March 2021 Monthly Management

Managing Cryptosporidium Problems on your farm

Neonatal scours are the most common cause of death in calves in the first 4-6 weeks. Calf scours can be caused by a variety of pathogens, but in many cases, Cryptosporidium parvum is the most frequently isolated bug found.

How calves get infected

Cryptosporidium is a small, single-celled parasite. It produces so-called oocysts: small eggs, with a thick wall, that are very difficult to kill. If oocysts are ingested by a calf, they infect the gut wall and cause severe damage to the gut lining. The gut wall cannot then absorb nutrients, so the calf stops growing and develops diarrhoea. After infecting the gut cells, the Cryptosporidium parasite will start to produce additional oocysts which are shed through the faeces. These can survive in the environment for a very long time, resulting in a high risk of infection to other calves present on the farm.

Clinical Signs & Diagnosis of Cryptosporidium

Most calves get infected when aged between 2-5 days and show signs of diarrhoea between 5 and 15 days of age. The clinical symptoms include a yellow/pale scour that has watery and slimy texture.

If calves are infected only with Cryptosporidium, they usually develop mild diarrhoea which responds slowly to treatment, but which does resolve within 10 days.

Mixed infections, particularly with rotavirus, are very common. These cause diarrhoea that is more severe, often characterised by marked weight loss, emaciation and even death. Without correct intervention, calves can become weak and dehydrated rapidly. For a conclusive diagnosis, faecal tests must be carried out on animals that have exhibited clinical signs.

Prevention

A protocol to prevent the spread of infection is critical once Cryptosporidium has established itself on a farm. Any protocol must include a combination of measures both to increase resistance/immunity in the calf and reduce infection pressure in the environment.

Reduce Infection pressure

Calves are most often infected by ingesting oocysts from the environment. It is important to realise that infected calves will begin to shed oocytes a few days before any signs of diarrhoea show. These calves should be separated from the group and treated accordingly. Oocysts can survive for several months in cool and moist conditions and many of the disinfectants commonly used by farmers (such as chlorine bleach) are ineffective. Drinagh branches stock Keno™Cox, which is one of the few disinfectants that are proven to be effective against Cryptosporidium. Pressure washing at temperatures above 65°C will also work.

Increasing Immunity & Resistance in The Calf

Appropriate feeding of at least 3 litres of high-quality colostrum immediately after birth is crucial to establishing a healthy immune status for the calf. Exposure to stress should be reduced as much as possible – feeding schedules should be constant, i.e., regular quantities, temperature and feeding times. Stress should be kept to a minimum when carrying out sensitive procedures like weaning and dehorning.

Treatment

A product called Halocur™ can be used preventatively in new-born calves at risk of Cryptosporidium infection. It significantly reduces the severity of scours and reduces the excretion of infectious oocysts.

Outside of this treatment, these parasites are not susceptible to any vaccines, antibiotics or coccidiostatic treatments (Vecoxan™, Baycox™, etc..).

Most calves will survive the infection, but they do need intensive supportive care. Sick calves should be moved to a clean, warm, and dry environment. They need fluid therapy to treat dehydration and nutritional support to give them energy to recover and repair their bodies.

Conclusion

Cryptosporidium parvum is the most common cause of scours on Irish farms. On its own, it causes mild scours, but mixed infections (particularly with those with rotavirus) are very common and will lead to diarrhoea that is much more severe. Calves can make a positive recovery in most cases but in some severe instances, calves will sustain damage to the gut, which in turn will have a negative impact on their growth and future production.

Once cryptosporidiosis is present on a farm, it is very difficult to fight. So, to avoid economic losses, a control protocol is vital, one that addresses immunity in the calf and reduces infection pressure as much as possible.

Protein Requirement for Derogation Farms

All Nitrate Derogation farms should now be aware that there are reduced levels of crude protein permissible in concentrates fed to grazing livestock from 1st April to the 15th of September 2021.

All meals being fed to cows on a 100% grass-based diet will be required to limit the crude protein (CP) of rations to a maximum of 15%.

Drinagh have a range of suitable diets to comply with this regulation to ensure cow production is not affected.

Diets include:

• Supergraze & Buffer Nuts - 14.5% protein & balanced for Cal-Mag at 3kg feeding rate.
• Fertility Booster Nuts - 14% protein & balanced for Cal-Mag at 2kg feeding rate.
• Summer Dairy Nuts - 14% protein & balanced for Cal-Mag at 3kg feeding rate.

The protein content of feeds will be clearly outlined for your records.

Fertiliser for First Cut Silage

Nitrogen (N) - the amount nitrogen required to spread for first cut silage will depend on the age of the sward, the planned cutting date, and the grazing history. Recently reseeded swards (0-3 years) will have 25% higher N demand versus older swards. Typically, 90-100 units of N per acre are required for recently reseeded swards with older swards requiring 80-85 units (depending on cutting date). If nitrogen was applied in early spring, assume that 20% of this remains available for first cut silage.

Phosphorus (P) and Potassium (K) are essential to maximize grass yields, therefore adequate supply of these nutrients in the soil is critical. P and K requirement for a productive crop of silage are 20 units of P and 100 units of K per acre. Cattle slurry can provide a large proportion of P and K requirements at relatively low cost. 1,000 gallons of cattle slurry at 7% DM has a similar N-P-K value as one bag of 5-7- 30 fertiliser. When formulating a fertiliser plan, the nitrogen content of slurry needs to be considered, particularly when low emission slurry spreading is used. Slurry and chemical fertiliser application should be kept one week apart. also requires 16 units of Sulphur/acre is also beneficial to first cut silage. Contact the Drinagh Advisory team for further fertiliser plans and information.

Grass & Grazing

Cows are out night and day since the start of the week. During the unsettled weather last week cows were out by day and back in on grass silage (6kg DM) at night.

Much of the grazing platform is heavy and as a result we find it very difficult to graze a significant area of the farm in February. We use techniques such as spur roads, back fencing and 3–4-hour grazings to get as much grass into the cow and area grazed as possible.

We have approx. 30% grazed to date (16th March). Currently, the second-round of grazing start date looks to be around the 12th-15th of April. The focus now is at grazing the lighter covers in order to speed up the rotation.

Milk Production

When the cows were in at night, milk yield dropped from 25 litres at 3.60% protein & 4.75% butterfat at the end of February to 24 litres at 3.31% protein and 4.91% butterfat last weekend. This will hopefully improve and return to the normal levels as the cows are back out full- time now.

Fertiliser

The whole farm received 35 units of urea in February and 50% of the farm was spread with slurry (umbilical system). The plan going forward is to follow the cows with two bags of 18-6-12 per acre. The farm is index 2&3 for P&K and we find a great response to 18-6-12 at this time of the year. After this fertiliser application, we intend on using protected urea after the cows during the summer.