Document Type

Thesis - University Access Only

Award Date

2006

Degree Name

Doctor of Philosophy (PhD)

Department / School

Dairy Science

Abstract

Lysine is the first limiting amino acid in distillers grains and deficiency may negatively impact milk protein synthesis, especially when cows are fed a diet containing mostly corn-based feeds. In experiment I, ruminal crude protein degradability and intestinal digestibility differed greatly among various sources of distillers grains. Dried distillers grains had a lower concentration of lysine in the digestible feed compared to wet distillers grains but generally did not decrease estimated total tract protein digestibility. In the second experiment, replacing soybean meal with dried distillers grains from three different sources increased yields of milk, 4% fat-corrected milk, and energy-corrected milk and improved feed efficiency. Milk fat content did not differ among diets but milk protein percentages were greater for cows fed soybean meal compared to distillers grains. Concentrations of arterial lysine were lower in cows fed distillers grains compared to soybean meal. Overall, the source of distillers grains used in this study did not affect lactation performance. In the third experiment, cows were fed a total mixed diet containing corn silage, 50% corn silage and 50% alfalfa hay, or alfalfa hay as the forage source with 1 5% dried distillers grains all m diets containing a 50:50 forage to concentrate ratio. Yields of milk increased linearly but 4% fat-corrected milk and energy-corrected milk were similar for all diets as alfalfa replaced corn silage. Feed efficiency was greater when forage was solely alfalfa in the diet. Milk fat content tended to decrease linearly but no effect on fat yield was observed by replacing corn silage with alfalfa. Milk protein concentration was not affected, but yield tended to increase linearly by feeding alfalfa hay, due to an increased uptake of essential amino acids, particularly lysine, by the mammary gland. In conclusion, replacing corn silage with alfalfa hay in diets containing 1 5% dried distillers grains plus solubles increased yields of milk from cows in late lactation, which tended to increase yields of milk protein. Furthermore, feeding alfalfa instead of corn silage as the primary forage source increased milk production without affecting feed intake, thus improving feed efficiency.

Library of Congress Subject Headings

Dairy cattle -- Feeding and feeds

Distillers feeds

Amino acids in animal nutrition

Milk proteins

Format

application/pdf

Number of Pages

152

Publisher

South Dakota State University

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