High temperature and pressure processing of maize cobs. II. Animal response and effect of sodium metabisulphite

Animal Feed Science and Technology, 14 (1986) 161--169 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

161

H I G H T E M P E R A T U R E A N D PRESSURE PROCESSING OF MAIZE COBS. II. A N I M A L R E S P O N S E A N D E F F E C T O F S O D I U M M E T A B I S U L P H I T E *

N.N. UMUNNA**, R.R. BARTLING*** and T.J. KLOPFENSTEIN

Department o f Animal Science, Institute o f Agriculture and Natural Resources, University o f Nebraska, Lincoln, NE 68583 (U.S.A.) (Received 28 September 1983; accepted for publication 19 July 1985)

ABSTRACT Umunna, N.N., Bartling, R.R. and Klopfenstein, T.J., 1986. High temperature and pressure processing of maize cobs. II. Animal response and effect of sodium metabisulphite. A nim. Feed Sci. Technol., 14: 161--169. In two separate trials with lambs, high temperature (250¢C) and pressure (17.5 kg c m 2 ) processing of maize cobs increased (P < 0.05) dry matter digestibility, intake and weight gain. However, the increase in dry matter intake was maintained only for the first 28 days of the trial. The later decrease in intake could have been related to non-enzymic browning reaction which accompanied processing. The efficiency of sodium metabisulphite in reducing or eliminating the effects on animal performance of the browning reaction was tested in three subsequent studies. The addition of 1% sodium metabisulphite to processed cobs improved (P <: 0.05) digestibility in vitro and in vivo but did not affect protein digestibility nor nitrogen retention. Protein digestibility was also improved (P < 0.05) by processing pressure. In a growth study, the addition of the chemical (1.5%) was associated with a depression in feed intake which could be attributed to the deleterious effects of high residual sulphur.

INTRODUCTION Several reports have shown that steam processing of low quality roughages r e s u l t s in i n c r e a s e d a v a i l a b i l i t y o f e n e r g y b y s o l u b i l i z a t i o n o f t h e cell w a l l c o n s t i t u e n t ( G u g g o l z e t al., 1 9 7 1 ; Oji a n d M o w a t , 1 9 7 8 ) . I n e a r l i e r w o r k , ( U m u n n a e t al., 1 9 8 5 ) p r o c e s s i n g o f m a i z e c o b s b y e x p o s u r e t o high t e m p e r a t u r e a n d p r e s s u r e was f o u n d t o i m p r o v e d i g e s t i b i l i t y in v i t r o . I t w a s also n o t e d t h a t t h e p r o c e s s e d c o r n c o b s w e r e d a r k b r o w n i n c o l o u r . V a n S o e s t ( 1 9 6 5 ) h a d n o t e d a s i m i l a r c o l o u r c h a n g e o f h e a t e d f o r a g e s as a r e s u l t o f n o n - e n z y m i c b r o w n i n g r e a c t i o n w h i c h also led t o i n c r e a s e d *Published with the approval of the Director, Nebraska Agricultural Experiment Station. **Present address: Animal Science Department, Faculty of Agriculture, Ahmadu Bello University, P.M.B. 1044, Zaria, Nigeria. ***Present address: P.O. Box 1559, Guymon, OK 73842, U.S.A. 0377-840 t/86/$03.50

6) 1986 Elsevier Science Publishers B.V.

162 y i e l d s o f lignin a n d f i b r e . S i n c e b o t h f a c t o r s c o u l d r e d u c e t h e u t i l i z a t i o n o f p r o c e s s e d m a t e r i a l , t h e p r e s e n t s t u d y w a s u n d e r t a k e n to d e t e r m i n e (1) a n i m a l r e s p o n s e t o high t e m p e r a t u r e - a n d p r e s s u r e - t r e a t e d m a i z e c o b s a n d (2) w h e t h e r s o d i u m m e t a b i s u l p h i t e c o u l d be e f f e c t i v e in r e d u c i n g t h e effect of non-enzymic browning reaction. MATERIALS AND METHODS T h e m a i z e c o b s u s e d in this s t u d y w e r e p r o c e s s e d b y a m e t h o d s i m i l a r to that of Erlinger and Klopfenstein (1975). The cobs were ground through a 1 . 2 - c m s c r e e n a n d p r o c e s s e d in a p r e s s u r e vessel b y i n j e c t i o n o f s t e a m . T h e vessel w a s e m p t i e d b y o p e n i n g a ball valve at its b o t t o m a n d b l o w i n g t h e m a t e r i a l i n t o a c y c l o n e s e p a r a t o r w h e r e t h e s t e a m a n d gases p r o d u c e d d u r i n g p r o c e s s i n g w e r e d r i v e n off.

