Seasonal changes of some mineral status in mares

Scientific Papers Seasonal Changes of Some Mineral Status in Mares Hakan Biricik, DVM, PhDa; Naci Ocal, DVM, PhDb; Ali I. Gucus, PhDc; Bulent Ediz, PhDd; and Mehmet Uzman, DVMe REFEREED

SUMMARY

Twenty-three Standardbred mares (4 to 8 years old) were used to determine the effects of season on mineral metabolism. Diet was formulated to supply recommended protein and energy requirement.1 No additional mineral was supplied in the diet. Blood samples were collected from the horses at the beginning and the end of January, April, July, and November. In addition, hair samples from 8 different parts of the body were collected on January and July. Mineral concentrations of feeds were higher in summer months than those in other seasons and lower in autumn than those in other seasons. Serum copper and zinc levels were the highest in the summer months. Serum iron levels were the highest during the spring. Except for copper, mineral contents of the hair were significantly lower in winter than those determined in summer months. INTRODUCTION

Minerals have many functions in the body, including the formation of the body structure, cofactor for enzymes, and transformation of energy. Availability of minerals in horses is closely related to mineral concentrations in their rations. Mineral contents of the feedstuffs may vary according to region, soil and plant types, vegetation phase, and harvesting time of the plant.2 These variations may cause some problems in ratio formulations to provide a

From the Department of Animal Nutrition and Nutritional Diseases, Faculty of Veterinary Medicinea and Department of Biostatistics, Faculty of Medicine,d Uludag University, Bursa, Turkey; Department of Internal Medicine, Faculty of Veterinary Medicine, Kırıkkale University, Kırıkkale, Turkeyb; TAEA Nuclear Research Center in Agriculture and Animal Science, Ankara, Turkeyc; and Military Veterinary School, Gemlik, Bursa, Turkey.e Reprint requests: Dr. Hakan Biricik, U. Univ. Veterinary Faculty, 16059 Bursa, Turkey. 0737-0806/$ - see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jevs.2005.07.003

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stable intake of minerals. The National Research Council1 suggests the minimum requirements of horses on the basis of age and weight. In particular, optimal trace mineral intakes and mineral interactions for horses are poorly understood.3 As an example for this, no difference has been detected on the serum trace mineral levels of horses in different groups as opposed to an increase in their diets.4 In general, mineral requirements of horses have not been studied extensively, and existing literature focuses mainly on macro-elements.5,6 Therefore, further investigations are necessary for trace mineral requirements of horses. In addition, trace mineral deficiencies in mares may cause severe reproductive disorders besides problems in growth and development. Anke7 found that zinc deficiency may decrease semen quality and libido in stallions and cause delayed ovulation in mares. Herrington et al8 indicated that 5 mg per kg zinc in foal diet caused parakeratosis in the skin. It was also postulated that low zinc in the ration may lead to slow growth, low serum alkaline phosphatase activity, and decreased tissue zinc concentrations in growing horses. Wisniewski9 showed that the parakeratosis and mycosis symptoms were diminished by increased serum and hair zinc concentrations. Asia et al10 have reported associations between low pasture copper concentrations and the perceived incidence and severity of skeletal diseases in young horses. The aim of this study was to investigate both the effects of seasonal changes in the levels of zinc, copper, manganese, and iron in feed, serum, and hair and the correlations among feed, serum, and hair mineral values obtained. MATERIALS AND METHODS

Twenty-three 4-to-8-year-old Standardbred mares (non-pregnant) on a farm in Marmara region, Turkey, were used. Live weights of the horses were between 350 and 400 kg. Diet was formulated to supply protein and energy requirements according to the National Research Council.1 No additional mineral was supplied in diet. Horses were fed with pasture hay and oats in spring,

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Table 1

Chemical composition (100% of dry matter) of feeds Pasture hay

Oats

Concentrate mix

90.19 8.71 8.42 1.36 28.08 0.16 0.19 52 84 20 53

89.15 13.18 3.38 5.13 10.02 0.08 0.34 83 128 11 26

87.21 17.26 6.99 4.24 6.38 1.43 0.81 140 122 30 26

Dry matter % Crude protein % Crude ash % Ether extract % Crude fiber % Ca % P% Mn mg/kg Fe mg/kg Cu mg/kg Zn mg/kg

summer, and autumn, and during winter they were additionally fed with concentrate mix. Blood samples of the horses were obtained at the beginning and at the end of January, April, July, and November. Blood samples were collected into 10-mL Vacutainer tubes via venipuncture. Following collection, serum was separated by centrifuging the samples at 10,000 rpm for 10 minutes. Hair samples from 8 different parts of the body (left shoulder, right shoulder, left hip, right hip, abdominal region, wither high region, mane, and tail) from 1 horse were collected on January and July, and these samples were put together and analyzed. Feed (both hay and grain) was sampled monthly. All feed, hair, and serum samples were kept at 20°C until they were analyzed.

