Zinc Sulphate Turbidity as a Screening Test of Passive Transfer of Immunity in Newborn Foals

Endrigo Pompermayer, Flávio Desessards De La Cortê, Mara Iolanda Batistella Rubin


Background: Passive immunity acquired by colostrum ingestion is essential to prevent neonatal infections. Failure of passive transfer (FPT) of maternal immunity occurs in foals that fail to absorb enough immunoglobulins within 24 h after birth. Foals with FPT are at increased risk of infections and death. Serum samples from neonatal foals might be examined for FPT using the zinc sulphate turbidity (ZST) test. The aim of this study was to investigate the accuracy of the ZST test, performed at two different times after first suckling (12 and 18 h), to detect FPT in newborn foals. The effect of temperature on the turbidity intensity resulting from the ZST reaction was also investigated.

Materials, Methods & Results: Blood samples were collected from 112 newborn foals at 12 h after the first colostrum intake. In 36 foals, additional serum samples were collected at 18 h after first colostrum intake. The serum samples were tested with the ZST test and, later, in the laboratory setting, the ZST test was repeated. The IgG levels were measured by single radial immunodiffusion (SRID), which was used as the reference method. The standard solution used for the interpretation of results had a turbidity corresponding to approximately 800 mg/dL of immunoglobulins (IgG). The mean IgG concentration measured at 12 and 18 h after the first colostrum intake was analyzed using the t-test for paired samples. Values of absorbance of ZST test under different temperatures were analyzed using a one-way analysis of variance, and means were compared using the Tukey test. The relationship between the temperature of the solution and absorbance was determined using the Pearson’s correlation coefficient. Based on SRID results, 12 foals (10.7%) had serum IgG concentration < 400 mg and 26 foals (23.2%) had IgG levels between 400 and 800 mg/dL. Serum levels of IgG determined by SRID in 36 foals were similar (P > 0.05) between 12 h (943.9 ± 508.6 mg/dL) and 18 h (975.9 ± 525.6 mg/dL) after the first colostrum intake. The sensitivity values were 76.3% and 71.0% (P > 0.05) for tests performed at farm and laboratory, respectively. The specificity was higher (P < 0.05) for ZST tests performed at laboratory (94.6%) than at farms (73.0%). Twenty-nine of the 38 foals (76.3%) with IgG < 800 mg/dL were correctly detected using the ZST test at farms. There was a strong correlation (r = 0.92; P < 0.0001) between the temperature of the solution test and the degree of turbidity. The absorbance after the reaction of serum with zinc sulphate was similar between the temperatures of 30, 34 and 37ºC, which had higher values than 20 and 25ºC.

Discussion: The ZST test can be performed at 12 h after the first suckling. The lower specificity of tests run at farms compared to laboratory resulted in more foals with false positive diagnosis. The main cause of false positives at farms was probably the low temperature of the zinc sulphate solution at the time of testing, delaying the reaction and underestimating the IgG concentration. This assumption was reinforced by the increased specificity observed when the test was repeated with the same serum samples under controlled temperature of a laboratory. Additionally, the positive correlation observed between the temperature and degree of turbidity confirms that the reaction is temperature dependent. In the Southern hemisphere, most Thoroughbred foals are born during winter, when room temperature is far below the ideal temperature for good performance of the ZST test. Therefore, the number of false positives will likely be reduced if tests are performed at the farms under adequate temperature of solution (between 30 and 37ºC). This will reduce the number of foals receiving unnecessary treatment.

Full Text:



Axon J.E. & Palmer J.E. 2008. Clinical pathology of the foal. Veterinary Clinics Equine Practice. 24: 357-385.

Baird A.N., Pugh D.G., Rupp G.P., Shull J.W. & Field R.W. 1987. Detection of immunoglobulin G in the neonate. Journal of Equine Veterinary Science. 7(3): 124-129.

