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Utilization of alkali-treated grain. 2. Utilization by steers of diets based on hay or straw and mixed with either NaOH-treated or rolled barley
Animal Feed Science and Technology, 6 (1981) 347--354 Elsevier Scientific Publishing Company, Amsterdam - - Printed in The Netherlands
347
UTILIZATION OF ALKALI-TREATED G R A I N . 2. U T I L I Z A T I O N B Y STEERS OF DIETS BASED ON HAY OR STRAW AND MIXED WITH EITHER NaOH-TREATED OR ROLLED BARLEY
B.J. BARNES and E.R. ~)RSKOV R o w e t t Research Institute, Bucksburn, Aberdeen AB2 9SB (Gt. Britain)
(Received 13 November 1980; accepted for publication 16 March 1981)
SUMMARY Barnes, B.J. and Orskov, E.R., 1981. Utilization of alkali-treated grain. 2. Utilization by steers of diets based on hay or straw and mixed with either NaOH-treated or rolled barley. Anim. Feed Sci. Technol., 6: 347--354. In the first of three experiments, Hereford cross steers were fed ad libitum from 325 kg to slaughter at 425 kg on diets containing 50% hay and 50% rolled or NaOH-treated (30 g]kg) barley. Liveweight gain and food conversion ratios were similar for the two groups (1.24 vs. 1.42 kg/day; 7.0 vs. 7.0 kg dry matter intake/kg gain, respectively). Dry matter and organic matter digestibility was significantly higher (P < 0.01) when the diet contained rolled, rather than NaOH-treated, barley. There were no significant differences in fibre digestibility (51.2 vs. 59.1%, respectively). In the second experiment, the optimum level of NaOH was determined for the treatment of barley when given with hay. The level of NaOH required to achieve a digestibility in whole barley similar to rolled barley was 40 g NaOH]kg, i.e., approximately 10 g/kg more than when NaOH-treated barley formed the sole component of the diet. Dry matter and organic matter digestibility increased linearly as the level of NaOH applied increased (P < 0.05) and tended to peak at 40 g NaOH/kg barley. Starch digestibility also increased linearly (P < 0.001). Fibre digestibility did not vary significantly between treatments. In the third experiment, the voluntary intake of straw by steers given rolled or NaOHtreated barley at two levels of supplementation was determined. The intake of straw was slightly, but not significantly, greater when NaOH-treated rather than rolled barley was used. The digestibility of dry matter, organic matter, starch and fibre was not significantly affected by method of cereal treatment. No problems of animal health arose throughout the three experiments.
INTRODUCTION The extent of processing of cereals can have serious repercussions on the r a t e o f c e l l u l o s e d i g e s t i o n in t h e r u m e n . F o r e x a m p l e , w h e n w h o l e b a r l e y w a s given to sheep, there was a greater number of cellulolytic bacteria (Mann and O r s k o v , 1 9 7 5 ) , a g r e a t e r r a t e o f f i b r e d i g e s t i o n , a n d a g r e a t e r v o l u n t a r y intake of hay (0rskov and Fraser, 1975), than when a similar amount of pelleted b a r l e y w a s g i v e n . S i m i l a r l y , 0 r s k o v e t al. ( 1 9 7 8 ) s h o w e d t h a t t h e v o l u n t a r y
0377-8401[81/0000--0000]$02.50 © 1981 Elsevier Scientific Publishing Company
348 intake of hay by cattle was decreased as the degree of processing of the cereal given as a supplement was increased. A new m e t h o d of cereal processing was described by 0rskov and Greenhalgh (1977) and Orskov et al. (1978), in which NaOH was sprayed on the whole grain in order to soften the fibrous husk, and cause some hydrolysis of the starch. The experiments described here were conducted in order to provide more information on the utilization of the NaOH-treated grain when it was given as a supplement to hay. MATERIALS AND METHODS
Experiment 1: utilization and digestibility o f diets based on either rolled or NaOH-treated barley Whole barley was treated with 30 g NaOH/kg air dry weight, applied as a solution containing 432 g/l, in a feed-mixer trailer. The barley was mixed for 45 min and then stored for a minimum of 10 days before mixing with hay. A further amount of the same sample of barley was rolled. Each barley was mixed with an equal weight of hay in a feed-mixer trailer. The NaOH-treated barley provided the same a m o u n t of barley dry matter as in the rolled-barley mix. During mixing, 5 kg urea, 5 kg calcium chloride, 1.5 kg sodium sulphate and 1.25 kg of trace minerals and vitamins were added as an aqueous solution per 1000 kg of mix. The composition of the trace minerals and vitamin mix was as described by Orskov and Grubb (1977). Sixteen Hereford X Friesian steers were grown from 325 to 425 kg liveweight, eight animals being allocated at random to receive each diet ad libitum. The cattle were penned in groups of four, and individual food intakes were recorded using Calan feed access doors (Calan Electronics, Glenrothes, Fife, Scotland). The steers were weighed weekly and rumen contents and carcass weights were determined at slaughter. Two further groups of three Friesian steers, each of approximately 200 kg live weight, were used to measure the digestibility of the two diets in a changeover design. The cattle were penned individually, and the diets were offered ad libitum. Food intakes by each animal were recorded for 21 days, and faeces were collected during the last 7 days of each period, while the cattle were held in metabolism cages.
