Advice on feeding calves for good rumen development
© Tim Scrivener A cow spends 10-12 hours a day ruminating, so it is essential that her rumen is optimised early in life to convert feed into energy for growth and subsequent milk production.
A neonatal calf is dependent on milk as an energy source for its first few weeks. The lactose in the milk is digested in the abomasum – one of a cow’s four stomachs.
At this stage, the rumen is still small but by the time a calf reaches six months, its rumen is very nearly fully functional.
See also: 4 critical control points to improve calf rearing
This transformation does not just happen by magic; it requires careful nurturing to develop the rumen for optimum calf growth and health.
Ginny Sherwin, clinical assistant professor in farm animal medicine at Nottingham University, gives advice.
1. Introducing starch and forage
In a neonate, the abomasum makes up nearly 50% of the four stomachs by volume, and the rumen is tiny (the size of a fist).
Forage plays an important role in increasing the capacity of the rumen and getting it working effectively.
When calves eat starch, it gets broken down by a microbiome of bacteria, protozoa and fungi into volatile fatty acids (VFAs).
Rumen papillae (finger-like projections) create a huge surface area for the absorption of the VFAs across the rumen wall.
The VFAs then travel via the bloodstream to the liver, where they are converted to glucose for the maximum amount of energy to be released.
Calves are born without papillae and to stimulate their production, the presence of VFAs in the rumen is required.
However, a heavy starch diet made up of concentrate alone can create a lot of acid, which lowers the rumen pH below the recommended 6.
This causes sub-acute acidosis, killing the microbiome needed to break down feed.
To prevent this, forage must be offered to stimulate cudding and saliva production, to act as a buffer against this acidity.
Without this all-important fibre, parakeratosis occurs – this is when hardened keratin layers builds up on the papillae, reducing the absorption of VFAs and restricting blood flow to the papillae.
Parakeratosis can cause poor growth rates and loose faeces. Fibre acts like a “toothpick” to remove the build-up of keratin, and this is often referred to as “scratch factor”.
Take-home messages
- Introduce starter feed in small amounts from birth (a handful at a time). The longer you delay it, the longer it takes for a calf to derive any energy from it
- The starter feed takes three to four weeks from when it is offered for the concentrate to contribute significantly to the ingested energy of the calf
- Make sure feed is fresh and palatable so calves want to eat it
- Consider using shallow aluminium dog bowls rather than blue buckets (they also fit inside calf hutch hoops) because they are easy to clean and not as deep
- Provide fresh, clean water from day one.
2. Take advantage of early feed efficiency
Feed efficiency is at its best pre-weaning: for every 2kg of dry matter (DM) intake, a calf gains 1kg in daily liveweight gain (DLWG).
“We need to be thinking about utilising this feed conversion efficiency (FCE) to get the best growth,” explains Dr Sherwin. “The calf is effectively a monogastric and you can pile the weight on.”
Research by Alex Bach at the Catalan Institution for Research and Advanced Studies in Barcelona shows that pre-weaning growth can have a positive effect on milk production.
A 100g/day increase in DLWG results in an additional 220kg of milk in first lactation.
For weaned calves that are being fed 25-30% forage and 70% concentrate, FCE is still 3:1 or 4:1, so that should continue to be utilised.
This is because FCE becomes much lower in older heifers, at 8:1 to 15:1, depending on diet as well as age.
Take-home messages
- Do not wean calves based on age – ensure they have at least doubled their birthweight and are eating at least 1.5kg of concentrate/day before weaning
- Do not limit growth pre-weaning
- Make the most of the good FCE before weaning and cost-effective FCE in weaned calves.
3. Introducing grass silage
Avoid feeding grass silage to calves until they are at least six months old – their rumen is not fully functioning until this point, and they cannot use this energy.
Dr Sherwin says: “Farmers like to feed an adult ration to heifers, but we really want to avoid this if we can because we have a mismatch of crude protein (CP) and energy.”
The adult ration is too high in energy and lacks CP (it should be 18% but is usually 16%).
If an adult ration is fed on farm, consider reducing the energy by increasing the amount of chopped straw and using other protein sources.
Instead, calves should be fed straw or mature hay alongside 2-3kg a head a day of an 18% crude protein until at least six months, but ideally until 12 months.
Take-home messages
- Delay introducing grass silage until calves are six months old
- Keep It Simple, Stupid (Kiss) by feeding straw
- If you are feeding leftovers to youngstock, are they providing the right energy?
- The type of straw does not matter, but chop length does – ideally 5cm
- Make diet changes gradually and check faeces for signs of it being too loose.
4. Measure weight to make informed decisions
Heifers should be 55-60% of their mature weight at service, and 85-95% of their mature weight at calving.
For a Holstein Friesian, that equates to putting on 550kg in the 670 days from birth to calving. To achieve that, the heifer must grow at 800g a day.
Linear growth at 800g a day is not economically ideal, so consider targeting different growth rates at different points, based on what feed is available and the age of the heifer.
Regular weighing is vital, as you can’t manage what you don’t measure.
The gold standard is to use electronic weigh scales that have been properly calibrated each time they are used.
Weigh tapes can be accurate to within 50g a day, as long as they are used at a cohort level and enough calves are weighed within a sufficient time between weigh-ins.
If you increase the time between measurements, you need fewer calves – for example, 18 calves weighed at an interval of 28 days or seven calves at an interval of 42 days.
Take-home messages
- Ideally, calves should be weighed at birth, at three to four weeks after birth, at the start of weaning, and four weeks after that.
5. Grazing heifers
Heifers should not be “chucked out” to grass if conditions could negatively impact growth.
Dr Sherwin says: “We don’t need to teach our baby heifers how to be grazing cattle when they are young.
“If they don’t eat grass in the first season, it doesn’t mean they will not be effective grazers and there is research to prove this.”
Although having an experienced companion helps heifers learn how to graze, Dr Sherwin says farmers should consider whether it would be better to keep calves indoors or give them supplementary feed to keep growth rates on track.
“This is best determined by routine weighing and assessment of grass quality, with heifers requiring the best grass on the grazing platform.”
Calves are inefficient graziers and eat less than 60% of what an adult animal would consume. This makes it hard to hit residuals without affecting growth rates and DMI.
To help utilise grass, leader-follower systems can be implemented whereby youngstock are given priority to grass and older animals (pregnant heifers or low yielders) clean up afterwards.
The financial burden will be greater if heifers are not at target weight at service.
Take-home messages
- Measure and sample grass
- Sward height should be 7-9cm on entry and 5-6cm on exit
- Energy of grass should be 11.5 MJ/kg – but it can vary hugely in quality, so supplementary feed might be needed
- Test grass for trace elements
- Run leader-follower systems to reduce parasite burden and improve grass utilisation.
Ginny Sherwin was speaking on an AHDB webinar called “Developing the rumen for optimum calf health”.
Workshops are still running – details are available on the AHDB website.