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A STUDY OF H AY DI GEST I BILITY
USIN G AN IN V I TRO FERMENTATION TECHNI QUE
A THESIS
PRESENTED IN PARTI AL FULFILMENT FOR THE REQUIREMENTS FO R THE DE GREE OF
MASTER OF AGRICULTURAL SCIENCE AT MASSEY UNIVERSITY
SHI N HO PARKS DECEMBER 1 966
ACKNOWLEDGEMENTS
Grate ful acknowledgement is made to my superv isor Mr A . W. F.
Dav ey , and Professors I . L . Campbe l l and D . S . Flux for guidanc e and critic ism throughout this p ro j ec t .
The author is indebted t o Mr G. F. Wilson for his valuabl e criticism; Mr A . C . Glenday for his guidanc e in stati stical treatment of the data; the Supervisor and staff of the Animal Physiology Uni t for fac i li ties and help giv en; and Mr N . A . Thomson for his invaluab le help in numerous ways in the laboratory .
Thanks are further due to Mr D . L . Jenkins , Miss M . G. C ampbell and the staff o f the Massey Univ ersity Lib rary , for th eir assistanc e in obtaining lit erature .
Special thanks are acc orded Miss S . E . Schamroth for typing the draft and final copies of th e thesis .
Thi s thesis was c arri ed out under the Colombo P lan awarded by the New Zealand Government .
CH APTER
1
1 • 1 •
1 . 2 .
1.4.
1.6.
2
2 . 1 . 2 . 2 . 2 . 3 . 2 . 4 .
3
3 . 2 .
CONTENTS
INTRODUCTION
PART I
ESTIMATION OF APPARENT DI GES TI BILI TY REVIEW OF LI TERATURE
Between species v ariation in apparent digestibility in ruminants
wi thin spec ies variation
The e ffec t of lev e l o f intake on apparent digestib ility
Assoc iative digestibility Grindi ng and pelleting
Variations in apparent diges t ibility as affected by e xp erimental technique
MATERI ALS AND METHODS Ani mals
Feeds
Experimental design
S ampling o f feeds and fae c e s
RESULTS Animals
Digestibility of the mixed hay
Digestibility t rial using individual hays
C omparison o f different lengths o f preliminary and c ol l ection period
i
PAGE 1
6 6
9 1 1
1 3 14 1 6
25 25 25 28 29
31 31 31 35 39
4
5
6
4 . 1 . 4 . 2 .
4 . 4 .
5 . 1 . 5 . 2 .
6 . 1 . 6 . 2 . 6 . 3 . 6 . 4 . 6 . 5 .
6 . 6 .
DISC USSION Animals
Digest i bility of the mixed hay
Digestibility trial using individual hays
Comparison o f di fferent lengths o f preliminary and collection period
PART I I
I N VI TRO FERMENTATION STUDIES
REVIEW OF LITERATURE Type o f in vi tro system
Sourc e and preparation o f inoculum Preparation o f substrata
Length o f fermentation p eriod
The amount of substrata and ratio of substrata to arti ficial mixture
Effe c t of pH
Accuracy o f in v itro technique
MATERI ALS AND METHO DS General descript ion Repeatability trial
Comparison of sourc e o f inoculum
Comparison o f two cows as donors o f rumen inoculum Time o f rumen liquor collec t ion in relation to t ime sinc e last grazing
I n v it ro digesti bility s t udie s w i th hay A, B and C samples
ii
43 43 43 45 46
49 49 52 57 59 61
62 63
68 68 71 72 72 72
73
7
8
9
7 . 1 . 7 . 2 . 7 - 3 ·
7 . 4 . 7 - 5·
7 . 6 .
8 . 1 .
8 . 2 . 8 . 3 . 8 . 4 . 8 . 5.
8 . 6 .