Experiment 2: determination o f the optimum level o f NaOH application to barley given with hay The rate of NaOH-application adopted in Experiment 1 (30 g NaOH/kg air dry barley) was based on work in which NaOH-treated barley was the main ingredient of the diet (Orskov et al. 1980). The lower digestibility with NaOHtreated than with rolled grain found in Experiment 1 led us to believe that the o p t i m u m rate of NaOH application might be higher when grain was given
349
with roughages. Levels of 20, 30, 40 and 50 g NaOH/kg air-dry barley were used to determine the o p t i m u m application rate for barley destined to be given to steers with hay. The NaOH-treated barley--hay mixes were prepared as in Experiment 1 so as to provide diets containing equal amounts of barley dry matter and hay. In addition, a diet containing rolled barley was prepared, b u t the treatment was not part of the statistical design. Diets containing the NaOH-treated barley were given to 6 Hereford × Friesian steers, each weighing approximately 320 kg, and an incomplete latin square design of four periods was used. The arrangement of the animals was such that during any one period, two animals received one diet, t w o another, and the remainder each received one of the remaining mixes. The diets were offered ad libitum for 31 days, during the last 21 days of which voluntary food intake was determined. Faeces were collected for the last 7 days. The rolled barley and hay mix was given to all the animals in a fifth period.
Experiment 3: the effect o f the method o f processing barley on the uoluntary intake of straw and on the digestibility of fibre and starch by steers Whole barley was treated with NaOH solution to a level of 45 g NaOH/kg air
Experiment 1 The effects of using complete diets of hay with either NaOH-treated or rolled barley are given in Table I. The live weight gains were exceptionally good for the t y p e of animals. None of the differences between the two methods of processing cereal in Table I was statistically significant.
350 TABLE I Experiment 1 : the effect of feeding steers on NaOH-treated (30 g/kg) or rolled barley with chopped hay on food utilization Treatment NaOH-treated barley Growth trial Live weight gain Dry matter intake (kg/day) Food conversion (kg dry matter/ kg gain) Rumen contents (kg) Killing-out percentage Digestibility trial Dry matter intake (kg/day) Apparent digestibility (%) of: Dry matter Organic matter Acid-detergent fibre
