ALKALI TREATMENTS OF CORN STOVER TO INCREASE NUTRITIVE VALUE 1

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1 ALKALI TREATMENTS OF CORN STOVER TO INCREASE NUTRITIVE VALUE 1 U. I. Oji 2, D. N. Mowat 2 and J. E. Winch 3 University of Guelph, Guelph, Ontario, Canada NIG 2W1 SUMMARY Chopped corn stover was reconstituted, treated and stored in 205 liter drums with plastic liners at room temperature for at least 30 days. Treatments were: (1) control, 50% H20; (2) 2% Ca(OEt) 2, 50% H20; (3) 3% NH3,30% H20;(4) 5% NH3, 30% H20. Treatments were evaluated with eight wether lambs in a double 4 4 latin square design. Ammoniated materials were aerated before feeding. Control and hydroxide-treated stover were supplemented with urea. Organic matter intakes increased (P<.001) by 45 to 51% with the different alkali treatments. Treatments also increased (P<.05) gross energy digestibility from 12 to 14%. Nitrogen digestibility tended to decrease slightly with treatments. Treatment with 3% NH3 increased total nitrogen content (P<.001) by 94% over control. Much of this added nitrogen was analyzed as ammonia-n. However, true protein contents were increased (P<.05) with ammoniated stover over control silage. Negligible amounts of lactic acid were contained in the NHa-treated materials. However, NHa treatments increased (P<.05) acetic acid content. (Key Words: Corn Stover, Alkali Treatment, Sheep, Intake, Digestibility.) INTRODUCTION Only a small portion of the millions of tons of corn stover available is utilized as feed. Processing stover to increase energy availability could enable feeding this crop residue to grow- This investigation was supported by the National Research Council of Canada and the Ontario Ministry of Agriculture and Food. Financial sponsorship provided by the National Cereals Research Institute, Ibadan, Nigeria, to the senior author is gratefully acknowledged. 2 Department of Animal and Poultry Science. Department of Crop Science. ing or lactating beef cattle in addition to maintaining dry beef cows. Ammonia treatment has increased energy availability and also crude protein content of cereal straws (Martynov, 1972; Waiss et al., 1972). Ammonia treatment might suit systems for harvesting the stover dry or semi-dry. However, wet corn stover could be treated while ensiting with a combination of NaOH and Ca(OH)2. Recent animal studies suggested that combinations of these two alkalis were more effective than NaOH alone (Kormshchikov, 1969; Rounds and Klopfenstein, 1974). This study was aimed at investigating the effectiveness of treatment with two levels of ammonia or NaOH plus Ca(OH)2 in improving the feeding value of corn stover. EXPERIMENTAL PROCEDURE Corn stover, stacked over the winter of 1974 to 1975, was chopped through a 5 cm screen and given the following treatments: (1) control, 50% H20; (2) 2% Ca(OH) 2, 50% H20; (3) 3% NH3,30% H20;(4) 5% NH3,30% H20. Alkalies were added on a dry matter basis. Ammonia was included in a water solution. Materials were stored in 205 liter drums with plastic liners for at least 30 days. Prior to feeding, the NH3-treated corn stover was aerated to allow excess NH3 to escape and then water added to 50% moisture in order to reduce dustiness. Urea was included with the control and hydroxide-treated materials to provide at least 11% crude protein. Ingredient and chemical composition of rations fed are shown in table 1. Eight wether lambs averaging 26 kg were used in a double 4 x 4 latin square design. The trial consisted in each period of 10 days preliminary adjustment, 10 days ad libitum intake, 4 days restricted intake adjusted to 90% of the lowest ad libitum intake among the lambs and finally 7 days of total collection of urine and feces, during which animals were fed the re- 798 JOURNAL OF ANIMAL SCIENCE, Vol. 44, No. 5 (1977)

