Effect of Tannin Content in Horse Bean on Rumen Fermentation in vitro

The objective of the experiments was to demonstrate the influence of lowand high-tannin horse bean on the selected fermentation indicators. The sheep rumen content with the addition of 1, 2 and 5 g of highand low-tannin horse bean was incubated in vessels of 250 ml volume. A significant increase of ammonia, lactic acid, CO2 and methane as well as pH decrease in samples with addition of horse bean seed was demonstrated. While comparing highand low-tannin horse bean varieties, it was observed that in the case of small doses of 1 and 2 g a higher intensity of fermentation takes place in the samples with the addition of high-tannin horse bean. In the case of larger doses of 5 g per sample, a higher intensity of fermentation takes place in the samples with the addition of low-tannin horse-bean. A probable reason for the decrease in the fermentation process intensity in the samples with the addition of 5 g of high-tannin horse bean is a high content of tannins, which reduce fermentation processes. Sheep, fermentation, rumen, horse bean, in vitro A ban on the inclusion of meat-bone meal in the ruminant feeding has resulted in a greater interest of breeders in high-protein plant fodders. These fodders are considerably cheaper than the meat-bone meal and do not involve a risk of infectious diseases. One disadvantage of the fodders is worse protein balance in the amino-acid composition. Horse bean belongs to this type of fodders. Its high nutritive value is associated with a high protein content of high biological value. The horse bean seeds contain approximately 26-30% of the total protein. Globulins are the main protein, which constitutes 55% to 70% of the total protein (Jasińska and Kotecki 1998a; 2003). A disadvantage of the protein contained in the horse bean is the low content of some amino acids, i.e. methionine, cysteine, tryptophan and threonine, whereas its content of lysine is high (Jasińska and Kotecki 1993). The fat content in the horse bean seeds is very low. The horse bean also contains a substantial amount of sugar, including a lot of starch and hemicellulose amounting to approximately 58%. It is also rich in minerals and vitamins (Jasińska and Kotecki 2003; Pavlata et al. 2002). There are certain compounds in the horse bean that limit the bioavailability of nutritive components and disturb the functions of glands and internal organs through which they worsen health and reduce animal productivity. The following compounds belong to the above-mentioned ones: tannins, protease inhibitors, lectins, glycosides, phytates, alphaamylase and oligosaccharide inhibitors (Jasińska and Kotecki 1998b). Tannins are intermediate metabolites of the plant synthesis. They are structurally divided into two groups: proanthocyanidins (the condensed tannins) and polyesters of the gallic acid and the hexahydroxydiphenic acid (Hasam 1981). Tannins have the task of protecting the plants against herbivorous animals and those microorganisms that are pathogenic to plants (fungi, bacteria) (Provenza 1995; Scalbert 1991; Hart and Hillis 1972). Tannins have an impact on decreasing the animal’s appetite, which already appears 20-60 min after administration of the horse bean fodder (a short-term effect). The addition of the horse ACTA VET. BRNO 2010, 79: 217-224; doi:10.2754/avb201079020217 Address for correspondence: Wojciech Zawadzki Department of Animal Physiology Wrocław University of Environmental and Life Sciences ul. Norwida 31, 50-375 Wrocław, Poland Phone: 48 71 320 54 91 Fax: 48 71 320 54 01 E-mail:[email protected], [email protected] http://www.vfu.cz/acta-vet/actavet.htm bean in the fodder has also a long-term effect on a decrease in the feed consumption (a long-term effect). The short-term effect is associated with changes within the oral cavity, whereas the long-lasting feeding results in a decrease in the concentration of ammonia and volatile fatty acids in the rumen contents. In the long-term effect, the fermentation process in the rumen is limited and a decrease in energy is