Rolled barley
SE of treatment differences
Level significance
1.42
1.24
0.149
NS
9.7
8.7
0.56
NS
7.0
7.0
0.67
NS
46.2
41.4
3.05
NS
51.2
51.0
1.01
NS
6.8
6.6
0.2
NS
60.2
66.2
1.4
**
59.5
66.8
1.6
**
59.1
51.2
5.6
NS
**Significant at P < 0.01. NS = not significant.
T h e effects o f t h e m e t h o d o f cereal processing o n f o o d i n t a k e and digestibili t y are also given in T a b l e I. Again, t h e r e w e r e no significant d i f f e r e n c e s in f o o d i n t a k e , b u t t h e digestibility o f b o t h DM a n d OM was g r e a t e r f o r t h e steers w h i c h received rolled r a t h e r t h a n N a O H - t r e a t e d b a r l e y (P < 0.01). T h e d i f f e r e n c e in t h e digestibility o f A D F was non-significant. Experiment 2 T h e e f f e c t o n t h e digestibility o f t h e w h o l e diet o f d i f f e r e n t rates o f applicat i o n o f N a O H t o b a r l e y is given in T a b l e II. T h e digestibility o f a diet in w h i c h rolled b a r l e y r e p l a c e d N a O H - t r e a t e d b a r l e y is also s h o w n , b u t since this treatm e n t did n o t f o r m p a r t o f t h e m a i n e x p e r i m e n t a l design, t h e s t a n d a r d errors are n o t a p p l i c a b l e t o this t r e a t m e n t . T h e r e w e r e no significant d i f f e r e n c e s in f o o d i n t a k e , a l t h o u g h t h e r e a p p e a r s to b e a m a x i m u m at a b o u t 40 g N a O H / k g b a r l e y . T h e digestibility o f DM a n d OM increased linearly as t h e a m o u n t o f N a O H a p p l i e d increased (P < 0.05). This increase a p p e a r e d t o level o f f at ap-
351 TABLE II Experiment 2 : the intake and digestibility of diets containing 50% hay and either whole barley, treated with various amounts of NaOH, or rolled barley NaOH application (g[kg barley)
Dry matter intake (g/kg W°'TS/day)
Apparent digestibility (%) of Dry matter
Organic matter
Acid-detergent fibre
Starch
20 30 40 50 SE of treatment differences Rolled barley I
77.4 78.8 87.8 80.2
60.9 62.0 65.7 64.1
62.0 64.0 66.2 65.1
43.2 44.6 45.6 43.4
79.6 77.8 86.7 88.0
+-6.94 75.9
-+1.96 66.2
51.99 67.4
±5.84 42.7
±2.86 97.6
SE not applicable to this treatment.
plication greater than 40 g NaOH, b u t the curvilinear trend was not significant None of the differences in the digestibility of ADF were significant. The digestibility of starch increased linearly with NaOH application (P < 0.001), and again, whereas there appeared to be a diminishing response to NaOHtreated, the curvilinear trend was not significant. Although no statistical comparison can be made, the digestibility of the diet containing rolled barley appeared to be similar to that of the diets containing barley treated with 40 or 50 g NaOH/kg. The digestibility of starch, however, was clearly greatest with the rolled barley diet.
Experiment 3 The effect of giving different amounts of either rolled or NaOH-treated barley to steers is given in Table III. The intake of straw b y the steers was, as expected, reduced when a higher level of grain was given (P < 0.001). The TABLE III Experiment 3 : voluntary intake of long straw and digestibility of the total diet by steers given either NaOH-treated (45 g]kg) or rolled barley as a supplement Barley supplemerit (g]kg W°'TS/day)
Processing
25 25 50 50 SE of treatment differences
NaOH treated Rolled NaOH treated Rolled
Intake (g DM/kg Apparent digestibility (%) of W°'TS/day) Dry Organic Acid-deterStraw Barley matter matter gent fibre
Starch
43.3 42.5 33.5 30.6 ± 3.0
24.7 25.1 47.7 48.3
55.9 55.3 65.8 64.9
55.8 56.5 65.9 66.4
51.6 48.6 47.1 44.0
87.9 95.4 92.8 97.6
-+2.0
± 2.3
± 8.5
-+1.5
352 small differences in intake between steers given NaOH-treated and rolled barley were not significant. The digestibility of DM (P < 0.001), OM (P 0.001) and starch (P < 0.01) in the total diet increased as the amount of grain given increased, but differences due to barley treatment were non-significant. There was no significant difference between treatments in the digestibility of ADF. DISCUSSION In Experiment 1, the results for digestibility, and to some extent, for food conversion of the diet containing NaOH-treated barley, were somewhat disappointing. It might have been expected that food utilization would have been superior for NaOH-treated rather than for rolled barley, since food intake tended to be higher when the NaOH-treated grain was used. However, when digestibility was determined, it was clear that intake of digestible OM was similar for the two treatments since the digestibility was lower for the diet which contained NaOH-treated barley. This led us to examine whether the optimum