Step up early nutrition, step-down at (late) weaning: New study finds ticket forward for sustained growth in calves
In the debate on optimal nutrition in dairy calves, for many years the pendulum swung in the direction of early rumen development at the expense of higher early nutrition, improved growth and better welfare. Today, we know that a high plane of nutrition in pre-weaned calves promotes improved growth, welfare and health. But what does science tell us about the tricky business of weaning in the context of higher plane nutrition?
Having higher body weight and less stress at weaning are both essential to sustain rapid growth rates and animal welfare. But how are higher body weight and less stress achieved simultaneously? And what is the optimal time of weaning? It turns out the answers to these questions are not just linked, but that together they help provide the key to successful weaning.
Does step-down weaning make the difference?
It has already been shown that calves weaned later in life after being fed elevated milk levels experience less weight loss and have fewer behavioural signs of stress.1 A 2015 joint study2 by the University of Alberta, and Trouw Nutrition R & D in the Netherlands, set out to determine whether boosting these already proven methods by adding a step-down strategy to minimise abrupt changes which occur during weaning, would result in enabling even greater growth rates as well as better gut development. In the study, over 100 calves were fed elevated planes of nutrition and were weaned through a step-down process at either 8, 10 or 12 weeks of age. The results of the step-down approach were encouraging both in higher growth rates and in reduced weaning stress, especially for later weaning.
Growth rates boosted and gut development is smoother, with less stress
While calves weaned at 8 weeks of age had a 46% reduction in ADG during step-down, they recovered ADG levels by week 9 (to just under 1 kg). These results were similar to calves who were weaned at week 10. However, calves weaned at 12 weeks maintained over 1 kg of ADG during step-down and therefore had a greater total weight gain over the trial period. Their final body weight was 4.2% higher than those weaned at 8 weeks.
Though blood serum ßHBA levels increased sharply after weaning for calves weaned at 8 and 10 weeks, calves weaned at 12 weeks displayed a less sharp increase in ßHBA, and therefore experienced less systemic stress. Higher blood serum ßHBA is related to increasing ruminal mass and cell number. A gradual ßHBA increase would be consistent with smoother activation of the fore-stomach with potentially beneficial effects on calf growth and intake during the weaning period.
Some things get better with age
While calf growth decreased at weaning regardless of age, this is not as pronounced as reported in previous research3 and is less severe the later the calves are weaned.4 Indeed, the growth advantage is evident in body weight between calves weaned at 8 weeks versus those weaned at 12 weeks, indicating that calves may benefit from delayed weaning when fed an elevated plane of nutrition pre-weaning and when weaned using a step-down method. Ultimately, delaying the age of weaning lessens the reduction of ADG and leads to more gradual increases in ßHBA, while better nutrition pre-weaning leads to overall better weight gain. This elevation of pre-weaning nutrition not only improves potential production performance later on, but also minimizes the very real welfare concerns that arise during the potentially stressful time of weaning.