Rumen degradation in sacco in sheep of wheat straw treated with calcium oxide, sodium hydroxide and sodium hydroxide plus hydrogen peroxide

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1 Animal Feed Science and Technology 83 (2000) 313±323 Rumen degradation in sacco in sheep of wheat straw treated with calcium oxide, sodium hydroxide and sodium hydroxide plus hydrogen peroxide A.S. Chaudhry * Department of Agriculture, University of Newcastle, Newcastle-upon-Tyne NE1 7RU, UK Received 7 June 1999; received in revised form 28 September 1999; accepted 22 October 1999 Abstract This split unit study involved two sheep, seven incubation times and four test straws to compare with untreated straw the effect, kg 1 straw dry matter (DM), of CaO (160 g CaO plus 2 l of water), NaOH (80 g NaOH in 3 l of water) and alkaline hydrogen peroxide (NaOH plus 132 g H 2 O 2 in 3 l of water, AHP) treatments on composition and rumen degradation in sacco of wheat straw in sheep. After 14 days of storage, each straw was mixed with molasses, dried, ground, weighed into nylon bags and incubated ruminally for various hours in sheep fed daily 1 kg dried grass cubes. After removal, the residues within bags were washed together with unincubated samples (0 h) of straws, dried and analysed for DM, organic matter (OM) and neutral-detergent bre (NDF) to estimate nutrient disappearance from straws. The data on nutrient disappearance were tted exponentially to estimate quick- (a), slow (b) and predicted (P ) degradable fractions and degradation rate (c) for b. NDF and hemicellulose were reduced in treated compared with untreated straw (p < 0.001). Disappearance of nutrients from treated straws was signi cantly greater than that from untreated straw at almost all incubations (p < 0.001). The a, b, c and P estimates were signi cantly increased by all treatments (p < 0.001). AHP treatment increased straw degradation more than NaOH and CaO treatments. Although, CaO improved rumen degradation less than NaOH, its use to increase straw digestion even moderately may be more desirable because it is readily available, cheap and less dangerous for the users and the environment. # 2000 Published by Elsevier Science B.V. All rights reserved. Keywords: Rumen degradation; Straw; Calcium oxide; Sodium hydroxide; Hydrogen peroxide * Tel.: ; fax: address: a.s.chaudhry@newcastle.ac.uk (A.S. Chaudhry) /00/$ ± see front matter # 2000 Published by Elsevier Science B.V. All rights reserved. PII: S (99)

2 314 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313± Introduction Rumen degradation is critical in the utilization of cereal straws by ruminant animals. However, using straws as an energy feed for ruminants is limited because their cell walls contain three dimensional structures that are less available for microbial degradation in the rumen (Wilkie, 1979; Sundstol and Owen, 1984; Chaudhry, 1998a). Consequently, major nutrients from straws escape digestion and are wasted as faeces by the ruminants. However, the energy value of straws can be increased if their cell wall structure is modi ed. Chemical treatments can modify cell wall to increase microbial degradation and thus utilization of straws by ruminants (Jung et al., 1993). Recently, Chaudhry (1997) following reports from Gould (1984) and Kerley et al. (1986) con rmed the effectiveness of alkaline hydrogen peroxide (NaOH H 2 O 2, AHP) to modify cell wall composition and in vitro dry matter digestibility (DMD) of wheat straw. However, the need for a high amount (13 or 26 l kg 1 DM) of water and NaOH to maintain the ph of AHP around 11.5 was considered a limitation for the on-farm application of AHP. In another series of in vitro experiments, although the amount of water was reduced, the use of calcium oxide (CaO) as an alternative alkali to maintain the ef cacy of AHP treatment even at a ph of 11.5 did not succeed (Chaudhry, 1998b). In contrast, CaO alone increased the in vitro DMD of wheat straw under speci c conditions. In another study, Chaudhry (1998c) supported the ef cacy of CaO and NaOH alone and AHP in improving composition, nutrient digestion and fermentation of straw-based diets in sheep. The increased digestion was perhaps due to the increased rate and extent of straw degradation by rumen microbes. However, this assumption can only be substantiated if the rumen degradation kinetics were studied. Moreover, as Chaudhry (1998c) fed each straw together with a concentrate to sheep, it was not clear whether the increased digestion was solely a consequence of a chemical treatment or was partly due to its interaction with the concentrate. Since rumen is the primary site of digestion for brous feeds in ruminants, it is important to monitor degradation kinetics in response to modi cation of cell wall caused by alkali treatments. This may be achieved by using in sacco technique which is quicker and cheaper than whole animal studies. Therefore, this study examined the effect of CaO, NaOH and AHP on the rate and extent of degradation in sacco of wheat straw in sheep. Treatment with CaO was tested as a cheap and a safe alternative to NaOH in improving the rate and extent of straw degradation whereas NaOH also served as a control for AHP. 2. Materials and methods 2.1. Chemicals, straw and treatments NaOH (32% w/w, speci c gravity 1.35) and H 2 O 2 (27.5% w/w, speci c gravity 1.1) as solutions and CaO as a ne powder were purchased from, respectively, Ellis and Everrard, and BDH, UK and used to treat wheat straw variety Norman (straw, chopped through an 8 mm sieve) as described by Chaudhry (1998c). Each treatment was applied on kg 1 straw DM basis as described below:

