- Email: [email protected]
Wood ash, sodium hydroxide and urine to increase sorghum straw utilization by sheep
Small Ruminant Research, 5 ( 1991 ) 83-92 Elsevier Science Publishers B.V., Amsterdam
83
Wood ash, sodium hydroxide and urine to increase sorghum straw utilization by sheep R.G. Ramirez ~, J. Garza, J. Martinez and N. Ayala Facultad de Agronomia, Universidad Aut6noma de Nuevo Le6n, San Nicol6s de los Garza, N.L. M~xico (Accepted 6 June 1990)
ABSTRACT Ramirez, R.G., Garza, J., Martinez, J. and Ayala, N., 1991. Wood ash, sodium hydroxide and urine to increase sorghum straw utilization by sheep. Small Rumin. Res., 5: 83-92. In experiment 1, 12 lambs (30.3 Kg BW) were fed 4 diets containing 85% sorghum straw treated with 0% wood ash (WA) solution (w/v) (0WA), 10% (10WA), 20% (20WA) and 30% (30WA). Dry matter (DM) digestibility was affected quadratically (P < 0.01 ) by WA treatment, from 49.6% to 60.0% for ilambs fed the 30WA and 20WA diets. Organic matter (OM) and crude protein (CP) digestibilities did not differ (P> 0.05) among diets. Acid detergent fiber (ADF) digestibility was affected quadratically (P< 0.05) from 45.8% to 49.1% for controls vs. 20WA diets, respectively. Neutral detergent fiber (NDF) digestibility changed (P<0.01) from 51.5% to 63.1% for controls vs. 20 WA diets, reslpectively.In experiment II, 18 whether lambs (28.7 Kg BW) were fed 6 diets containing untreated (control) sorghum straw or treated with 20% solutions (w/v) ofWA (20WA), or with 4 g NaOH/100 g straw DM (4NaOH), or 20WA plus urea, or 20WA plus urine, or urine only. Lambs digested greal~er (P < 0.05 ) amounts of DM and OM, respectively when fed diets containingsorghum straw with 20WA (56.9%, 61.4%), 20WA plus urea (62.1%, 64.3%), and urine (58.5%, 57.4%) compared with untreated diets (51.7%, 52.0%), 4NaOH (50.2%, 53.8%) and 20WA plus urine (47.7%, 47.8%), respectively. Lambs digested greater (P< 0.05%) amounts of ADF and NDF, respectively, when fed sor:ghum straw treated with 20WA (56.7%, 63.1%), 4NaOH (56.3%, 62.2%), 20WA plus urea (61.3%, 66.5%), and urine only (52.4%, 60.5%) compared with controls (48.6%, 55.2%) and 20WA plus urine (43.8%, 51.2%), respectively. Results of this study suggest that treatment of sorghum straw with 20% WA solutions or with animal urine can increase fiber utilization by lambs in amounts comparable to the increase observed with NaOH treatment.
INTRODUCTION
Sorghum straw is a lignocellulosic crop residue produced in considerable amounts in the sorghum grain-producing region of northeastern Mexico. In some are~Ls, sorghum straw surplus is ploughed back into the soil. However, in areas where feed for animal production is limited, most producers use ~Correspondence Address: Apartado Postal 142, Sucursal F, Cd. Universitaria, San NicolAs de los Garza, N.L. 66450, M6xico.
0921-4488/91/$03.50
© 1991 - - Elsevier Science Publishers B.V.
84
R.G. RAMIREZ ET AL.
sorghum straw as animal feed. The low digestibility and nutritive value of sorghum straw limits animal intake and cannot support growth of adult ruminants, without adequate supplementation (Males, 1987). Several methods can enhance feed value of straw by biological, physical or chemical treatments, or their combinations. Chemical treatments increase lignin solubility, reduce cell wall volume and increase cell content digestibility. The most common alkalis used are NaOH, Ca (OH)2 and urea-ammonia (Trung and Devendra, 1987). Sodium hydroxide treatment of straw results in greater digestibility and animal performance than ammonia (NH3) treatment. However, NH3-treated straw has the advantage of added nitrogen (N) which reduces the need for supplemental N (Males, 1987 ). All chemical processes are technologically possible, but many are not economically feasible (Trung and Devendra, 1987 ). One economical alkaline resource is cattle urine, which has been used as an effective source of urea-derived NH3 for straw treatment. Saadullah et al. ( 1980 ) reported that rice straw treated with urine in 1 : 1 ratio improved sheep N-balance and digestibilities of dry matter (DM), organic matter (OM) and crude fiber (CF) compared with untreated rice straw. Another economical alkaline source is wood ash (WA). Nolte et al. ( 1987 ) found that treatment of wheat straw with 30% solution of WA for 6 h increased digestibility of DM, OM, neutral detergent fiber ( N D F ) and acid detergent fiber (ADF) in goats. The two experiments reported here consisted of digestion trials using lambs to test the effectiveness of treating sorghum straw with WA, NaOH and animal urine to improve digestibility. MATERIALS AND METHODS
Wood ash was collected from barbecue restaurants in the City of Monterrey, N.L., Mexico. All impurities and incompletely burned pieces of wood were removed by hand. Sorghum straw was taken from sorghum grain fields at the Experimental Station of Facultad de Agronomia, Universidad Aut6noma de Nuevo Le6n, Marin, N.L., Mexico. The straw was hand-harvested after mechanical removal of grain. Sorghum straw (Asgrow-Topaz) harvested in the summer of 1987 and 1988 was used in Experiments I and II, respectively. It was dried in the shade for approximately 60 days. Before treatment, straw was ground in a hammer mill to pass through a 5 cm screen. Solutions of WA consisted of the supernatant fluid when the concentration of ash exceeded solubility (Nolte et al., 1987). Wood ash solutions ranging from 10 to 30% concentration were tested for pH value. Concentrations of K, Na, Mg and Ca were determinated by atomic absorption spectrophotometry (Diaz-Romeau and Hunter, 1978 ); phosphorus was determinated by colorimetric procedure (AOAC, 1975). Preparation of solutions with 10, 20 and 30% (w/v) WA was according to
ADDITIVESTO INCREASESTRAW UTILIZATION
85
Nolte et al. (1987). Approximately 350 1 of WA solution was used to soak about 60 kg of ground straw. Sorghum straw was treated with 4 g NaOH/100 g straw Did following procedures by Jackson (1978). Soaking of sorghum straw with alkaline solutions was carried out in a 1000-1 container.
