higher pvCO₂, [HCO₃⁻], [Cl⁻], cholesterol, and glucose, and lower blood [Lac⁻], [H⁺], and triglycerides during exercise. The sprint training and corn oil/lecithin diet may act synergistically to enhance performance in horses’ by maintaining a lower [H⁺] during high intensity exercise. There were differences between skin, rectal, blood, and muscle temperatures during incremental exercise and recovery in horses. The pH and blood gases adjusted to rectal, blood, and muscle temperatures were also different during exercise and recovery. Muscle and blood temperature may be predicted from rectal or skin temperature during exercise, and from skin temperature during recovery.
Alkanes as Internal Markers to Estimate Digestibility in Horses
Ordakowski, Amy L. (Virginia Tech, 1998-08-10)
Fecal recoveries of n-alkanes were determined in three digestion balance experiments consisting of two periods each. Each experiment compared two diets in a switch-back design using eight mature Thoroughbred geldings. Horses were randomly assigned to two groups of four and offered one of two mixed grass/legume hays (Diets 1 and 2) in Exp. 1, mixed grass/legume hay and one of two concentrates (Diets 3 and 4) in Exp. 2, and mixed grass/legume pasture (Diets 5 and 6) in Exp. 3. In Exp. 1 and 2, horses were housed in stalls and in Exp. 3, two horses from each diet were housed in stalls and two horses remained on pasture. Balance periods lasted 11 days with d 1 to d 7 consisting of a dietary accommodation period, followed by 4 days of total collection. Results indicated that fecal recoveries of odd-chain alkanes (C25 to C33) were less than 100 % and similar between chain lengths. Estimates of DMD (DE) were similar to the total collection DMD (DTC) for Diet 1 in Exp. 1, but underestimated DTC for Diet 2 in Exp. 1 (P < .05) and Diets 3 and 4 in Exp. 2 (P < .05). For Diet 5 in Exp. 3, the DE for stall-fed horses using C25 and C33 was similar to DTC, whereas C27, C29, and C31 underestimated DTC (P < .05). For pastured horses, the DE using C29 and C31 were similar to DTC, whereas C25, C27, and C33 underestimated DTC (P < .05). For Diet 6 in Exp. 3, the DE for stalled horses calculated using C25 was similar to the DTC, whereas use of C27, C29, C31, and C33 underestimated DTC (P < .05). For pastured horses, the DE using C29 was similar to DTC, whereas all other alkanes underestimated DTC (P < .05). When DE was adjusted (DA1) using the mean recovery of each odd-chain alkane, DA1 was similar to DTC for Diet 2 in Exp. 1, Diets 3 and 4 in Exp. 2, and stalled horses offered Diets 5 and 6 in Exp. 3. The DA1 using C25 underestimated DTC for Diet 1 in Exp. 1 (P < .05). For pastured horses offered Diet 5, DA1 for C33 was not different from the DTC estimate, whereas all other DA1 for n-alkanes overestimated DTC (P < .05). For pastured horses offered Diet 6, DA1 for C29 and C31 overestimated, but were similar to the DTC, whereas the DA1 for C33 underestimated DTC and was similar to the DTC. The DA1 for C25 and C27 overestimated DTC (P < .05). When DE was adjusted for the mean recovery of all n-alkanes (DA2), all DA2 estimates for stalled horses in Exp. 1, 2, and 3 were similar. In pastured horses offered Diets 5 and 6 in Exp. 3, the DA2 overestimated DTC (P < .05). These results suggest that accurate mean estimates of DMD can be obtained by adjusting for mean recovery of each odd-chain alkane in a specific diet.
