Management practices associated with udder health of first-parity dairy cows in early lactation

This study aimed at investigating associations between management routines including feeding, housing, and milking around calving, and udder health of first-parity cows in early lactation in Swedish large, high producing, low bulk-milk somatic cell count (SCC) dairy herds housed in free stalls. Seventy-two dairy herds participated and data concerning 1189 first-parity cows calving during the study period (October 2005-January 2006) was collected. Multivariable regression analysis were performed with three different outcomes; within-herd number of first-parity cows veterinary treated for clinical mastitis at days -10 to 60 after calving, within-herd number of first-parity cows with a SCC> or =200,000cells/mL at first test-day, and SCC of first-parity cows at first test-day. Cow factors significantly associated with good udder health of first-parity cows (few cases of clinical mastitis and or low SCC) were being of the Swedish Red breed, having a high milk yield at first test-day, and a milk-urea > or =5mmol/L at first test-day. Herd factors significantly associated with good udder health were having mattresses as flooring in the cubicles in the lactating cow housing, and to house the first-parity cows in tie stalls 1 month before calving. Cow factors significantly associated with poor udder health of first-parity cows were having a milk-urea <4mmol/L at first test-day. Herd factors significantly associated with poor udder health of first-parity cows were feeding first-parity cows sugar-beet pulp or corn silage, and to give silage from a different batch to pregnant heifers than to lactating cows. Moreover, to have sawdust or shavings in the calving pen, to be moved from the calving pen > or =2 days after calving, to milk first-parity cows at the calving site instead of in the parlor, and to rinse, clean or disinfect milking units before a first-parity cow was milked were also significantly associated with poor udder health of first-parity cows. The results indicate that different control measures must be taken depending on the nature of the udder health problem.     

Effect of setting a maximum milking time,from peak lactation,on production,milking time and udder health

Abstract

AIM: To examine the effect of setting a maximum milking time, from peak lactation until drying-off, on production, duration of milking, and udder health of dairy cows.

METHODS: Forty cows were assigned in twin-pairs to be either milked until cups were removed at a milk flow-rate threshold of 0.35 kg/minute (Control), or until cups were removed at a milk flow-rate threshold of 0.35 kg/minute, or maximum time, whichever came first (MaxT). The maximum time was set by determining the milking time of the 70th percentile cow when ranked from fastest to slowest, irrespective of yield. The milking routine was typical of that practised on dairy farms in New Zealand, and involved no pre-milking preparation. The study began at peak lactation (68 (SD 7) days in milk; DIM) and continued for 26 weeks. Duration of milking and milk yield were measured for each milking. Composition of milk was determined from weekly herd tests, and milk quality from fortnightly somatic cell counts (SCC). Completeness of milking and teat condition were assessed during the study. The bacterial status of quarter milk samples was determined at the beginning and end of the study, and all treated cases of clinical mastitis recorded. ANOVA was used to examine the effect of treatment group on variables of interest.

RESULTS: Total milk, fat and protein yields during the study period did not differ between treatments. On average, 30.3% of the morning and 27.6% of the afternoon milkings of MaxT cows reached the maximum time at which cups were removed, and were therefore shortened. While the average milking time of the slowest-milking cow was longer for the Control compared with MaxT group in Weeks 1–18, the average milking time did not differ between treatments. There was no difference in overall SCC, and the incidence of clinical mastitis, or the percentage of infected quarters at drying-off, was similar for the MaxT and Control cows.

CONCLUSION: The results show that setting a maximum milking time can reduce the milking time of slower-milking cows in a herd without compromising overall herd production and udder health.

CLINICAL RELEVANCE: Although the numbers of cows in the study were small there was no evidence of a major increase in SCC, or subclinical or clinical mastitis when a maximum milking time was set for slower-milking cows.     

