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Title:Effects of mixer type on utilization of diets with increasing amounts of modified wet distillers grains with solubles for lactating dairy cattle
Author(s):Ploetz, Jacquelyn C.
Advisor(s):Drackley, James K.
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):TMR mixer
distillers grains
milk fat
total mixed ration (TMR)
Abstract:Our objective was to determine if methods for preparing TMR [Keenan MechFiber (KMF) technology vs. vertical auger (VA) mixer] would alter physical form of the TMR and affect utilization of modified wet distillers grains with solubles (MWDGS). Holstein cows (n = 24 with 12 ruminally cannulated; 144 DIM ± 31 d at start) were used in a split-plot design with mixer type as the whole plot and MWDGS concentrations as subplots in a 3 x 3 Latin square arrangement with 35-d periods. Inclusion rates of MWDGS were 10, 20, and 30% of dietary DM, primarily replacing corn, SBM, and whole cottonseed. Feed DMI was less for KMF (P = 0.05), but was unaffected by MWDGS concentration (P = 0.39). Milk production did not differ (P = 0.75) by concentration of MWDGS or by interaction of MWDGS × mixer (P = 0.18). Milk protein content tended (P = 0.09) to decrease linearly with increasing MWDGS. Milk fat percentage declined with increasing MWDGS (P = 0.003) but the interaction between mixer wagon and MWDGS (P = 0.006) showed that decreases were larger with VA mixing. Cows fed the diet containing 30% MWDGS mixed with KMF averaged 3.45% (1.24 kg/d) milk fat; whereas, cows fed the same diet mixed with VA averaged 2.81% (1.10 kg/d) fat. Concentrations of CLA trans-10, cis-12 in milk likely explain the differences in milk fat; the concentration of CLA t-10, c-12 increased as MWDGS was increased (P < 0.0001) and the MWDGS × mixer interaction (P = 0.03) showed that VA had greater concentrations. Greater mean particle size and variation with VA may partially explain differences in milk fat via increased sorting that allowed for an altered rumen environment and favored alternative biohydrogenation pathways. Feed conversion efficiency (FCE; energy-corrected milk/DMI) decreased linearly (P = 0.007) as MWDGS increased, but FCE tended to be maintained when higher MWDGS diets were mixed using KMF rather than VA (mixer, P = 0.12). Ruminal pH (P = 0.05) and ammonia concentration (P < 0.001) decreased linearly as MWDGS increased. Using the KMF mixer wagon resulted in better FCE when higher amounts of MWDGS were fed, primarily because milk fat content and yield were not as depressed and DMI was lower.
Issue Date:2012-02-06
Rights Information:Copyright 2011 Jacquelyn C. Ploetz
Date Available in IDEALS:2012-02-06
Date Deposited:2011-12

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