3 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313± Control Untreated straw served as a control CaO The straw was mixed with 2 l of water in a mixer, dusted with 160 g CaO and the contents were then re-mixed for ca. 1 h. The treated straw was then placed into a plastic bag, tied up and stored at ca. 128C. The added amount of CaO was 160 g kg 1 straw DM with a liquid : straw ratio of 2 : 1 and an initial ph of > NaOH The straw was mixed with 3 l of solution containing 80 g NaOH for ca. 1 h, placed into a plastic bag and stored as described above. The added amount of NaOH was 80 g kg 1 DM at a liquid : straw ratio of 3 : 1 with an initial ph of >12 during 1 h of mixing. The NaOH-treated straw also served as a control for AHP-treated straw AHP Another batch of NaOH-treated straw was prepared as described in Section After 27 h pre-soaking, 480 ml of H 2 O 2 solution containing 132 g H 2 O 2 were added, mixed for 5 h and stored as described earlier. During mixing, the ph of treated straw was monitored at 30-min intervals and was observed to remain around The amounts of added NaOH and H 2 O 2 were 80 and 132 g kg 1 straw DM, respectively Preparation of straws for rumen incubation After 14-days storage in an open shed (average temperature 128C), each kg DM of each treated and untreated straw was separately mixed with 100 g molasses (Molaferm- 50; United Molasses) in line with that described by Chaudhry (1998c). No other reason for adding molasses into straws is offered. As hot water was added into molasses to facilitate mixing, the molasses DM was reduced from 65 to 55% and hence the added molasses in straw on DM basis was 55 g kg 1. The straws were dried and ground through a 4 mm sieve before in sacco rumen incubations Animals, housing and feeding Two Suffolk Mule wether sheep weighing between 60 and 64 kg were used in this experiment. The sheep were tted with rumen cannulae and housed individually on concrete oors covered with sand. Each sheep was adapted to a xed daily intake of 1 kg dried grass cubes containing 160 g crude protein for 14 days before in sacco degradability was examined Experimental design and chemical analysis A split-unit design involved two sheep (blocks), seven incubation times (main units) and four test straws (sub-units) to study in sacco degradability of untreated and treated