Experiment 1 T w e l v e S u f f o l k w e t h e r s w e r e assigned t o t h r e e t r e a t m e n t s at r a n d o m . T h e d i e t s w e r e : (1) c o n t r o l , u n p r o c e s s e d m a i z e c o b s ; (2) c o b s p r o c e s s e d f o r 35 s at 17.5 kg c m - 2 ; a n d (3) c o b s p r o c e s s e d f o r 65 s at 17.5 kg c m -2. E a c h l a m b was i n d i v i d u a l l y f e d o n 8 0 0 g o f d r y m a t t e r o f t h e r a t i o n s cons i s t i n g o f 29% a l f a l f a h a y a n d 71% c o b s a n d h a v i n g a c r u d e p r o t e i n c o n t e n t o f 12.5% ( d r y m a t t e r basis). T h e l a m b s w e r e f e d o n c e d a i l y f o r a p r e l i m i n a r y p e r i o d o f 7 d a y s w h i c h was i m m e d i a t e l y f o l l o w e d b y a 7 - d a y t o t a l f a e c a l collection. TABLEI Composition of diets used in Experiments 2, 4 and 5 (%) Ingredients

Maize cobs ~ Cane molasses Hay Soya bean meal Salt Dicalcium phosphate Trace mineral and vitamins2 Trace mineralsa Vitamin A4 Vitamin D4

Experiment 2

4

5

50.0 5.0 27.2 17.0 0.3 0.45 0.50 --

84.88 2.96 3.33 8.41 0.13 0.29 -0.02 -

70.00 5.0 6.73 17.27 0.30 0.65 -0.05 + +

1 Control or treated cobs according to treatments. 2 Added to provide 10 000 and 3000 I.U. head -I day -I of vitamins A and D, respectively. 3 Contained 10% Mn, 10% Zn, 1% Cu, 0.3% I and 0.1% Co. 4 Added to provide 10 000 and 3000 I.U. head -1 day -1 of vitamins A and D, respectively.

163

Experiment 2 This lamb growth trial was conducted to compare the performance lambs fed on unprocessed cobs in restricted quantities (Treatment 1), ad libitum (Treatment 2), and processed cobs restricted (Treatment 3) ad libitum (Treatment 4). Cobs were processed at a pressure of 17.5 cm -2 for 50 s at 250°C. T w e n t y Suffolk wether lambs were used in the study which lasted for 54 days. On the basis of initial weight, the lambs were r a n d o m l y allotted to the four treatments. They were individually fed on the experimental diets shown in Table I, the only variable being the maize cobs portion (i.e., processed versus unprocessed). In order to m o n i t o r the progress of the lambs, bi-weekly weights were recorded. All weights (initial, bi-weekly and final) were taken after a 16-h fast (without feed and water).

of or or kg

Experiment 3 This study was carried out to determine the effect of sodium metabisulphite on dry matter disappearance in vitro (IVDMD) of processed ground maize cobs (Tilley and Terry, 1963). The moisture content of the ground cobs was increased to 65% by the addition of water; sodium meLabisulphite was then added at 0, 1, 2 and 3% of dry matter. Each batch of cobs was then processed for 30 s at 6, 10.5, 17.5, 21, 24.5 and 28 kg cm -2 pressure at 250°C. Samples from each level of chemical and pressure treatments were oven-dried at 70°C prior to IVDMD analysis.

