应用体细胞计数监测奶牛隐性乳房炎

奶牛乳汁中体细胞数的变化受多方面因素的影响。本文主要论述用体细胞计数检测奶牛隐性乳房炎技术、以及将体细胞数作为标记性状、选育具有乳房炎抗性奶牛的研究。     

Reliability in somatic cell count measurement of clinical mastitis milk using DeLaval cell counter

Somatic cell counts (SCC) measurements are typically performed using quantitative methods, such as the Breed method (Breed) and the Fossomatic method (FSCC). The DeLaval cell counter (DCC) developed recently is a quantitative somatic cell counter with a low initial cost and superior portability. However, since the DCC was specifically developed for measuring SCC of ≤ 4 × 10⁶ cells/mL milk from bulk tanks or individual cows, its reliability for estimating SCC that exceed this concentration has not yet been clarified. This study therefore examined whether it is possible to accurately measure SCC by diluting milk samples with initial SCC of 4 × 10⁶ cells/mL, as seen in clinical mastitis milk. We collected milk samples from 99 quarters of 99 Holstein cows with clinical mastitis. These milk samples were diluted 10‐fold with saline and thoroughly mixed before performing SCC measurement with the DCC. The correlation coefficients of SCC measured by the FSCC, Breed and DCC methods indicated strong correlations between each pair of methods. The findings showed that DCC can be used to identify bovine clinical mastitis milk and is useful as a quantitative SCC measurement device on farm sites.     

A method to estimate the somatic cell count of milk from a mastitic quarter using composite somatic cell count.

The purpose of the study was to estimate the extent to which one quarter could be inflamed relative to the other three quarters of a cow, given that knowledge only of the composite milk somatic cell count (SCC) was available. An algebraic relationship, which incorporated the parameters of composite milk SCC, production loss associated with composite milk SSC, SCC of milk from an inflamed quarter, and SCC from three non-inflamed quarters, was used to derive hypothetical estimates of the SCC in one inflamed quarter. A simple case was considered in which one quarter was mastitic, the SCC in milk of the noninflamed quarters was equal, and there was no production compensation by the noninflamed quarters. Previously published estimates were used for production loss associated with composite milk SCC. For moderate composite milk SCC (300,000-500,000 cells/mL) and low-to-moderate SCC in milk of noninflamed quarters (100,000 cells/mL), the SCC of milk from one inflamed quarter was predicted to be very high, ranging from about 1.26 million (log10 SCC = 6.1) to 6.3 million (log10 SCC = 6.8) cells/mL, and compatible with signs of clinical mastitis. These results suggest that in order to screen cows with clinical mastitis in only one quarter, composite milk SCC should be considerably lower than values presented previously by other investigators.     

Normal somatic cell count and subclinical mastitis in Murrah buffaloes

This study was conducted to investigate the normal somatic cell count (SCC) and to define subclinical mastitis in Murrah buffaloes. Data were collected from 60 clinically normal buffaloes stationed at five farms of Chitwan Nepal and Buffalo Research Center, Hissar, India. Somatic cell count was measured using the Newman-Lampert staining technique. The upper limit of SCC was determined >or=200 000/ml of milk based on the mean +/- 2SD of a total SCC. Abnormal data of the SCC was repeatedly removed, which lie beyond the values of more than mean + 2SD until all the data come to lie within (mean + 2SD). Averages of SCC of right front and right hind quarters were significantly higher than left front and left hind quarters. Nearly 94% of California mastitis test (CMT) negative quarters were having somatic cells >or=200 000/ml. The mean SCC of CMT positive quarter was significantly higher (P < 0.01) than CMT negative quarters. Subclinical mastitis was diagnosed on the basis of samples with SCCs >or=200 000/ml with positive bacterial cultures. Subclinical mastitis was found in 21.7% buffaloes and 8% of the quarter foremilk samples. Neutrophil counts were significantly higher in subclinical mastitis milk.     

Antibiotic therapy for subclinical mastitis in early lactation; effects on infection, somatic cell count and milk production

Cows with consistently high somatic cell counts (SCC) and bacterial infection, but no clinical signs of mastitis, were identified early in lactation. Some of these quarters were treated with Cloxacillin, while other similar quarters were left untreated. Prior to treatment, 74% of infected quarters had SCC higher than 300,000 cells/ml while 85% of uninfected quarters has SCC lower than 300,000 cells/ml. Infection was eliminated by treatment in five out of the eight quarters treated with Cloxacillin, and in these quarters SCC decreased from 4,200,000 cells/ml before treatment to 160,000 cells/ml after treatment. Milk production and composition were not affected significantly although production was about 14% higher in treated quarters than untreated quarters. The possible role of antibiotic therapy for subclinically infected quarters early in lactation was discussed in relation to a reduced rate of new infection in a herd.     

