Oral and intravenous immunoglobulin therapy in neonatal foals

Newborn foals, deprived of colostrum and its rich supply of immunoglobulin G (IgG), were supplemented both orally and intravenously with purified equine immunoglobulin G (Lyphomune^®). Data were obtained from 18 foals given oral administration of IgG at Colorado State University and 26 foals given IgG intravenously at the Jockey Club de Sao Paulo in Brazil.Oral administration of 10-gm doses of Lyphomune^® in 18 colostrum-deprived Arabian foals, at various intervals within the first 24 hours after birth, resulted in increased serum concentrations of IgG. Administration of one 10-gm dose of Lyphomune^® immediately following birth provided a mean serum IgG level of 125 mg/dl after two hours. The recommended dosage of two 10-gm doses per 15 kg of body weight produced mean IgG serum concentrations of approximately 400 mg/dl by 14 hours. It was determined that an early bolus of IgG was most effective, although administration at any period during the first 24 hours would increase IgG levels significantly and in direct relationship to grams of Lyphomune^® administered.After the 24-hour study period, colostrum from each respective mare was provided by bottle feeding (200 ml) to 10 of the foals that were then allowed to nurse their dams normally. Significant increases in circulating IgG were observed in nine of these ten animals at four and eight hours after colostrum administration. No interfering effect was noted when colostrum and Lyphomune^® were given to the same foal.Intravenous administration of 10-gm doses of Lyphomune^® in Thoroughbred foals, immediately after birth, resulted in serum concentrations of IgG of 200–300 mg/dl six hours later. A second intravenous dose, at six hours after the initial dose, resulted in an additional average increase of 184 mg/dl. Four of six foals administered 10 gm of Lyphomune^® for each 15 kg of body weight reached serum concentrations greater than 400 mg/dl. It was demonstrated that Lyphomune^® was able to increase circulating levels of IgG, by either oral or intravenous administration, to levels considered protective in the newborn foal.     

Absorption of bovine colostral immunoglobulins G and M in newborn foals

The uptake of colostral IgG and IgM, their serum half-lives, and the rates of endogenous synthesis of IgG and IgM were evaluated in 6 newborn foals fed bovine colostrum (principals) and 6 foals allowed to suckle their dams (controls). The principal foals were fed 400 ml of bovine colostrum (IgG, 10,000 mg/dl and IgM, 200 mg/dl) at 2-hour intervals, from 2 to 20 hours after foaling (total dose, 4 L). Serum IgG and IgM concentrations were determined by single radial immunodiffusion from birth to 98 days of age. At foaling, principal foals had no detectable serum equine IgG, but 1 control foal had serum equine IgG of 185 mg/dl. After ingestion of colostrum, there was no significant difference in the maximal serum bovine IgG concentration (range, 1,350 to 3,300 mg/dl) in the principal foals, and maximal serum equine IgG concentration in the control foals (range, 500 to 6,000 mg/dl). The calculated biological bovine and equine IgG half-life in the principal and control groups was 9.4 and 26 days, respectively. Endogenous IgG synthesis was first detected in 1 principal foal at 3 days of age, but was detected first between 28 and 42 days in the other principal foals. Starting on day 56 there was no significant difference in serum equine IgG concentration between groups. At foaling, foals in both groups had low equine IgM concentrations. In the control foals, there was marked individual variation in the increases in equine IgM concentration (range, 5 to 73 mg/dl) after ingestion of colostrum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of intravenous administration of concentrated immunoglobulin G to colostrum-deprived foals.

Ten foals of various breeds were deprived of colostrum from birth to 36 hours of age, then were allotted to 2 groups. Foals of group 1 (n = 6) were given 20 g (200 ml) of purified equine IgG IV in a 10% solution, and foals of group 2 (n = 4) were given 30 g (300 ml) of the same preparation. Total administration time for each 10 g of IgG in 100 ml was approximately 10 minutes. Serum IgG concentration in foals was assessed prior to, between 24 and 48 hours, and at 7 and 14 days after IgG administration. Between 24 and 48 hours after IgG administration, mean serum IgG concentration in group-1 foals was 425 mg/dl (range, 350 to 480 mg/dl). Mean body weight for this group of foals was 50.3 kg (range, 43.3 to 54.7 kg). For group-2 foals, mean serum IgG concentration was 768 mg/dl (range, 640 to 920 mg/dl) between 24 and 48 hours after administration of IgG. Foals of this group had mean body weight of 43.2 kg (range, 36.5 to 47.5 kg). Serum IgG concentration in group-2 foals at 24 to 48 hours was significantly (P = 0.005) greater than that in group-1 foals. Mean total IgG recovery at 24 to 48 hours, calculated on the basis of 94.5 ml of plasma volume/kg of body weight, was approximately 100%. Values of IgG measured in all foals 1 and 2 weeks after administration of the IgG concentrate were equivalent to values expected after normal decay of passively acquired IgG.(ABSTRACT TRUNCATED AT 250 WORDS)     

