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The use of barley straw as a feed
Animal Feed Science and Technology, 14 (1986) 29--39 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
29
THE USE OF BARLEY STRAW AS A FEED
T. SMITH, J.J. GRIGERA-NAONa, W.H. BROSTER and J.W. SIVITER National Institute for Research in Dairying, Shin field, Reading RG2 9 A T (Gt. Britain) b (Received 16 November 1984; accepted for publication 21 May 1985)
ABSTRACT Smith, T., Grigera-Na6n, J.J., Broster, W.H. and Siviter, J.W., 1986. The use of barley straw as a feed. Anita. Feed Sci. Technol., 14: 29--39. Season of planting, level of inclusion in the diet, treatment with NH3 and N supplementation of barley straw have been considered in four experiments with dairy heifer replacements. Spring-sown straw had a greater nutritive value, and tended to be more readily eaten than winter-sown straw, but the differences were small. Some improvement was noted from stack treatment of straw with NH3, but benefits were not consistent between batches. Fishmeal was a more effective N supplement than rape seed meal, soya bean meal or urea in supporting live-weight gain, especially when straw was more than 50% of the DM intake.
INTRODUCTION
Barley straw has long been accepted as a useful feed for cattle (Kay, 1982). However, over the last 10 years there has been an increase in the total cereal area and a change in arable practice in the U.K. away from springsown varieties o f barley towards winter-sown, and hence the production of straws with a lower nutritive value according to the Ministry o f Agriculture, Fisheries and F o o d (M.A.F.F.) (1975) assessment. However, many factors other than season of planting will affect the nutritive value of individual samples o f straw (Wilson and Brigstocke, 1977; Nicholson, 1984). Chemical treatment of the straw will increase its use as a ruminant feed (Jackson, 1977; Sundst~l, 1981). The role o f protein supplementation in diets in which straw is a major c o m p o n e n t (Smith et al., 1980a) needs further appraisal in order to find an alternative effective supplement to fishmeal. In a series o f experiments the effects of season of planting (winter or spring), treatment with aqueous ammonia and supplementation of the diet with various nitrogen sources on the utilization of barley straw as a ruminant feed have been considered. i
apermanent address: Dept. Zootecnia, Fac. Agronomica, University of Buenos Aires, Argentina. bGrant-aided institute of the Agricultural and Food Research Council. 0377-8401/86/$03.50
© 1986 Elsevier Science Publishers B.V.
30 EXPERIMENTAL PROCEDURE AND RESULTS The research programme consisted of four experiments: (1) a feeding trial; (2) a f e e d i n g trial w i t h m e a s u r e m e n t s o f s t r a w i n t a k e ; (3) a feeding trial w i t h m e a s u r e m e n t s o f digestibility a n d s t r a w i n t a k e ; (4) m e a s u r e m e n t s o f s t r a w i n t a k e . A n i m a l s t a k i n g p a r t in f e e d i n g trials w e r e f e d o n fixed a m o u n t s o f t h e diets ( ~ 1 . 3 - - 1 . 6 m a i n t e n a n c e ) w i t h t h e d a t a for at least t h e first t h r e e w e e k s o f e a c h trial b e i n g d i s c a r d e d t o a v o i d c o n f o u n d i n g live-weight gain w i t h c h a n g e s in gut fill. W h e n v o l u n t a r y i n t a k e o f s t r a w was m e a s u r e d , a n i m a l s h a d access t o t h e s t r a w f o r t w o 3-h p e r i o d s e a c h day. T h e a n i m a l s u s e d w e r e y e a r l i n g British Friesian heifers. F u r t h e r details o f t h e e x p e r i m e n t a l p r o c e d u r e s u s e d f o r trials o f this n a t u r e w e r e given b y S m i t h et al. ( 1 9 8 0 b ) . Within e a c h e x p e r i m e n t s t r a w a n d r a p e s e e d m e a l w e r e f r o m single b a t c h e s a n d o t h e r f e e d s t u f f s w e r e d r a w n f r o m f a r m stocks. A m m o n i a t r e a t m e n t o f TABLE I Chemical analysis of feedingstuffs (g kg-1 DM) used in Experiments 1--3
Experiment 1 Barley Fishmeal Soya bean meal Spring barley straw Experiment 2 Barley Fishmeal Rapeseed meal Winter barley straw: Treated (NH3) Untreated Experiment 3 Barley Fishmeal Untreated winter barley straw Treated (NH3) winter barley straw Untreated spring barley straw Treated (NH3) spring barley straw
Dry matter
Crude fibre
854 918 867 837
57 -107 427 57
Ether extract
Nitrogen
Organic matter
19 99 18 17
20 109 74 7
978 820 929 954
23 113 65
975 802 921
854 903 876
117
29 92 35
851 852
447 402
26 21
12 7
953 938
53
20 114 10
974 795 931
-
-
872 903 864
419
18 58 13
844
425
11
15
925
859
404
19
14
928
830
403
18
17
926
-
-
31 straw was effected b y adding 35 kg NH3 t- 1 to stacks o f straw covered with plastic sheets (HFI Agriculture, BritAg Ltd). Stacks were treated during August in each year and left for 6--8 weeks before opening. New plastic sheets were used on b o t h occasions. Chemical analyses o f the feedstuffs are given in Table I. Estimated metabolizable energy (ME) of the diets was obtained using the values o f Ministry o f Agriculture, Fisheries and F o o d (1975), except for rolled barley (Feedingstuffs Evaluation Unit, 1975). To determine total volatile fatty acids (TVFA, mmol 1-1) and molar proportions of VFA, samples of rumen liquor were removed by stomach tube 2.5 and 7 h after the morning feed, on one day during a feeding trial. A portion of the 2.5 h sample was used to determine rumen NH3-N concentrations.
Experiment 1 The first experiment consisted of a feeding trial in which diets of differing proportions of spring barley straw and concentrates (53 and 23%, respectively, o f DM o f straw, and 47 and 77%, respectively, of DM o f concentrates) were given either w i t h o u t nitrogen supplementation or with fishmeal, soya bean meal or urea. The remainder o f the concentrates were rolled barley. Details of the diets are given in Table II. The eight treatments were arranged in a 2 × 4 factorial design. F o r t y yearling heifers, initial live weight 199 kg, t o o k part in the trial, which lasted for 104 days.
