ARCHIVE FILE

---

This article was published in 1968-69
See the original document

---

Control and Prevention of Mastitis in Dairy Cattle

K. G. JOHNSTON, B.V.Sc., Dip.Bact.(Lond.)

INTRODUCTION

It is a remarkable fact that when CSIRO'S research programme stopped shortly after World War II, mastitis research in Australia virtually came to a halt with the sole exception perhaps of the South Australian work (Pulsford 1954, Aust. Vet. J. 30:245).

The 1960s have seen a renascent effort, particularly in Queensland and West Australia. This changed situation is reflected in the number of papers being published on the subject and two reports which have been prepared, viz., that presented to the Commonwealth Animal Production Committee and produced by an expert panel commissioned for the task and led by Professor D. C. Blood of the University of Melbourne. The February, 1967, issue of the Australian Veterinary Journal carries an excellent statement prepared by a Committee of the Association and embodies current thought on the control of the disease and a summary of the important relevant information on the incidence of the disease such as we now have available.

	% Proportion Cows Infected
Infection	Reading (1964)	Camden (1964)	N.Z. (1965)	(Frost) Brisbane (1961)	S.A. (1954)	W.A. (1966)
Strep. ag.	12	14	16	30	16	2
Staph.	23	23	27	47	.	.

The figures show one or two interesting features:

1. There may be area differences. The 2 per cent cows with Strep. ag. in W.A. is an outstandingly good result.

2. The Camden results show half the prevalence of staphylococci that Frost first obtained although in another area he found results approximating the Camden figures.

3. Reading, N.Z. and Camden figures similar.

STREP AGALACTIAE

An old scourge of dairy herds and still with us 70 per cent at Camden and 86 per cent of herds in the first Brisbane area. However, in some herds the level of infection is low, presumably due to nearly two decades of the use of penicillin, although it is quite apparent that indiscriminate use of penicillin has left us with many heavily infected herds in the overall picture: up to 33 per cent of cows in some Camden herds. Some N.Z, herds found to be 65 per cent infected.

This need not be. We have the technical know-how to eradicate, or at least effectively control, this infection if we deem it necessary to do so.

CONTROL PROGRAMMES

The sheer physical enormity of monitoring herds is a daunting problem. In control work culture of milk from individual cows becomes an impossible task.

An alternative method of assessment is through cell count appraisal and the introduction of detergents for this purpose has been a tremendous stimulus to workers in mastitis control. Not only is it possible to rapidly appraise a herd for its cell count status on an individual quarter sample basis but standards are being developed for the appraisal of bulk milk. This has two important implications:

1. In relation to quality payments if cell counts are included as a third component to fat and S.N.F. in quality assessment. This is a contentious political problem but if cell counts were introduced in the quality scheme it would be an enormous incentive to effective mastitis control. One recommended standard in the U.S.A. is 1,000,000 cells per ml which closely approximates "+" on RMT scale.

2. Even in the event of this not happening, appraisal at the point of receival in a control programme would rapidly indicate the herds where problems existed.

ECONOMIC LOSS

It has frequently been stressed that sub-clinical mastitis is important in this respect. The acute flare-ups which are so easily recognised attract the farmer's attention and these he understands as the secretion is an unsaleable product or the gland severely damaged.

But clinical flare-ups are the visible part of the iceberg. The figures calculated for national losses are so astronomical, e.g., £19,000,000 p.a. in U.K. and $225,000,000 to $500,000,000 in the United States as to almost fail to register.

Some of the smaller figures are more comprehensible.

In a careful study in California, Gray and Schalim (1962, American Journal of Veterinary Research 94:541) examined 12,438 composite samples from 1,243 cows and calculated the depression in yield in relation to elevation of cell counts as indicated by the detergent California Mastitis Test when compared with CMT -ve cows.

