Variation In Somatic Cell Count Research Articles

Seasonal dynamics of bulk milk somatic cell count in grazing Norwegian dairy goats

Somatic cell count (SCC) is a widely used indicator of milk quality in the dairy industry. It is a relatively good indicator of udder health in dairy cows, but strongly confounded by non-infection factors, including season, in dairy goats. This study's objectives were to estimate the variation in SCC explained by season and stage of lactation. We also investigated associations between SCC and other milk quality parameters routinely measured, including total bacterial count, fat, protein, and lactose content, in different seasons and stages of lactation. In this observational study, we included results from the routine analyses of bulk milk samples (n = 5,180) collected every third day in 88 Norwegian goat herds through one year. Herd information was collected via a questionnaire and from the dairy herd recording system. The herds had a notable increase in bulk SCC associated with the pasture season. The median bulk SCC was 470,000 cells/mL in deliveries from the indoor spring period and 1,100,000 cells/mL in the pasture season. During the indoor fall season, when most goat herds are in late lactation, the median SCC was 940,000 cells/mL. The combined effect of the season and herd stage of lactation explained 53.5% of the variation in bulk milk SCC. Fat and protein contents varied significantly with season and stage of lactation, and the association with SCC was non-significant for fat content and explained less than 3% of the variation in protein content. Lactose content was associated with SCC, stage of lactation, and season. Total bacterial count was associated with SCC and the indoor seasons. Determination of normal seasonal variation of goat bulk milk SCC is necessary to establish thresholds for defining milk as abnormal and unacceptable for further processing and improving the usefulness of SCC as a tool for milk quality improvement in dairy goats. The results suggest that SCC thresholds for taking action to improve the milk quality should be adjusted for season and stage of lactation.

Distribution of somatic cell count and udder pathogens in Norwegian dairy goats

Compared with dairy cows, goat somatic cell count (SCC) is higher and probably more affected by physiological factors such as parity, stage of lactation, and season. Thus, SCC is believed to be a less precise indicator of intramammary infections in dairy goats, and no consensus exists on SCC thresholds for considering goats as infected. The Norwegian Goat Recording System maintains individual goat production records and results from microbiological analyses of milk samples. In this retrospective observational study, we used recordings over a 10-yr period (2010 to 2020) to describe the association between individual goat SCC and noninfectious factors, as well as intramammary infections. The median SCC in the 1,000,802 milk recordings included in the study was 440,000 cells/mL, and the mode was 70,000 cells/mL. Somatic cell count increased with parity, days in milk, estrus, pasture season, and intramammary infections. The effect of parity and stage of lactation was significantly higher in infected compared with uninfected goats. Staphylococci dominated as causes of intramammary infections, with Staphylococcus aureus as the udder pathogen associated with highest SCC. The most prevalent non-aureus staphylococci were Staphylococcus warneri, Staphylococcus epidermidis, and Staphylococcus caprae. This study provides guidelines for interpretation of goat SCC at different parities and stages of lactations under Norwegian management conditions. We revealed a considerable variation in SCC associated with physiological factors, indicating that the cutoff for identifying infected goats should be a dynamic threshold adjusted for parity, stage of lactation, and season.

Progression of different udder inflammation indicators and their episode length after onset of inflammation using automatic milking system sensor data

