Mineral status of sheep in the Paramo region of Colombia. II. Trace minerals

SmallRuminant Research, 5 ( 1991 ) 23-34

23

Elsevier Science Publishers B.V., Amsterdam

Mineral status of sheep in the Paramo region of Colombia. II. Trace minerals R. Pastrana a, L.R. McDowell b'*, J.H. Conrad b, and N.S. Wilkinsonb ~lnstituto Cglombiano Agropecuario, Tibaitata, Apdo. Aereo 151123 Eldorado, Bogota, Colombia bAnimal Science Department, University of Florida, Gainesville, FL 32611-0691, USA (Accepted 13 July 1990)

ABSTRACT Pastrana, R., McDowell, L.R., Conrad, J.H., Wilkinson, N.S., 1991. Mineral status of sheep in the Paramo region of Colombia. II. Trace minerals. Small Rumin. Res., 5" 23-34. Three sheep classes (pregnant-lactating ewes, lambs and yearlings) were studied to determine the trace mineral status of grazing animals from three sheep farms located in the Paramo region of the Cordillera Oriental in Colombia. At the end of the rainy season (May-June, 1987) and middle to end of the dry season (February, 1988), soil, forage, blood and liver samples were collected. Soil Zn and forage Co, Cu, Mn and Mo concentrations were affected by season (P<0.05). Soil Se and Mn concentrations were deficient during both rainy and dry seasons (100% and 54%, respectively). Forage Co and Cu were deficient (87% and 75%, respectively); but Cu was 94% during the dry season. Mo values were below the toxic limit for sheep of 6 ppm, and the Cu: Mo ratio was at least 4: I. Fe and Mn were in excess of requirements for sheep but below maximum tolerable levels. Blood serum analyses showed only small deficiencies, liver for Cu (59%), Zn (44%), and for Co (55%) during the dry season. No differences ( P ~ 0.05 ) were found among animal classes for any plasma and liver trace elements in both seasons. Ewes were more deficient in liver Zn (58%) and liver Cu (71%); yearlings in liver Co but lambs were about as deficient in liver Cu (69%) as ewes. Based primarily on liver analyses it was concluded that Cu, Zn and Co were the most deficient trace elements. These plus Se should be continually supplemented in the Paramo of Colombia. There was no direct relationship between soil and plant trace mineral concentrations, however, mineral imbalance problems in livestock could be predicted from forage and animal tissue analyses.

INTRODUCTION

Ruminants grazing forages in severely mineral-deficient areas may even be more limited by this condition than by a lack of energy or protein (McDowell and Conrad, 1977 ), and that trace element deficiencies or imbalances in soils and forages are responsible for low production and reproduction among grazing livestock (McDowell et al., 1984). As grazing livestock may not receive mineral supplementations except for common salt, they must depend upon *Author for correspondence

0921-4488/91/$03.50

© 1991 - - Elsevier Science Publishers B.V.

24

R. PASTRANAET AL.

forages for their requirements. Only rarely can forages completely satisfy all mineral requirements (Miles and McDoweU, 1983 ). It has been found that forages are low in Cu, Co and Zn in the Colombian Paramo and high in Fe and Mo. This imbalance might be one of the causes for low productivity of sheep in the area (Proyecto Ovino Colombo Britanico, 1979). The objectives of this study were to evaluate the trace element status of grazing sheep, soils and forages on three sheep farms during two seasons in the Paramo region of Colombia. MATERIALS A N D M E T H O D S

Sampling periods corresponded to the rainy season (May-June, 19870 and the middle to end of the dry season (February, 1988 ). A total of 113 soil, 131 forage, 207 serum and 113 liver biopsy samples were obtained during the rainy season (May-June, 1987)and dry season (February, 1988)periods. Methods, location, animals, management procedures and statistical evaluations are presented elsewhere by Pastrana et al. ( 1991 ). Soil samples were analyzed by standard methods in the Laboratorio Nacional de Suelos oflCA in Bogota for Cu, Fe, Mn and Zn. Se analyses of soil, forages, blood and liver were achieved by fluorometry (Whetter and Ullrey, 1978). Forage Fe, Cu, Mn and Zn; blood Cu and Zn; and liver Cu, Fe, Mn and Zn were determined by atomic absorption spectrophotometry with a Perkin-Elmer AAS 5000 (Perkin-Elmer, 1980 ). An atomic absorption spectrophotometer with a graphite furnace and Zeeman background corrector (Perkin-Elmer Model 3030) was used to determine forage and liver Co and Mo. RESULTS A N D D I S C U S S I O N

