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Document Type

Dissertation - University Access Only

Award Date

1989

Degree Name

Doctor of Philosophy (PhD)

Department

Dairy Science

First Advisor

David J. Schingoethe

Abstract

Readily fermentable nonstructural carbohydrates in diets can dramatically effect milk production in early lactation dairy cows. In the first trial, 60 Holstein cows were used in a 3 x 2 factorial to evaluate three sources of carbohydrates that differed in solubility and degradability (corn, barley, and dried whey) with two sources of crude protein solubility (soybean meal and urea). Milk production (32.8, 31.5, and 31.3 kg/d) was highest for cows fed corn, whereas 4% fat-corrected milk (30.0, 27.9, and 29.5 kg/d) was similar for cows fed corn and dried whey and lower for cows fed barley. Solubility of protein did not affect production of milk (32.2 and 31.5 kg/d) and 4% fat-corrected milk (29.4 and 28.9 kg/d). Intake of dry matter was lowest for cows fed barley (20.4, 18.8, and 20.5 kg/d) and was similar (19.9 and 19.9 kg/d) for cows fed soybean meal and urea. Sources of carbohydrates that are more soluble and degradable (i.e., barley or dried whey) did not give the expected increase in utilization of a highly soluble crude protein source for milk production. In the second trial, 40 Holstein cows were used in a 2 x 2 factorial design to test the hypothesis that increasing the amount of fermentable carbohydrates (corn versus dried whey) in a high fat diet (soybean meal versus extruded soybeans) may prevent the depression in milk protein percentages that usually occurs with high fat diets. Production of milk (32.7 and 33.6 kg/d) and 4% fat-corrected milk (28.3 and 29.4 kg/d) increased with dried whey in the diet. Production of milk (31.7 and 34.6 kg/d) increased when fed extruded soybeans, but production of 4% fat-corrected milk (28.7 and 29.0 kg/d) was similar due to lower percentages of fat (3.26 and 2.98) and protein (3.03 and 2.95) for cows fed extruded soybeans. Feeding a readily fermentable carbohydrate source with a high fat diet (dried whey-soybean) did not increase the concentration of milk fat (2.91 and 3.05%) or protein (2.96 and 2.94%) relative to corn-soybean, but increased production of milk (35.3 and 33.8 kg/d). Samples of corn, dried whey were evaluated for midwest barley, northwest barley, and nonstructural carbohydrate degradation. Rates of nonstructural degradation were greatest for dried whey, and were greater for northwest barley than for midwest barley and corn. The degradation of nonstructural carbohydrates in the concentrate mixes from the lactation trial was greatest for dried whey, but similar for corn and barley concentrate mixes. The rate of nonstructural carbohydrate degradability in barley may be affected by variety, geographical location, growing season, or other factor(s).

Library of Congress Subject Headings

Cattle -- Feeding and feeds
Milk yield

Format

application/pdf

Publisher

South Dakota State University

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