In automatic milking systems (AMS), sensors can measure cow behavior and milk composition at every milking. The aim of this observational study of previously collected data was to gain insight into the differences in dynamics of udder inflammation indicators between cows that recover and those that do not recover after detection of an initial inflammation. Milk diversion (milk separated from the bulk tank and thus indicating farmer intervention), conductivity, and somatic cell count (SCC) data from 4 wk before the initial inflammation to 12 wk after the initial inflammation were used to analyze 2,584 cases of udder inflammation. An udder inflammation case was defined as an initial observation of SCC ≥200,000 cells/mL as well as 1 additional SCC measurement >200,000 cells/mL within 10 d after the initial case, among other requirements. The data originated from 15 AMS herds in 6 countries. Four subsets of cows were created based on whether milk was diverted after the initial inflammation and whether the udder inflammation cases recovered, using a 10-d rolling average SCC threshold of 200,000 cells/mL and checking whether this rolling mean was below the threshold within 90 d after the initial inflammation as the indication of recovery. This formed the following subsets of cow lactations: milk diverted-recovered, milk diverted-not recovered, no milk diverted-not recovered, no milk diverted-recovered. Thresholds of 100,000 SCC/mL and 300,000 SCC/mL for the definition of case and recovery were also applied in a sensitivity analysis but with no substantial difference in results. Linear mixed models were used for each subset to study the variation in SCC (natural logarithm of SCC divided by 1,000) and σ-conductivity (natural logarithm of standard deviation of quarter conductivities). When observing the fraction of cows with SCC <200,000 cells/mL in the recovery subsets, most cows recovered within 20 d after the initial inflammation. In the recovery subsets, both σ-conductivity and SCC stabilized, mostly within 3 to 4 wk after the initial inflammation. σ-Conductivity stabilized above the pre-onset level in all subsets and did not show a clear increase in the no-milk-diverted subgroups, whereas SCC stabilized closer to the pre-onset level. Overall, this study indicated a cutoff point between nonchronic and chronic changes in indicators 3 to 4 wk after the initial inflammation for SCC and σ-conductivity.

Dynamics of somatic cell count and intramammary infection in lactating dairy cows.

Objective:The influence of intramammary infection (IMI) and types of bacteria was assessed on somatic cell count (SCC) in dairy cows’ milk with respect to breed, age, parity, stage of lactation, milk production, and mammary quarter location.Materials and methods:After recording data in a structured questionnaire, 360 samples of quarter milk were collected. The samples were subjected to SCC and isolation and identification of bacteria. The data were analyzed to find out the significant influence of independent factors on SCC and IMI.Results:The infected quarters had a significantly higher mean SCC (210.52 × 103 cells/ml) compared to uninfected ones (32.72 × 103 cells/ml). The mean SCC was the highest for IMI with Enterobacter spp. (338.00 × 103 cells/ml) followed by Bacillus spp. (319.20 × 103 cells/ml), coagulase-negative Staphylococci (CNS) (268.17 × 103 cells/ml), Staphylococcus aureus (218.31 × 103 cells/ml), and Escherichia coli (200.75 × 103 cells/ml) and the lowest for Pseudomonas aeruginosa (66.33 × 103 cells/ml). Milk of rear quarters had a significantly higher SCC than the front quarters. SCC increased with increasing age, parity, and lactation stage regardless of whether cows are infected or not. The IMI was more prevalent in rear quarters (42.2%) and cows at early (≤7 days) lactation (100.0%). Cows having a parity of ≥5 and crossbred and high yielding (>5 l) cows had also a higher rate of IMI of 38.2%, 36.7%, and 38.2%, respectively.Conclusion:The IMI and type of bacteria were the principal factors for SCC variation. Besides, mammary quarter location, age, and parity should be taken into consideration during the interpretation of SCC.

Genetic relationships of alternative somatic cell count traits with milk yield, composition and udder type traits in Italian Jersey cows.

The aim of this study was to estimate genetic associations between alternative somatic cell count (SCC) traits and milk yield, composition and udder type traits in Italian Jersey cows. Alternative SCC traits were test-day (TD) somatic cell score (SCS) averaged over early lactation (SCS_150), standard deviation of SCS of the entire lactation (SCS_SD), a binary trait indicating absence or presence of at least one TD SCC >400,000cells/ml in the lactation (Infection) and the ratio of the number of TD SCC >400,000 cells/ml to total number of TD in the lactation (Severity). Heritabilities of SCC traits, including lactation-mean SCS (SCS_LM), ranged from 0.038 to 0.136. Genetic correlations between SCC traits were moderate to strong, with very few exceptions. Unfavourable genetic associations between milk yield and SCS_SD and Infection indicated that high-producing cows were more susceptible to variation in SCC than low-producing animals. Cows with deep udders, loose attachments, weak ligaments and long teats were more susceptible to an increase of SCC in milk. Overall, results suggest that alternative SCC traits can be exploited to improve cow's resistance to mastitis in Italian Jersey breed.