Experiment 4 The cobs used in this study were processed for 50 s at 250°C and pressure levels of 10.5, 14 and 17.5 kg cm -2 and 66% moisture, with sodium metabisulphite added at levels of 0, 1 and 2% of the cobs dry matter. The lambs were given the experimental diets (Table I) individually, once daily for an adjustment period of 7 days which was immediately followed by a 7-day total collection period. Two collection periods were run with three lambs per treatment per diet.

Experiment 5 Twenty-four Suffolk wether lambs were used in this 69-day growth study. On the basis of initial weight, lambs were assigned randomly to four treatments: (1) unprocessed maize cobs; (2) processed cobs (14 kg cm-2); (3) processed cobs (17.5 kg cm-2); (4) processed cobs (17.5 kg cm -2) with 1.5% sodium metabisulphite. Maize cobs used in Treatments 2, 3 and 4 were brought to 50% moisture before processing for 50 s at 250°C. The experimental diets (Table I), which included 70% cobs, were

164 g i v e n ad l i b i t u m o n a n i n d i v i d u a l basis. S a m p l e s o f t h e d i e t w e r e l a t e r assayed for IVDMD. A n a l y s e s of dry m a t t e r a n d n i t r o g e n in feed and faecal samples were made according to the Association of Official Analytical Chemists (1970). S t a t i s t i c a l a n a l y s e s o f t h e d a t a w e r e d o n e a c c o r d i n g to S t e e l a n d T o r r i e (1960). RESULTS AND DISCUSSION

Experiment 1 D r y m a t t e r d i g e s t i b i l i t y w a s i m p r o v e d (P < was unaffected by length of processing (Table i b i l i t y was n e i t h e r a f f e c t e d b y p r o c e s s i n g n o r b y i n c r e a s e d s o l u b i t i z a t i o n o f cell w a l l c o n s t i t u e n t s

0.05) by processing but II). C r u d e p r o t e i n d i g e s t length of processing. The which accompanies steam

TABLE II Experiment 1. Dry matter and crude protein digestibility t Treatment:

Dry matter digestibility (%) Protein digestibility (%)

Control

Processed maize cobs

1

2 35 s

3 65 s •

63.0 b 64.5

64.2 b ÷ 1.22 67.3 _, 1.54

57.7 a 68.0

SE

Average of four replications. 2Treatment 2 was pressure-treated at 17.5 kg cm -2 for 35 s and treatment 3 for 65 s at the same pressure. Values in the same row with different superscripts differ significantly (P < 0.05). TABLE III Experiment 2. Results of lamb growth study I Unprocessed maize cobs Processed maize cobs

Average daily gain (g) Average daily feed intake (g) Feed/gain

Restricted Ad libitum

Restricted Ad libitum

69.0 a 699.0 a 10.1 a

64.9 a 713.0 a 11.0 a

99.9 b 876.0 b 8.8 a ' b

180.7 c 1144.0 c 6.35

i No standard errors are included in this table because they were lost after the completion of the statistical analysis. Values in the same row with different superscripts differ significantly (P < 0.05).

165 processing of low quality roughages could account for the increased digestibility observed in this study (Guggolz et al., 1971; Oji and Mowat, 1978; U m u n n a et al., 1985). The lack of further increase in digestibility with increase in processing time would seem to suggest that 35 s was adequate for the reactions that are involved in solubilizing the cell wall constituents.

Experiment 2 Processing of cobs increased (P < 0.05) average daily gains (ADG) when the diets were given ad libitum (Table III). However, when the diets were restricted, there was no difference in daily gain between lambs fed on processed or unprocessed cobs. The restriction of feed intake would have the effect of limiting the nutrients available to the lambs. Given that feed intakes of all lambs on the restricted treatments were almost equal, the level of energy available from the processed cobs fed restricted would not be expected to produce significantly higher gains. However, when the diets were offered free choice, the increased intake by lambs of the processed and, therefore, more digestible material gave higher gains than for lambs fed the unprocessed material. Feed efficiency followed a similar pattern as ADG. Average daily feed consumption was highest (P < 0.05) for the lambs fed on processed cobs ad libitum; however, this lasted for only the first 28 days of the experiment. Overall performance of animals fed on processed cobs ad libitum would probably have been better if initial levels of intake had been maintained. A similar reduction in the intake of high-temperatureand pressure-processed wheat straw had been observed with lambs (N.N. U m u n n a and T.J. Klopfenstein, unpublished data, 1972). The processed maize cobs were dark brown in colour. Van Soest (1965) noted a similar colour change for forage dried by heating especially in the presence of moisture and reported that the colour change was due to non-enzymic browning reaction. Since non-enzymic browning reaction leads to increase in artefact lignin, fibre and insoluble protein, it is not clear whether the reaction was responsible for the reduced intake noted after the first 28 days. However, since sodium metabisulphite has been successfully used to reduce the damage caused by non-enzymic browning reaction (Van Soest, 1965) it was t h o u g h t that the chemical may prove beneficial to animal response.