Basic horsemanship
Lawrence, Larry A. (Virginia Cooperative Extension, 2002)
Carbohydrate and Fat Supplementation in Grazing Mares and Foals
Hoffman, Rhonda M. (Virginia Tech, 1997-06-30)
The objective of these studies was to design an optimal nutritional supplement suitable for grazing horses using fat and fiber to replace the grain and molasses in the traditional sweet feed. Thoroughbred mares and foals grazing bluegrass/clover pastures were used in these studies, twenty mares and their foals in 1994 to 1995, and twenty mares and foals in 1995 to 1996. Seasonal variation in pasture was examined, and the need for supplementation of nutrients and fibers was assessed. The nutritional status of grazing mares, foals, weanlings and yearlings, fed either a starch and sugar supplement (SS) or a fat and fiber supplement (FF), was examined using growth measurements, radiographic bone evaluations, milk composition and glucose tolerance tests. These studies suggest that fiber may be an important component of an ideal supplement for improved grass/legume pastures. Seasonal variation in pasture indicated an increase in hydrolyzable and rapidly fermed carbohydrates during periods of rapid growth. The FF supplement may have buffered seasonal changes and the increased hydrolyzable carbohydrate content in rapidly growing pasture, as evidenced by smoother growth curves in the yearlings. Young horses, after weaning until the following May, had lower estimated bone mineral content when fed the FF supplement. The lower bone mineral content in the FF supplemented horses may have been due to decreased absorption of calcium or metabolic and hormonal changes associated with adaptation to the different energy sources in the supplements. Milk composition of FF supplemented mares was influenced in ways likely to improve foal health. The FF supplemented mares had enhanced linoleic acid content, which may reduce the risk of gastric ulcers in foals, and increased immunoglobulin G concentration, which may enhance passive immunity. The carbohydrate status of mares, as assessed by glucose tolerance tests, indicated a slower glucose clearance that could be a metabolic adaptation of the mares to the SS and FF supplements.
Dietary calcium and cation-anion difference influences calcium status and bone remodeling in exercising and sedentary Arabian horses
Porr, Cheryl Ann (Virginia Tech, 1996)
Diet and exercise are two manageable factors that affect bone remodeling. Experiments were designed to test the hypothesis that bone density and calcium status would be affected by conditioning and deconditioning, and by dietary Ca and cationanion difference (DCAD). In experiment one, 12 Arabian horses were conditioned for 12 wk on a high speed equine treadmill. Diets were designated LH, which contained low Ca (.35%)-high Cl (.6%), LL, low Ca-low Cl (no added Cl), HH, high Ca (.7%)- high Cl, and HL, high Ca-low Cl. Data were collected while horses were at rest every 21 d. Serum and plasma were analyzed for total and ionized Ca, P, Mg, Cl, total protein, albumin, parathyroid hormone (PTH), osteocalcin, and hydroxyproline. Radiographs of the left third metacarpal bone were taken. An aluminum step wedge exposed simultaneously was used as a reference standard for estimating bone mineral content (BMC) with an image analysis program. Bone measurements, including BMC, bone and medullary width, and cortical area, were taken in the proximal diaphyseal and proximal metaphyseal area. Bone variables increased with training and with high Ca diets as compared to horses fed low Ca diets. Serum Ca decreased and serum PTH increased with training. Hydroxyproline was unchanged in horses fed the low Ca diets and decreased in horses fed the high Ca diets. Serum osteocalcin increased then decreased with training. The high Ca diet appeared to facilitate bone remodeling in response to training, but dietary Cl, hence DCAD, had no effect. In experiment two, 11 conditioned Arabian horses were taken out of training and placed in stalls for 12 wk. They were walked on a mechanical walker in two 30 min sessions 7 d/wk. Diets were designated LC (.35% Ca) and HC (.7% Ca). Data collection and analysis were identical to those in experiment one. Bone variables decreased with deconditioning but were unaffected by dietary Ca. Serum Ca increased with deconditioning and was greater in horses fed the HC diet, but PTH did not change. Horses fed the HC diet had greater serum osteocalcin, which decreased with deconditioning. Dietary Ca influenced bone remodeling in response to training, but did not have an effect on bone response to deconditioning. Loss of BMC during 12 wk of stall confinement may predispose horses to skeletal injuries when training is resumed.
