Somatic Cell Concentration Research Articles

Natural Protective Factors in Bovine Mammary Secretions Following Different Methods of Milk Cessation

Bovine mammary secretions were obtained during late lactation and early involution to determine if different methods of milk cessation influenced milk yield, composition, and in vitro growth of coliform mastitis pathogens. Cows (n=8/group) producing about 13kg of milk prior to experimentation were dried off by abrupt or intermittent milk cessation. An additional group was dried off by intermittent milk cessation and fed only hay during the last week of lactation. Cows milked intermittently produced significantly less milk during the last week of lactation than cows dried off by abrupt milk cessation. Mammary secretions from cows milked intermittently and fed only hay contained higher concentrations of somatic cells, lactoferrin, immunoglobulin G, and bovine serum albumin, a lower citrate:lactoferrin molar ratio, and were more inhibitory to in vitro growth of Escherichia coli and Klebsiella pneumoniae throughout most of the experimental period than mammary secretions from cows dried off by intermittent or abrupt milk cessation. Few differences in mammary secretion composition or in vitro growth of mastitis pathogens were observed between cows dried off by intermittent or abrupt milk cessation. Data suggest that growth of mastitis pathogens in mammary secretions may be related to natural protective factors, which can be manipulated by different methods of milk cessation.

Secretion composition during bovine mammary involution and the relationship with mastitis

1. 1. Bacteriological analysis revealed that 30% of quarters contained coagulase-negative staphylococci, Staphylococcus aureus, Corynebacterium bovis, or streptococci. 2. 2. As involution progressed, somatic cell counts, percent protein, pH, and concentrations of serum albumin, lactoferrin, and immunoglobulin G increased while percent fat, concentrations of citrate, and the citrate to lactoferrin molar ratio decreased. 3. 3. Mammary secretion from infected quarters had significantly higher numbers of somatic cells, percent polymorphonuclear leukocytes, and pH, but lower percentage lymphocytes, fat, and lactoferrin concentrations compared to uninfected quarters. 4. 4. Results suggest intramammary infection altered normal secretion composition during bovine involution and lactogenesis. 5. 5. Lower levels of antibacterial components in bovine mammary secretion during the peripartum period may have reduced the natural defense potential of the gland.

Potential of Somatic Cell Concentration in Milk as a Sire Selection Criterion to Reduce Mastitis in Dairy Cattle

Lactation records for somatic cell counts in milk, bacteriological culture results, antibiotic treatment for mastitis, and production were formed for cows in 30 cooperating dairy herds in Virginia. A second data set, including somatic cell counts and production information for cows in approximatley 400 herds in Virginia (not including the original 30), was used to evaluate sires genetically for somatic cell count.Approximate genetic correlations between measures of cell count and measures of infection ranged from .36 to .67. These were highest (lowest) for frequency of infection by major (minor) pathogens. Corresponding phenotypic correlations were similar but slightly smaller. Neither somatic cell counts nor measures of infection were well correlated with treatment. Production traits generally had small, negative genetic and phenotypic relationships with cell counts, rates of infection, and measures of treatment.Correlations for evaluations of sires for cell count were positive with daughter averages for infection rates (.20 to .38) and treatment measures (.02 to .13). Largest (absolute value) correlations between evaluations of sires for cell count and production traits were for fat percentage (−.38) and fat yield (−.28). Evaluation and selection of sires for decreased somatic cell count may augment management and treatment programs in the reduction of mastitis incidence.

Use of Laboratory Mice to Study Genetic Relationships Among Milk Yield and Number of Somatic Cells

Preliminary results of bidirectional selection for increased and decreased somatic cell counts in milk of laboratory mice were used to assess the usefulness of the laboratory mouse as a pilot organism for the study of yield and somatic cell count relationships in dairy cattle.Procedures developed permit relatively rapid and accurate determination of somatic cell counts in milk of mice. Concentration of somatic cells was three to four times greater in mice than in dairy cows, but counts were distributed similarly. A large effect for stage of lactation existed with high counts in late lactation. Within lactation, repeatability of somatic cell counts and relationships between somatic cell counts and milk yield were similar to those reported for dairy cattle. Heritability of lactation average somatic cell count (3 sample d, log base 2, adjusted for stage of lactation) was .24, indicating lines genetically divergent for somatic cell count can be developed.

