J. Anim. Sci. 2002. 80:2787-2791
© 2002 American Society of Animal Science
Effect of corn- vs molasses-based supplements on trace mineral status in beef heifers1
J. D. Arthington2 and
F. M. Pate
University of Florida, Range Cattle Research and Education Center, Ona 33865
2 Correspondence:
Range Cattle Research and Education Center, 3401 Experiment Station, Ona, FL 33865 phone: 863-735-1314; fax: 863-735-1930; E-mail:
jdarthington{at}mail.ifas.ufl.edu.
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Abstract
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Two studies were conducted to compare the availability of trace minerals offered to Brahman-crossbred heifers in either grain- or molasses-based supplements. Heifers were randomly assigned to bahiagrass pastures of equal size (n = 3 and 2 heifers/pasture with 6 and 4 pastures/treatment for Experiment 1 and 2, respectively). Two supplements were formulated using corn and cottonseed meal (DRY) or molasses and cottonseed meal (LIQ). In Experiment 2, a third treatment consisted of the DRY supplement with additional S to equal the amount naturally supplied by the LIQ treatment (DRY+S). Supplements were formulated to provide, on average, 1.5 kg of TDN and 0.3 kg of CP/heifer daily and were fed three times weekly. Supplements also were fortified to provide 140, 76, and 63 mg of Cu, Mn, and Zn per heifer daily. Individual heifer weights were collected at the start and conclusion of the study, following a 12-h shrink. Plasma ceruloplasmin and liver Cu, Mn, Mo, Fe, and Zn concentrations were determined on d 0, 29, 56, and 84 in Experiment 1, and d 0, 32, 57, and 90 in Experiment 2. No differences were detected in heifer BW change (-9.3 and -7.3 kg for DRY and LIQ in Experiment 1, and 51.7, 46.3, and 46.7 kg for DRY, DRY+S, and LIQ in Experiment 2, respectively). In both experiments, liver Fe, Mn, and Zn concentrations were not affected by supplement treatment. Molybdenum tended (P = 0.06 and 0.10 for Experiments 1 and 2, respectively) to accumulate in the liver of heifers fed molasses-based supplements. In Experiment 1, Cu accumulation was less (P < 0.001) in heifers fed the liquid supplements (271 vs 224, 286 vs 202, and 330 vs 218 ppm, for DRY and LIQ supplements on d 29, 56, and 84, respectively). In Experiment 2, heifers receiving Cu from DRY supplements had a 155-ppm increase in liver Cu concentration, which was greater (P = 0.03) than DRY+S (87 ppm increase) and LIQ (P < 0.001; 13 ppm increase). Although lower than heifers receiving DRY, heifers receiving DRY+S had greater (P = 0.02) liver Cu concentrations than heifers receiving LIQ by the end of the study. In both experiments, plasma ceruloplasmin concentrations were highest (P < 0.04) in heifers receiving DRY supplement. The results of these studies suggest that components in molasses-based supplements decrease the accumulation of Cu in the liver of beef heifers. The S and Mo components of molasses may be responsible, at least in part, for this antagonism.
Key Words: Copper • Corn • Molasses • Sulfur • Trace Elements
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Introduction
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Most grazing beef cattle are provided supplemental minerals via free-choice, salt-based mineral mixtures. Depending on the region of the country, these products are formulated for a target intake of 57 to 170 g/heifer daily. Not all animals eat the desired quantity of minerals. Some animals may eat more or less, whereas some may eat no minerals at all. It is this averaging effect, over time, which allows free-choice mineral supplements to be the most practical choice for most situations. The design, formulation, and feeding of free-choice supplements to cattle on pasture has been previously reviewed (McDowell, 1996; McDowell, 2002). Seasonal variation in mineral intake is evident. A 2-yr review of weekly mineral intake at the University of Florida, Range Cattle Research and Education Center in Ona, revealed that cattle readily consume salt-based mineral supplements in the wetter summer months. By contrast, during the dryer winter months, free-choice intake may be decreased by a seasonal average of 15% or more (Arthington and Pate, unpublished results).
