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.

Fractures in Heifers

Over the last 10 or so years, there has been an increase in the number of cases regarding heifers with fractures in their front legs and in particular, the humerus. Keren Dittmer is a Veterinary pathologist at Massey University and is researching this syndrome along with two PhD students. She is requesting bones from affected animals to be sent in in order to understand this better. The bones are CT scanned to look at densities; so far the affected heifers have smaller, thinner and weaker bones compared to their counterparts. Affected properties can also participate by completing a questionnaire about the farming system. Furthermore, additional farms are being sought to participate by enrolling into another study and being followed over the next few years to see if any risk factors can be identified or not.

Overall, this syndrome is poorly understood due to the nature of the presentation. Fractures are seen as 2 year old and less commonly as three year olds but current research indicates that the problem arises whilst the heifer is developing her bones.

2 syndromes need to be differentiated:

• “Rickets” type = defective bone mineralisation. This is seen in some heifers that are fed fodderbeet which is low in phosphorus. Bones are weak and at a higher risk of fracturing. It is important to supplement heifers with an appropriate phosphorus source whilst on fodderbeet.

• “Osteoporosis” type = reduced quantity of a normal bone quality. Again, the bone is weaker and therefore more susceptible to fractures. The most significant reason for this is a feed shortage but can sometimes be associated with copper deficiency, calcium deficiency and parasitism.

We are interested in collecting samples for further research. Please contact us if you think you have a case.

Calf Disbudding - Changes for 2019

The calf sheds are filling up which means that disbudding is just around the corner.

• The new welfare regulations which require all calf disbudding to use local anesthetic don't come into effect until October 2019. So you are still able to disbud without local this season as long as it is completed prior to this date.

• If you are wanting to disbud your own calves using local anesthetic there is a requirement to go through a training and accreditation process with one of our vets. MPI may conduct an audit to ensure compliance. If you haven't booked this in yet, please contact the clinic now as we are wanting to complete on farm accreditations by the 14th August.

• This year we are using a new product Tri-solfen on all calves we disbud. Clinical trials have shown that Tri-solfen significantly reduces pain after disbudding and results in greater average daily weight gains after disbudding.