Relationship of Somatic Cell Count and Total Sulfhydryls in Milk

Individual milk samples from 32 cows were analyzed to determine the relationship between somatic cell concentration and total sulfhydryl concentration (cysteine plus reduced cystine). A significant relationship was detected between somatic cell count, which ranged from 1.7 × 104 to 1.0 × 107 cells/ml, and total sulfhydryls per gram of milk protein. The regression equation, total sulfhydryls/g of milk protein = 31.96 + 7.99 (log10 somatic cell count) with r2 = 0.19, was calculated. The mean total sulfhydryl concentration was 73.1 μmol/g of protein. The minimal effect of somatic cell concentration on total sulfhydryl concentration indicates that somatic cell concentration should have little influence on chemical parameters of milk protein determined by sulfhydryl analysis when proper experimental controls are used.

N-Acetyl-B-D-Glucosaminidase in Milk and Blood Plasma During Dry and Early Postpartum Periods

Milk and plasma N-acetyl-B-D-glucosaminidase activity was determined for cows during the dry and early postpartum periods. Milk samples were taken from individual quarters of 12 cows from 7 d preceding dry off until calving. Weigh jar milk samples were taken daily for 28 d postpartum from 9 of the 12 cows. Somatic cell concentration was also measured in the postpartum samples.N-Acetyl-B-D-glucosaminidase activity of mammary secretions was significantly elevated in the dry period. Activity in mammary secretions was significantly higher than blood plasma concentrations during the dry period, which suggests that the enzyme present in mammary secretions comes mainly from within the gland. Milk enzyme concentrations declined sharply by 4 d postpartum and gradually declined through 28 d postpartum. Activity was still slightly elevated at 28 d postpartum as compared with normal lactation. Greater daily variability was seen with somatic cells than with N-acetyl-B-D-glucosaminidase. However, somatic cells were more responsive to clinical infections postpartum, showing significant elevations in both clinical episodes. The enzyme was elevated in one clinical case, but relatively unchanged in the other. Plasma levels were constant throughout both trials.

Proteolysis in Milk Associated with Increasing Somatic Cell Counts

Individual cow samples were collected and preserved with potassium dichromate. Somatic cells counts were determined. Tyrosine value was used as an index of proteolysis. Sixty-six samples ranged in somatic cell count from < 50,000 to > 2,000,000/ml. Initial milk tyrosine values and tyrosine values for milks incubated for 24h at 37°C showed proteolytic activity increased with increasing somatic cell count. The increase in proteolysis in preserved milk refrigerated for 72h at 6.7°C was over 1.5 times greater in milks with > 1,000,000 cells/ml than in milks with < 60,000 cells/ml. When preserved milks were laboratory pasteurized, cooled, and stored at 6.7°C for 14 d, some proteolytic activity was detected in milks at all concentrations of somatic cells, and proteolysis increased as somatic cell counts increased. Laboratory-pasteurized samples of milk with various somatic cell counts were also incubated at 30°C for 3 and 6h to duplicate the proteolysis that could occur during the ripening, coagulation, cutting, and cooking steps of cheese making. Again, the greatest increases in tyrosine were in milks with high somatic cell count. Protease(s) associated with elevated somatic cell counts will damage raw milk quality upon storage, pasteurized fluid milk over shelf-life, and milk during cheese making.

Factors Related to Milk Loss in Quarters with Low Somatic Cell Counts

Relationship between milk production and milk composition was studied through comparisons of udder halves within cow. Cows were milked by milking unit for separate quarters of udder. Six trials had six cows per trial. Trial length was 3 d, and milkings were at 12-h intervals. Foremilk samples were taken aseptically for bacterial analysis. Milk weights by quarter were recorded, and samples by quarter were analyzed for concentrations of lactose, somatic cells, and chloride. Milk cell differential counts and N-acetyl-B-D-glucosaminidase activity also were determined. Eighty-four percent of quarter milk samples contained less than 400,000 cells/ml. Differences between right and left udder halves with respect to all measurements were computed. For halves of udders within-cow correlation coefficients for differences between production and log(base 2) somatic cell count, lactose, chloride, bacterial presence, neutrophil percent, lymphocyte percent, macrophage percent, and N-acetyl-B-D-glucosaminidase activity were −.16, .23, −.31, .09, .12, .01, −.14, and −.41. Regression coefficients of milk production (kg) on somatic cell count log(base 2) cells per milliliter, lactose (%), chloride (mg/100ml), and N-acetyl-B-D-glucosaminidase (nmol/min per ml) were −.12, .57, −.05, and −.46. From negative correlations between production and concentrations of chloride, somatic cells, and N-acetyl-B-D-glucosaminidase activity, differences between udder halves in production may be related to changes of the blood-milk barrier, leukocyte diapedesis, and loss of integrity of secretory cells.

