Milk Quality Investigations - part 2

This week we continue our conversation with Dr. Cathy Bauman of Ontario Veterinary College in Guelph, Ontario, Canada about conducting a milk quality investigation on a goat dairy by walking through the process for tracking down a high  bulk tank bacterial count.

Helpful Links:

Luminometer FAQ
https://www.gov.mb.ca/agriculture/food-safety/at-the-food-processor/luminometers.html

Small Ruminant Veterinarians of Ontario
https://srvo.ca/

Dr. Cathy Bauman - Ontario Veterinary College
https://ovc.uoguelph.ca/population-medicine/faculty/Cathy-Bauman

American Association of Small Ruminant Practitioners - find a vet
http://www.aasrp.org/about/find_a_vet.asp

This podcast is sponsored by the American Association of Small Ruminant Practitioners as well as USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Program, Antimicrobial Resistance grant # 2020-04197.

Questions or comments about today's episode can be directed to DairyGoatExtension@iastate.edu

Transcript

Michelle: 0:33

Hello, I'm Dr. Michelle Buckley from Iowa State University's College of Veterinary Medicine. Thanks so much for joining us on Baas and Bleats, sponsored by the American Association of Small Direction Practitioners. Just a quick note before we get started. This work is also supported by the USDA National Institute of Food and Agriculture, Agricultural and Food Research Initiative Competitive Program, Antimicrobial Resistance Grant Number 2020-04197, which funds my research on improving antibiotic stewardship and dairy coats to assure food safety and health quality. As always, if you have any questions about any of our episodes, please email them to dairygoat extension@ iastate.edu. I hope you enjoyed today's show. This season, we are focusing on improving milk quality and food safety in Dairy Goats. Before we get started, I'd like to make a special request as the season winds down and we prepare to shift topics and hosts. We would really appreciate hearing from you out there, our listeners. If you have questions related to any of our episodes or feedback about the show, or if you just want to let us know who you are, where you're from, and why you love Dairy Goat Podcasts, send us an email at dairygoat extension at iastate.edu. We'd love to hear from you. For today's episode, we'll be continuing our conversation with Dr. Kathy Bauman from Ontario Veterinary College in Guelph, Ontario, Canada. Let's pick up where we left off last time with Dr. Bauman's explanation of how she works up a milk quality issue. Take it away, Dr. Bauman.

