Pro-active dairy herd udder health management decisions based on micro-biology and cytology of milk samples

Please read abstract on the documentThesis (PhD)--University of Pretoria, 2018.Animal and Wildlife SciencesPhDUnrestricte

Efficacy of different dry-cow intramammary antimicrobial products on the prevalence of mastitis in a high-producing dairy herd

The objectives of the study were to compare the efficacy of six intramammary dry-cow antibiotic preparations for curing existing IMI and for preventing the introduction of new IMI during the dry period. The effect of factors such as parity, milk yield, udder depth, teat canal integrity, number of infected quarters per cow, quarter-site infections and somatic cell count at drying off on cure-rates and new IMI as well as the length of the dry period and rainfall during the dry period were examined. The possible influence of treatment on the SCC during the subsequent lactation was also examined. Prior to the study a herd survey was performed to determine the basic udder health status of the trial herd. Cows due for drying off were clinically evaluated for enrollment and randomly allocated to receive one of the six dry-cow intramammary products under investigation. The six products that were studied were Nafpenzal DC (procaine benzylpenicillin, nafcillin and dihydrostreptomycin), Rilexine 500 DC (cephalexin and neomycin sulphate), Orbenin Extra DC (cloxacillin), Cepravin Dry Cow (cephalonium), Bovaclox DC (cloxacillin and ampicillin) and Dispolac Dry Cow (procaine benzylpenicillin and dihydrostreptomycin). Quarter milk samples were collected at drying off, (prior to treatment), and 1 to 6 days after calving for determination of the SSC and presence of micro-organisms in the milk. Cows were closely observed during the dry period and udders were clinically examined on a weekly basis and post-calving till udder oedema disappeared. Data from 162 cows and 648 quarters are summarized. The following were determined · Prevalence of pathogens at drying off and post-calving · Overall cure-rate and new intramammary infection rate. · Comparative efficacy of dry-cow treatment on cure-rate and prevention of new IMI. · Effect of parity, milk yield at drying off, udder depth, teat canal integrity, SCC, quarter-site infection, number of infected quarters at drying off, length of the dry period and rainfall during the dry period. · Effect of treatment on three SCC post calving during the subsequent lactation. Clinical mastitis developed in two quarters of two cows (1,03%) during the dry period which was less than described in literature, and they were removed from the trial. The prevalence of pathogens at drying off was 29,78%, of which 7,87% and 21,91% were due to major and minor pathogens respectively. The prevalence of pathogens post-calving was 22,22%, a net reduction of 7,56%, of which 4,47% and 17,75% were due to major and minor pathogens respectively. The overall cure-rate was 83,94% for quarters and varied between 72,3% and 93,9% for the various products. The overall difference in the percentage of cases cured, compared to the different micro-organisms, was found to be only marginally significant (p<0,057). High cure- rates were observed for STA, SAG and non-agalactiae pathogenic streptococci compared to studies previously done, while lower cure-rates than described were observed with CNS. Antimicrobial products used in this trial differed substantially in their efficacy to cure Gram-positive IMI. Cure rates for Cepravin Dry Cow was 93,9%, Orbenin Extra DC 91,5%, Rilexine 500 DC 85,7%, Nafpenzal DC 79,2%, Bovaclox DC 75,0% and Dispolac Dry Cow 72,4%. Interestingly, but not of any significance, was an observation that the two products with the highest overall cure-rates both contained only one antimicrobial agent compared to the other 4 products which were combinations of two or more antimicrobials. There was no significant association between parity, milk yield, teat canal integrity, number of infected quarters per cow, quarter-site infections at drying off, length of the dry period and rainfall during the dry period and the cure-rate. However, there was a significant association between udder depth (p<0,0056) and SCC (p<0,005) at drying off and cure-rate. The cure-rate was significantly less in cows with udder depth scores of 1 and 2 or SCC of more than 750 000 cells per ml milk at drying off. The overall rate of new IMI during the dry period was 17,44%. The new intramammary infection rate for quarters which received dry-cow treatment varied between 13,4% and 24,1% for the different products. The majority (70,8%) of new IMI were caused by CNS during the dry period. Almost all (96,6%) major pathogens isolated post-calving were new IMI, while 74,1% of minor pathogens were new IMI. Antimicrobial products differed in their efficacy in preventing new IMI during the dry period. The percentages of new IMI observed in cows treated with the six products were: 13,2% for Cepravin Dry Cow, 16,3% for Rilexine 500 DC, 16,7% for Dispolac Dry Cow, 17,3% for Bovaclox DC, 21,4% for Nafpenzal DC and 25,9% for Orbenin Extra DC. The probability of quarters developing new IMI during the dry period was significantly increased when cows were dried off with milk yields higher than 18kg (p<0,0037) or had low udder depth (scores of 1 or 2) (p<0,0003). Higher parity cows (p<0,005) and those that had a teat canal score of 4 (p<0,039) and above at drying off were also at an increased risk for new IMI. Marginally significantly (p<0,06) more IMI were contracted on the left side of the udder than the right side of the udder and cows at drying off and cows with dry periods longer than 80 days had marginally (p<0,06) more new IMI during the dry period. A positive correlation was found between low SCC (<250 000 cell per ml milk) and number of infected quarters per cow and parity (less than 3 lactations) at drying off. There was no significant association between the SCC at drying off and new IMI during the dry period. Significantly fewer new IMI (p<0,05) were observed when no rain fell during the dry period, compared to cows that experienced rain during their dry period. A comparison between the six antibiotic intramammary dry-cow products in relation to their efficacy in curing existing IMI and preventing new IMI showed qualitative differences between them, ranked as follows: Dispolac Dry Cow was the most effective and Orbenin Extra dry the least effective in preventing new IMI with major pathogens and Cepravin Dry Cow was to most and Nafpenzal DC the least effective in preventing new IMI with minor pathogens. Cepravin Dry cow was the most effective in the overall prevention of new IMIduring the dry period. Due to the random selection of cows the percentage of IMI differed for each product at the start of the trial. To compensate for this initial variation, percentage point improvement from drying off until calving was calculated for each antimicrobial product, taking both the cure-rates and new IMI into account. The efficacy of antimicrobial products during the dry period differed substantially when percentage point improvements were utilised: from an increase in IMI post-calving of 11,73% with Nafpenzal DC to a decrease of more than 50% in IMI at calving with both Cepravin Dry Cow and Rilexine 500 DC. Cows dried off with Rilexine 500 DC had a significantly lower SCC for the first two months post-calving than those dried off with the other five products in this trial. It is concluded that a substantial difference in efficacy exists between antimicrobial intramammary dry-cow products in their ability to cure and prevent new IMI during the dry period. Dry cow therapy should form part of a holistic approach towards the dry period, which also includes cow factors, dry-cow management, micro-organisms and the environment of the dry cow. Cow factors (milk yields, udder depth, parity, TCS and quarter-site infections) mainly have an influence on new IMI but a few cow factors (udder depth and SCC) are associated with the cure-rate of IMI. Management and rainfall during the dry period mainly affected new IMI rather than the cure-rate of existing IMI.Dissertation (MSc (Veterinary Science))--University of Pretoria, 2004.Production Animal Studiesunrestricte