Short communication: The main factors affecting somatic cell count in organic dairy farming

Preventive management practices are essential for maintaining acceptable udder health status, especially in organic farming, in which the use of antimicrobials is restricted. The contribution of the following factors to somatic cell count (SCC) was assessed in 788 cows from 15 organically reared herds in northern Spain: milk production, lactation number, treatments applied, selective dry cow therapy and teat dipping routines. The data were examined by linear logistic regression. Lactation number was the main factor affecting logSCC (β= 0.339, p&lt;0.001) followed in order of importance by milk production (β= -0.205, p&lt;0.001), use of alternative treatments (β=0.153, p&lt;0.001), selective dry cow therapy (β=0.120, p=0.005) and teat dipping routines (β=-0.076, p=0.028). However, the model only explained 17.0% of the total variation in SCC. This variable depends on factors other than those considered here, amongst which udder infection is probably one of the most important. Nonetheless, the study findings enabled us to determine the contribution of the main management factors that should be taken into account to improve udder health status on organic farms.

Genome-wide association study for milk somatic cell score in holstein cattle using copy number variation as markers.

Mastitis, the most common and expensive disease in dairy cows, implies significant losses in the dairy industry worldwide. Many efforts have been made to improve genetic mastitis resistance in dairy populations, but low heritability of this trait made this process not as effective as desired. The purpose of this study was to identify genomic regions explaining genetic variation of somatic cell count using copy number variations (CNVs) as markers in the Holstein population, genotyped with the Illumina BovineHD BeadChip. We found 24 and 47 copy number variation regions significantly associated with estimated breeding values for somatic cell score (SCS_EBVs) using SVS 8.3.1 and PennCNV-CNVRuler software, respectively. The association analysis performed with these two software allowed the identification of 18 candidate genes (TERT, NOTCH1, SLC6A3, CLPTM1L, PPARα, BCL-2, ABO, VAV2, CACNA1S, TRAF2, RELA, ELF3, DBH, CDK5, NF2, FASN, EWSR1 and MAP3K11) that result classified in the same functional cluster. These genes are also part of two gene networks, whose genes share the 'stress', 'cell death', 'inflammation' and 'immune response' GO terms. Combining CNV detection/association analysis based on two different algorithms helps towards a more complete identification of genes linked to phenotypic variation of the somatic cell count.

Short communication: Influence of the sampling device on somatic cell count variation in cow milk samples (by official recording)

&lt;p&gt;The objective of this study was to investigate the variability in cow´s milk somatic cell counts (SCC) depending on the type of milk meter used by dairy farms for official milk recording. The study was performed in 2011 and 2012 in the major cattle area of Spain. In total, 137,846 lactations of Holstein-Friesian cows were analysed at 1,912 farms. A generalised least squares regression model was used for data analysis. The model showed that the milk meter had a substantial effect on the SCC for individual milk samples obtained for official milk recording. The results suggested an overestimation of the SCC in milk samples from farms that had electronic devices in comparison with farms that used portable devices and underestimation when volumetric meters are used. A weak positive correlation was observed between the SCC and the percentage of fat in individual milk samples. The results underline the importance of considering this variable when using SCC data from milk recording in the dairy herd improvement program or in quality milk programs.&lt;/p&gt;

Locus BoLA-DRB3 is just an ordinary site of the polygene when explaining genetic variance of somatic cell count and milk yield

The study aimed at clarifying the problem of the hitherto contradictory results regarding usefulness of BoLA-DRB3 locus as a marker in selection against mastitis and for milk yield. Treating the BoLA-DRB3 locus effect as random was proposed in place of considering it fixed. Somatic cell counts and milk yields recorded monthly on a test day (22,424) of 619 Polish Holstein cows genotyped for BoLA-DRB3 were analysed with an animal model including a random effect for genotype at this locus. The BoLA-DRB3 alleles were defined as restriction patterns obtained with three endonucleases. Two alternative BoLA-DRB3 additive genotype (co)variance structures were constructed for 161 genotypes recorded. One was based on the allelic similarity of the genotypes resulting in element values of 0 (no common allele), 0.5 (one allele in common), and 1 (diagonal). The other considered restriction site similarity (up to 3 in 1 allele) giving element values of 0 (no common restriction sites) and then increasingly in steps of 1/6 up to 6/6 (diagonal), where the numerator represents the number of common sites between genotypes. The DRB3 variance component for the natural logarithm of somatic cell count did not exceed 0.006 of the polygenic additive component or 0.003 for milk yield. Hence, unless we fail to detect the causative site or to properly define traits being the projection of a site, the effect of the genotype at the BoLA-DRB3 locus does not explain variation in somatic cell count and milk yield at a degree expected of a genetic marker.