Cathy: 2:38

And so here we are, we have an elevated back to scan, right? May or may not have a high somatic cell count. So what's our first plan of action? So I I often get calls from the processors, and you know, they've just got a general elevation, and I keep harping back. We need to know, you know, and again, um with bacterial levels, everyone historically has talked about it. It's a bit like a war anytime we have infections and things like that. And if we think about it in that sense, we have to know who we're fighting against, and we can't do that unless we know the identity of the bacteria. Okay, so our first way of action is to always culture the bulk tank. And culturing is telling us who is living there. Do we know if they're good guys or bad guys? And to determine the main bacteria that's growing there and causing the elevation. And so we'll often get that back with elevations in numbers like one plus, two plus, and three plus, and don't let those fool you. It just means that there's a large number of one growing, but it doesn't necessarily mean that that's the complete cause of the elevation. So, for example, we can have a bulk tank that's three plus on staph, two plus on pseudomonas, and it doesn't mean that the staph is the sole cause of the bacteria, and I'll get into that later on. Because if we're fooled into thinking of going with the bigger number, we may get rid of a bunch of goats that have staph from the herd, and our back to scan may still be elevated. It's just telling you that how well is that bacteria growing on the actual media. Okay, so sorry about that. But um by culturing the bulk tank and getting familiar with the bugs that are there, and I even encourage people to culture their bulk tank even when their numbers are not elevated, just so that they know what they've got going on on their farm because every farm is different. They bed differently, they use different post-dip and detergents and what have you. And so it's really good to know just what's going on on your farm. So we know that the source of the bacteria that ends up in the bulk tank, we we know it originates in the goats, and it also is coming from the environment, and we know it's never going to be entirely zero, like we're fooling ourselves that the bacterial count will ever be zero. But if we've got those coming into the into the bulk tank, the bacteria can then multiply. And so they take advantage of you when you let your guard down. So, again, a bit like building up defenses to you know to keep uh an army out of your little castle, right? They can multiply in unclean milkers, so attack you that way in the pipelines, and then um again in the bulk tank. So it's ensuring that all those are in proper working order and clean and smooth to make sure that those little soldiers that are trying to get in can't kind of adhere to that. So, especially on the cooling end, if cooling doesn't occur immediately or the system is not functioning properly, boy, they love to take advantage of that. And for a certain class of bacteria that like to grow at cooler temperatures, they can exponentially grow with every day of storage until your milk is picked up. So identifying what bacteria these are can help determine where they come from, or at least narrow it down, or tell us where to start looking at what to cleave first or what step to take first. So let's go back to the goats. So if the bacteria are coming from them, they're typically of utter origin and are frequently in the staph family, the staphylococcal family. So we can break that down into individual names within that staph family. So we have staphylococcal aureus, which are this a major pathogen that a lot of people are familiar with. People have it on their skins and in wound infections, and hospitals are very worried about drug-resistant forms of staph aureus. But it's a major mastitis pathogen for cows, also for sheep and goats. Um, but as I said, uh it's a particular health concern for humans, and not just for skin infections, but foodborne infections, because this bacteria can produce a toxin that if milk gets warm, it starts making this toxin, and they can have vomiting and diarrhea within 24 hours of consuming that. And it can be related to other infections I won't go into. Um, staph aureus. We also call it uh a coagulase positive bacteria, and this is just a lab diagnosis, it has nothing to do with looking at it or seeing it, but it's just describing the way it behaves in the lab when it grows, and there's certain things they do at the lab to kind of screen for this. We also have another family, and the reason I tell you that is because we have another family of staphylococcal bacteria, and they're called coagulase negative staph. And this encompasses a whole bunch of bacteria called staph capri, staph epidermis, staph stimulants, staph xylosis, and chromogenes, and these are more of goat origin. So you'll find if you have a dairy cattle farmer friend, and they're mainly focused on staph aureus, and then they'll be you know not as concerned about the CLAG negative staff, and there's some issues about is it actually caused mastitis in cows or not when it's present. But we do know, especially these five, are associated with causing mastitis in goats. So if we see these in the bulk tank, we typically think that they're coming from the goat itself. Staph aureus and all these other little CLAG-negative staff, they can't grow in the environment. They're coming from the goat, they love that nice warm environment of growth of growing in the goat. Um, and then that then seeds uh the bulk tank.

Michelle: 8:24

So, can you give us some insight as to why we might not be seeing any clinical mastitis on farm and yet we're culturing these staphylococcal bacteria from the bulk tank that we know have to be coming from the goats, um, but we're not seeing a clinical problem.

