Mares, like other animals, consume various kinds of microorganisms with their feed that do not always have a positive effect on host health. In controlled feeding environments, the development of positive bacterial microflora in the gastrointestinal tract (GIT) can be stimulated by introducing probiotics or prebiotic substances to diets.
These substances act to boost the immune system of the host animal by stimulating the growth of microbial populations that are beneficial to the GIT in preventing or fighting infections caused by pathogenic bacteria or in diminishing the effects of toxins produced by some bacteria (Flickinger, 2003). Among the most efficient immunomodulators are the prebiotic mannan oligosaccharides obtained from the cell wall of Saccharomyces cerevisiae (Nakakuki, 2003). Mannan oligosaccharides stimulate the local protective immunologic mechanisms of the intestine, neutralizing the effects of harmful bacteria.
Immunologic mode of action is also related to its ability to block potential sites of adherence by pathogenic bacteria with Type-1 fimbriae, e.g., certain Escherichia coli or Salmonella spp. In so doing, pathogenic bacteria harmlessly pass through the host (Flickinger, 2003). The introduction of Bio-Mos®, a mannan oligosaccharide produced by Alltech Inc., to mare diets reduced the incidence of diarrhea in foals and increased the level of immunoglobulins both in the blood and milk of mares (Ott, 2002; 2005).
Hitherto, investigations have been conducted dealing with the dietary supplementation of Bio-Mos® in poultry (Ferket et al., 2002), piglets (LeMieux et al., 2003), calves (Heinrichs et al., 2003), and rabbits (Fonseca et al., 2004). However, few investigations have focused on the effect of this prebiotic on the health of mares and on the composition of colostrum and milk. Therefore the aim of this investigation was to determine the effect of using Bio-Mos® in mare diets on hematologic parameters and on colostrum and milk composition.
Material and methods
The investigation was conducted during March and April 2004 using Thoroughbred mares at Horse Stud of Kozienice (Poland). Twenty mares were divided into two groups based on body weight and age: control (C) and Bio-Mos® (BMOS). All received the same ration, which was formulated to NRC (1989) specifications (Table 1). The horses in the treatment group received 10 g mannan oligosaccharide (Bio-Mos®, Alltech Inc.) per head daily as an additive for 30 days pre-partum.
Horses were housed individually, with temperature and humidity conditions standard for horses. They were fed three times daily and had free access to water. At each feeding meadow hay was offered, and at the morning and evening feedings horses were fed crushed oats. At the midday feeding a concentrate mixture based on crushed oats, ground corn, and wheat and faba bean seeds was given. This mixture was moistened with water containing some molasses. Mares had free access to water.
Table 1. Composition of mare diet.aContained per kg: 195 g Ca; 6.3 g P (Ca (H2PO4); 0.34 g Na (NaCl); 154 mg Fe (Fe(SO4)•7H2O); 44 mg Zn (ZnO); 30 mg Cu (CuSO4•5H2O); 12 mg I (CaI2); 3 mg Se (Na2SeO3); 640 000 IU vit. A; 1000 IU vit. B3; 600 IU vit. E; 60 mg vit. K; 40 mg riboflavin; 220 mg niacin; 150 mg pantothenic acid; 0.2 mg vit. B12; 7500 mg choline, 17.9 g lys, 3.8 g met, 11.8 g thr, 2.2 g trp.
At the end of the 10th month of gestation (beginning of the experimental period) and after 4 weeks of Bio-Mos® supplementation, blood samples (from external jugular vein) were taken from all mares before the morning feeding. The following hematological indices in whole blood were determined: hematocrit (%) (Ht), hemoglobin (Hb), number of red blood cells (RBCs) and white blood cells (WBCs). A leucogram was prepared by Pappenheim’s method.
Blood plasma levels were measured for glucose, total protein, uric acid (UA), urea, triglycerides (TG), total cholesterol (Chol), high and low density lipoproteins (HDL and LDL) and activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and alkaline phosphatase (AP). Iron, copper and zinc content of plasma were determined using atomic absorption spectroscopy, and activities of catalase (E-CAT) and superoxide dismutase (EC-SOD) were determined using a spectrophotometric method.