The effect of pasture turnout on milk somatic cell count,polymorphonuclear leukocytes and milk composition in cows housed in tie stalls

Abstract

This study investigated milk somatic cell count (SCC), polymorphonuclear leukocytes (PMNs) and milk composition in dairy cows, which were kept in tie stalls, during the first days after pasture turnout. Thirty-five cows of the Swedish Red Breed, free of clinical signs of mastitis and with a geometric mean of SCC 67 × 10³ cells/mL, were turned out to pasture after the morning milking on day 0 and then monitored for the next five days on pasture. Samples of cow composite milk were taken at every milking and analysed for SCC, PMN percentage of the total SCC and milk composition. There was a marked increase in both PMN proportion and SCC with the highest SCC value during the study recorded at the evening milking on day 0. The highest value in morning milk was observed on day 1. Milk SCC values in evening and morning milk declined after day 0 and day 1, respectively, but remained on a higher level compared with before turnout to pasture. Milk composition was only slightly altered. Since the changes in SCC and milk composition were of low magnitude, although statistically significant, these effects of pasture turnout can be considered as of minor importance for the milk quality.     

Incidence and transmission of Mycoplasma bovis mastitis in Holstein dairy cows in a hospital pen: A case study

The objective was to determine the incidence and transmission of mycoplasma mastitis in the hospital pen in a dairy herd of 650 lactating cows after a hospital pen was established following an outbreak of this disease. Mycoplasma mastitis status was monitored for 3 months through repeated collection of milk samples from cows with clinical mastitis (CM) and from bulk tank milk. During the outbreak 13 cows were diagnosed with Mycoplasma bovis CM, 1 cow with Mycoplasma sp. mastitis and 8 cows showed signs of arthritis, 3 of which were confirmed as having M. bovis arthritis. M. bovis isolates from cows with CM, arthritis and bulk tank milk had indistinguishable chromosomal digest pattern fingerprints. Incidence rates of M. bovis CM cases in the milking and hospital pens were 0.01 and 1.7 cases per 100 cow-days at risk. Approximately 70% of cows with M. bovis CM became infected within 12 days of entering the hospital pen. Transmission of M. bovis in the hospital pen occurred as 3 episodes. Each episode corresponded to the introduction of a cow with M. bovis CM from a milking pen. Evidence indicates that cows with M. bovis CM from milking pens were the source of transmission of the disease in the hospital pen and thus their presence in the hospital pen appeared to be a risk factor for transmission of M. bovis mastitis in this single case study herd.     

Efficacy of specific egg yolk immunoglobulin (IgY) to bovine mastitis caused by Staphylococcus aureus

The objective of this study was to estimate the efficacy of specific egg yolk immunoglobulin (IgY) to bovine mastitis caused by Staphylococcus aureus. Eighteen lactating cows with clinical mastitis and 18 lactating cows with experimental mastitis (1 quarter per cow) were randomly assigned to three treatments: IgY (20mg/ml) infusion, penicillin (100mg/ml) infusion and no infusion. Treatments for clinical mastitis and experimental mastitis were performed by a 6-day course of intramammary infusion with a dosage of 10ml at an interval of 12h. Milk samples were collected at morning milking time for testing color, clot, somatic cell counts (SCC) and bacterial count. For most of the cows treated with IgY and penicillin, the milk color and clot recovered to normal form during the therapy course. The milk SCCs and bacterial counts of treated cows decreased compared to those of untreated cows (p<0.05). The cure rates by IgY for experimental and clinical mastitis were 83.3% and 50%, respectively, and those by penicillin were 66.7% and 33.3%, respectively. These results showed the potential of specific IgY to be an alternative therapy for mastitis caused by S. aureus.     

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.     

A descriptive epidemiological study of mastitis in 12 Irish dairy herds

: Factors relating to the occurrence of mastitis were studied on 12 Irish dairy herds with histories of elevated somatic cell count (SCC) and/or increased incidence of clinical mastitis cases. Milk recording data were analysed, housing conditions and calving areas were examined; dry cow therapy, clinical mastitis records, milking technique and aspects of milking machine function were assessed.Herds with a ratio of less than 110 cubicles per 100 cows were more likely to experience environmental mastitis. Herds with inadequate calving facilities, where cows spent prolonged periods on straw bedding, were likely to acquire environmental mastitis. In the majority of the herds, the selection of dry cow therapy lacked adequate planning. The majority of farmers took no action to reduce pain experienced by cows suffering mastitis. Deficiencies in parlour hygiene were evident in all herds experiencing elevation in SCC.     

