Variation in somatic cell counts of milk samples from individual cows

Somatic cell counts of 2570 milk samples from 765 cows collected bimonthly from November 1975 to May 1976 were transformed to logarithmic values and analysed statistically. Components of variance were estimated as follows: Herds 0.033 (13 %), age groups 0.021 (8%), cows (within herds and age groups) 0.080 (31%), months 0.014 (6%), residual 0.107 (42%). Correction of actual cell counts for the influence of milk yield on the day of sampling led to only small changes in the magnitude of the various components. The coefficient of correlation between samples from the same cow was computed as 0.60 when the samples were from the same lactation, and 0.37 for samples from consecutive lactations.The proportionately small variation among herds as compared to the variation among cows of the same herd throws doubt on the efficiency of cell counting in samples of herd milk as a way of identifying cows with high cell counts.     

Observations on intramammary infection and somatic cell counts in cows treated with recombinant bovine somatotropin.

Data were collected on udder health variables as part of a study of the effects of recombinant bovine somatotropin on production in lactating dairy cows. Milk samples, obtained at three intervals during the study, were assessed for their somatic cell count and bacteriological culture result. There was an increase in the prevalence of infection at mid-lactation in the 20.6 and 41.2 mg per day treatment groups as compared to the controls. There was no difference detected in the mean cell count between groups from the samples collected pretrial, mid-lactation, or late lactation. However, analysis of the individual cow Dairy Herd Improvement somatic cell count data showed a difference between groups which was most evident in mid-lactation.     

Dietary factors associated with milk somatic cell counts in dairy cows in Brittany, France

A survey (Enquête Ecopathologique Bretagne) was conducted in France for 4 years (1986–1990) in 48 commercial dairy herds (25–80 cows per herd) located in Brittany. Three groups of herd-years were made up to study peripartum dietary factors associated with milk somatic cell counts in the early lactation period (ECC). The first group included 20 herd-years with high ECC (over 400 000 cells ml⁻¹). The second group included herdyears with medium ECC (n = 20, median ECC 222 000) and the last group herd-years with low ECC (n = 20, median ECC 95 000). Herd data (components of the diet, milk yield and reproduction parameters, clinical diseases, biochemical and hematological indicators, body and dirtiness scores) were analyzed using discrimination by barycentric analysis. Two separate analysis were conducted according to study period (LG period, last 60 days of gestation; EL period, first 60 days of lactation).

The high ECC group had the following characteristics: (1) higher plasma gamma glutamyl transferase levels in the LG period; (2) higher quantities of cereal-based concentrates in the diet in the EL period; (3) shorter durations of feeding with Italian rye grass silage in the EL period. The relevance of the risk factors for high ECC are discussed with reference to dietary linolenic acid/linoleic acid ratio (through the synthesis of leukotrienes as chemotactic agents for the polymorphonuclear leukocytes), dietary energy supplies and liver fluke infestation in the herds. We speculate that nutritional factors could modulate the leukocyte activity in the milk and that supplementations with certain polyunsaturated fatty acids would be able to prevent the development of inflammation in the udder.     

Influence of storage and preservation of milk samples on microscopic and Fossomatic somatic cell counts.

Milk somatic cell counting was carried out by Fossomatic and microscopically. In unpreserved milk samples Fossomatic counts increased by up to 100% during the first 24 hours after milking. During the next 24 hours the counts increased by 5% whereafter they remained stable until at least 80 hours after milking, when the samples were stored at 5 degress C. On microscopical counting using methylene blue for staining, the results were stable from shortly after milking. In counting, attention had to be paid to the fact that within the first 24 hours a certain part of the cells would stain but faintly. After preservation with potassium bichromate the Fossomatic counts increased more rapidly. Stable results were found 5--8 hours after preservation. The final level of the Fossomatic counts was found to be app. 10% higher in preserved than in unpreserved samples. A smaller increase was found by microscopic counting. The rise of the cell counts during the first 24 hours after milking is probably due to inadequate stainability of living cells with ethidium bromide, resulting in a certain part of them being recorded by the Fossomatic. During the first day the vitality of the cells diminishes whereby they become stainable and countable. This process in hastened by potassium bichromate treatment.     