Soil Fe was higher (P< 0.05 ) in Don Benito than San Francisco during the dry season which was above the minimum level of 2.5 p.p.m. (Viets and Lindsay, 1973) (Table 1 ). Concentrations were considerably in excess of normal values, and could result in a reduced availability of P to plants (Lindsay, 1972). The San Francisco farms had lower (P< 0.05 ) soil Zn values than the other two farms during the rainy season. Individual evaluation of samples based on a critical level of 1 p.p.m., when pH is below 6.5 (Rhue and Kidder, 1983), indicated that none of the samples during the rainy seasons, and only 13% during the dry season were deficient for this element. Farms were not a source of variation (P> 0.05 ) for Cu and Mn during both seasons, for iron during the rainy season and for Zn during the dry season. The only trace mineral affected (P<0.05) by season was Zn which had a

rainy dry rainy dry rainy dry rainy dry rainy

Fe

453 +40.5 307 +33.3 a 2.0+0.35 1.0+0.26 12.5+_2.11 10.5+_ 1.42 2.7 + 0.22 ¢ 2.2+_0.27 0.03

0 0 0 0 30 35 0 15 100

660 +77.0 622 +135 e 2.6+0.70 0.4+0.08 6.2+0.89 4.5+_0.49 2.8 + 0.16 e 1.8+_0.23 0.05

Mean

(%)

Mean 1,2

Deficiency

Don Benito

San Jorge

0 0 0 57 53 79 0 21 100

(%)

Deficiency 411 +32.7 224 +19.5 f 1.0+0.12 0.9+0.12 5.4+_0.62 4.8+_0.32 1.7 + 0.11 f 1.1+_0.04 0.03

Mean

San Francisco

0 0 0 5 50 70 0 5 100

(%)

Deficiency 505 388 1.88 1.16 8.06 6.78 2.40 f 1.69 i

Mean

Overall

0 0 0 17 44 59 0 13

(%)

Deficiency

tMeans based on the following number of composite samples: 20, 20 in San Jorge, 19, 14 in Don Benito and 20, 20 in San Francisco, for rainy and dry seasons, respectively. 2Standard error of mean. 3Critical levels (p.p.m.) are: Fe, 2.5 (Viets and Lindsay, 1973 ); Cu, 0.3 (Rhue and Kidder, 1983 ); Mn. 5 (Rhue and Kidder, 1983 ); Zn 1 (Rhue and Kidder, 1983) and Se, .5 (McDowell et al., 1990). Critical levels were derived from Florida (U.S.A.). Selenium was not included in the statistical analyses. e.fMeans among farms in row with different superscripts differ ( P < 0.05 ). "hMeans between seasons in a column with different superscripts differ P < 0.05 ).

Se +

Zn

Mn

Cu

Season

Variahle (p.p.m.)

Soil trace element micromineral analyses by season and farms (dry basis ).

TABLE 1

t~

,-0

t-n

7.

tO

t") ©

©

26

R. PASTRANA ET AL.

lower value during the dry season. Cu, Fe and Mn had lower values during the dry season but were not different ( P > 0.05 ). There was no sample below the critical level of 0.3 p.p.m, for Cu (Rhue and Kidder, 1983) during the rainy season, but 17% deficiency was found during dry season. Most of the deficient samples for Cu were in Don Benito, with 57% of the samples deficient during the dry season. For Mn, the percentage of samples below the critical level of 5 p.p.m. (Rhue and Kidder, 1983 ) was 44% during the rainy and 59% during the dry season. Among farms, the deficiency was at San Jorge, 30 and 35%; at Don Benito 53 and 79%; at San Francisco, 50 and 70% for rainy and dry seasons, respectively. Se concentrations of soils reflected the parent material (Reid and Horvath, 1980). Some research has indicated that soil Se concentrations of less than 0.5 p.p.m, are found in areas where Se deficiency also occurs in livestock (McDowell et al., 1990). Based on this critical level, all samples were deficient in Se.