application rate of NaOH determined in experiments in which barley was the main ingredient was valid when the grain was given as a supplement to roughage. The results from Experiment 2 showed that 40 g NaOH/kg air dry barley was required, whereas the experiments of 0rskov et al. (1980) indicated that 30 g NaOH/kg was sufficient to achieve o p t i m u m digestibility when grain was the sole feed. The difference in the application rate required may be due to the effect of roughage on the rate of passage of small particles from the rumen. The observation that the outflow rate of small particles from the rumen can be accelerated when small particles form part of a diet consisting of long particles was first made by Balch (1950). He demonstrated that the rate of passage of small particles from the rumen was considerably greater when they were given with a long roughage diet than when t h e y formed part of a completely ground diet. These observations have since been confirmed m a n y times for the outflow of starch (0rskov et al. 1969; Thomson and Lamming, 1972), for protein supplements (Ganev et al., 1979), and for whole grains given to sheep (0rskov and Fraser, 1975) and cattle (Nordin and Campling, 1976). The same observation has also been made when NaOHtreated grains have been included in silage-based diets (0rskov et al., 1981). Since it was shown by 0rskov and Greenhalgh (1977) that the rate of digestion of NaOH-treated grain increased as the rate of application of NaOH increased, the difference in application rate between 30 and 40 g/kg may be due to the fact that a faster rate of digestion is required to ensure a more complete digestion of the grain before it leaves the rumen. The fact that the organic matter digestibility of NaOH-treated grain was equal to that of rolled barley, but that the starch digestion was clearly better with rolled than with NaOH-treated barley, may indicate a greater digestibility of fibre given with the NaOH-treated grain.
353
The high starch
REFERENCES Balch, C.C., 1950. Factors affecting the utilization of food by dairy cows. 1. Rate of passage of food through the digestive tract. Br. J. Nutr., 4 : 361--388. Ganev, G., 0rskov, E.R. and Smart, R.I., 1979. The effect of roughage or concentrate feeding and rumen retention time on total degradation of protein in the rumen. J. Agric. Sci. (Cambridge), 93: 651--656. Mann, S.O. and 0rskov, E.R., 1975. The effect of feeding whole or pelleted barley to lambs on some parameters of their rumen microbial population. Proc. Nutr. Soc., 34 : 63A. Nordin, M. and Campling, R.C., 1976. Effect of the amount and form of roughage in the diet on digestibility of whole maize grains in cows and steers. J. Agric. Sci. (Cambridge), 87 : 213--219. ~}rskov, E.R., Barnes, B.J. and Lukins, B.A., 1980. A note on the effect of different amounts of NaOH application on digestibility by cattle of barley, oats, wheat and maize. J. Agric. Sci. (Cambridge), 94: 271--273. ~}rskov, E.R., Barnes, B.J., Macdearmid, A., Williams, P.E.V. and Innes, G.M., 1981. Utilization of alkali-treated grain. 3. Utilization by steers of NaOH-treated and rolled barley in silage-based diets. Anita. Feed Sci. Technol., 6: 355--365. ~)rskov, E.R. and Fraser, C., 1975. The effects of processing of barley-based supplements on rumen pH, rate of digestion and voluntary intake of dried grass in sheep. Br. J. Nutr., 34 : 493--500.
354 Orskov, E.R., Fraser, C. and Kay, R.N.B., 1969. Dietary factors influencing the digestion of starch in the rumen and small and large intestine of early weaned lambs. Br. J. Nutr., 23: 217--226. Orskov, E.R. and Greenhalgh, J.F.D., 1977. Alkali treatment as a method of processing whole grain for cattle. J. Agric. Sci. (Cambridge), 89: 253--255. Orskov, E.R. and Grubb, D.A., 1977. The use of a whole barley diet fortified with solutions of urea, minerals and vitamins for Iambs. Anita. Feed Sci. Technol., 2: 307--314. Orskov, E.R., Soliman, H.S. and Macdearmid, A., 1978. Intake of hay by cattle given supplements of barley subjected to various forms of physical treatment or treatment with alkali. J. Agrie. Sci. (Cambridge), 90 : 611--615. Thivend, P., Mercier, C. and Guillot, A., 1965. Estimation of starch in complex media. Ann. Biol. Anita. Biochem. Biophys., 5: 513--526. Thomson, F. and Lamming, G.E., 1972. The flow of digesta, dry matter and starch to the duodenum in sheep given rations containing straw of varying particle size. Br. J. Nutr., 28 : 391--403. Van Soest, P.J., 1963. Use of detergents in the analysis of fibrous feeds. II. A rapid method for determination of fibre and lignin. J. Assoc. Off. Agric. Chem., 46: 829--835.