康贝防治奶牛隐性乳房炎疗效观察及对乳汁体细胞数的影响

奶牛乳房炎的研究至今已有100多年的历史,虽然取得一些令人可喜的成果,但奶牛乳房炎仍是当今奶牛场的常发病和难以防治的疾病之一.特别是奶牛隐性乳房炎,由于无明显的临床症状,隐蔽性强,发病率高,主要影响奶牛泌乳量和乳汁的质量,造成严重损失,是影响世界乳业发展的重要因素之一.奶牛隐性乳房炎在我国发病率较高,据笔者调查表明,河北省部分地区奶牛隐性乳房炎发病率高,乳区阳性率为40.1%,头阳性率为68.45%,这与其他学者报道相符[1、2、3].自1945年抗生素应用到兽医临床上以来,奶牛乳房炎的防治有了重大突破.但是由于抗生素的滥用,致使病原抗药性增强,且高药物残留等问题一直是困扰兽医工作人员的难题.因此寻求一种高效、绿色、简便易行的防制奶牛隐性乳房炎的方法一直是兽医科技人员的研究热点.康贝是一种生物活性制剂,不含有任何激素及抗生素.本试验的目的在于试验研究康贝对奶牛隐性乳房炎的防治作用,试验包括康贝防治奶牛隐性乳房炎疗效观察、康贝对奶牛血液流变学指标的影响及康贝清除氧自由基试验等内容,现将康贝防治奶牛隐性乳房炎疗效及对乳汁体细胞的影响做一初报,其他内容另文发表.     

Relationships between the phagocytic ability of milk macrophages and polymorphonuclear cells and somatic cell counts in uninfected cows

Phagocyte numbers and activities were compared in milk from 2 groups of uninfected mammary-gland quarters from 3 cows each: 6 quarters with a high (> or = 200 000/mL) somatic cell concentration (SCC), analyzed as 4 individual quarters and 1 pooled sample; and 12 quarters with a low SCC (< 200 000/mL), analyzed as 6 paired samples. The concentrations and ability of macrophages and polymorphonuclear (PMN) cells to phagocytize fluorescent microspheres were determined by flow cytometry after exposure of the cells to the microspheres. The macrophages and PMNs contained 2 major subpopulations, characterized by low phagocytic (LP) or high phagocytic (HP) ability. The quarters with high SCCs had significantly lower percentages of HP cells than did the quarters with low SCCs (P < 0.01). Whether mammary-gland quarters or cows were the unit of analysis, the HP/LP ratio was negatively related to the SCC (P < 0.04), which explained more than 50% of the SCC variability. Thus, poor bovine mammary-gland phagocytic ability may be associated with high SCC. Longitudinal studies are suggested to further explore and characterize these relationships.     

Potential of differential somatic cell counts as indicators of mastitis in quarter milk samples from dairy cows

Bacteriological status, somatic cell counts and proportions of lymphocytes, granulocytes and monocytes were determined in 1,659 quarter milk samples from 39 dairy cows. Discriminant analysis was performed in order to assess the ability of total and differential somatic cell counts and combinations of total somatic cell count and each of the differential cell counts, to discriminate between infected and pathogen-free quarters, as well as between quarters infected with minor pathogens and quarters infected with major pathogens. Total somatic cell count classified 82.9% of all quarters correctly with respect to bacteriological status. Differential somatic cell count was less effective than total somatic cell count in discriminating between infected and pathogen-free quarters, as well as between quarters infected with minor vs. major pathogens. Combination of total and differential somatic cell counts did not improve the rate of correctly classified quarters. Inclusion of demographic data into the discriminant function increased the number of quarters correctly classified, mainly through an increase in the proportion of correctly classified infected quarters.     

The association between high milk somatic cell counts in the first lactation and somatic cell counts in the second lactation

With the advent of web-based recording and analysis systems, individual cow composite somatic cell count (SCC) data are being increasingly used for decision support in mastitis control at both the individual cow and herd level. SCC data from first and second lactation dairy cows (n=1912) from 12 farms were analysed using multinomial logistic regression to investigate possible associations between high SCC patterns in the first lactation and the subsequent lactation. Animals with three non-consecutive counts >200,000 cells/mL in their first lactation were significantly more likely to have three non-consecutive counts >200,000 cells/mL (OR 3.11; 95% CI 1.72-5.62) or three consecutive counts >200,000 cells/mL (OR 2.00; 95% CI 1.09-3.68) in their second lactation. Similarly animals with three consecutive counts >200,000 cells/mL in their first lactation were significantly more likely to have three non-consecutive counts >200,000 cells/mL (OR 1.90; 95% CI 1.13-3.19) or three consecutive counts >200,000 cells/mL (OR 4.14; 95% CI 2.81-6.08) in their second lactation. These findings suggest that patterns established in the first lactation may have an impact on udder health in the subsequent lactation. However, simulation modelling of positive predictive values for the first lactation cell count patterns as predictors of second lactation patterns demonstrated that, at prevalences likely to be encountered on UK dairy farms, the associations were not a sufficient basis for major management decisions such as culling.     

