Selenium (Se) is an essential mineral for animal
health. Deficiencies result in white muscle
disease (40), retained placenta, and ill thrift in
cattle. These health problems are known to occur
in some northern California herds. This survey was
initiated to provide knowledge on the epidemiological
features of Se deficiency in cattle in this region.

Blood samples were drawn from 10 cows on each
of 10 ranches in each of the northern 22 counties.
Whole blood Se and glutathione peroxidase (GBH-Px)
activities were determined, and these values were
statistically compared with each other and with data
obtained by questionnaire. The latter included
information on animal diseases, soils, forages, and
general ranch descriptors like elevation and rainfall.
The GSH-Px spot test produced either a positive
(+), negative (-) or intermediate (+/-) enzyme
activity classification for each cow. Herd
classification was identified as + or - if >70%
cow-values fell in that class, otherwise it was identified
as +/-.

The overall geometric mean blood-Se value was
47.6 ng/ml. Regressions of individual and herd
GSH-Px-class against blood-Se values produced
r = .75 and r = .82, respectively. Significantly
low blood-Se levels were recorded in herds with:
1) negative GSH-Px values, 2) past histories of WMD
and ill thrift, 3) predominantly hay diet, 4) pregnant
and early lactating cows, and 5) pure bred
cows. The Se status of herds using Se-salt blocks
was not different from non- supplemented herds. Descriptive
ranch variables did not reliably assess
the Se status of herds in this study

Dunbar, J.R.

Johnson, W.H.

Mayland, H.F.

Norman, B.B.

Williams, J.D.

Northwest Irrigation & Soils Research Laboratory Publications

Epidemiological features of the selenium status in cattle of northern California

Selenium (Se) is an essential mineral for animal
health. Deficiencies result in white muscle
disease (WMD), retained placenta, and ill thrift in
cattle. These health problems are known to occur
in some northern California herds. This survey was
initiated to provide knowledge on the epidemiological
features of Se deficiency in cattle in this region.

Blood samples were drawn from 10 cows on each
of 10 ranches in each of the northern 22 counties.
Whole blood Se and glutathione peroxidase (GSH-Px)
activities were determined, and these values were
statistically compared with each other and with data
obtained by questionnaire. The latter included
information on animal diseases, soils, forages, and
general ranch descriptors like elevation and rainfall.
The GSH-Px spot test produced either a positive
(+), negative (-) or intermediate (+/-) enzyme
activity classification for each cow. Herd
classification was identified as + or - if > 70%
cow-values fell in that class, otherwise it was identified
as +/-.

The overall geometric mean blood-Se value was
47.6 ng/ml. Regressions of individual and herd
GSH-Px-class against blood-Se values produced
r = .75 and r = .82, respectively. Significantly
low blood-Se levels were recorded in herds with:
1) negative GSH-Px values, 2) past histories of WMD
and ill thrift, 3) predominantly hay diet, 4) pregnant
and early lactating cows, and 5) pure bred
cows. The Se status of herds using Se-salt blocks
was not different from non-supplemented herds. Descriptive
ranch variables did not reliably assess
the Se status of herds in this study