Carabetta D., Fernández D., Etcheverría A., Valle M. & Padola N.L. 2016. Evaluación de la transferencia pasiva de la inmunidad en equinos mediante el uso de diferentes pruebas. InVet. 18(2): 333-340.

Clabough D.L., Levine J.F., Grant G.L. & Conboy H.S. 1991. Factors associated with failure of passive transfer of colostral antibodies in Standardbred foals. Journal of Veterinary Internal Medicine. 5(6): 335-340.

Crisman M.V. & Scarratt W.K. 2008. Immunodeficiency disorders in horses. Veterinary Clinics Equine Practice. 24: 299-310.

Davis R. & Giguère S. 2005. Evaluation of five commercially available assays and measurement of serum total protein concentration via refractometry for the diagnosis of failure of passive transfer of immunity in foals. Journal of the American Veterinary Medical Association. 227(10): 1640-1645.

Erhard M.H., Luft C., Remler H.P. & Stangassinger M. 2001. Assessment of colostral transfer and systemic availability of immunoglobulin G in new-born foals using a newly developed enzyme-linked immunosorbent assay (ELISA) system. Journal of Animal Physiology and Animal Nutrition. 85: 164-173.

Franz L.C., Landon J.C., Lopes L.A., Marinho L.A., Sarma C., Bruemmer J. & Squires E.L. 1998. Oral and intravenous immunoglobulin therapy in neonatal foals. Journal of Equine Veterinary Science. 18(11): 742-748.

Giguère S. & Polkes A.C. 2005. Immunologic disorders in neonatal foals. Veterinary Clinics Equine Practice. 21: 241-272.

Hofsaess F.R. 2001.Time of antibody absorption in neonatal foals. Journal of Equine Veterinary Science. 21(4): 158-159.

Jeffcott L.B. 1974. Some practical aspects of the transfer of passive immunity to newborn foals. Equine Veterinary Journal. 6(3): 109-115.

Kalinbacak A., Guzel M. & Altintas I. 2005. Incidence of failure of immune passive transfer (FPT) in thoroughbred foals - Interest of a rapid diagnosis for FPT. Revue de Médecine Vétérinaire. 156(3): 163-165.

Kent J.E. & Blackmore D.J. 1985. Measurement of IgG in equine blood by immunoturbidimetry and latex agglutination. Equine Veterinary Journal. 17(2): 125-129.

Kummer L.L., Govaere J. & Egri B. 2018. Comparison of the reliability of snap foal Ig test, Gamma-Check E test, refractometry and electrophoresis for determining the immune status of newborn foals in the first hours of life. Acta Veterinaria Hungarica. 66(4): 573-586.

Lang A., Souza M.V., Salcedo J.H.P., Sossai S., Araújo R.R., Lourenço G.G. & Maia L. 2007. Imunidade passiva em eqüinos: comparação entre a concentração de IgG do soro materno, colostro e soro do neonato. Revista Ceres. 54(315): 405-411.

Le Blanc M.M. 2001. Update on passive transfer of immunoglobulins in the foal. Pferdeheilkunde. 17(6): 662-665.

LeBlanc M.M., Hurtgen J.P. & Lyle S. 1990. A modified zinc sulfate turbidity test for the detection of immune status in newlyborn foals. Equine Veterinary Science. 10(1): 36-39.

McEwan A.D., Fisher E.W., Selman I.E. & Penhale W.J. 1970. A turbidity test for the estimation of immune globulin levels in neonatal calf serum. Clinica Chimica Acta. 27: 155-163.

McGuire T.C., Crawford T.B., Hallowell A.L. & Macomber L.E. 1977. Failure of colostral immunoglobulin transfer as an explanation for most infections and deaths of neonatal foals. Journal of the American Veterinary Medical Association. 170(11): 1302-1304.

McGuire T.C., Poppie M.J. & Banks K.L. 1975. Hypogammaglobulinemia predisposing to infection in foals. Journal of American Veterinary Medical Association. 166(1): 71-75.

