Recent calf-rearing events, hosted by AHDB, explored how producers can optimise calf health by focusing on nutrition and weaning. We spoke to three experts to find out more.
TEXT ALIX MORLEY
Optimal feeding and nutrition is just one aspect of calf-rearing success, and this starts with colostrum, which is vital to help protect calves from disease. There are a range of factors that can affect how well colostrum is ‘absorbed’ by a calf, including quality, quantity, and cleanliness, as well as how quickly the calf feeds.
“If you look at UK studies, somewhere between about 14% and 26% of calves experience a failure of passive transfer,” says SRUC Veterinary Services’ Dumfries-based vet Colin Mason. “Colostrum protocols fail to provide them with the immunity and protection they need.” Canadian research has also assessed suck reflex in calves, by inserting fingers into the calf’s mouth to score it. Researchers looked at the data in relation to whether the calf consumed sufficient colostrum within the first four hours of life. “In unassisted calvings, 78% of calves with a poor suck reflex failed to consume sufficient colostrum. While in the difficult, assisted-calving category, this increased to close to 100% of calves,” says Mr Mason.
Stillbirth rate is also worth considering in relation to colostrum-feeding success. “Stillbirths are the tip of the iceberg. There will also be calvings where the calf is alive, but extremely compromised at birth and, therefore, less likely to drink or absorb enough colostrum. In herds with a high stillbirth rate there are likely to be issues with live calves failing to take on enough colostrum.
“So reviewing stillbirth rate and suck reflexes can provide easy measures to help inform colostrum management.”
He also says producers should work with their vet to test either blood total protein or zinc sulphate turbidity (ZST) as an indication of how well colostrum is being absorbed.
Colostrum quality is important too. “There are some easy ways to help ensure you are optimising quality such as using a Brix refractometer,” he says. Cleanliness is also vital. “If we feed colostrum with a high bacterial load to calves, the bacteria in that colostrum compete for the same sites on the gut wall that should be used for absorbing the antibodies. Bacteria will block the absorption of good-quality antibodies into the calf’s blood stream. It is vital to minimise bacterial load.
“Bacterial counts will continue to rise in colostrum stored in a fridge, so freezing is the best option for reducing bacterial multiplication. And producers may want to consider pasteurisation as part of their disease-control programme.”
However, calf rumens will not be fully functional until at least six months of age and will only reach adult capacity at around 13 months.
“Eating solid feed is a learned response involving a process of sampling different food types, and how feed is presented will have a significant influence on how likely calves are to eat it,” says University of Nottingham’s Ginny Sherwin.
“Introducing forage into the diet helps stimulate cudding and saliva production to balance pH, important because a heavy starch diet can lower rumen pH and cause acute acidosis.”
Forage is a bulking agent and helps stretch the rumen and increase capacity. “It also prevents parakeratosis, which affects the proper function of the papillae in the
rumen and can lead to lower growth rates and poor feed-conversion efficiency. Stimulating the growth of papillae and incorporating fibre into the diet can help increase absorption of the energy released from starch by the rumen microbes,” explains Dr Sherwin.
It takes calves three to four weeks to start to take energy from solid feed, so introducing the starter feed later delays its utilisation. “While muesli or pellets are good starter-feed options, it’s more important to consider how it’s presented and whether there is enough feed space and access to water,” she adds.
Growth monitoring: check heifers are on track throughout the rearing period
As calves mature, feed-conversion efficiency changes. For pre-weaned calves, 2kg dry matter (DM) will fuel 1kg of growth, which will increase to between 3kg to 4kgDM per kilogramme of growth post weaning. By the time they’re around nine months old it can take between 8kg and 15kgDM for them to achieve the same growth rate. It’s during the first six months of a calf’s life that 50% of skeletal growth takes place. This is important because it’s closely linked with future yield. Increasing daily liveweight gain (DLWG) by 0.1kg a day in the first two months of life can deliver an additional 226kg of milk in the first lactation.
Deciding when to wean calves should be based on the amount of concentrate they are eating – not their age or weight. “The recommendation is to wean calves when, for three consecutive days, they eat at least 1kg of concentrate if the calf starter is greater than 22% crude protein, or 2kg of concentrate if the calf starter is less than 22% crude protein,” says AHDB’s Jenny Gibbons.
“Weaning should be gradual and milk should be reduced during a seven to 14-day period. This will increase concentrate intakes, avoid a growth check after weaning, and minimise weaning distress. Reducing milk can be done either by decreasing the volume of milk fed per feed or by reducing the number of feeds per day.”
Consideration should also be given to what calves are fed post weaning. “Where starch-based pellets are offered they should form 70% of the diet with 30% forage. Grass silage should not be introduced into the diet until calves are at least six months old,” adds Dr Sherwin.
“Once heifers are at grass, it’s important to remember that they only have 60% of the grazing efficiency of an adult cow. Getting low residuals off a paddock will come at the expense of dry matter intake and DLWG will suffer. Typically, there will be plenty of protein at grazing, but energy will be the limiting factor.
"Heifers should have access to high-quality, leafy grass swards throughout the grazing system, and ideally at the two-leaf stage. Grass availability will vary, and supplementary feeding may be required to achieve targets. Rotating paddocks is also important and can benefit growth rates.”
She stresses that there are financial consequences with under-performing calves. The aim is to calve down at between 22 and 24 months old when they’re between 85% and 90% of their adult third-lactation bodyweight. “Making up any weight deficits at a later stage in the heifer’s life can be expensive. So investing in calves at an early age, and getting them off to the best possible start in life, will deliver future results.”