347
UTILIZATION OF ALKALI-TREATED G R A I N . 2. U T I L I Z A T I O N B Y STEERS OF DIETS BASED ON HAY OR STRAW AND MIXED WITH EITHER NaOH-TREATED OR ROLLED BARLEY
B.J. BARNES and E.R. ~)RSKOV R o w e t t Research Institute, Bucksburn, Aberdeen AB2 9SB (Gt. Britain)
(Received 13 November 1980; accepted for publication 16 March 1981)
SUMMARY Barnes, B.J. and Orskov, E.R., 1981. Utilization of alkali-treated grain. 2. Utilization by steers of diets based on hay or straw and mixed with either NaOH-treated or rolled barley. Anim. Feed Sci. Technol., 6: 347--354. In the first of three experiments, Hereford cross steers were fed ad libitum from 325 kg to slaughter at 425 kg on diets containing 50% hay and 50% rolled or NaOH-treated (30 g]kg) barley. Liveweight gain and food conversion ratios were similar for the two groups (1.24 vs. 1.42 kg/day; 7.0 vs. 7.0 kg dry matter intake/kg gain, respectively). Dry matter and organic matter digestibility was significantly higher (P < 0.01) when the diet contained rolled, rather than NaOH-treated, barley. There were no significant differences in fibre digestibility (51.2 vs. 59.1%, respectively). In the second experiment, the optimum level of NaOH was determined for the treatment of barley when given with hay. The level of NaOH required to achieve a digestibility in whole barley similar to rolled barley was 40 g NaOH]kg, i.e., approximately 10 g/kg more than when NaOH-treated barley formed the sole component of the diet. Dry matter and organic matter digestibility increased linearly as the level of NaOH applied increased (P < 0.05) and tended to peak at 40 g NaOH/kg barley. Starch digestibility also increased linearly (P < 0.001). Fibre digestibility did not vary significantly between treatments. In the third experiment, the voluntary intake of straw by steers given rolled or NaOHtreated barley at two levels of supplementation was determined. The intake of straw was slightly, but not significantly, greater when NaOH-treated rather than rolled barley was used. The digestibility of dry matter, organic matter, starch and fibre was not significantly affected by method of cereal treatment. No problems of animal health arose throughout the three experiments.
INTRODUCTION The extent of processing of cereals can have serious repercussions on the r a t e o f c e l l u l o s e d i g e s t i o n in t h e r u m e n . F o r e x a m p l e , w h e n w h o l e b a r l e y w a s given to sheep, there was a greater number of cellulolytic bacteria (Mann and O r s k o v , 1 9 7 5 ) , a g r e a t e r r a t e o f f i b r e d i g e s t i o n , a n d a g r e a t e r v o l u n t a r y intake of hay (0rskov and Fraser, 1975), than when a similar amount of pelleted b a r l e y w a s g i v e n . S i m i l a r l y , 0 r s k o v e t al. ( 1 9 7 8 ) s h o w e d t h a t t h e v o l u n t a r y
0377-8401[81/0000--0000]$02.50 © 1981 Elsevier Scientific Publishing Company
348 intake of hay by cattle was decreased as the degree of processing of the cereal given as a supplement was increased. A new m e t h o d of cereal processing was described by 0rskov and Greenhalgh (1977) and Orskov et al. (1978), in which NaOH was sprayed on the whole grain in order to soften the fibrous husk, and cause some hydrolysis of the starch. The experiments described here were conducted in order to provide more information on the utilization of the NaOH-treated grain when it was given as a supplement to hay. MATERIALS AND METHODS
Experiment 1: utilization and digestibility o f diets based on either rolled or NaOH-treated barley Whole barley was treated with 30 g NaOH/kg air dry weight, applied as a solution containing 432 g/l, in a feed-mixer trailer. The barley was mixed for 45 min and then stored for a minimum of 10 days before mixing with hay. A further amount of the same sample of barley was rolled. Each barley was mixed with an equal weight of hay in a feed-mixer trailer. The NaOH-treated barley provided the same a m o u n t of barley dry matter as in the rolled-barley mix. During mixing, 5 kg urea, 5 kg calcium chloride, 1.5 kg sodium sulphate and 1.25 kg of trace minerals and vitamins were added as an aqueous solution per 1000 kg of mix. The composition of the trace minerals and vitamin mix was as described by Orskov and Grubb (1977). Sixteen Hereford X Friesian steers were grown from 325 to 425 kg liveweight, eight animals being allocated at random to receive each diet ad libitum. The cattle were penned in groups of four, and individual food intakes were recorded using Calan feed access doors (Calan Electronics, Glenrothes, Fife, Scotland). The steers were weighed weekly and rumen contents and carcass weights were determined at slaughter. Two further groups of three Friesian steers, each of approximately 200 kg live weight, were used to measure the digestibility of the two diets in a changeover design. The cattle were penned individually, and the diets were offered ad libitum. Food intakes by each animal were recorded for 21 days, and faeces were collected during the last 7 days of each period, while the cattle were held in metabolism cages.
