250 Laboratory Animals (1988) 22, 250-254

Osmotic fragility of erythrocytes of two breeds of domestic fowlin the warm humid tropicsJ. O. OYEWALE & L. A. DUROTOYE

Department of Veterinary Physiology and Pharmacology, University of Ibadan, Ibadan, Nigeria

SummaryErythrocyte (RBC) count, packed cell volume(PCV) and haemoglobin (Hb) values were foundto be higher in Nigerian domestic fowls thanthose in Hubbard fowls. PCV and Hb valueswere higher in males than in females in bothbreeds. Erythrocytes of the Nigerian fowl wereobserved to be more susceptible to osmotichaemolysis than were erythrocytes of theHubbard fowl. Erythrocytes of male fowls wereosmotically more fragile than were those offemale fowls in both breeds.

Keywords: Erythrocyte osmotic fragility;Domestic jowl; Warm humid tropics

The resistance of erythrocytes to osmotichaemolysis has been investigated in variousanimal species (Perk et al., 1964; Soliman &Amrousi, 1966; Jain, 1973). Even for the sameanimal species, several authors have presentedvaried values (Schalm et al., 1975), probably asa result of differences in the factors known toinfluence osmotic fragility, such as size, volumeand age of erythrocytes, temperature and pH ofthe medium (Stone et al., 1953; Perk et al., 1964;Schalm et al., 1975). Data for fowl are especiallyrare. Perk et al. (1964)and Soliman and Amrousi(1966) reported marked differences between theosmotic behaviour of erythrocytes of fowl andother domestic animals in a temperateenvironment. Jaffe (1960) also in a temperatearea observed a difference in the resistance oferythrocytes to osmotic pressure between inbred

Received 13 November 1986; accepted 23 December 1987

White Leghorn strains C and W. It may,however, be necessary to extend the study to fowlin the tropical environment, considering theclinical importance of the values of theerythrocyte osmotic fragility and the many bloodparasitic diseases which are prevalent in thisenvironment. It has been shown that theresistance of erythrocytes to osmotic haemolysismay increase or decrease in some haematologicaldisorders (Jain, 1973). In an earlier study,Durotoye and Oyewale (1986) found the valueof erythrocyte osmotic fragility of the Nigeriandomestic fowl to be lower than that of the semi-domesticated guinea-fowl in the same environ-ment. The aim of the present study was tocompare the erythrocyte osmotic fragility of theNigerian domestic fowl with that of an exoticdomestic fowl, the Hubbard fowl, in the warmhumid tropics.

Materials and methodsAdult Nigerian domestic fowl and adultHubbard fowl which belonged to the Universityof Ibadan Teaching and Research Farm wereused. The birds were housed in deep litter pensand given a balanced poultry feed (Pfizer Ltd,Ibadan, Nigeria) and water ad libitum. Twenty-six clinically healthy Nigerian domestic fowls (13males, 13 females) and 20 clinically healthyHubbard fowls (8 males, 12 females) weresampled.

Blood was drawn from the jugular vein of eachfowl into bottles, using ethylene diaminetetraacetic acid (EDT A, 2 mg/ml) asanticoagulant, and was analysed within 2 h ofcollection. From a 1fr/o phosphate buffered(Na2HP04 l' 37 mg/ml,. and NaH2P04.2H20

Erythrocyte osmotic fragility of fowl

o· 24 mg/ml) sodium chloride (NaCl 9 mg/ml)solution 5ml of each of various concentrationsof NaCl solution (0'85, 0'80, 0'75, 0'70, 0'65,0'60,0'55,0'50,0'45,0'40,0'35,0'30,0'25,0·20 and 0'10070)were prepared in 15centrifugetubes, while the 16th tube contained 5ml ofdistilled water. The pH of the distilled water(7' 2) and the NaCl solutions (7· 4- 7, 9) weremeasured using a pH meter (Model 7050,Electronic Instruments Ltd, Chertsey, Surrey,UK). To each concentration of the NaCl solutionand the distilled water, O' 02 ml of blood wasadded. The contents were mixed and allowed tostand at room temperature (28-29°C) for30min. The tubes were then centrifuged at2000r.p.m. for 10min and about 3'5 ml of thesupernatant in each tube was later transferred toanother set of tubes. The optical density of eachsolution was read on a CE404 Colorimeter (CecilInstruments, Cambridge, UK) at a wavelengthof 540 J.tM,using distilled water as the blank. Acumulative erythrocyte osmotic fragiligram wasobtained by plotting the percentage haemolysisagainst the concentration of the NaCl solutions.The derivative fragiligram was obtained from thevalues of percentage haemolysis by using theprinciple of 'haemolytic increaments' (Suess etal., 1948).

