the permission of the Author.
RABBIT MEAT HYGIENE
A thesis presented in partial fulfilment (60%) of the requirements for the Degree of Master of Philosophy in
Veterinary Pathology and Public Health at MASSEY UNIVERSITY
Evangelos Christofi Evangeli
1992
ABSTRACT
Thi s s tudy i nvolves work carried out a t the abat to i r i n Mas terton and in the l aboratory o f the Vet erinary Facu l t y o f Mas s e y Un i vers i ty , on aspects o f rabb i t meat hyg i ene and factors wh i ch may a f fe c t the qual i ty of rabb i t mea t .
The European rabb i t ( Oryctolagus cun i c u l u s ) , i s the anc e s tor of a l l breeds of dome s t i c rabb i t s , among whi ch the New Z e a l and Wh i te i s one o f the bes t meat producers , the Angora the bes t fur producer and the Rex i s a breed commonly used for exh ibi t i on purpo s e s onl y .
The feed convers i on ratio , whi ch for an e f f i c i ent commerc i a l un i t s hould b e l e s s than 3.5:1 ( Anon , 1987), comb ined w i th the abi l i ty of the rabbi t to consume f ibrous food unsu i table for human consumpt i on and the h i gh reproductive per formance , contr ibute to the rabb i t being an exce l l ent meat produc i ng animal . The product ion of rabb i t meat , i s s t i l l i n su f f i c i en t for the demands of the world markets and e f fort s should be made to increase rabb i t meat produc t i on .
D i s locat ion of the neck during slaughter of rabb i t s resul t s i n i mmobi l i z a t i on , but n o evidence was obt a in e d t o show that t h i s techn i que i nduced i mmedi a t e i nsensibi l i t y . Penetra t i ve and nonpene trative percuss iv e s tunning , probably induced i mmedi at e insens i b i l i ty b u t caused vi gorous body movements . I t w a s found i n t h i s s t udy that pupi l lary d i l atation in rabb i t s , general l y does not occur unt i l 8 - 1 0 minutes a f ter s laughter , s o pup i l l ar y d i l a t a t i on i s o f n o v a l u e as a cri ter i on f o r the a s s e s sment o f the a c tual t ime of ons e t of insens ibil i ty .
I n v e s t igat i on of carc a s s y i elds of rabb i t s s howed that s l augh tering rabbits at ages greater than e i ght weeks , resul ted in onl y marginal increases in carcass y i elds .
I mmers ion of carcas s e s in water for periods longer than 30 m i nu t e s can result in a 10.70% increase in the i r we i gh t , but the commerc i al technique i nve s t igated , resu l t ed i n approx . 7%
incre a s e . Wash i ng carca s s e s did not reduce bac terial l eve l s , but instead tended to increase carcass surface counts from 4.20 x 1 02/ cm2 to 1. 3 3 X 1 03/ cm2•
The mean u l t imate pH o f rabb i t meat was i n the reg ion of
5. 40-6.25. Factors affect ing the u l t i mate pH i nc luded concurrent d i s ea s e s and intensive mus cular ac t i v i ty . The rate of pH decline was a f fec ted by the degree of s truggl i ng a t the t i me of s l augh t e r .
The ma j or gros s l e s ions observed in the carcass and v i s cera of the rabbits s tudi ed , were those of hepa t i c cocc idios i s and to a l es s er degree , absce s s e s . The s tudy o f the accuracy of det e c t i on of hepatic coc c i d i o s i s in the aba t t o i r was des i gned a s a mod e l for t h e s tudy of s imi lar meat inspect i on procedures i n other animal s . I t was found that , based o n h i s tolog i cal exam i n a t ion of the l iver , the sens i t iv i ty was 41% and the spe c i f i c i ty 100%. A s tudy of the epidemiology of hepa t i c coc c i d i o s i s in rabb i t s , revealed that under New Zealand cond i t i ons , i t i s unl ike l y that any farm i s free of in fect ion w i th E imer i a s t i edae . However , if infect ions are of low intens i ty , rabb i t s may not develop macroscopi c hepa t i c l e s i ons . I t a l s o appears that h i s tological l e s i ons of the l i ver ( bi l i ary prol i fe r a t ion , f i bros i s , c e l lular i n f i l tr a t i on o f the b i l e duc t s w i t h i nf l ammatory cell s , i n cluding eos inoph i l s and l ymphocytes ) are pathognomon i c for detect ing past or present infect i on by � s t i eda e .