Activity of SOD in blood plasma was determined by the adrenalin method according to Misra modified by Bartosz (1995). Catalase activity in blood was assayed using an Oxis kit. Serum lysozyme level was determined with the turbidimetric method (Siwicki and Anderson, 1993). Low density lipoprotein (LDLchol) was calculated using the Friedewald (1972) formula:
- LDL cholesterol (mmol/L) = total cholesterol – HDL cholesterol – triglycerides/2.2
Colostrum samples were taken 4–6 hrs after parturition, and milk samples were taken on the 21st day of lactation from all mares. Basic nutrients in colostrum and milk (i.e., dry matter, crude protein, fat, lactose, crude ash) were determined using a Milk-scan apparatus. In colostrum and milk fat, fatty acid composition was determined using a gas chromatographic method (Rotenberg and Andersen, 1980) after saponification and esterification with 14% BF3 in methanol and graining with saturated KCl solution. From the graphs derived, using the standards of the Applied Science Laboratory firm, specific fatty acids were identified. Data were analyzed using ANOVA procedures.
Results and discussion
HEMATOLOGIC INDICES
Hematologic indices (Table 2) of mares from both experimental groups were within normal ranges (Cebulj-Kadunc et al., 2002; Piccione et al., 2005; Winnicka, 2004). In the control group, RBC indices (Ht, Hb, RBC) decreased (P≤0.05) (e.g., red blood cell count by about 13% compared with the initial level (day 0)), whereas in mares given Bio-Mos®, no significant reduction in these parameters was noted. Thus, supplementation with Bio-Mos® resulted in a RBC count about 20% higher than controls. This difference was likely the cause of the superior physical condition noted in supplemented animals, probably the product of an improved immune response (Ott, 2005).
The other blood morphological indices appeared to be unaffected by the prebiotic supplement, however WBC counts of controls were increased over those on day 0, which did not occur in mares given Bio-Mos® (Table 2). This finding, plus a 9% decrease in neutrophil count in the experimental group, support a beneficial effect of Bio-Mos® on immune response. Neutrophils act to control invading pathogens and remove necrotic tissue.
In the absence of pathogenic bacteria, e.g. due to Bio-Mos® intervention, counts remain stable. In addition, lymphocyte count tended to increase in the supplemented group.
Table 2. Hematologic parameters of mares fed diets with or without Bio-Mos®.abMeans in the same row differ, P≤0.05The available literature provides little information concerning the effect of mannan oligosaccharide supplements on blood indices in horses. The results obtained in this experiment are consistent with our previous investigations performed on foals (Czech et al., 2005). Studies by Ott (2005) revealed an increase of serum IgG and IgA immunoglobulins in foals supplemented with Bio-Mos® for 28 days.
PLASMA BIOCHEMISTRY
Biochemical indices in mare blood plasma in both control and experimental groups were within normal ranges (Queiroz-Neto et al., 2002; Harvey et al., 2005; Winnicka, 2004). Alkaline phosphatase activity and lactate dehydrogenase were about 30% higher in mares given Bio-Mos® (P≤0.05) (Table 3). Inhibition of LDH activity in control mares could be the result, in part, of free radicals produced by pathogens living in the alimentary tract of host animals.
In mares supplemented with Bio-Mos®, enteric pathogenic bacteria are bound by the prebiotic, and therefore potential inflammatory foci in the host are eliminated. Slightly different results were obtained by Czech et al. (2005), who used dietary Bio-Mos® in foals and reported a 34% increase in alkaline phosphatase activity and a 10% decrease in lactate dehydrogenase activity in blood plasma. In plasma of test group mares a decrease (P≤0.05) in alanine aminotransferase was detected. The Czech et al. (2005) studies did not find this same relationship.
Bio-Mos® exerted a substantial impact on lysozyme activity (+22.5%) in blood plasma of mares, as confirmed by Czech et al. (2005). It is claimed that this enzyme, released from the lysozymic structures, enters plasma and measures of its activity constitute a phagocytic index. Therefore, it is a vital component of humoral immune response and its activity is related mainly to lysis of the affected cells, thus suppressing pathogen colonization (Rzedzicki and Kowalska, 1988). This increase in lysozyme activity may be evidence of immune system modulation by mannan oligosaccharide, as suggested by work by Ott (2005). No significant differences were noted in the aspartate aminotransferase activity in foal plasma.
Table 3. Plasma enzyme activities in mares fed diets with or without Bio-Mos®.abMeans in the same row differ, P≤0.05Changes in total protein, glucose and triglycerides in the blood plasma of mares in control and experimental animals were similar over the course of the experiment (Table 4). Likewise, the other blood lipid indices were unaffected. Different results were reported by Czech et al. (2005), whose studies on foals fed Bio-Mos® revealed a decrease of 16% in total cholesterol, inversely correlated to an increase of the same magnitude in the HDL fraction.