Wood ash trial (I) Twelve ,zrossbred (Rambouillet × Pelibuey) wether lambs ( 30.3 kg BW) were assigned randomly (Three animals per treatment) to 4 diets: control, 10 (10WA), 20 (20WA) and 30% (30WA) WA for a digestion trial. Untreated sorghum straw was mixed by hand with the other ingredients to yield isocaloric and isonitrogenous diets (Table 1 ) that met the maintenance, energy and protein requirements (NRC, 1985) of wether lambs (about 10% CP and 2.0 Mcal/kg DM). Chemical analyses of untreated and treated sorghum straw and complete mixed diets are in Table 2. A 10-day adjustment period, in which lambs were individually fed respective diets, was followed by a seven-day collection pe:riod during which samples of diets and total feces were collected daily, measured and 10% aliquots removed and frozen for further analyses. Lambs were maintained in individual metabolism crates during the two periods. During the adjustment, intake was maintained at about 3% of BW (as fed) and this amount was fed in two equal portions daily (0800 and 1600) for the duration of Experiment I. There were no feed refusals during the collection period. Feces were dried at 55 °C for 3 d in a forced-air oven. Dried feces and feed samples were ground to pass through a 2 m m screen in a Willey mill and analysed tbr DM, ash, CP (AOAC, 1975 ) ADF, N D F and acid detergent lignin (ADI_,) (Goering and Van Soest, 1970 ). Apparent digestion coefficients for DM, OM, CP, ADF and N D F were calculated. In vitro OM digestibility (IVOMD) was determined (Table 2 ) on untreated and treated sorghum straw and on the complete mixed diets, as described by Tilley and Terry (1963). Data were,' analysed as a completely randomized design. Treatment response was evaluated using orthogonal polynomials (Steel and Torrie, 1980). Alkali, i'~rea and urine trial (II) Eighteen crossbred (Rambouillet × Pelibuey) wether lambs (28.7 kg BW ) were assigned to a completely randomized design with 6 treatments and 3 animals per treatment in a conventional digestion trial. Lambs were fed twice daily (08,00 and 1600) diets containing sorghum straw untreated (control) or treated with 20WA, 4NaOH, 20WA plus urea, 20WA plus urine or urine only (Table 1 ). Sorghum straw in the 20WA plus urea diet was treated with a 20% solulion of WA mixed with 1.2 kg of urea to provide approximately 7.0% CP in the straw. Sorghum straw in the 20WA plus urine diet was first soaked for 6 hr in a 20% solution (w/v) of WA, drained, dried outdoors for approximately 3 d and then sprayed with sheep urine (106 1 per 60 kg straw) col-
~Vitamins and minerals were not included. 2Wood ash. 3Treated with 4 g NaOH / 100 g straw DM. 4Wood ash plus urea. 5Wood ash plus urine.
Sorghum straw without treatment 10% wood ash-treated sorghum straw 20% wood ash-treated sorghum straw 30% wood ash-treated sorghum straw 4% NaOH-treated sorghum straw 20% wood ash plus urea-treated sorghum straw 20% wood ashes plus urine-treated sorghum straw Urine-treated sorghum straw Soybean meal, 44% Molasses Sorghum grain, ground Urea
Ingredients t
Composition of diets in Experiments I and II
TABLE 1
8 5 1 1
85
Control
8 5 1 1
1 1
85
20WA
8 5
85
10WA 2
Treatment diets (% as fed)
1 1
8 5
85
30WA
1 1
8 5
85
4NaOH 3
2
8 5
85
20WAU 4
2
8 5
85
20WAUR 5
85 8 5 2
Urine
r"
N ,..]
OO
87
ADDITIVES TO INCREASE STRAW UTILIZATION
TABLE 2 Chemical composition (%), in vitro digestibility (%) and macro mineral content (g/kg) of sorghum straw and complete mixed diets in Experiment I Item ~
OM CP ADF NDF IVOMD K Na Mg Ca P
Sorghum straw
Diets
Control
10WA2
20WA
30WA
Control
10WA
20WA
30WA
98.4 4.7 46.9 83.9 442.1 16.4 1.9 3.8 3.0 0.2
97.5 4.3 47.9 84.2 341.5 15.7 2.7 3.0 4.2 0.2
98.1 3.4 43.9 75.2 59.2 75.2 20.0 5.0 14.2 0.2
97.8 3.6 43.3 68.7 65.4 184.2 46.8 6.8 23.3 0.2
92.7 10.3 40.6 51.5 57.1 10.4 2.0 1.0 2.9 0.3
92.1 10.0 442.5 553.3 55.9 13.8 2.8 0.8 7.9 0.3
91.0 9.8 43.7 53.1 61.7 34.0 4.9 3.0 10.7 0.2
90.9 9.9 43.5 51.7 56.0 35.2 9.4 4.7 22.3 0.3
t Dry matter basis. 2WA = Wood ash. OM = Organic matter; CP = crude protein; ADF = acid detergent fiber; N D F = neutral detergent fiber; IVOMD = in vitro organic matter digestibility. TABLE3 Chemical composition (%) of sorghum straw and diets in Experiment II Item ~
OM
Sorghum straw Control 20WA 4NaOH 20WA+urea 20WA+ urine Urine
88.6 89.6 90.0 81.7 78.8 78.8
Diets Control 20WA 4NaOH 20WA + urea 20WA+ urine Urine
84.7 89.6 90.6 84.8 80.3 84.8
CP
ADF
NDF
5.1 4.7 4.5 4.8 6.7 9.8
42.3 45.9 49.2 50.5 48.1 46.6
70.1 66.0 76.6 73.2 61.3 61.5
9.8 10.8 11.7 8.1 12.4 11.6
41.3 40.6 42.0 44.1 39.7 42.4
63.3 63.8 62.7 61.7 52.2 50.3
t Dry matter basis.
lected in Experiment I. Untreated ground sorghum straw used in the urineonly diet was sprayed with sheep urine ( 106 1 per 60 kg straw) secured from the previous trial; approximately 3 d were required to obtain the necessary amount of urine, which was sprayed on the straw twice daily immediately
88
R.G. RAMIREZ ET AL.
after collection. To prevent the loss of NH3, the sorghum straw treated with urine was covered with black plastic for 15 d. After the 15-d period, the straw was uncovered and then dried in the shade for 4 d, before being mixed with the other dietary ingredients (Table 1 ). Chemical analyses of sorghum straw and diets are in Table 3. Adjustment and collection periods, details of collection and chemical analyses of fecal and diet samples were conducted as in Experiment I. Means were separated using the least significant difference, when significant F tests were observed (Steel and Torrie, 1980). RESULTS AND DISCUSSION
Mineral analyses of wood ash used in both experiments showed the following composition (g/kg); P, 0.5; Ca, 172.7; K, 395.6; Na, 129.8; and Mg, 87.6. The domestic water used to make wood ash solutions had the following mineral composition (g/kg); P, 0.3; Ca, 1.7; K, 7.5; Na 1.5 and Mg, 1.2. Mineral concentrations of wood ash were different from those fund by Nolte et al. (1987) who reported lower values for K, Na and Mg, and greater values for Ca and P. Differences in mineral concentrations of WA might be related to wood source. In the present study, WA was obtained from mesquite wood charcoal. Mineral composition of WA is highly variable. Ellis (1962) reported that mineral content is mainly influenced by tree species, geographic location, season, and anatomical region where wood is obtained from the tree. Solutions with 10, 20 and 30% concentration (w/v) of WA in domestic water had pH values of 10.6, 11.2 and 11.3, respectively. Nitrogen in sheep urine, collected in Experiment I, used to spray sorghum straw, ranged from 0.5 to 0.8% and urine pH values were around 7.0.
