Association of BoLA-DRB3 alleles identified by a sequence-based typing method with mastitis pathogens in Japanese Holstein cows

The association of the polymorphism of bovine leukocyte antigen ( BoLA-DRB3 ) genes identified by the polymerase chain reaction sequence-based typing (PCR-SBT) method with resistance and susceptibility to mastitis caused by pathogenic bacteria was investigated. Blood samples for DNA extraction were collected from 194 Holstein cows (41 healthy cows and 153 mastitis cows including 24 mixed-infection cows infected with 2 or 3 species of pathogens) from 5 districts of Chiba prefecture, Japan. Sixteen BoLA-DRB3 alleles were detected. The 4 main alleles of DRB3*0101 , *1501 , *1201 , and *1101 constituted 56.8% of the total number of alleles detected. Mastitis cows were divided into 2 groups: group 1 with single-infection cows and group 2 with all mastitis cows including 24 mixed-infection cows. The differences in the frequencies of BoLA-DRB3 alleles and the number of cows homozygous or heterozygous for each BoLA-DRB3 allele between healthy cows and the 2 groups of mastitis cows were evaluated. Furthermore, similar comparisons were performed between healthy cows and the 2 groups of mastitis cows for each mastitis pathogen. It was considered that the 4 alleles, namely, DRB3*0101 , *1501 , *1201 , and *1101 had specific resistance and susceptibility to 4 different mastitis pathogens. Thus, DRB3*0101 might be associated with susceptibility to coagulase-negative Staphylococci and Escherichia coli , and DRB3*1501 might be associated with susceptibility to Escherichia coli . However, DRB3*1101 might be associated with resistance to Streptococci and coagulase-negative Staphylococci , and DRB3*1201 , with resistance to Streptococci , Escherichia coli , and Staphylococcus aureus .     

Allelic frequency of PCR-RFLP type of the BoLA-DRB3 in Japanese Holstein herds and the relation to mastitis

Holstein Cows ( n  = 702) from 26 dairy herds in the Tama area of Tokyo, Japan were examined for polymorphisms of the BoLA-DRB3 allele using a PCR-RFLP method. Twenty alleles were observed and allelic frequencies ranged from < 1% to 20.3%. Nine alleles ( DRB3.2 * 24, * 16, * 8, * 23, * 22, * 3, * 11 , * 10 and * 7 in order) constituted 90.0% of all alleles. Somatic cell counts (SCC) were used to classify healthy (group 1), mastitis (group 2) and suspected (group 3) cows. Frequencies of DRB3.2 * 11 and DRB3.2 * 23 were slightly higher in group 1 than in group 2, whereas, frequencies of DRB3.2 * 8 and DRB3.2 * 16 were slightly higher in group 2 than in group 1. However, none of the differences in frequencies between the two groups were statistically significant. For combinations of alleles, frequencies of DRB3.2 * 8/ * 23 ( P  < 0.1) and DRB3.2 * 16/ * 24 ( P  < 0.05) were significantly higher in group 2 than in group 1, and their odds ratios were 2.1, 2.5, respectively. However, there were no significant differences between genotypes in their effects for SCC. On the other hand, frequency of DRB3.2 * 23/ * 23 including combinations of DRB3.2 * 23 with minor alleles was significantly higher in group 1 than in group 2 ( P  < 0.01), and the odds ratio was 0.3. Therefore, it was considered that mastitis resistance or susceptibility of cows may vary with the combination of BoLA-DRB3 alleles.     

Analysis of Relationship between Bovine Lymphocyte Antigen DRB3.2 Alleles, Somatic Cell Count and milk Traits in Iranian Holstein Population

