Animal Feed Science and Technology, 9 (1983) 181--183 181 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

M E T H O D S O F I M P R O V I N G THE U T I L I Z A T I O N O F C E R E A L S T R A W BY R U M I N A N T S . III . A N O T E ON THE E F F E C T O F E N S I L I N G S T R A W T R E A T E D WITH U R E A

P.B.A. MBATYA*

Rowet t Research Institute, Bucksburn, Aberdeen AB2 9SB (Gt. Britain)

(Received 30 September 1982; accepted for publication 30 March 1983)

ABSTRACT

Mbatya, P.B.A., 1983. Methods of improving the utilization of cereal straw by ruminants. III. A note on the effect of ensiling straw treated with urea. Anita. Feed Sci. Technol., 9: 181--183.

Straw treated with urea was offered to lambs either freshly prepared (EN0) or after ensiling with urea for 30 days (EN3.~). The lambs also received l0 g dry matter (DM) of shredded, artificially dried grass per day per kg of metabolic liveweight. Ensiling straw significantly increased its intake from 32 to 41 g DM per day per kg of metabolic liveweight, and its DM digestibility from 375 to 450 g per kg.

INTRODUCTION AND OBJECTIVES

Urea is n u t r i t i o n a l l y valueless to the hos t (McDona ld , 1952) , bu t serves as a subs t r a t e for the e n z y m e urease resu l t ing in evo lu t i on of a m m o n i a in the r u m e n , and as a source o f n i t rogen for o p t i m i s a t i o n o f m i c r o b i a l f l o r a g rowth in the digest ive t rac t . Urea is also h y d r o l y s e d to a m m o n i a by u r e o l y t i c bac t e r i a in s t raw. H o r t o n and S t eacy (1979) , a m o n g o thers , have s h o w n t h a t t r ea t ing s t raw wi th a m m o n i a increases i ts i n t a k e and digest- ib i l i ty . I t was a n t i c i p a t e d t h a t if u r e a - t r e a t e d s t raw was ens i led in c losed con- ta iners , the l i be ra t ed a m m o n i a cou ld reac t wi th the s t raw and thus increase its i n t a k e and d iges t ib i l i ty . With this in mind , a t r ia l was des igned to investi- gate t he e f f ec t o f ensi l ing u r e a - t r e a t e d s t raw.

EXPERIMENTAL

Spr ing ba r ley s t raw (cv. ' G o l d e n P r o m i s e ' ) (Table I) was t r e a t e d wi th u r ea 30 days o r I d a y be fo re the e x p e r i m e n t s t a r t e d ( t r e a t m e n t s EN30, and EN0, r e spec t ive ly ) . E igh t l ambs (34 .9 ± 2 .98 kg) were d iv ided in to two

*Present address: University of the West Indies, Department of Livestock Science, St. Augustine, Trinidad.

0377-8401/83/$03.00 ~) 1983 Elsevier Science Publishers B.V.

182

TABLE I

Diet ingredients and composition

Ingredient (kg)

Straw 100.00 Urea 1.00 Water 25.00 Composition {g/kg DM) Crude protein 7.30 Ash 3.81

(%)

79.4 0.8

19.8

g roups acco rd ing to l iveweight , and a l loca ted to the two s t raw diets. S t raw and wa te r were o f f e r ed ad l ib i tum. All the l ambs were s u p p l e m e n t e d with 10 g D M / h e a d / d a y per uni t m e t a b o l i c l iveweight (kgW °.~s) o f sh redded , ar t i f ical ly dr ied ryegrass (150 g CP/kg DM). The l ambs were p e n n e d in- d ividual ly dur ing the 10-day p re l imina ry per iod , and then in m e t a b o l i s m cages. Feed in take and faecal o u t p u t were r eco rded for 7 days.

RESULTS

The l ambs were hea l thy and had good appet i tes . The ensiled s t raw s to red ve ry well (i.e. there was no m o u l d growth}. The re was on ly a fa in t smell o f a m m o n i a f rom the straw. T h e ensiled s t raw (EN3o) had a so f t e r con- s is tency t h a n the freshly p r e p a r e d s t raw (EN0). L a m b s on the EN0 s t raw d ie t se lec ted against the s t raw stalks, bu t those on die t EN30 did not . En- siling increased the in take and digest ibi l i ty o f the s t raw signif icant ly (Table II) .