The variation of somatic cell count and of relative and specific viscosity with boiling treatment of cow milk

The variation of somatic cell count and of relative and specific viscosity with boiling treatment of cow milk

Impact of seasonal grazing on udder health of cows

The somatic cell count (SCC) in individual cow milk was used as an indicator of the udder health of cows in the mountain area in the Czech Republic. The monthly test-day records on SCC in milk of total 12,788 cows from 26 herds were scrutinized in order to elucidate the impact of the seasonal grazing on occurrence of milk secretion disorders. The interaction between the season (summer: May−October; winter: November−April) and the feeding system (seasonal grazing; permanently-indoor feeding) effects was used as a measure of the effect of pasture on SCC. The effect of season significantly interacted with the effect of farm (P &lt; 0.001) and the between-farm variation in SCC was higher than the seasonal variation on particular farms. In both the feeding systems, the SCC was lower in the summer season than in the winter season (P &lt; 0.01). The effect of season did not interact with the effect of feeding system (P &gt; 0.05). The Holstein cows had on average higher SCC than the Czech Fleckvieh cows (P &lt; 0.001) and this genetic effect did not interact with the season nor with the season and the farm effects (P &gt; 0.05). The results indicated a higher importance of the management and the genetic factors for the occurrence of milk secretion disorders in comparison to the seasonal factors. No negative effect of the seasonal grazing on udder health was identified.

Associations of udder-health indicators with cow factors and with intramammary infection in dairy cows

The objective of this study was to investigate if and how cow factors and intramammary infection (IMI) are associated with 4 different udder-health indicators in dairy cows as a first step in investigating whether the diagnostic performance of these indicators can be improved. The investigated indicators were somatic cell count (SCC), lactate dehydrogenase (LDH), N-acetyl-β-d-glucosaminidase (NAGase), and alkaline phosphatase (AP) measured in milk. In this cross-sectional study, approximately 1,000 cows from 25 dairy herds were sampled for bacteriology (quarter milk samples) during 3 consecutive days: the day before test milking, at the day of test milking, and at the day after test milking. The whole-udder test milking sample was analyzed for milk composition, SCC, LDH, NAGase, and AP. Cow data (parity, breed, milk yield, percentage of milk fat and protein, milk urea concentration, and days in milk from the sampled test milking) were collected from the Swedish milk-recording scheme. Of the sampled cows 485 were considered IMI negative and were used in multivariable mixed-effect linear regression models to investigate associations between cow factors and the udder-health indicators. A second modeling including all cows, both IMI negative and IMI positive (256 cows), was also performed. The results showed that all udder-health indicators were affected by cow factors but that different cow factors were associated with different indicators. Intramammary-infection status was significantly associated with all udder-health indicators except AP. Parity and milk urea concentration were the only cow factors associated with all indicators in all models. The significant cow factors explained 23% of the variation in SCC and >30% of the variation in LDH, NAGase, and AP in IMI-negative cows, showing that LDH, NAGase, and AP are more affected than SCC by cow factors. The IMI status explained 23% of the variation in SCC in the model with all cows but only 7% of the variation in LDH and 2% of the variation in NAGase, indicating that SCC has the best potential as a diagnostic tool in finding cows with IMI. However, further studies are needed to investigate whether the diagnostic properties of these udder-health indicators will improve with adjustment according to their associations with different cow factors when used as a diagnostic tool for finding cows with IMI.

Isolation of coagulase negativeStaphylococciand variation in somatic cell count in buffalo milk samples