A study of bovine and equine immunoglobulin levels in pony foals fed bovine colostrum

As part of a project to raise specific pathogen free (SPF) Welsh Mountain Pony foals, free from exposure to Equid herpesvirus type 1, foals were removed from their dams at birth and fed bovine colostrum. This study characterises the uptake of bovine colostral immunoglobulin and production of endogenous immunoglobulin, in 10 SPF foals. An enzyme-linked immunoadsorbent assay was developed to measure serum concentrations of bovine IgG1 (boIgG1) to assess the efficiency of transfer, and rate of elimination of boIgG1 by the foal. The endogenous production of equine IgG was studied using a single radial immunodiffusion test. Foals were given 1.2 to 2 litres of bovine colostrum achieving peak serum boIgG1 concentrations of 18.9 to 34.2 g/litre (mean 28.0). The mean half-life of boIgG1 in the foals was 7.4 days. Endogenous immunoglobulin production resulted in equine IgG concentrations greater than 2 g/litre in six of 10 foals by 14 to 19 days of age, and greater than 7 g/litre in eight of 10 foals by 37 to 50 days of age. All foals had equine IgG serum concentrations greater than 10 g/litre by 102 to 135 days of age.     

Factors that influence passive transfer of immunoglobulins in foals.

Effects of farm management, breed, mare age, gestation duration, and climatologic factors on colostral specific gravity, colostral IgG concentration, and foal serum IgG concentration were evaluated. Climatologic variables measured were daily maximal, minimal, and mean air temperature, precipitation, average relative humidity, and total solar radiation. Presuckle, postpartum colostrum samples were collected from 140 Standardbred, 94 Thoroughbred, and 59 Arabian mares from January through June during 1985 and 1986. Thoroughbred (farm A, n = 61; farm B, n = 33) and Arabian (farm C, n = 45; farm D, n = 14) mares were located in Ocala, Fla; Standardbred mares (farm E) were in Montgomery, NY. Mares from farms A, B, D, and E foaled in box stalls, and mares from farm C foaled in sand paddocks. Mares with premature lactation greater than 12 hours were not included in the study. Foals were clinically normal at birth and suckled colostrum without assistance within 2 hours of parturition. Specific gravity of presuckle colostrum samples was measured by use of an equine colostrometer. Blood samples were collected 18 hours after parturition from 253 of the 293 foals (n = 45, 25, 32, 13, 138 on farms A through E, respectively) to determine serum concentration of IgG. The IgG concentrations in colostrum and serum were measured by single radial immunodiffusion. Data were analyzed by multiple regression or chi 2 analysis. The most important determinants of foal serum IgG concentration were the IgG content and specific gravity of presuckle colostrum samples (P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationships among serum immunoglobulin concentration in foals, colostral specific gravity, and colostral immunoglobulin concentration

Postpartum, presuckle, colostrum samples were collected from 100 mares. Colostral specific gravities significantly correlated (r = 0.9) with colostral immunoglobulin (Ig)G concentrations. Foal serum IgG concentrations highly correlated (r = 0.82) with specific gravities of the colostrum each foal ingested. Eight of 48 foals (17%) had serum IgG concentrations less than 400 mg/dl. The dams of these 8 foals had colostral sp gr less than 1.06 and colostral IgG concentrations less than 3,000 mg/dl. Foals had serum IgG concentrations greater than 520 mg/dl 24 hours after parturition, when the colostral specific gravity of the dam was greater than or equal to 1.06. Effects of breed on colostral specific gravity, colostral IgG concentrations, foal serum IgG concentrations, and mare serum IgG concentrations were not significant.     

