While the traditional approach to rearing dairy calves has focused on restricting the amount of milk or milk replacer as a means to stimulate early solid feed intake, increasingly dairy farms are adopting the feeding of higher planes of nutrition which support greater growth relative to the outcomes of the restricted conventional feeding plans. These intensified feeding programs allow for quantities of milk that are more closely aligned with levels that a suckling calf would consume in nature. Thus, whereas the conventional milk feeding rate of approximately 10% of a calf's birth weight (usually between 4L and 5L per day) would support just under 0.5 kg/d of weight gain, these intensified plans have been shown to produce weight gains between 0.75kg and 1 kg per day. What are the short- and long-term benefits of these intensified feeding programs on both growth and behavior of dairy calves? And, what are the implications for calf management with this newer approach to feeding? Dr. Emily Miller-Cushon of the University of Florida, explored these questions in her 2015 literature review, "Intensified Pre-Weaning Calf Feeding Programs: Impacts on Growth and Behavior."
Improvement of growth and welfare in early life
In terms of the connection between plane of nutrition and growth, in contrast to the conventional, restricted feeding mentioned above, when calves are provided milk ad libitum, they consume between 8L and 16L per day, doubling nutrient intakes. And, with milk replacer, intensified programs also double the amount of dry matter fed (DM) on a body weight (BW) basis (instead of 1-1.5%, it's 2-3%). These programs therefore have great impact on early life calf performance in terms of improvement in rate of weight gain (as mentioned above), structural growth (both girth and height) and efficiency of feed conversion.
Intensified feeding programs also show great advantages in terms of early life calf welfare. These feeding systems, especially when provided on an ad libitum basis, allow calves to feed closer to the way they would in nature, by consuming 8 to 10 meals per day (instead of the conventional, restricted practice of two meals per day) and thus spending a greater amount of time feeding (45 to 60 minutes per day feeding, compared to about 10 minutes per day feeding via the conventional method). Those on restrictive programs, by comparison, exhibit greater signs of hunger (non-nutritive sucking and frequent unrewarded visits to the feeder). Intensified feeding systems thus have quite clear implications for calf welfare in terms of reducing hunger and restoring natural feeding behavior patterns, when feed is provided ad libitum.
Potential for long-term production benefits
In order for these intensified calf feeding programs to make economic sense for dairy farmers, there must be the potential for increased long-term performance. Indeed, elevating the early plane of nutrition has been shown to have long-term production potential. Research on the quantity and quality of milk replacer have shown reductions in age at first calving and have also identified the positive link between pre-weaning growth and eventual milk production. One such study by Soberon et al. (2012) showed the positive correlation between pre-weaning average daily gain (ADG) and milk yield in 1st lactation in that for every 1 kg of pre-weaning ADG, there was an improvement in milk yield of between 850 and 1,113kg. Thus, the increased costs of intensified calf feeding programs can be recouped by the 1st lactation.
Managing intensely fed calves
Implementing these intensified feeding programs requires certain on-farm management techniques for weaning and housing that recognize the challenges associated with upping the early plane of calf nutrition.
As rumen development is delayed a bit with more intense milk feeding programs, it can be a challenge to support consistent growth through weaning. Therefore, post-weaning performance depends on a successful transition at weaning which can be achieved by weaning later and gradually, via a step-down method. (See also http://ruminants.lifestartscience.com/en/featured-articles/recent-research/research-round-up/)
Additionally, intensified feeding systems generally utilize group housing, whereas conventional feeding systems typically house neonatal calves individually. The good news is that calves housed in groups usually consume more solid feed prior to weaning. And, social housing also tends to reduce stress and is more consistent with weight gain through weaning.
Ultimately, the short- and long-term benefits of intensified feeding systems including greater rates of growth, more natural feeding behaviour (again, if fed ad libitum), and the potential for both earlier calving age and increased eventual milk production need to be understood in light of the requisite management techniques that must be implemented in order for intensified feeding systems to be successful.