Morris D.D., Meirs D.A. & Merryman G.S. 1985. Passive transfer failure in horses: incidence and causative factors on a breeding farm. American Journal of Veterinary Research. 46(11): 2294-2299.

Perkins G.A. & Wagner B. 2015. The development of equine immunity: Current knowledge on immunology in the young horse. Equine Veterinary Journal. 47: 267-274.

Raidal S.L. 1996. The incidence and consequences of failure of passive transfer of immunity on a Thoroughbred breeding farm. Australian Veterinary Journal. 73(6): 201-206.

Raidal S.L, McTaggart C. & Penhale J. 2005. Effect of withholding macromolecules on the duration of intestinal permeability to colostral IgG in foals. Australian Veterinary Journal. 83(1-2): 78-81.

Riley C.B., McClure J.T., Low-Ying S. & Shaw R.A. 2007. Use of fourier-transform infrared spectroscopy for the diagnosis of failure of transfer of passive immunity and measurement of immunoglobulin concentrations in horses. Journal of Veterinary Internal Medicine. 21: 828-834.

Rumbaugh G.E., Ardans A.A., Ginno D. & Trommershausen-Smith A. 1978. Measurement of neonatal equine immunoglobulins for assessment of colostral immunoglobulin transfer: comparison of single radial immunodiffusion with zinc sulfate turbidity test, serum electrophoresis, refractometry for total serum protein, and the sodium sulfite precipitation test. Journal of American Veterinary Medical Association. 172(3): 321-325.

Rumbaugh G.E., Ardans A.A., Ginno D. & Trommershausen-Smith A. 1979. Identification and treatment of colostrum-deficient foals. Journal of American Veterinary Medical Association. 174(3): 273-276.

Sedlinská M., Krejcí J. & Vyskocil M. 2005. Evaluation of field methods for determining immunoglobulins in sucking foals. Acta Veterinaria Brno. 74: 51-58.

Silva C.A.M., Rubin M.I.B., Waihrich F.L. & Pelegrini J.L.M. 1984. Diagnóstico da imunidade passiva adotiva adquirida através do colostro no potro recém-nascido. Pesquisa Veterinária Brasileira. 4(1): 11-15.

Silva C.A.M., Silva J.F.S., Alda J.L., Silva J.H.S. & Rubin M.I.B. 1988. Diagnóstico imediato da imunodeficiência do potro recém-nascido. Revista Brasileira de Reprodução Animal. 12(4): 203-212.

Sprayberry K.A. 2003. Neonatal transfusion medicine: the use of blood, plasma, oxygen-carrying solutions, and adjunctive therapies in foals. Clinical Techniques in Equine Practice. 2(1): 31-41.

Tallmadge R.L., McLaughlin K., Secor E., Ruano D., Matychak M.B. & Flaminio J.B.F. 2009. Expression of essential B cell genes and immunoglobulin isotypes suggests active development and gene recombination during equine gestation. Developmental and Comparative Immunology. 33: 1027-1038.

Tallmadge R.L., Miller S.C., Parry S.A. & Felippe M.J.B. 2017. Antigen-specific immunoglobulin variable region sequencing measures humoral immune response to vaccination in the equine neonate. PLoS One. 12(5): e0177831.

Tyler-McGowan C.M., Hodcson J.L. & Hodgson D.R. 1997. Failure of passive transfer in foals: incidence and outcome on four studs in New South Wales. Australian Veterinary Journal. 75(1): 56-59.

Young K.M. & Lunn D.P. 2000. Immunodiagnostic testing in horses. Veterinary Clinics of North America: Equine Practice. 16: 79-103.

DOI: https://doi.org/10.22456/1679-9216.96105

Copyright (c) 2019 Endrigo Pompermayer, Flávio Desessards De La Cortê, Mara Iolanda Batistella Rubin

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.