Cathy: 8:42

For those of you who milk and are familiar with with goats milking on your farm, you'll know that clinical mastitis is not all that common in goats, and that can just lull you into this false sense of security that you don't have it. And that couldn't be any further from the truth, is that goats are very prone to subclinical mastitis. So, again, just because they don't have blood in their milk, they're not systemically ill, doesn't mean that this isn't uncomfortable for them. Um, this means that the milk is just unable to be detected as being mastitic unless until you get a the bacterial enzymatic cell count back, or that you physically see a few little speckles of milk clots on on your sample. So I'm gonna talk shortly about how to try and narrow the source down of you know of these mastitis cases within your herd, because a lot of us are dealing with herds that are two and three hundred um head, and so how do we economically kind of narrow that down? And we'll talk about that shortly. But I just want to kind of reiterate that staph is nasty in other ways for the milk system. Some strains of Staph aureus and some of the quagnegative staph are able to form these things called biofilms on stainless steel surfaces. So there's a gene in some of them, and that can be passed on to other forms of the bacteria that preferentially allows them to grow on these surfaces and also on the inside aspects of polystyrene tubing. So, just to reiterate, for those that are not familiar with biofilms, they're kind of a combination of fat, protein, and then the bacteria themselves. And it's advantageous to the bacteria to kind of take these sources from the milk and almost form like a protective layer on the inside of these surfaces. And it allows the bacteria to grow, kind of have a food supply, and it also protects them from a detergent and drying out. So you'll recognize that you often can't visually see it, it's often clear, but it feels slimy. So if you've ever put your finger on the inside of tubing, it felt like a mucusy buildup, that's what a biofilm is. And again, it's just to the advantage of the bacteria to prevent you from trying to get rid of them inside the tubing. So they attach, the biofilm allows them to attach and adhere and to stay adherent to the surfaces. So they don't break down very well with detergents and have to often be manually kind of removed in a forceful way. So having said that, they're they don't generally accumulate on equipment that's normally you know being replaced regularly. They tend to take advantage of surfaces that are rough and not cleaned properly. Um sometimes if if water is circulating in a pipeline and missing a corner, it'll tend to build up in that corner where the water's not as turbulent. Sometimes if there's not enough pressure used on the cleaning water or a hot enough temperature, um, but they are they're really resilient. They're able to grow at temperatures above what milk is typically stored at, which is your four to eight degrees Celsius or 40 to 45 degrees Fahrenheit. So any this means that any time these bacteria are identified, so the staffs, we still have to re-evaluate our cleaning protocols. So I'm just telling you that if staff is picked up on your bulk tank, it doesn't mean it's only coming from the goats. It could be coming from the goats originally and then amplifying in your equipment if there's a breakdown in your cleaning protocol. So we still need to investigate to make sure no biofilms have accumulated. And um, because we've had producers where they got rid of all the staff goats and they still had some staff showing up. So we need to make sure that we haven't had staff biofilms build up in the equipment.

Michelle: 12:39

Awesome. Thank you for that insight. I think that's a really important distinction to make between goat dairy production and bovine production. So I'm glad that we could highlight that. Are there any other pathogens that we need to be aware of?