Dietary Protein Moderates Acid-Base Responses to Repeated Sprints in Exercising Horses
Graham-Thiers, Patricia M. (Virginia Tech, 1998-11-30)
Restricting dietary protein may reduce endogenous acid load. Horses were fed diets with 10% supplemental corn oil in experiment one and either 0% or 10% supplemental corn oil in experiment two. Also, low protein (7.5% crude protein, LP) fortified with .5% lysine and .3% threonine or high protein (14.5% crude protein, HP) was fed. Horses underwent similar interval training and standard exercise tests. In experiment two, horses performed an SET prior to conditioning. The SET consisted of warm ups at the walk and trot followed by six repeated sprints and concluding with a 30 minute recovery at the walk. All sprints were at 10 m/s except the SET prior to conditioning in experiment two, which were at 7 m/s. Blood samples were taken every two weeks and as part of SETs. Samples were analyzed for pH, pCO₂, pO2, Na⁺, K⁺, Cl⁻, lactate, total protein (TP), albumin, creatinine and plasma urea-N (PUN). Bicarbonate, strong ion difference (SID) and total weak acids (Atot) were calculated. Plasma urea-N concentrations were higher in the HP group. Plasma creatinine was not different in experiment one but was higher in the LPHF group in experiment two. Also, the LPHF group had a low body condition score and the same weight therefore had a higher lean body mass. Plasma albumin was not different in either experiment and TP was not different in experiment one. Total protein was higher in the HF groups in experiment two. Protein moderated acid-base responses to SETs in both experiments. The LP group had higher pH and bicarbonate levels as well as a tendency for a higher SID in experiment one and in the SET prior to conditioning for experiment two. Lower lactate levels were observed in the LP group in experiment one. Following conditioning in experiment two, the LP group had higher pH and bicarbonate levels but only combined with HF. Restricting dietary protein can increase pH and bicarbonate levels and high fat has been shown to improve fatty acid oxidation and spare muscle glycogen. Therefore, restricting dietary protein especially in combination with high fat may be beneficial for the exercising horse.
Fecal Kinetics and Digestibilities of Hays and Supplements Estimated by Marker Methods in the Horse
Hargreaves, Belinda Jane (Virginia Tech, 1998-11-20)
A marker model of fecal kinetics using chromic oxide (Cr) or ytterbium chloride (Yb) is being developed for grazing horses. The model consists of removal of feces at a constant rate from a single compartment, the prefecal mass. It was tested in experiments on stall-fed horses in the context of digestion balance trials. Following the preliminary work of Holland et al., (1998), three improvements in experimental design were tested. First, the rate constants were determined from both the administration and post-administration curve of the one-compartment model. Second, markers were administered three times a day to reduce diurnal variation in fecal marker concentration. Third, yttrium (Y) and Yb were tested were tested as internal markers, for the estimation of digestibility of hay and supplements, respectively. Eight horses were fed Diet 1 (orchardgrass/alfalfa mixed, OG) or Diet 2 (tall fescue/alfalfa mixed, TF) in Exp.1, and Diet 3 (OG plus fat-and-fiber supplement, OGFF) or Diet 4 (OG plus sugar-and-starch supplement, OGSS) in Exp.2. Balance-marker experiments were conducted for 17 and 20 d, with 7 and 10 d of dietary accommodation in Exp.1 and 2, respectively. Chromic oxide and Yb were administered orally and fecal samples were collected every 8 h for 8 d. Dry matter, Cr, Yb and Y were measured in feeds and feces. In balance experiments, estimates of DMD (D_E) using Y, were determined precisely (SE 1 to 3 %) for hay and hay and supplement diets. Linear relationships, correlations and calibration curves were determined, validating Y as a marker. Mean daily fecal Cr data (C_t) at time t (days) including a delay (d) were fitted to a single exponential, with one rate constant (k), rising to an asymptote (C_a): C_t = C_a - C_a·e^-k(t-d) Diets 1 and 2 had two sets of C_tdata, total collection (a) and fecal grab data (b), and each set was used in model development. Diets 3 and 4 had two sets of C_t data (both using fecal grab data), Cr marker dilution (3Cr and 4Cr) and Yb marker dilution (3Yb and 4Yb). For pooled data, delays of 3 to 6 h (Diets 1a, 1b, 2a and 2b) and delays of 5 to 7 h (Diets 3Cr, 4Cr, 3Yb and 4Yb) gave best fits (highest estimates of R²). The delays introduced to the Cr model for both 3Cr and 4Cr diets did not correspond to the preliminary study (Holland et al., 1998), where a 2 h delay gave the best fit in the model for horses fed hay and supplement. The present estimates may more realistically relate to mouth-to-cecum transport times, because the marker was administered three times a day instead of once, and the initial part of the tracer curve was more precisely defined. The results showed that fecal Cr kinetics could be calibrated precisely (SE 1 to 3 %) to predict fecal DM output of horses fed Diets 1b, 2b, 3a but not 4a. Similarly, fecal Yb kinetics could be calibrated to predict fecal DM output of horses fed Diet 3b but not 4b. The rate constants yielded turnover times (TT) that were longer with hay and supplement diets, than with hay alone, and which contrast with previous findings in the horse. However, the longer TT were similar to slower rates of marker excretion in sheep fed concentrates instead of all-roughage diets, suggesting that the lower fiber content retarded the rate of propulsion of digesta through the digestive tract. For two of the eight models of fecal kinetics, the rate constants of the post-administration curve were not well determined by the data, and rate constants from the administration curve were used. In future experiments, more frequent fecal sample collection during the post-administration period may improve rate constant determination. Improvements in diurnal variation of fecal marker concentration were obtained by dosing three times a day. But discrepancies between Cr and Yb concentration means of diurnal samples and combined samples showed incomplete mixing, the major source of tracer error. Therefore more frequent marker administration and fecal samples should be tested in future experiments to achieve more thorough mixing in the prefecal mass for modeling fecal kinetics, and in the small intestine for estimating digestibility.