Experiment 2: determination o f the optimum level o f NaOH application to barley given with hay The rate of NaOH-application adopted in Experiment 1 (30 g NaOH/kg air dry barley) was based on work in which NaOH-treated barley was the main ingredient of the diet (Orskov et al. 1980). The lower digestibility with NaOHtreated than with rolled grain found in Experiment 1 led us to believe that the o p t i m u m rate of NaOH application might be higher when grain was given
349
with roughages. Levels of 20, 30, 40 and 50 g NaOH/kg air-dry barley were used to determine the o p t i m u m application rate for barley destined to be given to steers with hay. The NaOH-treated barley--hay mixes were prepared as in Experiment 1 so as to provide diets containing equal amounts of barley dry matter and hay. In addition, a diet containing rolled barley was prepared, b u t the treatment was not part of the statistical design. Diets containing the NaOH-treated barley were given to 6 Hereford × Friesian steers, each weighing approximately 320 kg, and an incomplete latin square design of four periods was used. The arrangement of the animals was such that during any one period, two animals received one diet, t w o another, and the remainder each received one of the remaining mixes. The diets were offered ad libitum for 31 days, during the last 21 days of which voluntary food intake was determined. Faeces were collected for the last 7 days. The rolled barley and hay mix was given to all the animals in a fifth period.
Experiment 3: the effect o f the method o f processing barley on the uoluntary intake of straw and on the digestibility of fibre and starch by steers Whole barley was treated with NaOH solution to a level of 45 g NaOH/kg air
Experiment 1 The effects of using complete diets of hay with either NaOH-treated or rolled barley are given in Table I. The live weight gains were exceptionally good for the t y p e of animals. None of the differences between the two methods of processing cereal in Table I was statistically significant.
350 TABLE I Experiment 1 : the effect of feeding steers on NaOH-treated (30 g/kg) or rolled barley with chopped hay on food utilization Treatment NaOH-treated barley Growth trial Live weight gain Dry matter intake (kg/day) Food conversion (kg dry matter/ kg gain) Rumen contents (kg) Killing-out percentage Digestibility trial Dry matter intake (kg/day) Apparent digestibility (%) of: Dry matter Organic matter Acid-detergent fibre