II SIMPÓSIO DE QUALIDADE DE LEITE O II Simpósio de Qualidade de Leite aconteceu nos dias 05, 06 e 07 de setembro de 2014, no Centro de Convenções da Faculdade de Ciências Agrárias e Veterinárias, Unesp, Câmpus de Jaboticabal, SP. Foi um evento organizado por pós-graduandos do Departamento de Medicina Veterinária Preventiva, sob a supervisão do Prof. Dr . Antonio Nader Filho (homenageado do V Congresso Brasileiro de Qualidade de Leite, 2013, pelos importantes trabalhos desenvolvidos na área). Tendo em vista o sucesso obtido na edição anterior, o II Simpósio de Qualidade de Leite apresentou uma nova programação, com palestras que abordaram assuntos atuais relacionados à cadeia do leite no Brasil aliados à presença de palestrantes renomados. Temas como fraudes e adulteração do leite; resíduos químicos; programas de autocontrole e boas práticas de fabricação; zoonoses veiculadas pelo leite; tratamento da mastite; manejo alimentar e ambiental do gado de leite; aproveitamento de dejetos; a importância da extensão rural como uma aliada; o controle estratégico de parasitas e análises sobre CBT e CCS, e uma mesa redonda para discutir a Instrução Normativa nº 62, do Ministério da Agricultura, Pecuária e Abastecimento, foram alguns dos principais assuntos abordados durante o evento. O público esperado envolveu profissionais de indústrias de laticínios, criadores de gado de leite, estudantes de graduação e de pós-graduação da área de qualidade de leite, pesquisadores e demais profissionais do segmento envolvidos com a pecuária leiteira. Outro aspecto inovador do Simpósio foi a apresentação de resumos expandidos de trabalhos científicos e de extensão rural relacionados ao tema de qualidade do leite. Os resumos estão publicados na Revista Brasileira de Higiene e Sanidade Animal , no formato de resumo expandido, o que permite maior visibilidade e divulgação das pesquisas relacionadas ao tema. Dessa forma, a Comissão Organizadora do II Simpósio de Qualidade de Leite, agradece a todos que de alguma forma colaboraram para o sucesso dessa edição. Em especial, agradecemos nossos patrocinadores, pelo apoio essencial ao evento e aos palestrantes, que foram de suma importância para o enriquecimento e sucesso do Simpósio. Muito obrigado a todos pela participação! Comissão Organizadora II Simpósio de Qualidade de Leite URL do Portal: http://www.higieneanimal.ufc.br/seer/index.php/index/index 2014 setembro; 8(5 Supl 1): p. 01- 552

전남지방 산양유의 성분 및 체세포수의 계절적 변화

Consistent information on the chemical composition and its seasonal variation of goat udder half milk is limited in Korea. The objective of this study was to analyze the seasonal variation of the chemical composition of goat milk to take establish various parameters into consideration on the pricing of the goat milk. Variations in chemical composition, somatic cell count (SCC) and bacterial count of 1,038 udder half milk samples from 650 heads raised in 7 farms of Jeonnam province were determined by season. Fat, protein, lactose, non-fat solids, milk urea nitrogen (MUN), pH, SCC and bacterial counts were also analyzed. The average composition of the milk was: fat 3.80±1.36%, protein 3.23±0.80%, lactose 4.39±0.54%, total solids 12.18±1.80%, non-fat solids 8.38±0.80%, and milk urea nitrogen 28.44±5.00 mg/dL. The average pH was 6.81±0.24. The average of SCC and bacterial counts were 2.54±4.60×10 6 cells/mL and 1.25±3.76×10 5 CFU/mL, respectively. Chemical composition, pH, SCC and bacterial counts of dairy goat milk varied widely during the lactation period and by season. The fat concentration was the lowest in spring (3.39±1.53%) and the highest in autumn and winter (3.98±1.30% and 3.98±1.48%). Protein concentration was the lowest during summer (2.92±0.48%) and the highest in winter (3.81±0.95%). Lactose concentration was the lowest in autumn (4.24±0.41%) and the highest in spring (4.58±0.35%). The lowest total solid value was obtained in the spring season (11.75±1.80%) which was then increased in winter (12.85±1.96%). Non-fat solid concentration was the lowest in summer (8.07±0.64%) and the highest in autumn (8.94±0.82%). MUN concentration was the highest in summer (8.07±0.64%), and the pH concentration was the highest in spring at 6.93±0.27%. Seasonal variation of SCC and bacterial count were the lowest in spring (0.94±1.54×10 6 cells/mL and 0.22±0.61×10 5

Microbiological quality and somatic cell count in bulk milk of dromedary camels (Camelus dromedarius): Descriptive statistics, correlations, and factors of variation

