Relationships between starch concentration of dry feed, diet digestibility, and growth of dairy calves up to 16 weeks of age

ABSTRACT Our objective was to examine the potential relationship between starch concentration of dry feed and growth performance of young dairy calves via mixed-effects model analyses. A database was developed from 6 published studies conducted at the Nurture Research Center, Provimi (Brookville, OH), from 2008 to 2017 that included 18 dietary treatments and 372 calves at 0 to 8 wk of age in 5 nursery trials and 26 dietary treatments and 660 calves at 8 to 16 wk of age in 8 grower trials. The dry feeds ranged from 10.1 to 53.3% starch, 12.1 to 45.3% neutral detergent fiber, and 2.7 to 3.0 Mcal/kg of metabolizable energy [dry matter (DM) basis]. In all nursery trials, with increasing starch concentration in starter, average daily gain (ADG), hip width change, and starter intake linearly increased. In all grower trials, as starch concentration of dry feed increased, ADG, hip width change, and ADG/DM intake linearly increased; DM intake and DM intake/body weight were unaffected. In addition, the calves at 6 to 16 wk of age had greater digestibility of DM and crude protein with increasing starch concentration of dry feed. As indicated by meta-regression analysis, growth responses to starch concentration were influenced by metabolizable energy concentration in dry feed fed to the calves up to 16 wk of age. Changing starch from 23 to 43% on a DM basis (a typical range in the US industry) was predicted to increase ADG and hip width change by 5.8 and 5.0%, respectively, for calves at 0 to 8 wk of age and by 9.6 and 11.2%, respectively, for calves at 8 to 16 wk of age. Positive linear relationships between starch concentration of dry feed with DM digestibility, ADG, and hip width change reflect the importance of starch in the diets of young dairy calves.