Results All animals completed the experiment and there were no refusals o f food. Statistical analysis of daily live-weight change and rumen NH3-N concentration data showed no evidence o f an interaction between diet composition and either protein level or source. Daily live-weight gain was greatest with the lower straw:concentrates ratio (P < 0.01) and with fishmeal supplementation (P < 0.01). R u m e n NH3-N concentration was unaffected by the straw:concentrates ratio (P > 0.05), but differences caused b y N supplementation were in the order: control < fish meal = soya bean m e a l < urea, all significant at P < 0.001. Individual ~rea.tment means are shown in Table II.
Experiment 2 The second experiment compared diets based on winter barley straw, treated with aqueous ammonia, when given at two straw:concentrates ratios (52:48; 18:82) together with rolled barley. Within each ratio either no nitrogen supplementation, or fishmeal, rapeseed meal or urea was included in the diet. An extra treatment at the 52:48 ratio contained untreated straw from the original batch and urea, so that the total nitrogen content was
Intake Dry matter (kg) Organic matter (kg) Crude fibre (g kg-1 DM) Crude protein (g kg-1 DM) Daily live-weight gain (g) Rumen NH3-N (mg 1-~) 4.539 4.325 244 127 566 83.2
4.487 4.306 257 121 408 90.6
4.573 4.358 246 126 449 179.0
3.655 3.555 142 104 471 20.8
3.715 3.556 135 160 587 82.2
3.663 3.537 149 153 516 80.6
3.749 3.589 138 158 484 183.2
Urea Control Fishmeal Soya bean meal
Control Fishmeal Soya Urea bean meal
4.479 4.324 251 81 372 20.0
23% straw
53% straw
Treatments and nitrogen source
Daily intake, live-weight gain and rumen NH~-N concentration measured during Experiment 1
TABLE II
32.7 11.48
+
S.E. of mean a
t'O
R u m e n NH3-N (mg I 1) Daily live-weight gain (g) Days 40--124 Days 124--191
T V F A ( m m o l I 1) VFA : Acetate Propionate Isobutyrate Normal-butyra te Isovalerate Normal-valerate
Intake Dry m a t t e r (kg) Organic matter (kg) Crude fibre (g kg -~ DM) Crude protein (g k g x DM) Observed ME intake (MJ day -1 )
70.1
63.9
514 559
542 559
0.669 0.156 0.007 0.139 0.014 0.012
0.680 0.150 0.007 0.136 0.012 0.011
0.667 0.160 0.007 0.141 0.010 0.010
690 --
69.1
72.1
69.6
36.3
4.648 4.457 262 130 49
4.650 4.440 254 136 50
4.603 4.435 259 107
599 534
147.6
0.666 0.156 0.006 0.145 0.012 0.010
78.7
4.653 4.458 256 137 50
424 507
144.8
0.677 0.151 0.007 0.142 0.010 0.011
68.5
4.656 4.460 256 121 47
489
37.0
0.609 0.169 0.008 0.171 0.024 0.016
74.5
3.755 3.646 128 132
594
84.0
0.585 0.181 0.010 0.182 0.021 0.017
81.8
3.803 3.652 123 164
528
68.4
0.605 0.178 0.009 0.168 0.021 0.018
77.6
3.800 3.667 134 159
NH3 NH3 Fishmeal Rapeseed meal
573
140.3
0.607 0.182 0.007 0.165 0.024 0.014
84.8
3.805 3.669 126 167
NH3 Urea
33.3 34.1
6.92
0.0080 0.0101 0.0005 0.0084 0.0018 0.0010
4.8~
NH3 Control
-Urea
NH 3 Con~ol
NH3 Urea
+
18% straw
52% straw NH3 NH3 Fishmeal Rapeseed meal
S.E. o f a mean
T r e a t m e n t s and nitrogen source
Daily intakes, total volatile fatty acids ( T V F A ) , m o l a r p r o p o r t i o n s of V F A , r u m e n NH3-N c o n c e n t r a t i o n and daily live-weight gain measured during the feeding trial of E x p e r i m e n t 2
T A B L E III
34 similar to that of the supplemented diets (Table III). A feeding trial was supported by measurements of intake of straw. Forty-five 10-month-old heifers, initial live weight 201 kg, took part in the feeding trial, which lasted for 128 days for all nine treatments and 192 days for the diets containing 52% straw (except that supplemented with fishmeal). Variables measured in the first 125 days were statistically analysed in two ways: (a) all treatments were arranged in a randomized block design; (b)the eight treatments containing ammonia treated straw were arranged in a 2 × 4 factorial design. Intake of NH~-treated straw when given with the same amount of concentrates offered with the 52% straw diets was measured with four heifers, initial live weight 216 kg, and arranged in a latin square design trial. Digestibility, nitrogen retention and rate of passage data relating to four of the diets used will be reported separately (J.J. Grigera-Na6n, Ph.D. thesis, University of Reading), although available digestibility readings have been used to calculate observed ME intakes. Results
All animals completed the experiment and there were no refusals of food. Between days 40 and 125 growth rate was increased by NH3 treatment of the straw (P < 0.01) and by the addition of fishmeal (P < 0.01) and urea (P < 0.05) to the diet. There was no interaction between diet ratio and source of protein although the response to fishmeal was greatest with 52% straw. Daily live-weight gains in the second period (days 128--191) were of the same order as in the first period except that those animals receiving untreated straw increased their growth rate (Table III). During days 40--191 ammonia treatment of the straw gave an extra 110 g day I growth (P < 0.01). Concentration of rumen N H r N was unaffected by the proportion of straw and was similar for the diets containing treated straw plus urea and untreated straw plus urea. There were significant differences between the control diets and those supplemented with fishmeal and rapeseed meal (P < 0.001) and between these two supplements and urea (P <: 0.001; Table III). Total VFA concentration was not significantly affected by the treatments, although it tended to be greater with the 18% straw diets. The proportions of acetate were increased by the 52% straw diets (P < 0.001); the same diets caused significant reductions in isobutyrate (P < 0.05), normal butyrate (P < 0.001), isovalerate (P < 0.001) and normal valerate (P <: 0.001). Isobutyrate was increased (P < 0.05) by the inclusion of fishmeal and rapeseed meal. Patterns of VFA production were similar from diets containing untreated and NHrtreated straw (Table III). Voluntary intake of NH3-treated straw was unaffected by amount and source of nitrogen supplementation, and averaged 1.34 kg straw dry matter per 100 kg live weight per day.