Analysis Crude protein, crude fiber, ether extract, and ash content of feeds were determined by methods outlined by the Association of Official Analytical Chemists.11 Feeds were kept at 60°C for 48 hours to determine dry matter. A 0.5-mL serum was mixed with 4.5 mL of 10% sodium chloride solution for zinc and iron and with 4.5 mL of 6% butanol solution for copper; and 0.5 gram of each hair sample for copper, iron, manganese, and zinc was digested in boiling acid mixture (3 mL HNO3 + 2 mL HCl + 2 mL HClO4). The same procedure was followed for the feed samples. Mineral concentrations in serum, hair, and feed samples were determined by flame atomic absorption spectrophotometers.

Statistical Analysis Correlations12 among the mineral concentrations of feed, serum, and hair samples from different seasons were determined by Statistical Analysis Systems.13 Significant changes in the concentrations of mineral ele-

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Table 2

Amounts of minerals on daily intake of horse diets in different season (mg/d, n = 23)

Seasons Feed Cu Winter Spring Summer Autumn

Feed Fe

Feed Zn

121.5 ±3.5 290.7 ± 4.6 46.8 ± 1.65 121.2 ± 3.01 287.4 ± 5.02 53.64 ± 2.10 169.2 ± 2.9 336.6 ± 4.90 64.8 ± 2.85 112.5 ± 2.5 244.8 ± 4.3 43.2 ± 2.11

Feed Mn 183.6 ± 3.05 202.6 ± 3.65 210.6 ± 4.80 153.9 ± 4.01

ments in feed, serum and hair were determined by MannWhitney U test analysis.13 RESULTS AND DISCUSSION

Ingredients and chemical analysis of the ration consumed by horses are presented in Table 1. In addition, dietary zinc, iron, manganese, and copper concentrations in different seasons are outlined in Table 2. Mineral concentrations and correlation with season of feed, serum, and hair are given in Tables 3 and 4, respectively. Mineral concentrations of feed were found to be similar to the values provided by the National Research Council.1 In general, mineral concentrations of feeds were higher in summer months than those in other seasons and lower in autumn than those in other seasons (Table 2). Serum mineral results were similar to those reported by Ott and Asquith.4 The highest and the lowest serum copper levels were in summer and in spring, respectively (Table 4). Although copper concentrations were similar in autumn and winter, they were lower in the spring than in the summer (P < .05). The highest serum iron concentration was obtained in the spring (Table 4). There were differences among seasons in serum iron concentrations (P < .05). Although it was not significant, serum zinc concentrations in summer had the highest numeric value (Table 4). Except for copper, mineral contents of hair samples were significantly lower in winter than in summer (P < .05). The correlations among feed, hair, and serum are presented in Table 3. Negative correlations were found between season and feed copper (r = -40), iron (r = -40), zinc (r = -20), manganese (r = -40), and hair copper (r = -80), and positive correlations (P < .005) were found between season and hair iron (r = 0.68), zinc (r = 0.86), and manganese (r = 0.41). There was no significant correlation between seasonal change and serum copper and zinc values. Serum and hair copper concentrations did not reflect the copper levels used in diet (feed copper vs serum copper: r = 0.22; and feed copper vs. hair copper: r = -80).