Lyophilized hyperimmune equine serum as a source of antibodies for neonatal foals

In a study with 15 neonatal foals (5 per treatment group), foals were fed within 4 hours of birth as follows: 250 ml of colostrum, 250 ml of lyophilized serum reconstituted at 5 times the original concentration, or 250 ml of a mixture (1:1) of colostrum and lyophilized serum. Foal serum samples were tested for immunoglobulin (Ig)G concentration and titrated for anti-equine rhinovirus 1 and anti-equine influenza A1 and A2 antibodies at 0 and 24 hours after foals were born. Except in a foal which had suckled the dam before treatment, there was no evidence of IgG or specific viral antibodies in the samples taken at birth. There were no significant differences found in the serum IgG concentrations and antibody titers among the 3 treatment groups. Seemingly, IgG was absorbed efficiently from both serum and colostrum, so that the use of reconstituted lyophilized serum as a prophylactic measure of conferring passive immunity to a newborn foal deserves serious consideration.     

Passive transfer failure in horses: incidence and causative factors on a breeding farm

A prospective study was performed to determine the incidence and associated maternal and managemental factors of failure of passive transfer (FPT) in foals on a breeding farm. The zinc sulfate turbidity test (ZSTT) and latex agglutination test (LAT) were compared for accuracy in estimating serum immunoglobulin (Ig)G of foals, as determined by single radial immunodiffusion (SRID). Complete past and present foaling histories of 136 Standardbred mares were obtained. All foalings were witnessed by farm attendants, and colostral samples were collected from mares within 2 hours after parturition. Foals that did not rise and nurse were supplemented with colostrum from the dam, using a bottle or nasogastric tube. Serum samples were prepared from foals and mares between 24 and 36 hours after parturition, and from some mares 45 to 90 days before parturition. Serum IgG concentrations of mares and foals and colostral whey were determined, using SRID. Serum IgG also was estimated in foals, using ZSTT and a commercially available LAT. Four of the 136 foals (2.9%) had FPT (serum IgG less than or equal to 400 mg/dl). Serum IgG concentrations in foals significantly correlated with colostral IgG (P less than 0.001). A significantly larger proportion of foals with FPT were bottle-fed their colostrum (P less than 0.01). Month of parturition, mare age, parity, number of barren seasons, incidence of assisted births or retained placenta, or prepartum serum IgG concentrations did not significantly affect colostral IgG concentrations or serum IgG concentrations in foals. As serum IgG concentrations in foals decreased and as colostral IgG concentrations decreased, the proportion of mares that prelactated significantly (P less than 0.01) increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of delays in feeding colostrum and the relationship between immunoglobulin concentration in the serum of neonatal calves and their rates of growth

SUMMARY Eighty-five unsuckled newborn calves, were fed 1.5 L of colostrum of known IgG concentration at either 2, 4, 6 or 8 hours after birth with no additional colostrum feeding. Another group of 11 calves were left with their dam for 16 hours after birth, before separation. Blood samples were taken from all calves 24 hours after colostrum feeding or separation from the dam and serum Ig concentrations were measured by electrophoresis. There were no significant differences in mean serum Ig concentrations between calves fed at the different times after birth. Three of the 11 calves left to suckle were hypogamma-globulinaemic. Other calves in this group had higher serum Ig concentrations than the means of all other groups. All groups had mean serum Ig concentrations higher than the suggested minimum concentration required for adequate calf health. There were a number of calves that did not reach the suggested minimum serum concentration after feeding, but calf mortality was low and all calves were healthy apart from a slight scour for a few weeks after birth. There was no significant relationship between serum Ig concentration 24 to 48 hours after birth and either calf mortality or average growth rate over an 8- to 10-month period.     

Complement activity and selected hematologic variables in newborn foals fed bovine colostrum

Serum complement activity and selected hematologic variables were evaluated in 5 newborn foals fed bovine colostrum (principal group) and 6 foals allowed to nurse their dam (control group). Also, bovine colostrum was evaluated for anti-equine antibodies. Precolostral serum hemolytic and conglutinating complement activities were low and increased similarly in foals of both groups to reach adult values between 1 and 3 weeks after birth. Bovine colostrum strongly agglutinated, but did not hemolyse principal foals' RBC and blood containing all known equine blood group alloantigens. Hemolysis was not detected after administration of bovine colostrum. Physiologic anemia developed in foals of principal and control groups during the first week of life. Erythrocyte osmotic fragility in foals of the principal group prior to and after the ingestion of colostrum remained unchanged. However, at 36 hours after birth, there was a significant decrease in erythrocyte osmotic fragility in foals fed homologous colostrum.     