35
Experiment 3 In the third feeding trial winter- and spring-sown varieties of barley straw were compared with and w i t h o u t treatment with NH3. Forty-eight 15month-old heifers, initial live weight 217 kg, t o o k part in the trial, which lasted for 63 days. The heifers used were in the second stage o f a trial to measure compensatory growth (T. Smith et al., unpublished data) and therefore received the concentrates allocation pertaining to that experiment, together with the appropriate straw. The distribution o f the animals was arranged orthogonally between the two trials. Because the animals were on fixed amounts of feed for 3.5 months before the present trial started and supplies o f the spring barley straw were limited, all the live weight data (63 days) have been included in the statistical analysis. The diets are described in Table IV. Digestibility o f the diet and voluntary dry matter intake of straw were measured in four steers, initial live weight 257 kg, arranged in a 4 × 4 latin square design, with a total period length o f 43 days. The steers received fixed amounts of feed for 26 days (same amount o f straw as in the feeding trial; 1.657 kg barley DM day-l; 0.361 kg fishmeal DM day-l), the last five of which were used to measure digestibility, and then the same fixed amount of concentrate with free access to straw for 17 days, the last seven of which were used to measure straw intake. TABLE IV Daily intakes and live-weight gain measured during the feeding trial of Experiment 3, together with digestibility coefficients of the diets S.E. of a mean ±
Season and treatment Winter
Intake (kg DM) Barley Fishmeal Straw Total DM (kg) Organic matter (kg) Crude fibre (g kg-I DM) Crude protein (g kg-1DM) Observed ME intake (MJ day -~) Live-weight gain (g) Digestibility coefficients Dry matter Organic matter Crude fibre Ether extract
Winter
Spring
Spring
+
+
NH3
NH3
1.433 0.385 2.376 4.248 3.932 253 172 39 525
1.433 0.385 2.110 3.928 3.650 248 158 37 530
0.64 0.66 0.65 0.47
0.66 0.68 0.67 0.52
1.433 0.385 2.147 4.019 3.711 235 191 37 521 0.64 0.67 0.60 0.48
1.433 0.385 2.075 3.893 3.620 235 173 37 555 0.66 0.69 0.66 0.49
27.7 0.009 0.009 0.012 0.014
36
Results There were no refusals o f f o o d and all animals completed the experiment. No differences were measured in daffy live-weight change (Table IV). However, a small discrepancy between weighing scales resulted in animals receiving untreated winter barley straw consuming about 200 g straw dry matter extra per day. This may have enhanced their growth rate by up to 50 g day -1 (Ministry o f Agriculture, Fisheries and Food, 1975). Dry matter digestibility o f the total diet (Table IV) was raised by 0.02 b y NH3 treatment of the straw (P > 0.05). Intake of straw dry matter was greater with the spring sown (3.827 kg day -~) than with the winter sown straw (3.522 kg day -~) (P < 0.05), while the smaller increase following NH3 treatment was not significant.
Experiment 4 In this experiment, intake of NH3-treated winter barley straw was measured when the concentrates allocation was varied. Three steers, mean live weight 378 kg, t o o k part in a latin square design trial in which three fixed levels o f concentrates of 3.2, 2.2 or 1.2 kg air-dry feed (rolled barley plus soya bean meal) were given each day, together with NH3-treated winter barley straw (same batch as used in Experiment 2). The proportions of rolled barley and soya bean meal were such that all the mixes supplied equal amounts of crude protein ( a b o u t 420 g day-l). Intakes o f straw were measured over the last seven days o f the 28-day periods.
Results Although differences in intake between treatments were only significant at P ~ 0.10 the trend was that as concentrates were reduced so straw intake increased, from 1.246 to 1.475 kg straw dry matter per 100 kg live weight. DISCUSSION Winter- and spring-sown barley straws have supplied 18--55% of the dry matter intake in all the feeding trials described here. In the first trial spring barley straw was given as collected from the field, and in the second, untreated winter barley straw was compared with that treated with aqueous ammonia. In the third trial both forms of straw, either untreated or treated with NH3, were given. The diets were formulated to support growth rates of 0.5--0.7 kg day -1 in yearling dairy heifers, as r e c o m m e n d e d by Foldager et al. (1980). The approach o f giving a set amount of the diet in feeding trials and measuring straw intake separately has allowed changes in nutritive value o f treated straws to be observed independently of changes in straw consumption.
37 In the first experiment the fishmeal-supplemented diets produced similar rates o f growth at both levels of straw inclusion. Between the first and second experiments the 53% spring barley straw plus urea diet of Experiment 1 and the 52% untreated winter barley straw plus urea diet of Experiment 2 resulted in similar rates o f growth. In Experiment 3 there were only marginal differences in live-weight change attributable to source of straw, similar to those reported b y Barber et al. (1984). It should be noted that the chemical analyses of the two straws show only small differences between those used in Experiments 1 and 2, b u t with a greater N content in the untreated straws of Experiment 3. Treatment with NH3 increased DM digestibility of the straw, estimated by difference, by a b o u t 0.07 units in Experiment 2 and 0.04 units in Experiment 3. This improvement is considerably less than the average of 0.09 units for all forms o f NH3 treatment q u o t e d b y Alderman and Mason (1984), b u t similar to that reported by Smith et al. (1983/84), and the difference between the experiments demonstrates the difficulty of making an economic assessment prior to applying the treatment. However, in Experiment 2 there was an overall benefit to growth rate from the NH3 treatment so that in contrast to Experiment 1 no advantage was gained from the lower rate of straw inclusion. At the start o f Experiment 2 straw was given at 90% of the maxim u m intake. No explanation can be given for the poor response to NH3 treatment o f the straws used in Experiment 3, where live-weight gain was greater with all diets than would be predicted from the ME intake (Ministry of Agriculture, Fisheries and Food, 1975). The response in live-weight gain (Experiment 1) to a supplement o f fishmeal was similar to that predicted by Oldham and Smith {1982), both with straw-rich and barley-rich diets. With NH3-treated straw (Experiment 2) the response confLrms that reported in earlier trials (Kay, 1982; Smith et al., 1983/84). Supplementation with either rapeseed meal or soya bean meal resulted in