Experiment 3 Sodium metabisulphite addition resulted in increased (P < 0.05) IVDMD over the control (Table IV) which appeared to be maximized at a pressure of 21 kg cm -2 across bisulphite levels.

166 T A B L E IV E x p e r i m e n t 3. E f f e c t o f pressure and s o d i u m m e t a b i s u l p h i t e on I V D M D ~ Pressure (kg c m ~)

S o d i u m m e t a b i s u l p h i t e (%) 0

1

2

3

Mean

P o o l e d SE

0 7 10.5 14 17.5 21 24.5 28

55.7 61.2 63.6 66.8 69.6 72.8 72.1 68.4

-60.1 65.8 69.7 72.0 74.9 74.1 71.1

-58.4 65.0 68.0 72.8 78.0 74.8 73.2

-59.0 65.2 72.0 77.8 77.0 74.5 69.4

55.7 59.7 64.9 69.1 73.0 75.7 73.9 70.5

±0.490

Mean

67.8

69.7

70.0

70.7

P o o l e d SE ± 0 . 3 7 0 i I V D M D was significantly (P < 0.05) a f f e c t e d b y pressure and s o d i u m m e t a b i s u l p h i t e . T h e r e were also significant (P < 0.05) linear, q u a d r a t i c and cubic r e l a t i o n s h i p s b e t w e e n I V D M D and pressure.

TABLE V E x p e r i m e n t 4. E f f e c t o f pressure and s o d i u m m e t a b i s u l p h i t e on the digestibility o f dry m a t t e r , p r o t e i n and n i t r o g e n r e t e n t i o n I Sodium Pressure (kg cm -2) metabisulphite (%) 10.5 14 17.5

P o o l e d SE Mean

Dry m a t t e r digestibility (%)

0 1 2 Mean

63.2 66.3 66.3 65.3 a

62.9 64.7 67.2 64.9 a

70.7 72.1 73.3 72.0 b

65.6 c 67.7 d 68.9 d

=0.600

P r o t e i n digestibility (%)

0 1 2 Mean

65.3 63.3 63.6 64.0 c

71.0 68.2 70.6 70.0 f

69.4 70.2 71.2 70.2 f

68.6 67.2 68.5

-+0.680

N i t r o g e n r e t e n t i o n (g day - j )

0 1 2 Mean

7.7 7.1 6.5 7.1 g

4.8 4.6 5.1 4.9 h

5.7 5.5 4.8 5.3 h

6,1 5,7 5,5

-*0.236

1Values in the same row o r c o l u m n w i t h d i f f e r e n t s u p e r s c r i p t s differ significantly (P < O.O5).