Wood ash trial (I) No differences ( P > 0.05 ) between treatments were found in BW and intake of DM, OM, CP, ADF and N D F by the lambs fed diets containing sorghum straw treated with WA (Table 4). Dry matter digestibility was affected quadratically ( P < 0.05 ) by WA treatment from 49.6% for lambs fed the 30WA diet to 60.0% for the 20WA diet. OM and CP digestibilities did not differ ( P > 0.05 ) from controls; ADF digestibility was affected quadratically ( P < 0.05 ) by WA treatment ranging from 45.8% for controls to 49.1% for the 20WA diet. Digestibility of NDF was affected quadratically (P<0.05) by WA treatment from 51.5% for controls to 63.1% for lambs fed the 20WA diet. The quadratic responses in nutrient digestibilities suggest that the best treatment occurred with a 20% WA (w/v) solution, which implies that optimum solubility of cations occurs at 20% concentration of WA. Further, Cruz and Ramirez (1989) found that corn stover treated with 20% WA (w/v) solution also increased fiber digestibility for sheep to a degree comparable to that observed in our study. However, Nolte et al. (1987) determined that a 30%
ADDITIVESTO I[NCREASESTRAWUTILIZATION
89
TABLE4 Body weight, t~ed intake and digestibility in Iambs fed diets containing sorghum straw treated with wood ash in Experiment I Item Body weight 3 (kg) Intake (collecl:ion period) DM (g/d) OM (g/d) CP (g/d) ADF (g/d) NDF (g/d) Digestibility (%) DM OM CP ADF NDF
Control
10WA
20WA
30WA
SE l
26.3
31.9
32.4
30.7
2.2
856.2 794.0 87.8 347.4 561.4
871.5 803.0 87.0 370.3 579.5
873.5 795.3 85.5 381.4 578.5
849.9 772.2 83.9 368.4 540.1
3.2 3.0 0.3 1.7 2.1
53.0 54.0 61.6 45.8 51.5
52.4 54.3 40.4 47.2 53.3
60.0 61.1 64.2 49.1 63.1
49.6 52.0 57.0 47.2 51.7
1.3 1.3 1.6 2.1 1.6
Contrast 2
Quadratic (P<0.01)
Quadratic (P< 0.05) Quadratic (P<0.01)
~SE = Standard Error, n = 3. 2Orthogonal polynomials. 3Weight of larabs at the beginning of collection period (mean 30.3 kg). D M = D r y n~atter; OM=Organic matter; C P = C r u d e protein; A D F = A c i d detergent fiber; NDF = Neutral detergent fiber.
solution (w/v) of WA was the optimum treatment for increasing utilization of fiber from wheat straw by goats. IVOMD of straw was increased by WA treatment ranging from 55.9% for the 10WA diet to 61.7% for the 20WA diet (Table 2). Alkali, urea and urine trial (II) No differences were found ( P > 0.05 ) in DM, OM, ADF and NDF intake of lambs fled the sorghum straw diets after alkaline treatment (Table 5 ). On the other hand, lambs fed 4NaOH, 20WA plus urine and urine-only diets consumed greater ( P < 0 . 0 5 ) amounts of CP. Lower ( P < 0 . 0 5 ) CP consumption was observed in lambs fed the 20WA and 20WA plus urea. DM digestibilities in lambs fed the 20WA, 20WA plus urea and urine diets were similar ( P > 0.05 ), but were greater ( P < 0.05 ) than the controls, 4NaOH or 20WA plus urine diets. Lambs fed the 20WA, 20WA plus urea and urine diets digested more ( P < 0.05 ) OM than the controls, 4NaOH and 20 WA plus urine. CP digestibilities were not different ( P > 0.05) among controls, 20WA or 4NaOH, but were greater ( P < 0.05) than 20WA plus urea and urine-only diets, which were also greater ( P < 0.05 ) than the 20WA plus urine. ADF digestibilities were not different ( P > 0.05 ) for 20WA, 4NaOH, 20WA plus urea or urine-only diets, but were greater than controls and 20WA plus urine. Lambs fed the 20WA, 3NaOH or 20WA plus urea diets digested similar ( P > 0.05 )
90
R.G. RAMIREZ ET AL.
TABLE 5 Body weight, intake and digestibility in lambs fed diets containing sorghum straw treated with alkaline solutions in Experiment II Item
Body weight 2 (kg) Intake (collection period) DM ( g / d ) OM ( g / d ) CP ( g / d ) ADF (g/d) NDF (g/d) Digestibility (%) DM OM CP ADF NDF
Treatment diets
SE
Control
20WA
4NaOH
20WAU
27.3
25.2
35.4
29.0
29.0
26.4
721.3 630.1 81.3 b~ 300.1 506.4
668.4 583.5 72.0 ~ 300.0 468.2
957.0 866.6 112.0 a 498.9 755.8
819.1 694.9 66.6 ~ 361.7 505.1
816.5 655.4 101.3 "b 346.3 426.4
735.1 583.8 85.8 a~ 291.5 370.0
97.4 83.6 8.9 42.4 58.0
47.7 d 47.8 c 39.2 c 43.8 ~ 51.2 d
58.5 "b 57.4 ab 48.6 b 52.4 "b 60.5 b
2.2 2.4 2.2 2.1 1.9
51.7 ~d 52.0 ~ 66.6 ~ 48.6 b~ 55.2 cd
56.9 a~ 61.4 a 65.0 a 56.7 ~ 63.1 "b
50.2 cd 53.8 ~ 65.6" 56.3 a 62.2 "b
62.1 a 64.3 a 51.7 b 61.3 ~b 66.5 a
20WAUR
Urine 3.6
tSE = Standard Error, n = 3; 2Weight at beginning of collection period (mean 28.7 kg). abCdMeans in a row with different superscripts differ ( P < 0.05 ).
