|ARNDT, CLAUDIA - University Of Wisconsin|
|ARMENTANO, LOUIS - University Of Wisconsin|
|Hall, Mary Beth|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2014
Publication Date: 8/15/2014
Citation: Arndt, C., Armentano, L.E., Hall, M. 2014. Corn bran versus corn grain at 2 levels of forage: Intake, apparent digestibility, and production responses by lactating dairy cows. Journal of Dairy Science. 97:5676–5687.
Interpretive Summary: Corn bran is the fibrous outer layer of corn grain present in small amounts in corn grain and corn silage, and as a larger part of various co-products of corn processing. The energy value of corn bran is not well established, but can be predicted from analyzed chemical composition. This study measured the feeding value of relatively pure corn bran derived from dry-mill fractionation of corn grain. Substituting corn bran for corn grain decreased diet digestibility and milk yield and indicated that corn grain fiber digestibility predicted from chemical composition overestimated in vivo digestibility.
Technical Abstract: The objective of this study was to determine the effect of substituting corn bran (CB) for dried ground corn grain (CG) in the supplement portion of high-forage (HF) and low-forage (LF) diets. Twelve multiparous and 12 primiparous Holsteins were assigned to 4 diets using six 4 x 4 Latin squares with 3-wk periods. Forage was 64 or 38% of the total mixed ration [% of dry matter (DM)]. On a DM basis, the HFCG diet had 20% CG, 30% neutral detergent fiber (NDF), and 26% starch; the LFCG diet had 39% CG, 23% NDF, and 34% starch; the HFCB diet had 19% CB, 43% NDF, and 15% starch; and the LFCB diet had 38% CB, 48% NDF, and 13% starch. Digestible organic matter intake (OMI) and milk energy yield were lower for CB compared with CG within forage level. Digestible OMI was greater (1.9 kg/d) for the LFCG compared with HFCG treatment. When CB replaced forage (LFCB vs. HFCB) digestible OMI was not different. However, milk energy yield was greater with the LFCB diet. The LFCG diet supported the greatest milk, milk protein, and milk energy yield. Decreased concentration of milk protein and increased concentration of milk urea nitrogen when feeding CB compared to CG suggests that lack of fermentable energy in the CB-supplemented diets may have limited rumen microbial protein synthesis. Total substitution of CG supplement with CB supplement did not support maximum milk production, even when forage was reduced at the same time (HFCG vs. LFCB). Predicted NDF digestibility at 1 times maintenance based on chemical analysis of the individual feeds was 22 percentage units greater for CB than for the forage mix (68.9 vs. 46.9%). In vitro NDF digestibility at 30 hours of fermentation was 19.4 percentage units greater for CB than for the forage mix (68.9 vs. 49.5%). However, based on linear extrapolation of in vivo NDF digestibility, NDF digestibility was only 1.3 percentage units greater for the CB supplement than for the forage mix (45.0 vs. 43.7%). Similarly, predicted total digestible nutrients at production level of intake based on chemical analysis were greater for the CB treatments and lower for the CG treatments than those observed in vivo.