Folate Status and Supplementation in the Horse
Ordakowski, Amy L. (Virginia Tech, 2001-07-10)
A series of studies were conducted to evaluate effects of lactation, exercise, and anti-folate drugs on folate status in the horse, and the bioavailability of supplement and feed folate in the horse. In the first study, mares and foals had adequate plasma folate, RBC folate, and plasma homocysteine concentrations during 6 mo of lactation and growth. Therefore, mares and foals maintained on quality grass/legume pastures and offered a pasture supplement did not require additional folate supplementation to maintain folate status during lactation and growth. In the second study, 25 mg of oral folic acid (FA) supplemented 5 times/wk to 11 mature horses engaged in routine submaximal exercise did not improve folate status, submaximal athletic performance, or combat the increase in oxidative stress during the 12 wk supplementation period compared to 11 horses not given supplemental folate. The common practice of supplementing horses with oral FA in vitamin supplements appears to be of little benefit to horses engaged in routine submaximal exercise. In the third study, daily oral administration of pyrimethamine (PYR) and sulfadiazine (SDZ) for 9 wk followed by 6 wk of coadministration of either Peptidoglycan or FA was associated with a decline in folate status resulting in moderate hyperhomocysteinemia, but not clinical signs of anemia. Peptidoglycan as a source of formylated folate and FA were not effective in improving folate status in horses coadministered PYR and SDZ, two anti-folate drugs commonly administered in equine veterinary practice. The last study assessed the bioavailability of oral and i.v. 5-methyltetrahydrofolate (5-mTHF), 5-formyltetrahydrofolate (5-fTHF), or FA, and the bioavailability of folate from concentrates fed to horses. The minimum efficiency of absorption for supplemental FA was 11 %. The low bioavailability of FA indicates a need for further research on the potential benefits of alternative sources of folate, including 5-fTHF, on increasing folate status in the horse.
Glycemic Response in Thoroughbred Mares
Williams, Carey Ann (Virginia Tech, 2000-08-09)
The objective of this study is to determine if fat as an energy source, and fiber in a pasture supplement will be beneficial when compared to a concentrate high in sugar and starch. In the first experiment, 12 pregnant and lactating mares were used in three different glycemic response tests to determine the effect of feeds on pregnant mares. The mares were fed a pelleted concentrate (PC) three months before foaling; after foaling they were divided into two groups and fed a feed high in sugar and starch (SS), or a feed high in fat and fiber (FF). The second experiment, used the same 12 mares (R mares) and 10 barren mares (B mares) in three different tests to determine the effects of the feeds, season and reproductive stage. A series of blood samples was collected via a jugular catheter from 0 to 390 min after consuming a meal. Glucose and insulin baseline and peak values, increments and areas under curves (AUC) were compared by ANOVA. For the first experiment, responses to PC did not differ between the two groups. Peak plasma glucose and insulin concentrations were higher in SS group than in FF during both early and late lactation. Glucose and insulin AUCs were higher in SS than in FF during both early and late lactation. In the second experiment, peak glucose increments had differences for the main effects feed, pregnancy and season, and interactions feed by pregnancy and feed by season. The glucose AUC values showed similar differences for the main effects and the interaction feed by pregnancy. Peak insulin increments had a difference for feed and pregnancy, but not the interactions. Insulin AUCs also revealed a difference between feed and pregnancy, and also for season, and the interaction feed by pregnancy. These results indicate that metabolic fluctuations are moderated by the replacement of sugar and starch with fat and fiber. This replacement may reduce the risk of certain digestive and metabolic disorders.