less live-weight gain than when fishmeal was used. In Experiment 1 the effect of adding urea to the diet, at both levels o f straw inclusion, was similar to that reported b y Oldham and Smith {1982). In Experiment 2 the apparent response to urea during days 40--124 was unexpected, as both control diets contained adequate rumen degradable protein judged by the standards of the Agricultural Research Council (1980). In the first two feeding trials rumen N H r N concentrations were increased by all the N supplements, especially urea. They were similar both between experiments and between straw:concentrates ratios. With the control diets the peak values were below the mean value recommended by Satter and Roffler (1975). However, this is probably not the cause of the response in live weight to urea feeding because the high peak concentration associated with this supplement was followed by a rapid decline to a value similar to the control diet (Grigera-NaSn, unpublished data). The changes noted in VFA production (Experiment 2) were generally small and similar to those reported by Smith et al. (1980a). Reducing the amount of straw in the diet
38
reduced proportions of acetate and increased propionate and normal butyrate. There were no differences between NHs-treated and untreated straw. Intake of straw, measured in Experiment 2, was unaffected by the addition of supplementary N, confirming the observations of Andrews et al. (1972) and Smith et al. (1980a) that maximum DM intake of a mixed diet, rich in roughage, is reached at 85--90 g CP per kg DM. In Experiment 4 consumption of straw increased as the amount of cereal starch in the diet fell, suggesting better conditions for the growth of cellulolytic bacteria (E1-Shazly et al., 1961). For each 100 g concentrate DM removed, straw intake increased by 50 g, a similar value to that found in sheep fed on poor quality hay by Blaxter et al. (1961) and greater than that in very young calves fed on barley straw by Leaver (1973)o Extrapolation from Experiment 2, where the calculated ME intakes suggested that the ME of the treated straw was ~8.5 MJ ME per kg DM, indicates that the lower concentrate diet was capable of supplying maintenance plus 350 g live-weight gain per day. Intakes of ME were calculated as DOMD% X 0.15 X DM intake (kg day -1 ) (Ministry of Agriculture, Fisheries and Food, 1975). The concentrates given in this experiment were formulated to ensure that shortage of protein would not limit straw intake, although the supplement used would probably not have maximised growth rate. This study, together with that reported by Smith et al. (1984) shows that when given as 50--60% of the DM intake, spring barley straw is a marginally better feed than winter barley straw. However the differences are neither marked nor consistent, which supports the contention of Wilson and Brigstocke (1977) and Nicholson (1984) that other factors together with season of planting must be considered in judging the nutritive value of barley straw. ACKNOWLEDGEMENTS
Our thanks are due to Miss S. Warrener for care of the animals, Mr. E. Florence and his staff for chemical analyses and HFI Agriculture, BritAg Ltd. for assistance with the preparation of the NH3-treated straw.
REFERENCES
Agricultural Research Council, 1980. The Nutrient Requirements of Ruminant Livestock. Commonwealth Agricultural Bureaux, Slough. Alderman, G. and Mason, V.C., 1984. Straw as animal feed. In: D.J. White (Editor), Straw Disposal and Utilisation, A Review of Knowledge. Ministry of Agriculture, Fisheries and F o o d , I.~ndon, pp. 46--55. Andrews, R.P., Escuder-Volonte, J., Curran, M.K. and Holmes, W., 1972. The i n f l u e n c e of supplements of energy and protein o n the intake and performance of cattle fed on cereal straws. Anita. Prod., 15: 167--176. Barber, W.P., Alderman, G., Adamson, A.H., Mansbridge, R.J. and Williams, T.R., 1984. Evaluation of untreated and alkali treated cereal straw. Proceedings of the S e c o n d
39
Seminar on the Upgrading of Crops and By-products. Ministry of Agriculture, Fisheries and Food, London, pp. 38--49. Blaxter, K.L, Wainman, F.W. and Wilson, R.S., 1961. The regulation of food intake by sheep. Anita. Prod., 3: 51--61. EI-Shazly, K., Dehority, B.A. and Johnson, R.R., 1961. Effect of starch on the digestion of cellulose in vitro and in vivo by rumen microorganisms. J. Anim. Sci., 20: 268--273. Feedingstuffs Evaluation Unit, 1975. First Report, Department of Agriculture and Fisheries for Scotland. Foldager, J., Sejrsen, K. and Larsen, J.B., 1980. Milk production in heifers reared on ad libitum intake of rations with different energy concentrations. E.A.A.P. Energy Symposium in Munich. Jackson, M.G., 1977. Review article: the alkali treatment of straws. Anita. Feed Sci. Technol., 2: 105--130. Kay, M., 1982. Chemical treatment of straw for animal feed. Proceedings of the Sixth Straw Utilisation Conference. H.M.S.O., Birmingham, pp. 13--18. Leaver, J.D., 1973. Rearing o f dairy cattle. 4. Effect of concentrate supplementation on the live-weight gain and feed intake of calves offered roughages ad libitum. Anim. Prod., 17: 43--52. Ministry o f Agriculture, Fisheries and Food, 1975. Energy allowances and feeding systems for ruminants. M.A.F.F., Technical Bulletin No. 33, H.M.S.O., London. Nicholson, J.W.G., 1984. Digestibility, nutritive value and feed intake. In: F. Sundst~$1 and E. Owen (Editors), Straw and Other Fibrous By-products as Feed. Elsevier, Amsterdam, pp. 340--372. Oldham, J.D. and Smith, T., 1982. Protein--energy interrelationships for growing and for lactating cattle. In: E.L. Miller, I.H. Pike and A.J.H. van Es (Editors), Protein Contribution of Feedstuffs for Ruminants. Butterworths, London, pp. 103--130. Satter, L.D, and Roffler, R.E., 1975. Nitrogen requirement and utilisation in dairy cattle. J. Dairy Sci., 58: 1219--1237. Smith, T., Broster, V.J. and Hill, R.E., 1980a. A comparison of sources of supplementary nitrogen for young cattle receiving fibre-rich diets. J. Agric. Sci., 95: 687---695. Smith, T., Broster, W.H. and Siviter, J.W., 1980b. An assessment of barley straw and oat hulls as energy sources for yearling cattle. J. Agric. Sci., 95: 677--686. Smith, T., Grigera-Nadn, J.J., Broster, W.H. and Siviter, J.W., 1984. Ammonia versus sodium hydroxide treatment o f straw for growing cattle. Anita. Feed Sci. Technol., 10: 189--197. Sundst$1, F., 1981. Methods for treatment of low quality roughages. In: J.A. Kategile, A.N. Said and F. Sundst~$1 (Editors), Utilization of Low Quality Roughages in Africa. AUN -- Agricultural Development Report No. 1,/~s, Norway, pp. 61--80. Wilson, P.N. and Brigstocke, T.D.A., 1977. The commercial straw process. Process Biochem., 12: 17--21.