Forage analyses Forage Co was higher ( P < 0.05 ) in San Jorge in comparison to Don Benito and San Francisco during the rainy season (Table 2 ). A similar tendency was observed during the dry season, but was not significant ( P > 0.05 ). According to the critical level of 0.1 p.p.m. (NRC, 1985 ), 79% of samples were deficient in Co during the rainy and 95% during the dry season. Deficiencies in Co for: San Jorge was 54 and 90%; Don Benito, 100 and 100%; San Francisco 95 and 100% for rainy and dry seasons, respectively. McDowell et al. (1982) reported that, with the exception of P and Cu, Co deficiency is the most serious mineral limitation to grazing livestock in many countries, and sheep are more severely affected than other ruminants. Manganese concentration was higher ( P < 0 . 0 5 ) in San Francisco when compared with San Jorge during the dry season. Using the minimum of 20 p.p.m. (NRC, 1985), only 1% of the samples were deficient during the rainy but none during the dry season. All concentrations were in excess of requirements for sheep. Several studies indicated a high tolerance for Mn (Hansard, 1983 ). Mineral imbalances typified by excesses of Fe and Mn may interference with metabolism of other minerals (Lebdosoekojo et al., 1980). Farm means were well below the maximum tolerable level of 1000 p.p.m. (NRC, 1985). Forage Se was higher ( P < 0.05 ) at Don Benito than at the other two farms during the rainy season. Forty-three percent of the samples during the rainy and 69% during the dry season were deficient according to the 0.1 p.p.m. values for sheep (NRC, 1985 ). San Jorge had 50 and 70°/0; deficiencies Don Benito, 25 and 53%; and San Francisco, 53 and 80% for rainy and dry seasons, respectively. Underwood ( 1981 ) considered that for all ordinary grasses

rainy dry rainy dry rainy dry rainy dry rainy dry rainy dry rainy dry

Cu

7.52+0.65 2.92+0.34 0.11 +0.01 e 0.06 + 0.02 113 + 16.2 119 +11.7 167 + 16.0 211 +17.6 f 0.87+0.14 f 0.44 + 0.09 0.11 +0.01 f 0.10+0.01 24.4 _+2.24 18.3 +1.32 37 97 54 90 14 0 4 0 50 70 11 57

6.91 +0.43 3.87+0.52 0.01 + 0.00 r 0.03 + 0.00 106 _+ 14.5 144 +18.1 228 + 17.1 381 +33.4 e 1.59+0.18 e 0.79+0.18 0.15+0.01 e 0.10+0.01 24.3 + 1.11 26.2 +2.10

Mean

(%)

Mean 1,2

Deficiency

Dnn I~enito

San 3orge

65 87 100 100 0 0 0 0 25 53 20 13

(°/o)

Deficiency

0.04 + 0.00 f 0.03 + 0.00 89 +9.2 150 + 12.2 231 +26.4 402 + 27.9 c 0.66+0.06 r 0.64+0.11 0.09+0.01 f 0.08+0.01 19.4 +0.87 20.4 +2.05

6.97+0.64

Mean

San Francisco

79 95 95 100 0 0 0 0 53 80 63 50

Deficiency (%) 7.18 3.07 0.06 0.05 104 135 203 309 1.03 0.58 0.11 0.09 25.0 20.7

Mean

Overall

57 94 79 95 6 0 1 0 43 69 28 45

Deficiency (%)

tMeans based on the following number of composite samples; 28, 29 in San Jorge, 20, l 5 in Don Benito and 19, 20 in San Francisco, for rainy and dry seasons, respectively. 2Standard error of means. 3Critical levels (p.p.m.) suggested by NRC (1985 ) are Cu (7), Co (0.1 ), Fe (30), Mn (20), Se (0.1) and Zn (20), for Mo ( > 6) (McDowell, 1984). e,fMeans among farms in a row with different superscripts differ ( P < 0.05 ). g'hMeans between seasons in a column with different superscripts differ ( P < 0.05 ).

