Effect of Heat Treatment of Alfalfa Prior to Ensiling on Nitrogen. Journal of Dairy Scienc, 1989

8/14/2019 Effect of Heat Treatment of Alfalfa Prior to Ensiling on Nitrogen. Journal of Dairy Scienc, 1989

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E f f e c t o f He a t T r e a t m e n t o f A l f a l f a P r i o r t o E n s i l i n g o n N i t r o g e nS o l u b i l i t y a n d I n V i t r o A m m o n i a P r o d u c t i o nI . B . M A N D E L L , 1 D . N . M O W A T , 1 W . K . B I L A N S K I , 2 a n d S . N . R A I 3Universi ty of GuelphGuelph, Ontar io N1G 2Wl, Canada

A B S T R A C T I N T R O D U C T I O NTwo e x p e r ime n t s we re conducted toa s se s s h e a t ~ e a tme n t o f a l f a l fa p r io r toens i l ing . In Exper iment 1 , d i rec t -cu t a l -f a l fa (2 6 % D M ) w a s s u b je c te d to d ry h e a t(a i r tempera ture 400"C) fo r e i the r 0 , 7 ,

14 , 21 , o r 29 s p r io r to ens i l ing . Wil teda l fa l fa (5 0 % DM ) wa s t r e a te d s imi la r lyfor e i the r 0 , 5 , o r 6 s . Hea t t rea tmentdecreased the so lub le N conten t o f s i lagewi th o u t in d u c in g h e a t d a ma g e . Ac ro s s a l lhours o f incuba t ion , hea t ing pr io r to ens i -l ing decreased in v i t ro NH 3 N p roduc t ionin comparison wi th un trea ted s i lage (d i -rec t -cu t o r wi l ted) . Dura t ion of t rea tmenta f fe c te d NH3 p ro d u c t io n . T re a tme n t o fd irec t -cu t mate r ia l fo r a t leas t 14 s wasnecessary to decrease NH3 produc t ion inc o mp a r i s o n wi th u n h e a te d a l fa l fa o r a l -fa l fa t rea ted fo r 7 s p r io r to ens i l ing .Trea tment (6 s dura t ion) fo l lowing wi l t -in g d e c re a se d NH3 p ro d u c t io n in c o mp a r -ison wi th hea t- t rea ted , d i rec t -cu t a l fa l fa(7 , 14 , 29 s t rea tments ) . In Exper im ent 2 ,d i rec t -cu t a l fa l fa (36% DM) was sub-je c te d to mic ro wa v e h e a t in g fo r e i th e r 0 ,30, 60, 120, or 180 s prior to ensil ing.Hea t t rea tment decreased the so lub le Nc o n te n t o f s i l a g e . T re a tme n t fo r a t l e a s t60 s resu l ted in a fu r ther decrease in Nsolub i l i ty . In add i t ion , t rea tment fo r a tleas t 60 s w as necessary to decrease N H 3produc t ion . Thus , shor t - te rm hea t t rea t -me n t o f a l f a l fa p r io r to e n s i l in g ma y b ean e ffec t ive a l te rna t ive fo r improving theu t i l iza t ion of s i lage N in ruminants .

Th e CP c o n te n t o f h ig h q u a l i ty h a y c ro ps i la g e s e x c e e d s th e re c o m me n d e d re q u i re me n tsfor young growing ca lves (18) . However , sev-e ra l r e c e n t s tu d ie s h a v e s h o wn a ma rk e d im-p ro v e me n t in th e p e r fo rma n c e o f c a lv e s f e de i ther ea r ly cu t , wi l ted a l fa l fa -grass si lages (16)or d i rec t -cu t g rass s i lages (5 , 25) when supple -me n te d w i th a p ro te in s o u rc e o f lo w ru me ndegradabi l i ty . Th is paradox is due to the fac ttha t fo rage pro te in undergoes ex tens ive degra -da t ion dur ing wi l t ing and the ens i lage process(6, 23) . Var ious che mica ls ( fo rm ic ac id , fo rmal-d e h y d e , NH3 ) h a v e b e e n u s e d a s a d d i t iv e s d u r -ing ens i l ing to improve s i lage s tab i l i ty and Nut i l iza t ion (7 , 13). How ever , these add i t ives don o t a lwa y s p re v e n t e x te n s iv e p ro te o ly s i s d u r in gens i l ing (15) nor improve an imal performance(7).Ar t i f i c i a l d ry in g o f fo ra g e s imp ro v e s th eu t i l iza t ion of fo rage pro te in by the ruminant .Dry in g d e c re a s es N s o lu b il i ty a n d ru m e n d e g ra -d a t io n o f fo ra g e p ro te in , a n d in c re a s e s mic ro -b ia l p ro te in syn thes is in the rumen (9 , 15) .Overa l l , th is inc reases the amount o f aminoacids entering the small intes tine (9, 23). Un-for tuna te ly , due to cos ts , a r t i f ic ia l d ry ing hasn o t b e e n d e v e lo p e d fo r o n - fa rm p ro c e s s in g , a n dfew producers a re ab le to take advantage of th ist e c h n o lo g y . Re c e n t ly , Ch a rmle y a n d Ve i ra (4 )demons tra ted tha t s team t rea tment (60 s dura -t ion) o f a l fa l fa p r io r to ens i l ing cou ld inh ib i tp ro teo lys is and markedly improve the u t i l iza -t ion of s i lage N by the ov ine . The ob jec t ive o fth i s s tu d y wa s to d e te rmin e th e e f fe c t s o f h e a tt rea tment (HT) of a l fa l fa p r io r to ens i l ing on Nsolub i l i ty and ava i lab i l i ty to rumen microbes .

