Lactococcus: Emerging Mastitis Pathogen

We are finding Lactococcus on more farms and management plans for it need to be developed. Historically these organisms were reported as other strep species and were expected to be treatable.  Other strep species included enterococci, lactococci, and aerococci and other species of strep.  Recently, Lactococcus has emerged in chronic high SCC cows and it takes additional testing to identify.  Our lab does this but many do not.  This is important because Lactococcus lacti only responded to treatment 33% of the time, while Strep dysglactiae and strep uberus responded to treatment 70 and 77% of the time.   Their cure definition was SCC less than 200K at 15 to 45 days after treatment.  That is pretty lenient with no culture done.  We have seen Lactococcus cows appear to respond to treatment only to reoccur weeks to months later.

There are two genuses of lactococci causing mastitis. Garvieae (usually more pathogenic) and Lactis (which is also used in food preservation).  Identification is less important than its’ location.  Within the udder is not good.  We have typed our on farm organisms as part of the development of vaccine process.  Vaccines have been helpful, but we are still learning how to use them.  Some farms immediately cull Lactococcus infected cows.  “Isolating” in a hospital or last milked pen may be helpful, but it is spread at milking time.  Backflush would be the minimum biosecurity to implement after milking a known Lactococcus cow before milking another cow.  Culture of cows leaving that pen may also have value.  We culture for Lactococcus every week. A sterile frozen sample is a start.  Cows not responding to treatment should be cultured.

Great Colostrum Management ‘Frenemy’ of Immunity  Colostrum management has improved significantly on most dairies in recent years.  Most dairies get 3 to 4 quarts of colostrum into calves within hours of birth. Then offer 2 more quarts at the

next feeding time. When we check total proteins, almost all are above 5.5.  The immunity from colostrum is the majority of protection calves have in the first few months.  This is called passive immunity.  Active immunity comes from giving vaccines and usually lasts longer than passive immunity or maternal antibodies.  Great colostrum management gives a high level of passive immunity, but it also blocks active immunity from conventional vaccination.  Intranasal vaccines bypass maternal antibody block, but they don’t last as long and they don’t contain the most important virus, BVD.  An attempt was made to create an intranasal BVD vaccine and it was a disaster.

Giving conventional vaccination too early results in limited response that doesn’t last very long.  We then get disease in the face of vaccine given at the wrong time.  Calves will be variable in maternal antibody decay. Some can be effectively vaccinated with conventional modified live vaccines at 3 months and some, in the same pen, it might be at 7 months. So if you give the 7 month receptive calves vaccine at 3 months, you will get limited response.  If you wait until 7 months to vaccinate the calves that that were receptive and less protected at 3 months, there is a period of vulnerability.

We now have tools to beat this challenge and we have trialed them on some farms for over a year.  The difference has been the availability of adjuvanted modified live vaccine.  Pyramid is one such vaccine. We have it available with and without lepto depending on your needs for your program.  We can give Pyramid as young as 30 days, but we have usually pushed it later due to the adjuvant can causing some slow days for the calves.  There may be other vaccines with potential to penetrate maternal antibodies.  

The Cost and Frustration of Lameness

Dr. Stayduhar

 

On some farms, the prevalence of lameness is high enough that it can be one of the biggest economic losses. One study found the prevalence of lameness on US dairies ranged from 13 to 55%. Depending on the type of lesion the economic effects of reproduction, direct costs, and production can vary. For the most severe lesions (foot rot and sole ulcers) 305 day milk yield can be reduced by over 700 pounds. When you break down the costs of lameness on a percentage basis reproduction losses are the highest followed by milk yield and culling costs. Direct treatment costs make up the smallest percentage. When the costs are so high it is imperative that we do our best to limit lame cows as much as possible.

Locomotion scoring should be done at least once a week in every pen and all cows should be evaluated at dry off. Make sure when you score cows they are on an even, well lit, and non-slip surface. An ideal place can be in the return lane after milking. Be sure to make sure you are evaluating all views on the cows, especially her rear legs. There are several scoring systems that can be used but there can be lots of success by using a simple 3 point score system. If you are interested in learning more let us know and we can direct you towards a phone app that can help you score cows.

It is important to make sure cows get to the trimmer regularly, especially since lameness tends to peak around 3-4 months into their lactation. In addition to all lame cows, the following guidelines can be used to form the hoof trimming list: 1. All heifers before calving, 2. All lactating cows twice per lactation (early and at dry off), 3. All cows that have had a previous lesion should see the trimmer every 3-4 months. Once cows are seen by the trimmer it is also important to note what lesions they have and their response to treatment. If trimming reports are documented correctly records should be analyzed to determine if there is a correlation of lameness and parity, DIM, or month of the year. This report can identify if we do not have routine trims scheduled appropriately, if heat stress is a contributing factor, or if housing modifications need to be made. It is also important to document cases since the economic costs vary greatly based on the type of lesion, with sole ulcers being the most costly.

It is also important to look at housing. Grooves are critical to cow traction and they must be done correctly to provide the desired effect. V shaped grooves are not recommended; vertical grooves that are parallel to the feed bunk are desired. The grooves should be ½ inch deep, ¾ inch wide, and spaced 3.25 inches apart (measured from one center of groove to the next). Rubber flooring should also be considered in high traffic areas when appropriate. Footbaths are another key element in prevention of lameness and they need to be long enough so that she gets two immersions per foot, minimum of 5 inches deep, and is in an area where only one cow/heifer can go through it at a time.

Especially over the summer months it is important to consider heat abatement strategies. It is as simple as when cows are heat stressed they do not lie down, and spending more time on their feet makes them more prone to lameness. Looking at time away from stalls is important as well, ideally they are standing on hard surfaces for less than 3 hours a day. Rubber mats can be advantageous if they have a long walk to the holding pen or will be in the holding pen for an extended period of time.