29
THE USE OF BARLEY STRAW AS A FEED
T. SMITH, J.J. GRIGERA-NAONa, W.H. BROSTER and J.W. SIVITER National Institute for Research in Dairying, Shin field, Reading RG2 9 A T (Gt. Britain) b (Received 16 November 1984; accepted for publication 21 May 1985)
ABSTRACT Smith, T., Grigera-Na6n, J.J., Broster, W.H. and Siviter, J.W., 1986. The use of barley straw as a feed. Anita. Feed Sci. Technol., 14: 29--39. Season of planting, level of inclusion in the diet, treatment with NH3 and N supplementation of barley straw have been considered in four experiments with dairy heifer replacements. Spring-sown straw had a greater nutritive value, and tended to be more readily eaten than winter-sown straw, but the differences were small. Some improvement was noted from stack treatment of straw with NH3, but benefits were not consistent between batches. Fishmeal was a more effective N supplement than rape seed meal, soya bean meal or urea in supporting live-weight gain, especially when straw was more than 50% of the DM intake.
INTRODUCTION
Barley straw has long been accepted as a useful feed for cattle (Kay, 1982). However, over the last 10 years there has been an increase in the total cereal area and a change in arable practice in the U.K. away from springsown varieties o f barley towards winter-sown, and hence the production of straws with a lower nutritive value according to the Ministry o f Agriculture, Fisheries and F o o d (M.A.F.F.) (1975) assessment. However, many factors other than season of planting will affect the nutritive value of individual samples o f straw (Wilson and Brigstocke, 1977; Nicholson, 1984). Chemical treatment of the straw will increase its use as a ruminant feed (Jackson, 1977; Sundst~l, 1981). The role o f protein supplementation in diets in which straw is a major c o m p o n e n t (Smith et al., 1980a) needs further appraisal in order to find an alternative effective supplement to fishmeal. In a series o f experiments the effects of season of planting (winter or spring), treatment with aqueous ammonia and supplementation of the diet with various nitrogen sources on the utilization of barley straw as a ruminant feed have been considered. i
apermanent address: Dept. Zootecnia, Fac. Agronomica, University of Buenos Aires, Argentina. bGrant-aided institute of the Agricultural and Food Research Council. 0377-8401/86/$03.50
© 1986 Elsevier Science Publishers B.V.
30 EXPERIMENTAL PROCEDURE AND RESULTS The research programme consisted of four experiments: (1) a feeding trial; (2) a f e e d i n g trial w i t h m e a s u r e m e n t s o f s t r a w i n t a k e ; (3) a feeding trial w i t h m e a s u r e m e n t s o f digestibility a n d s t r a w i n t a k e ; (4) m e a s u r e m e n t s o f s t r a w i n t a k e . A n i m a l s t a k i n g p a r t in f e e d i n g trials w e r e f e d o n fixed a m o u n t s o f t h e diets ( ~ 1 . 3 - - 1 . 6 m a i n t e n a n c e ) w i t h t h e d a t a for at least t h e first t h r e e w e e k s o f e a c h trial b e i n g d i s c a r d e d t o a v o i d c o n f o u n d i n g live-weight gain w i t h c h a n g e s in gut fill. W h e n v o l u n t a r y i n t a k e o f s t r a w was m e a s u r e d , a n i m a l s h a d access t o t h e s t r a w f o r t w o 3-h p e r i o d s e a c h day. T h e a n i m a l s u s e d w e r e y e a r l i n g British Friesian heifers. F u r t h e r details o f t h e e x p e r i m e n t a l p r o c e d u r e s u s e d f o r trials o f this n a t u r e w e r e given b y S m i t h et al. ( 1 9 8 0 b ) . Within e a c h e x p e r i m e n t s t r a w a n d r a p e s e e d m e a l w e r e f r o m single b a t c h e s a n d o t h e r f e e d s t u f f s w e r e d r a w n f r o m f a r m stocks. A m m o n i a t r e a t m e n t o f TABLE I Chemical analysis of feedingstuffs (g kg-1 DM) used in Experiments 1--3
Experiment 1 Barley Fishmeal Soya bean meal Spring barley straw Experiment 2 Barley Fishmeal Rapeseed meal Winter barley straw: Treated (NH3) Untreated Experiment 3 Barley Fishmeal Untreated winter barley straw Treated (NH3) winter barley straw Untreated spring barley straw Treated (NH3) spring barley straw
Dry matter
Crude fibre
854 918 867 837
57 -107 427 57
Ether extract
Nitrogen
Organic matter
19 99 18 17
20 109 74 7
978 820 929 954
23 113 65
975 802 921
854 903 876
117
29 92 35
851 852
447 402
26 21
12 7
953 938
53
20 114 10
974 795 931
-
-
872 903 864
419
18 58 13
844
425
11
15
925
859
404
19
14
928
830
403
18
17
926
-
-
31 straw was effected b y adding 35 kg NH3 t- 1 to stacks o f straw covered with plastic sheets (HFI Agriculture, BritAg Ltd). Stacks were treated during August in each year and left for 6--8 weeks before opening. New plastic sheets were used on b o t h occasions. Chemical analyses o f the feedstuffs are given in Table I. Estimated metabolizable energy (ME) of the diets was obtained using the values o f Ministry o f Agriculture, Fisheries and F o o d (1975), except for rolled barley (Feedingstuffs Evaluation Unit, 1975). To determine total volatile fatty acids (TVFA, mmol 1-1) and molar proportions of VFA, samples of rumen liquor were removed by stomach tube 2.5 and 7 h after the morning feed, on one day during a feeding trial. A portion of the 2.5 h sample was used to determine rumen NH3-N concentrations.
Experiment 1 The first experiment consisted of a feeding trial in which diets of differing proportions of spring barley straw and concentrates (53 and 23%, respectively, o f DM o f straw, and 47 and 77%, respectively, of DM o f concentrates) were given either w i t h o u t nitrogen supplementation or with fishmeal, soya bean meal or urea. The remainder o f the concentrates were rolled barley. Details of the diets are given in Table II. The eight treatments were arranged in a 2 × 4 factorial design. F o r t y yearling heifers, initial live weight 199 kg, t o o k part in the trial, which lasted for 104 days.