USDA - ARS - NWISRL

Proceedings, Western Section, American Society of Animal ScienceVol. 36, 1985EPIDEMIOLOGICAL FEATURES OF THE SELENIUM STATUSIN CATTLE OF NORTHERN CALIFORNIAH.F. Mayland, USDA-ARS, Kimberly, Idaho 83341;J.A. Williams, previously UC-Davis, NSW Dept. of Agr., aP.O. Box 488, Lismore, NSW, Australia8.8. Norman, W.H. Johnson and J.R. Dunbar, University of California, Davis, California.Selenium (Se) is an essential mineral for ani-mal health. Deficiencies result in white muscledisease (t44D), retained placenta, and ill thrift incattle. These health problems are kncwn to occurin sane northern California herds. This survey wasinitiated to provide knowledge on the epidemiologi-cal features of Se deficiency in cattle in this re-gion.Blood samples were drawn fran 10 cows on eachof 10 ranches in each of the northern 22 counties.whole blood Se and glutathione peroxidase (GSH-Px)activities were determined, and these values werestatistically canpared with each other and with da-ta obtained by questionnaire. The latter includedinformation on anima/ diseases, soils, forages, andgeneral ranch descriptors like elevation and rain-fall. The GSH-Px spot test produced either a posi-tive (+), negative (-) or intermediate (+/-) en-zyme activity classification for each cow. Herdclassification was identified as + or - if > 70%cow-values fell in that class, otherwise it was i-dentified as +/- .The overall geometric mean blood-Se value was47.6 ng/ml. Regressions of individual and herdGSH-Px-class against blood-Se values producedr = .75 and r = .82, respectively. Significantlylow blood-Se levels were recorded in herds with:1) negative GSH-Px values, 2) past histories of WMDand ill thrift, 3) predominantly hay diet, 4) preg-nant and early lactating cows, and 5) pure bredcows. The Se status of herds using Se-salt blockswas not different fran non-supplemented herds. Des-criptive ranch variables did not reliably assessthe Se status of herds in this study.IntroductionSelenium deficiency in grazing animals isknaan to occur in the eastern and western regions ofthe United States (Kubota and Alloway, 1972). De-ficiencies are quite severe in western Oregon andWashington and in northern California. This paperreports the results of a survey undertaken to pro-vide information on the epidemiological factorsassociated with selenium deficiency in northernCalifornia.•Materials and MethodsRived samples were collected in a conveniencesaaale of 1465 adult cows from 150 herds in 22counties in northern California over a five monthperiod from January to May 1980. A maximum of 10cos in no more than 10 herds in each county wereincluded in the survey. Samples were obtained fromcows that had 1) had at least one calf-, 2) been onthe ranch for at least 60 days and 3) been grazingthe same pasture for at least 30 days prior to sam-pling. These stipulations ensured that all animalsin the survey had blood selenium chemistry indica-tive of local management practices and environmentalconditions. Nearly all cows sampled were beefcattle.	 -Blood samples were collected into purple-topcollection tubes containing EDTA and forwarded onice (not frozen) to Davis. At Davis, the gluta-thione peroxidase (GSH-Px) spot test was performedusing the method of Segall et al. (1977). This pro-cedure produced either a positive (+), negative (-)or intermediate (+/-) enzyme activity classificationfor each cow. These categories corresponded to val-ues observed in selenium-supplemented calves whichshowed increased weight gains (+ group) and unsupaplemented calves which showed aaor weight gains(- group). All GSH-Px spot tests were performedwithin seven days of collection.Individual GSH-Px classifications were used toassign a GSH-Px classification to the herd. A herdwas arbitrarily assigned to group 1 if 70% or morecows in the sample returned negative (-) enzyme ac-tivity results. Similarly a herd was assigned togroup 3 if 70% or more cows returned positive (+)enzyme activity results. Herds with GSH-Px valuesfalling between these categories were classified asgroup 2.The selenium concentration in the whole blood- was determined at the USDA-ARS laboratory nearKimberly, Idaho using the fluoragetric method ofCason et al (1975). The herd-selenium concentra-tion was calculated as the mean blood selenium con-centration for cows in the herd.At the time of blood sampling, a questionnaireon various ranch and animal characteristics was com-pleted. The ranch variables included topography,elevation, rainfall, fertilizer history, soil type,feed type, disease history, selenium supplementa-tion history and herd size, as well as individualanimal variables like production and breed data forthe sample cows.Questionnaire responses to all disease varia-bles referred to the past disease history of theranch and the disorders were not necessarily appar-ent at the time of sampling. Responses to the re-maining variables referred to the status of the cowsat the time of sampling and for at least one monthprior to that. In many cases the animals in thissurvey had been under the same ranch conditions forthe previous four months.The injectable supplementation group referredto supplementation via either injections of vitaminE (vitamin ADE ccraaex) alone or in combination withsodium selenite (vitamin E 68 IU/ml, Na selenite10.95 mg/ml). Only one of these ranches was also95TARLP 1.	 SOME RESULTS OF THE ONE-WAY ANALYSIS OFVARIANCE COMPARING THE GEOMEFRIC MEAN HERDSELUNIUM CONCENTRATIONS BETWEEN GROUPSWITHIN GIVEN RANCH VARIABLESNo.herds1/ inVariable	 Group - groupGroup	 ANOVAherd	 level ofblood	 2i signifi-ng Se/ml- canoe (P)Herd GSH-Px	 1 52 25a .0002 41 43b3 49 94cWhite muscle	 No 110 53a .000diaeaae	 Yes 27 31b13 38abIll thrift	 No 107 52a .006Yes 26 33b17 40abWeak calf	 No 102 50a .083syndrome	 Yes 39 38a9 48aRetained	 No 71 45a .76placenta	 Yes 71 48a8 52aUndiagnosed	 No 74 48a .84abortions	 Yes 61 46a15 43aGoiter	 No 125 48a .16Yes 10 52 a15 34 aFeed	 Pasture 36 58a .009Both 88 46abHay 26 34bSupplementa-	 Nation	 Vit E + Seinjection1281446a56a.53Se Salt blk a 42aGreat soil	 Alfisol 35 50a .45groups	 Entisol 10 44aInceptisol 15 48aMollisol 25 38aVertisol 15 57aUltisol 7 38aElevation	 0- 999' 87 46ab .0061000-1999' 25 60b2000-2999' 13 51ab3000-3999' 8 21a4000-4999' 13 44ab5000' 4 58ab1See text for description of GSH-Px, feed and sup-plement groups. Disease variables are: no historyof the disease (No), disease has occurred in herd(Yes), or history not known (7).2Variable-group means followed by a similar letterare not different (P = .05).supplementing with selenium salt blocks.Logarithmic (base 10) transformation of incdual and herd selenium data allowed all variab:used in the study to be normally distributed(BMDP 2D) for subsequent analyses using the ETZmedical Computer Prayrams (Dixon and Brawn, 19;Cne-way analysis of variance (BMDP 7D) was madethe transformed blood selenium data, as the resvariable, and the different groups within eachscriptor (Table 1). Differences between groupwere evaluated at P L.05 (Rleinbaum and Kupger1978). Duncans multiple range test was used ftpairwise testing for differences between herd yat different elevations. The data were also arlyzed (BMDP 1F) by the Chi Square frequency diehition test (Remington and Schork, 1970) to carthe results of the one-way analysis of variance(Table 2).The variances of the selenium response dataindividual animals were not homogenous. Thus PWallis non-parametric one-way analysis of varia(BMDP 35) was used to statistically ascertain teffect of animal groupings (Table 3). Differerbetween grraaa or ranks were evaluated at P = .using Dunns multiple comparison procedure awland WOlfe, 1973). Simple linear regression ofGSH-Px on herd selenium values and animal GSH-Ewhole blood selenium concentrations was perfornusing BMDP 1R.A non parametric discrimnant analysis usingclassification of Anderson (1966) was conductedusing herd GSH-Px and all other ranch variablesa biased data base (BMDP 7M). The 50 lowest seium value herds (range 6.4 to 31.7 ng Se/ml) arhighest value herds (range 62 to 219 ng Se/n1)used to determine if the remaining ranch varlethad any ability to discriminate herd selenium 4Since there was no significant difference atween supplemented and non-supplemented herds(Table 1) no further distinction was made beta%these subpopulations in aby analyses of the datResultsThe overall geometric mean blood selenium Ifor cows in this study was 47.6 ng/ml.. Belaw aage county values occurred in the coastal regicabove Sonoma, the northern mountain regions, nccentral Sierra Nevadas and eastern Sacramento VAbove average values occurred in the north centcoastal, western Sacramento Valley and TrinityLassen and Plumes counties in the mountain regiA significant correlation (r = .75, P t .0001)measured between the individual animal GSH-Px stest classifications and individual blood selemconcentrations. A significant correlation (r =P .0001) was also measured between the herdGSH-Px spot test classifications and herd bloodlenium concentrations.Tables 1 and 3 detail the geomutric group rfof blond selenium for some of the variables. 7cje,:curAric means are the antilog la values of themeans of the initial logarithmic transformationthe blood selenium data. Table 2 lists the resof the Chi squared frequency distribution analythe following significant details can be extracfrom the data summaries.96TABLE 2. RESULTS OF THE CHI SQUARE FREQUENCYDISTRIBUTION ANALYSIS OF VARIABLE GROUPSVERSUS ICW OR HIGH SELENIUM HERDS.DegreesVariable	 of freedom X2 valueLevel ofsignificanceRanch variables'Herd GSH-Px	 2 84. .000White muscle	 2disease7.55 .022Illthrift	 1 4.95 .027Weak calf syndrome 1 2.84 .11Retained placenta 	 2 2.61 .27Undiagnosedabortions	 2 .28 .87Goiter	 2 1.30 .52Feed	 2 7.86 .017Supplementation	 2 7.05 .025Great soil groups	 5 3.02 .70Elevation	 5 5.76 .33Herd size	 4 4.17 .38Rainfall 8.23 .41TOpography	 4 6.86 .14Time on ranch	 4 7.97 .093Time on pasture	 5 3.99 .55Fertilization	 1 .03 .86Animal variablesProduction	 4 54. .000BreedPurebred vscrossbred 14.3 .001Hereford vs Angusvs crossbred	 2 6.4 .041Animal GSH-Px	 2 834. .000Herds reporting the occurrence of white muscledi==k=== had a mean blood selenium level of 31 ng/mlwhereas those not reporting the di sorder had a meanvalue of 53 ng/ml. An arbitrary level of 40 ng Se/mlwas selected as a critical level to categorize herdsinto selenium deficient (<40 ng Se/ml) or seleniumadequate (>40 ng Se/m1). Herds in which illthriftoccurred also had lower blood selenium (33 vs 52nci/M1) than did honis Free of illthrift. Weak calfsyndruiv(xxairrili in ht , rds will; low ::uleninm levoh;(35 vs 50 ng/m11, but this relationship was signifi-cant only at P = .083.. Retained placenta and undi-agnosed abortions were not related to herd blood se-lenium (P = .76 and .84, respectively) in this study.Significantly higher (P = .009) blood seleniumlevels were associated with herds grazing pasture(58 ng/m1) than those fed hay (34 ng/ml). Blood se-lenium values were intermediate (46 ng/ml) for herdsgrazing pasture and receiving hay. Low blood selen-ium (21 ng/ml) was associated with herds on rancheslying at 3000 to 3999 feet elevation (900 to 1200m)and this was less (P S .05) than the high value(60 ng/ml) for herds maintained on ranches at 1000to 1900 feet (300 to 600m). All other comparisons ofelevational groupings were non-significant (P =1.05).No significant difference in mean blood seleniumlevels was nhenrved between herds that were 1) in-jected with vitamin E and or selenium, 2) given ac-cess to selenium salt block or 3) not given any sup-plement (Table 1). However, under Chi squared anal-ysis, significantly (1, = .025) more ranches usinginjectable vitamin E alone or in combination withselenium were observed than expected with blood lev-els above 40 ng Se/m1 (not shown). A similar differ-ence was not observed for the ranches using seleniumsalt block supplementation or no supplementation.Dry pregnant and early (0 3 months) lactationcows had lower blood selenium levels than non-preg-nant or late (over 3 months) lactation cows (Table 3).This relationship was also supported by the Chisquared analysis as many more than expected dry preg-nant and early lactation cows were recorded in thelow selenium group.Both statistical procedures (Tables 2 and 3) re-veal purebreds to have lower blood selenium concen-tration than crossbreds. No difference (1) < .05) wasobserved in blood selenium values in Hereford andAngus, but Angus cows. had significantly (P < .05)lower selenium values than the Hereford-Angus cross-bred cows.The 3 GSH-Px groups (-, +, t) were each associatedwith significantly (P 4.000) different blood selen-ium concentrations when based on either mean herdvalues (Tables 1 and 2) or