Curb mastitis with fast diagnosis

No abstract available.http://www.dairyconnect.co.za/dairyMail

Effects of milking machine settings and teat liners on bovine udder health

The purpose of milking machines is to harvest milk at an optimum speed while maintaining cow comfort and preserving teat defence mechanisms against the invasion of mastitis pathogens, thus making machine settings critical in dairy herds. The various settings and combinations for milking machines were reviewed to enable operators to optimize them to preserve teat canal integrity and minimize mastitis. All databases of Web of Science and relevant websites were used to document machine settings and teat liners. All vacuum levels in milking systems need to be monitored. In addition, liners, milk yield, and automated cluster removal switch-point settings need to be regarded as bearing a risk of teat damage. They affect milking speed and vacuum levels at total, peak, and over-milking. An equilibrium should be reached between optimal milking speed and risk of teat damage. An increased switch-point setting shortens milking time and decreases overmilking and claw vacuum to preserve teat-canal integrity. Analysis of milk flow dynamics with a VaDia instrument highlights opportunities to improve milking protocols and equipment functions that align with the physiology of the cow. This knowledge can be applied on individual farms, in which herd milk yield, parlour layout, milking machine system, parlour management, and economics should be considered to obtain a balance between milking efficiency, udder health, and cow comfort. Standards for switch-point settings were identified in this review.Milk South Africa (Milk SA).http://www.sasas.co.zaam2023Production Animal Studie

Host adapted intramammary infections in pregnant heifers which were co-housed and reared on fresh milk as calves