4 316 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313±323 straws. Duplicate samples of ca. 2.5 g DM of each test straw were weighed into separate nylon bags which were then tied up by a plastic string to a 16 cm long exible polypropylene tube and suspended in the rumen of each sheep for 6, 12, 24, 48, 72 and 96 h. Given the limited rumen capacity of sheep, the samples were incubated as groups so that only one group of four straws in duplicate was incubated in the rumen at any given time. Samples of 0 h representing water-soluble fraction (a) were prepared by washing bags, in duplicate, containing test straws for 30 min in a domestic washing machine. After removal from the rumen at each incubation time, the residues within bags were washed, freeze dried, ground through a 1 mm sieve and analysed together with unincubated samples for DM, organic matter (OM) and neutral detergent bre (NDF) (Van Soest et al., 1991). Disappearance of nutrients from each straw was calculated by difference between nutrient composition of the unwashed and unincubated dried sample of that straw and its residue after each incubation time in the rumen. Disappearance was assumed to be due to degradation in the rumen. Samples of unwashed and unincubated straws were also analysed for acid-detergent bre (ADF) and acid-detergent lignin (ADL) to estimate cellulose and hemicellulose contents for each straw by subtracting ADL from ADF and ADF from NDF, respectively Calculations and statistical analysis The data from in sacco studies were tted into the exponential model {p ˆ a b(1 e ct )} of érskov and McDonald (1979) by using the Maximum Likelihood Programme to obtain estimates of a, b and c for each straw in each sheep. Here, a represented water-soluble (or quickly degradable) and b insoluble (or slowlydegradable) fractions whereas c degradation rate of b and t the hours of incubation. While apparent degradability was represented by a b (asymptote), predicted rumen degradability (P ) for each straw was also calculated from an equation, P ˆ a (bc/c k), where k was the rumen out ow rate at per hour (h) for animals fed at a slightly above maintenance level (AFRC, 1993). The estimates of a, b, c, asymptote and P were statistically analysed by using ANOVA in GENSTAT to test the effect of chemical treatments on cell wall composition and the rate and extent of in sacco degradability of straw. 3. Results 3.1. Cell wall composition Table 1 presents mean cell wall composition of untreated and treated straws together with their standard errors of differences (SED). All treatments reduced NDF and hemicellulose contents in straw compared with untreated straw (p < 0.001). However, CaO reduced NDF content more than NaOH and AHP did (p < 0.001). In contrast, cellulose content was increased by all treatments whereas lignin content was increased by NaOH and AHP (p < 0.05) but decreased by CaO (p < 0.05).

5 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313± Table 1 Cell wall composition (g kg 1 OM) of molassed untreated and treated straws Composition Straw treatments a 3.2. Nutrient disappearance Untreated CaO NaOH AHP SED Neutral detergent bre 841 a 676 c 781 b 776 b 16 Cellulose 451 c 528 b 533 b 562 b 13 Hemicellulose 259 a 29 b 67 b 23 b 26 Lignin 104 c 92 d 129 a 115 b 4 a Untreated, CaO, NaOH and AHP were respectively, untreated, CaO-, NaOH- and alkaline hydrogen peroxide (NaOH H 2 O 2, AHP) treated wheat straw. After 14-days storage at 128C, molasses was added to each straw at 55 g molasses DM kg 1 straw DM; neutral detergent bre represented total cell wall; means with different superscripts in a same row were signi cantly different. Figs. 1±3 illustrate the patterns of DM, OM and NDF disappearance from each test straw during rumen incubation for various times together with SED for each incubation Fig. 1. Pattern of disappearance of dry matter (DM) from molassed wheat straw, untreated (Untr) or treated respectively with CaO (CaO), NaOH (NaOH) and NaOH plus H 2 O 2 (AHP) during rumen incubation for various times in sheep. The lines represent data being tted for each test straw according to the exponential model. The standard errors of difference for 0, 6, 12, 24, 48, 72 and 96 h of incubation were 6, 29, 18, 14, 26, 19 and 5, respectively.

6 318 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313±323 Fig. 2. Pattern of disappearance of organic matter (OM) from molassed wheat straw, untreated (Untr) or treated respectively, with CaO (CaO), NaOH (NaOH) and NaOH plus H 2 O 2 (AHP) during rumen incubations for various times in sheep. The lines represent data being tted for each test straw according to the exponential model. The standard errors of difference for 0, 6, 12, 24, 48, 72 and 96 h of incubation were 9, 25, 32, 15, 18, 21 and 16, respectively. time. The disappearance of DM, OM and NDF was signi cantly greater for treated straws than for untreated straw at almost all incubation times (p < 0.001). The incubation at 6 h was an exception where disappearance of NDF from CaO-treated straw was not signi cantly greater than that of untreated straw. However, the loss of NDF from CaOtreated straw on washing with water was less than untreated straw (p < 0.001). In contrast, the losses of DM and OM from treated straws on washing with water (0 h) were greater than that from untreated straw. Signi cant differences between treatments for the disappearance of DM, OM and NDF during each incubation time were also observed (p < 0.001). AHP treatment caused the greatest disappearance of DM, OM and NDF from straws followed by NaOH and CaO. Untreated straw showed increased disappearance of DM, OM and NDF with increasing incubation time to 96 h (p < 0.001). In contrast, the disappearance of nutrients from NaOH and AHP straws almost peaked at 48 h whereas the disappearance from CaO straw continued to increase to 72 h (p < 0.001).