Zn, ppm

Se

Mo

Mn

Fe

Co

Seasen

Variable

Forage trace element concentrations by season and farms (dry basis)

TABLE 2

t,~

>

K

28

R. PASTRANA ET AL.

and legumes the primary determinant of Se concentration was the level of available soil Se. Forage Mo concentrations were different ( P < 0 . 0 5 ) among farms during the rainy season. Don Benito had higher values than the other farms. However, none of these values were above the 6 p.p.m. (dry basis) toxic limit (McDowell et al., 1984). According to Suttle (1986), only a small increase in Mo and S concentrations will cause major reduction in Cu availability. Differences of 3 p.p.m. Mo ( 1-4 p.p.m. ) and 0.5 p.p.m, of S (2.5-3) between two pastures are sufficient to have Cu availability. Farms were not a source of variation ( P > 0.05 ) for Cu, Fe and Zn during both seasons; for Co, Mo and Se during the dry, and for Mn during the rainy season. Season was a source of variation ( P < 0.05 ) for Co, Cu, Mn and Mo; all except Mn had lower ( P < 0.05 ) concentrations during the dry season. Se and Zn were also depleted during the dry season, but not significantly ( P > 0.05 ). In contrast, Fe and Mn concentrations were higher during the dry season. For the rainy season 57% of forages were below 7 p.p.m. Cu (NRC, 1985 ) and 94% in the dry season. San Jorge was 36 and 97% deficient; Don Benito, 65 and 87%; San Francisco, 79 and 95% for rainy and dry seasons, respectively. Ratios of Cu: Mo were at least 6: 1 in San Jorge and San Francisco and 4:1 in Don Benito, and Mo levels were not higher than 4 p.p.m, in each case. Cu concentration was marginal in forages during the rainy and deficient during the dry season. Animals, in this situation, might respond to appropriate Cu supplementation. Twenty-eight percent of samples were below the dietary Zn requirement of 20 pp, (NRC, 1985 ) during the rainy, and of 45% during the dry season. San Jorge had 11 and 57%; Don Benito, 20 and 13%; and San Francisco, 63 and 50% deficient samples for rainy and dry seasons, respectively. Ruminants exhibit signs of Zn deficiency when grazing forage containing 20-30 p.p.m. Zn (Pierson, 1966). However, a marginal Zn deficiency appears to be widespread (Spears, 1989). Only 6% of forage samples had less than 30 p.p.m. Fe (NRC, 1985) in the rainy and none during dry season. This coincides with a zero incidence of deficiencies in soil samples. McDowell ( 1985 ) stated that ruminant animals grazing pastures are not likely to suffer from Fe deficiency. No samples reached the maximum tolerable level of 500 p.p.m. Fe (NRC, 1985 ). Blood serum analyses There were no significant farm x animal class interactions ( P > 0 . 0 5 ) for any serum trace elements when considering seasons separately (Tables 3 and 4). The Fe, Se and Zn concentrations tended to be higher during the rainy season, and Cu higher during the dry season, but none was affected ( P > 0.05 ) by season.

rainy dry rainy dry rainy dry rainy dry

Season

18 29 82 74 18 32 53 74 0 35

0

0.90+0.10

19 0 22 24 0 38

364 +48.9 519 _+77.6 47.8 _+7.78 59.5 _+10.6 7.69+0.48 11.18-+0.88 87.6 +-8.48 83.7 -+8.11 0.25_+0.02 0.12_+0.02 0.63 + 0.13 0.03 -+_0.00

0.79-+ 0.04 1.02 + 0.03 0.70_+0.03 0.78 + 0.10 0.11 _+0.01 0.05 + 0.00 2.37_+0.12 2.08_+0,13

1.09-+0.14

419 _+84.3 482 _+59.6 35.3 _+6.62 109.3 +20.8 12.37+_1.02 12.96+-1.30 97.5 _+7.21 108.2 -+10.4 0.27_+0.04 0.12_+0.02 0.56 _+0.09 0.05 +-0.01