amounts of NDF. Lambs fed the urine-only diet digested similar ( P > 0.05 ) amounts of N D F to 20WA or 4NaOH, but greater ( P < 0.05 ) amounts than controls or 20WA plus urine diets. The results suggest that treatment of sorghum straw with a 20% solution (w/v) of WA increased digestibility comparable to the increase promoted by sorghum straw treated with 4% NaOH. Extensive studies have evaluated NaOH as a chemical treatment resulting in improved digestibility and animal performance when treated straw is compared with non-treated straw (Trung and Devendra, 1987). Males (1987) reported improvement in feed intake and increased DM digestibility in vivo caused by NaOH-treated straw, associated with a decrease in ruminal retention time. Sodium hydroxide also increased solubilization of cellulose (Males, 1987 ). Fiber digestion by lambs increased in diets containing sorghum straw treated with 20% WA plus urea solutions and diets containing sorghum straw treated with urine. The increases were comparable to those observed in lambs fed 4NaOH diets. Urea plus NaOH solutions have been used with success as a treatment to upgrade straws for feeding goats (Owen et al., 1987). Urine treatment has not been evaluated extensively as a treatment of straw to improve fiber digestion. However, Saadullah et al. (1980) reported that when rice straw was treated with cattle urine, CP content was improved from 3.3 to
ADDITIVES TO INCREASE STRAW UTILIZATION
91
5.6%. Moreover, sheep N balance for 24 h was improved from - 2 . 9 to - 1.2 and, DM, OM and CP apparent digestibilities and feed intake also improved. In this study, urine treatment of sorghum straw may have increased lignin solubility or decreased the strength of bonds between lignin and polysaccharides, resulting in better fiber utilization by lambs. However, N from urine had low availability resulting in low CP digestibility in lambs fed the 20WA plus urine and urine-only diets (Table 5). Urea in urine would be converted to rumen ammonia, hence the low CP digestibility of urine-treated sorghum straw is not clear. CONCLUSION
Wood ash and animal urine are readily available low-cost products that can be used to improve fiber digestibility of straw in a manner comparable to NaOH treatment. Therefore, sorghum straw treated with a 20% solution of WA, 20% WA plus urea or with urine could economically supply a major proportion of the energy and protein needs of wintering ruminants. ACKNOWLEDGEMENTS
We thank the director of The Facultad de Agronomia, Universidad Aut6noma de Nuevo Le6n for supporting the publication of this manuscript. Financial support was provided by the Consejo Nacional de Ciencia y Tecnologia and Centro de Investigaciones de la Facultad de Agronomia, U.A.N.L.; both are gratefully acknowledged.
REFERENCES AOAC, 1975. Official Methods of Analysis, ( 13th. Edn. ) Assoc. Official Anal. Chemists, Washington, D.C. Cruz, F. anti Ramirez, R.G., 1989. Efecto en la digestion de borregos consumiendo raciones conteniendo rastrojo de maiz tratado con cenizas de madera (Effect on digestion of sheep fed diets containing corn stover treated with wood ashes). Proc. Segundo Congrso Nacional de producci6n Ovina, San Luis Potosi, S.L.P., M6xico, pp. 65-67. Diaz-Romeau, R. and Hunter, A, 1978. Metodologia del muestreo de suelos y tejido vegetal y de investigaciones en invernadero (Methodology of sampling soil and crop tissues in greenhouse re.,~earch (CATIE (MIMEO). P. 68. Turrialba, Costa Rica. Ellis, E.L., 1962. Inorganic constituents of wood. For. Prod. J., 12: 271-276. Goering, H. K. and Van Soest, P.J., 1970. Forage fiber analysis (Apparatus, reagents, procedures and some applications). USDA/ARS. Handbook No. 379., Washington, D.C. Jackson, MG., 1978. Treating straw for animal feeding: An Assessment of its technical and economical feasibility. FAO, Rome 10, p. 2. Males, J.R., 1987. Optimizing the utilization of cereal crop residues for beef cattle, J. Anim. Sci., 65:1124-1130.
92
R.G. RAMIREZ ET AL.
NRC, 1985. Nutrient Requirements of Sheep. National Academy Press, 6th Edn. Washington, D.C., pp. 42-49. Nolte, M.E., Cline, J.H., Dehority, B.A., Loerch, S.C. and Parker, C.F., 1987. Treatment of wheat straw with alkaline solutions prepared from wood ashes to improve fiber utilization by ruminants. J. Anim. Sci., 64: 669-677. Owen, E., Wahed, R.A., Alimon, R. and E1Naim, W., 1987. Strategies for feeding straw to small ruminants, upgrading or generous feeding to allow selective feeding. African Research Network for Agricultural By-products (ARNAB). Workshop Bamenda, Cameroon, pp. 60-70. Saadullah, M., Hanke, M. and Dolberg, F., 1980. Treatment of rice straw with animal urine. Trop. Anim. Prod., 5: 273-277. Steel, R.G.D. and Torrie, R.A., 1980. Principles and Procedures of Statistics. McGraw-Hill, New York. Tilley, J.M.A. and Terry, R.A., 1963. A two-stage technique for the in-vitro digestion of forage crops. J. Br. Grassl. Soc., 18:104-111. Trung, L.T. and Devendra, C., 1987. Options for increasing the utilization of cereal straws. Proc. IV Int. Conf. on Goats. Brazilia, Brazil, March 1987, pp. 1161-1183. RESUMEN Ramirez, R.G., Garza, J., Martinez, J. and Ayala, N., 1991. Wood ashes, sodium hydroxide and urine to increase sorghum straw utilization by sheep. SmallRumin. Res., 5: 83-92. En el experimento I, 12 borregos (30.3 kg) fu6ron alimentados con 4 dietas conteniendo 85% paja de sorgo, tratado con 0, 10, 20 y 30% soluciones ( p / v ) de cenizas de madera (CM). La digestibilidad de la materia seca fue afectada cuadr~ticamente ( P < 0.01 ) por el tratamiento de CM. Las digestibilidades de la materia org~inica (MO) y proteina cruda (PC) no fueron diferentes ( P > 0.05) entre tratamientos. Sin embargo, la digestibilidad de la fibra detergemte ~cido (FDA) fue afectada cuadr~iticamente (P<0.05), debido al tratamiento con CM. Adem~s, la digestibilidad de la fibra detergente neutro ( F D N ) fue afectada cuadr~ticamente ( P < 0.05). En el Experimento II, 18 borregos (28.7 kg) fu6ron alimentados con dietas conteniendo 85% paja de sorgo no tratada, tratada con 20% soluciones (p/v) de CM, 4 g NaOH/100 g paja, 20% soluciones (p/v) de CM m~is urea, 20% soluciones (p/v) de CM m~s orina y solamente orina. Los borregos que consumi6ron dietas conteniendo paja tratada con 20% soluciones de CM, 20% soluciones de CM m~is urea y solo orina digiri6ron mayor ( P < 0.05) cantidad de MS y MO, comparados con la de los borregos alimentados con paja sin tratar, 6 4% NaOH 6 20% soluciones de CM m~s orina. La digestibilidad de la PC on fu6 diferente ( P > 0.05 ) entre borregos alimentados con paja sin tratar y tratada con 20% soluciones de CM 4% NaOH, pero fu6ron m~s altos ( P < 0.05) que los borregos alimentados con otras dietas. Los borregos alimentados con paja tratada con 20% soluciones de CM, 4% NaOH, 20% soluciones de CM m~is urea y orina, digiri6ron mayores ( P < 0.05) cantidades de FDA comparados con las de los borregos alimentados con las otras dietas. E1 mismo patr6n de comportamiento fu6 observado para la digestibilidad de la FDN. Los resultados de este estudio sugieren que el tratamiento de la paja de sorgo tratada con soluciones al 20% (p/v) de CM, 20% CM m~s urea y con orina pueden incrementar la utilizaci6n de la fibra por los borregos en una manera comparable al tratamiento con NaOH.