Cathy: 12:55

Um, other pathogens that we can culture from the bulk tank include crinibacteria, um, truparella is another one, streptococcus, and again, just to recognize that sometimes you'll get streptococcus just in a general term coming back on the bulk tank. And it's worth following up on your lab to with your lab at how well they're differentiating these pathogens. Because you can't just make the assumption that streptococcal dys, galactia or agalactia, it may be something completely unique to GOAT. So if you're at all confused and they haven't given you the full bacterial name, is to follow back up with them to see if you need to go with more specific subculture like with the multi-toff. Um most utter pathogens uh are so these the carini, the tubrella, the strap, the or not the strap, the staff, um some straps, sorry. Um most utter pathogens are what we call mesophyll bacteria. And this is just referring to phylomines like, and so they like kind of medium temperatures. So they like to grow at temperatures that are similar to what you would find in the body. So if milk is stored properly, um they don't grow substantially between when the milk enters the tank and when it's picked up because it's too cold for them. But one enters tends to stay at that level and just grow slightly incrementally over time. So that's how they perform going into the bulk tank, okay? Some bacteria though enter milk during the procedure of milking, but then they come from the environment. And these bacteria are generally found in feces, so the fecal material, straw, things like that. So they're enterococcus and E. coli, and then there's some that are often associated with water, and you know, milk parlors tend to be a very wet environment. Um, we're always hosing things down, animals are urinating and what have you, and other bacteria come from the soil. So bacteria that like water and soil are often Pseudomonas, Clebsiella, and other less well-known bacteria. So dry, dry, dry is such an important concept. Um, and cleaning. So if udders are not clean and then subsequently dry during milking, they can be a real source of bacteria because where these fecal bacteria are entering the milk system is when we're not cleaning off those others. They're laying in the straw that's contaminated with fecal bacteria, walking into the part of them, and milkers go on. Milk or hands, if you know, if they're for stripping or wiping of teeth and not being regularly washed, they're a source of bacteria. And then so is the equipment. So, you know, the the milkers falling to the ground, coming in contact with um the environment, other than the udders. The milk canisters can often be a source of the bacteria if they're not washed and then dried properly, which is really hard to do, and then the bulk tanks themselves. So the bacteria that come from the environment and like to live in the pipelines and wet environments, if you think about it, they kind of prefer to live in cooler temperatures. And so they're a problem more in the wet seasons, spring, fall, and winter. And these are guys that really like to grow at the temperature that the bulk tank milk is stored at. Um, and so they tend to multiply the longer that the milk is stored on farm. So, you know, we'll often check on a farm that's having trouble with pseudomonas, we'll check their bacterial count after one milking and then compare it to the one at pickup and just to see if that those bacteria are really growing during that time period. So that's kind of two groups of bacteria. But we then have a third group, and these bacteria are not pathogenic to the goats per se, um and that are typically present in the milk. So they're not causing any pain to the goat, any abnormality, but they then like to overgrow in unclean equipment. So, again, kind of taking advantage of anything that you're not doing properly. These bacteria are often associated with cheese and yogurt making, um, so lactococcal bacteria. And so, if milk, you know, in the old days was left alone, people were making cheese and yogurt long before there was cultures you could buy at the store. And it's just because there is natural bacteria already in the milk that was causing them to turn into these products. So we often kind of discount them because they look a bit more innocent compared to these other ones that are more health risk to the goat and the human. But they do cause off odors and are often a sign of unclean equipment. In summary, I think the bacteria identified by culture on your boat tank really helps to track down um the source of origin and to tell you where to focus or at least where to start, um, such as the utter end or the hand cleaning. And for a lot of boat tanks, it's such a mixed population that we're often dealing with with all of these. Um, know that they're really often multifactorial and are just building up in the pipeline and bulk tank as we go. So it's my experience, it's really rare to culture one bacteria from a bulk tank. And it's often a little bit of an onion where we're peeling back the layers of okay, let's let's deal with this bacteria and figure out how we can prevent it from entering and then do the next one. So slowly targeting each one and knowing that sometimes a milk quality problem takes a little while to figure out what's going on and to fix it.

Michelle: 19:42

That's a wonderfully comprehensive um explanation of you know, step-by-step how we can let our bacterial cultures guide our milk quality investigations. And I learned a ton, my mind is blown. Um one thing that I want to make sure that folks pick up on when they're listening to this is that bulk tank culture is where we're gonna start, but it is also very likely going to be valuable to culture your milk lines, um, different parts of your pipeline potentially, um, as well as milking equipment and going back to culturing individual animals or groups of animals too, so that you can differentiate where that bacteria is coming from. Um and I think you did a great job of breaking that down, but I just really want to spell it out for people that the bulk tank is not the end-all be-all culture, and you need to compare bacterial growths from different points in the milk collection process.

Cathy: 20:40

No, you're exactly right, Michelle, and it's really confirmatory for someone when you're able to make that connection back to the goat and show that it's also in the bulk tank. So, and then that's where we get more buy-in from everyone in the whole process to be on board for the prevention and the treatment of tackling those.

Michelle: 21:01

Thank you for that very comprehensive explanation of that that process. Um, can we dig a little bit more into how we trace infections in goats themselves? So, kind of the other end of the process from the bulk tank that we were just discussing.