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.     

我国规模牛场奶牛个体生鲜乳体细胞数水平及影响因素探析

本研究旨在探析我国规模奶牛场奶牛个体生鲜乳体细胞数（SCC）的水平、分布和影响因素。利用SAS9.0的GLM模型,统计分析覆盖16个省（市、区）,33个规模奶牛场,23 351头中国荷斯坦牛,从2007年至2009年连续3年的225 775条奶牛个体生鲜乳SCC检测记录。结果表明：奶牛个体生鲜乳SCC的总体均值为48×104cell/mL,标准差为117×104cell/mL,个体生鲜乳SCC波动范围较大;其中,77.9%的奶牛个体,其生鲜乳SCC小于50×104cell/mL,对群体混合样生鲜乳SCC的影响系数为0.26;11.3%的奶牛个体,其生鲜乳SCC介于50×104～100×104cell/mL之间,乳房处于隐性感染状态,对群体混合样生鲜乳SCC的影响系数为0.16;10.8%的奶牛个体,生鲜乳SCC大于100×104cell/mL,理论上乳房处于临床感染状态,对群体混合样生鲜乳SCC的影响系数为0.58。奶牛个体生鲜乳体细胞数评分（SCS）呈正态分布,与奶牛个体因素（产奶量、乳脂率、乳蛋白含量、胎次和泌乳阶段）和环境因素（泌乳月份、泌乳季节）差异极显著（P〈0.01）,与奶牛养殖区域、奶牛场差异不显著（P〉0.05）。我国规模奶牛场奶牛个体生鲜乳SCC主要在50×104cell/mL以下,依据影响参数能实现对生鲜乳SCC水平的调控。     

Intramammary treatment of clinical mastitis of dairy cows with a combination of lincomycin and neomycin, or penicillin and dihydrostreptomycin

AIM: To compare clinical and bacteriological cure rates of clinical mastitis following treatment with intramammary preparations containing either lincomycin and neomycin or penicillin and dihydrostreptomycin. METHODS: Cases of clinical mastitis were sourced from four seasonal-calving dairy herds in the central Waikato region of New Zealand during the first 120 days of lactation. Affected quarters were infused three times at 12 h intervals with either 333 mg lincomycin plus 100 mg neomycin (lin/neo; 197 glands),or 1,000 mg penicillin plus 500 mg dihydrostreptomycin (pen/DHS; 207 glands). Milk samples were collected for bacteriology from each quarter immediately before and approximately 21 days after initiation of treatment. Additionally, a composite milk sample from each cow was collected, on average, 54 days after enrolment for assessment of milk yield, composition and somatic cell count (SCC). The probability of bacterial cure was initially analysed using Chi-squared analysis, and factors that were associated (p<0.2) were offered to a reverse stepwise logistic regression model. Continuous variables (e.g. milk solids production and log10 SCC) were analysed using general linear models. RESULTS: A total of 404 quarters diagnosed with clinical mastitis, from 282 cows in the first 120 days of lactation, were included. Streptococcus uberis, coagulase-negative staphylococci and Staphylococcus aureus were isolated from 56.5%, 18.8% and 10.0% of the bacteriologically positive quarters. There was no difference in the bacteriological cure rate (76.7% vs 76.7%, OR=0.94; p>0.8), the log10 SCC (2.1, SE 0.1, vs 2.0, SE 0.1; p>0.3) or milk production (1.2, SE 0.1, vs 1.2, SE 0.1, kg milksolids/cow/day; p>0.7) between lin/neo vs pen/DHS treatments, respectively. However, the proportion of cows re-treated following initial treatment was higher for the lin/neo compared to pen/DHS-treated group (16.3% vs 5.2%, OR=3.46; p<0.05). CONCLUSIONS: No difference in bacteriological cure rate, milk production or SCC was evident between lin/neo and pen/DHS intramammary treatments for clinical mastitis in dairy cows during the first 120 days of lactation. KEYWORDS: Dairy cow, mastitis, intramammary, antibiotic, treatment, somatic cell count.     