The major histocompatibility complex (MHC) is a gene complex closely linked to the vertebrate immune system due to its importance in antigen recognition and immune response to pathogens. To improve our understanding of the MHC and disease resistance in dairy cattle, we gathered 5119 test day records of somatic cell count (SCC) and performance traits of 262 Holstein dairy cows to determine whether the DRB region of the MHC contains alleles that are associated with elevated SCC, milk yield, protein and fat percent of milk. To this purpose, genotyping of animals for DRB3 gene was investigated by polymerase chain reaction‐based restriction fragment length polymorphism (PCR‐RFLP) assay. A two‐step PCR was carried out so as to amplify a 284 base‐pair fragment of exon 2 of the target gene. Second PCR products were treated with three restriction endonuclease enzymes RsaI, BstYI and HaeIII. Twenty‐eight BoLA‐DRB3 alleles were identified including one novel allele (*40). The results in general are in good accordance with allele frequencies of Holstein cattle populations reported by previous studies. Analyses of associations were modeled based on repeated measurement anova and generalized logistic linear methods for production traits and SCC data, respectively. The results of this study showed a significant relationship between the elevated SCC reflecting an increased probability of occurrence to subclinical mastitis and DRB3.2 allele *8 (p < 0.03). The results also revealed significant positive relationships of alleles*22 (p < 0.01) and allele*11 (p < 0.05) with milk fat percent as well as of alleles*24 (p < 0.03) and *22 (p < 0.05) with protein percent. The present study failed to find any association between milk yield and tested alleles. Because of the lack of consistency among results of similar studies, we suggest further investigations to determine the precise nature of these associations with the high polymorphic bovine MHC region to be performed based on haplotypes.     

Study on the association of BoLA-DRB3.2 alleles with clinical mastitis in Norwegian Red cows

Genotyping of bovine leucocyte antigen DRB3.2 (BoLA-DRB3.2) in a total of 523 Norwegian Red (NR) cows from two groups selected for high protein yield and low clinical mastitis, respectively, identified 27 previously reported BoLA-DRB3.2 alleles across the groups. Significant differences in BoLA-DRB3.2 allele frequencies were found between the selection groups. Alleles *13, *18, *22 and *27 had a significantly higher frequency in cows selected for low clinical mastitis, while alleles *3, *9, *11 and *26 had a higher frequency in cows selected for high protein yield. Associations between BoLA-DRB3.2 alleles and clinical mastitis were analysed based on mastitis data from 741,072 first-lactation NR cows, of which 452 were genotyped. Alleles *22 and *26 were found to be associated with increased clinical mastitis, while alleles *7, *11, *18 and *24 had a favourable effect on mastitis resistance. Contradictory results from different studies investigating associations between BoLA-DRB3.2 alleles and mastitis indicate that future studies should focus on associations of mastitis with BoLA haplotypes rather than with single BoLA genes.     

Association of BoLA‐DRB3 alleles with mastitis resistance and susceptibility in Japanese Holstein cows

In this study, 714 cows from 26 dairy herds were reclassified as healthy or mastitic cows on the basis of long‐term somatic cell count (SCC) in milk. Cows with more than three consecutive lactation records of SCC from the first or second to fifth lactation, were selected, and their BoLA‐DRB3 (DRB3) alleles were identified using polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) method. Cows with an SCC of < 200 000 cells/mL in all monthly records were classified as healthy (n = 91). Cows with an SCC of > 300 000 cells/mL in two consecutive tests or four non‐consecutive tests or cows with an SCC of > 500 000 cells/mL in any one test during lactation, regardless of parity, were classified as mastitic (n = 201). Mastitic cows (n = 153) from another 40 herds were considered to be infected if bacteriological testing revealed mastitis pathogens in milk. Their DRB3 alleles were identified using PCR‐sequence‐based typing (PCR‐SBT). The differences in DRB3 allelic frequencies between healthy cows and cows with various degrees of mastitis were re‐investigated. Moreover, the associations of various amino acid motifs in DRB3 alleles with resistance or susceptibility to mastitis pathogens were re‐examined. DRB3.2*8(DRB3*1201) and DRB3.2*16(DRB3*1501) alleles were found to be associated with susceptibility, while DRB3.2*22(DRB3*1101), DRB3.2*23(DRB3*2703), and DRB3.2*24(DRB3*0101) alleles were found to be associated with resistance.     

Association of the amino acid motifs of BoLA-DRB3 alleles with mastitis pathogens in Japanese Holstein cows

The association of the polymorphism of bovine leukocyte antigen ( BoLA-DRB3 ) genes, identified by the polymerase chain reaction sequence-based typing (PCR-SBT) method, with resistance and susceptibility to mastitis caused by Streptococci , coagulase-negative Staphylococci, Escherichia coli and Staphylococcus aureus was investigated. Blood samples for DNA extraction were collected from 170 Holstein cows (129 mastitis and 41 healthy cows) from 5 districts in Chiba prefecture, Japan. Susceptibility or resistance to the mastitis-causing pathogens was thought to vary by the presence of amino acid substitutions at the 9, 11, 13, and 30 positions. DRB3*0101 and DRB3*1501 had amino acid motifs of Glu⁹, Ser¹¹, Ser¹³, and Tyr³⁰, and they were considered to have susceptibility to all 4 mastitis pathogens. In contrast, DRB3*1101 and DRB3*1401 had amino acid motifs of Gln⁹, His¹¹, Gly¹³, and His³⁰ in these positions, and they also had Val⁸⁶, so these alleles were considered to have resistance to Streptococcal and coagulase-negative Staphylococcal mastitis. However, in the case of Escherichia coli mastitis, amino acid substitutions at the 9, 11, 13, and 30 positions had little effect, but rather substitutions at the 47, 67 positions of pocket 7, and at the 71, 74 positions of pocket 4, Tyr⁴⁷, Ile⁶⁷, Ala⁷¹, and Ala⁷⁴, were associated with resistance. This motif was present in DRB3*1201 .     