7 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313± Fig. 3. Pattern of disappearance of neutral detergent bre (NDF) from molassed wheat straw, untreated (Untr) or treated, respectively with CaO (CaO), NaOH (NaOH) and NaOH plus H 2 O 2 (AHP) during rumen incubation for various times in sheep. The lines represent data being tted for each test straw according to the exponential model. The standard errors of difference for 0, 6, 12, 24, 48, 72 and 96 h of incubation were 7, 35, 31, 15, 20, 26 and 7, respectively Degradation characteristics Table 2 presents estimates of a, b, a b, c and P for untreated and treated straws Quickly (a) and slowly degradable (b) fractions Quickly- and slowly-degradable fractions for DM, OM and NDF were signi cantly affected by treatments (p < 0.001). Quickly degradable fractions of DM, OM and NDF were greatest for AHP treated straw compared with untreated or other treated straws (p < 0.001). In contrast, the slowly degradable fractions of DM and NDF and OM were greatest respectively for CaO- and NaOH-treated straws. However, the quickly degradable fraction of NDF in untreated straw was greater compared with NaOH- and CaO-treated straws (p < 0.01) but was less in all straws compared with AHP-treated straw (p < 0.01).

8 320 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313±323 Table 2 Degradable fractions of nutrients (g kg 1 ) in molassed untreated, CaO-, NaOH- and AHP-treated wheat straws after in sacco rumen incubations in sheep (Means with standard error of difference, SED) a Parameters Untreated CaO NaOH AHP SED Dry matter a b c (per hour) a b P at Organic matter a b c (per hour) a b P Neutral detergent bre a b c (per hour) a b P a AHP, alkaline hydrogen peroxide (NaOH H 2 O 2 ); a and b respectively, quickly and slowly degradable fractions; c, degradation rate of b; a b and P represent apparent (asymptote) and predicted extent of degradation, respectively Degradation rate (c) and predicted degradability (P ) The degradation rates of DM, OM and NDF were signi cantly faster for treated compared with untreated straw (p < 0.001). However, AHP treatment increased degradation rates most compared with NaOH and CaO. Predicted degradability of DM, OM and NDF was signi cantly greater for treated compared with untreated straw (p < 0.001). However, predicted degradability was greatest for AHP (p < 0.001) compared with NaOH and CaO. 4. Discussion Following previous studies (Chaudhry, 1998b, c), this study examined the effects of already determined best levels of CaO, NaOH and AHP treatments on rumen degradation in sacco in sheep. While treatments modi ed cell wall composition and increased in sacco rumen degradation of straw compared with untreated straw, the extent of increase depended on the type of chemical used. The reasons for those differences between treatments are discussed by comparing the results with published information. The reduction in NDF by different treatments was mainly due to the decreased hemicellulose content of straw (Table 1). The chemical treatments may have removed some linkages within hemicelluloses and thus enhanced their solubility in detergent

