Dr Marcos Veiga is a noted academic, holding the position of Professor in the Department of Animal Nutrition and Production at the School of Veterinary Medicine and Animal Science at the University of São Paulo in Brazil. M2 magazine asked Dr Veiga about his work on bovine mastitis, past and present.
M2 magazine. You have a longstanding involvement in research into bovine mastitis. How has your research developed over the years?
Dr Veiga. During the last 20 years, Brazil’s milk production has grown by about 4% per year, mainly due to increased farm productivity. Currently, Brazil is among the five largest milk producers in the world, producing over 35 million tonnes of milk per annum in 2019, a growth of 3.1% on 2018. (see Table 1). The milk production, concentrated in the states in the south and east of Brazil (see Table 2) is directed mainly at the domestic market, which is a different situation of other agricultural commodities in Brazil, where the main market is for export to other countries. The outlook is for milk production to grow by 2% in 2020.
Although mastitis is the disease that causes the most economic losses to the dairy industry, the research on bovine mastitis in Brazil is still quite incipient and with relatively few research groups in operation.
The main challenges for research in mastitis control and milk quality during the last two decades were the lack of laboratory structures for the evaluation of Somatic Cell Count (SCC), the logistical difficulties of shipping samples in what is a large, continental country, only recent legislation setting limits for SCC in bulk tank milk and a limited use of microbiological diagnoses to identify the causes of mastitis.
Thus, during the last number of years the main focus of research projects developed at Qualileite-USP (the Milk Quality Research Laboratory, at the University of São Paulo (www.qualileite.org) has been in the development of studies on the impact of SCC on the quality of milk for liquid consumption and for dairy products, such as cheeses; the evaluation of rapid diagnostic methods for bovine mastitis; and mastitis control measures in dairy herds.
M2 magazine. What were the major challenges confronting the industry?
Dr Veiga. The challenges for improving milk production in Brazil are the low productivity and the small scale of production on most farms, higher equipment costs for dairy production, insufficient infra-structure available, low milk quality and a lack of long-term governmental dairy policies applicable to the dairy sector.
The first legal limit for SCC in milk was effective in the year 2005 (set at 1,000,000 cells/ml) and in 2019 the limit was set to 500,000 cells/ml. However, despite some initiatives by some industries to encourage improvement in milk quality through a quality payment program, the average SCC has remained at 400,000 cells/ml in recent years. Among the reasons for the lack of an on-going and consistent reduction of SCCs in herds is the low application of effective practices of control of contagious mastitis, insufficient public policies for training small producers and developing national mastitis control programs. It is estimated that about 70% of the herds present Streptococcus agalactiae in bulk tank milk, which indicates a great need to improve mastitis control practices on dairy farms.
M2 magazine. How have the tools and techniques in research changed and developed over the years?
Dr Veiga. During the last few years, there have been great advances in milk production in commercial farms, which required the improvement of mastitis diagnosis methods, new control measures and a need for training of dairy producers and farm personnel involved in milk production. Among the main diagnostic tools and techniques that have brought a major revolution in the microbiological diagnosis of mastitis-causing agents is the use of Matrix Assisted Laser Desorption and Ionization Time-of-Flight Mass Spectrometry. (MALDI-TOF MS).
Our research group was one of the pioneers in the evaluation of this technique for the identification of bacteria causing bovine mastitis, and the first studies were published in 2010. The MALDI-TOF technique is based on the analysis of mass spectra (mass to charge ratios) of ribosomal proteins of bacteria, which are compared with a reference database, for bacterial identification.
The use of this technique allowed greater speed (about 24 hours) and high accuracy in the identification of mastitis-causing bacteria, especially some groups of bacteria that have great diagnostic limitations with the use of conventional microbiology, for example, the groups of non-aureus Staphylococcus, Streptococcus, Enterococcus and Lactococcus and coliforms.
M2 magazine. Now, in 2020, what topics are you and your research colleagues focusing on in bovine mastitis research?
Dr Veiga. The latest research projects of our group aims to evaluate the accuracy of chromogenic culture media* for on-farm culture systems.