TABLE II

Dry matter intake and digestibility (means of four animals)

Straw Straw intake Digestibility of DM (g day-' ) (g/day/kgW °'Ts ) (g kg-' )

EN0 450 32 375 EN3o 579 41 450 SED 32.9 1.8 13.8 Significance (P < 0.1 ) (P < 0.05) (P ~. 0.05)

SED = Standard error of difference.

DISCUSSION

A high c o n c e n t r a t i o n o f a m m o n i a is usual ly requ i red to i m p r o v e t h e in take and digest ibi l i ty o f cereal s t raw ( H o r t o n and Steacy , 1979 ; L a w l o r and O 'Shea , 1979; Abid in and K e m p t o n , 1981 ; Bo rhami and Sundst~l ,

183

1982) . In this e x p e r i m e n t the a m m o n i a l ibe ra ted was bare ly de tec tab le . I t is poss ible t h a t the ra te o f u r ea app l i ca t ion (Table I) was t o o low, because M b a t y a (1980) de t ec t ed m o r e a m m o n i a when 2.3 kg u rea was used to t r e a t 100 kg o f bar ley s t raw. I t is, t he re fo re , un l ike ly t h a t a m m o n i a was respon- sible fo r the s ignif icant increase in the DM in take and DM digest ibi l i ty o f s t raw. I t is poss ible , however , t ha t the ensfled s t raw m i g h t have been p red iges ted (dur ing ensilage) b y bacter ia , o r it m igh t have u n d e r g o n e a s t ruc tu ra l change. Since EN30 was ensi led in c losed conta iners , the wa t e r m i g h t have caused the p l an t cell walls to swell, in a m a n n e r s imilar t o t h a t d e m o n s t r a t e d by Watson (1941) a f t e r t r ea t ing s t raw wi th 1 .5%.caus t i c so lu t ion fo r 24 h, and b e c o m e m o r e pene t r ab l e to ce l lu lolyt ic m ic robes and digest ive juices in the a l i m e n t a r y t r u c t than EN0" This is a l ikely p rop- os i t ion because o f the so f t e r cons i s t ancy o f EN30 which c o n t r i b u t e d to the h igher DM in take .

CONCLUSION

Ensi l ing u rea - t r ea t ed s t raw can be o f par t ica l s ignif icance as the s t raw can be ensiled in the s u m m e r fo r win te r feeding in t e m p e r a t e coun t r i e s or dur ing the d ry season in t rop ica l count r ies . This wou ld increase the u t i l i za t ion o f p o o r - q u a l i t y roughages and i m p r o v e the b o d y c o n d i t i o n o f r u m i n a n t s which tends to de t e r io ra t e in win te r and d ry seasons. More research is, howev e r , r equ i red in this area.

ACKNOWLEDGEMENT

Special t h a n k s to m e m b e r s o f the R o w e t t Research Ins t i t u t e especia l ly Mr. R.I . Smar t , Pe te r D e w e y and all the s t o c k m e n , and Mrs. A. Mor land and Mrs. M. Rose fo r t y p i n g this paper .

REFERENCES

Abidin, Z. and Kempton, T.J., 1981. Effects of treatment of barley straw with an- hydrous ammonia and supplementation with heat-treated protein meals on feed intake and liveweight performance of growing lambs. Anim. Feed Sci. Teehnol., 6: 145--155.

Borhami. B.E.A. and Sundst61, F., 1982. Studies on ammonia-treated straw. I. The effect of type and level of ammonia, moisture content and treatment time on the digestibility in vitro and ezyme soluble organic matter of oat straw. Anim. Feed Sci. Technol., 7: 45--51.

Horton, G.M.J. and Steacy, G.M., 1979. Effect of anhydrous ammonia treatment on the intake and digestibility of cereal straws by steers. J. Anim. Sci., 48: 1239--1249.

Lawlor, M.J. and O'Shea, J., 1979 The effect of ammoniation on the intake and nutritive value of straw. Anita. Feed Sci. Technol., 4: 169--175.

• Mbatya, P.B.A., 1980. High quality forage as a supplement to ruminants offered barley straw. Ph.D. Thesis, University of Aberdeen.

McDonald, I.W. 1952. The role of ammonia in ruminal digestion of protein. Biochem. J., 51: 86--90.

Watson, S.J., 1941. Increasing the feeding value of cereal straws. J.R. Agrie. Soc., 101: 37--43.