新疆石河子地区某规模化奶牛场乳房炎患病率调查

对新疆石河子地区某规模化奶牛场的712 头澳系荷斯坦泌乳牛进行乳房炎患病率调查。调查结果显示,40 头奶牛患临床型乳房炎,患病率为5.62%。从剩余的未表现出临床乳房炎症状的672 头奶牛中随机选出180 头奶牛,共682 个乳区（720 个乳区中有38 个瞎乳头）,分别进行兰州乳房炎检测（LMT）和乳样体细胞数（SCC）检测。经LMT诊断发现,180 头奶牛中有56 头患隐性乳房炎,患病率为31.11%;经SCC检测发现,180 头奶牛中有60 头患隐性乳房炎,患病率为33.33%。数据分析发现：各乳区患乳房炎阳性率差异不显著（P>0.05）,说明各乳区阳性率之间没有必然规律;6岁以上奶牛的乳房炎患病率与2~3岁、4~5岁的患病率相比差异显著（P<0.05）,说明6岁及以上奶牛乳房炎的患病率要高于2~3岁、4~5岁奶牛;6胎及以上的奶牛乳房炎患病率与其他胎次之间差异极显著（P<0.01）,说明6胎及以上奶牛的乳房炎患病率要远高于1胎、2胎、3胎、4胎、5胎奶牛。     

凉州区奶牛乳房炎主要病原分离鉴定及药敏试验

乳房炎是奶牛最常见的疾病,随着奶牛产业的蓬勃发展,乳房炎已经成为制约该产业的瓶颈之一。从甘肃省武威市凉州区5个奶牛养殖场采集了1 000头荷斯坦奶牛共计3 991份奶样,对临床型和非临床型(隐性)乳房炎分别通过临床症状和兰州隐性乳房炎诊断液(LMT)进行诊断。结果显示:该地区奶牛临床型乳房炎发病率18.20%,亚临床型乳房炎发病率36.50%,总阳性率54.70%,总阳性乳区率54.72%。从阳性奶样中分离纯化得到的主要病原菌为链球菌属、金黄色葡萄球菌和大肠杆菌,且在不同类型乳房炎中的分布情况不同,临床型中链球菌属最多(54.37%),亚临床型中金黄色葡萄球菌最多(48.56%)。对主要病原菌进行药敏试验,结果表明治疗凉州区奶牛乳房炎的最佳药物应为喹诺酮类和庆大霉素类。     

BoLA-DQA、DRB3* exon2多态性及其与奶牛乳房炎的关联分析

采用PCR-SSCP技术，检测到9种中国荷斯坦牛BoLA-DQA^＊ exon2基因基因型、15种BoLA-DRB3^＊ exon2基因的基因型和3种单体型，分析比较了各基因型、单体型与奶牛乳房炎的关联性。结果在中国荷斯坦牛中，没有发现与乳房炎易感性或抗性有关联的基因和基因型，但发现DQA-B／DRB3-C、DQA-G／DRB3-F两种单体型可能与奶牛乳房炎易感性有关，而DQBF／DRB3-E单体型可能与奶牛乳房炎抗性有关。     

Effects of clinical mastitis on reproductive and milk performance of Holstein cows in Morocco