Effects of Adding Beta-Carotene to Rations of Lactating Cows Consuming Different Forages1,2

Thirty-six Holstein cows fed a corn silage-based ration and 34 fed an alfalfagrass silage-based ration were assigned according to calving date to receive either 300 mg/head per day of synthetic betacarotene in a gelatin capsule or an empty gelatin capsule daily for the first 100 days postpartum. Supplemental vitamin A was provided at 3919 IU/kg of ration dry matter. Cervix diameters for cows supplemented with betacarotene were smaller at 21 days and 28 days postpartum. Days from parturition to first observed estrus were less when betacarotene was added and less when corn silage was fed. Means of other reproductive traits were more favorable for cows treated with beta-carotene (fewer services per conception and shorter intervals between parturition and conception). Milk progesterone at 21 and 28 days postpartum was not affected by either roughage or beta-carotene treatment. Milk from cows receiving alfalfa-grass silage contained lower somatic cell concentrations than that produced by cows fed corn silage. Milk somatic cell concentrations were lower in both roughage treatment groups for cows supplemented with beta-carotene. No effects of roughage or beta-carotene on milk production or milk fat percentages were significant.

Effect of Growth Hormone on Milk Yields and Related Physiological Functions of Holstein Cows Exposed to Heat Stress

Responses of milk production and other physiological functions to daily subcutaneous injections of bovine growth hormone (16.6 mg/cow) were studied in six Holstein cows in midlactation under environmental heat stress. Five days were assigned for each treatment of thermoneutral (18.3°C), heat (28.9°C), heat plus growth hormone, and heat2. Each period was preceded by at least 3 days of adjustment. Feed and water were available ad libitum. Feed intake, milk production, and rectal temperature were measured twice daily. Blood, energy metabolism, and body weight were measured every 1st, 3rd, and 5th day of each period.Administration of growth hormone under heat stress increased milk production by 3.8 and 12% and fat yield by 9.5 and 12.7% over heat and heat2. Feed intake declined by 5.8% with no significant increase of heat production or body weight loss during treatment with bovine growth hormone. Heat increased somatic cell concentration.

Prevalence and Ultrastructural Characteristics of Bovine Mammary Corpora Amylacea During the Lactation Cycle

Morphologic and histochemical study of spherical, lamellated inclusion bodies in bovine mammary parenchyma established presence of corpora amylacea. The majority (90%) were in alveolar lumina, followed by stroma (7%) and epithelium (3%). Occurrence of corpora amylacea was unrelated to lactation age, intra-mammary infection status, milk somatic cell concentration, or milk production. Quantitative analysis demonstrated a progressive increase of prevalence of these structures from the early to later stages of lactation, followed by a return during the late dry period to concentrations at early lactation. Ultrastructural study revealed deeply basophilic, dense, lamellated deposits (70%) and less dense, fibrillar deposits (30%). Dense bodies stained partially or not at all for amyloid but stained for presence of calcium salts, whereas fibrillar bodies were amyloid positive and calcium negative. Corpora amylacea were most prevalent in fully differentiated parenchymal areas (47.1 bodies/unit tissue area of 2.4×106μm2), less numerous in intermediately differentiated areas (23.4), and sparse in nonsecretory areas (7.1). Morphologic relationships between deposits and parenchyma suggest that corpora amylacea suppress milk secretion and flow during late lactation in isolated areas by engorging luminal spaces and clogging small ducts, leading to milk stasis and involution.

Effect of Infection Status on Quarter Milk Production and Composition Following Omitted Milking

Sixteen cows in middle to late lactation were milked for 3.5 days at 12-h intervals except for a 24-h interval between third and fourth milkings. A cowside quarter milking unit was used. Quarters were classified by infection status. Milk chloride, lactose, somatic cell concentrations, N-acetyl-B-D-glucosaminidase activity, and cell differential counts were determined. Following the omitted milking, concentrations of milk chloride and somatic cells were elevated and lactose concentration reduced in infected quarters. In uninfected quarters, chloride concentration increased, and lactose concentration decreased after the 24-h interval. The milk N-acetyl-B-D-glucosaminidase activity was elevated only in quarters infected with major pathogens. Changes of milk secretion induced by an omitted milking are affected by infection status, and additional secretory cell damage in quarters infected with a major pathogen may result from an omitted milking.