2 ALKALI TREATMENTS OF CORN STOVER 799 TABLE 1. COMPOSITION OF RATIONS lnternat'l Item Ref. No. Control 2% Ca(OH) z 3% NH 3 5% NH~ Percent dry matter basis Ingredients Corn stover Urea Mineral-vitamin mix a Salt 6 ;4-52.S.....S Potassium sulphate b Limestone 6qJ2~ Chemical analyses Gross energy, kcal/g Acid detergent fibre, % Cellulose, % Crude protein, % Ash, % acommereial mix containing 24% P, 5% Fe,.05% I,.005% Co,.02%. Cu,.18% Mn, 40,000 IU vitamin A, 15,000 IU vitamin D. bcommercial, feed grade, mn 41% K, mn 17% S. stricted intake. Lambs were confined individually to metabolism crates except for 7 days during each adjustment phase when they exercised in floor pens. During the collection phase, grab samples of feed were taken daily and stored at -10 C as were the feces and urine. Urine was collected in dilute H2SO4. At the end of each period, collected materials were thawed, composited and subsampled for analysis. As corn stovers were being removed from storage, samples were taken from different levels of the drums and ammoniated materials aerated. Samples were analyzed for the following fractions: dry matter of feed and feces by freeze drying; dry matter of stored corn stovers by toluene distillation (A.O.A.C., 1970); gross energy using a Parr oxygen bomb calorimeter; total nitrogen by the macro-kjeldahl technique; non-protein nitrogen after extraction with.1n HCI and precipitation of protein with.8n TeA; organic matter by heating in a muffle furnace at 600 C for 12 hr; acid detergent fibre and cellulose by Goering and Van Soest (1970); ph of the silage by using a glass electrode; lactic acid by the colorimetric method of Barker and Summerson (1941); ammonia nitrogen by the indophenol-blue method of Novozamsky et al. (1974) and volatile fatty acids by J. G. Buchanan-Smith and Y. T. Yao (unpubtisbed data). The method consisted of extracting the acids with absolute alcohol and valeric acid standard, neutralizing with.1n NaOH and determining the VFAs in a 1.83 m glass column packed with 100-mesh chromosorb 101. Results were subjected to standard analysis of variance procedures and Tukey's w-procedure used to separate the means (Steel and Torrie, 1960). R ESU LTS Organic matter intakes of corn stover increased (P<.001) by 45 to 51% with the different treatments (table 2). Intakes were similar (P<.05) among chemical treatments. Treatments increased (P<.001) apparent digestibilities of dry matter, organic matter, gross energy, acid detergent fibre and cellulose. Digestibilities of these constituents were similar (P<.05) among alkali treatments. Nitrogen digestibility tended to decrease slightly with treatments particularly with the 5% NH3 level (P<.05). Differences among stored corn stovers occurred in ph, organic acids and content of various nitrogen fractions (table 3). Treatment with 3% NH 3 increased total nitrogen content (P<.001) by 94% over control. At least 47% and 53% of the added ammonia with the 3% and 5% treatment levels, respectively, were lost by evaporation before feeding. Much of the remaining bound nitrogen was analyzed as ammonia-n. True protein contents were increased (P<.05)

3 800 oji, MOWAT AND WINCH TABLE 2. EFFECTS OF TREATMENT OF CORN STOVER ON INTAKE AND DIGESTIBILITX/a Item Control 2% Ca(OH)z 3% NH 3 5% NH 3 + SE Intake, g/day Dry matter 664 b 986 c 949 c 984c 38.2 Organic matter 582 b 855 c 846 c 876 c 32.8 Apparent digestibility, % Dry matter 51.6 b 57.9 c 60.1 c 60.3 c 1.1 Organic matter 57.2 b 63.7 c 65.3 c 66.5 c 1.2 Gross energy 54.6b 61-0c 61.1 c 62.0 c.9 Nitrogen 60.8 b 57.3 bc 57.1bc 54.4 c 1.2 Acid detergent fiber 47.7 b 58.1 c 61.7 c 59.5 c 1.4 Cellulose 65.6 b 76.2 c 77.6 c 78.5 c 1.7 ameans of eight observations. b'cmeans in same row with unlike superscripts are different (P<.05). with alkali treatments