Received September 30. t988.Accepted February 22, 1989.1Department of An imal and Pou ltry Science.~School of Engineering.3present address: National Dairy Research Institute,Kam al 132001, 1-Iaryana, India .

M A T E R I A L S A N D M E T H O D SE x p e r i m e n t 1

Firs t -cu t a l fa l fa (ea r ly b loom) was cu t andth e n c h o p p e d b y a fo ra g e h a rv e s te r wh e n th e1989 J Da iry Sci 72:2046-2054 20 46


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HEAT TREATMENT OF FORAGES PRIOR TO ENSILING 204 7

D M c o n t e n t w a s 2 6 % . R a n d o m p o r t i o n s o f t hec h o p p e d f o r a g e we r e a l l o we d to w i l t 2 4 h u n t i lt h e D M a t t a i n e d 5 0 % . D i r e c t - c u t a n d w i l t e da l f a l f a we r e h e a t t r e a t e d a t 4 0 0 C ( a i r a mb ie n tt e mp e r a tu r e ) , u s in g a c o n t in u o u s f l o w u n i t ( 2 8 )in wh ic h h e a t wa s s u p p l i e d b y 2 6 , 7 5 0 - W c a l -r o d h e a t e r s . F o r a g e t r a n s i t t ime th r o u g h th ec o n t in u o u s f l o w u n i t wa s e i t h e r 0 , 7 , 1 4 , 2 1 , o r29 s fo r d i rec t -cu t a l fa l fa and e i the r 0 , 5 , o r 6 sf o r w i l t e d a l f a l f a . W i l t e d a l f a l f a c o u ld n o t b eh e a t t r e a t e d f o r mo r e t h a n 6 s d u e t o t h ed e v e l o p m e n t o f ch a r r in g a n d c o m b u s t i o n . E a c ht r e a t m e n t w a s p r o c e s s e d i n q u a d r u p l i c a t e . I m -m e d i a t e l y p o s t t r e a t m e n t , d u p l i c a t e s a m p l e s o fa l f a l f a we r e e i t h e r f r o z e n a t - 2 0 C o r e n s i l e d i np o l y e t h y l e n e c o n t a i n e r s ( 3 2 0 0 m l c a p a c i t y ) f o r3 5 d . No n e n s i l e d a n d e n s i l e d a l f a l f a we r ef r e e z e - d r i e d a n d t h e n g r o u n d t o p a s s t h r o u g h a2 - m m s c r e e n ( C h r i s t y - N o r r i s H a m m e r m i l lC h r i s ty a n d No r r i s L td . , C h e lms f o r d , E n g la n d ) .

A n a l y s e s o f D M , o r g a n i c m a t t e r (O M ) , a n dto t a l N ( T N) we r e c o n d u c t e d a c c o r d in g t oAOAC ( 1 ) p r o c e d u r e s . Ne u t r a l d e t e r g e n t f i b e r ,A D F , a n d A D I N w e r e d e t e r m i n e d a c c o r d i n g t oth e s e q u e n t i a l me th o d s d e s c r ib e d b y Va n S o e s ta n d R o b e r t s o n ( 2 4 ) . H o t w a t e r i n s o l u b l e N w a sd e t e r m i n e d a c c o r d i n g t o G o e r i n g a n d V a nS o e s t ( 8 ) a n d s o lu b l e N c a l c u l a t e d . E x p e r ime n -t a l d e s ig n wa s a f a c to r i a l a r r a n g e me n t w i th in ar a n d o m i z e d c o m p l e t e b l o c k w i t h t h e t w o s i l o s( r e p l i c a te s ) s e r v in g a s b lo c k s . An a ly s i s o f v a r i -a n c e w a s c o n d u c t e d o n t h e c h e m i c a l c o m p o s i -t i o n d a t a w i th s t o r a g e f o r m o f a l f a l f a , HT , a n db lo c k s a s f a c to r s i n th e m o d e l . D i f f e r e n c e sa m o n g t r e a t m e n t m e a n s w e r e d e t e r m i n e d b yn o n o r th o g o n a l c o n t r a s t s ( 2 2 ) .