Cathy: 21:15

Right, Michelle. And and late Michelle said, you know, some of these you know, culture organisms we can trace back to the pipeline and what have you. I'm gonna talk about how do we trace the infections that we know were coming from the goats themselves. So we've got Staph aurea sort. Coagulase negative staff or some type of strap in the bulk tank. And then how do we figure out exactly which goats to treat within the herd because it's not economical to treat them all? And how many we might consider removing? And again, not economical to remove goats that aren't the cause of the elevations, right? We really want to target the ones that are shedding the most bacteria. So once we know that the other pathogens are the main cause, we need to start screening goats. With antimicrobial stewardship that Michelle talked about, it's really prudent that we don't overuse antibiotics. And it's not just the overuse, but it's the improper use of the wrong drug for the infection. So picking an antibiotic that a bacteria is not sensitive to is going to cause more harm than good. And since we have goat herds that are really high in numbers, and then the individual animal value tends to be quite low, you know, under four or five hundred dollars up here. It's hard to really justify spending not just the money on treatment, but also on diagnostics. In an ideal world, firms would be doing quarterly testing of goats for back to scan and somatic cell count. And for us, that would run about $2 a goat. And this would be really worthwhile testing to do because we know that about 95% of animals with a somatic cell count over a million had a mastitis pathogen identified. So if we're screening those animals for high somatic cell count, 95% of the time if we pull them out, they probably were shedding a mastitis pathogen in the milk. But it may have been a low level or high level, we don't know unless we're also doing a somatic cell count and BACTIS can. So if BACTIS can't available, screening those individuals with a somatic cell count would be great. And as to whether that's done at the lab with the phosmetic and flow cytometry or whether that's done with your California mastitis test sets up to you and to what's available where you live. But this would allow you a way of identifying the animals for treatment. So, like Michelle said, we can be culturing some of those animals to see if they're staph aureus or something else, also for isolating them or culling them where necessary. So another method though, instead of doing individual goat sampling, is what we call composite sampling. And so we too tend to do this based on the animals coming into the parlor, so it really is dependent on the size of your parlor. But as the herd is standing there, you know, prior to milking, is take take composites of three to four strips of each half of each goat on one side of the parlor. So this could be anywhere from 12 to 24 goats into one small container. And then we'll go ahead and then do the other side. And so this breaks a really big herd down into smaller chunks, and they'll then we'll run back to scan or somatic cell counts or both on those individual vials. And then we'll highlight the vials, you know, for example, some vials that have a somatic cell count over a million or back to scan over a hundred thousand, and then investigate those further. So it does involve keeping track of who's going into each vial. So individual goat IDs, and I've been to farms where the goats aren't identified, and we cannot solve them at quality issues, but especially when it comes from the udder if the animals are not properly identified. So again, going back to just some basic record keeping and ensuring every animal can be traced back so we know which ones we want to target afterward for removal.

Michelle: 25:17

So, can you talk a little bit more about how we might be able to utilize the California mastitis test instead of tests like the back to scan or phosmatic that are going to require being sent out to a lab and incurring an additional cost with that?

Cathy: 25:33

In areas that don't have access to this type of testing, though, or you'd rather not, that's fine with me. The California mastitis helps as well. And it can be performed at the individual level if you want to screen every every goat that goes through on a quarterly basis. Um, but it consistently detects high somatic cells of a million or higher. Um you know, at three million or higher, they tend to be really egg-like, yeah, like in the in the cup, but a million you can easily determine as being abnormal, and to screen those for further culture and further workup is a really economical way of doing it. There are a few situations, though I just have to warn you, where a low somatic cell count has had a goat, has missed identifying a goat as shedding a high level of bacteria. So it's not foolproof. And like I say, you may still have goats that have high somatic cell count and aren't shedding a lot of bacteria. Um, but this is a way of trying to tackle on a large scale a large herd that has a big mastitis issue. So it's not full.

Michelle: 26:39

Um, quick question for you. Um, there is a scale out there that compares your CMT score to an actual somatic cell count approximation. Do you know how accurate that is on goat milk versus uh I mean, I know I understand it's calibrated to cow's milk, but is it about the same?