particularly with NH3. Negligible amounts of lactic acid were contained in the NH3-treated materials. However, NH 3 treatments increased (P<.05) acetic acid level. Treatment with the combined hydroxides slightly increased butyric acid content (P<.05). Discussion The marked improvements in intake with all treatments were similar to those obtained pre- viously with NaOH-treated straws (Mowat and Ololade, 1970). However, other studies (Kormshchikov, 1969; Rounds and Klopfenstein, 1974) have demonstrated improved intakes and weight gains with poor quality roughages treat- ed with combinations of NaOH and Ca(OH) 2 compared to NaOH alone. Replacing some NaOH with Ca(OH) 2 also reduces treatment costs, lowers level of sodium fed and eliminates any need for supplemental calcium. Increased intake and energy digestibility following NH3 TABLE 3. CHEMICAL CHARACTERISTICS OF TREATED CORN STOVERa Item Control 2% Ca(OH) 2 3% NH 3 5% NH 3 + SE Dry matter, % 50-0b 48.6 b 77.9 c 74.1 c 2.01 ph 4-3 b 6.8 c 7.9 d 8.8 d.26 Crude protein, % of DM Total 8.8 b 8.2 b 17.1 c 20.9 d.57 Ammonia 1.1b.8 b 9.3 c 12.4d.56 Non protein 6.3 b 4.6 b 12.1 c 15.0 d.57 True protein 2.6 b 3-6 b 5.0 c 5.9 c.34 Organic acids, % of DM Lactic 3.05 b 1.36 c.01 d.01d.08 Total VFA 2.12 b 3.10 c 3.20 c 3.64 c.10 Acetic 2.07 b 2.35 b 3.09 c 3.54 c.17 Propionic.02 b.04 c.03 bc.01 b.01 Isobutyric Butyric.003 b.62 c.02 b.004 b.06 Isovaleric -02b.07 c.05 bc.07 c.01 astored for at least 30 days. b'c'dvalues with unlike superscripts are different (P<.05).

4 ALKALI TREATMENTS OF CORN STOVER 801 treatment were also noted in studies with straw (Garrett et al., 1974; Martynov, 1972). Presumably, the increased rate (Ololade et al., 1970) and extent of cell wall digestibility caused by alkali treatments account for the increased voluntary intakes. Ammonia is a slow-reacting alkali requiring processing times of several days (Waiss et al., 1972). This probably misled some previous investigators into believing that NH3 was not an effective alkali. Furthermore, no advantage in digestibility from NH3 treatments exists with moisture levels higher than 30% (Waiss et al., 1972). In contrast, the penetration and/or reactivity of NaOH is greater at higher moisture levels (Phoenix et al., 1972). Nitrogen digestibility decreased (P<.05) for corn stover treated with 5% NH 3. A similar decrease in nitrogen digestibility with rice straw treated with 5% NH3 was also reported by Garrett et al. (1974). Treating straw (Martynov, 1972) or wood (Schuerch and Davidson, 1971) with anhydrous or liquid ammonia at room temperatures results in pronounced color changes. Schuerch and Davidson (1971) postulated that the color changes are chemical reactions arising from the oxidation of phenols or condensation of aldehydic fractions in sugars with nitrogenous bases, via the Maillard reaction to a number of colored products. Presumably, some nitrogen tied up as a result of this could partly account for the decreased nitrogen digestibility. Treatment with 3% NH 3 appears adequate with little, if any, further improvement in intake and digestibility at 5% NH3. After removal from sealed storage, excess NH3 dissipated rapidly at the moisture level present. Approximately 50% of the added nitrogen remained in the arnmoniated stover at feeding time, most of which was analyzed as NH 3 nitrogen. However, NH3 treatments increased true protein content as compared to control stover silage. Non-protein nitrogen content of materials increase with ensiling due to plant and microbial proteoiysis (Bergen et al., 1974). Previous silage studies have shown that alkali additives such as ammonia (Henderson et al., 1971; Mowat et al., 1976) or NaOH (Flipot et al., 1976) increased true protein content probably due to decreased proteolysis. Artifact nitrogen, earlier