|De Veth, Michael|
Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2012
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Feeding rumen-protected methionine (RPM) and lysine (RPL) may allow feeding lower crude protein (CP) diets to dairy cows, thereby increasing nitrogen efficiency and reducing environmental impact. Moreover, RPL supplementation may improve the value of corn distillers dried grains plus solubles (DDGS) because its rumen-undegraded protein (RUP) is limiting in lysine (Lys). A trial tested experimental preparations of RPM and RPL that provided 15 g/d of DL-Met and 26 g/d of L-Lys. Forty lactating Holstein cows were blocked by days-in-milk and parity into 8 squares in a replicated 5 x 5 Latin square trial with five dietary treatments: 1) low CP control (14.9% CP) without supplement, and diet one top-dressed with 2) RPM, 3) RPL, 4) RPM + RPL, and 5) high CP control (16.8% CP) without supplement. As fed, all diets contained (dry matter basis): 31% alfalfa silage, 31% corn silage, 7.7% DDGS, 2.4% mineral-vitamin premix and 31% neutral detergent fiber (NDF). Diets 1-4 contained 25% corn grain plus 3.3% solvent soybean meal (SBM); diet 5 contained 21% corn grain, 1.9% solvent SBM, 3.6% expeller SBM, and 1.9% corn gluten meal. Periods were 3 weeks each (total: 15 weeks); data from week 3 were analyzed using Proc Mixed in SAS. Relative to the low CP control, feeding higher CP increased dry matter intake (DMI) and yield of milk and protein, but also increased milk urea nitrogen. No RPM main effect was observed; however, the RPM*RPL interaction for milk yield was significant because RPM increased milk 1.2 kg/d, but milk was unaltered on RPM + RPL. Feeding RPL reduced energy-corrected milk/DMI because numerically greater DMI had no effect on energy-corrected milk yield. In this trial, feeding RPM, but not RPL, increased milk yield on low CP diets containing SBM plus DDGS.