Monitoring udder health and milk quality using somatic cell counts

In this article the use of somatic cell counts for monitoring udder health and milk quality is discussed. Somatic cell count dynamics at quarter, cow, herd and population level are discussed and illustrated with examples. Quarter and cow somatic cell counts directly represent the inflammatory status of the mammary gland. Herd and population somatic cell count are related to the inflammatory process in individual cows but much more reflect the udder health status of the herd and the quality of the raw milk in the herd and the population. Application of monitoring tools in herd health management are illustrated using a case study. Understanding infection dynamics requires precise longitudinal data. Monitoring tools are required to find the areas of risk in the herd. It is inevitable that more complete udder health programs and monitoring systems are to be developed and implemented. These programs are necessarily dynamic and complex. Implementation of complete udder health programs should be accompanied by research efforts to further fine-tune these complete udder health control and monitoring programs.     

Associations between somatic cell count patterns and the incidence of clinical mastitis

Associations between clinical mastitis (CM) and the proportional distribution of patterns in somatic cell count (SCC) on a herd level were determined in this study. Data on CM and SCC over a 12-month period from 274 Dutch herds were used. The dataset contained parts of 29,719 lactations from 22,955 cows of different parities. In total, 207,079 SCC test-days were recorded with 5719 cases of CM; 1561 cases were associated with environmental pathogens (ENV_CM), and 2681 with contagious pathogens (CONT_CM). Definitions of patterns in SCC were based on 3, 4, or 5 consecutive test-day recordings of SCC that differentiated between short or longer periods of increased SCC, and also between lactations with and without recovery. The distribution of those patterns (relative to their maximum) varied among herds. The distribution of SCC patterns was correlated with the incidence rate of CM. Herds with a relatively frequent quick recovery pattern had a 2.5 times more chance of being classified in the upper quartile for CM. These herds also had 2.1 times more chance of being classified in the upper quartile for ENV_CM but only 0.4 times for CONT_CM. Herds with a relatively frequent no recovery pattern had less chance (odds ratio=0.5) of being classified in the lower quartile for CONT_CM. Since the distributions of SCC patterns were indicative for overall, environmental and contagious CM, the necessity to introduce pathogen-specific mastitis control programs in a herd could be determined based on the mean incidences of SCC patterns in that herd.     

Relation of milk production loss to milk somatic cell count.

Milk production loss was studied in relation to increased somatic cell count (SCC). Available data were weekly test-day milk yields and SCC (in 1,000 cells/ml), and mastitis incidences. In total, 18,131 records from 274 cows were used. Production loss was determined for test-day kg milk, kg protein, and kg energy-corrected milk. Least-squares analysis of variance was used to estimate the direct effect of Log10(SCC) on production. The recorded measures of production were first corrected for fixed effects, with adjustment factors estimated from a healthy data-set. The average daily milk yield was 19.7 kg/day in first lactation and 22.0 in later lactations. The geometric mean of SCC was 63.1 in first lactation and 107.2 in later lactations. The incidence of clinical mastitis treated by a veterinarian was 19.8% of the lactations-at-risk. Linear relationships were found between the production parameters and Log10(SCC). Quadratic and cubic effects were evaluated, but were found to contribute little to the overall fit of the models. The individual milk yield loss was 1.29 kg/day for each unit increase in Log10(SCC) for cows in first lactation. Milk yield decreased by 2.04 kg/day per unit Log10(SCC) for older cows. Corresponding values for protein yield were 0.042 and 0.067 kg/day for first and later lactations, respectively.     

Mastitis control services and utilization of milk somatic cell count data by veterinarians in Ohio

A telephone survey was conducted of 50 randomly selected Ohio-licensed veterinarians engaged in dairy practice. The survey's purpose was to determine the extent of mastitis control services offered by practitioners and to assess their utilization of milk somatic cell count (SCC) data on individual cows available from the Dairy Herd Improvement Association (DHIA). During the preceding year, 96% (48/50) of practitioners surveyed had performed bacteriologic culture of milk samples. Practitioners were twice as likely to have performed culture on milk from mastitic cows that failed to respond to treatment as they were to have performed culture for purposes of identifying pathogen trends within a herd. Veterinarians in predominantly dairy practices were more likely to have completed bacteriologic examination of milk in their own laboratories than were veterinarians who were engaged in less than 50% dairy practice (P = 0.016). Most veterinarians (83%) reported that coagulase test results were available or that Staphylococcus aureus was differentiated from other staphylococcal species. Streptococcus agalactiae was not differentiated from other streptococcal species by 35% of practitioners surveyed. For veterinarians with clients enrolled in the DHIA, 91% (43/47) reported looking at, discussing, or otherwise using the DHIA records. Eighty-one percent (35/43) of veterinarians who had clients using services from the DHIA reported that clients also received individual cow milk SCC results. Veterinarians engaged in predominantly, dairy practice expressed a greater familiarity with the linear score method of SCC reporting than did veterinarians whose practices were less than 50% dairy (P = 0.085); however, both groups reported a preference for raw SCC data.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of storage temperature on goat milk somatic cell count using the DeLaval counter