CMT	Trace	+	++	+++
Reduction in yield	6%	10%	16%	25%

These are startling figures. Calculating on a similar basis Brookbanks (1966 New Zealand Veterinary Journal 14:62) estimated that sub-clinical mastitis cost N.Z. at least £3,500,000 p.a. (1962 figures on 1,900,000 cows with b. fat average of 295 lb. at 32 pence/lb.). Approx. £140/herd/year.

It is pertinent to note that a milk sample may have a CMT 3 plus reaction with a very high and grossly abnormal cell count and yet to the naked eye appear perfectly normal.

It should be a cardinal aim to keep the younger cows free from infection for as long as possible. Wheelock, Rook, Neave and Dodd (1966 J. Dairy Res. 33:199) experimentally infected heifers with a view to studying long-term results.

After infection the following took place:

1. There was invariably a fall in yield.

2. Lactose and potassium content fell.

3. Sodium, chloride and non-casein protein increased.

These effects persisted into the second lactation if the infection was not eliminated.

If the infection was eliminated in the first lactation or dry period and there was complete recovery before second calving, milk composition reverted to normal in the second lactation but recovery in yield was not complete.

CULLING RATES

Udder health problems and low production (some or many of the latter undoubtedly due to the former) are prime causes for culling in dairy herds.

The problem of early infections and their sequelae is reflected by the fact that an enormous number of cattle are culled long before they reach their physiological peak of production at the 5th-7th lactation.

W.A. Figures

(a) Whole milk area 4-5 years Average age.

(b) Butter fat area 3-7 years Average age.

Less than 15 per cent cows ever reached 6-7½ years of age and peak potential.

STREP. AND STAPH. ECOLOGY

1. The organisms have a limited distribution of any consequence.

2. The udder and teats inside and out are the major sources of the organisms.

3. Survival in the environment is limited and, depending on heat, light and humidity probably rarely exceeds 21-28 days.

4. The reservoirs of infection are the adult animals of the milking herd.

5. Colonisation of the skin leads to their establishment in the teat orifice. All the common pathogens are capable of this colonisation, This infection may remain localised for as long as 18 weeks, disappear spontaneously or invade the lactiferous duct and infect the gland itself.

6. The teat orifice may have a different flora to that of an infected gland. (Beech and Forbes, 1965, Vet. Rec., 77:1085.)

7. When staphylococci are prevalent at sites on the body rather than skin of udder, teats and in the glands this is a reflection of high incidence at these sites. If the incidence is reduced on teat and udder skin and in the glands, then the recovery rate at other sites falls. (Davidson, 1961, Res. Vet. Sci., 2:22.)

8. Strep. uberis has the skin as its most important reservoir especially lips and belly. Skin of udder relatively unfavourable. Rare in faeces. Population subject to seasonal variation. Glandular infection secondary to skin infection. (Cullen, 1966, Brit. vet. J., 122:333.)

INTERVENTION IN THE ECOLOGICAL SITUATION

1. Strep. agalactiae. In the case of this organism, because of its susceptibility to penicillin and the excellent response obtained, intervention with this antibiotic allows of dramatic alteration in the prevalence of the organism.

2. Staphylococci. Direct frontal attack with antibiotics does not produce the same elimination rate and an indirect approach through management, hygiene and strategic use of antibiotics has to be applied.

ERADICATION OF STREP AGALACTIAE

In a heavily infected herd the reinfection rate is high. Eradication requires a concentrated burst of activity for a short period. Bacteriological support is essential.

1. Quarter sample all cows for laboratory culture.

2. Each quarter identified as shedding Strep. ag. is treated with 100,000 u. penicillin—preferably in a slow release base.

3. Three weeks later repeat. Treat residue.

4. Three weeks later repeat. Treat residue.

5. When two negatives obtained, surveillance through culture of composite quarter samples. Note: The first treatment will produce 90 per cent negatives at 20 days.

The second sampling detects treatment failures (ca. 5 per cent), new infections (ca. 5 per cent) and copes with human errors; samples in wrong bottle according to label, penicillin infused into wrong quarter, etc.