167

Experiment 4 T h e a d d i t i o n o f 1% s o d i u m m e t a b i s u l p h i t e increased (P < 0 . 0 5 ) d r y m a t t e r digestibility (Table V) b u t f u r t h e r increases h a d no effect. D r y m a t t e r digestibility was highest (P <: 0 . 0 5 ) w h e n c o b s w e r e p r o c e s s e d at p r e s s u r e o f 17.5 kg c m -2. P r o t e i n digestibility increased (P < 0.05) as processing p r e s s u r e increased f r o m 10.5 to 14.0 o r 17.5 kg c m - 2 ; o n t h e o t h e r h a n d , n i t r o g e n r e t e n t i o n t e n d e d to d e c r e a s e w i t h increase in p r o c e s s i n g pressure. P r o t e i n digestibility was n o t a f f e c t e d a n d n i t r o g e n r e t e n t i o n s e e m e d t o be d e p r e s s e d b y t h e c h e m i c a l . T h e i n c r e a s e d digestibility in v i t r o a n d in vivo ( E x p e r i m e n t s 3 a n d 4, r e s p e c t i v e l y ) w i t h t h e c h e m i c a l a d d i t i o n c o u l d be b y its i n h i b i t o r y e f f e c t o n t h e p r o d u c t i o n o f i n s o l u b l e p r o t e i n , a r t e f a c t lignin and f i b r e w h i c h are k n o w n t o a c c o m p a n y t h e b r o w n i n g r e a c t i o n . H o w e v e r , no a t t e m p t was m a d e to d e t e r m i n e the c o n c e n t r a t i o n o f these in this s t u d y .

Experiment 5 L a m b s t h a t c o n s u m e d the p r e s s u r e - p r o c e s s e d c o b s had i m p r o v e d perf o r m a n c e (P < 0.05) in all t h e variables m e a s u r e d relative to t h o s e fed t h e c o n t r o l c o b s (Table VI). C o b s p r o c e s s e d at 17.5 k g c m -2 i m p r o v e d average daily gain and feed e f f i c i e n c y w h e n c o m p a r e d to c o b s p r o c e s s e d at 14 kg c m -2. T h e I V D M D o f t h e c o b s p r o c e s s e d a t 14 kg c m -2 was n e a r l y e q u a l to t h a t o f c o b s p r o c e s s e d at 17 kg c m -2, b u t gains a n d e f f i c i e n c y values o b t a i n e d in this s t u d y suggest t h a t digestibility in vivo m a y be s o m e w h a t lower. T h e a d d i t i o n o f s o d i u m m e t a b i s u l p h i t e t e n d e d to depress daily f e e d i n t a k e w h e n c o m p a r e d to e q u a l p r e s s u r e t r e a t m e n t w i t h o u t t h e addit i o n o f the c h e m i c a l . TABLE VI Experiment 5. Daily gain, feed intake and efficiency of lambs and IVDMD of the diets I Treatments 1 2 Pressure (kg c m -:) Sodium metabisulphite (%)

Daily gain (g) Daily feed (g) Feed conversion IVDMD 2 (%)

3

4

0 0

14 0

17.5 0

17.5 1.5

55.8 672.0 a 12.0 a 50.4

99.9 1035.0 a

149.8 1180.0 b

137.6 1062.0 b 7.7 b 66.7

1 0 . 4 a'b

62.0

7.9 b

67.0

!

No standard errors are included in this table because they were lost after the statistical analysis had been completed. Values in the same row with different superscripts differ significantly (P < 0.05). 2 IVDMD of the complete diet was not analyzed statistically.

168 The addition of sodium metabisulphite at lower levels improved performance in terms of digestibility in vitro and in vivo. Such improvements support the view that the effects of non-enzymic browning reaction produced during processing were counteracted by the chemical. However, in Experiment 5, feed intake of lambs on the processed material with the chemical added was slightly depressed with a possible consequent reduction in daily gain. Such responses m a y be due to the high residual sulphur from the sodium metabisulphite. In the ruminal metabolism of sulphur, the element is first reduced to sulphite before being finally converted to sulphide (Hume and Bird, 1970; Bird, 1972) which is the form that mediates sulphur toxicity (Bird, 1972). Lewis (1954) has also shown that the conversion efficiency of sulphite to sulphide in the rumen is almost the same as the reduction of sulphate. It could be argued that the production of hydrogen sulphide from the sodium metabisulphite was responsible for the decrease in feed intake and, consequently, the effect on growth (Experiment 5). Alhassan and Satter (1968) have shown that a daily infusion of 60 g and above of sodium sulphite to cows reduced feed intake to zero. Albert et al. (1956) have also reported that, whereas lower levels of dietary sodium sulphite improved gains, levels higher than 1.76% depressed feed intake and growth. Bolsen (1971) similarly reported that high dietary sulphur depressed feed intake. According to H u m e and Bird (1970), o p t i m u m daily sulphur (in any form) should n o t exceed 4.0 g or 0.2% of dry matter of various forms of sulphur for both cattle and sheep (Bird, 1972). The calculated sulphur intake by lambs in Experiment 5 deduced from the sodium metabisulphite alone was 4.7 g. This level is higher than the 4.0 g recommended. Furthermore, in the same experiment, the chemical was added at 1.5% of the maize cobs dry matter. Given that maize cobs comprised 70% of the diet, the dietary concentration of sulphur was definitely higher than the 0.2% level r e c o m m e n d e d and could be responsible for the reduced feed intake and lowered growth rate. Also, given the high level of basal maize cobs, energy could have been a limiting factor in the efficient removal of the offending substance (sulphide) in microbial protein synthesis. Bird and H u m e (1971) and Bird (1972) have shown that where sulphate is ingested the response of animals is refusal of feed and toxicity s y m p t o m s could go unrecognized. However, in excess intake of sulphates, feed intake could be depressed, even if marginally, by the sulphide produced. It is, therefore, possible that the reduced performance recorded was a manifestation of the deleterious effects of excessive intake of dietary sulphur.