Growth and the Somatotropic Axis in Young Thoroughbreds
Staniar, William Burton (Virginia Tech, 2002-01-25)
This group of experiments focused on relationships between diet, somatotropic axis, and growth. Growth hormone (GH) and insulin-like growth factor I (IGF-I) are factors in the somatotropic axis, and important to development of growth cartilage in the young animal. The entire study was divided into four main experiments. Characteristics of growth in 113 Thoroughbred foals born over a five year period were described with a series of empirical and physiological equations. Glycemic and insulinemic responses to different feed compositions were evaluated with glycemic response tests. The 24 hr pattern of plasma glucose, insulin, GH, and IGF-I was described in yearlings fed two meals a day. Finally, an association between ADG and IGF-I was described in Thoroughbreds from birth to 16 mo of age. Feeding diets to the foal that influence the somatotropic axis during growth may affect development of growth cartilage in unexpected or detrimental ways. The pattern of weight in Thoroughbred foals from birth to 16 mo of age was most closely described by multiple regression with a combination of age, girth, body length, and physeal circumference (R2 = 0.99). Glycemic and insulinemic responses were significantly higher in yearlings fed a sugar and starch supplement when compared to those fed a fat and fiber supplement (P = 0.043 and 0.031; respectively). Glucose and insulin secretion was significantly affected by the feeding of two meals in a 24 hr period (P < 0.0001). Plasma IGF-I was positively correlated with ADG from birth to 16 mo of age in foals fed either a fat and fiber or sugar and starch supplement (r = 0.34, P < 0.0001). The results from the series of experiments described here suggest a possible role of dietary mangement in reducing the risk of skeletal disorders that involve the influence of IGF-I on chondrocyte maturation.
Growth of Thoroughbreds fed Different Levels of Protein and Supplemented with Lysine and Threonine
Staniar, William Burton (Virginia Tech, 1998-11-20)
Currently accepted optimum protein levels for growth in the horse may be reduced with amino acid supplementation. This study investigated the effects on growth and protein status of Thoroughbred foals offered a supplement with a typical CP level to a supplement that had a lower CP level fortified with limiting amino acids. The control supplement (CS) contained 14% CP, 3.0 Mcal/kg DM, 10% corn oil, 22% soybean meal, 1.4% calcium, and three sources of fiber. The experimental supplement (LTS) contained 9% CP, 3.0 Mcal/kg DM, 10% corn oil, 3% soybean meal, 1.4% calcium, three sources of fiber, and was fortified with .6% lysine and .4% threonine. Lysine and threonine are the first two limiting amino acids in common diets of the horse. Mares and foals were fed twice daily (0700 and 1400) and kept on 30-acre pastures (mixed grass/white clover) until weaning (7 months). Weanlings continued on specified supplements and pastures for seven additional months. Physical measurements and blood samples were taken monthly. Measurements included weight, average daily gain (ADG), body condition (BC), wither height, hip height, length, girth, forearm length, front and hind cannon length, physis and fetlock circumference. Blood analysis included total protein (TP), albumin (ALB), creatinine (CREA), and plasma urea nitrogen (PUN). Effect of diet and time were evaluated by analysis of variance with repeated measures. No differences were found in physical measurements between the CS and LTS groups (ADG 0.8(0.4 kg/day, BC 4.9(0.05) for the observational period. Blood data also showed no difference for the period (ALB 2.9 ( 0.03 g/dl, TP 5.7 ( 0.10 g/dl, CREA 1.1 ( 0.02 mg/dl). These results suggest that the foals offered the LTS faired as well or better than foals on the CS. Lower levels of crude protein (CP) in the diet will result in less nitrogen pollution of pasture lands due to better utilization in the horse. By fortifying a low protein diet with the first two limiting amino acids, the protein is used more efficiently for growth and development, thereby benefiting both the horse and the land.
Horsemaster
Lawrence, Larry A. (Virginia Cooperative Extension, 2003)
Horsemaster
Lawrence, Larry A. (Virginia Cooperative Extension, 1999)
Horses are fun
Lawrence, Larry A. (Virginia Cooperative Extension, 2001)
Leader's guide : Virginia 4-H horse program
Huff, Arden N.; Lawrence, Larry A. (Virginia Cooperative Extension, 2004)
Leader's Guide, Virginia 4-H Horse Program
Lawrence, Larry A. (Virginia Cooperative Extension, 2001)
This is the leader's guide for the Virginia 4-H horse programs.