In addition beware of introductions (safest to treat empirically if cultures not readily available; beware dry cows coming into herd (treat precalving); check machines and tighten up hygiene. See Roberts et al. (1963. J. Amer. vet. med. Ass. 143:1193) for an excellent account of the methods used by New York State Mastitis Control authorities.

RAPID MASTITIS TESTS USING DETERGENTS

Developed at Davis in 1956. Rapid, simple. Reagent non-toxic; long shed life when mixed with normal milk there is no change. A gel or precipitate begins to appear as the cell count approaches 500,000/ml.

Leucocyte + Detergent → gel.

DNA.

Used on:

(1) Individual quarter samples beside cow or in lab. May be stored overnight in cold but warm to 37°C, or at least room temperature.

(2) Composite milk samples.

(3) Bulk milk.

Method for Individual Samples:

1. Put enough milk in each respective compartment to cover the bottom.

2. They can be equalised by tilting to 45 degrees.

3. Return to horizontal and add equal volume of detergent.

4. Swirl tray 12 times. Observe reaction.

5. Examine and record. Do not delay reading because of fade due to DNAase.

0. No ppt.

(T. Trace ppt. some include this category.)

1. Slight slime.

2. Thick slime. Does not leave edge of paddle.

3. Thick slime which leaves edge and cones up in centre like an oyster.

Note:

1. Gives a good quick assessment of cell status.

2. Negative samples infrequently give positive culture.

3. As RMT increases in strength so more pathogens are found. This relationship is fair to good but not perfect.

4. If we accept Schalm's data on fall in yield correlated with increasing CMT reading, then pathogens or not, the elevated cell count is important.

Compared with CMT -ve cows the depression in yield for CMT categories on composite samples was:

RMT	T	1	2	3
% depression	6	10	16	25

Schalm (1962, Canad. vet. J. 3:90), in discussing control, stated that in 1243 Friesians capable of 50 lb. milk/day at peak production the loss per day when composite samples read as follows was:

RMT	T	1	2	3
Loss lb./day	3	5	7	10

Working on bucket milk he said if 80-85 per cent -ve then herd has no problem. Some had 80 per cent one plus or more. Quarters give RMT 2 and especially 3 readings contribute massively to such a situation.

There is adequate data to indicate chemical changes in milk composition with CMT +ves. These are detectable in milks giving as little as trace reactions.

QUARTER SAMPLES: PERCENTAGE PROPORTION IN RMT AND BACTERIOLOGICAL CATEGORIES

Category	Camden Standards	MF	No. 1	No. 2	MH	CLL	AD	J-DO
	%	%	%	%	%	%	%	%
RMT O	63	91	71	56	35	86	53	72
RMT 1	16	7	11	15	17	4	19	9
RMT 2	11	1	11	17	14	5	17	6
RMT 3	10	0.7	7	11	34	5	10	12
Bact. NSG	76	90	57	73	.	80	75	75
Staph.	8	0.7	17	17	35	10	5	0.6
Agal.	6	0	12	4	5	0	17	15

The Camden standards are from Table I in Johnston, K. G., et al. (1966, Aust. vet. J. 42:405) and are an "average" from nearly 1600 cows, 6300 quarter samples in 30 herds.

REFERENCES

Gray and Schalm (1960) - J. Amer. vet. med. Ass. 136:195. Deal with quarter, bucket and bulk milk.

Barnum and Newhould (1961) - Canad. vet. J. 2:83. Similar.

Scheider et al. (1966) Am. J. vet. Res. 27:1169. Detail study of bulk milk.

RMT	Neg	Trace	1	2	3
Cells/ml.	100,000	300,000	900,000	2,700,000	8,100,000

These Davis workers predicted that for bulk milk not to exceed 1,000,000 cells/ml. not more than 18 per cent of the milk volume or 20 per cent of composite cow samples could score CMT 2 or CMT 3.

On the other hand, if a bulk rank scored CMT 3, then at least 80 per cent of the cows would react CMT 2 or 3.