General problems in assessing the nutritive value of Mediterranean forages

Transcription

1 General problems in assessing nutritive value Mediterranean forages Susmel P., Stefanon B., Mills C.R. in Tisser J.L. (ed.), Alibés X. (ed.). Fourrages et sousproduits méditerranéens Zaragoza : CIHEAM Options Méditerranéennes : Série A. Séminaires Méditerranéens; n pages 1722 Article available on line / Article disponible en ligne à l adresse : To cite this article / Pour citer cet article Susmel P., Stefanon B., Mills C.R. General problems in assessing nutritive value Mediterranean forages. In : Tisser J.L. (ed.), Alibés X. (ed.). Fourrages et sousproduits méditerranéens. Zaragoza : CIHEAM, p (Options Méditerranéennes : Série A. Séminaires Méditerranéens; n. 16)

2 General problems in assessing nutritive P. SUSMEL, B. STEFANON, C.R. MILLS ISTITUO DI PRODUZIONE ANIMALE UNIVERSITA DEGLI STUDI DI UDINE VIA. S. MAURO, PAGNACCO (UD) ITALY Some with feedingstuffs tables se in value conclude that in situ nylon bag system has considerable potential for resolving many practical dificulties associated with producing feedingstuff tables. However, in situ technique must be stardised to be valid. assays can be used to replace nylon bug technique for characterisation protein. posés par l appréciation de la valeur des fourrages méditerranéens. Les auteurs présentent des problèmes concernant les tables de prévision des aliments. Les méthodes et les équations pour l évaluation de la digestibilité de la matière sèche, organique et azotée sont analysées. Les auteurs remarquent la possibilité d utiliser les in sacco des sachets de nylon pour étudier la valeur éhergétique et azotée des aliments, comment les sousproduits, qui varient beaucoup avec les diverses conditioas géografiques et de climat. La nécessité d une stardisation comme les méthodes in sacco est enfin soulignée. Introduction feedingstuffs tables, chemical as well as some to feed 1980, 1988). data tables it is assumed that same feed has an almost constant composition value, but this is only most convegetable oil some animal meals. besides stage involved in both chemical composition biological availability because light applications all to modifying plant Even though tables can detailed analysis, al vitamin contents, data to sity digestible metabolizable using statistically equations, can ten be useless poses, as with chemical composition can be utilised with efficiencies by animals. instance, it is well known that polyphenols, especially those classified as tannins, have an effect on digestibility 1987; Susmel et al., 1989b; Waghom et al. 1987) is not evident Van Soest with method to a change in value; one most causes gestibility (Van Soest, 1983). speaking, obtainable tables useful only in in which A possible solution to this wouldbe to implement tables with chemical data highly to values. The use se chemical components in equations digestibility would be se established feeds (1981, 1983) have tables in which chemical data in vivo best way to estimate value feedstuffs. The measurement nutritive value feedstuffs Energy The value feeds, be digestibility in which total faeces in a : 1722

3 Table 1. Previsional equations organic matter digestibility based on chemical composition feeds. Von (1989) Sauvant et al. (1985) (1988) (maintenance; SOL = cell soluble; (1981) NET et al. (1985) feeds) (14 et al. (1984) * day to intake. se ments, coefficients digestibility fat cellulose hemicellulose) can be is well known that this method is time consuming expensive. Tamminga et al. (1989) have some feed components, indigestible indigestible cellulase indigestible lignin, soluble insoluble lignin), as digestibility. The use such as acid lignin lignin, to estimate in vivo digestibility has been also applied et al (1988) Susmel et al. (1990). is accepted that simple analysis cannot be used to estimate availability in by Van Soest has been used successfully (table 1) to digestibility hay silage, some is likely that feeds with high levels ligninlike compounds, especially those coming counhot climates, above equations wouldnot function adequately. 18 Some in vitro techniques, such as Tilley method, havebeen developed nused widely to define content feeds, in The Tilley method is most accubut it has disadvantage liquid thus availability fistulated cattle sheep to be Some methods use enzymes, fungal cellulase, alone with pepsin (table 2), that simulate whole digestive The between in vivo in vitro data hay genhigh statistical analysis gives good low (table 3). this enzymatic analysis has in past few suggest use estimation value feeds. Table 3 shows that Thus in vitro much difficult to define methods seem unable, in some cases, to conditions existing in host animal continuous with data obtained in animal. At time, investigation in one most have been effectively used intake

4 Table 2. Prediction digestibility using enzymes (Tilley Statistical data et al., 1984 y= 0.99 X 5.9 et al., 1984 y= 1.01 X et al., 1984 X CELLULASE OF Collins, 1977 y= 0.59 X Collins, 1982 y= 0.70 X y= 0.72 X y= 0.55 X y= 0.83 X y= 0.83 X et al, 1978 y=0.70 X (insoluble hay 22 silages silage maize silage hay alkali 39 compounds with alkali Jones 1975 y=o.54 X Goto 1977 y= 0.69 X y= 0.87 X et al., 1984 y= 0.49 X et al., 1984 y= 0.68 X et al., 1984 X hays y= 0.74 X et al., 1984 y= 0.56 X 30.2 et al., 1984 y= 0.84 X et al., 1984 X hays 24 Table 3. Use nylon bag technique to predict dry matter digestibility estimated: vivo *(a+b) *(a+b)+39.0*~ *a+O.064O*b+37.7*~ et al., 1988a) (Susmel et al., 1990) " (a+b) vivo *(24 h 1989) 48 h et al., 1988) et al., 1988) 0.33 O based diets diet feeds 19