Results All animals completed the experiment and there were no refusals o f food. Statistical analysis of daily live-weight change and rumen NH3-N concentration data showed no evidence o f an interaction between diet composition and either protein level or source. Daily live-weight gain was greatest with the lower straw:concentrates ratio (P < 0.01) and with fishmeal supplementation (P < 0.01). R u m e n NH3-N concentration was unaffected by the straw:concentrates ratio (P > 0.05), but differences caused b y N supplementation were in the order: control < fish meal = soya bean m e a l < urea, all significant at P < 0.001. Individual ~rea.tment means are shown in Table II.
Experiment 2 The second experiment compared diets based on winter barley straw, treated with aqueous ammonia, when given at two straw:concentrates ratios (52:48; 18:82) together with rolled barley. Within each ratio either no nitrogen supplementation, or fishmeal, rapeseed meal or urea was included in the diet. An extra treatment at the 52:48 ratio contained untreated straw from the original batch and urea, so that the total nitrogen content was
Intake Dry matter (kg) Organic matter (kg) Crude fibre (g kg-1 DM) Crude protein (g kg-1 DM) Daily live-weight gain (g) Rumen NH3-N (mg 1-~) 4.539 4.325 244 127 566 83.2
4.487 4.306 257 121 408 90.6
4.573 4.358 246 126 449 179.0
3.655 3.555 142 104 471 20.8
3.715 3.556 135 160 587 82.2
3.663 3.537 149 153 516 80.6
3.749 3.589 138 158 484 183.2
Urea Control Fishmeal Soya bean meal
Control Fishmeal Soya Urea bean meal
4.479 4.324 251 81 372 20.0
23% straw
53% straw
Treatments and nitrogen source
Daily intake, live-weight gain and rumen NH~-N concentration measured during Experiment 1
TABLE II
32.7 11.48
+
S.E. of mean a
t'O
R u m e n NH3-N (mg I 1) Daily live-weight gain (g) Days 40--124 Days 124--191
T V F A ( m m o l I 1) VFA : Acetate Propionate Isobutyrate Normal-butyra te Isovalerate Normal-valerate
Intake Dry m a t t e r (kg) Organic matter (kg) Crude fibre (g kg -~ DM) Crude protein (g k g x DM) Observed ME intake (MJ day -1 )
70.1
63.9
514 559
542 559
0.669 0.156 0.007 0.139 0.014 0.012
0.680 0.150 0.007 0.136 0.012 0.011
0.667 0.160 0.007 0.141 0.010 0.010
690 --
69.1
72.1
69.6
36.3
4.648 4.457 262 130 49
4.650 4.440 254 136 50
4.603 4.435 259 107
599 534
147.6
0.666 0.156 0.006 0.145 0.012 0.010
78.7
4.653 4.458 256 137 50
424 507
144.8
0.677 0.151 0.007 0.142 0.010 0.011
68.5
4.656 4.460 256 121 47
489
37.0
0.609 0.169 0.008 0.171 0.024 0.016
74.5
3.755 3.646 128 132
594
84.0
0.585 0.181 0.010 0.182 0.021 0.017
81.8
3.803 3.652 123 164
528
68.4
0.605 0.178 0.009 0.168 0.021 0.018
77.6
3.800 3.667 134 159
NH3 NH3 Fishmeal Rapeseed meal
573
140.3
0.607 0.182 0.007 0.165 0.024 0.014
84.8
3.805 3.669 126 167
NH3 Urea
33.3 34.1
6.92
0.0080 0.0101 0.0005 0.0084 0.0018 0.0010
4.8~
NH3 Control
-Urea
NH 3 Con~ol
NH3 Urea
+
18% straw
52% straw NH3 NH3 Fishmeal Rapeseed meal
S.E. o f a mean
T r e a t m e n t s and nitrogen source
Daily intakes, total volatile fatty acids ( T V F A ) , m o l a r p r o p o r t i o n s of V F A , r u m e n NH3-N c o n c e n t r a t i o n and daily live-weight gain measured during the feeding trial of E x p e r i m e n t 2
T A B L E III
34 similar to that of the supplemented diets (Table III). A feeding trial was supported by measurements of intake of straw. Forty-five 10-month-old heifers, initial live weight 201 kg, took part in the feeding trial, which lasted for 128 days for all nine treatments and 192 days for the diets containing 52% straw (except that supplemented with fishmeal). Variables measured in the first 125 days were statistically analysed in two ways: (a) all treatments were arranged in a randomized block design; (b)the eight treatments containing ammonia treated straw were arranged in a 2 × 4 factorial design. Intake of NH~-treated straw when given with the same amount of concentrates offered with the 52% straw diets was measured with four heifers, initial live weight 216 kg, and arranged in a latin square design trial. Digestibility, nitrogen retention and rate of passage data relating to four of the diets used will be reported separately (J.J. Grigera-Na6n, Ph.D. thesis, University of Reading), although available digestibility readings have been used to calculate observed ME intakes. Results
All animals completed the experiment and there were no refusals of food. Between days 40 and 125 growth rate was increased by NH3 treatment of the straw (P < 0.01) and by the addition of fishmeal (P < 0.01) and urea (P < 0.05) to the diet. There was no interaction between diet ratio and source of protein although the response to fishmeal was greatest with 52% straw. Daily live-weight gains in the second period (days 128--191) were of the same order as in the first period except that those animals receiving untreated straw increased their growth rate (Table III). During days 40--191 ammonia treatment of the straw gave an extra 110 g day I growth (P < 0.01). Concentration of rumen N H r N was unaffected by the proportion of straw and was similar for the diets containing treated straw plus urea and untreated straw plus urea. There were significant differences between the control diets and those supplemented with fishmeal and rapeseed meal (P < 0.001) and between these two supplements and urea (P <: 0.001; Table III). Total VFA concentration was not significantly affected by the treatments, although it tended to be greater with the 18% straw diets. The proportions of acetate were increased by the 52% straw diets (P < 0.001); the same diets caused significant reductions in isobutyrate (P < 0.05), normal butyrate (P < 0.001), isovalerate (P < 0.001) and normal valerate (P <: 0.001). Isobutyrate was increased (P < 0.05) by the inclusion of fishmeal and rapeseed meal. Patterns of VFA production were similar from diets containing untreated and NHrtreated straw (Table III). Voluntary intake of NH3-treated straw was unaffected by amount and source of nitrogen supplementation, and averaged 1.34 kg straw dry matter per 100 kg live weight per day.