9 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313± solutions (Wilkie, 1979; Chaudhry, 1998a, c). The modi ed cell wall composition of straw in response to NaOH and AHP was comparable to that of Chaudhry (1997, 1998c) for the same levels of those chemicals. However, the absolute NDF in untreated and NaOH and AHP-treated straws of this study were greater than those of Chaudhry (1997). The variation in NDF was perhaps due to the use of different straw variety and method by Chaudhry (1997). The ranking of untreated and treated straws based on an increased in sacco degradation was comparable to those of in vitro (Chaudhry, 1998b) and in vivo (Chaudhry, 1998c) digestibility of straw treated with the same chemicals. However, the absolute degradation for various straws differed with the change in chemicals and incubation times. The NDF disappearance from straws was relatively less than those of DM and OM during all incubation times. The difference between losses of different nutrients was larger during the initial 12 h of incubation. The NDF loss from untreated straw (368 g kg 1 ) after rumen incubation of 96 h was less than that (500 g kg 1 ) of Miller and Oddoye (1989) for the same incubation time. The degradation rate (c, 0.012) for NDF was also slower than that (0.042) of the same researchers. The difference may be attributed to the difference in straw variety (Huntingdon and Givens, 1995), particle size (Hovell et al., 1987), and rumen conditions and diet composition of the host animal (Ramanzin et al., 1997). In general, the degradation pattern for untreated and NaOH and AHP-treated straws of this experiment agreed with published studies (Bharghava et al., 1989; Adebowale et al., 1989). The nutrient disappearance from CaO-treated straw was reasonably close to that from NaOH-treated straw at 72 h of incubation and thereafter. However, the degradation pattern of CaO of this study cannot be compared with that in the literature because almost no published information on the degradation pattern of CaO-treated straws could be found. The a b value (541 g kg 1 ) for DM in untreated straw of this study was comparable to that (599 g kg 1 ) reported by Adebowale et al. (1989). The a b value for DM in CaO was greater compared with NaOH. This represented the greater washing loss in water of residual CaO from straw simply because more CaO than NaOH was initially used to treat the straw. However, it is noted that this variation was not caused by the washing loss of added molasses since the same amounts of molasses were added across treatments. The a b values of OM and NDF for CaO and NaOH were closer to each other despite signi cantly different degradation rates (c values, vs for OM; and vs for NDF). The non-signi cant difference between CaO and NaOH for the apparent extent of degradation (a b or asymptote) in this study, was comparable to that of in vitro digestibility (Chaudhry, 1998b) but was contrary to the in vivo digestibility (Chaudhry, 1998c) where NaOH was better than CaO. However, when degradation (c) and rumen out ow rates (k) were taken into consideration, the differences between the predicted degradability (P ) of different straws were comparable to those of in vivo digestibility (Chaudhry, 1998c). The decreased losses of DM and OM from untreated and DM from CaO at 6 h were perhaps due to the particle-associated microbes that increased residual weights of straw during incubation. AHP was the most effective treatment in improving degradation of wheat straw. The results agreed with the previous reports where AHP was better than its NaOH-control and CaO in improving in vitro and in vivo digestibility of wheat straw (Chaudhry, 1997,

10 322 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313± b, c). Although CaO greatly reduced NDF and lignin of straw, it did not improve rumen degradation as much as NaOH and AHP did. It may be due to the greater effect of CaO on the lignin molecule (Table 1) to release phenolics to inhibit rumen microbes and consequently rumen degradation of straw (Marvin et al., 1996). In contrast, Silanikove (1994) reported a greater deligni cation in cotton straw when NaOH instead of CaO was used as an alkali in AHP treatment. However, no difference was reported between the two chemicals for in vitro digestibility of cotton straw. Chaudhry (1998a, b, c), has discussed the potential and problems associated with chemical treatments in improving nutritive value of cereal straws. In summary, the study supported the hypothesis that the increased digestion of cereal straws by ruminants was a consequence of increased rate and extent of their rumen degradation. In conclusion, CaO modi ed cell wall composition and increased rumen degradation in sacco of wheat straw and therefore could be used as an alternative to NaOH to increase the digestible OM intake of sheep fed treated straw. Although CaO improved rumen degradation less than NaOH did, its use to increase straw digestion even moderately may be more desirable because it is readily available, cheap and less dangerous for the users and the environment. However, it is essential to reduce the level of chemicals but without reducing their effect to improve straw digestion in ruminants. It is also essential to perform a cost-bene t analysis before applying treatment on-farm to improve low quality forages. The bene ts of using chemical treatments would be determined by the availability and price of other animal feeds in different regions of the world at a particular time. Acknowledgements ASC thanks Dr. E.L. Miller for his invaluable advice and comments during studies at the University of Cambridge, UK and Mr. Allan Lisle from the University of Queensland at Gatton, Australia for his statistical advice. References Adebowale, E.A., érskov, E.R., Hotton, P.M., Rumen degradation of straw. 8. Effect of alkaline hydrogen peroxide treatment on degradation of straw using NaOH and ammonia as source of alkali. Anim. Prod. 48, 553±560. AFRC, Energy and protein requirements of ruminants. An advisory manual prepared by AFRC Technical Committee on Responses to Nutrients. CAB international, Wallingford, UK. Bharghava, P.K., érskov, E.R., Walli, T.K., Effect of soaking, ensilage and hydrogen peroxide treatment of barley straw on rumen degradability. Anim. Feed Sci. Technol. 22, 295±303. Chaudhry, A.S., Washing and ltration of wheat straw treated with sodium hydroxide alone or with hydrogen peroxide to modify cell wall composition and in vitro digestibility. Austr. J. Exp. Agric. 37, 617± 621. Chaudhry, A.S., 1998a. Biological and chemical procedures to upgrade cereal straws for ruminants. Nutr. Abst. Rev. Series B. 68, 319±331. Chaudhry, A.S., 1998b. In vitro and in sacco digestibility of wheat straw treated with calcium oxide and sodium hydroxide alone or with hydrogen peroxide. Anim. Feed Sci. Technol. 74, 301±313.