Colostral and serum IgG, IgA, and IgM concentrations in Standardbred mares and their foals at parturition

Immunoglobulin G, IgM, and IgA concentrations were measured in serum collected from 36 Standardbred mares within 12 hours of foaling, in colostrum collected within 6 hours of foaling, and in serum collected from foals 24 to 48 hours after birth. In serum collected from mares after parturition, mean concentrations of IgG, IgM, and IgA were 2,463.9 +/- 1,337.3 mg/dl, 136.4 +/- 218 mg/dl, and 305.2 +/- 237.5 mg/dl, respectively. In serum from foals, mean concentrations of IgG, IgM, and IgA were 1,953.3 +/- 1,635 mg/dl, 33.8 +/- 30.4 mg/dl, and 58.4 +/- 42.2 mg/dl, respectively. In colostrum, mean concentrations of IgG, IgM, and IgA were 8,911.9 +/- 6,282.2 mg/dl, 957 +/- 1088.1 mg/dl, and 122.9 +/- 77.3 mg/dl, respectively. The IgG concentrations in foal serum were poorly correlated with IgG concentrations in colostrum (r = 0.462, P less than 0.01). Correlations of IgM or IgA concentrations in serum from foals with IgM or IgA concentrations in colostrum and correlations of IgG concentrations in serum from mares with those in colostrum were not significant (P less than 0.01). Of 36 foals, 1 (2.8%) had a serum IgG concentration less than 400 mg/dl. Of 36 foals monitored for 4 months, 6 developed infectious respiratory tract disease requiring antimicrobial therapy at ages varying from 55 to 113 days; these infections were probably not related to failure or partial failure of passive transfer of antibody.     

Transfer of tumour necrosis factor-α via colostrum to foals

This study aimed to determine whether TNF-α is transferred to equine neonates via colostrum and the relationship between TNF-α and IgG concentrations in the equine neonate. Colostrum, presuckle and postsuckle foal serum samples were collected from healthy mares and their foals. Equine TNF-α ELISA and IgG SRID kits were used to determine the concentrations of TNF-α and IgG, respectively. Statistical analysis was performed using the Spearman rank correlation. TNF-α concentrations in all presuckle foal serum were below the limit of detection in 15/16 foals and increased in postsuckle foal serum to a mean concentration of 7.7 x 10(4) pg/ml. TNF-α concentrations in postsuckle foal serum and colostrum showed significant correlation (rho=0.668; P=0.005). However, TNF-α and IgG concentrations in colostrum or postsuckle foal serum did not correlate (rho<-0.016; P>0.05). Ratios of TNF-α/IgG in colostrum or postsuckle foal serum showed significant correlation (rho=0.750; P=0.0008). These results indicate that TNF-α is transferred to the foal via colostrum absorption and may play a role in early immunity.     

Effect of method and time of first colostrum feeding on serum immunoglobulin concentration, health status and body weight gain in mithun (Bos frontalis) calves

The effect of method and time of first colostrum feeding on the concentration of serum immunoglobulin (Ig) was evaluated in mithun (Bos frontalis) calves. The hypotheses were that the variable method and time of first colostrum feeding might affect the level of serum Ig and in turn the growth performance and health status of the claves during the early age. The newborn calves were randomly allotted to one of the four experimental groups - G-1: allowed to suckle the dam at own choice, G-2: separated immediately after birth and allowed to suckle the dam first at 6 h and then at own choice, G-3: bottle fed ad libitum colostrum of its own dam first at 6 h and then at 6-h intervals until 24 h, G-4: bottle fed ad libitum colostrum of its own dam within 1 h, at 6 h and then at 6-h intervals until 24 h. The concentrations of IgG, IgM, and IgA were lowest (p < 0.01) at birth and increased following colostrum feeding irrespective of the experimental group. Highest concentrations of all the Ig classes were observed at 12-24 h after birth. The concentrations then transiently decreased from day 7 to 14, and then steadily increased after day 28. The concentrations of IgG (p < 0.01) and IgA (p < 0.05) were higher in G-1 in relation to the other groups during the first week after birth. Similarly, higher concentration of IgA (p < 0.05) was found in G-1 in relation to the other groups during the rest of the experimental period. The apparent absorption efficiency of colostral IgG was higher (p < 0.05) in G-4 in relation to G-3. Growth rate and health status were not influenced by the method and time of first colostrum feeding. In conclusion, a 6-h delay in the first colostrum feeding reduced the level of serum Ig noticeably.     