S a m p l e s w e r e s e l e c t e d f r o m w i l t e d a n d d i -r e c t - c u t a l f a l f a ( n o n e n s i l e d ) a n d s i l a g e a n d t h e ni n c u b a t e d a t 39 " C w i t h 1 0 m l o f r u m e n b u f f e r( 8 ) a n d 5 ml o f s t r a in e d r u m e n f l u id f o r 0, 1 , 3 ,6 , 1 2 , a n d 2 4 h . De x t r o s e ( . 9 2 g /L ) wa s a d d e dt o t h e r u m e n b u f f e r m i x t u r e t o p r o v i d e a d d i -t i o n a l e n e r g y f o r r u r n e n mic r o o r g a n i s ms ( 8 ) .B la n k i n c u b a t io n s w i th o u t s u b s t r a t e we r e c o n -d u c t e d a t a l l h o u r s o f i n c u b a t io n t o d e t e r m i n eN H 3 p r o d u c ti o n f r o m r u m e n f l u id a l o ne . P r i o rto t h e a .m . f e e d in g , r u me n f l u id wa s o b t a in e df r o m a n o n la c t a t i n g , r u me n - f i s t u l a t e d d a i r y c o wf e d a n a l f a l f a / g r a s s h a y . R u m e n f l u i d w a ss t r a in e d t h r o u g h f o u r l a y e r s o f c h e e s e c lo th a n dth e n k e p t a t 3 9 C p r io r t o u s e . Af t e r d i s p e n s in g

5 m l o f r u m e n b u f f e r in t o e a c h i n c ub a t io n t u b e ,1 0 m l o f t he c o m p l e t e i n c u b a ti o n m i x t u r e ( 5 m lr u m e n f l u i d , 5 m l r u m e n b u f f e r ) w e r e a d d e dp r io r t o th e t u b e s b e in g g a s s e d w i th C O 2 , s t o p -p e r e d w i th b u n s e n v a lv e s , a n d t h e n i n c u b a t e d i na wa te r b a th a t 3 9 " C .

I n c u b a t io n s we r e s t o p p e d a t t h e a p p r o p r i a t ein t e r v a l s b y t h e a d d i t i o n o f 2 ml . 4 N H2 S O 4 .S a m p l e s o f t u b e c o n t e n t s w e r e c o l l ec t e d a f t e rv o r t e x in g a n d t h e n c e n t r i f u g e d a t 1 3 ,0 0 0 x gf o r 3 r a in . S u p e r n a t a n t wa s k e p t f r o z e n a t- 2 0 " C u n ti l a n a l y z e d f o r N H 3. A m m o n i a Nc o n c e n t r at i o n s w e r e d e t e r m i n e d u s i n g a p h e n o l -h y p o c h lo r i t e c o lo r ime t r i c p r o c e d u r e ( 2 ) . Ac c u -m u l a t i o n o f N H 3 N a t e a c h i n t e rv a l w a s c a l c u -l a te d a s t h e d i f f e r e n c e b e t w e e n N H 3 N c o n c e n -t r a ti o n s o f t u b e s c o n t a i n i n g s u b s t ra t e a n d N H 3N c o n c e n t r a t i o n s i n b l a n k i n c u b a t io n s .

E x p e r i m e n t a l d e s i g n f o r t h e N H 3 N d a t a w a sa r a n d o m i z e d c o m p l e t e b l o c k w i t h t h e t w o r u n ss e r v i n g a s b l o c k s . F o r e a c h h o u r o f i n c u b at i o n ,a n a l y s i s o f v a r i a n c e w a s c o n d u c t e d w i t h H Ta n d b lo c k s a s f a c to r s i n t h e mo d e l . D i f f e r e n c e sa m o n g t r e a t m e n t m e a n s w e r e d e t e r m i n e d b yn o n o r th o g o n a l c o n t r a s t s ( 2 2 ) .Experiment 2

T h i r d - c u t a l f a l f a ( e a r l y b l o o m ) w a s c u t a n dt h e n c h o p p e d b y a f o r a g e h a r v e s t e r w h e n t h eD M w a s 3 6 % . F i b e r b o a r d t r a y s c o n t a in i n g 1 0 0g f r e s h we ig h t o f a l f a l f a we r e p l a c e d i n ac o n v e n t i o n a l k i t c h e n m i c r o w a v e ( M W ) o v e n( 7 0 0 W , 2 4 5 0 M Hz ) a n d t h e n h e a t t r e a t e d f o re i the r 0 , 30 , 60 , 120 , o r 180 s . Each HT wasr e p l i c a t e d 2 0 t ime s . Af t e r t r e a tme n t , d u p l i c a t es a m p l e s o f a l fa l f a w e r e e n s i l e d i n p o l y e t h y l e n ec o n ta in e r s ( 5 5 0 ml c a p a c i t y ) f o r 3 5 d . A s a mp leo f n o n e n s i l e d , n o n h e a t - t r e a t e d a l f a l f a wa s f r o -z e n a t - 2 0 " C . A f t e r e n s il i n g, s a m p l e p r o c e s s i n g ,c h e m i c a l a n a l y s e s , a n d i n v i t ro N H 3 p r o d u c t i o nwe r e c o n d u c t e d a c c o r d in g t o t h e me th o d s d e -s c r i b e d i n E x p e r i m e n t 1 . A r a n d o m i z e d c o m -p l e t e b l o c k d e s i g n w a s u s e d i n w h i c h t h e t w os i l o s ( r e p l i c a t e s ) s e r v e d a s b lo c k s . An a ly s i s o fv a r i a n c e w a s c o n d u c t e d o n t h e c h e m i c a l c o m -p o s i t io n a n d i n v i t r o N H 3 d a t a w i t h H T a n db lo c k s s e r v in g a s f a c to r s i n t h e mo d e l . D i f f e r -e n c e s a m o n g t r e a t m e n t m e a n s w e r e d e t e r m i n e db y n o n o r th o g o n a l c o n t r a s t s .