Effect of Intramammary Device on New Infection Rate, Milk Yield, and Milk Somatic Cell Counts in Maryland Dairy Herds

Effectiveness of a polyethylene intramammary device against naturally occurring infections was evaluated in three Maryland herds over 2 yr. Treated cows [62] were fitted with intramammary devices in all quarters of udders. Control cows [62] were sham treated. Rates of new intramammary infection over single lactation in treated and control quarters of primiparous cows averaged 18 and 27%. Reduction of infection rate was due primarily to fewer Corynebacterium bovis infections. Infection rate between multiparous cow treatments were similar.In uninfected quarters cell counts in strippings averaged .11 to .13×106/ml and in quarters fitted with intramammary devices concentrations were only .22 to .31×106 cells/ml. But in infected quarters with intramammary devices, cell counts of strippings were 1.38 to 1.48×106/ml. Concentrations of somatic cells of strippings in infected quarters without devices averaged .48 to .63×106/ml.Dairy herd improvement cell counts for primiparous and multiparous cows with and without intramammary devices were similar and averaged .2×106/ml. Neither milk nor fat production differed.The intramammary device as currently designed is incapable of stimulating a leukocytosis sufficient in stripping milk to prevent intramammary infection.

Phenotypic and Genetic Statistics of Components of Milk and Two Measures of Somatic Cell Concentration

Heritabilities, genotypic and phenotypic correlations for milk, fat, and protein yields, and two traits related to somatic cell concentration (cumulative lactation score and lactational somatic cell concentration) were estimated. A total of 18,416 first lactations of Holstein cows were analyzed by a new procedure for estimating variance components. Heritabilities were .21, .23, .19, .17, and .61 for milk, fat, and protein yields, cumulative lactation score, and lactational somatic cell concentration. Addition of protein yields to the current selection for two traits with nil economic value for protein would improve genetic gains for fat and milk yields in the northeastern United States. If cumulative lactation score and lactational somatic cell concentration were incorporated in current selection for two traits, restricted selection indexes should be used to avoid reduction in genetic gains for milk and fat yields.

Effect of Parity, Stage of Lactation, and Intramammary Infection on Concentration of Somatic Cells and Cytoplasmic Particles in Goat Milk

Aseptic foremilk samples (about 15ml) were collected biweekly for four samplings and then monthly throughout lactation from 35 does in three herds on Dairy Herd Improvement test. Bacteriology, direct microscopic somatic cell counts, and cytospin differential cell counts were performed on all samples. Milk yield was obtained from monthly Dairy Herd Improvement records. Thirty-nine percent of udder halves were infected, and coagulase negative staphylococci were the most frequent isolates (201 of 205). Somatic cell counts were influenced by lactation number, stage of lactation, and intramammary infection. Also, infection of one udder half increased somatic cells in the corresponding uninfected mammary half of the same animal. Cytoplasmic particles were not affected by stage of lactation or by intramammary infection but were greater for goats in first lactation. Milk yield was influenced by lactation number, stage of lactation, and intramammary infection.

Influence of Adrenocorticotropin upon Milk Production, Milk Constituents, and Endocrine Measures of Dairy Cows

Ten lactating Holstein cows were injected intramuscularly with either 200 IU of adrenocorticotropin or saline every 6h for 42h. Blood concentrations of corticosteroids, glucose, sodium, and potassium, and milk yield and constituents were measured before, during, and after the injection period. Mean corticosteroid increased eightfold for adrenocorticotropin 1h after first injection, remained significantly higher than controls during the injection period, and then decreased to preinjection concentrations 13h after last injection. Mean milk yields were similar at 8h after first injection, then decreased for adrenocorticotropin during the injection period. Increases in glucose concentrations accompanied suppression of milk yield for adrenocorticotropin. After injections glucose concentrations returned to preinjection concentrations at 13h after last injection whereas milk yield for adrenocorticotropin remained suppressed for several milkings. Milk protein yields decreased for adrenocorticotropin during and after the injection period. Fat percentage for adrenocorticotropin increased though fat yield was unaffected. Concentrations of somatic cells in milk were unchanged by adrenocorticotropin treatment, but sodium was increased and potassium decreased during injection. Mammary gland function in lactating dairy cows may be affected adversely by exaggerated increases of concentrations of corticosteroids in blood.

