In recent years there has been a lot of focus on ensuring newborn calves are fed colostrum with sufficient antibody content, but it is sometimes forgotten that the bacterial load in the colostrum is also important, a leading calf researcher has said.

Addressing a Thompsons Feeds and Bonanza Calf Nutrition event in Portadown, Dr Katie Denholm from the University of Glasgow explained that bacteria block the channels through which antibodies move through the gut wall of the calf, ultimately reducing absorption rates.

She said work from the US has set the threshold for bacterial load in colostrum fed to calves at less than 100,000cfu/ml total bacterial count (TBC) and less than 10,000cfu/ml total coliform count (TCC).

Tests on colostrum-fed anumals on farms suggest one third of samples exceed the TBC threshold, while one fifth are contaminated due to high TCC. A high TCC is associated with faecal contamination and it is these coliform bacteria which are most likely to block antibodies, explained Denholm.

Stages

In a separate study on 11 dairy units in Scotland, milk was assessed for bacterial loads from 15 cows per farm at four different stages – samples were taken straight from the teat, from the harvesting equipment, buckets used to transfer the colostrum and from feeders.

The milk straight from the teat was low in bacteria, but the loads increased at each stage and when it came to the feeders, three-quarters were “filthy dirty”, said Denholm.

She told farmers they need to properly clean equipment after use with a scrubbing brush, hot water and detergent. Plastic buckets should be replaced regularly or ideally, stainless steel buckets used.

Streamline

“Have a look at how cleanable your feeding equipment is and streamline the process – fewer people involved, fewer buckets and some elbow grease,” she said.

As well as poor hygiene, the other factor is where colostrum is left to stand too long before feeding.

“If left at ambient temperatures, bacterial colonies double every 30 mins. If it sits for six hours in a bucket it will be filthy,” she added.

Colostrum or transition milk can be stored in a fridge for two to three days, and if really clean, it could last for up to five days, however, it is important to check the fridge is set at 4°C.

Where colostrum is frozen, it can keep for up to 12 months, but the freezer needs to be at minus 20°C. It is also good practice to note the date and cow tag number on each bottle.

Stabiliser

However, if space in a fridge or freezer is lacking, Denholm said an alternative is to add in a stabiliser.

Her research has looked at spiking colostrum with potassium sorbate, which is a preservative widely used in home-brewing and in cheese production.

She recommends adding 50g of potassium sorbate to 100ml of clean water, with 1ml of that solution then added into every 100ml of colostrum or transition milk.

“It works at cold and ambient temperatures. Bacterial counts stayed really low, even up to 7 days. However, it is not a magic wand – it is not going to destroy the bugs that are already there. You still need to do a good job harvesting milk,” she said.

Pasteuriser

Some farms now pasteurise colostrum and it can make a positive difference where colostrum being fed has a high bacterial count. However, Denholm pointed out that the immunoglobulins (antibodies) in colostrum are very fragile and if the settings on the machine are slightly off, then it could do “more harm than good”.

The most abundant antibody in cow colostrum is immunoglobulin G (IgG) and good quality colostrum should have at least 50g/l of IgG.

To assess quality, Katie Denholm said all farmers should use a Brix refractometer, with a 22% reading on the device equating to the 50g/l target.

Newborn calves should receive 10% of bodyweight, so for a 40kg calf it is 4l, or a total mass of IgG of 200g. Colostrum should be fed within 6 hours of life and “the quicker the better”, she said.

Initially the calf can absorb 50% of IgG, but this drops to 10% by six hours and to zero by 24 hours after birth.

Work done at Harper Adams University in Shropshire has shown that calves kept on transition milk to day five after birth had higher weight gains to weaning than those moved straight to milk replacer from day two onwards.

In her presentation at the Thompsons event, Harper Adams researcher Dr Emma Bleach defined colostrum as that taken from the first and potentially the second milking, with transition milk then collected to day three post calving.

By feeding transition milk, she said it is replicating what the cow would do, starting off with colostrum that is high in fat (around 6.7%) and protein (14%) and gradually stepping this down, while at the same time, lactose in the milk is on the rise.

However, milk replacer is much lower in fat and protein and has much higher lactose content than colostrum.

“If we switch straight from colostrum to milk replacer, we are giving these animals a feed which is really quite different,” said Bleach.

As well as antibodies, colostrum and transition milk contain sugar molecules which promote the growth of beneficial bacteria in the gut, as well as hormones such as insulin-like growth factor which improve development of the intestine.

There are a lot of different milk replacer products on the market, and it is necessary to look beyond the percentage values on the label attached to the bag, said Dr Amanda Dunn from Bonanza Calf Nutrition.

She gave the example of crude protein percentages, which could be the same on various products, but the actual ingredients are very different. “Your calf does not have a requirement for crude protein percentage – it has a requirement for amino acids. It can only digest specific amino acids,” she said.

It is also not as simple as thinking a product with a high fat content is better than one with lower fat.

“We want lean growth. It is about feeding the right balance at the right stage of development,” Dunn added.

When it comes to practical management on farms, her advice is to maintain the same routine every day and keep a clean and dry environment in the calf house at all times.

When compared to feeding lactating cows, knowledge is quite limited around how to maximise colostrum production and quality, suggested Dr Ronald Annett from Thompsons Feeds.

He said dry cow diets are generally formulated to meet 100% of energy needs and typically are based on feeding 10ME silage along with 2 to 2.5kg of a pre-calver ration and 1 to 2kg of straw.

US research which compared this type of controlled diet with one where cows received an extra 20% of energy, suggests meeting 100% of requirements leads to the best outcomes for a freshly calved cow. However, the “one negative” was around colostrum production, which was lower when a controlled diet is fed – this difference was minimised when cows were offered a higher energy diet close to calving.

“That to me says that energy and protein intake in the close-up period does have an impact on colostrum yield,” said Annett.

He suggested that sometimes in NI we can struggle to get sufficient intakes from a 10ME silage to meet energy needs of cows, so it might be worthwhile to aim to make a slightly higher quality product (10.5ME) or feed 3kg of ration rather than 2.5kg.

When it comes to colostrum quality, Annett maintained that anything which boosts the immune system (such as vaccines) will improve antibody levels, while mineral nutrition has a positive impact as well.