251

Other haematological parameters analysedincluded packed cell volume (PCV) usingthe microhaematocrit method; haemoglobin(Hb) content using the cyanmethaemoglobinmethod; erythrocyte (RBC) count using thehaemocytometer and the mean corpuscularvolume (MCV) calcualted from the values ofRBC and PCV as described by Schalm et al.(1975).

ResultsThe mean values of PCV, Hb, erythrocyte count,MCV and the NaCI concentrations at whichminimum (less than 10070)and maximum (over90070)haemolysis of the erythrocytes occurred inNigerian domestic fowl and Hubbard fowl areshown in Table I. The PCV was significantlyhigher (P<O'OI) in males than in females in thetwo breeds of fowl. The mean PCV in Nigeriandomestic fowl was significantly higher (P<O'()()l)than the value in Hubbard fowl. Although nosignificant sex difference was found in theerythrocyte count in either breed, the mean countwas significantly higher (P<O'OI) in Nigeriandomestic fowl than in Hubbard fowl. The Hbvalue was significantly higher in males than infemales in Nigerian domestic fowl (P<O·Ol) andin Hubbard fowl (P<O·05). The former breed

Table 1. Haematological values (mean ± SD) and osmotic fragility of erythrocytes of Nigerian domestic fowl and Hubbard fowl

Parameters Sex Nigerian domestic fowls Hubbard fowls

PCV (070) Male 35·77±2·97 (13) 33, 25 ± 3, 31 (8)Fema]e 33'39± 1·70 (13) 28'29±2'16 (12)Male and female 34'08±2'95 (26) 30, 28 ± 3 ·6] (20)

RBC (l06/mm) Male 2'55±0'42 (13) 2'33±0'17 (8)Fema]e 2'42±0'38 (13) 2'14±0'25 (12)Male and female 2'48±0'40 (26) 2'22±0'24 (20)

Hb (g/dl) Male 1]'31 ± 1·06 (13) 10'06±0'95 (8)Female 9'84± 1'01 (13) 9'19±0'65 (12)Male and female 10, 58± I' 27 (26) 9'54±0'89 (20)

MCV (fl) Male 142·87 ± 15· 87 (13) 142· 66 ± I ] .67 (8)Fema]e 137·23 ± 22 ·15 (13) 133'08± 11·67 (12)Male and female 140'05± 19·47 (26) 136'96± 12'46 (20)

Minimum fragility Male 0'70 (31) 0,70 (8)(OJoNaCI10070haemolysis) Fema]e 0'65 (13) 0'55 (12)

Male and female 0,70 (26) 0'60 (20)Maximum fragility Male 0·20 (13) 0,10 (8)(OJoNaCI900/0haemolysis) Female 0'10 (13) 0,10 (12)

Male and female 0·20 (26) 0,10 (20)

Number of birds shown in parentheses

252 Oyewale & Durotoye

PERCENT"C,E SOOIUM CHLORIDE SOLJTION

\, PERCENT4GE SODIUM cHLORIDE SOLUTION

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Fig. 1. Cumulative (A) and derivative (B) erythrocyte osmoticfragiligrsms for male (0---0 and female (.--.)

Nigerial domestic fowl.

Fig. 3. Cumulative (A) and derivative (B) erythrocyte osmoticfrsgiligrams for Hubbard fowl (0---0) and Nigerian

domestic fowl (....---.).

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Fig. 2. Cumulative (A) and derivative (B) erythrocyte osmoticfragiligrsms for male (0---0) and female (. .)

Hubbard fowl.

showed a significantly higher (P <0·01) meanHb value than the latter. There were nosignificant sex differences in the values of MeVwithin and between the breeds.

In both breeds, the osmotic fragility oferythrocytes of the male fowl was higher thanthat of the female (Table 1). Haemolysiscommenced and was completed in a higher salineconcentration in Nigerian domestic fowl than inHubbard fowl, indicating a higher osmoticfragility of erythrocytes of the former breed.Figures 1-3 show the cumulative (A) andderivative (B) erythrocyte osmotic fragiligramsfor male and female Nigerian domestic fowl,male and female Hubbard fowl, and the twobreeds of fowl. The cumulative curves were allsigmoid in shape, but steeper for the Nigerianfowl than that for the Hubbard fowl. Thederivative curves showed differences in the peakof haemolytic increments, being higher for malesthan for females of each breed, and for Nigeriandomestic fowl than for Hubbard fowl. The lattercurves also showed one peak for the Nigerian

Erythrocyte osmotic fragility of fowl

domestic fowl and two or more peaks for theHubbard fowl.