Rolled barley
SE of treatment differences
Level significance
1.42
1.24
0.149
NS
9.7
8.7
0.56
NS
7.0
7.0
0.67
NS
46.2
41.4
3.05
NS
51.2
51.0
1.01
NS
6.8
6.6
0.2
NS
60.2
66.2
1.4
**
59.5
66.8
1.6
**
59.1
51.2
5.6
NS
**Significant at P < 0.01. NS = not significant.
T h e effects o f t h e m e t h o d o f cereal processing o n f o o d i n t a k e and digestibili t y are also given in T a b l e I. Again, t h e r e w e r e no significant d i f f e r e n c e s in f o o d i n t a k e , b u t t h e digestibility o f b o t h DM a n d OM was g r e a t e r f o r t h e steers w h i c h received rolled r a t h e r t h a n N a O H - t r e a t e d b a r l e y (P < 0.01). T h e d i f f e r e n c e in t h e digestibility o f A D F was non-significant. Experiment 2 T h e e f f e c t o n t h e digestibility o f t h e w h o l e diet o f d i f f e r e n t rates o f applicat i o n o f N a O H t o b a r l e y is given in T a b l e II. T h e digestibility o f a diet in w h i c h rolled b a r l e y r e p l a c e d N a O H - t r e a t e d b a r l e y is also s h o w n , b u t since this treatm e n t did n o t f o r m p a r t o f t h e m a i n e x p e r i m e n t a l design, t h e s t a n d a r d errors are n o t a p p l i c a b l e t o this t r e a t m e n t . T h e r e w e r e no significant d i f f e r e n c e s in f o o d i n t a k e , a l t h o u g h t h e r e a p p e a r s to b e a m a x i m u m at a b o u t 40 g N a O H / k g b a r l e y . T h e digestibility o f DM a n d OM increased linearly as t h e a m o u n t o f N a O H a p p l i e d increased (P < 0.05). This increase a p p e a r e d t o level o f f at ap-
351 TABLE II Experiment 2 : the intake and digestibility of diets containing 50% hay and either whole barley, treated with various amounts of NaOH, or rolled barley NaOH application (g[kg barley)
Dry matter intake (g/kg W°'TS/day)
Apparent digestibility (%) of Dry matter
Organic matter
Acid-detergent fibre
Starch
20 30 40 50 SE of treatment differences Rolled barley I
77.4 78.8 87.8 80.2
60.9 62.0 65.7 64.1
62.0 64.0 66.2 65.1
43.2 44.6 45.6 43.4
79.6 77.8 86.7 88.0
+-6.94 75.9
-+1.96 66.2
51.99 67.4
±5.84 42.7
±2.86 97.6
SE not applicable to this treatment.
plication greater than 40 g NaOH, b u t the curvilinear trend was not significant None of the differences in the digestibility of ADF were significant. The digestibility of starch increased linearly with NaOH application (P < 0.001), and again, whereas there appeared to be a diminishing response to NaOHtreated, the curvilinear trend was not significant. Although no statistical comparison can be made, the digestibility of the diet containing rolled barley appeared to be similar to that of the diets containing barley treated with 40 or 50 g NaOH/kg. The digestibility of starch, however, was clearly greatest with the rolled barley diet.
Experiment 3 The effect of giving different amounts of either rolled or NaOH-treated barley to steers is given in Table III. The intake of straw b y the steers was, as expected, reduced when a higher level of grain was given (P < 0.001). The TABLE III Experiment 3 : voluntary intake of long straw and digestibility of the total diet by steers given either NaOH-treated (45 g]kg) or rolled barley as a supplement Barley supplemerit (g]kg W°'TS/day)
Processing
25 25 50 50 SE of treatment differences
NaOH treated Rolled NaOH treated Rolled
Intake (g DM/kg Apparent digestibility (%) of W°'TS/day) Dry Organic Acid-deterStraw Barley matter matter gent fibre
Starch
43.3 42.5 33.5 30.6 ± 3.0
24.7 25.1 47.7 48.3
55.9 55.3 65.8 64.9
55.8 56.5 65.9 66.4
51.6 48.6 47.1 44.0
87.9 95.4 92.8 97.6
-+2.0
± 2.3
± 8.5
-+1.5
352 small differences in intake between steers given NaOH-treated and rolled barley were not significant. The digestibility of DM (P < 0.001), OM (P 0.001) and starch (P < 0.01) in the total diet increased as the amount of grain given increased, but differences due to barley treatment were non-significant. There was no significant difference between treatments in the digestibility of ADF. DISCUSSION In Experiment 1, the results for digestibility, and to some extent, for food conversion of the diet containing NaOH-treated barley, were somewhat disappointing. It might have been expected that food utilization would have been superior for NaOH-treated rather than for rolled barley, since food intake tended to be higher when the NaOH-treated grain was used. However, when digestibility was determined, it was clear that intake of digestible OM was similar for the two treatments since the digestibility was lower for the diet which contained NaOH-treated barley. This led us to examine whether the optimum application rate of NaOH determined in experiments in which barley was the main ingredient was valid when the grain was given as a supplement to roughage. The results from Experiment 2 showed that 40 g NaOH/kg air dry barley was required, whereas the experiments of 0rskov et al. (1980) indicated that 30 g NaOH/kg was sufficient to achieve o p t i m u m digestibility when grain was the sole feed. The difference in the application rate required may be due to the effect of roughage on the rate of passage of small particles from the rumen. The observation that the outflow rate of small particles from the rumen can be accelerated when small particles form part of a diet consisting of long particles was first made by Balch (1950). He demonstrated that the rate of passage of small particles from the rumen was considerably greater when they were given with a long roughage diet than when t h e y formed part of a completely ground diet. These observations have since been confirmed m a n y times for the outflow of starch (0rskov et al. 1969; Thomson and Lamming, 1972), for protein supplements (Ganev et al., 1979), and for whole grains given to sheep (0rskov and Fraser, 1975) and cattle (Nordin and Campling, 1976). The same observation has also been made when NaOHtreated grains have been included in silage-based diets (0rskov et al., 1981). Since it was shown by 0rskov and Greenhalgh (1977) that the rate of digestion of NaOH-treated grain increased as the rate of application of NaOH increased, the difference in application rate between 30 and 40 g/kg may be due to the fact that a faster rate of digestion is required to ensure a more complete digestion of the grain before it leaves the rumen. The fact that the organic matter digestibility of NaOH-treated grain was equal to that of rolled barley, but that the starch digestion was clearly better with rolled than with NaOH-treated barley, may indicate a greater digestibility of fibre given with the NaOH-treated grain.