This study investigated the influence of storage temperature and storage time on goat milk somatic cell counts (SCCs) determined using the DeLaval cell counter (DCC). SCCs were measured in 40 Majorera goat milk samples using the DCC device. Samples were grouped from high score (>2,750 × 10³ cells/mL) to low score (<630 × 10³ cell/mL) according to the SCC. Each milk sample was divided into four aliquots and stored at four different temperatures (4°C, 21°C, 36°C or 45°C). The SCC was recorded every hour for 12 hours. Storage of goat milk with a high SCC for 5, 5, 2 or 1 hour at 4°C, 21°C, 36°C or 45°C, respectively, decreased the SCC value compared to fresh milk. The goat milk SCC was lower after 1 hour of storage than that determined for fresh milk at any tested temperature in low-SCC samples. The data presented herein suggest that regardless of storage temperature, goat milk samples should not be stored for more than 1 hour before measurement of SCC with a DCC device.     

体细胞数对牛奶品质及产量的影响

根据宁夏地区某奶牛场的DHI检测获得的体细胞数据(SCS),利用SAS软件实现单因素方差分析,探讨不同乳中SCS对产奶量和乳中主要成分的影响,并对它们之间的相关性进行分析。结果表明:乳中SCS与日产奶量呈显著负相关(P0.01);与乳糖和胎次呈正相关(P0.01);乳中SCS水平与乳脂率、乳蛋白率和尿素氮没有明显的相关性。本试验通过对SCS的研究为乳品质的测定提供一定依据和参考。     

Effect of puerperal mastitis in primiparous cows on milk production, cell count and culling

A retrospective cohort study was performed to investigate the effect of clinical mastitis in heifers during the first week post partum (p.p.) on subsequent health and productivity. Primiparous cows that had calved between August 15th, 1996 and August 14th, 1997 (n = 1389) were included in the study. Milk samples were collected from each quarter post partum prior to first milking. The predominant group of bacteria found were Staphylococcus spp. (69%) followed by Streptococcus spp.(12%) and E. coli (5%). Intramammary infections at calving increased the risk of clinical mastitis within the first week p.p. The cow incidence of mastitis until day 7 p. p. was 38%. Cows were classified into three groups. Group 1: Animals with clinical mastitis prior to calving (n = 35); Group 2: Animals with clinical mastitis between calving and 7 days p. p. (n = 503); Group 3: Animals without mastitis until 7 days p. p. (n = 851). Mastitis prior to parturition and mastitis within the first week p.p. increased the risk of further cases of mastitis and culling during the first 45 days of lactation. Milk yield of Group 2 was lower and somatic cell counts were higher than in Group 3.     

Effect of intramammary injection of rboGM-CSF on milk levels of chemiluminescence activity, somatic cell count, and Staphylococcus aureus count in Holstein cows with S. aureus subclinical mastitis

The effect of intramammary injection of recombinant bovine granulocyte-macrophage colony-stimulating factor (rboGM-CSF, 400 microg/10 mL) on quarter milk levels of chemiluminescence (CL) activity, and somatic cell count (SCC) and shedding pattern of Staphylococcus aureus was investigated. Ten Holstein cows, naturally infected with S. aureus were used, with either early-stage or late-stage subclinical mastitis. Injection of rboGM-CSF caused a remarkable increase in milk CL activity with a peak at 6 h after the cytokine injection in the early- and late-stage groups. In the early-stage group, milk SCC stayed around preinjection level at 6 h, rose significantly on days 1 and 2, and was followed by a smooth and significant decline to an under preinjection level (below 200 000 cells/mL) on day 7 postinjection. Alternatively, in the late-stage group, milk SCC rose significantly at 6 h after the cytokine injection and maintained high levels thereafter. The milk S. aureus count decreased drastically by the cytokine injection in the early-stage group. The bacterial count was moderately decreased in the late-stage group, but increased back to preinoculation levels on day 7 after the cytokine injection. The results suggest that the rboGM-CSF has a potential as a therapeutic agent for S. aureus infection causing subclinical mastitis of dairy cows, if the cytokine is applied at the initial stage of infection.     

