We often focus strongly on getting the best growth out of our young calves by implementing staff calf-rearing training, FPT testing and thorough health and feed plans, but once this stage is complete, it is easy to forget the importance of growing our weaned calves well through to mating.
Now that those same calves are about to head off to the runoff, we need to ensure their growth continues on your chosen trajectory, to guarantee they produce to their full potential when in the herd.
Firstly, let us remind ourselves why this stage is so important. Look at the graph below (reproduced from Rhiannon Handcock’s work at Massey University in 2019). This study involved 140,113 heifers, and it shows the milk solids (MS) produced in the first lactation relative to their weights as R1 and R2s. The red lines compare the difference in MS production for 6-month-old calves at weights of 120kg versus 200kg. The heavier animals produced around 60kg extra MS.
Consider how many ‘tail-end’ calves you have each season. Do any of them fall into this lighter bracket?
Overseas work has shown that over-feeding energy relative to protein, results in heifers depositing excess fat in the mammary gland, thus inhibiting milk production later in life. In our grass-based systems, where the protein content of the grass is quite high, we do not usually see this occur – hence Handcock’s findings. So, if you hear a rumour that we should not be over-feeding our youngstock, this is probably where it originates.
You may also have concerns that excessive growth may lead to poor reproduction. Handcock, however, has also shown that the limiting effect on reproduction is minimal until a 15-month-old crossbred animal is over 400kg. Therefore we really have no justification to limit feed to our young dairy heifers.
So, how do we maximise productivity at this stage?
Firstly, we strongly recommend weighing at least every 4-6 weeks. Without this information, it is easy to get caught out by thinking a big group of calves look ‘pretty good’ visually. When weighing, it is important to keep the time of day and feed available beforehand consistent, otherwise the varied rumen fill between weighs can make the results difficult to interpret. Calibrate the scales every time and also halfway through the weigh session.
Weighing regularly acts as an early alert system, allowing for quick intervention. Using MINDA weights, we would recommend >95% calves are at or above target at every weigh. Every calf that is under target weight will produce less milk than her genetic potential once she is in the herd.
To achieve the required growth rate (>700g/ day for crossbreds) at the runoff, calves need to be offered the best quality feed, long residuals and new breaks every day or two to encourage good intakes. If possible, use older cattle or other stock types to tidy up the paddock. At weaning, calves should be eating at least 1.5kg of calf meal, to ensure their rumen is well enough developed to handle fermenting grass. When they are moved to the runoff, calf meal should continue to be fed, in order to smooth the transition and avoid any post-weaning checks. Ideally, they should be grazed in the smallest mobs possible to reduce competition – less than 150 calves/mob is ideal.
Feed conversion efficiency is better the younger the calves are, so for tail-end calves, preferentially feed early in life until they have caught up with the rest of the mob. Also, where practical, reduce mixing; changing social structure has also been shown to reduce weight gain.
A robust health plan, covering gutworm and lungworm monitoring and control, ectoparasites, trace elements and infectious disease prevention, is essential to prevent any unnecessary setbacks. Set aside the time with your veterinarian to create a plan that you understand and can work with. Every season we see problems or poor growth in calves that, in many cases, with a good plan, could have been prevented. Save yourself the stress later on, and book in a health planning visit with your veterinarian in order to address these issues now.