HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Interpretive Summary Alert me when this article is cited Alert me if a correction is posted Services Related articles in JDS Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Weiss, W. P. Articles by Willett, L. B. PubMed PubMed Citation Articles by Weiss, W. P. Articles by Willett, L. B.

Varying type of forage, concentration of metabolizable protein, and source of carbohydrate affects nutrient digestibility and production by dairy cows

W. P. Weiss^*,1, N. R. St-Pierre and L. B. Willett^*

^* Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691
Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Columbus 43210

¹ Corresponding author: weiss.6{at}osu.edu

The effects of forage source, concentration of metabolizable protein (MP), type of carbohydrate, and their interactions on nutrient digestibility and production were evaluated using a central composite treatment design. All diets (dry basis) contained 50% forage that ranged from 25:75 to 75:25 alfalfa silage:corn silage. Rumen-degradable protein comprised 10.7% of the dry matter (DM) in all diets, but undegradable protein ranged from 4.1 to 7.1%, resulting in dietary MP concentrations of 8.8 to 12.0% of the DM. Dietary starch ranged from 22 to 30% of the DM with a concomitant decrease in neutral detergent fiber concentrations. A total of 15 diets were fed to 36 Holstein cows grouped in 6 blocks. Each block consisted of three 21-d periods, and each cow was assigned a unique sequence of 3 diets, resulting in 108 observations. Milk production and composition, feed intake, and digestibility of major nutrients (via total collection of feces and urine) were measured. Few significant interactions between main effects were observed. Starch concentration had only minor effects on digestibility and production. Replacing corn silage with alfalfa decreased digestibility of N but increased digestibility of neutral detergent fiber. Increasing the concentration of MP increased N digestibility. The concentration (Mcal/kg) of dietary digestible energy (DE) increased linearly as starch concentration increased (very small effect) and was affected by a forage by MP interaction. At low MP, high alfalfa reduced DE concentration, but at high MP, increasing alfalfa increased DE concentration. Increasing alfalfa increased DM and DE intakes, which increased yields of energy-corrected milk, protein, and fat. Increasing MP increased yields of energy-corrected milk and protein. The response in milk protein to changes in MP was much less than predicted using the National Research Council (2001) model.

Key Words: digestibility • starch • alfalfa • protein

Related articles in JDS:

Varying forage type, metabolizable protein concentration, and carbohydrate source affects manure excretion, manure ammonia, and nitrogen metabolism of dairy cows

W. P. Weiss, L. B. Willett, N. R. St-Pierre, D. C. Borger, T. R. McKelvey, and D. J. Wyatt
JDS 2009 92: 5607-5619. [Abstract] [Full Text]