Udder health and risk factors for subclinical mastitis in organic dairy farms in Switzerland

A study was performed in 1997 to estimate the prevalence and to investigate the etiology of subclinical mastitis in Swiss dairy herds managed under guidelines of controlled organic farming. It was planned as a longitudinal study over a period of 1 year and included a stratified random sample of 152 certified organic farms and 1907 cows. Two farm visits (the first from June to October when cows were on pasture, the second from January to March when cows were confined to barns) were performed on each farm. At each visit, farm management and individual-cow data (with emphasis on milking procedures and udder sanitation) were recorded. California mastitis tests (CMTs) were performed on each udder quarter of all cows in lactation. Milk samples with CMT >1+ were submitted for somatic cell counting (SCC), bacteriological examination and to test for antibiotic susceptibility. The SCC and germ-cell counts of monthly bulk-tank milk samples were available through Dairy Inspection and Advisory Services and milk production data of 567 herd-book cows were available from breeding associations. Possible individual and environmental predictors of subclinical mastitis were identified using logistic models adjusted for clustering of the data at herd and cow levels. Data were analyzed separately for cows from 7 to 100 and from 101 to 305 days post partum. Prevalences of subclinical mastitis at the quarter level were 21.2% for lactation period 7–100 days and 34.5% for 101–305 days post partum. The geometric mean SCC in bulk-tank milk samples was 85.6×10³ cells/ml. Samples at 7–100 and 101–305 days post partum were positive for Staphylococcus aureus in 16.0 and 7.4%, for coagulase-negative Staphylococci in 51.5 and 50.6%, for Streptococcus agalactiae in 0.0 and 0.8%, for other Streptococci in 19.4 and 15.6%, for E. coli in 1.0 and 0.4%, and for Corynebacterium bovis in 25.7 and 45.1%, respectively. Risks of subclinical mastitis increased significantly with increasing days post partum and advancing age of cow. Cows that were sampled when staying in alpine dairies had considerably higher risks of subclinical mastitis than cows staying in home barns. Significantly lower risks of subclinical mastitis were observed in farms where CMT was performed regularly as a control measure. Bacteria in milk from cows with mastitis exhibited antibiotic resistance at a comparable frequency as found previously in conventional farms.     

Quarter,cow, and farm risk factors for intramammary infections with major pathogens relative to minor pathogens in Thai dairy cows

A cross-sectional study was carried out from May to September 2011 on 35 smallholder dairy farms in Chiang Mai, Thailand, to identify the quarter, cow, and farm factors that relate to intramammary infections (IMI) from major specified pathogens, compared to infections from minor pathogens. Data on general farm management, milking management, and dry cow management were recorded for each herd. Quarter milk samples were collected from either clinical or subclinical mastitis quarters. Dependent variables were binary data defining the specified major pathogens, including Streptococcus agalactiae (7.1 %), Streptococcus uberis (9.4 %), Streptococcus dysgalactiae (4.0 %), and other streptococci (16.7 %), as a case, and all minor pathogens as a control, in each dependent variable. The occurrence of S. agalactiae IMI was lower in first-parity cows and cows with short milking time. Cows with body condition score (BCS) <2.5 had higher occurrence of S. agalactiae IMI. The occurrence of S. uberis IMI was higher in quarters with California mastitis test (CMT) score 2, score 3, and having clinical mastitis and in farms with increasing age of vacuum system. Quarters with CMT score 3, having clinical mastitis, cow with manual milking after detaching milking cluster, and farms with high bulk milk somatic cell counts (BMSCC >500,000 cells/ml) had higher occurrence of S. dysgalactiae IMI. For other streptococci, quarters having clinical mastitis, BCS <2.5, and pulling down of milking cluster while milking increased occurrence of other streptococci IMI relative to minor pathogen IMI. These results highlight the importance of individual cow factors, milking characteristics, and BMSCC in determining the risk of IMI from major pathogens.     