Estimation of genetic parameters for somatic cell count in the first three lactations using random regression

Genetic parameters were estimated for log_e somatic cell count (LSCC) for the first three lactations of 31 236 Holstein/Friesian cows with 308 534, 236 277 and 206 729 test day yields in parities 1, 2 and 3, respectively. An animal random regression model was employed in the analyses using Gibbs sampling with each parity regarded as different traits. Linear and quadratic functions were fitted for the animal and permanent environmental effects respectively, using orthogonal polynomials. Daily heritabilities increased with days in milk (DIM) and averaged about 0.07 in all three parities. This increase in heritabilities with DIM was due to an increase in genetic variance and decreases in both permanent and residual environmental variances with DIM. Environmental effects have a large influence on LSCC in early lactation in all three parities. Within lactation, genetic correlations were highest between adjacent DIM but decreased as DIM got further apart. However, this decrease was slowest in parity one and greatest in parity three. The lowest correlation within lactation was 0.10 between DIM 7 and 305 in parity 3. Across lactations, genetic correlations were highest between parities 2 and 3, intermediate between 1 and 3, and lowest between 1 and 2. The genetic correlations computed for completed lactations were 0.69, 0.79 and 0.98 between parities 1 and 2, 1 and 3, and 2 and 3, respectively. Corresponding phenotypic correlations between parities were 0.38, 0.31 and 0.52, respectively. A test day model, accounting for these variations in heritabilities and genetic correlations, should result in a more accurate evaluation.     

Veterinary and nonveterinary costs of disease in 29 California dairies participating in the National Animal Health Monitoring System from 1988 to 1989

Twenty-nine California dairy herds were studied over a 12-month period from 1988 to 1989 as part of the National Animal Health Monitoring System. Monthly interviews administered to dairy producers were used to measure the costs of all health-related expenditures and disease incidence in these herds. Of the total $1,523,558 reported, $1,355,467 (89%) was attributed to cost of disease events and $168,091 (11%) to cost of disease prevention. Most (78%) of the cost of disease events was attributable to death and culling losses. Veterinary services accounted for only $54,099 (4%) of total costs, 64% of which was used for disease prevention, compared with 36% for disease treatment. Udder disease was the most costly category of diseases reported at an average of $49.85/head at risk annually, followed by reproductive problems at $38.05. Through the use of sampling strategies less biased than those used in other surveys, the National Animal Health Monitoring System is designed to provide statistically-valid estimates of disease incidence and costs across broad geographic areas, potentially benefiting all those interested in the economics of livestock diseases in the United States.     

Fertility, somatic cell count and milk production in Swedish organic and conventional dairy herds

The share of organic dairy production in EU is increasing and this study describes the herd structure and cow performance in organic and conventional dairy production systems in Sweden. The data included records from 2 902 718 lactations, collected in organic (n = 471) and conventional (n = 13 976) herds between 1998 and 2005. Compared with conventional herds, the organic herds were larger and increased more rapidly in size. The replacement rate was slightly lower in organic herds and fewer Swedish Holsteins were used. The statistical analysis of cow performance in the first three lactations showed lower milk, fat and protein production in organic herds, but the increase in production from first to second lactation was larger when expressed in kg milk. Fertility was better for organically managed cows compared to conventionally managed cows, but the somatic cell count (SCC) was higher. However, at a given production level the fertility was slightly worse in organic herds while there was no difference in SCC. No interactions of importance were found between production system and breed for any trait.The results showed that organic and conventional dairy production differed regarding herd structure and cow performance. However, the differences in fertility and SCC found were to a high extent explained by the lower milk yield in organic production and no breed was found to perform better in either system.     

Relationship between somatic cell count status and subsequent clinical mastitis in Dutch dairy cows