Journal of Da iry Scienc e Vo l. 72, N o. 8, 1989


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RESULTS AND DISCUSSION

E x p e r i m e n t 1E f f e c t o f H T w i t h t h e c o n t i n u o u s f l o w s y s -t e m o n t h e c h e m i c a l c o m p o s i t i o n o f a l f a lf a is i nT a b l e 1 . H e a t tr e a t m e n t i n c r e a s e d ( P < . 0 1 ) t h e

D M c o n t e n t o f a l f a l f a ( d i r e c t - c u t o r w i l t e d ) .T h e l o s s i n m o i s t u r e m a y b e d u e i n p a r t t osyneres i s assoc ia ted wi th the rmal dena tura t iono f s o l u b l e p r o t e i n s f r o m t h e d i s r u p t i o n o f h y -d r o g e n b o n d i n g ( 2 0 ). I n c r e a s in g t h e d u r a t i o n o fH T f u r t h e r i n c r e a s e d ( P < . 0 1 ) D M c o n t e n t o fd i rec t -cu t a l fa l fa . H ea t t r ea t ing d i rec t -cu t a l fa l fac o u l d b e a d v a n t a g e o u s t o p r o d u c e r s b y i n c r e a s -i n g f o r a g e D M p r i o r t o e n s i l i n g . T h i s c o u l dp r e v e n t n u l r i e n t l o s s e s d u r i n g w i l t i n g w i t h o u tt h e p o t e n t ia l p r o b l e m s o f e f f l u e n t r u n - o f f fr o mens i l ing a low DM forage (26) . Hea t t r ea t ingw i l t e d a l f a l f a m a y p r e s e n t a s t o r a g e p r o b l e md u e t o t h e r e s u l t a n t h i g h D M a n d t h e p o t e n t i a lf o r h e a t d a m a g e ( 1 0 ) .H e a t t r e a t m e n t i n c r e a s e d ( P < . 0 1 ) t h e N D Fc o n t e n t o f w i l te d a l f a l f a b u t d i d n o t a f f e c t t h eN D F c o n t e n t o f d i r e c t - c u t a l f a l f a . A l t h o u g har t i f i c ia l hea t ing has been shown to inc rease theN D F a n d A D F c o n t e n t o f a l f a l f a h a y l a g e ( 1 0 ) ,t h e A D F c o n t e n t o f a l f a l f a w a s u n a f f e c t e d b yH T i n o u r s t u d y . T h e T N c o n t e n t o f al f a lf a w a su n a f f e c t e d ( P > . 1 0 ) b y H T a n d i s i n a g r e e m e n tw i t h Y u a n d V e i r a ( 2 9 ) . H e a t t r e a t m e n t d e -c reased (P . 1 0 ) N s o l u -b i l i t y . T h i s i s i n a g r e e m e n t w i t h M c D o n a l d(15) , who s ta ted tha t wi l t ing p r io r to ens i l ingd o e s n o t n e c e s s a r i l y i n h i b i t p r o te o l y s i s n o r p r o -v i d e a n y b e n e f i c i a l e f f e c t in p r e v e n t i n g p r o t e i nbreakdown dur ing ens i l ing . In con t ras t , Jan ick iand S ta l l ings (10) repor ted tha t as the DM