Novice
Lawrence, Larry A. (Virginia Cooperative Extension, 1999)
Nutrient requirements and balancing rations for horses
Lawrence, Larry A. (Virginia Cooperative Extension, 2000)
Pasture Intake, Digestibility and Fecal Kinetics in Grazing Horses
Holland, Janice Lee (Virginia Tech, 1998-11-18)
Pasture intake of grazing livestock needs to be estimated to allow determination of energy and nutrient intakes. It is commonly estimated by difference, subtracting intakes of other feeds from estimated needs for dry matter or energy. However, these estimates are often erroneous, because they do not take individual animal variation for growth, reproductive status or activity level into account. One method that has had success in grazing ruminants has been the use of markers, or tracers, to estimate fecal output and nutrient digestibility. External markers are dosed to the animal and can be used to determine fecal output. Internal markers are an inherent part of the diet in question and can be used to determine dry matter and nutrient digestibilities. These estimates can then be used to give estimates of intake. These studies were conducted to evaluate the effectiveness of traditional marker methods in determining fecal output, digestibility, and thus intake in grazing horses. The first trial was conducted on 8 mature mares and geldings, housed in stalls, to determine if a common external marker, Cr, could be used to determine fecal output. Horses were dosed once daily with a molasses, Cr, and hay mixture for 12 d. Feces were collected throughout the day into individual tubs so that total fecal output (TC) could be measured. Daily fecal Cr excretion values (Ct, mg/kg DM) were fit to a monoexponential equation with one rate constant (k), rising to an asymptote (Ca): Ct = Ca - Ca.e-kt. Superior fits were found when a delay (d) was incorporated into the equation, estimating the time required for Cr to enter the prefecal pool: Ct = Ca - Ca.e-k(t-d). Estimates of fecal output (FO) were calculated using the equation: FO = Cr dose-d / Ca and provided good estimates when compared to TC values. Subsequent trials evaluated to use of internal markers and more frequent dosing of Cr to improve estimates of intake. Eight mature geldings were housed in stalls and were fed 2 hays in a replicated Latin Square design. The monoexponential equation with the delay continued to fit the data well. Thrice daily dosing of Cr improved the predictions of FO, when dosing was every 8 h. The internal marker, yttrium (Y) consistently overestimated digestibility (D). The internal markers, n-alkanes, gave a better estimate of digestibility. When the digestibility estimates were combined with the FO estimates to estimate dry matter intake (DMI, kg/d): DMI = [FO / (1-D)]*100, the combination including n-alkanes gave better estimates. Further studies found that dosing Cr for 12 d did not improve the fit of the monoexponential equation compared to dosing for only 8 d. Marker methods that had been developed in stalls were applied to grazing horses, and results continued to be promising.
Pre-weaning diet and stall weaning method influences on stress response in foals
Hoffman, Rhonda M. (Virginia Tech, 1994-09-15)
The response of foals to the stress of weaning was examined in terms of a behavioral protocol and the responses of plasma ascorbate, serun1 cortisol, and the serum cortisol response to an ACTH challenge. Behavior scores (1 to 10) as an index of stress were assigned to each foal daily, with high scores indicating less stress and better adjustment. The experimental plan was a 2 X 2 factorial of pre-weaning diet and stall weaning method. Foals were raised on pasture supplemented with hay and a pelleted concentrate (PHC) or pasture supplemented with hay only (PH). Foals were placed in stalls singly or in pairs for weaning. Gender influences were also examined. The foals exhibited characteristic behavioral and physiological responses to the social dislocative stress of weaning. Behavior scores were lower in paired than in single foals (p = .008) and tended to be lower in PH than PHC foals (p = .15). No differences in post-weaning plasma ascorbate concentrations were found among treatments. Responses of serum cortisol to an ACTH challenge were lower in PH than PHC foals (p = .001) and in paired than single foals (p = .058), and lower responses were taken to represent adrenal depletion arising from stress. Behavior scores were positively correlated with the response of serum cortisol to ACTH. Both behavioral data and the serum cortisol response to ACTH indicate that foals were better able to cope with weaning stress when supplemented with concentrate prior to weaning and when weaned singly.

Browsing by Author "Lawrence, Larry A."

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