Date of Award

Winter 1996

Project Type

Dissertation

Program or Major

Animal and Nutritional Sciences

Degree Name

Doctor of Philosophy

First Advisor

Charles Schwab

Abstract

The primary objectives of experiment 1 were to determine the effects of changes in feed intake associated with the periparturient period (late gestation to early lactation) on passage of nitrogen fractions and amino acids to the small intestine and to determine if changes occurred in the profile of amino acids presented to the small intestine that could not be explained by diet composition. A secondary objective was to obtain preliminary data on changes in plasma concentrations of nonesterified fatty acids during the periparturient period when cows were fed nutrient-dense diet prepartum diets. Beginning 14 days before expected calving, 10 multiparous cows, five with ruminal and duodenal cannula, were fed prepartum diets containing (% of dry matter) 33.2 corn silage, 22.1 haycrop silage, 29.9 ground shelled corn, 11.6 solvent-extracted soybean meal, 0.7 blood meal, 0.7 tallow, and 1.9 mineral mix. On the day of calving through 12 days of lactation cows were fed a diet of (% of dry matter) 20.6 corn silage, 20.6 haycrop silage, 35.9 ground shelled corn, 17.0 soybean meal, 1.4 blood meal, 1.4 tallow, and 4.0 mineral mix. Feeding a nutrient-dense prepartum diet with the same ingredients as the postpartum diets stabilized rumen fermentation during the periparturient period and minimized the decrease in feed intake that accompanies parturition. Similar proportional flows of bacterial N and non-ammonia non-microbial N to the small intestine throughout the periparturient period resulted in a stable profile of amino acids in duodenal protein prepartum diets than cows fed the low ruminally undegradable protein diets and greater for cows fed the lysine and methionine supplemented lactation diet that cows fed the unsupplemented diet. Increases in milk protein with postpartum lysine and methionine were greatest when high ruminally undegradable protein prepartum diets were fed vs. when low ruminally undegradable protein prepartum diets were fed and when amino acids were not included in the prepartum diets vs. when they were included in the prepartum diets. Concentration of ruminally undegradable protein and concentrations of lysine and methionine in ruminally undegradable protein of prepartum diets both appear to affect the milk protein content response of early lactation cows to supplemental lysine and methionine.

The primary objectives of experiment 3 were to determine the effects of, and interaction between, feeding greater amounts of ruminally undegradable protein and supplemental lysine and methionine during the last 3 weeks of gestation and supplemental lysine and methionine during the first 10 weeks of lactation on selected blood metabolites and hormones when soybean products provided all of the supplemental protein. The same cows used in experiment 2 were used in this experiment. Blood samples were taken daily beginning 10 days before calving through 7 days of lactation, after which samples were taken three times weekly for weeks 2 through 10 of lactation. Urine sampling followed the same scheme as blood samples. Concentrations of ruminally undegradable protein increased prepartum insulin, increased postpartum glucose, and reduced urine ketone concentrations.

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