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Table 3 Fd Cu Fd Fe Fd Zn Fd Mn Hr Cu Hr Fe Hr Zn Hr Mn Sm Cu Sm Fe Sm Zn

Correlation among season, feed, hair, and serum Season

Fd Cu

Fd Fe

Fd Zn

Fd Mn

Hr Cu

Hr Fe

Hr Zn

Hr Mn

Sm Cu

Sm Fe

-0.40* -0.40* -0.20* -0.20* -0.80* 0.684* 0.865* 0.414* 0.159 -0.46* 0.112

1.00* 0.80* 0.80* -0.80* 0.684* 0.865* 0.414* 0.229* -0.244* -0.239*

0.80* 0.80* -0.80* 0.684* 0.865* 0.414* 0.229* -0.244 -0.239

1.00* -0.80* 0.684* 0.865* 0.414* 0.082 -0.16 -0.209*

-0.80* 0.684* 0.865* 0.414* 0.082 -0.16 -0.209*

-0.439* -0.596* -0.227 -0.278 0.700* 0.227

0.639* 0.213 0.287 -0.46* -0.033

0.439* 0.170 -0.558* -0.155

0.339* -0.157 -0.029

-0.175 0.002

0.189

Asterisk indicates significance within column for that effect (P < .05). Fd, feed; Hr, hair; Sm, serum.

Table 4

Different season on hair and serum (µg/mL, n = 23)

Winter SEM Spring SEM Summer SEM Autumn SEM

Serum Cu

Serum Fe

Serum Zn

Hair Cu

Hair Fe

Hair Zn

Hair Mn

0.38a 0.02 0.27b 0.03 0.45i 0.03 0.38la 0.02

2.28c 0.15 2.79d 0.18 1.06j 0.21 1.69k 0.22

0.46 0.02 0.47 0.02 0.59 0.12 0.55 0.04

8.91e 1.07

32.5e 4.18

39.48e 2.25

11.92g 1.92

3.39f 0.43

187.6f 3.28

220.44f 3.81

201.9h 6.61

Superscript indicates significance within column for that effect (P < .05).

There was an increase in iron concentrations in hair in relation to the increase in iron level in the diet, but this type of change was not observed either in iron serum concentrations (r = 0.68 and r = 0.24, respectively) or in zinc concentrations with respect to feed. Dietary zinc levels seemed to affect the zinc concentrations of hair but not those of serum (r = 0.86 and r = -0.20, respectively). For the manganese status of animals, neither serum nor hair concentration was found to be a good indicator of dietary manganese concentrations at these levels. CONCLUSION

In addition to seasonal changes, dietary changes had significant effects on serum mineral levels, but not on hair mineral levels. In the future, similar, detailed, and large-scale studies have to be performed, particularly with various amounts of trace minerals in horse diets, and seasonal changes should be observed. Thus, trace mineral requirements of horses belonging to a specific region can be determined more precisely with respect to season. Also, sample type should be precisely defined for the correct determination of the specific trace mineral in horses.

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National Research Council. Nutrient requirement of horses, 5 rev. ed. National Academy Press; 1989. Cunha TJ. Horse feeding and nutrition, 2nd ed. Academic Press (San Diego, CA); 1991. Hoskin SO, Gee E. Feeding value of pastures for horses. New Zealand Vet J 2004;52:332-41. Ott EA, Asquith RL. Trace supplementation of yearling horses. J Anim Sci 1995;73:466-71. Hintz HF, Schryver HF, Lowe JE. Calcium for pregnant mares and growing horses. Equine Prac 1986;8:5-8. Nielsen BD, Potter GD, Greene LW, Morris EL, Murray-Gerzik M, Smith WB, et al. Response of young horses in training to varying concentrations of dietary calcium and phosphorus. J Equine Vet Sci, 1998;18:397-404. Anke M. Die Bedeutung der Mengen—und Spurenelemente in der Fütterungg von Zucth—und Sportpferden. Tierzuch 1977;7:310-12. Herrington DD, Walsh J, White V. Clinical and pathological findings in the horses fed zinc deficient diets. Proc 3rd Equine Nutr Physiol Symp (Gainesville, Fla); 1973. pp 51-4. Wisniewski E. Preventive and therapeutic applications of zinc in bovine dermatomycosis. Bull Vet Inst Pulawy 1984;27: 22-35. Asai Y, Mizuno Y, Yamamoto Y, Fujikawa H. Requirements of copper and zinc for foles in connection with the incidence of epiphysitis. Anim Sci Tech 1993;64:193-200. AOAC. Official methods of analysis, 14th ed. Assoc Agr Chem (Washington, DC); 1984. Zar JH. Biostatistical analysis, 3rd ed. Prentice-Hall (London); 1996. SAS Institute. Statistical analysis systems user’s guide, 5th ed. SAS Institute (Raleigh, NC); 1985.

Journal of Equine Veterinary Science

August 2005