35
Experiment 3 In the third feeding trial winter- and spring-sown varieties of barley straw were compared with and w i t h o u t treatment with NH3. Forty-eight 15month-old heifers, initial live weight 217 kg, t o o k part in the trial, which lasted for 63 days. The heifers used were in the second stage o f a trial to measure compensatory growth (T. Smith et al., unpublished data) and therefore received the concentrates allocation pertaining to that experiment, together with the appropriate straw. The distribution o f the animals was arranged orthogonally between the two trials. Because the animals were on fixed amounts of feed for 3.5 months before the present trial started and supplies o f the spring barley straw were limited, all the live weight data (63 days) have been included in the statistical analysis. The diets are described in Table IV. Digestibility o f the diet and voluntary dry matter intake of straw were measured in four steers, initial live weight 257 kg, arranged in a 4 × 4 latin square design, with a total period length o f 43 days. The steers received fixed amounts of feed for 26 days (same amount o f straw as in the feeding trial; 1.657 kg barley DM day-l; 0.361 kg fishmeal DM day-l), the last five of which were used to measure digestibility, and then the same fixed amount of concentrate with free access to straw for 17 days, the last seven of which were used to measure straw intake. TABLE IV Daily intakes and live-weight gain measured during the feeding trial of Experiment 3, together with digestibility coefficients of the diets S.E. of a mean ±
Season and treatment Winter
Intake (kg DM) Barley Fishmeal Straw Total DM (kg) Organic matter (kg) Crude fibre (g kg-I DM) Crude protein (g kg-1DM) Observed ME intake (MJ day -~) Live-weight gain (g) Digestibility coefficients Dry matter Organic matter Crude fibre Ether extract
Winter
Spring
Spring
+
+
NH3
NH3
1.433 0.385 2.376 4.248 3.932 253 172 39 525
1.433 0.385 2.110 3.928 3.650 248 158 37 530
0.64 0.66 0.65 0.47
0.66 0.68 0.67 0.52
1.433 0.385 2.147 4.019 3.711 235 191 37 521 0.64 0.67 0.60 0.48
1.433 0.385 2.075 3.893 3.620 235 173 37 555 0.66 0.69 0.66 0.49
27.7 0.009 0.009 0.012 0.014
36
Results There were no refusals o f f o o d and all animals completed the experiment. No differences were measured in daffy live-weight change (Table IV). However, a small discrepancy between weighing scales resulted in animals receiving untreated winter barley straw consuming about 200 g straw dry matter extra per day. This may have enhanced their growth rate by up to 50 g day -1 (Ministry o f Agriculture, Fisheries and Food, 1975). Dry matter digestibility o f the total diet (Table IV) was raised by 0.02 b y NH3 treatment of the straw (P > 0.05). Intake of straw dry matter was greater with the spring sown (3.827 kg day -~) than with the winter sown straw (3.522 kg day -~) (P < 0.05), while the smaller increase following NH3 treatment was not significant.
Experiment 4 In this experiment, intake of NH3-treated winter barley straw was measured when the concentrates allocation was varied. Three steers, mean live weight 378 kg, t o o k part in a latin square design trial in which three fixed levels o f concentrates of 3.2, 2.2 or 1.2 kg air-dry feed (rolled barley plus soya bean meal) were given each day, together with NH3-treated winter barley straw (same batch as used in Experiment 2). The proportions of rolled barley and soya bean meal were such that all the mixes supplied equal amounts of crude protein ( a b o u t 420 g day-l). Intakes o f straw were measured over the last seven days o f the 28-day periods.
Results Although differences in intake between treatments were only significant at P ~ 0.10 the trend was that as concentrates were reduced so straw intake increased, from 1.246 to 1.475 kg straw dry matter per 100 kg live weight. DISCUSSION Winter- and spring-sown barley straws have supplied 18--55% of the dry matter intake in all the feeding trials described here. In the first trial spring barley straw was given as collected from the field, and in the second, untreated winter barley straw was compared with that treated with aqueous ammonia. In the third trial both forms of straw, either untreated or treated with NH3, were given. The diets were formulated to support growth rates of 0.5--0.7 kg day -1 in yearling dairy heifers, as r e c o m m e n d e d by Foldager et al. (1980). The approach o f giving a set amount of the diet in feeding trials and measuring straw intake separately has allowed changes in nutritive value o f treated straws to be observed independently of changes in straw consumption.
37 In the first experiment the fishmeal-supplemented diets produced similar rates o f growth at both levels of straw inclusion. Between the first and second experiments the 53% spring barley straw plus urea diet of Experiment 1 and the 52% untreated winter barley straw plus urea diet of Experiment 2 resulted in similar rates o f growth. In Experiment 3 there were only marginal differences in live-weight change attributable to source of straw, similar to those reported b y Barber et al. (1984). It should be noted that the chemical analyses of the two straws show only small differences between those used in Experiments 1 and 2, b u t with a greater N content in the untreated straws of Experiment 3. Treatment with NH3 increased DM digestibility of the straw, estimated by difference, by a b o u t 0.07 units in Experiment 2 and 0.04 units in Experiment 3. This improvement is considerably less than the average of 0.09 units for all forms o f NH3 treatment q u o t e d b y Alderman and Mason (1984), b u t similar to that reported by Smith et al. (1983/84), and the difference between the experiments demonstrates the difficulty of making an economic assessment prior to applying the treatment. However, in Experiment 2 there was an overall benefit to growth rate from the NH3 treatment so that in contrast to Experiment 1 no advantage was gained from the lower rate of straw inclusion. At the start o f Experiment 2 straw was given at 90% of the maxim u m intake. No explanation can be given for the poor response to NH3 treatment o f the straws used in Experiment 3, where live-weight gain was greater with all diets than would be predicted from the ME intake (Ministry of Agriculture, Fisheries and Food, 1975). The response in live-weight gain (Experiment 1) to a supplement o f fishmeal was similar to that predicted by Oldham and Smith {1982), both with straw-rich and barley-rich diets. With NH3-treated straw (Experiment 2) the response confLrms that reported in earlier trials (Kay, 1982; Smith et al., 1983/84). Supplementation with either rapeseed meal or soya bean meal resulted