83
Wood ash, sodium hydroxide and urine to increase sorghum straw utilization by sheep R.G. Ramirez ~, J. Garza, J. Martinez and N. Ayala Facultad de Agronomia, Universidad Aut6noma de Nuevo Le6n, San Nicol6s de los Garza, N.L. M~xico (Accepted 6 June 1990)
ABSTRACT Ramirez, R.G., Garza, J., Martinez, J. and Ayala, N., 1991. Wood ash, sodium hydroxide and urine to increase sorghum straw utilization by sheep. Small Rumin. Res., 5: 83-92. In experiment 1, 12 lambs (30.3 Kg BW) were fed 4 diets containing 85% sorghum straw treated with 0% wood ash (WA) solution (w/v) (0WA), 10% (10WA), 20% (20WA) and 30% (30WA). Dry matter (DM) digestibility was affected quadratically (P < 0.01 ) by WA treatment, from 49.6% to 60.0% for ilambs fed the 30WA and 20WA diets. Organic matter (OM) and crude protein (CP) digestibilities did not differ (P> 0.05) among diets. Acid detergent fiber (ADF) digestibility was affected quadratically (P< 0.05) from 45.8% to 49.1% for controls vs. 20WA diets, respectively. Neutral detergent fiber (NDF) digestibility changed (P<0.01) from 51.5% to 63.1% for controls vs. 20 WA diets, reslpectively.In experiment II, 18 whether lambs (28.7 Kg BW) were fed 6 diets containing untreated (control) sorghum straw or treated with 20% solutions (w/v) ofWA (20WA), or with 4 g NaOH/100 g straw DM (4NaOH), or 20WA plus urea, or 20WA plus urine, or urine only. Lambs digested greal~er (P < 0.05 ) amounts of DM and OM, respectively when fed diets containingsorghum straw with 20WA (56.9%, 61.4%), 20WA plus urea (62.1%, 64.3%), and urine (58.5%, 57.4%) compared with untreated diets (51.7%, 52.0%), 4NaOH (50.2%, 53.8%) and 20WA plus urine (47.7%, 47.8%), respectively. Lambs digested greater (P< 0.05%) amounts of ADF and NDF, respectively, when fed sor:ghum straw treated with 20WA (56.7%, 63.1%), 4NaOH (56.3%, 62.2%), 20WA plus urea (61.3%, 66.5%), and urine only (52.4%, 60.5%) compared with controls (48.6%, 55.2%) and 20WA plus urine (43.8%, 51.2%), respectively. Results of this study suggest that treatment of sorghum straw with 20% WA solutions or with animal urine can increase fiber utilization by lambs in amounts comparable to the increase observed with NaOH treatment.
INTRODUCTION
Sorghum straw is a lignocellulosic crop residue produced in considerable amounts in the sorghum grain-producing region of northeastern Mexico. In some are~Ls, sorghum straw surplus is ploughed back into the soil. However, in areas where feed for animal production is limited, most producers use ~Correspondence Address: Apartado Postal 142, Sucursal F, Cd. Universitaria, San NicolAs de los Garza, N.L. 66450, M6xico.
0921-4488/91/$03.50
© 1991 - - Elsevier Science Publishers B.V.
84
R.G. RAMIREZ ET AL.
sorghum straw as animal feed. The low digestibility and nutritive value of sorghum straw limits animal intake and cannot support growth of adult ruminants, without adequate supplementation (Males, 1987). Several methods can enhance feed value of straw by biological, physical or chemical treatments, or their combinations. Chemical treatments increase lignin solubility, reduce cell wall volume and increase cell content digestibility. The most common alkalis used are NaOH, Ca (OH)2 and urea-ammonia (Trung and Devendra, 1987). Sodium hydroxide treatment of straw results in greater digestibility and animal performance than ammonia (NH3) treatment. However, NH3-treated straw has the advantage of added nitrogen (N) which reduces the need for supplemental N (Males, 1987 ). All chemical processes are technologically possible, but many are not economically feasible (Trung and Devendra, 1987 ). One economical alkaline resource is cattle urine, which has been used as an effective source of urea-derived NH3 for straw treatment. Saadullah et al. ( 1980 ) reported that rice straw treated with urine in 1 : 1 ratio improved sheep N-balance and digestibilities of dry matter (DM), organic matter (OM) and crude fiber (CF) compared with untreated rice straw. Another economical alkaline source is wood ash (WA). Nolte et al. ( 1987 ) found that treatment of wheat straw with 30% solution of WA for 6 h increased digestibility of DM, OM, neutral detergent fiber ( N D F ) and acid detergent fiber (ADF) in goats. The two experiments reported here consisted of digestion trials using lambs to test the effectiveness of treating sorghum straw with WA, NaOH and animal urine to improve digestibility. MATERIALS AND METHODS
Wood ash was collected from barbecue restaurants in the City of Monterrey, N.L., Mexico. All impurities and incompletely burned pieces of wood were removed by hand. Sorghum straw was taken from sorghum grain fields at the Experimental Station of Facultad de Agronomia, Universidad Aut6noma de Nuevo Le6n, Marin, N.L., Mexico. The straw was hand-harvested after mechanical removal of grain. Sorghum straw (Asgrow-Topaz) harvested in the summer of 1987 and 1988 was used in Experiments I and II, respectively. It was dried in the shade for approximately 60 days. Before treatment, straw was ground in a hammer mill to pass through a 5 cm screen. Solutions of WA consisted of the supernatant fluid when the concentration of ash exceeded solubility (Nolte et al., 1987). Wood ash solutions ranging from 10 to 30% concentration were tested for pH value. Concentrations of K, Na, Mg and Ca were determinated by atomic absorption spectrophotometry (Diaz-Romeau and Hunter, 1978 ); phosphorus was determinated by colorimetric procedure (AOAC, 1975). Preparation of solutions with 10, 20 and 30% (w/v) WA was according to
ADDITIVESTO INCREASESTRAW UTILIZATION
85
Nolte et al. (1987). Approximately 350 1 of WA solution was used to soak about 60 kg of ground straw. Sorghum straw was treated with 4 g NaOH/100 g straw Did following procedures by Jackson (1978). Soaking of sorghum straw with alkaline solutions was carried out in a 1000-1 container.