REFERENCES Albert, W.W., Garrigus, U.S., Forbes, R.M. and Norton, H.W., 1956. The sulphur requirement of growing-fattening lambs in terms of methionine, sodium sulphate and elemental sulphur. J. Anita. Sci., 15: 559--569.

169 Alhassan, W.S. and Satter, L.D., 1968. Effect of sodium sulphite on ruminants. J. Dairy Sci., 57 : 981 (abstract). Association of Official Analytical Chemists, 1970. Official Methods of Analysis, l l t h edn. A.O.A.C., Washington, DC. Bird, P.R., 1972. Sulphur metabolism and excretion studies in ruminants. X. Sulphide toxicity in sheep. Aust. J. Biol. Sci., 25: 1087--1098. Bird, P.R. and Hume, I.D., 1971. Sulphur metabolism and excretion studies in ruminants. IV. Cystine and sulphate effects upon the flow of sulphur from the rumen and upon sulphur excretion by sheep. Aust. J. Agric. Res., 22: 443--452. Bolsen, K., 1971. Methionine and a m m o n i u m sulphates as sulphur sources in ruminant finishing rations. Ph.D. Thesis, University of Nebraska, Lincoln, NE. Erlinger, L.L. and Klopfenstein, T.J., 1975. Ammoniated acid hydrolyzed wood residue as a source of nitrogen for ruminants. J. Anim. Sci., 41: 1189--1198. Guggolz, J., Kohler, G.O. and Klopfenstein, T.J., 1971. Composition and improvement of grass straw for ruminant nutrition. J. Anim. Sci., 33: 151--156. Hume, I.D. and Bird, P.R., 1970. Synthesis of microbial protein in the rumen. IV. The influence of the level and form of dietary sulphur. Aust. J. Agric. Res., 21: 315-322. Lewis, D., 1954. The reduction of sulphate in the rumen of the sheep. Biochem. J., 5 6 : 3 9 1 - - 3 9 9 (cited by Bird, 1972). Oji, U.I. and Mowat, D.N., 1978. Nutritive value of steam treated cornstover. Can. J. Anita. Sci., 58: 177--181. Steel, R.G.D. and Torrie, J.H., 1960. Principles and Procedures of Statistics. McGraw-Hill, New York, 481 pp. Tilley, J.M.A. and Terry, R.A., 1963. A two-stage technique for the in vitro digestion of forage crops. J. Br. Grassl. Soc., 18: 104--111. Umunna, N.N., Battling, R.R. and Klopfenstein, T.J., 1985. High temperature and pressure processing of maize cobs. I. Digestibility in vitro of processed cobs. Anita. Feed Sci. Technol., 12: 151--158. Van Soest, P.J., 1965. Use of detergents in analysis of fibrous feedstuffs. III. Study of effects of heating and drying on yield of fiber and lignin in forages. J. Assoc. Off. Agric. Chem., 48: 785--790.