Staph aureus screening

At the risk of putting the commentators curse on you all, it does seem that many of your pregnancy rates are likely to be better than last year. If this turns out to be correct there will be the opportunity to make some “voluntary culling decisions” this season. If improving mastitis control in your herd is a priority then consider at your last herd test doing a Staph aureus screening test. This test is done on the individual milk samples already collected at herd testing. You can either provide a list of cows you would like screened or even easier provide a list of criteria that decides which cows to screen. For example you could request only 3rd lactation or older cows with a SCC greater than 250 are screened less any cows recorded as empty. Obviously the last SCC won’t be through until after the samples have been processed so if this is something you are likely to consider doing please ring us so we can put a hold on your samples at the lab so they don’t get discarded i.e. let us know so we can warn LIC that based on the last herd test results some of the samples will be required for a Staph screen.

Lameness

The summer period is often a time when lame cow numbers increase, this can be a result of how cows have been managed in the season so far, wet weather, thin soles and stressors that have occurred during the calving period. The numbers can be made worse with people having time off.

• If we get a bout of wet weather it is worth taking the time to improve drainage off the edge of tracks. Take a spade and open up the grass, a spades width wide at regular intervals to allow water to drain off the track. The grey box shows a good spot to cut away the grass.

• If you have an underpass, keep it free of water and slurry. Make sure that sump pumps are working properly, sumps are cleaned out and pumps are turned on when it rains.

• If you have a section of lane that is chronically wet, especially just prior to the yard, consider scrapping the surface. Wet areas slow cow flow which means that more pressure has to be put on cows to get them on the yard and the moisture increases the foot problems. Scrapping lanes can damage the top surface of the lane, but these are often damaged when you get to this stage anyway, however it can allow them to dry out faster and improve cow flow. Look at a more permanent fix over the dry period.

• Have someone who can do lame cows every day or every other day. It becomes much harder to start treating doing them when there are heaps in the mob. They also get a lot worse.

Causes of Mastitis We Have Identified this Month

It seems that most of our clients are having a pretty good run mastitis wise this month. We have not noticed the almost predictable spike in number of mastitis cases and BMSCC that often occurs a couple of weeks into mating. Red mobs also seem smaller than normal so presumably there are also not many lame cows around either. There does appear to be more of you mowing in front of the cows this year. There is a very small risk that you could get a thermoduric alert/grade if the grass is mown too far in front of the cows. Prolong wilting conditions allow decomposition of the grass to occur, and then thermoduric spores are ingested and concentrated in the cows’ faeces that may contaminate the bulk milk. This happens rarely, but if you do get a thermoduric alert and the rubberware is not past its “use by date”(liners only 2500 milkings) and there are no protein deposits in the pipes this is a possibility to consider. Mowing in the dry and feeding within 36 hours should be fine.

The majority of mastitis cases we have cultured this last month have been “coliform/gram negative”bugs and thankfully they are not causing toxic cows. It is likely these represent opportunistic infections when the udder has come into contact with mud/slurry. When you get the chance, check the entrance and exit ways and give them a scrape, if they are ponding water or damp. It is invariably the area closest to the shed that is the problem (or around underpasses). Cows during AI are often using these areas more than twice a day or being held on the race near the shed. Scrape under the fence so that you do not get a ridge or gutter that prevents drainage.

Bull Management

‘Rule of thumb’ is to have 1 sound bull to 30 non-pregnant cows. Ideally there should be two teams of bulls and these should be changed every second day.

A bull is capable of mating up to 3 cows a day before semen quality drops. The daily work rate in most herds will be the same after the 3rd week as it is in the 5th week as the number of cows coming on heat on a daily basis will be similar. Like-wise the work rate will be similar between the 6th week and the 8th week.

Therefore in a 700 cow herd which is doing 4 weeks of AI, they will need (based on 3 weeks of mating):

• 700 cows x 82% submission rate x 52% conception rate = 300 pregnant,

• this leaves 400 non-pregnant, which requires 13 sound bulls in the herd at all times

In a 700 cow herd which is doing 6 weeks of AI, they will need:

• 700 cows with 65% 6 week-in-calf rate = 455 pregnant

• This leaves 245 non-pregnant, which requires 8 sound bulls in the herd at all times.

Bull numbers in general can be reduced by about 40% at the end of each cycle. Remember to ensure that bulls have been both vaccinated and tested clear for BVD.

Coccidiosis Prevention of Calves

We often see coccidia outbreaks in calves that are greater than 4 weeks of age that still aren't eating enough meal (<1kg per day). However the other time we see coccidia problems are when calves have the meal removed after weaning. The coccidiostats in calf meal inhibit coccidia growth, when the meal is removed the coccidia will continue their development and complete their life cycle which can result in disease. Trial work in NZ has shown that calves treated with Toltrazuril (Toltrox) when meal is removed are 3-5kg heavier 5 weeks post meal removal than those that aren't treated. This was in an environment with a relatively low coccidia burden. A lot of our farms will have much higher burdens than this so perhaps we could expect even greater weight gains. If you have had calves in previous seasons that just don't do well when meal is removed it would be advisable to consider the use of Toltrox in calves at calf meal removal.