11 A.S. Chaudhry / Animal Feed Science and Technology 83 (2000) 313± Chaudhry, A.S., 1998c. Nutrient digestion and rumen fermentation in sheep of wheat straw treated with calcium oxide, sodium hydroxide and alkaline hydrogen peroxide. Anim. Feed Sci. Technol. 74, 315±328. Gould, J.M., Alkaline peroxide deligni cation of agricultural residues to enhance enzymatic sacchari cation. Biotech. Bioeng. 26, 46±52. Jung, H.G., Buxton, D.R., Hat eld, R.D., Ralph, J., Forages cell wall structure and digestibility. Am. Soc. Agron., Wisconsin, USA. Hovell, F.D.DeB., Campos-Arceu, R., Kyle, D.J., The effect of grinding and pelleting of roughages of known degradability on voluntary intake and digestibility by sheep. Proc. Br. Soc. Anim. Prod. (Science), Winter Meeting Scarborough, UK, paper 57. Huntingdon, J.A., Givens, D.I., The in situ technique for studying the rumen degradation of feeds: a review of the procedures. Nutr. Abstr. Rev. Series B 65, 63±91. Kerley, M.S., Fahey Jr., G.C., Berger, L.L., Merchen, N.R., Gould, J.M., Effect of alkaline hydrogen peroxide treatment of wheat straw on site and extent of digestion in sheep. J. Anim. Sci. 63, 868±978. Marvin, H.J.P., Krechting, C.F., Loo, E.N., van Snijders, C.H.A., Lommen, A., Dolstra, O., Relationship between phenolic acids formed during rumen degradation of maize samples and in vitro digestibility. J. Sci. Food Agric. 71, 111±118. Miller, E.L., Oddoye, E.O.K., Prediction of voluntary intake of conserved forages by cattle from degradability characteristics determined by using synthetic bre bags in sheep. Proc. Br. Soc. Anim. Prod. (Science), Winter Meeting Scarborough, UK, paper 70. érskov, E.R., McDonald, I., The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passages. J. Agric. Sci. Cambridge 92, 499±503. Ramanzin, M., Bailoni, L., Schiavon, S., Effect of forage to concentrate ratio on comparative digestion in sheep, goat and fallow deer. Anim. Sci. 64, 163±170. Silanikove, N., Effect of CaO or NaOH-hydrogen peroxide treatments on the composition and in vitro digestibility of cotton straw. Bioresource Technol. 48, 71±73. Sundstol, F., Owen, E., Straw and other brous by products as feed. Elsevier, Amsterdam. Van Soest, P.J., Robertson, J.B., Lewis, B.A., Methods of dietary bre, neutral detergent bre and non starch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583±3597. Wilkie, K.C.B., The hemicelluloses of grasses and cereals. Adv. Carb. Chem. Biochem. 36, 215±264.