Effects of systematic influences and intramammary infection on differential and total somatic cell counts in quarter milk samples from dairy cows

Effects of bacteriological status, stage of lactation, parity and season of sampling on differential and total somatic cell counts were estimated in quarter milk samples taken from 39 dairy cows. Log somatic cell count was affected by the bacteriological status of the quarter, as well as by the bacteriological status of adjacent quarters. Differential cell counts were affected by presence or absence of pathogens in the quarters themselves, but not by the bacteriological status of the adjacent quarters. Log somatic cell count was clearly affected by stage of lactation, due mainly to physiological variation, but possibly also accentuated by variation in infection rates throughout lactation. With the exception of early lactation, little physiological variation throughout lactation was detected for differential cell counts. Presence of infections seemed to have some indirect effect on trends throughout lactation as regards percentages of granulocytes and monocytes. Variation in somatic cell counts due to parity could be explained by variation in infection rates, rather than being physiologically determined.     

The polymorphism in the β4-defensin gene and its association with production and somatic cell count in Holstein-Friesian cows

The aim of this study was to find a polymorphism of the bovine β4‐defensin gene and search for its association with milk yield and composition and with the somatic cell count in milk. The data were from the years 1999 to 2004 on 212 Holstein‐Friesian (HF) dairy cows, descended from 70 sires. Based on the sequence of the bovine β4‐defensin gene (GenBank no. AF008307 ) the primers were designed for the amplification of the 924‐bp or 393‐bp long fragments. The 924‐bp long fragment was sequenced and the sequence was compared with that available in the GenBank. Ten putative nucleotide sequence polymorphisms were found in the intron of the bovine β4‐defensin gene. One of them, a C→T transition at position 2239, that creates a new NlaIII (Hin1II) restriction site, was genotyped with polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) in a cohort of 212 HF cows. The CC genotype was the most common (72%). The heterozygous CT genotype was found in 26% of the genotyped cows and four cows (2%) were TT homozygotes. In order to determine the relationship between the polymorphism of the β4‐defensin gene and milk production traits a multi‐trait repeatability test‐day animal model was used. The Derivative‐free Multivariate analysis program was used for computation. The differences between estimates for genotypes were checked using Student's t‐test. The model included the animal genotype, year‐season of calving and parity as fixed effects and the animal additive genetic effect and permanent environmental effect of individual cows as well as dates of the tests as random effects. Significant associations were found between the RFLP‐NlaIII and milk fat, protein and lactose contents. Also, a significant effect was shown of the defensin genotype on the somatic cell count in the milk.     

Dynamics and regulation of bulk milk somatic cell counts.

Somatic cell count (SCC) in milk is inversely related to dairy cow productivity and milk quality. In an effort to improve product quality, and indirectly farm productivity, regulatory limits on somatic cell counts have been established by many of the major dairy producing countries. The purpose of this paper was to assess the impact of regulations on bulk milk somatic cell counts in Ontario and to assist producers in meeting regulatory limits through development of prediction models. Through the use of a transfer function model, provincial SCC was found to have dropped by approximately 60,000 as a result of the reduction program. Limits of the regulatory program, seasonality and herd characteristics were found through time series cross-sectional models to have an impact on prediction of SCC at the farm level, but the major influence was historical SCC levels.     

Microbiological screening test validation for detection of tylosin excretion in milk of cows with low and high somatic cell counts

Antibiotic residues in milk above tolerance levels interfere with dairy product processing and pose potential health risks to consumers. Residue avoidance programmes include, among other components, the observance of withdrawal times indicated in label instructions. Persistence of antibiotics in milk following treatment is influenced by drug, dosage, route of administration, body weight and mammary gland health status. Compositional changes that take place during intramammary infection (IMI) can affect antibiotic excretion in milk, thus modifying milk withdrawal time. The objectives of this study were to validate sensitivity and specificity of a qualitative microbiological method (Charm AIM-96) to detect tylosin in bovine composite milk and to determine the influence of subclinical IMI in tylosin excretion following intramuscular administration. For test validation, two groups of approximately 120 cows were used; one received a single intramuscular injection of tylosin tartrate at a dose of 20 mg/kg, while the other group remained as untreated control. Test sensitivity and specificity were 100% and 94.1% respectively. To determine the influence of subclinical IMI in tylosin excretion, two groups of seven cows, one with somatic cell counts (SCC) < or =250 000 cells/ml and the other with SCC > or =900 000, were administered a single intramuscular injection of tylosin tartrate at a dose of 20 mg/kg. Milk samples were obtained every 12 h for 10 days following treatment. Milk tylosin excretion averaged between 5 and 9 days for cows with low and high SCC respectively (P < 0.0001). Compositional changes in cows with high SCC most likely affect the pharmacokinetic characteristics of tylosin, extending the presence of the antibiotic in milk, thus influencing milk withdrawal times.