ACKNOWLEDGEMENTS
My part i cular and s incere thanks are d i re c t ed toward my superv i sors Professor D . K . Blackmore and Mr . P . Mad i e , for the i r a s s i s tance and guidance , not only i n t h i s i nve s t i g a t i on , but throughout my s tudy at Massey .
I would also l i ke to thank Dr . W . A . G . Charle s ton , Mr . W . E . Pomroy and M i s s A . k . Soe , for g u i d i ng me w i th the proce s s i ng of the mater i al related to the epidemiolog i c a l part o f my i nve s t igat i on , and as s i s tance in the wri t i ng of the relevant part of my thes i s . I am grate ful to Dr . R . Marsh a l l and Mr . S . Fenw i ck , for the i r advice on the m i crob i olog i ca l part of my i nve s t i gat i ons , Mr . W . Chen and Mr . L . M . Badcoe , for a s s i s t i ng me w i th the exam i na t ion of the s amples from rabb i t l i vers , Mrs . P. Davey and Mrs . P S lack for prepar i ng h i s tolog i c al mater i a l , Mrs . J. S chrama for prepar i ng the medi a u s ed for the m i crobiolog i cal i nv e s t igat ions , Mr . Tom Law for photographs and Mrs . O . Harr i s , Mr . z. F . Fu , M i s s T . L i ndholm , and Mrs S . Spanou for typing my the s i s . I am a l s o grate ful to Mrs G . Absolon for her great help k i nd l y offered to me dur i ng my exp e r i ment a l work e i ther at the abatto i r or in her rabbi try . Dr Ch . Kakoy i ann i s and Mr A . Orphanides are also among the people of Mea t Hygi ene of my coun try C yprus , who kindly o f fered me guidance and a s s i s tance dur i ng the wri t i ng of my Thes i s . Spec i al thanks go to Mr . A . Orphan ides who also did the s t a t i s t i cs .
The f r i endsh i p and ass i s tance k indl y of fered to me by the o f f i cers of the reg i s try and U . G . C . , as wel l a s by the l ibrary personnel , i s well known and extremel y appre c i a t ed .
I would also wi sh to expres s my gra t i tude to the Gov ernment of New Z ea l and , for providing the s cholarship to enabl e me to undertake t h i s course of s tudy and to the government of my country , C yprus , for the f inan c i al s uppor t , g i ve n to my f ami l y duri ng t h e course .
F i nal l y , I would like to thank my GOD for pro t e c t i ng me and my fami l y during t h i s s tudy .
ABSTRACT
AKNOWLEDGEMENTS TABLE OF CONTENTS L IST OF TABLES L IST OF F I GURES CHAPTER ONE : CHAPTER TWO : CHAPTER THREE : CHAPTER FOUR : CHAPTER F IVE :
CHAPTER S IX : CHAPTER SEVEN :
CHAPTER EI GHT :
CHAPTER NINE : CHAPTER TEN : REFERENCES
TABLE OF CONTENTS
GENERAL INTRODUCTION THE PROCESS ING ABATTOIR SLAUGHTER OF RABBITS AND RATES OF BLEEDING CARCAS S YIELDS AND RELATIVE ORGAN WE IGHTS EFFECTS OF CARCASS WASHING ON RABBIT MEAT QUAL ITY THE PH OF RABB IT MEAT PATHOLOGICAL LESIONS OF THE CARCASSES AND VI SCERA OF RABBITS ACCURACY OF INSPECTION PROCEDURES IN RELATION TO HEPATIC COCCIDIOSIS EPIDEMIOLOGY OF HEPATIC COCCIDIOS I S OF RABBITS GENERAL DI SCUSS ION
PAGE NO .
1 3 4
5
9 1 1 23
32
5 4
7 1
92
11 6
12 4
1 42 163
167
LIST OF TABLES
3.1 The e f fects o f bleed i ng on the dur a t i on of s pontaneous body movements of rabb i t s , s tunned by the pene tra t i ve percus s ive method .
3 . 2 Comparative blood loss and rates o f bleeding of rabb i t s subsequent to a transverse i nc i s ion o f t h e neck .