J o u r n a l o f D a i r y S c i e n c e V o l . 7 2 , N o , 8 , 1 9 8 9


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HEAT TREATMENT OF FORAGES PRIOR TO ENSILING 20 49

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c o n t e n t o f f o r a g e t o b e e n s i l e d d e c r e a s e d , Nso lub i l i ty a f te r ens i l ing increased . Increas ingt h e d u r a ti o n o f H T d e c r e a s e d ( P < . 0 5 ) N s o l u -b i l i t y . I n t h e p r e s e n t s t u d y , H T o f d i r e c t - c u ta l fa l fa fo r 21 and 29 s p reven ted a decrease inN s o l u b i l i t y a n d m a y p r o v i d e a n a l t e r n a t i v e t owi l t ing a l fa l fa p r io r to ens i l ing . Hea t t r ea tmentfo r shor t t imes (7 and 14 s , d i rec t -cu t a l fa l fa ; 5s , w i l t e d a l f a l f a ) m a y n o t i n a c t i v a t e p l a n t e n -z y m e s t o t a l l y ( 1 4 , 2 1 ) , e n a b l i n g m o d e r a t e p r o -teo lys i s .E x c e s s i v e h e a t i n g o f f o r a g e s i n c r e a s e s r i s kof hea t damage , thus l imi t ing N ava i lab i l i ty int h e f o r a g e ( 3 , 1 2 ) . A l t h o u g h H T i n c r e a s e d( P < . 0 5 ) t h e A D I N c o n t e n t o f a l f a l f a , a l l v a l u e si n o u r s t u d y w e r e l o w e r t h a n t h e 1 0 % f i g u r esugges ted by Jan ick i and S ta l l ings (10) to rep-r e s e n t l i m i t e d h e a t d a m a g e .T o t a l N a n d s o l u b l e N c o n t e n t o f a l fa l f ad i f f e r e d ( P < . 0 5 ) b e t w e e n s t o r a g e f o r m s ( n o n e n -s i l ed vs . ens i led) . Al thou gh the d i f fe renc e inT N c o n t e n t ( n o n e n s i l e d , 3 % ; e n s i l e d 3 . 0 5 % )was smal l , the so lub i l i ty o f ens i led a l fa l fa ex-c e e d e d ( P < . 0 1 ) t h a t o f n o n e n s i l e d a l f a l f a ( n o n -e n s i l e d , 3 6 .4 % o f T N ; e n s i l e d , 4 5 .3 % o f T N ) .T h e i n c r e a s e i n N s o l u b i l i t y u p o n e n s i l i n g i sa t t r ibu ted to p lan t p ro teo lys i s dur ing the ens i -l i n g p r o c e s s ( 1 5 ) .A s t o r a g e f o r m b y t r e a t m e n t i n t e r a c t i o n( P < . 0 1 ) o c c u r r e d f o r N s o l u b i l i t y ( T a b l e 2 ) .T h e i n t e r a c t i o n w a s d u e t o a d e c r e a s e i n Ns o l u b i l i t y f r o m e n s i l i n g o f c o n t r o l ( d i r e c t - c u tand wi l ted) a l fa l fa and a l fa l fa hea t t r ea ted fo re i ther 5 , 7 , o r 14 s . In con t ras t , ens i l ing d id no ta f fec t N so lub i l i ty in a l fa l fa hea t t r ea ted fo r 21or 29 s (d i rec t -cu t a l fa l fa ) o r 6 s (wi l t ed a l fa l -f a ) . A c c o r d i n g t o C h a r m l e y a n d V e i r a ( 4 ) , H Tr e d u c e s p r o t e o l y s i s d u ri n g t h e e n s i l a g e p r o c e s s ,r e s u l t i n g i n h i g h e r c o n c e n t r a t i o n s o f i n s o l u b l eN a n d l o w e r c o n c e n tr a t io n s o f N H 3 N . T h ed i f f e r e n c e i n N s o l u b i li t y b e t w e e n c o n t r o l a n dhea t -p rocessed s i l ages in the p resen t s tudy a req u i t e s i m i l a r t o t h o s e p r e v i o u s l y r e p o r t e d ( 4 ) .I n t h e l a t t e r w o r k , H T p r i o r t o e n s i l i n g i n -c r e a s e d t h e f l o w o f n o n - N H 3 N t o t h e d u o d e -n u m i n s h e e p .E f f e c t o f H T o n N H 3 N p r o d u c t io n i n v i tr oi s i n T a b l e 3 . A l t h o u g h r u m e n f l u id w a so b t a i n e d f r o m t h e s a m e f i s t u l a t e d c o w o n b o t hd a y s o f i n c u b a t io n , r u n - t o - r u n v a r i a t io n ( P < . 0 1 )o c c u r r e d t h r o u g h o u t a l l h o u r s o f i n c u b a t i o n .T h i s r e s u l t e d i n l a r g e S E . B r o d e r i c k ( 2 ) a l s o

Journal of Dairy Science Vo l. 72, No. 8, 1989


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HEAT TREATMENT OF FORAGES PRIOR TO ENSILING 2051

n o t e d r u n - t o - r u n v a r i a ti o n i n N H 3 N p r o d u c t i o nin v i t ro us ing case in as a subs t ra te . In thep r e s e n t s t u d y , r u n - t o - r u n v a r i a t i o n w a s e x p e c t -e d , a s N H 3 N c o n c e n t r a t i o n s p r o d u c e d f r o mr u m e n f l u i d i n c u b a t e d w i t h o u t s u b s t r a t e d i f -f e r e d b e t w e e n d a y s o f in c u b a t i o n . A l t h o u g h a l lN H 3 N v a l u e s w e r e c o r r e c t e d f o r N H 3 N p r o -d u c t i o n f r o m r u m e n f l u i d a l o n e , d a y - t o - d a yv a r i a t i o n m a y b e p r e s e n t f o r t h e d e g r a d a t i v ea c t i v it y o f r u m e n f l u i d ( 2 ). T h e l a r g e r u n - t o - r u nv a r i a ti o n in N H 3 N p r o d u c t i o n a t 0 h c a n n o t b ee x p l a i n e d a s t h e f e r m e n t a t i o n i s s t o p p e d i m m e -d i a t e l y w i t h H 2 S O 4 a f t e r a d d i ti o n o f t h e b u f f e r -r u m e n f l u i d i n o c u l u m .