Interpretation of the detection of Sarcocystis neurona antibodies in the serum of young horses

Horses that are exposed to Sarcocystis neurona, a causative agent of equine protozoal myeloencephalitis, produce antibodies that are detectable in serum by western blot (WB). A positive test is indicative of exposure to the organism. Positive tests in young horses can be complicated by the presence of maternal antibodies. Passive transfer of maternal antibodies to S. neurona from seropositive mares to their foals was evaluated. Foals were sampled at birth (presuckle), at 24h of age (postsuckle), and at monthly intervals. All foals sampled before suckling were seronegative. Thirty-three foals from 33 seropositive mares became seropositive with colostrum ingestion at 24h of age, confirming that passive transfer of S. neurona maternal antibodies occurs. Thirty-one of the 33 foals became seronegative by 9 months of age, with a mean seronegative conversion time of 4.2 months. These results indicate that evaluation of exposure to S. neurona by WB analysis of serum may be misleading in young horses.     

Serum lactoferrin and immunoglobulin G concentrations in healthy or ill neonatal foals and healthy adult horses

BACKGROUND: Lactoferrin is a colostral glycoprotein with antimicrobial properties. HYPOTHESES: (1) Serum lactoferrin and immunoglobulin G (IgG) concentrations are correlated and increase in healthy foals after ingestion of colostrum; (2) compared to healthy foals, ill foals will have lower lactoferrin concentrations that correlate with their IgG concentration, neutrophil count, the diagnosis of sepsis, and survival; and (3) plasma concentrations of lactoferrin will be less than serum concentrations. ANIMALS: Healthy foals (n = 16), mature horses (n = 10), and ill foals 1-4 days old (n = 111) that were examined for suspected sepsis were used for blood collection. Colostrum was obtained from 10 healthy mares unrelated to the foals. METHODS: Blood was obtained from the healthy foals at birth and 1-3 days of age and from the ill foals at admission. Serum IgG was quantified by single radial immunodiffusion (SRID). Lactoferrin concentrations in colostrum and blood were determined by an enzyme-linked immunosorbant assay. The sepsis score, blood culture results, neutrophil counts, and survival were obtained on ill foals. RESULTS: The mean colostral lactoferrin concentration was 21.7 microg/mL. Compared to values at birth, serum IgG (18+/-2 versus 2,921+/-245 mg/dL, SEM) and lactoferrin (249+/-39 versus 445+/-63 ng/mL, SEM) concentrations were significantly greater in healthy foals 1-3 days old. Serum lactoferrin concentration in 1-3-day-old healthy foals was not different from mature horses or ill foals. IgG and lactoferrin concentrations were significantly correlated only in healthy foals. Serum lactoferrin concentrations were significantly lower in ill neutropenic foals. The serum IgG concentration was significantly lower in ill foals as compared to healthy foals. Only serum IgG was significantly less in ill foals with a positive sepsis score and in nonsurvivors, Plasma lactoferrin concentrations were lower than serum concentrations, although values were significantly correlated. CLINICAL IMPORTANCE: Although both serum IgG and lactoferrin concentrations increase in healthy foals after ingestion of colostrum, only serum IgG is significantly correlated with the sepsis score and outcome.     

Effect of withholding macromolecules on the duration of intestinal permeability to colostral IgG in foals

OBJECTIVE: To quantify absorption of colostral IgG by healthy neonatal foals and to test the hypothesis that delayed ingestion of macromolecules prolongs the duration of intestinal permeability to immunoglobulins (Ig) in newborn foals. ANIMALS: Thirteen mixed breed foals. PROCEDURE: Foals were randomly assigned to two treatment groups, which were fed either a glucose-electrolyte solution or a commercial milk replacer for 12 h after birth, before being fed a known amount of colostral IgG. A control group was fed a known amount of colostral IgG from birth. The efficiency of IgG absorption was calculated following determination of plasma IgG concentration for each foal. RESULTS: Foals given colostrum immediately after birth transferred approximately 51% of ingested IgG into their vascular space. Delayed colostral ingestion significantly reduced the amount of IgG absorbed by foals. Withholding macromolecules for 12 h had no effect on the subsequent efficiency of IgG absorption. CONCLUSIONS: Colostrum should be supplied to foals within 12 h of birth for best uptake of Ig. The type of fluid administered to foals before the ingestion of colostrum does not influence subsequent absorption of Ig, suggesting that the process of gut closure in foals is not mediated by a finite capacity for macromolecular uptake.     