DiscussionThe higher PCY and Hb values in males than infemales in the two breeds of domestic fowl aresimilar to observations in other avian species(Domm et al., 1943; Newell & Saffner, 1950;Tanaka & Rosenberg, 1954; Nirmalan &Robinson, 1971). Testosterone has been shownto increase the PCY and Hb values in the male(Domm et al., 1943; Newell & Saffner, 1950;Panda & Juhn, 1961; Fred et al., 1964). Weobserved higher RBC count, PCY and Hb valuesin the Nigerian fowl than in the Hubbard fowl.This may suggest a better adaptation of theNigerian fowl than the Hubbard fowl to thewarm humid tropics, where metabolic activityand oxygen requirement are likely to be higherthan in the temperate environment.

The mean PCY reported in the White Leghornfowl is 29'6±2'8OJo (Medway & Kare, 1959)or ranges between 28· 8 and 30% (Lucas &Denington, 1957). This is closer to the meanvalue in the Hubbard fowl (30'28±3'61%)than that in the Nigerian fowl (34'08 ± 2·95%).The RBC counts in the present study arelower than those reported in the BrownLeghorn (2'7-3'6x 1Q6/mm3; Domm et al.,1943) and in the White Leghorn breeds(3'08-3'36x 106/mm3; Lucas & Denington,1957). The mean Hb values are similarto those reported in the New Hampshirefowl (8'61-13'19g/dl; Tanaka & Rosenberg,1954).

Although the MCY values were not sig-nificantly different between the Nigerian fowland the Hubbard fowl, the values are higher thanthose reported in the inbred White Leghornstrains C and W by Jaffe (1960). The values ofmean corpuscular haemoglobin (MCH) andmean corpuscular haemoglobin concentration(MCHC) were also not significantly differentbetween the Nigerian fowl and the Hubbardfowl, as observed in a previous study (Oyewale,1987).

The erythrocytes of the Nigerian fowl

253

appeared more susceptible to osmotic haemolysisthan were those of the Hubbard fowl. Osmoticfragility varies with the age of red cells (Perk etal., 1964), the old cells being more fragile(Prankerd, 1961 cited by Perk et al., 1964), andthe proportion of erythrocytes of different agesin the blood may vary with the level of metabolicactivity (March et al., 1966). The difference inthe erythrocyte osmotic fragility betweenNigerian fowl and Hubbard fowl may thereforebe associated with a difference in the metabolicrates of the birds, as suggested between WhiteLeghorn and New Hampshire breeds (March etal., 1966). It is however doubtful whether thismay be responsible for the difference obtainedin the osmotic haemolysis between males andfemales of both breeds. The fact that erythro-cytes from male fowls were more susceptible toosmotic lysis than were those from female fowlis in accord with the report of March et al. (1966)in White Leghorns and New Hampshires. Theseworkers observed that oestrogen increases theresistance of erythrocytes to osmotic haemolysis,while androgen- shows no effect on red cellfragility in birds.

The NaCl concentrations at which theminimum and maximum haemolysis of erythro-cytes occurred, respectively, in this study(0' 7-0' 6% and O· 2-0' 1%) are different fromthose reported in adult domestic fowl by Jaffe(1960) (0' 495-0' 420% and O· 300-0' 285%),Perk et al. (1964)(0' 34% and 0'25%), Soliman& Amrousi (1966) (0'39% and 0'28%) andSwenson (1970) (0·41-0'40% and 0'32-0'28%).All these workers did their studies on birdsin the temperate environment, whereas thepresent study was done in a tropical environ-ment. Also, the breeds used by them weredifferent. As reported in the present studyand in that of March et al. (1966), a breeddifference exists in erythrocyte osmotic fragilityin domestic fowl. It is hoped, however, that thedata presented in this study should be of help inassessing the significance of the values that maybe obtained in the tropical environment in diseaseconditions, at least in Nigerian and Hubbardfowl.

254

AcknowledgmentsThe authors thank Messrs Akin Olowookorun,

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