W i t h t h e e x c e p t i o n o f 6 - a n d 1 2 - h i n c u b a -t io n s , N i l 3 N p r o d u c t i o n f r o m t h e n o n e n s i l e da l f a lf a w a s l e s s ( P < . 0 5 ) t h a n t h a t f r o m u n h e a t e ds i lage (d i rec t -cu t o r wi l t ed) . In v ivo s tud ies (6 ,9 ) s h o w e d t h a t f e e d i n g f r e s h f o r a g e s i n c r e a s e dt h e a m o u n t o f f o r a g e a m I n o a c i d s e n t e r in g t h es m a l l i n t e s t i n e i n c o m p a r i s o n t o f e e d i n g s i -l a g e s. T h e i n e f f i c i e n t u ti l iz a t i o n o f s i l a g e N b yt h e r u m i n a n t i s d u e t o e x t e n s i v e p r o t e o l y s i sd u r i n g t h e e n s i l a g e p r o c e s s a n d t o r a p i d a n dc o m p l e t e d e g m d _ a t i o n o f N P N i n t h e r u m e n( 2 3 ). E x t e n s i v e p r o t e o l y s i s o c c u r r e d i n t h e c o n -t r o l s i l a g e s a s n o t e d i n T a b l e 2 b y t h e i r h i g hs o l u b l e N c o n t e n t . T h u s , a c r o s s a l l h o u r s o fi n c u b a t i o n , H T p r i o r t o e n s i l i n g d e c r e a s e d( P < . 1 0 ) N H 3 N p r o d u c t i o n i n b o t h d i r e c t - c u ta n d w i l te d s i l ag e s . H e a t t r e a t m e n t p r o b a b l y d e -c r e a s e d N a v a i l a b i l i t y t o p l a n t a n d m i c r o b i a le n z y m e s d u e t o e n z y m e i n a c ti v a t io n ( 1 1 ) a n d t ot h e r m a l d e n a t u r a t i o n o f p r o t e i n , w h i c h p r e -v e n t e d p r o t e o l y s i s d u r i n g e n s i l i n g a n d i n v i t r oi n c u b a t i o n . T h i s i s s u p p o r t e d b y t h e s i m i l a rconcen t ra t ions o f so lub le N in hea t - t rea ted s i -l ages re la t ive to nonens i led con t ro l a l fa l fa (Ta-b l e 2 ) . S i m i l a r ly , K r a u s e a n d K l o p f e n s t e i n ( 1 2 )d e m o n s t r a t e d t h a t a r t i f i c i a l d r y i n g o f a l f a l f ad e c r e a s e d N H 3 N p r o d u c t i o n i n v i t r o .

D u r a t i o n o f H T a f f e c t e d ( P < . 0 5 ) N H 3 Np r o d u c t i o n i n v i t r o. A c r o s s a l l h o u r s o f i n c u b a -t i o n , N H 3 N p r o d u c t i o n f r o m a l f a l f a h e a t -t rea ted fo r on ly 7 s was s imi la r to tha t f rom thec o n t r o l d i r e c t - c u t s i l a g e . H o w e v e r , H T f o r 1 4 sd e c r e a se d ( P < . 0 1 ) N H 3 N p r o d u c t io n i n c o m -p a r i s o n w i t h H T f o r 7 s d u r a t io n . W i l t in g p r i o rt o H T d e c r e a s e d ( P < . 0 5 ) N H 3 N p r o d u c t i o n inc o m p a r i s o n w i t h d i r e c t - c u t f o r a g e . W i l t i n g d e -

c r e a s e d t h e t i m e r e q u i r e d f o r H T t o r e d u c e Nso lub i l i ty o f s i l age and to decrease N ava i lab i l -i t y t o r u m e n m i c r o o r g a n i s m s .Exper iment 2

E f f e c t o f M W p r o c e ss i n g o n t h e D M c o n t e n ta n d N f r a c t i o n s o f a lf a l f a i s i n T a b l e 4 . M i c r o -w a v e h e a t i n g i n c r e a s e d ( P < . 0 1 ) t h e D M c o n t e n to f a l f a l f a . T h i s i s c o n s i s t e n t w i t h u s e o f t h eM W f o r r a p id d r y i n g o f h e r b a g e s a m p l e s ( 2 7 ).I n c r e a s i n g d u r a t i o n o f M W t r e a t m e n t r e s u l t e di n a f u r t h e r i n c r e a s e ( P < . 0 1 ) i n D M c o n t e n t . I na d d i t i o n t o i n c r e a s i n g f o r a g e D M , N s o l u b i l i t yw a s m a r k e d l y d e c r e a s e d ( P < . 0 1 ) o v e r t h a t o fc o n t r o l s i l a g e . A l t h o u g h M W p r o c e s s i n g f o r 3 0s decreased N so lub i l i ty , fu r ther decreases in Ns o l u b i l i t y o c c u r r e d b y i n c r e a s i n g t h e d u r a t i o no f M W t r e at m e n t . D e c r e a s e s ( P < . 0 1 ) i n N s o l u -b i li ty b y M W t r ea t m e n t is e i t h e r d u e t o e n z y m ei n a c t i v a t i o n ( 2 1 ) o r t o t h e r m a l d e n a t u r a t i o n o fp r o t e i n ( 1 1 ). L o w e r r e s p o n s e i n N s o l u b i li t y b yM W t r e a t m e m f o r 3 0 s m a y b e r e l a t e d t o t h es a m p l e s i z e ( 1 0 0 g f r e s h w e i g h t ) p r o c e s s e d i nt h i s s t u d y o r t o t h e p o w e r o f t h e M W s y s t e me m p l o y e d (1 9 ) . W o l f an d C a r s o n ( 2 7 ) r e p o r t e dt h a t r e sp i r a t io n w a s c o m p l e t e l y i n a c t iv a t e d a f t e r2 5 g f r e s h a l f al f a w a s M W p r o c e s s e d f o r 3 0 s .In add i t ion , Smi th (21) no ted tha t rap id d ry ingc a n n o t o c c u r i f a t h i c k o r m a s s i v e l a y e r o ff o r a g e i s s u b j e c t e d t o h e a t o r f r e e z e d r y i n g .I n c r e a s i n g t h e d u r a t i o n o f M W p r o c e s s i n g b e -y o n d 6 0 s d i d n o t r e s u l t i n f u r t h e r d e c r e a s e s(P>.10) in N so lub i l i ty . Th is i s p robab ly a t t r ib -u t e d t o t h e f a c t t h a t 7 0 t o 8 0 % o f t h e T N i nf resh a l fa l fa i s t rue p ro te in (17) . Desp i te in -c r e a s e s ( P < . 0 5 ) i n t h e A D I N c o n t e n t o f a l f a l f aw i t h c e r t a i n M W t r e a t m e n t s , v a l u e s d o n o ti n d i c a t e e v e n m o d e r a t e h e a t d a m a g e .E f f e c t o f M W t r e at m e n t o n i n v i t ro p r o d u c -t i o n o f N H 3 N i s i n T a b l e 5 . R u n - t o - r u n v a r i a -t ion (P . 1 0 ) N H 3 N p r o d u c -