The objectives of two recent projects were to evaluate the accuracy of three chromogenic culture media for the identification of bacteria that cause clinical and subclinical mastitis, as well as for use in post-partum cows. The results indicated that these chromogenic culture media could be excellent tools for diagnosing specific groups of mastitis-causing agents, such as Staphylococcus aureus, Streptococcus uberis, Escherichia coli and Klebsiella, with a high accuracy of identification after 24 hours of incubation.
Based on these results, milk producers can make better treatment decisions and use selective treatment protocols, which has the potential to reduce unnecessary antimicrobial treatments by about 50%.
In addition, our research group has established international research collaborations to evaluate molecular virulence factors characteristics of mastitis-causing agents, such as Staphylococcus aureus and Streptococcus uberis, which allows comparing virulence differences of these agents in different regions of the world.
Recently, in collaboration with a group from the University of Milan (with Prof. Paolo Moroni) and six other research groups around the world, we conducted a study to evaluate the production of toxins and other virulence genes of Staphylococcus aureus (10.3390/toxins10060247).
The results of this study demonstrated the wide variety of S. aureus genotypes found in dairy cattle, worldwide and suggests that a knowledge of the region of interest may help to formulate strategies for reducing the spread of the infection.
* M2 magazine note. Chromogenic culture medium is used to isolate, identify and differentiate specific microorganism from a heterogeneous population. The medium contains chromogenic substrate, which is utilized by the microorganism to give colored colonies, specific for each microorganism. Depending on the color of the result, the presence or absence of a target organism is determined and is accurately differentiated from others. Whereas classical culture media are based on the principle of a change in color of the pH indicator, the chromogenic media are based on enzymatic utilization of chromogenic substrates.
M2 magazine. Thinking about the future, how will your research on bovine mastitis develop going forward?
Dr Veiga. Our main focus for future research is to develop tools for on-farm use, mainly diagnostic tools for mastitis treatment decision and control measures.
For example, as is the case in other countries, the Brazilian dairy industry is going to face restrictions on the use of antimicrobials in food-animal production. This trend has already been seen in the poultry and swine industries, and in time, will probably affect the dairy industry. Even thought, there is no legal restriction so far, we have seen initiatives, from some in the dairy industry and also from consumers, to encourage the use of antimicrobials more responsibly. Therefore, further studies on selective treatment protocols for clinical mastitis and for selective treatment of dry cow will be necessary.
In addition to the methodologies of diagnosis of the mastitis-causing pathogens, there is a lack of simple techniques for antimicrobial sensitivity testing. The use of these techniques could help producers and veterinarians to define better treatment protocols and to reduce cure failures that occur in a significant percentage of cases of clinical mastitis. Considering the current advances in mastitis control and prevention tools, the development of vaccines against specific agents could also be very useful as an additional control tool.
M2 magazine. How do the dairy companies in Brazil incentivise their farmer-suppliers to produce good quality milk?
There is no unique standard for bulk milk quality among the dairy processors. In general, most milk payment systems include a premium and penalty structure, according to milk composition. This is based on solids-not-fat or protein and butterfat) and includes SCC and total bacterial count (TBC). For cell count, most processors use a limit of SCC of less than 250,000 cells/ml for applying a bonus to the milk price. The bonus is of the order of 5% to 10% of the total milk price, the exact amount varies from company to company.
Dr Veiga - Veterinarian Marcos Veiga dos Santos completed his Ph.D. in Food Science at the University of São Paulo in 2001. In 2006, he was awarded the title of Associate Professor at the School of Veterinary Medicine and Animal Science at the University of São Paulo in Brazil (FMVZ-USP). He is currently Full Professor at the Department of Animal Nutrition and Production of FMVZ-USP. He has published 116 papers in scientific journals and 3 books. He supervised 26 master's dissertations and 7 at doctorate level and has supervised 4 post-doctoral projects in the area of dairy production. He has coordinated 22 research projects. He was Head of the Department of Animal Nutrition and Production of FMVZ-USP (April 2016 to April 2020), and coordinator of the Postgraduate Program in Animal Nutrition and Production (from 2008 to2012). He co-ordinates QUALILEITE-FMVZ-USP, the Laboratory of Research on Milk Quality. He is a member of the Editorial Committee of the Brazilian Journal of Veterinary Research and Animal Science, as editor in the area of Nutrition and Animal Production. He was President of the Brazilian Quality Council Milk (CBQL) from 2009 to 2011. He is a contributor to the publication Milkpoint.