Wood ash trial (I) Twelve ,zrossbred (Rambouillet × Pelibuey) wether lambs ( 30.3 kg BW) were assigned randomly (Three animals per treatment) to 4 diets: control, 10 (10WA), 20 (20WA) and 30% (30WA) WA for a digestion trial. Untreated sorghum straw was mixed by hand with the other ingredients to yield isocaloric and isonitrogenous diets (Table 1 ) that met the maintenance, energy and protein requirements (NRC, 1985) of wether lambs (about 10% CP and 2.0 Mcal/kg DM). Chemical analyses of untreated and treated sorghum straw and complete mixed diets are in Table 2. A 10-day adjustment period, in which lambs were individually fed respective diets, was followed by a seven-day collection pe:riod during which samples of diets and total feces were collected daily, measured and 10% aliquots removed and frozen for further analyses. Lambs were maintained in individual metabolism crates during the two periods. During the adjustment, intake was maintained at about 3% of BW (as fed) and this amount was fed in two equal portions daily (0800 and 1600) for the duration of Experiment I. There were no feed refusals during the collection period. Feces were dried at 55 °C for 3 d in a forced-air oven. Dried feces and feed samples were ground to pass through a 2 m m screen in a Willey mill and analysed tbr DM, ash, CP (AOAC, 1975 ) ADF, N D F and acid detergent lignin (ADI_,) (Goering and Van Soest, 1970 ). Apparent digestion coefficients for DM, OM, CP, ADF and N D F were calculated. In vitro OM digestibility (IVOMD) was determined (Table 2 ) on untreated and treated sorghum straw and on the complete mixed diets, as described by Tilley and Terry (1963). Data were,' analysed as a completely randomized design. Treatment response was evaluated using orthogonal polynomials (Steel and Torrie, 1980). Alkali, i'~rea and urine trial (II) Eighteen crossbred (Rambouillet × Pelibuey) wether lambs (28.7 kg BW ) were assigned to a completely randomized design with 6 treatments and 3 animals per treatment in a conventional digestion trial. Lambs were fed twice daily (08,00 and 1600) diets containing sorghum straw untreated (control) or treated with 20WA, 4NaOH, 20WA plus urea, 20WA plus urine or urine only (Table 1 ). Sorghum straw in the 20WA plus urea diet was treated with a 20% solulion of WA mixed with 1.2 kg of urea to provide approximately 7.0% CP in the straw. Sorghum straw in the 20WA plus urine diet was first soaked for 6 hr in a 20% solution (w/v) of WA, drained, dried outdoors for approximately 3 d and then sprayed with sheep urine (106 1 per 60 kg straw) col-
~Vitamins and minerals were not included. 2Wood ash. 3Treated with 4 g NaOH / 100 g straw DM. 4Wood ash plus urea. 5Wood ash plus urine.
Sorghum straw without treatment 10% wood ash-treated sorghum straw 20% wood ash-treated sorghum straw 30% wood ash-treated sorghum straw 4% NaOH-treated sorghum straw 20% wood ash plus urea-treated sorghum straw 20% wood ashes plus urine-treated sorghum straw Urine-treated sorghum straw Soybean meal, 44% Molasses Sorghum grain, ground Urea
Ingredients t
Composition of diets in Experiments I and II
TABLE 1
8 5 1 1
85
Control
8 5 1 1
1 1
85
20WA
8 5
85
10WA 2
Treatment diets (% as fed)
1 1
8 5
85
30WA
1 1
8 5
85
4NaOH 3
2
8 5
85
20WAU 4
2
8 5
85
20WAUR 5
85 8 5 2
Urine
r"
N ,..]
OO
87
ADDITIVES TO INCREASE STRAW UTILIZATION
TABLE 2 Chemical composition (%), in vitro digestibility (%) and macro mineral content (g/kg) of sorghum straw and complete mixed diets in Experiment I Item ~
OM CP ADF NDF IVOMD K Na Mg Ca P
Sorghum straw
Diets
Control
10WA2
20WA
30WA
Control
10WA
20WA
30WA
98.4 4.7 46.9 83.9 442.1 16.4 1.9 3.8 3.0 0.2
97.5 4.3 47.9 84.2 341.5 15.7 2.7 3.0 4.2 0.2
98.1 3.4 43.9 75.2 59.2 75.2 20.0 5.0 14.2 0.2
97.8 3.6 43.3 68.7 65.4 184.2 46.8 6.8 23.3 0.2
92.7 10.3 40.6 51.5 57.1 10.4 2.0 1.0 2.9 0.3
92.1 10.0 442.5 553.3 55.9 13.8 2.8 0.8 7.9 0.3
91.0 9.8 43.7 53.1 61.7 34.0 4.9 3.0 10.7 0.2
90.9 9.9 43.5 51.7 56.0 35.2 9.4 4.7 22.3 0.3
t Dry matter basis. 2WA = Wood ash. OM = Organic matter; CP = crude protein; ADF = acid detergent fiber; N D F = neutral detergent fiber; IVOMD = in vitro organic matter digestibility. TABLE3 Chemical composition (%) of sorghum straw and diets in Experiment II Item ~
OM
Sorghum straw Control 20WA 4NaOH 20WA+urea 20WA+ urine Urine
88.6 89.6 90.0 81.7 78.8 78.8
Diets Control 20WA 4NaOH 20WA + urea 20WA+ urine Urine
84.7 89.6 90.6 84.8 80.3 84.8
CP
ADF
NDF
5.1 4.7 4.5 4.8 6.7 9.8
42.3 45.9 49.2 50.5 48.1 46.6
70.1 66.0 76.6 73.2 61.3 61.5
9.8 10.8 11.7 8.1 12.4 11.6
41.3 40.6 42.0 44.1 39.7 42.4
63.3 63.8 62.7 61.7 52.2 50.3
t Dry matter basis.
lected in Experiment I. Untreated ground sorghum straw used in the urineonly diet was sprayed with sheep urine ( 106 1 per 60 kg straw) secured from the previous trial; approximately 3 d were required to obtain the necessary amount of urine, which was sprayed on the straw twice daily immediately
88
R.G. RAMIREZ ET AL.
after collection. To prevent the loss of NH3, the sorghum straw treated with urine was covered with black plastic for 15 d. After the 15-d period, the straw was uncovered and then dried in the shade for 4 d, before being mixed with the other dietary ingredients (Table 1 ). Chemical analyses of sorghum straw and diets are in Table 3. Adjustment and collection periods, details of collection and chemical analyses of fecal and diet samples were conducted as in Experiment I. Means were separated using the least significant difference, when significant F tests were observed (Steel and Torrie, 1980). RESULTS AND DISCUSSION
Mineral analyses of wood ash used in both experiments showed the following composition (g/kg); P, 0.5; Ca, 172.7; K, 395.6; Na, 129.8; and Mg, 87.6. The domestic water used to make wood ash solutions had the following mineral composition (g/kg); P, 0.3; Ca, 1.7; K, 7.5; Na 1.5 and Mg, 1.2. Mineral concentrations of wood ash were different from those fund by Nolte et al. (1987) who reported lower values for K, Na and Mg, and greater values for Ca and P. Differences in mineral concentrations of WA might be related to wood source. In the present study, WA was obtained from mesquite wood charcoal. Mineral composition of WA is highly variable. Ellis (1962) reported that mineral content is mainly influenced by tree species, geographic location, season, and anatomical region where wood is obtained from the tree. Solutions with 10, 20 and 30% concentration (w/v) of WA in domestic water had pH values of 10.6, 11.2 and 11.3, respectively. Nitrogen in sheep urine, collected in Experiment I, used to spray sorghum straw, ranged from 0.5 to 0.8% and urine pH values were around 7.0.