individual animal data(Table 3).Using non parametric techniques and a biased database of the 50 lowest and 50 highest blood seleniumherds, good discrimination was obtained using threevariables; herd GSH-Px, herd size and ranch historyof retained placenta to correctly classify 80% ofthe herds into the low or high selenium categories.Similar techniques correctly classified 72% of thelow and high selenium categories when the discrimin-ating variables included feed, white muscle disease,retained placenta and time on the ranch. Parametrictechniques indicated that the last four variablescorrectly accounted for 67% of the herd seleniumwhen using the biased data hagP Good discrimina-tion of herd selenium status was only achieved inthis study by use of the GSH-Px spot test data incombination with some of the simple ranch variables.DiscussionBiasing of this survey was unavoidable, but nev-ertheless imposed scene statistical limitations andresults can be extrapolated only cautiously. Sam-pling criteria minimized a source of error in thatblood selenium levels respond rapidly to changes inselenium intake while GSH-Px would lag by 10 le 30days (Hoffman et al, 1978). The lower correlationsbetween blood selenium levels and GSH-Px values,when compared with other studies (Scholz andHutchinson, 1979), may have resulted from limitingthe GSH-Px classification to three categories.The selenium uptake in forage plants is deter-mined by the availability of soil selenium. Avail-ability is a function of soil type, form and levelof selenium and sulfur and soil pi. Soils of vol-canic origin generally have low selenium levelswhile sedimentary soils have higher levels (Muth andAllaway, 1963). Many soils in northern Californiaare of volcanic origin. For purposes of the survey,9?TABLE 3. SIGNIFICANT RESULTS OF 	 Swit-WALLIS CUEWAY ANALYSIS CF VARIANCE (X) CCMPARINC MEANBLOOD SELENIUM CONCENTRATIONS BETWEEN DIFFER-ENT ANIMAL VARIABLE GROUPS AND THE LEVEL OFSIGNIFICANCE (P).VariableGroup# CowsingroupBloodSe	 ,ng/m1 32 df X2ProductionDry, nonpregnant 71 63a 4 90 .000Dry, pregnant 318 40bLactating,43 mo. 517 42bLactating, >3 mo. 444 51aDry 15 45abBreedPurebred 976 42a 1 25 .000Crossbred 390 50bHereford 747 42ab 2 .02SeVAngus 195 40aHereford X Angus 178 49bGSH-PxGSH-Px 1 587 25a 2 866 .000GSH-Px 2 210 39bGSH-Px 3 578 82c1Variable-group means followed by a similar letterare not different (P = .05).2These data were analyzed by the cannon one wayanalysis or variance.the predominate great soil group occurring on eachranch was identified even tough other soils were of-ten present.Contrary to the well established relationship be-tween selenium deficiency'and retained placenta(Julien et al., 1976) it appears that the low inci-dence (< 10% in reporting herds) here may involvesane other factor. The occurrence of illthrift inthis area, however might respond to selenium supple-mentation (Andrews et al., 1976).Blood selenium in herds provided the FDA approvedselenium levels of 20 ppm were not different fromthose values in non selenium herds (P = .53). Suitstantially higher selenium concentrations (300 ppm)are undoubtedly required in northern California(Hathaway et al., 1980).Crossbred animals had higher selenium then pure-breds in agreement with the findings of Langlands etal. (1980). They reported that genotype was a signi-ficant source of variation in blood selenium andGSH-Px in cattle and sheep. It is postulated thatthe physiological demands for selenium are higherduring pregnancy and early lactation, thus depressingblood selenium values below those measured in othergroups.The results of this survey have confined thegnee relationship of GSH-Px with blood selenium con-centrations in cattle and verified that GSU-Px is agood indicator of animal and herd selenium status.It is also apparent that many cattle sampled wouldrespond to increased selenium supplementation.Anderson, T.W. 1966. Some non-parametric multi-variate procedures bases on statistically equiv-alent blneke P.R. Krishnaiah (ed.) In: Proc.Int'l. Symp. Multivariate Anal. Dayton, Ohio.1965. Academic Press, NY.Andrews, E.D., W.J. Hartley and A.B. Grant. 1968.Selenium responsive diseases of animals in NewZealarid. N.Z. Vet. J. 16:3.Dixon, W.J. and M.B. Brown (eds.) 1979. BMDP Bio-medical Computer PrograMs, P-series. Univ. ofCalifornia Press. Berkeley. 880p.Hathaway, R.L., J.E. Oldfield, M.R. Buettner, M.Hansen and G.E. Carter. 1980. Effective levelsof selenium in mineral-salt mix for supplemen-ting grazing heifers. Proc. Western SectionAm. Soc. Anim. Sci. 31:223.Hoffman, C., B. Rivinus and L. Swanson. .1978. Ef-fect of intramuscular administration of selen-ium and vitamin E in diary heifers on erythro-cyte glutathione peroxidase activity and bloodselenium levels. J. Anim. Sci. 47:192.Hollander, M. and D.R. Wolfe. 1973. Mon parametricstatistical methods. John Wiley and Sons.NY. p 115-132.Julien, W.E., H.R. Conrad and.A.L. Mexon. 1976.Selenium and vitamin E and incidence of re-tained placentae in parturient dairy cows. J.Dairy Sci. 59:1954.Kleinbaum, D.G. and L.L. Kupper. 1978. Applied re-gression analysis nod other multivariatemethods. nnehery Press. North Scituate, Mass.p 263-265.Kubota, J., W.H. Allaway, D.L. Carter, E.E. Cary andV.A. Lazar. 1967. Selenium in crops in theUnited States in relation to selenium responsivediseases of animals. J. Agric. Food Chem.15:448.Langlands, J.P., J.E. Bowles, G.E. Donald, T.S.Ch'ang, R. Evans, H. Hearnshaw and T.B. Post.1980. Genotype as a source of variation in se-lenium and glutathione peroxidase activity ofwhole blood from grazing sheep and cattle.Aust. J. Agric. Res. 31:839.Muth, O.H. and W.H. Allaway. 1963. The relation-ship of white muscle disease to the distribu-tion of naturally occurring selenium. J. Am.Vet. Neel. Assoc. 142:1179.Olson, 0.E., LS. Palmer and E.E. Cary. 1975. Med-ification of the fluorimetric method of selen-ium in plants. J. Assoc. Official Anal.Chemists. 58:117.Remington, R.D. and M.A. Schork. 1970. Statisticswith application to the biological and healthsciences. Prentice-Hall. New Jersey.p 229-244.Scholz, R.W. and L.J. Hutchinson. 1979. Distribu-tion of glutathione peroxidase activity andselenium in the blood of dairy cows. tan. J.Vet. Res. 40:245.Segall, H.J., D.M. Siege, B.B. Norman and M.N.Oliver. 1977. A rapid screening blood spottest for selenium-responsive disease in cattle.Calif. Vet. 31:10.98