The aim of this study was to determine the influence of clinical mastitis and time of first mastitis occurrence on reproductive and milk performance of Holstein cows. Data were collected in a dairy farm from 2008 to 2012 on 1725 cows, among which 464 cows with mastitis. To determine the influence of clinical mastitis on reproductive and milk performance, models included fixed effects of parity, calving season, calving year, and group (cows with and with no mastitis). To determine the effect of time of 1st mastitis occurrence on reproductive performance, the mastitic cows group was further reclassified into three groups: prior to 60 days, between 60 and 90 days and greater than 90 days postpartum. For milk performance, the mastitic cows group was divided into two groups: before and after peak milk yield. Clinical mastitis had significant effects on calving to first AI interval, milk yield, and fat yield, but a non-significant effect on days open, number of inseminations per conception, and milk fat percentage. Mastitic cows had a calving to first AI interval 6.1 days longer and 549.6 kg milk and 20.4 kg fat per 305 days of lactation lower than those with no mastitis. Time of 1st mastitis occurrence did not have any significant effect on reproductive performance. Further, milk and fat yields of cows diseased before peak milk yield were 506 kg and 23.9 kg, respectively, lower than those of cows affected after peak milk yield. Extra attention needs to be paid to mastitis during the early postpartum period.

     

Prevalence and major bacterial causes of bovine mastitis in Asella,South Eastern Ethiopia

A cross sectional study was conducted in and around Asella town from November 2007 to April 2008 on dairy cows to determine the prevalence of mastitis, impact of risk factors and isolate the dominant mastitis causing bacteria on total of 223 lactating cows, of which 92 were indigenous Arsi, and 131 Holstein Zebu cross by using clinical examination and California mastitis test (CMT). Of these 144 (65.6 %) were positive by clinical examination and CMT for clinical and sub clinical mastitis, with prevalence of 26.5 % and 38 %, respectively. There was a significant difference (P < 0.05) on the prevalence of mastitis between cows kept under different hygiene of milking process. Similarly a significant difference on the prevalence of mastitis between the two breeds (P < 0.05) was also observed. From 144 CMT and clinically positive milk samples analyzed microbiologically, 133 were culturally positive for known mastitis pathogens and while 11 were negative. The dominant bacterial isolates in the study animals were Staphylococcus species (41.4 %), Streptococcus species (24.8 %), and other Gram positive rods and Gram negative enteric bacteria (33.8 %). Good hygiene in milking process, milking clinically infected cows at last, culling chronic mastitis carriers, treating clinically infected cows and dry period therapy could reduce the prevalence of contagious mastitis in the study area.     

乳房炎乳与正常乳中六种微量元素含量测定与分析

为研究微量元素含量与乳房炎发生的相关性,采集健康荷斯坦牛与乳房炎奶牛的乳汁各15份,用火焰原子吸收光谱法（FAAS）测定了6种矿物元素铁（Fe）、铜（Cu）、锌（Zn）、锰（Mn）、镁（Mg）、钴（Co）含量,并进行了对比分析。结果表明患乳房炎乳汁中Cu、Fe、Co和Zn含量显著低于正常乳汁（P〈0.05或P〈0.01）,而Mn和Mg含量差异不显著（P〉0.05）。乳房炎与微量元素含量具有相关性。     

Clinical mastitis in dairy cattle in Ontario: frequency of occurrence and bacteriological isolates.

The objective of this study was to describe the frequency of occurrence of clinical mastitis in dairy herds in Ontario. The study group consisted of 65 dairy farms involved in a 2-year observational study, which included recording all clinical mastitis cases and milk sampling of quarters with clinical mastitis. Lactational incidence risks of 9.8% for abnormal milk only, 8.2% for abnormal milk with a hard or swollen udder, and 4.4% for abnormal milk plus systemic signs of illness related to mastitis were calculated for 2840 cows and heifers. Overall, 19.8% of cows experienced one or more cases of clinical mastitis during location. Teat injuries occurred in 2.1% of lactations. Standard bacteriology was performed on pretreatment milk samples from 834 cows with clinical mastitis. The bacteria isolated were Staphylococcus aureus (6.7%), Streptococcus agalactiae (0.7%), other Streptococcus spp. (14.1%), coliforms (17.2%), gram-positive bacilli (5.5%), Corynebacterium bovis (1.7%), and other Staphylococcus spp. (28.7%). There was no growth in 17.7% of samples, and 8.3% of samples were contaminated. Clinical mastitis is a common disease in dairy cows in Ontario; approximately 1 in 5 cow lactations have at lease one episode of clinical mastitis. There is, however, considerable variation in the incidence of clinical mastitis among farms. The majority of 1st cases of clinical mastitis occur early in lactation, and the risk of clinical mastitis increases with increasing parity. Environmental, contagious, and minor pathogens were all associated with cases of clinical mastitis.     

