Avances nutriion

EXTENSION CIRCULAR 422

FROM FEED TO MILK: UNDERSTANDING RUMEN FUNCTION

CONTENTS
Part I: Background in Basic Nutrition of Dairy Cattle ........................... 1
Rumen physiology ................................................................................................................ 1 Rumination and saliva production..................................................................................... 3 Function of the rumen ........................................................................................................... 3 Rumen microbiology ............................................................................................................. 4 Microbial digestion in the rumen........................................................................................ 6 Carbohydrates ................................................................................................................ 6 Protein ............................................................................................................................. 8 Lipids............................................................................................................................... 8 Vitamins .......................................................................................................................... 8 Basic nutritional concepts behind feeding dairy cattle .................................................... 8 Dry matter intake and its effect on the cow ..................................................................... 11

Part II: Feedand Feed Nutrients for Dairy Cattle .............................. 13
Carbohydrates ...................................................................................................................... 13 Fats ......................................................................................................................................... 15 Protein................................................................................................................................... 17 Energy ................................................................................................................................... 21 Minerals ................................................................................................................................ 23 Vitamins................................................................................................................................ 25 Water ...................................................................................................................................... 26

List of Figures
Figure 1. Summary of digestion and absorption in the ruminant. ............................................ 2Figure 2. Ruminal fermentation as a consequence of adaptation due to pH regulation. .......... 6 Figure 3. Feed, nutrient flow from the rumen, and milk components. ..................................... 6

List of Tables .......................................................... Inside back cover

Prepared by Virginia Ishler, extension assistant in the Department of Dairy and Animal Science; JudHeinrichs, professor of dairy and animal science; and Gabriella Varga, associate professor of animal science. Development of this publication was made possible through a grant from Church & Dwight Co., Inc., manufacturers of ARM & HAMMER® feed ingredients.

TABLES
Table 1. Rate of passage of feed for dry cows and lactating cows. ................................ 1 Table 2. Effect of ration oneating rate and on saliva production. ................................. 3 Table 3. Chemical composition of saliva from cattle. ....................................................... 3 Table 4. Typcial composition of rumen gases. ................................................................... 4 Table 5. Grouping of rumen bacterial species according to the type of substrates fermented....