Document Type

Thesis - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)


Animal Science


The purpose of this study was to evaluate the effects of feeding moldy alfalfa hay to dairy steers on their growth rate , rumen fermentative activities, rumen protozoa counts and rumen volatile fatty acid production. Good quality and molded alfalfa hays prepared from the same fields were chemically analyzed. Molded hay was lower in dry matter, ether extract, nitrogen-free-extract and higher in crude fiber, ash and pH values than good alfalfa hay. A higher percentage of total protein of moldy hay appeared as ammoniacal nitrogen. Two dairy steer-feeding experiments were conducted. The first experiment involving two groups of five steers each was conducted over three 35-day experimental periods to observe the influence of different grain feeding levels on the steers separately fed moldy and good alfalfa hay. The second steer feeding trial involved a double-reversal design over three 70-day periods with two groups of five steers each. Steers on good hay consumed more dry matter. They showed slightly high body weight gains; higher production of rumen ammonia, total VFA, propionic, isobutyric, isovaleric, and valeric acids than the other group. Moldy hay feeding increased the rumen pH and rumen acetic acid concentration. Acetic to propionic acid ratio was higher in the rumen samples of moldy hay fed steers. Moldy hay feeding seemed to reduce total ruminal protozoa count, Isotricha, Dasytricha and Entodinium populations, but increased the Diplodinium population. Moldy hay fed steers developed rough hair coats. Two digestion experiments were conducted. The first experiment involved a single-reversal digestion trial with a pair of twin Holstein steers. The second trial was performed using four Holstein steers in a double-reversal design. The results of both experiments were quite similar. Digestibility of dry matter, protein, and energy from moldy hay was significantly lower than for good quality hay, but crude fiber digestibility was higher from moldy hay. Molding seemed to cause some increase in lignin digestibility of alfalfa hay. Steers on moldy hay consumed more dicalcium phosphate and trace mineral salts than the other group. To check for the presence of any toxic substance(s) in moldy alfalfa hay two four-week chick feeding trials involving 192 day-old chicks with four treatments per experimental hay were conducted. Extracts from the experimental hays made with chloroform and distilled water were separately fed to six groups of four chicks per treatment. Chicks fed chloroform and water extracts from the experimental hays grew more slowly than the control groups. There was no difference in the feed consumption and growth rates of chicks fed chloroform extracts from good and moldy alfalfa hays. Feeding of water extract from good quality hay depressed the feed consumption and growth rates of the experimental chicks in comparison to the chicks fed water extracts from moldy hay. Chicks developed rough feathers one week after feeding chloroform extracts from moldy hay. Twenty-five different species of molds were identified from the moldy hay samples.

Library of Congress Subject Headings


Dairy cattle -- Feeding and feeds

Molds (fungi)



Number of Pages



South Dakota State University