There is a large degree of variation in calf rearing practices and accommodation design on local dairy farms, a team of researchers has concluded.
As part of the Optihouse project, researchers from the Agri Food and Biosciences Institute (AFBI) and Queen’s University Belfast carried out an in-depth survey of 66 dairy farms across NI.
Housing design and layout, particularly aspects relating to ventilation, were found to be “a potential limiting factor for calf health and performance” on many units.
The researchers also concluded that there was “a lack of appropriate monitoring and measuring” in several key areas within calf sheds, such as assessing feed intakes and recording liveweight gains.
Results from the survey, which have been published in the scientific journal Animals, give a comprehensive insight into typical heifer rearing practices on local dairy farms.
The researchers point out that there is a wide variation in dairying systems and heifer rearing practices across NI. For example, average milk yields among the surveyed farms ranged from 5,000l to 11,000l, and the duration of calving seasons ran from 77 days to 365 days.
However, average milk yield across the 66 herds was 8,000l, with the majority calving from approximately September to March (47%) or all year round (41%).
The main calf rearer on the surveyed farms spent an average of 125 minutes each day feeding calves and completing other calf related tasks. On 42% of the farms, a second person also assisted with calf rearing.
Only 3% of surveyed farms let newborn calves suckle the cow after calving. Over three-quarters of farms gave more than 3l of colostrum in the first feed, but just 14% regularly tested colostrum to assess its quality.
If colostrum quality is poor, there is a risk that the calf will not receive adequate passive immunity from its dam. Testing colostrum is described in the study as an “inexpensive and relatively quick” practice and is recommended by the authors.
Of the farms surveyed, 82% fed milk replacer and 18% fed cows’ milk. The average concentration of milk replacer was 152g/l and automatic feeders were used on 21% of farms.
The peak milk volume offered to calves averaged 5.5l in the survey, but ranged from 4l to 8l across the farms. The researchers suggest that this difference in energy intake “may have significantly impacted” the performance of calves.
Over three-quarters of survey participants did not measure the amount of starter ration that calves were consuming before weaning, which is something that the researchers also recommend.
On the farms that did record intakes, the average daily intake by weaning was 2.1kg, although this ranged from 1.5kg to 3.5kg.
Water was available to calves from birth on 68% of farms and the average age for offering both water and forage was four days old. Straw (excluding bedding) was the main forage offered to calves on 65% of farms, hay was used on 25% of farms, while others used either haylage, lucerne or a mixed ration.
One-fifth of survey participants did not offer an additional forage other than bedding, but this is not advised as it can lead to reduced dry matter intakes and an increased risk of infection.
The average age of weaning was 58 days and 33% of survey participants weaned calves based on their age. Concentrate intake was the sole weaning criteria on 14% of farms, 8% used visual appearance and 36% based weaning on a combination of factors.
Weaning method varied across the surveyed farms, with 32% using abrupt weaning, 27% took a two-step reduction in milk volume and 29% used a three-step approach. A gradual transition off milk to a post-weaning diet is generally recommended.
Calf jackets were available on 74% of farms and 29% of survey respondents used them routinely. Heat lamps were mainly used for sick or small calves, but 54% of farms did not use them at all.
The AFBI and Queen’s researchers surveyed calf accommodation during farm visits and found that 92% of sheds used natural ventilation, so no mechanical air tubes or fans were present. However, they concluded that 53% of sheds had “inadequate” air inlet and outlet areas to achieve optimum ventilation.
Over half of the sheds surveyed were adjoined to other farm buildings. The study states that this can limit ventilation and can facilitate the spread of airborne infections, particularly if young calves share air space with older animals.
Over 90% of the surveyed farms used straw for bedding and the average stocking density in group pens was 3.4m2/calf. This is above the general recommendation of 3m2/calf, which brings benefits for air quality and calf welfare.
The researchers suggest that brightness is not a limiting factor in local calf sheds, as the average light intensity was found to be 257 lux.
Previous studies associated lower feed intakes, reduced social behaviour and increased lying times with calves housed in sheds where average light intensity is below 100 lux.
The researchers found that 58% of farms had solid concrete floors under calves, but the ability of floors to drain urine, spilled milk, and water could “vary significantly” between sheds.
It is recommended that sick calves are separated from the group to prevent disease spread and 42% of survey respondents said they isolate calves at the first sign of ill health. However, on 24% of the farms, calves were not separated until severe signs of sickness appeared and 18% did not isolate sick calves at all.