Induction of parturition in mares: effect on passive transfer of immunity to foals

Parturition was induced in 11 mares, using a synthetic prostaglandin. Eight mares, not treated, were used as controls. There was no significant difference between the serum immunoglobulin G (IgG) concentrations of the treated and control mares. The concentration of IgG in the colostrum of treated mares compared favorably with that reported for naturally foaling mares. Four foals from treated mares died or were euthanatized because of weakness during the 1st 24 hours after birth. The mean IgG concentration in the surviving foals from treated mares at 24 to 36 hours of age was 1,561 mg/100 ml, which was significantly (P less than 0.01) lower than the mean concentration of 2,731 mg/100 ml in foals from control mares. The mean serum IgG concentration in foals from control mares was significantly (P less than 0.01) greater than that of their dams, whereas the mean serum IgG concentration of the foals from treated mares was significantly (P less than 0.01) lower than that of their dams.     

Increase of serum gamma-glutamyltransferase in neonatal Standardbred foals

Serial blood samples were obtained from 16 Standardbred foals from time of birth to postpartum day 28. Sera were obtained and analyzed for gamma-glutamyltransferase (GGT), aspartate transaminase, and immunoglobulin (Ig) G. Presuckle colostrum from the respective mares of these foals was analyzed for GGT activity. Mean serum aspartate transaminase activities were significantly increased above presuckle values by postpartum hour 48 (P less than 0.01) and increased gradually over the first 14 days. Mean serum IgG concentrations were significantly greater than presuckle values by 5 hours after foals first suckled (P less than 0.01) and remained significantly increased during the 28-day sampling period. Serum GGT activity did not differ significantly over the period sampled. The SD were large, since there was a large degree of interindividual variation. Serum GGT activity in the foals was significantly increased over that in the mares throughout the period of the study. The profile of serum GGT activity over time in each foal did not show a pattern of change. There was no postsuckle increase in serum GGT activity nor a correlation between serum GGT activities and IgG concentrations at 24 hours after foals first suckled. Evidence was not obtained to support a colostric source of GGT involved in the increase of serum GGT activity in foals. Serum GGT activity seems to be increased in foals due to endogenous sources.     

Immunoglobulin derived from bovine plasma as a replacement for colostrum in newborn lambs

Newborn lambs (n = 45) at the Agricultural Research Institute of Northern Ireland were fed either 50 grams of commercial lamb milk replacer or 50 grams of commercial colostrum replacer (bovine origin) in 200 ml of water four times during the first 24 hours of life or were given ad libitum access to the ewe. Total plasma protein at 24 hours of age was highest in lambs allowed to suckle the ewe (76.9 g/L). However, by 14 days of age, there were no differences in plasma protein levels among the three treatments. Bovine IgG was measured in lambs fed colostrum replacer and ovine IgG was measured in other lambs. Mean plasma IgG concentrations at 24 hours of age were 0.7 (milk replacer), 18.0 (colostrum replacer), and 26.6 (dam's milk) g/L. Bovine IgG administered orally to newborn lambs was adequately absorbed, and circulating IgG concentrations were sufficiently maintained throughout this study.     

Comparison of four screening techniques for the diagnosis of equine neonatal hypogammaglobulinemia

Using radial immunodiffusion as a standard, 4 screening techniques for detection of failure of passive transfer in equine neonates were compared for sensitivity, specificity, positive and negative predictive values, efficiency, and cost. The techniques compared were latex agglutination test, membrane filter ELISA, dipstick ELISA, and glutaraldehyde coagulation (GC) test. Test results of 50 serum samples from foals 24 to 60 hours old revealed consistently highest accuracy in the GC test at IgG concentrations of 400 and 800 mg/dl, and lowest cost per test, using the GC test. Two hundred fifty-three serum samples from foals 24 to 60 hours old were evaluated for comparison of results of GC and radial immunodiffusion tests. Overall efficiency was 92 and 91% at serum IgG concentrations of 400 and 800 mg/dl, respectively. Under most field circumstances, the GC test would be the preferred screening test for detection of failure of passive transfer in equine neonates.