ARS | Publication request: Impact of Alfalfa Hay Neutral Detergent Fiber Concentration and Digestibility on Holstein Dairy Cow Performance: I. Hay Analyses and Lactation Performance-Usdfrc

Submitted to: Journal of Dairy Science
Publication Type: Abstract
Publication Acceptance Date: April 1, 2005
Publication Date: July 24, 2005
Citation: Mertens, D. R., Raeth-Knight, M. L., Linn, J. G., Jung, H. G., and Peterson, P. R. 2005. Impact of alfalfa hay neutral detergent fiber concentration and digestibility on Holstein dairy cow performance: I. Hay analyses and lactation performance - USDFRC. [abstract] Journal of Dairy Science. 88(Suppl.1):250.

Technical Abstract: Our objective was to evaluate the impact of amylase-treated NDF (aNDF) and 48-h in vitro NDF disappearance (NDFD) of alfalfa hay on milk production when fed as 15% or 30% of ration DM at the Univ. of Minnesota (UMN) and US Dairy Forage Research Center (DFRC), respectively. Samples of 22 commercial hays were evaluated to identify four alfalfa hays that differed in aNDF and NDFD based on chemical, in vitro and NIRS analyses. After delivery, core samples were taken at each location and analyzed for aNDF and NDFD at the DRFC. Composite hay samples were made for each location during lactation trials. Sixty-eight cows were assigned to one of four TMR, each containing one of the hays. Ration DM consisted of 30% alfalfa hay, 16.1% corn silage, 25.3% ground corn, 2.7% molasses, 5% roasted soybeans, and 20.9% concentrate mixture, which contained soybean meal, soybean hulls, distiller's grains, minerals and vitamins. Cows averaged 46.5 kg milk/d and 86 days in lactation at the beginning of the trial. Cows were fed a covariate diet for two weeks, followed by experimental diets for 12 weeks. Production trial means were analyzed with covariance using Proc GLM in SAS. Initial samples indicated the aNDF of hays low in fiber and high in digestibility (LFHD), low in fiber and digestibility (LFLD), high in fiber and digestibility (HFHD) and high in fiber and low in digestibility (HFLD) were 37.2, 36.4, 41.7 and 40.8 %, respectively. The NDFD of initial samples were 41.3, 37.9, 44.6 and 41.1% of NDF for LFHD, LFLD, HFHD and HFLD, respectively. The 4 to 5 %-unit difference between high and low aNDF and NDFD was similar between locations and among bale core and experimental composite samples. However, variation was observed between laboratories and methods in aNDF and NDFD determinations. Least-squared means for milk production were 43.8, 45.0, 46.9 and 45.4 for LFHD, LFLD, HFHD and HFLD, respectively (P = 0.07). We concluded that small differences in aNDF and NDFD among the alfalfa hays have limited impact on milk production when included as 30% of the diet DM.