5 et al, 1988b) digestibility et al., 1988; Von ; Susmel et al., 1990). digestibility availability byucts depends mainly on composition (Van Soest, 1983; Susmel et al, 1990). The equations in table 4 shows that a digestibility can be lities The potentially able in situ, was highly with digestibility et al., 1988a) in (1989) also digestibility tions based on potentially on bag 24 with an level Susmel et al. (1990) values using effective than potentially (i.e. hemicellulose et al. (1988) concluded that a single incubation time 48 could be sufficient to class feedstuffs to digestibility metabolisable content. Table 4. Correlation coefficients (r) between in situ degradability nitrogen in vitro degradability. situ in vitro et (1978) al. 2 h VS 2 h 0.66 Susmel (1990) et al. VS 1 h Enzyme 0.78 (1988) VS Enzyme 0.95 et al., (1985) 12 h VS 12 h Enzyme 0.88 et al. (1983) VS Enzyme 0.78 Stem (1984) 1 h VS 1 h Enzyme 0.79 can be by means in situ technique 1979), but this method has same limitations seen in vivo digestibility. Antongiovanni et al. od value feedstuffs aminoacid feed incubation in a tube to Tilley methodology. The values highly to those obtained in situ. use enzymes has been to estimate but coefficients obtained not always adequate (table 5). Table 5. Comparison degradability coefficients effective degradability eir in situ or in rusitec. Feed Soya situ ** Oats situ ** Wheat situ ** situ ns y=a+b*(lect); = a+(b*c)/(c+k); k in situ = 0.06 k = *I * *X ** * *Q ** * ** * ns ns Protein Since beginning 1980s, a systems have been 1980, 1988; WC, 1985; Susmel Stefanon, 1987) in which able has been taken into account. All systems between availability in as main in, especially total digestibility. As shown above, can value, in value. 20 conducted by Susmel et al. (1990), Streptomyces griseus at 1 24 in situ coefficients (i.e. a, b, values less than 0.7. A highly significant was between in situ effective in vitro bility value at 1 h. Good between in situ values 1 to 4 incubation times in enzyme solutions also et al (1978), et al (1983), (1984) Floyd et al. (1985). ed a high 0.95) between effective gen in situ that obtained with an enzymatic technique with incubation times.

6 The use continuous devices to simulate is also conducted at tute Animal Udine (Susmel,.. Stefanon, communication) 4 feeds simultaneously in situ (4 cows, duplicate) in a O, 2, 4, The in table 6 show that in vitro data significantly those obtained in situ gen. se difficulty simulating conditions found in evident. have adapted to enhanced ability to digest lignocellulose. References biosynsis by an 2~ vitro l Conclusions The equations in this only a small a much published but some conclusions can be The values feeds needs to be stated a specific feed type, since equations can fail to give estimates., lignin additional above equations, it seems that se highly with digestibility that Soest indigestible compounds is useful. The in situ method has advantage ease use, with fact that it exposes test to an adequate od time in slightly conditions. The situ technique can be used to study a incubated feedstuffs with one basal diet to study effect a basal diets on one incubated feedstuffs. The adoption assays allows a simultaneous estimate both gen; in this way value a feed can be easily 1987). should be estimation in situ such as hay wheat in in on same chemical same time, in vitro deteminations should be adopted to find close tions with in vivo data with chemical feeds. The in situ technique needs to be using basal diets animas, although it is as yet difficult to apply obtained one species to is valid animal species found inadeveloping animals 21 méthode de 37, agoza. Spain. agoza. Spain une de la digestibilité des meta by means Anim. Sci., 66, Suppl.l,495(A). et animal feeds. digestibility silages using cellulase et et W.O. de la Zar C.J. The use enzymes to les méthodes de dosage de la lignine utiliséés en alimentation animale. Ann. Zootech., 34, Effect on digestiblity by J. Anim. Sci., 68, Sci. Technol., 2,

7 SOEST, 568. U., C.J., to estimate J in succo Janige Alimentation des bovins, ovins et INRA, as 582. as i Anim., 13,567 3, , STEFANON, tem Supp1.25,920. J The basis Zootech. 38, itz situ in nol., 7,8392. e in situ Feedcomponents as cows. Anim. Feed Sci. Technol., 27,4957. passage. E. G. W. 1988a. A study on in digestibility intake intake by Evaluation E. W. tant non 35, in in vitro Ass., 18, The effect condensed tannins on site digestion amino on Lotus corniculutus L. J. 57, in situ Sci. 69, O & NW by J. Anim. 22