Free-choice, salt-based supplements are not the only method for supplementing minerals to grazing cattle. Minerals can be provided to cattle via fertilizers, in fortified water, oral drenches, boluses, injections, and through energy and protein supplements (Greene, 2000). Efforts showed that fortification of alfalfa-based range cubes was an effective means of increasing mineral nutrition of beef cows during the winter supplementation period (Arthington and Corah, 1999). In Florida, as well as in much of the Gulf Coast region, the use of molasses-based supplements for beef cows is common (Pate and Kunkle, 1989). The objective of the current study was to investigate the trace mineral status of growing beef heifers offered trace minerals in corn- vs molasses-based supplements.
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Materials and Methods
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Animal Care, Handling, and Diet.
The animals utilized in these experiments were cared for by acceptable practices (FASS, 1999), and the protocol was approved by the University of Florida, Institutional Animal Care and Use Committee (#A603 and #A695). Liver biopsy collections were performed by a trained technician using techniques previously described (Arthington and Corah, 1995).
In Experiment 1, 36 nonpregnant Simbrah-sired heifers (average initial BW = 296 kg; approximate age = 13 mo) with adequate liver Cu concentrations were randomly assigned to bahiagrass (Paspalum notatum) pastures of equal size (1.22 ha; 3 heifers per pasture). Two supplements were formulated (Table 1
) using corn and cottonseed meal (n = 6 pastures) or molasses and cottonseed meal (n = 6 pastures). Each supplement was formulated to provide, on average, 1.5 kg of TDN and 0.3 kg of CP/heifer daily. Supplements were fed three times weekly (3.5 and 0.7 kg of TDN and CP/heifer, provided on Monday, Wednesday, and Friday) and were fortified to provide 140, 76, and 63 mg of Cu, Mn, and Zn/heifer daily. Complete consumption of the supplement offer was achieved within approximately 24 to 36 h. The study was conducted during the winter months when pasture forage might be limiting, therefore heifers in each pasture were provided free-choice access to longstem limpograss (Hemarthria altissima) hay (Table 2). To assess the effect of supplement composition on animal performance, individual heifer weights were collected at the start and conclusion of the study, following a 12-h shrink. To assess the effect of supplement composition on trace mineral availability, plasma ceruloplasmin and liver Cu, Mo, Fe, Mn, and Zn concentrations were determined on d 0, 29, 56, and 84.
In Experiment 2, 24 pregnant Braford-sired heifers (average initial BW = 342 kg; approximate age = 27 mo) with adequate liver Cu concentrations were randomly assigned to bahiagrass pastures of equal size (1.22 ha; two heifers per pasture). Three supplement treatments (four pastures per treatment) were formulated (Table 1
) using 1) corn and cottonseed meal; 2) molasses and cottonseed meal; and 3) corn, cottonseed meal, and added S to equal the amount provided by the molasses-based treatment. As in Experiment 1, supplements were fed three times weekly (Monday, Wednesday, and Friday) and were fortified to provide 140, 76, and 63 mg of Cu, Mn, and Zn per heifer daily. Complete consumption of the supplement offer was achieved within approximately 24 to 36 h. To assess the effect of supplement composition on animal performance and trace mineral availability, individual heifer weights and liver biopsy samples were collected on d 0, 32, 57, and 90, following a 12-h shrink.
Feed, Plasma, and Liver Analysis.
Random samples of pasture (hand-clipped), hay, corn, and cottonseed meal were collected and analyzed for mineral concentration by a commercial laboratory (SDK Laboratories, Hutchinson, KS). Following collection of liver biopsy samples, samples were frozen and sent to Michigan State University (Animal Health Diagnostic Laboratory, Lansing, MI) for analysis of trace mineral concentration using inductively coupled plasma-atomic emission spectroscopy as described by Braselton et al. (1997). Blood was collected by jugular venapuncture into heparin-coated, evacuated tubes. Plasma was harvested from blood following centrifugation at 2,400 x g for 20 min and then frozen at -20°C until analyzed for ceruloplasmin concentration using colorimetric procedures (Demetriou et al., 1974).
Statistical Analysis.
Statistical analysis of liver mineral and plasma ceruloplasmin concentration was achieved by ANOVA for a repeated-measures experiment within a completely randomized design using the PROC MIXED procedure of SAS (SAS Inst. Inc., Cary, NC). The model statement contained the effects of treatment and day and the interaction for treatment x day. Data were analyzed using the pasture x treatment interaction as random effects. Statistical analysis for overall change in liver Cu concentration was achieved by ANOVA for a completely randomized design using PROC GLM of SAS with pasture x treatment as the error term. Pasture was the experimental unit. The model statement contained the effect of treatment.