BACKGROUND:Heifers can calve down with intramammary infections (IMI) and udder damage. This will have a negative impact on their longevity, future milk yield and financial return. Co-housed pre-weaned calves that are fed fresh milk have the opportunity to suckle each other's teats and may infect udders of fellow heifer calves with pathogens present in milk. The prevalence of IMI in pregnant heifers in South Africa (SA) which were co-housed and reared on fresh milk as calves, is not known. Quarter secretion samples from both pregnant heifers (n=2065) and dry cows (n=5365) were collected for microbiological analysis from eight SA dairy herds. All heifers tested in this study were co-housed pre-weaning and were fed fresh milk as calves. RESULTS: The prevalence of coagulase negative staphylococci, Staphylococcus aureus, Streptococcus agalactiae, environmental streptococci, coliforms and samples with no bacterial growth in heifers was 26%, 0.9%, 0.08%, 1.4%, 0.4% and 66%, respectively. The overall prevalence ratio between heifers and cows for Staphylococcus aureus IMI was 0.76 (95% CI: 0.59, 0.98). Four of the individual herds had prevalence ratios of less than one (p<0.05), one herd had a prevalence ratio of 3.15 (95% CI: 1.52, 6.32), and the remaining 3 herds had a prevalence ratio not significantly different from 1.0. Marginally significant differences were found between Staphylococcus aureus IMI in pregnant heifers compared to cows in their second and later lactations (p=0.06, p=0.05, respectively) but no significant differences between heifers and cows in their first lactation. CONCLUSIONS: The presence of Streptococcus agalactiae IMI in heifers came as a surprise, especially as herd infection rates were low. The high prevalence ratio of Staphylococcus aureus between heifers and cows in one herd warrants further investigation due to the potential danger of udder damage in a young cow at the start of her productive life. The IMI in heifers with host adapted pathogens can also act as a source of new IMI for lactating dairy cows

Sensitivity and specificity of a hand-held milk electrical conductivity meter compared to the California mastitis test for mastitis in dairy cattle

Screening tests for mastitis can play an important role in proactive mastitis control programs. The primary objective of this study was to compare the sensitivity and specificity of milk electrical conductivity (EC) to the California mastitis test (CMT) in commercial dairy cattle in South Africa using Bayesian methods without a perfect reference test. A total of 1848 quarter milk specimens were collected from 173 cows sampled during six sequential farm visits. Of these samples, 25.8% yielded pathogenic bacterial isolates. The most frequently isolated species were coagulase negative Staphylococci (n = 346), Streptococcus agalactiae (n = 54), and Staphylococcus aureus (n = 42). The overall cow-level prevalence of mastitis was 54% based on the Bayesian latent class (BLC) analysis. The CMT was more accurate than EC for classification of cows having somatic cell counts >200,000/mL and for isolation of a bacterial pathogen. BLC analysis also suggested an overall benefit of CMT over EC but the statistical evidence was not strong (P = 0.257). The Bayesian model estimated the sensitivity and specificity of EC (measured via resistance) at a cut-point of >25 mO/cm to be 89.9% and 86.8%, respectively. The CMT had a sensitivity and specificity of 94.5% and 77.7%, respectively, when evaluated at the weak positive cut-point. EC was useful for identifying milk specimens harbouring pathogens but was not able to differentiate among evaluated bacterial isolates. Screening tests can be used to improve udder health as part of a proactive management plan.http://www.elsevier.com/ locate/tvjlhb2013ab201

Fluctuations in the glucose level of cow's milk from normal and subclinically diseased udders

Individual quarter samples from some 19 cows on average were investigated monthly over 12 months for determining the udder health status of cows and the glucose concentrations of foremilk and strippings. Foremilk showed a mean 0,1311 mM concentration of glucose which remained fairly stable during the period of investigation and lactation. A fluctuating mean value of 0,2037 mM was determined in strippings in which glucose levels were consistently and appreciably higher than those of foremilk. Foremilk from completely normal quarters and others affected by non-specific cellular reaction, relevant or irrelevant teat canal infection and aseptic or septic subclinical mastitis, showed mean glucose concentrations of 0,1410; 0,1392; 0,1337; 0,1417; 0,1262 and 0,1248 mM, respectively. Strippings from the same quarters showed corresponding values of 0,2056; 0,2861 ; 0,2100; 0,1733; 0,1661 and 0,1617 mM glucose.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.am201

Antimicrobial resistance patterns and biofilm formation of coagulase-negative Staphylococcus species isolated from subclinical mastitis cow milk samples submitted to the Onderstepoort Milk Laboratory