in less live-weight gain than when fishmeal was used. In Experiment 1 the effect of adding urea to the diet, at both levels o f straw inclusion, was similar to that reported b y Oldham and Smith {1982). In Experiment 2 the apparent response to urea during days 40--124 was unexpected, as both control diets contained adequate rumen degradable protein judged by the standards of the Agricultural Research Council (1980). In the first two feeding trials rumen N H r N concentrations were increased by all the N supplements, especially urea. They were similar both between experiments and between straw:concentrates ratios. With the control diets the peak values were below the mean value recommended by Satter and Roffler (1975). However, this is probably not the cause of the response in live weight to urea feeding because the high peak concentration associated with this supplement was followed by a rapid decline to a value similar to the control diet (Grigera-NaSn, unpublished data). The changes noted in VFA production (Experiment 2) were generally small and similar to those reported by Smith et al. (1980a). Reducing the amount of straw in the diet
38
reduced proportions of acetate and increased propionate and normal butyrate. There were no differences between NHs-treated and untreated straw. Intake of straw, measured in Experiment 2, was unaffected by the addition of supplementary N, confirming the observations of Andrews et al. (1972) and Smith et al. (1980a) that maximum DM intake of a mixed diet, rich in roughage, is reached at 85--90 g CP per kg DM. In Experiment 4 consumption of straw increased as the amount of cereal starch in the diet fell, suggesting better conditions for the growth of cellulolytic bacteria (E1-Shazly et al., 1961). For each 100 g concentrate DM removed, straw intake increased by 50 g, a similar value to that found in sheep fed on poor quality hay by Blaxter et al. (1961) and greater than that in very young calves fed on barley straw by Leaver (1973)o Extrapolation from Experiment 2, where the calculated ME intakes suggested that the ME of the treated straw was ~8.5 MJ ME per kg DM, indicates that the lower concentrate diet was capable of supplying maintenance plus 350 g live-weight gain per day. Intakes of ME were calculated as DOMD% X 0.15 X DM intake (kg day -1 ) (Ministry of Agriculture, Fisheries and Food, 1975). The concentrates given in this experiment were formulated to ensure that shortage of protein would not limit straw intake, although the supplement used would probably not have maximised growth rate. This study, together with that reported by Smith et al. (1984) shows that when given as 50--60% of the DM intake, spring barley straw is a marginally better feed than winter barley straw. However the differences are neither marked nor consistent, which supports the contention of Wilson and Brigstocke (1977) and Nicholson (1984) that other factors together with season of planting must be considered in judging the nutritive value of barley straw. ACKNOWLEDGEMENTS
Our thanks are due to Miss S. Warrener for care of the animals, Mr. E. Florence and his staff for chemical analyses and HFI Agriculture, BritAg Ltd. for assistance with the preparation of the NH3-treated straw.
REFERENCES
Agricultural Research Council, 1980. The Nutrient Requirements of Ruminant Livestock. Commonwealth Agricultural Bureaux, Slough. Alderman, G. and Mason, V.C., 1984. Straw as animal feed. In: D.J. White (Editor), Straw Disposal and Utilisation, A Review of Knowledge. Ministry of Agriculture, Fisheries and F o o d , I.~ndon, pp. 46--55. Andrews, R.P., Escuder-Volonte, J., Curran, M.K. and Holmes, W., 1972. The i n f l u e n c e of supplements of energy and protein o n the intake and performance of cattle fed on cereal straws. Anita. Prod., 15: 167--176. Barber, W.P., Alderman, G., Adamson, A.H., Mansbridge, R.J. and Williams, T.R., 1984. Evaluation of untreated and alkali treated cereal straw. Proceedings of the S e c o n d
39
Seminar on the Upgrading of Crops and By-products. Ministry of Agriculture, Fisheries and Food, London, pp. 38--49. Blaxter, K.L, Wainman, F.W. and Wilson, R.S., 1961. The regulation of food intake by sheep. Anita. Prod., 3: 51--61. EI-Shazly, K., Dehority, B.A. and Johnson, R.R., 1961. Effect of starch on the digestion of cellulose in vitro and in vivo by rumen microorganisms. J. Anim. Sci., 20: 268--273. Feedingstuffs Evaluation Unit, 1975. First Report, Department of Agriculture and Fisheries for Scotland. Foldager, J., Sejrsen, K. and Larsen, J.B., 1980. Milk production in heifers reared on ad libitum intake of rations with different energy concentrations. E.A.A.P. Energy Symposium in Munich. Jackson, M.G., 1977. Review article: the alkali treatment of straws. Anita. Feed Sci. Technol., 2: 105--130. Kay, M., 1982. Chemical treatment of straw for animal feed. Proceedings of the Sixth Straw Utilisation Conference. H.M.S.O., Birmingham, pp. 13--18. Leaver, J.D., 1973. Rearing o f dairy cattle. 4. Effect of concentrate supplementation on the live-weight gain and feed intake of calves offered roughages ad libitum. Anim. Prod., 17: 43--52. Ministry o f Agriculture, Fisheries and Food, 1975. Energy allowances and feeding systems for ruminants. M.A.F.F., Technical Bulletin No. 33, H.M.S.O., London. Nicholson, J.W.G., 1984. Digestibility, nutritive value and feed intake. In: F. Sundst~$1 and E. Owen (Editors), Straw and Other Fibrous By-products as Feed. Elsevier, Amsterdam, pp. 340--372. Oldham, J.D. and Smith, T., 1982. Protein--energy interrelationships for growing and for lactating cattle. In: E.L. Miller, I.H. Pike and A.J.H. van Es (Editors), Protein Contribution of Feedstuffs for Ruminants. Butterworths, London, pp. 103--130. Satter, L.D, and Roffler, R.E., 1975. Nitrogen requirement and utilisation in dairy cattle. J. Dairy Sci., 58: 1219--1237. Smith, T., Broster, V.J. and Hill, R.E., 1980a. A comparison of sources of supplementary nitrogen for young cattle receiving fibre-rich diets. J. Agric. Sci., 95: 687---695. Smith, T., Broster, W.H. and Siviter, J.W., 1980b. An assessment of barley straw and oat hulls as energy sources for yearling cattle. J. Agric. Sci., 95: 677--686. Smith, T., Grigera-Nadn, J.J., Broster, W.H. and Siviter, J.W., 1984. Ammonia versus sodium hydroxide treatment o f straw for growing cattle. Anita. Feed Sci. Technol., 10: 189--197. Sundst$1, F., 1981. Methods for treatment of low quality roughages. In: J.A. Kategile, A.N. Said and F. Sundst~$1 (Editors), Utilization of Low Quality Roughages in Africa. AUN -- Agricultural Development Report No. 1,/~s, Norway, pp. 61--80. Wilson, P.N. and Brigstocke, T.D.A., 1977. The commercial straw process. Process Biochem., 12: 17--21.