Epidemiological Features of the Selenium Status in Cattle of Northern California

Proceedings, Western Section, American Society of Animal ScienceVOL 36, 1985EPIDEMIOLOGICAL FE ORES OF THE SELENIUM STATUSIN CATTLE CF NORTHERN CALIFORNIAH.F. Mayland, USak-ARS, Kimberly, Idaho 83341;J.D. Williams, previously UC-Davis, NSW Dept. of Agr., P.O. Box 488, Lis ore, NSW, AustraliaM.B. Norman, W.H. Johnson and J.R. Dunbar, University of California, Davis, California.SummarySelenium (Se) is an essential mineral for ani-mal health. Deficiencies result in white muscledisease (40), retained placenta, and ill thrift incattle. These health problems are known to occurin sore northern California herds. This survey wasinitiated to provide knowledge on the epidemiologi-cal features of Se deficiency in cattle in this re-gion.Blood samples were drawn from 10 cows on eachof 10 ranches in each of the northern 22 counties.Whole blood Se and glutathione peroxidase (GBH-Px)activities were determined, and these values werestatistically compared with each other and with da-ta obtained by questionnaire. The latter includedinformation on animal diseases, soils, forages, andgeneral ranch d=ci-riptors like elevation and rain-fall. The GSH-Px spot test produced either a posi-tive (+), negative (-) or intermediate (-1-./-) en-zyme activity classification for each cow. Herdclassification was identified as + or - if >70%cow-values fell in that class, otherwise it was i-dentified as +/-.The overall geometric mean blood-Se value was47.6 ngiml. Regressions of individual and herdGSH-Px-class against blood-Se values producedr = .75 and r = .82, respectively. Significantlylow blood-Se levels were recorded in herds with;1) negative GSH-Px values, 2) past histories of WMDand ill thrift, 3) predominan tly hay diet, 4) preg-nant and early lactating cows, and 5) pure bredcows. The Se status of herds using Se-salt blockswas not different from non- supplemented herds. Des-criptive ranch variables did not reliably assessthe Se status of herds in this study.IntroductionSelenium deficiency in grazing animals isknown to occur in the eastern and western regions ofthe United States (Kubota and Alloway, 1972). De-ficiencies are quite severe in western Oregon andWashington and in northern California. This paperreports the results of a survey undertaken to pro-vide information on the epidemiological factorsassociated with selenium deficiency in northernCalifornia.Materials and MethodsBlood samples were collected in a conveniencesample of 1465 adult cows fran 150 herds in 22counties in northern California over a five monthperiod fran January to May 1980. A maximum of 10cows in no more than 10 herds in each county wereincluded in the survey. Samples were obtained fromcows that had 1) had at least one calf, 2) been onthe ranch for at least 60 days and 3) been grazingthe same pasture for at least 30 days prior to sam-pling, These stipulations ensured that all animalsIn the survey had blood selenium chemistry indica-tive of local management practices and environmentalconditions. Nearly all cows sampled were beefcattle.Blood samples were collected into purple-topcollection tubes containing MIA and forwarded onice (not frozen) to Davis. At Davis, the gluta-thione peroxidase (GSH-Px) spot test was performedusing the method of Segall et al. (1977). This:pro-cedure produced either a positive (+), negative (-)or intermediate (+/-) enzyme activity classificationfor each cow. These categories corresponded to val-ues observed in selenium-supplemented calves whichshowed increased weight gains (+ group) and unsup-plemented calves which showed poor weight gains(- group). All GSH-Px spot tests were performedwithin seven days of collection.Individual GSH-Px classifications were used toassign a GSH-Px classification to the herd. A herdwas arbitrarily assigned to group 1 if 70% or worecaws in the sample returned negative (-) enzyme ac-tivity results. Similarly a herd was assigned togroup 3 if 70% or more caws returned positive (+)enzyme activity results. Herds with GSH-Px valuesfalling between these categories were classified asgroup 2.The selenium concentration in the whole bloodwas determined at the USDA-ARS laboratory nearKimberly, Idaho using the fluorometric method ofCason at al (1975). The herd-selenium concentra-tion was calculated as the mean blood selenium con-centration for cows in the herd.At the time of blood sampling, a questionnaireon various ranch and animal characteristics was Com-pleted. The ranch variables included topography,elevation, rainfall, fertilizer history, soil type,feed type, disease history, selenium supplementa- .tic= history and herd size, as well as individualanimal variables like production and breed data forthe sample cows.Questionnaire responses to all disease varia-bles referred to the past disease history of theranch and the disorders were not neo,q=nrily