The objectives of the present study were to monitor the microbiological quality and somatic cell count (SCC) of bulk tank milk at the world’s first large-scale camel dairy farm for a 2-yr period, to compare the results of 2 methods for the enumeration of SCC, to evaluate correlation among milk quality indicators, and to determine the effect of specific factors (year, season, stage of lactation, and level of production) on milk quality indicators. The study was conducted from January 2008 to January 2010. Total viable count (TVC), coliform count (CC), California Mastitis Test (CMT) score, and SCC were determined from daily bulk milk samples. Somatic cell count was measured by using a direct microscopic method and with an automatic cell counter. In addition, production parameters [total daily milk production (TDM, kg), number of milking camels (NMC), average milk per camel (AMC, kg)] and stage of lactation (average postpartum days, PPD) were recorded for each test day. A strong correlation (r=0.33) was found between the 2 methods for SCC enumeration; however, values derived using the microscopic method were higher. The geometric means of SCC and TVC were 394×103cells/mL and 5,157cfu/mL during the observation period, respectively. Somatic cell count was >500×103 cells/mL on 14.6% (106/725) and TVC was >10×103cfu/mL on 4.0% (30/742) of the test days. Both milk quality indicators had a distinct seasonal pattern. For log SCC, the mean was lowest in summer and highest in autumn. The seasonal pattern of log TVC was slightly different, with the lowest values being recorded during the spring. The monthly mean TVC pattern showed a clear difference between years. Coliform count was <10cfu/mL in most of the samples (709/742, 95.6%). A positive correlation was found between log SCC and log TVC (r=0.32), between log SCC and CMT score (r=0.26), and between log TVC and CC in yr 1 (r=0.30). All production parameters and stage of lactation showed strong seasonal variation. Log SCC was negatively correlated with TDM (r=−0.35), AMC (r=−0.37), and NMC (r=−0.15) and positively correlated with PPD (r=0.40). Log TVC had a negative correlation with AMC (r=−0.40) but a positive correlation with NMC (r=0.32), TDM (r=0.16), and PPD (r=0.45). The linear mixed model with stepwise variable selection showed that the main sources of log SCC variation were PPD, TDM, PPD × season, and season. For log TVC, the same factors and year contributed to the variation.

VARIAÇÃO E MONITORAMENTO DA QUALIDADE DO LEITE ATRAVÉS DO CONTROLE ESTATÍSTICO DE PROCESSOS

The aim of this study was to evaluate the statistical process control (SPC) as an identification tool of non-natural effects on milk quality, which may be manipulated. Data of milk production, somatic cell count (SCC) and total bacterial count (TBC) from 384 farms were used. Natural effects (season and volume) on the variation of SCC and TBC were evaluated; furthermore, control charts of somatic cell score (SCS) and total bacterial count transformed (TBCt) were designed to find non-natural variation resources on four farms. It was observed that the season affected significantly the SCS and TBCt. Control charts, in each season, indicated the non-natural variation in SCS and TBCt on the four farms evaluated. Therefore, the application of SPC as a tool at farm level is an additional instrument for monitoring milk quality.KEYWORDS: control charts; somatic cell count; sigma; total bacterial count.

Effects of storage temperature and milk sample age on the somatic cell count of goat milk

In goat milk, storage temperature and milk age has been identified as one of possible factors affecting the somatic cell count (SCC). To establish the effect of the storage temperature and milk age used for SCC in goat milk, counts were performed on 320 aliquots of milk sample from 20 goats using Somacount 300 (Bentley Instruments). The milk samples were preserved with bronopol, kept at 5o, 10o, 20o and 30oC and analyzed 1, 3, 5 and 7 day post-collection. The temperature storage and milk age did not modify the SCC of the milk samples significantly (P>0,05). The results of SCC in milk samples incubated at 10o, 20o and 30oC were slightly lower than those incubated at 5oC. Considering SCC variation lower than 9%, the results of SCC under experimental conditions can be acceptable for monitoring both the udder health and milk quality in dairy goats.

