STUDIES ON THE QUALITY OF SUBCLINICAL MASTITIC MILK
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Date
1993-09
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT:
Teat w i s e screening of individual m i l k s a m p l e s f r o m
16 c o w s situated a t college dairy and 69 crossbred c o w s
sltuated a t TTD farm w e r e done using CMT and SLST test.
B a s e d upon gel f o r m a t i o n m i l k samples w e r e graded into
negative, doubtful, 1+. 2+ and 3+. The proportion of
~verall'ne~ativt eea t s i n the population w e r e 57.8,
67.96% and doubt w e r e 9.58 and 8.53% as revealed by CMT
1
and SLST test respectively.
Irrespective of the position of teats the frequency
of negativee i n the population w e r e h i g h e s t , next i n the
descending order w e r e I+, f and the least w e r e 2+ or 3+.
Breed w i s e studies showed that jersey breed was highly
resistant t o subclinical mastitis being maximum proportion
of population showed negative followed by HF
and miscellaneous breeds and the lowest were FB crosses
of the college dairy farm. Somatic c e l l count between
CMT and SLST t e s t in different grades of subclinical
mastitis milk showed no difference concluding any one -
t e s t was equally good.
Highly significant differences were observed between
grades in a l l the parameters namely SCC, SPC, chloride
content and pH and a l l are showing ascending with
increase in grade of milk. However COB t e s t showed no
coagulation and RRT showed significant difference between
the grades both in college as well as TTD farm.
The milk samples graded 1+ and abwe exceeded the l i m i t s
of quality in a l l the parameters requiring rejection of
milk samples salvaging doubtful cases t o some extent.
The parameter studies of t e a t w i s e samples showed
no significant differences between the position of teats
and breeds similar were the cases with age wise studies,
lactation numbers, stage of lactation and farms indicating
these factors were not influencing the parameters to a
signi f ican t extent.
There was no correlation between two parameters
stuaied so f a r except i n two cases i n college dairy farm.
Shelf l i f e studies of different grades of subclinical
mastitis milk and control milk samples stored a t room
temperature showed no significant variation i n the levels
of acidity be tween a torage timing but significant dif f erences
i n RRT between timings and tendency to coagulate
on heating i n 9th hour storage onwards indicating the
pattern of quality of milk stored a t room temperature.
Refrigerated storage samples showed significant
degradation of quality from 36 hour storage onwards.
Mixed milk samples stored a t room temperature showed
significant difference between different grades as well
as between storage timing in the estimates of t i t r a t a b l e
acidity and only between storage timings i n the estimates
of RRT the pattern of variation revealed mixing of each
grade of milk into normal milk decreased the tendency
of acid production beyond 9th hour storage i n a l l proportions.
Refrigerated storage of mixed milk samples showed
the lowering acidity a t 72 hour of incubation to a level
a t 12 hour storage w i t h decreasing RRT. A definite
reduction of acidity was indicated as storage time advances
48 hour and above with s l i g h t decrease i n RRT due to
possible proliferation of Psychrophilics and s i m u l -
taneous reduction of acid producing mesophilics.
. Shelf .life..of curd samples of d i f f e r e n t grades
of subclinical mastitis milk and normal milk kept a t
room temperature reveals s i g n i f i c a n t t o highly siqnificant
differences i n the means of a c i d i t y between
grades as well as between t i m e intervals. The finding
that decrease i n a c i d i t y a t 12th hour indicated the
upper l i m i t of shelf l i f e of curd at room temperature.
Curd samples stored a t r e f r i g e r a t i o n temperature
showed s i g n i f i c a n t &iff erence in a c i d i t y between
grades and intervals and highly s i g n i f i c a n t r e s u l t s
in curd tension between grades only indicating the
pattern of quality of milk curd was good upto 24 hour
storage as long as the a c i d i t y was increasing phase
irrespective of the grades.
It would be concluded that the grades of subc
l i n i c a l mastitis milk 1+ and above require t o t a l
rb jsction on par with mastitis milk samples. Routine
t e s t i n g of the t e a t with milk samples is necessary
using e i t h e r CMT or SLST t e s t which ever i s available
i n addition t o s t r i p cup t e s t t o eradicate the daily
Samples showing 1+ and above grades of subclinical
mastitis. Only 50-60% of population showing negative
quarters i n the population showing negative could be
milked safely and those doubtful cases salvaged i f
necessary and others should be discarded outrightedly.
Proper package practices should be restored for
improving the udder health and the milk quality i n
the present production systems for the supply of milk
and i n the preparation of fermented milk and milk products.
Further studies are necessary t o find out exact.
bacteriological picture of different grades of milk t o
come up with further conclusions.
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