353
The high starch
REFERENCES Balch, C.C., 1950. Factors affecting the utilization of food by dairy cows. 1. Rate of passage of food through the digestive tract. Br. J. Nutr., 4 : 361--388. Ganev, G., 0rskov, E.R. and Smart, R.I., 1979. The effect of roughage or concentrate feeding and rumen retention time on total degradation of protein in the rumen. J. Agric. Sci. (Cambridge), 93: 651--656. Mann, S.O. and 0rskov, E.R., 1975. The effect of feeding whole or pelleted barley to lambs on some parameters of their rumen microbial population. Proc. Nutr. Soc., 34 : 63A. Nordin, M. and Campling, R.C., 1976. Effect of the amount and form of roughage in the diet on digestibility of whole maize grains in cows and steers. J. Agric. Sci. (Cambridge), 87 : 213--219. ~}rskov, E.R., Barnes, B.J. and Lukins, B.A., 1980. A note on the effect of different amounts of NaOH application on digestibility by cattle of barley, oats, wheat and maize. J. Agric. Sci. (Cambridge), 94: 271--273. ~}rskov, E.R., Barnes, B.J., Macdearmid, A., Williams, P.E.V. and Innes, G.M., 1981. Utilization of alkali-treated grain. 3. Utilization by steers of NaOH-treated and rolled barley in silage-based diets. Anita. Feed Sci. Technol., 6: 355--365. ~)rskov, E.R. and Fraser, C., 1975. The effects of processing of barley-based supplements on rumen pH, rate of digestion and voluntary intake of dried grass in sheep. Br. J. Nutr., 34 : 493--500.
354 Orskov, E.R., Fraser, C. and Kay, R.N.B., 1969. Dietary factors influencing the digestion of starch in the rumen and small and large intestine of early weaned lambs. Br. J. Nutr., 23: 217--226. Orskov, E.R. and Greenhalgh, J.F.D., 1977. Alkali treatment as a method of processing whole grain for cattle. J. Agric. Sci. (Cambridge), 89: 253--255. Orskov, E.R. and Grubb, D.A., 1977. The use of a whole barley diet fortified with solutions of urea, minerals and vitamins for Iambs. Anita. Feed Sci. Technol., 2: 307--314. Orskov, E.R., Soliman, H.S. and Macdearmid, A., 1978. Intake of hay by cattle given supplements of barley subjected to various forms of physical treatment or treatment with alkali. J. Agrie. Sci. (Cambridge), 90 : 611--615. Thivend, P., Mercier, C. and Guillot, A., 1965. Estimation of starch in complex media. Ann. Biol. Anita. Biochem. Biophys., 5: 513--526. Thomson, F. and Lamming, G.E., 1972. The flow of digesta, dry matter and starch to the duodenum in sheep given rations containing straw of varying particle size. Br. J. Nutr., 28 : 391--403. Van Soest, P.J., 1963. Use of detergents in the analysis of fibrous feeds. II. A rapid method for determination of fibre and lignin. J. Assoc. Off. Agric. Chem., 46: 829--835.