IBR - Infectious Bovine Rhinotracheitis

IBR is caused by infection with bovine herpes virus type 1 and is highly prevalent in New Zealand cattle. Approximately 90% of local dairy herds will have been exposed to IBR and it is the most common reason for China export heifers being rejected.

IBR causes herpes virus lesions in the respiratory tract and/or the reproductive tract. Typical of herpes virus, once an animal is infected it is infected for life. Infected animals can shed the virus on multiple occasions, especially when the animal is under stress and the immune system is overwhelmed.

Clinical signs of IBR are usually associated with an upper respiratory tract viral infection:

• High fever.

• Runny eyes

• Nasal discharge. This is highly irritating, and animals will often rub their nose on sticks which can become stuck up the nose.

• Coughing.

• Difficulty breathing.

• Anorexia occurs, as a result the animals are lethargic and appear ill thrifty with reduced milk production.

IBR can also cause vesicles on the vulva and penis, neither of which is desirable during mating. IBR tends to be a problem in herds when naive heifers enter the herd and are exposed to the herpes virus for the first time.

Treatment

While there is no direct treatment to eliminate the viral infection. Infected animals should be isolated from the rest of the herd and treated with anti-inflammatories and antibiotics.

Prevention

Vaccine is available to prevent herpes virus infection in cattle and can be used in herds where IBR is problematic. It is especially useful to vaccinate naive heifers prior to entering the herd.

First Two Months of Lactation - Minimising Weight Loss

A good start to a cow’s season requires careful management through the springer and colostrum period to ensure that she maintains a high dry matter intake. Initial focus should be placed on prevention of metabolic disease, optimising immune function, adequate feed allocation and manipulating cow behaviour.

However, the first month of lactation beyond the colostrum mob is still very critical. Most cows will spend this period in negative energy balance – i.e. more energy is leaving their system than coming in and therefore they will lose body condition. This is why providing consistently high feed quality is imperative. We are already seeing many farms that are struggling to manage very high pre-graze covers due to good growth rates through the winter. These are impacting voluntary intakes and may have lower ME.

Cows in significant negative energy balance may develop clinical or sub-clinical ketosis. Ketones are a by-product of inefficient fat break down and have a side effect of further appetite suppression.

Cows which are well fed/have a good appetite in the first month of lactation will lose less weight and have better mating performance. Try some of the following:

• Optimal pre-graze covers of 3,000 to 3,400 kgDM/ha in the first round will ensure good quality and easy harvest for the cow. You still need to maintain a residual at 1,550-1,600kgDM/ha to ensure quality in subsequent rounds.

• Aim to get your milking cows eating 4% of body weight in dry matter ASAP.

• Know what your daily cow requirement is and calculate your allocation every day - where feed deficits exist on any given day fill it with appropriate supplement.

• Use monensin (Rumenox), to increase feed conversion efficiency, by driving proprionate production. Clinical trials show boost in milk protein production and far less BCS loss. Use strategically from calving up until end of mating.

• Internal parasites – the biggest impact these have is on appetite suppression. Almost all farms will have high levels of over wintered larvae this year. Aim to drench your herd by early/mid September.

• Vitamin B12 – is a requirement for energy extraction. Deficient cows will lose appetite. We see B12 levels drop at the same time as spring grass goes lush. This is partly due to rapid transit times through the gut impeding B12 absorption. A good rule of thumb is when faeces starts becoming loose look to give Vit B12.

Cow Flow - Solutions to Poor Cow Flow

With the new season starting, cow flow issues often begin to arise with training heifers, cows establishing hierarchy and possibly staff changes. Good staff training and potentially some infrastructure changes within the shed can lead to a dramatic improvement in cow flow and associated lameness.

