On effects of stage of lactation and subclinical mastitis on milk quality

in goats

Nissim SilanikoveBiology of Lactation Lab,

Agricultural Research Organization,The Volcani Center, Israel

Uzi MerinDepartment of Food Science,

Agricultural Research Organization,The Volcani Center, Israel

Gabriel LeitnerKimron Veterinary Institute, Israel

Milk quality:fat, total proteins, casein, curd and are affected by

intramammary Infection and stage of lactation

Cheese quality:yield, structure, smell, flavor,

shelf life and all these factors are subjected to the effect ofintramammary Infection and stage of lactation

Traditional farming

1. Along the lactation different products are produced2. Milk from clinically infected

glands is discarded

Modern dairy forming

1. Animals are milked while at different stages of lactation2. A large number of glands are

infected with a variety of bacteria

Animal model built on the gland level

One udder-half identified with CNS species and the contra-lateral being free of bacteria

+ -

S. caprae S. chromogenes S. epidermidis S. simulans S. xylosus

+ -

Milk yield (half) of sheep or goat infected with CNS specie in one gland and the contra-lateral being free.

Open bars – S; Hatched bars – G

0.0

0.5

1.0

1.5

2.0

Uninfected Infected

Milk

yie

ld (

kg/d

ay)

1 2 3

Curd firmness(volts)

Clotting time(sec)

Cork 2005

Curd yield and clotting time of goat milk from infected vs. uninfected udder-halves

Uninfect

ed

0

100

200

300b P < 0.02

Clo

tting

tim

e (s

)

200

210

220

230

240

aP < 0.0001

Cur

d yi

eld

(g/L

; wet

bas

is)

Infected

0.5

3.5

Milk

K/d

ay

Day in milk

SCC

(100

0)

1000

100

Milk yield and SCC along the lactation of uninfected glands

0.5

3.5

Milk

(K/d

ay)

Days in milk

SCC

(x 1

000)

1000

100

Milk yield and SCC along the lactation of infected glands

Parameter MLG-Fb MLG-Ib LLGb R2 P [F]

DIM 129 ± 15.9b 121 ± 6.3b 269 ± 4.8a 0.476 <0.001

Milk (L d−1) 3.07 ± 0.2a 2.64 ± 0.16b 0.80 ± 0.2c 0.542 <0.001

SCC (×1000) 292 ± 46c 2861 ± 642b 6274 ± 710a 0.253 <0.001

Fat (g L−1) 33.2 ± 2.4b 36.0 ± 1.9b 50.5 ± 1.9a 0.303 <0.001

Protein (g L−1) 32.0 ± 2.8b 34.7 ± 2.2b 56.6 ± 2.2a 0.380 <0.001

Casein (g L−1) 23.1 ± 1.9b 23.3 ± 1.6b 40.3 ± 1.5a 0.423 <0.001

%Caseinc 74.16 ± 0.6a 68.26 ± 0.84c 70.59 ± 0.80b 0.157 <0.001

Lactose (g L−1) 47.2 ± 0.4a 44.1 ± 1.0b 37.0 ± 1.0c 0.266 <0.001

RCT (s) 443 ± 50c 621 ± 30b 2107 ± 230a 0.236 <0.001

CF-60 (V) 8.57 ± 1.91a 1.26 ± 2.77b 5.2 ± 1.30b 0.094 0.038

Days in milk (DIM), milk yield, SCC, gross milk composition (fat, protein, casein, lactose), rennet clotting time (RCT) and curd firmness (CF) of goats’ milk for mid-lactation, bacteria-free (MLG-F), mid-lactating, infected (MLG-I), and late-lactation, bacteria-free (LLG)a.

* Many of the animals with subclinical chronic infection are not noted because there are no recognizable symptoms and the milk appearance is normal

* End of lactation goats show increased SCC regardless of IMI

** Routine milk testing such as CMT on the animal side or more advanced techniques like the sophisticated cell counters allow the identification of subclinically infected animals close to the occurrence of the infection. However, it is laborious and/or require special equipment to perform

*** On-line computerized milking systems are designed in part to overcome these conditions and to apply genuine real-time data acquisition on individual animals, including milk yield and conductivity

Healthy gland ~ 50,000 Cows

~ 300,000 goats and sheep

Infected gland ~ 3,000,000

CASEINOLYSIS INDEX

Cell depended

Bacteria and Cells depended

Low quality curd

100

1000

10000

0 5 10 15 20 25 30 35 40

Curd firmness (Cf)

correlation ( r= -0.4(

Log SCC and Cf of curd of goat milk at mid lactation with and without IMI and at the end of lactation

without IMI- SCC is not the best predicting variable for milk quality

Log

SCC

Clotting time and curd firmness

Curd firmness(V)

Clotting time (sec)

Bacteria

6.58±0.2 650±63 NBF

1.02±0.3 2490±340 Strep.