Controlling highly prevalent Staphylococcus aureus mastitis from the dairy farm

In 57 Holstein cows where the dairy farm uses a milking parlor system, the somatic cell count (SCC) increased persistently in the bulk milk (monthly mean 52.3 x 10(4) cells/ml; range 21 to 94 x 10(4) cells/ml). We detected S. aureus in 24 (41.2%) of the 54 lactating cows and in 29 (12.8%) of 227 quarters of the 57 milking cows in the herd. A control program was implemented in an effort to eradicate S. aureus mastitis from this dairy farm. The control plan established improved handling of the lactating cows, improved milking procedures, dry-cow therapy, and culling of infected cows. The program was monitored for 3.5 years by frequent checkups on the rate of S. aureus infection, the SCC, and the changes in milk composition. Eighteen months after the control program was started, the rate of S. aureus infection in the quarter milk decreased dramatically, and no S. aureus isolates were found in the milk of the remaining cows. The SCC in the bulk milk of the herd dropped to a monthly mean of <20 x 10(4) cells/ml. In conclusion, the control program was effective for controlling persistent S. aureus mastitis in this dairy herd.     

乳房炎对中国荷斯坦牛测定日泌乳性能及体细胞数变化的影响

旨在研究乳房炎及病原菌组成对中国荷斯坦牛测定日泌乳性能及体细胞数变化的影响.本研究于2009年9月对江苏某奶牛场140头成年中国荷斯坦泌乳牛进行乳房炎检测和DHI测定,同时对隐性乳房炎阳性乳区进行病原菌分离鉴定,并分析了不同乳房炎类型和隐性乳房炎病原菌组成对测定日泌乳性能和乳中SCC变化的影响.结果表明,该牛场临床乳房炎、隐性乳房炎和正常奶牛比例分别为10.00％、51.10％和37.90％,其中隐性乳房炎以大肠杆菌和链球菌混合感染最多(19头,占26.00％),其次为链球菌单独感染(17头,占23.30％).由1种细菌单独感染的比例为26头(占36.11％),2种或2种以上细菌混合感染为44头(占61.11％).乳房炎类型对测定日产奶量、乳糖含量、体细胞数和体细胞评分4个指标影响达到极显著水平(P＜0.01),临床乳房炎和隐性乳房炎奶牛日产奶量和乳糖含量极显著低于正常奶,同时体细胞数和体细胞评分极显著高于正常奶,而临床乳房炎奶和隐性乳房炎奶在所有检测指标上均无显著差异,但临床乳房炎奶比隐性乳房炎奶体细胞数高出约100万·mL-1.不同病原菌组成类型对乳中体细胞数和体细胞评分有极显著影响(P＜0.01),而对其它性状无显著影响(P＞0.05).混合感染奶牛测定日产奶量极显著低于单独感染奶牛(P＜0.01),同时乳中体细胞数显著高于单独感染奶牛(P＜0.01).乳房炎类型对乳中SCC的变化趋势有显著影响(P＜0.01),正常奶牛维持较低SCC的能力较强,隐性乳房炎奶牛在下一泌乳月体细胞增加的可能性较大.不同隐性乳房炎病原菌组成类型对乳中SCC的变化无显著影响.奶牛生产中隐性乳房炎发病率高,危害性也最大,不同病原菌混合感染引起的隐性乳房炎对测定日产奶量和乳中体细胞数影响最大.该结果为奶牛场采取合理措施,降低隐性乳房炎发生率提供了参考.     

乳头封闭剂和不同干奶药品对预防奶牛产后乳房炎的研究

奶牛乳腺健康直接关系到奶牛生产性能,和牧场效益息息相关。如何有效预防奶牛乳房炎的发生,是牧场的重中之重。干奶期是奶牛乳腺机能恢复健康的一个重要阶段,对预防奶牛产后乳房炎的发生有着重要意义。本文利用长达1 年的时间,对635 头奶牛进行分组试验,并追踪观察其产后90 天内乳房炎的发生情况和产奶量情况。通过数据分析发现,奶牛干奶期联合使用抗生素和乳头封闭剂对奶牛进行干奶,比单独使用抗生素干奶,产后7 天的体细胞阳性率降低了28.58%;产后60 天临床乳房炎发病率降低了35.40%,产后90天降低了41.32%;各组之间的产奶量并无显著差异（P>0.05）。     

Variants of somatotropin in cattle: gene frequencies in major dairy breeds and associated milk production