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Results and Discussion
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Liver concentrations of Zn, Mn, and Fe were not affected by supplement type in either experiment (Table 3). In contrast, mean liver Mo concentrations tended (P = 0.06 and 0.10 for Experiments 1 and 2, respectively) to be greater in heifers fed molasses-based supplements (Table 3). This response is likely due to the higher amount of Mo provided by molasses- vs corn-based supplements (3.2 vs 1.3 mg daily for molasses- and corn-based supplements, respectively; Table 4).
Supplemental Cu was provided at approximately two times the NRC (1996) suggested dietary requirement of 10 ppm. Nevertheless, in both experiments, liver Cu accumulation was less in heifers provided molasses supplements than heifers fed dry supplements (Figures 1 and 2). This response is possibly the result of decreased Cu absorption due to the formation of ruminal thiomolybdates. Thiomolybdates can impact Cu nutrition in ruminants by two means: 1) irreversibly binding Cu in the gut, thereby preventing absorption, or 2) postabsorption systemic depletion of Cu from tissue sites (Mason, 1990). The formation of thiomolybdates is directly dependent upon available dietary S, and S intake is a major factor influencing the sensitivity of ruminants to Mo (Mason, 1981). In the current study, the inclusion of added dietary S to a corn-based supplement (Experiment 2) resulted in the partial inhibition of liver Cu accumulation noted in heifers fed the molasses-based supplement (Figure 2). This partial inhibitory response on liver Cu accumulation may be the result of the inability of the ruminal microbial population to fully reduce the supplemental S provided in the molasses-based treatment containing supplemental S. Dietary S must first be reduced to sulfide before it can interact with Mo to form thiomolybdates (Mason, 1986). Another explanation may be related to an insufficient quantity of Mo in the corn-based supplement to fully participate with S for the formation of thiomolybdate. Although minor, the molasses did contain a greater concentration of Mo than the corn used in these experiments (Table 4). This difference in Mo concentration of the base supplement may be sufficient to explain the differences seen in liver Cu accumulation between the molasses-based and corn-based + S supplements (Figure 2).
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Figure 1. The effect of dry vs liquid supplement on liver Cu concentration, Experiment 1. Pooled SEM = 38.0 ppm. Values are provided on a DM basis. Supplements were formulated to provide 1.5 kg of TDN and 0.3 kg of CP/heifer daily and were fed three times weekly. ** = P < 0.01.
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Figure 2. The effect of dry vs liquid supplement and dry supplement + S on liver Cu concentration, Experiment 2. Pooled SEM = 9.2 ppm. Values are on a DM basis. Supplements were formulated to provide 1.5 kg of TDN and 0.3 kg of CP/heifer daily and were fed three times weekly. Single degree of freedom contrasts; corn- vs molasses-based supplements (P = 0.01), and corn- vs molasses-based supplement, and corn-based + S supplement (P < 0.01).
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Sulfur also may decrease Cu availability independent of Mo. In a series of experiments by Suttle (1974), the addition of both organic and inorganic S to the diets of Cu-deficient sheep decreased the rate and extent of Cu repletion. These responses were attributed to the formation of insoluble Cu sulfide complexes in the gut. Their data suggested that an increase of dietary S from 0.1 to 0.4% of the total diet may result in a 50% increase in the overall dietary Cu requirement.
Ceruloplasmin concentrations were lower in heifers supplemented with molasses-based supplements vs those fed corn-based supplements in both studies (Table 5). This response may be a result of thiomolybdate formation in molasses-supplemented heifers, as decreased ceruloplasmin activity has been shown in both sheep (Mason, 1986) and cattle (Lannon and Mason, 1986) infused with thiomolybdate.
Copper deficiency in grazing cattle has been linked to suppressed immune competence, altered hair coat color, skeletal abnormalities, decreased growth rate, and in extreme cases, anemia (Mills, 1987). The animals in the current study were not considered Cu deficient (Ammerman, 1969), and therefore clinical signs of production loss associated with Cu deficiency were not evident. Also, prior to the start of the study, heifers from both Experiments were maintained on bahiagrass pasture, in a single group, with free-choice access to a completely balanced, salt-based mineral supplement. In both experiments, change in heifer BW was not affected by treatment (Table 5). Effects of supplement type on heifer performance were not expected as liver mineral values obtained from the heifers in these studies fell within the adequacy range.
