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C HANGES IN BOV INE MAMMARY ENZYME ACTIVITIES AND MILK COMPOS ITION
WILLIAM BRUCE CURRIE
A the s i s presented in part ful filmen t o f the r e qu irements for t he de gree o f Xaste r o f Agric ultural S c i enc e i n Animal S c ie nc e .
M assey Univers i t y De c e mber 1969
ACKNOWLEDGEMENTS
I wish to acknowledge my gratitude to the fol l o w ing who made the pre sentation o f thi s the s i s possibl e:
Pro fe ssor R .E . Mun ford for his inte rest and guidanc e throughout the whole study , for o r ganising the producti o n te s t ing and for his partic i pation in the pro c e s s in g of tne re sults;
J . E . Ormsby for his c ontribution to the development o f the surgic al method and re gular ass istanc e with t he sampling;
T . J . Lynch and the farm sta f f for the i r c o o peratio n throughout the e xperiment in the c are o f the expe rimental animal s;
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The tec hnical sta f f o f the Dairy Husbandry De pt . who c o ntributed to the production testing;
D r J . Kirkman and D r R . Ho dges who made e quipme nt available for in fra-re d spectro s c o py;
D r N. Walke r and M r I . K . Gray , New Zealand Dairy Res earc h Institute, who made the ir laboratory and e quipment available for gas -li quid c hromato graphy;
Pro fe s s o r D .S Flux and the staff o f the Dairy Husbandry Dept . who made fac i l itie s available and provided use ful disc u s s i on during the experiment;
Mary Bisho p and my wi fe J ean for the i r help in the final pre s entation o f the the sis;
The N e w Zealand M ilk Board who made a grant to the autho r c o ve ring the c o st of presentation o f this the sis.
PREFACE
Concurre n t s t udy o f mammary b i o c h e mical parameters and c hange s i n the c ompo s i ti o n o f t he s e c re t e d pro duc t all ows an e xaminat i o n of possible c ausal relat ions and i s fundamental in i d e nt i fying s ites of ac t ion of phy s i o l o gical fac t o rs i n fluenc ing the s e c re tory ac t iv i t y o f t h e gland . C hange s in b i o c he mical parame t ers a c c o mpanying
various physiologic al states are now w e l l docume n t e d fo r rodent s pe c i e s , e . g . Bal dwin & Mi ll igan ( 1 966) , but the r e l a t i o n s h i ps these bear w i th t rans-lac tation c hange s in the c ompo s i t io n o f milk have not b e e n studie d . The bovine provides ample mat e rial of s u ffic ient divers i ty to c harac t e ri s e c hanges in milk c ompo s i t io n and t h e s pe c i e� impor tanc e as a foo d produc er j us t i fi e s a n y at tempt to determine how milk produc tion i s c o n trolled and s e ek pos s i b i l i t i e s o f arti fi c ial re gulat ion .
Pre r e qu i s i t e t o such a s tudy is a t e c hnique for r e pe a t e dly
o b taining tissue f�om lac tat ing udders wi thout s e r i o usly in flue nc ing future produc t i o n . The pre sent expe riment was unde rtaken to develop such a sampl ing me thod and use i t in a first at tempt to study milk pro duc tion a t the synthetic level throu ghout whol e lac t a t ions in dairy c a t t l e .
r
C hapt e r One
C hapter Two 2.1
TABLE OF CONTENTS
REVIEW
Introduction
Milk Fat Synthesis
�ilk Protein Synthesis Lactose Synthesis
Changes in the Composition of Milk Fat
METHODS
Design
2.2 ·cows and Xanagement 2.3 Surgical BiOJ2S:t 2.4 Biochemical Analyses
2.5 Milk Production and ComEosition 2.6 Statistical Methods
C hapter Three RESULTS
Experimental Methods Biochemical Results Milk Production
Milk Fat Fatty Acid Compositions
3.5 Relationships Between �ilk Composition and Mammary Enzyme Acti vities
1
1 2
12 15
20
25
25 27 28 31 39 42
44
44 47 51 58
64
Chapter Four
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4.1 4.2
D ISCUSS I ON
Discussion of Methods Used
Discussion of Experimental Results Conclusions
REFERENCES APPENDICES
68
68 71 78
Figure
1.1
L I S T O F FIGURES
Re pre s e ntation o f a cycle o f the Acyl C arrie r Prote in bound fatty ac i d synthetic system o f cyto plasm.