The amino acid sequence of bovine somatotropin (bST) varies at position 127 where either valine or leucine is found. The frequencies of leucine₁₂₇ and valine₁₂₇ bST gene alleles in cows (n = 302) and sires (n = 70) from major dairy breeds (Holstein, Brown Swiss, Guernsey, Jersey, and Ayrshire) were determined using DNA extracted from whole blood or spermatozoa. A 428 base pair fragment of the bST gene was amplified using polymerase chain reaction (PCR) and variants of the bST gene were detected as polymorphisms by Alu I restriction endonuclease digestion of PCR products. Restriction enzyme DNA fragments for the leucine₁₂₇ variant were 265, 96, 51, and 16 base pair and for the valine₁₂₇ variant were 265, 147, and 16 base pair as a polymorphism of bST was present in the 147 base pair DNA fragment. Frequencies of leucine₁₂₇ and valine₁₂₇ alleles for cows (n=302) were 1.0 and 0 for Brown Swiss, .93 and .07 for Holstein, .92 and .08 for Guernsey, .79 and .21 for Ayrshire, and .56 and .44 for Jersey, respectively. In Holstein sires used for artificial insemination (n=70), the frequency of leucine₁₂₇ and valine₁₂₇ alleles was .96 and .04. Estimates of transmitting ability for milk production tended to be greater for Holstein cows that were homozygous for leucine₁₂₇ bST and Jersey cows that were homozygous for valine₁₂₇ bST whereas Holstein sires with different bST genotypes were similar. In summary, frequencies of alleles for the bST gene were not similar in different dairy breeds and estimates of milk production were correlated with bST gene variant in cows but not sires.     

乳房炎源生鲜乳中病原微生物的污染现状及防控措施

主要介绍了乳房炎患病牛乳中病原微生物污染情况、耐药情况及防控措施。总结出乳房炎患病牛乳中的病原微生物种类较多, 主要有大肠杆菌、金黄色葡萄球菌、链球菌和克雷伯菌, 不同地区乳房炎乳样中的病原微生物不同, 产生的耐药性和耐药基因存在差异。旨在为减少因滥用和乱用抗生素导致药物残留和耐药性产生、降低乳房炎患病牛乳中病原微生物的污染以及科学、合理用药提供参考。     

Effect of supplementing a high-protein ram press sunflower cake concentrate on smallholder milk production in Zimbabwe

Ram press sunflower cake protein concentrate was formulated locally and its effect on the performance of dairy cows was compared with that of a commercial dairy concentrate. The effects of concentrate on roughage dry matter intake, milk yield and milk composition, live weight and calving intervals were similar for all concentrates, which indicated that the home grown dairy concentrates were as effective as the dairy commercial concentrate. The lack of significant differences in the concentrations of rumen NH₃-N, pH, VFAs and total AA in all the cows between concentrate types supported this. The results indicated that in the low-resource and low-input production systems, crossbreds were as productive as Jersey and Red Dane cows. The exotic cows were more susceptible to tick-borne diseases and mastitis, and showed higher incidences of calving problems and retained placenta compared with crossbred cows. The economics of feeding ram press sunflower concentrate were compared with those of a commercial dairy concentrate on the performance of crossbred, Red Dane and Jersey cows. The gross margin was higher when feeding sunflower cake than when feeding commercial dairy concentrate (p < 0.05).     

Lactoferrin Concentration in Milk of Bovine Clinical Mastitis

The lactoferrin (LF) concentration in the milk from dairy cows with clinical mastitis was determined to evaluate the relationship between the LF concentration (LFC) in milk and the non-specific defensive capability of the udder. The mean LFC in 368 milk samples from 319 cows with clinical mastitis was significantly higher (p<0.01) than that of normal cows. The mean LFC in milk from quarters infected with Mycoplasma bovis or Staphylococcus aureus was significantly higher (p<0.05) than that of quarters infected with coagulase-negative staphylococci (CNS). In Escherichia coli mastitis, the level of LFC in milk from cows with peracute mastitis was significantly lower (p<0.01) than that from cows with acute mastitis. In cases of mastitis due to E. coli, the mean LFC in milk from cows that needed more than 10 days to recover from the mastitis or were not cured was significantly lower (p<0.05) than that for cows which took less than 10 days to be cured. The mean LFC in milk from cows with peracute E. coli mastitis was significantly lower (p<0.05) than that for cows with mastitis associated with environmental streptococci or CNS, although these low LF levels were somewhat increased after 46 h from the occurrence of mastitis. These results suggest that the decreased levels of LF in peracute E. coli mastitis may be associated with the progress of inflammation in the early phase of mastitis.