Semester

Spring

Date of Graduation

2010

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

K. Marie Krause.

Abstract

The effects of concentrate supplementation on milk production and ruminal fermentation was evaluated in six ruminally cannulated lactating Holstein dairy cows in a Latin rectangle design. Cows were fed 4 (C4), 8 (C8), and 12 (C12) kg DM/d of a concentrate supplement. Increasing amounts of concentrate supplement decreased pasture intake, but increased overall dry matter intake (DMI) and increased milk production without changing milk composition. Daily mean and minimum ruminal pH was similar for all treatments. Increasing supplementation increased time spent below pH 5.8, and resulted in a reduction in the in situ degradability of DM and NDF at 24 hrs. Total tract digestibility, total volatile fatty acid, ammonia concentrations, and microbial protein synthesis were not affected by increasing levels of supplementation. The highest level of supplementation of 12 kg DM/cow/d had negative effects on rumen fermentation and may not be beneficial in a pasture based system.

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