appar-ent at the tiMe of sampling. Responses to the re-maining variables referred to the status of the cowsat the time of sampling and for at least one monthprior to that. In many cases the animals in thissurvey had been under the same ranch conditions forthe previous four months.The injectable supplementation group referredto supplementation via either injections of vitaminE (vitamin ADE complex) alone or in combination 4410hsodium selenite (vitamin E 68	 Na selenite10.95 mg/ma). Only one of these ranches was also.006The variances of the selenium response data forindividual animals were not homogenous. Thus Kruska-Wallis non-parametric one-way analysis of variance	102	 50a	 .083	 (BMDP 3S) was used to statistleally ascertain the	39	 38a	 effect of animal groupings (Table 3). Differences	9	 48a	 between groups or ranks were evaluated at P = .05using Dunns multiple comparison procedure (Hollander	71	 45a	 .76	 and Wolfe, 1973). Simple linear regression of herd	71	 48a	 GSH-Px on herd selenium values and animal GSH-Px on	8	 52a	 whole blood selenium concentrations was performedusing BMDP 1R.A non parametric discrimnant analysis using theeleceification of Anderson (1966) was conductedusing herd GSH-Px and all other ranch variables, on	125	 48a	 .16	 a biased data base (BMDP 7M). The 50 lowest selen-	le	 52a	 ium value herds (range 6.4 to 31.7 ng Se/ma) and 50	15	 34 a	 highest ,value herds (range 62 to 219 ng Se/ml) wereused to determine if the remaining  ranch variehles	.009	 had any ability to discriminate herd selenium status.Since there was no significant difference be-tween supplemented and non-supplemented herds	128	 46a	 .53	 {Table 1) no further distinction was wade betweenthese subpopulations in any analyses of the data.107	52a26	 33b17	40ab74	 48a	 .8461	46a15	 43a36	 58a88	 46ab26	34bIllthrift	 NoYesWeak calf	 Nesyndrome	 YesNa7RetainedplacentaUndiagnosedabortionsGoiterYesNoYes7NoYes7Feed	 PastureBothHaySupplenenta- Notion Vit E ± SeinjectionSe Salt blkGreat soil	 Alfisolgroups	 EntisolInceptisolMollisolVertisolUltisolElevation	 0- 999'1000-1999'2000-2999'3000-3999'4000-4999'5000'14	 56a8	 42a35	 50a	 .4510	 44a15	 48a25	 38a15	 57a7	 38a872512813446ab60b51ab21a44ab58ab.006'mere 1. SOME RESULTS OF THE ONE-eMY ANALYSIS OFVARIANCE COMPARING THE GECMETRIC NEAN HERDSELENIUM CONCENTRATIONS BETNEEN GROUPSWITHIN GIVEN RANCH VARIABLES.No.	 Group	 ANOVAherds	 herd	 level ofVariable	 Group - group1/ in	ng Se/hay cance (P)blood	 signifi-Herd GSH-Px	 1	 52	25a	 .0002	 41	43b3	 49	94cWhite muscle	 No	 110	53a	 .000disease	 Yes	 27	31b13	38absupplementing with selenium salt blocks.Logarithmic (base 10) transformation of indivi-dual and herd selenium data allowed all variablesused in the study be be normally distributed(BMDP 2D) for subsequent analyses using the BMDP Bio-medical Computer Program (Dixon and Brown, 1979).Cne-way analysis of variance (BMDP 7D) was made ofthe transformed blood selenium data, as the responsevariable, and the different groups within each de-scriptor (Table 1). Differences between group meanswere evaluated at P L.05 (Kieinbaum and Kupper,1978). Duncans multiple range test was used forpairwise testing for differences between herd meansat different elevations. The data were also anae. lyzed (BMDP 1F) by the Chi Square frequency distri-bution test (Remington and Schork, 1970) to confirmthe results of the one-way analysis of variance(Table 2).ResultsThe overall geanetric mean blood selenium levelfor cows in this study was 47.6 ng/ma. Below aver-age county values occurred in the coastal regionsabove Sonoma, the northern mountain regions, northcentral Sierra Nevadas and eastern Sacramento Valley.Above average values occurred in the north centralcoastal, western Sacramento Valley and TrinityLassen and Plumes counties in the mountain regions.A significant correlation (r = .75, P 4 .0001) wasmeasured between the individual animal GSH-Px spottest classifications and individual blood seleniumconcentrations. A significant correlation (r = .82,P L .0001) was also measured between the herdGSH-Px spot test classifications and herd blood se-lenium concentrations.Tables 1 and 3 detail the geometric group meansof blood selenium for same of the variables. Thesegeometric means are the anti/ogle values of themeans of the initial logarithmic transformations ofthe blood selenium data. Table 2 lists the resultsof the Chi squared frequency distribution analysis.Tice following significant details can be extractedfrom the data summaries.ISee text for description of GSH-Px, feed and sup-plement groups. Disease variables are no historyof the disease (No), disease has occurred in herd(Yes), or history not known (?).kariable-group means followed by a similar letterare not different (P = .05).TART; 2. RESULTS OF THE CHI SQUARE FREQUENCYDISTRIBUTION ANALYSIS OF VARIABLE GROUPSVERSUS LOW OR HIGH SELENIUM HERDS.DegreesVariable	 of freedom