Relationship b etwe en chemical components and in vitro O . M . digestib ility o f feed
RES ULTS
Repeatability
Comparison o f s ource o f inoculum Lengths of fermentation period Fineness of grinding
In vitro O . M . digestibility o f hay A , B and C Relationships bet ween chemical components and in v itro O . M . digestibility o f hays and grasses
DISCUSSION
Reproducibility o f in vitro t echnique Comparison of sourc e of inoculum Lengths o f fermentation period Fineness of grinding
In vitro O . M . digestibility of hay A, B and C Relationships between chemical c omponents and in vitro O . M . digestibility of hay s and grasses
GENERAL DISC USSION AND CONCL USIONS REFERENCES
APPENDICES
i i i
77
78 78 8o 81 87 89 93
99 99 1 01 1 04
1 07 1 08 1 09
1 1 1 1 1 4 1 38
TABLE 1 . 1 .
1 . 2 .
1 . 4 .
1 . 6 .
2 . 1 . 2 . 2 .
3 . 6 .
LIST OF TABLES
Comparison of abiliti es o f dairy cows and sheep to digest herbage
The average di f ferenc es in digestibility by cattle and she ep of feeds after adjustment for proximate composition
Effe c t o f di fferent t im e on O . M . digestibility of sheep
Ef fe c t o f lev e l of intake and phy sical form on apparen t digestibility with sheep
Relationship b etw een the variability of the observ ed v alue o f digestibility o f D .M . and the numb ers o f sheep r epresented
Relationship b e tween the v ariation of D .M . digestibility and the numb er o f animals
Numb er of animals required for a giv en probab ili ty o f ob taining a signi ficant result
Desc ription of hays
Exp erimental design used in digestibility trial for the mixed hay and hay A, B and C
Live wi ghts o f experi mental sheep
D . M . intake during ad l ib . feeding p eriod with mixed hay
Mean daily D . M . intake o f mixed hay during the preliminary p eriod
Mean daily O . M . intake and faeces produced during the collection period and O . M . digestibility of mixed h ay
Mean daily D . M . intake during ad lib . feeding p eriod with hay A, B and C
F eed c o nsumed , faec es v oided and digestibi l i ty o f hay A , B and C
C omparison o f different l engths o f preliminary and c ollec tion period
iv
P AGE 6
7
1 0
1 5
1 9
21
22
26 27
32 33
37
42
6 . 1 .
7.4.
The design o f in v itro digestibility e xperiment for hay A , B , C and mixed hays
I n vitro O .M. digestibility o f standard grass a nd wi thi n and between trial variability
Comparison o f di fferent lengths o f sec ond stage fermentation using four substrate s
I n vi tro O . M . digestibility o f hay A , B and C , and withi n and b e t ween trial variability
Chemical composition and i n vitro O .M. digestibility o f hay and grass samples
V
74 79 82
91
FIGURE
LIST OF FIGURES
O . M . intake during the collec tion p eriod with hay A, B and C
The effec t of length o f fermentation on in vitro O . M . digestibi li ty of hay A , B , C and standard grass Proportion o f O . M . digested in vitro for di fferent
fermentation periods
pH change during fermentation with hay A , B , C and standard grass
Regressions of in vivo digestibility on in v itro digestibili ty of three di ffereut�lengths of fermentation p eriod using hay A , B and C
Regression o f in v ivo O . M. digestibility on in v i t ro O . M . digestibility o f t wo di f ferent particle sizes on 72 hrs (R . L .) + 48 hrs (pepsin) fermentation periods
V ariation o f i n vitro O. M . digestibility o f hay A , B , C and standard grass b etween trials
Regression of in v itro O . M. digestibility of hay s on in v itro O . M. digestibility of s tandard grass
Regression of in v ivo digestibility on in vi tro di gestibility usi ng 48 hr + 48 hr fermentation periods with 4 hays
Regressi on o f in v itro O . M . digestib ility on c rude protein c ontent and c rude fibre content of feed
vi
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86 88
90
92 94
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