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Document Type

Thesis - University Access Only

Award Date

2012

Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

David J. Schingoethe

Abstract

A study was conducted to determine the response of feeding two different crude protein (CP) concentrations (15% and 17%) and sources [ canola meal (CM) and h-ighprotein dried distillers grain (HPDDG)] on dry matter intake, milk production and composition, blood and ruminal parameters of high producing dairy cows. Sixteen Holstein cows (12 multiparous and 4 primiparous) with 90 ± 26 days in milk (DIM) were used in a replicated 4 x 4 Latin square with a 2 x 2 factorial arrangements of treatments. Cows were blocked by parity, production and DIM. Feeding periods were 4 wks long and data were collected during wk 3 and 4 of each period. Diets were formulated with 15% CP with CM (15CM), 15% CP with HPDDG (l 5DG), 17% CP with CM (17CM) and 17% CP with HPDDG (l 7DG). All diets contained 55% forage (50% alfalfa hay and 50% com silage) and 45% concentrate and approximately 4.1 % ether extract. Dry matter intake was different (P = 0.03) between concentrations (24.6 vs. 25.9 kg/d for 15 and 17% CP, respectively), but similar between sources of dietary protein. Milk yield was greater (P = 0.002) for cows fed 17% CP (34.0 vs. 36.4 kg/d), but similar between sources. Milk fat percentage was greater (P = 0.02) for cows fed 17% CP (3.14) compared to 15% CP (2.97) but similar between sources. Somatic cell count and lactose percentage were similar between dietary prot~in concentrations, but different (P<0.05) between sources. Milk urea nitrogen concentration was greater (P<0.00 I) for cows fed 17% CP and HPDDG (P = 0.005). Fat-corrected milk feed efficiency (1.18 vs. 1.25) and energy-corrected milk feed efficiency (1.30 vs. 1.37) were greater in cows fed 17% CP (P<0.05) than 15% CP, but similar (P>0.05) between sources. Average initial body weight (679.7kg) and body condition score (3.01) for the experiment were not affected (P>0.05) by the treatments (687.3 kg and 3.12). Concentration of blood urea nitrogen (BUN) from coccygeal artery, subcutaneous abdominal vein and their differences was higher (P < 0.01) for cows fed 17% CP diets than the 15% CP diets, but similar between CM and HPDDG. Total essential amino acid (EAA) concentrations of plasma from coccygeal artery, subcutaneous abdominal vein and their differences were higher (P<0.01) for cows fed 17% CP diets compared to 15% CP diets, but similar for CM and HPDDG. Mammary gland extraction efficiency of EAA indicated that Met was the first limiting AA for CM based diets followed by Lys, Arg, and Phe, while Lys was first limiting for HPDDG based diets followed by Met, Arg, and Phe. Ammonia and volatile fatty acid (VFA) concentrations in the rumen were not affected by experimental diets. This study demonstrated that use of CM or HPDDG for the lactating dairy cows had similar effects on milk production and the composition, but the CP concentrations had a greater impact on milk production and milk composition. The order of limiting AA for milk production can be altered by the types of protein sources used in the ration.

Library of Congress Subject Headings

Dairy cattle -- Feeding and feeds
Proteins in animal nutrition
Lactation
Milk yield

Description

Includes bibliographical references (pages 69-90)

Format

application/pdf

Number of Pages

106

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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