Lactational response of early-lactation Holstein cows fed starch or floury corn silage

摘要

The study objective was to evaluate the lactationalperformance of early-lactation dairy cows fed a totalmixed ration (TMR) based on corn silage producedfrom a standard starch hybrid compared with 2 flourystarch hybrids. Twenty-one (6 primiparous and 21 multiparous)high-producing, early-lactation Holstein cowswere blocked by calving date and parity and randomlyassigned to 1 of 3 experimental corn silages from wk 4through wk 12 postpartum using a randomized completeblock design with wk 3 as a covariate. The Dekalbblend (STA; Monsanto Company, St. Louis, MO), MastersChoice 527 (LF_1; Masters Choice, Anna, IL), andMasters Choice 5250 (LF_2) treatments were plantedand harvested as corn silage using a kernel processorsilage harvester, inoculated, and ensiled in individualAg-Bags (Ag-Bag, St. Nazianz, WI). The TMR wereformulated to be isonitrogenous at 17.5% crude proteinconsisting of 15.9% alfalfa hay, 35.1% concentrate mix,and 48% of the respective experimental corn silage ona dry matter basis. Crude protein content of STA andLF2 was lower than LF_1 corn silage. Starch content washigher for STA compared with LF_1 and LF_2 silage. TheTMR digestible fiber (neutral detergent fiber) concentrationwas lower for STA than LF_1 and LF_2 (14.0,15.5, and 17.9% dry matter for STA, LF1, and LF_2,respectively). Growing crop year affected corn silagevomitoxin (0.60, 1.45, and 1.56 mg/kg) concentrations,which may have affected lactational performance asSTA corn silage was from 2013, whereas LF_1 and LF_2were from the 2012 crop year. Dry matter intake (22.9,23.5, and 22.4 kg/d), milk yield (35.6, 34.8, and 36.1kg/d), 3.5% fat-corrected milk yield (38.7, 36.5, and37.6 kg/d), energy-corrected milk yield (38.2, 36.1, and38.1 kg/d), feed efficiency (1.79, 1.61, and 1.67 kg/kg;3.5% fat-corrected milk/dry matter intake), milk fat(4.17, 3.94, and 3.71%), milk protein (3.12, 3.09, and3.03%), lactose (4.93, 4.92, and 4.92%), solids-not-fat(8.96, 8.92, and 8.85%), body weight change (−0.10,−0.06, and −0.08 kg/d), and body condition scorechange (−0.05, −0.04, and −0.05 score/d) were similarfor early-lactation dairy cows fed all corn silage hybrids.Lower ruminal pH and acetate along with higherpropionate molar percentages were reported for cowsfed STA compared with cows fed LF_1 and LF_2. Earlylactationdairy cows fed a corn silage with lower starchand higher digestible fiber concentrations resulted insimilar milk production compared with cows fed higherstarch and lower digestible fiber concentrations.