Wood ash trial (I) No differences ( P > 0.05 ) between treatments were found in BW and intake of DM, OM, CP, ADF and N D F by the lambs fed diets containing sorghum straw treated with WA (Table 4). Dry matter digestibility was affected quadratically ( P < 0.05 ) by WA treatment from 49.6% for lambs fed the 30WA diet to 60.0% for the 20WA diet. OM and CP digestibilities did not differ ( P > 0.05 ) from controls; ADF digestibility was affected quadratically ( P < 0.05 ) by WA treatment ranging from 45.8% for controls to 49.1% for the 20WA diet. Digestibility of NDF was affected quadratically (P<0.05) by WA treatment from 51.5% for controls to 63.1% for lambs fed the 20WA diet. The quadratic responses in nutrient digestibilities suggest that the best treatment occurred with a 20% WA (w/v) solution, which implies that optimum solubility of cations occurs at 20% concentration of WA. Further, Cruz and Ramirez (1989) found that corn stover treated with 20% WA (w/v) solution also increased fiber digestibility for sheep to a degree comparable to that observed in our study. However, Nolte et al. (1987) determined that a 30%
ADDITIVESTO I[NCREASESTRAWUTILIZATION
89
TABLE4 Body weight, t~ed intake and digestibility in Iambs fed diets containing sorghum straw treated with wood ash in Experiment I Item Body weight 3 (kg) Intake (collecl:ion period) DM (g/d) OM (g/d) CP (g/d) ADF (g/d) NDF (g/d) Digestibility (%) DM OM CP ADF NDF
Control
10WA
20WA
30WA
SE l
26.3
31.9
32.4
30.7
2.2
856.2 794.0 87.8 347.4 561.4
871.5 803.0 87.0 370.3 579.5
873.5 795.3 85.5 381.4 578.5
849.9 772.2 83.9 368.4 540.1
3.2 3.0 0.3 1.7 2.1
53.0 54.0 61.6 45.8 51.5
52.4 54.3 40.4 47.2 53.3
60.0 61.1 64.2 49.1 63.1
49.6 52.0 57.0 47.2 51.7
1.3 1.3 1.6 2.1 1.6
Contrast 2
Quadratic (P<0.01)
Quadratic (P< 0.05) Quadratic (P<0.01)
~SE = Standard Error, n = 3. 2Orthogonal polynomials. 3Weight of larabs at the beginning of collection period (mean 30.3 kg). D M = D r y n~atter; OM=Organic matter; C P = C r u d e protein; A D F = A c i d detergent fiber; NDF = Neutral detergent fiber.
solution (w/v) of WA was the optimum treatment for increasing utilization of fiber from wheat straw by goats. IVOMD of straw was increased by WA treatment ranging from 55.9% for the 10WA diet to 61.7% for the 20WA diet (Table 2). Alkali, urea and urine trial (II) No differences were found ( P > 0.05 ) in DM, OM, ADF and NDF intake of lambs fled the sorghum straw diets after alkaline treatment (Table 5 ). On the other hand, lambs fed 4NaOH, 20WA plus urine and urine-only diets consumed greater ( P < 0 . 0 5 ) amounts of CP. Lower ( P < 0 . 0 5 ) CP consumption was observed in lambs fed the 20WA and 20WA plus urea. DM digestibilities in lambs fed the 20WA, 20WA plus urea and urine diets were similar ( P > 0.05 ), but were greater ( P < 0.05 ) than the controls, 4NaOH or 20WA plus urine diets. Lambs fed the 20WA, 20WA plus urea and urine diets digested more ( P < 0.05 ) OM than the controls, 4NaOH and 20 WA plus urine. CP digestibilities were not different ( P > 0.05) among controls, 20WA or 4NaOH, but were greater ( P < 0.05) than 20WA plus urea and urine-only diets, which were also greater ( P < 0.05 ) than the 20WA plus urine. ADF digestibilities were not different ( P > 0.05 ) for 20WA, 4NaOH, 20WA plus urea or urine-only diets, but were greater than controls and 20WA plus urine. Lambs fed the 20WA, 3NaOH or 20WA plus urea diets digested similar ( P > 0.05 )
90
R.G. RAMIREZ ET AL.
TABLE 5 Body weight, intake and digestibility in lambs fed diets containing sorghum straw treated with alkaline solutions in Experiment II Item
Body weight 2 (kg) Intake (collection period) DM ( g / d ) OM ( g / d ) CP ( g / d ) ADF (g/d) NDF (g/d) Digestibility (%) DM OM CP ADF NDF
Treatment diets
SE
Control
20WA
4NaOH
20WAU
27.3
25.2
35.4
29.0
29.0
26.4
721.3 630.1 81.3 b~ 300.1 506.4
668.4 583.5 72.0 ~ 300.0 468.2
957.0 866.6 112.0 a 498.9 755.8
819.1 694.9 66.6 ~ 361.7 505.1
816.5 655.4 101.3 "b 346.3 426.4
735.1 583.8 85.8 a~ 291.5 370.0
97.4 83.6 8.9 42.4 58.0
47.7 d 47.8 c 39.2 c 43.8 ~ 51.2 d
58.5 "b 57.4 ab 48.6 b 52.4 "b 60.5 b
2.2 2.4 2.2 2.1 1.9
51.7 ~d 52.0 ~ 66.6 ~ 48.6 b~ 55.2 cd
56.9 a~ 61.4 a 65.0 a 56.7 ~ 63.1 "b
50.2 cd 53.8 ~ 65.6" 56.3 a 62.2 "b
62.1 a 64.3 a 51.7 b 61.3 ~b 66.5 a
20WAUR
Urine 3.6
tSE = Standard Error, n = 3; 2Weight at beginning of collection period (mean 28.7 kg). abCdMeans in a row with different superscripts differ ( P < 0.05 ).