Evaluation of somatic cell count thresholds to detect subclinical mastitis in Gyr cows

The objectives of this study were (1) to determine the sensitivity (Se) and specificity (Sp) of somatic cell count (SCC) thresholds to identify subclinical mastitis in Gyr cows caused by major and minor pathogens; (2) to study the effects of month of sampling, rear or front mammary quarters, herd, intramammary infection (IMI), and bacterial species on SCC at quarter level; and (3) to describe the prevalence of IMI in Gyr cows in commercial dairy herds. In total, 221 lactating Gyr cows from 3 commercial dairy farms were selected. Milk samples were collected from individual quarters once a month for 1 yr from all lactating cows for SCC and bacteriological analysis. Mammary quarters were considered the experimental units and the SCC results were log10-transformed. Four SCC thresholds (100, 200, 300 and 400 × 103 cells/mL) were used to determine Se and Sp to identify infected mammary quarters. The overall prevalence of IMI in quarter milk samples of Gyr cows was 49.8%, and the prevalence of minor pathogens was higher (31.9%) than that of major pathogens (17.8%). Quarter samples with microbial isolation presented higher SCC compared with negative samples. Sensitivity and Sp of selected SCC thresholds varied according to the group of pathogen (major and minor) involved in the IMI definition. Sensitivity increased and Sp decreased when mammary quarters with only major pathogens isolation were considered positive. The use of a single SCC analysis to classify quarters as uninfected or infected in Gyr cows may not be a useful test for this breed because Se and Sp of SCC at the studied thresholds were low. The occurrence of IMI and the bacterial species are the main factors responsible for SCC variation in mammary quarters of Gyr cows. Milk samples with major pathogens isolation elicited higher SCC than those with minor pathogens.

Factors influencing variation of bulk milk antibiotic residue occurrence, somatic cell count, and total bacterial count in dairy sheep flocks

To study the variations of bulk tank milk variables in dairy ewe flocks and to identify the main target practices and flock groups to improve milk quality and safety, a total of 71,228 records of antibiotic residue (AR) and milk yield and 68,781 records of somatic cell count (SCC) and total bacterial count (TBC) were obtained over 5 yr from the same 209 dairy ewe flocks of the Assaf breed belonging to the Consortium for Ovine Promotion of Castilla-León (Spain). Based on a logistic regression model, year, month, semester, SCC, TBC, dry therapy, and milk yield significantly contributed to AR variation. High SCC was associated with increased AR violations. When antibiotic dry therapy was implemented, AR occurrence was higher than when this practice was not used. A polynomial monthly distribution throughout the year was observed for AR occurrence; the highest values were in autumn, coinciding with low milk yields per flock. Yearly occurrences drastically diminished from 2004 (1.36%) to 2008 (0.30%), probably as a result of effective educational programs. The mixed-model ANOVA of factors influencing variation in SCC and TBC indicated that year, month, AR, dry therapy group, milking type, and year interactions were significant variation factors for SCC and TBC; mathematical model accounted for 74.1 and 35.4% of total variance for each variable, respectively. Differences in management and hygiene practice caused significant SCC and TBC variations among flocks and within flocks throughout the 5-yr study. Over time, continuously dry treated flocks showed lower logSCC (5.80) and logTBC (4.92) than untreated (6.10 and 5.18, respectively) or discontinuously dry treated (6.01 and 5.05, respectively) flocks. Continuously dry treated flocks had lower AR occurrences than did discontinuously dry treated flocks. As a whole, AR occurrence and SCC and TBC bulk tank milk variables can be used for monitoring mammary health and milk hygiene and safety in dairy sheep throughout time.

Variação da contagem de células somáticas em vacas leiteiras de acordo com patógenos da mastite

Avaliou-se o efeito de patógenos da mastite sobre a contagem de células somáticas (CCS) em leite. Foram coletadas 3.987 amostras de leite de 2.657 animais oriundos de 24 rebanhos leiteiros localizados nos estados do Rio de Janeiro e Minas Gerais. As amostras de leite foram usadas para CCS e identificação de patógenos da mastite. Estatísticas descritivas, teste T para amostras independentes e modelo linear generalizado foram usados para análise dos dados. O modelo linear generalizado identificou os efeitos de rebanho, animal dentro de rebanho, ordem de parto, estação do ano e infecção intramamária causada por Streptococcus agalactiae e Streptococcus spp. que não S. agalactiae como significativos na variação da CCS. O efeito de animal dentro de rebanho foi maior que o efeito de rebanho. S. agalactiae foi o patógeno responsável pelo maior aumento da CCS em vacas e apresentou em média 1.520.000 células/mL. Foi observado efeito específico dos patógenos na variação da CCS.