provided for the animal (Silanikove et al. 2001). On account of the tannin content in the horse bean seeds, different horse bean varieties have been divided into lowand high-tannin ones. In the low-tannin varieties, the content of condensed tannins in the coated seeds does not exceed 0.04 mg/g dry mass of the seeds. The low-tannin varieties studied in this work include the following varieties (contents of tannin are given in parentheses in milligrams per gram of dry mass): Allbus (0.034 mg/g d. m.), Leo (0.026 mg/g d. m.), Olga (0.038 mg/g d. m.), Kasztelan (0.027 mg/g d. m.), Merlin (0.031 mg/g d. m.), and Mistral (0.021 mg/g d. m.). The high-tannin varieties were as follows: Akord (0.594 mg/g d. m.), Martin (0.725 mg/g d. m.), Neptun (0.750 mg/g d. m.), Optimal (0.755 mg/g d. m.), Redos (0.689 mg/g d. m.), and Sonet (0.716 mg/g d. m.). The current knowledge of feeding of horse bean in ruminants is unsatisfactory and more data are needed. Materials and Methods The study was carried out on 15 sheep, (Polish Merino × Polish Heather Sheep hybrid at the age from 2 to 4 years and of the body mass of 30-45 kg) from which samples of the rumen fluid and contents were taken 2.5 h after the morning feeding. The sheep were fed hay and concentrate mixture J-161 DB411X manufactured by Provimi-Rolimpex S.A. The material for analysis was collected through the cannule of the dorsal rumen sack, made in accordance with Dejneka and Zięba’s method (1965). Incubation of the collected contents was conducted in the vessels in accordance with Barnett and Reid’s method (1961) with Zawadzki’s modification (1993). The incubation environment in the vessels included 50 ml of the collected rumen fluid contents, 50 ml of distilled water and 50 ml of McDougall’s artificial saliva of pH = 6.9 with the following composition (in 1 dm3 of distilled water): NaHCO3 – 9.60 g, KCl – 0.60 g, CaCl2 – 0.04 g, Na2HPO4·12H2O – 9.15 g, NaCl – 0.45 g, MgSO4·7H2O – 0.11 g, ZnSO4·H2O – 0.06 g, CaCl2·6H2O – 0.01 g, NH4HCO3 – 0.5 g. A control sample consisted of vessels including 50 ml of the collected contents, 50 ml of distilled water and 50 ml of artificial saliva. A control sample was prepared individually for each experiment in order to eliminate differences in the fermentation activity of the rumen contents collected. The next vessels included 50 ml of the filtered rumen contents, 50 ml of distilled water and 50 ml of artificial saliva as well as ground seeds of the lowand high-tannin horse bean at 3 different doses of 1, 2 and 5 g. Twenty fermentations were performed for each variant. The doses of 1, 2 and 5 g were adopted from previous research. The total incubation volume of the samples in the vessels amounted to 150 ml (with the total vessel volume of 250 ml). The vessel was made leak-proof by polished plugs and valves, covered with sealing silicon lubricant. Nitrogen was added to vessels under pressure to obtain anaerobic conditions. The gas was passed through the vessel contents for 10-15 min. Then, all the valves were closed. The maintaining of anaerobic conditions was checked with a DO-5508 device (manufactured by Lutron). The vessels prepared in this way were then placed in the seats of a shaker with a water bath of 39-42 °C and amplitude of 4 cycles per min. During incubation, samples of the contents were collected at the 4th and 6th hour of incubation in order to determine the content of ammonia, lactic acid, methane, CO2 as well as the pH of the fermented rumen contents. The ammonia level was determined using the Conway method, and the lactic acid and CO2 concentration was determined using the titration method. Methane concentration was measured using a methanometer of Barbara-3 type. The pH of the collected samples of the incubated rumen contents was measured with a pH-meter (pX-processor PM-600). The research results were elaborated statistically by Student’s t-test and the ANOVA variation analysis. The experiment was conducted in accordance with protocol approved by the II Local Ethics Commission located at the Wroclaw Uviwersity of Enviromental and Life Sciences Poland.