3.80±0.8 1255±468 CNS

E. coli

3.28±0.7 1078±193 S. aureus

100

1000

0 1 2 3 4 5 6

Strep. dysgalactiae S. aureus

Curd firmness (A30 Optigraph)

log

Som

atic

Cel

l Cou

nt

Strep. dysgalactiae

Staph. chromogenes

Healthy Infected

Correlations and respective probability (P[r]) for cows, goats, and) sheep between levels of protein, casein, (protein + fat), % casein and lactose, SCC, and log SCC, and curd firmness (CF) of milk:

– ∗ P > 0.001; – ∗∗ P > 0.05; NS – not significant

Low quality curd

1

2

3

4

5

6

0 5 10 15 20 25 30 35 40

% L

acto

se

Lactose lower than 4%

% lactose and Cf of curd of goat milk at mid lactation with and without IMI and at the end of

lactation without IMI

Curd firmness (Cf)

0

1

2

3

4

5

6

0 5 10 15 20 25 30 35

Curd firmness (V)

Perc

en

t la

cto

se in

milk

Sheep Goat Cow

Influence of percent lactose in milk on curdfirmness as measured by the Optigraph

* It was found that lactose content in milk is the best indicator for milk quality for cheese making. * It is already implemented in Afilab (Kibutz Afikim, Israel) On- line FTIR-based recording system in dairy cows milking parlors The system enables to separate on-line milk unfit for cheese making from milk suitable for cheese on the pipe-line between the milking parlor and the tank during milking and store them in separate tanks

* Feasibility test of the system for small ruminants was conducted The system will enable direct and cheap daily identification of animals with milk unsuitable for cheese making and perhaps to separate it as already done with cows

0

10

20

30

40

50

60

Uninfected Infected

SheepGoat

PL

ac t

ivit

y , u

nits

/mL

Plasmin activity: sheep or goat with one gland infected with CNS specie and the

contra-lateral being free Sheep + 195%, P < 0.0003Goat + 73%, P < 0.0007

SDS PAGE Tricine

0% 0% 50% 50% 100% 100%

52

35

28

2114

Preparation Healthy (10) S. chromogenes (4) E. coli (7)

Str. dysgalactiae (5)

p–p 160 ± 50 180 ± 70 360 ± 40 320 ± 60FE 7.2 ± 1.2 8.4 ± 1.4 23 ± 2.0 27.3 ± 2.2% FE of p–p 4.5 4.4 6.3 8.4

Amounts of p–p and FE obtained from milk samples.Numbers in parenthesis indicate the number of glands tested. Proteose peptone determined using the Bradford (1976) method, FE estimated as the area under the OD280 values of the FPLC

chromatogram; values are given as mean and SD in mg L−1.

Dose–response effect of the addition of fraction E (FE) from milk obtained from healthy glands (open bars) and from Str. dysgalactiae-infected glands (hatched bars) to milk from healthy glands on rennet clotting time and curd firmness, as assessed using the Optigraph.

The effect of addition of up to 5 mg fraction E (FE) to 10 mL of milk obtained from healthy or Str. dysgalactiae-infected glands, in the presence of calcium ions, to milk from healthy glands, on rennet clotting time (RCT) and curd firmness (CF), as assessed using the Optigraph.

Anti-Lactogenic hormones

e.g., Cortisol, Estrogen

Lactogenic hormones e.g., GH,

Prolactin

alveoli

PA

PL

PLG

Frequent milking or suckling

Reaction type 1

Reactiontype 2

12

Blood

Lumen

External effects:Milking, suckling, bacterial invasion

Milk stasis or bacterial invasion

Cork 2005

Bacterial infection

Cellularresponse

Cytokines, SCC (PMN)

Plasmin

SCC = somatic cell countPMN = polymorphonuclear

Caseinolysis

Oxidatiive response by

NO-derived NO2 radical

Lipidoxidation

Activation of the

innate system

Proteinoxidation

SCC is a good reference for milk quality if we compare good quality (300000

cell/ml) with low quality one (1 million cells and above). Milk for cheese

production and caseinolysis are bacteria species-dependent and are poorly

predicted by SCC

Bacteriological status

Carotene destruction,nMsec-1

FRAP, Ascorbic acid, µM

Ntyr, nMg-1 Lpx,mEqv g-1

Non-infected 669 +121a 413 + 27a 143 + 11a 110 + 47 1.3 +0.3a

Infected with coagulase-negative staphylococci

2006 + 215b 305 36b 91 + 7b 170 + 41 2.8 + b

Effect of subclinical mastitis on oxidative, antioxidative and formation of oxidized substance

in milk

subclinical mastitis is associated with significant losses in milk yield and quality for cheese production. Milk of subclinically infected glands is subjected to considerable NO-derived oxidative stress, which only moderately impose nitrosative stress on milk proteins. However, it is associated with significant loss of milk antioxidant capacity and vitamin C levels, which are particularly high in goats.

Thus, it is concluded that subclinical mastitis induces unfavorable changes in milk quantity and composition, which affects considerably both to the farmers and the dairy sector that depend on goat’s milk.

Thanks, on behalf of the heroes!