1.2 Milk fat fatty ac i d molar pro po rtions from the data of D e c ae n & Adda (1966).
2.1 Sc hematic r e pre s e ntation o f the syntheti c pathways and enzyme s c hosen f o r study i n bovine mammary tissue .
2.2 Re pre sentation o f the r ight udder sur fac e sho�ing the r e gion sampled in relation to
following page
2
22
25
the fore quarter c i ste rn . page 28
2.3 C hromatogram o f milk fat fatty a c i d methyl e sters se parated on diethylene glyc o l
suc c inate . 39
2.4 I n fra Red S pe ctra . page 41
3.1 The e ffect o f s urgical biops i e s o n milk yie lds i n mid-lactation .
3.2 D i phenylamine reaction for deo xyribonuc
l e i c ac i d .
3·3 Ac etate thiokinase as say .
3.4 C onc entratio n o f DNA in b iopsy s ample s taken at d i f fe r e nt stages o f lactatio n .
3.5 a C hange s in e n zyme activities with stage o f l actation .
44
46
47
3- 5 b
3 . 6 a 3 . 6 b
3 . 6 c
3 . 6 d
C hanges in enzyme ac tiv itie s with stage o f lactation .
Mil k Producti on: Dail y Milk Y i e l d .
Milk Production : Fat C onte nt and Daily Y i e l d .
Milk Pro duction : Prote in Conte nt and Daily Yield .
M ilk Producti o n : Lacto s e C ontent an d Daily Y i e l d .
Milk Fat Fatty Ac id Molar C o mpositions .
3.8 Variations in the c ontent o f total , cis and trans octade cenoic ac ids in milk
fat acc o rding to seasonal peri o d .
3 . 9 S i mple linear r e gre s s ions o f milk fat c o nte nt on Acetate Thiokinase activity .
3 . 1 0
..
.
S impl e l inear r e gressions o f milk fat c ontent ( ad j uste d to fatty ac ids synth
e s i s e d de novo ) on Ac etate Thiokinase activity •
51
5 1
5 1
51
6 1
64
6 6
LI S T OF TABLES
2 . 1 D e s c ription o f indi ces used in the general s t a t i s t i c al model
3 . 1 Compo s i t i o n o f Sample Milks take n Be fore and A fter Biopsy i n Mid
Lac tation
3. 2 Det e rmination o f DNA in repe ated extrac t s o f mammary homogenates wi t h perc hloric acid at 7 0°C
3. 3 S ummary o f Analys e s o f Varianc e for Mammary E nzyme Ac t i v i t ies
3. 4 S ummary o f Analyses of Variance for the Milk Produc t i o n Variab l e s
3.5 Ranked Means obtained fro m estimates during 3 way and 1 way analyses o f varianc e for fat c ontent
3. 6 Two Way Analyses o f Variance w i t h Interac tion f o r F a t C on tent
3. 7 S ummary o f Analys e s o f Variance for Molar Propo rt ions o f Fat ty Ac ids i n M i l k Fat
3. 8 C o rrelation c o e ffic ients and % Coeffic ients of Det erminati o n for pair s o f milk fat fatty a c i ds
3.9 S imple l i near regr e ssions o f milk fat c ontent on acetate thiokinase ac t i v i ty
4 6
4 8
5 2
5 9
6 2
6 4
3.11 a
b
r
S impl e linear re gre s s i o ns o f milk fat c o n te n t ( adjus ted for f a t ty ac i d co mp
o s i t i o n ) o n a c e t a t e thiokinase a c t i vi ty
S imple l inear re gre s s i o n s o f the c onten t o f 14:0 in milk on ac e ta t e thiokinase a c t i v i ty (DNA)
S i mple linear re gre ss ions o f the c on t e nt o f ac ids chain length l e ss than 16 C in milk on ace tate t hiokinase ac tivi ty (DNA)
66
67
67
. I
Plate I
Plate II
LIST OF PLATES
The c anul a used and a fre s hl y obtained t is s ue sample .
The c lo s e d inc ision showing two pre vious s i t e s above .
following page
29
2 9