X2 valueLevel of .significanceRanch variablesHerd GSH-Px	 2 84. .000White muscle	 2disease7.55 .022Illthrift	 1 4.95 .027Weak calf syndrome 1 2.84 .11Retained placenta	 2 2.61 .27Undiagnosedabortions	 2 .28 .87Gaiter	 2 1.30 .52Feed	 2 7.86 .017Supplementation	 2 7.05 .025Great soil groups	 5 3.02 .70Elevation	 5 5.76 .33Herd size	 4 4.17 .38Rainfall	 8 8.23 .41Topography	 4 6.86 .14Time on ranch	 4 7.97 .093Time on pasture	 5 3.99 .55Fertilization	 1 .03 .86Animal variablesProduction	 4 54. .000BreedPurebred vscrossbred	 1 14.3 .001Hereford vs Angusvs crossbred	 2 6.4 .041Animal GSH-Px	 2 834. .000Herds reporting the occurrence of white muscledisease had a mean blood selenium level of 31 ng/mlwhereas those not reporting the disorder had a meanvalue of 53 ng/ml. An arbitrary level of 40 ng Se/MIwas selected as a critical level to categorize herdsinto selenium deficient (4.40 ng Se/ml) or seleniumadequate (>40 ng Se/ml). Herds in which illthriftoccurred also had laver blood selenium (33 vs 52ng/ml) than did herds free of illthrift. Weak calfsyndrome occurred in herds with low selenium levels(38 vs 50 ng/ml), but this relationship was signifi-cant only at P = .083. Retained placenta and undi-agnosed abortions were not related to herd blood se-lenium (P = .76 and .84, respectively) in this study.Significantly higher (P = .009) blood seleniumlevels were associated with herds grazing pasture(58 ng/ml) than those fed hay (34 ng/ml). Blood se-lenium values were intermediate (46 ng/ml) for herdsgrazing pasture and receiving hay. Law blood selen-ium (21 ng/ml) was associated with herds on rancheslying at 3000 to 3999 feet elevation (900 to 1200m)and this was less (P $ .05) than the high value(60 ng/m1) for herds maintained on ranches at 1000to 1900 feet (300 to 6000. All other comparisons ofelevational groupings were non-si pificant (P a. S .05).NO significant difference in wean blood seleniumlevels was observed between herds that were 1) in-jected with vitamin E and or selenium, 2) given ac-cess to selenium salt block or 3) not given any sup-plement (Table 1). However, under Chi squared anal-ysis n significantly (P = .025) mare ranches usinginjectable vitamin E alone or in combination withselenium were observed than expected with blood lev-els above 40 ng Se/ml (not Shawn). A similar differ-ence was not observed for the ranches using seleniumsalt block supplementation or no supplementation.. Dry pregnant and early (0 - 3 months) lactationcows had lower blood selenium levels than non-preg-nant or late (over 3 months) lactation cows (Table 3).This relationship was also supported by the Chisquared analysis as many more than expected dry preg-nant and early lactation cows were recorded in thelow selenium group.Both statistical procedures (Tables 2 and 3) re-veal purebreds to have lower blood selenium concen-tration than crossbreds. No difference (P < .05) uesobserved in blood selenium values in Hereford andAngus, but Angus cows had significantly (Pi .05)lower selenium values than the Hereford-Angus cross-bred cows.m 3 GSH-Px groups (-, +, e) were each associatedwith significantly (P 4.000) different blood selen-ium concentrations when based on either mean herdvalues (Tables 1 and 2) or individual animal data(Table 3).Using non parametric techniques and a biased database of the 50 lowest And 50 highest biped seleniumherds, good discrimination was obtained using threevariables; herd GSH-Px, herd size and ranch historyof retained placenta to correctly classify 80% ofthe herds into the low or high selenium categories.Similar techniques correctly classified 72% of thelow and high selenium categories when the discrimin-ating variables included feed, white muscle disease.retained placenta and time on the ranch. Parametrictechniques indicated that the last four variablescorrectly accounted for 67% of the herd seleniumwhen using the biased data base. Good discrimina-tion of herd selenium status was only achieved inthis study by use of the GSH-Px spot test data incombination with some of the simple ranch variables.DiscussionBiasing of this survey was unavoidable, but nev-ertheless imposed some statistical limitations andresults can be extrapolated only cautiously. Sam-pling criteria minimized a source of error in thatblood selenium levels respond rapidly to changes inselenium intake while GSH-Px would lag by 10 to 30days (Hoffman et al, 1978). The lower correlationsbetween blood selenium levels and GSH-Px values,when compared with other studies (Scholz andHutchinson, 1979), may have resulted from limitingthe GSH-Px classification to three categories.The selenium uptake in forage plants is deter-mined by the availability of soil selenium. Avail-ability is a function of soil type, form and levelof selenium and sulfur and soil pH. Soils of vol-canic origin generally have low selenium levelswhile sedimentary soils have higher levels (Mut/a:andAllaway, 1963). Many soils in northern Californiaare of volcanic origin. For purposes of the survey,TABLE 3. siGarnuer RESULTS OF KNSKAL-WMLLIS CNEWAY ANALYSIS CF VARIANCE (X 4 ) CCMPARING MEANBLOOD SELENIUM CONCENTRATIONS BETWEEN DIFFER-ENT ANIMAL VARIABLE GROUPS AND THE LEVEL OFSIGNIFICANCE (P).VariableGroup# CowsingroupBloodSeng/m.1.2i df X2 PProductionDry, nonpregnant 71 63a 4 90 .000Dry, pregnant 318 40blactating, 43 mo. 517 42bLactating, >3 mo. 444 51aDry 15 45abBreed--7Purebred 976 42a 1 25 .000Crossbred 390 50bHereford 747 42ab 2 at . 