High composite somatic cell counts (CSCC) in dairy cows may develop into clinical mastitis (CM), suggesting that prevention or intervention of high CSCC may prevent CM later in lactation. The objective of this study was to quantify the relationship between high CSCC in dairy cows and the first subsequent case of CM in the same lactation. Farmer-diagnosed cases of CM and test day CSCC measurements during 1 year of 13,917 cows in 196 randomly selected Dutch dairy herds were available for analysis. Cows were followed in 1 lactation from the first test day postpartum until CM, drying off, culling or end of study. Cox proportional hazards models with time-varying CSCC levels were used to estimate the effect of high CSCC (≥200,000cells/ml) on the time until the first case of CM. A shared frailty effect was included to adjust for clustering of cows within herds. The proportion of cows developing CM after a CSCC measurement was 11%. Primiparae with a high CSCC had a 4-fold higher hazard for subsequent CM than primiparae with a low CSCC; multiparae with a high CSCC had a 2-fold higher hazard than multiparae with a low CSCC. Additionally, multiparae with a low CSCC had a 2-fold higher hazard for CM occurrence than primiparae with a low CSCC. Increasing the threshold for high CSCC showed that the risk for CM increased. If the last CSCC before CM was low, CSCC information of 2 preceding test days was more predictive than CSCC information from only the last test day. When the last CSCC was high, CSCC information of 2 preceding test days did not have added predictive value. This study identified that approximately 25% of first subsequent CM cases after a CSCC measurement can potentially be prevented when cows are prevented to get high CSCC or when high CSCC cows are removed from the population. This corresponded with a decrease in the proportion of lactating cows with CM after a CSCC measurement from 11% to 7%.     

The detection of subclinical mastitis in the bactrian camel (Camelus bactrianus) by somatic cell count and California mastitis test

Milk samples (n=160) from 7 clinically healthy bactrian camels were cultured to detect subclinical udder infection. The samples were assessed by the Californian mastitis test (CMT) and somatic cell count (SCC). Bacteria were recovered from 36 (22.5%) of the milk samples. Staphylococcus aureus and coagulase-negative staphylococci (CNS) were the main organisms found.Infected quarters had significantly higher mean values for the SCC (p<0.01) and CMT (p<0.001) than non-infected quarters. All 7 camels were infected with CNS but only 4 with S. aureus. CMT values for S. aureus-infected camels were significantly higher than for those only infected with CNS. The values for SCC and CMT were significantly influenced by the stage of lactation (p<0.05). No significant difference was found from the effect of the quarters. Both SCC and CMT were of value in predicting the infection status of the udder.Abbreviations CMT California mastitis test - SCC somatic cell count - CNS coagulase-negative staphylococci     

2018年天津市原料奶细菌总数、体细胞数及奶牛乳房炎病原菌、耐药基因调研报告

本研究旨在调查天津市原料奶细菌总数、体细胞数及乳房炎病原菌、耐药基因,了解全市原料奶的质量状况及引起奶牛乳房炎发生的主要原因。采集天津市5家乳品加工企业奶罐车的原料奶样品,用于检测体细胞数和菌落总数;采集天津市奶牛养殖场储奶罐奶样品,用于检测体细胞数;采集奶牛场临床型乳房炎发病乳区的牛奶样品,用于检测乳房炎病原菌及耐药基因。结果显示:2018年天津市乳品加工企业原料奶体细胞数平均值为44.65万/mL,标准差42.41万/mL,变异系数94.97%,最大值为225.50万/mL,最小值为1.20万/mL,SCC≤50万/mL的样品占74.37%,50万/mL200万/mL的样品占3.13%;细菌总数平均值11.54万CFU/mL,标准差26.28万CFU/mL,变异系数227.66%,最大值190.00万CFU/mL,最小值0.095万CFU/mL,细菌总数≤10万CFU/mL的样品占74.37%,10万CFU<细菌总数≤50万CFU/mL的样品占21.25%,50万CFU<细菌总数≤100万CFU/mL的样品占1.88%,100万CFU/mL<细菌总数≤200万CFU/mL的样品占2.50%。2018年天津市奶牛养殖场原料奶体细胞数平均值为38.81万/mL,标准差36.49万/mL,变异系数94.03%,最大值为210.00万/mL,最小值为0.80万/mL,SCC≤50万/mL的样品占79.17%,50万/mL200万/mL的样品占0.83%。乳房炎病原菌检测结果显示:36个样品检出病原菌,总检出率为94.74%;共检出8种病原菌,检出率最高的是乳房链球菌,检出率为73.68%,其他病原体检出率依次为:牛支原体34.21%,牛棒状杆菌13.16%,无乳链球菌10.53%,大肠杆菌5.26%,白色念球菌5.26%,停乳链球菌2.63%,铜绿假单胞菌2.63%。14个样品检出耐药基因,总检出率为36.84%;2种耐药基因的检出率分别为β-内酰胺耐药基因CTX-M934.21%,耐甲氧西林葡萄球菌耐药基因MecA 2.63%。研究表明,2018年天津市原料奶SCC及细菌总数大部分接近欧盟标准,但仍有待进一步提高;引起天津地区临床型乳房炎的3种主要致病菌为乳房链球菌、牛支原体和牛棒状杆菌。