Lactation Stage, Parity, and Infection Affecting Somatic Cells, Electrical Conductivity, and Serum Albumin in Milk

Effects of stage of lactation and parity on cell concentration, electrical conductivity, and serum albumin concentration of milk from quarters of known infection status were examined.For quarters free from infection, somatic cell concentration rose from 80 to 160 X 103 cells/ml between 35 and 285 days postpartum whereas for quarters infected with Staphylococcus aureus the increase was from 250 to about 1000 X 103 cells/ml. As lactation number advanced, there was little change in cell concentration for quarters free from infection, whereas for quarters infected with Staphylococcus aureus, cell concentration rose from approximately 450 X 103 cells/ml for first lactation to about 1500 X 103 cells/ml for cows in their sixth or more lactations.Trends in electrical conductivity were similar to those for cell concentration, with the main influence on electrical conductivity being Staphylococcus aureus infection. For serum albumin concentration only the effect of stage of lactation was significant. Concentration of serum albumin rose from 150 mg/liter at the beginning of lactation to 280 mg/liter at 215 days postpartum.Effects of stage and number of lactation were minor compared with effects of infection by Staphylococcus aureus.

Relationship Between Lactation Measures of Somatic Cell Concentration and Milk Yield

Data were from herds on Dairy Herd Improvement in Wisconsin which were regularly tested for somatic cells. Lactation cell counts were taken as the average of either actual or natural log of individual tests during the lactation. Lactation milk yield was regressed on somatic cell concentration, among other concomitant variables, for each of the first four lactations. The amount of data ranged from 4,912 cows in 346 herds for lactation 1 to 1,759 cows in 202 herds for lactation 4. Yield loss per unit increase in average loge cell count was 135±20kg in first lactation and 270±30kg for all other lactations. These relationships were linear, indicating that loss per unit increase in actual cell count is greatest when cell count is low. Linearity of the regression of yield on average log cell count makes this more desirable than actual cell count as a potential trait for indirect selection for genetic resistance to mastitis. The effect on yield in a given lactation of increased average log cell concentration in the previous lactation was not statistically significant. However, the magnitude of estimates for carry-over effects were as much as 50% of concurrent effects. This suggests the possibility of an important amount of carry-over.

The detection of mastitis in individual quarters using electrical conductivity or somatic cell concentration.

In this investigation electrical conductivity (EC) and somatic cell concentration (SCC) were compared in 3 herds for their ability to correctly identify the infection status of quarters. For EC, thresholds of 6.0 and 6.8 mS/cm were used and comparisons were made between quarters within each cow. The method of comparison between quarters was the same as that described by the manufacturers of the AHI Mastitis Detector. For SCC a threshold of 500 x 10(3) cells/ml was used. For both EC and SCC considerable variation was found between herds for sensitivity (the proportion of quarters infected with a major pathogen and detected as abnormal), and specificity (the proportion of quarters free from infection and detected as normal). The mean sensitivity and specificity of EC for the three herds was 49% and 79% respectively, whereas for SCC the means were 71% and 81% respectively. The variation in sensitivity and specificity of EC between herds was attributed to differences in the distribution of EC for quarters of similar infection status. It was concluded that these differences in herd EC precluded the use of pre-determined EC thresholds which were applicable for detecting mastitis in all herds.

Concentrations fo Glucocorticoids, Bovine Serum Albumin, and Somatic Cells in Mastitic Milk

Milk glucocorticoids, bovine serum albumin, and somatic cells were measured during experimental mastitis. Six cows were allotted evenly into injected and control groups. Injected cows received a single intramammary infusion of .5mg sterile Escherichia coli endotoxin in a quarter chosen at random. Control cows were untreated. Milk quarter samples were taken from all cows at both milkings and 9h following midnight milking 1 day prior to and for 7 days following injection. Peak glucocorticoid concentrations occurred 9h postinjection and were 17.5ng/ml (± 10.2), and 4.4ng/ml (± 2.3) in injected and noninjected quarters of the same cows. In injected cows glucocorticoid concentrations returned to baseline within 36h. Glucocorticoids in control quarters were .4ng/ml (± .3). Peak bovine serum albumin was 27.8ng/ml (± 22.8) and .56ng/ml (± .09) in injected and noninjected quarters in the same cows as compared to a baseline of .2 mg/ml (± .04) in control cows. In injected quarters, bovine serum albumin remained elevated for 4 days, and somatic cells were elevated for 6 days after injection. Glucocorticoids, bovine serum albumin, and somatic cells were elevated markedly in injected quarters, and unlike concentrations of bovine serum albumin and somatic cells, elevated glucocorticoids in injected quarters were short lived.