Micronized versus super-conditioned corn: Effects on starch digestion, performance, and blood metabolites of Holstein dairy calves.

Micronization, a dry-heat process, generates infrared electromagnetic short waves that can affect starch granules and gelatinization. A new method of corn processing, super-conditioned corn, a moisture-heat process, has potential to increase starch digestion and performance in calves. Therefore, incorporating super-conditioned or micronized corn in starter feed may enhance growth performance by improving total-tract starch digestion. This study aimed to evaluate the impacts of heat (micronizing and super-conditioning) and conventional processing method (grinding) of corn grain on the starch digestion, skeletal growth, feeding behavior, biochemical status of blood, and performance of dairy calves. Thirty-six Holstein female dairy calves [40 ± 1.8 kg of body weight (BW)] were assigned to 3 groups that starter feed contained 58% of one of the following corn types: the control group with dry ground corn (n = 12, GC), a group receiving micronized corn (n = 12, MC), or a group receiving super-conditioned corn (n = 12, CC). Three mash starter feeds with an identical nutritional composition were blended with 5% chopped alfalfa hay and fed to individually housed calves from wk 1 to 11 of their birth. All calves were fed 4 L/d of pasteurized whole milk twice daily since d 3 to wk 8, followed by 2 L/d of morning feeding from wk 10 to 11 of age. Calves were weaned on wk 9 and remained in the study until wk 11. Intake of feed was reported weekly and body measurements were recorded on d 3, wk 9, and 11 of age. Blood samples were collected from jugular vein on the last day of wk 11 of age. Behavioral data were recorded by direct observations of all the calves equal to 12 h before (d 61 to 63 of age) and 12 h after (d 75 to 77 of age) weaning. Final BW, average daily gain (ADG) and feed efficiency (FE) increased in calves fed CC compared with GC and MC in the overall period. An interaction of treatment × week was detected for total DMI on wk 10 and 11 of age where it was lower in the CC than in the GC and MC counterparts. However, feeding starter feed containing CC increased total-tract DM and starch digestibility compared with MC and GC. Rumination time and eating time decreased in CC calves than MC and GC calves. Moreover, significant treatment × week interactions were observed for the skeletal growth. On wk 11 of age, compared with the GC and MC, wither height and hip height was greater in calves fed CC. The CC formulation increased the concentrations of insulin and glucose fraction in blood while these parameters were not different between GC and MC. In conclusion, CC improved the ADG, FE, and skeletal growth, while reduced total DM intake during post-weaning period compared with MC and GC. Based on the positive changes in ADG, FE, and skeletal growth; CC was superior to the MC and GC, due to improved starch digestion.