0.69_+ 0.04 1.20 _+0.05 0.75_+0.03 0.68 +-0.03 0.14_+0.01 0.10 _+0.00 2.79+-0,15 2.07_+0.09

Mean

(%)

Mean~,2

Deficiency

Don Benito

San Jorge

0

7 0 93 57 0 0 13 21 0 29

30 0 12 32 6 3

(%)

Deficiency

1.01 -+0.06

315 _+33.3 291 +31.9 97.7 _+15.7 125.1 +12.0 11.45+0.56 8.43-+0.28 82.2 +3.87 93.8 +3.58 0.18_+0.04 0.03_+0.00 0.50_+ 0.04 0.03 -+0.00

1.04_+ 0.03 1.34_+ 0.05 0.85+0.04 0.75 _+0.05 0.04+0.00 0.07 + 0.00 2.17_+0.12 2.87_+0.16

Mean

San Francisco

0

17 17 44 23 0 3 56 27 0 87

0 0 4 26 50 13

(%)

..........

0.99

363 409 62.0 99.3 10.4 10.3 88.6 93.3 0.23 d 0.08 e 0.56 d 0.03 e

0.82 1.20 0.76 0.74 0. I0 0.07 2.47 2.39

•,,,-

Overall

0

14 19 72 51 6 15 42 45 0 55

18 0 14 27 15 18

(%)

r~c,~;~,~y

~Means based on the following number of samples: serum 36, 34 in San Jorge farm, 33, 34 in Don Benito and 24, 46 in San Francisco. Liver 17, 23 in San Jorge farm; 15, 14 in Don Benito and 18, 30 in San Francisco, for rainy and dry seasons, respectively. 2Standard error of means. 3Critical levels (McDowell et al., 1984): serum (p.p.m.), Cu (0.6), Zn (0.6) and Se (0.03); Liver (p.p.m.), Fe (180), Cu (75), Mn (75), Zn (84), Co (0.05), Mo ( > 4) and Se (0.25). a'eMeans among farms in a row with different superscripts differ ( P < 0.05 ). r'SMeans between seasons in a column with different superscripts differ ( P < 0.05 ).

Liver (D.M. basis ) Fe ramy dry Cu rainy dry Mn rainy dry Zn rainy dry Co rainy dry Mo rainy dry Se rainy dry

Fe

Se

Zn

Cu

Serllm

Variable (p.p.m.)

Blood serum and liver trace elements by season and farm.

I ABLE 3

D~ t~

7

©

Season

19 0 11 21 16 18 0 7 8 30 80 60 4 25 52 65 0 55

0.82 + 0.05 1.31 +0.06 0.80+0.04 0.70 + 0.03 0.12+0.01 0.07 + 0.01 2.47_+0.13 2.61 +0.18

344 _+27.6 301 -+28.5 56.9 -+11.3 90.7 _+18.9 10.35_+0.53 9.70+0.77 82.6 +3.51 81.5 _+6.79 0.26_+0.03 0.08_+0.01 0.51_+0.06 0.04_+0.00 . . 0.87_+0.06 .

214 +50.2 913 +213 33.2 +6.63 91.9 _+31.9 7.96+1.31 9.12-+3.01 76,0 _+11.2 116.3 +26.2 0.23+0.04 0.06_+0.01 0.65+0.32 0.01 +0.00 . 0.97_+0.26

0.70 + 0.05 0.99+0.05 0.78+0.03 0.99 + 0.14 0.10+0.01 0.06 + 0.00 2.90+0.14 2.86-+0.19

Mean

Mean~,2

Deficiency

Lambs

Ewes

43 0 100 33 29 33 43 33 0 50

24 0 5 22 5 37 0 0

(%)

Deficiency

448 +74.8 380 -+32.1 80.4 _+12.4 103.3 _+10.1 11.5 +0.94 10.70+0.53 102.0 _+7.91 94.5 _+40.3 0.18+0.02 0.08_+0.01 0.59+0.04 0.03+__ 0.00 1.04+0.07

