An elevated plane of nutrition pre-weaning + later weaning age = less weaning stress and long-term growth advantages in heifers
Over the past decade there has been a shift away from weaning calves as early as possible. While this had originally been done in order to decrease feed costs and speed up rumen development, feeding calves restricted levels of milk not only creates weaning stress and negatively affects growth rates, but it also leads to other significant welfare issues. The recent shift towards feeding calves an elevated plane of nutrition pre-weaning brings with it a host of benefits including improvements in health, growth rates, feed efficiency and lifetime milk production.
Even so, part of the reason this recent shift in understanding hasn't been universally implemented is the concern that delaying solid feed intake may negatively affect post-weaning growth as well as rumen development, both before and during weaning. But is this so? A recent joint study by the University of Guelph, the University of Alberta, and Trouw Nutrition R & D, sought to find out. In the study, 20 female Holstein calves, placed in individual pens, were fed an elevated plane of nutrition from birth to weaning at either 6 or 8 weeks. Their dietary intake, growth, digestive tract development and feeding behaviour were tracked. The results show that cows weaned at 8 weeks instead of 6 weeks were "better able to cope with the transition from milk to solid feed" and had higher growth rates during and after weaning which were maintained for months beyond.
Better growth, development and feeding behaviour with less stress and higher dietary intake
Calves weaned at 8 weeks (8 WW) had higher ADG during step-down and post weaning and were heavier at 10 weeks, compared to those weaned at 6 weeks. By a lot. ADG for the 8 week group was more than double that of the 6 week group in the step-down week (0.79 kg per day vs. 0.34 kg per day) and triple that of the 6 week group in the week after weaning (1.05 kg per day vs. 0.35 kg per day). The 8 week group also weighed 9.8% more than the 6 week group at 10 weeks (99.9 kg vs. 91.0 kg).
Calves in the 8 week group also handled the dramatic steep increase in ruminal fermentation, incorporated and utilized βHBA more efficiently post weaning, and digested starch in a manner that indicates better overall digestive tract development than the 6 WW group. Additionally, calves in the 8 WW group had greater solid feed intakes before, during and after weaning than the younger group, providing further evidence of their smoother transition from milk to solid feed.
Behaviourally, the 8 WW group also showed fewer signs of systemic and weaning stress than the younger group, shown through fewer vocalizations and oral behaviours due to hunger. Additionally, rumination time was increased fourfold for the 8 WW group over the 6 WW group, which may be beneficial for rumen fermentation as well, due to the concentration of bicarbonate from improved intake.
Growth advantages well beyond time of weaning
The differences in body weight between the two groups seen at the time of weaning continued throughout the entire 5 months of tracking. While the gap began at the step down week for the 6 WW calves, the growth advantage for the 8 WW calves continued and even increased the longer the weight was tracked. At d 90, the 8WW calves weighed 127 kg vs. 118 kg for the 6 WW calves and at d 150, the gap grew to 194 kg for the 8 WW calves vs. 183 kg for the 6 WW calves. This shows that the growth advantages of using an elevated plane of nutrition combined with weaning later do not stop at the time of weaning, but rather that this weaning strategy continues to promote long-term growth advantages as well.