A case study of improving milking cow performance and milking system performance with using a flow simulator

Efforts to improve dairy performance have been focused on increasing milk productivity of cows through improved feeding systems and genetic potential. However, methods for evaluating milking system performance based on milk productivity have not yet been established. Milking system performance was evaluated by measuring the claw vacuum at five flow rates (1.9–8.7 kg/min) produced using a flow simulator for a single eight‐swing milking parlor with a high‐line system. Based on these results, a double eight‐parallel milking parlor with a low‐line system was installed and tested. Farmers can take data obtained from evaluations of milking system performance into account for future management decisions, such as renewing the milking system. By renewing the milking system, average milking productivity, somatic cell linear score (LS) of bulk milk, and LS of each cow were significantly improved in the year after installing the new system (p < .01). In addition to checking conventional milking systems, this novel diagnostic method using a flow simulator can be used for checking new installations and also for proposing renovations.     

Milking performance evaluation and factors affecting milking claw vacuum levels with flow simulator

Milking performance of milking machines that matches the production capability of dairy cows is important in reducing the risk of mastitis, particularly in high‐producing cows. This study used a simulated milking device to examine the milking performance of the milking system of 73 dairy farms and to analyze the factors affecting claw vacuum. Mean claw vacuum and range of fluctuation of claw vacuum (claw vacuum range) were measured at three different flow rates: 5.7, 7.6 and 8.7 kg/min. At the highest flow rate, only 16 farms (21.9%) met both standards of mean claw vacuum ≥35 kPa and claw vacuum range ≤ 7 kPa, showing that milking systems currently have poor milking performance. The factors affecting mean claw vacuum were claw type, milk‐meter and vacuum shut‐off device; the factor affecting claw vacuum range was claw type. Examination of the milking performance of the milking system using a simulated milking device allows an examination of the performance that can cope with high producing cows, indicating the possibility of reducing the risk of mastitis caused by inappropriate claw vacuum.     

Impact of Mastitis Control Measures on Milk Production and Mastitis Indicators in Smallholder Dairy Farms in Kiambu District,Kenya

Bovine mastitis and mastitis control were investigated on smallholder farms in central Kenya. After an initial observational study, a clinical trial to assess the impact of three different mastitis control strategies – (1) improved udder hygiene, (2) treatment of subclinical cases, and (3) a combination of these – was conducted on 100 randomly selected farms with 332 lactating cows. Before the implementation of control measures, the milk yield was low (mean 6.5 kg/day; median 6 kg/day) and somatic cell counts (SCC) were high, with 80% and 43% of cows having milk with SCC greater than 250×10³ cells/ml and 600×10³ cells/ml, respectively. Infectious pathogens were also commonly isolated, with 63% of cows being positive for pathogenic bacteria. Neither intervention strategy alone had any effect on mastitis indicators or milk yield. In combination, the measures had some impact, lowering the prevalence of contagious pathogens by 18%, but this was not reflected in a significantly increased milk yield, lowered SCC or reduced incidence of clinical mastitis.     

Milk flow and udder health in cows after treatment of covered teat injuries via theloresectoscopy: 52 cases (2000-2002)