Journal of D airy Science Vo l. 72, N o. 8, 1989


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H E A T T R E A T M E N T O F F O R A G E S P R I O R T O E N S I L I N G 2053

t ion in comparison wi th the con tro l s i lage .Lo n g e r d u ra t io n s o f M W t re a tme n t a p p e a r to b erequired to inac t iva te p lan t enzymes or dena-tu re p lan t p ro te in . Microwave t rea tment a t o rexceed in g 60 s decreases in v i t ro NH 3 N pro-d u c t io n a n d N s o lu b i l i ty f ro m th a t o f th e 3 0 sM W t rea tme n t. U n fo r tu n a te ly , o p e ra t in g c o s t sa s s o c ia te d w i th lo n g t r e a tme n t d u ra t io n s w o u ldprobably be imprac t ica l fo r on-fa rm process ing(19 ). In c re as in g MW t re a tme n t b e y o n d 6 0 s d idn o t r e d u c e fu r th e r (P > .1 0 ) NH 3 N p ro d u c t io n .Ni t rogen so lub i l i ty was a lso s imila r among the60, 120, and 180 s HT.

CONCLUSIONSThese resu l ts sugges t tha t shor t - te rm HT ofa l fa l fa p r io r to ens i l ing may be an e ffec t ivea l te rna t ive fo r improving the u t i l iza t ion of s i -l a g e N in ru min a n t s . He a t t r e a tme n t p r io r toens i l ing decreased N so lub i l i ty in s i lage and theava i lab i l i ty o f s i lage N for rumen degrada t ion .Th i s ma y in c re a s e th e a mo u n t o f ru me n mic ro -b ia l p ro te in syn thes is as wel l a s fo rage pro te inen te r ing the smal l in tes t ine . S imila r f ind ings

wi th d e h y d ra te d a l fa lfa h a v e b e e n d e mo n s t ra te din v ivo in sheep (9) . Because the ADIN conten to f th e s i la g e wa s o n ly m a rg in a l ly in c re a se d b yHT, p o s t ru min a l d ig e s t io n o f a n y b y p a s s p ro -te in should no t be reduced .This s tudy was res t r ic ted to the e ffec ts o fd i f fe ren t I - IT on N qua l i ty o f a l fa l fa s i lage .Other paramete rs o f s i lage qua l i ty (e .g . , pH,lac t ic ac id) , whi le importan t , were no t conduc t-ed . Viab i l i ty o f HT p r io r to ens i l ing wi l l bedependent on ins ta l la t ion and opera t ing cos tsfor the t rea tment technology , and the resu l tan tan imal performance re la t ive to tha t us ing con-ven t iona l p ro te in supplements .

ACKNOWLEDGMENTSFinanc ia l ass is tance was prov ided by theOn ta r io Min i s t ry o f Ag r ic u l tu re a n d F o o d .

REFERENCES

1 As socia tion of Official A naly tical Chemists. 1980. Offi-cial metho ds of analysis. 12th ed. Assoc. An al. Chem.,Wash ing ton , DC.2 B roderick, G. A. 1978. In vi t ro procedu res for est imat ingra t e s o f rumina l p ro t e in degrada t ion and p ropor t ions o fprote in escaping the rumen undegraded. J . N utr. 108:181.

3 Bums, J . C . 1981 . Dry ing o f f r e sh he rbage samples fo rlaboratory est imates of qual i ty . Page 131 in Forageevaluat ion: concep ts and techniques. J . L. Wheeler and R.D. Moehrie , ed. CSIRO/Am. Forage an d Grassl . Counc. ,Netley, Anst.4 Charm ley, E. , and D . M . Veira . 1987. The effec t ofinl' tibit ing plant proteolysis o n prote in digest ion in sheepgiven lucerne silages. Pag e 155 in Proc. 8th Silage Conf.,Hurley, UK.5 E ngland, P. , and M. Gi l l . 1985. The effec t of f ishmeal andsucrose supplem enta t ion on the volun tary intake of grasssi lage and l iveweight gain of young catt le . Anim . Prod.40 :259 .6 Flores, D . A., L. E. Phill ip, D. M . Veira, and M. Ivan.1986. Digest ion in the lum en an d amino acid supply to theduoden um o f sheep fed ensi led and fresh al fa l fa . Can. J .Anita. Sci. 66:1019.7G lerm , B. P., and D. R. W aldo. 1986. Alfa l fa andorchardgrass si lages t rea ted wi th formaldehyde and for-mic ac id or anhyd rous amm onia for heifers . J . Dairy Sci .69:1317.8 Goe ring, H. K. , and P. J . Van Soest . 1970. Forage f iberanalyses. Agric. Handbook No. 379. Agric. Res. Serv.,US Dep. Agric . Washington, DC.9 Goering , H. K. , and D. R. Waldo. 1978. The effec ts ofdehyd rat ion on prote in ut i liza t ion in ruminan ts. Page 277in Proc . of the 2r id Int . Green Crop Drying Congr. ,Saskatoon, Can.10 Janick i, F. J. , and C. C. Stallings. 1987. Nitrogen frac tionsof a l fa l fa si lage from oxygen-l imi t ing and convent ionalupright silos. J. Dairy Sci. 70:116.