BACKGROUND : Increased prevalence of antimicrobial resistance, treatment failure, and financial losses have been reported in dairy cows with coagulase-negative Staphylococcus (CoNS) clinical mastitis, however, studies on CoNS infections are limited in South Africa. Therefore, the objectives of this study were to investigate the antimicrobial resistance patterns and biofilm formation in CoNS isolated from cow milk samples submitted to the Onderstepoort Milk Laboratory. RESULTS : A total of 142 confirmed CoNS isolates were used for this study. Biofilm formation was identified in 18% of CoNS tested. Staphylococcus chromogenes (11%) had the highest proportion of biofilm formation followed by S. haemolyticus (4.0%), S. epidermidis, S. hominis, S. xylosus, and S. simulans with 1% respectively. Ninety percent (90%) of CoNS were resistant to at least one antimicrobial (AMR) and 51% were multidrug-resistant (MDR). Resistance among CoNS was the highest to ampicillin (90%) and penicillin (89%), few isolates resistant to cefoxitin and vancomycin, 9% respectively. Similarly, MDR-S. haemolyticus (44%), MDR-S. epidermidis (65%), and MDR-S. chromogenes (52%) were mainly resistant to penicillins. The most common resistance patterns observed were resistance to penicillin-ampicillin (16%) and penicillin-ampicillin-erythromycin (10%). Only 42% of biofilm positive CoNS were MDR. CONCLUSION : The majority of CoNS in this study were resistance to penicillins. In addition, most isolates were β- lactam resistant and MDR. Biofilm formation among the CoNS in this study was uncommon and there was no significant difference in the proportion of MDR-CoNS based on the ability to form a biofilm.The Research Development Programme (RDP) of the University of Pretoria and the Milk Producers’ Organisation (MPO).https://bmcvetres.biomedcentral.comam2020Paraclinical SciencesProduction Animal Studie

Species identification and cow risks of non-aureus staphylococci from South African dairy herds

DATA AVAILABILITY : Data supporting the findings of this study are available from the corresponding author, I.-M.P., on request.Detailed information on specific species of non-aureus staphylococci (NAS) has become a necessity for effective udder health control programs in South Africa. The main objective of this preliminary study was to identify the different NAS species and strains present in dairy herds in South Africa using a cost-effective method. A further objective was to investigate the effects of cow risk factors and farming systems on the NAS isolates identified. A total of 214 NAS, isolated from milk collected from 17 South African dairy herds, were identified using three diagnostic tests (API Staph test, MALDI-TOF and 16s rRNA). There was a good observed agreement between the MALDI-TOF and 16S rRNA sequencing (92.2%) and a poor observed agreement between the MALDI-TOF and API Staph (25.7%). The genetic relatedness within species was investigated in 128 of these isolates using random polymorphic amplified deoxyribonucleic acid (DNA) (RAPD), verified by multilocus sequence typing (MLST), and phylogenetic analysis and cow risk factors were investigated on species level. The main NAS species isolated were Staphylococcus chromogenes (75.2%), Staphylococcus epidermidis (9.4%) and Staphylococcus haemolyticus (8.9%). The RAPD test identified 34 Staphylococcus chromogenes, 13 Staphylococcus epidermidis and nine Staphylococcus haemolyticus strains, indicating genetic diversity amongst strains and herds. The presence of NAS intramammary infections was found to be significantly related to the farming systems, composite cow milk somatic cell count (SCC), parity and days in milk (DIM). Significantly more NAS were isolated from primiparous and from older cows. This knowledge could assist with the management of NAS on dairy farms.The National Research Foundation of South Africa and Milk SA.http://www.ojvr.orgam2023Production Animal Studie

The effect of various automatic cluster removal switch-point settings on milking and overmilking duration and total, peak and overmilking claw vacuum in dairy cows

This research communication describes the effect of three automatic cluster removal (ACR) switch-point settings on machine-on time, overmilking duration, and the mean, peak-flow and overmilking vacuums. The objective was to reduce the overmilking and milking time, attaining a lower mean claw vacuum during overmilking. In a randomised experiment, 25 cows were subjected to three ACR switch-point settings at flow rates of 0.840 kg/min, 0.630 kg/min and 0.504 kg/min each for 15 morning-milkings. Pre-milking preparations and cow comfort were observed and evaluated, showing evidence that the switch-point setting of 0.840 kg/ml denoted the least proportion of behavioural problems (1.1% ± 0.6) compared to the settings at 0.640 kg/ml (16.0% ± 2.2) and 0.504 kg/ml (9.4% ± 1.7). A VaDia device (Biocontrol) determined the machine-on time and vacuum levels at the claw, mouthpiece and pulsator chamber. The machine-on time varied from 290 ± 72.8 (mean ± sd) to 289 ± 64.4 and 303 ± 66.3 for the 0.840, 0.630 and 0.504 kg/min settings, respectively. Overmilking was shortened by 29.3% and 26.4% and the claw vacuum during overmilking was reduced by 3.7 kPa and 4.3 kPa when using the 0.840 kg/min switch-point setting, compared to the others. An increased cluster-removal milk flow threshold reduced both overmilking and vacuum level during overmilking, lowering the risk of teat damage. Adapting ACR switch-point settings offers a valuable opportunity to increase parlour efficiency and cow comfort in dairy herds.The National Research Foundation (NRF) and Milk South Africa partly supported this research.https://www.cambridge.org/core/journals/journal-of-dairy-researchhj2023Production Animal Studie