amounts of NDF. Lambs fed the urine-only diet digested similar ( P > 0.05 ) amounts of N D F to 20WA or 4NaOH, but greater ( P < 0.05 ) amounts than controls or 20WA plus urine diets. The results suggest that treatment of sorghum straw with a 20% solution (w/v) of WA increased digestibility comparable to the increase promoted by sorghum straw treated with 4% NaOH. Extensive studies have evaluated NaOH as a chemical treatment resulting in improved digestibility and animal performance when treated straw is compared with non-treated straw (Trung and Devendra, 1987). Males (1987) reported improvement in feed intake and increased DM digestibility in vivo caused by NaOH-treated straw, associated with a decrease in ruminal retention time. Sodium hydroxide also increased solubilization of cellulose (Males, 1987 ). Fiber digestion by lambs increased in diets containing sorghum straw treated with 20% WA plus urea solutions and diets containing sorghum straw treated with urine. The increases were comparable to those observed in lambs fed 4NaOH diets. Urea plus NaOH solutions have been used with success as a treatment to upgrade straws for feeding goats (Owen et al., 1987). Urine treatment has not been evaluated extensively as a treatment of straw to improve fiber digestion. However, Saadullah et al. (1980) reported that when rice straw was treated with cattle urine, CP content was improved from 3.3 to
ADDITIVES TO INCREASE STRAW UTILIZATION
91
5.6%. Moreover, sheep N balance for 24 h was improved from - 2 . 9 to - 1.2 and, DM, OM and CP apparent digestibilities and feed intake also improved. In this study, urine treatment of sorghum straw may have increased lignin solubility or decreased the strength of bonds between lignin and polysaccharides, resulting in better fiber utilization by lambs. However, N from urine had low availability resulting in low CP digestibility in lambs fed the 20WA plus urine and urine-only diets (Table 5). Urea in urine would be converted to rumen ammonia, hence the low CP digestibility of urine-treated sorghum straw is not clear. CONCLUSION
Wood ash and animal urine are readily available low-cost products that can be used to improve fiber digestibility of straw in a manner comparable to NaOH treatment. Therefore, sorghum straw treated with a 20% solution of WA, 20% WA plus urea or with urine could economically supply a major proportion of the energy and protein needs of wintering ruminants. ACKNOWLEDGEMENTS
We thank the director of The Facultad de Agronomia, Universidad Aut6noma de Nuevo Le6n for supporting the publication of this manuscript. Financial support was provided by the Consejo Nacional de Ciencia y Tecnologia and Centro de Investigaciones de la Facultad de Agronomia, U.A.N.L.; both are gratefully acknowledged.
REFERENCES AOAC, 1975. Official Methods of Analysis, ( 13th. Edn. ) Assoc. Official Anal. Chemists, Washington, D.C. Cruz, F. anti Ramirez, R.G., 1989. Efecto en la digestion de borregos consumiendo raciones conteniendo rastrojo de maiz tratado con cenizas de madera (Effect on digestion of sheep fed diets containing corn stover treated with wood ashes). Proc. Segundo Congrso Nacional de producci6n Ovina, San Luis Potosi, S.L.P., M6xico, pp. 65-67. Diaz-Romeau, R. and Hunter, A, 1978. Metodologia del muestreo de suelos y tejido vegetal y de investigaciones en invernadero (Methodology of sampling soil and crop tissues in greenhouse re.,~earch (CATIE (MIMEO). P. 68. Turrialba, Costa Rica. Ellis, E.L., 1962. Inorganic constituents of wood. For. Prod. J., 12: 271-276. Goering, H. K. and Van Soest, P.J., 1970. Forage fiber analysis (Apparatus, reagents, procedures and some applications). USDA/ARS. Handbook No. 379., Washington, D.C. Jackson, MG., 1978. Treating straw for animal feeding: An Assessment of its technical and economical feasibility. FAO, Rome 10, p. 2. Males, J.R., 1987. Optimizing the utilization of cereal crop residues for beef cattle, J. Anim. Sci., 65:1124-1130.
92
R.G. RAMIREZ ET AL.
NRC, 1985. Nutrient Requirements of Sheep. National Academy Press, 6th Edn. Washington, D.C., pp. 42-49. Nolte, M.E., Cline, J.H., Dehority, B.A., Loerch, S.C. and Parker, C.F., 1987. Treatment of wheat straw with alkaline solutions prepared from wood ashes to improve fiber utilization by ruminants. J. Anim. Sci., 64: 669-677. Owen, E., Wahed, R.A., Alimon, R. and E1Naim, W., 1987. Strategies for feeding straw to small ruminants, upgrading or generous feeding to allow selective feeding. African Research Network for Agricultural By-products (ARNAB). Workshop Bamenda, Cameroon, pp. 60-70. Saadullah, M., Hanke, M. and Dolberg, F., 1980. Treatment of rice straw with animal urine. Trop. Anim. Prod., 5: 273-277. Steel, R.G.D. and Torrie, R.A., 1980. Principles and Procedures of Statistics. McGraw-Hill, New York. Tilley, J.M.A. and Terry, R.A., 1963. A two-stage technique for the in-vitro digestion of forage crops. J. Br. Grassl. Soc., 18:104-111. Trung, L.T. and Devendra, C., 1987. Options for increasing the utilization of cereal straws. Proc. IV Int. Conf. on Goats. Brazilia, Brazil, March 1987, pp. 1161-1183. RESUMEN Ramirez, R.G., Garza, J., Martinez, J. and Ayala, N., 1991. Wood ashes, sodium hydroxide and urine to increase sorghum straw utilization by sheep. SmallRumin. Res., 5: 83-92. En el experimento I, 12 borregos (30.3 kg) fu6ron alimentados con 4 dietas conteniendo 85% paja de sorgo, tratado con 0, 10, 20 y 30% soluciones ( p / v ) de cenizas de madera (CM). La digestibilidad de la materia seca fue afectada cuadr~ticamente ( P < 0.01 ) por el tratamiento de CM. Las digestibilidades de la materia org~inica (MO) y proteina cruda (PC) no fueron diferentes ( P > 0.05) entre tratamientos. Sin embargo, la digestibilidad de la fibra detergemte ~cido (FDA) fue afectada cuadr~iticamente (P<0.05), debido al tratamiento con CM. Adem~s, la digestibilidad de la fibra detergente neutro ( F D N ) fue afectada cuadr~ticamente ( P < 0.05). En el Experimento II, 18 borregos (28.7 kg) fu6ron alimentados con dietas conteniendo 85% paja de sorgo no tratada, tratada con 20% soluciones (p/v) de CM, 4 g NaOH/100 g paja, 20% soluciones (p/v) de CM m~is urea, 20% soluciones (p/v) de CM m~s orina y solamente orina. Los borregos que consumi6ron dietas conteniendo paja tratada con 20% soluciones de CM, 20% soluciones de CM m~is urea y solo orina digiri6ron mayor ( P < 0.05) cantidad de MS y MO, comparados con la de los borregos alimentados con paja sin tratar, 6 4% NaOH 6 20% soluciones de CM m~s orina. La digestibilidad de la PC on fu6 diferente ( P > 0.05 ) entre borregos alimentados con paja sin tratar y tratada con 20% soluciones de CM 4% NaOH, pero fu6ron m~s altos ( P < 0.05) que los borregos alimentados con otras dietas. Los borregos alimentados con paja tratada con 20% soluciones de CM, 4% NaOH, 20% soluciones de CM m~is urea y orina, digiri6ron mayores ( P < 0.05) cantidades de FDA comparados con las de los borregos alimentados con las otras dietas. E1 mismo patr6n de comportamiento fu6 observado para la digestibilidad de la FDN. Los resultados de este estudio sugieren que el tratamiento de la paja de sorgo tratada con soluciones al 20% (p/v) de CM, 20% CM m~s urea y con orina pueden incrementar la utilizaci6n de la fibra por los borregos en una manera comparable al tratamiento con NaOH.