Some focus areas that will help cow flow are -

• Patience – it is important to take your time with heifers

• Backing gate use – don’t move the backing gate within the first 20 minutes of milking and only move small distances at a time

• Top gate use – should be limited to small amounts or not at all – farms can go whole seasons without needing to use the top gate

• Entry and exit on to platform (rotary) – entry only needs to be around 900mm wide, and exit should ideally be 3 bails wide to prevent excess pressure on feet

• Foot baths – ideally these should be permanent structures that can be emptied and refilled – this allows cows to become used to them and when needed they flow smoothly through stepping through it rather than jumping

• Tracks – structure, width, camber and maintenance are all very important in lameness reduction and prevention e.g. no crusher dust within 300m of collecting yard. Good tracks will allow for good cow flow to and from the shed

• Breast rail height (herringbone) – if cows are hesitant to enter the shed, changes from 800mm high to only 740mm can make big improvements in cow comfort during milking (by reducing pressure on point of the shoulder) and therefore improve cow flow

Implementing a good plan from the outset of the season and some simple changes in management and potentially shed structure can have very positive outcomes in reducing cow flow issues and lameness.

Keeping the Winter Diet Balanced for Pregnant Cows

Over the last 10 years farmer focus has been on improving cow condition over the winter period. This has been mainly facilitated by setting realistic figures on crop utilisation and ME requirements for condition gain, maintenance and pregnancy.

The winter diet for a pregnant cow, through until about the last 3 weeks of pregnancy, requires about 11-12% crude protein in the diet (or 1.2-1.4kg of crude protein). As well as cow’s normal base protein requirements, she has the demands of a rapidly growing calf, the development of new udder tissue and production of colostrum antibodies. Cows under protein stress for significant periods of time will break down their own body tissues to meet foetal demands, but the end result may be muscle loss (calving difficulty), poor udder development, poor colostrum quality and poor cow immunity (placing her at greater risk of mastitis or metritis).

Optimal crude protein requirements increase to 16-17% in the last 3 weeks before calving. Typically Fodder beet bulbs have crude protein levels less than 10%, whereas the leaf is in the 15-20% range. If the crop you are feeding is losing leaf yield in July, ensure that cows are receiving an additional supplement that has higher protein content.

Clostridial Deaths

Having recently dealt with a case of ‘sudden death’ in R1 dairy heifers (7-8 months old) due to clostridial disease, it came as a timely reminder of the importance and effectiveness of a vaccination programme against this group of diseases.

• 16 heifers out of 360 were lost sporadically over a period of 5-6 weeks whilst grazing a high clover content sward.

• Post-mortems were performed - a diagnosis of clostridial deaths was made.

• Although they had been vaccinated with a 10 in 1 as calves (Covexin-10) it is believed that they had not received their booster vaccination.

• They have since had a sensitiser followed up by a booster vaccination 4 weeks later.

• One week on since booster and we have had no further deaths.

Clostridial diseases are a group of infections that cause sudden death. Death is very rapid and usually occurs before the animals are even noticed. There are dozens of Clostridial species whose spores survive in the soil indefinitely. Control therefore relies on vaccination.

Calves usually receive their first vaccination at the time of disbudding. This should be followed up with a booster vaccination four weeks later. Full protection is not achieved until 10 days after the booster vaccination. It is now also advised that stock grazing crops – particularly Fodder Beet – get a booster against clostridial diseases two weeks before going onto the crop, regardless of their previous vaccination history.

The risk of clostridial deaths is higher for stock grazing crop due to a combination of factors but largely due the high ‘sugar’ level in the crop and high soil intake. When grazing fodder beet, once fully transitioned the main risk of disease comes from clostridial infections.

Covexin 10 in 1 vaccine is considered the ‘Rolls Royce’ of clostridial protection covering 10 different strains of the disease. Cost = $1.44 excl. per 2ml dose.

Vaccination is extremely effective at preventing and minimising losses associated with this group of diseases. It is also cost effective and losses of even small numbers of stock will cover the cost of vaccination. Because the bacteria form spores that are resistant in the environment, every animal is likely to experience a challenge in their lifetime.