Cathy: 27:00

From experience, Michelle, I found it's not accurate for um for goats. It's really hard above a million to gauge. So a one is pretty confirmatory of a million in in goats. I found out something between a one to two to a two of what you would say in a cow is pretty much a million in our higher somatic cell. And then it's pretty easy to judge those guys that are anything above three million with a three or three plus, but I really find that two zone much harder to differentiate. And my concern is a million or higher anyway, and I would just work those up further. I've also found that if you make the solution more concentrated, so instead of eight to one and b or seven to one, it's four to one, that it's much easier to pick them up when it's just not as dilute, the CNT solution. The other aspect seems to be is just waiting just a little bit longer. There's this kind of optimum time when it when it should be red, but it just seems to take a little bit longer for the goat um to mix with the solution for it to show up. So don't be afraid to just wait a little bit longer, but don't leave it, you know, for 10 or 15 minutes and come back to it.

Michelle: 28:12

Okay, well, those are great goat-specific insights to have. Um so I guess my last question for this episode is if someone's ready to get into um some you know milk quality investigations really dive in, what tools should they have in their toolkit, like physical toolkit, um, that will get them off to a good start?

Cathy: 28:37

So I'm sure there's others. These are the ones that along myself and the milk inspector, and I've learned from him what he carries and they carry in the out in the field. But uh I learned first and foremost it's a good flashlight, is because you know, within the bulk tank, we can't see the upper crevices, the outflow valve where things tend to accumulate. And also historically, you know, go barns are very dark and the lighting is is poor, so it's really helpful to kind of pick up on a lot of things. It also helps to pick up the accumulation on the inside of pails, like the scale that builds up with the flashlight and it kind of shining off the stainless steel. So real helpful tool and low cost. Um, another one being the data logger that you can leave in a bowl tank and then over time from first milking to pick up, it can measure the highs and low bacteria over time so we can see where the spikes are occurring, you know, as the milk is entering the tank, or is it you know building up on those hot summer days? So someone can be lulled into thinking they don't have a problem that we can actually show the pattern of the spikes in the temperature. Um, and then I've been using the luminometer that a colleague of mine was using to prove cleanliness on calf cleaning equipment. And it you know, sadly doesn't work on identifying samples that are high in bacterial counts, but it works really well to identify kind of biofilms on equipment, so milk tubes, um, the inside of the rim of the bulk tank and things like that. And I just find when you can measure something and show it to a producer, it resonates really well. Like they understand like a high, really high number. So I found anything kind of over 500 to be concerning. Some people would react, you know, when it's a little bit lower, but it's just not as consistently reliable there. But I've had some levels that have been 1800, 2500, and I can say, you know, water should be five, and you know, maybe milk should be a hundred, and then to have 300, 500, or 1000, it really brings it home for the producer that that something's not working properly. Um, I've also tested pipeline rinse water to try and pick up bacteria that are are um adhering to the inside of the pipeline and cultured that and done bacterial counts and also milkers. So we've rinsed the milkers and and pulled the runoff of that to narrow down where the biofilms have been located. So, for example, in milk measuring jars attached to the milkers, the containers, um, is often a really good breeding ground for Simonas, and we've picked that up through rinsing of the equipment.

Michelle: 31:20

Awesome. And just to clarify, that data logger is that that's looking at temperature, right? Which is gonna be a more favorable environment for bacteria.

Cathy: 31:28

Yes.

Michelle: 31:29

Well, Dr. Bowman, I really appreciate all of your time in really breaking down milk quality investigations very thoroughly for us. Um if folks want to uh get a little bit more um case-based insight, we're gonna be releasing a uh follow-up bonus episode here shortly, um, where we'll be presenting three cases that Dr. Bowman's seen that um that might make this a little more uh clinically um make sense in in folks' minds. So stay tuned for that. Um but Dr. Bowman, thank you so much for your time today, and um it's been lovely chatting with you.

Cathy: 32:10

Thank you, Michelle. Thank you for inviting me.