11 Jones, P.I .H. , an d G. Gri ff i th . 1968. Microw ave drying ofherbage. J. Br. Grassl . Soc. 23:202.12 Krause, V., and T. Klopfenstein. 1978. In vitro studies ofd r i ed a l fa lfa and com plementa ry e f fec ts o f dehydra t edal fa l fa and urea in rum inant rat ions. J . Anim . Sci . 46:499.13 Kung, Jr. , L., W. M . Craig, L. D. S atter, and G. A.Broderick. 198 6. Effec t of adding formaldehyde, g luta-ra ldehyde, or d imethylo lurea to a l fa l fa before ensil ing. J .Dairy Sci. 69:2846.14 M angan, J . L. 1982. The ni t rogen ous const i tuents of f reshforages. Page 25 in Forage p ro t e in i n ruminan t an ima lproduction. D. J. Tho ma s, D. E. Be ever, and R. G. Durra,ed. Br. So(: . An im. Prod. O ccas. Publ. No. 6.15 McDonald, P. 198 1. The b iochem ist ry of si lage . Jo hnWiley & Sons, Inc . , New York, NY.16 M owat , D. N. , and J . G. Bu chanan-S mith. 19 88. Prote insupplem enta t ion of a l fa l fa /grass si lages for ca tt le . Page181 in Proc. Am. Fora ge Grassl . Counc.17 Muc k, R. E.0 and J. T. Dickerson. 1987. Stora ge tem pera -ture effec ts on pro teolysis in a l fa l fa silage . AS AE PaperNo. 87-1078, Am. Soc. Agric. Eng., St. Joseph, MI.18 Nat ional Rese arch Council . 1984. Nu tr ient requirem entsof bee f cattle. 6 th ed. Natl . Acad. Sci. , W ashin gton , DC.19 Nelso n, S. O. 1987. Potential agricultural app lications forRF an d micro wav e energy. Trans. A m. Soc. Agric . Eng.30:818.

Pathak, J . P. , R. H. MacMil lan, D. G. Evans, and D. R.Murray. 1978. The effec ts of temperature on the re tent ionand den atura t ion of prote in in lucerne leaves sub jected tomech anical dewater ing. J . Sci. Food Agric. 29:835.Smith, D. 1973. Inf luence of drying and storage condi-t i ons on nons t ruc tu ra l ca rbohydra t e ana lys i s o f h e rbage

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tiss ue -a review. J. Br. Grassl. S oc. 28:129.22 Steel. R.G.D., a nd J. H. Torrie. 1980. Princ iples andprocedures of sta t i s t ics. McGraw-Hil l , New York, NY.23 Thom as, P. C. 1982. Ut i l iza t ion of co nserve d forages.Page 55 in Forage prote in in rum inant animal product ion.D. J . Thomso n, D. E. Beever , and R. G. Gunn , ed. Occas.Publ. No. 6. Br. Soc. Anim. Prod.24 Van Soest , P. J ., and J . B. Robertson. 1980 . System s ofana lys is fo r eva lua t ing f i b rous feeds. Page 4 9 /n S t an-dardizat ion of analyt ica l methodology for feeds. W. J .Pigden, C. C. Balch, and M. Grah am, ed. IDRC, O t tawa,Can.25 Veira , D. M., G. B ut ler , M. Ivan , and J . G. Proulx. 1985.

Ut i l iza t ion of grass si lage by cat tle : e ffec t of bar ley andfishm eal supplements. Can. J. An im. Sci. 65:897.26 Wi lk inson , J . M. 1981 . Losses i n t he conse rva t ion andut i l iza t ion of grass an d forage crops. Ann. Appl . Biol. 98:365.27 W olf , D. D. , and E. W. C arson. 1973. Respira t ion duringdryin g of a l fa l fa herbage. Crop Sci . 13:660.28 Wood ly, A., J. D. Summ ers, and W. K. Bilanski. 1972.Ef fec t s o f hea t t r ea tment on the nu t r it i ve va lue o f wholerapeseed for poultry. Can. J. Anim. Sci. 52:189.29 Y u, Y., an d D. M. Veira. 1977. Effe ct of artificial h eatingof a l fa l fa hay lage on chemica l compos i t i on and sheepperformance. J . Ani ta . Sci . 44:1112.

Journal of Dairy Science Vol . 72, No. 8 , 1989

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