Table 4. Plasma biochemical parameters in mares fed diets with or without Bio-Mos®.Biochemical indices in mare blood were consistent with those presented in other works (Greppi et al., 1996; Watson et al., 1992). Responses may differ under different conditions since these indices are known to be affected by sex, age, breed, season, and feed supply (Grela et al., 2003).
PLASMA ANTIOXIDANTS
The blood plasma includes the complete panel of endogenous antioxidants, i.e., bilirubin, uric acid, urea and glutathione as well as trace elements involved in antioxidative activity, i.e., copper, iron, zinc, selenium, and manganese. Oxidative stress may be evoked by factors such as bacterial infection that can deplete antioxidants in a fixed order. The available studies show ascorbate is used up fastest followed by protein thiol groups, bilirubin, uric acid, and α-tocopherol (Sitarska et al., 1997; Wayner et al., 1987).
Many other antioxidative enzymes respond similarly, including superoxide dismutase, peroxidase, reductase, and catalase. The present investigation showed that plasma superoxide dismutase activity was 24% higher (P≤0.05) in mares supplemented with Bio-Mos®. That finding suggests the presence of undetected pathologic states in the control mares.
In eukaryotic cells three types of superoxide dismutase (SOD) exist: mitochondrial MnSOD, cytoplasmic Cu/ZnSOD, and extracellular (EC) SOD. Extracellular SOD also contains copper and zinc ions, yet its appearance in organisms is limited to plasma and some other extracellular fluids including lymph, synovial or interstitial tissue fluid (Bis-Wencel et al., 2002). Enhancement of SOD activity was correlated with a substantial increase in copper level (about 40%) in plasma of mares given Bio-Mos® (Table 5). A relationship between copper concentration in blood plasma and SOD activity has been reported in other studies (Bertinato et al., 2003; Kleczkowski et al., 2003). Similar relationships were established for zinc levels (Table 5). Higher activity of catalase is also worth noting since it is an enzyme that breaks down hydrogen peroxide produced in oxidase reactions.
In contrast, iron content in treated mares was significantly lower (~17%) compared to controls. The decline may have been caused by increased SOD or catalase activity since iron, like manganese, selenium, copper, and zinc, is an enzyme co-factor. Iron is an element associated with antioxidative activity, but it also participates in the Haber-Weiss reaction, contributing to the generation of toxic free radicals in organisms (Kleczkowski et al., 2004).
Uric acid and urea content of plasma were unaffected by treatment.
Table 5. Selected antioxidant parameters in blood plasma of mares fed diets with or without Bio-Mos®.abMeans in the same row differ, P≤0.05The data presented herein should be considered as preliminary since no similar studies have been performed and no reference values are available. To determine the influence of mannan oligosaccharide supplementation on the blood metabolic profile in the mare, especially the immune indices, further detailed investigations are required.
COLOSTRUM AND MILK COMPOSITION
The analysis of colostrum and milk nutrient content (Table 6) showed higher crude protein levels (+3.5% in colostrum and +17.3% in milk) in mares supplemented with Bio-Mos®, possibly due to greater quantities of immunoglobulins, in particular γ- globulins. Similarly, in colostrum from the supplemented mares, lactose level was significantly increased; this pattern was unexplained. The levels of other nutrients were similar. These results are consistent with the findings of other investigators (Csapó et al., 1995; Csapó-Kiss et al., 1995; Tischner et al., 1996; Malacarne et al., 2002; Wlodarczyk-Szydlowska et al., 2005).
Bio-Mos® did not significantly affect the fatty acid composition in mare colostrum and milk (Table 7). Only the myristic acid content (14:0) in both mare colostrum and milk appeared significantly lower (~13%) in mares given Bio-Mos®. The milk fatty acid composition was consistent with results obtained by Orlandi et al. (2003).
Table 6. Colostrum and milk composition (%) of mares fed diets with or without Bio-Mos®.abMeans in the same row differ, P≤0.05
Table 7. Fatty acid composition (%) in colostrum and milk of mares fed diets with or without Bio-Mos®.abMeans in the same row differ, P≤0.05
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Authors: ANNA CZECH1 and EUGENIUSZ R. GRELA2
1 Department of Biochemistry and Toxicology, Agricultural University of Lublin, Poland
2 Institute of Animal Nutrition, Agricultural University of Lublin, Poland