0.05 + 0.03 1.23+0.04 0.69+0.02 0.64 + 0.02 0.09+0.01 0.08 + 0.00 2.21 -+0.12 2.03-+0.09

Mean

Yearlings

-

11 16 50 49 0 8 28 39 0 55

14 0 23 33 20 7 3 2

(%)

Deficiency

0.99

363 409 62.0 99.3 10.4 10.3 88.6 93.3 0.23 a 0.08 e 0.56 a

0.82 1.20 0.76 0.74 0.10 0.07 2.47 2.39

Mean

Overall

0

14 19 72 51 6 15 42 45 0 55 55

18 0 14 27 15 18

(%)

Deficiency

'Means based on the following number of samples: serum 37, 33 in ewes, 21, 27 in lambs and 35, 54 in yearlings; Liver 25, 20 in ewes, 7, 6 in lambs and 18, 49 in yearlings, for rainy and dry seasons, respectively. 2Standard error of means. 3Critical levels (p.p.m.) (McDowell et al., 1984): Serum, Cu (0.6) and Se (0.03); Liver Fe (180), Cu (75), Mn (6), Zn (84), Co (0.05), Mo ( > 4) and Se (0.25). ~'eMeans among animal classes in a row with different superscripts differ ( P < 0.05 ).

rainy dry Zn rainy dry Se rainy dry Fe rainy dry Liver (D.M. basis) Fe ramy dry Cu rainy dry Mn rainy dry Zn rainy dry Co rainy dry Mo rainy dry Se rainy dry

Serum Cu

Variable

Blood serum and liver trace elements by season and animal class

TABLE 4

rn

MINERAL STATUS OF COLOMBIAN SHEEP

31

Serum samples were deficient in Cu, i.e., below 0.6 p.p.m. (McDowell et al., 1984) with 18% in rainy and 0% in dry season. Cu deficiencies were 19% for ewes, 24% for lambs and 14% for yearlings during rainy season. Forage Cu was deficient, especially during dry season (94%). Serum Cu is affected by dietary Cu intake (Rowlands, 1980). However, serum Cu often does not reflect dietary Cu. Cu deficiency is often caused by Mo and S interfering with Cu utilizaltion (Underwood, 1981 ). Only 15 and 18% of serum Se samples were deficient (0.03 p.p.m. McDowell et al., 198,+) for rainy and dry seasons, respectively. This was in disagreement with forages that were low in Se. Serum samples below 0.6 p.p.m. Zn (McDowell et ai., 1984) were 14 and 27% for rainy and dry seasons, respectively. Deficiencies for ewes were: 11 and 21; Iambs, 5 and 22; yearlings, 23 and 33% for rainy and dry seasons, respectively. Signs of Zn deficiency are nonspecific, therefore Zn status should be considered in cases of unexplained reproductive problems in ewes (Apgar and Fitzgerald, 1985). Serum Zn is a reasonable status criterion, however, values are susceptible to animal stress during sampling and can fluctuate rapidly (Und~erwood, 1981 ).

Liver analyses Liver Co and Mo were higher ( P < 0.05 ) during rainy season. Based on the upper critical value (75 p.p.m. ) suggested by McDowell et al., 1984), Co and Mo deficient livers were 72% for rainy and 51% for dry season, and 30% for rainy and 20% for the dry seasons, using 25 p.p.m, as the lower critical limit. Among farms with marginal Cu deficiencies (75 p.p.m. ) were San Jorge, 82 and 74%; Don Benito, 93 and 57%; San Francisco, 44 and 23% for rainy and dry seasons, respectively. Percentage marginal Cu deficiencies were ewes, 80 and 60%; lambs, 100 and 33%; yearlings, 50 and 49% for the seasons, respectively. Undoubtedly, Cu is marginal and should be included in mineral supplements especially at San Jorge and Don Benito. For Zn, liver samples below the critical level of 84 p.p.m. (McDowell et al., 1984) were 42% for rainy and 45% for dry season. There is no "best" analysis to determine Zn status in the animal (McDowell, 1985). In general agreement with liver analysis, overall forage Zn deficiency was 36%. Selenium deficiency below the critical value of 0.25 p.p.m. (McDowell et al., 1984 ), was 0% for the dry season. This is in disagreement with McDowell et al. (1990) that serum and liver Se concentrations provide good Se status indicators in cattle. Se deficiencies in this study were 100, 56, 16 and 0% for soil, forage, serum and liver, respectively. These data are similar to the data ofValdes et al. (1988). Liver Co was adequate in the rainy season, i.e., greater than critical value of 0.05 p.p.m. (McDowell et al., 1984). However, 55% were deficient in dry season, with most of the deficiency localized at San Francisco farm (87% of