OBJECTIVE: To determine milk flow, somatic cell counts (SCCs), and the incidence of clinical mastitis in cows that had undergone theloresectoscopy for treatment of teat stenosis caused by mucosal detachment in the region of the streak canal or Fürstenberg's rosette. DESIGN: Retrospective study. ANIMALS: 52 cows with teat stenosis that were treated via theloresectoscopy. PROCEDURE: Medical records of eligible cows were reviewed. Additional data regarding milking ease, SCC, development of clinical mastitis of the affected gland, and whether the cow remained in the herd were collected via owner-completed questionnaires. RESULTS: 49 of 52 questionnaires were completed. At referral, teat sinusitis was diagnosed in 29 of 52 cows. Milk flow was normal in 38 of 41 treated teats at discharge and in 24 of 40 during the next lactation. Thirteen of 49 cows were culled during the next lactation because of abnormal udder health. High SCC and teat sinusitis at referral and development of clinical mastitis during the 10-day period after surgery resulted in high SCCs in the remainder of the current lactation. The incidence of clinical mastitis during the remainder of the current and during the next lactation was higher in cows that had teat sinusitis at the time of surgery, compared with those that did not. CONCLUSIONS AND CLINICAL RELEVANCE: Teat stenoses resulting from mucosal lesions in the region of the streak canal or Fürstenberg's rosette may be successfully treated via theloresectoscopy. Inflammation of the teat sinus and gland at the time of surgery may adversely affect udder health.     

Efficacy of intramuscular treatment of beef cows with oxytetracycline to reduce mastitis and to increase calf growth

Spring-calving multiparous Angus x Hereford cows were used to determine the efficacy of intramuscular treatment with oxytetracycline to reduce the incidence of mastitis-causing bacteria, decrease milk somatic cell counts (SCC), and increase calf growth. During 2 yr, milk samples were collected from each quarter from a total of 319 cows at 8 to 14 d after calving and at weaning, to determine the presence of bacteria and SCC. A California mastitis test (CMT) was performed on milk from each quarter of each cow at the initial sample collection. Cows with a CMT score of 1, 2, or 3 in at least one quarter, were randomly assigned to receive either an intramuscular injection of oxytetracycline (n = 63) or the control vehicle (n = 60), and cows with a CMT score of 0 or trace in all four quarters were not treated (n = 196). Calf weights were determined at birth, early lactation, and weaning. The number of somatic cells in milk and the percentage of quarters that were infected increased as CMT score increased (P < 0.01). The presence of mastitis-causing bacteria at calving increased (P < 0.05) the incidence of infection at weaning. The presence of mastitis-causing bacteria at weaning was associated with increased SCC for quarters and average SCC for cows (P < 0.01). Average SCC per cow at weaning increased (P < 0.05) as the number of infected quarters per cow increased. Treatment did not alter (P > 0.10) the percentage of cows or quarters infected with mastitis-causing bacteria or SCC of cows or quarters at weaning. Average SCC per cow was negatively correlated (P < 0.05) with calf weights at early lactation, but not with weaning weights of calves. Treatment did not influence (P > 0.10) calf weights at early lactation or at weaning. Cows with one or more dry quarters after calving had calves that weighed less at early lactation and weaning than cows with four functional quarters (P < 0.01). Intramuscular oxytetracycline treatment of beef cows that had CMT scores of 1 or greater after calving did not reduce intramammary infection rates or increase calf weights at weaning.     

Norfloxacin pharmacokinetics in lactating cows with sub-clinical and clinical mastitis

