Date of Award:

1977

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Advisor/Chair:

John C. Malechek

Abstract

Part I
A study of animal performance was made with goats fed, ad libitum ground and pe11eted mixtures of Gambe1 oak and alfalfa. Intake, digestibility, metabolizable nitrogen, and metabolized energy of oak diets were generally lower than those for a control alfalfa diet. However, no significant differences in live weight gains of experimental animals were found. No apparent toxicity was detected in goats fed diets containing up to 80 percent oak for 72 days.

Part II
Mixtures of oak (Quercus gambelii) and alfalfa (Medicago sativa) were used to evaluate three laboratory techniques, the Tilley and Terry (1963) two-stage technique, the Van Soest et al. (1966) neutral detergent technique, and the Van Soest (1967) summative equation for their accuracy and precision to estimate in vivo digestibility. Additionally, the effects of inoculum donors' diet, oak phenology, and temperature of drying oak foliage were evaluated in terms of their independent and combined effects upon estimates of in vitro digestibility.

The Tilley and Terry (1963) acid pepsin digestion technique was the best indicator of in vivo digestibility (r2 = 0.97), followed 2 by the Van Soest et al. (1966) neutral detergent method (r2 = 0.76), while estimates from the Van Soest (1967) summative equation were not significantly correlated (P < 20.05) with in vivo digestion. However, the use of either in vitro method for predicting in vivo digestibility requires development of separate regression equations because both techniques generally over-estimated in vivo digestion. Also, separate regression relationships would be required for plant material varying widely in maturity.

In vitro digestibility of oak-containing rations was inversely related to both percentage of oak in the diets and the amount of oak in the inoculum donors' diet. However, oak content of diets was of much greater importance. Digestibility was also depressed by high drying temperatures and the effect was greater for material collected in early summer when foliage was relatively immature than it was in late summer when foliage reached maturity.

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