mentioned could partly account for this increase in true protein. The negligible levels of lactic acid with NH3- treated stover is indicative of the absence of fer- mentation during storage. No molds were observed. Ammonia is reported to be an effective fungicide or preservative for moist hay (Knapp et al., 1974) or grains (Botbast et al., 1973). The increased acetic acid content of the stored material especially the ammoniated stover agrees with the reports of Tarkow and Feist (1969). Structurally, the polysaccharide units contain xylan chains to which are attached acetyl groups. Ammonolysis readily liberates these acetyl groups as acetic acid. LITERATURE CITED A.O.A.C Official Methods of Analysis (11th Ed.). Association of Official Analytical Chemists. Washington, DC. Barker, S. B. and W. H. Summerson The colorimetric determination of lactic acid in biological material. J. Biol. Chem. 138:535. Bergen, W. G., E. H. Cash and H. E. Henderson Changes in nitrogenous compounds of the whole corn plant during ensiling and subsequent effects on dry matter intake by sheep. J. Anim. Sci. 39: 629. Bothast, R. J., E. B. Lancaster and C. W. Hessehine Ammonia kills spoilage molds in corn. J. Dairy Sci. 56:241. Flipot, P., D. N. Mowat, J. J. Parkins and J. G. Buchanan-Smith Ensiling characteristics of silages treated with sodium hydroxide. Can. J. Anim. Sci. (In press). Garrett, W. N., H. G. Walker, G. O. Kohler, A. C. Waiss, Jr., R. P. Graham, N. E. East and M. R. Hart Nutritive value of NaOH and NH~treated rice straw. Proc. W. Sect. Amer. Soc. Anita. Sci. 25:317. Goering, H. K. and P. J. Van Soest Forage Fiber Analysis. Agricultural Handbook No Agricultural Research Service, U.S. Dept. of Agr., Washington, DC. Henderson, H. E., D. R. Beattie, M. R. Geasler and W. G. Bergen Molasses, minerals, ammonia and Pro-Sil additions to corn silage for feedlot cattle. Mich. State Univ. Res. Rep Knapp, W. R., D. A. Holt and V. L. Lechtenberg Anhydrous ammonia and propionic acid as hay preservatives. Agron. J. 66:823. Kormshchikov, P. A Digestibility of the nutrients of straw in relation to chemical treatment. Chem. Abstr. 70:55386f. Martynov, S. V Treatment of straw with anhydrous ammonia. Nutr. Abstr. and Rev. 43 ".247. Mowat, D. N. and B. G. Ololade Effect of level of sodium hydroxide treatment on digestibility and voluntary intake of straw. Can. Soc. Anita. Proc. p. 35 (Abstr.). Mowat, D. N., J. E. Core, J. G. Buchanan-Smith and G. K. Macleod Nitrogen additives to corn silage fed to growing calves. Can. J. Anim. Sci. (In press). Novozamsky, 1., R. van Eck, J. Ch. van Schouwenburg and I. Walinga Total nitrogen determination in plant material by means of the indophenolblue method. Neth. J. Agric. Sci. 22:3.

5 802 oji, MOWAT AND WINCH Ololade, B. G., D. N. Mowat and J. E. Winch Effect of processing methods on the in vitro digestibility of sodium hydroxide treated roughages. Can. J. Anim. Sci. 50:657. Phoenix, S. L., W. K. Bilanski and D. N. Mowat In vitro digestibility of barley straw treated with sodium hydroxide. Trans. A.S.A.E. 15 : Rounds, W. and T. J. Klopfenstein Chemicals for treating crop residues. J. Anim. Sci. 39:433. (Abstr.). Schuerch, C. and R. W. Davidson Plasticizing wood with ammonia - control of color changes. J. Pol. Sci. Part C. 36:231. Steel, R. G. and J. H. Torrie Principles and Procedures of Statistics. McGraw-Hill Book Co., New York. Tarkow, H. and W. C. Feist A mechanism for improving the digestibility of lignocellulosic materials with dilute alkali and liquid ammonia, p In Robert F. Gould (Ed.) Celluloses and Their Applications. Advan. Chem. Set., No. 95. Amer. Chem. Soc., Washington, DC. Waiss, A. C. Jr., J. Guggolz, G. O. Kohler, H. G. Walker, Jr. and W. N. Garrett Improving digestibility of straws for ruminant feed by aqueous ammonia. J. Anim. Sci. 35:109.