February Production Drop and Heat Stress

For many of our clients (especially those more inland), late January/February saw some significant drops in production. Many farms reported cows being listless and inappetant, despite them going into some good quality feed.

I don’t have to labour the point that this summer has been hot (and humid on many days). For a period there was little reprieve as night temperatures failed to dip below 20 degrees. Friesian cows are comfortable in temperatures less than 20 degrees (Jerseys less than 24 degrees). Above these temperatures cows must work to keep their body temperature under 39.0 degrees.

Cows are essentially a large fermentation tank on legs. The rumen produces a lot of heat. This is great in the winter but in higher summer temperatures it means they will struggle to keep their body temperature low. Night time should provide some reprieve if a cow over-heats during the day, but when temperatures stay high throughout the night they may be starting the new day already in heat stress.

Cows in heat stress will open mouth breath (pant), seek shade and spend more time standing to try to reduce body temperature. Think back to when we had bountiful shelter belts as to where the cows would have been standing on these hot days. Once the body temperature raises above 39.5, cows will be less inclined to eat, will have poor immune function and production and body condition may drop.

We cannot replace tree shelter quickly where it has been lost, but other shorter term strategies may be used.

• Cool drinking water is hugely important. Install multiple water troughs in main lanes to and from the shed.

• Wet down the hot concrete before the cows come on the yard.

• Install sprinklers on the yard (these might be used morning and afternoon if the night was hot).

• Put sprinklers on the shed roof (and/or misters inside the shed).

• Try to avoid milking in the heatof the day.

• Milk smaller herd sizes to minimise the time spent on the yard.

• Let cows move at their own pace – chasing slow cows down the lane will just heat them up more.

Recording Clinical Mastitis Cases

Please record your clinical mastitis cases

The rules are getting more restrictive about being able to use whole herd antibiotic dry cow therapy (DCT). Most of you are steadily transitioning away from whole herd antibiotic DCT and are comfortable with it. However some herds will still require whole herd antibiotic DCT but there are criteria that the Vet Council are expecting us as the authorising vets to have met, to authorise the usage of whole herd antibiotic DCT. Two of the five criteria are based on the incidence rate of clinical mastitis (number of cases per 100 cows). One of these measures is the amount of dry period mastitis – this is traditionally very poorly recorded – if you did have some please record it into MINDA. Even if you are not considering using whole herd antibiotic DCT please get your mastitis records entered in MINDA as this data is also valuable for making decisions at the individual cow level.

To make the best decisions regarding a cow at drying off for selective DCT (is she a high or low risk of having an infection?) we do need data. Herd test data is the best, and the addition of her treatment history (clinical mastitis records) is likely to make a difference to an individual cow. Interestingly the proportion of cows correctly classified does not seem to have altered much (in some papers that have looked at the best decision-making rules) whether mastitis data is included or excluded, but these results are at a population level not for an individual cow. An individual cow is either infected or clean, not 70% infected, so please enter your mastitis data.

Polioencephalomalacia

We are once again seeing several cases of P.E. (polio encephalomalacia), a nervous disease seen primarily in calves and younger stock. P.E. is caused by a lack of vitamin B1 (not to be confused with a cobalt deficiency, which is associated with a vitamin B12 deficiency). P.E is thought to be nutritionally induced, when there is a sudden change in diet from stalky, higher DM diet, to a lush, low fibre diet. A high dietary sulphur intake, especially with brassicas, has also been incriminated as a cause of P.E.

Calves with P.E. appear blind, may walk aimlessly, appear wobbly, have muscle tremors and head press. If calves are treated early in the disease process with a series of vitamin B1 injections, survival rates are good. In an outbreak situation we have had good success, by prophylactically treating the remaining, unaffected calves, in the group with an oral vitamin B1 drench. This has proved a very cost effective preventative measure.

Pink Eye Update

Whilst Pinkeye can be tricky to see, it can certainly become an eyesore if left to brew away! Pink eye is caused by bacteria (Moraxella bovis). It becomes a pesky problem heading into the summer months as wind, heat, dust, flies and long grass can weaken the natural defences of the eye and cause an infection.

Pink eye is incredibly contagious and can rapidly move through a mob, so it pays to get on top of it quickly. Signs of pink eye begin with weepy, clear discharge and squinting which then can progress to discoloured/white eyes which can develop deep ulcers. If left untreated, it is very painful and uncomfortable. It can lead to nasty ulcers, blindness and reduced growth rates, as well as it being a significant welfare issue. Lesions quickly worsen for an animal and eye damage can be irreversible (partial or complete blindness).

Treatment of pink eye is either with Orbenin eye ointment OR injectable tetracyclines (Engemycin or Bivatop). If you are having particularly bad problems this year, or it is becoming an annual problem, then come talk to us to see what management factors may be of help. A single dose of Piliguard vaccine given 3-6 weeks before the risk period will significantly reduce the risk of an outbreak.

Calf Weaning

Making sure a calf is fully prepared before weaning reduces the chance that they will need preferential treatment post-weaning. Preferentially managing small groups of animals to ‘catch them up’ is time consuming and can be difficult to manage, so it is best avoided by good management early on.

Factors to consider before weaning calves:

1) Rumen Development – Are they consuming the desired amount of feed? Is its rumen sufficiently developed to be weaned off milk?

• The only way this can be assessed is by measuring the amount of concentrate or pasture they are readily eating, which should be at least 1kg/day of meal or 2kg/day of pasture.

2) Weight – Individual calves should reach a minimum weight prior to weaning.

• No specific weaning weight has been defined by research, however common weights used are 70kg for Jerseys, 80kg for Crossbreds, and 90kg for Friesians.

• Reaching a minimum weight is an important milestone as it indicates that they are ready to transition from individual to group management.

3) Age – A combination of weight and age is often good to use when making the weaning decision eg. a minimum of 8 weeks AND 90kg.

4) Ability to Compete Within a Group – Is the calf able to compete within the group before they are weaned? Any that aren’t should be held back until they are.

The aim is to have calves that continue to gain weight post-weaning - they should never lose weight or remain static. Some animals don’t thrive post-weaning so it is a good idea to weigh them 7-10 days post-weaning to make sure they have gained weight. Any that haven’t may need continued access to calf meal, regardless of weight or age, or examination by a vet.

Relocating Calves

Relocating calves can result in growth checks, or be a trigger for other animal health issues including pneumonia, scouring and parasites. Recently weaned calves are at particular risk as they are also undergoing changes in diet, rumen development and are usually younger in age.

A few criteria to consider for relocating recently weaned calves include:

• Fully weaned and off milk for at least two weeks.

• Meet the minimum target weight for their age.

• Transitioned onto a full pasture diet or supplement provided for transition.

• Competing and coping well within the group.

• Drenched and vaccinated.

• In good health.