3 . 3 Sub j ect ive de t e c t ion of whether or not rabbi t carcasses have been bled .
4.1 L i ve weights ( g ) , carcass y i elds ( g ) and blood l o s s ( ml ) of 2 4 rabb i t s s l aughtered at the abatto i r .
4 . 2 L i ve wights ( g ) and carcass y i elds ( g ) , blood loss ( ml ) , weights ( g ) and relat ive we ights of organs of 2 0 New Zealand Whi te rabb i t s s l aughtered in the l aboratory .
4 . 3 L i v e weights , carcass y i elds , blood los s , we i ghts and relat ive wei ghts of organs o f two young adu l t
4 2
4 7
4 8
5 8
5 9
New Z ea l and Wh i t e rabb i t s ki lled i n the laboratory . 6 0
4 . 4 Mean l ive we i gh t s and carcass yi e l d s o f di f ferent groups of rabb i ts .
4 . 5 Mean values o f c arca s s y i elds , blood loss and relat ive organ w e i ghts of 22 rabb i t s w i th a mean l i veweight o f 2 4 2 3 grams , s laughtered i n t h e l aboratory .
6 2
6 3
4 . 6 Live we i ght ( g ) , c arcass y i eld ( g ) , b lood loss ( ml ) and r e l a t ive organ we ights o f 1 5 bled rabb i ts .
4 . 7 Live we i ght , carc a s s y ield and rel a t i ve organ we i ghts i n grams o f seven
unbled rabbi ts .
4 . 8 Compar i son o f the mean values o f l ive we igh t s , carcas s y i elds , blood loss and relat i v e organ weights o f nine rabbits > 2 0 0 0g l i ve w e i ght , w i th the mean values of s i x rabb i t s < 2 0 0 0g l i ve we i ght .
5 . 1 Water uptake o f rabbit carcasses a f t e r d i f ferent periods o f immers ion .
( Exper i ment " a " )
5 . 2 Water uptake by the carcass of a wi ld rabbi t . ( Exper iment " b " )
5 . 3 Water uptake by four hind legs f rom t wo dome s t i c rabb i t s ( 4 - 5 hrs a fter k i l l i ng ) .
( Experiment " c " )
5 . 4 Water uptake by 1 5 N . Z Whi te carcas s e s with l ow pH ( 6 . 0 0 ) . ( Experiment " d " )
5 . 5 Water uptake by f i ve N . Z . Whi te carcas ses wi th h i gh pH ( 6 . 7 0) . ( Experiment " e " )
5 . 6 Bacteriolog i cal results from swabbing ten c arca s s e s before ( right hind leg) and a fter
( le f t h i nd leg) washing . ( Incubat ion a t 37 °C ) .
P age No
6 4
6 5
6 5
8 0
8 1
8 2
8 3
8 3
8 4
5.7 B a c teriologi cal resu l t s from four water s amples t aken before and a f te r carcass washing .
6 . 1 pH values o f the musc l e s o f 1 2 dome s t i c rabb i t s three hours a ft e r s tunni ng by
the neck d i s locat i on method at the abat toi r .
6.2 pH values o f the mus c l e s o f 2 5 dome s t i c aba t t o i r
85
9 9
rabb i t s s tunned b y the neck d i s locat ion method . 1 0 0
6. 3 pH values o f the mus c l e s o f three rabb i t s condemned a t the aba t to i r ( No . 1 and 2 w i th y e l low fat , No . 3 ema c i ated ) .
6. 4 pH values o f the musc l e s of f ive dome s t i c rabb i t s a f ter s tunn ing b y the neck
d i s loc a t i on method .
6. 5 pH values o f the mus c l e s o f f i ve dome s t i c rabb i t s a f ter s tunn ing b y the non-penetrat i ve pe rcuss ive me thod .
6.6 pH values o f the mus c l e s o f two dome s t i c
rabb i t s a f t e r s tunni ng b y the non-pene trative percuss ive me thod .
6.7 pH values o f the mus c l e s of f ive domes t i c rabb i t s s to raged a t - 1 ° C a ft e r the f i r s t measurement a f t e r s tunn i ng by the penetrat i ve percus s iv e me th od . Mean carcass temperature at 4 h r s
=+ 1 2 ° C and a t 2 4 h r s =+4° C .