025yAngus 195 40aHereford X Angus 178 49bGSH-PxGSH-Px 1 587 25a 2 866 .000GSH-Px 2 210 39bGSH-Px 3 578 82c1Variable-group means followed by a similar letterare not different (P = .05).2These data were analyzed by the common one wayanalysis of variance.the predominate great soil group occurring on eachranch was identified even though other soils ware of-ten present.Contrary to the well established relationship be-tween selenium deficiency and retained placenta(Julien et al., 1976) it appears that the low inci-dence (410% in reporting herds) here may involvesome other factor. The occurLeu/ce of illthrift inthis area, however might respond to selenium supple-mentation (Andrews et al., 1976).Blood selenium in herds provided the FDA approvedselenium levels of 20 ppm were not different framthose values in non selenium herds (P = .53). Sub-stantially higher selenium concentrations (300 ppm)are undoubtedly required in northern California(Hathaway et al., 1980).Crossbred animals had higher selenium then pure-breds in agreement with the findings of Langlands etal. (1980). They reported that genotype was a signi-ficant source of variation in blood selenium andGSH-Px in cattle and sheep. It is postulated thatthe physiological demands for selenium are higherduring pregnancy and early lactation, thus depressingblood selenium values below those measured in othergroups.The results of this survey have confirmed thegood relationship of GSH-Px with blood selenium con-centrations in cattle and verified that GSH-Px is agood indicator of animal and herd selenium status.It is also apparent that many cattle sampled wouldrespond to increased selenium supplementation.Anderson, T.W. 3966. Some non-parametric multi-variate pLuLedures bases on statistically equiv-alent blocks. P.R. Krishnaiah (ed.) In: Proc.Int'l. Symp. Multivariate Anal. Dayton, Ohio.1965. Academic- Press, NY.Andrews, E.D., W.J. Hartley and A.B. Grant. 1968.Selenium responsive diseases of animals in NewZealand. N.Z. Vet. J. 16:3.Dixon, W.J. and M.B. Brown (eds.) 1979. BMDP Bio-medical Computer Programs, P-series. Univ. ofCalifornia Press. Berkeley. 880p..Hathaway, R.L., J.E. Oldfield, M•R• Buettner, M.'Hansen and G.E. Carter. 1980. Effective levelsof selenium in mineral-salt mix for supplemen-ting grazing heifers. Proc. Western SectionAm. Soc. Anim. Sci. 31:223.Hoffman, C., B. Rivinus and L. Swanson. 1978. Ef-fect of intramuscular administration of selen-ium and vitamin E in diary heifers on erythro-cyte glutathione peroxidase activity and bloodselenium levels. J. Anim. Sci. 47:192.Hollander, M. and D.R. Wolfe. 1973. Non peLdretricstatistical methods. John Wiley and Sons.NY. p 115-132.Julien, W.E., H.R. Conrad and A.L. Moxon. 1976.Selenium and vitamin E and incidence of re-tained placentae in parturient dairy cows. J.Dairy Sci. 59:1954.Kleinbaum, D.G. and L.L. Kupper. 1978. Applied re-gression analysis and other multivariatemethods. Duxbury Press. North Scituate, Mass.p 263-265.Kubota, J., W.H. Allaway, D.L. Carter, E.E. Cary andV.A. Lazar. 1967. Selenium in crops in theUnited States in relation to selenium responsivediseases of animals. J. Agric. Food Chen.15:448.Langlands, J.P., J.E. Bowles, G.E. Donald, T.S.Chang, R. Evans, H. Hearnshaw and T.B. Post.1980. Genotype as a source of variation in se-lenium and glutathione peroxidase activity ofwhole blood from grazing sheep and cattle.Aust. J. Agric. Pes. 31:839.Muth, O.H. and W.H. Allaway. 1963. The relation-ship of white muscle disease to the distribu-tion of naturally occurring selenium. J. Pin.Vet. Med. Assoc. 142:1379.Olson, 0.E„ I.S. Palmer and E.E. Cary. 1975. Mod-ification of the fluorimetric method of selen-ium in plants. J. Assoc. Official Anal.Chemists. 58:117.Remington, R.D. and M.A. Schork. /970. Statisticswith application to the biological and healthsciences. Prentice-Hall. New Jersey.p 229-244.Scholz, R.W. and L.J. Hutchinson. 1979. Distribu-tion of glutathione peroxidase activity andselenium in the blood of dairy cows. Am. J.Vet. Res. 40:245.Segall, H.J., D.M. Siege, B.B. Norman and M.N.Oliver. 1977. A rapid screening blood spottest for selenium-responsive disease in cattle.Calif. Vet. 31:10.

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Epidemiological features of the selenium status in cattle of northern California

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