Bovine Mastitis: The Differential Cell Content of Milk in Relation to Sub-Clinical Mastitis

Blackburn, Philip Stanley (1952) Bovine Mastitis: The Differential Cell Content of Milk in Relation to Sub-Clinical Mastitis. PhD thesis, University of Glasgow.

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Using a differential staining technique, total and differential cell counts were carried out on more than 5,000 milk samples. A bacteriological examination of the samples was also made. In 1,710 of the samples the stage of lactation of the cows was known. Pathological and bacteriological examinations were made on the udders of 13 of the heifers, from which milk samples had been examined at regular intervals. The following is a brief list of the main findings. 1. The majority of cells in both normal and abnormal milk fall into three groups: a. granular leucocytes, b. lymphocytes and c. epithelial cells. 2. In the diagnosis of mastitis the total and differential cell counts combined showed no marked advantage over the total cell count alone, except when the milk came from cows in late lactation. 3. A rise in cell count with a high proportion of granular leucocytes in the milk, was invariably associated with acute mastitis as shown by pathological examination of the quarter. Acute mastitis may however exist if the proportion of granular leucocytes is low. 4. The presence of 150,000 to 200,000 granular leucocytes per ml. in the milk was found to correlate with the fact that about 4 per cent, of the lobules of the mammary tissue were affected with acute mastitis. 5. The earliest lesion of mastitis in a lactating udder consists of an acute cellular exudate into the acini of a lactating lobule. As a rule an acute lesion causes the affected lobule to involute. 6. A lobule which has undergone post-inflammatory involution may be differentiated from one which has involuted normally by the cellularity of its intralobular tissue. 7. The occurrence of post-inflammatory involution indicates that acute lesions have existed in a quarter. Lesions in the ducts appear to be, as a rule, secondary to lesions in the lobules. 8. Of the 52 quarters of the 13 heifers examined post-mortem 25 were normal and 27 abnormal. Only 4 quarters found to be normal had cell counts of over 100,000 per ml. and in three of these the proportion of granular leucocytes was under 30 per cent. This shows that during normal involution these cells may escape into the milk up to a proportion of 30 per cent. of the cells present. 9. The micro-organisms found in the milk ante-mortem and in the tissues post-mortem of the 52 quarters examined were haemolytic staphylococci, non-haemolytic staphylococci, atypical streptococci, Streptococcus bovis and diphtheroids. Except for Streptococcus bovis there was little or no difference in the incidence of the various organisms in the normal and abnormal quarters. With the exception of haemolytic staphylococci, none of the typical mastitis organisms were obtained from the milk or the tissues. Evidence is presented to show that infection of the udder by way of the blood stream is probable.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Animal diseases, Cellular biology
Date of Award: 1952
Depositing User: Enlighten Team
Unique ID: glathesis:1952-78912
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 28 Feb 2020 12:09
Last Modified: 28 Feb 2020 12:09

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