Heifers are the future of the herd, representing the best opportunity for genetic improvement. Calving them at the target age is fundamental to running an efficient system and maximising their genetic potential, and is achievable with proactive and appropriate management. Íæż½ã½ã reports.
Dairy farmers should be aiming to calve heifers at 24 months, as research shows this allows for the greatest lifetime performance.Laura Monk, calf and youngstock specialist at Wynnstay, says however that this target is reliant on heifers reaching the right weights for serving.
The target weight for first service is 50 to 60 per cent of mature bodyweight and the target for calving is 80 to 90 per cent of mature bodyweight. There is a direct correlation between the percentage of mature bodyweight at first calving and the percentage of mature yield produced in the first lactation.
Mature bodyweight is herd specific and is the average weight of third and fourth lactation cows.
Meeting these weight targets starts before the heifer is born, through preparing her dam to produce good quality colostrum. Ms Monk recommends a 45 to 60-day planned dry period, with higher body condition score cows dried off later.
Setting dry cows up to produce calves with good lifetime productivity can be split into two focus areas; calf survivability and colostrum production, says Ms Monk.
Both can be negatively impacted by reduced dry matter intakes which can be caused by factors such as lameness, incorrect body condition, heat stress, feed space, overstocking, and lack of water.
It is also worth remembering that immunoglobulins in colostrum are proteins, therefore feeding the correct quality and quantity of protein pre-calving will impact colostrum testing results.
Panel - Colostrum management
Colostrum management is essential to calf health and for ensuring animals remain healthy and productive. Ms Monk stresses the importance of cleanliness, timing, and quantity when putting together a colostrum policy.
Calves are born with a permeable gut lining which allows the large antibody molecules in colostrum to be absorbed, she says.
This permeability is non-specific which means pathogens can also pass through, so dirty colostrum can do more harm than good. All aspects of handling colostrum from collection to feeding must be carried out in as sterile an environment as possible.
The permeability is lost as time progresses and the most efficient absorption of antibodies happens within six hours of birth. The first colostrum feed should be given within that time frame, and research supports administering within the first two hours for the best results.
The first feed should be 10 per cent of the calfs bodyweight, adds Ms Monk. Feeding colostrum and transition milk beyond the first feed also has long term gut health benefits. Transition milk has higher levels of fat, protein, amino acids, sugars; specifically bovine oligosaccharides, vitamins and minerals for around seven milkings after calving.
Panel - Growth and weights
The appropriate daily growth target can be calculated using the target serving size and the birth weight Ms Monk says: Growth efficiency reduces as animals get older so hitting these targets while the calf is at her most efficient is best practice.
Ms Monk recommends calves receive a minimum of six litres of milk per day at feed curve peak, stating the calfs size can limit their uptake in the first three weeks so feeding a high energy milk replacer can make up for some of the shortfall.
Calves should be weaned at a minimum of eight weeks of age and weaning should be governed by the amount of starter feed they are eating.
They must be eating at least 2kg per day before milk is removed completely, or they will not be able to maintain target growth rates. Starter feed and roughage in the diet support rumen development, so choosing the best quality starter and offering it ad-lib pre-weaning will pay dividends in the heifers lifetime performance.
Careful concentrate selection and forage feeding in the first six months builds the engine that the animal relies on to support her performance for the rest of her time on farm.
Panel - Joining the herd
Once heifers have achieved their growth targets and have been served, they still need to navigate the potential stress of joining the dairy herd. At 80 per cent of mature weight heifers are smaller than the other cows and need enough energy to grow, produce milk and get back in calf. The change in social group and hierarchy, diet transition, and potentially a move to concrete surfaces can also be a challenge.
Where possible it is beneficial to keep heifers in a separate group where their specific needs for hoof management and additional energy requirements for growth can be met, says Ms Monk.
Including components from the milking cow diet in the close-up dry heifer diet allows time for the rumen microflora to adapt to the post- calving diets, she adds.
In the field: Jon Bult, Somerset
Jon Bult and his family farm 700 all year round calving cows in Somerset. Their careful heifer management has resulted in an average age at first calving of 21 months for the last four years.
We have dedicated calf rearers who focus exclusively on youngstock, he says. This ensures that the calves get the best treatment.
Heifers are served to sexed semen, with the majority of cows receiving beef straws. At calving, all calves are fed powdered colostrum as part of a Johnes eradication policy, and then move onto a milk replacer.
Our calves are fed three times a day, says Mr. Bult. Heifer calves are fed 1,200g of milk replacer for eight weeks.
When the weaning process begins, they go down to two feeds for a week, then once daily for another week. The slow transition off milk avoids the heifers taking any setbacks. They are eating 4kg of cake a day by the time they are fully weaned at ten weeks.
The calves environment is carefully managed to provide optimum ventilation and a clean, dry bed. Calves stay in their own pens until they move into larger groups, and we clean those pens thoroughly before new calves are introduced.
Alongside their milk, calves are fed ad-lib concentrates and straw. The vaccination policy covers pneumonia and coccidiosis.
The Bults focus on heifer care continues post-calving, with heifers being kept in a separate group for their first lactation. This preserves the social cohesion built up pre-calving and avoids the stress of mixing with bigger and more dominant animals.
Heifers dry off into a mixed age dry cow group and then enter the main herd as second lactation animals.
Our number one thing is attention to detail and giving heifers special treatment to maximise their health and welfare and achieve targets, says Mr. Bult.
Having people who work solely with the calves makes this the focus from day one.
