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-conditioning, is a moist-heat process that 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 effects of heated (micronizing and super-conditioning) and conventional (grinding) processing methods of corn grain on the starch digestion, skeletal growth, feeding behavior, blood biochemistry, and performance of dairy calves. Thirty-six Holstein female dairy calves (40 ± 1.8 kg of BW) were assigned to 3 groups fed starter feed containing 58% of one of the following corn types: dry ground corn (GC) as a control (n = 12), micronized corn (MC; n = 12), or super-conditioned corn (CC; n = 12). 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 after their birth. All calves were fed 4 L/d of pasteurized whole milk twice daily from d 3 to wk 7, followed by 2 L/d of morning feeding from wk 8 to 9 of age. Calves were weaned in wk 9 and remained in the study until wk 11. Intake of feed was reported weekly, and body measurements were recorded on wk 1, 9, and 11 of age. Blood samples were collected from the jugular vein on the last day of wk 11 of age. Behavioral data were recorded by direct observations of all the calves 12 h before (d 61 to 63 of age) and 12 h after (d 75 to 77 of age) weaning. Final BW, 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 at wk 10 and 11 of age, where it was lower in the CC group than in the GC and MC groups. 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 compared with MC and GC calves. Moreover, significant treatment × week interactions were observed for skeletal growth. At wk 11 of age, compared with the GC and MC calves, wither height and hip height were greater in calves fed CC. The CC formulation increased the blood concentrations of insulin and glucose, but these parameters were not different between GC and MC. In conclusion, CC improved the ADG, FE, and skeletal growth but reduced total DMI during the postweaning period compared with MC and GC. Based on the positive changes in ADG, FE, and skeletal growth, CC was superior to MC and GC due to improved starch digestion.