32

R. PASTRANA ET AL.

samples). Among animal classes all three had similar deficiencies ( 55% ) during the dry season. Overall deficiency for this element was 21% in liver and 87% in forage. Deficiency of liver Mn was 6% in rainy and 15% in dry season, based on a 6 p.p.m, critical level (McDowell et al., 1984). The deficiency was localized at San Jorge during both seasons. For liver Mn, ewes were 13% deficient, lambs, 31 and yearlings, 6%. In contrast, only 1% of forages was deficient in Mn. Liver Fe means for the three farms were higher than the proposed critical level of 180 p.p.m. (McDowell et al., 1984). In agreement, no soils, and only 1% of forages were Fe deficient. All liver Mo samples were below the suggested toxic level of 4 p.p.m. (McDowell et al., 1984). Molybdenum is an essential component of certain ruminant enzyme systems, but can be toxic if it blocks Cu utilization (McDowell et al., 1983 ). Correlations among minerals Serum and liver correlation coefficients (P < 0.05 ) of r_+ 0.50 between levels of trace minerals during rainy season were: serum Cu-liver Cu ( r = 0.86 ); serum Cu-liver Co ( r = - 0 . 7 5 ). During dry season correlations were: serum Zn-liver Fe (r=0.90); serum Fe-liver Mn ( r = -0.91 ); serum Fe-liver Co ( r = -0.81 ); serum Se-liver Se (r=0.84). In general, the only positive correlations found between serum and liver trace minerals were for Cu and Se. CONCLUSIONS

Based on soil, forage and animal tissue analyses, Cu, Zn, Co and Se deficiencies may be limiting sheep production in the Paramo region of Colombia. Supplementation studies are needed to determine need and economic benefits of trace mineral supplementation. ACKNOWLEDGMENTS

Florida Agricultural Experiment Station, Journal Series No. R-00305 research was supported by the U.S. Department of Agriculture under CRSR special grant No. 86-CRSR-2-2843 managed by the Caribbean Basin Advisory Group (CBAG). Appreciation is due Dr. F.G. Martin and Dr. Steve Linda for statistical assistance, Dr. O. Ospina (Caja Agraria ) and Dr. A. Naranjo (ICA), for sample collection, to Dr. R. Lora for soil analyses and to Dr. J. Neira for whole blood analyses at ICA laboratories.

MINERALSTATUSOF COLOMBIANSHEEP

33

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Spears, J.W., 1989. Zinc methionine for ruminants: relative bioavailability of zinc in lambs and effects of growth and performance of growing heifers. J. Anim. Sci., 67: 835-843. Suttle, N.F., 1986. Copper deficiency in ruminants; recent developments. Vet. Record., 119: 519-522. Underwood, E.J., 1981. The Mineral Nutrition of Livestock (2nd Edition), Commonwealth Agricultural Bureau, Farnham Royal, England, pp. 163. Valdes, J.L., McDowell, L.R. and Koger, M., 1988. Minerals status and supplementation of grazing beef cattle under tropical conditions in Guatemala. II. Microelements and animal performance. J. Prod. Agric., 1:351-355. Viets, F.G. and Lindsay, W.L., 1973. Testing soils for zinc, copper, manganese and iron. In: L.M. Walsh and J.D. Beaton (Editors.), Soil testing and plant analysis. Soil Science Society of America Inc., Madison, Wisconsin, pp. 153-172. Whetter, P.A. and Ullrey, D.E., 1978. Improved fluorometric methods of determining selenium. J. Assoc. Anal. Chem., 61: 927-930.