Single-dose pharmacokinetics of norfloxacin after intravenous administration of norfloxacin nicotinate at 10 mg norfloxacin/kg body weight was investigated in cows with healthy udders and in cows with chronic subclinical and postacute clinical mastitis. An HPLC method was used to determine the norfloxacin concentrations in serum and milk. Significant differences were observed in norfloxacin pharmacokinetics when administered to cows with infected udder quarters. The clearance (Cl) values were 10.4+/-2.5, 13.2+/-1.9 and 14.2+/-2.1 mL/min/kg (mean +/-SD) in the control (healthy udder) cows and in cows with subclinical and postacute clinical mastitis, respectively. There appeared to be a trend of increasing clearance according to severity of the disease. The volume of distribution at steady state (Vss) in the respective groups was 3.1+/-0.7, 2.2+/-0.6 and 1.3+/-0.2 L/kg. The volume of distribution was significantly decreased in the cows with postacute clinical mastitis. The half-lives (t1/2) and mean residence times (MRT) of norfloxacin were 353, 206 and 115 min (harmonic means) and 306+/-76, 168+/-39 and 95+/-9 min in control cows or in cows with subclinical and postacute clinical mastitis, respectively. The half-lives in the clinical mastitis group were significantly shorter than in the control group and the mean residence times were significantly shorter in the two mastitis groups when compared to the control group. Norfloxacin concentrations in milk were extremely high when compared to the respective serum concentrations. The area under the concentration vs. time curve (AUC) of norfloxacin in milk was 23899+/-6206 mg/L x min in the control cow group. The AUC in milk was significantly lower in the infected udder quarters of the mastitis groups (5075+/-1887 mg/L x min and 7484+/-4645 mg/L x min in the subclinical and the clinical group). The AUC values were significantly lower in milk from the infected udder quarters of the cows with chronic subclinical and postacute clinical mastitis when compared to the values in milk from the healthy quarters of the same udder. Norfloxacin was marginally bound to serum protein. The binding was concentration dependent and was 19, 13 and 6% at 0.2, 1.0 and 8.4 mg/L, respectively. Binding to milk protein was 46-51% and concentration independent. An in vitro dialysis model was used to simulate drug transport between serum and milk as a function of protein binding. The results showed that the rate of norfloxacin disposition from milk to serum was slower than from serum to milk, which was in agreement with the findings obtained in the pharmacokinetic study. Norfloxacin was poorly soluble in organic solvents and our results suggest that changes in the degree of ionization of the drug in different body fluids considerably affect its disposition.     

Lactoferrin concentrations in milk from normal and subclinical mastitic cows

The concentrations of lactoferrin (Lf) in quarter milk from normal lactating cows and subclinical mastitic cows were measured to determine whether the Lf concentration in milk is influenced by the age of the cow, the stage of lactation, number of milk somatic cells and the presence of pathogens. Lf concentrations in 111 quarter milk samples from 28 normal lactating cows and 270 quarter milk samples from 198 subclinical mastitic cows were measured by means of a single radial immunodiffusion test. Lf concentrations (means +/- standard deviations; logarithmic form) in normal cows and subclinical mastitic cows were 2.23 +/- 0.39 and 2.70 +/- 0.39, respectively. The mean milk Lf concentration (log) in subclinical mastitic cows was significantly (p<0.01) higher than that in normal cows. The mean milk Lf concentration (log) in normal lactating cows aged 5 years was lower than those in normal lactating cows aged 2 years (p<0.01) and 3 years (p<0.05). The results showed that the milk Lf concentration (log) is associated with age of the dairy cow (one-way analysis of variance test, p<0.01). The mean milk Lf concentration (log) in the latter lactational period tended to be higher than those in the peak and middle periods. Milk Lf concentrations (log) tended to be proportional to the level of the somatic cell count (SCC) score. Mean milk Lf concentrations (log) in subclinical mastitic cows infected with Staphylococcus aureus and with other streptococci species were significantly (p<0.01) higher than those in cows infected with coagulase-negative staphylococci and with Corynebacterium bovis.     

基于DHI平台开展奶牛乳房炎诊断及治疗效果的研究

为评估DHI中的体细胞值对奶牛乳房炎的预警作用,以湖南省DHI中心对宁乡某规模化奶牛场2019年3-4月份DHI数据为基础,结合乳房炎快速检测液,筛选临床或隐性乳房炎奶牛,确定为药物治疗效果试验组。采集筛选牛群奶样,进行细菌分离培养、鉴定,结合药敏实验开展针对性治疗,观察治疗效果。结果发现:从试验组奶样中均分离出各种乳房炎致病菌,其中主要是大肠杆菌和金黄色葡萄球菌;经敏感药物治疗后,患牛乳中体细胞数(SCC)下降极显著(P<0.01)。结论:体细胞数(SCC)作为DHI检测的一项重要指标,对奶牛乳房炎起到第一预警作用;DHI报告同时针对出现的问题提出相应的改进措施,以期使DHI成为牛场发现管理问题、增加养殖效益的有效工具,切实服务于奶牛场的实际生产。