In most production situations, cattle would only consume molasses-based supplements during the winter months when forage availability is limiting. Even though molasses may decrease heifer Cu status during the winter supplementation period, heifers are likely able to replenish their reserves during the summer grazing season.
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Implications
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These results suggest that components within molasses decrease the accumulation of liver Cu in heifers. This effect is likely the result of high concentrations of S naturally found in molasses, as the inclusion of added S to corn-based supplements resulted in a slower rate of Cu accumulation, which was similar to that realized with the molasses-based supplement. In production environments where risk of Cu deficiency may be present, attention to the S content of supplemental feeds is warranted.
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Footnotes
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1 Contribution No. R-08734 from the Florida Agriculture Experiment Station. Appreciation is expressed to Carol Piacitelli and Toni Wood for their technical assistance during the conduct of this experiment. 
Received for publication May 17, 2002.
Accepted for publication July 2, 2002.
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Literature Cited
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Ammerman, C. B. 1969. Recent developments in cobalt and copper in ruminant nutrition: A review. J. Dairy Sci. 53:1097–1107.
Arthington, J. D., and L. R. Corah. 1995. Liver biopsy procedures for determining the trace mineral status in beef cows; Part II (Video, AI 8134). Extension TV, Dept. of Communications. Cooperative Extension Service, Kansas State University, Manhattan.
Arthington, J. D., and L. R. Corah. 1999. Trace mineral fortification of winter supplement is an effective means of addressing trace mineral deficiency in spring-calving beef cows. J. Anim. Sci. 77(Suppl. 1):154 (Abstr.).[Abstract/Free Full Text]
Braselton, W. E., K. J. Stuart, T. P. Mullaney, and T. H. Herdt. 1997. Biopsy mineral analysis by inductively coupled plasma-atomic emission spectroscopy with ultrasonic nebulization. J. Vet. Diagn. Investig. 9:395–400.[Abstract/Free Full Text]
Demetriou, J. A., P. A. Drewes, and J. B. Gin. 1974. Ceruloplasmin. In: D. C. Cannon and J. W. Winkelman (ed.) Clinical Chemistry. P 857. Harper and Row, Hagerstown, MD.
FASS. 1999. Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching. 1st ed. Federation of Animal Science Societies, Savoy, IL.
Greene, L. W. 2000. Designing mineral supplementation of forage programs for beef cattle. Proc. Am. Soc. Anim. Sci. 1999. Available at: http://www.fass.org/dasees/nutrition/0913.pdf. Accessed March 7, 2002.
Lannon, B., and J. Mason. 1986. The inhibition of bovine ceruloplasmin oxidase activity by thiomolybdates in vivo and in vitro: a reversible interaction. J. Inorg. Biochem. 26:107–115.[Medline]
Mason, J. 1981. Molybdenum-copper antagonism in ruminants: A review of the biochemical basis. Ir. Vet. J. 35:221–229.
Mason, J. 1986. Thiomolybdates: Mediators of molybdenum toxicity and enzyme inhibitors. Toxicology 42:99–109.[Medline]
Mason, J. 1990. The biochemical pathogenesis of molybdenum-induced copper deficiency syndromes in ruminants: Towards the final chapter. Ir. Vet. J. 43:18–22.
McDowell, L. R. 1996. Feeding minerals to cattle on pasture. Anim. Feed Sci. Technol. 60:247–271.
McDowell, L. R. 2002. Mineral supplementation for ruminants in tropical regions emphasizing organic selenium. In: T. P. Lyons and K. A. Jacques (ed.) Proc. 18th Ann. Alltech Symp. Nottingham University Press, Nottingham, UK. p. 193.
Mills, C. F. 1987. Biochemical and physiological indicators of mineral status in animals: Copper, cobalt and zinc. J. Anim. Sci. 65:1702–1711.[Abstract/Free Full Text]
NRC. 1996. Nutrient Requirements of Beef Cattle (7th ed.) National Academy Press, Washington, DC.
Pate, F. M., and W. E. Kunkle. 1989. Molasses-based feeds and their use as supplements for brood cows. Circular No. S-365. Florida Agriculture Experiment Station, Institute of Food and Agricultural Sciences, Gainesville.
Suttle, N. F. 1974. Effects of organic and inorganic sulphur on the availability of diet copper to sheep. Br. J. Nutr. 32:559–568.[Medline]
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Abstract
Introduction