6.8 pH values o f the mus c l e s o f f i ve dome s t i c rab b i t s one t o three hours after s tunni ng b y t h e penetrat i ve percus s ive method .
1 0 1
1 03
1 04
1 0 5
1 0 6
1 0 7
6 . 9 pH values o f the mus c l e s o f four w i ld rabb i t s 2 4 h r s post-mortem .
6. 1 0 Mus c l e pH of two w i l d rabbi ts .
8 . 1 Compari son o f speci f i c h i s tolog i c al change s a s s o c i ated wi th E . s t i edae infect i on at
d i f f erent s i te s within the l iver ( nine s i t e s from e ach o f e ight l ivers wi th macroscopic l e s ions ) .
8 . 2 Compari son o f preval ence o f macroscop i c and m i c roscopi c l e s i ons i n rabb i t s subm i t ted for s l aughter .
8 . 3 Spe c i f i c h i s tological changes i n rabb i t l i vers
1 0 8 1 0 9
1 3 2
1 3 3
from groups w i th and w i thout macros cop i c l e s i ons . 1 3 7 9 . 1 D e t e c t ion of oocys t s i n f aeces .
9.2 Re s u l t s o f microscop i c a l examinat ion o f two l i vers from rabb i t s f rom a hepa t i c cocc idios i s free farm .
1 5 8
1 5 9
LIST OF FIGURES
2 . 1 The abattoir at Mas terton . L oad out area .
2 . 2 Plan o f the rabb i t proces s ing p l an t a t Mas t e r ton .
2 . 3 Pel t removal showing poi n t s o f det achment on l egs .
3 . 1 Sma l l hammer and s teel rod and tube used for penetrat ive percuss ive s tunning .
3.2 Schema t i c drawing o f rabb i t head s howi ng the targ e t of penetrat ive percu s s i v e s tunning .
3 . 3 Pup i l l ary cons t r i c t ion . 3 . 4 Pup i l l ary d i latat ion .
3 . 5 Typ i ca l skull les ion wi th b i lateral prolapse o f t h e eyeballs caused by the pene trat ive percu s s ive s tunn ing .
3 . 6 The r e l a t i onship between l ive we ight and volume o f blood collected during bleeding .
Y = - 8 + 2 0 . 9 1 X
( Change o f blood loss per Kg change i n
2 5
2 6
2 9
3 8
3 9 4 3 4 3
4 5
l ive we ight ) 4 9
4 . 1 Carc a s s y i eld and blood los s of 2 4 rabb i ts
sl aught ered at the aba t to i r . 6 6
4 . 2 Carca s s y i eld and relative organ weights o f 1 5 bled and seven unbled rabb i t s.
5 . 1 I l l u s trat i on of the water uptake by the carc a s s of a w i ld rabb i t ( Experiment " b " ) and four r abb i t h i nd legs ( Experiment " c " ) . 5 . 2 Water uptake by tame rabbi t s .
6 . 1 Dec l ine i n pH o f Semi tendinosus musc l e s of groups of rabb i t s , f ive per g roup , s tunned by three d i f ferent methods .
6 . 2 Decl i ne i n pH of Psoas mus c l e s o f three di f ferent groups of rabb i t s , f ive per group , s tunned by d i f ferent me thods .
7 . 1 Abs c ess i nvolving the mand ible of an Angora rabb i t . - Side numbers ind i cate cent ime ters .
8 . 1 Rabb i t l i ver showing the nine s i te s f rom where the sec t i ons were taken for the pre l imi nary h i s tolog i cal inve s t igation .
8 . 2 S e c t ion f rom a l iver showing prol i ferat ion o f t h e bi l e duct epi thelium and fibros i s around the bi l e duc ts ( x7 5 ) .
8. 3 L i ver s e c t ion wi thout any h i s topatholog ical c h anges ( x7 5 ) .
8 . 4 Ooc y s t s o f E . s t i edae in the bile duc t of a
P age No
6 7
8 6 8 7
1 1 0
1 1 1
1 2 1
1 2 8
1 3 0
1 3 4
rabb i t l iver . The bile duct shows f ibros i s ( x 7 5 ) . 1 3 5 8 . 5 Oocy s t s o f E . s t i edae i n the bile duct lumen
of rabb i t l iver (X3 0 0 ) . 1 36
